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Title: Multi-species prostate implant treatment plans incorporating {sup 192}Ir and {sup 125}I using a Greedy Heuristic based 3D optimization algorithm

Abstract

The goals of interstitial implant brachytherapy include delivery of the target dose in a uniform manner while sparing sensitive structures, and minimizing the number of needles and sources. We investigated the use of a multi-species source arrangement ({sup 192}Ir with {sup 125}I) for treatment in interstitial prostate brachytherapy. The algorithm utilizes an 'adjoint ratio', which provides a means of ranking source positions and is the criterion for the Greedy Heuristic optimization. Three cases were compared, each using 0.4 mCi {sup 125}I seeds: case I is the base case using {sup 125}I alone, case II uses 0.12 mCi {sup 192}Ir seeds mixed with {sup 125}I, and case III uses 0.25 mCi {sup 192}Ir mixed with {sup 125}I. Both multi-species cases result in lower exposure of the urethra and central prostate region. Compared with the base case, the exposure to the rectum and normal tissue increases by a significant amount for case III as compared with the increase in case II, signifying the effect of slower dose falloff rate of higher energy gammas of {sup 192}Ir in the tissue. The number of seeds and needles decreases in both multi-species cases, with case III requiring fewer seeds and needles than case II. Further,more » the effect of {sup 192}Ir on uniformity was investigated using the 0.12 mCi {sup 192}Ir seeds in multi-species implants. An increase in uniformity was observed with an increase in the number of 0.12 mCi {sup 192}Ir seeds implanted. The effects of prostate size on the evaluation parameters for multi-species implants were investigated using 0.12 mCi {sup 192}Ir and 0.4 mCi {sup 125}I, and an acceptable treatment plan with increased uniformity was obtained.« less

Authors:
; ; ;  [1];  [2];  [2];  [2]
  1. Department of Engineering Physics and Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20951036
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 2; Other Information: DOI: 10.1118/1.2400827; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ALGORITHMS; BRACHYTHERAPY; CARCINOMAS; DOSIMETRY; EVALUATION; IODINE 125; IRIDIUM 192; OPTIMIZATION; PROSTATE; RADIATION DOSES; RADIATION SOURCE IMPLANTS; RECTUM; URINARY TRACT

Citation Formats

Chaswal, V., Yoo, S., Thomadsen, B. R., Henderson, D. L., Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, Department of Engineering Physics, Department of Medical Physics, University of Wisconsin-Madison, and Department of Human Oncology, University of Wisconsin Medical School, Madison, Wisconsin 53706, and Department of Engineering Physics and Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706. Multi-species prostate implant treatment plans incorporating {sup 192}Ir and {sup 125}I using a Greedy Heuristic based 3D optimization algorithm. United States: N. p., 2007. Web. doi:10.1118/1.2400827.
Chaswal, V., Yoo, S., Thomadsen, B. R., Henderson, D. L., Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, Department of Engineering Physics, Department of Medical Physics, University of Wisconsin-Madison, and Department of Human Oncology, University of Wisconsin Medical School, Madison, Wisconsin 53706, & Department of Engineering Physics and Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706. Multi-species prostate implant treatment plans incorporating {sup 192}Ir and {sup 125}I using a Greedy Heuristic based 3D optimization algorithm. United States. doi:10.1118/1.2400827.
Chaswal, V., Yoo, S., Thomadsen, B. R., Henderson, D. L., Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, Department of Engineering Physics, Department of Medical Physics, University of Wisconsin-Madison, and Department of Human Oncology, University of Wisconsin Medical School, Madison, Wisconsin 53706, and Department of Engineering Physics and Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706. Thu . "Multi-species prostate implant treatment plans incorporating {sup 192}Ir and {sup 125}I using a Greedy Heuristic based 3D optimization algorithm". United States. doi:10.1118/1.2400827.
@article{osti_20951036,
title = {Multi-species prostate implant treatment plans incorporating {sup 192}Ir and {sup 125}I using a Greedy Heuristic based 3D optimization algorithm},
author = {Chaswal, V. and Yoo, S. and Thomadsen, B. R. and Henderson, D. L. and Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710 and Department of Engineering Physics, Department of Medical Physics, University of Wisconsin-Madison, and Department of Human Oncology, University of Wisconsin Medical School, Madison, Wisconsin 53706 and Department of Engineering Physics and Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706},
abstractNote = {The goals of interstitial implant brachytherapy include delivery of the target dose in a uniform manner while sparing sensitive structures, and minimizing the number of needles and sources. We investigated the use of a multi-species source arrangement ({sup 192}Ir with {sup 125}I) for treatment in interstitial prostate brachytherapy. The algorithm utilizes an 'adjoint ratio', which provides a means of ranking source positions and is the criterion for the Greedy Heuristic optimization. Three cases were compared, each using 0.4 mCi {sup 125}I seeds: case I is the base case using {sup 125}I alone, case II uses 0.12 mCi {sup 192}Ir seeds mixed with {sup 125}I, and case III uses 0.25 mCi {sup 192}Ir mixed with {sup 125}I. Both multi-species cases result in lower exposure of the urethra and central prostate region. Compared with the base case, the exposure to the rectum and normal tissue increases by a significant amount for case III as compared with the increase in case II, signifying the effect of slower dose falloff rate of higher energy gammas of {sup 192}Ir in the tissue. The number of seeds and needles decreases in both multi-species cases, with case III requiring fewer seeds and needles than case II. Further, the effect of {sup 192}Ir on uniformity was investigated using the 0.12 mCi {sup 192}Ir seeds in multi-species implants. An increase in uniformity was observed with an increase in the number of 0.12 mCi {sup 192}Ir seeds implanted. The effects of prostate size on the evaluation parameters for multi-species implants were investigated using 0.12 mCi {sup 192}Ir and 0.4 mCi {sup 125}I, and an acceptable treatment plan with increased uniformity was obtained.},
doi = {10.1118/1.2400827},
journal = {Medical Physics},
number = 2,
volume = 34,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • Purpose: To compare the urethral and prostate absolute and biologic effective doses (BEDs) for {sup 131}Cs and {sup 125}I prostate permanent implant brachytherapy (PPI). Methods and Materials: Eight previously implanted manually planned {sup 125}I PPI patients were replanned manually with {sup 131}Cs, and re-planned using Inverse Planning Simulated Annealing. {sup 131}Cs activity and the prescribed dose (115 Gy) were determined from that recommended by IsoRay. The BED was calculated for the prostate and urethra using an {alpha}/{beta} ratio of 2 and was also calculated for the prostate using an {alpha}/{beta} ratio of 6 and a urethral {alpha}/{beta} ratio of 2.more » The primary endpoints of this study were the prostate D{sub 90} BED (pD{sub 90}BED) and urethral D{sub 30} BED normalized to the maximal potential prostate D{sub 90} BED (nuD{sub 30}BED). Results: The manual plan comparison ({alpha}/{beta} = 2) yielded no significant difference in the prostate D{sub 90} BED (median, 192 Gy{sub 2} for both isotopes). No significant difference was observed for the nuD{sub 30}BED (median, 199 Gy{sub 2} and 202 Gy{sub 2} for {sup 125}I and {sup 131}Cs, respectively). For the inverse planning simulated annealing plan comparisons ({alpha}/{beta} 2), the prostate D{sub 90} BED was significantly lower with {sup 131}Cs than with {sup 125}I (median, 177 Gy{sub 2} vs. 187 Gy{sub 2}, respectively; p = 0.01). However, the nuD{sub 30}BED was significantly greater with {sup 131}Cs than with {sup 125}I (median, 192 Gy{sub 2} vs. 189 Gy{sub 2}, respectively; p = 0.01). Both the manual and the inverse planning simulated annealing plans resulted in a significantly lower prostate D{sub 90} BED (p = 0.01) and significantly greater nuD{sub 30}BED for {sup 131}Cs (p = 0.01), compared with {sup 125}I, when the prostate {alpha}/{beta} ratio was 6 and the urethral {alpha}/{beta} ratio was 2. Conclusion: This report highlights the controversy in comparing the dose to both the prostate and the organs at risk with different radionuclides.« less
  • Permanent and removable interstitial implantation techniques for neoplasm radiotherapy using absorbable and unabsorbable sutures are described. Most of these techniques can be performed in the clinic easily and quickly with basic instruments: needle holder, needle book, and hemoclips. Specifically, $sup 192$Ir (74.4 day half life, 300 to 610 keV, and 6.0 cm hvl in tissue) nylon ribbon and $sup 125$I (60 day half life, 27 to 35 keV, and 2.0 cm hvl in tissue) Vicryl sutures are described. A major advantage of the $sup 125$I over the $sup 192$Ir seed (other than the fact that it can be permanently implantedmore » and needs less radiation protection) is that the patient does not remain highly radioactive for as long a period due to the extremely low $sup 125$I energy and may be allowed to leave the hospital. Both nuclides have the advantage of a long shelf life, making their use practical and economically feasible. (auth)« less
  • Purpose: To compare stranded seeds (SSs) with loose seeds (LSs) in terms of prostate edema, dosimetry, and seed loss after {sup 125}I brachytherapy. Methods and Materials: Two prospective cohorts of 20 men participated in an institutional review board-approved protocols to study postimplant prostate edema and its effect on dosimetry. The LS cohort underwent brachytherapy between September 2002 and July 2003 and the SS cohort between April 2006 and January 2007. Both cohorts were evaluated sequentially using computed tomography-magnetic resonance imaging fusion-based dosimetry on Days 0, 7, and 30. No hormonal therapy or supplemental beam radiotherapy was used. Results: Prostate edemamore » was less in the SS cohort at all points (p = NS). On Day 0, all the prostate dosimetric factors were greater in the LS group than in the SS group (p = 0.003). However, by Days 7 and 30, the dosimetry was similar between the two cohorts. No seeds migrated to the lung in the SS cohort compared with a total of five seeds in 4 patients in the LS cohort. However, the overall seed loss was greater in the SS cohort (24 seeds in 6 patients; 1.1% of total vs. 0.6% for LSs), with most seeds lost through urine (22 seeds in 5 patients). Conclusion: Despite elimination of venous seed migration, greater seed loss was observed with SSs compared with LSs, with the primary site of loss being the urinary tract. Modification of the technique might be necessary to minimize this. Prostate dosimetry on Days 7 and 30 was similar between the SS and LS cohorts.« less
  • Sixty-three consecutive patients with cancer of the prostate treated by pelvic lymphadenectomy, I-125 implantation +/- Co60 therapy were studied regarding the impact of extension of cancer beyond the capsule and minimal nodal involvement. Extension of cancer beyond the prostatic capsule, Stage T3, constituted 34%, while Stages T0-2 comprised 66% of the cases. The features of T3 compared with T2 or less were: higher incidence of younger age (50s), 29% vs. 19%; less well-differentiated cancer, 29% vs. 64%; higher incidence of pelvic node involvement, 52% vs. 18%; and higher incidence of recurrence, 24% vs. 4.7%. The involvement of only one ormore » two pelvic nodes by microscopic cancer did not adversely affect the prognosis in T2 group over a relatively short period of follow-up. No local recurrence occurred in T2. In the T3 group, two of 21 (9.5%) developed local recurrence.« less
  • Purpose: The aim of this work is to validate a deterministic radiation transport based treatment planning system (TPS) for single {sup 192}Ir brachytherapy source dosimetry in homogeneous water geometries. Methods: TPS results were obtained using the deterministic radiation transport option of a BRACHYVISION v. 8.8 system for three characteristic source designs (VS2000, GMPlus HDR, and GMPlus PDR) with each source either centered in a 15 cm radius spherical water phantom, or positioned at varying distance away from the phantom center. Corresponding MC simulations were performed using the MCNPX code v.2.5.0 and source geometry models prepared using information provided by themore » manufacturers. Results: Comparison in terms of the AAPM TG-43 dosimetric formalism quantities, as well as dose rate distributions per unit air kerma strength with a spatial resolution of 0.1 cm, yielded close agreement between TPS and MC results for the sources centered in the phantom. Besides some regions close to the source longitudinal axes where discrepancies could be characterized as systematic, overall agreement for all three sources studied is comparable to the statistical (type A) uncertainty of MC simulations (1% at the majority of points in the geometry increasing to 2%-3% at points lying both away from the source center and close to the source longitudinal axis). A corresponding good agreement was also found between TPS and MC results for the sources positioned away from the phantom center. Conclusions: Results of this work attest the capability of the TPS to accurately account for the scatter conditions regardless of the size or shape of a given geometry of dosimetric interest, and the position of a source within it. This is important since, as shown in the literature and summarized also in this work, these factors could introduce a significant dosimetric effect that is currently ignored in clinical treatment planning. It is concluded that the implementation of the deterministic radiation transport option of the BRACHYVISION v. 8.8 system for {sup 192}Ir brachytherapy dosimetry in homogeneous water geometries yields results of comparable accuracy to the golden standard of Monte Carlo simulation, in clinically viable calculation times.« less