1. |
- Alshamari, Muhammed, 1975-, et al.
(author)
-
Diagnostic accuracy of low-dose CT compared with abdominal radiography in non-traumatic acute abdominal pain : prospective study and systematic review
- 2016
-
In: European Radiology. - New York : Springer. - 0938-7994 .- 1432-1084. ; 26:6, s. 1766-1774
-
Research review (peer-reviewed)abstract
- Objectives: Abdominal radiography is frequently used in acute abdominal non-traumatic pain despite the availability of more advanced diagnostic modalities. This study evaluates the diagnostic accuracy of low-dose CT compared with abdominal radiography, at similar radiation dose levels.Methods: Fifty-eight patients were imaged with both methods and were reviewed independently by three radiologists. The reference standard was obtained from the diagnosis in medical records. Sensitivity and specificity were calculated. A systematic review was performed after a literature search, finding a total of six relevant studies including the present.Results: Overall sensitivity with 95 % CI for CT was 75 % (66-83 %) and 46 % (37-56 %) for radiography. Specificity was 87 % (77-94 %) for both methods. In the systematic review the overall sensitivity for CT varied between 75 and 96 % with specificity from 83 to 95 % while the overall sensitivity for abdominal radiography varied between 30 and 77 % with specificity 75 to 88 %.Conclusions: Based on the current study and available evidence, low-dose CT has higher diagnostic accuracy than abdominal radiography and it should, where logistically possible, replace abdominal radiography in the workup of adult patients with acute non-traumatic abdominal pain.Key points: • Low-dose CT has a higher diagnostic accuracy than radiography. • A systematic review shows that CT has better diagnostic accuracy than radiography. • Radiography has no place in the workup of acute non-traumatic abdominal pain.
|
|
2. |
- Alshamari, Muhammed, 1975-, et al.
(author)
-
Impact of iterative reconstruction on image quality of low-dose CT of the lumbar spine
- 2017
-
In: Acta Radiologica. - London : Sage Publications. - 0284-1851 .- 1600-0455. ; 58:6, s. 702-709
-
Journal article (peer-reviewed)abstract
- Background: Iterative reconstruction (IR) is a recent reconstruction algorithm for computed tomography (CT) that can be used instead of the standard algorithm, filtered back projection (FBP), to reduce radiation dose and/or improve image quality.Purpose: To evaluate and compare the image quality of low-dose CT of the lumbar spine reconstructed with IR to conventional FBP, without further reduction of radiation dose.Material and Methods: Low-dose CT on 55 patients was performed on a Siemens scanner using 120 kV tube voltage, 30 reference mAs, and automatic dose modulation. From raw CT data, lumbar spine CT images were reconstructed with a medium filter (B41f) using FBP and four levels of IR (levels 2-5). Five reviewers scored all images on seven image quality criteria according to the European guidelines on quality criteria for CT, using a five-grade scale. A side-by-side comparison was also performed.Results: There was significant improvement in image quality for IR (levels 2-4) compared to FBP. According to visual grading regression, odds ratios of all criteria with 95% confidence intervals for IR2, IR3, IR4, and IR5 were: 1.59 (1.39-1.83), 1.74 (1.51-1.99), 1.68 (1.46-1.93), and 1.08 (0.94-1.23), respectively. In the side-by-side comparison of all reconstructions, images with IR (levels 2-4) received the highest scores. The mean overall CTDIvol was 1.70 mGy (SD 0.46; range, 1.01-3.83 mGy). Image noise decreased in a linear fashion with increased strength of IR.Conclusion: Iterative reconstruction at levels 2, 3, and 4 improves image quality of low-dose CT of the lumbar spine compared to FPB.
|
|
3. |
|
|
4. |
- Alshamari, Muhammed, 1975-, et al.
(author)
-
Low-dose computed tomography of the lumbar spine: a phantom study on imaging parameters and image quality
- 2014
-
In: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 55:7, s. 824-832
-
Journal article (peer-reviewed)abstract
- Background: Lumbar spine radiography has limited diagnostic value but low radiation dose compared with computed tomography (CT). The average effective radiation dose from lumbar spine radiography is about 1.1 mSv. Low-dose lumbar spine CT may be an alternative to increase the diagnostic value at low radiation dose, around 1 mSv. Purpose: To determine the optimal settings for low-dose lumbar spine CT simultaneously aiming for the highest diagnostic image quality possible. Material and Methods: An ovine lower thoracic and lumbar spine phantom, with all soft tissues around the vertebrae preserved except the skin, was placed in a 20 L plastic container filled with water. The phantom was scanned repeatedly with various technical settings; different tube potential, reference mAs, and with different convolution filters. Five radiologists evaluated the image quality according to a modification of the European guidelines for multislice computed tomography (MSCT) quality criteria for lumbar spine CT 2004. In a visual comparison the different scans were also ranked subjectively according to perceived image quality. Image noise and contrast were measured. Results: A tube potential of 120 kV with reference mAs 30 and medium or medium smooth convolution filter gave the best image quality at a sub-millisievert dose level, i.e. with an effective dose comparable to that from lumbar spine radiography. Conclusion: Low-dose lumbar spine CT thus opens a possibility to substitute lumbar spine radiography with CT without obvious increase in radiation dose.
|
|
5. |
- Alshamari, Muhammed, 1975-, et al.
(author)
-
Low dose CT of the lumbar spine compared with radiography : a study on image quality with implications for clinical practice
- 2016
-
In: Acta Radiologica. - London, United Kingdom : Sage Publications. - 0284-1851 .- 1600-0455. ; 57:5, s. 602-611
-
Journal article (peer-reviewed)abstract
- Background: Lumbar spine radiography is often performed instead of CT for radiation dose concerns.Purpose: To compare image quality and diagnostic information from low dose lumbar spine CT at an effective dose of about 1 mSv with lumbar spine radiography.Material and Methods: Fifty-one patients were examined by both methods. Five reviewers scored all examinations on eight image quality criteria using a five-graded scale and also assessed three common pathologic changes.Results: Low dose CT scored better than radiography on the following: sharp reproduction of disc profile and vertebral end-plates (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3-2.5), intervertebral foramina and pedicles (OR, 4.3; 95% CI, 3.1-5.9), intervertebral joints (OR, 139; 95% CI, 59-326), spinous and transverse processes (OR, 7.0; 95% CI, 4.3-11.2), sacro-iliac joints (OR, 4.2; 95% CI, 3.2-5.7), reproduction of the adjacent soft tissues (OR, 2.9; 95% CI, 2.1-4.0), and absence of any obscuring superimposed gastrointestinal gas and contents (OR, 188; 95% CI, 66-539). Radiography scored better on sharp reproduction of cortical and trabecular bone (OR, 0.3; 95% CI, 0.2-0.4). The reviewers visualized disk degeneration, spondylosis/diffuse idiopathic skeletal hyperostosis (DISH) and intervertebral joint osteoarthritis more clearly and were more certain with low dose CT. Mean time to review low dose CT was 204 s (95% CI, 194-214 s.), radiography 152 s (95% CI, 146-158 s.). The effective dose for low dose CT was 1.0-1.1 mSv, for radiography 0.7 mSv.Conclusion: Low dose lumbar spine CT at about 1 mSv has superior image quality to lumbar spine radiography with more anatomical and diagnostic information.
|
|
6. |
- Andersson, Karin M., 1989-, et al.
(author)
-
Visual grading evaluation of commercially available metal artefact reduction techniques in hip prosthesis computed tomography
- 2016
-
In: British Journal of Radiology. - London, United Kingdom : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 89:1063
-
Journal article (peer-reviewed)abstract
- Objectives: To evaluate metal artefact reduction (MAR) techniques from four computed tomography (CT) vendors in hip prosthesis imaging.Methods: Bilateral hip prosthesis phantom images, obtained by using MAR algorithms for single energy CT data or dual energy CT (DECT) data and by monoenergetic reconstructions of DECT data, were visually graded by five radiologists using ten image quality criteria. Comparisons between the MAR images and a reference image were performed for each scanner separately. Ordinal probit regression analysis was used.Results: The MAR algorithms in general improved the image quality based on the majority of the criteria (up to between 8/10 and 10/10) with a statistically improvement in overall image quality (P<0.001). However, degradation of image quality, such as new artefacts, was seen in some cases. A few monoenergetic reconstruction series improved the image quality (P<0.004) for one of the DECT scanners, but it was only improved for some of the criteria (up to 5/10). Monoenergetic reconstructions resulted in worse image quality for the majority of the criteria (up to 7/10) for the other DECT scanner.Conclusions: The MAR algorithms improved the image quality of the hip prosthesis CT images. However, since additional artefacts and degradation of image quality were seen in some cases, all algorithms should be carefully evaluated for every clinical situation. Monoenergetic reconstructions were in general concluded to be insufficient for reducing metal artifacts. Advances in knowledge: Qualitative evaluation of the usefulness of several MAR techniques from different vendors in CT imaging of hip prosthesis.
|
|
7. |
- Geijer, Håkan, 1961-, et al.
(author)
-
Added value of double reading in diagnostic radiology, a systematic review
- 2018
-
In: Insights into Imaging. - : Springer. - 1869-4101. ; 9:3, s. 287-301
-
Research review (peer-reviewed)abstract
- OBJECTIVES: Double reading in diagnostic radiology can find discrepancies in the original report, but a systematic program of double reading is resource consuming. There are conflicting opinions on the value of double reading. The purpose of the current study was to perform a systematic review on the value of double reading.METHODS: A systematic review was performed to find studies calculating the rate of misses and overcalls with the aim of establishing the added value of double reading by human observers.RESULTS: The literature search resulted in 1610 hits. After abstract and full-text reading, 46 articles were selected for analysis. The rate of discrepancy varied from 0.4 to 22% depending on study setting. Double reading by a sub-specialist, in general, led to high rates of changed reports.CONCLUSIONS: The systematic review found rather low discrepancy rates. The benefit of double reading must be balanced by the considerable number of working hours a systematic double-reading scheme requires. A more profitable scheme might be to use systematic double reading for selected, high-risk examination types. A second conclusion is that there seems to be a value of sub-specialisation for increased report quality. A consequent implementation of this would have far-reaching organisational effects.KEY POINTS: • In double reading, two or more radiologists read the same images. • A systematic literature review was performed. • The discrepancy rates varied from 0.4 to 22% in various studies. • Double reading by sub-specialists found high discrepancy rates.
|
|
8. |
|
|
9. |
- Geijer, Mats, 1957-, et al.
(author)
-
Tomosynthesis of the thoracic spine : added value in diagnosing vertebral fractures in the elderly
- 2017
-
In: European Radiology. - New York : Springer. - 0938-7994 .- 1432-1084. ; 27:2, s. 491-497
-
Journal article (peer-reviewed)abstract
- Objectives: Thoracic spine radiography becomes more difficult with age. Tomosynthesis is a low-dose tomographic extension of radiography which may facilitate thoracic spine evaluation. This study assessed the added value of tomosynthesis in imaging of the thoracic spine in the elderly.Methods: Four observers compared the image quality of 50 consecutive thoracic spine radiography and tomosynthesis data sets from 48 patients (median age 67 years, range 55-92 years) on a number of image quality criteria. Observer variation was determined by free-marginal multirater kappa. The conversion factor and effective dose were determined from the dose-area product values.Results: For all observers significantly more vertebrae were seen with tomosynthesis than with radiography (mean 12.4/9.3, P < 0.001) as well as significantly more fractures (mean 0.9/0.7, P = 0.017). The image quality score for tomosynthesis was significantly higher than for radiography, for all evaluated structures. Tomosynthesis took longer to evaluate than radiography. Despite this, all observers scored a clear preference for tomosynthesis. Observer agreement was substantial (mean κ = 0.73, range 0.51-0.94). The calibration or conversion factor was 0.11 mSv/(Gy cm(2)) for the combined examination. The resulting effective dose was 0.87 mSv.Conclusion: Tomosynthesis can increase the detection rate of thoracic vertebral fractures in the elderly, at low added radiation dose.KEY POINTS:• Tomosynthesis helps evaluate the thoracic spine in the elderly. • Observer agreement for thoracic spine tomosynthesis was substantial (mean κ = 0.73). • Significantly more vertebrae and significantly more fractures were seen with tomosynthesis. • Tomosynthesis took longer to evaluate than radiography. • There was a clear preference among all observers for tomosynthesis over radiography.
|
|
10. |
- Ah, Rebecka, et al.
(author)
-
Prognostic Value of P-POSSUM and Osteopenia for Predicting Mortality After Emergency Laparotomy in Geriatric Patients
- 2019
-
In: Bulletin of emergency and trauma. - : Shiraz University of Medical Sciences. - 2322-2522 .- 2322-3960. ; 7:3, s. 223-231
-
Journal article (peer-reviewed)abstract
- Objective: To evaluate the Portsmouth-Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM) in comparison with other risk factors for mortality including osteopenia as an indicator for frailty in geriatric patients subjected to emergency laparotomy.Methods: All geriatric patients (≥65 years) undergoing emergency laparotomy at a single university hospital between 1/2015 and 12/2016 were included in this cohort study. Demographics and outcomes were retrospectively collected from medical records. Association between prognostic markers and 30-day mortality was assessed using Poisson and backward stepwise regression models. Prognostic value was assessed using receiver operating characteristic (ROC) curves.Results: =0.004) while osteopenia was not. P-POSSUM had poor prognostic value for 30-day mortality with an area under the ROC curve (AUC) of 0.59. The prognostic value of P-POSSUM improved significantly when adjusting for patient covariates (AUC=0.83).Conclusion: P-POSSUM and osteopenia alone hardly predict 30-day mortality in geriatric patients following emergency laparotomy. P-POSSUM adjusted for other patient covariates improves the prediction.
|
|
11. |
- Alshamari, Muhammed, 1975-
(author)
-
Low-dose computed tomography of the abdomen and lumbar spine
- 2016
-
Doctoral thesis (other academic/artistic)abstract
- Radiography is a common radiologic investigation despite abundant evidence of its limited diagnostic value. On the other hand, computed tomography (CT) has a high diagnostic value and is widely considered to be among the most important advances in medicine. However, CT exposes patients to a higher radiation dose and it might therefore not be acceptable simply to replace radiography with CT, despite the powerful diagnostic value of this technique. At the expense of reduced CT image quality, which could be adjusted to the diagnostic needs, low-dose CT of abdomen and lumbar spine can be performed at similar dose to radiography. The aim of the current thesis project was to evaluate low-dose CT of the abdomen and lumbar spine and to compare it with radiography. The hypothesis was that CT would give better image quality and diagnostic information compared to radiography at similar dose levels. Firstly, the diagnostic accuracy of low-dose CT of the abdomen was evaluated. Results showed that low-dose CT of abdomen has a high sensitivity and specificity compared to radiography, i.e., it has higher diagnostic accuracy. Similar results were obtained from our systematic review. Secondly, in a phantom study, an ovine phantom was scanned at various CT settings. The image quality was evaluated to obtain a protocol for the optimal settings for low-dose CT of lumbar spine at 1 mSv. This new protocol was then used in a clinical study to assess the image quality of low-dose CT of the lumbar spine and compare it to radiography. Results showed that low-dose CT has significantly better image quality than radiography. Finally, the impact of Iterative reconstruction (IR) on image quality of lumbar spine CT was tested. Iterative reconstruction is a recent CT technique aimed to reduce radiation dose and/or improve image quality. The results showed that the use of medium strength IR levels in the reconstruction of CT image improves image quality compared to filtered back projection. In conclusion, low-dose CT of the abdomen and lumbar spine, at about 1 mSv, has better image quality and gives diagnostic information compared to radiography at similar dose levels and it could therefore replace radiography.
|
|
12. |
- Arbeus, Mikael, et al.
(author)
-
Five-year patency for the no-touch saphenous vein and the left internal thoracic artery in on- and off-pump coronary artery bypass grafting
- 2021
-
In: Journal of cardiac surgery. - : Wiley-Blackwell Publishing Inc.. - 0886-0440 .- 1540-8191. ; 36:10, s. 3702-3708
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Randomized trials show high long-term patency for no-touch saphenous vein grafts in coronary artery bypass grafting. The patency rate in off-pump coronary bypass surgery for these grafts has not been investigated. Our center participated in the CORONARY randomized trial, NCT00463294. This is a study aimed to assess the patency of no-touch saphenous veins in on- versus off-pump coronary bypass surgery at five-year follow-up.METHODS: Fifty-six patients were included. Forty of 49 patients, alive at 5 years, participated in this follow-up. There were 21 and 19 patients in the on- and off-pump groups respectively. No-touch saphenous veins were used to bypass all targets and in some cases the left anterior descending artery. Graft patency according to distal anastomosis was evaluated with computed tomography angiography.RESULTS: The five-year patency rate was 123/139 (88.5%). The patency for the no-touch vein grafts was 57/64 (89.1%) in the on-pump versus 37/45 (82.2%) in the off-pump group. All left internal thoracic arteries except for one, 29/30 (96.6%), were patent. All vein grafts used to bypass the left anterior descending and the diagonal arteries were patent 32/32. The lowest patency rate for the saphenous veins was to the right coronary territory, particularly in off-pump surgery (80.0% vs. 62.5% for the on- respective off-pump groups).CONCLUSIONS: Comparable 5-year patency for the no-touch saphenous veins and the left internal thoracic arteries to the left anterior descending territory in both on- and off-pump coronary artery bypass grafting. Graft patency in off-pump CABG is lower to the right coronary artery.
|
|
13. |
- Bäck, Anna, 1976-, et al.
(author)
-
Diuretic decision seven minutes post Tc-99m-MAG3 administration in a renography
- 2018
-
In: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer. - 1619-7070 .- 1619-7089. ; 45:Suppl. 1, s. S765-S765
-
Journal article (other academic/artistic)abstract
- Aim: The F+10 method in supine position, which has been implemented at our Nuclear Medicine department since 2015, involves a 30- minute long dynamic acquisition. The diuretic is only administered when necessary and decision is taken by the radiographers in a semi-automated fashion without consulting a physician, by calculating the remaining activity in the kidneys seven minutes post 99mTc-MAG3 injection and comparing the value with an arbitrary threshold of 75 %. If needed, the diuretic is injected three minutes later. The aim of this study was to correlate our method with the established previously used F+20 protocol in adults. Is the currently used threshold of 75% of activity left in any kidney at seven minutes the optimal cut-off value for diuretic administration?Material and Methods: This is an ongoing retrospective study which include 320 F+20 examinations of adult patients performed during 2013-2015. They were all re-evaluated according to the currently used F+10 method, categorized as requiring diuretic or not and correlated to the original F+20 examination. A ROC-curve was drawn to delineate the best cut-off value for remaining renal activity. Sensitivity, specificity and accuracy were calculated.Results: Preliminary results indicate that the F+10 re-evaluations with the currently used cut-off value of 75% did not correlate with the original F+20 examinations. In 80% (255 examinations) of the F+10 re-evaluations diuretic would have been considered necessary while only 52% (167 examinations) received diuretics in the original F+20 renographies (sensitivity 1.0, specificity 0.42). However, all the patients who required furosemide in the original F+20 renographies would have received diuretic if they had been imaged with the F+10 protocol. Furthermore, examination time is considerably reduced. After an evaluation of the ROC-curve the optimal cut-off value was 94% (sensitivity 0.92, specificity 0.84, accuracy 0.88). However, by implementing this value, 13 patients (4%) would have been falsely categorized as not requiring diuretic.Conclusions: The 99mTc-MAG3 renography with the F+10 protocol in supine position is a feasible and acceptable method in clinical practice.
|
|
14. |
- Bäck, Anna-Karin, 1971-, et al.
(author)
-
Renography with a semiautomated algorithm for diuretic decision 7 min postradiopharmaceutical administration : a feasibility study
- 2020
-
In: Nuclear medicine communications. - : Lippincott Williams & Wilkins. - 0143-3636 .- 1473-5628. ; 41:10, s. 1018-1025
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: The F+10 method for diuretic renography (diuretics given 10 min after the radiopharmaceutical) could be a time-conserving method. This method involves a 30-min dynamic acquisition where diuretics are administered only when necessary by the Nuclear Medicine technologist performing the examination. The purpose of this study was to assess the method's performance and to discover the optimal threshold of residual activity for a diuretic administration 7 min into the F+10 renography by reprocessing raw data from prior performed examinations with 20-min acquisitions without diuretics.METHODS: Retrospectively, raw data from 320 original examinations of adult patients performed from 2013 to 2015 were reprocessed into 7-min series and categorized as requiring diuretic or not. The diuretic decisions made by an expert panel were used as a reference. A receiver-operating characteristic curve was drawn to assess the optimal cutoff value for the residual renal activity. Sensitivity, specificity, positive and negative predictive values, as well as the Youden J index were calculated.RESULT: The experts classified 50% (160 examinations) as in need of diuretics. The receiver-operating characteristic curve demonstrated the theoretical optimal cutoff value at 7 min to be 94% of maximum activity (sensitivity 0.93, specificity 0.81, Youden J index 0.73). A clinically acceptable threshold is suggested to be 85% (sensitivity 0.99, specificity 0.59, Youden J index 0.58).CONCLUSION: Tc-mercaptoacetyltriglycine renography with the F+10 method and the threshold 85% for diuretic decision 7 min into the renography is a feasible and acceptable method in clinical practice.
|
|
15. |
- Bäck, Anna-Karin, 1971-, et al.
(author)
-
Timing of diuretics in diuresis renography
- 2022
-
In: Clinical and translational imaging. - : Springer. - 2281-5872 .- 2281-7565. ; 10, s. 37-43
-
Research review (peer-reviewed)abstract
- Purpose: The aim of this systematic literature review was to obtain an overview of when to administer the diuretics in relation to the radiopharmaceutical during a diuresis renography.Methods: A systematic literature search was performed in three different databases (Embase, PubMed/Medline and Cochrane Library) together with an information specialist. The review question was: when should diuretics be administered in relation to the radiopharmaceutical in a diuresis renography? Studies of adults were included together with guidelines published in collaboration with an organization.Results: Seventeen articles and four guidelines were retrieved in the literature search. The F - 15 method (diuretics administered 15 min before the radiopharmaceutical) was the one that was studied and described most and was compared with other time points for diuretic administration. The retrieved articles and guidelines report of advantages with different time points for diuretics. Both F - 15 and F + 0 are reported to clarify washout in equivocal cases compared to F + 20.Conclusion: No consensus could be found for a preferred time point of diuretics administration during a diuresis renography.
|
|
16. |
- Bäck, Anna-Karin, 1971-, et al.
(author)
-
Troubled but in good hands : A qualitative study on patient experiences in diuresis renography examinations
- 2024
-
In: Radiography. - : Elsevier. - 1078-8174 .- 1532-2831.
-
Journal article (peer-reviewed)abstract
- INTRODUCTION: Diuresis renography is a nuclear medicine examination that can distinguish between obstructive and non-obstructive uropathy. Renography has been investigated before, but not from a patient perspective. The aim of this study was to gain knowledge and understanding of patient experiences with the diuresis renography process.METHODS: The study had a qualitative descriptive design; data was collected through semi-structured interviews with 17 adult patients that had recently undergone diuresis renography. The transcripts were analysed using inductive qualitative content analysis to identify their manifest and latent content.RESULTS: One main theme was identified: 'Not smooth all the way through, but still in good hands'. The participants understood the necessity of the performed renography and endured the examination despite its worrying elements. They were bothered by diuretic effects, worried about radioactivity and felt isolated during the imaging. The technologists' caring and informative approach eased their experience. The main theme was identified from three subthemes: 'I experienced inconvenience', 'I was worried' and 'I felt safe'.CONCLUSION: The participants experienced worry throughout the renography process but were still satisfied with the examination, mostly because of the technologists being involved. Communication and interaction between patient and technologist are important for creating a good experience. Improved knowledge of patient experiences during renographies could be used to develop patient information and increase technologists' awareness of factors patients may experience as troubling.IMPLICATIONS FOR PRACTICE: This study describes issues that contribute to both negative and positive experiences. Improved professional awareness and knowledge about these issues can contribute to the development of patient information and professional encounters, and may improve patients' compliance and overall experience.
|
|
17. |
- Cao, Yang, Associate Professor, 1972-, et al.
(author)
-
The statistical importance of P-POSSUM scores for predicting mortality after emergency laparotomy in geriatric patients
- 2020
-
In: BMC Medical Informatics and Decision Making. - : BioMed Central. - 1472-6947. ; 20:1
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Geriatric patients frequently undergo emergency general surgery and accrue a greater risk of postoperative complications and fatal outcomes than the general population. It is highly relevant to develop the most appropriate care measures and to guide patient-centered decision-making around end-of-life care. Portsmouth - Physiological and Operative Severity Score for the enumeration of Mortality and morbidity (P-POSSUM) has been used to predict mortality in patients undergoing different types of surgery. In the present study, we aimed to evaluate the relative importance of the P-POSSUM score for predicting 90-day mortality in the elderly subjected to emergency laparotomy from statistical aspects.METHODS: One hundred and fifty-seven geriatric patients aged ≥65 years undergoing emergency laparotomy between January 1st, 2015 and December 31st, 2016 were included in the study. Mortality and 27 other patient characteristics were retrieved from the computerized records of Örebro University Hospital in Örebro, Sweden. Two supervised classification machine methods (logistic regression and random forest) were used to predict the 90-day mortality risk. Three scalers (Standard scaler, Robust scaler and Min-Max scaler) were used for variable engineering. The performance of the models was evaluated using accuracy, sensitivity, specificity and area under the receiver operating characteristic curve (AUC). Importance of the predictors were evaluated using permutation variable importance and Gini importance.RESULTS: The mean age of the included patients was 75.4 years (standard deviation =7.3 years) and the 90-day mortality rate was 29.3%. The most common indication for surgery was bowel obstruction occurring in 92 (58.6%) patients. Types of post-operative complications ranged between 7.0-36.9% with infection being the most common type. Both the logistic regression and random forest models showed satisfactory performance for predicting 90-day mortality risk in geriatric patients after emergency laparotomy, with AUCs of 0.88 and 0.93, respectively. Both models had an accuracy > 0.8 and a specificity ≥0.9. P-POSSUM had the greatest relative importance for predicting 90-day mortality in the logistic regression model and was the fifth important predictor in the random forest model. No notable change was found in sensitivity analysis using different variable engineering methods with P-POSSUM being among the five most accurate variables for mortality prediction.CONCLUSION: P-POSSUM is important for predicting 90-day mortality after emergency laparotomy in geriatric patients. The logistic regression model and random forest model may have an accuracy of > 0.8 and an AUC around 0.9 for predicting 90-day mortality. Further validation of the variables' importance and the models' robustness is needed by use of larger dataset.
|
|
18. |
- Dreifaldt, Mats, 1959-, et al.
(author)
-
Pedicled versus skeletonized internal thoracic artery grafts : a randomized trial
- 2021
-
In: Asian cardiovascular & thoracic annals. - : Medikaru Toribyun. - 1816-5370 .- 0218-4923. ; 29:6, s. 490-497
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: Concerns have been raised regarding whether skeletonization of the internal thoracic artery could damage the graft and thereby reduces its patency. The objective of this study was to compare patency rates at mid- and long-term follow-up between pedicled and skeletonized left internal thoracic artery grafts.METHODS: This randomized controlled trial included 109 patients undergoing coronary artery bypass surgery. The patients were assigned to receive either one pedicled or one skeletonized left internal thoracic artery graft to the left anterior descending artery. Follow-up was performed at 3 years with conventional angiography, and at 8 years with computed tomography angiography. Differences between patency rates were analyzed with Fisher's exact test and a generalized linear model.RESULTS: The patency rates for pedicled and skeletonized left internal thoracic artery grafts were 46/48 (95.8%) versus 47/52 (90.4%), p = 0.44 at 3 years, and 40/43 (93.0%) versus 37/41 (90.2%), p = 0.71 at 8 years, respectively. The difference in patency rates for pedicled and skeletonized grafts was 5.4% (95% confidence interval: -4.2-14.5) at 3 years and 2.8% (95% confidence interval: -9.9-14.1) at 8 years. All failed grafts, except for one with a localized stenosis, were anastomosed to native coronary arteries with a stenosis less than 70%. Three patients suffered sternal wound infections (two in the pedicled group, one in the skeletonized group).CONCLUSIONS: The skeletonization technique can be used without jeopardizing the patency of the left internal thoracic artery. The most important factor in graft failure was target artery stenosis below 70%.
|
|
19. |
- Dreifaldt, Mats, 1959-, et al.
(author)
-
The no-touch saphenous vein is an excellent alternative conduit to the radial artery 8 years after coronary artery bypass grafting : A randomized trial
- 2021
-
In: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier. - 0022-5223 .- 1097-685X. ; 161:2, s. 624-630
-
Journal article (peer-reviewed)abstract
- Background: In 2004, a prospective randomized trial demonstrated that after 3 years, saphenous veins (SVs) harvested with a no touch (NT) technique had a greater patency than radial grafts for coronary bypass surgery. Here we report the 8-year follow-up data of this trial.Methods: The trial included 108 patients undergoing coronary artery bypass grafting (CABG). Each patient was assigned to receive 1 NT SV and 1 radial artery (RA) graft to either the left or right coronary territory to complement the left internal thoracic artery (LITA). Sequential grafting was common, so overall graft patency as well as the patency of each anastomosis were assessed.Results: Angiography was performed in 84 patients (78%) at mean of 97 months postoperatively. Graft patency were high and similar for both NT and RA: 86% for NT versus 79% for RA (P = .22). The patency of coronary anastomoses was significantly higher with the NT SV grafts (91% vs 81%; P = .046). The NT grafts also had excellent patency in coronary arteries with <90% stenosis (93% patency) and in coronary arteries of small diameter (87% patency) or with mild calcification (88% patency). Patency for the LITA was 92%.Conclusions: NT SV grafts have excellent patency similar to that of RA grafts after 8 years. In addition, NT SV grafts can be used in situations that are not ideal for RA grafts.
|
|
20. |
- Edin, Victor, et al.
(author)
-
A Case of Using No-Touch Saphenous Vein Graft in Redo CABG after Multiple Failed Percutaneous Coronary Interventions
- 2022
-
In: Brazilian Journal of Cardiovascular Surgery. - : Brazilian Society for Cardiovascular Surgery. - 0102-7638 .- 1678-9741. ; 37:1, s. 135-138
-
Journal article (peer-reviewed)abstract
- The modality of repeat revascularization due to late graft failure is a debated topic. The latest available European guidelines recommend redo coronary artery bypass graft (CABG) for cases of extensively diseased and/or occluded grafts and those with diffuse native vessel disease. We present the case of a patient being relieved of recurrent unstable angina pectoris with redo CABG using no-touch saphenous vein grafts after repeated and unsuccessful attempts with percutaneous coronary intervention (PCI). This could be an alternative to PCI in patients with a complex medical history. Teamwork between cardiologists and surgeons is pivotal in deciding the best treatment modality.
|
|
21. |
- Ferrari, Gabriele, 1984-, et al.
(author)
-
Long-term results of percutaneous coronary intervention in no-touch vein grafts are significantly better than in conventional vein grafts
- 2024
-
In: Perfusion. - London : Sage Publications. - 0267-6591 .- 1477-111X.
-
Journal article (peer-reviewed)abstract
- Introduction: Conventional vein grafts have a high risk of thrombosis and early atherosclerosis. Percutaneous coronary intervention (PCI) in conventional vein grafts is associated with a higher incidence of late adverse cardiac events. The aim of this study was to evaluate the long-term results after PCI in saphenous vein grafts (SVG) harvested with the no-touch technique compared to the conventional technique. Methods: This was a single-center, retrospective, cohort study, based on data from the Swedeheart register. The inclusion criterion was individuals who underwent CABG using different vein graft techniques between January 1992 and July 2020, and who required a PCI in SVGs between January 2006 and July 2020. The primary end point was long-term in-stent restenosis. The secondary endpoints were long-term major adverse cardiac events (MACE) and 1-year re-hospitalization rates. The associations between the graft types and the endpoints were evaluated using the Fine and Gray competing-risk regression analysis. Results: The study included 346 individuals (67 no-touch, 279 conventional). The mean clinical follow-up time was 6.4 years with a standard deviation of 3.7 years. The long-term in-stent restenosis rate for the no-touch grafts was 3.2% compared to 18.7% for the conventional grafts (p <.01), with a subdistribution hazard ratio (SHR) of 0.16 (p =.010). The long-term MACE rate was 27.0% in the no-touch group and 48.3% in the conventional group (p <.01) with a SHR of 0.53 (p =.017). The short-term results were similar in both groups. Conclusions: Percutaneous coronary intervention in a no-touch vein graft was associated with statistically significantly fewer in-stent restenoses and MACE at long-term follow-up compared to a conventional SVG. © The Author(s) 2024.
|
|
22. |
- Ferrari, Gabriele, 1984-, et al.
(author)
-
PCI in saphenous vein graft after CABG : a review of the international literature
- 2019
-
In: Book of abstracts. - : School of Health Sciences and School of Medical Sciences, Örebro University. - 9789187789304
-
Conference paper (peer-reviewed)abstract
- Background/objectives: To review the international literature about the use of Percutaneous Coronary Intervention (PCI) in vena saphena magna graft after a Coronary Artery Bypass Grafting (CABG).Methods: We reviewed, from three different databases, the recent international literature (published between January 1, 2000 and December 31, 2018) regarding the use of PCI invenous grafts. Two independent researchers performed the literature search, designed after a PICO model. Forty articles were selected and a quality assessment was performed.Results: We noticed a high percentage of short and long-term cardiac events. The peri-procedural failure rate, due to residual stenos, had a mean value around 10%. The 30-days MACE (major adverse cardiac event) had a mean value of 6-7%, with the lower rates associated with the use of embolic protection devices. The MACE rates at 1 year reported were above 10% for most reports (up to over 30%; mean 16%), with better results after the use of a drug-eluting stent (DES) instead of a bare-metal stent. The long-term MACE (2-5 years) reported was high in all studies, with values ranging between 18% and 58%, with target vessel revascularization rates between 9% and 44%. The benefits of DES no longer remain in the long term.Conclusions: The percutaneous intervention of an occluded or stenosed saphenous vein graftis a challenge for the angiographer and is still associated with high rates of failure, MACE and restenosis. The key of the success of the procedure seems to be to optimize the quality of the venous graft itself.
|
|
23. |
- Ferrari, Gabriele, 1984-, et al.
(author)
-
Percutaneous coronary intervention in saphenous vein grafts after coronary artery bypass grafting : a systematic review and meta-analysis
- 2021
-
In: Scandinavian Cardiovascular Journal. - : Taylor & Francis. - 1401-7431 .- 1651-2006. ; 55:4, s. 245-253
-
Research review (peer-reviewed)abstract
- To investigate the results of percutaneous coronary intervention (PCI) in saphenous vein grafts after coronary artery bypass grafting (CABG). Design. MEDLINE, Embase, and the Cochrane library were searched for relevant articles published between 1 January 2000 and 29 February 2020. The PICO (population, intervention, comparison, outcome) model was applied in constructing the clinical question. Two independent researchers performed the literature search. Thirty-six articles were identified and subjected to a quality assessment. The primary outcomes of the meta-analysis were long-term in-stent restenosis and long-term major adverse cardiac events (MACE). Results. In-stent restenosis was 9.4% (95% CI: 4.2-14.7%) and MACE was 35.3% (95% CI: 27-43.7%) at mean time 2.7 ± 1.0 years. The secondary outcomes were the unsuccessful PCI rate (7.7%; 95% CI: 2.9-12.5%), 30-day MACE (4.3%; 95% CI: 2.5-6.1%), and 1-year MACE (15.5%; 95% CI: 11.7-19.3%). The use of drug-eluting stents resulted in better outcomes at least in term of in-stent restenosis, while the benefit of using embolic protection devices was questionable. Conclusions. PCI of a stenosed or occluded saphenous vein graft is a challenge for interventional cardiologists, and is still associated with relatively high rates of restenosis, MACE, and procedural failure. All efforts to enhance the results are warranted, including improved quality of the venous grafts used during CABG.
|
|
24. |
- Ferrari, Gabriele, 1984-, et al.
(author)
-
Quality of Life After Percutaneous Coronary Intervention in No-Touch Saphenous Vein Grafts is Significantly Better Than in Conventional Vein Grafts
- 2022
-
In: Brazilian Journal of Cardiovascular Surgery. - : Sociedade Brasileira de Cirurgia Cardiovascular. - 0102-7638 .- 1678-9741. ; 37:4, s. 430-438
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: To compare health-related quality of life (HRQoL) of patients primarily treated with a no-touch saphenous vein graft with that of patients who received a conventional graft.METHODS: The study included all individuals treated with a percutaneous coronary intervention (PCI) on a saphenous vein graft (SVG) between January 2006 and June 2020. The RAND-36 health survey was used to assess HRQoL. The Mann-Whitney U test was used to test differences in HRQoL between the two groups. Effect size was estimated via Cohen's d. The average treatment effect between the groups was tested by propensity score matching (PSM).RESULTS: Of the 346 patients treated with a PCI in a stenosed or occluded SVG, 165 responded to RAND-36 (no-touch: n=48; conventional: n=117). Patients with a no-touch graft reported better mean values on seven of the eight health survey domains. Statistically significant differences were observed for four of the domains, all in favour of the no-touch group. The effect size estimates indicated a small difference for five domains, with the highest values (>0.40) seen for the general health and energy/fatigue domains. PSM confirmed a statistically significant difference for the physical functioning and general health domains.CONCLUSION: At a mean follow-up of 5.4 years, patients who received a PCI in no-touch vein grafts showed significantly better HRQoL than those who received a PCI in conventional vein grafts.
|
|
25. |
- Geijer, Håkan, 1961-, et al.
(author)
-
Dendrochronology with a medical X-ray photon counting computed tomography scanner
- 2024
-
In: Dendrochronologia. - : Elsevier. - 1125-7865 .- 1612-0051. ; 86
-
Journal article (peer-reviewed)abstract
- Dendrochronology traditionally involves invasive techniques that might harm cultural heritage artifacts. Noninvasive approaches using X-ray technology and computed tomography (CT) have emerged, but dedicated CT systems are limited in availability. This study explored the viability of using a recently developed photon counting medical CT scanner for growth ring analysis. Six wood samples from pine, oak and beech with varying growth rates were studied. Comparisons were made between traditional methods and CT scanning with measurements performed on the untreated surface, a prepared surface and on CT images. For samples with annual rings wider than 0.3-0.4 mm, CT scanning performed well, while samples with thinner rings or indistinct ring boundaries presented challenges. The combination of traditional tree-ring measurements and analyses of CT scanned images might be a superior study approach generating extra data and information.
|
|
26. |
- Geijer, Håkan, et al.
(author)
-
Digital Radiography of Scoliosis with a Scanning Method : Initial Evaluation
- 2001
-
In: Radiology. - 0033-8419 .- 1527-1315. ; 218, s. 402-410
-
Journal article (peer-reviewed)abstract
- PURPOSE: To evaluate the radiation dose, image quality, and Cobb angle measurements obtained with a digital scanning method of scoliosis radiography.MATERIALS AND METHODS: Multiple images were reconstructed into one image at a workstation. A low-dose alternative was to use digital pulsed fluoroscopy. Dose measurements were performed with thermoluminescent dosimeters in an Alderson phantom. At the same time, kerma area-product values were recorded. A Monte Carlo dose calculation also was performed. Image quality was evaluated with a contrast-detail phantom and visual grading system. Angle measurements were evaluated with an angle phantom and measurements obtained on patient images.RESULTS: The effective radiation dose was 0.087 mSv for screen-film imaging, 0.16 mSv for digital exposure imaging, and 0.017 mSv for digital fluoroscopy; the corresponding kerma area-product values were 0.43, 0.87, and 0.097 Gy · cm2, respectively. The image quality of the digital exposure and screen-film images was about equal at visual grading, whereas fluoroscopy had lower image quality. The angle phantom had lower angle values with digital fluoroscopy, although the difference in measured angles was less than 0.5°. The patient images showed no difference in angles.CONCLUSION: The described digital scanning method has acceptable image quality and adequate accuracy in angle measurements. The radiation dose required for digital exposure imaging is higher than that required for screen-film imaging, but that required for digital fluoroscopy is much lower.
|
|
27. |
- Geijer, Håkan, et al.
(author)
-
Digital Radiography of Scoliosis with a Scanning Method : Radiation Dose Optimization
- 2003
-
In: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 13:3, s. 543-551
-
Journal article (peer-reviewed)abstract
- The aim of this study was optimization of the radiation dose–image quality relationship for a digital scanning method of scoliosis radiography. The examination is performed as a digital multi-image translation scan that is reconstructed to a single image in a workstation. Entrance dose was recorded with thermoluminescent dosimeters placed dorsally on an Alderson phantom. At the same time, kerma area product (KAP) values were recorded. A Monte Carlo calculation of effective dose was also made. Image quality was evaluated with a contrast-detail phantom and Visual Grading. The radiation dose was reduced by lowering the image intensifier entrance dose request, adjusting pulse frequency and scan speed, and by raising tube voltage. The calculated effective dose was reduced from 0.15 to 0.05 mSv with reduction of KAP from 1.07 to 0.25 Gy cm2 and entrance dose from 0.90 to 0.21 mGy. The image quality was reduced with the Image Quality Figure going from 52 to 62 and a corresponding reduction in image quality as assessed with Visual Grading. The optimization resulted in a dose reduction to 31% of the original effective dose with an acceptable reduction in image quality considering the intended use of the images for angle measurements.
|
|
28. |
- Geijer, Håkan, et al.
(author)
-
Image quality vs radiation dose for a flat-panel amorphous silicon detector : a phantom study
- 2001
-
In: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 11:9, s. 1704-1709
-
Journal article (peer-reviewed)abstract
- The aim of this study was to investigate the image quality for a flat-panel amorphous silicon detector at various radiation dose settings and to compare the results with storage phosphor plates and a screen-film system. A CDRAD 2.0 contrast-detail phantom was imaged with a flat-panel detector (Philips Medical Systems, Eindhoven, The Netherlands) at three different dose levels with settings for intravenous urography. The same phantom was imaged with storage phosphor plates at a simulated system speed of 200 and a screen-film system with a system speed of 160. Entrance surface doses were recorded for all images. At each setting, three images were read by four independent observers. The flat-panel detector had equal image quality at less than half the radiation dose compared with storage phosphor plates. The difference was even larger when compared with film with the flat-panel detector having equal image quality at approximately one-fifth the dose. The flat-panel detector has a very favourable combination of image quality vs radiation dose compared with storage phosphor plates and screen film.
|
|
29. |
|
|
30. |
- Geijer, Håkan, et al.
(author)
-
Optimizing the tube potential for lumbar spine radiography with a flat-pane digital detector
- 2009
-
In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 82:973, s. 62-68
-
Journal article (peer-reviewed)abstract
- The purpose of this study was to find the optimal settings for lumbar spine radiography with a flat-panel detector. A CDRAD contrast-detail phantom was imaged at various tube potentials, system speeds and filtration settings. Factorial experiments yielded a range of optimized exposure settings, which were submitted to visual grading analysis with images of an Alderson phantom. The first optimized settings involved a system speed increase from 400 to 800. For anteroposterior projection, the optimal tube potential was reduced from the default of 77 kV to 60 kV to give the best image quality without increasing the effective dose, or to 66 kV to give the lowest dose without reducing image quality. For lateral projection, the tube potential was similarly reduced from the default of 90 kV to 70 kV or 77 W. Visual grading analysis confirmed the results, with significantly better image quality when optimizing for image quality. The study thus shows that the tube potential can be reduced as long as the system speed is increased simultaneously. This leads to a lower effective dose and/or increased image quality depending on the settings chosen. The factorial experiments provided a powerful way to evaluate several parameters concomitantly.
|
|
31. |
- Geijer, Håkan
(author)
-
Radiation dose and image quality in diagnostic radiology : optimization of the dose - image quality relationship with clinical experience from scoliosis radiography, coronary intervention and a flat-panel digital detector
- 2001
-
Doctoral thesis (other academic/artistic)abstract
- Det är känt att röntgenstrålning kan orsaka cancersjukdomar, hudskador och andra sidoeffekter. Därför är det viktigt och även föreskrivet i lag att strålexpaneringen inom diagnostisk radiologi skall sänkas så långt som möjligt. Detta kallas på engelska ALARA-principen (As Low As Reasonably Achievable). stråldosen är kopplad till bildkvalitet och denna får inte sänkas så långt att det diagnostiska värdet av en undersökning äventyras. Processen att nå en sådan balans mellan dos och bildkvalitet kallas optimering. Syftet med denna avhandling är att fmna och utvärdera metoder för att optimera förhållandet mellan stråldos och bildkvalitet inom diagnostisk radiologi med fokus på klinisk användbarhet. Arbetet utfördes i tre huvuddelar.Optimering av skoliosröntgen: I första delen utvärderades två nyligen utvecklade metoder får digital skoliosröntgen (digital exponering och pulsad genomlysning). De järnfårdes även med film-skärmsystem som var den tidigare standardmetoden. Stråldosen mättes som Kerma area-produkt (KAP), ytdos (Entrance surface dose, ESD) och effektiv dos; bildkvaliteten värderades med ett kontrast-detaljfantom och genom visuell analys på kliniska bilder. Noggrannheten i vinkelmätningar värderades också. stråldosen för digital exponering var nästan dubbelt så hög som för film med jämförbar bildkvalitet medan pulsad genomlysning hade en mycket låg dos men betydligt sämre bildkvalitet. Variabiliteten i vinkelmätningar var tillräckligt låg i alla metoder. Därefter optimerades inställningarna för digital exponering till en betydligt lägre stråldos med viss sänkning av bildkvaliteten jämfört med utgångsläget.Direktdigital detektor: I den andra delstudien utvärderades en direktdigital detektor med ett kontrast-detaljfantom där stråldosen mättes som ingångsdos i fantomet. Den direktdigitala detektorn gav bättre bildkvalitet vid lägre dos jämfört med både bildplattor och film. Jämförbar bildkvalitet med bildplattor nåddes vid ungefär en tredjedel av dosen.Optimering av perkutan koranar intervention (PCI): I tredje delstudien undersöktes påverkan på stråldos och bildkvalitet av olika inställningar vid kranskärlsröntgen och PCI. Utifrån dessa fynd sänktes dosraten för genomlysning till en tredjedel. Dossänkningen utvärderades i en serie bestående av 154 PCI-procedurer före och 138 efter optimeringen. Genom denna optimering sänktes det totala KAP-värdet signifikant till två tredjedelar av ursprungsvärdet.Sammanfattningsvis påvisar denna avhandling möjligheterna till dossänkning i diagnostisk radiologi genom optimering av den radiografiska processen.
|
|
32. |
- Geijer, Håkan
(author)
-
Radiation dose and image quality in diagnostic radiology
- 2002
-
In: Acta Radiologica. - 0284-1851 .- 1600-0455. ; 427
-
Journal article (peer-reviewed)abstract
- Radiation dose and image quality in diagnostic radiology. Optimization of the dose-image quality relationship with clinical experience from scoliosis radiography, coronary intervention and a flat-panel detector.
|
|
33. |
|
|
34. |
- Geijer, Håkan, et al.
(author)
-
Radiation dose optimization in coronary angiography and percutaneous coronary intervention (PCI) : I. Experimental studies
- 2002
-
In: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 12:10, s. 2571-2581
-
Journal article (peer-reviewed)abstract
- The objectives of this study were to evaluate the influence on image quality and dose to the patient and operator of various equipment settings for percutaneous coronary intervention (PCI), and to optimize the set-up. With an Alderson phantom, different settings, such as projection, protective screens, filtration, image intensifier size and collimation, were evaluated. Kerma-area product (KAP) was recorded as a measure of patient dose and scattered radiation was measured with an ionization chamber. Effective dose for a standardized PCI procedure was measured with thermoluminescent dosimeters inside the phantom. Image quality was evaluated with a contrast-detail phantom. Based on these findings, the equipment set-up was optimized to a low fluoroscopy dose rate with a sufficient image quality. Several operating parameters affected dose, particularly scattered radiation. The optimization reduced the fluoroscopy KAP rate from 44 to 16 mGy cm2/s using 15 cm of acrylic. The effective dose was reduced from 13 to 4.6 mSv for a standardized PCI procedure. Radiation dose to patient and operator in PCI is heavily dependent on both equipment set-up and operating parameters which can be influenced by the operator. With a careful optimization, a large reduction of radiation dose is possible.
|
|
35. |
- Geijer, Håkan, et al.
(author)
-
Radiation dose optimization in coronary angiography and percutaneous coronary intervention (PCI) : II. Clinical evaluation
- 2002
-
In: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 12:11, s. 2813-2819
-
Journal article (peer-reviewed)abstract
- In a previous part of this study, the fluoroscopy dose rate was reduced in a cardiac catheterization laboratory. The objectives of the present study were to evaluate the effects in a clinical population undergoing percutaneous coronary intervention (PCI) of the dose-reducing measures detailed previously. Kerma area-product (KAP) values were first recorded for 154 patients undergoing PCI. Then, the fluoroscopy KAP rate was reduced from 44 to 16 mGy cm2/s by increasing filtration and reducing the image intensifier dose request. After this optimization, KAP was recorded for another 138 PCI procedures. After adjustment for differing proportions of combined procedures (coronary angiography+PCI), the total KAP was reduced to 67% of the original value with a 95% confidence interval from 57 to 78%, statistically significant. The mean total KAP values were 93.6 Gy cm2 before and 69.1 Gy cm2 after optimization. The KAP for digital acquisition did not change significantly. It is possible to make a large dose reduction in PCI by reducing the fluoroscopy dose rate. This dose reduction is beneficial for both patients and staff.
|
|
36. |
- Geijer, Håkan, 1961-, et al.
(author)
-
Somatostatin receptor PET/CT in neuroendocrine tumours : update on systematic review and meta-analysis
- 2013
-
In: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer. - 1619-7070 .- 1619-7089. ; 40:11, s. 1770-1780
-
Research review (peer-reviewed)abstract
- Purpose Neuroendocrine tumours (NET) are uncommon and may be localized in many different places in the body. Traditional imaging has mainly been performed with CT and somatostatin receptor scintigraphy (SRS). Recently, it has become possible to use somatostatin receptor PET/CT (SMSR PET) instead, which might improve diagnostic quality. To evaluate the diagnostic quality of SMSR PET we performed a meta-analysis as an update of a previous study published in 2012. A literature search was performed searching MEDLINE, Embase and five other databases with a combination of the expressions "PET", "positron emission tomography", "neuroendocrine" and "NET". The search was updated to 31 December 2012. Studies were selected which evaluated the sensitivity and specificity of SMSR PET for NET in the thorax or abdomen with a study size of at least eight patients. The methodological quality of the included studies was evaluated with QUADAS-2. Eight studies fulfilled the inclusion criteria and were selected for final analysis, and 14 articles from a previous meta-analysis were added for a total of 22 articles. A total of 2,105 patients were included in the studies, an increase from 567 in the previous meta-analysis. The pooled sensitivity was 93 % (95 % CI 91 - 94 %) and specificity 96 % (95 % CI 95 - 98 %). The area under the summary ROC curve was 0.98 (95 % CI 0.95 - 1.0). In the previous meta-analysis the pooled sensitivity was 93 % (95 % CI 91 - 95 %) and specificity 91 % (95 % CI 82 - 97 %). SMSR PET has good diagnostic performance for evaluation of NET in the thorax and abdomen, better than SRS which has been the previous standard method. This meta-analysis gives further support for switching to SMSR PET.
|
|
37. |
- Geijer, Håkan, 1961-, et al.
(author)
-
Temperature measurements with a temporal scanner : systematic review and meta-analysis
- 2016
-
In: BMJ Open. - London, United Kingdom : BMJ Group. - 2044-6055. ; 6:3
-
Research review (peer-reviewed)abstract
- Objectives: Systematic review and meta-analysis on the diagnostic accuracy of temporal artery thermometers (TAT).Design: Systematic review and meta-analysis. The index test consisted of temperature measurement with TAT. The reference test consisted of an estimation of core temperature.Participants: Clinical patients as well as healthy participants, with or without fever.Interventions: Literature search in PubMed, Embase, Cinahl and Web of Science. Three reviewers selected articles for full-text reading after which a further selection was made. Risk of bias was assessed with QUADAS-2. Pooled difference and limits of agreement (LoA) were estimated with an inverse variance weighted approach. Subgroup and sensitivity analyses were performed. Sensitivity and specificity were estimated using hierarchical models. Quality of evidence was assessed according to the GRADE system.Primary and secondary outcome measures: The primary outcome was measurement accuracy expressed as mean difference ±95% LoA. A secondary outcome was sensitivity and specificity to detect fever. If tympanic thermometers were assessed in the same population as TAT, these results were recorded as well.Results: 37 articles comprising 5026 participants were selected. Pooled difference was -0.19°C (95% LoA -1.16 to 0.77°C), with moderate quality of evidence. Pooled sensitivity was 0.72 (95% CI 0.61 to 0.81) with a specificity of 0.94 (95% CI 0.87 to 0.97). The subgroup analysis revealed a trend towards underestimation of the temperature for febrile patients. There was a large heterogeneity among included studies with wide LoA which reduced the quality of evidence.Conclusions: TAT is not sufficiently accurate to replace one of the reference methods such as rectal, bladder or more invasive temperature measurement methods. The results are, however, similar to those with tympanic thermometers, both in our meta-analysis and when compared with others. Thus, it seems that TAT could replace tympanic thermometers with the caveat that both methods are inaccurate.Trial registration number: CRD42014008832.
|
|
38. |
- Gustafsson, Agneta, et al.
(author)
-
A visual grading study for different administered activity levels in bone scintigraphy
- 2015
-
In: Clinical Physiology and Functional Imaging. - : Wiley-Blackwell. - 1475-0961 .- 1475-097X. ; 35:3, s. 231-236
-
Journal article (peer-reviewed)abstract
- Introduction: The aim of the study is to assess the administered activity levels versus visual-based image quality using visual grading regression (VGR) including an assessment of the newly stated image criteria for whole-body bone scintigraphy.Materials and methods: A total of 90 patients was included and grouped in three levels of administered activity: 400, 500 and 600 MBq. Six clinical image criteria regarding image quality was formulated by experienced nuclear medicine physicians. Visual grading was performed in all images, where three physicians rated the fulfilment of the image criteria on a four-step ordinal scale. The results were analysed using VGR. A count analysis was also made where the total number of counts in both views was registered.Results: The administered activity of 600 MBq gives significantly better image quality than 400 MBq in five of six criteria (P<005). Comparing the administered activity of 600 MBq to 500 MBq, four criteria of six show significantly better image quality (P<005). The administered activity of 500 MBq gives no significantly better image quality than 400 Mbq (P<005). The count analysis shows that none of the three levels of administrated activity fulfil the recommendations by the EANM.Conclusion: There was a significant improvement in perceived image quality using an activity level of 600 MBq compared to lower activity levels in whole-body bone scintigraphy for the gamma camera equipment end set-up used in this study. This type of visual-based grading study seems to be a valuable tool and easy to implement in the clinical environment.
|
|
39. |
- Jansson, Margareta, et al.
(author)
-
Reducing dose in urography while maintaining image quality - a comparison of storage phosphor plates and a flat-panel detector
- 2006
-
In: European Radiology. - Berlin / Heidelberg : Springer. - 0938-7994 .- 1432-1084. ; 16:1, s. 221-226
-
Journal article (peer-reviewed)abstract
- The introduction of new flat-panel detector technology often forces us to accept too high dose levels as proposed by the manufacturers. We need a tool to compare the image quality of a new system with the accepted standard. The aim of this study was to obtain a comparable image quality for two systems-storage phosphor plates and a flat-panel system using intravenous urography (IVU) as a clinical model. The image quality figure was calculated using a contrast-detail phantom (CDRAD) for the two evaluated systems. This allowed us to set a dose for the flat-panel system that gave equivalent image quality to the storage phosphor plates. This reduced detector dose was used in an evaluation of clinical images to find out if the dose reduction from the phantom study indeed resulted in images of equal clinical image quality. The image quality was assessed using image criteria of the European guidelines for IVU with visual grading analysis. Equivalent image quality in image pairs was achieved at 30% of the dose. The CDRAD contrast-detail phantom makes it possible to find dose levels that give equal image quality using different imaging systems.
|
|
40. |
- Jendeberg, Johan, 1972-, et al.
(author)
-
Prediction of spontaneous ureteral stone passage : Automated 3D-measurements perform equal to radiologists, and linear measurements equal to volumetric
- 2018
-
In: European Radiology. - : Springer. - 0938-7994 .- 1432-1084. ; 28:6, s. 2474-2483
-
Journal article (peer-reviewed)abstract
- OBJECTIVES: To compare the ability of different size estimates to predict spontaneous passage of ureteral stones using a 3D-segmentation and to investigate the impact of manual measurement variability on the prediction of stone passage.METHODS: We retrospectively included 391 consecutive patients with ureteral stones on non-contrast-enhanced CT (NECT). Three-dimensional segmentation size estimates were compared to the mean of three radiologists' measurements. Receiver-operating characteristic (ROC) analysis was performed for the prediction of spontaneous passage for each estimate. The difference in predicted passage probability between the manual estimates in upper and lower stones was compared.RESULTS: The area under the ROC curve (AUC) for the measurements ranged from 0.88 to 0.90. Between the automated 3D algorithm and the manual measurements the 95% limits of agreement were 0.2 ± 1.4 mm for the width. The manual bone window measurements resulted in a > 20 percentage point (ppt) difference between the readers in the predicted passage probability in 44% of the upper and 6% of the lower ureteral stones.CONCLUSIONS: All automated 3D algorithm size estimates independently predicted the spontaneous stone passage with similar high accuracy as the mean of three readers' manual linear measurements. Manual size estimation of upper stones showed large inter-reader variations for spontaneous passage prediction.KEY POINTS:• An automated 3D technique predicts spontaneous stone passage with high accuracy.• Linear, areal and volumetric measurements performed similarly in predicting stone passage.• Reader variability has a large impact on the predicted prognosis for stone passage.
|
|
41. |
|
|
42. |
- Jendeberg, Johan, 1972-, et al.
(author)
-
Size matters : The width and location of a ureteral stone accurately predict the chance of spontaneous passage
- 2017
-
In: European Radiology. - : Springer. - 0938-7994 .- 1432-1084. ; 27:11, s. 4775-4785
-
Journal article (peer-reviewed)abstract
- OBJECTIVES: To determine how to most accurately predict the chance of spontaneous passage of a ureteral stone using information in the diagnostic non-enhanced computed tomography (NECT) and to create predictive models with smaller stone size intervals than previously possible.METHODS: Retrospectively 392 consecutive patients with ureteric stone on NECT were included. Three radiologists independently measured the stone size. Stone location, side, hydronephrosis, CRP, medical expulsion therapy (MET) and all follow-up radiology until stone expulsion or 26 weeks were recorded. Logistic regressions were performed with spontaneous stone passage in 4 weeks and 20 weeks as the dependent variable.RESULTS: The spontaneous passage rate in 20 weeks was 312 out of 392 stones, 98% in 0-2 mm, 98% in 3 mm, 81% in 4 mm, 65% in 5 mm, 33% in 6 mm and 9% in ≥6.5 mm wide stones. The stone size and location predicted spontaneous ureteric stone passage. The side and the grade of hydronephrosis only predicted stone passage in specific subgroups.CONCLUSION: Spontaneous passage of a ureteral stone can be predicted with high accuracy with the information available in the NECT. We present a prediction method based on stone size and location.KEY POINTS: • Non-enhanced computed tomography can predict the outcome of ureteral stones. • Stone size and location are the most important predictors of spontaneous passage. • Prediction models based on stone width or length and stone location are introduced. • The observed passage rates for stone size in mm-intervals are reported. • Clinicians can make better decisions about treatment.
|
|
43. |
- Johansson, Benny L., et al.
(author)
-
Slower progression of atherosclerosis in vein grafts harvested with 'no touch' technique compared with conventional harvesting technique in coronary artery bypass grafting : an angiographic and intravascular ultrasound study
- 2010
-
In: European Journal of Cardio-Thoracic Surgery. - : Oxford University Press (OUP). - 1010-7940 .- 1873-734X. ; 38:4, s. 414-419
-
Journal article (peer-reviewed)abstract
- Objectives: In a long-term randomised coronary artery bypass grafting (CABG) study, the patency rate using a new 'no touch' (NT) vein-graft preparation technique was superior to the conventional (C) technique. This cineangiographic and intravascular ultrasound (IVUS) substudy examined possible mechanisms.Methods: A total of 45 patients (118 grafts) in the NT group and 46 patients (112 grafts) in the C group had patent grafts at short-term follow-up after 18 months. Thirty-seven patients (91 grafts) in the NT group and 37 patients (77 grafts) in the C group had patent grafts at long-term follow-up after 8 5 years, and were evaluated on a scale from 0 (normal) to 2 (significant stenosis) by cineangiogram. IVUS was performed in 15 NT grafts and 14 C grafts in the short-term follow-up, and 27 NT grafts and 26 C grafts in the long-term follow-up, in grafts considered normal by the cineangiogram. The grafts were evaluated with respect to lumen volume, intimal thickness, incidence of plaque and plaque components.Results: In the short-term follow-up, the cineangiogram showed more normal grafts (89.0% in the NT group compared with 75.0% in the C group), and the number of grafts with stenosis was 11.0% in the NT group compared with 25.0% in the C group (p = 0.006). IVUS showed less mean intimal thickness (0.43 (0.07) mm vs 0.52 (0.08) mm; p = 0.03), less grafts with considerable intimal hyperplasia (>= 0.9 mm; 20% vs 78.6%; p = 0.011) and fewer patients with considerable hyperplasia (>= 0.9 mm; 25% vs 100%; p = 0.007). In the long-term follow-up, the cineangiogram showed more normal grafts, with 91.2% in the NT group compared with 83.1% in the C group; there were fewer grafts with significant stenosis, with 7.7% in the NT group compared with 15 6% in the C group (p = 0.14). IVUS showed fewer grafts containing multiple plaques (14.8% vs 50%; p = 0.008), less advanced plaque with lipid (11.8% vs 63.9%; p = 0.0004) and less maximal plaque thickness (1.04 (0.23) mm vs 1.32 (0.25) mm; p = 0.02) in the NT group compared with the C group.Conclusion: The superior long-term patency rate using the NT vein-graft technique at CABG could be explained by a significantly slower progression of atherosclerosis. (C) 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.
|
|
44. |
- Kataria, Bharti, 1955-
(author)
-
Visual grading evaluation of reconstruction methods and dose optimisation in abdominal Computed Tomography
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- Since its introduction in the 1970’s CT has emerged as a modality of choice because of its high sensitivity in producing accurate diagnostic images. A third of all Computed Tomography (CT) examinations are abdominal CTs which deliver one of the highest doses among common examinations. An increase in the number of CT examinations has raised concerns about the negative effects of ionising radiation as the dose is cumulative over the life span of the individual. Image quality in CT is closely related to the radiation dose, so that a certain dose with an associated small, but not negligible, risk is a prerequisite for high image quality. Typically, dose reduction in CT results in higher noise and a decrease in low contrast resolution which can be detrimental to the image quality produced. New technology presents a wide range of dose reduction strategies, the latest being iterative reconstruction (IR).The aim of this thesis was to evaluate two different classes of iterative reconstruction algorithms: statistical (SAFIRE) and model-based (ADMIRE) as well as to explore the diagnostic value of a low-dose abdominal CT for optimisation purposes.This thesis included a total of 140 human subjects in four image quality evaluation studies, three of which were prospective studies (Papers I, II and IV) and one retrospective study (Paper III). Visual grading experiments to determine the potential dose reductions, were performed with pairwise comparison of image quality in the same patient at different tube loads (dose) and reconstructed with Filtered back projection (FBP) and SAFIRE strength 1 in a low-dose abdominal CT (Paper I) and FBP and ADMIRE strengths 3 and 5 in a standard dose abdominal CT (Paper II). Paper IV evaluated the impact of slice thicknesses in CT images reconstructed with ADMIRE strengths 3 and 5 when comparing multiplanar reconstruction (MPR) formatted images in a standard dose abdominal CT. Paper III, on the other hand, was an absolute assessment of image quality and pathology between the three phases of a CT Urography (CTU) protocol to explore the diagnostic value of low-dose abdominal CT. The anonymised images were displayed in random order and image quality was assessed by a group of radiologists using image quality criteria from the “European guidelines of quality criteria for CT”. The responses from the reviewer assessment were analysed statistically with ordinal logistic regression i.e. Visual Grading Regression (VGR).Results in Paper I show that a small dose reduction (5-9 %) was possible using SAFIRE strength 1and indicated the need for further research to evaluate the dose reduction potential of higher strengths of the algorithm. In Paper II a 30% dose reduction was possible without change in ADMIRE algorithm strength as no improvement in image quality was observed between tube loads 98- and 140 mAs. When comparing tube loads 42 and 98 mAs, further dose reduction was possible with ADMIRE strength 3 (22-47%). However, for images reconstructed with ADMIRE strength 5, a dose reduction of 34-74% was possible for some, but not all image criteria. Image quality in low-contrast objects such as the liver parenchyma, was affected and a decline in diagnostic confidence was observed. Paper IV showed potential dose reductions are possible with increasing slice thickness from 1 mm to 2 mm (24-35%) and 1 mm to 3mm (25-41%). ADMIRE strength 3 continued to provide diagnostically acceptable images with possible dose reductions for all image criteria assessed. Despite objective evaluations showing a decrease in noise and an increase in contrast to noise ratio, ADMIRE strength 5 had diverse effects on the five image criteria, depending on slice thickness and further dose reductions were limited to certain image criteria. The findings do not support a general recommendation to replace ADMIRE3 with ADMIRE5 in clinical abdominal CT protocols.Paper III studied another aspect of optimisation and results show that visualisation of renal anatomy was as expected in favour of the post-contrast phases when compared to the native phase. Assessment of pathology showed no significant differences between the three phases. Significantly higher diagnostic certainty for renal anatomy was observed for the post-contrast phases when compared to the native phase. Significantly high certainty scores were also seen for the nephrographic phase for incidental findings. The conclusion is that a low-dose series seems to be sufficient as a first-line modality in certain patient groups.This thesis clinically evaluated the effect of IR in abdominal CT imaging and estimated potential dose reductions. The important conclusion from papers I, II and IV is that IR improves image quality in abdominal CT allowing for some dose reductions. However, the clinical utility of the highest strength of the algorithm is limited to certain criteria. The results can be used to optimise the clinical abdominal CT protocol. The conclusion from paper III may increase clinical awareness of the value of the low-dose abdominal protocol when choosing an imaging method for certain patient groups who are more sensitive to radiation.
|
|
45. |
- Kähäri, Anders, et al.
(author)
-
Assessment of left ventricular function from M-mode measurement of circumflex artery motion recorded by coronary angiography.
- 2003
-
In: Scandinavian Cardiovascular Journal. - : Informa Healthcare. - 1401-7431 .- 1651-2006. ; 37:5, s. 259-265
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: To evaluate the usefulness of M-mode measurement of circumflex artery motion (CAM) for assessment of left ventricular (LV) function.DESIGN: Seventy-two patients referred for coronary angiography and LV angiography were included. Ejection fraction (EF) was calculated from LV angiography and systolic and diastolic parameters of CAM were measured by M-mode from coronary angiography. Twenty-three patients, examined by echocardiography of mitral annulus motion (MAM) within 24 h before the angiographic examination, formed a subgroup for comparison between angiographic M-mode of CAM and echocardiographic M-mode of MAM.RESULTS: In addition to previous reported CAM amplitude and longitudinal fractional shortening (FSL) the maximal systolic velocity of CAM can be reliably recorded by M-mode. The diastolic indices, atrial contribution to the total amplitude and maximal early and late diastolic velocities, are also well monitored by M-mode of CAM in comparison with echocardiographic MAM.CONCLUSION: LV systolic and diastolic function can be assessed by M-mode of CAM.
|
|
46. |
- Larzon, Thomas, et al.
(author)
-
Fascia suturing of large access sites after endovascular treatment of aortic aneurysms and dissections
- 2006
-
In: Journal of Endovascular Therapy. - 1526-6028 .- 1545-1550. ; 13:2, s. 152-157
-
Journal article (peer-reviewed)abstract
- PURPOSE: To evaluate a technique for closure of a femoral artery access in which the cribriform fascia covering the common femoral artery is sutured.METHODS: A consecutive series of 127 patients (103 men; median age 74 years, range 45- 89) underwent endovascular aortic aneurysm repair between August 2001 and September 2004. Twelve patients underwent a secondary intervention for a total of 139 procedures in the group. Sixty-one (43.9%) of the 139 operations were acute. Among the 257 femoral arteries used for access, a fascia suturing technique was performed in 131 (51.0%). Data were collected for analysis of access site complications, bleeding, thrombosis, pseudoaneurysm, and stenosis. A subgroup of 72 patients had ankle-brachial indexes (ABI) recorded; another subgroup of 50 patients were also investigated by duplex ultrasonography.RESULTS: Complications occurred in 18 (13.7%) of the 131 sutured cases. The majority (n = 16) arose within 24 hours: 8 cases of perioperative bleeding or thrombosis required open surgery and 8 cases were reoperated within 24 hours for bleeding (n = 4), thrombosis (n = 3), and 1 intimal dissection. The acute failure rate was 12.2%. Two patients had late complications: 1 case of neuralgia and 1 pseudoaneurysm that required acute surgery 28 months postoperatively. The ABI did not change significantly from pre- to postoperatively in the 72 patients examined. Five patients with stenoses did not have a reduction in ABI. In the 66 sites examined with ultrasound in 50 patients, 3 minor pseudoaneurysms were detected.CONCLUSION: The fascia suturing technique for closure of a femoral artery access during endovascular repair of aortic diseases is feasible, even in acute situations. Failures can be managed easily. Late complications requiring additional procedures are rare.
|
|
47. |
- Lidén, Mats, et al.
(author)
-
Alternative user interface devices for improved navigation of CT datasets
- 2011
-
In: Journal of digital imaging. - : Springer. - 0897-1889 .- 1618-727X. ; 24:1, s. 126-134
-
Journal article (peer-reviewed)abstract
- The workflow in radiology departments has changed dramatically with the transition to digital PACS, especially with the shift from tile mode to stack mode display of volumetric images. With the increasing number of images in routinely captured datasets, the standard user interface devices (UIDs) become inadequate. One basic approach to improve the navigation of the stack mode datasets is to take advantage of alternative UIDs developed for other domains, such as the computer game industry. We evaluated three UIDs both in clinical practice and in a task-based experiment. After using the devices in the daily image interpretation work, the readers reported that both of the tested alternative UIDs were better in terms of ergonomics compared to the standard mouse and that both alternatives were more efficient when reviewing large CT datasets. In the task-based experiment, one of the tested devices was faster than the standard mouse, while the other alternative was not significantly faster. One of the tested alternative devices showed a larger number of traversed images during the task. The results indicate that alternative user interface devices can improve the navigation of stack mode datasets and that radiologists should consider the potential benefits of alternatives to the standard mouse.
|
|
48. |
- Lidén, Mats, et al.
(author)
-
Making renal stones change size : impact of CT image post processing and reader variability
- 2011
-
In: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 21:10, s. 2218-2225
-
Journal article (peer-reviewed)abstract
- Objectives The objectives of this study were to quantify the impact of image post-processing parameters on the apparent renal stone size, and to quantify the intra- and inter-reader variability in renal stone size estimation. Methods Fifty CT datasets including a renal or ureteral stone were included retrospectively during a prospective inclusion period. Each of the CT datasets was post-processed in different ways regarding slice thickness, slice increment and window setting. In the first part of the study a single reader repeated size estimations for the renal stones using different post-processing parameters. In the intra-reader variability experiment one reader reported size estimations for the same images with a one-week interval. The inter-reader variability data were obtained from 11 readers reporting size estimations for the same renal stones. Results The apparent stone size differed according to image post-processing parameters with the largest mean differences seen with regard to the window settings experiment (1.5 mm, p < 0.001) and slice thickness (0.8 mm, p < 0.001). Changes in parameters introduced a bias and a pseudo-random variability. The inter-reader variability was considerably larger than the intra-reader variability. Conclusion Our results indicate a need for the standardisation of making measurements on CT images.
|
|
49. |
- Lidén, Mats, 1974-
(author)
-
The stack mode review of volumetric datasets : applications for urinary stone disease
- 2013
-
Doctoral thesis (other academic/artistic)abstract
- During the last decades the acquisition and visualization of radiological images have rapidly evolved. The increasing amounts of volumetric image data particularly from modern CT systems necessitate a constant evolution of the radiological visualization techniques.The dominating display mode for volumetric images has been the stack mode display since its introduction in computerized image review. In the increasing amounts of image data, the stack mode display needs to be analyzed so that the information content in the high resolution datasets can be transformed into clinically relevant information for the management of the individual patient. In the present thesis some aspects of the stack mode display were analyzed using for the most part the size estimation of urinary stones in unenhanced CT as a model.The estimated size has an important correlation to the prognosis for spontaneous passage of an obstructing ureteral stone. In the present thesis the reader variations in the size estimation of urinary stones were quantified, using different visualization parameters and after an attempt to reduce the variations with a training session for the readers. The influence on the estimated stone size of CT image post processing parameters was quantified. A segmentation algorithm was developed and demonstrated to reduce the reader variability through reader independent computer aid. One limitation of the stack mode display concerns three-dimensional shapes, which was modeled by a comparison between the estimated length and width of urinary stones in two- and three-dimensional segmentation. The increasing number of image slices in the acquisitions introduces a need for efficient navigation of the image volumes. In the present thesis the navigation of CT datasets using different user interface devices was evaluated.The rapid evolution of the MRI and CT systems necessitates a constant refinement and evaluation of the cornerstone for radiological volumetric reviewing – the stack mode display of volumetric datasets.
|
|
50. |
- Lidén, Mats, 1976-, et al.
(author)
-
Two- and three-dimensional CT measurements of urinary calculi length and width : a comparative study
-
Other publication (other academic/artistic)abstract
- The standard imaging procedure for a patient presenting with renal colic is unenhanced CT. The CT measured size has a close correlation to the estimated prognosis for spontaneous passage of a ureteral calculus. Size estimations of urinary calculi in CT images are still based on 2d-reformats. In the present study we developed and validated a calculus oriented 3dmethod for measurements of length and width of urinary calculi and compared those with corresponding 2d measurements in axial and coronal reformats.Methods: Fifty unenhanced CT examinations demonstrating urinary calculi were included. A 3d-symmetric segmentation algorithm was validated against reader size estimations. The calculus-oriented size from the segmentation was then compared to the size in axial and coronal reformats.Results: The validation showed 0.1±0.7 mm agreement against reference measure. There was a 0.4 mm median bias for 3d-estimated calculus length compared to 2d (p<0.001), but no significant bias for 3d-width compared to 2d.Conclusion: The size of the urinary calculus becomes underestimated if its orientation is not aligned to the axial or coronal image plane. Future studies aiming to correlate calculus size with patient outcome should use a calculus oriented size estimation.
|
|