JRSBRT 8.2, p. 105-108

Quantitative Evaluation of Volume Change of Perirectal Hydrogel Spacer by Dixon-Based Water-Only Images
Yukihiro Hama and Etsuko Tate

Purpose: There are no detailed data on volume changes of SpaceOAR hydrogel spacer. The purpose of this study was to quantitatively evaluate the volume changes of SpaceOAR during radiation therapy for prostate cancer.

Materials: The volume of SpaceOAR in seven prostate cancer patients was quantitatively measured every two weeks by Dixon-based water-only MRI scans.

Results: The volume of SpaceOAR increased and remained increased for 11 weeks after placement in all cases. The day to reach the maximum volume was 49.9 +/- 9.2 (mean +/- standard deviation [SD]) days after placement. The maximum rate of increase in Space OAR volume was 20% +/- 9% (mean +/- SD).

Conclusion: The volume of SpaceOAR was shown to be greater than the initial volume for 11 weeks after placement, with an increase of up to 20%. Therefore, care should be taken when creating a radiation treatment planning and positioning a patient during radiation therapy.

Keywords: prostatic neoplasms, radiotherapy, adverse effects, radiosurgery, intensity-modulated radiotherapy

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