| 1. |
- Piippo-Huotari, Oili, 1959-, et al.
(författare)
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New patient-controlled abdominal compression method in radiography : radiation dose and image quality
- 2018
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Ingår i: Acta Radiologica Open. - : Sage Publications. - 2058-4601. ; 7:5, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Background: The radiation dose for patients can be reduced with many methods and one way is to use abdominal compression. In this study, the radiation dose and image quality for a new patient-controlled compression device were compared with conventional compression and compression in the prone position.Purpose: To compare radiation dose and image quality of patient-controlled compression compared with conventional and prone compression in general radiography.Material and Methods: An experimental design with quantitative approach. After obtaining the approval of the ethics committee, a consecutive sample of 48 patients was examined with the standard clinical urography protocol. The radiation doses were measured as dose-area product and analyzed with a paired t-test. The image quality was evaluated by visual grading analysis. Four radiologists evaluated each image individually by scoring nine criteria modified from the European quality criteria for diagnostic radiographic images.Results: There was no significant difference in radiation dose or image quality between conventional and patient-controlled compression. Prone position resulted in both higher dose and inferior image quality.Conclusion: Patient-controlled compression gave similar dose levels as conventional compression and lower than prone compression. Image quality was similar with both patient-controlled and conventional compression and was judged to be better than in the prone position.
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| 2. |
- Alshamari, Muhammed, 1975-, et al.
(författare)
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Impact of iterative reconstruction on image quality of low-dose CT of the lumbar spine
- 2017
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Ingår i: Acta Radiologica. - London : Sage Publications. - 0284-1851 .- 1600-0455. ; 58:6, s. 702-709
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Tidskriftsartikel (refereegranskat)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.
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| 3. |
- Alshamari, Muhammed, 1975-, et al.
(författare)
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Low-dose computed tomography of the lumbar spine: a phantom study on imaging parameters and image quality
- 2014
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 55:7, s. 824-832
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Tidskriftsartikel (refereegranskat)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.
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| 4. |
- Alshamari, Muhammed, 1975-, et al.
(författare)
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Low dose CT of the lumbar spine compared with radiography : a study on image quality with implications for clinical practice
- 2016
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Ingår i: Acta Radiologica. - London, United Kingdom : Sage Publications. - 0284-1851 .- 1600-0455. ; 57:5, s. 602-611
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Tidskriftsartikel (refereegranskat)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.
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| 5. |
- Amanda, Demir, et al.
(författare)
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The Influence of Mesenteric Defects Closure on the Use of Computed Tomography for Abdominal Pain 5 Years After Laparoscopic Gastric Bypass-a Post Hoc Analysis of a Randomized Clinical Trial
- 2022
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Ingår i: Obesity Surgery. - : Springer. - 0960-8923 .- 1708-0428. ; 32:2, s. 266-272
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Abdominal pain after laparoscopic Roux-en-Y gastric bypass (LRYGB) is a common and unwanted complication that typically leads to further exploration through radiology. Concerns have been raised regarding the consequences of this radiation exposure and its correlation with the lifetime risk of cancer. The aim of this study was to evaluate the differences in computed tomography (CT) use between LRYGB patients with open and closed mesenteric defects and to assess the radiological findings and radiation doses.METHODS: This subgroup analysis included 300 patients randomized to either closure (n = 150) or nonclosure (n = 150) of mesenteric defects during LRYGB. The total number of CT scans performed due to abdominal pain in the first 5 postoperative years was recorded together with the radiological findings and radiation doses.RESULTS: A total of 132 patients (44%) underwent 281 abdominal CT scans, including 133 scans for 67 patients with open mesenteric defects (45%) and 148 scans for 65 patients with closed mesenteric defects (43%). Radiological findings consistent with small bowel obstruction or internal hernia were found in 31 (23%) of the scans for patients with open defects and in 18 (12%) of the scans for patients with closed defects (p = 0.014). The other pathological and radiological findings were infrequent and not significantly different between groups. At the 5-year follow-up, the total radiation dose was 82,400 mGy cm in the nonclosure group and 85,800 mGy cm in the closure group.CONCLUSION: Closure of mesenteric defects did not influence the use of CT to assess abdominal pain.
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| 6. |
- Andersson, Karin M., 1989-, et al.
(författare)
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Metal artefact reduction in CT imaging of hip prostheses-an evaluation of commercial techniques provided by four vendors
- 2015
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 88:1052
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this study was to evaluate commercial metal artefact reduction (MAR) techniques in X-ray CT imaging of hip prostheses.Methods: Monoenergetic reconstructions of dual-energy CT (DECT) data and several different MAR algorithms, combined with single-energy CT or DECT, were evaluated by imaging a bilateral hip prosthesis phantom. The MAR images were compared with uncorrected images based on CT number accuracy and noise in different regions of interest.Results: The three MAR algorithms studied implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to the prostheses and between the two prostheses. The application of monoenergetic reconstruction, without any MAR algorithm, did not decrease the noise in the regions close to the prostheses to the same extent as did the MAR algorithms and even increased the noise in the region between the prostheses.Conclusion: The MAR algorithms evaluated generally improved CT number accuracy and substantially reduced the noise in the hip prostheses phantom images, both close to the prostheses and between the two prostheses. The study showed that the monoenergetic reconstructions evaluated did not sufficiently reduce the severe metal artefact caused by large orthopaedic implants.Advances in knowledge: This study evaluates several commercially available MAR techniques in CT imaging of large orthopaedic implants.
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| 7. |
- Andersson, Karin M., 1989-, et al.
(författare)
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Metal Artifacts in CT Imaging of Hip Prostheses : Evaluation of Metal Artifact Reduction Techniques Provided by Four Vendors
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- PURPOSE: The aim of this study was to evaluate metal artifact reduction (MAR) techniques, provided by four vendors, in CT imaging of hip prostheses.METHOD AND MATERIALS: A water phantom containing hip prostheses mounted in calf bones was scanned with four CT scanners; Philips Ingenuity; Toshiba Aquilion ONE Vision edition; GE Discovery 750 HD and Siemens SOMATOM Definition Flash. An uncorrected (reference) image was obtained for every CT and compared with images acquired with the scanner specific MAR technique; either monoenergetic reconstruction of Dual Energy CT (DECT) data (GE and Siemens) or the use of a MAR algorithm software (Philips and Toshiba), or a combination of the two (GE). The MAR techniques were applied for varying tube voltage, kernel and reconstruction technique. The reference images were quantitatively compared to the MAR images by analyzing the noise and the CT number accuracy in region of interests (ROIs). Visual grading was performed by five radiologists based on ten image quality (IQ) criteria.RESULTS: The MAR algorithms implied a general noise reduction (by up to 77%) and improved IQ based on the majority of the visual grading criteria. The use of monoenergetic reconstructions of DECT data, without any MAR algorithm, did not decrease the noise in the ROIs to the same extent as the MAR algorithms (up to 41%) and did even increase the noise in one ROI. The visual grading evaluation showed that monoenergetic reconstructions in general degraded the IQ for one of the DECT scanners and improved the IQ for only a few of the criteria for the other DECT scanner.CONCLUSION: The quantitative analysis and the visual grading evaluation showed that the IQ was generally improved when the MAR algorithms were used. However, additional artifacts and degradation of the IQ were noted in some MAR image regions. The use of monoenergetic reconstruction was concluded to not reduce metal artifacts to the same extent as the MAR algorithms and to even degrade the IQ in several image regions.CLINICAL RELEVANCE/APPLICATION: This study points out advantages and potential risks of using MAR techniques in CT imaging of hip prostheses and will be useful for clinics when optimizing CT scan protocols and purchasing new CT systems.
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| 8. |
- Andersson, Karin M., 1989-, et al.
(författare)
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Visual grading evaluation of commercially available metal artefact reduction techniques in hip prosthesis computed tomography
- 2016
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Ingår i: British Journal of Radiology. - London, United Kingdom : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 89:1063
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Tidskriftsartikel (refereegranskat)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.
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| 9. |
- Andersson, Karin, 1989-
(författare)
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Metal artifacts in computed tomography : impact of reduction methods on image quality and radiotherapy treatment planning
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Degradation of image quality by metal artifacts is a common problem in computed tomography (CT) imaging, which can limit the diagnostic value of a CT examination and also introduce inaccuracies in radiotherapy (RT) treatment planning. In recent years, commercial metal artifact reduction (MAR) methods have been launched by several CT vendors. The overall aim of this thesis was to evaluate MAR methods in diagnostic imaging and RT treatment planning.Evaluations of hip prosthesis phantom CT images showed that MAR algorithms in general improved image quality, based on both visual grading analysis and quantitative measures, while the application of virtual monoenergetic reconstructions insufficiently reduced metal artifacts. In some cases additional artifacts were introduced by the MAR algorithms. MAR algorithms were also evaluated in hip prosthesis phantom CT imaging used for proton therapy treatment planning, where improvements in dose calculation accuracy were observed.Studies of Head & Neck (H&N) implant CT images in RT treatment planning were also performed. By visual grading of anatomy visualization with respect to target delineation in dental implant patient images, MAR algorithms were shown to significantly improve image quality. However, only minor effects of H&N implant artifacts on proton dose distributions were seen. The impact might be greater for more severe artifacts than those studied here, and thus further investigations of such cases are needed.In conclusion, MAR algorithms have been shown to enhance image quality for diagnostic applications and to improve anatomy visualization in RT treatment planning. The MAR algorithms led to increased proton dose calculation accuracy in some cases, while in other situations only minor changes were seen.
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| 10. |
- Norrman, Eva, 1966-
(författare)
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Optimisation of radiographic imaging by means of factorial experiments
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the optimisation process of radiographic imaging, factorial designed experiments can be applied. The parameters (factors) are varied together instead of one at a time, making it possible to discover interactions between the factors as well as main influences of them on the result variable. A 2k design implies having k number of factors each one set to two different levels (low and high).A computer program, CoCIQ, designed to automatically analyse and evaluate test images of a contrast-detail phantom, was evaluated and adjusted to clinical situations using a flat panel detector. The program gives a quantified measurement of image quality by calculating an Image Quality Figure (IQF) for the X-ray image. It was shown that the program produces IQF with small variations. It was also found that there was a strong linear statistical relation between the computerised evaluation and the evaluation performed by human observers.2k factorial experiments were evaluated by investigating the influence of tube potential, tube loading, focus size and filtration on the result variables IQF, Kerma Area Product (KAP) and effective dose using a flat panel detector. It was found that the result variables were mainly influenced by tube loading, tube potential and filtration. Interactions between tube potential and filtration as well as between tube loading and filtration were observed, too. This work demonstrates that accepted knowledge was reproduced and that the effects of interactions between parameters were revealed.Extended 2k experiments were then applied at three different optimisation procedures. Two studies were performed using a flat panel detector for lumbar spine radiography. The aim was to find optimal settings for tube potential, system sensitivity and filtration for different sized patients and, in a separate study, to investigate the effect of the image post processing parameters and the possibility for dose reduction by adjusting these. The parameters are ROI (Region Of Interest) density, gamma, detail contrast enhancement, unsharp masking, kernel size and noise compensation.After determining the optimal settings from these experiments, X-ray images of the lumbar spine of an Alderson phantom were acquired and evaluated in a visual grading analysis (VGA).The results illustrated that the image quality was maintained at a lower effective dose by operating with a reduced tube potential and increased sensitivity of the X-ray system.The experiments on image post process parameters revealed their influence on image quality and indicated that image quality could be improved by changing the settings of the process parameters.Factorial experiments were also performed, using a multislice CT scanner to investigate the possibility for dose reduction at paediatric head examinations. An anthropomorphic phantom simulating a one-year-old child was scanned using different settings of tube potential, tube loading and reconstruction filter.The study showed that a 25 % reduction of dose was possible with maintained image quality by reducing the tube loading.Factorial designed experiments provide an effective method to simultaneously predict the influence of various parameters on image quality and radiation dose in the optimisation in diagnostic radiology.
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