The added value of advanced neuro-imaging (MR diffusion, perfusion and proton spectroscopy) in diagnosis of primary CNS lymphoma

Abstract

Introduction: Primary CNS lymphoma is difficult to diagnose with conventional imaging modalities. Magnetic resonance proton spectroscopy, dynamic susceptibility contrast DSC perfusion and diffusion weighted images have been recently investigated as a problem-solving tool for evaluation of primary CNS lymphoma with favorable results.
Aim of the work: To assess the value of advanced neuro-imaging (MR diffusion, perfusion and proton spectroscopy) in diagnosis of primary CNS lymphoma.
Patients and methods: Five adult patients with suspected primary CNS lymphoma (as suggested by clinical or conventional imaging techniques) were prospectively studied by magnetic resonance proton spectroscopy, dynamic susceptibility contrast DSC perfusion and diffusion weighted images aiming to confirm the suspected diagnosis. The examinations were done on 1.5T machines using diffusion weighted, dynamic susceptibility contrast perfusion and chemical shift CSI imaging sequences.
Results: Regarding DWI, all patients show low ADC values ranging from 0.61 to 0.67 · 10^-3 mm²/s with a mean ADC value of 0.63 ±0.025(SD) 10^-3 mm²/s, regarding the DSC perfusion. The max rCBV ratios are ranging from 0.23 to 1.52 with a mean ratio of 1.14 ± 0.54(SD). Regarding the MRI spectroscopy Cho/Cr ratios are ranging from 1.9 to 63 with a mean ratio of 19.16 ±26 (SD), Cho/NAA ratios are ranging from 3.7 to 50 with a mean ratio of 14.8± 19.8, NAA/Cr ratios are ranging from 0.09 to 1.6 with a mean ratio of 0.72 ±0.59, NAA/Cho ratios are ranging from 0.02 to 0.3 with a mean ratio of 0.19 ± 0.1 Lactate peak was found in three cases. Lipid peak was found in two cases. Myo inositol peak was found in one case. 
Conclusions: Restricted diffusion, relative hypo perfusion, increased Cho/Cr, Cho/NAA, decreased NAA/Cho, NAA/Cr and presence of lactate or lipid peaks are consistent imaging finding in CNS lymphoma.

KEYWORDS Primary central nervous system lymphoma; Magnetic resonance imaging; Diffusion weighted images; Perfusion weighted images; Proton magnetic resonance spectroscopy