Optimal Parameters for Virtual Mono-Energetic Imaging of Liver Solid Lesions / 中国医学科学院学报

Objective To explore the optimal parameters for virtual mono-energetic imaging of liver solid lesions. Methods A retrospective analysis was performed on 60 patients undergoing contrast-enhanced spectral CT of the abdomen.The iodine concentration values of hepatic arterial phase images and the CT values of different mono-energetic images were measured.The correlation coefficient and coefficient of variation were calculated. Results The average correlation coefficients between iodine concentrations and CT values of hepatic solid lesion images at 40,45,50,55,60,65,and 70 keV were 0.996,0.995,0.993,0.989,0.978,0.970,and 0.961,respectively.The correlation coefficients at 40(P=0.007),45(P=0.022),50 keV (P=0.035)were higher than that at 55 keV,and the correlation coefficients at 40 keV(P=0.134) and 45 keV(P=0.368) had no significant differences from that at 50 keV.The coefficients of variation of the CT values at 40,45,and 50 keV were 0.146,0.154,and 0.163,respectively. Conclusion The energy of 40 keV is optimal for virtual mono-energetic imaging of liver solid lesions in the late arterial phase,which is helpful for the diagnosis of liver diseases.

A semi-supervised material quantitative intelligent imaging algorithm for spectral CT based on prior information perception learning / 南方医科大学学报

OBJECTIVE@#To propose a semi-supervised material quantitative intelligent imaging algorithm based on prior information perception learning (SLMD-Net) to improve the quality and precision of spectral CT imaging.@*METHODS@#The algorithm includes a supervised and a self- supervised submodule. In the supervised submodule, the mapping relationship between low and high signal-to-noise ratio (SNR) data was constructed through mean square error loss function learning based on a small labeled dataset. In the self- supervised sub-module, an image recovery model was utilized to construct the loss function incorporating the prior information from a large unlabeled low SNR basic material image dataset, and the total variation (TV) model was used to to characterize the prior information of the images. The two submodules were combined to form the SLMD-Net method, and pre-clinical simulation data were used to validate the feasibility and effectiveness of the algorithm.@*RESULTS@#Compared with the traditional model-driven quantitative imaging methods (FBP-DI, PWLS-PCG, and E3DTV), data-driven supervised-learning-based quantitative imaging methods (SUMD-Net and BFCNN), a material quantitative imaging method based on unsupervised learning (UNTV-Net) and semi-supervised learning-based cycle consistent generative adversarial network (Semi-CycleGAN), the proposed SLMD-Net method had better performance in both visual and quantitative assessments. For quantitative imaging of water and bone materials, the SLMD-Net method had the highest PSNR index (31.82 and 29.06), the highest FSIM index (0.95 and 0.90), and the lowest RMSE index (0.03 and 0.02), respectively) and achieved significantly higher image quality scores than the other 7 material decomposition methods (P < 0.05). The material quantitative imaging performance of SLMD-Net was close to that of the supervised network SUMD-Net trained with labeled data with a doubled size.@*CONCLUSIONS@#A small labeled dataset and a large unlabeled low SNR material image dataset can be fully used to suppress noise amplification and artifacts in basic material decomposition in spectral CT and reduce the dependence on labeled data-driven network, which considers more realistic scenario in clinics.

A nonlocal spectral similarity-induced material decomposition method for noise reduction of dual-energy CT images / 南方医科大学学报

OBJECTIVE@#To propose a nonlocal spectral similarity-induced material decomposition network (NSSD-Net) to reduce the correlation noise in the low-dose spectral CT decomposed images.@*METHODS@#We first built a model-driven iterative decomposition model for dual-energy CT, optimized the objective function solving process using the iterative shrinking threshold algorithm (ISTA), and cast the ISTA decomposition model into the deep learning network. We then developed a novel cost function based on the nonlocal spectral similarity to constrain the training process. To validate the decomposition performance, we established a material decomposition dataset by real patient dual-energy CT data. The NSSD-Net was compared with two traditional model-driven material decomposition methods, one data-based material decomposition method and one data-model coupling-driven material decomposition supervised learning method.@*RESULTS@#The quantitative results showed that compared with the two traditional methods, the NSSD-Net method obtained the highest PNSR values (31.383 and 31.444) and SSIM values (0.970 and 0.963) and the lowest RMSE values (2.901 and 1.633). Compared with the datamodel coupling-driven supervised decomposition method, the NSSD-Net method obtained the highest SSIM values on water and bone decomposed results. The results of subjective image quality assessment by clinical experts showed that the NSSD-Net achieved the highest image quality assessment scores on water and bone basis material (8.625 and 8.250), showing significant differences from the other 4 decomposition methods (P < 0.001).@*CONCLUSION@#The proposed method can achieve high-precision material decomposition and avoid training data quality issues and model unexplainable issues.

Role of Dual-layer Detector Energy Spectral CT in Resting Myocardial Perfusion Imaging for Patients with Normal Coronary Artery / 中国医学科学院学报

Objective To investigate the role of dual-layer detector energy spectral CT in resting myocardial perfusion imaging for patients with normal coronary artery. Methods One hundred and fifty-six patients with suspected coronary heart disease underwent dual-layer detector energy spectral CT coronary angiography,and resting myocardial perfusion imaging was performed for 28 patients with normal coronary artery.According to American Heart Association's 17-segmentmodel,the iodine density and effective atomic number(Z

Reproducibility Analysis of Iodine Concentrations of Abdominal Parenchymal Organs Based on Spectral CT / 中国医学科学院学报

Objective To investigate the intra-and inter-observer reproducibility of iodine concentrations of abdominal parenchymal organs based on spectral CT.Methods The water-free iodine images of the venous phase were retrospectively obtained from 50 patients with abdominal dynamic spectral CT scans.The iodine concentrations were measured in the left,right and caudate lobes of liver,spleen,pancreas and bilateral kidneys.Intraclass correlation coefficient(ICC)and Bland-Altman plot were employed to analyze the intra-and inter-observer reproducibility.Results The intra-observer ICCs of the left,right and caudate lobes of liver,spleen,pancreas,and left and right kidneys were 0.938(0.894,0.965),0.932(0.884,0.961),0.939(0.895,0.965),0.947(0.909,0.970),0.912(0.851,0.949),0.946(0.906,0.969)and 0.907(0.842,0.946),which indicated good intra-observer reproducibility.The inter-observer ICCs of the left,right and caudate lobes of liver,spleen,pancreas,and left and right kidneys were 0.947(0.909,0.970),0.927(0.875,0.958),0.943(0.902,0.968),0.956(0.924,0.975),0.934(0.887,0.962),0.927(0.875,0.958)and 0.892(0.818,0.937),which indicated good inter-observer reproducibility.Bland-Altman plots presented that more than 95% points of the intra-observer differences located within 95% CI of limits of agreement for the caudate lobe of liver,spleen,pancreas and bilateral kidneys,which was same as inter-observer differences of the caudate lobe of liver,spleen and right kidney.Conclusion The iodine concentration measurement based on the spectral CT presented good intra-and inter-observer reproducibility for the caudate lobe of liver and spleen.

The diagnostic value of dual-layer detector spectral CT calcium suppression technique in acute and chronic thoracolumbar compression fractures / 中华放射学杂志

Objective:To evaluate the diagnostic value of spectral CT calcium suppression (CaSupp) technique in acute and chronic thoracolumbar compression fractures.Methods:A total of 31 patients with thoracolumbar compression fractures were given spectral CT and MR scans from March to October 2020 in the Second Hospital of Shanxi Medical University. Acute and chronic vertebral fractures were diagnosed by doctor A and B based on CaSupp diagram, and the consistency between the two doctors was evaluated by Kappa test. CT values of fractured vertebra and adjacent normal vertebra were measured on conventional CT and CaSupp graphs respectively, and the CT value difference between fractured vertebra and adjacent vertebra was calculated. Independent sample t-test was used to compare the conventional CT value and CT value difference, CaSupp CT value and CT value difference between acute and chronic fractured vertebra. Using MRI as the gold standard, the ROC curves were drawn to evaluate the subjective diagnostic efficacy of physicians and the diagnostic efficacy of each quantitative parameter. DeLong test was used to compare the area under the curve (AUC) of each quantitative parameter in pairs. Results:The number of vertebral bodies in acute and chronic compression fractures diagnosed by MRI was 48 and 11 respectively. The Kappa value of subjective diagnosis of acute and chronic vertebral fractures by doctors A and B was 0.782, and the AUC, sensitivity, specificity were 0.882 and 0.857, 85.4% and 89.6%, 90.9% and 81.8%, respectively. The differences of conventional CT value, CaSupp CT value and CaSupp CT value difference between acute and chronic compression fractures were statistically significant (all P<0.05), and the AUC values of conventional CT value, CaSupp CT value, conventional CT value difference and CaSupp CT value difference were 0.824, 0.930, 0.706 and 0.934, respectively. Pair comparison showed that the AUC of the CaSupp CT value and CaSupp CT value difference was greater than that of conventional CT value difference, with statistically significant differences ( Z=2.014, P=0.044, Z=2.028, P=0.043), while there were no statistically significant differences between other AUC values (all P>0.05). Conclusion:The dual-layer detector spectral CT CaSupp technique has high value in differentiating acute and chronic thoracolumbar compression fractures, and the CaSupp CT value and CaSupp CT value difference are recommended for diagnosis.

Gout of feet and ankles in different disease durations: diagnostic value of single-source DECT and evaluation of urate deposition with a novel semi-quantitative DECT scoring system

Abstract Objectives: To investigate the diagnostic performance of single-source dual-energy computed tomography (DECT) based on gemstone spectral imaging technology (including Discovery CT750HD and Revolution CT) in patients with suspected feet/ankles gouty arthritis, and evaluate the urate deposition with a novel semi-quantitative DECT scoring system. Methods: A total of 196 patients were consecutively included. Feet and ankles were evaluated in all patients by single-source DECT scan. The 2015 EULAR/ACR criteria were used as the reference for the diagnosis of gout. The sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of DECT for the diagnosis of gout in the early (≤1 year), middle (1-3 years), and late (> 3 years) disease durations were calculated. Besides, a novel semi-quantitative DECT scoring system was assessed for the measurement of urate deposition, and the correlation between the scores and the clinical and serological data were also evaluated. Moreover, the influences of artifacts on the diagnostic performance of DECT were also determined. Results: The sensitivity, specificity, and AUC of DECT in 196 patients were 38.10, 96.43%, and 0.673 in the early-stage group; 62.96, 100.00%, and 0.815 in the middle-stage group; and 77.55, 87.50%, and 0.825 in the late-stage group, respectively. The overall diagnostic accuracies in the AUC of DECT (Discovery CT750HD and Revolution CT) in the middle and late stages of gout were higher than that in the early stage of gout. Besides, the monosodium urate crystals were deposited on the first metatarsophalangeal joints and ankles/midfeet. Age, the presence of tophus, bone erosion, and disease duration considerably affected the total urate score. No statistical difference in the positive detection of nail artifact, skin artifact, vascular calcification, and noise artifact was found between the case and control groups. Conclusion: DECT (Discovery CT750HD and Revolution CT) showed promising diagnostic accuracy for the detection of urate crystal deposition in gout but had limited diagnostic sensitivity for short-stage gout. Longer disease duration, the presence of tophus, and bone erosion were associated with the urate crystal score system. The artifacts do not remarkably affect the diagnostic performance of DECT in gout.

Quantification of Fat Concentration and Vascular Response in Brown and White Adipose Tissue of Rats by Spectral CT Imaging

Effect of Monochromatic Energy Image Synthesized from Dual-layer Detector Spectral CT on Imaging of Inferior Vena Cava / 中国医学科学院学报

To evaluate the effect of monochromatic energy image on inferior vena cava imaging quality on dual-layer detector spectral CT. Totally 39 patients who were clinically suspected of abdominal disease and referred to perform contrast-enhanced computed tomography(CT)were prospectively enrolled and underwent abdominal examination using a single-source,dual-detector spectral CT.The delayed phase scan was performed 3 minutes after injection of 60 ml of iopamidol(320 mg/ml)at a rate of 3 ml/s.The raw images were reconstructed to obtain conventional mixed energy images and spectral based images(SBI).The 40,50,60,and 70 keV single energy images were obtained.The CT value,noise,and signal-to-noise(SNR)of inferior vena cava and the contrast-to-noise(CNR)of inferior vena cava relative to psoas major on conventional mixed energy images and the 40,50,60,70 keV single energy images were measured.The SNRs and CNRs on monoenergetic 40-70 keV images were compared with polychromatic 120 kVp images.ANOVA was used to compare the CT value,noise,SNR,and CNR among these five groups.The optimal monoenergetic image set was chosen. The differences in CT value,noise,SNR,CNR of inferior vena cava were statistically significant among five groups(all <0.05).The SNR and CNR in 40 keV group and 50 keV group were significantly higher than those in other groups(all <0.05).The SNR of 40 keV group was significantly higher than that of 50 keV group(=0.002).The CNR of 40 keV group was not statistical different compared with that of 50 keV group(=0.630). 40 keV is the optimal monoenergetic energy level for the inferior vena cava on dual-layer detector spectral CT and may be valuable for the diagnosis of inferior vena cava disease.

Optimal Mono-energy in Mono-energetic Spectral Computed Tomography of Enhanced Renal Cortex in Cortical Phase Based on Iodine Concentration / 中国医学科学院学报

Objective To identify the optimal mono-energetic enhanced spectral CT for renal cortex in cortical phase based on the iodine concentration. Methods Fifty patients with normal renal function received the abdominal enhanced spectral CT examination.The iodine concentration and CT values of the multiple mono-energetic spectral images were measured on renal cortex in cortical phase,and the correlation between the iodine concentration and the CT values and the coefficient of variation(CV)were analyzed. Results The correlation analysis demonstrated that the correlation coefficient was 0.994,0.994,0.993,0.987,0.976,0.960,and 0.938 between mono-energetic spectral CT images(40-100 keV with interval 10 keV,respectively)and iodine concentration(all

Assessing the Blood Supply Status of the Focal Ground-Glass Opacity in Lungs Using Spectral Computed Tomography

OBJECTIVE: To exploit material decomposition analysis in dual-energy spectral computed tomography (CT) to assess the blood supply status of the ground-glass opacity (GGO) in lungs. MATERIALS AND METHODS: This retrospective study included 48 patients with lung adenocarcinoma, who underwent a contrast-enhanced dual-energy spectral CT scan before treatment (53 GGOs in total). The iodine concentration (IC) and water content (WC) of the GGO, the contralateral and ipsilateral normal lung tissues were measured in the arterial phase (AP) and their differences were analyzed. IC, normalized IC (NIC), and WC values were compared between the pure ground-glass opacity (pGGO) and the mixed ground-glass opacity (mGGO), and between the group of preinvasive lesions and the minimally invasive adenocarcinoma (MIA) and invasive adenocarcinoma (IA) groups. RESULTS: The values of pGGO (IC = 20.9 ± 6.2 mg/mL and WC = 345.1 ± 87.1 mg/mL) and mGGO (IC = 23.8 ± 8.3 mg/mL and WC = 606.8 ± 124.5 mg/mL) in the AP were significantly higher than those of the contralateral normal lung tissues (IC = 15.0 ± 4.9 mg/mL and WC = 156.4 ± 36.8 mg/mL; IC = 16.2 ± 5.7 mg/mL and WC = 169.4 ± 41.0 mg/mL) and ipsilateral normal lung tissues (IC = 15.1 ± 6.2 mg/mL and WC = 156.3 ± 38.8 mg/mL; IC = 15.9 ± 6.0 mg/mL and WC = 174.7 ± 39.2 mg/mL; all p < 0.001). After normalizing the data according to the values of the artery, pGGO (NIC = 0.1 and WC = 345.1 ± 87.1 mg/mL) and mGGO (NIC = 0.2 and WC = 606.8 ± 124.5 mg/mL) were statistically different (p = 0.049 and p < 0.001, respectively), but not for the IC value (p = 0.161). The WC values of the group with preinvasive lesions and MIA (345.4 ± 96.1 mg/mL) and IA (550.1 ± 158.2 mg/mL) were statistically different (p < 0.001). CONCLUSION: Using dual-energy spectral CT and material decomposition analysis, the IC in GGO can be quantitatively measured which can be an indicator of the blood supply status in the GGO.

Optimal Monochromatic Imaging of Spectral Computed Tomography Potentially Improves the Quality of Hepatic Vascular Imaging

OBJECTIVE: To investigate the efficiency of spectral computed tomography (CT) optimal monochromatic images in improving imaging quality of liver vessels. MATERIALS AND METHODS: The imaging data of 35 patients with abdominal CT angiography were retrospectively analyzed. Hepatic arteries, portal veins, and hepatic veins were reconstructed with mixed energy (quality check, QC), 70 keV and optimal monochromatic mode. Comparative parameters were analyzed including CT value, image noise (IN), contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and subjective qualitative analysis. RESULTS: The optimal monochromatic value for assessment of the common hepatic artery, portal vein, and hepatic vein ranged between 49 keV and 53 keV, with a mean of 51 keV. There were statistically significant differences (p < 0.001) among the optimal monochromatic, 70 keV and QC images with regards to the hepatic vascular CT value, IN, CNR, SNR, and subjective qualitative score. CNR of the common hepatic artery in the optimal monochromatic, 70 keV and QC groups was 24.6 ± 10.9, 18.1 ± 8.3, and 11.6 ± 4.6, respectively (p < 0.001) with subjective scores of 4.7 ± 0.2, 4.0 ± 0.3, and 3.6 ± 0.4, respectively (p < 0.001). CNR of the hepatic portal vein was 6.9 ± 2.7, 4.3 ± 1.9, and 3.0 ± 2.1, respectively (p < 0.001) with subjective scores of 4.5 ± 0.3, 3.9 ± 0.4, and 3.3 ± 0.3, respectively (p < 0.001). CNR of the hepatic vein was 5.7 ± 2.3, 4.2 ± 1.9, and 2.7 ± 1.4, respectively with subjective scores of 4.3 ± 0.3, 3.8 ± 0.4, and 3.2 ± 0.3, respectively (p < 0.001). CONCLUSION: Optimal monochromatic images can lead to improvement in the imaging parameters and optimization of the image quality of the common hepatic artery, hepatic portal vein and hepatic vein compared with conventional mixed kV and with 70 keV datasets.

Application of Gemstone Spectrum Imaging for anterior spinal artery in patients with cervical spinal injury / 中国骨伤

<p><b>OBJECTIVE</b>To discuss the value of Gemstone Spectrum Imaging (GSI) CT anterior spinal artery angiography in the patients with cervical spinal cord injury, and to evaluate the correlation between the change of the blood flow of the anterior spinal artery and the postoperative recovery of nerve function.</p><p><b>METHODS</b>From January 2014 to June 2016, thirty patients who underwent cervical open door laminoplasty for spinal cord injury were retrospective analyzed and included 21 males and 9 females with an average age of (46.4±9.7) years old ranging from 33 to 59 years. Within 2 weeks after injury, open door laminoplasty was performed through cervical posterior approach. Among them, there were 8 cases of 3 segments of open door decompression, 18 cases of 4 segments, 4 cases of 5 segments. GSI CT were performed at 3 days before operation and 5 days after operation. The anterior spinal artery was reconstructed and evaluated the improvement of blood flow after operation. The cervical JOA score was calculated at 1 day before operation, 5 days after operation and 1, 6 and 12 months after operation, and the JOA score improvement rate of the corresponding follow-up points was calculated.</p><p><b>RESULTS</b>All patients were followed up for 12 to 30 months with an average of (17.4±7.6) months. The iodine content ratio (ASA/VA) of the anterior spinal artery before and after operation was 0.75±0.20 and 0.89±0.02 respectively, the postoperative improvement was significantly higher than that before operation(<0.01). The average ASA/VA improvement rate was(21.05±12.45)% after operation. There was a positive linear correlation between the improvement of blood flow and the improvement of JOA score at 1, 6 and 12 months after operation.</p><p><b>CONCLUSIONS</b>GSI CT anterior spinal artery angiography is safe and feasible, the imaging is satisfactory, it can quantitatively evaluated the blood flow of the anterior spinal artery. There was a positive linear correlation between the improvement of blood flow in anterior spinal artery and the recovery of neurological function. Early postoperative improvement of blood flow in the anterior spinal artery can be used as a reference index for predicting the recovery of neurological function in patients.</p>

A study on the influence of contrast agent protocol on gem spectrum CT pulmonary angiography quality / 重庆医学

Objective To compare the image quality between large dose smart tracking technique and low dose test bolus technique for gem spectral CT pulmonary angiography(CTPA).Methods A total of 106 cases with suspected pulmonary embolism were divided into two groups.Group A(54 cases)was carried out with large dose smart tracking technique.Group B(52 cases)was carried out with low dose test bolus technique.We compared the image quality between the two groups.Results There were significant differences in the CT value of the right pulmonary artery and the content of iodine in the lower lobe of the right pulmonary artery of two groups(P<0.01).There was significant difference of image quality between the two groups(P<0.05).The rate of excellent or good image quality in group A was higher than that in group B,and the difference was statistically significant(P<0.05).Conclusion Large dose smart tracking technique can track the artifacts of pulmonary artery imaging with less artifacts and uniform vascular fixation.The image quality of pulmonary artery imaging is better than that of small dose contrast agent.

Clinical application progresses of gemstone spectral CT / 医疗卫生装备

The progress of the gemstone spectral CT was introduced in clinical application. Review was executed from the aspects of energy spectrum technique and clinical application. The clinical application of the gemstone spectral CT was discussed in monochromatic imaging, materials decomposition, spectral curve, effective atomic number and analysis tool of the energy spectrum technique as well as in its clinical application to head, neck, chest, abdomen, musculoskeletal system and etc. Gemstone spectral CT could implement multi-parameter imaging and data analysis with analysis platform and tools and facilitate the qualitative and location diagnoses as well as treatment planning of the diseases, and thus could be promoted for comprehensive diagnosis, differential diagnosis, location diagnosis, postoperative imaging of iatrogenic metal implants, angiography, analysis on stone composition and etc of the tumors.

The application research of low-dose spectral CT imaging combined with ASIR reconstruction in different- ing peripheral lung cancer from inflammatory mass / 实用医学杂志

Objective To evaluate the value of low-dose spectral CT imaging combined with ASIR recon-struction in differenting peripheral lung cancer from inflammatory mass. Methods We retrospectively analyzed the imaging data of 147 cases with 165 pulmonary nodules or masses underwent enhanced CT scans with spectral imag-ing mode from June 2015 to May 2016. Spectral curves,normalized slope rates,iodine-water concentration were measured on the lesions in arteral phase images. The differences of the spectral characteristic parameters were eval-uated statistically by indepengdent samples t test. Results Among 165 pulmonary nodules or masses,including 68 inflammatory mass and 97 peripheral lung cancer. In the arterial phase,the iodine concentration,water concentra-tion and normalized spectral curves rates of peripheral lung cancer were 10.93 ± 5.12,1033.96 ± 9.74,0.998 ± 0.66,which was obviously higher than those in inflammatory mass in 5.29 ± 0.96,1028.85 ± 9.31,0.620 ± 0.16. There were significant difference between peripheral lung cancer and inflammatory mass(0.000 ,0.008 ,0.001 in P values). Conclusion The iodine concentration,water concentration and normalized spectral curves rates has high value for differential diagnosis of peripheral pung cancer and pneumonia mass in the arterial phase using low-dose spectral CT imaging combined with ASIR reconstruction.

A study on radiation dose and image quality of chest spectral imaging and conventional CT in anthropomorphic phantom / 中华放射医学与防护杂志

Objective To obtain the parameters of optimal spectral scanning mode in chest spectral CT imaging,radiation doses,image quality,CNR and subjective scores are compared in spectral and conventional scan modes with anthropomorphic chest phantom.Methods An anthropomorphic chest phantom underwent both conventional scan and spectral scan using three different protocols:GSI assist mode (protocol A);GSI mode with mean tube current (protocol B);GSI mode with maximum tube current (protocol C).All above scans were performed with the noise index (NI) as 9 and 11 respectively.The radiation dose was recorded,and the SD values of adipose tissue and muscle tissue of 5 different sections were measured in regions of interest (ROls) to evaluate the image quality.All scans were subjectively scored in 5 score system by two senior radiologists on lung markings and branches with the lung window technique.Results The effective dose (E) values of conventional CT scan and protocols A,B and C were 8.0,8.5,6.2,10.4 and 5.3,5.1,4.3,6.2 mSv.When NI =9,the difference of SD values had statistically significance between conventional scan and protocols A,C (F =4.496,P ＜ 0.05).When NI =11,there was statistically significant difference of SD value between conventional scan and protocols A,B,C (F =8.425,P ＜ 0.05).In conventional chest scan,the difference of SD values was statistically significant between NI =9 and 11 (t =-2.570,P ＜ 0.05),while other protocols had no statistically significant difference (P ＞ 0.05).The difference of CNR and subjective score had no statistically significance in either the same NI different scanning modes or the same scanning mode with different NIs.Conclusions Appropriate spectral scanning mode had no significant difference with conventional CT scanning in radiation dose,yet higher image quality can be obtained.Furthermore,appropriate NI can reduce the radiation dose obviously while the similar image quality was achieved.Considering the two factors,GSI assist mode can achieve balance between radiation dose and image quality.

Preliminary application of low dose contrast agent in CTPA with spectral CT imaging / 医疗卫生装备

Ojective To investigate the clinical application value of low dose contrast agent in computerized tomography pulmonary angiography (CTPA) with spectral CT imaging.Methods Totally 52 patients suspected with pulmonary embolism underwent multi-slice spiral CT pulmonary angiography,and were randomly divided into a control group (n =27) and a research group (n=25).The research group used spectral CT with 35 ml of contrast medium and the control group used 64-slice CT with conventional 80 to 90 ml of contrast medium.The CT values of the pulmonary trunk,left pulmonary artery (LPA),right pulmonary artery (RPA),pulmonary vein and ascending aorta were measured.The contrast to noise ratio (CNR) of the pulmonary artery was also calculated.In addition,the image quality of CTPA was evaluated independently by two experienced radiologists.Results The CT values (HU) of the pulmonary trunk,left pulmonary artery(LPA),right pulmonary artery (RPA) in the research group were (432.2±63.4),(373.5±48.8),(381.4±53.6) and (62.5-±6.4),respectively,and significantly higher than those in the control group,showing statistical differences (P＜0.05).The evaluation results of the CTPA images by two radiologists showed that the image quality in the research group was better than that in the control group (P＜0.05).Conclusion The image quality of pulmonary angiography with spectral CT using low contrast medium dose can be improved compared with the conventional spiral CT.

Dual-Energy CT: New Horizon in Medical Imaging

Dual-energy CT has remained underutilized over the past decade probably due to a cumbersome workflow issue and current technical limitations. Clinical radiologists should be made aware of the potential clinical benefits of dual-energy CT over single-energy CT. To accomplish this aim, the basic principle, current acquisition methods with advantages and disadvantages, and various material-specific imaging methods as clinical applications of dual-energy CT should be addressed in detail. Current dual-energy CT acquisition methods include dual tubes with or without beam filtration, rapid voltage switching, dual-layer detector, split filter technique, and sequential scanning. Dual-energy material-specific imaging methods include virtual monoenergetic or monochromatic imaging, effective atomic number map, virtual non-contrast or unenhanced imaging, virtual non-calcium imaging, iodine map, inhaled xenon map, uric acid imaging, automatic bone removal, and lung vessels analysis. In this review, we focus on dual-energy CT imaging including related issues of radiation exposure to patients, scanning and post-processing options, and potential clinical benefits mainly to improve the understanding of clinical radiologists and thus, expand the clinical use of dual-energy CT; in addition, we briefly describe the current technical limitations of dual-energy CT and the current developments of photon-counting detector.

Monochromatic energy images from spectral CT in diagnosing X-ray negative biliary stones / 中华肝胆外科杂志

Objective To study the role of monochromatic energy images from spectral CT in diagnosing X-ray negative biliary stones.Methods 32 patients who were diagnosed to have X-ray negative biliary stones were retrospectively studied.They were examined by spectral CT scanning and the spectral CT data were loaded into a spectrum analysis software.The optimal contrast-to-noise ratio (CNR) of the monochromatic energy images were exposed and the contrast ratio between the X-ray negative stones and bile on the optimal monochromatic and hybrid energy CT images were compared,respectively.The monochromatic and hybrid energy CT images for diagnosing X-ray negative biliary stones were validated by two senior radiologists based on postoperative histology.Results The corresponding KeV of optimal CNR for X-ray negative stones were not quite consistent.They were 140KeV in 19 patients,40KeV in 8 patients,53KeV,57KeV,62KeV,64KeV and 73KeV in one patient each.The contrast between the negative stones and the adjacent bile were (6.4 ±5.6) HU on hybrid energy CT images and (50.4 ±24.4) HU on optimal monochromatic energy CT images.The Eff-Z of negative stones and bile were 6.6 ± 0.6 and 7.9 ± 0.2,respectively.In our study,the diagnostic accuracy of hybrid energy CT images was 34.38％ and that of optimal monochromatic energy CT images was 78.13％.Conclusion The optimal monochromatic energy CT images were more valuable in diagnosing X-ray negative bile duct stones,which were obviously better than the hybrid energy images from traditional CT.