An update survey of UK in vivo radiotherapy dosimetry practice.

A questionnaire was distributed in 2004 to 59 radiotherapy physics departments in the UK to determine whether in vivo dosimetry practice had changed since a similar survey conducted 10 years earlier. The number of centres carrying out central axis dosimetry had increased slightly from 17 centres in 1994 to 22 centres in 2004, with a diode alone being the most commonly used detector. Twice as many centres (43) carried out critical organ dosimetry compared with those carrying out central axis measurements, and this number had also increased slightly above the 1994 value (38). A diode was used by most centres carrying out central axis dosimetry and by about 50% of centres carrying out critical organ dosimetry. The action level adopted by each centre for central axis measurements varied from >+/-3% to >+/-10% difference between the measured and the prescribed dose, with >+/-5% being the most frequent value. It was concluded that there had been little change in in vivo dosimetry practice during the time between the two surveys, and that guidance on the method and applications for in vivo dosimetry is required before recent recommendations for its widespread adoption for routine use can be satisfied.