ArticlePublisher preview available

BrachyView: initial preclinical results for a real-time in-body HDR PBT source tracking system with simultaneous TRUS image fusion

IOP Publishing
Physics in Medicine & Biology
Authors:
Saree Alnaghy at University of Wollongong
Saree Alnaghy
Dean Cutajar at University of Wollongong
Dean Cutajar
M. Safavi-Naeini at Australian Nuclear Science and Technology Organisation
M. Safavi-Naeini
S George
S George
S George
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Show all 12 authorsHide
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

A prototype in-body gamma camera system with integrated trans-rectal ultrasound (TRUS) and associated real-time image acquisition and analysis software was developed for intraoperative source tracking in high dose rate (HDR) brachytherapy. The accuracy and temporal resolution of the system was validated experimentally using a deformable tissue-equivalent prostate gel phantom and a full clinical HDR treatment plan. The BrachyView system was able to measure 78% of the 200 source positions with an accuracy of better than 1 mm. A minimum acquisition time of 0.28 s/frame was required to achieve this accuracy, restricting dwell times to a minimum of 0.3 s. Additionally, the performance of the BrachyView-TRUS fusion probe for mapping the spatial location of the tracked source within the prostate volume was evaluated. A global coordinate system was defined by scanning the phantom with the probe in situ using a CT scanner and was subsequently used for co-registration of the BrachyView and TRUS Fields of View (FoVs). TRUS imaging was used to segment the prostate volume and reconstruct it into a three-dimensional image. Fusion of the estimated source locations with the 3D prostate image was performed using integrated 3D visualisation software. HDR BrachyView is demonstrated to be a valuable tool for intraoperative source tracking in HDR brachytherapy, capable of resolving source dwell locations relative to the prostate anatomy when combined with TRUS.
Figures - available from: Physics in Medicine & Biology
This content is subject to copyright. Terms and conditions apply.
A preview of this full-text is provided by IOP Publishing.
Learn more
Content available from Physics in Medicine & Biology 
This content is subject to copyright. Terms and conditions apply.
© 2019 Institute of Physics and Engineering in Medicine
1. Introduction
High dose rate (HDR) brachytherapy is emerging as a promising treatment option for the treatment of
nonmetastatic prostate cancer (Khoo 2005, Zamboglou et al 2013, Zaorsky et al 2017). HDR brachytherapy
allows greater dose escalation that can not be safely achieved with external beam radiation therapy (EBRT),
while delivering less dose to the surrounding critical tissue and structures and therefore offering more effective
tumour control (Challapalli et al 2012, Morton and Hoskin 2013, Zaorsky et al 2017). The procedure involves
the temporary local placement of a single source, which remains (dwells) for a limited period of time in a series
of discrete pre-calculated positions (Voulgaris et al 2008). One of the most common radioisotopes used in
HDR brachytherapy is 192Ir, with a
γ
photon energy range from 136 keV to 1062 keV and a mean energy of
approximately 380 keV.
Accurate placement of the source within the prostate is a critical factor in delivering the correct dose cover-
age to the prostate. Inaccurate source placement can result in a sub-optimal dose distribution, with erroneously
high doses potentially being delivered to surrounding critical organs, such as the rectum, bladder, and urethra, or
insufficient doses being applied to the tumour (Batič et al 2010).
Transrectal ultrasound (TRUS) is the standard imaging modality used in prostate cancer for needle guidance
(Applewhite et al 2001). TRUS imaging is an excellent modality for viewing soft tissue volumes; however, due to
its poor spatial resolution, its usefulness in catheter position verification is limited. Computed tomography (CT)
is commonly combined with TRUS for treatment planning and for verifying catheter positions. However, it can
S Alnaghy et al
BrachyView: initial preclinical results for a real-time in-body HDR PBT source tracking system with simultaneous TRUS image fusion
Printed in the UK
085002
PHMBA7
© 2019 Institute of Physics and Engineering in Medicine
64
Phys. Med. Biol.
PMB
1361-6560
10.1088/1361-6560/ab0a7e
8
1
12
Physics in Medicine & Biology
IOP
5
April
2019
BrachyView: initial preclinical results for a real-time in-body HDR
PBT source tracking system with simultaneous TRUS image fusion
S Alnaghy1, D L Cutajar1, M Safavi-Naeini1, S George1, A Howie2, A B ece2, J A Bucci2, J Jakubek3,
S Pospisil3, M L F Lerch1, M Petasecca1 and A B Rosenfeld1
1 Centre for Medical Radiation Physics, University of Wol longong, Wollongong, Australia
2 St George Cancer Care Centre, St George Hospital, Kogarah, New South Wales, Australia
3 Institute of Experimental and Applied Physics, Czech Technical University of Prague, Prague, Czech Republic
E-mail: saree@uow.edu.au and anatoly@uow.edu.au
Keywords: BrachyView, HDR brachytherapy, dosimetry, quality assurance
Abstract
A prototype in-body gamma camera system with integrated trans-rectal ultrasound (TRUS) and
associated real-time image acquisition and analysis software was developed for intraoperative source
tracking in high dose rate (HDR) brachytherapy. The accuracy and temporal resolution of the system
was validated experimentally using a deformable tissue-equivalent prostate gel phantom and a full
clinical HDR treatment plan. The BrachyView system was able to measure 78% of the 200 source
positions with an accuracy of better than 1 mm. A minimum acquisition time of 0.28 s/frame was
required to achieve this accuracy, restricting dwell times to a minimum of 0.3 s. Additionally, the
performance of the BrachyView-TRUS fusion probe for mapping the spatial location of the tracked
source within the prostate volume was evaluated. A global coordinate system was defined by scanning
the phantom with the probe in situ using a CT scanner, and was subsequently used for co-registration
of the BrachyView and TRUS fields of view (FoVs). TRUS imaging was used to segment the prostate
volume and reconstruct it into a three-dimensional (3D) image. Fusion of the estimated source
locations with the 3D prostate image was performed using integrated 3D visualisation software.
HDR BrachyView is demonstrated to be a valuable tool for intraoperative source tracking in HDR
brachytherapy, capable of resolving source dwell locations relative to the prostate anatomy when
combined with TRUS.
PAPER
2019
RECEIVED
10 October 201 8
REVISED
22 February 2019
ACCEPTED FOR PUBLICATION
26 February 2019
PUBLISHED
5 April 2 019
https ://doi.org/10.108 8/1361-65 60/ab0 a7e
Phys. Med . Biol. 64 (2019) 085002 (12pp)
ResearchGate has not been able to resolve any citations for this publication.
MR-based source localization for MR-guided HDR brachytherapy
Article
Full-text available
For the purpose of MR-guided high-dose-rate (HDR) brachytherapy, a method for real-time localization of an HDR brachytherapy source was developed, which requires high spatial and temporal resolutions. MR-based localization of an HDR source serves two main aims. First, it enables real-time treatment verification by determination of the HDR source positions during treatment. Second, when using a dummy source, MR-based source localization provides an automatic detection of the source dwell positions after catheter insertion, allowing elimination of the catheter reconstruction procedure. Localization of the HDR source was conducted by simulation of the MR artifacts, followed by a phase correlation localization algorithm, applied to the MR images and the simulated images, to determine the position of the HDR source in the MR images. To increase the temporal resolution of the MR acquisition, the spatial resolution was decreased, and a subpixel localization operation was introduced. Furthermore, parallel imaging (sensitivity encoding) was applied to further decrease the MR scan time. The localization method was validated by a comparison with CT, and the accuracy and precision were investigated. The results demonstrated that the described method could be used to determine the HDR source position with a high accuracy (0.4-0.6 mm) and a high precision (≤0.1 mm), at high temporal resolutions (0.15-1.2 s per slice). This would enable real-time treatment verification as well as an automatic detection of the source dwell positions.
View
Electromagnetic tracking for treatment verification in interstitial brachytherapy
Article
Full-text available
  • Oct 2016
Electromagnetic tracking (EMT) is used in several medical fields to determine the position and orientation of dedicated sensors, e.g., attached to surgical tools. Recently, EMT has been introduced to brachytherapy for implant reconstruction and error detection. The manuscript briefly summarizes the main issues of EMT and error detection in brachytherapy. The potential and complementarity of EMT as treatment verification technology will be discussed in relation to in vivo dosimetry and imaging.
View
Analytical Modelling and Simulation of Single and Double Cone Pinholes for Real-Time In-Body Tracking of an HDR Brachytherapy Source
Article
Full-text available
  • Jun 2016
The choice of pinhole geometry is a critical factor in the performance of pinhole-collimator-based source tracking systems for brachytherapy QA. In this work, an analytical model describing the penetrative sensitivity of a single-cone pinhole collimator to photons emitted from a point source is derived. Using existing models for single-cone resolution and double-cone sensitivity and resolution, the theoretical sensitivity and resolution of the single-cone collimator are quantitatively compared with those of a double-cone collimator with an equivalent field of view. Monte Carlo simulations of the single and double-cone pinhole collimators using an accurate 3D model of a commercial high dose rate brachytherapy source are performed to evaluate the relative performance of each geometry for a novel real-time HDR brachytherapy QA system, HDR BrachyView. The theoretical penetrative sensitivity of the single-cone pinhole is shown to be higher than the double-cone pinhole, which is in agreement with the results from the Monte Carlo simulations. The wider pinhole response function of the single-cone collimator results in a larger total error between the projected center of the source and the estimated center of mass of the source projection for the single-cone collimator, with the greatest error (at the maximum FoV angle) being 0.54 mm for the double-cone pinhole and 1.37 mm for the single-cone at . The double-cone pinhole geometry is determined to be the most appropriate choice for the pinhole collimator in the HDR BrachyView probe.
View
Usefulness of direct-conversion flat-panel detector system as a quality assurance tool for high-dose-rate 192Ir source
Article
Full-text available
The routine quality assurance (QA) procedure for a high‐dose‐rate (HDR) 192Ir radioactive source is an important task to provide appropriate brachytherapy. Traditionally, it has been difficult to obtain good quality images using the 192Ir source due to irradiation from the high‐energy gamma rays. However, a direct‐conversion flat‐panel detector (d‐FPD) has made it possible to confirm the localization and configuration of the 192Ir source. The purpose of the present study was to evaluate positional and temporal accuracy of the 192Ir source using a d‐FPD system, and the usefulness of d‐FPD as a QA tool. As a weekly verification of source positional accuracy test, we obtained 192Ir core imaging by single‐shot radiography for three different positions (1300/1400/1500 mm) of a check ruler. To acquire images for measurement of the 192Ir source movement distance with varying interval steps (2.5/5.0/10.0 mm) and temporal accuracy, we used the high‐speed image acquisition technique and digital subtraction. For accuracy of the 192Ir source dwell time, sequential images were obtained using various dwell times ranging from 0.5 to 30.0 sec, and the acquired number of image frames was assessed. Analysis of the data was performed using the measurement analysis function of the d‐FPD system. Although there were slight weekly variations in source positional accuracy, the measured positional errors were less than 1.0 mm. For source temporal accuracy, the temporal errors were less than 1.0%, and the correlation between acquired frames and programmed time showed excellent linearity (R2=1). All 192Ir core images were acquired clearly without image halation, and the data were obtained quantitatively. All data were successfully stored in the picture archiving and communication system (PACS) for time‐series analysis. The d‐FPD is considered useful as the QA tool for the 192Ir source. PACS number: 87.56.Fc
View
High dose rate prostate brachytherapy: An overview of the rationale, experience and emerging applications in the treatment of prostate cancer
Article
Full-text available
  • Nov 2012
The technological advances in real-time ultrasound image guidance for high dose rate (HDR) prostate brachytherapy places this treatment modality at the forefront of innovation in radiotherapy. This review article will explore the rationale for HDR brachytherapy as a highly conformal method of dose delivery and safe dose escalation to the prostate, in addition to the particular radiobiological advantages it has over low dose rate and external beam radiotherapy. The encouraging outcome data and favourable toxicity profile will be discussed before looking at emerging applications for the future and how this procedure will feature alongside stereotactic radiosurgery.
View
The evolution of brachytherapy for prostate cancer
Article
  • Jun 2017
Brachytherapy (BT), using low-dose-rate (LDR) permanent seed implantation or high-dose-rate (HDR) temporary source implantation, is an acceptable treatment option for select patients with prostate cancer of any risk group. The benefits of HDR-BT over LDR-BT include the ability to use the same source for other cancers, lower operator dependence, and — typically — fewer acute irritative symptoms. By contrast, the benefits of LDR-BT include more favourable scheduling logistics, lower initial capital equipment costs, no need for a shielded room, completion in a single implant, and more robust data from clinical trials. Prospective reports comparing HDR-BT and LDR-BT to each other or to other treatment options (such as external beam radiotherapy (EBRT) or surgery) suggest similar outcomes. The 5-year freedom from biochemical failure rates for patients with low-risk, intermediate-risk, and high-risk disease are >85%, 69–97%, and 63–80%, respectively. Brachytherapy with EBRT (versus brachytherapy alone) is an appropriate approach in select patients with intermediate-risk and high-risk disease. The 10-year rates of overall survival, distant metastasis, and cancer-specific mortality are >85%, <10%, and <5%, respectively. Grade 3–4 toxicities associated with HDR-BT and LDR-BT are rare, at <4% in most series, and quality of life is improved in patients who receive brachytherapy compared with those who undergo surgery.
View
View
Quantifying Worry in the Face of Uncertainty: Radiation Exposure from Medical Imaging
Article
  • Feb 2017
Background The degree to which people worry about radiation exposure from medical imaging has not been quantified. Such concern is important for clinical decision making and policy generation. Objective The aim of this study was to quantify the degree of worry as a consequence of radiation exposure. Design A time trade-off methodology was used to estimate health state utilities associated with radiation exposure from computed tomography scans in an inclusive sample of physicians. Health state utilities were elicited from in-person interviews using a software-guided, hypothetical scenario in which the subject is exposed to two separate computed tomography scans. Results One hundred and eighteen interviews were conducted. The overall mean and median utility values for the health state of concern due to radiation exposure were 0.95 (95% confidence interval: 0.94–0.96) and 0.98 (interquartile range: 0.91–1.00), respectively. The utility score distribution was highly skewed toward higher values. Five respondents (4.3%) recorded a utility score of ≤0.8 and 17 respondents (14.5%) were willing to sacrifice at least 5 or more years of life to live free of the radiation-exposure worry. Conclusions and relevance The physician respondents generally demonstrated low levels of disutility; however, a subset of physicians expressed much greater disutility for the future risk of malignancy. Given the potential for physicians to influence health care decisions and policies, further study of radiation-related concerns seems warranted. Physicians, patients, and the general public should be aware of the potential impact such differing views held by physicians may have on their clinical recommendations.
View
Intraoperative ultrasound-based planning can effectively replace postoperative CT-based planning for high-dose-rate brachytherapy for prostate cancer
Article
  • May 2016
Purpose: Ultrasound (US)-based planning for high-dose-rate brachytherapy allows prostate patients to be implanted, imaged, planned, and treated without changing position. This is advantageous with respect to accuracy and efficiency of treatment but is only valuable if plan quality relative to CT is maintained. This study evaluates any dosimetric impact of changing from CT- to US-based planning. Methods and materials: Thirty patients each were randomly selected from CT-planned and US-planned cohorts. All received single fraction high-dose-rate brachytherapy (15 Gy) followed by 37.5 Gy in 15 fractions external beam radiation therapy. Prostate V90, V100, V150, V200, D90, and the dose homogeneity index were compared. For the rectum, Dmax, D0.5cc, D1cc, V10, V50, and V80 were examined. For the urethra, only Dmax and D10 were considered. Results: US plans had smaller 200% hot spots, although the dose homogeneity index for both was 0.7 ± 0.1. On average, plans using either modality satisfied planning goals. Although several parameters were significantly different between the two modalities (p < 0.05), the absolute differences were small. Of greatest, clinical relevance was the difference in frequency with which upper dose goals were exceeded. The prostate V200 goal was exceeded in 53% of CT-planned cases, but only 20% of those planned with US. The urethral D10 goal was never exceeded using US but was exceeded in 13% of CT cases. Conclusions: US planning results in plans that, clinically, are dosimetrically equivalent to CT-based planning. Upper dosimetric goals are, however, exceeded less often with US than with CT.
View
BrachyView, a novel in-body imaging system for HDR prostate brachytherapy: Experimental evaluation
Article
  • Dec 2015
Purpose: This paper presents initial experimental results from a prototype of high dose rate (HDR) BrachyView, a novel in-body source tracking system for HDR brachytherapy based on a multipinhole tungsten collimator and a high resolution pixellated silicon detector array. The probe and its associated position estimation algorithms are validated and a comprehensive evaluation of the accuracy of its position estimation capabilities is presented. Methods: The HDR brachytherapy source is moved through a sequence of positions in a prostate phantom, for various displacements in x, y, and z. For each position, multiple image acquisitions are performed, and source positions are reconstructed. Error estimates in each dimension are calculated at each source position and combined to calculate overall positioning errors. Gafchromic film is used to validate the accuracy of source placement within the phantom. Results: More than 90% of evaluated source positions were estimated with an error of less than one millimeter, with the worst-case error being 1.3 mm. Experimental results were in close agreement with previously published Monte Carlo simulation results. Conclusions: The prototype of HDR BrachyView demonstrates a satisfactory level of accuracy in its source position estimation, and additional improvements are achievable with further refinement of HDR BrachyView’s image processing algorithms.
View