Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Jul;19(4):163-172.
doi: 10.1002/acm2.12360. Epub 2018 Jun 1.

HDR brachytherapy in vivo source position verification using a 2D diode array: A Monte Carlo study

Joel Poder  1   2 , Dean Cutajar  1   2 , Susanna Guatelli  1 , Marco Petasecca  1 , Andrew Howie  2 , Joseph Bucci  2 , Anatoly Rosenfeld  1
Affiliations

HDR brachytherapy in vivo source position verification using a 2D diode array: A Monte Carlo study

Joel Poder et al. J Appl Clin Med Phys. 2018 Jul.

Abstract

Purpose: This study aims to assess the accuracy of source position verification during high-dose rate (HDR) prostate brachytherapy using a novel, in-house developed two-dimensional (2D) diode array (the Magic Plate), embedded exactly below the patient within a carbon fiber couch. The effect of tissue inhomogeneities on source localization accuracy is examined.

Method: Monte Carlo (MC) simulations of 12 source positions from a HDR prostate brachytherapy treatment were performed using the Geant4 toolkit. An Ir-192 Flexisource (Isodose Control, Veenendaal, the Netherlands) was simulated inside a voxelized patient geometry, and the dose deposited in each detector of the Magic Plate evaluated. The dose deposited in each detector was then used to localize the source position using a proprietary reconstruction algorithm.

Results: The accuracy of source position verification using the Magic Plate embedded in the patient couch was found to be affected by the tissue inhomogeneities within the patient, with an average difference of 2.1 ± 0.8 mm (k = 1) between the Magic Plate predicted and known source positions. Recalculation of the simulations with all voxels assigned a density of water improved this verification accuracy to within 1 mm.

Conclusion: Source position verification using the Magic Plate during a HDR prostate brachytherapy treatment was examined using MC simulations. In a homogenous geometry (water), the Magic Plate was able to localize the source to within 1 mm, however, the verification accuracy was negatively affected by inhomogeneities; this can be corrected for by using density information obtained from CT, making the proposed tool attractive for use as a real-time in vivo quality assurance (QA) device in HDR brachytherapy for prostate cancer.

Keywords: in vivo; Magic Plate; brachytherapy; diode; source tracking.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Schematic of Flexisource Ir‐192 source24 modeled in this study. All dimensions are in millimeters.
Figure 2
Figure 2
(a) Schematic of the Magic Plate diode spacing, the origin of the coordinate system is defined as the bottom left corner diode of the Magic Plate, (b) Close up of the diode design (distances in mm).
Figure 3
Figure 3
Partial axial view of voxelized patient geometry in Geant4 source position simulations. The carbon couch is shown below the patient geometry outlined in green, the Kapton substrate in blue, and the diode array in pink.
Figure 4
Figure 4
Comparison of calculated radial dose function with studies by Granero24 and Taylor & Rogers.41
Figure 5
Figure 5
Comparison of calculated 2D anisotropy function at a radial distance of 10 mm with studies by Granero24 and Taylor & Rogers.41
Figure 6
Figure 6
(a) Difference between MP predicted and actual source position for heterogeneous and water only simulations in X direction, (b) difference in Y direction, (c) difference in Z direction, and (d) 3D difference vector. Coordinate system orientation is shown in Figs. 1 and 2.
See this image and copyright information in PMC

References

    1. Hoskin PJ, Rojas AM, Bownes PJ, et al. Randomised trial of external beam radiotherapy alone or combined with high‐dose‐rate brachytherapy boost for localised prostate cancer. Radiother Oncol. 2012;103:217–222. - PubMed
    1. Michalski JM, Moughan J, Purdy J, et al. A randomized trial of 79.2 Gy versus 70.2 Gy radiation therapy (RT) for localized prostate cancer. J Clin Oncol (Meeting Abstracts). 2015;33:4.
    1. Tanderup K, El Naqa I, Carlson DJ, Klein EE. Advances in Image‐Guided Brachytherapy. Int J Radiat Oncol Biol Phys. 2017;97:873–875.
    1. Tanderup K, Fokdal LU, Sturdza A, et al. Effect of tumor dose, volume and overall treatment time on local control after radiochemotherapy including MRI guided brachytherapy of locally advanced cervical cancer. Radiother Oncol. 2016;120:441–446. - PubMed
    1. Nkiwane KS, Pötter R, Tanderup K, et al. Single line source with and without vaginal loading and the impact on target coverage and organ at risk doses for cervix cancer Stages IB, II, and IIIB: treatment planning simulation in patients treated with MRI‐guided adaptive brachytherapy in a multicentre study (EMBRACE). Brachytherapy. 2013;12:317–323. - PubMed

Substances

LinkOut - more resources