| 1. |
- Dahlström, Nils, 1969-
(författare)
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Magnetic Resonance Imaging of the Hepatobiliary System Using Hepatocyte-Specific Contrast Media
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are two Gadolinium-based liver-specific contrast media for Magnetic Resonance Imaging on the market, Gd-BOPTA (MultiHance®, Bracco Imaging, Milan, Italy) and Gd-EOB-DTPA (Primovist®, Bayer Schering Pharma, Berlin, Germany). The aim of this study in two parts was to evaluate the dynamics of biliary, parenchymal and vascular enhancement using these contrast media in healthy subjects. Ten healthy volunteers were examined in a 1.5 T magnetic resonance system using three-dimensional Volumetric Interpolated Breath-Hold (VIBE) sequences for dynamic imaging with both contrast media – at two different occasions – until five hours after injection. The doses given were 0.025 mmol/kg for Gd-EOB-DTPA and 0.1 mmol/kg for Gd-BOPTA. The enhancement over time of the common biliary duct in contrast to the liver parenchyma was analyzed in the first study. This was followed by a study of the image contrasts of the hepatic artery, portal vein and middle hepatic vein versus the liver parenchyma.While Gd-EOB-DTPA gave an earlier and more prolonged enhancement of the biliary duct, Gd-BOPTA achieved higher image contrast for all vessels studied, during the arterial and portal venous phases. There was no significant difference in the maximal enhancement obtained in the liver parenchyma.At the obtained time-points and at the dosage used, the high contrast between the common biliary duct and liver parenchyma had an earlier onset and longer duration for Gd-EOB-DTPA, while Gd-BOPTA achieved higher maximal enhancement of the hepatic artery, portal vein and middle hepatic vein than Gd-EOB-DTPA. Diseases of the liver and biliary system may affect the vasculature, parenchyma, biliary excretion or a combination of these. The clinical context regarding the relative importance of vascular, hepatic parenchymal and biliary processes should determine the choice of contrast media for each patient and examination.
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| 2. |
- Stenman, Carina
(författare)
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New workflow method for ultrasound examinations
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Growing demand for ultrasound examinations and higher quality requirements motivate searching for routines combining the diagnostic accuracy of radiologist-performed examinations with the economical advantages of sonographerperformed examinations. One possible approach is to use strictly standardized examination protocols and documentation made by cine-loops that will give the radiologist access to all relevant information after the examination. Ultrasound examinations are usually regarded as observer dependent, but using documentation with cine-loops acquired in a standardized way attempts to reduce this problem.Aims: The aim of study I was to compare a recently introduced routine, combining acquisition by a radiographer, documentation as standardized cine-loops, and review by a radiologist (“standardized method”), with the formerly used routine where the diagnosis is made bed-side by the radiologist (“traditional method”). The aim of study II was to evaluate the intra-observer and inter-observer agreement of the standardized method in ultrasound liver examinations.Material and Methods: In study I there was 64 policlinic patients examining the kidneys ( n = 27) or the gallbladder ( n =37) by both the standardized and the traditional method. The radiologists’ findings of hydronephrosis, tumors, cysts, echogenicity changes, and cortical thickness (in the kidneys), and wall thickness, concrements, and polyps (in the gallbladder) were compared between the methods with respect to agreement as well as systematic differences. In study II 98 out-patients were examined by a radiographer using the standardized method. Three radiologists with 10 – 20 years of experience of ultrasound reviewed the cine-loops retrospectively and independently filled out a predetermined protocol. After 4 weeks, the review was repeated, blinded to the initial reading.Results: Study I showed for the gallbladder examination a median agreement of 97% (86 – 100%; kappa =0.64 – 1.00) and for the kidney examination an agreement of 90% (78 – 100%; kappa = 0.69 – 1.00). There were no significant systematic differences between the two methods. In study II, the intra-observer agreement was highest for concrements in the gallbladder (kappa = 0.91 to 0.96) and lowest when assessing the need for further examination (kappa = 0.38 to 0.64). For increased liver echogenicity, kappa varied between 0.51 and 0.85, and for skip areas between 0.73 and 0.90. The interobserver agreement was also highest for concrements in the gallbladder (kappa = 0.84 to 1.00) and lowest for need for further examination (kappa = -0.12 to 0.46). For most other findings, substantial intra-observer agreement (kappa ≥ 0.61) was found.Conclusion: The satisfactory agreement in study I indicates that the new workflow with ultrasound examinations performed by a radiographer and analyzed off-line by a radiologist is promising. Study II shows a fairly good inter-observer agreement for ultrasound examinations acquired with a standardized technique by an experienced radiographer and reviewed by experienced radiologists. In general, intra-observer agreement was higher than inter-observer agreement.
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| 3. |
- Wang, Chunliang, 1980-
(författare)
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Computer Assisted Coronary CT Angiography Analysis : Disease-centered Software Development
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The substantial advances of coronary CTA have resulted in a boost of use of this new technique in the last several years, which brings a big challenge to radiologists by the increasing number of exams and the large amount of data for each patient. The main goal of this study was to develop a computer tool to facilitate coronary CTA analysis by combining knowledge of medicine and image processing.Firstly, a competing fuzzy connectedness tree algorithm was developed to segment the coronary arteries and extract centerlines for each branch. The new algorithm, which is an extension of the “virtual contrast injection” method, preserves the low density soft tissue around the coronary, which reduces the possibility of introducing false positive stenoses during segmentation.Secondly, this algorithm was implemented in open source software in which multiple visualization techniques were integrated into an intuitive user interface to facilitate user interaction and provide good over¬views of the processing results. Considerable efforts were put on optimizing the computa¬tional speed of the algorithm to meet the clinical requirements.Thirdly, an automatic seeding method, that can automatically remove rib cage and recognize the aortic root, was introduced into the interactive segmentation workflow to further minimize the requirement of user interactivity during post-processing. The automatic procedure is carried out right after the images are received, which saves users time after they open the data. Vessel enhance¬ment and quantitative 2D vessel contour analysis are also included in this new version of the software. In our preliminary experience, visually accurate segmentation results of major branches have been achieved in 74 cases (42 cases reported in paper II and 32 cases in paper III) using our software with limited user interaction. On 128 branches of 32 patients, the average overlap between the centerline created in our software and the manually created reference standard was 96.0%. The average distance between them was 0.38 mm, lower than the mean voxel size. The automatic procedure ran for 3-5 min as a single-thread application in the background. Interactive processing took 3 min in average with the latest version of software. In conclusion, the presented software provides fast and automatic coron¬ary artery segmentation and visualization. The accuracy of the centerline tracking was found to be acceptable when compared to manually created centerlines.
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