Impact of different optimization strategies on the compatibility between planned and delivered doses during radiation therapy of cervical cancer

PurposeTo analyse the impact of different optimization strategies on the compatibility between planned and delivered doses during radiotherapy of cervical cancer.Material/methodsFour treatment plans differing in optimisation strategies were prepared for ten cervical cancer cases. These were: volumetric modulated arc therapy with (_OPT) and without optimization of the doses in the bone marrow and for two sets of margins applied to the clinical target volume that arose from image guidance based on the bones (IG(B)) and soft tissues (IG(ST)). The plans were subjected to dosimetric verification by using the ArcCHECK system and 3DVH software. The planned dose distributions were compared with the corresponding measured dose distributions in the light of complexity of the plans and its deliverability.ResultsThe clinically significant impact of the plans complexity on their deliverability is visible only for the gamma passing rates analysis performed in a local mode and directly in the organs. While more general analyses show statistically significant differences, the clinical relevance of them has not been confirmed. The analysis showed that IG(ST)_OPT and IG(B)_OPT significantly differ from IG(ST) and IG(B). The clinical acceptance of IG(ST)_OPT obtained for hard combinations of gamma acceptance criteria (2%/2 mm) confirm its satisfactory deliverability. In turn, for IG(B)_OPT in the case of the rectum, the combination of 2%/2 mm did not meet the criteria of acceptance.ConclusionDespite the complexity of the IG(ST)_OPT, the results of analysis confirm the acceptance of its deliverability when 2%/2 mm gamma acceptance criteria are used during the analysis

The new two-component conformity index formula (TCCI) and dose-volume comparisons of the pituitary gland and tonsil cancer IMRT plans using a linear accelerator and helical Tomotherapy

Background/AimTo examine the new dose-volume verification tool, called the two-component conformity index formula (TCCI), for tumours of the pituitary gland and tonsil cancer IMRT plans using helical Tomotherapy and a linear accelerator.Material and Methods10 medically inoperable patients – 5 with tumour of the pituitary gland and 5 tonsil cancers – were considered. Tomotherapy and Eclipse plans were compared by DVH analysis and new TCCI analysis including: 1/ the physician's intents for dose distribution in PRVs, 2/ more than one dose-volume constraint for dose distribution in PTV and healthy tissues, and 3/ separation between coverage and excess components.ResultsDVH analysis shows differences for the PTV received doses close to the prescription dose (PD): 1/in pituitary gland, Eclipse – 61% of PTV volume enclosed by PD and Tomotherapy – 50%, and 2/in tonsil cancer, Eclipse plans – 44% and Tomotherapy – 55%. These differences were clinically confirmed for tonsil cancer through TCCI analysis. Moreover, TCCI analysis shows better coverage of PTV volume through 90% and 95% isodose levels for Tomotherapy plans. Better high dose region reduction for brain stem and optic chiasm in pituitary gland and middle dose region reduction for parotids and spinal cord in tonsil and dose reduction in healthy tissues reported by TCCI analysis were observed for Tomotherapy plans.ConclusionsThe usefulness of the information provided means that TCCI could be used as a primary or alternative method of quick dose-volume verification finally supported by advanced DVH analysis

Evolution of treatment planning and dose delivery methods during radiotherapy for patients undergoing bone marrow transplantation : a review

Background and objectives: This study describes the treatment planning and dose delivery methods of radiotherapy for patients undergoing bone marrow transplantation. The analysis was carried out in the context of the evolution of these methods over the last 60 years. Materials and methods: A systematic literature search was carried out using the PubMed search engine. Overall, 90 relevant studies were included: 24 general studies, 10 describing isotopes usage, 24 related to conventional and 32 to advanced methods. Results: The analysis of the evolution of radiotherapy methods shows how signifi cantly the precision of dose planning methods and its delivery have changed. The atypical positioning caused by geometrical requirements for applications of isotopes or conventional techniques has been replaced by positioning on a therapeutic couch, which allows a more precise setup of the patient that is necessary for an exact delivery of the planned dose. The dose can be fully optimized and calculated on tomographic images by algorithms implemented in planning systems. Optimization process allows to reduce doses in organs at risk. The accuracy between planned and delivered doses can be checked by pretreatment verifi cation methods, and the patient positioning can be checked by image guidance procedures. Interpretation and conclusions: Current radiotherapy solutions allow a precise delivery of doses to the planning target volume while reducing doses to organs at risk. Nevertheless, it should be kept in mind that establishing radiotherapy as an important element of the whole therapeutic regimen resulted from the follow-up of patients treated by conventional techniques. To confi rm the clinical value of new advanced techniques, clinical trials are required

Dosimetric Comparison of Ultra-Hypofractionated and Conventionally Fractionated Radiation Therapy Boosts for Patients with High-Risk Prostate Cancer

Recent comparison of an ultra-hypofractionated radiotherapy (UF-RT) boost to a conventionally fractionated (CF-RT) option showed similar toxicity and disease control outcomes. An analysis of the treatment plans for these patients is needed for evaluating calculated doses for different organs, treatment beam-on time, and requirements for human and financial resources. Eighty-six plans for UF-RT and 93 plans for CF-RT schemes were evaluated. The biologically equivalent dose, EQD2, summed for the first phase and the boost, was calculated for dose-volume parameters for organs at risk (OARs), as well as for the PTV1. ArcCHECK measurements for the boost plans were used for a comparison of planned and delivered doses. Monitor units and beam-on times were recorded by the Eclipse treatment planning system. Statistical analysis was performed with a significance level of 0.05. Dosimetric parameter values for OARs were well within tolerance for both groups. EQD2 for the PTV1 was on average 84 Gy for UF-RT patients and 76 Gy for CF-RT patients. Gamma passing rate for planned/delivered doses comparison was above 98% for both groups with 3 mm/3% distance to agreement/dose difference criteria. Total monitor units per fraction were 647 ± 94 and 2034 ± 570 for CF-RT and UF-RT, respectively. The total delivery time for boost radiation for the patients in the UF-RT arm was, on average, four times less than the total time for a conventional regimen with statistically equal clinical outcomes for the two arms in this study