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Objective: The purpose of this article is to present a method for the calculation of effective dose using the DICOM header information of CT images., Materials and Methods: Using specialized software, the DICOM data were automatically extracted into a spreadsheet containing embedded functions for calculating effective dose. These data were used to calculate the dose-length product (DLP) fraction that corresponds to each image, and the respective effective dose was obtained by multiplying the image DLP by a conversion coefficient that was automatically selected depending on the CT scanner, the tube potential, and the anatomic position to which each image corresponded. The total effective dose was calculated as the sum of effective doses of all images plus the contribution of overscan. The conversion coefficient tables were derived using dosimetry calculator software for both the International Commission on Radiological Protection (ICRP) 60 and ICRP 103 organ-weighting schemes. This method was applied for 90 chest, abdomen-pelvis, and chest-abdomen-pelvis examinations performed in three different MDCT scanners., Results: The DLP values calculated with this method were in good agreement with those calculated by the CT scanners' software. The effective dose values calculated using the ICRP 103 conversion coefficient compared with those calculated using the ICRP 60 conversion coefficient were roughly equal for the chest-abdomen-pelvis examinations, smaller for the abdomen-pelvis examinations, and larger for the chest examinations. The applicability of this method for estimating organ doses was also explored., Conclusion: With this method, all patient dose-related quantities, such as the DLP, effective dose, and individual organ doses, can be calculated.

Purpose: To determine, based on preoperative imaging findings, which patients treated with endovascular abdominal aneurysm repair are at high risk for the development of persistent type II endoleaks., Materials and Methods: Preoperative computed tomography (CT) angiographies of 136 patients, treated endovascularly, were retrospectively examined for possible anatomic predictors of type II endoleak development. Specifically, the number of patent aortic branches and thrombus load parameters (i.e., thickness, perimeter, area, and localization) were recorded. Thrombus load parameters were evaluated at the level of maximum aneurysm diameter, at the level of sac lumbar arteries' ostia, and at the level of inferior mesenteric artery ostium. Follow-up CT angiographies were also studied for the presence of persistent type II endoleaks (present at six-month follow-up examination). The association of these anatomic features with the development of persistent type II endoleaks was assessed using logistic regression analysis., Results: Aortic branch patency increased the risk for persistent type II endoleak development, while thrombus load parameters decreased this risk. In multiple logistic regression analysis, the total number of patent aortic branches (odds ratio = 4.23, 95% confidence interval = 1.72-10.42, P = 0.002 for each additional branch), and the percentage of aortic perimeter covered by a thrombus at the level of the sac lumbar arteries' ostia (odds ratio = 0.16, 95% confidence interval = 0.06-0.44, P < 0.001 for a 15% increase) were independent predictors., Conclusion: Anatomic characteristics of a preoperative aorta can be used to predict patients with higher risk for persistent type II endoleak development.

Catheter ablation is an established therapeutic option for certain patients with atrial fibrillation (AF), but the reported success rates of anatomically oriented ablation techniques are low compared with those for other ablation indications, particularly for persistent AF. Electrophysiologically oriented ablation techniques have emerged over the last decade that aim at modifying the arrhythmogenic substrate to the extent that it cannot maintain fibrillatory activity. Electrogram-guided ablation procedures are the most common substrate-targeted ablation approaches and can be broadly divided into procedures that target atrial sites with particular electrogram characteristics in either the time domain (complex fractionated electrograms) or frequency components in the frequency domain (dominant frequencies). The concept of electrogram-based catheter ablation of AF by identifying complex fractionated electrograms and dominant frequency sites is valid only if these sites are temporally stable.

Following the development of the first automated methods in the 1980s, quantitative coronary angiography (QCA) has undergone substantial evolution from simplistic computer-assisted methods of visual interpretation of coronary angiograms to recently introduced three-dimensional reconstruction and quantitative analysis algorithms. The ability of QCA to provide objective dimensional assessment of coronary lesions is still useful and has led to its widespread application in both scientific research and clinical practice. Most of the systems available nowadays are based on vessel edge detection algorithms to designate the arterial lumen on conventional two-dimensional coronary angiograms. Three generations of these systems have been developed with improved accuracy and precision of obtained measurements. Techniques for reconstruction of the two-dimensional coronary angiogram in space have allowed the implementation of three-dimensional QCA. This new technology may solve many of the limitations inherent in two-dimensional QCA and provide stenosis assessment capabilities not available with two-dimensional imaging.

Purpose: To investigate the correlation between the degree of hepatic, splenic, pancreatic, vertebral bone marrow (VBM), and myocardial siderosis, as expressed by relaxation rate (R2 = 1/T2) values, in patients with thalassemia., Materials and Methods: R2 relaxation rate values of liver, spleen, VBM, pancreas, and myocardium were estimated in 68 consecutive transfusion-dependent patients with beta-thalassemia major and 10 healthy controls using a respiratory triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin echo sequence., Results: Hepatic R2 values were significantly increased in all 68 patients; VBM, pancreatic, and myocardial R2 values were increased in 67/68, 35/47, and 47/61 patients, whereas five patients showed decreased pancreatic R2 attributed to fatty degeneration. Of the 39 nonsplenectomized patients, splenic R2 values were decreased in 30 and normal in nine patients. Hepatic R2 values correlated with splenic (r = 0.63, P < 0.001), VBM (r = 0.52, P < 0.001), but not with myocardial and pancreatic R2 values., Conclusion: Despite positive correlations between the degree of hepatic, splenic, and VBM siderosis, as expressed by respective R2 values, there was variability of iron distribution patterns in thalassemic patients. Unpredictable patterns of iron distribution may be seen, such as normal signal of the spleen in the presence of siderotic liver, resembling primary hemochromatosis. Fatty degeneration of the pancreas was not uncommon.

Interventional cardiology procedures result in substantial patient radiation doses due to prolonged fluoroscopy time and radiographic exposure. The procedures that are most frequently performed are coronary angiography, percutaneous coronary interventions, diagnostic electrophysiology studies and radiofrequency catheter ablation. Patient radiation dose in these procedures can be assessed either by measurements on a series of patients in real clinical practice or measurements using patient-equivalent phantoms. In this article we review the derived doses at non-pediatric patients from 72 relevant studies published during the last 22 years in international scientific literature. Published results indicate that patient radiation doses vary widely among the different interventional cardiology procedures but also among equivalent studies. Discrepancies of the derived results are patient-, procedure-, physician-, and fluoroscopic equipmentrelated. Nevertheless, interventional cardiology procedures can subject patients to considerable radiation doses. Efforts to minimize patient exposure should always be undertaken.

Introduction: There is growing evidence that atherosclerosis, as well as endothelial biology, depend on arterial wall shear stress (WSS). Several methods of WSS calculation with varying degrees of complexity have been proposed. This study aimed at investigating whether the most straightforward and easier to apply of these methods give comparable results in clinical practice., Methods: Complete velocity encoding measurements using phase contrast magnetic resonance imaging were performed in 20 patients at a level perpendicular to the long axis of the ascending aorta approximately 2cm above the aortic valve. WSS was calculated at this location on maximum systole. MR imaging was accomplished on a 1.5T scanner. Four methods were applied to calculate WSS; three of them are based on the predictions of Poiseuille's theory of flow, while the last one is based on calculations resulting by the application of the definition of WSS., Results: WSS calculated with the above mentioned methods was found to be in the range 4.2+/-1.8 to 3.5+/-1.7dynes/m(2). The velocity profile at the site of measurements can be described with a parabolic equation of the form u=ar(2)+br+c with an average r(2)=0.83, which is in good agreement with Poiseuille's theory of flow. Comparison of the results shows no statistically significant differences between WSS measurements calculated with these methods., Discussion: The four methods are equivalent in calculating WSS at the ascending aorta when blood flow velocities have a good parabolic distribution.

Purpose: Wall shear stress (WSS) appears to contribute significantly in the initiation and progression of atherosclerotic disease. The purpose of this work is to present in vivo systolic and diastolic WSS calculations in the human ascending aorta by the application of three straightforward methodologies based on Poiseuille's theory of flow., Materials and Methods: Blood flow measurements were performed retrospectively in the ascending aorta of 20 non-atherosclerotic patients using phase-contrast MRI. WSS calculations were performed assuming Poiseuille's theory of flow based on average flow volume, average flow velocity and maximum flow velocity. Systolic and diastolic WSS values were calculated and compared with the calculated maximum and minimum values of WSS throughout the cardiac cycle., Results: Systolic WSS values calculated by average flow volume, average flow velocity and maximum flow velocity were similar (0.4+/-0.2N/m(2), 0.4+/-0.3N/m(2)and 0.4+/-0.2N/m(2), respectively). Diastolic WSS values calculated by maximum flow velocity were significantly higher (11.6+/-7.0x10(-2)N/m(2)) compared to values calculated by average flow volume (0.3+/-0.9x10(-2)N/m(2)) and average flow velocity (0.3+/-1.0x10(-2)N/m(2)). Comparison of systolic and diastolic WSS values with maximum and minimum WSS values showed that time instances of maximum and minimum blood flow velocities do not coincide with time instances of maximum and minimum blood flow volume., Conclusion: In vivo calculation of WSS in the ascending aorta is feasible by phase-contrast MRI flow measurements and straightforward methodologies based on Poiseuille's theory of flow. However, measurements based on maximum flow velocity show larger deviations compared to measurements based on mean flow volume or mean flow velocity.

Purpose: To evaluate the usefulness of a time-efficient MRI method for the quantitative determination of tissue iron in the liver and heart of beta-thalassemic patients using spin-spin relaxation rate, R2, measurements., Materials and Methods: Images were obtained at 1.5 T from aqueous Gd-DTPA solutions (0.106-8 mM) and from the liver and heart of 46 beta-thalassemic patients and 10 controls. The imaging sequence used was a respiratory-triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin-echo (SE) pulse sequence (TR = 2000 msec, TE(min) = 5 msec, echo spacing (ES) = 5 msec, matrix = 192 x 256, slice thickness = 10 mm). Liver iron concentration (LIC) measurements were obtained for 22 patients through biopsy specimens excised from the relevant liver segment. Biopsy specimens were also evaluated regarding iron grade and fibrosis. Serum ferritin (SF) measurements were obtained in all patients., Results: A statistically significant difference was found between patients and healthy controls in mean liver (P < 0.004) and myocardium (P < 0.004) R2 values. The R2 values correlated well with Gd DTPA concentration (r = 0.996, P < 0.0001) and LIC (r = 0.874, P < 0.0001). A less significant relationship (r = 0.791, P < 0.0001) was found between LIC measurements and SF levels. R2 measurements appear to be significantly affected (P = 0.04) by different degrees of hepatic fibrosis. The patients' liver R2 values did not correlate with myocardial R2 values (r = 0.038, P < 0.21)., Conclusion: Tissue iron deposition in beta-thalassemic patients may be adequately quantified using R2 measurements obtained with a 16-echo MRI sequence with short ES (5 msec), even in patients with a relatively increased iron burden., ((c) 2005 Wiley-Liss, Inc.)

A 72-year-old patient with liver cirrhosis and cavernomatous portal vein occlusion presented with refractory ascites. We treated the patient with transjugular intrahepatic portosystemic shunt: transjugular transhepatic puncture of an intrahepatic hilar collateral vein was performed; transjugular intrahepatic portosystemic shunt was created between the right hepatic vein and the patent superior mesenteric vein using this hilar collateral vein as the connecting pathway. The ascites was resolved and the patient remains asymptomatic, while shunt patency is maintained 16 months after the intervention.