Background and purpose: Total body irradiation (TBI) is a treatment used in the conditioning of patients prior to hematopoietic stem cell transplantation. We developed an extended-distance TBI technique using a conventional linac with multi-leaf collimator to deliver a homogeneous dose, and spare critical organs. Materials and methods: Patients were treated either in lateral recumbent or in supine position depending on the dose level. A conventional linac was used with the patient midline at 350 cm from the beam source. A series of beams was prepared manually using a 3D treatment planning system (TPS) aiming to improve dose homogeneity, spare the organs at risk and facilitate accurate patient positioning. An optimized dose calculation model for extended-distance treatments was developed using phantom measurements. During treatment, in-vivo dosimetry was performed using electronic dosimeters, and accurate positioning was verified using a mobile megavoltage imager. We analyzed dose volume histogram parameters for 19 patients, and in-vivo measurements for 46 delivered treatment fractions. Results: Optimization of the dose calculation model for TBI improved dose calculation by 2.1% at the beam axis, and 17% at the field edge. Treatment planning dose objectives and constraints were met for 16 of 19 patients. Results of in-vivo dosimetry were within the set limitations (±10%) with mean deviations of 3.7% posterior of the lungs and 0.6% for the abdomen. Conclusions: We developed a TBI treatment technique using a conventional linac and TPS that can reliably be used in the conditioning regimen of patients prior to stem cell transplantation.
To report on the ''Dutch Quality Improvement Project" regarding external beam (EBRT) and brachytherapy (BT) contouring and treatment planning for locally advanced cervical cancer (LACC). Material and methods: Two rounds of three workshops were organized. Data from two patients with LACC were made available for homework exercises. Contouring and treatment planning was asked for according to the EMBRACE-II protocol. The submissions were analysed and the results were addressed during the workshops. Results: Almost all invited centres participated. EBRT contouring guidelines were followed within acceptable range, with major effort needed with regard to the ITV concept. BT contouring was of good quality, with especially small discrepancies for centres already participating in EMBRACE. EBRT treatment planning results improved between workshops with more centres being able to fulfil the planning aims. Guidance was especially necessary to improve the coverage probability planning for affected nodes. For BT planning prioritizing between target coverage and OAR sparing improved over time; the variation in dose to vaginal points remained considerable, as did variation in loading patterns and spatial dose distribution. The project was highly appreciated by all participants. Conclusion: Homework and workshop activities provide a suitable platform for discussion, exchange of experience and improvement of quality and conformity. Due to this project, radiotherapy for LACC can be administered with better and more comparable quality throughout the Netherlands.
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