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MR-spectroscopy guided target delineation for high-grade gliomas
A Pirzkall1, T R McKnight, E E Graves
1Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA 94143-0226, USA. pirzkall@radonc17.ucsf.edu
Summary
Magnetic Resonance Spectroscopy (MRS) may offer a more accurate method than standard MRI for defining active brain tumor volumes in radiation therapy planning. This could improve treatment efficacy and reduce complications.
Area of Science:
- Neuro-oncology
- Radiology
- Medical Physics
Background:
- Magnetic Resonance Imaging (MRI) is crucial for malignant brain tumor assessment.
- However, functional/metabolic information from Magnetic Resonance Spectroscopy (MRS) suggests MRI may not reliably indicate active or microscopic disease.
- This study investigates the impact of MRS on radiation therapy (RT) target volumes for high-grade gliomas.
Purpose of the Study:
- To assess the impact of MR-spectroscopy (MRSI) on radiation therapy target volumes for high-grade gliomas.
- To compare MRSI-defined active tumor volumes with standard MRI-based volumes (T1 contrast enhancement, necrosis, T2 hyperintensity).
Main Methods:
- Evaluated 34 high-grade glioma patients (22 Grade III, 12 Grade IV astrocytomas) with pre-operative MRI and MRSI.
- Contoured MRI for T1, necrosis, and T2 regions.
- Used a multivoxel MRSI technique to assess choline (Cho) and N-acetylaspartate (NAA) metabolite levels via an abnormality index (AI).
- Aligned and compared 3D AI contours with MRI-defined volumes.
Main Results:
- MRSI revealed metabolically active tumor extending beyond T2 regions in 88% of patients, by up to 28 mm.
- T2 regions underestimated microscopic disease extent compared to MRSI.
- T1 contrast enhancement suggested smaller volumes and different active disease locations than MRSI.
Conclusions:
- Incorporating MRSI into RT treatment planning can increase and relocate boost dose volumes.
- It may also reduce standard dose volumes.
- MRSI has the potential to improve tumor control and minimize treatment-related complications.