In intracavitary radiotherapy, incorrect source locations can result in excessive doses to normal tissues. Therefore, it is essential to accurately evaluate the source location. In this study, we investigated a digital line dosimeter based on thallium (I) bromide (TlBr) to improve the existing analogue verification method. Therefore, a polycrystalline TlBr unit cell dosimeter was manufactured, and the measurement performance of iridium-192 (Ir-192) sources was evaluated. We found that the dosimeter's reproducibility satisfied the evaluation criteria of 1.5% with a relative standard deviation of 1.44%. Moreover, the linearity showed excellent results (linear coefficient, R 2 = 0.9999). The distance dependence showed a difference of 0.03 cm at 50% intensity when compared to the inverse square value, whereas the angular dependence showed a large difference when compared to a diode. As the angle increased, the intensity gradually decreased, resulting in a difference of up to 41.9%. These results demonstrate the excellent performance of the TlBr dosimeter. However, because of the significant influence of angular dependence, a measurement distance that minimises this error should be applied when manufacturing line dosimeters in the future.

In radiotherapy, dose assessment is performed as part of quality assurance (QA) to verify the dose accuracy of the treatment administered to patients. Various dosimeters are used depending on the part of the body and the desired purpose, and tools such as the thermoluminescent dosimeter (TLD) and semiconductor dosimeter are used as in vivo dosimeters. However, TLDs have demonstrated measurement errors of approximately 11.8%, and the diodes used in semiconductor dosimeters fluctuate in performance owing to radiation damage. Consequently, various photoconductor materials are being researched to replace diodes. In particular, Thallium (I) bromide (TlBr) is being used as a substitute material for semiconductors because of its low cost and high performance. Therefore, this study determined the optimised performance of TlBr, which is a potential photoconductor material to replace other materials commercially, using the particle-in-binder deposition method. Upon evaluating the reproducibility and linearity, all sensors demonstrated remarkable performance at 6 MV and 15 MV as the results demonstrated a relative standard deviation (RSD) less than 1.5% and R2 value above 0.9998, which were the evaluation criteria. A 3:1 material ratio was chosen, as the performance demonstrated in this case was superior to that of other material ratios. The results of the monitor unit rate dependence and percent depth dose (PDD) were compared with those of silicon diode and thimble chambers, which are widely used for dose measurement. According to the monitor unit rate dependence results, the RSD was 0.66% at 6 MV and 0.27% at 15 MV with the standard set at 100 MU, indicating that the diode was outperformed by less than 1%. Similar results were obtained for the PDD with the ion chamber, and the surface dose required for in vivo dose measurement indicated an error within 8.67%. Therefore, this study provides basic data for polycrystalline TlBr dosimeters, which can replace the existing semiconductor dosimeters for QA.

Generally, electron therapy is applied to tumors on or close to the skin surface. However, this causes a variety of skin-related side effects. To alleviate the risk of these side effects, clinical treatment uses skin dosimeters to verify the therapeutic dose. However, dosimeters suffer from poor accuracy, because their attachment sites are approximated with the help of naked eyes. Therefore, a dosimeter based on a flexible material that can adjust to the contours of the human body is required. In this study, the reproducibility, linearity, dose-rate dependence, and percentage depth ionization (PDI) of PbO and HgO film-based dosimeters are evaluated to explore their potential as large-scale flexible dosimeters. The results demonstrate that both dosimeters deliver impressive reproducibility (within 1.5%) and linearity (≥ 0.9990). The relative standard deviations of the dose-rate dependence of the PbO and HgO dosimeters were 0.94% and 1.16% at 6 MeV, respectively, and 1.08% and 1.25% at 9 MeV, respectively, with the PbO dosimeter outperforming the 1.1% of existing diodes. The PDI analysis of the PbO and HgO dosimeters returned values of 0.014 cm (–0.074 cm) and 0.051 cm (–0.016 cm), respectively at 6 MeV (9 MeV) compared to the thimble chamber and R50. Therefore, the maximum error of each dosimeter is within the allowable range of 0.1 cm. In short, the analysis reveals that the PbO dosimeter delivers a superior performance relative to its HgO counterpart and has strong potential for use as a surface dosimeter. Thus, flexible monoxide materials have the necessary qualities to be used for dosimeters that meet the requisite quality assurance standards and can satisfy a variety of radiation-related applications as flexible functional materials.

In radiotherapy, point doses via surface dose measurement are confirmed using a dosimeter attached to the patient's skin. This results in an error margin of about 11.8% or higher because the attachment site is visually confirmed. Thus, a digital flexible array dosimeter that can analyse body surface area is needed. Here, a lead (II) iodide (PbI 2 )-based unit cell flexible dosimeter was developed, and its electrical properties were evaluated based on its mechanical flexibility by assessing its reproducibility and linearity for bending. The relative standard deviation (RSD) for measurement by the sensor over 10,000 cycles was 1.74% and 2.21% at 6 MV and 15 MV, respectively, which is higher than RSD's evaluation criterion (<1.5%). Although the linearity of measurement by the sensor over 10,000 cycles met the evaluation criteria of a coefficient of determination R 2 > 0.9990, the sensitivity at 15 MV was lower than that at 6 MV. The results of this study confirm the applicability and usefulness of the PbI 2 -based flexible dosimeter in radiation measurements. K: Dosimetry concepts and apparatus; Materials for solid-state detectors; Radiation damage to detector materials (solid state); Radiotherapy concepts 1Corresponding author.

Radiation therapy uses high-energy radiation that can cause various side effects depending on the patient's exposure. In particular, side effects occur in the skin due to its radiation exposure to reach the target volume. Therefore, side effects are reduced by clinical trials using various skin dosimeters such as lms and glass detectors to determine the dose exposed to the skin. However, accurately measuring the doses using these dosimeters is challenging due to human curvature. In this study, a exible skin dosimeter was produced using the photoconductor materials mercury oxide (HgO) and lead oxide (PbO).The performance of the proposed dosimeter was evaluated by measuring reproducibility, linearity, dose rate independency according to dose, and percent depth dose (PDD) at photon energy beam. The results showed that the exible skin dosimeter using HgO material has high applicability as a skin dosimeter due to its stability compared to PbO. The results provide useful insights for the radiation therapy eld, particularly in areas where radiation measurement is di cult, depending on the human curvature. The proposed exible skin dosimeter could serve in various radiation detection areas as a exible, functional material

Normal tissues are also exposed during radiation therapy. In particular, the skin is highly sensitive to radiation. Therefore, care should be taken regarding excessive exposure, and the dose irradiated to the skin should be measured accurately. In this study, a skin dosimeter that can be attached to the human body was manufactured using a silicone binder, and a new type of passive layer using silicon was applied. In addition, the manufactured dosimeter was evaluated to establish whether it could be used with a skin dosimeter. The observation of the surface of the dosimeter through SEM analysis showed that cracks did not occur on the surface of the silicon passive layer PbO dosimeter when it was bending. The bending silicon passive layer PbO dosimeter's relative standard deviation was 1.45%, meeting the evaluation criteria of 1.5%. The linearity evaluation showed that the R 2 of the bending silicon passive layer PbO dosimeter was 0.9996, satisfying the evaluation criterion R 2 of 0.9990. The PDD measurements showed that the D_max points matched. As the silicon passive layer PbO dosimeters showed no cracks when bending, high signal stability, and accuracy in reproducibility, linearity, and PDD measurement results, it could be suitable for application as skin dosimeters.

Brachytherapy is a cancer treatment that involves intensively irradiating a tumor by placing a sealed radioactive isotope inside the body. Determining the position of the source through accurate quality assurance (QA) is important, because brachytherapy uses radioactive isotope sources with high dose rates. However, in clinical practice, the source position is determined with the naked eye through the use of a ruler, autoradiograph, video monitor, etc., which yields inaccurate results. Therefore, in this study, a lead (II) iodide (PbI2) based polycrystalline digital dosimeter that can measure the relative dose was developed for the QA of the brachytherapy device, and its applicability was evaluated in terms of reproducibility, linearity, percentage interval distance (PID), and angular dependence. Reproducibility evaluation yielded a relative standard deviation value of 1.41%, which satisfied the evaluation criterion of 1.5%. The linearity evaluation yielded an R2 value of 0.9993, which satisfied the evaluation criterion of 0.9990. The PID evaluation revealed that, as the distance from the source increased, the signal decreased according to the inverse-square law. When the PbI2-based digital dosimeter was rotated up to 45°, a difference of up to 13.20% in the angular dependence was observed. Thus, the dosimeter fabricated in this experiment met all the criteria of the aforementioned evaluations. Therefore, it is considered to be highly applicable as a dosimeter for the QA of brachytherapy devices.

In the field of radiation therapy, the need for a flexible dosimeter that can be applied on the flexor surface for precise measurement of the surface dose is increasing. In particular, electron beam therapy has a shorter treatment depth than photon beam therapy; therefore, the surface dose must be measured accurately. This study investigates attenuation errors in a dosimeter. We demonstrated that the attenuation error depends on the thickness of the flexible functional materials, and it can serve as fundamental research for creating a flexible dosimeter that can be applied on the human body. The results indicated that the maximum attenuation error of a polyethylene terephthalate film with a thickness of 75 μm was 0.40% and 0.027% at 6 MeV and 9 MeV, respectively. Moreover, when using HgI2 and PbI2 as photoconductor materials, the maximum attenuation errors at 6 MeV were 1.35% and 1.67%, respectively. This study provides fundamental insights into dose errors by using a surface dosimeter and error variables to produce a surface dosimeter. Further, because the study investigates flexible materials, the findings can be extended to various applications in the field of radiation therapy.