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Abstract Background Phantom limb pain (PLP) occurs after amputations and can persist in a chronic and debilitating way. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neuromodulation method capable of influencing brain function and modulating cortical excitability. Its effectiveness in treating chronic pain is promising. Objective To evaluate the evidence on the efficacy and safety of using rTMS in the treatment of PLP, observing the stimulation parameters used, side effects, and benefits of the therapy. Methods This is a systematic review of scientific articles published in national and international literature using electronic platforms. Results Two hundred and fifty two articles were identified. Two hundred and forty six publications were removed because they were duplicated or met the exclusion criteria. After selection, six studies were reviewed, those being two randomized clinical trials and four case reports. All evaluated studies indicated some degree of benefit of rTMS to relieve painful symptoms, even temporarily. Pain perception was lower at the end of treatment when compared to the period prior to the sessions and remained during patient follow-up. There was no standardization of the stimulation parameters used. There were no reports of serious adverse events. The effects of long-term therapy have not been evaluated. Conclusion There are some benefits, even if temporary, in the use of rTMS to relieve painful symptoms in PLP. High-frequency stimulation at M1 demonstrated a significant analgesic effect. Given the potential that has been demonstrated, but limited by the paucity of high-quality studies, further controlled studies are needed to establish and standardize the clinical use of the method.
Resumo Antecedentes A dor do membro fantasma (DMF) ocorre após amputações e pode persistir de forma crônica e debilitante. A estimulação magnética transcraniana repetitiva (EMTr) é um método de neuromodulação não invasivo capaz de influenciar a função cerebral e modular a excitabilidade cortical. Sua eficácia no tratamento da dor crônica é promissora. Objetivo Avaliar as evidências sobre a eficácia e segurança do uso da EMTr no tratamento da DMF, observando os parâmetros de estimulação utilizados, efeitos colaterais e benefícios da terapia. Métodos Trata-se de uma revisão sistemática de artigos científicos publicados na literatura nacional e internacional utilizando plataformas eletrônicas. Resultados Foram identificados 252 artigos. Duzentas e quarenta e seis publicações foram removidas por estarem duplicadas ou atenderem aos critérios de exclusão. Após a seleção, foram revisados seis estudos, sendo dois ensaios clínicos randomizados e quatro relatos de caso. Todos os estudos avaliados indicaram algum grau de benefício da EMTr no alívio dos sintomas dolorosos, mesmo que temporariamente. A percepção da dor foi menor ao final do tratamento quando comparada ao período anterior às sessões e permaneceu durante o acompanhamento do paciente. Não houve padronização dos parâmetros de estimulação utilizados. Não houve relatos de eventos adversos graves. Os efeitos da terapia a longo prazo não foram avaliados. Conclusão Existem alguns benefícios, mesmo que temporários, no uso da EMTr para alívio dos sintomas dolorosos na DMF. A estimulação de alta frequência em M1 demonstrou um efeito analgésico significativo. Dado o potencial demonstrado, mas limitado pela escassez de estudos de alta qualidade, são necessários mais estudos controlados para estabelecer e padronizar o uso clínico do método.
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Objective:To explore the value of the deep learning image reconstruction (DLIR) algorithm in improving the CT image quality of abdominal phantoms under different radiation doses by comparing the DLIR algorithm with the conventional Adaptive Statistical Iterative Reconstruction-V (ASIR-V) technique.Methods:Two groups with tube voltages of 100 kV and 120 kV (also referred to as the 100 kV and 120 kV groups, respectively) were involved. Each group was further divided into six subgroups based on different volumetric CT dose indices (CTDI vol: 2, 4, 6, 8, 10 and 15 mGy). Subsequently, CT images based on the filtered back projection (FBP) algorithm were obtained and were then reconstructed using the ASIR-V algorithm with different weights (ASIR-V 50%, 80%, and 100%) and the DLIR algorithm with different levels (DLIR-L, M, and -H). As a result, 84 groups of images were obtained in total. Afterward, this study compared and analyzed the variations in CT values, noise, signal-to-noise ratios (SNRs), contrast-to-noise ratios (CNRs), and subjective scores of various parts in various CTDI vol subgroups under different reconstruction conditions. In addition, the subjective scores of the image quality were compared using the Kruskal-Wallis H test, while objective indices and radiation doses were compared through the univariate analysis of variance (ANOVA) and the paired t test. Results:Under the same tube voltage, there were statistically significant differences in the noise, SNRs, and CNRs of various parts in various CTDI vol subgroups under different reconstruction conditions ( F = 415.39, 315.30, P < 0.001), while there was no statistically significant difference in the noise, SNRs, and CNRs of images constructed using ASIR-V 50% and DLIR-L ( P > 0.05). Under different tube voltages, the subjective scores of both groups show statistically significant differences (100 kV group: H = 13.47, P = 0.036; 120 kV group: H = 12.99, P = 0.043). Moreover, two physicians offered consistent subjective scores, with Kappa values > 0.70. Among these images, DLIR-H images showed the highest subjective scores, followed by DLIR-M and ASIR-V 50% images, which had roughly consistent subjective scores. Moreover, the subjective scores of the 100 kV group were slightly higher than those of the 120 kV group. With the ASIR-V 50% images of the subgroup with a CTDI vol of 15 mGy as references, the DLIR-L, -M, and -H reduced radiation doses by more than 30%, 70% and 85%, respectively on the premise that diagnostic requirements were met. Conclusions:The DLIR algorithm can not only significantly reduce the image noise and improve the image quality, but also effectively decrease the radiation doses on the premise of meeting the diagnostic requirements. It is recommended that 100 kV tube voltage combined with a medium- or high-level DLIR algorithm should be applied to low-dose abdominal CT scans in clinical applications.
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Objective:To evaluate the effects of split-filter dual-energy CT (SF-DECT) in improving image quality at low doses in the process of abdominal examinations for children.Methods:A preliminary study was conducted using child phantoms. Furthermore, 20 children aged 4-6 years were recruited prospectively for clinical validation from June 2020 to December 2020. Conventional single-energy CT (SECT) and SF-DECT were employed to scan the abdominal areas of the phantoms and children. Then, the CT values, image noise, contrast to noise ratios (CNRs), and image subjective scores of SF-DECT and SECT were compared under various doses (1, 2, 3, and 4 mGy).Results:For the phantoms under doses of 3 and 4 mGy, SF-DECT decreased the image noise by 18.9% and 23.6%, respectively, and increased the liver and kidney CNRs (CNR liv and CNR kid) by 12.8% and 31.9% at most, respectively, compared to SECT ( Z = 3.00, 5.17, P < 0.001). For children, SF-DECT decreased image noise ( Z = 4.64, P < 0.001) and increased CNR liv and CNR kid ( Z = 3.78, 3.39, P < 0.001). For both the phantoms and the children, the subjective scores of images scanned using the SF-DECT were higher than those scanned using the SECT ( Z = 1.96-3.80, P < 0.05). Conclusions:Compared with SECT, SF-DECT can improve the quality of children′s abdominal images. This technique has a certain prospect of optimizing abdominal CT for children. However, it is necessary to conduct in-depth clinical research to verify the result.
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The quality control of nuclear medicine imaging equipment is essential to ensure the quality and safety of nuclear medicine imaging. Phantoms are indispensable tools in quality control, performance comparison, and multicenter clinical trials of nuclear medicine imaging equipment. The structure of phantoms is developed from a simple form to a complicated form which can simulate real clinical conditions, and they are provided in various forms in combination with modern technologies. Different types of phantoms have their unique advantages and application situations. This article investigated and summarizes common phantoms and their performance evaluation indicators used in nuclear medicine imaging to provide a reference for the quality control of nuclear medicine equipment and selection of phantoms for clinical research.
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Objective:To investigate the dosimetric effects of prone immobilization devices combined with a belly board (PIDBBs) in the intensity-modulated radiotherapy (IMRT) for gynecologic cancers.Methods:A total of 20 patients with cervical or endometrial cancer treated with radiotherapy in the Third Affiliated Hospital of Sun Yat-sen University from August 2020 to June 2021 were retrospectively analyzed. Two sets of body contours were outlined for each patient. One set of body contours did not contain the immobilization devices, and the other contour set included the immobilization devices. For each patient, doses were calculated for the two sets of contours using the same 7-field IMRT plan and were recorded as Plan without and Plan with. The dosimetric difference caused by the immobilization devices was assessed by comparing the parameter values in the dose-volume histograms (DVHs) and by plan subtraction. The Gafchromic EBT3 film and anthropomorphic phantom were used to verify the calculated doses. Results:The target coverage and average dose of Plan with were lower than those of Plan without. Specifically, the V50 Gy, V49 Gy, and Dmean of planning target volume (PTV) decreased by 19.75%, 7.99%, and 2.54% ( t = 8.96, 10.49, 22.09, P < 0.01), respectively. The V40 Gy, V30 Gy, V20 Gy, V15 Gy, and Dmean of skins increased by 51.79%, 51.05%, 45.72%, 33.63% and 10.80% ( t = -2.54, -5.63, -15.57, -24.06, -13.88, P < 0.01), respectively. Doses to other organs at risk (OARs) showed no significant differences. As indicated by the EBT3 measurements, the doses to skins of the abdomen and pelvis on the anthropomorphic phantom increased by approximately 37.24% ( t = 10.86, P<0.01). Conclusions:Although PIDBBs can effectively reduce the low dose to the small intestine, the radiation attenuation caused by them can reduce the PTV coverage of radiotherapy plans and increase the doses to abdominal and pelvic skins sharply, especially for patients requiring irradiation of the groin and perineum.
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Objective To develop a simplified phantom for the calibration of whole-body counters. Methods A simplified phantom design method for the calibration of whole-body counters was established based on the process and method of calibrating whole-body counters. By using the established method and Monte Carlo method, a simplified phantom including the total body, thyroid, lungs, and gastrointestinal tract was designed to calibrate the ORTEC-Stand FAST II whole-body counter. The simplified phantom was compared with the BOMAB phantom through experimental measurements. Results Within the range of 50 keV to 2 MeV, for rays of the same energy in the same organ of the simplified phantom and BOMAB phantom, the simulated data of detection efficiency by whole-body counting showed an error within 5%, and the experimental measurements showed an error within 10%. Conclusion We developed a simplified phantom for the calibration of the whole-body counter, demonstrating the feasibility of using the simplified phantom instead of a physical body phantom for whole-body counter calibration, which can greatly facilitate whole-body counter calibration for internal radiation monitoring.
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@#<b>Objective</b> To apply a phantom for dose measurement in interventional therapy for pediatric vascular diseases, and calculate the effective dose (<i>E</i>) and conversion coefficient of dose area product (DAP) to <i>E</i>, and to provide a dose reference for studying radiation dose and radiation protection in children. <b>Methods</b> Thermoluminescent dosimeters were placed in the organs of the phantom. Low-, medium-, and high-dose groups were set for three types of vascular anomalies based on the duration of fluoroscopy. Digital subtraction angiography was used to simulate exposure conditions at different dose levels. The organ dose was measured, and the effective dose was calculated. <b>Results</b> For the three groups of vascular anomalies in the head and face, the red bone marrow doses were 8.15, 30.34, and 43.53 mGy, respectively, the effective doses were 12.88, 47.84, and 73.12 mSv, respectively; and the average conversion coefficient of DAP to <i>E</i> was 2.16. For the three groups of vascular anomalies in the trunk, the red bone marrow doses were 2.11, 15.62, and 31.21 mGy, respectively; the effective doses were 12.39, 70.56, and 134.60 mSv, respectively, and the average conversion coefficient of DAP to <i>E</i> was 3.03. For the three groups of vascular anomalies in the lower extremities, the red bone marrow doses were 3.58, 6.50, and 12.28 mGy, respectively, the effective doses were 3.64, 7.04, and 14.85 mSv, respectively, and the average conversion coefficient of DAP to <i>E</i> was 0.73. <b>Conclusion</b> Patient dose and DAP-to-<i>E</i> conversion coefficient are in the following order: vascular anomalies in the trunk > vascular anomalies in the head and face > vascular anomalies in the lower extremities. The dose data obtained can be used to estimate children’s radiation exposure.
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Objective To calculate the doses and their dose conversion coefficients for the personnel whose organs were under accidental exposure to three types of X-ray machines and two γ radiation sources, and to provide a simple method for rapid estimation of accidental doses. Methods The radiation source models of X-ray machines and two γ sources were established with the FLUKA simulation software and a Chinese reference voxel phantom was imported. The organ absorbed dose, dose conversion coefficient between organ absorbed dose and air Kerma, and conversion coefficient between organ absorbed dose and radiation source were calculated for a simulated scenario where the personnel were under antero-posterior exposure to radiation sources 1 meter away. Results For the lungs, heart, muscles, soft tissue, liver, skin, and brain, the conversion coefficient between organ absorbed dose and air Kerma was 0.30-1.19 (Gy/Gy). For X-ray machines, the conversion coefficient between organ absorbed dose and output for the six organs ranged from 6.12 × 10−3 to 2.90 × 10−2 Gy·m2/(mA·min). For γ radiation sources, the conversion coefficient between organ absorbed dose and activity for the six organs ranged from 1.12 × 10−8 to 7.01 × 10−8 Gy·m2/(GBq·s). Conclusion The conversion coefficient between organ absorbed dose and air Kerma and the conversion coefficient between organ absorbed dose and output or activity of a flaw detector can provide important dosimetric parameters for rapid assessment of similar radiation accidents.
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Introducción: La amputación de la extremidad con frecuencia da lugar a alteraciones sensoriales, dolorosas o no, tales como el síndrome del miembro fantasma, que dificulta el proceso de rehabilitación y afecta el estado psicológico del paciente. El dolor de miembro fantasma ha sido descrito como una condición en la que los pacientes experimentan una sensación dolorosa en el miembro ausente. Objetivo: Describir aspectos esenciales del dolor fantasma como complicación en los pacientes amputados Métodos: Se realizó una búsqueda de la literatura publicada durante el período comprendido entre enero de 2015 y diciembre de 2021 que hiciera referencia al dolor en miembro fantasma en paciente amputado. Resultados: Entre las causas que conllevan a la amputación de una extremidad se encuentran los problemas vasculares, trauma, cáncer y alteraciones congénitas, es importante tenerlas en consideración debido a los efectos psicológicos y socioeconómicos que puede tener en el paciente. El síndrome del miembro fantasma se divide en miembro o sensación fantasma, dolor de miembro fantasma y muñón doloroso. Es importante hacer distinciones entre ellos, lo que ayuda a evaluar la magnitud del problema y el tratamiento que es diferente. El tratamiento convencional no ha sido muy efectivo. Conclusiones: Se describieron los aspectos esenciales del dolor fantasma como complicación en los pacientes amputados, el manejo y tratamiento del dolor de miembro fantasma en miembros amputados, constituye una prioridad a vencer dentro de las pautas de la medicina moderna(AU)
Introduction: Limb amputation often gives rise to sensory alterations, painful or not, such as phantom limb syndrome, which hinders the rehabilitation process and affects the patient's psychological state. Phantom limb pain has been described as a condition in which patients experience a painful sensation in the missing limb. Objective: To describe essential aspects of phantom pain as a complication in amputee patients. Methods: A search of the literature published between January 2015 and December 2021 that referred to phantom limb pain in amputee patients was carried out. Results: Among the causes that lead to the amputation of a limb are vascular problems, trauma, cancer and congenital alterations, it is important to take them into consideration due to the psychological and socioeconomic effects that they can have on the patient. Phantom limb syndrome is divided into phantom limb or sensation, phantom limb pain, and painful stump. It is important to make distinctions between them, which helps to assess the magnitude of the problem and the treatment that is different. Conventional treatment has not been very effective. Conclusions: The management and treatment of phantom limb pain in amputated limbs is a priority to be overcome within the guidelines of modern medicine, which is why care intervention is necessary in order to improve the quality of life of the amputated patient and their better rehabilitation(AU)
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Objective To investigate the dose of radiation in children under going X-ray-guided air enema reduction, and to provide a basis for reducing the risk of radiation injury in pediatric patients. Methods Data were collected from children with intussusception who were treated with air enema. The experimental conditions of high, medium, and low doses of three age groups were analyzed. Phantoms were used to simulate the operation, and the radiation dose was measured using a thermoluminescence system. Results In children with intussusception, the success rate of air enema under the guidance of X-ray was 88% (including secondary intussusception), with anearly re-intussusception rate of 8%. The effective dose of treatment ranged from 0.57 to 12.33 mSv, and the tissues and organs with high absorbed dose were mainly in the chest and abdomen. Conclusion Children in different groups are exposed to significantly differentand relatively high doses. The operators are recommended to use ultrasonic guidance. With X-ray guidance, the exposure time should be minimized and protective equipment for children should be used.
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Objective To investigate the influence of PET/CT imaging conditions (acquisition time, bed overlap, reconstruction matrix, iteration times, filter kernel size, and attenuation correction) on the spatial resolution of images. Methods Two PET/CT devices, GE Discovery Elite and GE Discovery ST-16, were used to scan the elliptical column resolution model in one and two beds (list mode, acquisition time of 6 min). Images were reconstructed under the commonly used clinical reconstruction conditions (Elite: VPFX-S algorithm, ST-16: VUE Point HD algorithm) at 1-6 min/bed, different iteration times of 2-10 times, different filter kernel sizes of 2.0-10.0 mm (Elite), and different reconstruction matrices, with attenuation correction or not. The spatial resolution of reconstructed PET images was represented by the full width at half maximum (FWHM) of the line spread function. Results Under the clinical acquisition conditions, when the acquisition time was 1 min, 2 min, 3 min, 4 min, 5 min, and 6 min, the FWHMElite of spatial resolution at the center of field of view was (4.06 ± 0.08) mm, (4.05 ± 0.20) mm, (4.01 ± 0.01) mm, (4.05 ± 0.07) mm, (4.05 ± 0.03) mm, and (4.08 ± 0.06) mm, and the FWHMST-16 was (5.76 ± 0.12) mm, (5.72 ± 0.11) mm, (5.74 ± 0.09) mm, (5.78 ± 0.05) mm, (5.75 ± 0.09) mm, and (5.77 ± 0.07) mm. When the phantom was located in the center of one bed and the overlap of two beds, the line FWHMElite at the center was (4.04 ± 0.01) mm and (4.04 ± 0.01) mm, and the FWHMST-16 was (5.39 ± 0.19) mm and (5.38 ± 0.07) mm, respectively. The FWHMElite at the center was (4.07 ± 0.18) mm, (4.25 ± 0.10) mm, and (4.73 ± 0.08) mm at the matrices of 256 × 256, 192 × 192, and 128 × 128, respectively. The FWHMElite at the center was (4.65 ± 0.43) mm, (4.77 ± 0.27) mm, (4.02 ± 0.01) mm, (4.11 ± 0.04) mm, and (9.94 ± 0.01) mm at the filter kernel sizes of 2.0 mm-10.0 mm (interval of 2.0 mm), respectively. The FWHMElite at the center was (4.17 ± 0.27) mm, (4.27 ± 0.21) mm, (4.11 ± 0.05) mm, (4.18 ± 0.04) mm, and (4.12 ± 0.06) mm at 2-10 iterations (interval of 2 times), respectively. The FWHMElite at the center was (4.14 ± 0.01) mm and (4.18 ± 0.08) mm with and without attenuation correction, respectively. At the same acquisition time and bed, the spatial resolution of Elite images was improved by about 40.57% compared with that of ST-16 images. Conclusion The spatial resolution of images obtained at the matrix of 256 × 256 is higher than that of images obtained at the matrices of 192 × 192 and 128 × 128 in the same model. Elite images have the best spatial resolution at the reconstruction filter kernel size of 6.0 mm. Under the same imaging conditions, Elite images show significantly better spatial resolution compared with ST-16 images. Acquisition time, overlap of beds, iteration times, and attenuation correction have no significant effect on the spatial resolution of PET images.
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Objective To discuss 7Be and a 77.2 keV full-energy peak with short half-life found in the water sample from the 3D water phantom of a proton therapy system. Methods We measured the water sample from the 3D water phantom of a proton therapy system according to Determination of Radionuclides in Water by Gamma Spectrometry (GB/T 16140—2018). Results The activity concentration of 7Be in the water sample was 1.30 × 101 Bq·L−1 on December 24, 2018; 4.3 × 101 Bq·L−1 on March 22, 2019; and 1.41 × 101 Bq·L−1 at the time of sampling on December 19, 2018. On December 24, 2018, the net peak area of the 77.2 keV full-energy peak in the sample was 683 ± 45, and the measurement time was 26123.02 s; on March 22, 2019, the net peak area decreased to the background level of 194 ± 49, and the measurement time was 86400.00 s. Conclusion In the 3D water phantom of the proton therapy system, 7Be can be generated from the spallation reaction between high-energy neutrons and oxygen in water. In addition, we find a full-energy peak at 77.2 keV with short half-life. The activity concentration of 7Be in the water sample is lower than the exemption level, but the activity concentration at sampling may not be the maximum activity concentration in the process of quality control. The inductive radionuclide 7Be produced in the 3D water phantom should be identified and properly evaluated in the assessment of occupational radiation hazards of proton therapy system.
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Objective:To compare the comprehensive performance of three Varian on-board image (OBI) image systems (KV-CBCT, KV-planar and MV-EPID) and to explore the value of the combined application of these three systems in daily image-guided radiotherapy for nasopharyngeal cancer.Methods:KV-CBCT, KV-planar and MV-EPID scanning and registration were carried out in the left and right/abdominal and back/head and foot direction on human head and neck phantom. The set-up error, registration time, additional radiation dose and image quality of the three systems were compared by F-test.Results:KV-CBCT, kV-planar and MV-EPID were scanned for 55 times, respectively, and the set-up errors in the left and right/abdominal and back/head and foot direction of the three image-guided systems were (0.00±5.43)/(-0.02±5.49)/(0.02±5.58) mm, (0.04±5.49)/(0.02±5.56)/(0.02±5.54) mm, (0.02±5.22)/(0.11±5.34)/(-0.04±5.33) mm, respectively ( P=0.999, 1.000, 0.989). The average time consuming was (200±45) s, (120±36) s and (115±42) s; the additional radiation dose from low to high was kV-planar, KV-CBCT and MV-EPID; the image quality from low to high was MV-EPID, kV-planar and KV-CBCT. Conclusions:Three image-guided systems can meet the requirements of image-guided radiotherapy for nasopharyngeal cancer. Based on the overall performance of the three systems, 1 CBCT+ 4 kV planar per week is recommended and EPID should be used as a backup system in daily image-guided radiotherapy for nasopharyngeal cancer. This scheme makes full use of the high image quality of CBCT and the low radiation of kV planar to realize the regular detection of nasopharyngeal cancer volume change and the implementation of high-precision radiotherapy.
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Objective:To simulate the effects of different thyroid-neck phantoms and monitoring positions on the detection efficiency of portable γ spectrometer, and to provide guidance for more accurate on-site measurement of 131I activity in the human thyroid. Methods:Based on the models of 4 typical thyroid-neck phantoms and a 3-inch NaI (TI) γ spectrometer used for the measurement of 131I in the thyroid and combined with the possible field monitoring scenarios, the Monte Carlo method was used to simulate and calculate the detection efficiency of the spectrometer under different conditions of monitoring distance, thyroid depth and thyroid volume. Results:The detection efficiency decreased significantly with the increase in the distance between the detector and the neck surface. The efficiency close to the neck surface was about 15 times that at 15 cm away from the neck surface. The detection efficiency decreased significantly with the increase in thyroid depth. When it was measured at the surface of the neck, the detection efficiency of thyroid at depth of 2 mm was about 3.6 times that of 30 mm. The detection efficiency decreases with the increase in thyroid volume. When it was measured at the neck surface, the detection efficiency of thyroid with 1 ml volume was 1.71 times that with 30 ml. The detection efficiency decreased with the center-point offset of the detector, especially at the neck surface, an offset of 2 cm would reduce the detection efficiency by about 15%.Conclusions:Not only the measurement distance used in calibration, but also the information of the depth and volume of thyroid in the neck-thyroid phantom, is important to know in advance for an accurate measurement of 131I activity in thyroid by using a portable gamma spectrometer.
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Objective:To analyze the clinical reliability of neonatal bedside photography protection and body position fixing device during neonatal bedside X-ray photography.Methods:A mobile X-ray diagnostic machine was used to project the phantom of children. The samples were divided into group A with conventional bedside photography mode, and group B using neonatal bedside X-ray photography protection device. X-ray diagnostic level dosimeters were placed at the projection and radiation sensitive sites, respectively. The three parts of the chest, pelvis and skull were used as the projection center, and the radiation dose to the projection site and the radiation sensitive site were collected and recorded, and the statistical analysis was carried out.Results:When the chest was taken as the center of the projection, the radiation doses to the lens of the eye, thyroid and gonad in the body model group B of children were 94.4%, 96.9% and 96.7% lower than those in the non-injected part of group A, respectively ( t=-152.55, -445.16, -129.07, P<0.05). When the pelvis was taken as the projection center, the radiation doses to the lens, thyroid and thymus in the body model group B were 85.5%, 87.1% and 94.9% lower than those in the non-projection part of group A, respectively ( t=-50.68, -194.18, -535.94, P<0.05). When the head was taken as the projection center, the radiation doses to thyroid, thymus and gonad in the body model group B were 99.3 %, 97.4 % and 94.3 % lower than those in the non-projection position of group A, respectively ( t=-1 859.97, -542.08, -66.26, P< 0.05). Conclusions:The use of neonatal bedside photography protection and position fixing device during neonatal bedside X-ray photography can significantly reduce the radiation dose to children in non-projected areas under the premise of ensuring image quality. At the same time, it can fix and protect the children, improve the success rate of examination, being worthy of clinical promotion.
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Objective:To evaluate the effects of the changes in respiratory status on gated stereotactic radiotherapy under free breathing guided by real-time position management (RPM).Methods:This study simulated the baseline shift, change in respiratory rate, end-expiratory delay, end-inspiratory delay, and irregular breathing using an in-house developed motion phantom. Moreover, this study analyzed the correlation between the changes in the above states of three plans, three-dimensional conformal radiotherapy(3D-CRT), intensity modulated radiotherapy(IMRT), and volumetric modulated arc therapy(VMAT) and the position of the ball at the center of the motion phantom (L) and the exposed dose of the phantom in the ionization chamber (the dose).Results:The in-house developed phantom presented high setup repeatability and measurement stability. There was a positive correlation between L and the baseline shift ( r = 0.99, P < 0.01). The change in the dose was less than 4% when the baseline shift was less than the setup error, while the dose declined rapidly and was negatively correlated with the baseline shift otherwise ( r= -0.95, P < 0.01). Moreover, there was statistically significant difference in dose when the baseline shift exceeded the setup error or not ( Z = -3.06, P < 0.01). There was no significant difference in the rate of the dose affected by baseline shift in the three plans ( P > 0.05). The changes in respiratory rate had little effect on L and the dose. Both end-inspiratory delay and end-expiratory delay reduced the planned dose of the three plans, with a maximum decrease of up to -1.74%. Furthermore, the end-inspiratory delay has greater effects on the planned dose than the end-expiratory delay( Z = -2.67, P< 0.01). However, there was no significant correlation between the dose and the delay duration ( P > 0.05), and no significant difference in the rate of the planned dose of the three plans affected by respiratory waveform change ( P > 0.05). Irregular breathing had greater effects on the dose. Specifically, the dose from six repeated measurements of 3D-CR, IMRT, VMAT was (709.68±180.00), (751.40±127.16), and (750.00±185.60) cGy, respectively, all less than the prescribed dose with a poor consistency. Conclusions:The changes in the patients′ respiratory status will reduce the dose, especially when the baseline shift exceeds the setup error threshold or large respiratory waveform variation corresponding to irregular breathing occurs. Moreover, there is no correlation between the decrease in the dose and the radiotherapy technology.
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Objective:To provide a new morning check method for the output dose stability of the multileaf collimator (MLC) of the CyberKnife M6 (CK-M6) system.Methods:The CT images of a verification phantom with a size of 20 cm × 20 cm × 10 cm were transmitted into the Precision Treatment Plan ning System (ver. 1.1.1.1). The high-precision alignment between the accelerator output front and the fixed position of the phantom surface was achieved using the fiducial tracking method. A 10 cm × 10 cm radiation field was formed by the MLC and a DailyCheck plan with an output of 200 MU was designed. The repeatability, sensitivity, and accuracy of the DailyCheck plan were measured, and the CK-M6 system was continuously tested for one month using the artificial fixed method and the DailyCheck plan designed in this study. Results:The average and the standard deviation of 10 repeated measurements by the DailyCheck plan were 492.28 pC and 0.09, respectively, indicating good stability. There was a linear correlation between the measured values and the output dose, with a correlation coefficient of R2 > 0.999. Moreover, there was a position deviation of 2 mm between the phantom and the accelerator output front, and the result ant effect on the measured values was equivalent to a dose deviation caused by an output of 1.24 MU. The result from the continuous measurement of both the artificial fixed method and the DailyCheck plan fell within permissible limits, showing high consistency. Conclusions:The DailyCheck plan established through the fiducial tracking of a verification phantom can achieve the convenient, quick, and accurate daily detection of the output dose stability of the MLC of CK-M6. Therefore, this method can be widely applied in the clinical quality control of the CK-M6 system.
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Objective To explore the effect of respiratory movement on the dose distribution in the TOMO therapy target area. Methods The motion phantom was used to simulate human respiratory movement. The SNC patient analysis software was used to compare the films of the study group with those of the control group, and the effect of respiratory movement on the dose distribution in the TOMO target area was evaluated by the “pass rate” index. Results Visual observation showed that the distribution of film gray in the head-foot direction (i.e., direction of movement) was significantly different with or without respiratory movement. Film analysis showed that the maximum deviation between the width of the target wrapping curve and the treatment plan value was about 2.4 mm at no respiratory movement and about 27.2 mm at respiratory movement; the penumbra width of the target area was 31 mm (head direction) and 28.5 mm (foot direction) at no respiratory movement and 39.7 mm (head direction) and 37 mm (foot direction) at respiratory movement; the “pass rate” of target dose distribution was only 12.3%. Conclusion Respiratory movement has a great impact on the dose distribution in the TOMO target area in the direction of movement. When making clinical treatment plan, the impact of respiratory movement on the dose distribution in the TOMO target area can not be ignored.
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@#<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.
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@#The radiation risk caused by CT examination is of great concern. Organ dose is considered to be the most significant technical parameter for quantifying the patient radiation dose and assessing the corresponding risk. At present, the methods to obtain patient organ dose caused by CT examination mainly include physical phantom measurement, direct human body measurement, dose conversion coefficient, Monte Carlo simulation, and dose calculation software. Although different methods have their own characteristics and application, the individualization of organ dose is always the goal of radiation protection and dosimetry research. Patient-specific phantom developed with artificial intelligence and GPU-accelerated Monte Carlo simulation make it possible to calculate the patient-specific organ dose, and the patient-specific organ dose extrapolated by the CT detector signal provides a new solution.