Objective To compare the effect on image quality of low-dose upper abdominal CT reconstructed with the new version of model-based iterative reconstruction (MBIRn) focused on low-contrast resolution (MBIRNR40),conventional model-based iterative reconstruction (MBIRc),adaptive statistical iterative reconstruction (ASIR) and routine-dose CT reconstructed with filtered back projection (FBP).Methods Water plantom at rest was scanned with CT,and spatial resolution and density resolution were compared among FBP,ASIR,MBIRc,and MBIRNR40.Sixty patients with 2 times CT in the upper abdomen within a year were enrolled.The initial examination was acquired at a standard radiation dose (noise index [NI] of 10 HU) and reconstructed with the conventional FBP algorithm.The follow-up scan was acquired at a lowdose (NI=20 HU) and reconstructed with the standard ASIR,MBIRc and MBIRNR40.All images were obtained with 0.625 mm slice thickness.CT values and noise of fat,muscle as well as the liver and kidney parenchyma were measured and CNR of liver and kidney parenchyma using the fat SD as background image noise were calculated.Two radiologists independently graded images for noise,sharpness of details of structures and lesion.The quantitative image quality scores of different reconstructions were analyzed with one-way ANOVA using FBP reconstruction as reference of standard.The degree of interobserver consistency was evaluated using Kappa test.Results The phantom study revealed the highest spatial resolution with MBIRc and highest density resolution with MBIRNR40 among all reconstructions.The dose-length product and radiation dose for the first inspection was (93.18 ± 41.21) mGy · cm,(1.40 ± 0.62) mSv,respectively,and were (368.03 ± 146.25)mGy · cm,(5.52 ± 2.19)mSv for the second inspection,representing an approximate overall dose reduction of 74.68％ and 74.64％.The mean image noise of muscle and fat for MBIRNR40 was significantly lower than that of MBIR,ASIR and FBP(P＜0.05).The mean CNR values of liver and spleen for MBIRNR40 were significantly higher than that of ASIR,MBIRc and FBP (P＜0.05).Two radiologists had a good subjective score consistency.Low-dose MBIRNR40 subjective image noise was the lowest,showing the most detailed on the upper abdominal detail structure and lesion edge,better than MBIRc,MBIRc was superior to routine-dose FBP,low dose ASIR was worst,the difference was statistically significant (P＜0.05).Conclusion With 75％ dose reduction in upper abdominal CT,the MBIRNR40 can provide well objective and subjective image quality than MBIRc and ASIR40,and the routine-dose FBP.

Objective To investigate the impact on image quality of bone imaging and patients safety when whole body bone imaging was performed on the sme day of renal dynamic imaging.Methods Fifty-three adult patients underwent renal dynamic imaging and whole body bone imaging were selected as observation group.Firstly,99 Tcm-DTPA renal dynamic imaging was performed,and 2 h later,99Tcm-MDP was injected,then whole body bone imaging was performed according to technological process.The other 53 patients received bone imaging only were selected as control group.After injection of 99Tcm-MDP immediately and 30 min,1 h,2 h,4 h,6 h,and 24 h later,physiological response of all patients was observed,and image quality of bone imaging between the two groups was compared.Then the ratio of subjective excellent images of the two groups was calculated.Radioactivity counting of T12,L4,iliac crest,middle humerus,middle femur and soft tissue above 2 cm of ilium on posterior image was measured,and target/non target (T/NT) was calculated.Statistical analysis was performed on the two groups.Results Adverse reaction was not found in all patients in two groups.Subjective excellent rate was 90.57％ (48/53) in observation group,and 92.45％ (49/53) in control group (x2 =0.12,P＞0.05).T/NT of T12,L4,middle humerus and middle femur had no significant differences between two groups (all P＞0.05).The difference of T/NT of iliac crest was statistically significant between two groups (t=3.45,P＜0.05).Conclusion Radionuclide renal dynamic imaging on the same day has no significant impact on the image quality of whole body bone imaging.

Objective To explore the 18F-FDG PET/CT features of sacral insufficiency fracture.Methods 18 F-FDG PET/CT imaging and clinical data of 8 patients with sacral insufficiency fracture were retrospectively analyzed.Results All 8 patients had different degrees of radioactivity uptake in sacra with the maximum standardized uptake value (SUVmax)from 2.7 to 7.2.Four patients had lesions in their left sacra,2 in the bilateral sacral wings and sacral promontories,1 in the bilateral sacral wings,and 1 in the left sacral wing and sacral promontory.There were 8 patients of longitudinal fractures in sacral wings,which of 6 patients involving S1-2 and 2 patients involving S3.Three patients had transverse fractures in sacral promontories,with 2 located at S2 and 1 at S3.The sacral bone density increased in 5 cases,and the density was not changed in 3 cases.Conclusion Sacral insufficiency fracture had specific 18F-FDG PET/CT characteristics.

Objective To explore changes of parameters of compressed nerve roots on diffusion tensor imaging (DTI) and relationship between the parameters and symptoms assessed with Oswestry disability index (ODI) and visual analogue score (VAS) in patients with lumbar disc herniation.Methods Twenty-five patients confirmed by surgery for single compressed nerve root with lumbar disc herniation who underwent DTI scanning before operation were enrolled.All patients were scored using ODI and VAS,and the areas of characteristic leg pain were compared with compressed nerve root for ODI and VAS.Results FA values of the compressed and normal nerve roots of these patients were 0.26 ±-0.05 and 0.36-±-0.05,while ADC values were (1.69 ±-0.32) × 10-3 mm2/s and (1.56 ± 0.21) × 10-3 mm2/s,respectively.Negative correlation was found between FA values of the compressed nerve roots and ODI (r=-0.88,P＜0.01) as well as VAS (r=-0.66,P＜0.01),but no correlation between ADC values and ODI (r=0.30,P =0.15) nor VAS (r=0.36,P =0.08) was found.Conclusion FA values derived from DTI maybe vital parameters of quantifying changes of structure of nerve root.Injury of nerve root structure in patients with lumbar disc herniation could be crucial for clinical symptoms.

Objective To observe value of high frequency ultrasound for inspection of T7-8 paravertebral space and adjacent structures.Methods Color Doppler ultrasonic diagnostic apparatus with linear array transducer (frequency 3-12 MHz) were used.Taking shoulder blade,ribs,thoracic spine and transverse process as anatomical marks,T7-8 paravertebral spaces of 30 normal adult (a total of 60 side) were examined.Ultrasonographic features of T7-8 paravertebral space and the adjacent structures were observed.Results T7-8 thoracic paravertebral showed as similar triangular shape with ultrasonography,interior solid homogeneously hypoechoic was noticed.Adjacent muscles of T7-8 paravertebral space included the trapezius,latissimus dorsi,spinalis,semispinalis,multifidus,rotatores and intercostal muscles.Color Doppler or power Doppler flow imaging could demonstrate posterior intercostal artery in the paravertebral space.Conclusion High frequency ultrasound can clearly show T7-8 paravertebral space and adjacent structures,thus providing ultrasonic references for clinical diagnosis and treatment of lesions of thoracic space and adjacent structures.

4D Flow MRI is a new phase contrast MR technique,which can spatially encode velocity in three-direction,collect multi-directional blood flow data,and result in complex three-dimensional dynamic parameters.4D Flow MRI is more accurate and comprehensive than 2D phase contrast MRI and Doppler echocardiography.However,4D Flow MRI have some disadvantages,such as long scanning time,noise,etc.,which are the future key technical issues to be addressed.4D Flow MRI technology has a great potential in clinical applications,such as intracranial vascular diseases,cardiac magnetic resonance imaging,and other aspects of aortic diseases.Research advances in clinical application of 4D Flow MRI were reviewed in this paper.

Objective To quantitatively observe the value of relationship between nodule and corresponding capsular with ultrasonography in assessment of malignant and benign thyroid nodules.Methods A total of 79 cases with subcapsular tumors of thyroid gland confirmed pathologically were analyzed retrospectively,and the relationship between tumors and capsule was analyzed.Longitudinal diameter of nodules (from the junction of nodule and capsule to the deepest of nodule,V) and distance from nodule protruding thyroid capsule to the highest point of nodule (L) were measured,and L/V was evaluated.Diagnostic efficiency of L/V in diagnosis of malignant thyroid nodule was evaluated.Results The average L/V of benign and malignant nodules was 0.241± 0.041 and 0.162± 0.054,respectively (t=-7.367,P＜0.01).The area under ROC curve of L/V in diagnosis of benign and malignant thyroid nodules was 0.87 (P＜0.01).When L/V=0.225,the sensitivity was 82.17％,and the specificity was 87.53％;when L/V=0.245,the sensitivity was 67.10 ％,and the specificity was 95.12％.Conclusion Ultrasonography can clearly show the relationship between thyroid nodules and capsule,and L/V can be used for differential diagnosis of benign and malignant thyroid nodules.

Objective To investigate the value of ultrasonic direct signs and indirect signs in diagnosis of rotator cuff tears (RCTs).Methods Fifty-two patients underwent ultrasonography before arthroscopy were enrolled.The efficacy of ultrasonic direct and indirect signs in diagnosis of RCTs was calculated,and the accuracy of ultrasonic direct signs in diagnosis of subtypes for RCTs was compared with arthroscopic results.Results The accuracy of ultrasonic direct signs in diagnosis of the presence of tears,full-thickness tears and partial-thickness tears was 90.38％ (47/52),96.15％ (50/52)and 86.54％ (45/52),respectively.Additionally,the consistency of ultrasonic direct signs in diagnosis of subtypes for RCTs with arthroscopic results was good.With regard to ultrasonic indirect signs,the specificity of effusions including all subacromial/subdeltoid bursa effusions,intra-articular fluid and biceps tendon sheath effusions,subdeltoid bursa hernia and cartilage demarcation sign was 80.95％(17/21),90.48％ (19/21) and 95.24％ (20/21),respectively.Conclusion Ultrasonic direct signs combined with indirect signs have high clinical value in diagnosis of subtypes for RCTs.

Objective To explore 18F-FDG PET/CT characteristics of extramedullary relapse in patients with acute leukemia (AL).Methods Thirty AL patients with extramedullary relapse were retrospectively evaluated.The infiltrated organs or tissues and the maximum standardized uptake value (SUVmax) were recorded and compared between patients with acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML).FDG uptake pattern of bone marrow was also recorded.Results Forty-five extramedullary lesions were found in 16 ALL patients,while 29 were found in 14 AML patients.The average SUVmax was 7.38±4.46 in ALL patients and 4.87±2.66 in AML patients (t=3.022,P=0.003).Among ALL patients,lymph node and soft tissue involvement were detected each in 10,with SUVmax of 6.38 ± 3.55 and 10.12± 5.48,respectively.Among AML patients,lymph node and soft tissue involvement were detected in 6,with SUVmax of 4.82 ±1.43 and 6.60±4.58,respectively (P＞0.05).Multiple focal bone marrow uptakes of FDG were found in 5 of 5 intramedullary recurrence ALL patients and 2 of 5 intramedullary recurrence AML patients.The other 3 intramedullary recurrence AML patients showed diffuse bone marrow uptake.Conclusion There are certain imaging characteristics of 18 F-FDG PET/CT in extramedullary relapse of AL.The common relapse sites are lymph node and soft tissues in both ALL and AML.FDG uptakes of extramedullary relapse lesions in ALL are significantly higher than those of AML.Multiple focal bone marrow uptake of FDG is valuable in predicting intramedullary recurrence.

Objective To explore the application value of CEUS in diagnosis of renal occupying lesions.Methods Totally 67 patients with renal occupying lesions underwent conventional ultrasound and CEUS before surgical operation.CEUS enhancement characteristics were observed and compared between 40 patients with clear cell renal cell carcinoma (CCRCC)and 14 patients with angiomyolipoma (AML).Meanwhile the time-intensity curves were analyzed,including peak intensity (IMAX),rise time (RT),time-to-peak time (TTP) and mean transit time (mTT).Results There were significant differences in enhancement patterns,degrees,homogeneity of enhancement and pseudocapsule sign between CCRCC and AML (all P＜0.01).Compared with AML,IMAX of CCRCC was higher,RT and mTT were both earlier (P＜0.05).The sensitivity,specificity and accuracy of CEUS in diagnosis of malignant renal occupying lesions was 91.49 ％ (43/47),75.00 ％(15/20) and 86.57％ (58/67),respectively.Conclusion CEUS combined with quantitative analysis software is helpful to diagnosis and identification of CCRCC and AML.