Target definition by C11-methionine-PET for the radiotherapy of brain metastases

Int J Radiat Oncol Biol Phys. 2009 Jul 1;74(3):714-22. doi: 10.1016/j.ijrobp.2008.08.056. Epub 2008 Dec 25.


Purpose: To evaluate the ability of 11C-methionine positron emission tomography (MET-PET) to delineate target volumes for brain metastases and to investigate to what extent tumor growth is presented by magnetic resonance imaging (MRI) and MET-PET.

Materials and methods: Three observers undertook target definition in 19 patients with 95 brain metastases by MRI and MET-PET images. MRI gross target volume (GTV) (GTV-MRI) was defined as the contrast-enhanced area on gadolinium-enhanced T1-weighted MRI. MET-PET GTV (GTV-PET) was defined as the area of an accumulation of MET-PET apparently higher than that of normal tissue on MET-PET images. The size of occupation ratio was determined using the following equation: SOR (%) of MET are within x mm margin outside GTV-MRI = the volume of the GTV-PET within x mm outside the GTV-MRI/the volume of the GTV-PET.

Results: For GTV-MRI volumes of <or=0.5 mL, the sensitivity of tumor detection by MET-PET was 43%. For GTV-MRI volume of >0.5 mL, GTV-PET volumes were larger than GTV-MRI volumes and a significant correlation was found between these variables by linear regression. For all tumor sizes and tumor characteristics, a 2-mm margin outside the GTV-MRI significantly improved the coverage of the GTV-PET.

Conclusions: Although there were some limitations in our study associated with spatial resolution, blurring effect, and image registrations with PET images, MET-PET was supposed to have a potential as a promising tool for the precise delineation of target volumes in radiotherapy planning for brain metastases.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Aged
  • Aged, 80 and over
  • Brain Neoplasms / diagnostic imaging*
  • Brain Neoplasms / pathology
  • Brain Neoplasms / radiotherapy
  • Brain Neoplasms / secondary*
  • Breast Neoplasms / pathology
  • Carbon Radioisotopes*
  • Carcinoma, Non-Small-Cell Lung / diagnostic imaging
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Carcinoma, Non-Small-Cell Lung / radiotherapy
  • Carcinoma, Non-Small-Cell Lung / secondary
  • Female
  • Gadolinium
  • Humans
  • Lung Neoplasms / pathology
  • Magnetic Resonance Imaging / methods
  • Male
  • Methionine*
  • Middle Aged
  • Positron-Emission Tomography / methods*
  • Sensitivity and Specificity
  • Tumor Burden*


  • Carbon Radioisotopes
  • carbon-11 methionine
  • Methionine
  • Gadolinium