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  • Author: Tomasz Piotrowski x
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Abstract

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 significantly 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The atypical positioning caused by geometrical requirements for applications of isotopes or conventional techniques has been replaced by positioning on a therapeutic couch, which allows a more precise setup of the patient that is necessary for an exact delivery of the planned dose.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 verification 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 confirm the clinical value of new advanced techniques, clinical trials are required.

Abstract

Background and objectives: To justify the concept of validating conformal versus intensity-modulated approach in the treatment of non-small cell lung cancer (NSCLC). Materials and methods: For 10 patients representative of the spectrum of tumour sizes and locations, two plans were prepared: one with three-dimensional conformal radiation therapy (3DCRT) technique and the other with intensity-modulated radiation therapy (IMRT) technique. Preliminary measurements were performed in static conditions. For each of the field angles considered, the motion kernel was generated to simulate tumour motion trajectories, with the largest amplitude in the cranio-caudal direction of 4, 6, and 8 mm. The measurement results determined the agreement between the planned and measured doses. Results: No statistically significant differences were found between the motion patterns, with the smallest amplitudes for clinical target volume in 3DCRT. For IMRT, the significant differences between 0 mm vs. 6 mm and 0 mm vs. 8 mm amplitudes were found. The motion impact on delivered vs. planned doses had less effect on the oesophagus in 3DCRT compared to that in IMRT. The observed differences were comparable for the heart. Interpretation and conclusions: For maximal amplitudes below 4 mm, the disagreement between planned and delivered doses can be neglected. However, the amplitudes above 5 mm and 7 mm lead to significant changes in IMRT and 3DCRT dose distribution, respectively.

Abstract

Background: The paper shows the methodology of an in-phantom study of the protection level of the bone marrow in patients with cervical or endometrial cancer for three radiotherapy techniques: three-dimensional conformal radiotherapy, intensity modulated radiotherapy, and volumetric modulated arc therapy, preceded by the procedures of image guidance.

Methods/Design: The dosimetric evaluation of the doses will be performed in an in-house multi-element anthropomorphic phantom of the female pelvic area created by three-dimensional printing technology. The volume and position of the structures will be regulated according to the guidelines from the Bayesian network. The input data for the learning procedure of the model will be obtained from the retrospective analysis of imaging data obtained for 96 patients with endometrial cancer or cervical cancer treated with radiotherapy in our centre in 2008-2013. Three anatomical representations of the phantom simulating three independent clinical cases will be chosen. Five alternative treatment plans (1 × three-dimensional conformal radiotherapy, 2 × intensity modulated radiotherapy and 2 × volumetric modulated arc therapy) will be created for each representation. To simulate image-guided radiotherapy, ten specific recombinations will be designated, for each anatomical representation separately, reflecting possible changes in the volume and position of the phantom components.

Discussion: The comparative analysis of planned measurements will identify discrepancies between calculated doses and doses that were measured in the phantom. Finally, differences between the doses cumulated in the hip plates performed by different techniques simulating the gynaecological patients' irradiation of dose delivery will be established. The results of this study will form the basis of the prospective clinical trial that will be designed for the assessment of hematologic toxicity and its correlation with the doses cumulated in the hip plates, for gynaecologic patients undergoing radiation therapy.

Abstract

Vegetable oils belong to a large group of substances consumed on a daily basis. World vegetable oil production is soaring, reducing the popularity of animal fats. Heavy metals pose a threat to human health. It is estimated that about 80% of the daily dose of heavy metals enters the human body through the consumption of food. Hence, it is necessary to monitor their concentrations in food products. Besides, the presence of heavy metals is thought to have possible negative influence on the quality of oils, especially on their taste and smell. Heavy metals may also accelerate the process of the rancidifiction of oils. Rapeseeds, soybean seeds and linseeds were selected for the analysis because they are one of the most popular oilseeds and at the same time they differ in terms of growing conditions. The analyses of different fractions and the ready-made product were also performed. The aim of the study was to determine the variation in concentrations of heavy metals, iron and manganese in different fractions during production. The significant concentrations of iron, manganese and zinc were observed in oilseeds. It was also shown that during different stages of oil refining the concentrations of metals decrease. The concentrations of metals are compared with those reported in literature.

Abstract

Introduction. The rapid development of new radiotherapy technologies, such as intensity modulated radiotherapy (IMRT) or tomotherapy, has resulted in the capacity to deliver a more homogenous dose in the target. However, the higher doses associated with these techniques are a reason for concern because they may increase the dose outside the target. In the present study, we compared 3DCRT, IMRT and tomotherapy to assess the doses to organs at risk (OARs) resulting from photon beam irradiation and scattered neutrons.

Material and methods. The doses to OARs outside the target were measured in an anthropomorphic Alderson phantom using thermoluminescence detectors (TLD 100) 6Li (7.5%) and 7Li (92.5%). The neutron fluence rate [cm−2·s−1] at chosen points inside the phantom was measured with gold foils (0.5 cm diameter, mean surface density of 0.108 g/cm3).

Results. The doses [Gy] delivered to the OARs for 3DCRT, IMRT and tomotherapy respectively, were as follows: thyroid gland (0.62 ± 0.001 vs. 2.88 ± 0.004 vs. 0.58 ± 0.003); lung (0.99 ± 0.003 vs. 4.78 ± 0.006 vs. 0.67 ± 0.003); bladder (80.61 ± 0.054 vs. 53.75 ± 0.070 vs. 34.71 ± 0.059); and testes (4.38 ± 0.017 vs. 6.48 ± 0.013 vs. 4.39 ± 0.020). The neutron dose from 20 MV X-ray beam accounted for 0.5% of the therapeutic dose prescribed in the PTV. The further from the field edge the higher the contribution of this secondary radiation dose (from 8% to ~45%).

Conclusion. For tomotherapy, all OARs outside the therapeutic field are well-spared. In contrast, IMRT achieved better sparing than 3DCRT only in the bladder. The photoneutron dose from the use of high-energy X-ray beam constituted a notable portion (0.5%) of the therapeutic dose prescribed to the PTV.