Jessica Swanson
Royal Adelaide Hospital
Radiation Therapist

Alexandre Santos
Medical Physicist
Royal Adelaide Hospital

Jessica Swanson1 and Alexandre Santos1,2

1 – Department of Radiation Oncology, Royal Adelaide Hospital, Adelaide, South Australia

2 – School of Physical Sciences, University of Adelaide, Adelaide, South Australia

Purpose: Hydrogels are utilised to increase the distance between the rectum and prostate, since the rectum is an organ at risk (OAR), increasing the separation means reducing the dose to the OAR. The purpose of this study was to investigate the effect that hydrogel (Duraseal, Integra) has on the Ultrasound (US) quality when inserted between the rectum & prostate during High Dose Rate (HDR) Brachytherapy treatment.

Material and Methods: Image acquisitions of a tissue equivalent ultrasound prostate phantom – Model number 053 (CIRS Inc., Norfold, VA, USA) were carried out at various stages of the HDR prostate brachytherapy process (ie, prior to needle or hydrogel insertion, after needle insertion with no hydrogel & finally following hyrdrogel & needle insertion). Image acquisition was performed via US (Flex Focus 400, BK Medical) along with CT (Aquilion LB, Canon, Japan) and stainless steel needles were (GM11009520, Varian, USA) used. The three sets of US and CT images were contoured & the image sets containing needles also had needle reconstruction. The image quality & the needle reconstruction were evaluated qualitatively. Quantitatively, US prostate contour volumes were compared between the three image sets. Needle tips were compared between US and CT image sets, and any artefacts were recorded.

Results: Image quality was observed to degrade following the introduction of hydrogel but this was not observed to affect the contouring or needle reconstruction. The US prostate volume was contoured to be 64.03 cm3, 61.16cm3, 60.37cm3 for the no needles, needles & needles with hydrogel cases respectively. For the needle tip identification the agreement between US and CT image sets was 0.11 ± 0.21 mm and 0.04 ± 0.12 mm, for the no hydrogel and hydrogel, respectively.

Conclusions: In summary, the hydrogel was not observed to degrade the image quality significantly and did not affect the contouring ability or accuracy. The needle tip agreement between US and CT was better for the hydrogel image sets, however this was not significant.

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