Feasibility study for evaluating lumbar intervertebral disc degeneration using histogram analysis of T2* values.

PURPOSE: To evaluate the feasibility of histogram analysis of T2* value for the detection and grading of degenerative lumbar intervertebral discs (IVDs) and for the characterization of microstructural heterogeneity of discs. METHODS: Two hundred fourteen lumbar IVDs of 44 subjects with chronic low back pain were examined using sagittal T2WI and axial T2* mapping. All IVDs were classified according to the Pfirrmann grade on T2WI. The correlations between histogram-derived parameters based on T2* values (T2*-HPs) of IVDs and Pfirrmann grade as well as between "red zone ratio" (area of "red zone" on T2* color maps over cross-sectional area of corresponding IVDs) and Pfirrmann grade were calculated. RESULTS: The agreement for Pfirrmann grade of IVDs was excellent (κ = 0.808, P < 0.001). The consistency of the measured T2*-HPs was excellent, with ICCs ranging from 0.828-0.960. Each histogram-derived parameter had a statistically significant relationship with Pfirrmann grade (P < 0.001). The bright "red zone" on T2* color maps of IVDs displayed as a separated peak relative to the rest of voxels in histograms. The mean area ratio of "red zone" over the corresponding IVD was 9.234% ± 6.680 and ranged from 0.517% to 30.598%. The "red zone ratio" was highly related to Pfirrmann grade (r = - 0.732, P < 0.001). CONCLUSION: Histogram analysis of T2* value is an effective tool for the detection and grading of degenerative IVDs. Identification of the "red zone" may provide new breakthroughs in the study of disc degeneration initiation and generate new hypotheses in anatomical and histological studies of IVDs.

The Diagnostic Value of MR IVIM and T2 Mapping in Differentiating Autoimmune Myositis From Muscular Dystrophy.

RATIONALE AND OBJECTIVES: To confirm the feasibility and compare the accuracy of magnetic resonance imaging intravoxel incoherent motion (IVIM) and T2 mapping models for the differentiation of autoimmune myositis from muscular dystrophy. MATERIALS AND METHODS: Fourty-two autoimmune myositis and 11 muscular dystrophy patients proven by diagnostic criteria were enrolled in the study. Conventional MR sequences, IVIM, and T2 mapping through the bilateral thighs were obtained as well as blood samples for all patients. IVIM and T2 mapping parameters as well as serum markers were compared between the autoimmune myositis and muscular dystrophy groups. Mann-Whitney U tests were performed for statistical analysis along with receiver operating characteristic curves. Spearman correlation coefficient models were constructed to analyze the correlation between IVIM and T2 mapping with serological parameters. RESULTS: The intramuscular apparent diffusion coefficient, tissue diffusivity (D), perfusion fraction (fp), and T2 relaxation time values were statistically significantly different between the autoimmune myositis and muscular dystrophy groups (p < 0.05). Pseudo diffusivity (Dp) values showed no statistical difference between the groups (p > 0.05). D parameter of IVIM sequences differentiated autoimmune and muscular dystrophy with a higher specificity of 75.60%. T2 values within the thighs were correlated with serum creatine kinase and lactate dehydrogenase levels (p < 0.05). CONCLUSION: Thigh muscle IVIM and T2 mapping parameters are useful in differentiating autoimmune myositis from muscular dystrophy, particularly the IVIM parameters.

Recognition of sacroiliac joint structural lesions: Comparison of volumetric interpolated breath-hold examination (VIBE) sequences with different slice thicknesses to T1-weighted turbo-echo.

PURPOSE: To compare volumetric interpolated breath-hold examination (VIBE) with different slice thicknesses to T1-weighted turbo-echo (T1 TSE) for identification of sacroiliac joint structural lesions in patients suspected of spondyloarthritis (SpA) using CT as the gold standard. METHODS: 192 sacroiliac joints (including VIBE with both 1.2 mm and 3 mm slice thickness, T1 TSE) from 96 patients suspected of SpA were included. Joint space changes and sclerosis were evaluated for each joint. Erosions were assessed both at the level of the individual sacral and iliac bones and at the level of the entire joint for calculation of sensitivity, specificity, and accuracy. MRI and CT correlation was performed and inter-reader reliability was determined. Fat infiltration on MRI was scored. RESULTS: VIBE with a 1.2 mm slice thickness was the most sensitive and accurate for erosion detection at the bone level followed by 3 mm thickness VIBE and then T1 TSE (p < 0.05). At the whole-joint level, only the 1.2 mm slice thickness VIBE was superior to T1 TSE in sensitivity and accuracy (p > 0.05). For joint space changes, both VIBE sequences were superior to T1 TSE in sensitivity and accuracy (p < 0.05) and had more consistency with CT. T1 TSE was slightly more sensitive for detection of sclerosis (p < 0.05). The MR sequences did not differ in detection of fat infiltration. CONCLUSION: A VIBE sequence with 1.2 mm slice thickness and less than one-minute acquisition time was superior to T1 TSE for detection of sacroiliac joint space changes and erosions in patients with suspected SpA, while the utility of the 3 mm slice thickness VIBE remains questionable.