Prostate brachytherapy post-implant dosimetry: A comparison between higher and lower source density

Thomas, C.; Kruk, Alexandra; McGahan, Colleen; Spadinger, Ingrid; Morris, William

doi:10.1016/j.radonc.2007.02.004

Cited by 19 publications

(4 citation statements)

References 23 publications

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“…Then, each region is further divided into posterior, anterior and lateral parts. Quadrant-based division of the prostate is a common approach in the literature (Sidhu et al, 2002;Thomas et al, 2007). However, for our application, this subdivision scheme provides more detailed reporting of results for different regions of the gland.…”

Section: Evaluation Methodsmentioning

confidence: 99%

New Image-Based Techniques for Prostate Biopsy and Treatment

Moradi¹

2012

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE April 2012 REPORT TYPE Annual Summary DATES COVERED PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBERUniversity of British Columbia Vancouver, CA V6T 1Z4 SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) U.S. Army Medical Research and Materiel Command Fort Detrick, Maryland 21702-5012 SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTApproved for Public Release; Distribution Unlimited SUPPLEMENTARY NOTES ABSTRACTThis report details the research and training outcomes of a prostate cancer postdoctoral training award. The work resulted in technologies for segmentation, cancer detection, and brachytherapy seed detection that take advantage of ultrasound vibroelastography and ultrasound RF signals. In segmentation, we report a fully automatic algorithm that combines B-mode and elastography data within an active shape model approach. For cancer detection, we report the sensitivity of 75.5% for elastography in cancer detection. In brachytherapy seed detection and dosimetry, we showed that the use of raw RF ultrasound signals can result in partial detection of the seed clouds, sufficient for registration to C-arm fluoroscopy for the purpose of dosimetry. The results were published in form of five journal publications and six conference presentations in international journals and conferences. The PI attended nine conferences and meetings during the course of the award. SUBJECT TERMS IntroductionThis documents reports the accomplishments of the PI, Dr Mehdi Moradi, supported by the postdoctoral training Award W81XWH-10-1-0201, from April 1, 2010 to March 31, 2012. The progress on the specific task listed in the award will be listed. Since this is a training award, other achievements of the trainee during the award will be enumerated as well. The technology developed for vibroelastography was described in the annual report. We will focus on progress towards specific clinical outcomes and achievements of the trainee.The rationale of the proposal is that prostate tumors cannot be visualized in the ultrasound Bmode i...

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Section: Evaluation Methodsmentioning

confidence: 99%

New Image-Based Techniques for Prostate Biopsy and Treatment

Moradi¹

2012

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“…Although there are no criteria in the clinical treatment guidelines that consider spatial properties, there are a few evaluation criteria in the literature that consider spatial properties: for BT there are the contiguous V 150 (Thomas et al 2007, Poulin et al 2013 and the contiguous V 200 (Thomas et al 2007), both related to the corresponding dosimetric index, and for EBRT there is the large cold spot metric (LCS D ), see Said et al (2017). The LCS D takes values between zero and one, and is defined as…”

Section: Spatial Propertiesmentioning

confidence: 99%

A mathematical optimization model for spatial adjustments of dose distributions in high dose-rate brachytherapy

2019

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High dose-rate brachytherapy is a modality of radiation therapy used for cancer treatment, in which the radiation source is placed within the body. The treatment goal is to give a high enough dose to the tumour while sparing nearby healthy tissue and organs (organs-at-risk). The most common criteria for evaluating dose distributions are dosimetric indices. For the tumour, such an index is the portion of the volume that receives at least a specified dose level (e.g. the prescription dose), while for organs-at-risk it is instead the portion of the volume that receives at most a specified dose level. Dosimetric indices are aggregate criteria and do not consider spatial properties of the dose distribution. Further, there are neither any established evaluation criteria for characterizing spatial properties, nor have such properties been studied in the context of mathematical optimization of brachytherapy. Spatial properties are however of clinical relevance and therefore dose plans are sometimes adjusted manually to improve them. We propose an optimization model for reducing the prevalence of contiguous volumes with a too high dose (hot spots) or a too low dose (cold spots) in a tentative dose plan. This model is independent of the process of constructing the tentative plan. We conduct computational experiments with tentative plans obtained both from optimization models and from clinical practice. The objective function considers pairs of dose points and each pair is given a distance-based penalty if the dose is either too high or too low at both dose points. Constraints are included to retain dosimetric indices at acceptable levels. Our model is designed to automate the manual adjustment step in the planning process. In the automatic adjustment step large-scale optimization models are solved. We show reductions of the volumes of the largest hot and cold spots, and the computing times are feasible in clinical practice.

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“…The dose-volume characteristics of the largest high-dose subvolume for a range of dose levels expressed as a percentage of the prescription dose is reflected in the contiguous dose-volume histogram (DVH c ). Thomas et al (2007) used the DVH c to quantify dose heterogeneity and perform a contiguous volume analysis in post-implant dosimetry of permanent prostate brachytherapy.…”

Section: High-dose Subvolumesmentioning

confidence: 99%

Dwell time modulation restrictions do not necessarily improve treatment plan quality for prostate HDR brachytherapy

et al. 2014

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Inverse planning algorithms for dwell time optimisation in interstitial high-dose-rate (HDR) brachytherapy may produce solutions with large dwell time variations within catheters, which may result in undesirable selective high-dose subvolumes. Extending the dwell time optimisation model with a dwell time modulation restriction (DTMR) that limits dwell time differences between neighboring dwell positions has been suggested to eliminate this problem. DTMRs may additionally reduce the sensitivity for uncertainties in dwell positions that inevitably result from catheter reconstruction errors and afterloader source positioning inaccuracies. This study quantifies the reduction of high-dose subvolumes and the robustness against these uncertainties by applying a DTMR to template-based prostate HDR brachytherapy implants. Three different DTMRs were consecutively applied to a linear dose-based penalty model (LD) and a dose-volume based model (LDV), both obtained from literature. The models were solved with DTMR levels ranging from no restriction to uniform dwell times within catheters in discrete steps. Uncertainties were simulated on clinical cases using in-house developed software, and dose-volume metrics were calculated in each simulation. For the assessment of high-dose subvolumes, the dose homogeneity index (DHI) and the contiguous dose volume histogram were analysed. Robustness was measured by the improvement of the lowest D90% of the planning target volume (PTV) observed in the simulations. For (LD), a DTMR yields an increase in DHI of approximately 30% and reduces the size of the largest high-dose volume by 2-5 cc. However, this comes at a cost of a reduction in D90% of the PTV of 10%, which often implies that it drops below the desired minimum of 100%. For (LDV), none of the DTMRs were able to improve high-dose volume measures. DTMRs were not capable of improving robustness of PTV D90% against uncertainty in dwell positions for both models.

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Prostate brachytherapy post-implant dosimetry: A comparison between higher and lower source density

Cited by 19 publications

References 23 publications

New Image-Based Techniques for Prostate Biopsy and Treatment

New Image-Based Techniques for Prostate Biopsy and Treatment

A mathematical optimization model for spatial adjustments of dose distributions in high dose-rate brachytherapy

Dwell time modulation restrictions do not necessarily improve treatment plan quality for prostate HDR brachytherapy

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