COMPUTED TOMOGRAPHIC SIMULATION OF CRANIOSPINAL FIELDS IN PEDIATRIC-PATIENTS - IMPROVED TREATMENT ACCURACY AND PATIENT COMFORT

Purpose: To reduce the time required for planning and simulating crani ospinal fields through the use of a computed tomography (CT) simulator and virtual simulation, and to improve the accuracy of field and shie lding placement. Methods and Materials: A CT simulation planning techn ique was developed, Localization of critical anatomic features such as the eyes, cribriform plate region, and caudal extent of the thecal sa c are enhanced by this technique. Over a 2-month period, nine consecut ive pediatric patients were simulated and planned for craniospinal irr adiation. Four patients underwent both conventional simulation and CT simulation. Five were planned using CT simulation only, The accuracy o f CT simulation was assessed by comparing digitally reconstructed radi ographs (DRRs) to portal films for all patients and to conventional si mulation films as well in the first four patients. Results: Time spent by patients in the CT simulation suite was 20 min on average and 40 m in maximally for those who were noncompliant, Image acquisition time w as <10 min in all cases. In the absence of the patient, virtual simula tion of all fields took 20 min. The DRRs were in agreement with portal and/or simulation films to within 5 mm in five of the eight cases. Di screpancies of greater than or equal to 5 mm in the positioning of the inferior border of the cranial fields in the first three patients wer e due to a systematic error in CT scan acquisition and marker contouri ng which was corrected by modifying the technique after the fourth pat ient, In one patient, the facial shield had to be moved 0.75 cm inferi orly owing to an error in shield construction, Conclusions: Our analys is showed that CT simulation of craniospinal fields was accurate. It r esulted in a significant reduction in the time the patient must be imm obilized during the planning process. This technique can improve accur acy in field placement and shielding by using three-dimensional CT-aid ed localization of critical and target structures. Overall, it has imp roved staff efficiency and resource utilization. (C) 1998 Elsevier Sci ence Inc.