Simultaneous 68Ga-DOTATOC-PET/MRI for IMRT treatment planning for meningioma: first experience

Int J Radiat Oncol Biol Phys. 2011 Sep 1;81(1):277-83. doi: 10.1016/j.ijrobp.2010.10.078. Epub 2011 Feb 6.

Abstract

Purpose: To evaluate intensity-modulated radiotherapy (IMRT) treatment planning based on simultaneous positron-emission tomography and magnetic resonance imaging (PET/MRI) of meningioma.

Methods and materials: A meningioma patient was examined prior to radiotherapy with dedicated planning computed tomography (CT), MRI, PET/CT with gallium-68-labeled DOTATOC (68Ga-DOTATOC), and simultaneous 68Ga-DOTATOC-PET/MRI. The first gross target volume (GTV) was defined based on a combination of separate MR and 68Ga-DOTATOC-PET/CT imaging (GTVPET/CT+MR). Then, the simultaneous PET/MR images were used to delineate a second GTV (GTVPET/MR) by following exactly the same delineation strategy. After an isotropic expansion of those volumes by a 4-mm safety margin, the resulting planning target volumes (PTVs) were compared by calculating the intersection volume and the relative complements. A cross-evaluation of IMRT plans was performed, where the treatment plan created for the PTVPET/CT+MR was applied to the PET/MR-based PTVPET/MR.

Results: Generally, target volumes for IMRT treatment planning did not differ between MRI plus 68Ga-DOTATOC-PET/CT and simultaneous PET/MR imaging. Only in certain regions of the GTV were differences observed. The overall volume of the PET/MR-based PTV was approximately the same as that obtained from PET/CT data. A small region of infiltrative tumor growth next to the main tumor mass was better visualized with combined PET/MR due to smaller PET voxel sizes and improved recovery. An IMRT treatment plan was optimized for the PTVPET/CT+MR. The evaluation of this plan with respect to the PTVPET/MR showed parts of the target volume that would not have received the full radiation dose after delineation of the tumor, based on simultaneous PET/MR.

Conclusion: This case showed that differences in target volumes delineated on the basis of separate MR and PET/CT and simultaneous PET/MR may be observed that can have significant consequences for an effectively applied radiotherapy treatment plan.

Publication types

  • Case Reports
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Female
  • Gallium Radioisotopes
  • Humans
  • Incidental Findings
  • Magnetic Resonance Imaging / methods*
  • Meningeal Neoplasms / diagnosis*
  • Meningeal Neoplasms / diagnostic imaging
  • Meningeal Neoplasms / pathology
  • Meningioma / diagnosis*
  • Meningioma / diagnostic imaging
  • Meningioma / pathology
  • Neoplasm Recurrence, Local / diagnosis
  • Neoplasm Recurrence, Local / diagnostic imaging
  • Neoplasm Recurrence, Local / pathology
  • Octreotide / analogs & derivatives*
  • Organometallic Compounds*
  • Positron-Emission Tomography / methods*
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Radiotherapy, Intensity-Modulated / methods*
  • Tomography, X-Ray Computed / methods
  • Tumor Burden

Substances

  • Ga(III)-DOTATOC
  • Gallium Radioisotopes
  • Organometallic Compounds
  • Octreotide