Wyniki wyszukiwania - BazTech

1

Dose calculation accuracy for photon small fields in treatment planning systems with comparison by Monte Carlo simulations

Abazarfard Mojtaba, Azadeh Payam, Mostaar Ahmad

Polish Journal of Medical Physics and Engineering

|

2021

|

Vol. 27, Iss. 3

181--190

EN

Purpose: Advanced radiation therapy techniques use small fields in treatment planning and delivery. Small fields have the advantage of more accurate dose delivery, but with the cost of some complications in dosimetry. Different dose calculation algorithms imported in various treatment planning systems (TPSs) which each of them has different accuracy. Monte Carlo (MC) simulation has been reported as one of the accurate methods for calculating dose distribution in radiation therapy. The aim of this study was the evaluation of TPS dose calculation algorithms in small fields against 2 MC codes. Methods: A linac head was simulated in 2 MC codes, MCNPX, and GATE. Then three small fields (0.5×0.5, 1×1 and 1.5×1.5 cm2) were simulated with 2 MC codes, and also these fields were planned with different dose calculation algorithms in Isogray and Monaco TPS. PDDs and lateral dose profiles were extracted and compared between MC simulations and dose calculation algorithms. Results: For 0.5×0.5 cm2 field mean differences in PDDs with MCNPX were 2.28, 4.6, 5.3, and 7.4% and with GATE were -0.29, 2.3, 3 and 5% for CCC, superposition, FFT and Clarkson algorithms respectively. For 1×1 cm2 field mean differences in PDDs with MCNPX were 1.58, 0.6, 1.1 and 1.4% and with GATE were 0.77, 0.1, 0.6 and 0.9% for CCC, superposition, FFT and Clarkson algorithms respectively. For 1.5×1.5 cm2 field mean differences in PDDs with MCNPX were 0.82, 0.4, 0.6 and -0.4% and with GATE were 2.38, 2.5, 2.7 and 1.7% for CCC, superposition, FFT and Clarkson algorithms respectively. Conclusions: Different dose calculation algorithms were evaluated and compared with MC simulation in small fields. Mean differences with MC simulation decreased with the increase of field sizes for all algorithms.

2

Prospects for the production of radioisotopes and radiobioconjugates for theranostics

Choiński Jarosław, Łyczko Monika

Bio-Algorithms and Med-Systems

|

2021

|

Vol. 17, no. 4

241--257

EN

The development of diagnostic methods in medicine as well as the progress in the synthesis of biologically active compounds allows the use of selected radioisotopes for the simultaneous diagnosis and treatment of diseases, especially cancerous ones, in patients. This approach is called theranostic. This review article includes chemical and physical characterization of chosen theranostic radioisotopes and their compounds that are or could be useful in nuclear medicine.

3

Nanoscale dosimetric consequences around bismuth, gold, gadolinium, hafnium, and iridium nanoparticles irradiated by low energy photons

Mesbahi Asghar, Mansouri Elham, Mohammadzadeh Mohammad

Polish Journal of Medical Physics and Engineering

|

2020

|

Vol. 26, Iss. 4

225--234

EN

In the current study, nanoscale physical dose distributions around five potential nanoparticles were compared. Five potential nanoparticles including bismuth, gold, gadolinium, hafnium, and iridium nanoparticles in the form of a sphere with a diameter of 50 nm were simulated in a water medium. The MCNPX (2.7.0) Monte Carlo code with updated libraries was used for calculations of electron dose deposition and electron flux in water from 25 nm up to 4000 nm with a step of 25 nm. Also, secondary electron spectra after irradiation of nanoparticles with mono-energetic photons with energies of 30, 60, 100 keV were derived. The nano-scale distance-dose curves showed a very steep gradient with distance from nanoparticle surface up to 60 nm and after this point, a gradual decrease was seen. The dose deposition characteristics in the nano-scale were dependent on the type of nanoparticle as well as photon energy. Our results concluded that for each photon energy in the energy range of 30-100 keV, a suitable nanoparticle can be selected to boost the effect of energy deposition by low energy photon beams used in brachytherapy.

4

Developing of predictive models for pneumonitis with forward variable selection and LASSO logistic model for breast cancer patients treated with 3D-CRT

Abdali M. H., Khoshgard K., Pashaki A. S.

Polish Journal of Medical Physics and Engineering

|

2018

|

Vol. 24, Iss. 4

149--156

EN

Purpose: To develop a multiple logistic regression model as normal tissue complication probability model by least absolute shrinkage and selection operator (LASSO) technique in breast cancer patients treated with three-dimensional conformal radiation therapy (3D-CRT), we focused on the changes of pulmonary function tests to achieve the optimal predictive parameters for the occurrence of symptomatic radiation pneumonitis (SRP). Materials and methods: Dosimetric and spirometry data of 60 breast cancer patients were analyzed. Pulmonary function tests were done before RT, after completion of RT, 3, and 6 months after RT. Multiple logistic regression model was used to obtain the effective predictive parameters. Forward selection method was applied in NTCP model to determine the effective risk factors from obtained different parameters. Results: Symptomatic radiation pneumonitis was observed in five patients. Significant changes in pulmonary parameters have been observed at six months after RT. The parameters of mean lung dose (MLD), bridge separation (BS), mean irradiated lung volume (ILVmean), and the percentage of the ipsilateral lung volume that received dose of 20 Gy (IV20) introduced as risk factors using the LASSO technique for SRP in a multiple normal tissue complication probability model in breast cancer patients treated with 3D-CRT. The BS, central lung distance (CLD) and ILV in tangential field have obtained as 23.5 (20.9-26.0) cm, 2.4 (1.5-3.3) cm, and 12.4 (10.6-14.3) % of lung volume in radiation field in patients without pulmonary complication, respectively. Conclusion: The results showed that if BS, CLD, and ILV are more than 23 cm, 2 cm, and 12%, respectively, so incidence of SRP in the patients will be considerable. Our multiple NTCP LASSO model for breast cancer patients treated with 3D-CRT showed that in order to have minimum probability of SRP occurrence, parameters of BS, IV20, ILV and especially MLD would be kept in minimum levels. Considering dose-volume histogram, the mean lung dose factor is most important parameter which minimizing it in treatment planning, minimizes the probability of SRP and consequently improves the quality of life in breast cancer patients.

5

A review on the dosimetrical and radiobiological prediction of radiation-induced hypothyroidism in radiation therapy of head-and-neck cancer, breast cancer, and Hodgkin’s lymphoma survivors

Namdar A. M., Mohammadzadeh M., Okutan M., Mesbahi A.

Polish Journal of Medical Physics and Engineering

|

2018

|

Vol. 24, Iss. 4

137--148

EN

A review on the radiobiological modeling of radiation-induced hypothyroidism after radiation therapy of head-and-neck cancers, breast cancer, and Hodgkin’s lymphoma is presented. The current review is based on data relating to dose-volume constrains and normal tissue complication probability (NTCP) as a function of either radiobiological or (pre)treatment-clinical parameters. Also, these data were explored in order to provide more helpful criteria for radiobiological optimization of treatment plans involving thyroid gland as a critical normal organ.

6

Maria Skłodowska-Curie i powstanie Instytutu Radowego w Warszawie

Sobieszczak-Marciniak M.

Postępy Techniki Jądrowej

|

2017

|

z. 2

2--6

PL

Początki polskiej onkologii, to Maria Skłodowska-Curie. Jej dar dla społeczeństwa polskiego, będący jednocześnie darem Polaków dla uczonej - Instytut Radowy w Warszawie przy ul. Wawelskiej 15 został otwarty 29 maja 1932 r. Od tego dnia minęło dokładnie 85 lat. Druga po Paryżu, bliźniacza najnowocześniejsza w Europie placówka zajmująca się leczeniem chorób nowotworowych i prowadzeniem badań na te choroby ukierunkowanych, została zaprojektowana i w części wyposażona przez Marię Skłodowską-Curie. To z tego powodu jechała uczona do Stanów Zjednoczonych w roku 1929, po rad dla warszawskiego instytutu, po potrzebne urządzenia i wsparcie finansowe. Nawet to działanie było takie samo jak w przypadku Instytutu Radowego w Paryżu. W roku 1921 uczona pojechała bowiem do USA po wsparcie dla placówki paryskiej. Sytuacja ojczystego kraju Marii Skłodowskiej-Curie w początkach lat dwudziestych, kiedy to narodziła się idea stworzenia Instytutu była bardzo zła, po 123 latach zaborów, po dramacie I wojny światowej, wreszcie po morderczych zmaganiach o niepodległość, Polacy decydują się wesprzeć ideę uczonej, zbudować Instytut Radowy. Kupują cegiełki, wpłacają darowizny, włącza się prasa, powstaje Komitet budowy placówki. Na jej otwarcie, w maju 1932 r. uczona przyjeżdża do Polski po raz ostatni, cieszy się widząc ukończony szpital, taką zresztą decyzję podjęła, najpierw szpital, potem pracownie naukowe, niepokoi się nieco o dalszy los pracowni. Sadzi wówczas kilka pamiątkowych drzew, w imieniu swoim i przyjaciół zaangażowanych w sprawę. To dzięki niej w Instytucie pracują wykwalifikowani lekarze, to ona wykształciła ich pod swoim czujnym okiem w Instytucie w Paryżu. Zaczyna się nowy rozdział w polskiej medycynie….

EN

The beginnings of Polish oncology are linked to Maria Skłodowska-Curie. Her gift to the Polish society, at the same time being a gift of Poles to her as the scientist – the Radium Institute in Warsaw, 15 Wawelska Street, was opened on 29 May 1932. Since that day, exactly 85 years have passed. The second after Paris, the twin and most modern European cancer treatment center and research center for this disease was designed and partly equipped by Maria Skłodowska-Curie. This is why she travelled to the United States in 1929, to obtain radium, necessary equipment and financial support for the Radium Institute in Warsaw. Even this action was similar to that in the case of the Radium Institute in Paris. In 1921, the scientist went to the US to get support for the Parisian institution. When the idea of creating the Radium Institute was born, the situation of the motherland of Maria Skłodowska-Curie in the early twenties was very bad, after 123 years of partitions, after the drama of World War I, and after the murderous struggle for independence, Poles decided to support the scholar’s idea and build the Radium Institute. They paid financial contributions and made donations, the press joined in and the Building Committee was set up. At the opening ceremony of the Radium Institute in May 1932, the scientist arrived in Poland for the last time and was delighted to see a complete and finished hospital. Anyway, it was her decision to build the hospital first, and after that the research laboratories; she was concerned about the future of those laboratories. Maria Skłodowska-Curie planted several commemorative trees on her own behalf and on behalf of her friends involved in the activities. It is thanks to her that the qualified physicians worked for the Radium Institute as she had educated them under her watchful eye at the Radium Institute in Paris. A new chapter in Polish medicine began...

7

Neutron and photon scattering properties of high density concretes used in radiation therapy facilities: A Monte Carlo study

Mesbahi A., Khaldari R.

Polish Journal of Medical Physics and Engineering

|

2017

|

Vol. 23, Iss. 3

61--65

EN

In the current study the neutron and photon scattering properties of some newly developed high density concretes (HDCs) were calculated by using MCNPX Monte Carlo code. Five high-density concretes including Steel-Magnetite, Barite, Datolite-Galena, Ilmenite-ilmenite, Magnetite-Lead with the densities ranging from 5.11 g/cm3 and ordinary concrete with density of 2.3 g/cm3 were studied in our simulations. The photon beam spectra of 4 and 18 MV from Varian linac and neutron spectra of clinical 18 MeV photon beam was used for calculations. The fluence of scattered photon and neutron from all studied concretes was calculated in different angles. Overall, the ordinary concrete showed higher scattered photons and Datolite-Galena concrete (4.42 g/cm3 ) had the lowest scattered photons among all studied concretes. For neutron scattering, fluence at the angle of 180 was higher relative to other angles while for photons scattering fluence was maximum at 90 degree. The scattering fluence for photons and neutrons was dependent on the angle and composition of concrete. The results showed that the fluence of scattered photons and neutrons changes with the composition of high density concrete. Also, for high density concretes, the variation of scattered fluence with angle was very pronounced for neutrons but it changed slightly for photons. The results can be used for design of radiation therapy bunkers.

8

Dose sensitivity enhancement on polymer gel with suspended gold particles

Afonso L. C., Schöfer F., Hoeschen Ch., Caldas L. V. E.

Nukleonika

|

2012

|

Vol. 57, No. 4

467-472

EN

The presence of high Z material adjacent to soft tissue, when submitted to irradiation, enhances locally the absorbed dose in these soft tissues. Such an effect occurs due to the outscattering of photoelectrons from the high Z material. Polymer gel (PG) dosimeters were used to investigate this effect. Analytic calculations to estimate the dose enhancement were performed. Samples containing a polymer gel with 0.005 gAu/gPG and a pure polymer gel were irradiated using an X-ray beam produced by 150 kV, filtered with 4 mm Al and 5 mm Cu, which resulted in an approximately 20% greater absorbed dose in the samples with gold in comparison to those with the pure polymer gel. The analytic calculations resulted in a dose enhancement factor of approximately 30% for the gold concentration of 0.005 gAu/gPG.

9

Investigation of the dose enhancement factor of high intensity low mono-energetic X-ray radiation with labeled tissues by gold nanoparticles

Ranjbar H., Shamsaei M., Ghasemi M. R.

Nukleonika

|

2010

|

Vol. 55, No. 3

307-312

EN

The aim of radiotherapy is to maximize the dose applied to the tumor while keeping the dose to the surrounding healthy tissue as low as possible. To further enhance dose to a tumor, techniques to radiosensitization of the tumor, using high atomic number elements, have been proposed. The aim of this study was to investigate the influence of using gold nanoparticles as a contrast agent on tumor dose enhancement when the tissue is irradiated by a typical mono energy X-ray beam. To improve the conventional radiotherapy enhancement of the absorbed dose in a tumor tissue and to spare the skin and normal tissues during irradiation in the presence of concentration agent, a model based on a Monte Carlo N-Particle eXtended (MCNPX) computer code has been designed to simulate the depth dose in a phantom containing an assumed tumor. Test was carried out in two phases. In phase 1, verification of this model using the MCNPX was evaluated by comparing the obtained results with those of the published reports. In phase 2, gold was introduced into assumed tumor inside the phantom at different depths in the simulation program. Simulation was performed for four different concentrations of gold nanoparticles using a low mono-energetic parallel beam of synchrotron radiation. The obtained results show that the optimum energy for dose enhancement is found to be around 83–90 keV for all gold concentrations. The dose enhancement factor is increased linearly with concentration and diminished in depth along the central beam in the tumor. This approach of introducing contrast agents in conventional radiotherapy could hopefully prepare new treatment planning and improve the efficiency of tumor therapy.

10

Structural disorder of tooth germs in the antenatal period under low doses ionizing radiation exposure in acute experiment

Cheshko N. N., Berlov H. A., Pohodenko-Chudakova I. O., Gontchar F. L.

Engineering of Biomaterials

|

2010

|

Vol. 13, no. 99-101

9--10

11

Monte Carlo calculation of scattered radiation from applicators in low energy clinical electron beams

Jabbari N., Hashemi-Malayeri B., Farajollahi A. R., Kazemnejad A.

Nukleonika

|

2007

|

Vol. 52, nr 3

97-103

EN

. In radiotherapy with electron beams, scattered radiation from an electron applicator influences the dose distribution in the patient. The contribution of this radiation to the patient dose is significant, even in modern accelerators. In most of radiotherapy treatment planning systems, this component is not explicitly included. In addition, the scattered radiation produced by applicators varies based on the applicator design as well as the field size and distance from the applicators. The aim of this study was to calculate the amount of scattered dose contribution from applicators. We also tried to provide an extensive set of calculated data that could be used as input or benchmark data for advanced treatment planning systems that use Monte Carlo algorithms for dose distribution calculations. Electron beams produced by a NEPTUN 10PC medical linac were modeled using the BEAMnrc system. Central axis depth dose curves of the electron beams were measured and calculated, with and without the applicators in place, for different field sizes and energies. The scattered radiation from the applicators was determined by subtracting the central axis depth dose curves obtained without the applicators from that with the applicator. The results of this study indicated that the scattered radiation from the electron applicators of the NEPTUN 10PC is significant and cannot be neglected in advanced treatment planning systems. Furthermore, our results showed that the scattered radiation depends on the field size and decreases almost linearly with depth.

12

Modelling mould attenuation for liquid metal compensators

Goodband J., Haas O., Mills J.

Systems Science

|

2005

|

Vol. 31, no 1

45-52

EN

The paper reports on investigative work into the possibility of using a liquid-metal (e.g., mercury), as a viable substitute for solid metals in intensity-modulated radiation therapy (IMRT). As part of this work, the use of moulded plastic containers is studied. The attenuation characteristics of the moulds are found to significantly affect the accuracy of a dose distribution model. An algorithm is therefore devised to predict the change in attenuation properties and is integrated into the model, thereby halving the maximum predictor error.