Ricin is a plant toxin isolated from the seed of the castor plant(Ricinus communis). As a typical II ribosome inactivating protein,ricin consists of two polypeptide chains named ricin toxin A chain(RTA)and ricin toxin B chain(RTB),linked via a disulfide bridge. RTB binds to both glycopro?tein and glycolipid at the surface of the target cell and mediates ricin to be endocytosed and transported retro?gradely to the endoplasmic reticulum. After being reduced and retrotranslocated to the cytosol,RTA mediates its toxicity due to its activity of a RNA N- glycosidases. Aside from its main toxic effect of protein synthesis inhibition,ricin also displays other properties that contribute to its toxicity such as inducing apoptosis,cytokine secreting and peroxidation. Ricin is stable and can be easily isolated. It has many routes of intoxication with no specific antidotes. Due to its natural abundance,remarkable toxicity,and the potential to be used in biological warfare as well as terrorist attacks,ricin has been classified as a Category B biothreat agent. Here we reviewed its history as a biothreat agent,constitu?tion,intoxication mechanism,detection methods and the development of specific antitodes.

Objective To assess the usefulness of combined dual-energy CT pulmonary angiography (DE-CTPA) and indirect CT venography (CTV) in the diagnosis of venous thromboembolism (VTE).Methods Forty-nine patients with leg swelling suspected of pulmonary embolism (PE) underwent both DE-CTPA combined with CTV and lower extremity venous ultrasound (US) in 1-2 days prior to CT.Image quality of CTPA and dual energy lung perfusion image (DEPI) was rated using a 5-point scale and the coherence between CTPA and DEPI was analyzed by Kappa statistics.The ability of CTV and US in the diagnosis of deep venous thrombosis (DVT) was compared by Chi-square test.Results Twenty-nine of 49 patients were identified with PE by DE-CTPA,including 28 patients identified by CTPA and one more by DEPI,and 21 patients were found to have both PE and DVT.Both DE-CTPA and DEPI had positive findings for pulmonary embolism in 19 patients and both had negative findings in 18 patients.There was a moderate agreement between DEPI and DE-CTPA in the assessment of PE (Kappa value =0.7534).Thirty-eight patients with DVT were identified by US,while 35 patients were identified by CTV.Among the 35 patients with DVT identified by CTV,pelvic veins were involved in 25 patients,while the inferior vena cava was involved in 3 patients.There was no significant difference between CTV and US in the diagnosis of DVT(P =0.625).The detection rate of VTE with DE-CTPA combining CTV was 30.6％ higher than that with CTPA alone.Conclusions The combined DE-CTPA and CTV achievesone-stop examination.It not only provides evaluation of PE and DVT and increases detection of VTE,but also depicts perfusion defect of pulmonary parenchyma that corresponds to PE.

Objective:To survey and supervise the risk of infection control and radiation safety in the radiological diagnostic workplace for COVID-19, and provide data support for the safety protection of radiographers and related staff.Methods:4 emergency hospitals for COVID-19 including 2 makeshift hospitals, module hospital and brick pattern hospital in Hubei province were performed for testing and evaluation of imaging performance and radiological protection for the 8 new installed CT scanners and places according to the national standards of WS 519-2019 and GBZ 130-2013. The infection control safety factors such as the layout of the equipment room were monitored and investigated. Two COVID-19 designated hospitals including general hospital and infectious disease specialized hospital were selected to carry out field investigation and sampling of environmental biological samples for 4 CT rooms. Then the samples were detected for the nucleic acid of novel coronavirus. The results of radiodiagnostic workplace overall arrangement, infection prevention and the nucleic acid testing were analyzed, and the biological safety reliability and risk point were evaluated.Results:The indicators of imaging performance and radiation protection for 8 CT scanners in emergency hospitals could meet the requirements of national standards.Each of 2 makeshift hospitals had 3 CT rooms with the area of 38.8 m 2 and 4 mm Pb equivalent thickness of protective shielding. The CT rooms in module hospital and brick pattern hospital were 20.0 m 2, and 35.8 m 2 in areas, with 4 mm Pb equivalent and 3 mm Pb equivalent thickness of protection shielding, respectively. The 8 radiological diagnostic workplaces of the emergency hospitals were designed and constructed based on " three zones with two passage ways" . The result of the nucleic acid test indicated that the positive samples were found at the multiple sites such as scanning bed, internal of gantry and ground touched by patients in CT scanning room. The areas such as console panel and ground were risked of pollution by the virus infected hands and feet of radiographers. In addition, the similar positive samples were found in the areas in scanning room with no touch of patients, such as observation window and air outlet. Conclusions:8 CT scanners and rooms in 4 emergency hospitals basically meet the requirements of imaging performance and radiation protection. The disinfection of COVID-19 radiodiagnostic workplace should be standardized.

Objective:To investigate the value of the size-specific dose estimate (SSDE) on dose estimations of children's head CT scans.Methods:A retrospective study was conducted on plain head CT scans of 252 patients with the 64-row detector CT device of Discovery 750HD in the Union Hospital, Tongji Medical College, Huazhong University of Science and Technology from January to September in 2019. The volume CT dose index (CTDI vol)values were recorded. The head circumference (HC), area, and CT value were measured using a self-developed computer program, and the water equivalent diameter (WED), size-specific conversion factors ( f293 and f220), and absorbed dose (SSDE 293 and SSDE 220) were calculated according to the AAPM reports 293 and 220.The patients were divided into three groups by the quartering meth odaccording to their HC(<47.8 cm, 47.8-52.7 cm, >52.7 cm)and four groups based on their ages(0-2, 3-6, 7-10 and 11-14 years old). The difference between parameters ( f220 and f293, SSDE 220 and SSDE 293、SSDE 293 and CTDI vol) were compared for different groups, and the correlation of HC with f293 and SSDE 293 was analyzed. Results:There was an overestimation of f220 by 11.11% ( t=252.61, P<0.05) compared with f293. SSDE 220 was overestimated by 10.31% ( t=228.21, P<0.05) compared with SSDE 293, and SSDE 293 was underestimated by 9.60% ( t=-31.34, P<0.05)compared with CTDI vol. For the three HC groups, SSDE 220 was overestimated by 8.54%, 10.37%, and 11.57% ( t=73.73, 438.58, 275.52, P<0.05)compared with SSDE 293, and SSDE 293 was underestimated by 1.30%, 9.79%, and 14.61% ( t=-1.91, -60.95, -47.64, P<0.05)compared with CTDI vol. For the four age groups SSDE 220 was overestimated by 8.45%, 10.00%, 10.57%, and 11.36% ( t=63.58, 232.29, 247.84, 302.95, P< 0.05)compared with SSDE 293, and SSDE 293 was underestimated by 1.49%, 8.27%, 10.63%, and 13.78% ( t=-1.83, -28.27, -37.30, -49.80, P< 0.05)compared with CTDI vol. Furthermore, HC was highly correlated with f293 and SSDE 293 ( r2=0.88 and 0.76, respectively, P< 0.05). Conclusions:The radiation dose in children′s head CT scanning can be more accurately estimated according to the AAPM Report 293, while it can be overestimated by CTDI vol. Meanwhile, the CT radiation dose can be patently overestimated with the AAPM Report 220 compared with Report 293.HC is closely correlated with f293 and SSDE 293 and it can be used to estimatee more accurately for SSDE and the radiation dose received by children during head CT scanning.

Objective:To compare the image quality of turbo gradient and spin echo-BLADE diffusion weighted imaging (TGSE-BLADE-DWI) with that of readout segmentation of long variable echo-trains (RESOLVE) at the sellar region.Methods:From September 15 th, 2019 to February 15 th, 2020, 38 patients with suspected sellar abnormalities were enrolled prospectively to perform RESOLVE and TGSE-BLADE-DWI at a 3.0 T MR scanner in Department of Radiology, Union Hospital, Tongji Medical College of Huazhong University of Science and Technology. Totally, 32 patients were identified with sellar lesions. The DWI images were evaluated subjectively and objectively. Two experienced radiologists scored images of the two DWI methods for anatomical structures (including the internal carotid arteries, optic chiasm, pituitary stalk and pituitary gland), lesion conspicuity, susceptibility artifacts, geometric distortions and overall image quality using a five-point scale respectively. Objective parameters on the images of the two DWI methods were analyzed, including lesion size, signal to noise ratio (SNR) and apparent diffusion coefficient (ADC). The consistency of subjective scores of two radiologists was tested by Kappa test. Paired t-test, Wilcoxon signed rank test, Kappa statistics were used for statistical evaluation. Results:TGSE-BLADE-DWI performed significantly better than RESOLVE in depicting the sellar anatomical structures, lesion conspicuity, geometric distortion and overall image quality (all P<0.05). There were no significant differences in SNR, maximum longitudinal diameter of lesions and ADC of lesions between the two DWI methods(all P>0.05). The maximum transverse diameter measured by TGSE-BLADE-DWI was significantly smaller than that of RESOLVE ( Z=3.31, P=0.001). Conclusions:Compared with RESOLVE, TGSE-BLADE-DWI is superior in depicting the anatomical structures, decreasing susceptibility artifacts and geometric distortions at the sellar region and effectively improves the image quality of DWI, which has great value in clinical applications.