Cl. Hanna et al., Accuracy of patient positioning during radiotherapy for bladder and brain tumours (vol 11, pg 93, 1999), CL ONCOL-UK, 11(3), 1999, pp. 213-213
We report the results of a prospective study to quantify inaccuracies in pa
tient set-up during routine radiotherapy for tumours of the brain and bladd
er, which took place as part of our departmental development, Knowledge of
these inaccuracies is required to put into practice the ICRU 50 recommendat
ions regarding clinical target volume and planning target volume. We measur
ed inaccuracies in two dimensions by comparing portal beam films with the s
imulator check film. Our method used manual measurements, proved to be a ve
ry laborious technique, and demonstrated the need for portal imaging.
Ninety-five brain and 97 bladder portal films from 30 brain and 30 bladder
patients were examined. Displacements greater than 0.5 cm were seen in 13%
of brain treatments in the supero-inferior direction and 1% in the anteropo
sterior direction. With bladder treatments, displacements greater than 0.75
cm were seen in 12% in the supero-inferior direction and 5% in the lateral
direction. These results are consistent with other previous studies. We id
entified a very small systematic error in the department, which was not con
sidered to be clinically significant, These results are discussed with refe
rence to other similar studies and the ICRU 50 recommendations.