Comparison of prostate set-up accuracy and margins with off-line bony anatomy corrections and online implanted fiducial-based corrections
Summary The aim of the study was to determine prostate set‐up accuracy and set‐up margins with off‐line bony anatomy‐based imaging protocols, compared with online implanted fiducial marker‐based imaging with daily corrections. Eleven patients were treated with implanted prostate fiducial markers and...
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Veröffentlicht in: | Journal of medical imaging and radiation oncology 2008-10, Vol.52 (5), p.511-516 |
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Sprache: | eng |
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Zusammenfassung: | Summary
The aim of the study was to determine prostate set‐up accuracy and set‐up margins with off‐line bony anatomy‐based imaging protocols, compared with online implanted fiducial marker‐based imaging with daily corrections. Eleven patients were treated with implanted prostate fiducial markers and online set‐up corrections. Pretreatment orthogonal electronic portal images were acquired to determine couch shifts and verification images were acquired during treatment to measure residual set‐up error. The prostate set‐up errors that would result from skin marker set‐up, off‐line bony anatomy‐based protocols and online fiducial marker‐based corrections were determined. Set‐up margins were calculated for each set‐up technique using the percentage of encompassed isocentres and a margin recipe. The prostate systematic set‐up errors in the medial–lateral, superior–inferior and anterior–posterior directions for skin marker set‐up were 2.2, 3.6 and 4.5 mm (1 standard deviation). For our bony anatomy‐based off‐line protocol the prostate systematic set‐up errors were 1.6, 2.5 and 4.4 mm. For the online fiducial based set‐up the results were 0.5, 1.4 and 1.4 mm. A prostate systematic error of 10.2 mm was uncorrected by the off‐line bone protocol in one patient. Set‐up margins calculated to encompass 98% of prostate set‐up shifts were 11–14 mm with bone off‐line set‐up and 4–7 mm with online fiducial markers. Margins from the van Herk margin recipe were generally 1–2 mm smaller. Bony anatomy‐based set‐up protocols improve the group prostate set‐up error compared with skin marks; however, large prostate systematic errors can remain undetected or systematic errors increased for individual patients. The margin required for set‐up errors was found to be 10–15 mm unless implanted fiducial markers are available for treatment guidance. |
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ISSN: | 1754-9477 1754-9485 |
DOI: | 10.1111/j.1440-1673.2008.02005.x |