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CT-based post-implant dosimetry for I-125 prostate brachytherapy: a multi-centre audit in the UK and Ireland

Published online by Cambridge University Press:  22 April 2013

O. Hayman  and
A. Palmer
O. Hayman*
Affiliation:
Medical Physics Department, Queen Alexandra Hospital, Portsmouth Hospitals NHS Trust, UK
A. Palmer
Affiliation:
Medical Physics Department, Queen Alexandra Hospital, Portsmouth Hospitals NHS Trust, UK
*
Correspondence to: Orla Hayman, Medical Physics Department, Queen Alexandra Hospital, Cosham, Portsmouth PO6 3LY, UK. Tel: 02392286000 ext 4087. E-mail: [email protected]
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Abstract

Background and purpose

To assess the reliability of post-implant CT (PICT) dosimetry for I-125 prostate seed brachytherapy by investigating the variation between centres in performing PICT through a multi-centre audit.

Materials and methods

Computerised tomography data sets from four I-125 prostate brachytherapy patients were circulated to nine participating centres. Centres followed local protocol for PICT outlining and seed identification, dosimetry for D90, V100 and V150 for the prostate was reported. Outlines were compared to determine the variation in: quality parameters (D90, V100 and V150), dose-volume histograms and approach to PICT dosimetry between the centres.

Results

There was significant variation in the prostate outlines drawn by the nine centres; for a prostate with mean volume 43 cm3, the range was 39–57 cm3 which led to variations of D90 of 119–154 Gy (mean 140 Gy) and V100 of 80–93% (mean of 88%). Using automatic seedfinder software reduced discrepancies between centres identifying seeds; overall consistency in seed location was good.

Conclusions

There was a significant uncertainty in the outlining of the prostate volume for PICT dosimetry with an uncertainty value of around ± 20 Gy on D90. PICT is a valuable technique but its accuracy and consistency limitations must be appreciated.

Keywords

auditinterdepartmental auditI-125 brachytherapypost-implant dosimetryprostate brachytherapy
Type
Original Articles
Information
Journal of Radiotherapy in Practice , Volume 12 , Issue 4 , December 2013 , pp. 297 - 304
Copyright
Copyright © Cambridge University Press 2013 

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