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Open AccessFeature PaperArticle
Medicines 2018, 5(2), 32;

Dosimetric Implications of Computerised Tomography-Only versus Magnetic Resonance-Fusion Contouring in Stereotactic Body Radiotherapy for Prostate Cancer

Royal Marsden Hospital, Fulham Road, London SW3 6JJ, UK
Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK
The Cancer Centre, University Hospitals Birmingham, Mindelsohn Way, Edgbaston, Birmingham B15 2GW, UK
Author to whom correspondence should be addressed.
Received: 31 March 2018 / Revised: 2 April 2018 / Accepted: 3 April 2018 / Published: 5 April 2018
(This article belongs to the Special Issue Advances and Perspectives in Radiotherapy Treatments)
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Background: Magnetic resonance (MR)-fusion contouring is the standard of care in prostate stereotactic body radiotherapy (SBRT) for target volume localisation. However, the planning computerised tomography (CT) scan continues to be used for dose calculation and treatment planning and verification. Discrepancies between the planning MR and CT scans may negate the benefits of MR-fusion contouring and it adds a significant resource burden. We aimed to determine whether CT-only contouring resulted in a dosimetric detriment compared with MR-fusion contouring in prostate SBRT planning. Methods: We retrospectively compared target volumes and SBRT plans for 20 patients treated clinically with MR-fusion contouring (standard of care) with those produced by re-contouring using CT data only. Dose was 36.25 Gy in 5 fractions. CT-only contouring was done on two occasions blind to MR data and reviewed by a separate observer. Primary outcome was the difference in rectal volume receiving 36 Gy or above. Results: Absolute target volumes were similar: 63.5 cc (SD ± 27.9) versus 63.2 (SD ± 26.5), Dice coefficient 0.86 (SD ± 0.04). Mean difference in apex superior-inferior position was 1.1 (SD ± 3.5; CI: −0.4–2.6). Small dosimetric differences in favour of CT-only contours were seen, with the mean rectal V36 Gy 0.3 cc (95% CI: 0.1–0.5) lower for CT-only contouring. Conclusions: Prostate SBRT can be successfully planned without MR-fusion contouring. Consideration can be given to omitting MR-fusion from the prostate SBRT workflow, provided reference to diagnostic MR imaging is available. Development of MR-only work flow is a key research priority to gain access to the anatomical fidelity of MR imaging. View Full-Text
Keywords: prostate; MRI; CT; fusion; radiotherapy; stereotactic; contouring; planning prostate; MRI; CT; fusion; radiotherapy; stereotactic; contouring; planning

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Henderson, D.R.; Tree, A.C.; Harrington, K.J.; van As, N.J. Dosimetric Implications of Computerised Tomography-Only versus Magnetic Resonance-Fusion Contouring in Stereotactic Body Radiotherapy for Prostate Cancer. Medicines 2018, 5, 32.

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