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Dosimetrical assessment of jaw tracking technique in volumetric modulated arc therapy for a sample of patients with lateralised targets

Published online by Cambridge University Press:  15 February 2023

Rogelio Manuel Diaz Moreno Open the ORCID record for Rogelio Manuel Diaz Moreno [Opens in a new window] ,
Maria José Almada ,
Albin Ariel García Andino  and
Carlos Daniel Venencia
Rogelio Manuel Diaz Moreno*
Affiliation:
Instituto Zunino, Córdoba, Argentina
Maria José Almada
Affiliation:
Instituto Zunino, Córdoba, Argentina
Albin Ariel García Andino
Affiliation:
Instituto Zunino, Córdoba, Argentina
Carlos Daniel Venencia
Affiliation:
Instituto Zunino, Córdoba, Argentina
*
Author for correspondence: Dr Rogelio Manuel Diaz Moreno, Instituto Zunino, 9 de Julio Street, 2015th, 10, Córdoba, X5003CQI, Argentina. E-mail: rdiaz@institutozunino.org
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Abstract

Introduction:

In modulated radiotherapy treatments with the jaw tracking technique (JTT), the collimator jaws can dynamically follow the multileaf collimator apertures and reduce radiation leakage. This reduction protects normal tissue from unwanted doses. Previous research has highlighted the importance of defining which patients will benefit most from JTT. Besides, some authors have expressed their concerns about possible increases in monitor units (MUs). Treatments of patients with peripheral targets and isocentre located in the patient’s midline are of particular interest. The current work assessed the effect of JTT on these cases.

Methods:

JTT plans for thirty-two patients were compared to plans with the static jaws technique. The volumes of normal tissue receiving 5 Gy (V5), 10 Gy (V10) and 20 Gy (V20), mean dose (Dmean), target coverage parameters D95, D2% and Paddick’s conformity index (PCI) were compared. MUs were also registered for comparisons. The decrease in the jaws opening with JTT was correlated to the decrease in dose values in normal tissue.

Results:

Small decreases were observed in D95 and in D2% values, without statistical significance. A 5% average decrease in PCI values was noticed as well as significant decreases in V5, V10 and Dmean values, 9% on average. A 3% decrease in V20 was also observed. The number of MUs decreased by 2%. A significant correlation was found between the reduction of the secondary collimation opening areas and the dose delivered to normal tissue.

Conclusions:

JTT technique improved normal tissue protection in volumetric modulated arc therapy treatments for the patients included in the present study.

Keywords

jaw tracking techniquenormal tissue dose sparingoff-axis targetVMAT
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 22 , 2023 , e77
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Copyright
© The Author(s), 2023. Published by Cambridge University Press

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