Helical tomotherapy (HT) was introduced at the Greater Poland Cancer Centre (GPCC) in April 2009. Retrospective analysis included data from the treatments performed for the first 656 patients treated with HT between May 2009 and May 2012 at the GPCC. In order to evaluate the implications on daily workload and scheduling of patients, stepwise regression and time analysis for each component of the overall treatment time, such as positioning, imaging, registration, and irradiation were performed. A detailed analysis included: (1) learning curves and optimized time needed for positioning and registration; (2) relation between irradiation time and parameters used for plan creation; and (3) average time of daily imaging. The irradiation component has the highest influence on the overall treatment time (R = 0.911). The lowest influence was observed for the imaging (R = 0.670). The learning curve for positioning was 7 months while the reduction of the average daily time needed for registration was observed even after two years. The irradiation time strongly depends on the planning parameters. Changing the pitch from 0.215 to 0.287 for pelvic cancer cases decreased the average daily beam-on time per patient by about 2 minutes. Similar changes for head and neck reduced this time by 1.3 minutes. The limitation in the usage of 1 cm field width only for complex cases, lower than 10 cm in the cranio-caudal direction, reduced the beam-on time per patient by 2 minutes. The average overall treatment time decreased from 21.5 minutes per patient in the first year of the HT usage to 13.8 minutes per patient in current practice. Our current practice shows that for a group of patients including mainly those with pelvis and head and neck cancers, the HT treatment takes approximately 15 minutes per patient allowing 40 patients to be treated within 10 hours.

Aim of the studyHelical tomotherapy is one of the methods of radiotherapy. This method enables treatment implementation for a wide spectrum of clinical cases. The vast array of therapeutic uses of helical tomotherapy results directly from the method of dose delivery, which is significantly different from the classic method developed for conventional linear accelerators. The paper discusses the method of dose delivery by a tomotherapy machine. Moreover, an analysis and presentation of treatment plans was performed in order to show the therapeutic possibilities of the applied technology. Dose distributions were obtained for anaplastic medulloblastoma, multifocal metastases to brain, vulva cancer, tongue cancer, metastases to bones, and advanced skin cancer. Tomotherapy treatment plans were compared with conventional linear accelerator plans.ResultsFollowing the comparative analysis of tomotherapy and conventional linear accelerator plans, in each case we obtained the increase in dose distribution conformity manifested in greater homogeneity of doses in the radiation target area for anaplastic medulloblastoma, multifocal metastases to brain, vulva cancer, metastases to bones, and advanced skin cancer, and the reduction of doses in organs at risk (OAR) for anaplastic medulloblastoma, vulva cancer, tongue cancer, and advanced skin cancer. The time of treatment delivery in the case of a tomotherapy machine is comparable to the implementation of the plan prepared in intensity-modulated radiotherapy (IMRT) technique for a conventional linear accelerator. In the case of tomotherapy the application of a fractional dose was carried out in each case during one working period of the machine. For a conventional linear accelerator the total value of the fractional dose in the case of anaplastic medulloblastoma and metastases to bones was delivered using several treatment plans, for which a change of set-up was necessary during a fraction.ConclusionThe obtained results confirm that tomotherapy offers the possibility to obtain precise treatment plans together with the simplification of the therapeutic system.

Our study showed that for chemoradiation of oropharyngeal cancer, using daily image guidance and proper plan adaptation scheme, the current PRV margin for the SC could be reduced to 4 mm.

Objective: The aim of this study was to determine which physical delivery parameter changes are most suitable for multiple-level dose-painting treatment plans with helical tomotherapy (HT). Methods: A total of 96 treatment plans were generated for 12 patients who had undergone fluorine-18 fludeoxyglucose positron emission tomography/CT ( 18 F-FDG-PET/CT) scan to plan head and neck cancer treatment. Based on these PET-CT images, the dose was escalated to 96 Gy in 32 fractions as a function of PET intensity values. The intensity-based prescription was converted into seven discrete dose levels. For the same patient, different HT plans were optimized by varying parameters such as field width (FW), pitch (PF) and modulation factor (MF). Dose conformity was evaluated using quality-volume histograms, quality factors (QFs), weighted index of achievement (IOA w ), coldness (IOC w ) and hotness (IOH w ). Moreover, doses to organs at risk (OARs), target volumes and execution time were analyzed. Results: Median QFs were the best for FW 5 1.05 cm (QF 5 2.10) and the worst for FW 5 2.5 cm (QF 5 3.04). The same trend was observed for IOA w , IOC w and IOH w . Combination of FW 5 1.05 cm and MF 5 5 leads to the longest beam-on time (above 25 min), whereas FW 5 2.5 cm and MF 5 3 lead to the shortest time (below 8 min). Data analyzed based on dose-volume histogram showed that changes in FW had the strongest impact on plan quality, whereas the effect of MF and PF changes was moderate. Conclusion: HT is suitable for multiple-level dose-painting treatment plans. Advances in knowledge: Changes in FW and MF had the greatest impact on dose distribution quality and beam-on time. Changes in PF only influenced doses to the OARs.

HT is feasible for CSI, and in comparison with 3DCRT it improves PTV coverage. HT reduces high dose volumes of OARs, but larger volumes of normal tissue receive low radiation dose. HT requires further study to establish correlations between dosimetrical findings and clinical outcomes, especially with regard to late sequelae of treatment.