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Purpose Multiple metrics are proposed to characterize and compare the complexity of helical tomotherapy (HT) plans created for different treatment sites. Methods A cohort composed of 208 HT plans from head and neck (105), prostate (51) and brain (52) tumor sites was considered. For each plan, 14 complexity metrics were calculated. Those metrics evaluate the percentage of leaves with small opening times or approaching the projection duration, the percentage of closed leaves, the amount of tongue‐and‐groove effect, and the overall modulation of the planned sinogram. To enable data visualization, an approach based on principal component analysis was followed to reduce the dataset dimensionality. This allowed the calculation of a global plan complexity score. The correlation between plan complexity and pretreatment verification results using the Spearman’s rank correlation coefficients was investigated. Results According to the global score, the most complex plans were the head and neck tumor cases, followed by the prostate and brain lesions irradiated with stereotactic technique. For almost all individual metrics, head and neck plans confirmed to be the plans with the highest complexity. Nevertheless, prostate cases had the highest percentage of leaves with an opening time approaching the projection duration, whereas the stereotactic brain plans had the highest percentage of closed leaves per projection. Significant correlations between some of the metrics and the pretreatment verification results were identified for the stereotactic brain group. Conclusions The proposed metrics and the global score demonstrated to be useful to characterize and quantify the complexity of HT plans of different treatment sites. The reported differences inter‐ and intra‐group may be valuable to guide the planning process aiming at reducing uncertainties and harmonize planning strategies.

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This analysis points to barriers to quality care such as insufficient staffing, education/training, equipment and lack of quality management. It highlights the correlation between the human resources availability and quality of care. It has also identified common action items for enhancing quality of radiotherapy programmes in the Region.

Purpose To apply the recent code of practice from the IAEA/AAPM, TRS 483, to helical tomotherapy (HT) for reference and relative dosimetry obtaining correction factors for the Exradin A1SL ionization chamber. Methods The beam quality correction factor for the A1SL chamber was obtained through three different approaches following TRS 483 concepts and compared with published values. The determination of the reference absolute dose for the machine‐specific reference (msr) field was complemented with relative dosimetry through the determination of output factors of small fields using different detectors. The response of A1SL was compared with correction‐free film results and corrected output factors of other detectors. Results A weighted mean beam quality correction factor of 0.9945± 0.0073 was obtained for the A1SL chamber which is in agreement with values reported in the literature. Output factors obtained with different detectors were in agreement, given the uncertainty level. Considering the film output factors as free of corrections, the average value for A1SL output factors corrections was 1.000 ± 0.007. Conclusions The beam quality correction factors for the A1SL chamber obtained through the three different pathways recommended by TRS 483 agreed with each other and also with published values. The measurements from the A1SL chamber normalized to the msr field in HT can be taken as output factors for small clinical field sizes without further corrections.

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PurposeTo evaluate the differences between three methods of classification of recurrences in patients with head and neck tumours treated with Radiation Therapy (RT).Materials and methods367 patients with head and neck tumours were included in the study. Tumour recurrences were delineated in the CT images taken during patient follow-up and deformable registration was used to transfer this volume into the planning CT. The methods used to classify recurrences were: method CTV quantified the intersection volume between the recurrence and the Clinical Target Volume (CTV); method TV quantified the intersection between the Treated Volume and the recurrence (for method CTV and TV, recurrences were classified in-field if more than 95% of their volume were inside the volume of interest, marginal if the intersection was between 20-95% and outfield otherwise); and method COM was based on the position of the Centre Of Mass of the recurrence. A dose assessment in the recurrence volume was also made.ResultsThe 2-year Kaplan-Meier locoregional recurrence incidence was 10%. Tumour recurrences occurred in 22 patients in a mean time of 16.5 ± 9.4 months resulting in 28 recurrence volumes. The percentage of in-field recurrences for methods CTV, TV and COM was 7%, 43% and 50%, respectively. Agreement between the three methods in characterizing individually in-field and marginal recurrences was found only in six cases. Methods CTV and COM agreed in 14. The percentage of outfield recurrences was 29% using all methods. For local recurrences (in-field or marginal to gross disease) the average difference between the prescribed dose and D98% in the recurrence volume was -5.2 ± 3.5% (range: -10.1%-0.9%).ConclusionsThe classification of in-field and marginal recurrences is very dependent on the method used to characterize recurrences. Using methods TV and COM the largest percentage of tumour recurrences occurred in-field in tissues irradiated with high doses.Electronic supplementary materialThe online version of this article (doi:10.1186/s13014-015-0345-4) contains supplementary material, which is available to authorized users.