Intraoperative 3D quantitative magnetic resonance imaging in paediatric brain tumour surgery

What is it about?

The accuracy of R1 and R2, the effect of B1+-field inhomogeneity and how the flex coil position affected R1 and R2 were evaluated, both pre- and intraoperatively during surgery. Ten patients were recruited, six girls and four boys aged 2–15 years, with varying tumour entities, all referred to surgery with intraoperative MR. The patients were scanned using a head coil preoperatively and flex coils intraoperatively. Control experiments were performed on phantoms in various positions, equivalent to the patient positions. ROIs (Regions of Interest) were positioned in areas representing normal-appearing matter. Relaxation rates R1 and R2 were calculated from 3D-quantification using an interleaved Look-Locker acquisition sequence with T2 preparation pulse (3D-QALAS) data.

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Photo by Accuray on Unsplash

Photo by Accuray on Unsplash

Why is it important?

Broader goals; • To investigate whether R1 and R2 can be measured reliably with 3D quantitative MRI in an intraoperative environment during pediatric brain tumor surgery. • To determine whether B1+ inhomogeneities affect R1 and R2 measurements in normal-appearing white matter and thalamus, respectively, and how R1 and R2 measurements are influenced by different coils. • To assess how the relaxation parameters of brain tissue are affected by the intraoperative environment. The results show a significant increase in R2 in the intraoperative environment compared to the preoperative 3D-QALAS measurements. This contrasts with the controls where the use of relaxation phantoms did not show similar differences. We conclude that relaxometry appears feasible in the intraoperative environment. The observed differences between the quantitative R2 values in tissue pre- and intraoperatively seem to be explainable by the physiological conditions characteristic of the surgical situation.