Assessment of motion and field placement verification of the prostate using gold seed fiducial markers: a feasibility study

Purpose: The aim of this study was to determine the feasibility of using gold seed fiducial markers within the daily treatment of prostate cancer patients as a means of improving treatment field placement accuracy and minimising the effect of interfractional prostate movement. Methods: Ten patients had three fiducial markers inserted into the prostate gland under ultrasound guidance. Daily verification images were acquired throughout standard radiation therapy treatment with the measurement, comparison and analysis of bony anatomy displacement to fiducial marker displacement performed. Results: Greater than 20% of measurements in the superior/inferior (SI), anterior/posterior (AP) directions and displacement magnitude, would have resulted in a different action when using bony anatomy compared to fiducial markers, compared to less than 3% in the right/left (RL) direction. The mean prostate displacement was 0.46, 1.52 and 1.75 mm in the LR, SI, and AP directions respectively. The maximum prostate displacement was 10, 16 and 18 mm in the LR, SI, and AP directions respectively. Mean displacement magnitude was 6.32 mm, with a maximum displacement magnitude of 18 mm. Conclusion: This trial supports the growing body of evidence that there is benefit in the use of daily imaging with prostatic gold seed fiducial markers for more accurate treatment localisation.