[Use of real-time system of portal imaging in the daily monitoring of patients treated by radiotherapy for thoracic cancer].

Purpose: Retrospective analysis of the results obtained with daily interactive use of portal imaging for monitoring thoracic cancer radiotherapy.

Materials And Methods: A Siemens electronic portal imaging system called Beamviewplus was used daily in 15 lung cancer patients for each X-ray field. Out of the 714 expected portal images, 585 (82%), were obtained and printed.

Results: We counted 94 errors in the 585 successful controls (16%). Four main classes of errors were identified: irradiation field placement (47 cases, 50%), shielding placement (30 cases, 32%) patient's position on the till examining table (14 cases, 15%), and selection of the energy (3 cases, 3%). Forty percent of these errors were potentially serious in terms of treatment volume and vital organ protection.

Conclusion: Only portal imaging control could easily detect errors because they occurred randomly. We thus consider the use of this daily system helpful for patient management.