MR-spectroscopy guided target delineation for high-grade gliomas

Purpose: Functional/metabolic information provided by MR-spectroscopy (MRSI ) suggests MRI may not be a reliable indicator of active and microscopic di sease in malignant brain tumors. We assessed the impact MRSI might have on the target volumes used for radiation therapy treatment planning for high-g rade gliomas. Methods and Materials: Thirty-four patients (22 Grade III; 12 Grade IV astr ocytomas) were evaluated; each had undergone MRI and MRSI studies before su rgery, MRI data sets were contoured for T1 region of contrast enhancement ( T1), region of necrosis, and T2 region of hyperintensity (T2), The three-di mensional MRSI peak parameters for choline (Cho) and N-acetylaspartate (NAA ), acquired by a multivoxel technique, were categorized based on an abnorma lity index (AI), a quantitative assessment of tissue metabolite levels. The AI data were aligned to the MRI and displayed as three-dimensional contour s. AI vs. T conjoint and disjoint volumes were compared. Results: For both grades, although T2 estimated the region at risk of micro scopic disease as being as much as 50% greater than by MRSI, metabolically active tumor still extended outside the T2 region in 88% of patients by as many as 28 mm. In addition, T1 suggested a lesser volume and different loca tion of active disease compared to MRSI. Conclusion: The use of MRSI to define target volumes for RT treatment plann ing would increase, and change the location of, the volume receiving a boos t dose as well as reduce the volume receiving a standard dose, Incorporatio n of MRSI into the treatment-planning process may have the potential to imp rove control while reducing complications. (C) 2001 Elsevier Science Inc.