Linear-Quadratic Model for Planning Neutron Therapy with the Use of U-120 Cyclotron

2018 ◽  
pp. 41-47
Author(s):  
Валерий Лисин ◽  
V. Lisin
Keyword(s):  
Dose Fractionation ◽  
Quadratic Model ◽  
Time Interval ◽  
Skin Damage ◽  
Linear Quadratic ◽  
Standard Regimen ◽  
Neutron Therapy ◽  
Linear Quadratic Model ◽  
Radiation Induced ◽  
Early Radiation

Purpose: To estimate the feasibility of using linear-quadratic model (LQM) for planning neutron therapy regimens by the criterion of early radiation-induced reactions. Material and methods: The LQM, which described the reaction of tissues to fractionated irradiation, was used. The results obtained were compared with similar results found on the basis of the TDF model successfully used for neutron therapy planning. Results: The LQM parameters αn and βn for radiation induced skin damage were found. The dependence of a single dose of neutrons on the number of therapy sessions was obtained. This dependence was in good agreement with the analogous dependence found by the TDF model, which indicated the correctness of the method for calculating it. When using LQM for planning neutron therapy, the issue related with the time intervals between sessions was considered. For this purpose, the comparative calculations of the ratio of the total effect, determined by the LQM, and the TDF factor were carried out. The difference between the compared values did not exceed 6 %, thus allowing the time interval for planning neutron therapy using LQM to be excluded. Two methods to control the damage to normal tissue using LQM were considered. The first method was based on the evaluation of part of the used tolerance of the irradiated tissue, and the second one was carried out by transferring the applied dose fractionation regimen of neutron therapy to the isoeffective standard regimen of photon therapy. Conclusion: It was shown that LQM can be used for planning neutron therapy regimens in cancer patients by the criterion of early radiation-induced reactions. The results obtained extend the potential of radiobiological planning of neutron therapy and can serve as a basis for the development of the method of using LQM in prediction of late radiation-induced complications.

scholarly journals Free Educational Android Mobile Application for Radiobiology

2021 ◽  
Vol 28 (3) ◽  
pp. 315-319
Author(s):  
Camil Ciprian MIRESTEAN ◽  
◽  
Alexandru Dumitru ZARA ◽  
Roxana Irina IANCU ◽  
Dragos Petru Teodor IANCU ◽  
...  
Keyword(s):  
Target Volume ◽  
Tnm Staging ◽  
Dose Fractionation ◽  
Quadratic Model ◽  
Smart Devices ◽  
Smart Device ◽  
Linear Quadratic ◽  
Altered Fractionation ◽  
Linear Quadratic Model ◽  
Volume Delineation

The use of mobile devices and applications dedicated to different medical fields has improved the quality and facilitated medical care, especially in the last 10 years. The number of applications running on the software platforms of smart phones or other smart devices is constantly growing. Radiotherapy also benefits from applications (apps) for TNM staging of cancers, for target volume delineation and toxicity management but also from radiobiological apps for calculating equivalent dose schemes for different dose fractionation regimens. In the context of the increasingly frequent use of altered fractionation schemes, the use of radiobiological models and calculations based on the linear quadratic model (LQ) becomes a necessity. We aim to evaluate free radiobiology apps for the Android software platform. Given the global educational deficit, the lack of experts and the concordance between radiobiology education and the need to use basic clinical notions of modern radiotherapy, the existence of free apps for the Android platform running on older generation processors can transform even an old smart device in a powerful “radiobiology station.” Apps for radiobiology can help the radiation oncologist and medical physicist with responsibilities in radiotherapy treatment planning in the context of accelerated adoption of hypo-fractionation regimens and calculation of the effect of treatment gaps, a topic of interest in the COVID-19 pandemic context. Radiobiology apps can also partially fill the educational gap in radiobiology by arousing the interest of young radiation oncologists to deepen the growing universe of fundamental and clinical radiobiology.

scholarly journals Analytical solution to the radiotherapy fractionation problem including dose bound constraints

2021 ◽  
Author(s):  
Luis Alberto Fernández ◽  
Lucía Fernández
Keyword(s):  
At Risk ◽  
Radiation Effect ◽  
Organs At Risk ◽  
Dose Fractionation ◽  
Quadratic Model ◽  
High Dose ◽  
Bound Constraints ◽  
Linear Quadratic ◽  
Linear Quadratic Model ◽  
Radiotherapy Dose

Abstract This paper deals with the classic radiotherapy dose fractionation problem for cancer tumors concerning the following goals: a) To maximize the effect of radiation on the tumor, restricting the effect produced to the organs at risk (healing approach). b) To minimize the effect of radiation on the organs at risk, while maintaining enough effect of radiation on the tumor (palliative approach). We will assume the linear-quadratic model to characterize the radiation effect and consider the stationary case (that is, without taking into account the timing of doses and the tumor growth between them). The main novelty with respect to previous works concerns the presence of minimum and maximum dose fractions, to achieve the minimum effect and to avoid undesirable side effects, respectively. We have characterized in which situations is more convenient the hypofractionated protocol (deliver few fractions with high dose per fraction) and in which ones the hyperfractionated regimen (deliver a large number of lower doses of radiation) is the optimal strategy. In all cases, analytical solutions to the problem are obtained in terms of the data. In addition, the calculations to implement these solutions are elementary and can be carried out using a pocket calculator.

On the Selection of the Neutron to Photon Dose Ratio in Neutron-Photon Therapy for Cancer

2019 ◽  
Vol 64 (6) ◽  
pp. 57-63
Author(s):  
V. Lisin
Keyword(s):  
Subcutaneous Fat ◽  
Field Size ◽  
Quadratic Model ◽  
Dose Ratio ◽  
Linear Quadratic ◽  
Skin Reactions ◽  
Linear Quadratic Model ◽  
Photon Dose ◽  
Radiation Induced ◽  
Therapy Sessions

Purpose: To evaluate the methodological approaches to the prevention of radiation-induced complications after neutron-photon therapy considering the neutron-photon dose ratio in the tumor. Material and methods: The linear-quadratic model (LQM) and principles of neutron and photon dose distributions in a tissue-equivalent medium were used. Cases with the highest risk of radiation-induced complications (treatment by a single or two opposite fields) were discussed. The number of neutron-photon therapy sessions to ensure a combined total neutron and photon dose was determined where the RBE concept was used. When calculating the total effect (TE) and TDF factor characterizing the damage to the irradiated tissue, the effect of the radiation field size and subcutaneous fat layer on their values was taken into account. Results: Methods for selecting the ratio of the neutron and photon dose contribution to the total dose, providing the maximum permissible radiation dose, were developed. It was established that the dependences of TDF and TE factors and the differences in the values of the allowable number of photon therapy sessions on the depth of the tumor were less pronounced in cases with two opposite radiation fields compared to those with a single field. It can be explained by the fact that with increasing depth, an increase in the entrance dose is compensated by a decrease in the dose contribution formed during irradiation from the opposite field. Conclusion: For neutron-photon therapy using a linear-quadratic model, methodical approaches that might be used to provide an acceptable level of radiation-induced skin reactions for any ratio of neutron-photon doses in a tumor were proposed. The use of these techniques for planning neutron-photon therapy will minimize the risk of radiation-induced complications.

Determination of Monitor Doses in Neutron Therapy Using the U-120 Cyclotron

2021 ◽  
Vol 66 (6) ◽  
pp. 93-98
Author(s):  
V. Lisin
Keyword(s):  
Gamma Radiation ◽  
Radiation Effects ◽  
Neutron Dose ◽  
Dose Fractionation ◽  
Quadratic Model ◽  
Total Neutron ◽  
Linear Quadratic ◽  
Monitoring Method ◽  
Neutron Therapy ◽  
Photon Dose

Purpose Analyze the various methods for determining the monitor doses in neutron therapy using the U-120 cyclotron and to choose the monitoring method that provides the highest accuracy in dose delivery to the tumor. Material and methods The distributions of the absorbed dose of the therapeutic beam from the U-120 cyclotron were measured in a tissue-equivalent medium using the differential method, in which two ionization chambers with different sensitivity to neutron radiation were used. A comparison of radiation effects on tissues using various techniques of determining the monitor doses was made. The linear-quadratic model was used to assess responses to ionizing radiation. Results Dosimetry studies revealed that the therapeutic beam of the U-120 cyclotron contains concomitant gamma radiation, the contribution of which to the total neutron-photon dose increases with increasing depth of the irradiated medium. The presence of gamma radiation in the neutron beam dictate the need to find the correct method for monitoring neutron therapy. A comparison of radiation effects on the tumor tissue using different techniques of determining the monitor doses was made. It was found that at equal neutron-photon doses, the neutron dose in the tumor changed depending on its depth. It can lead to an incorrect conclusion about the effectiveness of neutron therapy depending on a single dose as well as in relation to various dose fractionation schedules. Conclusion The analysis of the results obtained showed that the problem can be most accurately solved using a technique in which the monitor coefficient and monitor doses are determined from the distribution of the neutron dose, taking into account the contribution of the gamma radiation dose to the total neutron-photon dose.

Evaluation of Therapeutic Gain \factor in Neutron Therapy Based on the Linear Quadratic Model

2017 ◽  
Vol 62 (1) ◽  
pp. 65-70
Author(s):  
Лисин ◽  
V. Lisin
Keyword(s):  
Normal Tissue ◽  
Gain Factor ◽  
Radiation Response ◽  
Quadratic Model ◽  
Linear Quadratic ◽  
Normal Tissues ◽  
Neutron Therapy ◽  
Linear Quadratic Model ◽  
Therapeutic Gain ◽  
Biological Effectiveness

Purpose: To study the dependencies of therapeutic gain factor (TGF) on dose of cyclotron-produced fast neutron beams using the linear-quadratic model (LQM) parameters characterizing radiation response in tumor and normal tissues. Material and methods: The TGF in neutron therapy was calculated as the ratio of the relative biological effectiveness of neutrons for tumor (RBE tumor) to relative biological effectiveness for normal tissue (RBE normal tissue). The LQM was used to calculate the dependencies of neutron RBE on the dose and therapeutic gain factor. We considered two cases: 1) neutron therapy for 3 types of tumors with different radiation response, where the same normal tissue was critical; 2) neutron therapy for the same tumor, when 3 types of normal tissues were taken as critical. Results: Based on calculations and analysis of published data, the dependencies of neutron RBE on dose for selected types of tumors and normal tissues were obtained. The following variants were considered: 1) RBE tumor > RBE normal tissue; 2) RBE tumor < RBE normal tissue, in both two variants, the dependen- cies in the therapeutic dose rate were convergent; 3) the dependencies of RBE tumor and RBE normal tissue on dose are crossed. The dependencies of TGF for neutron therapy on single boost doses and quantitative ratios between the LQM parameters characterizing radiation response of tumor and normal tissues were found. A multivariate ratio between the dependencies on dose of RBE tumor and RBE normal tissue was the cause of variety in the dependencies of TGF on dose. In the first case, the TGF increased with increasing (α/β)γ ratio and decreasing single dose, and the maximum value of TGF was equal to ~ 1.4. In the second case, TGF was < 1, i.e. the effectiveness of neutron therapy was lower than the effectiveness of gamma irradiation, but it was increased with higher single dose and lower radiosensitivity of normal tissue. In the third case, the dose at the intersection point (Di) was the boundary, and TGF was > 1 to the left of the boundary, and TPV was <1 to the right of the boundary, provided that D <Di, RBEtumor > OBEnormal tissue. Conclusion: The obtained results with known parameters of the LQM for tumor and normal tissues allowed us to make an appropriate choice between neutron and gamma- ray therapy in order to increase the effectiveness of treatment for cancer patients. It was shown that in the case of neutron therapy, the analysis of dependencies of TGF on dose allowed the optimal dose fractionation regimen to be selected.

scholarly journals Simulating Radiotherapy Effect in High-Grade Glioma by Using Diffusive Modeling and Brain Atlases

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Alexandros Roniotis ◽  
Kostas Marias ◽  
Vangelis Sakkalis ◽  
Georgios C. Manikis ◽  
Michalis Zervakis
Keyword(s):  
High Grade Glioma ◽  
Quadratic Model ◽  
Normal Brain ◽  
Linear Quadratic ◽  
Linear Quadratic Model ◽  
Diffusive Model ◽  
Glioma Model ◽  
Modern Application ◽  
Diffusion Tensors ◽  
Brain Atlases

Applying diffusive models for simulating the spatiotemporal change of concentration of tumour cells is a modern application of predictive oncology. Diffusive models are used for modelling glioblastoma, the most aggressive type of glioma. This paper presents the results of applying a linear quadratic model for simulating the effects of radiotherapy on an advanced diffusive glioma model. This diffusive model takes into consideration the heterogeneous velocity of glioma in gray and white matter and the anisotropic migration of tumor cells, which is facilitated along white fibers. This work uses normal brain atlases for extracting the proportions of white and gray matter and the diffusion tensors used for anisotropy. The paper also presents the results of applying this glioma model on real clinical datasets.

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