Potential impact of prostate edema on the dosimetry of permanent seed implants using the new {sup 131}Cs (model CS-1) seeds

Journal Article · Sat Apr 15 04:00:00 EDT 2006 · Medical Physics

DOI:https://doi.org/10.1118/1.2179170· OSTI ID:20775135

Zhe, Chen; Jun, Deng; Roberts, Kenneth; Nath, Ravinder ^[1]

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1. Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06504 (United States)

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. 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.

• OSTI ID: 20775135
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 4 Vol. 33; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ACCURACY
BRACHYTHERAPY
CESIUM 131
DOSIMETRY
EDEMA
ERRORS
HALF-LIFE
IODINE 125
NUCLEAR DECAY
PALLADIUM 103
PROSTATE
RADIATION DOSES
RADIATION SOURCE IMPLANTS
RADIATION SOURCES