Dosis de radiación por radiografías y factores asociados en neonatos de la Unidad de Recién Nacidos del Hospital Universitario San Ignacio, Bogotá, Colombia / X-ray radiation dose and associated factors in neonates from the newborn unit of Hospital Universitario San Ignacio, Bogotá, Colombia

Introducción. Las radiografías continúan usándose ampliamente, subestimando los riesgos. Esto sucede, especialmente, en las unidades de cuidado neonatal, lo que implica que los neonatos reciben una dosis de radiación ionizante mayor que los adultos. Objetivo. Cuantificar las dosis de radiación recibidas al tomar radiografías y evaluar los posibles factores asociados con el aumento de la dosis. Materiales y métodos. Se llevó a cabo un estudio observacional de 160 neonatos de la Unidad de Recién Nacidos del Hospital Universitario San Ignacio, Bogotá, Colombia. Se consideró como variable dependiente la dosis de entrada en piel por cada radiografía. Se hizo la caracterización de los pacientes, seguida de un análisis multivariado con regresión lineal múltiple para identificar factores asociados. Resultados. Se analizaron 160 pacientes y 492 radiografías en total. Entre los hallazgos más frecuentes, se encuentran: pacientes de sexo masculino (n=87; 54,4 %), nacimiento por cesárea (n=122; 76,3 %) e indicación de toma de radiografías por dificultad respiratoria (n=123; 24,9 %). El 1,8 % (n=9) de los pacientes no tenían una indicación para la toma de la radiografía. La radiografía más frecuente fue la de tórax (n=322; 65,4 %). La mayoría de las radiografías se tomaron con el equipo computarizado (n=352; 71,5 %) y no con el digital (n=140, 28,4 %). La mediana de la dosis de entrada en piel con el equipo computarizado fue de 0,112 mGy (0,022; 0,134 mGy) y, con el equipo digital, de 0,020 mGy (0,019, 0,022 mGy). Conclusiones. Se cuantificaron las dosis de radiación absorbida en neonatos, general y específica, con el equipo computarizado y el digital. Se identificaron mayores dosis con el equipo computarizado. Se reconoció la interacción entre el equipo computarizado con menores edades gestacionales corregidas como principal factor para el aumento de la dosis. Además, se reconoció la relación entre el equipo computarizado y una menor edad gestacional corregida, como principal factor para una mayor dosis.

Introduction. Radiographs are still widely used, underestimating the risks. This situation is frequent in neonatal care units, generating radiation doses than in adults. Objective. To quantify the received radiation doses when performing radiographs on neonates and the possible factors associated with higher doses. Materials and methods. We performed an observational study of 160 neonates from the newborn unit of the Hospital Universitario San Ignacio, Bogotá, Colombia. We considered the input dose of each radiograph as the dependent variable. Patients were characterized and a multivariate analysis with multiple linear regression was performed to identify associated factors. Results. We analyzed 160 newborns and 492 radiographs. The most frequent findings were male patients (n=87, 54.4%), cesarean delivery (n=122, 76.3%), and radiograph indication for respiratory distress (n=123, 24.9%). One-point eight percent of the patients (n=9) did not have radiograph indication. The most frequently taken radiograph was chest (322, 65.4%). Most radiographs were taken with a computerized equipment (n=352, 71.5%), compared to a digital one (n=140, 28.4%). The median input dose with computerized equipment was 0.112 mGy (0.022, 0.134 mGy), and with the digital equipment was 0.020 mGy (0.019, 0.022 mGy). Conclusions. The general and specific absorbed radiation doses were measured in neonates with a computerized and a digital equipment. We identified higher doses with the computerized equipment. In addition, it was recognized the correlation between computerized radiography equipment with lower corrected gestational ages as the main factor for dose increase.

Detection rate of pulmonary nodules by CT scan at different doses and application value of artificial intelligence assistance / 中国医师进修杂志

Objective:To investigate the detection rate of pulmonary nodules (PN) by CT scan at different doses and the application value of artificial intelligence(AI) system assistance.Methods:From October 2019 to October 2021, 210 patients with PN in Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, were retrospectively selected, and they were divided into the study group (106 cases) and the control group (104 cases) by CT scan at different doses. The control group used the conventional average dose (169 mAs) CT scan, the study group used an average low-dose (54 mAs) CT scan. The PN detection rate of different gender, age, body mass index (BMI) between the two groups were compared. The morphological characteristics, radiation dose, CT image quality between the two groups were compared. The diagnostic efficiency of radiologists and AI system was compared.Results:The detection rate of PN in the study group and the control group had no significant difference: 73.58% (78/106) vs. 80.77%(84/104), χ2 = 1.54, P>0.05. The detection rate of PN with different gender, age group and BMI in the two groups had no significant differences ( P>0.05). The diameter of nodules and the rates of calcification, cavitation, bronchial sign, lobar sign, burr sign and pleural adhesion sign in the two groups had no significant differences ( P>0.05). The mean effective tubular bulb dose, length product of radiation dose, total tubular bulb dose, radiation volume dose index in the study group were higher than those in the control group: (46.15 ± 7.38) mAs vs. (104.39 ± 10.53) mAs, (169.24 ± 19.77) mGy·cm vs. (427.17 ± 43.58) mGy·cm, (972.65 ± 58.34) mAs vs. (2 861.26 ± 181.37) mAs, (3.55 ± 1.16) mGy vs. (8.95 ± 2.07) mGy, there were statistical differences ( P<0.05). The excellent, good, acceptable, poor of 1.0 mm image quality in the study group were 26, 60, 18, 2, and in the control group were 32, 64, 8, 0, there was statistical difference ( u =1.71, P = 0.087). The excellent, good, acceptable, poor of maximum intensity projection (MIP) image quality in the study group were 58, 42, 6, 0 and in the control group were 70, 34, 0, 0, there was statistical difference ( u = 1.81, P = 0.070). The detection rate of PN by AI low-dose CT scan was higher than that of radiologists: 88.68%(94/106) vs. 73.58%(78/106), there was statistical difference ( χ2 = 7.89, P = 0.005). Conclusions:The low-dose CT chest scans for PN, the results of detection rate, morphological characteristics, CT image quality are basically the same as those of conventional-dose CT chest scans, and can greatly reduce the radiation dose, which is more suitable for PN screening, and combined with AI system can significantly improve the detection rate of PN.

Dosimetric comparison of intensity-modulated photon radiotherapy and intensity-modulated proton radiotherapy for non-small cell lung cancer / 肿瘤研究与临床

Objective:To investigate the difference of dose distribution between intensity-modulated photon radiotherapy (IMRT) and intensity-modulated proton radiotherapy (IMPT) in patients with non-small cell lung cancer.Methods:The clinical data of 8 patients with stage Ⅱ-Ⅲ non-small cell lung cancer who received radiotherapy in Ion Medical center of the First Affiliated Hospital of University of Science and Technology of China from November 2020 to April 2022 were retrospectively analyzed. IMRT and IMPT radiotherapy plans were created for each patient separately, the main evaluation indicators were targeted area dose distribution parameters [homogeneity index (HI), conformity index (CI) and the percent volume of volume wrapped by 95% and 100% of prescription dose profile in the targeted area (V 95% and V 100%)], and the average dose (D mean) to the organ at risk and the percent volume of a certain relative biological effect (RBE) dose exposure [D mean, V 5 Gy(RBE) and V 20 Gy(RBE) of ipsilateral lung, D mean, V 5 Gy(RBE) and V 20 Gy(RBE) of bilateral lung, D mean, V 30 Gy(RBE) and V 40 Gy(RBE) of heart, maximum dose (D max) of spinal cord, and D mean of esophageal]. Results:In comparison with IMRT, IMPT reduced the levels of dose parameters in bilateral lung, ipsilateral lung, spinal cord, esophagus, and heart with statistically significant differences (all P < 0.05), especially in D mean of bilateral lung [(4.1±1.8) Gy (RBE) vs. (6.9±1.9) Gy (RBE)], V 5 Gy(RBE) [(15.9±7.1) % vs. (28.5±8.6)%], V 20 Gy(RBE) [(7.4±3.5)% vs. (10.1±3.5)%], and D mean of ipsilateral lung [(9.1±4.5) Gy (RBE) vs. (11.9±3.3) Gy (RBE)], all decreased significantly (all P < 0.001), but the differences in the levels of targeted area dose distribution parameters between them were not statistically significant (all P > 0.05). Conclusions:For patients with non-small cell lung cancer, IMPT is superior to IMRT in the protection of bilateral lung, ipsilateral lung, spinal cord, esophagus and heart.

Application value of deep learning reconstruction algorithm in CT imaging of abdominal phantoms / 中华放射医学与防护杂志

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.

Simulación de dosis absorbida en terapia molecular mediante método de Montecarlo utilizando software libre GEANT4: GATE

RESUMEN Fundamento: aún no existe una forma óptima para determinar la dosis absorbida por los tumores; este desconocimiento es la causa de que la dosis final del tratamiento sea impredecible. Por esta causa los pacientes pueden estar recibiendo dosis mayores que las mínimas requeridas para su correcto diagnóstico. Objetivo: crear un código fuente para un proyecto de aplicación del programa GATE en la simulación de la dosis absorbida en radioterapia molecular, por método Montecarlo, para un maniquí de Giap. Métodos: se realizó la simulación por método de Montecarlo a partir de modelar el maniquí de Giap, mediante la plataforma de simulación GATE. Se compararon los resultados obtenidos con la información reflejada en la bibliografía sobre las mejores prácticas estandarizadas. Resultados: se confeccionó un código fuente implementado en GATE para la determinación de la dosis absorbida en radioterapia molecular. Se obtuvo distribución no uniforme de dosis en un medio de actividad uniforme y un 2 % de incertidumbre aproximado (en buena correspondencia con los valores reportados en la literatura), los resultados permiten afirmar que la simulación de dosis por medio de la plataforma GATE es confiable, de poco gasto computacional y altamente recomendable. Conclusiones: es recomendable utilizar la plataforma GATE para la simulación del cálculo de la dosis absorbida por ser rápida, de bajo costo computacional y confiable.

ABSTRACT Background: there is still no optimal way to determine the dose absorbed by tumors; this lack of knowledge is the reason why the final dose of treatment is unpredictable. For this reason, patients may be receiving doses greater than the minimum required for their correct diagnosis. Objective: to create a source code for an application project of the GATE program in the simulation of absorbed dose in molecular radiotherapy, by Monte Carlo method, for a Giap phantom. Methods: the simulation was carried out by the Montecarlo method from modeling the Giap phantom, using the GATE simulation platform. The results obtained were compared with the information reflected in the bibliography on standardized best practices. Results: a source code implemented in GATE was prepared for the determination of the absorbed dose in molecular radiotherapy. Non-uniform distribution of doses was obtained in a medium with uniform activity and an approximate 2% uncertainty (in correspondence with the values reported in the literature), the results allow to affirm that the dose simulation through the GATE platform is reliable, of little computational expense and highly recommended. Conclusions: it is advisable to use the GATE platform for the simulation of the calculation of the absorbed dose because it is fast, of low computational cost and reliable.

Calidad de la imagen de tomografía computarizada versus dosis en estudios híbridos: resultados preliminares en maniquí

RESUMEN Fundamento: los estudios híbridos producen una dosis total de radiación que es resultado de la dosis proveniente del radiofármaco y la emitida por la tomografía computarizada, por eso la optimización es indispensable. Objetivo: evaluar la relación de la dosis de tomografía computarizada con algunos parámetros de calidad de la imagen en protocolos de estudios híbridos. Métodos: para evaluar la calidad de la imagen se emplearon los maniquíes de Catphan y de Livermore en 12 protocolos preestablecidos de un equipo de tomografía por emisión del fotón único Mediso. Los datos de los descriptores de dosis de cada estudio se obtuvieron del cabezal DICOM. Se compararon los parámetros de calidad de imagen clásicos como ruido y la MTF 50 % para el maniquí de Catphan, y otros como la relación contraste ruido, el promedio de números de Hounsfield y su desviación estándar en las regiones de interés de los órganos correspondientes, en el maniquí de Livermore. Se analizó la relación de estos parámetros de calidad con los descriptores de dosis de los diferentes protocolos. Resultados: los parámetros relacionados con la calidad en el maniquí de Catphan no mostraron diferencias significativas (p<0,05) entre los diferentes protocolos para estudios híbridos. Se encontraron diferencias significativas entre los protocolos clínicos con diferentes calidades y el protocolo clínico estándar, para el maniquí antropomórfico, en la desviación estándar de los números de Hounsfield y en la relación contraste ruido (p<0,05). Conclusiones: el estudio de la relación contraste ruido y la desviación de los números de tomografía computarizada en las regiones de interés pueden servir de parámetro cuantitativo para la optimización de dosis en escenario clínico.

ABSTRACT Background: hybrid studies produce a total radiation dose that is the result of the dose imparted by the radiopharmaceutical and that emitted by the computed tomography, therefore optimization is essential. Objective: to evaluate the relationship of the computed tomography dose with some image quality parameters in hybrid study protocols. Methods: to evaluate the image quality, the Catphan and Livermore Phantom were used in 12 pre-established protocols of a Mediso single photon emission tomography equipment. The data for the dose descriptors for each study were obtained from the DICOM head. The classic image quality parameters such as noise and the MTF 50% for the Catphan manikin, and others such as the contrast-noise ratio, the average of Hounsfield numbers and their standard deviation in the regions of interest of the corresponding organs were compared, in Livermore's mannequin. The relationship of these quality parameters with the dose descriptors of the different protocols was analyzed. Results: the quality-related parameters in the Catphan manikin did not show significant differences (p <0.05) between the different protocols for hybrid studies. Significant differences were found between the clinical protocols with different qualities and the standard clinical protocol, for the anthropomorphic manikin, in the standard deviation of the Hounsfield numbers and in the contrast-to-noise ratio (p <0.05). Conclusions: the study of the contrast noise ratio and the deviation of the computed tomography numbers in the regions of interest can serve as a quantitative parameter for the optimization of doses in the clinical setting.

Effect of deep learning image reconstruction algorithm on CT image quality and detectability of hypovascular hepatic metastases at low radiation dose levels / 中华放射学杂志

Objective:To investigate the efficiency of deep learning image reconstruction (DLIR) algorithm in the image quality and detection of hypovascular hepatic metastases under low radiation doses in comparison with adaptive statistical iterative construction-V (ASiR-V).Methods:Fifty-six patients with suspected hypovascular hepatic metastases who needed abdominal enhanced CT scans were collected prospectively in the First Affiliated Hospital of Zhengzhou University from January to April 2021. The patients received conventional radiation dose with tube current-time products of 400 mA CT scans in the first venous phase, low-dose CT scans in the second venous phase, which were set as tube current-time products of 280 mA for group A (19 cases), 200 mA for group B (19 cases) and 120 mA for group C (18 case), respectively. The images of first venous phase and 3 groups of second venous phase were both reconstructed with ASiR-V60% and high-DLIR (DLIR-H). Quantitative parameters [image noise, liver and portal vein signal to noise ratio (SNR), contrast to noise ratio (CNR)] and qualitative parameters (overall image quality, lesion conspicuity, diagnostic confidence) were compared between ASiR-V60% and DLIR-H images, and the effective radiation dose (ED) and the lesion detectability of each group was recorded. The paired t test was used to compare quantitative parameters, whereas the Wilcoxon signed-rank test of paired data was used to compare qualitative parameters. Results:In the second venous phase, ED was (5.56±0.35) mSv in group A, (3.88±0.23) mSv in group B, and (2.42±0.23) mSv in group C, with a decrease of 30%, 50% and 70% compared with the first venous phase, respectively. Moreover, with the decrease of radiation dose, the noise gradually increased, and the CNR lesions, SNR liver and SNR portal vein all gradually decreased. DLIR-H images had statistically better quantitative scores than ASiR-V60% images when the same radiation dose was applied (all P<0.001). Furthermore, the qualitative parameters of each group decreased with the decrease of radiation dose. Under the same radiation dose, the overall image quality, lesion conspicuity and diagnostic confidence of DLIR-H were higher than those of ASiR-V60% (all P<0.001). All lesions [100% (84/84)] were detected by ASIR-V60% and DLIR-H in group A, 92.0% (75/81) in group B, and 88.0% (79/89) in group C. Conclusions:Compared with ASiR-V60%, DLIR-H could reduce image noise, improve overall image quality and lesion conspicuity of hypovascular hepatic metastases as well as increase diagnostic confidence under different radiation doses.

Investigation of radiation dose and diagnostic reference levels in CT scanning for children / 中华放射学杂志

Objective:To understand the current situation of CT radiation dose in children all over our country, and to explore the diagnostic reference level (DRL) of CT in children.Methods:The radiation dose reports of pediatric CT examination were collected end to November 30, 2021 and divided into five age groups: 0-1 month,>1 month-4 years,>4-10 years,>10-14 years and >14-18 years. There were 9 scanning item such as head, nasal sinus, temporal bone, neck, chest, abdomen, head enhanced CT, chest enhanced CT and abdomen enhanced CT. In each item, volume CT dose index (CTDI vol) and dose length product (DLP) were selected as radiation dose parameters, the 75% percentile were selected for DRL. The DRL results of head, chest and abdomen were compared with the DRL published by Chinese Society of Radiology and European Commission. Results:From March 2019 to November 2021, a total of 33 hospitals in 23 provinces were collected, including 20 children′s specialized hospitals, 11 women′s and children′s hospitals and 2 general hospitals, including 19 135 children′s CT scans. The DRL of 45 subgroups according to 5 age groups and 9 scanning items were obtained. The DRL results showed that the CTDI vol in five age groups was 26.9-42.8 mGy, and the DLP was 347-694 mGy·cm for head; 3.5-8.0 mGy, 54-293 mGy·cm for chest; and 6.3-13.2 mGy, 155-564 mGy·cm for abdomen. The DRL of the age group >4-10 years group in this investigation was agreed to the DRL of Chinese Society of Radiology. Compared with the European guidelines, there was little difference in the radiation dose of head scan, while the radiation dose of chest and abdomen in the young age group increased significantly. Conclusion:This survey reveals the radiation dose level distribution of children CT in our country. The radiation dose level of some items was inconsistent with the DRL of relevant international organizations. So our own DRL is needed to be set up according to the actual clinical reality of our country as a guideline.

Relationship between tube voltage kV value for head and neck CT angiography and body weight / 中国基层医药

Objective:To investigate the relationship between tube voltage kV value for head and neck CT angiography and body weight.Methods:A total of 120 patients with suspected vascular disease of the head and neck who underwent CT angiography of the head and neck in Beihai People's Hospital from January 2020 to May 2022 were included in this study. Patients were divided into three groups according to different tube voltages: group A (tube voltage 120 kV, n = 45), group B (tube voltage 100 kV, n = 45) and group C (tube voltage 80 kV, n = 30). Patients in group A were divided into group A1 (< 70 kg, n = 15), group A2 (70-85 kg, n = 15) and group A3 (> 85 kg, n = 15) according to different body weights. Patients in group B were divided into group B1 (< 70 kg, n = 15), group B2 (70-85 kg, n = 15) and group B3 (> 85 kg, n = 15) according to different body weights. Patients in group C were divided into group C1 (< 70 kg, n = 15) and group C2 (70-85 kg, n = 15) according to different body weights. Group C3 was not used. The contrast medium used was Loversol. The CT value, image noise, signal-to-noise ratio, contrast to noise ratio, and effective radiation dose of arterial vessels in each group were measured. The images were subjectively evaluated by two physicians who had senior professional titles using a 5-point rating scale. Results:Subjective score of image quality was all ≥ 3 grade in each group. There was no significant difference in image quality rating between groups A1 and A2 and groups B1, B2, and C1. There was a remarkable difference in image quality rating between groups A3, B3, and C2 and the other groups. There was a significant difference in the CT value of blood vessels at four different levels between groups A1, B1 and C1 ( F = 76.82, 64.62, 98.79, 71.85, all P < 0.001). There was a significant difference in CT value of blood vessels at four different levels between groups A2, B2 and C2 ( F = 159.82, 112.33, 108.22, 135.18, all P < 0.001). There was a significant difference in CT value of blood vessels at four different levels between groups A3 and B3 ( t = 4.40, 4.27, 3.91, 3.59, all P < 0.05). In groups B3 and C2, the image noise was remarkably increased, signal to noise ratio and contrast to noise ratio were remarkably decreased compared with those in the other groups. The effective radiation dose of arterial vessels in group B1 was 47% lower than that in group A1 and the effective radiation dose of arterial vessels in group C1 was 73% lower than that in group A1 ( F = 116.18, P < 0.001). The effective radiation dose of arterial vessels in group B2 was 49% lower than that in group A2, and the effective radiation dose of arterial vessels in group C2 was 66% lower than that in group A2 ( H = 35.40, P < 0.001). The effective radiation dose in group B3 was 35% lower than that in group A3 ( t = 3.59, P < 0.05). Conclusion:In CT angiography of the head and neck, the selection of tube voltage kV value is related to body weight. Tube voltage 80 kV is suitable for patients with a body weight < 70 kg, tube voltage 100 kV for patients with a body weight of 70-85 kg, and tube voltage 120 kV for patients with a body weight > 85 kg. These tube voltages can decrease effective radiation dose and ensure image quality, meeting the requirement for clinical diagnosis.

The clinical value of deep learning reconstruction in low-dose CT pulmonary angiography / 中华放射学杂志

Objective:To explore the effect of deep learning reconstruction (DLR) on radiation dosage reduction and image quality of CTPA compared with hybrid iterative reconstruction (HIR).Methods:A total of 100 patients with suspected pulmonary embolism (APE) or indications for CTPA due to other pulmonary artery diseases in Peking Union Medical College Hospital from December 2020 to April 2021 were prospectively enrolled and divided into HIR group and DLR group according to block randomization, with 50 cases in each group. The patient′s gender, age and body mass index (BMI) were recorded. HIR group and DLR group underwent standard deviation (SD)=8.8 and SD=15 CTPA protocols in combination with HIR and DLR algorithm respectively. Other scanning parameters and contrast medium injection plan were the same. The effective dose (ED) and size-specific dose estimate (SSDE) were calculated. Regions of interest (ROIs) were drawn in the lumen of Grade 1-3 pulmonary arteries and bilateral paravertebral muscles. The corresponding CT and SD values were recorded to acquire signal to noise ratio (SNR) and contrast noise ratio (CNR). Based on a double-blind method, two radiologists evaluated the subjective noise, visualization of pulmonary arteries, and diagnostic confidence of the two groups by 5-point Likert scales. The inconsistent results were judged comprehensively by the third radiologist. Independent samples t-test was used to compare the demographic data, radiation dosage and quantitative image quality of the two groups. Mann-Whitney U test was used to compare the subjective noise, visualization of pulmonary arteries and diagnostic confidence between the two groups. Linear weighted Kappa coefficient was calculated to analyze the consistency of the qualitative scores between the two radiologists. Results:There were no significant differences in gender, age and BMI between the two groups ( P>0.05). The CT values of Grade1-3 pulmonary arteries and paravertebral muscle had no significant differences ( P>0.05). Compared with HIR group, the ED and SSDE in DLR group decreased by about 35% to 1.3 mSv and 4.20 mGy respectively, while the SNR (30±5) and CNR (26±5) of CTPA images were higher in DLR group than those in HIR group (23±5 and 20±5, with t=-6.60 and -5.90, respectively, both P<0.001). The subjective noise score was higher in DLR group than that in HIR group ( Z=-7.34, P<0.001). In addition, two radiologists showed excellent interobserver agreement in DLR group (Kappa=0.847, 95%CI 0.553-1.000). No significant differences were found in visualization of pulmonary arteries and diagnostic confidence between the two groups ( P>0.05). Conclusion:DLR further reduced the radiation dosage and improved the image quality of CTPA, with no detriment to diagnostic confidence. Thus DLR is worthy of clinical promotion.

The application value of deep learning reconstruction algorithm in improving quality of low dose pancreatic CT images / 中华放射学杂志

Objective:To explore application value of improving quality of the low dose pancreatic CT images by using deep learning reconstruction (DLR).Methods:From August to December 2020, 68 patients who underwent contrast-enhanced pancreatic CT were prospectively collected in Peking Union Medical College Hospital. All patients were randomly divided into routine dose group (34 patients, with tube voltage of 120 kV) and low dose group (34 patients, with tube voltage of 100 kV). All patients underwent non-contrast, arterial phase, parenchymal phase and delay phase scans. The four-phase images of low dose group were reconstructed by using filtered back projection (FBP), hybrid iterative reconstruction (AIDR) and DLR which were marked with LD-FBP, LD-AIDR and LD-DLR, respectively. The four-phase images of routine dose group were reconstructed by using AIDR algorithm which were marked with RD-AIDR. The CT value, image noise (SD), signal to noise ratio (SNR) and contrast to noise ratio (CNR) of pancreas were measured. The ANOVA test was performed in comparison with objective parameters of different reconstruction algorithms, and LSD test was performed in pairwise comparison. The subjective image scores were obtained and were compared using Kruskal-Wallis test.Results:CT value, SD, SNR and CNR of non-contrast, arterial phase, parenchymal phase and delay phase had significant difference among different reconstruction images of routine dose group and low dose group (all P<0.05). The CT value of LD-FBP, LD-AIDR, and LD-DLR images were significantly higher than those of RD-AIDR images in parenchymal phase and delay phase (all P<0.05). There were statistically significant differences in each pairwise comparison of SD and SNR of four phase images (all P<0.05). There were statistically significant differences of CNR among LD-FBP, LD-DLR and RD-AIDR in four phase images (all P<0.05). The CNR of RD-AIDR was better than that of LD-FBP, and CNR of LD-DLR was better than that of RD-AIDR. DLR algorithm improved the SD, SNR and CNR of four phases of pancreatic images. The improvement of SNR was more significant after contrast enhancement, and the improvement of CNR was more significant in the non-contrast and delay phases. Subjective image scores of different reconstruction images were statistically different in four phase images (all P<0.001). Overall image scores of LD-DLR and RD-AIDR had no significant differences in four phase ( Z value of four phases were 1.00, 2.24, 0.45 and 1.34, respectively; P value of four phases were 0.317, 0.025, 0.655 and 0.180, respectively). Conclusion:The DLR technology can decrease radiation dose of pancreatic CT, improve image quality and satisfy diagnostic requirement. The DLR technology can also reduce image noise, improve the SNR and CNR in low dose contrast-enhanced pancreatic CT.

Current status survey of coronary CT angiography scan protocol and radiation dose in China / 中华放射学杂志

Objective:To explore current status of scanning protocol and radiation dose of coronary CT angiography (CCTA) in China from 2017 to 2018.Methods:Cluster sampling was conducted according to the number and distribution of tertiary and secondary hospitals in provinces across the country, and 75 hospitals (30 secondary hospitals and 45 tertiary hospitals) were finally included. The patients who underwent CCTA from October 2017 to May 2018 were systematically sampled, and 1 312 patients were finally included. Patients were divided into two groups according to the level of hospital. Basic clinical characteristics were collected, including age, sex, height, weight, CT scanning equipment, scanning parameters, scanning model, post-processing scheme and radiation dose. Wilcoxon rank sum test, χ 2 tes were used in statistical analysis. Radiation dose was compared between different tube voltage, scanning model and post-processing solutions groups. Results:The ratio of employing low tube voltage (≤100 kV) was 35.4% (464/1 312). The rate of using low tube voltage in different weight groups (<60, 60-90,>90 kg) were 45.0%(126/280), 39.6%(256/647), 33.3%(8/24) in tertiary hospitals respectively, and 27.8%(25/90), 18.5%(49/265), 0(0/6) in secondary hospitals respectively. The rate of using low tube voltage in different weight groups (<60, 60-90,>90 kg) was significantly higher in tertiary hospitals than in secondary hospitals (χ2=34.25, 51.05, 207.05, P<0.001). Prospective electrocardiogram triggering model was used in 38.5% (505/1 312) of the patients. Application rate of iterative reconstruction was 82.5% (1 082/1 312). Among the patients who applied iterative reconstruction, tube voltage of 120 kV and above was used in 58.8% (636/1 082) of the patients. The effective radiation dose (ED) of CCTA was 11.84 (6.33, 16.66) mSv. The ED of CCTA examination in tertiary hospitals was slightly lower than that of secondary hospitals ( Z=-5.73, P<0.001). The ED of CCTA examination using prospective electrocardiogram triggering model was lower than that of retrospective electrocardiogram triggering model ( Z=-15.76, P<0.001). The ED of CCTA examination with iterative reconstruction [11.76 (6.94, 17.58) mSv] was slightly lower than those without iterative reconstruction ( Z=-3.45, P=0.004). Conclusions:The problems were focused on tube voltage fixation, low application proportion of low tube voltage and prospective electrocardiogram triggered protocol, and nonstandard application of iterative reconstruction technology during CCTA examination in the investigated hospitals. The nonstandard scanning protocol was an important causation of high ED in CCTA examination. Although the scanning standardization degree of tertiary hospitals was higher than that of secondary hospitals, but it still did not meet the guidelines.

Application value of deep learning reconstruction to improve image quality of low-dose chest CT / 中华放射学杂志

Objective:To evaluate the effectiveness of deep learning reconstruction (DLR) compared with hybrid iterative reconstruction (Hybrid IR) in improving the image quality in chest low-dose CT (LDCT).Methods:Seventy-seven patients who underwent LDCT scan for physical examination or regular follow-up in Peking Union Medical College Hospital from October 2020 to March 2021 were retrospectively included. The LDCT images were reconstructed with Hybrid IR at standard level (Hybrid IR Stand) and DLR at standard and strong level (DLR Stand and DLR Strong). Regions of interest were placed on pulmonary lobe, aorta, subscapularis muscle and axillary fat to measure the CT value and image noise. The signal to noise ratio (SNR) and contrast to noise ratio (CNR) were calculated. Subjective image quality was evaluated using Likert 5-score method by two experienced radiologists. The number and features of ground-glass nodule (GGN) were also assessed. If the scores of the two radiologists were inconsistent, the score was determined by the third radiologist. The objective and subjective image evaluation were compared using the Kruskal-Wallis test, and the Bonferroni test was used for multiple comparisons within the group.Results:Among Hybrid IR Stand, DLR Stand and DLR Strong images, the CT value of pulmonary lobe, aorta, subscapularis muscle and axillary fat had no significant differences (all P>0.05), but the image noise and SNR of pulmonary lobe, aorta, subscapularis muscle and axillary fat had significant differences(all P<0.05), and the CNR of images had significant difference( P<0.05), too. The CNR of Hybrid IR Stand images, DLR stand images and DLR strong images were 0.71 (0.49, 0.88), 1.06 (0.78, 1.32) and 1.14 (0.84, 1.48), respectively. Compared with Hybrid IR images, DLR images had lower objective and subjective image noise,higher SNR and CNR (all P<0.05). The scores of DLR images were superior to Hybrid IR images in identifying lung fissures, pulmonary vessels, trachea and bronchi, lymph nodes, pleura, pericardium and GGN (all P<0.05). Conclusions:DLR significantly reduced the image noise, and DLR images were superior to Hybrid IR images in identifying GGN in chest LDCT while maintaining superior image quality at relatively low radiation dose levels. Thus DLR images can improve the safety of lung cancer screening and pulmonary nodule follow-up by CT.

Study of PET automatic drug infusion system for radiation protection and precision injection in nuclear medicine nursing / 中华核医学与分子影像杂志

Objective:To evaluate the advantages of PET automatic drug infusion system in nuclear medicine nursing by comparing radiation dose and precision injection between artificial injection and automatic injection.Methods:From August 2021 to September 2021, 40 patients (27 males, 13 females, average age: 59.6 years) were divided into two groups (20 patients in each group) for the injection of 18F-FDG by artificial injection and automatic injection in Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine. Portable radiation detector was used to measure the peak values of dose-equivalent rate in the arm and trunk of the nurse during the administration. The duration of administration process was recorded and the annual radiation doses were estimated and compared between the two injection methods. Independent-sample t test was used to compare the differences of injection parameters between two methods. Results:Based on 5 000 patients injected annually by artificial injection, the estimated annual radiation doses were about 220.19 mSv in the arm and 2.09 mSv in the trunk, while the radiation doses were approximately 0.19 and 0.08 mSv by automatic administration, respectively. Compared with the artificial injection, the automatic drug infusion system could reduce by 99% and 95% of equivalent doses in the arm and trunk, respectively. The significant difference was found in the empty needle activity between artificial injection and automatic drug infusion system ((18.87±7.77) and (0.22±0.19) MBq; t=10.65, P<0.001), while there were no statistical differences in full needle activity, injection activity and injection/prescription activity ratio ( t values: from -0.03 to 1.37, all P>0.05). Conclusion:PET automatic drug infusion system provides better radiation protection for nuclear medicine nursing.

External exposure dose of 177Lu-PSMA-617 to the public in the treatment of prostate cancer / 中华核医学与分子影像杂志

Objective:To estimate the radiation dose (RD) to the public from patients undergoing 177Lu-prostate specific membrane antigen (PSMA)-617 therapy, and provide reference for the formulation of radiation protection measures. Methods:From July 2020 to January 2021, 10 patients with prostate cancer (age (71.1±5.9) years) who received 177Lu-PSMA-617 therapy in the Affiliated Hospital of Southwest Medical University were retrospectively analyzed. According to the different doses of 177Lu-PSMA-617, the patients were divided into the low-dose (5.55-6.29 GBq) group and high-dose (6.70-8.94 GBq) group. Respectively at 5, 30 min and 1, 2, 4, 24, 48, 72, 96, 144 h after intravenous injection of 177Lu-PSMA-617, whole-body initial dose-equivalent rate (DR) was measured with a radiation-survey meter at 0.3, 1.0 and 2.0 m from the patients. The statistics of ROI were analyzed by HERMES, and the corresponding equations were obtained by fitting the curve regression with double exponential function model. On the basis of human social contact model proposed by the National Council on Radiation Protection and Measurements (NCRP), the RD to the public from the patient discharged from the hospital at different times after completing the 177Lu-PSMA-617 injection was estimated. Results:All patients were discharged from the hospital at 72 h after treatment. The initial DR at 0.3, 1.0 and 2.0 m were (12.6±3.3), (4.7±1.2) and (1.6±0.4) μSv/h, respectively, and the RD to the co-sleeping partner, family members and colleagues who were in contact during the day were (999±253), (121±29) and (160±39) μSv, respectively. If the patients were discharged at 48 h after treatment, the RD to the adult family members could be controlled ≤5 mSv, and the RD to colleagues and children could be controlled ≤1 mSv. Starting from the injection of 177Lu-PSMA-617, the restriction duration for co-sleeping partner and colleagues were both 2 d and the restriction duration for children were 2 d (high-dose group) or 1 d (low-dose group). The patients needed to limit the time for public transportation from the 1st to 4th day after treatment, and there was no restriction from the 5th day. Conclusion:According to the current RD restrictions on the public, 177Lu-PSMA-617 is a relatively safe treatment modality for prostate cancer if good safety precautions are taken.

Computed tomography with low-dose radiation versus standard-dose radiation for diagnosing fractures: systematic review and meta-analysis

BACKGROUND: Computed tomography (CT) accounts for 13% of all radiological examinations in the United States and 40-70% of the radiation that patients receive. Even with the advent of magnetic resonance imaging (MRI), CT continues to be the gold standard for diagnosing bone fractures. There is uncertainty as to whether CT with a low radiation dose has a fracture detection rate similar to that of standard-dose CT. OBJECTIVE: To determine the detection rate of low-dose radiation CT and standard-dose radiation CT for fractures, in patients with suspected fractures. DESIGN AND SETTING: Systematic review of comparative studies on diagnostic accuracy within the evidence-based health program at a federal university in São Paulo (SP), Brazil. METHODS: We searched the electronic databases Cochrane Library, MEDLINE, EMBASE and LILACS up to June 29, 2020, for studies evaluating the detection rates of low-dose CT and standard-dose CT for diagnosing bone fractures. The Research Triangle Institute (RTI) item bank tool was used for methodological quality evaluation. RESULTS: The fracture detection rate according to the number of bones evaluated, using CT with low-dose radiation was 20.3%, while with standard-dose radiation it was 19.2%, and the difference between the methods was not significant. The fracture detection rate according to the number of patients, using CT with low-dose radiation was 56.0%, while with standard-dose radiation it was 58.7%, and this difference between the methods was not significant, either. CONCLUSION: CT with low-dose radiation presented detection rates similar to those of CT with standard-dose radiation, regardless of the bones evaluated. REGISTRATION NUMBER: CRD42019148491 at the PROSPERO database.

Short-term effectiveness and dosimetry evaluation for 125I seeds implantation in treatment of lymph nodes metastasis from radioactive iodine-refractory differentiated thyroid carcinoma / 中华核医学与分子影像杂志

Objective:To evaluate the efficacy and safety of 125I seeds implantation for lymph nodes metastasis (LNM) from radioactive iodine-refractory differentiated thyroid carcinoma (RAIR-DTC), and to verify the computer three-dimensional treatment planning system (TPS) from the dosimetry accuracy in assisting seeds implantation to treat LNM. Methods:Retrospective analysis was performed on 17 RAIR-DTC patients with LNM admitted to the General Hospital of Northern Theater Command from December 2016 to January 2019 (8 males, 9 females, median age 58 years). All patients underwent preoperative TPS planning design, CT-guided puncture and 125I seeds implantation (seed activity 14.8-25.9 MBq). The dosimetric results of postoperative validation were compared with those of preoperative planning, including the dosimetric parameters such as target volume before and after surgery and the dose received by 90% and 100% gross tumor volume (GTV) ( D90, D100), the percentage received by 100% and 150% of the prescription dose ( V100, V150), homogeneity index (HI). All patients underwent CT after 6 months to compare the LNM size, serum thyroglobulin (Tg) level, and the improvement of complications before and after treatment. Efficacies were divided into complete remission (CR), partial remission (PR), stable disease (SD), and progressive disease (PD). Paired t test or Wilcoxon signed rank test were used to analyze the data. Results:Among 17 patients, a total of 226 125I radioactive seeds were implanted. Among them, 1 achieved CR, 10 achieved PR, 4 were with SD, and 2 were with PD. The diameter of LNM was 1.40(0.65, 3.05) cm before treatment and was 0.40(0.21, 0.91) cm 6 months after treatment ( z=-3.95, P<0.05). The Tg before treatment was 23.50(20.94, 72.92) μg/L and was 8.90(3.20, 40.22) μg/L 6 months after treatment ( z=-5.009, P<0.001). Tg antibody were all negative. There were 90.90% (20/22) of patients had slightly lower D90 than the prescribed dose ((12 378.8±3 182.0) vs (12 497.8±1 686.4) cGy; t=0.251, P>0.05). The postoperative dose parameters D100 and V150 ((6 881.5±1 381.8) cGy, (58.5±18.4)%) were both lower than those of preoperative plan ((8 085.8±2 330.0) cGy, (66.5±17.7)%; t values: 8.913, 3.032, both P<0.05), and the remaining indicators were not significantly different from those of the preoperative plan ( t values: 0.251, 1.493, z values: from -1.604 to -0.593, all P>0.05). Conclusions:According to the TPS preoperative plan, 125I seeds implantation for treating RAIR-DTC LNM can achieve the expected dose distribution, and the short-term tumor local control is effective. It is a safe and effective treatment method.

Application of a deep learning image reconstruction algorithm to improve the measurement accuracy of vessel wall thickening in pediatric patients with Takayasu arteritis / 中华放射学杂志

Objective:To demonstrate whether image quality and measurement accuracy of vessel wall thickening could be improved using a deep learning image reconstruction (DLIR) algorithm in children with Takayasu arteritis.Methods:From September 2019 to April 2020, 32 patients with Takayasu arteritis underwent low-dose contrast-enhanced CT with 100 kVp in Beijing Children′s Hospital were enrolled retrospectively. The raw data were reconstructed at 0.625 mm slice thickness using the filtered back projection (FBP), 50% adaptive statistical iterative reconstruction-V (ASIR-V) at 50% (50%ASIR-V), ASIR-V at 100% (100%ASIR-V) and DLIR. Subjective evaluation including the image quality of vessel wall identification, overall image noise and diagnostic confidence were evaluated using a 5 points scales by 2 observers. Objective evaluation including the thickness and standard deviation of vessel wall were measured, then the coefficient of variation (CV) was calculated. The CT value and noise of aorta were measured to calculate the contrast to noise ratio (CNR) of image. Friedman test was used to compare the differences of subjective scores among the four groups, and the analysis of variance of random blocks was used to compare the differences of objective measurement indices.Results:In terms of subjective score results, there was no significant difference between 100%ASIR-V and DLIR of overall image noise ( P>0.05), and the image scores of the two groups were higher than those of FBP and 50%ASIR-V (all P<0.05). The vessel wall identification and diagnostic confidence of DLIR were higher than those of other images (all P<0.05). The objective measurement results showed that the standard deviation and CV of vessel wall thickness in DLIR were significantly lower than those in other images (all P<0.05). There was no significant difference in vascular noise, muscle noise and CNR between 100%ASIR-V and DLIR (all P>0.05), which were lower than those in FBP and 50%ASIR-V (all P<0.05). Compared with 50%ASIR-V, the CV of DLIR was reduced by 22.9%, and the CNR was increased by 46.8%. Conclusion:DLIR can improve the overall image quality of CECT in children with Takayasu arteritis and the measurement accuracy of vascular wall, making it possible to further reduce the radiation dose.

Comparison on radiation dose of direct aspiration one-time thrombectomy and stent thrombectomy in treatment of acute middle cerebral artery occlusion / 中国介入影像与治疗学

Objective: To compare the radiation dose of direct aspiration first-pass thrombectomy (ADAPT) and conventional stent thrombectomy in treatment of acute middle cerebral artery occlusion. Methods: Totally 54 middle cerebral artery occlusion patients were retrospectively analyzed. The patients were divided into ADAPT group (n=29) and stent group (conventional stent removal, n=25) according to interventional treatment method. The intraoperative fluoroscopy time, air kerma (AK), dose area product (DAP), the number of photographic sequences and photographic frames were recorded and compared between 2 groups, and the correlations of the above indicators were analyzed. Results: The fluoroscopy time, AK, DAP, the number of photographic sequences and photographic frames in ADAPT group were all lower than those in stent group (all P<0.05). There were 25 cases (25/29, 86.21%) in ADAPT group and 13 cases (13/25, 52.00%) in stent group AK value <1.0 Gy, and the rate of patients with DAP value <1.0 Gy in ADAPT group was higher than that in stent group (P<0.01). There were 22 cases (22/29, 75.86%) in ADAPT group and 11 cases (11/25, 44.00%) in stent group DAP value <100 Gy•cm2, and the rate of patients with DAP value <100 Gy•cm2 in ADAPT group was higher than that in stent group (P=0.01). The fluoroscopy time was positively correlated with DAP (r=0.60, P<0.01) and AK (r=0.69, P<0.01), so was DAP and AK (r=0.81, P<0.01). Conclusion: The radiation dose of ADAPT technology was lower than conventional stent removal for treatment of acute middle cerebral artery occlusion.

Feasibility of narrowing acquisition time window of 320-slice CT coronary angiography / 中国医学影像技术

Objective: To explore the feasibility of narrowing acquisition time window of 320-slice CT coronary angiography (CCTA). Methods: Totally 90 patients with suspected coronary heart disease who received CCTA were collected. The best time phase of blood vessels and patients were obtained according to image quality scores, and the critical heart rate from diastole to systole was observed according to the best time phase of CCTA in patients with different heart rates, then the range of narrowing acquisition time window was estimated. The image quality of estimated narrowing acquisition time window (narrowing time window group) and preset time phase with CT machine (preset time phase group), and the radiation dose before and after estimated narrowing acquisition time window were compared. Results: The critical heart rate of patients for CCTA optimal phase transfer was 70 bpm. In patients with heart rate of 65-70 bpm, CCTA acquisition time window could be narrowed to 72%-80% of R-R interval, while in patients with rate of 70-95 bpm could be narrowed to 40%-50% of R-R interval. Statistical differences were found in imaging quality of the best blood vessels time phase and the best patient time phase between 2 groups (all P<0.05). ED reduced by about 43% after estimated narrowing the acquisition time window (t=44.14, P<0.01). Conclusion: For patients with stable heart rate after breathholding (heart rate fluctuation ≤5 bpm), it is estimated that the acquisition time window of CCTA can be narrowed according to different heart rate, which can improve the image quality, and reduce the radiation dose.