Target Definition by C11-Methionine-PET for the Radiotherapy of Brain Metastases
Received 2 April 2008; accepted 26 August 2008. published online 18 December 2008.
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 × mm margin outside GTV-MRI = the volume of the GTV-PET within × mm outside the GTV-MRI/the volume of the GTV-PET.
Results
For GTV-MRI volumes of ≤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.
∗Department of Radiation Oncology, Chubu Medical Centre for Prolonged Traumatic Brain Dysfunction, Kizawa Memorial Hospital, Minokamo, Japan
†Department of Neurosurgery, Chubu Medical Centre for Prolonged Traumatic Brain Dysfunction, Kizawa Memorial Hospital, Minokamo, Japan
‡Department of Radiology, Kizawa Memorial Hospital, Minokamo, Japan
§Department of Neurosurgery, Gifu University School of Medicine, Gifu, Japan
‖Department of Radiology, Gifu University School of Medicine, Gifu, Japan
Reprint requests to: Masayuki Matsuo, M.D., Department of Radiation Oncology, Kizawa Memorial Hospital, 590 Shimokobi, Minokamo 505–8503, Japan. Fax: (+81) 574-25-2181; Phone: (+81) 574-26-2181
Parts of this article were presented at 49th Annual Meeting of American Society for Therapeutic Radiation Oncology (ASTRO), October 28–November 1, 2007, Los Angeles, CA.
ABSTRACT