open access

Vol 64, No 3 (2014)
Research paper (original)
Published online: 2014-06-13
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The influence of photon energy on dose distribution for IMRT and VMAT plans

Michał Radwan, Aleksandra Grządziel, Leszek Hawrylewicz, Krzysztof Ślosarek, Wojciech Osewski
DOI: 10.5603/NJO.2014.0037
·
Nowotwory. Journal of Oncology 2014;64(3):230-236.

open access

Vol 64, No 3 (2014)
Original article
Published online: 2014-06-13

Abstract

Purpose. Estimation of the difference between photon X-6MV and X-20MV beams for IMRT and VMAT plan’s, in respect to dose-volume results and irradiation time (MU).

Materials and methods. For each of 74 selected patients four plans, two IMRT with X-6MV & X-20MV beams and two VMAT: X-6MV & X-20MV arcs, were performed. Patients were divided into two groups according to tumor localization: head & neck (H&N) and pelvis. Those localizations were chosen to highlight potential differences regarding the depth of target volume. Each plan was optimized using the same plan objectives and constraints. Plans were compared according to dose-volume results for target and Organs at Risk (OaR’s) with Radiation Planning Index (RPI), and beamon time regarding the monitor units (MUs).

Results. The mean RPI factor for both technique (IMRT/VMAT) and energies (X-6MV/X-20MV) were similar for H&Nregion in the range of 0.2310–0.2934 and for the pelvis region the range was 0.3683–0.4007. The difference were not statistically significant (p > 0.05), showing the photon between 6–20 MV, doesn’t influence the dose-volume results, for both localization: H&N and pelvis. The mean monitor units in IMRT plans varied from 765 MU to 1116 MU, as inVMAT plans it was from 325 MU to 492 MU. Generally, the number of MU on IMRT technique is greater than MU’s inVMAT (difference statistically significant), regardless of the beam energy (X-6MV, X-20MV) and localization (H&N, pelvis). Both techniques; IMRT and VMAT plans with higher photon energy, showed shorter irradiation time (expressedin MU). But, only for pelvic region on VMAT technique, is statistically significant (p = 0.0467).

Conclusions. On average, photons beam, between 6–20 MV don’t induce significant dose-volume difference. However, higher energy used for planning regions other than head & neck, minimizes the number of MUs and significantly reduces the time of irradiation. Furthermore, reduction of beam on time can be achieved by using VMAT plan rather than IMRT plan.

Abstract

Purpose. Estimation of the difference between photon X-6MV and X-20MV beams for IMRT and VMAT plan’s, in respect to dose-volume results and irradiation time (MU).

Materials and methods. For each of 74 selected patients four plans, two IMRT with X-6MV & X-20MV beams and two VMAT: X-6MV & X-20MV arcs, were performed. Patients were divided into two groups according to tumor localization: head & neck (H&N) and pelvis. Those localizations were chosen to highlight potential differences regarding the depth of target volume. Each plan was optimized using the same plan objectives and constraints. Plans were compared according to dose-volume results for target and Organs at Risk (OaR’s) with Radiation Planning Index (RPI), and beamon time regarding the monitor units (MUs).

Results. The mean RPI factor for both technique (IMRT/VMAT) and energies (X-6MV/X-20MV) were similar for H&Nregion in the range of 0.2310–0.2934 and for the pelvis region the range was 0.3683–0.4007. The difference were not statistically significant (p > 0.05), showing the photon between 6–20 MV, doesn’t influence the dose-volume results, for both localization: H&N and pelvis. The mean monitor units in IMRT plans varied from 765 MU to 1116 MU, as inVMAT plans it was from 325 MU to 492 MU. Generally, the number of MU on IMRT technique is greater than MU’s inVMAT (difference statistically significant), regardless of the beam energy (X-6MV, X-20MV) and localization (H&N, pelvis). Both techniques; IMRT and VMAT plans with higher photon energy, showed shorter irradiation time (expressedin MU). But, only for pelvic region on VMAT technique, is statistically significant (p = 0.0467).

Conclusions. On average, photons beam, between 6–20 MV don’t induce significant dose-volume difference. However, higher energy used for planning regions other than head & neck, minimizes the number of MUs and significantly reduces the time of irradiation. Furthermore, reduction of beam on time can be achieved by using VMAT plan rather than IMRT plan.

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About this article
Title

The influence of photon energy on dose distribution for IMRT and VMAT plans

Journal

Nowotwory. Journal of Oncology

Issue

Vol 64, No 3 (2014)

Article type

Research paper (original)

Pages

230-236

Published online

2014-06-13

DOI

10.5603/NJO.2014.0037

Bibliographic record

Nowotwory. Journal of Oncology 2014;64(3):230-236.

Authors

Michał Radwan
Aleksandra Grządziel
Leszek Hawrylewicz
Krzysztof Ślosarek
Wojciech Osewski

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