The British journal of radiology
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We have studied and analysed the magnitude of interfraction set-up errors and gold seed marker and prostate displacement in 118 patients using three gold seeds implanted within the prostate. Set-up errors and gold seed marker displacements were determined from bony anatomy and gold seed marker mismatch between the electronic portal image and the simulation digitally reconstructed radiograph (DRR), respectively. Prostate displacement relative to bony anatomy was determined from the difference between gold seed marker and bony anatomy displacement. ⋯ The isocentre set-up random errors were 1.6 mm (1.2-4.8 mm) for AP, 1.3 mm (0.6-2.5 mm) for L-R and 1.3 mm (1.0-2.6 mm) for SI directions. The mean and standard deviation of the prostate displacement systematic error relative to bony anatomy was 0.0+/-1.4 mm for AP, 0.0+/-1.1 mm for L-R and -0.2+/-2.4 mm for SI directions. Prostate displacement random errors were 1.5 mm (1.2-3.3 mm) for AP, 0.9 mm (0.4-1.5 mm) for L-R and 1.4 mm (1.2-2.4 mm) for SI directions.