Practical experience with intensity-modulated radiotherapy

At the Ipswich Hospital implementation of intensity-modulated radiotherapy (IMRT) commenced in February 2001 based on an established 3D conformal radiotherapy (3D CRT) service. This paper describes our experiences as we commissioned a fully-integrated IMRT planning and delivery system, and established IMRT within the department. Commissioning measurements incorporated a series of tests to ensure the integrity of the system and form the basis of routine quality assurance (QA) procedures. Potential IMRT patients proceeded through pre-treatment in the same way as standard 3D CRT patients. All were dual-planned for IMRT and 3D CRT with no change in established fractionation regimen, and the resulting plans evaluated. IMRT was selected for treatment where it offered a significant advantage by improving dose homogeneity and conformity within the target volume and/or reducing dose to organs at risk. Extensive pre-treatment verification was undertaken on all plans to check dynamic multileaf collimator (MLC) delivery and monitor unit calculation. Patients were monitored throughout treatment with amorphous silicon electronic portal imaging to ensure reproducibility of set-up. Between June 2001 and June 2003 21 patients were treated with inverse-planned IMRT to sites within the head and neck and lung. IMRT has enabled precise delivery to irregular shaped target volumes, avoiding organs at risk and enabling doses to be increased to radical levels in some cases. Additionally over 200 CT scanned breast patients were treated with forward-planned electronic compensation delivered by dynamic MLC, improving dose homogeneity within the breast volume compared with standard wedged plans. The IMRT programme will continue at the Ipswich Hospital with the introduction of further clinical sites and adoption of more aggressive fractionation regimens within the confines of multicentre clinical trials.