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Med Dosim. 1997 Spring;22(1):43-6.

Anterior-posterior treatment localization in pelvic radiotherapy: tattoos or fixed couch-to-isocentre distance.

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  • 1Oncology Department, Auckland Hospital, New Zealand. pgreer@ahsl.co.nz


The methods of determining the anterior-posterior isocentre location in pelvic radiotherapy are either by aligning lateral localization lasers to tattoo marks on skin, or by setting a constant daily couch-to-isocentre distance. While using the former method the day-to-day vertical couch movement was recorded and combined with measurements of day-to-day anterior-posterior patient movement made with an electronic portal imaging device to determine whether couch vertical movement contributes to anterior-posterior setup variation. Seven unimmobilized patients were studied, four supine prostate and three prone rectum patients. The two motions were found to be highly correlated (correlation coefficient = 0.82) which supports the constant couch-to-isocentre distance approach. When the day-to-day couch vertical movement was subtracted from the anterior-posterior movement results the setup variation was reduced in six of the seven patients.

[PubMed - indexed for MEDLINE]
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