Free-breathing accelerated gadolinium-enhanced MR Angiography in the Diagnosis of Renovascular Disease.

OBJECTIVE: The purpose of this study was to assess the feasibility and accuracy of accelerated free-breathing and breath-hold gadolinium-enhanced MR angiography of the main renal arteries compared with digital subtraction angiography. MATERIALS AND METHODS: Renal MR angiograms and catheter angiograms of 47 patients (19 men, 28 women; mean age, 68.1 +/- 15.1 years; range, 28-86 years) were reviewed. Thirty-one of the patients underwent free-breathing and 16 underwent breath-hold MR angiography with the same accelerated multiphase imaging protocol. Images were analyzed for examination quality, percentage narrowing of the main renal artery, and visibility of the branches. Diagnostic values of MR angiography were calculated with catheter angiography as the standard of reference. RESULTS: Sixty-five arteries, 24 of which (37%) had > 49% narrowing, were evaluated in the free-breathing group, and 37 arteries, six of which (16%) had > 49% narrowing, were evaluated in the breath-hold group. Comparison with digital subtraction angiography showed 100% (24/24) sensitivity and 95% (39/41) specificity for > 49% renal artery stenosis and 88% sensitivity (15/17) and 100% (48/48) specificity for > 74% renal artery stenosis in the free-breathing group. In the breath-hold group, sensitivity was 100% (6/6) and specificity 97% (30/31) for > 49% renal artery stenosis, and sensitivity was 100% (5/5) and specificity 100% (32/32) for > 74% renal artery stenosis. None of the examinations was nondiagnostic for the main renal arteries, but a smaller number of visible arterial tree subdivisions were found in the free-breathing group (average, 3.64 per patient) than in the breath-hold group (average, 5.87 per patient) (p = 0.035). CONCLUSION: Like breath-hold examinations, accelerated free-breathing MR angiographic examinations are feasible and accurate in evaluation of the main renal arteries.

Virtual dissection CT colonography: evaluation of learning curves and reading times with and without computer-aided detection.

PURPOSE: To prospectively evaluate the learning curves and reading times of inexperienced readers who used the virtual dissection reading method for retrospective computed tomographic (CT) colonography data sets, with and without concurrent computer-aided detection (CAD). MATERIALS AND METHODS: An Institutional Review Board approved this study; informed consent was waived. Four radiologists without experience in CT colonography evaluated 100 optical colonoscopy-proved data sets of 100 patients (49 men, 51 women; mean age, 59 years +/- 13 [standard deviation]; range, 21-85 years) by using the virtual dissection reading method. Two readers used concurrent CAD. Data sets were read during five consecutive 1-day sessions (20 data sets per session). Polyp detection and false-positive rates, receiver operating characteristics (ROCs), and reading times were calculated for individual, CAD group, and non-CAD group readings. Diagnostic values were compared by calculating the 95% confidence intervals (CIs) around the relative risk. Areas under ROC curves (AUCs) (Hanley and McNeil for paired analysis and z statistics for unpaired analysis) and reading times (Wilcoxon signed rank test) were compared across the sessions, within each session and for the whole study. RESULTS: The range of detection rates was 79 of 111 (.71 [95% CI: .61, .79]) to 91 of 111 (.82 [95% CI: .73, .88]). The range of false-positive rates was 17 of 111 (.15 [95% CI: .09, .23]) to 22 of 111 (.20 [95% CI: .12, .28]). All readers' AUCs rose from session 1 to session 4; this rise was significant (P < .05) for the non-CAD group. Only during session 1 was the CAD group AUC (.83) higher than the non-CAD group AUC (.54) (P < .05). Comparison of CAD and non-CAD reading times showed no significant difference for the whole study or during each session (P > .05). CONCLUSION: The virtual dissection reading technique allows short learning curves, which may be improved by the concurrent use of CAD, without significant effect on average reading time.

Adrenal ganglioneuroma.

BACKGROUND: A 20-year-old man was referred after having been discovered a left adrenal incidentaloma. Characteristics on magnetic resonance imaging (MRI) suggested the diagnosis of adrenal ganglioneuroma or carcinoma. Pathological examination after adrenalectomy concluded it was an adrenal ganglioneuroma. We studied the characteristics of adrenal ganglioneuroma. METHODS: We retrospectively reviewed hormonal status, computed tomography and MRI features, and histological findings of our series of 8 adrenal ganglioneuromas. RESULTS: Specific features were: (1) no hormonal hypersecretion; (2) presence of calcifications, no vessel involvement; and a non-enhanced attenuation of less than 40 Hounsfield units on computed tomography; and (3) low non-enhanced T1-weighted signal, a slightly high and heterogeneous T2-weighted signal, and a late and gradual enhancement on dynamic MRI, especially if associated with a whorled pattern. CONCLUSIONS: Even if many aggressive tumors share some of those radiological features, the presence of all or most of them must lead the clinician to consider the diagnosis of adrenal ganglioneuroma.

Hepatic flow parameters measured with MR imaging and Doppler US: correlations with degree of cirrhosis and portal hypertension.

PURPOSE: To determine the correlations between hemodynamic parameters of hepatic flow measured with magnetic resonance (MR) imaging and Doppler ultrasonography (US) and the severity of cirrhosis and portal hypertension. MATERIALS AND METHODS: Forty-six patients referred for measurements of portal venous pressure (three with normal liver, 12 with chronic hepatitis, and 31 with cirrhosis [10 with Child-Pugh class A cirrhosis; 13 with class B cirrhosis; and eight with class C cirrhosis]) were included in the study. Apparent liver perfusion, apparent arterial and portal perfusion, portal fraction, distribution volume, and mean transit time were measured with dynamic contrast material-enhanced MR imaging. Portal velocity, portal flow, congestion index, right hepatic artery resistance index, and modified hepatic index were measured with Doppler US. Results in patients with cirrhosis and those without cirrhosis were compared with the Wilcoxon rank sum test. Correlations were assessed with Spearman rank correlation coefficients. RESULTS: With MR imaging, all flow parameters except distribution volume were significantly different between patients with and those without cirrhosis (P <.05). There was a significant correlation between all flow parameters measured with MR imaging and portal pressure (P <.02). Apparent arterial (P =.024) and portal (P <.001) perfusion, portal fraction (P <.001), and mean transit time (P =.004) were correlated with Child-Pugh class. Flow parameters measured with Doppler US did not differ significantly between patients with and those without cirrhosis. Only right hepatic arterial resistance (P <.007) and portal flow (P <.043) were weakly (r < 0.7) correlated with portal pressure. No Doppler US parameter was correlated with Child-Pugh class. CONCLUSION: Hepatic flow parameters measured with MR imaging correlate with the severity of cirrhosis and portal hypertension. Doppler US parameters are only weakly correlated with portal pressure.

CF gene and cystic fibrosis transmembrane conductance regulator expression in autosomal dominant polycystic kidney disease.

Disease-modifying genes might participate in the significant intrafamilial variability of the renal phenotype in autosomal dominant polycystic kidney disease (ADPKD). Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) is a chloride channel that promotes intracystic fluid secretion, and thus cyst progression, in ADPKD. The hypothesis that mutations of the CF gene, which encodes CFTR, might be associated with a milder renal phenotype in ADPKD was tested. A series of 117 unrelated ADPKD probands and 136 unaffected control subjects were screened for the 12 most common mutations and the frequency of the alleles of the intron 8 polymorphic TN: locus of CF. The prevalence of CF mutations was not significantly different in the ADPKD (1.7%, n = 2) and control (3.7%, n = 5) groups. The CF mutation was DeltaF508 in all cases, except for one control subject (1717-1G A). The frequencies of the 5T, 7T, and 9T intron 8 alleles were also similar in the ADPKD and control groups. Two additional patients with ADPKD and the DeltaF508 mutation were detected in the families of the two probands with CF mutations. Kidney volumes and renal function levels were similar for these four patients with ADPKD and DeltaF508 CFTR (heterozygous for three and homozygous for one) and for control patients with ADPKD collected in the University of Colorado Health Sciences Center database. The absence of a renal protective effect of the homozygous DeltaF508 mutation might be related to the lack of a renal phenotype in CF and the variable, tissue-specific expression of DeltaF508 CFTR. Immunohistochemical analysis of a kidney from the patient with ADPKD who was homozygous for the DeltaF508 mutation substantiated that hypothesis, because CFTR expression was detected in 75% of cysts (compared with <50% in control ADPKD kidneys) and at least partly in the apical membrane area of cyst-lining cells. These data do not exclude a potential protective role of some CFTR mutations in ADPKD but suggest that it might be related to the nature of the mutation and renal expression of the mutated CFTR.

Assessment of knee cartilage in cadavers with dual-detector spiral CT arthrography and MR imaging.

PURPOSE: To assess dual-detector spiral CT arthrography in the evaluation of the entire knee cartilage obtained from cadavers. MATERIALS AND METHODS: Two independent observers characterized articular cartilage in 12 cadaver knees in which MR imaging and dual-detector spiral CT arthrography were performed and compared their findings to those found during macroscopic assessment. The sensitivity and specificity of MR imaging and spiral CT arthrography for detecting grade 2A or higher and grade 2B or higher cartilage lesions, the Spearman correlation coefficient between arthrographic and macroscopic grading, and kappa statistics for assessing interobserver reproducibility were determined. RESULTS: At spiral CT arthrography, sensitivities and specificities ranged between 80% and 88% for the detection of grade 2A or higher cartilage lesions and ranged between 85% and 94% for the detection of grade 2B or higher cartilage lesions. At MR imaging, sensitivities and specificities ranged between 78% and 86% and between 76% and 91% for the detection of grade 2A or higher and grade 2B or higher cartilage lesions, respectively. Spearman correlation coefficients between spiral CT arthrography or MR imaging and macroscopic grading of articular surfaces were 0.797 and 0.702, respectively. CONCLUSION: Dual-detector spiral CT arthrography of the knee is a valuable method for the assessment of open cartilage lesions of the entire knee.

Capillarization of the sinusoids in liver fibrosis: noninvasive assessment with contrast-enhanced MRI in the rabbit.

Sinusoidal capillarization induces microcirculatory changes in liver cirrhosis and fibrosis. The purpose of this study was to assess whether contrast-enhanced MRI can be used to demonstrate the effects of sinusoidal capillarization in liver fibrosis. Dynamic MRI after injection of a low-molecular-weight contrast agent of 0.56 kDa (Gd-DOTA), and two high-molecular-weight contrast agents of 6.47 kDa and 52 kDa (P792 and P717) was performed in rabbits with liver fibrosis induced by cholesterol and diethylstilbestrol. The hepatic distribution volume accessible to the high-molecular-weight agents decreased in the rabbits with liver fibrosis (P792: 7.8% +/- 1.7% vs. 10.1% +/- 1.8% in normal rabbits, P =.038; P717: 6.2% +/- 2.1% vs. 9.7% +/- 1.6% in normal rabbits, P =.007), whereas the hepatic mean transit time (MTT) of the low-molecular-weight agent was increased (15.9 +/- 8.0 s vs. 8.8 +/- 2.6 s in normal rabbits, P =.015). In rabbits with liver fibrosis, the clearance of indocyanine green (ICG) was correlated with the volume accessible to the high-molecular-weight agents (P792: r = 0.810, P =.015; P717: r = 0.857, P =.007). The collagen content of the liver was inversely correlated with the distribution volume of P717 (r = -.833, P =.010) and with the ICG clearance (r = -.810, P =.015). It was concluded that the microcirculatory changes induced by sinusoidal capillarization in liver fibrosis can be demonstrated noninvasively with MRI.

Dynamic computed tomography with low- and high-molecular-mass contrast agents to assess microvascular permeability modifications in a model of liver fibrosis.

Interstitial collagen formation and transformation of the fenestrated hepatic sinusoids into continuous capillaries are major ultrastructural changes that occur in liver cirrhosis and fibrosis. These modifications lead to progressive restriction of blood-liver exchanges. The purpose of our study was to evaluate the permeability changes in a model of hepatic fibrosis by using dynamic computed tomography (CT) enhanced with contrast agents of different molecular masses. Dynamic single-section CT of the liver was performed after intravenous bolus administration of a low-molecular-mass contrast agent (iobitridol) and an experimental high-molecular-mass agent (P840) in normal control rabbits and in rabbits with hepatic fibrosis. Hepatic, aortic and portal venous time-density curves were fitted with a dual-input one-compartmental model to calculate the hepatic mean transit time and distribution volume of the contrast agents. In the rabbits with liver fibrosis, the mean transit time of the high-molecular-mass agent was shorter than that of the low-molecular-mass agent (10.0+/-1.8 s and 12.0+/-1.2 s respectively; P<0.05). The distribution volume accessible to the high-molecular-mass agent was also smaller (22.2+/-4.8% compared with 32.0+/-6.7%; P<0.01). In the normal rabbits, the mean transit times of the high- and low-molecular-mass agents did not differ significantly, and nor did their distribution volumes. Our results demonstrate decreased sinusoidal permeability for the high-molecular-mass agent P840 in a model of hepatic fibrosis. Non-invasive assessment of permeability changes in liver fibrosis can be performed with dynamic CT and contrast agents of different molecular masses.

Body surface area and body weight predict total liver volume in Western adults.

Computed tomography (CT) is used increasingly to measure liver volume in patients undergoing evaluation for transplantation or resection. This study is designed to determine a formula predicting total liver volume (TLV) based on body surface area (BSA) or body weight in Western adults. TLV was measured in 292 patients from four Western centers. Liver volumes were calculated from helical computed tomographic scans obtained for conditions unrelated to the hepatobiliary system. BSA was calculated based on height and weight. Each center used a different established method of three-dimensional volume reconstruction. Using regression analysis, measurements were compared, and formulas correlating BSA or body weight to TLV were established. A linear regression formula to estimate TLV based on BSA was obtained: TLV = -794.41 + 1,267.28 x BSA (square meters; r(2) = 0.46; P <.0001). A formula based on patient weight also was derived: TLV = 191.80 + 18.51 x weight (kilograms; r(2) = 0.49; P <.0001). The newly derived TLV formula based on BSA was compared with previously reported formulas. The application of a formula obtained from healthy Japanese individuals underestimated TLV. Two formulas derived from autopsy data for Western populations were similar to the newly derived BSA formula, with a slight overestimation of TLV. In conclusion, hepatic three-dimensional volume reconstruction based on helical CT predicts TLV based on BSA or body weight. The new formulas derived from this correlation should contribute to the estimation of TLV before liver transplantation or major hepatic resection.