[The value of routine in vivo measurements in radiotherapy (author's transl)]

The authors carried out routine measurements in vivo, and emphasise their value in radiotherapy. After reviewing the objectives of in vivo measurements in general, and showing the problems posed by routine measurements, they describe the technique of measurement using thermoluminescent dosimeters and the problems associated with their use in patients treated with the aid of a 5.5 MV linear accelerator. Results based upon 232 routine measurements made it possible to establish a correlation between the dose delivered and the expected dose. Under optimal functional conditions, almost all the deviations seen were less than 5% whilst higher deviations occurred when the apparatus showed signs of instability. They conclude that routine in vivo measurements are extremely useful in ensuring that planned treatment is carried out in a satisfactory manner and also in the early detection of potential faults in equipment.