Objective To investigate the morphology,size and density characteristics of adult normal thyroid and to establish the normal reference range of thyroid.Methods 317 patients without thyroid disease underwent head and neck computed tomography angiography (CTA)examination from Jun.2011 to Jun.2012 in the First Affiliated Hospital of Chongqing Medical University.Their data were analyzed.The thyroid morphology including the outside angle,width,thickness,isthmus was observed and measured.Plain scan and arterial phase CT values of thyroid gland were measured.The age and sex of patients were recorded.The left and right lobe on the thyroid dimension and density were investigated,and the index 95％ normal reference range was calculated.Results ① Morphology:normal thyroid glands were butterfly-shaped on the axis,accounting for 95.9％(304/317),and absence of thyroid gland isthmus accounted for 4.1％(13/317).② There was no significant difference for the thyroid lateral angle between the lobes and sexes(P＞0.05).There was significant difference between age groups(P=0.00).The 95％ reference range:the outside angle was 111.7°± 31.6° in patients younger than 60 years old,and 101.3°± 36.7° in patients of or older than 60 years old.③ The dimensions of the right lobe were longer than those of the left.The dimensions of the lobes in males were longer than those in females.There was no statistical difference among decades(P＞ 0.05).There was no significant difference in the thickness of thyroid isthmus between genders and among different age groups (P＞ 0.05).95％ reference range of the thickness of thyroid isthmus was 1.1-7.3 mm.④ There was statistical difference for the plain scan and enhanced CT values between lobes and sexes and among age groups (P＜0.05).95％ reference range needed to be separately formulated between the lobes,sex and age＜30 years and ≥30 years.Conclusion Studying the morphology,size and density characteristics of adult normal thyroids can help to establish normal thyroid imaging anatomical data in this region,and provide reference basis for imaging diagnosis of thyroid disease.

Objective To investigate the morphological changes of the head,body and tail of the hippocampus in patients with Alzheimer's disease (AD).Methods Totally 30 AD (AD group),30 mild cognition impairment (MCI) patients (MCI group) and 30 normal old persons (normal control group) underwent brain MR scan.Based on the MR images,the head,body and tail of the hippocampus were segmented and the volume was measured.The difference of the volume in total,head,body and tail of hippocampus in AD group,MCI group and normal control group were compared.The correlation between hippocampal volume and the scores of neurological assessment scale was analyzed.Results The left total,head,body and tail volume were greater than those of the right side in 3 groups (all P＜0.05).For the comparison of total volume of left and right sides among the 3 groups,AD group was less than normal control group (both P＜0.01) and MCI group (both P＜0.05),MCI group was less than normal control group (both P＜0.05).Compared with the normal control group,the head,body and tail volume of hippocampus of both sides were decreased in AD group (all P＜0.05) and the volume of left head,body and right head of hippocampus in MCI group were decreased (all P＜0.05).Both sides hippocampus's head and body volume of AD group were less than those of MCI group (both P＜0.05).The scores of minimum mental state examination (MMSE) were positively correlated with the total and the head,body,tail volume of bilateral hippocampus.Except volume of left tail,there were negative correlations between the scores of activities of daily living (ADL),clinical dementia rating (CDR) and the volume of total and head,body,tail of bilateral hippocampus,which were positively correlated with Montreal cognitive assessment (MoCA) score.Conclusion The volume of bilateral hippocampus was significantly reduced in AD patients.The head of hippocampal volume was significantly reduced and the body and tail was not obvious.

Objective To explore the value of quantitative parameters of spectral CT imaging in the diagnosis of non-small cell lung cancer (NSCLC) with different pathological types. Methods One hundred and thirty-six patients with NSCLC proved by pathology underwent chest plain and enhanced CT scan with gemstone spectral imaging (GSI) mode by Discovery CT750 HD, including 57 cases of squamous cell carcinoma (SQCC) and 79 cases of adenocarcinoma (ADC). All the cases were divided into two groups of tumor diameter>2 cm (120 cases, including 50 cases of SQCC and 70 cases of ADC) and diameter≤2 cm (16 cases, including 7 cases of SQCC and 9 cases of ADC). The slope between 40 and 65 keV(K40-65 keV) of spectral attenuation curve, effective atomic number (Eff-Z) and calcium concentration in plain scan (PS) and K40-65 keV of spectral attenuation curve, iodine concentration and water concentration in arterial phase (AP) of SQCC and ADC in the two groups were measured and compared respectively. Furthermore, all cases were classified according to the trend of spectral attenuation curve in PS. These quantitative parameters satisfying normal distribution were compared by two independent samples t test, while those parameters not satisfying normal distribution were compared by rank sum test. ROC curves was drawn for these parameters with statistical difference and area under the curve (AUC) was used to measure the differential diagnostic performance of each parameter. Chi square test was used to compare the differences of the trend of spectral attenuation curve in PS between SQCC and ADC. Results In the group of diameter>2 cm: (1) Comparison of quantitative parameters of spectral CT in PS:K40-65 keV, Eff-Z and calcium concentration of ADC were 0.69 ± 0.56, 7.76±0.19, and (4.11±2.93) mg/cm3, respectively. The corresponding parameters of SQCC were 0.19± 0.23, 7.59 ± 0.14, and (1.25 ± 1.59) mg/cm3, respectively. These parameters of ADC were significantly higher than SQCC (Z=-7.000,-6.249, t=-6.884, P<0.01). (2) Comparison of quantitative parameters of spectral CT in AP:K40-65 keV, iodine concentration and water concentration of ADC were 2.61 ± 1.72, (1.24 ± 0.77) mg/cm3, and (1024.46 ± 14.06) mg/cm3, respectively. The corresponding parameters of SQCC were 2.00 ± 1.79, (0.94±0.86) mg/cm3, and (1027.77±9.47) mg/cm3, respectively. The difference between ADC and SQCC was statistically significant (Z=-3.082,-2.946,-3.045, P<0.01). (3) ROC curve analysis showed that these quantitative parameters in PS were helpful in differentiating SQCC and ADC, especially K40-65 keV of spectral attenuation curve in PS. The AUC for it was 0.876. The sensitivity and specificity were 91.4%and 80.0%, respectively. (4)According to the trend of spectrum attenuation curve in PS, type Ⅰ was more common in SQCC, while typeⅡwas more common in ADC (χ2=54.208, P<0.01). In the group of diameter≤2 cm:There was no significant difference in all quantitative parameters between ADC and SQCC (P>0.05). The trend of spectrum attenuation curve in PS of all cases showed type Ⅱ. Conclusions Lung ADC and SQCC have different quantitative parameters in spectral CT imaging. These quantitative parameters are valuable in classifying the pathological type of NSCLC with diameter more than 2 cm.

Objective The purpose of this study is to explore the clinical value of CT angiography( CTA) in the diagnosis of multiple intracranial aneurysms.Methods The data of CTA and DSA from 74 patients with multiple intracra-nial aneurysms from July 2011 to March 2015 were reviewed retrospectively.Results One hundred seventy-seven aneu-rysms were detected by DSA, and 175 aneurysms were detected by CTA.Among the aneurysms identified by CTA, 4 aneu-rysms were false positive and the correct detection rate of CTA was 96.6%.One hundred sixty-five aneurysms identified by CTA were confirmed by DSA and the correct diagnostic rate of CTA was 96.5%.CTA failed to detect 6 aneurysms and mis-diagnosed 10 aneurysms.Conclusions The correct detection rate and diagnostic rate of CT angiography ( CTA) in multiple intracranial aneurysms is relatively high.But previous surgery, spasm of the vessels, the size and number of aneurysms, radiologists'experience can influence the accuracy of ( CTA) in the diagnosis of multiple intracranial aneurysms, indicating that we should combine CTA with DSA to avoid the misdiagnosis and missed diagnosis.

Objective To compare the diagnostic value of MR examination with fast imaging employing steady state acquisition (FIESTA) and single shot fast spin echo (SSFSE) sequences for normal fetal thymuses.Methods Totally 366 normal fetuses were examined using MRI with FIESTA and SSFSE sequences,and the anatomy and MR manifestations of thymuses were observed.Kappa analysis and x2 test were performed.The transverse area (TA) and transverse diameter (TD) were measured on the "three vessel" level,while the superoinferior diameter (SID) was measured on the sagittal level.The mean value of these parameters at different gestational were calculated,and the regression equations of each parameter and gestational age were fitted.Results Two doctors had good agreements with the images of FIESTA and SSFSE sequences (Kappa=0.745,0.802,both P＜0.01).The clear rate of FIESTA and SSFSE sequences was 86.34％ (632/732) and 37.70％ (276/732) respectively,and the differences were significant (x2 =367.520,P＜0.001).The thymic size increased with the gestational age,and the regression equations and correlation coefficients were:TA =-5.80 + 0.35 ×gestational (r=0.820,P＜0.01),TD=-14.59+1.63×gestational (r=0.817,P＜0.01),and SID=-9.63+1.44×gestational (r=0.778,P＜0.01).Conclusion The subtle structure and contour of fetal thymus showed with FIESTA sequence are clearer than those of SSFSE sequence.MRI can clearly show fetal thymus after 22 weeks of pregnancy.

Objective To explore the value of prenatal MRI signs in diagnosis of placenta accreta.Methods MRI data of 163 pregnant women with suspected placenta accreta were retrospectively reviewed.According to the results of cesarean section,they were divided into placenta accreta group (n =136) or without placenta accreta group (n =27).The differencesof MRI signs between the two groups were compared.Taking cesarean section results as the gold standard,the sensitivity,specificity,positive and negative predictive value of MRI signs were calculated,respectively.Results Uterine bulging,abnormal vessels and hypointense T2WI bands at junction of placental and myometrium,as well as uterine recess had statistical differences between the two groups (all P＜0.05).No statistical difference of placental heterogeneity,focal interruptions in myometrial wall,uterine penetration and parametrium implantation nor protrusion of placenta into cervix was found between the two groups (all P＞0.05).The MRI signs of uterine penetration and parametrium implantation,uterine recess,protrusion of placenta into cervix yielded a specificity and positive predictive value of 100％,respectively.Conclusion Prenatal MRI has high efficacy in the diagnosis of placenta accrete.Placenta accrete should be highly suspected especially in the presence of uterine penetration and parametrium implantation,uterine recess and protrusion of placenta into the cervix.

Objective To explore the significance of lung window observation of head and neck CTA imaging for detecting lung lesions.Methods Head and neck CTA images of 1 000 patients were retrospectively analyzed.The patients were divided into the elderly group (≥ 60 years) and the young group (＜ 60 years),also smoking group and non-smoking group.The displaying of lung lesions on mediastinum window and lung window images were compared between the groups,respectively.Results Pulmonary lesions were found in 308 of 1 000 patients.The lesions were only visible on the lung window images in 283 patients,only visible in the mediastinum window images in 8 patients,visible in both lung and mediastinum window imaged in 17 patients.Lung cancers were detected in 8 patients,and ground glass lump in 1 patient was only visible in lung window images.The lesions only visible on lung window images in the elderly group (191/494,38.67％) was significantly higher than that in the young group (92/506,18.18％;x2=51.680,P＜0.001),and insmoking group (143/348,41.09 ％) was significantly higher than that in non-smoking group (140/652,21.47％;x2 =43.043,P＜0.001).Conclusion Lung window observation of head and neck CTA images can increase displaying rate of lung lesions,especially in elders (over 60 years) and long-term smokers.

Objective:To investigate the characteristics of thymus in patients with COVID-19, and to analyze the CT features and dynamic changes of thymus.Methods:Data of 241 patients diagnosed with COVID-19 admitted to Chongqing Three Gorges Central Hospital from Jan. to Mar. 2020 were retrospectively analyzed, and 242 consecutive subjects were selected as the control group from Nov. to Dec. 2019. The thymus classification, size, and average CT values between COVID-19 patients and the control group were compared, as well as those among different clinical types for COVID-19 patients, before and after treatment, were analyzed.Results:① The attenuation of the thymus: 64.7% (156/241) complete fatty replacement thymus, 17.8% (43/241) predominantly fatty thymus, 11.2% (27/241) approximately one-half fatty and one-half soft-tissue-attenuation thymus, and 6.2% (15/241) predominantly soft-tissue thymus in COVID-19 patients were found. 48.3% (117/242) complete fatty replacement thymus, 25.6% (62/242) predominantly fatty thymus, 10.3% (25/242) approximately one-half fatty and one-half soft-tissue-attenuation thymus, and 15.7% (38/242) predominantly soft-tissue thymus were found in the control group. Complete fatty replacement thymus was an independent factor affecting COVID-19 in 40 to 59 years old patients ( OR=3.071, P=0.000) . The rate of complete fatty replacement thymus: severe or critical type > common type > mild type. ② Size: There was no statistical difference of the thymus size between COVID-19 patients and the control group ( P>0.05) , no statistical difference among the mild type, common type and severe or critical type ( P>0.05) , no statistical difference between before and after treatment ( P>0.05) , and there was no correlation with treatment duration ( r=0.047, r=0.071) . ③ Density: There was no statistical difference of the CT value of thymus between COVID-19 patients and the control group ( P>0.05) , no statistical difference among the mild, common and severe type ( P>0.05) . One patient had a 17 HU increase in thymus density after treatment, but there was no statistical difference in 78 patients in thymus CT values between before and after treatment ( P>0.05) , and there was no correlation with treatment duration (r=0.013) . Conclusions:COVID-19 patients have a high rate of complete fatty replacement thymus. And the heavier the clinical classification, the higher the rate of complete fatty replacement thymus. Complete fatty replacement thymus is a risk factor for COVID-19 patients in 40 to 59 years old.

Objective To analyze the CT features of solitary pulmonary nodules(SPN) in patients with malignant tumor with the aim of improving its diagnosis and differential diagnosis in this special background .Methods From May 2014 to De-cember 2018, the CT data of 76 pathologically confirmed SPNs in patients with malignant tumor were retrospectively analyzed . The CT features of SPNs, including density, morphology and change of peripheral lung field and adjacent structures, were mainly analyzed.The characteristics of different types of nodules and their differences were summarized .Results Among the 76 SPNs, there were 41(53.9％) primary lung cancers, 14(18.5％) metastatic tumors, and 21(27.6％) benign lesions(in-cluding 12 inflammatory nodules, 7 tuberculous nodules and 2 benign tumors).Of all nodules, there were 57(75％) solid nodules, including 23(40.4％) primary lung cancers which mainly manifested as nodules with rough margin , close to adjacent vessel and bronchus and usually had internal or edge features(19, 82.6％), 14(24.6％) metastatic tumors which mainly showed as round or oval, homogeneous density, smooth margin nodules(12, 85.7％), and 18(31.6％) inflammatory nodules which mainly showed as lesions with rough and blurred margin accompanied by peripheral patch or fibrosis (14, 77.8％). There were 19(25％) sub-solid nodules, including 18(94.7％) primary lung cancers, which mainly manifested as nodules with heterogeneous density and clear border(14, 77.8％).There was only 1(5.3％) sub-solid inflammatory nodule.Conclu-sion The pathological nature of SPNs in patients with malignant tumors is various .Understanding their CT characteristics is helpful for diagnosing and differentiating and providing useful information for further treatment .

Objective:To evaluate the application value of bismuth shielding combined with organ tube current modulation (X-care) in brain CT scanning by measuring the radiation dose of sensitive organs.Methods:The head and neck phantom was scanned with Siemens dual source CT at the same volume CT dose index (CTDI vol) by X-care, bismuth shielding and x-care combined with bismuth shielding, and by dual energy CT angiography (DE-CTA) with and without bismuth shielding. The CT values of cerebral vessels, adjacent brain tissues and cerebrospinal fluid and image noise were measured, and the contrast noise ratio of cerebral vessels and brain parenchyma was calculated. Organ dose equivalent ( HT) was calculated by placing thermoluminescent personal dosimeter (TLD), and CTDI vol and dose length product (DLP) were recorded after each scan. Results:Under the same CTDI vol, the mean values of HT, lens with X-care, Bi shielding and X-care combined with Bi shielding were(37.89 ± 2.00), (42.20 ± 2.96) and (28.21 ± 1.31) mSv, respectively, significantly lower than those of conventional sequence scanning( F=186.52, P<0.05). The values of HT, thyroid with Bi shielding and X-care combined with Bi shielding were (0.77 ± 0.07) and (0.89 ± 0.08) mSv, lower than those of routine brain scan and X-care( F=103.26, P<0.05). The values of HT, lens and HT, thyroidof DE-CTA with bismuth shielding were (11.56 ± 1.04) and (0.32 ± 0.03) mSv, respectively, significantly lower than those without bismuth shielding( t=5.07, P<0.05). There was no significant difference in noise and CNR in routine brain scan between with and without X-care, bismuth shielding and X-care combined with bismuth shielding. There was no significant difference in noise and CNR in dual energy CTA scanning between with and without Bi shielding. Conclusions:Using bismuth shielding and organ tube current modulation, we can significantly reduce organ dose of lens and thyroid during brain CT scanning without sacrificing the image quality.