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Background and purpose The purpose of this study was to design a radiation therapy treatment planning approach that would spare hematopoietically active bone marrow using [ 18 F]FLT PET imaging. Materials and methods We have developed an IMRT planning methodology to incorporate functional PET imaging using [ 18 F]FLT scans. Plans were generated for two simulated cervical cancer patients, where pelvic active bone marrow regions were incorporated as avoidance regions based on the ranges: SUV4⩾4; 4>SUV3⩾3; and 3>SUV2⩾2. Dose objectives were set to reduce bone marrow volume that received 10 ( V 10 ) and 20 ( V 20 )Gy. Results Active bone marrow regions identified by [ 18 F]FLT with an SUV⩾2, SUV⩾3, and SUV⩾4 represented an average of 43.0%, 15.3%, and 5.8%, respectively of the total osseous pelvis for the two cases studied. Improved dose–volume histograms for all identified bone marrow SUV volumes and decreases in V 10 , and V 20 were achieved without clinically significant changes to PTV or OAR doses. Conclusions Incorporation of [ 18 F]FLT PET in IMRT planning provides a methodology to reduce radiation dose to active bone marrow without compromising PTV or OAR dose objectives in pelvic malignancies.

Background and purpose During cervical cancer treatment, target volumes change position and shape due to organ motion and tumour regression. An MRI-accelerator will provide information on these changes by online magnetic resonance imaging (MRI) guidance throughout each treatment fraction. The purpose of this intensity-modulated radiation therapy (IMRT) planning study is to assess the benefit of online MRI guidance in healthy tissue sparing. Materials and methods Weekly MRI scans of 11 cervical cancer patients were used. We created four IMRT plans per patient, based on these weekly MRI scans, to simulate an online-IMRT approach. We applied a primary and nodal planning target volume (PTV) margin of 4mm. As reference, we created an IMRT plan based on the pre-treatment MRI scan (pre-IMRT) using a primary and nodal PTV margin of 15 and 10mm. The weekly defined bladder, rectum, bowel, and sigmoid contours were evaluated on the online-IMRT and pre-IMRT dose distributions at six dose levels (V10 Gy , V20 Gy , V30 Gy , V40 Gy , V42.8 Gy , and V45 Gy ). Results Online-IMRT compared to pre-IMRT significantly reduced the volume of healthy tissue irradiated to all dose levels, except V10 Gy . Conclusions Online MRI guidance reduces healthy tissue involvement in patients with cervical cancer.

Background and purpose: IMRT necessitates extension of existing inter-centre quality assurance programs due to its increased complexity. We assessed the feasibility of an inter-centre verification method for different IMRT techniques. Materials and methods: Eight European radiotherapy institutions of the QUASIMODO network, have designed an IMRT plan for a horseshoe-shaped PTV surrounding a cylindrical OAR in a simplified pelvic phantom. All centres applied common plan objectives but used their own equipment for planning and delivery. They verified the delivery of this plan according to a common protocol with radiographic film and ionisation chamber measurements. The irradiated films, the results of the ionisation chamber measurements and the computed dose distributions were sent to one analysis centre that compared the measured and computed dose distributions with the gamma method and composite dose‐area histograms. Results: 4% (relative to the prescribed dose) and 3 mm (distance-to-agreement) were decided feasible gamma criteria. The composite dose‐area histograms showed a maximum local deviation of 3.5% in the mean dose of the PTV and 5% in the OAR. Systematic differences could be identified, and in some cases explained. Conclusions: This multi-centre dosimetric verification study demonstrated both the feasibility of a multi-centre quality assurance network to evaluate any IMRT planning and delivery system combination, as well as the validity of the methodology involved. q 2005 Published by Elsevier Ireland Ltd. Radiotherapy and Oncology 76 (2005) 340‐353.

cases, so for each case 3 different delivery techn cIMRT and HT) were used. The treatment plans were each other using the parameters of the target cov homogeneity (HI) for the planning target volume maximum and mean doses for organs at Results: Mean HI was 0.12 (±0.08), 0.13 (±0.10) and HT, n-cIMRT and cIMRT, respectively. Mean CI equale 1.35 (±0.16) and 1.32 (±0.22) for HT, n-cIMRT and cIMR The lowest maximum dose for lenses of 2.4% was achie plans, whereas for HT it was 3.95% and for cIMRT 4.4 was not exceeded in any treatment plan. For the b mean dose was significantly lower for HT than for bot value