Abstract
Positron emission tomography (PET) is an imaging technique utilizing radioisotopes. Most radioisotopes used for nuclear medicine imaging procedures decay by releasing energy as gamma rays. These photons are detected by gamma cameras using either the planar or SPECT mode. Other radioisotopes decay by positron emission. The high-energy photons are emitted at 180 degrees to each other and detected simultaneously by opposing detectors on the PET scanner. The image quality of PET is better than a gamma camera image. Today the field of PET is growing exponentially because it facilitates detection of cancer throughout the body without pain. The clinical uses of FDG-PET are to distinguish a benign from a malignant tumor, to determine the staging, to detect distant metastasis and/or recurrence, to evaluate the effectiveness of treatment response, and to estimate the prognosis. Since 2002 the Japanese government approves reimbursement of FDG-PET costs under the national health insurance program for ten types of tumor. Currently there are many PET centers engaged in cancer screening all over Japan. PET centers require a cyclotron unit with many staff members to serve as radiopharmacists. FDG-PET is not an all-around method for tumor imaging, and we have to diagnose images with consideration of normal distribution of F-18 FDG in the body and reference to morphological images. The development of PET/CT and new radiopharmaceuticals promises to play an important role in routine tumor imaging in the coming years.
