A Simple Method for 2-D In Vivo Dosimetry by Portal Imaging

Overview

Journal Technol Cancer Res Treat

Specialties Biomedical Engineering
Oncology
Pharmacology

Date 2017 Jun 7

PMID 28585491

Citations 3

Authors

Stefano Peca

Derek Wilson Brown

Wendy Lani Smith

Affiliations

Soon will be listed here.

Abstract

Purpose: To improve patient safety and treatment quality, verification of dose delivery in radiotherapy is desirable. We present a simple, easy-to-implement, open-source method for planar dosimetry of conformal radiotherapy by electronic portal imaging device (EPID).

Methods: Correlation ratios, which relate dose in the mid-depth of slab phantoms to transit EPID signal, were determined for multiple phantom thicknesses and field sizes. Off-axis dose is corrected for by means of model-based convolution. We tested efficacy of dose reconstruction through measurements with off-reference values of attenuator thickness, field size, and monitor units. We quantified the dose calculation error in the presence of thickness changes to simulate anatomical or setup variations. An example of dose calculation on patient data is provided.

Results: With varying phantom thickness, field size, and monitor units, dose reconstruction was almost always within 3% of planned dose. In the presence of thickness changes from planning CT, the dose discrepancy is exaggerated by up to approximately 1.5% for 1 cm changes upstream of the isocenter plane and 4% for 1 cm changes downstream.

Conclusion: Our novel electronic portal imaging device dosimetry allows clinically accurate 2-dimensional reconstruction of dose inside a phantom/patient at isocenter depth. Due to its simplicity, commissioning can be performed in a few hours per energy and may be modified to the user's needs. It may provide useful dose delivery information to detect harmful errors, guide adaptive radiotherapy, and assure quality of treatment.

Citing Articles

Evaluation of two-dimensional electronic portal imaging device using integrated images during volumetric modulated arc therapy for prostate cancer.

Inui S, Ueda Y, Ono S, Ohira S, Isono M, Nitta Y Rep Pract Oncol Radiother. 2021; 26(2):281-290.

PMID: 34211779 PMC: 8241304. DOI: 10.5603/RPOR.a2021.0041.

EPID-based daily verification of reproducibility of patients' irradiation with IMRT plans.

Kruszyna-Mochalska M Rep Pract Oncol Radiother. 2018; 23(5):309-314.

PMID: 30108458 PMC: 6088814. DOI: 10.1016/j.rpor.2018.05.003.

Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device.

Peca S, Sinha R, Brown D, Smith W Technol Cancer Res Treat. 2017; 16(6):956-963.

PMID: 28585490 PMC: 5762054. DOI: 10.1177/1533034617711519.

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