Effective atomic number of paraspinal muscles is associated with acute vertebral fracture risk.

OBJECTIVES: To investigate the relations among effective atomic number (Zeff), density, and area of paraspinal muscles, volumetric BMD (vBMD), and acute vertebral fractures (VF) by using spectral base images (SBIs) and routine CT images. METHODS: A total of 223 patients (52 men and 171 women) with acute VF and seven hundred and seventy-six subjects (286 men and 390 women) without VF of at least 60 years were enrolled and underwent dual-layer detector CT scans. We quantified the cross-sectional area (paraSMA), density (paraSMD) and Zeff of paraspinal muscles by CT images and SBIs and measured vBMD of the lumbar spine by quantitative CT. RESULTS: Higher vBMD was associated with lower VF risk in both sexes (adjusted OR, 0.33 and 0.43). After adjusting for age and BMI, the associations of ParaSMD with VF were not significant in men, and in women the association was borderline significant (OR, 0.80; 95% CI, 0.64 to 1.00). However, higher Zeff of paraspinal muscles was associated with lower VF risk in men (adjusted OR, 0.59; 0.36 to 0.96) but not in women. The associations of all muscle indexes with VF were not significant after further adjusting for vBMD. CONCLUSIONS: A higher Zeff of paraspinal muscles is associated with lower VF risk in older men but not in older women. The density, area and Zeff of paraspinal muscles were not vBMD independent risk factors for acute VF. ADVANCES IN KNOWLEDGE: The effective atomic number of paraspinal muscles might be a potential marker for vertebral fracture risk prediction.

Feasibility of Reduced Iodine Loads for Vascular Assessment Prior to Transcatheter Aortic Valve Implantation (TAVI) Using Spectral Detector CT.

Reduced iodine loads for computed tomography (CT)-based vascular assessment prior to transcatheter aortic valve implantation (TAVI) may be feasible in conjunction with a spectral detector CT scanner. This prospective single-center study considered 100 consecutive patients clinically referred for pre-TAVI CT. They were examined on a dual-layer detector CT scanner to obtain an ECG-gated cardiac scan and a non-ECG-gated aortoiliofemoral scan. Either a standard contrast media (SCM) protocol using 80 mL Iohexol 350 mgI/mL (iodine load: 28 gI) or a body-mass-index adjusted reduced contrast media (RCM) protocol using 40-70 mL Iohexol 350 mgI/mL (iodine load: 14-24.5 gI) were employed. Conventional images and virtual monoenergetic images at 40-80 keV were reconstructed. A threshold of 250 HU was set for sufficient attenuation along the arterial access pathway. A qualitative assessment used a five-point Likert scale. Sufficient attenuation in the thoracic aorta was observed for all patients in both groups using conventional images. In the abdominal, iliac, and femoral segments, sufficient attenuation was observed for the majority of patients when using virtual monoenergetic images (SCM: 96-100% of patients, RCM: 88-94%) without statistical difference between both groups. Segments with attenuation measurements below the threshold remained qualitatively assessable as well. Likert scores were 'excellent' for virtual monoenergetic images 50 keV and 55 keV in both groups (RCM: 1.2-1.4, SCM: 1.2-1.3). With diagnostic image quality maintained, it can be concluded that reduced iodine loads of 14-24.5 gI are feasible for pre-TAVI vascular assessment on a spectral detector CT scanner.

Dual-layer detector spectral CT-based machine learning models in the differential diagnosis of solitary pulmonary nodules.

The benign and malignant status of solitary pulmonary nodules (SPNs) is a key determinant of treatment decisions. The main objective of this study was to validate the efficacy of machine learning (ML) models featured with dual-layer detector spectral computed tomography (DLCT) parameters in identifying the benign and malignant status of SPNs. 250 patients with pathologically confirmed SPN were included in this study. 8 quantitative and 16 derived parameters were obtained based on the regions of interest of the lesions on the patients' DLCT chest enhancement images. 6 ML models were constructed from 10 parameters selected after combining the patients' clinical parameters, including gender, age, and smoking history. The logistic regression model showed the best diagnostic performance with an area under the receiver operating characteristic curve (AUC) of 0.812, accuracy of 0.813, sensitivity of 0.750 and specificity of 0.791 on the test set. The results suggest that the ML models based on DLCT parameters are superior to the traditional CT parameter models in identifying the benign and malignant nature of SPNs, and have greater potential for application.

Differential diagnosis of adrenal adenomas and metastases using spectral parameters in dual-layer detector spectral CT.

OBJECTIVE: To assess the diagnostic value of spectral parameters in differentiating adrenal adenomas from metastases based on dual-layer detector spectral CT (DLSCT). MATERIALS AND METHODS: Patients with adenomas or metastases who underwent enhanced DLSCT of the adrenals were enrolled. The CT values of virtual non-contrast images (CTVNC), iodine density (ID) values, and Z-effective (Z-eff) values, the normalized iodine density (NID) values, slopes of spectral HU curves (s-SHC), and iodine-to-CTVNC ratios of the tumors were measured in each phase. Receiver operating characteristic (ROC) curves were used to compare the diagnostic values. RESULTS: Ninety-nine patients with 106 adrenal lesions (63 adenomas, 43 metastases) were included. In the venous phase, all spectral parameters were significantly different between adenomas and metastases (all p < 0.05). The combined spectral parameters showed a better diagnostic performance in the venous phase than in other phase (p < 0.05). The iodine-to-CTVNC value had a larger area under the ROC curve (AUC) than the other spectral parameters in the differential diagnosis of adenomas and metastases, with a diagnostic sensitivity and specificity of 74.4% and 91.9%, respectively. In the differential diagnosis of lipid-rich adenomas, lipid-poor adenomas and metastases, the CTVNC value and s-SHC value also had a larger AUC than the other spectral parameters, with a diagnostic sensitivity of 97.7%, 79.1% and specificity of 91.2%, 93.1%, respectively. CONCLUSION: On DLSCT, the combined spectral parameters in the venous phase could help better distinguish adrenal adenomas from metastases. The iodine-to-CTVNC, CTVNC and s-SHC values had the highest AUC values in differentiating adenomas, lipid-rich adenomas and lipid-poor adenomas from metastases, respectively.

Dual-layer spectral CT improves the image quality of cerebral unenhanced CT scan in children.

PURPOSE: To evaluate the image quality and determine the optimal energies of virtual monoenergetic imaging (VMI) in unenhanced pediatric cerebral scans by dual-layer spectral detector computed tomography (DLCT). METHODS: Fifty-three consecutive unenhanced cerebral scans by a DLCT scanner in children (age ≤ 12 years) were retrospectively analyzed. Conventional images (CI) and VMIs were reconstructed. The gray matter (GM) and white matter (WM) noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), posterior fossa, and subcalvarial artifac tindex (PFAI, SAI) were calculated. Two radiologists independently determined the image quality using a 5-point Likert-type scale based on GM - WM differentiation (GWMA), subcalvarialspace (SAA), beam hardening artifacts in the posterior fossa (PFAA), and the overall diagnostic quality. The student t-test and Wilcoxon test were used to determining the statistical significance. RESULTS: Compared with CI, superior noise were observed in VMI at low keV levels and were lowest at 100 keV (P < 0.001); the SNR and CNR were significantly higher at the 45 keV to 75 keV levels (all Ps of <0.005). The best GWMA were noticed at the 50 keV level compared to other keV levels (all P < 0.05). The optimal SAA and PFAA were found at 100 keV, respectively. The assessment of overall diagnostic quality was the best at 50 keV (P < 0.013 to < 0.001). CONCLUSIONS: The VMI scan significantly improved the quality of pediatric cerebral images compared with those from CI. The optimal energy level for the brainparenchyma was 50 keV while those for subcalvarial space and posterior fossa were 100 keV.

[Optimal Parameters for Virtual Mono-Energetic Imaging of Liver Solid Lesions].

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.

Spectral CT: Current Liver Applications.

Using two different energy levels, dual-energy computed tomography (DECT) allows for material differentiation, improves image quality and iodine conspicuity, and allows researchers the opportunity to determine iodine contrast and radiation dose reduction. Several commercialized platforms with different acquisition techniques are constantly being improved. Furthermore, DECT clinical applications and advantages are continually being reported in a wide range of diseases. We aimed to review the current applications of and challenges in using DECT in the treatment of liver diseases. The greater contrast provided by low-energy reconstructed images and the capability of iodine quantification have been mostly valuable for lesion detection and characterization, accurate staging, treatment response assessment, and thrombi characterization. Material decomposition techniques allow for the non-invasive quantification of fat/iron deposition and fibrosis. Reduced image quality with larger body sizes, cross-vendor and scanner variability, and long reconstruction time are among the limitations of DECT. Promising techniques for improving image quality with lower radiation dose include the deep learning imaging reconstruction method and novel spectral photon-counting computed tomography.

Pros and Cons of Dual-Energy CT Systems: "One Does Not Fit All".

Dual-energy computed tomography (DECT) uses different energy spectrum x-ray beams for differentiating materials with similar attenuation at a certain energy. Compared with single-energy CT, it provides images with better diagnostic performance and a potential reduction of contrast agent and radiation doses. There are different commercially available DECT technologies, with machines that may display two x-ray sources and two detectors, a single source capable of fast switching between two energy levels, a specialized detector capable of acquiring high- and low-energy data sets, and a filter splitting the beam into high- and low-energy beams at the output. Sequential acquisition at different tube voltages is an alternative approach. This narrative review describes the DECT technique using a Q&A format and visual representations. Physical concepts, parameters influencing image quality, postprocessing methods, applicability in daily routine workflow, and radiation considerations are discussed. Differences between scanners are described, regarding design, image quality variabilities, and their advantages and limitations. Additionally, current clinical applications are listed, and future perspectives for spectral CT imaging are addressed. Acknowledging the strengths and weaknesses of different DECT scanners is important, as these could be adapted to each patient, clinical scenario, and financial capability. This technology is undoubtedly valuable and will certainly keep improving.

Value of dual-layer spectral detector CT in evaluating the intramedullary invasion of limb osteosarcoma / 中华放射学杂志

Objective:To explore the optimal keV value of the virtual monoenergetic image (VMI) for displaying the osteosarcoma by using the dual-layer spectral detector CT and to evaluate its application value in determining the extent of intramedullary invasion of osteosarcoma.Methods:From August 2021 to August 2022, 57 patients with conventional osteosarcoma of long bone confirmed by biopsy in Beijing Jishuitan Hospital, Capital Medical University were retrospectively analyzed. All patients completed dual-layer spectral CT enhanced examination before limb salvage surgery, and tumor segment resection specimens were obtained after surgery. Conventional 120 kVp image and VMI of 40, 50, 60, 70 and 80 keV were obtained by spectral CT examination, and the CT values of tumors, image noise were measured and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the corresponding images were calculated. The objective evaluation among the six groups of images were assessed with the Friedman test, and then determined the optimal keV value. The maximum distance between the intramedullary boundary of osteosarcoma and the adjacent articular surfaces was measured on the best keV VMI and the tumor segment resection specimens. The Wilcoxon signed rank test was used to find the differences and the Spearman correlation analysis was used to evaluate the correlation between the distance measured from the best keV VMI and the specimens.Results:There were significant differences in CT value, image noise, SNR and CNR between 40-80 keV VMI and 120 kVp conventional CT images ( P<0.05). The CT value, SNR and CNR of 40 and 50 keV VMI were better than 120 kVp ( P<0.001). The 50 keV VMI was chosen as the best keV VMI to measure the intramedullary extent of osteosarcoma. The distance measured from 50 keV VMI was 103.9 (80.4, 131.4) mm, while the distance measured from specimens was 113.5 (94.0, 142.0) mm, and the difference was statistically significant ( Z=-5.76, P<0.001). The 50 keV VMI measurements in 51 patients were smaller than the gross specimens, which underestimated the tumor intramedullary extent, with the difference was 11.1 (6.6, 13.8) mm. The Spearman correlation analysis demonstrated a high positive correlation of distance measured on gross specimens with the 50 keV VMI ( r s=0.960, P<0.001). Conclusions:Dual-layer spectral detector CT with 50 keV VMI is the best image to show the limb osteosarcoma. Compared with gross specimens, the distance measured from CT underestimated the intramedullary invasion range of limb osteosarcoma about 10 mm, but the two show a good correlation.

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.

Diagnostic value of dual-layer spectral detector CT in differentiating lung adenocarcinoma from squamous cell carcinoma.

Background and objective: The pathological type of non-small cell lung cancer is considered to be an important factor affecting the treatment and prognosis. The purpose of this study was to investigate the diagnostic value of spectral parameters of dual-layer spectral detector computed tomography (DLCT) in determining efficacy to distinguish adenocarcinoma (AC) and squamous cell carcinoma (SC), and their combined diagnostic efficacy was also analyzed. Methods: This is a single-center prospective study, and we collected 70 patients with lung SC and 127 patients with lung AC confirmed by histopathological examination. Morphological parameters, plain scan CT value, biphasic enhanced CT value, and spectral parameters were calculated. The diagnostic efficiency of morphological parameters, spectral parameters, and spectral parameters combined with morphological parameters was obtained by statistical analysis. Results: In univariate analysis, seven morphological CT features differed significantly between SC and AC: tumor location (distribution), lobulation, spicule, air bronchogram, vacuole sign, lung atelectasis and/or obstructive pneumonia, and vascular involvement (all p < 0.05). In the arterial phase and the venous phase, the spectral parameters of AC were higher than those of SC (AP-Zeff: 8.07 ± 0.23 vs. 7.85 ± 0.16; AP-ID: 1.41 ± 0.47 vs. 0.94 ± 0.28; AP-NID: 0.13 ± 0.04 vs. 0.09 ± 0.03; AP-λ: 3.42 ± 1.10 vs. 2.33 ± 0.96; VP-Zeff: 8.26 ± 0.23 vs. 7.96 ± 0.16; VP-ID: 1.18 ± 0.51 vs. 1.16 ± 0.30; VP-NID: 0.39 ± 0.13 vs. 0.29 ± 0.08; VP-λ: 4.42 ± 1.28 vs. 2.85 ± 0.72; p < 0.001). When conducting multivariate analysis combining CT features and DLCT parameters with the best diagnostic efficacy, the independent predictors of AC were distribution on peripheral (OR, 4.370; 95% CI, 1.485-12.859; p = 0.007), presence of air bronchogram (OR, 5.339; 95% CI, 1.729-16.484; p = 0.004), and presence of vacuole sign ( OR, 7.330; 95% CI, 1.030-52.184; p = 0.047). Receiver operating characteristic curves of the SC and AC showed that VP-λ had the best diagnostic performance, with an area under the curve (AUC) of 0.864 and sensitivity and specificity rates of 85.8% and 74.3%, respectively; the AUC was increased to 0.946 when morphological parameters were combined, and sensitivity and specificity rates were 89.8% and 87.1%, respectively. Conclusion: The quantitative parameters of the DLCT spectrum are of great value in the diagnosis of SC and AC, and the combination of morphological parameters and spectral parameters is helpful to distinguish SC from AC.

Parameters of Dual-layer Spectral Detector CT Could be Used to Differentiate Non-Small Cell Lung Cancer from Small Cell Lung Cancer.

BACKGROUND AND OBJECTIVE: Differentiating non-small cell lung cancer (NSCLC) from small cell lung cancer (SCLC) remains a substantial challenge. This study aimed at evaluating the performance of dual-layer spectral detector CT (DLCT) in differentiating NSCLC from SCLC. METHODS: Spectral images of 247 cancer patients confirmed by pathology were retrospectively analyzed in both the arterial phase (AP) and the venous phase (VP), including 197 cases of NSCLC and 50 cases of SCLC. Effective atomic number (Z-eff), Spectral CT-Mono Energetic (MonoE [40keV~90keV]), iodine density (ID) and thoracic aorta iodine density (IDaorta) in contrast-enhanced images were measured and compared between the SCLC and NSCLC subgroups of tumors. The slope of the spectral curve (λ, interval of 10 keV) and normalized iodine density (NID) were also calculated between the SCLC and NSCLC. Through the statistical analysis, the diagnostic efficiency of each spectral parameter was calculated, and the difference in their efficiency was analyzed. RESULTS: Both in NSCLS and SCLC, all parameters in VP were significantly higher than those in AP (p<0.001), except for λ90. There were significant differences in all spectral parameters between NSCLS and SCLC, both in AP and VP (p < 0.001). Except for VP-λ90, there was no significant difference in ROC curves of all spectral parameters. VP-NID exhibited the best diagnostic performance with an AUC value of 0.917 (95%[CI]: 0.870~0.965), sensitivity and specificity of 92.9% and 80%, and a diagnostic threshold of 0.217. CONCLUSION: All parameters of DLCT have high diagnostic efficiency in differentiating NSCLC from SCLC except for VP-λ90, and VP-NID has the highest diagnostic efficiency.

High-resolution model-based material decomposition in dual-layer flat-panel CBCT.

PURPOSE: Spectral CT uses energy-dependent measurements that enable material discrimination in addition to reconstruction of structural information. Flat-panel detectors (FPDs) have been widely used in dedicated and interventional systems to deliver high spatial resolution, volumetric cone-beam CT (CBCT) in compact and OR-friendly designs. In this work, we derive a model-based method that facilitates high-resolution material decomposition in a spectral CBCT system equipped with a prototype dual-layer FPD. Through high-fidelity modeling of multilayer detector, we seek to avoid resolution loss that is present in more traditional processing and decomposition approaches. METHOD: A physical model for spectral measurements in dual-layer flat-panel CBCT is developed including layer-dependent differences in system geometry, spectral sensitivities, and detector blur (e.g., due to varied scintillator thicknesses). This forward model is integrated into a model-based material decomposition (MBMD) method based on minimization of a penalized weighted least-squared (PWLS) objective function. The noise and resolution performance of this approach was compared with traditional projection-domain decomposition (PDD) and image-domain decomposition (IDD) approaches as well as one-step MBMD with lower-fidelity models that use approximated geometry, projection interpolation, or an idealized system geometry without system blur model. Physical studies using high-resolution three-dimensional (3D)-printed water-iodine phantoms were conducted to demonstrate the high-resolution imaging performance of the compared decomposition methods in iodine basis images and synthetic monoenergetic images. RESULTS: Physical experiments demonstrate that the MBMD methods incorporating an accurate geometry model can yield higher spatial resolution iodine basis images and synthetic monoenergetic images than PDD and IDD results at the same noise level. MBMD with blur modeling can further improve the spatial-resolution compared with the decomposition results obtained with IDD, PDD, and MBMD methods with lower-fidelity models. Using the MBMD without or with blur model can increase the absolute modulation at 1.75 lp/mm by 10% and 22% compared with IDD at the same noise level. CONCLUSION: The proposed model-based material decomposition method for a dual-layer flat-panel CBCT system has demonstrated an ability to extend high-resolution performance through sophisticated detector modeling including the layer-dependent blur. The proposed work has the potential to not only facilitate high-resolution spectral CT in interventional and dedicated CBCT systems, but may also provide the opportunity to evaluate different flat-panel design trade-offs including multilayer FPDs with mismatched geometries, scintillator thicknesses, and spectral sensitivities.

[Role of Dual-layer Detector Energy Spectral CT in Resting Myocardial Perfusion Imaging for Patients with Normal Coronary Artery].

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(Zeff value)of each myocardial segment(except for apical segment)were measured and normalized to those of the aorta.All the data were quantitatively evaluated using ANOVA or Friedman test. Results Iodine density and Zeff value of myocardial segments in middle plane were significantly different(all P<0.001).The iodine density and Zeff value showed no significant difference between segments in basal and apical plane(all P > 0.05). Conclusions Iodine density and Zeff value of myocardial segments can be quantitatively evaluated using dual-layer detector energy spectral CT.Resting myocardial perfusion of segments in middle plane are significantly different in patients with normal coronary artery.

Dual-layer detector spectral CT-a new supplementary method for preoperative evaluation of glioma.

PURPOSE: To investigate the value of the iodine concentration (IC) measured by dual-layer detector spectral CT (DLDSCT) in evaluating the factors related to the treatment scheme and survival prognosis of patients with glioma. METHODS: From 2018 to 2019, we prospectively collected the data of 99 patients with glioma. The degree of CT enhancement and the IC of low grade gliomas (LGGs, II), high grade gliomas (HGGs, III and IV), grade II and III gliomas, were compared. The predictive performance of the degree of CT enhancement and IC was examined via receiver operating characteristic (ROC) analysis. The correlations between IC and Ki-67 labeling index, isocitrate dehydrogenase (IDH) mutation, chromosome 1p/19q deletion status of the tumor were examined. RESULTS: Both IC and the degree of CT enhancement of patients with HGG were significantly higher than those of patients with LGG (p < 0.001; χ2 =41.707, p <  0.001); IC had large area under the ROC curve for diagnostic HGG (0.931; 95 % CI: 0.882-0.979; p <  0.001). The IC in the grade III gliomas was significantly higher than that in grade II gliomas (p < 0.001); IC had a large area under the ROC curve for diagnostic grade III gliomas (0.865; 95 % CI: 0.779-0.952; p <  0.001). There was a significant positive correlation between IC and Ki-67 LI (r = 0.679; p < 0.001). CONCLUSIONS: The DLDSCT technology can be used as a supplementary method to provide more information for preoperative grading of the gliomas and the prognosis assessment of the patients.

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

[Effect of Monochromatic Energy Image Synthesized from Dual-layer Detector Spectral CT on Imaging of Inferior Vena Cava].

Objective To evaluate the effect of monochromatic energy image on inferior vena cava imaging quality on dual-layer detector spectral CT. Methods 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. Results The differences in CT value,noise,SNR,CNR of inferior vena cava were statistically significant among five groups(all P<0.05).The SNR and CNR in 40 keV group and 50 keV group were significantly higher than those in other groups(all P<0.05).The SNR of 40 keV group was significantly higher than that of 50 keV group(P=0.002).The CNR of 40 keV group was not statistical different compared with that of 50 keV group(P=0.630). Conclusion 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.

Impact of Patient Size and Radiation Dose on Accuracy and Precision of Iodine Quantification and Virtual Noncontrast Values in Dual-layer Detector CT-A Phantom Study.

RATIONALE AND OBJECTIVES: Iodine quantification (IQ) and virtual noncontrast (VNC) images produced by dual-energy CT (DECT) can be used for various clinical applications. We investigate the performance of dual-layer DECT (DLDECT) in different phantom sizes and varying radiation doses and tube voltages, including a low-dose pediatric setting. MATERIALS AND METHODS: Three phantom sizes (simulating a 10-year-old child, an average, and a large-sized adult) were scanned with iodine solution inserts with concentrations ranging 0-32 mg/ml, using the DLDECT. Each phantom size was scanned with CTDIvol 2-15 mGy at 120 and 140 kVp. The smallest phantom underwent additional scans with CTDIvol 0.9-1.8 mGy. All scans were repeated 3 times. Each iodine insert was analyzed using VNC and IQ images for accuracy and precision, by comparison to known values. RESULTS: For scans from 2 to 15 mGy mean VNC attenuation and IQ error in the iodine inserts in the small, medium, and large phantoms was 1.2 HU ± 3.2, -1.2 HU ± 14.9, 2.6 HU ± 23.6; and +0.1 mg/cc ± 0.4, -0.9 mg/cc ± 0.9, and -1.8 mg/cc ± 1.8, respectively. In this dose range, there were no significant differences (p ≥ 0.05) in mean VNC attenuation or IQ accuracy in each phantom size, while IQ was significantly less precise in the small phantom at 2 mGy and 10 mGy (p < 0.05). Scans with CTDIvol 0.9-1.8 mGy in the small phantom showed a limited, but statistically significantly lower VNC attenuation precision and IQ accuracy (-0.5 HU ± 5.3 and -0.3 mg/cc ± 0.5, respectively) compared to higher dose scans in the same phantom size. CONCLUSION: Performance of iodine quantification and subtraction by VNC images in DLDECT is largely dose independent, with the primary factor being patient size. Low-dose pediatric scan protocols have a significant, but limited impact on IQ and VNC attenuation values.

Evaluating the temporomandibular joint disc using calcium-suppressed technique in dual-layer detector computed tomography.

OBJECTIVES: To investigate the application value of the calcium-suppressed (CaSupp) images of dual-layer detector computed tomography (DLCT) in the evaluation of the temporomandibular joint (TMJ) discs. METHODS: Thirty-three healthy subjects underwent DLCT and magnetic resonance imaging (MRI) examinations. CaSupp images were reconstructed from the spectral-based images using a calcium suppression algorithm. The location, morphology, and thickness of the posterior band of the TMJ discs were evaluated on the oblique sagittal proton-density weighted images and CaSupp images. RESULTS: Of the 66 TMJ discs, anterior displacement was observed on 9 TMJ discs on MR images and 6 TMJ discs on CaSupp images, and posterior displacement was present on 3 TMJ discs on MR and CaSupp images. No significant difference was observed in TMJ disc displacement between MR images and CaSupp images (P value = 0.730). The TMJ discs without displacement had no significant difference in the thickness of the posterior band between the MR and CaSupp images (P value = 0.401). CONCLUSIONS: The calcium-suppressed technique in DLCT may be a simple and preliminary way to evaluate the TMJ disc displacement and structure.

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.