Gamma passing rates of daily EPID transit images correlate to PTV coverage for breast cancer IMRT treatment plans

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Abstract

Purpose

The use of the transit image obtained with the electronic portal‐imaging device (EPID) is becoming an extended method to perform in‐vivo dosimetry. The transit images acquired during each fraction can be compared with a predicted image, if available, or with a baseline image, usually the obtained in the first fraction. This work aims to study the dosimetric impact of the failing fractions and to evaluate the appropriateness of using a baseline image in breast plans.

Material and methods

Twenty breast patients treated in a Halcyon were retrospectively selected. For each patient and fraction, the treatment plan was calculated over the daily CBCT image. For each fraction, the differences respect to the treatment plan values of OARs and PTV dosimetric parameters were analyzed: ΔD _mean, ΔD95%, ΔD98%, ΔD2%, ΔV36Gy, ΔV38.5Gy, and ΔV43.5Gy.

Daily fractions were ranked according to the differences found in the dosimetric parameters between the treatment plan and the daily CBCT to establish the best fraction. The daily transit images acquired in every fraction were compared to the first fraction using the global gamma index with the Portal Dosimetry tool. The comparison was repeated using the best fraction image as a baseline.

We assessed the correlation of the dosimetric differences obtained from the CBCT images‐based treatment plans with the gamma index passing rates obtained using first fraction and best fraction as baseline.

Results

Average values of ‐11.6% [‐21.4%, ‐3.3%] and ‐3.2% [‐1.0%, ‐10.3%] for the ∆PTVD98% and ∆PTVD95% per every 10% decrease in the passing rate were found, respectively.

When using the best fraction as baseline patients were detected with failing fractions that were not detected with the first fraction as baseline.

Conclusion

The gamma passing rates of daily transit images correlate with the coverage loss parameters in breast IMRT plans. Using first fraction image as baseline can lead to the non‐detectability of failing fractions.

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Most cited references 26

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Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries

Hyuna Sung, Jacques Ferlay, Rebecca Siegel … (2021)

This article provides an update on the global cancer burden using the GLOBOCAN 2020 estimates of cancer incidence and mortality produced by the International Agency for Research on Cancer. Worldwide, an estimated 19.3 million new cancer cases (18.1 million excluding nonmelanoma skin cancer) and almost 10.0 million cancer deaths (9.9 million excluding nonmelanoma skin cancer) occurred in 2020. Female breast cancer has surpassed lung cancer as the most commonly diagnosed cancer, with an estimated 2.3 million new cases (11.7%), followed by lung (11.4%), colorectal (10.0 %), prostate (7.3%), and stomach (5.6%) cancers. Lung cancer remained the leading cause of cancer death, with an estimated 1.8 million deaths (18%), followed by colorectal (9.4%), liver (8.3%), stomach (7.7%), and female breast (6.9%) cancers. Overall incidence was from 2-fold to 3-fold higher in transitioned versus transitioning countries for both sexes, whereas mortality varied <2-fold for men and little for women. Death rates for female breast and cervical cancers, however, were considerably higher in transitioning versus transitioned countries (15.0 vs 12.8 per 100,000 and 12.4 vs 5.2 per 100,000, respectively). The global cancer burden is expected to be 28.4 million cases in 2040, a 47% rise from 2020, with a larger increase in transitioning (64% to 95%) versus transitioned (32% to 56%) countries due to demographic changes, although this may be further exacerbated by increasing risk factors associated with globalization and a growing economy. Efforts to build a sustainable infrastructure for the dissemination of cancer prevention measures and provision of cancer care in transitioning countries is critical for global cancer control.

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Correlation Coefficients

Patrick Schober, Christa Boer, Lothar A Schwarte (2018)

Correlation in the broadest sense is a measure of an association between variables. In correlated data, the change in the magnitude of 1 variable is associated with a change in the magnitude of another variable, either in the same (positive correlation) or in the opposite (negative correlation) direction. Most often, the term correlation is used in the context of a linear relationship between 2 continuous variables and expressed as Pearson product-moment correlation. The Pearson correlation coefficient is typically used for jointly normally distributed data (data that follow a bivariate normal distribution). For nonnormally distributed continuous data, for ordinal data, or for data with relevant outliers, a Spearman rank correlation can be used as a measure of a monotonic association. Both correlation coefficients are scaled such that they range from -1 to +1, where 0 indicates that there is no linear or monotonic association, and the relationship gets stronger and ultimately approaches a straight line (Pearson correlation) or a constantly increasing or decreasing curve (Spearman correlation) as the coefficient approaches an absolute value of 1. Hypothesis tests and confidence intervals can be used to address the statistical significance of the results and to estimate the strength of the relationship in the population from which the data were sampled. The aim of this tutorial is to guide researchers and clinicians in the appropriate use and interpretation of correlation coefficients.

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A technique for the quantitative evaluation of dose distributions.

D Low, W Harms, S Mutic … (1998)

The commissioning of a three-dimensional treatment planning system requires comparisons of measured and calculated dose distributions. Techniques have been developed to facilitate quantitative comparisons, including superimposed isodoses, dose-difference, and distance-to-agreement (DTA) distributions. The criterion for acceptable calculation performance is generally defined as a tolerance of the dose and DTA in regions of low and high dose gradients, respectively. The dose difference and DTA distributions complement each other in their useful regions. A composite distribution has recently been developed that presents the dose difference in regions that fail both dose-difference and DTA comparison criteria. Although the composite distribution identifies locations where the calculation fails the preselected criteria, no numerical quality measure is provided for display or analysis. A technique is developed to unify dose distribution comparisons using the acceptance criteria. The measure of acceptability is the multidimensional distance between the measurement and calculation points in both the dose and the physical distance, scaled as a fraction of the acceptance criteria. In a space composed of dose and spatial coordinates, the acceptance criteria form an ellipsoid surface, the major axis scales of which are determined by individual acceptance criteria and the center of which is located at the measurement point in question. When the calculated dose distribution surface passes through the ellipsoid, the calculation passes the acceptance test for the measurement point. The minimum radial distance between the measurement point and the calculation points (expressed as a surface in the dose-distance space) is termed the gamma index. Regions where gamma > 1 correspond to locations where the calculation does not meet the acceptance criteria. The determination of gamma throughout the measured dose distribution provides a presentation that quantitatively indicates the calculation accuracy. Examples of a 6 MV beam penumbra are used to illustrate the gamma index.

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Author and article information

Contributors

David Sánchez‐Artuñedo: david.sanchezartunedo@vallhebron.cat

Journal

Journal ID (nlm-ta): J Appl Clin Med Phys

Journal ID (iso-abbrev): J Appl Clin Med Phys

Journal ID (doi): 10.1002/(ISSN)1526-9914

Journal ID (publisher-id): ACM2

Title: Journal of Applied Clinical Medical Physics

Publisher: John Wiley and Sons Inc. (Hoboken )

ISSN (Electronic): 1526-9914

Publication date (Electronic): 26 January 2023

Publication date Collection: May 2023

Volume: 24

Issue: 5 ( doiID: 10.1002/acm2.v24.5 )

Electronic Location Identifier: e13913

Affiliations

[ ¹ ] Servei de Física i Protecció Radiològica Hospital Universitari Vall d'Hebron Vall d'Hebron Barcelona Hospital Campus Barcelona Spain

[ ² ] Servei d'Oncologia Radioteràpica Hospital Universitari Vall d'Hebron Vall d'Hebron Barcelona Hospital Campus Barcelona Spain

[ ³ ] Institut de Tècniques Energètiques Universitat Politècnica de Catalunya. Barcelona Spain

Author notes

[*] [* ] Correspondence

David Sánchez Artuñedo, Servei de Física i Protecció Radiològica, Hospital Universitari Vall d'Hebron, Vall d'Hebron Barcelona Hospital Campus, Passeig Vall d'Hebron 119‐129, 08035 Barcelona, Spain.

Email: david.sanchezartunedo@ 123456vallhebron.cat

Article

Publisher ID: ACM213913

DOI: 10.1002/acm2.13913

PMC ID: 10161046

PubMed ID: 36700363

SO-VID: b14d9f04-ae31-4962-ba6f-413508978fc1

License:

This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

History

Date revision received : 04 January 2023

Date received : 22 May 2022

Date accepted : 12 January 2023

Page count

Figures: 6, Tables: 2, Pages: 10, Words: 6175

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source-schema-version-number 2.0

cover-date May 2023

details-of-publishers-convertor Converter:WILEY_ML3GV2_TO_JATSPMC version:6.2.8 mode:remove_FC converted:05.05.2023

Gamma passing rates of daily EPID transit images correlate to PTV coverage for breast cancer IMRT treatment plans

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Abstract

Purpose

Material and methods

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Conclusion

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International Journal of Applied Technology in Medical Sciences

Most cited references 26

Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries

Correlation Coefficients

A technique for the quantitative evaluation of dose distributions.

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