A dosimetric evaluation of IGART strategies for cervix cancer treatment. Issue 10 (October 2016)

• Record Type: Journal Article
• Authors: O'Reilly, Frederika H.J.; Shaw, William
• Is Part Of: Physica medica. Volume 32:Issue 10(2016)
• Page Start: 1360
• Page End: 1367
• Publication Date: 2016-10
• Subjects: On-line -- Off-line -- IGART -- Cervix cancer -- EUD; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2016.06.003
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: A fixed margin approach yields a significant probability of CTV under-dosage. Both off-line and on-line adaptive strategies can restore CTV coverage to initial intended dose with notable OAR sparing. Considering workload and time on the treatment machine, the off-line strategy proves to be sufficient and more practical. Abstract: Purpose: Image guided adaptive radiotherapy (IGART) strategies can be used to include the temporal aspects of radiotherapy treatment. A dosimetric evaluation of on- and off-line adaptive strategies are done in this study. Methods: A library of equivalent uniform dose (EUD)-based Intensity Modulated Radiotherapy Treatment plans with incrementally increasing clinical target volume (CTV)-to-planning target volume (PTV) margins were developed for 10 patients. Utilizing daily computed tomography (CT) images an on-line strategy using a margin-of-the-day (MOD) concept that selects the best plan from the library was employed. This was compared to an off-line strategy with full analysis of accumulated dose between fractions where dosimetric deviations from the treatment intent triggered plan adaptation. A fixed margin treatment approach was used as benchmark. Results: Using fixed margins of <15 mm lead to under-dosages of more than 5 Gy in total delivered dose. The average CTV EUD for the off-line and on-line strategy was 50.0 ± 5.0 Gy and 50.4 ± 2.0 Gy respectively and OAR doses were comparable. Conclusion: A fixed margin treatment approach yields a significant probability of CTV under-dosage. Using EUD dose metrics CTV coverage can be restored in both the off-line and on-line adaptive strategies at acceptable OAR dose levels. Considering the workload and time on the treatment machine, the off-line strategy proves to be sufficient and more practical.