The utilization of PET has been increased so fast since the usefulness of the PET has been proved in various clinical and research fields. Among the many applications, the PET is especially useful in oncology and most of the clinical PET scans are performed for the oncologic examination including the different diagnosis of malignant and benign tumors and assessment of the treatment effects and recurrent tumors. As the PET-CT scanners are widely available, there is increasing interest in the application of the PET images to the radiation treatment planning. Although the CT images are conventionally used for the target volume determination in the radiation treatment planning, there are fundamental limitation in use of only the anatomical information. Therefore, the volume determination of the functionally active tumor region using the PET would be important for the treatment planning. However, the accurate determination of the tumor boundary is not simple in PET due to the relatively low spatial resolution of the currently available PET scanners. In this study, computer simulations were performed to study the relationship between the lesion size, PET resolution, lesion to background ratio and the threshold of image intensity to determine the true tumor volume.

KeywordsPET, Radiation treatment planning, Optimal threshold, Volume determination