Oral & Poster Presentations Archive

UK & Ireland Prostate Brachytherapy Conference 2022

Abstract number 2 

Multisector dosimetric analysis of the prostate gland for the determination of optimal positions for in-vivo dosimeters in LDR prostate brachytherapy

Houlihan OA* **, Esteve S†, McLaughlin O** †, Workman G†, Byrne M†, Prise KM**, Hounsell AR†, Mitchell DM*, Jain S * **
* Department of Clinical Oncology, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust
** Patrick G. Johnston Centre for Cancer Research, Queen’s University Belfast
^† Department of Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust 

PURPOSE: To determine the optimal positions within the prostate for in-vivo dosimeters, developed as part of the EU H2020 Origin project, using multisector dosimetric analysis. 

METHODS: Dosimetric data from post-implant CTs were obtained for 606 men treated with LDR prostate brachytherapy 2009-2020. Sectors were created by dividing the prostate into three equal thirds (base/midgland/apex), then each third into four axial sectors. Axial division was performed by two separate methods; plus-shape (“+”) and cross-shape (“x”). Dose to 90% of each sector (D90%) was compared to D90% of the global prostate gland for each method. 

RESULTS: Compared to the global D90% of 107.85%±11.07%, mean D90% of the anterior right base was lowest (86.77%±14.82%) and the anterior left base was second lowest (96.99%±19.38%) using the plus-shaped sector division, with the D90% < global D90% in 91.25% and 76.40% of cases respectively. Using the cross-shaped sector division, mean D90% of the anterior and left base were lowest at 86.76%±15.96% and 96.39%±15.27% respectively with D90% < global D90% in 92.41% and 77.06% of cases respectively. The posterior right midgland and posterior left midgland had the highest (142.82%±18.42%) and second highest (141.99%±19.39%) D90% respectively using the plus-shaped sector division, with the D90% > the global D90% in 96.37% and 95.87% of cases respectively. Using the cross-shaped sector division, the right and posterior midgland sectors received the highest mean dose at 142.82%±18.03% and 142.35%±19.25% respectively, with D90% > global D90% in 96.53% and 96.20% of cases respectively. 

CONCLUSION: The mean D90% was lowest for the anterior right and left base sectors and highest for the posterior right and left midgland sectors with a significant percentage of the D90% of these sectors < or > global D90% respectively. Overlapping sectors of interest are appropriate locations for in-vivo dosimeters to monitor radiation dose, given their propensity for D90% differing from global D90%. 

Finance-source: The ORIGIN project is an initiative of the Photonics Public Private Partnership (www.photonics21.org), and has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871324. Authors are also supported by the Research and Development Division of the Public Health Agency of NI (COM/5610/20).