A Monte Carlo study on the feasibility of real-time in vivo source tracking during ultrasound based HDR prostate brachytherapy treatments

Joel Poder; Dean Cutajar; Susanna Guatelli; Marco Petasecca; Andrew Howie; Joseph Bucci; Mauro Carrara; Anatoly Rosenfeld

doi:10.1016/j.ejmp.2019.02.012

A Monte Carlo study on the feasibility of real-time in vivo source tracking during ultrasound based HDR prostate brachytherapy treatments

Phys Med. 2019 Mar:59:30-36. doi: 10.1016/j.ejmp.2019.02.012. Epub 2019 Feb 26.

Authors

Joel Poder¹, Dean Cutajar², Susanna Guatelli³, Marco Petasecca⁴, Andrew Howie⁵, Joseph Bucci⁶, Mauro Carrara⁷, Anatoly Rosenfeld⁸

Affiliations

¹ Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia; St George Hospital Cancer Care Centre, Kogarah, NSW, Australia. Electronic address: Joel.Poder@health.nsw.gov.au.
² Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia; St George Hospital Cancer Care Centre, Kogarah, NSW, Australia. Electronic address: deanc@uow.edu.au.
³ Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia. Electronic address: susanna@uow.edu.au.
⁴ Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia. Electronic address: marcop@uow.edu.au.
⁵ St George Hospital Cancer Care Centre, Kogarah, NSW, Australia. Electronic address: Andrew.Howie@health.nsw.gov.au.
⁶ St George Hospital Cancer Care Centre, Kogarah, NSW, Australia. Electronic address: Joseph.Bucci@health.nsw.gov.au.
⁷ Medical Physics Unit, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy. Electronic address: Mauro.Carrara@istitutotumori.mi.it.
⁸ Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia. Electronic address: anatoly@uow.edu.au.

PMID: 30928063
DOI: 10.1016/j.ejmp.2019.02.012

Abstract

Purpose: This study aims to assess the accuracy of in-vivo source tracking during real-time trans-rectal ultrasound (TRUS) based high dose rate (HDR) prostate brachytherapy (pBT) through Monte Carlo simulations of multiple HDR pBT treatments with a two-dimensional (2D) diode array, the Magic Plate 900 (MP900), embedded below the patient in a carbon-fibre couch.

Method: Monte Carlo simulations of source positions representing three separate real-time TRUS based HDR pBT treatments were performed using the Geant4 toolkit. For each source position, an Ir-192 source was simulated inside a voxelized patient geometry. Dose deposited from each source position to the MP900 diodes was used to perform source tracking, and the MP900 calculated position compared to known source positions from the treatment plan. Thresholding techniques were implemented to improve source tracking accuracy with the TRUS probe present.

Results: The average three-dimensional source position reconstruction discrepancy was 11.9 ± 2.4 mm and 1.5 ± 0.3 mm with and without the TRUS probe, respectively. Thresholding techniques improved the source position reconstruction discrepancy in the presence of the TRUS probe to 1.8 ± 0.4 mm.

Conclusion: Inclusion of the TRUS probe inside the patient negatively affects source tracking accuracy when using the MP900 diode array for HDR pBT verification. Modification of the source tracking algorithm using thresholding techniques improves source tracking in the presence of the TRUS probe, achieving similar accuracy as when the TRUS probe is not present. This study demonstrates that accurate in-vivo source tracking during real-time TRUS based HDR pBT is feasible using the Magic Plate system.

Keywords: In vivo; MP900; Magic Plate; Monte Carlo; Real-time prostate brachytherapy; Source tracking.

MeSH terms

Brachytherapy / methods*
Feasibility Studies
Humans
Male
Monte Carlo Method*
Prostatic Neoplasms / diagnostic imaging*
Prostatic Neoplasms / radiotherapy*
Radiation Dosage*
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Time Factors
Ultrasonography