Acta Med. 2011, 54: 149-152

Daily Prostate Volume and Position Monitoring Using Implanted Gold Markers and On-Board Imaging during Radiotherapy

Linda Kašaováa,b, Igor Siráka, Jan Jansaa, Petr Paluskaa, Jiří Peteraa

aCharles University in Prague, Faculty of Medicine and University Hospital Hradec Králové, Czech Republic: Department of Oncology and Radiotherapy
bUniversity of Defence, Faculty of Military Health Sciences, Hradec Králové, Czech Republic

Received May 24, 2011
Accepted October 11, 2011

Purpose: This study aimed to evaluate prostate volume changes and prostate motions during radiotherapy. Methods: In 2010, twenty-five patients were treated for prostate cancer by external beam radiotherapy with implanted fiducial markers. Coordinates of three gold markers on kilovoltage images were calculated daily. Volume changes in target structure were observed through changes in intermarker distances. Differences in patient position between laser-tattoo alignment and gold marker localization were evaluated. Intrafraction motion was assessed by measuring marker displacement on kilovoltage images acquired before and after fraction delivery. Results: Prostate shrinkage was observed in 60% of patients. The average shrinkage was 7% of the prostate’s initial volume. Corrections after laser-tattoo alignment remained mostly below 1 cm. The difference between marker centroid position on the actual images and the planning images was 2 ± 1 mm on average. The extension of intrafraction movements was 7.6 ± 0.2 mm on average. Conclusions: In our retrospective study, the possibility for prostate volume changes during radiotherapy was revealed. Intrafraction movements turned out to be the limiting factor in safety margin reduction.


This study was supported by Charles University Grant Agency, no. 144210.


6 live references