DESIGN OF A FULLY INTEGRATED 3-DIMENSIONAL COMPUTED-TOMOGRAPHY SIMULATOR AND PRELIMINARY CLINICAL-EVALUATION

Purpose: We describe the conceptual structure and process of a fully i ntegrated three-dimensional (3-D) computed tomography (CT) simulator a nd present a preliminary clinical and financial evaluation of our curr ent system. Methods and Materials: This is a preliminary report on 117 patients treated with external beam radiation therapy alone on whom a 3-D simulation and treatment plan and delivery were carried out from July 1, 1992, through June 30, 1993. The elements of a fully integrate d 3-D CT simulator were identified: (a) volumetric definition of tumor volume and patient anatomy obtained with a CT scanner, (b) virtual si mulation for beam setup and digitally reconstructed radiographs, (c) 3 -D treatment planning for volumetric dose computation and plan evaluat ion, (d) patient-marking device to outline portal on patient's skin, a nd (e) verification (physical) simulation to verify portal placement o n the patient. Actual time-motion (time and effort) recording was made by each professional involved in the various steps of the 3-D simulat ion and treatment planning on computer-compatible forms. Data were cor related with the anatomic site of the primary tumor being planned. Cos t accounting of revenues and operation of the CT simulator and the 3-D planning was carried out, and projected costs per examination, depend ing on case load, were generated. Results: Average time for CT volumet ric simulation was 74 min without or 84 min with contrast material. Av erage times were 36 min for contouring of tumor/target volume and 44 m in for normal anatomy, 78 min for treatment planning, 53 min for plan evaluation/optimization, and 58 min for verification simulation, There were significant variations in time and effort according to the speci fic anatomic location of the tumor. Portal marking of patient on the C T simulator was not consistently satisfactory, and this procedure was usually carried out on the physical simulator. Based on actual budgeta ry information, the cost of a volumetric CT simulation (separate from the 3-D treatment planning) showed that 1500 examinations per year (si x per day in 250 working days) must be performed to make the operation of the device cost effective. The same financial projections for the entire 3-D planning process and verification yielded five plans per da y. Some features were identified that will improve the use of the 3-D simulator, and solutions are offered to incorporate them in existing d evices. Conclusions: Commercially available CT simulators lack some el ements that we believe are critical in a fully integrated 3-D CT simul ator. Sophisticated 3-D simulation and treatment planning can be carri ed out in a significant number of patients at a reasonable cost. Time and effort and therefore cost vary according to the anatomic site of t he tumor being planned and the number of procedures performed. Further efforts are necessary, with collaboration of radiation oncologists, p hysicists, and manufacturers, to develop more versatile and efficient 3-D CT simulators, and additional clinical experience is required to m ake this technology cost effective in standard radiation therapy of pa tients with cancer.