67. The Cancer Functional Diagnosis and the Evaluation of Therapeutic Effects Using Magnetic Resonance Imaging and Spectroscopy

Masahisa Koga, Kyosan Yoshikawa, Takayuki Obata, Hirotoshi Kato, Susumu Kandatsu, Masanori Kanai, Junetsu Mizoe, Hirohiko Tsujii, Katsuya Yoshida, Tetsuya Suhara, Kazutoshi Suzuki, and Hiroshi Yoshioka

Keywords: brain neoplasm, magnetic resonance spectroscopy, positron emission tomography, heavy ion therapy, choline

Thirty-eight patients with brain neoplasms were treated by heavy ion therapy and then followed for more than 12 months. After heavy ion therapy, brain damage due to high radiation dose, radiation encepharitis and necrosis occurs occasionary. But CT and MRI of a recurrent tumor are similar to those of necrosis and encepharitis. Differential diagnosis of brain necrosis and irradiation with regrowth of brain tumor are difficult with MRI and CT.

We studied 1H-CSI and PET (11C-methionine and 18F-Deoxyglucose) in cases of gliomas before and after heavy ion therapy. We compared each pattern of MRS signal (NAA, choline, creatinine, and lactate), and PET images before and after heavy ion radiation therapy. In cases of brain necrosis, loss of choline signal was observed in 7 of 9 cases, but a slight accumulation of methionine was seen in the PET study. In cases of regrowth tumor, elevation of choline signal was significant. MRS diagnosis had 90% sensitivity, 76% specificity, and 83% total accuracy. Methionine PET diagnosis for the same group had 100% sensitivity, 71% specificity and 88% total accuracy. MRS study of brain tumor after irradiation is highly sensitive in the diagnosis of tumor necrosis or recurrance.