Does Gadolinium Deposition Lead to Metabolite Alteration in the Dentate Nucleus? An MRS Study in Patients with MS.

BACKGROUND AND PURPOSE: Repeat contrast-enhanced MR imaging exposes patients with relapsing-remitting MS to frequent administration of gadolinium-based contrast agents. We aimed to investigate the potential metabolite and neurochemical alterations of visible gadolinium deposition on unenhanced T1WI in the dentate nucleus using MRS. MATERIALS AND METHODS: This prospective study was conducted in a referral university hospital from January 2020 to July 2021. The inclusion criteria for case and control groups were as follows: 1) case: patients with relapsing-remitting MS, visible gadolinium deposition in the dentate nucleus (ribbon sign), >5 contrast-enhanced MR images obtained; 2) control 1: patients with relapsing-remitting MS without visible gadolinium deposition in the dentate nucleus, >5 contrast-enhanced MR images obtained; 3) control 2: patients with relapsing-remitting MS without visible gadolinium deposition in the dentate nucleus, <5 contrast-enhanced-MR images obtained; and 4) control 3: adult healthy individuals, with no contrast-enhanced MR imaging. Dentate nucleus and pontine single-voxel 12 × 12 × 12 MRS were analyzed using short TEs. RESULTS: Forty participants (10 per group; 27 [67.5%] female; mean age, 35.6 [SD, 9.6] years) were enrolled. We did not detect any significant alteration in the levels of NAA and choline between the studied groups. The mean concentrations of mIns were 2.7 (SD, 0.73) (case), 1.5 (SD, 0.8) (control 1), 2.4 (SD, 1.2) (control 2), and 1.7 (SD, 1.2) (control 3) (P = .04). The mean concentration of Cr and mIns (P = .04) and the relative metabolic concentration (dentate nucleus/pons) of lipid 1.3/Cr (P = .04) were significantly higher in the case-group than in healthy individuals (controls 1-3). Further analyses compared the case group with cumulative control 1 and 2 groups and showed a significant increase in lactate (P = .02), lactate/Cr (P = .04), and Cr (dentate nucleus/pons) (P = .03) in the case group. CONCLUSIONS: Although elevated concentrations of Cr, lactate, mIns, and lipid in the dentate nucleus of the case group indicate a metabolic disturbance, NAA and choline levels were normal, implying no definite neuronal damage.

Dynamic contrast-enhanced MRI for differentiation of major salivary glands neoplasms, a 3-T MRI study.

OBJECTIVES: Pre-operative differentiation of salivary gland neoplasms is of great importance. This study was designed to evaluate the use of dynamic contrast-enhanced MRI (DCE-MRI) for differentiation between malignant, Warthin and benign non-Warthin (BNW) neoplasms of major salivary glands. METHODS: 46 major salivary gland tumours (SGTs) underwent pre-operative DCE-MRI. Post-surgical histopathological evaluation showed 30 BNW, 6 Warthin and 10 malignant tumours. Time-signal intensity curves (TICs) were categorized as (a) Tpeak >43 s and washout ratio at 180 s (WR180) <4.6%; (b) Tpeak <43 s and WR >22%; (c) Tpeak >43 s and WR180 = 4.6-22.0% RESULTS: Accuracy of Tpeak was 98.9% for differentiation between BNW and Warthin tumours, 83.7% between BNW and malignant and 80% between malignant and Warthin tumours. All Warthin tumours showed Tpeak ≤43 s, while one BNW had Tpeak <43 s. A Tpeak <63.5 s differentiated 8/10 (80%) malignant tumours from BNW tumours, whereas 4/30 of BNW tumours had a Tpeak <63.5 s. Two malignant tumours had Tpeak <43 s. WR180 had an accuracy of 100% for differentiation between Warthin and BNW tumours, 87.3% between BNW and malignant, and 93.3% between Warthin and malignant tumours. 29 (96.7%) BNW tumours had a washout <4.60%, while 8 (80%) malignant tumours had a washout >4.60%. All Warthin tumours had a WR180 >22%, while two malignant tumours had a WR180 >22%. 29/30 of BNW tumours demonstrated TIC curve Type A and 1 tumour demonstrated Type C. 6/10 of malignant tumours had TIC Type C, 2 had TIC Type A and 2 Type B. All Warthin tumours were categorized as Type B. CONCLUSIONS: This study showed that DCE-MRI could be helpful in pre-operative differentiation of SGTs; especially for discrimination between Warthin and BNW tumours.