Cochlear radiation dose and hearing loss in patients with vestibular schwannoma undergoing radiosurgery: systematic review

Abstract Objectives: To determine the cut-off point of the cochlear radiation dose as a risk factor for hearing loss in patients with vestibular schwannoma treated with radiosurgery. Methods: A systematic review of the literature was performed without language or publication year restrictions in the MEDLINE/PubMed, EMBASE, Web of Science, LILACS/VHL and Cochrane Library databases. Studies that met the following criteria were included: 1) population: adults of both sexes who underwent radiosurgery for vestibular schwannoma treatment; 2) exposure: cochlear radiation; 3) outcome: hearing loss; 4) type of study: cohort. Two independent reviewers conducted the entire review process. The registration number in PROSPERO was CRD42020206128. Results: From the 333 articles identified in the searches, seven were included after applying the eligibility criteria. There was no standardization as to how to measure exposure or outcome in the included studies, and most studies did not present sufficient data to enable meta-analysis. Conclusion: It was not possible to determine a cut-off point for high cochlear dose that could be considered a risk factor for hearing loss.

Computer-aided diagnosis system versus conventional reading system in low-dose (< 2 mSv) computed tomography: comparative study for patients at risk of lung cancer

ABSTRACT BACKGROUND: Computer-aided diagnosis in low-dose (≤ 3 mSv) computed tomography (CT) is a potential screening tool for lung nodules, with quality interpretation and less inter-observer variability among readers. Therefore, we aimed to determine the screening potential of CT using a radiation dose that does not exceed 2 mSv. OBJECTIVE: We aimed to compare the diagnostic parameters of low-dose (< 2 mSv) CT interpretation results using a computer-aided diagnosis system for lung cancer screening with those of a conventional reading system used by radiologists. DESIGN AND SETTING: We conducted a comparative study of chest CT images for lung cancer screening at three private institutions. METHODS: A database of low-dose (< 2 mSv) chest CT images of patients at risk of lung cancer was viewed with the conventional reading system (301 patients and 226 nodules) or computer-aided diagnosis system without any subsequent radiologist review (944 patients and 1,048 nodules). RESULTS: The numbers of detected and solid nodules per patient (both P < 0.0001) were higher using the computer-aided diagnosis system than those using the conventional reading system. The nodule size was reported as the maximum size in any plane in the computer-aided diagnosis system. Higher numbers of patients (102 [11%] versus 20 [7%], P = 0.0345) and nodules (154 [15%] versus 17 [8%], P = 0.0035) were diagnosed with cancer using the computer-aided diagnosis system. CONCLUSIONS: The computer-aided diagnosis system facilitates the diagnosis of cancerous nodules, especially solid nodules, in low-dose (< 2 mSv) CT among patients at risk for lung cancer.

Research Progress in Diagnostic Reference Levels in Interventional Radiology / 中国医学科学院学报

During interventional procedures,subjects are exposed to direct and scattered X-rays.Establishing diagnostic reference levels is an ideal way to optimize the radiation dose and reduce radiation hazard.In recent years,diagnostic reference levels in interventional radiology have been established in different countries.However,because of the too many indicators for characterizing the radiation dose,the indicators used to establish diagnostic reference levels vary in different countries.The research achievements in this field remain to be reviewed.We carried out a retrospective analysis of the definition,establishment method,application,and main factors influencing the dose difference of the diagnostic reference level,aiming to provide a basis for establishing the diagnostic reference level for interventional procedures in China.

Analysis of risk factors of radiation-induced toxicity in limited-stage small cell lung cancer treated with hypofractionated intensity-modulated radiotherapy / 中华肿瘤杂志

Objective: To compare the incidence of radiation-related toxicities between conventional and hypofractionated intensity-modulated radiation therapy (IMRT) for limited-stage small cell lung cancer (SCLC), and to explore the risk factors of hypofractionated radiotherapy-induced toxicities. Methods: Data were retrospectively collected from consecutive limited-stage SCLC patients treated with definitive concurrent chemoradiotherapy in Cancer Hospital of Chinese Academy of Medical Sciences from March 2016 to April 2022. The enrolled patients were divided into two groups according to radiation fractionated regimens. Common Terminology Criteria for Adverse Events (CTCAE, version 5.0) was used to evaluate the grade of radiation esophagus injuries and lung injuries. Logistic regression analyses were used to identify factors associated with radiation-related toxicities in the hypofractionated radiotherapy group. Results: Among 211 enrolled patients, 108 cases underwent conventional IMRT and 103 patients received hypofractionated IMRT. The cumulative incidences of acute esophagitis grade ≥2 [38.9% (42/108) vs 35.0% (36/103), P=0.895] and grade ≥ 3 [1.9% (2/108) vs 5.8% (6/103), P=0.132] were similar between conventional and hypofractionated IMRT group. Late esophagus injuries grade ≥2 occurred in one patient in either group. No differences in the cumulative incidence of acute pneumonitis grade ≥2[12.0% (13/108) vs 5.8% (6/103), P=0.172] and late lung injuries grade ≥2[5.6% (6/108) vs 10.7% (11/103), P=0.277] were observed. There was no grade ≥3 lung injuries occurred in either group. Using multiple regression analysis, mean esophageal dose ≥13 Gy (OR=3.33, 95% CI: 1.23-9.01, P=0.018) and the overlapping volume between planning target volume (PTV) and esophageal ≥8 cm(3)(OR=3.99, 95% CI: 1.24-12.79, P=0.020) were identified as the independent risk factors associated with acute esophagitis grade ≥2 in the hypofractionated radiotherapy group. Acute pneumonitis grade ≥2 was correlated with presence of chronic obstructive pulmonary disease (COPD, P=0.025). Late lung injuries grade ≥2 was correlated with tumor location(P=0.036). Conclusions: Hypofractionated IMRT are tolerated with manageable toxicities for limited-stage SCLC patients treated with IMRT. Mean esophageal dose and the overlapping volume between PTV and esophageal are independently predictive factors of acute esophagitis grade ≥2, and COPD and tumor location are valuable factors of lung injuries for limited-stage SCLC patients receiving hyofractionated radiotherapy. Prospective studies are needed to confirm these results.

Evaluación de los puntos "A" como parámetro dosimétrico en braquiterapia ginecológica guiados por imágenes tridimensionales

Objetivos: se evaluó si la técnica de prescripción de dosis puntual, punto "A", es adecuada para la estimación de dosis en el volumen de tratamiento clínico por alta tasa de dosis (CTV-HR), usando la braquiterapia ginecológica 3D. Métodos: se recopiló planes de tratamiento para 35 pacientes con cáncer cervicouterino estadio IB2-IVA (140 fracciones o planes de tratamiento) tratados entre los años 2019 al 2021, cuya dosis prescrita fue de 28 Gy en 4 fracciones. Se reconstruyeron los puntos "A", se normalizó la dosis prescrita a la isodosis del 100% para comparar con las dosis en CTV-HR (D90%). Resultados: el promedio de la dosis absorbida al CTV- HR (D90%) fue de 88,82 ± 2,53 Gy y al normalizar la isodosis del 100% al punto "A", se obtuvo dosis promedio en CTV-HR (D90%) de 99,3±5,85Gy. Esta variación de dosis promedio al CTV-HR (D90%) representó un incremento del 18%, dando como resultado que un 80% de los tratamientos correspondiente a 28 pacientes queden fuera de la variación aceptable del protocolo EMBRACE II y solo un 20% de los tratamientos correspondientes a 7 pacientes se encuentren dentro del rango de la variación aceptable del protocolo en mención. Conclusiones: la técnica de prescripción de dosis al punto "A", se traduce clínicamente en una sobredosis del tejido tumoral y sano (recto, sigmoide, vejiga e intestino).

Objective: to assess whether the punctual dose prescription technique, point A, is adequate for dose estimation in CTV-HR using 3D gynecological brachytherapy. Methods: treatment plans were collected for 35 patients with stage IB2-IVA (140 fractions or treatment plans) cervical cancer treated between 2019 and 2021, whose prescribed dose was 28Gy in 4 fractions. Points A were reconstructed, the prescribed dose was normalized to 100% isodose to compare with the doses in CTV- HR(D90%). Results: the average dose absorbed at CTV-HR(D90%) was 88.82 ±2.53 Gy and when normalizing the isodose of 100% at point A, average dose at CTV-HR(D90%) was obtained. of 99.3±5.85Gy. This average dose variation to the CTV-HR(D90%) represented an increase of 18%, resulting in 80% of the treatments corresponding to 28 patients falling outside the acceptable variation of the EMBRACE II protocol and only 20% of the treatments corresponding to 7 patients are within the range of the acceptable variation of the protocol in question. Conclusions: the dose prescription technique at point A clinically translates into an overdose of tumor and healthy tissue (rectum, sigmoid, bladder and intestine).

Activation of gelatinases in permanent human teeth after different experimental radiotherapy protocols

Abstract The objective of this study was to compare the activation of gelatinases in dentin-enamel junction (DEJ) and underlying dentin of permanent teeth after experimental radiotherapy in conventional and hypofractionated modalities. Newly extracted third molars (n = 15) were divided into three experimental radiotherapy groups: control, conventional (CR), and hypofractionated (HR) (n = 5 per group). After in vitro exposure to ionizing radiation, following standardized protocols for each modality, a gelatinous substrate was incubated on the tooth slices (n = 10 per group). Activation of gelatinases was measured by in situ zymography, expressed in arbitrary fluorescence units (mm2) from three tooth regions: cervical, cuspal, and pit. Fluorescence intensity was compared among radiotherapy protocols and tooth regions in each protocol, considering a significance level of 5%. Considering all tooth regions, the fluorescence intensity of the CR group was higher than the HR and control groups, both in DEJ and underlying dentin (p <0.001). In addition, the fluorescence intensity was higher in underlying dentin when compared to DEJ in all groups (p <0.001). Considering each tooth region, a statistically significant difference between CR and HR was only observed in the pit region of underlying dentin (p <0.001). Significant and positive correlations between fluorescence intensities in DEJ and underlying dentin were also observed (p <0.001). Experimental radiotherapy influenced the activation of gelatinases, as well as exposure to the conventional protocol can trigger a higher activation of gelatinases when compared to hypofractionated, both in DEJ and underlying dentin.

Resumo O objetivo deste estudo foi comparar a ativação de gelatinases na junção dentina-esmalte (DEJ) e na dentina subjacente de dentes permanentes após a radioterapia experimental nas modalidades convencional e hipofracionada. Os terceiros molares recém-extraídos (n = 15) foram divididos em três grupos de radioterapia experimental: controle, convencional (CR) e hipofracionada (HR) (n = 5 por grupo). Após a exposição in vitro à radiação ionizante, seguindo protocolos padronizados para cada modalidade, um substrato gelatinoso foi incubado nas fatias de dente (n = 10 por grupo). A ativação das gelatinases foi medida por zimografia in situ, expressa em unidades arbitrárias de fluorescência (mm2) de três regiões do dente: cervical, cúspide e fossa. A intensidade da fluorescência foi comparada entre os protocolos de radioterapia e as regiões do dente em cada protocolo, considerando um nível de significância de 5%. Considerando todas as regiões do dente, a intensidade de fluorescência do grupo CR foi maior do que a dos grupos HR e controle, tanto no DEJ quanto na dentina subjacente (p <0,001). Além disso, a intensidade da fluorescência foi maior na dentina subjacente quando comparada à DEJ em todos os grupos (p <0,001). Considerando cada região do dente, uma diferença estatisticamente significativa entre CR e HR foi observada apenas na região da fossa da dentina subjacente (p <0,001). Também foram observadas correlações significativas e positivas entre as intensidades de fluorescência no DEJ e na dentina subjacente (p <0,001). A radioterapia experimental influenciou a ativação das gelatinases, assim como a exposição ao protocolo convencional pode desencadear uma maior ativação das gelatinases quando comparada ao hipofracionamento, tanto no DEJ quanto na dentina subjacente.

Investigation and analysis of radiation doses to CT examinees in 11 medical institutions in Shijiazhuang, China / 中国辐射卫生

Objective To investigate radiation doses to examinees undergoing computed tomography (CT) scanning of different body parts (the head, chest, and abdomen) in medical institutions of Shijiazhuang, China, and to provide a reference for optimizing radiation protection for examinees in medical institutions. Methods March 2021 to March 2022, eleven medical institutions of radiation monitoring in Shijiazhuang were surveyed for the basic information, scanning parameters, and dosimetric data of a total of 930 adults and children who received CT examinations. The dosimetric data of the subjects were analyzed and compared with the domestic and international diagnostic reference levels and the results of other cities in China. Results In the above hospitals, the CTDIvol(P50) of CT subjects in children's group were 17.42-50.45 mGy, 2.13-14.01 mGy and 3.58-28.20 mGy, respectively. DLP(P50) ranges from 228.87 to 966.97 mGy·cm, 33.20 to 296.03 mGy·cm, and 74.90 to 926.53 mGy·cm, respectively. In the adult group, the CTDIvol(P50) in the head, chest and abdomen of CT subjects were 37.28-54.05 mGy, 6.43-14.99 mGy and 8.28-18.75 mGy, respectively. DLP(P50) ranges from 372.81 to 630.56 mGy·cm, from 219.77 to 467.93 mGy·cm, and from 313.86 to 689.87 mGy·cm, respectively. The distribution of radiation doses in different-grade hospitals varied greatly. The abdomen dose of the children's hospital was higher than other hospitals. Especially the primary hospitals were significantly higher than the recommended diagnostic reference level (DRL). Conclusion In some secondary and primary hospitals, the setting of CT scanning parameters was simplified, not specific to the subjects’ age and body types. They should strictly comply with the principal of optimizing radiation protection to strengthen radiation dose optimization and supervision, reducing the radiation dose of examinees in future examinations .

Analysis of radiation dose and influencing factors during interventional procedures for 94 patients with pediatric congenital heart disease / 中国辐射卫生

Objective To evaluate the radiation dose of interventional procedure for children with congenital heart disease, and to analyze the differences in radiation dose and influencing factors. Methods A total of 94 children who underwent interventional procedure for congenital heart disease at a grade A tertiary hospital in Jinan, Shandong Province, China from June 2021 to September 2022 were included in this study. The patients were divided into three groups according to the type of procedure: ventricular septal defect occlusion group (VSD, 48 cases), patent ductus arteriosus occlusion group (PDA, 29 cases), and atrial septal defect occlusion group (ASD, 17 cases). The basic information of patients and postoperative dose reports were recorded. A statistical analysis was performed using SPSS software. Results The median cumulative air kerma (CAK) of VSD, PDA, and ASD was 100.5, 43.7, and 12.1 mGy, respectively. The median air kerma area product (KAP) of VSD, PDA, and ASD was 3.309, 1.313, and 0.540 Gy·cm2, respectively. The median KAP·kg−1 of VSD, PDA, and ASD was 0.179, 0.088, and 0.031 Gy·cm2·kg−1, respectively. There were significant differences in fluoroscopy time, number of cine images, CAK, KAP, and KAP·kg−1 among the three types of interventional procedures (P<0.05). Compared with PDA and ASD, VSD showed significantly higher fluoroscopy time, number of cine images, CAK, KAP, and KAP·kg−1 (P<0.05). Multiple linear regression analysis found that age (B=52.445, P<0.05), weight (B=13.077, P<0.05), fluoroscopy time (B=0.425, P<0.05), tube current (B=0.872, P<0.05), and number of cine images (B=0.660, P<0.05) were positively correlated with KAP, while there was no significant association between height and KAP (P>0.05). Conclusion There are differences in radiation dose among the three types of procedures. Reducing fluoroscopy time, tube current, and number of cine images while meeting the procedure requirements is of great significance for reducing the radiation dose received by children.

Research advances in radiation exposure and the risk of thyroid cancer / 中国辐射卫生

The thyroid gland is highly sensitive to the carcinogenic effects of radiation exposure during childhood and adolescence. Epidemiological data have shown that exposure to ionizing radiation during childhood and adolescence results in an increased risk of thyroid cancer, and most cases of radiation-induced thyroid cancer are diagnosed with papillary thyroid carcinoma. The risk of radiation-induced thyroid cancer is affected by radiation dose, age, latency period, iodine status, chemotherapy, and body mass index. Therefore, proper use of physical shielding and prompt administration of stable iodine can be adopted to minimize the risk of radiation-induced thyroid cancer.

Research progress in the average glandular dose during mammography / 中华放射医学与防护杂志

Mammography has played an essential role in the screening and treatment of breast cancer. However, the application of X-rays will also increase the risks of breast cancer while improving its detection rate. Moreover, the risks will increase with an increase in the radiation dose. Since the glandular tissue in breasts is sensitive to radiation, the evaluation of the average glandular dose (AGD) in mammography has attracted considerable international attention. Compared to relatively mature dosimetric studies on traditional two-dimension mammography and digital breast tomosynthesis, the method for the dose evaluation of the new cone beam CT for breasts are still subjected to research. This paper reviews and explores the current status of studies on the assessment method and relevant influencing factors of AGD under different types of mammography equipment.

Feasibility of improving the quality of children′s abdominal images using split-filter dual-energy CT / 中华放射医学与防护杂志

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.

Study on radiation dose and image quality differences between cone-beam CT and multi-slice spiral CT for atlantoaxial spine imaging / 中华放射医学与防护杂志

Objective:To compare the differences in radiation dose and image quality between cone-beam CT (CBCT) and multi-slice spiral CT (MSCT) applied to atlantoaxial spine imaging.Methods:Head and neck phantom was scanned at 30 exposure parameter combinations using Pramerica CBCT scanner and 15 parameter combinations using Toshiba 320-row MSCT. The effective dose ( E) of CBCT was calculated based on the Monte Carlo dose estimation software PCXMC, the E value of MSCT was obtained by multiplying the dose length product (DLP) by the related factor. t-test for two independent samples or Wilcoxon rank sum test were used for comparison of radiation dose and subjective and objective image quality between two modalities. The subjective evaluation was a 5-point subjective scale using double-blind method for edge sharpness, contrast, soft tissue level, and artifacts of the images. The signal and noise in the region of interest (ROI) were measured and the contrast signal-to-noise ratio (CNR) was calculated. Results:For radiation dose, the volumetric dose index and E values of 2.9 mGy and 27.61 μSv for CBCT were lower than those of 8.8 mGy and 433.16 μSv for MSCT, and the differences were statistically significant( z=-3.05, -5.25, P<0.05). For objective evaluation of image quality, the noise and CNR were 27.74 HU and 3.69 in CBCT group, 7.84 HU and 27.1 in MSCT group. The difference between them were statistically significant( z=-5.39, -5.42, P<0.05). The overall image quality, contrast and artifact scores of the CBCT group were 3.5, 3.0 and 5 were higher than those of the MSCT group at 2.0, 2.0, and 4.0, respectively ( z=-2.32, -2.46, -3.31, P<0.05). Conclusions:Both atlantoaxial CBCT and MSCT scans provide image quality that meets diagnostic requirements. Compared to MSCT, CBCT atlantoaxial scans can effectively reduce radiation dose according to the principle of optimization of radiation protection.

Clinical application of bedside X-ray photography assistor in neonates / 中华放射医学与防护杂志

Objective:To assess the clinical application of bedside X-ray photography assistor (Patent No. 202 023 219 898.1) in neonatal bedside photography.Methods:From April 2021 to February 2022, a total of 180 pediatric patients were selected who underwent bedside chest X-ray photography in neonatal intensive care unit (NICU) of Union Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology. These patients were divided into contrpol group, consisting of 48 males and 42 females aged at (3.3 ± 2.0) d (0-10 d), and experimental group, including 50 males and 40 females aged (3.1±2.2) d (0-12 d). For chest photography, routine workflow was followed in the control group while in experimental group bedside photography protection and body position fixing device was used. The examination time, reshoot rate and image quality were compared between the two groups.Results:The diagnostic physician score and patient comfort score in the experimental group were higher than those in the control group, with statistically significant differences ( t = 3.98, 3.82, P < 0.001). The success rate in the experimental group was higher than that in the control group, with statistically significant difference ( χ2= 7.84, P < 0.05). The average time of examination in the experimental group was not significantly different from in the control group ( P>0.05 ). Conclusions:The application of bedside X-ray photography assistor in neonatal bedside photography can significantly improve the success rate and image quality and reduce the radiation dose to pediatric patients without significantly increased examination time, which is worthy of clinical application and promotion.

The necessity and countermeasures of strengthening radiation dose management in diagnostic radiology / 中华放射医学与防护杂志

In recent years, the diagnostic radiology, especially CT scanning, has a rapidly increased frequency in our country, becoming the largest artificial radiation source to the average individual doses to the population. In clinical diagnosis and treatment activities, the examined patients and individuals may undergo multiple procedures and multiple frequencies of medical imaging in a short period of time and receive high cumulative radiation doses even exceeding 50 or 100 mSv in a single day, posing a potential risk to their health. Therefore, it is necessary to carry out statistical analysis and management of diagnostic radiation dose information to minimize the probability of excessive dose and associated radiation risk. In this paper, the international cognition of radiation risks in diagnostic radiology, diagnostic equipment and medical imaging frequency, radiation dose and its management status are described. Four countermeasures for radiation dose management are put forward to provide reference for further improving radiation protection in clinical practice.

The influence of different CT scanning protocols on AI detection efficiency and radiation dose of solid nodules in chest phantom / 中华放射医学与防护杂志

Objective:To investigate the radiation dose and detection efficiency of artificial intelligence (AI) system for solid nodules in chest phantom with different scanning protocols.Methods:A total of 60 simulated nodules with different CT values and diameters were uniformly placed in each lung lobe and lung segment of the anthropomorphic chest phantom. GE Revolution evo CT was used to scan the chest phantom. 64 groups of images with different scanning parameters were collected at the tube voltage of 80, 100, 120, 140 kV, different noise indexes (NI 10-40 with interval 2), and other fixed parameters. The detection result of simulated nodules were recorded on AI software, and the detection rate and false detection rate were calculated, respectively, for different shapes of nodules. The mean volume CT dose index (CTDI vol) and dose length product (DLP) of each scan were recorded. Results:There were no statistically significant differences in the detection rate and false detection rate of spherical nodules and irregular nodules at different tube voltages( P > 0.05), but there were and statistically significant with different noise indices ( F=10.57, 17.77, 9.33, P < 0.001). Different tube voltages had no statistical significance for CTDI vol and DLP ( P > 0.05), while different noise indices had statistical significance for CTDI vol and DLP ( F=59.87, 60.92, P < 0.001). The detection rates of nodules were moderately or weakly correlated with noise indices, CTDI vol and DLP ( r=0.43, 0.56, -0.58, -0.78, P<0.05), but no correlation with tube voltage ( P>0.05). Conclusions:Scanning protocol has an impact on AI detection efficiency of pulmonary nodules. Reasonable scanning parameters should be selected according to different image quality requirements in clinical practice.

Analysis of CT doses to paediatric patients in four children′s hospitals in Shanghai / 中华放射医学与防护杂志

Objective:To study the distribution of CT doses to paediatric patients in Shanghai by investigating the CT dose parameters availiable in Shanghai′s children′s hospticals, and to provide the basis for establishing the diagnostic reference level for the paediatic patients subjected to CT scanning in Shanghai.Methods:In 2021, a general survey was carried out of the CT doses to the head, chest and abdomen of the scanned paediatric patients in four children′s hospitals in the municipality. The scanned paediatic patients were divided into four age groups of 0-, 1-, 5- and 10-15 years old, each with 30 subjects. The basic information were collected on the subjects, CT scanning parameters, volume CT dose index (CTDI vol) and dose length product (DLP). SPSS 16.0 was used to carry out statistical analysis of the differences in CTDI vol and DLP between different age groups at the same site and between different hospitals for the same age group at the same site. Results:The 75 th percentile values of CTDI vol and DLP for 0-, 1-, 5- and 10-15 age groups were 25, 25, 28, 43 mGy and 402, 477, 504, 752 mGy·cm, respectively, for head scanning; 2.7, 2.2, 2.8, 5.4 mGy and 40, 48, 75 and 176 mGy·cm for chest; and 4.9, 4.4, 8.2, 12 mGy and 106, 131, 273, 471 mGy·cm for abdomen. There were significant differences in CTDI vol and DLP between different age groups at the same site and between different hospitals for the same age group at the same site (head, chest and abdomen CTDI vol:χ2=221.68, 167.27, 127.07, DLP: χ2=220.63, 261.46, 216.61; for four age groups, CTDI vol: head χ2=30.46, 38.39, 25.21, 73.04, chest χ2=30.46, 35.69, 58.92, and 48.03, abdomen χ2=66.58, 41.62, 48.93, and 67.38; DLP: head χ2=28.82, 72.49, 47.72, 52.34, chest χ2=28.82, 35.95, 50.66, 41.64, abdomen χ2=45.53, 26.02 39.34, 44.24, P <0.05 ). Conclusions:The 75 th percentile values of CTDI vol and DLP for head, chest and abdomen in 4 children′s hospitals in Shanghai are lower or close to the values given in the relevant national standards and the diagnostic reference levels in some European countries, with higher DLP values on some scanning sites. The CT scanning procedures for paediatric patients needs to be further optimized.

A study of the effect of scanning center on the performance of organ dose modulation in head CT / 中华放射医学与防护杂志

Objective:To investigate the effect of different scanning centers on eye lens dose, image quality, and the dose reduction rate when using the organ dose modulation (ODM) technique in head CT.Methods:The porus acusticus externus of the head phantom was considered the scanning isocenter. The ODM was initiated and the spiral scans were performed at the scanning centers with the height of porus acusticus externus and its upper and lower 2, 4, and 6 cm, respectively. The scanning range was from the top of the head to the base of the head. Three thermoluminescent dosimeters (TLD) were placed on the surface of two eyes at each scan and the average measurement value was regarded as the radiation dose to the eye lens. The volume CT dose index (CTDI vol) and dose length product (DLP) were recorded. The scans were repeated with no ODM and the dose reduction rates at each scanning center were calculated. The regions of interest (ROI) in each group of images with ODM were drawn and the noise (SD), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were evaluated. Results:Compared with the isocenter, the maximum change rates of CTDI vol and DLP in each scanning center were 2.46% and 2.43%, respectively. The eye lens dose increased as the scanning centre moving upwars (i.e. the bed dropping) by 39.02% at the position of 6 cm above the isocenter and decreased by 35.91% at the position of 6 cm below the isocenter. With the seven groups of scanning centers, the reduction rates of CTDI vol and DLP caused by ODM were 7.95%-8.61%, 7.91%-8.61% respectively, and the difference in the reduction rate of each dose value was not statistically significant( P>0.05). The reduction rate for eye lens dose ranged from 18.09% to 26.14%, with the highest reduction rate at the position of 4 cm above the isocentre and the second rate at the isocentre (24.73%). The difference in the rate of reduction at each scanning center was statistically significant( t=0.13, P<0.05). As the scanning center moved up, the SD of the eye region decreased and the SNR increased, and the highest CNR at the isocentre was 239.79. The SD and SNR of the brain parenchyma region were 6.85-7.96 and 3.08-4.19 respectively, and the highest CNR at the isocentre was 244.79. Conclusions:When ODM technique is used in head CT, the scan centre has a significant effect on the eye lens dose and image quality. Meanwhile, the reduction rate of the eye lens dose caused by ODM is also affected. Therefore, porus acusticus externus is recommended as the scanning center in head CT.

A modal study of the effect of adjusting density exposure steps on image quality and radiation dose in digital mammography / 中华放射学杂志

Objective:To investigate the effect of adjusting density exposure steps on image quality and radiation dose in digital mammography.Methods:Using the automatic exposure control (AEC) mode of the digital mammography machine, five different gland thicknesses of 4.3, 5.3, 6.3, 7.3, and 8.3 cm were simulated by attaching 0, 1, 2, 3, and 4 PMMA plexiglass plates under the RMI-156 modal body, and the density exposure steps were adjusted to -3, -2, -1, 0, 1, 2, 3, and 4 for each thickness. The target/filter combination, tube voltage, tube current, incident body surface dose (ESD), incident surface air kerma (ESAK), half-value layer (HVL) and the average glandular dose displayed by the device (displayed AGD) were recorded at each step and thickness, and the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), figure of merit (FOM) and the calculated average glandular dose (calculated AGD) were calculated. Then, the display effects of simulated fibers, simulated calcifications and simulated masses within the modal body were scored subjectively, and the changes in image quality and radiation dose at different steps were analyzed, and the relationships between ESD and ESAK, displayed AGD and calculated AGD, and displayed AGD/ESD and calculated AGD/ESAK were analyzed. A linear fit was used for the steps with SNR, CNR, and FOM, and an exponential function curve fit was used for the steps with mAs, ESAK, and calculated AGD. The differences between ESD and ESAK, displayed AGD and calculated AGD, and displayed AGD/ESD and calculated AGD/ESAK were analyzed by paired-samples t test. Results:The CNR and SNR of mammographic images rose and fell by about 8% with each increase or decrease of one step. The scores of image simulated fibers, simulated calcifications, and simulated masses showed an overall upward trend with increasing steps, but there were still cases where the scores decreased with increasing grades. FOM varied from 97% to 104% at each grade with little variability. ESD, ESAK, displayed AGD, and calculated AGD, which could measure radiation dose, showed an exponential trend of increasing function with increasing steps, with a variation of about 63% to 165%. There were statistically significant differences ( t=-9.61, P=0.001) between ESD (15.14±10.08) and ESAK (16.66±11.07). However, there were no statistically significant differences ( t=1.20, P=0.240) between displayed AGD and calculated AGD, which were 3.66±2.18 and 3.61±1.99, respectively. Conclusions:The adjustment of density exposure steps can make the image quality change linearly and the radiation dose change exponentially with increasing speed, and the mode and magnitude of the adjustment are appropriately stable with high application value.

Toxicities of hypofractionated radiotherapy after breast-conserving surgery: a literature review / 中华放射肿瘤学杂志

Hypofractionated radiotherapy, which provides equivalent efficacy and dose not increase toxicity compared with conventional fractionated radiotherapy following breast-conserving surgery, has become a preferred choice for whole breast irradiation. Given the low local recurrence risk and long survival time for early breast cancer survivors, radiation-associated toxicities are the focus of clinical practice. However, in the era of hypofractionated radiotherapy, the risk factors for radiation-associated toxicity remain undefined and further research is warranted. In this review, we aim to provide an overview of the toxicities of hypofractionated radiotherapy following breast-conserving surgery.

Measurement and evaluation of thyroid 131I activity in iodine treatment workers / 中华放射医学与防护杂志

Objective:To understand the 131I activity in thyroid of therapy workers in nuclear medicine department, and estimate the annual committed effective dose, in order to analyze the internal exposure of them. Methods:Six hospitals were investigated and 131I activity of thyroid was measured. The detection rate and activity value of thyroid 131I activity of therapy workers in nuclear medicine department were obtained from the six hospitals, and then the intake and annual committed effective dose were calculated. Results:A total of 63 iodine therapy workers from six hospitals were measured and 131I was detected for 52 workers among them, with the detection rate of 83% and 131I activities mostly lower than 200 Bq. The estimated annual committed effective dose ranged from 0.23 to 7.78 mSv. The annual committed effective dose to 84.6% of the workers was less than 2 mSv. Conclusions:Iodine therapy workers in nuclear medicine department should receive routine internal exposure personal monitoring, and the radiation protection system in all hospitals needs to be further improved.