Clinical utility of intraoperative Arterial Spin Labeling for resection control in brain tumor surgery at 3 T

Abstract

Resection control in brain tumor surgery can be achieved in real time with intraoperative MRI (iMRI). Arterial spin labeling (ASL), a technique that measures cerebral blood flow (CBF) noninvasively without the use of intravenous contrast agents, can be performed intraoperatively providing morpho-physiological information.

This study aimed to evaluate the feasibility, image quality and potential to depict residual tumor of a pseudo-continuous-ASL (PCASL) sequence at 3T. 17 patients with brain tumors, primary (16) or metastatic (1), undergoing resection surgery with iMRI-monitoring were prospectively recruited (9 men, age:56±16.6 years).

A PCASL sequence with long labeling duration (3000ms) and postlabeling delay (2000ms) was added to the conventional protocol that consisted of pre- and post-contrast 3D-T1-weighted (T1w) images, optional 3D-FLAIR, and diffusion. Three observers independently assessed image quality (4-point scale) of PCASL-derived CBF maps. In those with diagnostic quality (scores 2-4) they evaluated the presence of residual tumor using the conventional sequences first, and the CBF maps afterwards (3-point scale). Inter-observer agreement for image quality and the presence of residual tumor was assessed using Fleiss-kappa statistics. Intraoperative CBF-ratio of the surgical margins (i.e., perilesional CBF values normalized to contralateral gray matter CBF) was compared to preoperative CBF-ratio within the tumor (Wilcoxon's test).

Diagnostic ASL image quality was observed in 94.1% of patients (inter-observer Fleiss-κ=0.76). PCASL showed additional foci suspicious of high-grade residual component in three patients, and a hyperperfused area extending outside the enhancing component in one patient. Interobserver agreement was almost perfect in the evaluation of residual tumor with the conventional sequences (Fleiss-κ=0.92) and substantial for PCASL (Fleiss-κ=0.80). No significant differences were found between pre and intraoperative CBF-ratios (p=0.578) in patients with residual tumor (n=7). iMRI-PCASL perfusion is feasible at 3T and is useful for the intraoperative assessment of residual tumor, providing in some cases additional information to the conventional sequences.

CITA DEL ARTÍCULO  NMR Biomed. 2023 Mar 26;e4938. doi: 10.1002/nbm.4938