Monoexponential and Biexponential Fitting of Diffusional Magnetic Resonance Imaging Signal Analysis for Prediction of Liver Fibrosis Severity.

OBJECTIVE: The objective of this study is to compare the value of monoexponential and biexponential approach to the diffusion-weighted magnetic resonance imaging signal in the prediction of the liver fibrosis. METHODS: Forty patients with hepatitis C were included. Quantification of the apparent diffusion coefficient (ADC) and pure molecular diffusion (D), pseudodiffusion (D*), and perfusion fraction (f) was performed using 9 b values (b = 0, 20, 50, 100, 200, 400, 600, 800, 1000 s/mm). RESULTS: Significant fibrosis was found in 14 subjects. Monoexponentally derived ADC parameters were significantly correlated. Apparent diffusion coefficient calculated from all b values and ADC based on high b values were significantly related to the fibrosis grade (P < 0.02), and none of intravoxel incoherent motion parameters presented such an association. Apparent diffusion coefficient based on high b values was the best predictor of significant fibrosis with area under the curve of 0.81, sensitivity of 0.57, and specificity of 0.92. CONCLUSION: Intravoxel incoherent motion parameters did not allow for prediction of the liver fibrosis. Apparent diffusion coefficient calculated based on high b values presents considerable specificity in predicting significant fibrosis.

Chest adipose tissue distribution in patients with morbid obesity.

PURPOSE: Obesity is a well-known of risk factor for atherosclerosis and the amount of visceral adipose tissue is considered as an independent predictor of coronary artery disease (CAD). An aim of the study was to investigate the distribution of intrathoracic adipose tissue in morbidly obese patients. MATERIAL AND METHODS: Fifty-one patients with morbid obesity (BMI ≥ 40 kg/m2) and thirty controls were scanned in a coronary calcium scoring protocol. Control group consisted of patients scanned due to a clinical suspicion of CAD, who did not fulfill obesity criteria. The amount of adipose tissue was measured as epicardial adipose tissue (EAT) thickness, pericoronary fat (PCF) thickness, total intra-pericardial fat (IPF) volume, and total intrathoracic fat (ITF) volume. RESULTS: Mean BMI of obese patients and controls was 47.3 and 26.5, respectively (p < 0.0001). Patients with obesity and controls did not differ with respect to mean EAT, mean PCF, and IPF. However, ITF was lower in obesity group than in control group (268 vs. 332 cm3, respectively; p < 0.03). Moreover, ROC analysis presented relation between obesity and the superior EAT thickness, PCF at LCX, mean PCF, ITF, and chest soft tissue (CST) thickness (p < 0.03). CST thickness of > 60 mm was the parameter that presented the strongest association with morbid obesity (AUC 0.95; p < 0.0001). CONLCUSIONS: Increased chest soft tissue thickness but not the increased intrathoracic adipose tissue volume was associated with morbid obesity. Since the quantity of the pericardiac fat is not directly related to the obesity, its accumulation may be related to a mechanism different than that of subcutaneous adipose tissue growth.

Evaluation the Aortic Aneurysm Remodeling After a Successful Stentgraft Implantation.

BACKGROUND: Routine imaging follow-up after endovascular treatment of abdominal aortic aneurysms (EVAR) is mainly aimed at detection of endoleaks. The aim of the study was to assess changes in the size of the abdominal aortic aneurysm sack using CT angiography (CTA) after successful treatment using endovascular stent graft implantation. MATERIAL/METHODS: A retrospective analysis of CTA results included 102 patients aged 54-88, who had no postoperative complications. Patients underwent CTA before EVAR and after the treatment (mean time between studies, 7.6 months). The largest cross-sectional area of the aneurysm sac was measured using a curved multiplanar reconstruction. A change of the aneurysm cross-sectional over 10% was considered significant. RESULTS: The average cross-sectional area decreased after EVAR by 3% and this change was not statistically significant. Regression of the cross-sectional area was observed in 18.6% of patients, progression was in 23.5%, and no change was seen in 57.8%. Cross-sectional areas before and after EVAR were significantly correlated (r=0.75, p<0.0001). There was no correlation between the cross-sectional area change after EVAR and patients' age or the time between the treatment and the follow-up CTA. Cross-sectional area before the treatment predicted changes in the aneurysm size after EVAR (p=0.0045). CONCLUSIONS: Remodeling of abdominal aortic aneurysms after EVAR is not uniform. The change of aneurysm size depends on the initial aneurysm size but not on the time from EVAR. The size of the aneurysm after EVAR should not be considered as a measure of the treatment efficacy.

Anatomical Evaluation of the Pulmonary Veins and the Left Atrium Using Computed Tomography Before Catheter Ablation: Reproducibility of Measurements.

BACKGROUND: Atrial fibrillation (AF) is a common supraventricular arrhythmia. ECG-gated MDCT seems to be currently a method of choice for pre-ablation anatomical mapping due to an excellent resolution and truly isotropic three-dimensional nature. The aim of this study was to establish the between-subject variability and inter-observer reproducibility of anatomical evaluation of the pulmonary veins (PV) and the left atrium (LA) using computed tomography. MATERIAL/METHODS: A retrospective analysis included 42 patients with AF, who were scheduled for a cardiac CT for ablation planning. Images were assessed by two independent radiologists using a semi-automatic software tool. The left atrium anatomy (volume, AP diameter), anatomy of the pulmonary veins (number, ostia diameters and surface area) were evaluated. The relative between-subject variability and the inter-observer variability of measurements were calculated. RESULTS: The heart rate during scanning ranged from 50 to 133/min. (mean 79.1/min.) and all examinations were of adequate image quality. Accessory pulmonary veins were found in 24% of patients. Between-subject variability of the PV ostial cross-sectional area ranged from 33% to 48%. The variability of the left atrium size was 21% for the diameter and 35% for the volume. The inter-observer agreement for the detection of accessory pulmonary veins was good (κ=0.73; 95% CI, 0.54-0.93). CONCLUSIONS: Between-subject variability of the pulmonary vein ostial cross-sectional area and the left artial volume is substantial. The anatomical assessment of the pulmonary vein ostia and the left atrium size in computed tomography presents a good inter-observer reproducibility.

Whole-organ and segmental stiffness measured with liver magnetic resonance elastography in healthy adults: significance of the region of interest.

PURPOSE: MR elastography (MRE) is a recent non-invasive technique that provides in vivo data on the viscoelasticity of the liver. Since the method is not well established, several different protocols were proposed that differ in results. The aim of the study was to analyze the variability of stiffness measurements in different regions of the liver. METHODS: Twenty healthy adults aged 24-45 years were recruited. The examination was performed using a mechanical excitation of 64 Hz. MRE images were fused with axial T2WI breath-hold images (thickness 10 mm, spacing 10 mm). Stiffness was measured as a mean value of each cross section of the whole liver, on a single largest cross section, in the right lobe, and in ROIs (50 pix.) placed in the center of the left lobe, segments 5/6, 7, 8, and the parahilar region. RESULTS: Whole-liver stiffness ranged from 1.56 to 2.75 kPa. Mean segmental stiffness differed significantly between the tested regions (range from 1.55 ± 0.28 to 2.37 ± 0.32 kPa; P < 0.0001, ANOVA). Within-method variability of measurements ranged from 14 % for whole liver and segment 8-26 % for segment 7. Within-subject variability ranged from 13 to 31 %. Results of measurement within segment 8 were closest to the whole-liver method (ICC, 0.84). CONCLUSIONS: Stiffness of the liver presented significant variability depending on the region of measurement. The most reproducible method is averaging of cross sections of the whole liver. There was significant variability between stiffness in subjects considered healthy, which requires further investigation.

Comparison of calcium scoring with 4-multidetector computed tomography (4-MDCT) and 64-MDCT: a phantom study.

OBJECTIVE: To determine differences in coronary artery calcium (CAC) measurement performed with the use of 2 generations of multidetector computed tomography (CT) scanners of the same manufacturer. METHODS: Agatston Score (AS) and calcium mass (CM) were measured with a 4-row scanner (AS4 and CM4) and a 64-row scanner (AS64 and CM64) using a cardiac phantom with calcium inserts. RESULTS: The results of the AS measurements (mean ± SD) varied significantly between the equipment: 880.6 ± 30.1 (AS4) vs 586.5 ± 24.0 (AS64; P < 0.0001). The AS interscanner variability was 31.6% for the phantom and from 25.5% to 110.1% for particular inserts. Mean ± SD CM values were different as well: 192.8 ± 5.0 mg (CM4) vs 152.4 ± 2.6 mg (CM64; P < 0.0001). Determination of CM with 64-row CT was more accurate than that with an older scanner; the mean relative error was -9.1% and 15.0%, respectively (P < 0.0001). The CM interscanner variability was 23.3% for the phantom and from 19.0% to 122.8% for particular inserts. The interexamination variability ranged from 1.7% (CM64) to 5.6% (AS4). CONCLUSIONS: Coronary artery calcium scoring with the 64-row CT scanner is more accurate than with the 4-row device The difference between the results of AS and CM measurements carried out with both scanners is statistically significant.