<abstract xmlns="http://www.w3.org/1999/xhtml"><sec id="j_raon-2016-0012_s_001_w2aab3b8c93b1b7b1aab1c14b1Aa"><h3>Background</h3><p>The purpose of the study was to analyse the dosimetric differences when using 10 MV instead of 6 MV for VMAT treatment plans for post-prostatectomy irradiation of the prostate bed.</p></sec><sec id="j_raon-2016-0012_s_002_w2aab3b8c93b1b7b1aab1c14b2Aa"><h3>Methods and materials</h3><p>Ten post-prostatectomy prostate bed irradiation cases previously treated using 6 MV with volumetric modulated arc therapy (VMAT) were re-planned using 10 MV with VMAT. Prescription dose was 66.6 Gy with 1.8 Gy per fraction for 37 daily fractions. The same structure set, number of arcs, field sizes, and minimum dose to the Planning Target Volume (PTV) were used for both 6 MV and 10 MV plans. Results were collected for dose to Organs at Risk (OAR) constraints, dose to the target structures, number of monitor units for each arc, Body V<sub>5</sub>, Conformity Index, and Integral Dose. The mean values were used to compare the 6 MV and 10 MV results. To determine the statistical significance of the results, a paired Student t test and power analysis was performed.</p></sec><sec id="j_raon-2016-0012_s_003_w2aab3b8c93b1b7b1aab1c14b3Aa"><h3>Results</h3><p>Statistically significant lower mean values were observed for the OAR dose constraints for the rectum, bladder-Clinical Target Volume (bladder-CTV), left femoral head, and right femoral head. Also, statistically significant lower mean values were observed for the Body V<sub>5</sub>, Conformity Index, and Integral Dose.</p></sec><sec id="j_raon-2016-0012_s_004_w2aab3b8c93b1b7b1aab1c14b4Aa"><h3>Conclusions</h3><p>Several dosimetric benefits were observed when using 10 MV instead of 6 MV for VMAT based treatment plans. Benefits include sparing more dose from the OAR while still maintaining the same dose coverage to the PTV. Other benefits include lower Body V <sub>5,</sub>Conformity Index, and Integral Dose.</p></sec></abstract>

BackgroundThe purpose of the study was to analyse the dosimetric differences when using 10 MV instead of 6 MV for VMAT treatment plans for post-prostatectomy irradiation of the prostate bed.Methods and materialsTen post-prostatectomy prostate bed irradiation cases previously treated using 6 MV with volumetric modulated arc therapy (VMAT) were re-planned using 10 MV with VMAT. Prescription dose was 66.6 Gy with 1.8 Gy per fraction for 37 daily fractions. The same structure set, number of arcs, field sizes, and minimum dose to the Planning Target Volume (PTV) were used for both 6 MV and 10 MV plans. Results were collected for dose to Organs at Risk (OAR) constraints, dose to the target structures, number of monitor units for each arc, Body V5, Conformity Index, and Integral Dose. The mean values were used to compare the 6 MV and 10 MV results. To determine the statistical significance of the results, a paired Student t test and power analysis was performed.ResultsStatistically significant lower mean values were observed for the OAR dose constraints for the rectum, bladder-Clinical Target Volume (bladder-CTV), left femoral head, and right femoral head. Also, statistically significant lower mean values were observed for the Body V5, Conformity Index, and Integral Dose.ConclusionsSeveral dosimetric benefits were observed when using 10 MV instead of 6 MV for VMAT based treatment plans. Benefits include sparing more dose from the OAR while still maintaining the same dose coverage to the PTV. Other benefits include lower Body V 5,Conformity Index, and Integral Dose.

The dosimetric significance of using 10 MV photons for volumetric modulated arc therapy for post-prostatectomy irradiation of the prostate bed

Department of Physiology and Biophysics, SUNY University at Buffalo, Buffalo, NY, USA

Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY, USA

Radiology and Oncology

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

BackgroundThe purpose of the study was to analyse the dosimetric differences when using 10 MV instead of 6 MV for VMAT treatment plans for post-prostatectomy...

Category	Dose Constraint
Bladder-CTV D₅₀	65 Gy
Bladder-CTV D₇₀	40 Gy
Rectum D₃₅	65 Gy
Rectum D₅₅	40 Gy
Right Femoral Head D₁₀	50 Gy
Left Femoral Head D₁₀	50 Gy

Category	6 MV Mean ± SDOM	10 MV Mean ± SDOM	Percent Increase	p-value	Power
Bladder-CTV D₅₀	32.5 ± 4.3 Gy	29.7 ± 3.9 Gy	−8.62%	0.013	0.79
Bladder-CTV D₇₀	18.5 ± 3.7 Gy	16.2 ± 3.2 Gy	−12.4%	0.011	0.81
Rectum D₃₅	49.5 ± 3.3 Gy	46.8 ± 3.9 Gy	−5.45%	6.6 × 10^-3	0.88
Rectum D₅₅	28.5 ± 2.7 Gy	26.7 ± 2.7 Gy	−6.32%	0.023	0.68
Right Femoral Head D₁₀	34.12 ± 0.86 Gy	29.80 ± 0.99 Gy	−12.66%	1.2 × 10-4	1.0
Left Femoral Head D₁₀	32.74 ± 0.94 Gy	29.4 ± 1.1 Gy	−10.20%	8.3 × 10-5	1.0
CTV Min Dose	65.53 ± 0.38 Gy	65.29 ± 0.21 Gy	−0.3662%	0.41	0.12
CTV Max Dose	71.01 ± 0.37 Gy	70.53 ± 0.31 Gy	−0.6760%	0.10	0.37
CTV Mean Dose	68.30 ± 0.29 Gy	67.68 ± 0.27 Gy	−0.9078%	0.019	0.72
CTV Percent Volume Covered by the 95% Isodose Line	100%	100%	0%	N/A	N/A
PTV Min Dose	64.42 ± 0.29 Gy	64.42 ± 0.29 Gy	0%	0.10	0.37
PTV Max Dose	71.78 ± 0.29 Gy	71.76 ± 0.33 Gy	−0.02786%	0.94	0.051
PTV Mean Dose	68.39 ± 0.38 Gy	67.94 ± 0.28 Gy	−0.6580%	0.063	0.47
PTV Percent Volume Covered by the 95% Isodose Line	100%	100%	0%	N/A	N/A
Body V₅	(27.0 ± 1.0)%	(26.5 ± 1.0)%	−1.85%	2.2 × 10-3	0.96
Global Max Dose	71.80 ± 0.38 Gy	71.76 ± 0.33 Gy	−0.05571%	0.89	0.052
Arc 1 Monitor Units	325 ± 17 MU	311.8 ± 9.8 MU	−4.06%	0.41	0.12
Arc 2 Monitor Units	330 ± 15 MU	312 ± 10 MU	−5.5%	0.19	0.24
Conformity Index	1.127 ± 0.013	1.091 ± 0.015	−3.194%	6.8 × 10-4	0.99
Integral Dose	207 ± 12 Gy-L	191 ± 11 Gy-L	−7.73%	1.1 × 10-5	1.0

The dosimetric significance of using 10 MV photons for volumetric modulated arc therapy for post-prostatectomy irradiation of the prostate bed

Article Category: Research Article

Data publikacji: 22 lut 2016

Zakres stron: 232 - 237

Otrzymano: 21 wrz 2015

Przyjęty: 08 sty 2016

DOI: https://doi.org/10.1515/raon-2016-0012

© 2016 Radiol Oncol

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Dose constraint limits adapted from RTOG protocol 0534

Mean, standard deviation of the mean, percent increase, p-value, and power for both 6 MV and 10 MV are displayed