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SU‐FF‐T‐119: Comparison of Compensator‐IMRT and Segmental MLC‐IMRT Techniques: A Retrospective Study On Treatment Time, Monitor Units, and Dosimetry in Clinical Application
Author(s) -
Chang S,
Levinson L,
Potter L,
Deschesne K,
Eljabaly K
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2760777
Subject(s) - dosimetry , medicine , medical physics , nuclear medicine , quality assurance , pathology , external quality assessment
Purpose: There are more than 150 radiotherapy centers in the US using compensators to deliver IMRT treatments. However, compensator‐IMRT is still not a well‐understood technique to many; better knowledge of the technology can encourage acceptance and proper use of this valuable IMRT delivery technology. We will present our compensator‐IMRT experience in clinical application using retrospective patient treatment data from eleven years (1100 patients) of compensator‐IMRT experience and five years (500 patients) of segmental MLC‐IMRT in parallel. Method and Materials: IMRT plans are designed by the in‐house IMRT TPS PLanUNC. The resulting continuous intensity maps are used for compensator design. The intensity maps are converted to discrete maps for MLC segment generation if segmental MLC‐IMRT technique is used. Compensators are fabricated using a Par Scientific milling machine and granular compensator material. This study uses data from the treatment R&V system and PLanUNC for both IMRT delivery techniques. IMRT dosimetry is compared between the two IMRT delivery techniques in terms of DVH and EUD. Results: Retrospective analysis of more than 200 clinical cases treated at our institution showed that 1) compensator‐IMRT treatment delivery time (time lapsed between the beam‐on of the 1st field and the beam‐off of the last field/segment) is significantly faster than segmental MLC‐IMRT, especially for treatments with large number of fields; 2) both IMRT delivery techniques use similar monitor units; and 3) the high spatial resolution compensator‐IMRT generally has a similar or better dosimetric quality compared to the segmental MLC‐IMRT technique. Conclusion: We evaluated both the compensator‐IMRT and segmental MLC‐IMRT delivery techniques in terms of treatment delivery time, treatment monitor units, and dosimetric quality (DVH and EUD). Our experience demonstrated that the compensator‐IMRT technique delivered high quality IMRT dosimetry, fast IMRT treatments, and similar monitor units compared to the segmental MLC‐IMRT technique.