skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Prostatic edema in {sup 125}I permanent prostate implants: Dynamical dosimetry taking volume changes into account

Abstract

The purpose of this study is to determine the impact of edema on the dose delivered to the target volume. An evaluation of the edema characteristics was first made, and then a dynamical dosimetry algorithm was developed and used to compare its results to a standard clinical (static) dosimetry. Source positions and prostate contours extracted from 66 clinical cases on images taken at different points in time (planning, implant day, post-implant evaluation) were used, via the mean interseed distance, to characterize edema [initial increase ({delta}r{sub 0}), half-life ({tau})]. An algorithm was developed to take into account the edema by summing a time series of dose-volume histograms (DVHs) with a weight based on the fraction of the dose delivered during the time interval considered. The algorithm was then used to evaluate the impact of edema on the dosimetry of permanent implants by comparing its results to those of a standard clinical dosimetry. The volumetric study yielded results as follows: the initial prostate volume increase was found to be 1.58 (ranging from 1.15 to 2.48) and the edema half-life, approximately 30 days (range: 3 to 170 days). The dosimetric differences in D{sub 90} observed between the dynamic dosimetry and the clinical onemore » for a single case were up to 15 Gy and depended on the edema half-life and the initial volume increase. The average edema half-life, 30 days, is about 3 times longer than the previously reported 9 days. Dosimetric differences up to 10% of the prescription dose are observed, which can lead to differences in the quality assertion of an implant. The study of individual patient edema resorption with time might be necessary to extract meaningful clinical correlation or biological parameters in permanent implants.« less

Authors:
; ; ; ;  [1];  [2];  [2];  [2]
  1. Departement de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4 (Canada) and Centre de Recherche en Cancerologie, CHUQ-Hotel-Dieu de Quebec, Quebec, G1R 2J6 (Canada)
  2. (Canada)
Publication Date:
OSTI Identifier:
20775082
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 33; Journal Issue: 3; Other Information: DOI: 10.1118/1.2168066; (c) 2006 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; DOSIMETRY; EDEMA; HALF-LIFE; IMAGES; IODINE 125; PATIENTS; PLANNING; PROSTATE; RADIATION DOSES; RADIATION SOURCE IMPLANTS

Citation Formats

Leclerc, Ghyslain, Lavallee, Marie-Claude, Roy, Rene, Vigneault, Eric, Beaulieu, Luc, Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4, Centre de Recherche en Cancerologie, CHUQ-Hotel-Dieu de Quebec, Quebec, G1R 2J6,, and Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4, Canada, and Centre de Recherche en Cancerologie, CHUQ - Hotel-Dieu de Quebec, Quebec, G1R 2J6. Prostatic edema in {sup 125}I permanent prostate implants: Dynamical dosimetry taking volume changes into account. United States: N. p., 2006. Web. doi:10.1118/1.2168066.
Leclerc, Ghyslain, Lavallee, Marie-Claude, Roy, Rene, Vigneault, Eric, Beaulieu, Luc, Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4, Centre de Recherche en Cancerologie, CHUQ-Hotel-Dieu de Quebec, Quebec, G1R 2J6,, & Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4, Canada, and Centre de Recherche en Cancerologie, CHUQ - Hotel-Dieu de Quebec, Quebec, G1R 2J6. Prostatic edema in {sup 125}I permanent prostate implants: Dynamical dosimetry taking volume changes into account. United States. doi:10.1118/1.2168066.
Leclerc, Ghyslain, Lavallee, Marie-Claude, Roy, Rene, Vigneault, Eric, Beaulieu, Luc, Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4, Centre de Recherche en Cancerologie, CHUQ-Hotel-Dieu de Quebec, Quebec, G1R 2J6,, and Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4, Canada, and Centre de Recherche en Cancerologie, CHUQ - Hotel-Dieu de Quebec, Quebec, G1R 2J6. Wed . "Prostatic edema in {sup 125}I permanent prostate implants: Dynamical dosimetry taking volume changes into account". United States. doi:10.1118/1.2168066.
@article{osti_20775082,
title = {Prostatic edema in {sup 125}I permanent prostate implants: Dynamical dosimetry taking volume changes into account},
author = {Leclerc, Ghyslain and Lavallee, Marie-Claude and Roy, Rene and Vigneault, Eric and Beaulieu, Luc and Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4 and Centre de Recherche en Cancerologie, CHUQ-Hotel-Dieu de Quebec, Quebec, G1R 2J6, and Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, G1K 7P4, Canada, and Centre de Recherche en Cancerologie, CHUQ - Hotel-Dieu de Quebec, Quebec, G1R 2J6},
abstractNote = {The purpose of this study is to determine the impact of edema on the dose delivered to the target volume. An evaluation of the edema characteristics was first made, and then a dynamical dosimetry algorithm was developed and used to compare its results to a standard clinical (static) dosimetry. Source positions and prostate contours extracted from 66 clinical cases on images taken at different points in time (planning, implant day, post-implant evaluation) were used, via the mean interseed distance, to characterize edema [initial increase ({delta}r{sub 0}), half-life ({tau})]. An algorithm was developed to take into account the edema by summing a time series of dose-volume histograms (DVHs) with a weight based on the fraction of the dose delivered during the time interval considered. The algorithm was then used to evaluate the impact of edema on the dosimetry of permanent implants by comparing its results to those of a standard clinical dosimetry. The volumetric study yielded results as follows: the initial prostate volume increase was found to be 1.58 (ranging from 1.15 to 2.48) and the edema half-life, approximately 30 days (range: 3 to 170 days). The dosimetric differences in D{sub 90} observed between the dynamic dosimetry and the clinical one for a single case were up to 15 Gy and depended on the edema half-life and the initial volume increase. The average edema half-life, 30 days, is about 3 times longer than the previously reported 9 days. Dosimetric differences up to 10% of the prescription dose are observed, which can lead to differences in the quality assertion of an implant. The study of individual patient edema resorption with time might be necessary to extract meaningful clinical correlation or biological parameters in permanent implants.},
doi = {10.1118/1.2168066},
journal = {Medical Physics},
number = 3,
volume = 33,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • Purpose: To study the influence of prostatic edema on postimplant physical and radiobiological parameters using {sup 131}Cs permanent prostate seed implants. Methods and Materials: Thirty-one patients with early prostate cancer who underwent {sup 131}Cs permanent seed implantation were evaluated. Dose-volume histograms were generated for each set of prostate volumes obtained at preimplantation and postimplantion days 0, 14, and 28 to compute quality indices (QIs) and fractional doses at level x (FD{sub x}). A set of equations for QI, FD{sub x}, and biologically effective doses at dose level D{sub x} (BED{sub x}) were defined to account for edema changes with timemore » after implant. Results: There were statistically significant differences found between QIs of pre- and postimplant plans at day 0, except for the overdose index (ODI). QIs correlated with postimplant time, and FD{sub x} was found to increase with increasing postimplant time. With the effect of edema, BED at different dose levels showed less improvement due to the short half-life of {sup 131}Cs, which delivers about 85% of the prescribed dose before the prostate reaches its original volume due to dissipation of edema. Conclusions: Results of the study show that QIs, FD{sub x}, and BEDs at the level of D{sub x} changed from preneedle plans to postimplant plans and have statistically significant differences (p < 0.05), except for the ODI (p = 0.106), which suggests that at the time of {sup 131}C seed implantation, the effect of edema must be accounted for when defining the seed positions, to avoid the possibility of poor dosimetric and radiobiologic results for {sup 131}Cs seed implants.« less
  • Purpose: In vivo dosimetry during brachytherapy of the prostate with {sup 125}I seeds is challenging because of the high dose gradients and low photon energies involved. We present the results of a study using metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters to evaluate the dose in the urethra after a permanent prostate implantation procedure. Methods and Materials: Phantom measurements were made to validate the measurement technique, determine the measurement accuracy, and define action levels for clinical measurements. Patient measurements were performed with a MOSFET array in the urinary catheter immediately after the implantation procedure. A CT scan was performed, and dose values,more » calculated by the treatment planning system, were compared to in vivo dose values measured with MOSFET dosimeters. Results: Corrections for temperature dependence of the MOSFET array response and photon attenuation in the catheter on the in vivo dose values are necessary. The overall uncertainty in the measurement procedure, determined in a simulation experiment, is 8.0% (1 SD). In vivo dose values were obtained for 17 patients. In the high-dose region (> 100 Gy), calculated and measured dose values agreed within 1.7% {+-} 10.7% (1 SD). In the low-dose region outside the prostate (< 100 Gy), larger deviations occurred. Conclusions: MOSFET detectors are suitable for in vivo dosimetry during {sup 125}I brachytherapy of prostate cancer. An action level of {+-} 16% (2 SD) for detection of errors in the implantation procedure is achievable after validation of the detector system and measurement conditions.« less
  • Our aim in this work was to study the potential dosimetric effect of prostate edema on the accuracy of conventional pre- and post-implant dosimetry for prostate seed implants using the newly introduced {sup 131}Cs seed, whose radioactive decay half-life ({approx}9.7 days) is directly comparable to the average edema resolution half-life ({approx}10 days) observed previously by Waterman et al. for {sup 125}I implants [Int. J. Radiat. Oncol. Biol. Phys. 41, 1069-1077 (1998)]. A systematic calculation of the relative dosimetry effect of prostate edema on the {sup 131}Cs implant was performed by using an analytic solution obtained previously [Int. J. Radiat. Oncol.more » Biol. Phys. 47, 1405-1419 (2000)]. It was found that conventional preimplant dosimetry always overestimates the true delivered dose as it ignores the temporary increase of the interseed distance caused by edema. The overestimation for {sup 131}Cs implants ranged from 1.2% (for a small edema with a magnitude of 10% and a half-life of 2 days) to approximately 45% (for larger degree edema with a magnitude of 100% and a half-life of 25 days). The magnitude of pre- and post-implant dosimetry error for {sup 131}Cs implants was found to be similar to that of {sup 103}Pd implants for typical edema characteristics (magnitude <100%, and half-life <25 days); both of which are worse compared to {sup 125}I implants. The preimplant dosimetry error for {sup 131}Cs implants cannot be compensated effectively without knowing the edema characteristics before the seed implantation. On the other hand, the error resulted from a conventional post-implant dosimetry can be minimized (to within {+-}6%) for {sup 131}Cs implants if the post-implant dosimetry is performed at 10{+-}2 days post seed implantation. This 'optimum' post-implant dosimetry time is shorter than those determined previously for the {sup 103}Pd and {sup 125}I implants at 16{+-}4 days and 6{+-}1 weeks, respectively.« less
  • The robustness of treatment planning to prostatic edema for three different isotopes ({sup 125}I, {sup 103}Pd, and {sup 131}Cs) is explored using dynamical dose calculations on 25 different clinical prostate cases. The treatment plans were made using the inverse planning by simulated annealing (IPSA) algorithm. The prescription was 144, 127, and 125 Gy for {sup 125}I, {sup 131}Cs, and {sup 103}Pd, respectively. For each isotope, three dose distribution schemes were used to impose different protection levels to the urethra: V{sub 120}=0%, V{sub 150}=0%, and V{sub 150}=30%. Eleven initial edema values were considered ranging from 1.0 (no edema) to 2.0 (100%).more » The edema was assumed to resolve exponentially with time. The prostate volume, seed positions, and seed activity were dynamically tracked to produce the final dose distribution. Edema decay half-lives of 10, 30, and 50 days were used. A total of 675 dynamical calculations were performed for each initial edema value. For the {sup 125}I isotope, limiting the urethra V{sub 120} to 0% leads to a prostate D{sub 90} under 140 Gy for initial edema values above 1.5. Planning with urethra V{sub 150} at 0% provides a good response to the edema; the prostate D{sub 90} remains higher than 140 Gy for edema values up to 1.8 and a half-life of 30 days or less. For {sup 103}Pd, the prostate D{sub 90} is under 97% of the prescription dose for approximately 66%, 40%, and 30% of edema values for urethra V{sub 120}=0%, V{sub 150}=0%, and V{sub 150}=30%, respectively. Similar behavior is seen for {sup 131}Cs and the center of the prostate becomes 'cold' for almost all edema scenarios. The magnitude of the edema following prostate brachytherapy, as well as the half-life of the isotope used and that of the edema resorption, all have important impacts on the dose distribution. The {sup 125}I isotope with its longer half-life is more robust to prostatic edema. Setting up good planning objectives can provide an adequate compromise between organ doses and robustness. This is even more important since seed misplacements will contribute to further degrade dose coverage.« 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