Patient activation with a 25 MV therapeutic X-ray beam

The authors conclude that because of the almost uniform distribution of induced activity, the sensitivity of an imaging device to differences in blood flow in the irradiated volume will be low with only relatively coarse resolution being achievable. In addition, the presence of both wash-in and wash-out effects could lead to difficulties in the quantitative interpretation of results from planar images. It may be possible, however, to identify radiation-induced blood flow changes in large organs such as the liver. Given the relative simplicity of the technique further investigation of its clinical value is merited. (author)