1. 11C-methionine positron emission tomography for differential diagnosis between radiation injury and tumor recurrence in the patients with brain metastasis after stereotactic radiosurgery.
- Author
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K. Yatsushiro, M. Ogita, K. Nakamura, and T. Fujimoto
- Subjects
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RADIATION injuries , *STEREOTACTIC radiosurgery , *STEREOTACTIC radiotherapy , *TUMOR treatment , *POSITRON emission tomography , *DIFFERENTIAL diagnosis , *THERAPEUTICS - Abstract
Purpose: Radiation injury is one of the most important problems after stereotactic radiosurgery (SRS) and radiotherapy (SRT). However differential diagnosis between radiation injury and tumor recurrence is difficult. We evaluate availability of 11C-Methionine positron emission tomography (Met-PET) in differential diagnosis after SRS and SRT in the patient with brain metastasis. Material and Method: Between January 2008 and May 2012, 42 patients who had expanding lesion of brain metastasis after stereotactic radiosurgery and radiotherapy were engaged on this study. Primary lesions of brain metastasis were lung cancer in 28 cases, breast cancer in 7cases, ovarian cancer in 3 cases and others in 4 cases. Gamma knife radiaosurgery and Cyberknife radiotherapy were performed in 30 cases and 12 cases, respectively. Met-PET images were obtained as a static scans of 10 minutes performed 20 minutes after injection of 11C-methionine. On Met-PET scans, the portion of the tumor with the highest accumulation was selected as the region of interest (ROI), tumor-versus-normal ratio (TN ratio) was defined as the ratio of the standardized uptake value (SUV) in the tumor (T), divided by SUV in normal gray matter (N). Met-PET scan accuracy was evaluated by histological assessment from removed tissue (12 cases) or, in cases without surgery or biopsy, by the subsequent MR findings (30 cases). Result: Met-PET images were obtained 459 days after SRS or SRT. Maximum TN ratio was 1.16 in the cases with radiation necrosis (25 cases) and 1.74 in the cases with tumor recurrence (14 cases). The cut-off value of SUV was about 1.5. Subsequent Met-PET was performed in the patients who had around 1.5 in the SUV and could not be evaluated differential diagnosis from initial Met-PET only. Maximum TN ratio elevated from 1.38 to 1.69 in the cases with recurrence. However, in the cases with radiation necrosis, it did not changed from 1.16 to 1.26. Conclusion: Met-PET proved useful for differential diagnosis for radiation injury and tumor recurrence. If the initial Met-PET could not reach diagnosis, subsequent examination was available for differential diagnosis. Disclosure: No significant relationships. [ABSTRACT FROM AUTHOR]
- Published
- 2013