Objective:To investigate the feasibility of ultra-low dose (ULD) CT pulmonary angiography (CTPA) combined with deep learning reconstruction (DLR) in the diagnosis of pulmonary embolism (PE).Methods:This cross-sectional study prospectively enrolled 100 patients with suspected PE who underwent CTPA examination in Zhongshan Hospital Fudan University, and Shanghai Geriatric Medical Center from April to July 2024, and were randomly divided into the routine dose (RD) group and ULD group according to block randomization. Effective dose (ED) were calculated. The noise index of RD group and ULD group was set to 10 and 20, respectively. Other scanning parameters and contrast agent injection protocol were the same. The CT images of RD group were reconstructed using hybrid iterative reconstruction (HIR), while ULD images were reconstructed with HIR and DLR (ULD-HIR subgroup and ULD-DLR subgroup). The image quality of the three groups of images was subjectively evaluated (overall image noise, pulmonary artery display) and objectively evaluated [signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) of the images] respectively. Finally, the diagnostic results of PE by the expert committee composed of three chief physicians were taken as the gold standard, and one physician with lower qualifications independently evaluated the diagnostic rate of PE in the three groups of images. Objective image quality parameters across the three groups were compared using ANOVA, with LSD post hoc test was used for multiple comparisons. Subjective scores among the three groups were analyzed using the Kruskal-Wallis H test, with Bonferroni corrected pairwise post hoc test was applied for multiple pairwise comparisons. Results:The ED in the RD group and ULD group were (2.7±0.5) mSv and (0.7±0.2) mSv, respectively, and the differences were statistically significant ( t=26.42, P<0.001). The overall differences in CT values of pulmonary arteries at all levels in the images of the RD group, the ULD-HIR subgroup, and the ULD-DLR subgroup were not statistically significant ( P>0.05).The RD group, ULD-HIR subgroup and ULD-DLR subgroup overall differences in SNR and CNR at all levels pulmonary arteries were statistically significant ( P<0.001), in which except for the differences in CNR and SNR values of the left pulmonary arterial trunk in the RD group and the ULD-HIR subgroup, and SNR values of basal segment pulmonary artery of the lower lobe of the left lung, which were not statistically significant ( P>0.05), the differences of the rest of the indexes in the pairwise comparisons between the groups were statistically significant ( P<0.05). The overall differences in the subjective scores of image pulmonary vascular display and image noise in the RD group, ULD-HIR subgroup and ULD-DLR subgroup were statistically significant ( P<0.001), except that the differences in the subjective scores of image pulmonary vascular display in the ULD-DLR subgroup were not statistically significant when compared with that of the RD group ( P>0.05) and that of the rest of the metrics in the between-groups two-by-two comparisons were all statistically significant ( P<0.05). The difference in diagnostic rates of PE in the pulmonary artery trunk, lobe and segmental levels in the images of the RD group, ULD-HIR subgroup and ULD-DLR subgroup was not statistically significant ( P>0.05). Conclusions:DLR can significantly reduce the radiation dose of CTPA examination. Even at ultra-low radiation dose, its image quality is still better than HIR reconstruction at conventional doses and preserve diagnostic accuracy of PE at the lobe level and segment level.

Objective:To investigate the feasibility of ultra-low dose (ULD) CT pulmonary angiography (CTPA) combined with deep learning reconstruction (DLR) in the diagnosis of pulmonary embolism (PE).Methods:This cross-sectional study prospectively enrolled 100 patients with suspected PE who underwent CTPA examination in Zhongshan Hospital Fudan University, and Shanghai Geriatric Medical Center from April to July 2024, and were randomly divided into the routine dose (RD) group and ULD group according to block randomization. Effective dose (ED) were calculated. The noise index of RD group and ULD group was set to 10 and 20, respectively. Other scanning parameters and contrast agent injection protocol were the same. The CT images of RD group were reconstructed using hybrid iterative reconstruction (HIR), while ULD images were reconstructed with HIR and DLR (ULD-HIR subgroup and ULD-DLR subgroup). The image quality of the three groups of images was subjectively evaluated (overall image noise, pulmonary artery display) and objectively evaluated [signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) of the images] respectively. Finally, the diagnostic results of PE by the expert committee composed of three chief physicians were taken as the gold standard, and one physician with lower qualifications independently evaluated the diagnostic rate of PE in the three groups of images. Objective image quality parameters across the three groups were compared using ANOVA, with LSD post hoc test was used for multiple comparisons. Subjective scores among the three groups were analyzed using the Kruskal-Wallis H test, with Bonferroni corrected pairwise post hoc test was applied for multiple pairwise comparisons. Results:The ED in the RD group and ULD group were (2.7±0.5) mSv and (0.7±0.2) mSv, respectively, and the differences were statistically significant ( t=26.42, P<0.001). The overall differences in CT values of pulmonary arteries at all levels in the images of the RD group, the ULD-HIR subgroup, and the ULD-DLR subgroup were not statistically significant ( P>0.05).The RD group, ULD-HIR subgroup and ULD-DLR subgroup overall differences in SNR and CNR at all levels pulmonary arteries were statistically significant ( P<0.001), in which except for the differences in CNR and SNR values of the left pulmonary arterial trunk in the RD group and the ULD-HIR subgroup, and SNR values of basal segment pulmonary artery of the lower lobe of the left lung, which were not statistically significant ( P>0.05), the differences of the rest of the indexes in the pairwise comparisons between the groups were statistically significant ( P<0.05). The overall differences in the subjective scores of image pulmonary vascular display and image noise in the RD group, ULD-HIR subgroup and ULD-DLR subgroup were statistically significant ( P<0.001), except that the differences in the subjective scores of image pulmonary vascular display in the ULD-DLR subgroup were not statistically significant when compared with that of the RD group ( P>0.05) and that of the rest of the metrics in the between-groups two-by-two comparisons were all statistically significant ( P<0.05). The difference in diagnostic rates of PE in the pulmonary artery trunk, lobe and segmental levels in the images of the RD group, ULD-HIR subgroup and ULD-DLR subgroup was not statistically significant ( P>0.05). Conclusions:DLR can significantly reduce the radiation dose of CTPA examination. Even at ultra-low radiation dose, its image quality is still better than HIR reconstruction at conventional doses and preserve diagnostic accuracy of PE at the lobe level and segment level.

Objective:To evaluate the mechanical stability of the bone block after LeFort Ⅰ osteotomy with maxillary advancement using absorbable plates fixed with tenon-and-mortise structures.Methods:This study developed three finite element models: one for the maxillary LeFort Ⅰ osteotomy with anterior advancement fixed with absorbable plates (Model 1); another for the maxillary LeFort Ⅰ osteotomy with anterior advancement fixed with absorbable plates assisted by tenon-and-mortise structures (Model 2); and the last one for the maxillary LeFort Ⅰ osteotomy with anterior advancement fixed with titanium plates and screws (Model 3). Simulated occlusal forces were applied on the anterior and posterior teeth in each model. The displacement changes of the nasal-palatine point (NP) and posterior nasal spine point (PNS) in the finite element coordinate system were compared and analyzed. The Mises equivalent stress distributions of the metal and absorbable plates were also examined to assess the mechanical stability of the three finite element models. Clinical data from 45 patients with dentofacial deformities treated from January 2017 to January 2023 at the Stomatology Hospital of China Medical University were collected. The age of the patients was 21±3 years. Among these, 15 patients had absorbable plates for fixation, 15 had absorbable plates assisted by tenon-and-mortise structures, and 15 had titanium plates and screws fixation after maxillary advancement. All patients underwent preoperative (T0), postoperative 3 days (T1), and 6 months (T2) spiral CT scans. The CT data in DICOM format were input into digital software, which was used to calculate the distances from the NP and PNS points to the horizontal plane (HP), right sagittal plane (FZSR), and coronal plane (CP) at T1 and T2. The distances at T1 and T2 were statistically analyzed using the Wilcoxon signed-rank test with SPSS 20.0, and a P value of<0.05 was considered statistically significant.Results:The finite element analysis showed that in the absorbable plate-only fixation group, the maximum displacement of the NP point (mm) under anterior and posterior tooth force conditions were 0.6 and 0.12, respectively, and for the PNS point, the maximum displacements were 0.5 and 0.11. In the tenon-and-mortise-assisted absorbable plate fixation group, the displacement of the NP point was 0.40 and 0.02 mm, and the displacement of the PNS point was 0.5 and 0.015 mm. In the titanium plate-screw fixation group, the NP point displacement was 0.33 and 0.055 mm, and the PNS point displacement was 0.16 and 0.1 mm. The Mises equivalent stress on the absorbable plates with tenon-and-mortise structure was significantly lower than that in the absorbable plate-only fixation group, while the titanium plate experienced the highest Mises equivalent stress. The clinical data analysis showed that in the horizontal direction, the postoperative stability of the three fixation methods was similar. However, in the vertical and anterior-posterior directions, the absorbable plate-only fixation group showed significant differences in the distances of PNS-HP, PNS-CP, and NP-CP between T1 and T2 ( P=0.018, P=0.009, P=0.017), suggesting significant postoperative bone displacement. In contrast, the tenon-and-mortise-assisted absorbable plate fixation group and the titanium plate-screw fixation group showed no significant differences in displacement during surgery and postoperatively(all P>0.05), demonstrating higher stability. Conclusions:The tenon-and-mortise-assisted absorbable plate fixation provides comparable stability to titanium plate fixation in clinical results, and it is more stable than absorbable plate-only fixation. In the mechanical study, when force was applied on the anterior teeth, the stability of the tenon-and-mortise-assisted absorbable plate fixation was slightly less than that of titanium plate fixation, but when posterior teeth were used, its stability exceeded both titanium plate fixation and absorbable plate-only fixation. The tenon-and-mortise-assisted absorbable plate fixation serves as an effective alternative to titanium plate fixation after LeFort Ⅰ osteotomy.

Objective:To investigate the efficacy of naloxone in improving health-related quality of life in patients with chronic arsenic exposure-related pruritus, and to explore the modification effect of gene polymorphisms associated with arsenic metabolism and endorphin receptors.Methods:A randomized, double-blind, placebo-controlled trial was conducted between January and March 2019 in Changde City, Hunan Province, China. Eligible patients with moderate to severe chronic pruritus under arsenic exposure were recruited, and randomly assigned to the naloxone group and the control group to receive sublingual naloxone and placebo (0.4 mg/d) respectively for 7 consecutive days. Outcomes were assessed before treatment and on day 7 after treatment, including the primary outcome (the dermatology life quality index [DLQI]) and secondary outcomes (depression symptoms, anxiety symptoms, and quality of sleep). Genotyping of the arsenic (+3 oxidation state) methyltransferase and 3 opioid receptor genes was performed using ligase detection reaction. Data analysis was performed using t test for normally distributed continuous variables, non-parametric tests for skewed continuous variables, and chi-square test for categorical data. Linear regression analysis was carried out to evaluate the effect of naloxone on outcome measures, while the interactive effect of demographic factors, genotypes and treatment methods on changes in DLQI were assessed by the generalized linear model. Results:A total of 126 patients with chronic arsenic exposure-related pruritus were enrolled, including 73 males and 53 females. They were randomly divided into the control group (64 cases) and the naloxone group (62 cases), with the ages being 60.0 ± 9.1 years and 58.4 ± 8.6 years, respectively. There were no significant differences between the two groups in terms of age, gender, income, education levels, or hair arsenic concentrations (all P > 0.05). After treatment, the decrease in DLQI scores was significantly higher in the naloxone group than in the control group (-8.79 ± 6.84 vs. -5.19 ± 8.10; P = 0.008). However, there were no significant changes in depression symptoms, anxiety symptoms, or quality of sleep between the naloxone group and control group (all P > 0.05). Linear regression analysis showed that naloxone significantly affected DLQI with a crude regression coefficient of -3.60 (95% CI: -6.25, -0.96; P = 0.008). Stratification analysis revealed that patients with the κ-opioid receptor gene rs1051660 (wild-type, CC) responded better to the treatment than those with the mutated genotype (CA), and there was a significant interaction between the rs1051660 genotype and therapeutic drugs in relation to DLQI changes ( P = 0.014) . Conclusion:Naloxone can effectively improve health-related quality of life in patients with chronic arsenic exposure-related pruritus, and its efficacy is modified by the gene polymorphism of the κ-opioid receptors.

ObjectiveTo analyze the genomic characteristics of Streptococcus pyogenes (GAS) isolated from children with respiratory tract infections in a tertiary hospital in Jinshan District of Shanghai during 2013‒2024, to compare the changes in trend for genomic characteristics before and after 2000, and to provide scientific data for the prevention and control of GAS infections. MethodsGAS strains isolated from children with respiratory tract infections in this hospital were collected from 2013 to 2024. Antimicrobial susceptibility of the isolated strains to 12 antibiotics, including penicillin, cefotaxime, cefepime, linezolid, vancomycin, meropenem, chloramphenicol, ofloxacin, levofloxacin, erythromycin, clindamycin, and tetracycline, was determined using broth microdilution plate method. Besides, whole genome sequencing (WGS) was used to analyze multilocus sequence type (MLST), emm typing, carriage of superantigen genes, mobile genetic element (MGE), carriage of virulence gene, and genomic phylogenetic tree of the isolated strains. ResultsA total of 50 GAS strains were collected and identified from children with respiratory tract infections aged 4‒14 years old, and the resistance rates of those isolates to erythromycin, clindamycin, and tetracycline were 100.00%, 100.00%, and 86.00%, respectively. There were two emm types in the GAS isolates; the emm12 type accounted for 76.00% (38/50), corresponding to ST36 type, and the emm1 type accounted for 24.00% (12/50), corresponding to ST28, ST1274, and new-1 types. There was a statistically significant difference in the constitution of the MLST before and after 2020 (P=0.015). All the isolates carried the superantigen genes speC, speG, ssa, and smeZ. The predominant emm12 isolates belonged to the Clade Ⅱ, carrying the mobile elements ICE-emm12 (harboring erythromycin-resistance gene ermB and tetracycline-resistance gene tetM) and ΦHKU.vir (carrying virulence genes speC and ssa). The emm1 isolates carried the mobile elements ICE-HKU488 (harboring erythromycin-resistance gene ermB and tetracycline-resistance gene tetM) and ΦHKU488.vir (carrying virulence genes speC and ssa), and had close phylogenetical relationships with isolates from Hong Kong, China. No M1_UK new clone strains were found. The ST1274 isolates of emm1 were newly discovered in 2020‒2024, and belonged to a separate phylogenetic clade. ConclusionGAS strains isolated from children with respiratory tract infections in a tertiary hospital in Jinshan District of Shanghai exhibit a high resistance to erythromycin, clindamycin, and tetracycline. It is recommended that the clinical treatments change to use other antimicrobial drugs, such as penicillin, third-generation cephalosporins, and fluoroquinolones. During 2020‒2024, a new ST1274 clone strain is discovered in emm1 GAS isolates, without M1_UK new clone strains being found. It is essential to continuously concern locally prevalent GAS strains and perform early identification of MLST types to promptly monitor the internal changes of the bacterial population and potential prevalence of new clones.

Objective To investigate the value of flexible subtraction CE-Boost technique combined with low dosage contrast agents for CT pulmonary angiography(CTPA).Methods A total of 68 patients who would undergo CTPA examination due to suspected pulmonary embolism(PE)were prospectively enrolled and randomly divided into study group(n=34)and control group(n=34)using block randomization method.After injecting 25 ml contrast agents at a flow rate of 2.5 ml/s in study group or 50 ml contrast agents at a flow rate of 3.5 ml/s in control group,CTPA scanning were performed with identical parameters.For images in study group,hybrid iterative reconstruction was performed,followed by flexible subtraction CE-Boost post-processing to obtain CE-Boost CTPA.For images in control group,conventional CTPA was obtained with hybrid iterative reconstruction.Subjective and objective evaluations of image quality were compared between groups.Taken the final clinical diagnosis as standard,the accuracy rate of diagnosing PE were compared between groups.Results There were 7 cases of pulmonary artery main trunk PE and 15 cases of pulmonary lobe-level PE in study group,while in control group there were 8 cases and 17 cases.No statistical difference of subjective scores of CTPA was found between groups(P＞0.05).CT values of the main pulmonary artery,bilateral pulmonary artery trunks and lower lobes of both lungs,signal-to-noise ratio or contrast-to-noise ratio in CTPA were not significantly different between groups(all P＞0.05),while no significant difference of the accuracy rate of CTPA for diagnosing PE of pulmonary artery main trunk(100％[7/7]vs.100％[8/8])nor pulmonary lobe-level PE(86.67％[13/15]vs.88.24％[15/17])was detected between groups(all P＞0.05).Conclusion Flexible subtraction CE-Boost technique combined with low dosage contrast agents for CTPA could reduce contrast agent dosage without affecting image quality.

Objective:To evaluate the mechanical stability of the bone block after LeFort Ⅰ osteotomy with maxillary advancement using absorbable plates fixed with tenon-and-mortise structures.Methods:This study developed three finite element models: one for the maxillary LeFort Ⅰ osteotomy with anterior advancement fixed with absorbable plates (Model 1); another for the maxillary LeFort Ⅰ osteotomy with anterior advancement fixed with absorbable plates assisted by tenon-and-mortise structures (Model 2); and the last one for the maxillary LeFort Ⅰ osteotomy with anterior advancement fixed with titanium plates and screws (Model 3). Simulated occlusal forces were applied on the anterior and posterior teeth in each model. The displacement changes of the nasal-palatine point (NP) and posterior nasal spine point (PNS) in the finite element coordinate system were compared and analyzed. The Mises equivalent stress distributions of the metal and absorbable plates were also examined to assess the mechanical stability of the three finite element models. Clinical data from 45 patients with dentofacial deformities treated from January 2017 to January 2023 at the Stomatology Hospital of China Medical University were collected. The age of the patients was 21±3 years. Among these, 15 patients had absorbable plates for fixation, 15 had absorbable plates assisted by tenon-and-mortise structures, and 15 had titanium plates and screws fixation after maxillary advancement. All patients underwent preoperative (T0), postoperative 3 days (T1), and 6 months (T2) spiral CT scans. The CT data in DICOM format were input into digital software, which was used to calculate the distances from the NP and PNS points to the horizontal plane (HP), right sagittal plane (FZSR), and coronal plane (CP) at T1 and T2. The distances at T1 and T2 were statistically analyzed using the Wilcoxon signed-rank test with SPSS 20.0, and a P value of<0.05 was considered statistically significant.Results:The finite element analysis showed that in the absorbable plate-only fixation group, the maximum displacement of the NP point (mm) under anterior and posterior tooth force conditions were 0.6 and 0.12, respectively, and for the PNS point, the maximum displacements were 0.5 and 0.11. In the tenon-and-mortise-assisted absorbable plate fixation group, the displacement of the NP point was 0.40 and 0.02 mm, and the displacement of the PNS point was 0.5 and 0.015 mm. In the titanium plate-screw fixation group, the NP point displacement was 0.33 and 0.055 mm, and the PNS point displacement was 0.16 and 0.1 mm. The Mises equivalent stress on the absorbable plates with tenon-and-mortise structure was significantly lower than that in the absorbable plate-only fixation group, while the titanium plate experienced the highest Mises equivalent stress. The clinical data analysis showed that in the horizontal direction, the postoperative stability of the three fixation methods was similar. However, in the vertical and anterior-posterior directions, the absorbable plate-only fixation group showed significant differences in the distances of PNS-HP, PNS-CP, and NP-CP between T1 and T2 ( P=0.018, P=0.009, P=0.017), suggesting significant postoperative bone displacement. In contrast, the tenon-and-mortise-assisted absorbable plate fixation group and the titanium plate-screw fixation group showed no significant differences in displacement during surgery and postoperatively(all P>0.05), demonstrating higher stability. Conclusions:The tenon-and-mortise-assisted absorbable plate fixation provides comparable stability to titanium plate fixation in clinical results, and it is more stable than absorbable plate-only fixation. In the mechanical study, when force was applied on the anterior teeth, the stability of the tenon-and-mortise-assisted absorbable plate fixation was slightly less than that of titanium plate fixation, but when posterior teeth were used, its stability exceeded both titanium plate fixation and absorbable plate-only fixation. The tenon-and-mortise-assisted absorbable plate fixation serves as an effective alternative to titanium plate fixation after LeFort Ⅰ osteotomy.

Objective:To investigate the efficacy of naloxone in improving health-related quality of life in patients with chronic arsenic exposure-related pruritus, and to explore the modification effect of gene polymorphisms associated with arsenic metabolism and endorphin receptors.Methods:A randomized, double-blind, placebo-controlled trial was conducted between January and March 2019 in Changde City, Hunan Province, China. Eligible patients with moderate to severe chronic pruritus under arsenic exposure were recruited, and randomly assigned to the naloxone group and the control group to receive sublingual naloxone and placebo (0.4 mg/d) respectively for 7 consecutive days. Outcomes were assessed before treatment and on day 7 after treatment, including the primary outcome (the dermatology life quality index [DLQI]) and secondary outcomes (depression symptoms, anxiety symptoms, and quality of sleep). Genotyping of the arsenic (+3 oxidation state) methyltransferase and 3 opioid receptor genes was performed using ligase detection reaction. Data analysis was performed using t test for normally distributed continuous variables, non-parametric tests for skewed continuous variables, and chi-square test for categorical data. Linear regression analysis was carried out to evaluate the effect of naloxone on outcome measures, while the interactive effect of demographic factors, genotypes and treatment methods on changes in DLQI were assessed by the generalized linear model. Results:A total of 126 patients with chronic arsenic exposure-related pruritus were enrolled, including 73 males and 53 females. They were randomly divided into the control group (64 cases) and the naloxone group (62 cases), with the ages being 60.0 ± 9.1 years and 58.4 ± 8.6 years, respectively. There were no significant differences between the two groups in terms of age, gender, income, education levels, or hair arsenic concentrations (all P > 0.05). After treatment, the decrease in DLQI scores was significantly higher in the naloxone group than in the control group (-8.79 ± 6.84 vs. -5.19 ± 8.10; P = 0.008). However, there were no significant changes in depression symptoms, anxiety symptoms, or quality of sleep between the naloxone group and control group (all P > 0.05). Linear regression analysis showed that naloxone significantly affected DLQI with a crude regression coefficient of -3.60 (95% CI: -6.25, -0.96; P = 0.008). Stratification analysis revealed that patients with the κ-opioid receptor gene rs1051660 (wild-type, CC) responded better to the treatment than those with the mutated genotype (CA), and there was a significant interaction between the rs1051660 genotype and therapeutic drugs in relation to DLQI changes ( P = 0.014) . Conclusion:Naloxone can effectively improve health-related quality of life in patients with chronic arsenic exposure-related pruritus, and its efficacy is modified by the gene polymorphism of the κ-opioid receptors.

Objective:To share our experience of single-port transoral Da Vinci robotic surgery for laryngeal and pharyngeal benign tumors.Methods:Three patients aged over 18 years and diagnosed respectively with epiglottic cyst, aryepiglottic fold cyst and thyroglossal duct cyst at tongue base were included who received operations in Hainan Hospital of Ruijin Hospital affiliated to Shanghai Jiao Tong University School of Medicine (Boao Research Hospital of Hainan) between August 1, 2023 and April 10, 2024. There were 1 male and 2 females, with an average age of 59 years old. The clinical diagnosis of these 3 patients was respectively epiglottic cyst, aryepiglottic fold cyst and thyroglossal duct cyst at tongue base. Intraoperative conversion rate, blood loss, operation time, hospital stay, pain score and swallowing function score were analyzed.Results:All three patients successfully underwent the operations with the single-port Da Vinci robotic system. The clean-contaminated resection rate of the tumors was 100%. The conversion rate was nil. The blood loss was 0-7 ml. The operation time was 5-30 minutes. There were no adverse events such as loosening of teeth and soft tissue abrasions of pharyngeal side wall. The rate of oral feeding within 24 hours after surgery was 100%. No postoperative coughing, bleeding, or dyspnea occurred. The average length of hospital stay was 3.7 days. The VAS score decreased 3 days after surgery compared to 1 day after surgery. The swallowing function recovered 1 month after surgery.Conclusion:The single-port transoral robotic surgery for laryngeal and pharyngeal benign lesions is safe and efficient, with fewer complications.

Objective To investigate the value of flexible subtraction CE-Boost technique combined with low dosage contrast agents for CT pulmonary angiography(CTPA).Methods A total of 68 patients who would undergo CTPA examination due to suspected pulmonary embolism(PE)were prospectively enrolled and randomly divided into study group(n=34)and control group(n=34)using block randomization method.After injecting 25 ml contrast agents at a flow rate of 2.5 ml/s in study group or 50 ml contrast agents at a flow rate of 3.5 ml/s in control group,CTPA scanning were performed with identical parameters.For images in study group,hybrid iterative reconstruction was performed,followed by flexible subtraction CE-Boost post-processing to obtain CE-Boost CTPA.For images in control group,conventional CTPA was obtained with hybrid iterative reconstruction.Subjective and objective evaluations of image quality were compared between groups.Taken the final clinical diagnosis as standard,the accuracy rate of diagnosing PE were compared between groups.Results There were 7 cases of pulmonary artery main trunk PE and 15 cases of pulmonary lobe-level PE in study group,while in control group there were 8 cases and 17 cases.No statistical difference of subjective scores of CTPA was found between groups(P＞0.05).CT values of the main pulmonary artery,bilateral pulmonary artery trunks and lower lobes of both lungs,signal-to-noise ratio or contrast-to-noise ratio in CTPA were not significantly different between groups(all P＞0.05),while no significant difference of the accuracy rate of CTPA for diagnosing PE of pulmonary artery main trunk(100％[7/7]vs.100％[8/8])nor pulmonary lobe-level PE(86.67％[13/15]vs.88.24％[15/17])was detected between groups(all P＞0.05).Conclusion Flexible subtraction CE-Boost technique combined with low dosage contrast agents for CTPA could reduce contrast agent dosage without affecting image quality.