Research progress on use of tissue equivalent filler in postmastectomy radiation therapy of breast cancer / 中华放射肿瘤学杂志

Although the use of postmastectomy radiation therapy (PMRT) has been proven to bring survival benefit to breast cancer patients, the use of chest wall tissue equivalent filler (bolus) remains controversial. In recent years, a large number of studies have shown that the use of bolus in PMRT does not significantly improve the local control rate, while it can significantly increase the acute skin toxicity, and even leads to more frequent and longer treatment interruption. Existing retrospective studies have indicated that for breast cancer patients undergoing mastectomy and systemic therapy, if there is no skin invasion, it is recommended not to routinely use bolus during radiotherapy. However, higher-level clinical studies are needed for further confirmation.

Experimental analysis of clinical applicability of homemade in homogeneous phantom / 中国辐射卫生

@#<b>Objective</b> To conduct experimental analysis of clinical applicability of a homemade phantom which is equivalent to multiple tissue densities of human body. <b>Methods</b> Materials with densities close to bone, lung, cavity, and soft tissue were manufactured and combined to obtain a homemade in homogeneous phantom. The electron density of equivalent materials was compared with the organs. Ten lung cancer patients in our department were recruited for dose verification of intensity modulated radiation therapy in the homemade phantom and solid-water phantom. The two phantoms were compared for characteristics in dose verification, and the dosimetric differences of the homemade phantom between the calculated values on treatment planning systemand measured values were statistically analyzed by SPSS 21.0 software. <b>Results</b> In the dose verification, the gamma pass rates (3 mm/3%) were more than 90% using both the homemade phantom and solid-water phantom. The measured values in homemade phantom were larger than those in solid-water phantom, and the maximum deviation was 11.5%. The AD and RD values of gamma pass rate in dose verification showed no significant differences between the two phantoms (<i>P</i> > 0.05). <b>Conclusion</b> The homemade phantom meets the accuracy requirement of clinical application and can be used in dose verification of intensity modulated radiation therapy plan.

Research on Individualized Phantom Based on 3D Printing for Radiotherapy Dose Verification / 中国医疗器械杂志

Dose verification is carried out on the individualized three-dimensional phantom based on 3D printing technology, which simulates the anatomical structure of human body, contour shape, tumor anatomical structure and other dangerous organs to the greatest extent, and produces a reasonable and effective dose validation phantom. According to the need to obtain effective patient data, import Mimics software to reconstruct the parts of the body and its surrounding tissues and organs that need to be measured, and make them into three-dimensional shell components. The 3D printing is used to assemble and fill the equivalent tissue, and then the body phantom is made. The phantom was scanned by CT and the data was transmitted to TPS system. The previously completed treatment plan was transplanted to the phantom. The phantom was placed according to the patient's location information, irradiated and measured data. The three-dimensional shell assembly is completely reconstructed according to the patient's data, and the contour difference is not significant. The shell is filled with tissue radiation equivalent material whose CT value is the same as the average CT value of the shell volume. The CT image data show that the radiation equivalence of the phantom is similar to the actual tissue of the patient, and the equivalent dose distribution conforms to the conventional treatment range. It can provide a reliable means of dose verification for the accurate design of intensity modulated radiation therapy.

Effective Atomic Number based on Energy Dispersive X-Ray (EDX) Analysis and Carbon Hydrogen Nitrogen (CHN) Analysis for Phantom Material in Medical Physics Applications

@#Introduction: In medical physics applications, effective atomic numbers are often employed to set apart and specify the interaction of ionizing radiation with matter. Methods: The effective atomic number of soy-lignin bonded with Rhizophora spp. particleboards were analyzed using Energy Dispersive X-ray analysis and Carbon Hydrogen Nitrogen Analyzer. The effective atomic number were compared and recorded with reference to the effective atomic value of water. Results: The result showed that the effective atomic number calculated for adhesive bound Rhizophora spp. samples were close to effective atomic value of water, with 3.34 – 3.47 % differences by using Energy Dispersive X-ray and 6.47 – 6.78 % differences by using Carbon Hydrogen Nitrogen analysis. The result revealed that through Energy Dispersive X-ray method, the effective atomic number was much closer to water compared to Carbon Hydrogen Nitrogen analysis. Conclusion: Despite the availability of hydrogen content in the samples in Carbon Hydrogen Nitrogen analysis, Energy Dispersive X-ray method was much more preferred and gave better result compared to Carbon Hydrogen Nitrogen analysis thus provide a compelling argument for the use of Energy Dispersive X-ray method to measure the effective atomic number of Rhizophora spp. particleboard in medical physics applications.

Localization and characterization of tissue changes by laser backscattering imaging and Monte Carlo simulation.

Laser backscattering from biological tissues depends on their composition and blood flow. The onset of the tissue abnormalities is associated with the change in composition at a specific location which may affect laser backscattering. The objective of the present work is to detect the compositional changes in tissue-equivalent phantom of fat, prepared by mixing paraffin wax with wax colors, and to characterize these in terms of their optical parameters. For this purpose these phantoms are scanned by a multi-probe non-contact automatic laser scanning system and images of the normalized backscattered intensity (NBI) are constructed. By scanning the background subtracted image of the phantom the location of the abnormality and its size from the full width at half maximum (FWHM) are determined. The data obtained by ultrasonic technique for localization of the abnormalities are in agreement with that as obtained by the present method. The optical parameters of the abnormality are obtained by matching the measured surface profiles of the abnormality with that of the profile obtained by Monte Carlo simulation. This analysis shows the possibility of detection of changes at the onset stage in tissues as required for planning of the photodynamic therapy.

Effect of chest wall radiotherapy in different manners using tissue equivalent bolus on skin and lung of cavia cobayas / 中华放射医学与防护杂志

Objective To probe the influence of electron beam radiotherapy in different manners using different tissue equivalent boluses on skin and lung.Methods Adult female cavia cobayas were randomly divided into four groups as control group,fuU-time with bolus group,half-time with bolus group and without bolus group.Acute-irradiation animal models were established using electron beam in different manners with or without 0.5 cm tissue equivalent bolus.Pathological changes in lung,hair vesicle and fibroblast cell count were analyzed 40 clays after irradiation.Results The radiation dermatitis in the group with bolus was slighter than that of the group without bolus,but the radiation pneumonia was reverse.With bolus,the radiation dermatitis of haft-time group was slighter than that of full-time group.The injury repair of half-time group was more active than full-time group.Conclusions The treatment of haft-time bolus could protect lung without serious skin complications.

Dose Effect of Tissue Compensator for 6 MV X-Ray / 대한치료방사선과학회지

It is ideal thing to compensate tissue deficit without skin contamination in curvatured irradiation field of high energy Photon beam. The 3-dimensional compensating technique utilizing tissue equivalent materials to ensure an adequate dose distribution and skin sparing effect was described. This compensator was made of paraffin(70%) and stearin wax (30%) compound. The parameters for evaluation of the effect on skin dose in application of compensator were considered in the size of the field, the thickness of the compensator and the source-to-axis distance. The results are as follows; the skin doses were not changed even though application of the compensator, but depended on the field size and the source-to-axis distance, and the skin doses were only slightly changed within 1% relative errors as increasing the thickness of the compensator in these experiments.

Dosimetric Characteristics of the KCCH Neutron Therapy Facility / 대한치료방사선과학회지

For the physical characterization of neutron beam, dosimetric measurements had been performed to obtain physical data of KCCH cyclotron-produced neutrons for clinical use. The results are presented and compared with the data of other institutions from the literatures. The central aixs percent depth dose, build-up curves and open and wedge isodose curve values are intermediate between that of a 4 and 6 MV X-ray. The build-up level of maximum dose was at 1.35 cm and entrance dose was approximately 40%. Flatness of the beam was 9% at Dmax and less than+/-3% at the depth of 80% isodose line. Penumbra begond the 20% line is wider than corresponding photon beam. The output factors ranged 0.894 for 6 x 6 cm field to 1.187 for 30 x 30 cm field. gamma contamination of neutron beam was 4.9% at 2 cm depth in 10 x10 cm field.