Reference value of surface radiation dose of digital radiography among adults in Beilun District / 预防医学

Objective@#To investigate the reference level of surface radiation dose of digital radiography (DR) among adult examinees in Beilun District, Ningbo City, so as to provide insights into the optimization of the parameters of DR systems and rational management of the radiation dose.@*Methods@#Based on the cloud imaging system covering 14 DR systems in 11 public hospitals in Beilun District, the diagnosis of adults receiving DR and DR systems check were collected from May 2020 to April 2021. The air kerma-area product ( PKA ) was selected as a measure, and the local diagnostic reference level ( LDRL ), the regional median dose ( RMD ), the regional lowest dose predicted level ( LDPL ) and the typical dose in the DR imaging room were defined using the quartile method according to the examination site, projection direction and radiography positions. The PKA value was transformed into incident air kerma ( Ka, e ), and compared with the recommended value in the Requirements for Radiological Protection in Diagnostic Radiology ( GBZ 130-2020 ).@*Results@#DR was performed among 133 065 person-times from May 2020 through April 2021 in Beilun District. The greatest RMD was found on abdomen AP DR in the supine position ( 120 μGy·m2 ), and the lowest RMD was seen on chest PA DR in the standing position ( 17 μGy·m2 ). The maximums of typical dose in the DR imaging room on chest PA ( 33 vs. 30 μGy·m2 ), abdomen AP ( 161 vs. 153 μGy·m2 ) and pelvis AP DR ( 164 vs. 162 μGy·m2 ) were greater than LDRL in the supine position, and the minimums of typical dose on chest PA ( 10 vs. 11 μGy·m2 ) and chest LAT DR ( 33 vs. 34 μGy·m2 ) were lower than LDPL in the standing position. Following transformation into Ka, e, the LDRL ranged from 0.27 to 3.80 mGy, and the maximums of typical dose ranged from 0.25 to 3.55 mGy, which was much lower than the recommended dose proposed in the national criteria.@*Conclusions@#The reference level of surface radiation dose of DR is established among adults in Beilun District, which is lower than the recommended dose in the national criteria of China. Such a reference level may be employed by medical institutions for optimization of the parameters of DR systems. Key words： digital radiography radiation dose diagnostic reference level air kerma-area product

Experimental study on measurement of short pulsed and high-dose-rate X-ray by therapeutic grade ionization chamber / 中华放射医学与防护杂志

Objective:To investigate the application of therapeutic grade ionization chamber to rapid measurement of short pulsed and high-dose-rate X-ray.Methods:The half-value layer of pulsed X-ray caused by an electron accelerator was measured by interpolation method and its equivalent energy was estimated. The cumulative doses from a certain amount of pulsed radiation at different distances in the same direction around the equipment were compared using the therapeutic grade ionization chamber and thermoluminescence measurement method . The relationship between the measurement result by using ionization chamber dosimeter and the distances away from source was analyzed. The cumulative doses from a certain amount of pulsed radiation at the same location at different frequencies were compared.Results:In working condition, 100 pulses of radiation were received accumulatively at 1 to 12 meters away from the outer wall of the equipment. The range of air Kerma was 0.08-9.65 mGy measured by using thermoluminescence dometers and 0.08 - 9.85 mGy using the ionization chamber dosimeters, respectively. The difference between both is within 10%. At different frequencies (1-10 Hz), there was no significant difference in X-ray air Kerma from 100 pulses measured by ionization chamber dosimeter at 2 m away from the front of the equipment ( P>0.05). Conclusions:The therapeutic grade ionization chamber dosimeter can be used for the rapid measurement of short pulsed X-ray radiation dose in the range of dose rates and pulse frequencies involved in the experimental accelerator device.

Establishment and application of standard radiation field for wrist dosimeter calibration / 中华放射医学与防护杂志

Objective To establish the standard X/γ radiation fields with respect to the wrist dosimeter calibration curve as required by the international electrotechnial commission (IEC) technical specifications and the relevant national standard.Methods Air-kerma rate was determined in the X-ray beams,137Cs and 60Co radiation fields by a standard dosimeter.The wrist thermduminescent dosimetry (TLD) dosimeter was calibrated with personal dose equivalent values Hp (0.07) on the organization for standardization(ISO) wrist-phantom based on the radiation fields.Results The standard X/γ radiation field for the wrist dosimeter irradiation was established.Conclusions Established X/γ standard radiation field can be used for suc h technical services as wrist dosimeter calibration curve and energy response characteristics experiment.

Evaluation of Mean Glandular Dose from Digital Mammography Exams at Qatar and Compared with International Guidelines Levels.

The primary objective of this study was to measure the mean glandular dose (MGD) from craniocaudal (CC) and mediolateral oblique (MLO) views from mammography patients in Hamad Medical Corporation (HMC) in the state of Qatar and to compare them with the international guidelines levels as well as to establish Dose Reference Level (DRL) for the country by applying the quality control (QC) protocol for the Digital mammography units and to reduce the patient dose and improve the image quality. All patients data was taken from two Selenia digital mammography units for 18 months period. Quality control was implemented for the two mammography machines and corrective actions have been done for the image quality evaluation with rejected film analysis. The total number of collected patient data was 4085 mammography exams which considered as around 93% of the overall mammography procedures done in Qatar during that period. Based on the IAEA selection criteria of breast thickness between 2-7 cm and kV machine value from 26 to 33 kV, only 3280 mammography procedures satisfies the above criteria and are analysed accordingly, National Centre for Cancer Care & Research (NCCCR) 949 and Hamad General Hospital (HGH) 2331 exposures. The present study revealed that there were significant differences between the MGD values for the CC and MLO views (p <0.006). Referring to the limiting dose values in the European guidelines, the results from the two mammography units showed that 94.5% and 99.7% of the mean glandular doses are acceptable from NCCCR and HGH respectively. Due to compression devise error in the NCCCR mammography machine, the MGD for some patients became more than the acceptable values especially at small breast thickness values (0-3 cm) which it seems 0% in the acceptable range.

Establishment and validation of finger-ring dosimeter standard calibration quality / 中国医学装备

Objective:According to the technical standard of ISO and current regulations in China, the X/γ standard calibration quality for the finger-ring dosimeter irradiation was established in Beijing SSDL, it can ensure the traceability of surveillance data within countrywide.Methods: Air kerma-rate was determined in the X-ray beams,137Cs and60Co by a standard dosimeter, combined transfer coefficientHp(0.07) provided by standards, and confirmed condition of X/γ standard calibration quality for the finger-ring dosimeter irradiation. Using finger-ring TLD dosimeter verified the radiation beam qualities Hp on the ISO finger-phantom.Results: The linearity and energy response of the TLD dosimeter met ISO and national standard in Beijing SSDL.Conclusion: The X/γ standard radiation field can be used for the calibration of finger-ring dosimeter standard curves and experiment of research, and can further promote the comparability and reliability of the surveillance data.

Magnitudes y unidades para dosimetría a pacientes en radiodiagnóstico e intervencionismo / Quantities and units for patient dosimetry in diagnostic and interventional radiology

Because diagnostic and interventional radiology procedures represent one of the main sources of irradiation by ionizing radiation in the population, it has become a priority to become familiar with the quantities and units that account for patient dosimetry. There are countless documents and international recommendations on names, concepts, definitions and areas of application for various quantities and units used in patient dosimetry, in interventional and diagnostic radiology procedures. However, national legislation is not updated in this regard and does not provide, in any of its documents, an updated glossary that enables finding this type of information quickly and precisely. Therefore, this review paper presents in a didactic way and in plain language, the main quantities and units to be used in the dosimetry of patients undergoing diagnostic and interventional radiology procedures.

Debido a que los procedimientos de radiodiagnóstico e intervencionismo representan una de las principales fuentes de irradiación a la población por radiaciones ionizantes, se vuelve prioritario conocer las magnitudes y unidades que dan cuenta de la dosimetría a los pacientes. Existen innumerables documentos y recomendaciones internacionales sobre nombres, conceptos, definiciones y campos de aplicación para diversas magnitudes y unidades utilizadas en la dosimetría de pacientes en procedimientos de radiodiagnóstico e intervencionismo. Sin embargo, la legislación nacional no se encuentra actualizada en este sentido y no contempla en ninguno de sus documentos, un glosario actualizado que permita encontrar en forma rápida y precisa este tipo de información. Por lo anterior, este trabajo de revisión presenta de manera didáctica y en un lenguaje sencillo, las principales magnitudes y unidades que se deben utilizar en la dosimetría de pacientes sometidos a procedimientos de radiodiagnóstico e intervencionismo.

Quantificação das grandezas dosimétricas em exames de tomografia computadorizada pediátricos do abdome / Determination of dosimetric quantities in pediatric abdominal computed tomography scans

Objetivo: Visando contribuir para o conhecimento das doses em tomografia computadorizada (TC), este trabalho teve o objetivo de quantificar grandezas dosimétricas associadas a exames do abdome em pacientes pediátricos, comparando-as com os níveis de referência em radiodiagnóstico (NRD). Materiais e métodos: O estudo foi realizado em dois hospitais, em um tomógrafo Toshiba Asteion single-slice e um GE BrightSpeed multi-slice. Medidas foram feitas com uma câmara de ionização tipo lápis e um objeto simulador de tronco de polimetilmetacrilato de 16 cm de diâmetro. Resultados: Os valores do índice ponderado de kerma no ar (CW) não apresentaram diferenças significativas, porém, para as grandezas índice de kerma no ar volumétrico (CVOL), produto kerma-comprimento (PKL,CT) e dose efetiva, as diferenças foram relevantes. Conclusão: Apenas o CW apresentou valores menores que os NRD, sugerindo que a otimização não seria necessária. Porém, os valores de PKL,CT e dose efetiva mostraram que há espaço para reduzir as doses de radiação pediátricas. Este trabalho ressalta a importância de avaliar todas as grandezas dosimétricas associadas aos exames por TC. .

Objective: Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL). Materials and methods: The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom. Results: No significant difference was observed in the values for weighted air kerma index (CW), but the differences were relevant in values for volumetric air kerma index (CVOL), air kerma-length product (PKL,CT) and effective dose. Conclusion: Only the CW values were lower than the DRL, suggesting that dose optimization might not be necessary. However, PKL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans. .

Practical Output Dosimetry with Undefined NdwCo-60 of Cylindrical Ionization Chamber for High Energy Photon Beams of Linear Accelerator / 의학물리

For the determination of absorbed dose to water from a linear accelerator photon beams, it needs a exposure calibration factor Nx or air kerma calibration factor Nk of air ionization chamber. We used the exposure calibration factor Nx to find the absorbed dose calibration factors of water in a reference source through the TG-21 and TRS-277 protocol. TG-21 used for determine the absorbed dose in accuracy, but it required complex calculations including the chamber dependent factors. The authors obtained the absorbed dose calibration factor NdwCo-60 for reduce the complex calculations with unknown Ndw only with Nx or Nk calibration factor in a TM31010 (S/N 1055, 1057) ionization chambers. The results showed the uncertainty of calculated Ndw of IC-15 which was known the Nx and Ndw is within -0.6% in TG-21, but 1.0% in TRS-277. and TM31010 was compared the Ndw of SSDL to that of PSDL as shown the 0.4%, -2.8% uncertainty, respectively. The authors experimented with good agreement the calculated Ndw is reliable for cross check the discrepancy of the calibration factor with unknown that of TM31010 and IC-15 chamber.

Radiation doses in interventional radiology procedures / 中华放射医学与防护杂志

Objective To investigate the radiation doses for the patients undergoing interventional radiology and to analyze the dose - influencing factors.MethodsThe clinical data of 461 patients undergoing interventional radiology,including cerebral angiography ( CEA ),cerebral aneurysm embolism ( CAE ),superselective hepatic arterial chemoembolization ( SHAG ),coronary angiography ( COA ),percutaneous intracoronary stent implantation ( PIS1 ),cardiac radiofrequency catheter ablation ( RFCA ),and permanent cardiac pacemaker implantation(PCPI) were collected to observe the cumulative air kerma (CAK),dose area product (DAP),and fluoroscopy time,and effective dose was estimated using the conversion factors.Results The effective doses for CEA,CAE,SHAG,COA,PISI,RFCA,and PCPI were (0.33 ±0.20),(0.49 ±0.35),(6.92 ±4.19),(0.76 ±0.91),(2.35 ± 1.47),(0.50 ±0.74),and (0.67 ±0.70) Sv,respectively.In 126 of the 416 patients (26%),the effective doses were greater than 1 Sv,and the effective doses of 10 person-times were greater than 10 Sv,all of which were observed in the patients undergoing SHAG.The CAK values for CEA,CAE,SHAG,COA,PISI,RFCA,and PCPIwere (0.55 ±0.43),(1.34 ± 1.11),(0.95 ±0.57),(0.32 ±0.31),(0.91 ±0.33),(0.16 ±0.22),and (0.15 ±0.14) Gy,respectively.The CAK values were greater than 1 Gy in 59 of the 461 patients ( 12.8% ),greater than 2 Gy in 11 cases (2.4%) ,and greater than 3 Gy in 1 CEA cases and 1 CEA case,respectively.Conclusions There is a wide variation range in radiation dose for different procedures.As most interventional radiology procedure can result in clinically significant radiation dose to the patient,stricter dose control should be carried out.

Estudo comparativo da qualidade da imagem e do kerma, de entrada e de saída, em simulador de tórax utilizando sistemas analógico e digitalizado CR de aquisição de imagens / Comparative study of image quality and entrance and exit air kerma measurements on chest phantom utilizing analog and CR digital imaging systems

OBJETIVO: O processo de migração de sistemas analógicos para digitalizados, para aplicações diagnósticas, requer cuidados específicos, a fim de manter a qualidade das imagens e minimizar a dose no paciente. Este trabalho tem como objetivo analisar e comparar a qualidade da imagem e o kerma num simulador não antropomórfico de tórax gerados por sistemas analógicos e digitalizados CR. MATERIAIS E MÉTODOS: Foram analisados a qualidade da imagem e o kerma, de entrada e saída, no simulador para dois equipamentos de raios X diferentes (Siemens e Emic), com diferentes sistemas de retificação de onda (12 pulsos e alta frequência). Ambos os sistemas (analógico e digitalizado) estavam sendo utilizados no mesmo local. Foram geradas imagens em filme e em image plates. RESULTADOS: Foi observado aumento na tensão e/ou na carga transportada pelo tubo de raios X quando houve a migração para o sistema CR, para manutenção das características diagnósticas da imagem. Isto resultou em aumento de kerma coletado. CONCLUSÃO: As maiores diferenças determinadas (aumento de dose e redução da qualidade da imagem) foram observadas no equipamento com retificação de onda de 12 pulsos e transdutor de imagem CR (image plates).

OBJECTIVE: The process of migration from analog to digital imaging system requires specific attention to preserve images quality and minimizing the dose to the patients. The present study was aimed at analyzing and comparing images quality and entrance and exist air kerma measurements in a non-anthropomorphic chest phantom with analog and CR digital imaging systems. MATERIALS AND METHODS: Two different X-ray units (Siemens and Emic) with different wave rectification systems (12-pulse and high-frequency) were utilized in a single institution along the process of migration from analog to CR digital imaging system. Images were acquired on films and image plates. RESULTS: An increase on the X-ray tube peak voltage and/or load was observed in the migration from analog to CR digital system to preserve the diagnostic quality of the image. As a result, an increase in the air kerma rate was observed. CONCLUSION: The greatest differences (increase in dose and decrease in image quality) were observed with the 12-pulse wave rectification system with the CR image transducer (imaging plates).

Quality Correction for Ir-192 Gamma Rays in Air Kerma Strength Dosimetry Using Cylindrical Ionization Chambers / 의학물리

The quality correction in the air kerma dosimetry for Ir-192 using farmer type ionization chambers calibrated by Co-60 quality is required. In this study we determined quality factor (kappa u) of two ionization chambers of PTW-N30001 and N23333 for Ir-192 source using dosimetric method. The quality factors for energy spectrum of microSelectron were determined as kappa u=1.016 and 1.017 for PTW-N30001 and N23333 ionization chambers respectively. We applied quality factors in air kerma dosimetry for microSelectron source and compared with reference values. As a results we found that the differences between reference air kerma rate and measured it with and without quality correction were about -0.5% and -2.0% respectively.

Development of a Dose Calibration Program for Various Dosimetry Protocols in High Energy Photon Beams / 대한방사선종양학회지

PURPOSE: To develop a dose calibration program for the IAEA TRS-277 and AAPM TG-21, based on the air kerma calibration factor (or the cavity-gas calibration factor), as well as for the IAEA TRS-398 and the AAPM TG-51, based on the absorbed dose to water calibration factor, so as to avoid the unwanted error associated with these calculation procedures. MATERIALS AND METHODS: Currently, the most widely used dosimetry protocols of high energy photon beams are the air kerma calibration factor based on the IAEA TRS-277 and the AAPM TG-21. However, this has somewhat complex formalism and limitations for the improvement of the accuracy due to uncertainties of the physical quantities. Recently, the IAEA and the AAPM published the absorbed dose to water calibration factor based, on the IAEA TRS-398 and the AAPM TG-51. The formalism and physical parameters were strictly applied to these four dose calibration programs. The tables and graphs of physical data and the information for ion chambers were numericalized for their incorporation into a database. These programs were developed user to be friendly, with the Visual C++ language for their ease of use in a Windows environment according to the recommendation of each protocols. RESULTS: The dose calibration programs for the high energy photon beams, developed for the four protocols, allow the input of informations about a dosimetry system, the characteristics of the beam quality, the measurement conditions and dosimetry results, to enable the minimization of any inter-user variations and errors, during the calculation procedure. Also, it was possible to compare the absorbed dose to water data of the four different protocols at a single reference points. CONCLUSION: Since this program expressed information in numerical and data-based forms for the physical parameter tables, graphs and of the ion chambers, the error associated with the procedures and different user could be solved. It was possible to analyze and compare the major difference for each dosimetry protocol, since the program was designed to be user friendly and to accurately calculate the correction factors and absorbed dose. It is expected that accurate dose calculations in high energy photon beams can be made by the users for selecting and performing the appropriate dosimetry protocol.