64. Clinical Application of Autoactivation PET Imaging Derived from C-12 Ion Radiotherapy and Its Fusion Imaging with Therapy Planning CT.

Kyosan Yoshikawa, Takehiro Tomitani, Mitsutaka Kanazawa, Tatsuaki Kanai, Katsumi Tamura, Takashi Tomemori, Susumu Kandatsu, Junetsu Mizoe, Fumio Shishido, Hiroshi Fukuda and Hirohiko Tsujii.

Keywords: autoactivation, carbon ion radiotherapy, HIMAC, PET, CT, fusion imaging

Clinical application of PET imaging of auto activation derived from C-12 ion radiotherapy (HIMAC) was studied. It is very important to perform the PET measurements under exactly the same patient positioning as in HIMAC therapy to compare RI distributions. We performed some clinical PET measurements and got superimposed images of PET and CT planning of HIMAC therapy patients. We tried to use a fitting method, the automatic multi modality image registration method (AMIR method) of the Dr. View applications. In this method, we fitted the transmission images of PET to planning CT images at the start, and then superimposed emission images on the planning CT images. Our fitting results were relatively good. But some problems were identified. The most important one was due to the difference in patients breathing phases between PET examination and CT imaging. The difference of patients breathing phases should cause fitting errors of the fusion images of PET and CT especially in chest and abdominal regions. To confirm this, we investigated a lung cancer patient who received HIMAC therapy with 15.0 GyE dose per fraction, totally 4 fractions (60 GyE). A PET measurement was done immediately after an irradiation. Two sets of CT images were also taken in both expiration phase and inhalation phase. PET fusion images with the two sets of CT images were calculated and compared with each fusion image. The PET fusion image with CT image in the expiration phase resulted in better quality compared to that in the inhalation phase. We think that the breathing phases of PET and CT should be in phase with each other to perform precise fitting of the two modalities.