Reproducibility of manual and semi-automated late enhancement quantification in patients with Fabry disease.

BACKGROUND: Late enhancement (LE) imaging is increasingly used for diagnosis of non-ischemic cardiomyopathy. However, the mostly patchy appearance of LE in this context may reduce the reproducibility of LE measurement. PURPOSE: To report intra- and inter-observer variabilities of LE measurements in Fabry disease using manual and semi-automated quantification. MATERIAL AND METHODS: Twenty MRI data-sets of male patients aged 44 ± 7 years were analyzed twice (interval 12 months) by one observer and additionally once by a second observer. Left ventricular (LV) parameters were determined using cine MRI. Gradient-echo LE images were analyzed by manual planimetry and by a semi-automatic prototype software. Variabilities were determined by Bland-Altman analyses and additionally intra-class correlation coefficient (ICC) values were calculated to survey intra- and inter-observer reproducibility. RESULTS: The amount of LE was 5.2 ± 5.1 mL or 2.8 ± 2.6 % of LV mass (observer 2). LE was detected predominantly intramurally in a patchy pattern. All patients had LE restricted to the basal infero-lateral parts of the LV. The extent of LE correlated to LV mass (207 ± 70 g, P < 0.05, r = 0.6). The intra- and inter-observer variabilities were -0.6 to 1.0 mL and -0.7 to 1.6 mL, respectively (95% confidence intervals). ICC values were 0.981-0.999. The semi-automatic software allowed quantification of LE areas in all patients. The comparison of LE amount determined by semi-automatic software versus manual planimetry yielded an intra-observer variability ranging from -1.9 to 2.3 mL. CONCLUSION: Semi-automatic planimetry of patchy LE in patients with Fabry disease is feasible. The determined intra- and inter-observer variabilities for manual and semi-automatic planimetry were in the range of 20-40% of LE amount with high ICC values.

Remodeling of the infarct territory in the time course of infarct healing in humans.

OBJECT: To analyze the remodeling processes of the infarct territory in the time course of infarct healing. MATERIALS AND METHODS: Serial late enhancement (LE) studies were performed in 30 patients following reperfused myocardial infarction (MI) in the first and second week post-MI and after 3 months. To characterize infarct remodeling over time, the following variables were derived and analyzed in a blinded fashion: Infarct size (IS, in mm(3)), maximum infarct thickness (IT(max), mm), mean infarct thickness (IT(mean), mm) and the variability of infarct thickness (VIT=IT(max)/IT(mean)). Further, a new parameter for the assessment of infarct remodeling, the infarct extent (IE, mm(2)) was computed. IE quantifies IS in two dimensions along the heart's circumferential and longitudinal directions. IS was divided by the IE to obtain IT(mean). RESULTS: Overall infarct thickness was highly variable. Infarct shrinkage due to infarct thinning and IE reduction was found in the first months of healing. IS, IT(mean) and IT(max) significantly decreased during follow-up. There was a less consistent change of the IE: IE decreased in 75% of all infarcts from the first week up to 3 months post-MI, whereas 25% of infarcts expanded. Infarct thinning was found in almost all patients (92%), hence occurring in patients with infarct expansion and in patients without infarct expansion. CONCLUSION: Infarct thinning and-to a lesser extent-IE reduction, contribute to infarct shrinkage in the time course of infarct healing. Infarct thinning may occur without infarct expansion.

Diffusion-weighted MRI of abscess formations in children and young adults.

BACKGROUND: Diffusion-weighted MRI (DWI) is helpful for detection of brain abscess and pelvic abscess in adults. In the present study, we evaluated the diagnostic performance of DWI in children and young adults with abdominal and soft tissue abscess formations. METHODS: Seventeen patients (11 females, aged 13 ± 6 years) with suspected abdominal or soft-tissue abscess underwent routine MRI including free-breathing DWI and contrast-enhanced T1w imaging. Seventeen random age-matched patients with non-purulent abdominal fluid collections served as controls. Mean apparent diffusion coefficent (ADC) was measured for abscess, muscle, liver, spleen and kidney tissue as well as for cerebrospinal fluid, urine and free abdominal fluid. RESULTS: All fluid collections were identified on diffusion-weighted images. Thirteen of 14 confirmed abscess formations showed an ADC < 1.0 × 10(-3) mm(2)/s with a mean value of 0.80 ± 0.38 mm(2)/s. One tuberculous soft-tissue abscess had a higher ADC of 1.85 × 10(-3) mm(2)/s. Ring enhancement on T1w imaging was seen in three non-purulent fluid collections. There were no false-positive findings in the control group. CONCLUSIONS: Diffusion-weighted MRI is highly sensitive for abscess and may add specificity to contrast-enhanced T1w imaging of ring-enhancing fluid collections. DWI with free-breathing rapid image acquisition and without the need of intravenous contrast application constitutes a particularly useful choice in pediatric imaging.

Hemodynamic assessment of severe aortic stenosis: MRI evaluation of dynamic changes of vena contracta.

PURPOSE: Direct magnetic resonance imaging (MRI) planimetry of the maximal systolic aortic valve area does not consider temporal variations of the opening area during the ejection period. We evaluated an MRI-based methodology for the assessment of valvular dynamics in patients with severe aortic stenosis by measuring the systolic variability of the valvular blood stream, that is, the "vena contracta." MATERIALS AND METHODS: With institutional review board approval, we examined 22 patients (13 male, 9 female; mean age, 68 ±10 years) with severe aortic stenosis using 1.5 T MRI and a standardized scanning protocol consisting of gradient-echo phase-contrast velocity imaging and steady-state free precession-cine MRI before and after valve replacement therapy. Temporal changes of the aortic valve area, represented by systolic variations of the area of poststenotic turbulent flow at its smallest convergence, that is, the proximal vena contracta, were determined by MRI and quantified by a calculated parameter of temporal valve dynamics (T). T was defined as the period which the aortic valve spent over its maximal opening area (>85%) during systole. MRI was also used to determine left ventricular hypertrophy before (LVMI) and its regression (LVMR) after valve replacement. Findings were compared with transthoracic echocardiography and cardiac catheterization. RESULTS: All patients had an echocardiographic effective orifice area, EOATTE, of <1.0 cm2. The comparison of T to LVMI and LVMR revealed significant correlations (LVMI: r = -0.62; P = 0.002; LVMR: r = 0.62; P = 0.002). Further significant correlations with aortic stenosis severity were observed in the comparison with manual planimetry, invasive measurements, and echocardiographic valve areas, as well as with pressure gradients. CONCLUSIONS: MRI can measure systolic variations of the aortic valve area. Quantitative parameters of the hemodynamic relevance of valve dynamics obtained by this method correlate with established parameters of aortic stenosis severity and LVMR.