Abstract
ObjectiveShort tau or short TI inversion recovery (STIR) MRI sequences are considered a robust fat suppression technique. However, STIR also suppresses signals from other tissues with similar T1 relaxation times. This study investigates the in vivo effect of intravenous gadolinium-based T1-shortening contrast agent on STIR signal.Materials and methodsInstitutional board approval and informed consent was obtained. MRI examinations (1.5-T or 3-T) of 31 prospectively included patients were analyzed by two readers. Signal intensity of degenerative bone marrow edema-like signal at the Lisfranc joint on precontrast STIR images and on STIR images acquired after intravenous contrast agent administration (gadoteric acid, gadolinium: 0.5 mmol/ml, 15 ml) was measured. The medial cuneiform bone without observable bone marrow edema-like signal was considered a healthy tissue and served as a reference. Relative changes in signal intensity between precontrast and postcontrast images were calculated for the two tissues. Wilcoxon signed-rank test served for statistical analyses.ResultsIn bone marrow edema-like signal, both readers observed a median signal change of -35% (interquartile range (IQR) 24) and -34% (IQR 21), respectively, on postcontrast STIR images compared to precontrast STIR. In healthy tissue, the signal remained constant on postcontrast STIR images (median change -2%, IQR 15, and 0%, IQR 17) respectively. For both readers, postcontrast signal change in bone marrow edema-like signal differed from that in healthy tissue (p < 0.001).ConclusionIntravenous gadolinium-based contrast agent causes a significant reduction of signal intensity in bone marrow edema-like signal on routine STIR images. Thus, pathological MRI findings may be obscured.
Highlights
Besides conventional T1-weighted and T2 weighted imaging, short tau inversion recovery or short TI inversion recovery (STIR) MR sequences with a short inversion time are used as a fat suppression technique
All patients referred to our institution for forefoot MRI with indication for intravenous gadolinium-based contrast agent administration were eligible for this study: At our institution, contrast-enhanced MR images are standard in forefoot protocols for the evaluation of osteomyelitis, Morton neuroma, neoplasm, vascular malformations including MR angiography, and rheumatic disorders
Interobserver agreement of average signal intensity was assessed by the two-way random effects intraclass correlation coefficient (ICC)
Summary
Besides conventional T1-weighted and T2 weighted imaging, short tau inversion recovery or short TI inversion recovery (STIR) MR sequences with a short inversion time (approximately 140 ms at 1.5-T) are used as a fat suppression technique. Fat suppression with STIR is based on short T1 relaxation rates and is not tissue specific. An appropriate degree of T1 shortening due to accumulation of paramagnetic contrast agent in tissue may decrease the signal intensity on STIR sequence MR images [1, 2]. In vitro studies have shown that the signal in STIR after administration of gadolinium-based contrast agent is concentration-dependent. Based on T1 shortening effect, gadolinium concentrations between approximately 0.5 and 1.0 mmol per liter result in very low or even neutralized signal intensity on STIR images [3, 4]
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