Computed tomography in therapy planning: Pelvic region

Since computed tomographic (CT) body scanning became generally available in 1977, it has proved valuable in diagnosing the extent of tumors as well as in the dynamic physiological localizing of certain pelvic organs for radio-oncologic treatment. CT provides a contour at multiple levels of tumor and frequently demonstrates disease not shown on other x-ray studies; it may also define nonpalpable disease. CT scans help to decide if the tumor is so extensive that a palliative pre- or postoperative approach is necessary. It also permits following tumor regression with decreasing portal size. CT is being used to refine tumor dose calculations by providing accurate density and inhomogeneity factors. Several authors have reported improved accurate density and inhomogeneity factors. Several authors have reported improved accuracy of dosimetry with CT data; it is hoped that the 30% alteration in treatment planning from information learned from CT scans will result in improved palliation, decreased injury to normal tissue, and increased survival. This chapter reviews the role of CT scanning in radio-oncologic treatment planning of the pelvis, i.e., bladder carcinoma (CA), prostate CA, recurrent rectal CA, gynecologic malignancy, and lymph nodal involvement in cancer and lymphoma