Proton MRS imaging in pediatric brain tumors

Abstract

Magnetic resonance (MR) techniques offer a noninvasive, non-irradiating yet sensitive approach to diagnosing and monitoring pediatric brain tumors. Proton MR spectroscopy (MRS), as an adjunct to MRI, is being more widely applied to monitor the metabolic aspects of brain cancer. In vivo MRS biomarkers represent a promising advance and may influence treatment choice at both initial diagnosis and follow-up, given the inherent difficulties of sequential biopsies to monitor therapeutic response. When combined with anatomical or other types of imaging, MRS provides unique information regarding biochemistry in inoperable brain tumors and can complement neuropathological data, guide biopsies and enhance insight into therapeutic options. The combination of noninvasively acquired prognostic information and the high-resolution anatomical imaging provided by conventional MRI is expected to surpass molecular analysis and DNA microarray gene profiling, both of which, although promising, depend on invasive biopsy. This review focuses on recent data in the field of MRS in children with brain tumors.

Advanced Techniques and Applications in Magnetic Resonance Spectroscopy for Pediatric Patients

“…Also, information gained from MRS has been used to guide biopsies, predict histologic aggressiveness/grade, and assess response to treatment. 4 The fundamental metabolites that are often evaluated by MRS are listed in ►Table 1. The MRS hallmark of brain tumors relative to normal tissue is increased choline (Cho) and decreased N-acetyl aspartate (NAA) levels.…”

“…30,31 Pediatric brain tumor metabolic profiles typically do not change significantly from diagnosis to the first relapse and thus can aid in the confirmation of recurrent/progressive disease. 4 The assessment of treatment response has traditionally been described using CSI MRS technique. Longitudinal studies in the evaluation of Cho/NAA ratios in patients with radiation therapy both in enhancing and nonenhancing components of the lesion demonstrate a decrease of this ratio at the response and increase at the recurrence of the tumor.…”

“…The disadvantage, however, is the overlap of the metabolite peaks. 4 Long TEs (135-288 ms) provide a clearer spectrum with sharper peaks and less metabolite overlap. However, fewer metabolites are detected, and the SNR is not as good as short echo technique.…”

“…However, fewer metabolites are detected, and the SNR is not as good as short echo technique. 4 Ultimately, the most important factor in the clinical application of MRS is not necessarily which technique is utilized, but the ability to adhere to that specific technique to generate consistent, comparable spectra over a long period with the same protocol.…”

Magnetic resonance spectroscopy in pediatric brain tumors: how to make a more confident diagnosis

“…MRS has been proven to provide additional clinically relevant information for several pediatric neurological disease processes such as brain tumors, infectious processes, white matter disorders, and neonatal injury [3]. When combined with high resolution anatomical imaging provided by conventional MRI, MRS biomarkers can complement neuropathological data and enhance insight into therapeutic options [4]. Although MRS is becoming widely available, few studies have evaluated how it can enhance conventional radiological reporting by adding value to information obtained through MRI alone [5].…”