A comprehensive dosimetric study on switching from a Type-B to a Type-C dose algorithm for modern lung SBRT

Autor: Christina Zhou, Andrew O. Wahl, Shuo Wang, Xiaoying Liang, Weining Zhen, Sumin Zhou, Megan A Hyun, Dandan Zheng, Nathan R. Bennion, R Ma, Xiaobo Li, Kristina Zvolanek, Chi Lin
Rok vydání: 2017
Předmět:
lcsh:Medical physics. Medical radiology. Nuclear medicine
Male
Organs at Risk
medicine.medical_specialty
Lung Neoplasms
medicine.medical_treatment
lcsh:R895-920
VMAT
Radiosurgery
lcsh:RC254-282
030218 nuclear medicine & medical imaging
03 medical and health sciences
0302 clinical medicine
Carcinoma
Non-Small-Cell Lung
medicine
Dosimetry
Humans
Radiology
Nuclear Medicine and imaging
Radiation treatment planning
Lung
Monte Carlo
Aged
Retrospective Studies
Aged
80 and over
SBRT
business.industry
Radiotherapy Planning
Computer-Assisted
Research
Small sample
Radiotherapy Dosage
Middle Aged
lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens
Prognosis
Dose algorithms
Radiation therapy
Target dose
Conformity index
Oncology
030220 oncology & carcinogenesis
Conventional PCI
Female
Radiology
Radiotherapy
Intensity-Modulated
business
Nuclear medicine
Algorithm
Algorithms
Homogeneity index
Follow-Up Studies
Zdroj: Radiation Oncology (London, England)
Radiation Oncology, Vol 12, Iss 1, Pp 1-11 (2017)
ISSN: 1748-717X
Popis: Background Type-C dose algorithms provide more accurate dosimetry for lung SBRT treatment planning. However, because current dosimetric protocols were developed based on conventional algorithms, its applicability for the new generation algorithms needs to be determined. Previous studies on this issue used small sample sizes and reached discordant conclusions. Our study assessed dose calculation of a Type-C algorithm with current dosimetric protocols in a large patient cohort, in order to demonstrate the dosimetric impacts and necessary treatment planning steps of switching from a Type-B to a Type-C dose algorithm for lung SBRT planning. Methods Fifty-two lung SBRT patients were included, each planned using coplanar VMAT arcs, normalized to D95% = prescription dose using a Type-B algorithm. These were compared against three Type-C plans: re-calculated plans (identical plan parameters), re-normalized plans (D95% = prescription dose), and re-optimized plans. Dosimetric endpoints were extracted and compared among the four plans, including RTOG dosimetric criteria: (R100%, R50%, D2cm, V105%, and lung V20), PTV Dmin, Dmax, Dmean, V% and D90%, PTV coverage (V100%), homogeneity index (HI), and Paddick conformity index (PCI). Results Re-calculated Type-C plans resulted in decreased PTV Dmin with a mean difference of 5.2% and increased Dmax with a mean difference of 3.1%, similar or improved RTOG dose compliance, but compromised PTV coverage (mean D95% and V100% reduction of 2.5 and 8.1%, respectively). Seven plans had >5% D95% reduction (maximum reduction = 16.7%), and 18 plans had >5% V100% reduction (maximum reduction = 60.0%). Re-normalized Type-C plans restored target coverage, but yielded degraded plan conformity (average PCI reduction 4.0%), and RTOG dosimetric criteria deviation worsened in 11 plans, in R50%, D2cm, and R100%. Except for one case, re-optimized Type-C plans restored RTOG compliance achieved by the original Type-B plans, resulting in similar dosimetric values but slightly higher target dose heterogeneity (mean HI increase = 13.2%). Conclusions Type-B SBRT lung plans considerably overestimate target coverage for some patients, necessitating Type-C re-normalization or re-optimization. Current RTOG dosimetric criteria appear to remain appropriate.
Databáze: OpenAIRE
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