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Using prospectively acquired T2-relaxometry data from 606 intervertebral discs in 101 volunteers without back pain in a narrow age range (25–35 years), the authors calculated intra- and intersubject variation in T2 times of IVDs graded by 2 neuroradiologists on the Pfirrmann scale. Intrasubject variation of IVDs was assessed relative to other healthy IVDs (Pfirrmann grade, #2) in the same individual. Multiple intersubject variability measures were calculated using healthy extraneous references ranging from a single randomly selected IVD to all healthy extraneous IVDs, without and with segmental stratification. They conclude that the study demonstrates a significantly higher variation in the T2 times of IVDs across subjects, and suggests that normative measures based on the T2 times of healthy lumbar IVDs from the same individual are likely to provide the most discriminating means of identifying degenerated IVDs on the basis of T2 relaxometry.

The aims of this study were to: 1) to design a new method of postprocessing time-intensity curves, which renders normalized curves, and 2) to test its feasibility and performance on the diagnosis of primary central nervous system lymphoma. Time-intensity curves of enhancing tumor and normal-appearing white matter were obtained for each case. Enhancing tumor time-intensity curves were normalized relative to normal-appearing white matter. The authors performed pair-wise comparisons for primary central nervous system lymphoma against the other tumor type. The best discriminatory time points of the curves were obtained through a stepwise selection. Logistic binary regression was applied to obtain prediction models. A total of 233 patients were included in the study with 47 primary central nervous system lymphomas, 48 glioblastomas, 39 anaplastic astrocytomas, 49 metastases, and 50 meningiomas. The classifiers satisfactorily performed all bilateral comparisons in the test subset. They conclude that the proposed method for DSC-PWI time-intensity curve normalization renders comparable curves beyond technical and patient variability. Normalized time-intensity curves performed satisfactorily for the presurgical identification of primary central nervous system lymphoma.