Improving image quality in portal venography with spectral CT imaging. Eur J Radiol. 2012;81:1677-1681. [PMID: 21444170 DOI: 10.1016/j.ejrad.2011.02.063]

Wide-Detector CT-Based optimized triple Rule-Out CT angiography for emergency chest pain: reducing contrast and radiation without compromising diagnostic quality

BACKGROUND

The triple rule-out computed tomography angiography (TRO-CTA) has recently emerged as a technique that noninvasively evaluates the coronary arteries (CAs), the pulmonary arteries (PAs) and the thoracic aorta (TA).

OBJECTIVE

To evaluate the feasibility of an optimized scanning protocol to reduce the volume of iodine contrast media (ICM), injection rate, and radiation dose in patients undergoing TRO-CTA.

METHODS

Patients undergoing TRO-CTA were assigned to either group A or group B using a 16 cm wide-detector CT. Patients in group A were imaged with a traditional triple scanning protocol with a sequence of the PA, CAs, and TA. Patients in group B were imaged using the modified protocol with scanning sequence of PA, TA, and CAs, ICM of 55 ml, and injection rate of 4.5 mL/s. The image quality and effective radiation dose (ED) were compared.

RESULTS

There were no significant differences in basic information between groups A and B. Other than the left PA, RA, and RV, there were no significant differences in the CT attenuation values of relevant vascular structures between groups A and B. There were no significant differences in CNR values between the two groups except the LAD-D and LCX. The image quality scores were comparable between groups A and B except the CAs. However, there were significant differences between the two groups in ICM (p < 0.05), scanning time (p < 0.001) and ED (p = 0. 023).

CONCLUSIONS

The optimized TRO-CTA scanning protocol can achieve less ICM and lower ED while maintaining image quality.

Reduction of radiation dose and contrast medium volume in computed tomography pulmonary angiography: adaptation of dual-energy computed tomography (CT) protocols to the body mass index

AIM

To evaluate the image quality and diagnostic value of a body mass index (BMI)-based dual-energy computed tomography (CT) protocol in computed tomography pulmonary angiography (CTPA) for reduction of radiation dose and contrast medium (CM) volume.

MATERIALS AND METHODS

Patients suspected of having pulmonary embolism were prospectively included and randomly assigned to one of three protocols: Protocol A (a standard protocol, 100 kV/140 mAs/50 mL iodinated CM), B (a conventional dual-energy protocol, 80-140 kV switching/automatic tube current/weight-dependent CM volume) and C (a BMI-based dual-energy protocol, 80-140 kV switching/BMI-based tube current/weight-dependent CM volume, BMI-based CM injection rate). Subjective and objective image analysis were performed by two radiologists independently. Diagnostic accuracy of pulmonary embolism were evaluated. Inter-group comparison was performed.

RESULTS

Ninety patients (mean age 54.1 ± 13.3 years, 57 men) were included, with 30 patients in each group. The CT values, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the pulmonary arteries in group C were significantly higher than those in group B (358.2 ± 50.5 vs 324.9 ± 57.2, p=0.047, 17.8 ± 3.2 vs 15.3 ± 2.9, p=0.010, 19.2 ± 4.1 vs 15.7 ± 3.8, p=0.014). The dose length product (DLP) and CM volume were significantly reduced in groups B and C (A vs B vs C, DLP, 287.9 ± 34.0 vs 177.2 ± 39.2 vs 183.8 ± 23.1 mGy·cm), p<0.001, CM, 50.0 ± 0.0 vs 22.1 ± 3.0 vs 23.2 ± 4.0 ml, p<0.001). There were no significant differences in diagnostic accuracy or subjective image quality among the three groups.

CONCLUSION

The BMI-based dual-energy CT protocol can reduce radiation exposure and iodine burden compared to routine CTPA without affecting the image quality and diagnostic accuracy in patients with a BMI under 30 kg/m2.

Assessment of Spectral Computed Tomography Image Quality and Detection of Lesions in the Liver Based on Image Reconstruction Algorithms and Virtual Tube Voltage

Background: Spectral detector computed tomography (SDCT) has demonstrated superior diagnostic performance and image quality in liver disease assessment compared with traditional CT. Selecting the right reconstruction algorithm and tube voltage is essential to avoid increased noise and diagnostic errors. Objectives: This study evaluated improvements in image quality achieved using various virtual tube voltages and reconstruction algorithms for diagnosing common liver diseases with spectral CT. Methods: This retrospective study involved forty-seven patients who underwent spectral CT scans for liver conditions, including fatty liver, hemangiomas, and metastatic lesions. The assessment utilized signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), with images reconstructed using various algorithms (IMR, iDose) at different levels and virtual tube voltages. Three experienced radiologists analyzed the reconstructed images to identify the best reconstruction methods and tube voltage combinations for diagnosing these liver pathologies. Results: The signal-to-noise ratio (SNR) was highest for spectral CT images using the IMR3 algorithm in metastatic, hemangioma, and fatty liver cases. A strong positive correlation was found between IMR3 at 120 keV and 70 keV (p-value = 0.000). In contrast, iDOSE2 at 120 keV and 70 keV showed a low correlation of 0.291 (p-value = 0.045). Evaluators noted that IMR1 at 70 keV provided the best visibility for liver lesions (mean = 3.58), while IMR3 at 120 keV had the lowest image quality (mean = 2.65). Conclusions: Improvements in image quality were noted with SDCT, especially in SNR values for liver tissues at low radiation doses and a specific IMR level. The IMR1 algorithm reduced noise, enhancing the visibility of liver lesions for better diagnosis.

Equilibrium phase images of the liver using a contrast-enhancement boost instead of the portal vein phase

BACKGROUND

Three-phase dynamic computed tomography imaging is particularly useful in the liver region. However, dynamic imaging with contrast media has the disadvantage of increased radiation exposure due to multiple imaging sessions. We hypothesized that the contrast enhancement boost (CE-boost) technique could be used to enhance the contrast in equilibrium phase (EP) images and produce enhancement similar to that of portal vein phase (PVP) images, and if this is possible, EP imaging could play the same role as PVP imaging. We also speculated that this might allow the conversion of three-phase dynamic imaging to biphasic dynamic imaging, reducing patients’ radiation exposure.

AIM

To determine if the CE-boost of EP, CE-boost (EP) is useful compared to a conventional image.

METHODS

We retrospectively analyzed the cases of 52 patients who were diagnosed with liver cancer between January 2016 and October 2022 at our institution. From these computed tomography images, CE-boost images were generated from the EP and plane images. We compared the PVP, EP, and CE-boost (EP) for blood vessels and hepatic parenchyma based on the contrast-to-noise ratio (CNR), signal-to-noise ratio, and figure-of-merit (FOM). Visual assessments were also performed for vessel visualization, lesion conspicuity, and image noise.

RESULTS

The CE-boost (EP) images showed significant superiority compared to the PVP images in the CNR, signal-to-noise ratio, and FOM except regarding the hepatic parenchyma. No significant differences were detected in CNR or FOM comparisons within the hepatic parenchyma (P = 0.62, 0.67). The comparison of the EP and CE-boost (EP) images consistently favored CE-boost (EP). Regarding the visual assessment, the CE-boost (EP) images were significantly superior to the PVP images in lesion conspicuity, and the PVP in image noise. The CE-boost (EP) images were significantly better than the EP images in the vessel visualization of segmental branches of the portal vein and lesion conspicuity, and the EP in image noise.

CONCLUSION

The image quality of CE-boost (EP) images was comparable or superior to that of conventional PVP and EP. CE-boost (EP) images might provide information comparable to the conventional PVP.

Impact of different concentration iodinated contrast media on pain and comfort in abdominal computed tomography

OBJECTIVES

To investigate whether high concentration iodinated contrast media (CM), compared with low concentration CM, could reduce pain and discomfort levels in patients who had level II and III venous conditions.

METHODS

This prospective, single-center study enrolled patients who had level II and III venous conditions and underwent abdominal contrast-enhanced CT scan between July 2021 and February 2022. The venous condition to establish peripheral venous access for CM injection was graded using the Intravenous Access Scoring system, of which level II and III indicated poor venous condition and difficult venous access. Patients received iomeprol 400 in high concentration group and ioversol 320 in low group at an identical iodine delivery rate of 1.12 gI/s. The primary outcomes were pain and comfort levels. The secondary outcomes included adverse events and image quality. Patients rated pain intensity via Numerical Rating Scale and comfort level via Visual Analogue Scale with higher scores indicating higher levels of pain and discomfort. Quantitative and qualitative image assessment were compared between two groups. Continuous variables were compared using Student's t test or Mann-Whitney U test. Categorical variables were compared using χ2 test, χ2 test for trend or Fisher's exact test.

RESULTS

A total of 206 patients (mean age, 60.13 ± 12.14 years; 81 males) were included with 99 in the high concentration group and 107 in the low concentration group. The high group had significantly lower pain scores (median 1 [IQR: 0-2] vs 2 (IQR 2-4), p < 0.001) and comfort scores (1 [IQR: 0-3] vs 3 [IQR: 2-5], p < 0.001) than the low group. Incidence of CM extravasation did not significantly differ (1.0 % vs 4.5 %, p = 0.214). No hypersensitivity reaction was observed. Qualitative assessment showed higher clarity scores of intrahepatic hepatic artery and portal vein in the high group. Quantitative assessment results were comparable between two groups.

CONCLUSION

High concentration iodinated CM could lower pain intensity and improve comfort levels without comprising image quality of CT scan. High concentration CM is a preferable choice in patients with poor venous conditions during contrast-enhanced CT scan.

Virtual Monoenergetic Images Facilitate Better Identification of the Arc of Riolan During Splenic Flexure Takedown

OBJECTIVE

This study aimed to investigate whether virtual monoenergetic images (VMIs) can aid radiologists and surgeons in better identifying the arc of Riolan (AOR) and to determine the optimal kilo electron volt (keV) level.

METHODS

Thirty-three patients were included. Conventional images (CIs) and VMI (40-100 keV) were reconstructed using arterial phase spectral-based images. The computed tomography (CT) attenuation and noise of the AOR, the CT attenuation of the erector spinal muscle, and the background noise on VMI and CI were measured, respectively. The signal-to-noise ratio, contrast-to-noise ratio (CNR), and signal intensity ratio were calculated. The image quality of the AOR was evaluated according to a 4-point Likert grade.

RESULTS

The CT attenuation, noise, CNR, and signal intensity ratio of the AOR were significantly higher in VMI at 40 and 50 keV compared with CI ( P < 0.001); VMI at 40 keV was significantly higher than 50 keV ( P < 0.05). No significant difference in signal-to-noise ratio, background noise, and CT attenuation of the spinal erector muscle was observed between VMI and CI ( P > 0.05). virtual monoenergetic image at 40 keV produced the best subjective scores.

CONCLUSIONS

Virtual monoenergetic image at 40 keV makes it easier to observe the AOR with optimized subjective and objective image quality. This may prompt radiologists and surgeons to actively search for it and encourage surgeons to preserve it during splenic flexure takedown.

Dual Energy CT in Oncology: Benefits for Both Patients and Radiologists From an Emerging Quantitative and Functional Diagnostic Technique

Dual-energy CT (DECT) imaging makes it possible to identify the characteristics of materials that cannot be recognized with conventional single-energy CT (SECT). In the postprocessing study phase, virtual monochromatic images and virtual-non-contrast (VNC) images, also permits reduction of dose exposure by eliminating the precontrast acquisition scan. Moreover, in virtual monochromatic images, the iodine contrast increases when the energy level decreases resulting in better visualization of hypervascular lesions and in a better tissue contrast between hypovascular lesions and the surrounding parenchyma; thus, allowing for reduction of required iodinate contrast material, especially important in patients with renal impairment. All these advantages are particularly important in oncology, providing the possibility of overcoming many SECT imaging limits and making CT examinations safer and more feasible in critical patients. This review explores the basis of DECT imaging and its utility in routine oncologic clinical practice, with particular attention to the benefits of this technique for both the patients and the radiologists.

A feasibility study of different GSI noise indexes and concentrations of contrast medium in hepatic CT angiography of overweight patients: image quality, radiation dose, and iodine intake

PURPOSE

To conduct a comparative study of image quality, radiation dose, and iodine intake in hepatic computed tomographic angiography (CTA) of overweight patients with different Gemstone Spectral Imaging (GSI) noise indexes combined with different concentrations of contrast medium.

MATERIALS AND METHODS

Ninety patients with a body mass index of ≥ 25 kg/m² were divided into three groups (A, B and C), each with 30 patients. The three groups underwent hepatic CTA with different NI of 7, 11 and 15, respectively, and were injected with different iodine concentrations of 370, 350 and 320 mgI/mL, respectively. Five sets of images at 40-60 keV (interval, 5 keV) were reconstructed in each group. The CT value, image noise, contrast-to-noise ratio (CNR) and subjective score of the hepatic artery and vein, and portal vein in different monochromatic image sets were analyzed to select the optimal energy level in each group. The differences in CT value, image noise, CNR and a subjective score of hepatic artery and vein, portal vein in the optimal monochromatic images among the three groups were compared, the volume CT dose index (CTDIvol) and dose-length product (DLP) were recorded, and the effective dose and iodine intake were calculated.

RESULTS

The 40 keV was determined to be the optimal energy level for the monochromatic image sets in each group. No significant group differences were noted in the CT value, image noise, CNR, and subjective image scores of the hepatic artery and vein, and portal vein for the optimal monochromatic images (P > 0.05). Compared with group A, the effective dose and iodine intake in group B were reduced by 50.18% and 9.3%, and by 58.12% and 14.23% in group C, respectively.

CONCLUSION

A low-concentration contrast medium combined with a high-noise GSI index in hepatic CTA of overweight patients can reduce the radiation dose and iodine intake while ensuring image quality.

Clinical application of the contrast-enhancement boost technique in computed tomography angiography of the portal vein

PURPOSE

The aim of this study was to explore the improved image quality of the portal vein using the contrast-enhancement boost (CE-boost) technique for the improved visibility of abdominal-enhanced computed tomography (CT) scans in clinical practice.

METHODS

This retrospective study included 50 patients in Group A who underwent routine abdominal-enhanced CT and 50 patients in Group B who underwent abdominal computed tomography angiography (CTA) with matched body mass index, age, and sex. Images in Group A were postprocessed with the CE-boost technique for further enhanced visibility of the portal vein. Both subjective and objective assessments of different branches of the portal vein in three types of images (i.e., Group A with CE-boost and without CE-boost, Group B) were statistically analyzed.

RESULTS

The subjective scores of two experienced radiologists showed good consistency (kappa value > 0.624, p < 0.001), and the score of Group A with CE-boost (mean, 4.64) was significantly higher than that of the others (p < 0.001). The liver parenchyma and most target veins in Group A with CE-boost showed the highest CT, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) values and the lowest standard deviation (SD), while the CNR of most portal veins in Group A without CE-boost had the lowest CNR (p < 0.001). There were no differences in the SNR of the portal vein in Group A without CE-Boost and Group B (p > 0.05).

CONCLUSION

CE-boost can significantly improve image quality in portal vein imaging without any additional scanning settings or changes in the clinical workflow.

Virtual Monoenergetic Spectral Detector CT for Preoperative CT Angiography in Liver Donors

OBJECTIVE

The purpose of this study was to evaluate the use of virtual monoenergetic images (VMI) in pre-operative CT angiography of potential donors for living donor adult liver transplantation (LDALT), and to determine the optimal energy level to maximize vascular signal-to-noise and contrast-to-noise ratios (SNR and CNR, respectively).

MATERIALS AND METHODS

We retrospectively evaluated 29 CT angiography studies performed preoperatively in potential liver donors on a spectral detector CT scanner. All studies included arterial, early venous, and delayed venous phase imaging. Conventional polyenergetic images were generated for each patient, as well as virtual monoenergetic images in 10 keV increments from 40 -100 keV. Arteries (aorta and celiac, superior mesenteric, common hepatic, right and left hepatic arteries) were assessed on arterial phase images; portal venous system branches (splenic, superior mesenteric, main, right, and left portal veins) on early venous phase images; and hepatic veins on late venous phase images. Vascular attenuation, background parenchymal attenuation, and noise were measured on each set of virtual monoenergetic and conventional images.

RESULTS

Background hepatic and vascular noise decreased with increasing keV, with the lowest noise at 100 keV. Vascular SNR and CNR increased with decreasing keV and were highest at 40 keV, with statistical significance compared with conventional ( P < 0.05).

CONCLUSIONS

In preoperative CT angiography for potential liver donors, the optimal keV for assessing the vasculature to improve SNR and CNR is 40 keV. Use of low keV VMI in LDALT CT protocols may facilitate detection of vascular anatomical variants that can impact surgical planning.

Dual-energy computed tomography for non-invasive prediction of the risk of oesophageal variceal bleeding with hepatitis B cirrhosis

OBJECTIVE

Oesophageal variceal bleeding (OVB) is a fatal complication of cirrhosis and/or portal hypertension. We aimed to develop a non-invasive prediction model for the risk of OVB using dual-energy computed tomography (CT).

METHODS

317 oesophageal varices (OV) patients with hepatitis B virus-related cirrhosis were retrospectively assessed from January 2018 to December 2018. All patients underwent dual-energy CT scans within 14 days before endoscopy. 222 of 317 patients (174 OVB-negative patients and 48 OVB-positive patients) were included in the training cohort and 95 patients (74 OVB-negative patients and 21 OVB-positive patients) were included in the validation cohort chronologically. A model with the selected conventional CT features and a model with the conventional CT and dual-energy CT features were developed. The prediction accuracy was evaluated using the receiver operating characteristic (ROC) curve. The accuracy and reproducibility of the models for OVB risk prediction of cirrhosis were validated by the validation cohort. The areas under the curve (AUC) of the two models were compared with Delong test.

RESULTS

Diameter of oesophageal vein (OV(mm)), diameter of splenic vein (SPV(mm)), ascites (AS), iodine concentration in short gastric vein (SGV(HU)), iodine concentration in spleen (SP(HU)) were independent predictors of OVB risk (P < 0.05). Then, we developed a model with the selected conventional CT features [OV(mm), SPV(mm), AS] and a model with the conventional CT and dual-energy CT features [OV(mm), SPV(mm), AS, SGV(HU), SP(HU)]. The AUCs of the model built with the conventional CT and dual-energy CT features were higher than the model built only with the conventional CT features in the training (0.839 vs 0.809) and validation cohorts (0.798 vs 0.738).

CONCLUSION

The non-invasive prediction model developed with the conventional CT and dual-energy CT features may have added value in noninvasively predicting OVB than the model built only with the conventional CT features and may have significant clinical implications on early prevention and treatment of OVB.

ADVANCES IN KNOWLEDGE

Combination of dual-energy CT with conventional CT may have added value for non-invasive prediction of OVB compared to conventional CT.

Ultra-Low-Dose Spectral CT Based on a Multi-level Wavelet Convolutional Neural Network

Spectral computed tomography (CT) based on a photon-counting detector (PCD) is a promising technique with the potential to improve lesion detection, tissue characterization, and material decomposition. PCD-based scanners have several technical issues including operation in the step-and-scan mode and long data acquisition time. One straightforward solution to these issues is to reduce the number of projection views. However, if the projection data are under-sampled or noisy, it would be challenging to produce a correct solution without precise prior information. Recently, deep-learning approaches have demonstrated impressive performance for under-sampled CT reconstruction. In this work, the authors present a multilevel wavelet convolutional neural network (MWCNN) to address the limitations of PCD-based scanners. Data properties of the proposed method in under-sampled spectral CT are analyzed with respect to the proposed deep-running-network-based image reconstruction using two measures: sampling density and data incoherence. This work presents the proposed method and four different methods to restore sparse sampling. We investigate and compare these methods through a simulation and real experiments. In addition, data properties are quantitatively analyzed and compared for the effect of sparse sampling on the image quality. Our results indicate that both sampling density and data incoherence affect the image quality in the studied methods. Among the different methods, the proposed MWCNN shows promising results. Our method shows the highest performance in terms of various evaluation parameters such as the structural similarity, root mean square error, and resolution. Based on the results of imaging and quantitative evaluation, this study confirms that the proposed deep-running network structure shows excellent image reconstruction in sparse-view PCD-based CT. These results demonstrate the feasibility of sparse-view PCD-based CT using the MWCNN. The advantage of sparse view CT is that it can significantly reduce the radiation dose and obtain images with several energy bands by fusing PCDs. These results indicate that the MWCNN possesses great potential for sparse-view PCD-based CT.

Spectral detector CT applications in advanced liver imaging

OBJECTIVE

Spectral detector CT (SDCT) has many applications in advanced liver imaging. If appropriately utilized, this technology has the potential to improve image quality, provide new diagnostic information, and allow for decreased radiation dose. The purpose of this review is to familiarize radiologists with the uses of SDCT in liver imaging.

CONCLUSION

SDCT has a variety of post-processing techniques, which can be used in advanced liver imaging and can significantly add value in clinical practice.

Comparison of spectral computed tomography imaging parameters between squamous cell carcinoma and adenocarcinoma at the gastroesophageal junction

OBJECTIVE

To compare the spectral computed tomography (CT) imaging parameters between squamous cell carcinoma (SCC) and adenocarcinoma (AC) at the gastroesophageal junction (GEJ).

METHODS

A total of 80 patients were enrolled in this retrospective study. Among them, 35 were diagnosed with SCC (SCC group) and 45 were diagnosed with AC (AC group). All patients underwent an enhanced scan with spectral CT. The following CT imaging parameters were evaluated: iodine concentration (IC), water content (WC), effective atomic number (Eff-Z) and slope of the spectral HU curve (λHU) of lesions. Receiver operating characteristic (ROC) curve was used to analyze the predictive value of spectral CT imaging parameters for diagnosis of SCC and AC.

RESULTS

Patients with SCC had lower IC, Eff-Z, and λHU in arterial phase and venous phase compared with AC (p< 0.05). There were no significant differences in WC between the two groups. ROC curve analyses revealed that IC, Eff-Z, and λHU in arterial phase and venous phase were predictors for diagnosis of SCC and AC (AUC > 0.5). Moreover, the IC, Eff-Z and λHU in venous phase had better differential diagnostic performances than that in arterial phase.

CONCLUSIONS

Spectral CT could be useful in the differential diagnosis of SCC and AC at the GEJ. Therefore, a routine spectral CT scan is recommended for patients with carcinoma of the GEJ.

Dual-energy CT enterography in evaluation of Crohn's disease: the role of virtual monochromatic images

PURPOSE

To assess the use of virtual monochromatic images (VMI) for discrimination of affected and non-affected bowel walls in patients with Crohn's disease (CD) as well as to compare mural enhancement between patients with and without CD.

MATERIALS AND METHODS

This retrospective study included 61 patients (47 with CD, 14 without CD). Attenuation value (AV), signal-to noise ratio (SNR), and contrast-to-noise ratio (CNR) were obtained at VMI energy levels from 40 to 110 keV in 10 keV increment. Analyses were performed among affected and non-affected bowel walls in CD patients, as well as from bowel walls in patients without CD. Image quality and mural enhancement were evaluated at VMI energy levels at 40, 70, and 110 keV.

RESULTS

At all energy levels of VMI, each quantitative data for AV, SNR, and CNR showed statistically significant difference between diseased and non-diseased bowel walls in CD patients. In the quantitative assessment of patients with and without CD, the optimal AV and SNR were obtained at 40 keV, and the optimal CNR was obtained at 70 keV. For the qualitative assessment, the best image quality and mural enhancement were obtained at 70 keV and 40 keV, respectively.

CONCLUSION

VMI are helpful for the differentiation of affected bowel walls in CD patients, providing high diagnostic accuracy.

Dual-Energy CT: A Paradigm Shift in Acute Traumatic Abdomen

Abdominal trauma, one of the leading causes of death under the age of 45, can be broadly classified into blunt and penetrating trauma, based on the mechanism of injury. Blunt abdominal trauma usually results from motor vehicle collisions, fall from heights, assaults, and sports and is more common than penetrating abdominal trauma, which is usually seen in firearm injuries and stab wounds. In both blunt and penetrating abdominal trauma, an optimized imaging approach is mandatory to exclude life-threatening injuries. Easy availability of the portable ultrasound in the emergency department and trauma bay makes it one of the most commonly used screening imaging modalities in the abdominal trauma, especially to exclude hemoperitoneum. Evaluation of the visceral and vascular injuries in a hemodynamically stable patient, however, warrants intravenous contrast-enhanced multidetector computed tomography scan. Dual-energy computed tomography with its postprocessing applications such as iodine selective imaging and virtual monoenergetic imaging can reliably depict the conspicuity of traumatic solid and hollow visceral and vascular injuries.

Reducing Radiation Dose and Improving Image Quality in CT Portal Venography Using 80 kV and Adaptive Statistical Iterative Reconstruction-V in Slender Patients

OBJECTIVE

To explore the feasibility of reducing radiation dose and improving image quality in CT portal venography (CTPV) using 80 kV and adaptive statistical iterative reconstruction-V(ASIR-V) in slender patients in comparison with conventional protocol using 120 kV and ASIR.

METHODS

Sixty slender patients for enhanced abdominal CT scanning were randomly divided into group A and group B. Group A used the conventional 120 kV tube voltage, 600 mgI/kg contrast dose and reconstructed with the recommended 40% ASIR. Group B used 80 kV tube voltage, 350 mgI/kg contrast dose and reconstructed with ASIR-V from 40% to 100% with 10% interval. The CT values and standard deviation (SD) values of the main portal vein, left branch, and right branch of portal vein, liver, and erector spinae at the same level were measured to calculate the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The image quality was subjectively scored by two experienced radiologists blindly using a 5-point criterion. The contrast dose, volumetric CT dose index, and dose length product were recorded in both groups and the effective dose was calculated.

RESULTS

There was no significant difference in general data between the two groups (p > 0.05), the effective dose and contrast dose in group B were reduced by 63.3% (p < 0.001) and 39.7% (p < 0.001), respectively compared with group A. With the percentage of ASIR-V increased in group B, the CT values showed no significant difference, while the SD values gradually decreased and SNR values and CNR values increased accordingly. Compared with group A, group B demonstrated similar CT values (p > 0.05), while the SD values with 80% ASIR-V to 100% ASIR-V were significantly lower than those of 40% ASIR (p < 0.001), and the SNR values and CNR values with 70% ASIR-V to 100% ASIR-V were significantly higher than those of 40% ASIR (p < 0.001). The subjective image quality scores by the two radiologists had excellent consistency (kappa value>0.75, p < 0.001), and the final subjective image quality scores and the subjective scores in each of the 5 scoring categories with 60% ASIR-V to 100% ASIR-V were all significantly higher than those of 40% ASIR, and 80% ASIR-V obtained the highest subjective score among different reconstructions.

CONCLUSION

In CTPV, the application of 80 kV and ASIR-V reconstruction in slender patients can significantly reduce radiation dose (by 63.3%) and contrast agent dose (by 39.7%). Compared with the recommended 40% ASIR using 120 kV, ASIR-V with 80% to 100% percentages can further improve image quality and with 80% ASIR-V being the best reconstruction algorithm.

ADVANCES IN KNOWLEDGE

CTPV with 80 kV and ASIR-V algorithm in slender patients can significantly reduce radiation dose and contrast agent dose as well as improve image quality, compared with the conventional 120 kV protocol using 40% ASIR.

Iodine load reduction in dual-energy spectral CT portal venography with low energy images combined with adaptive statistical iterative reconstruction

OBJECTIVE

To study the application of using low energy images combined with adaptive statistical iterative reconstruction (ASiR) in dual-energy spectral CT portal venography (CTPV) to reduce iodine load.

METHODS

41 patients for CTPV were prospectively and randomly divided into two groups. Group A ( n = 21) used conventional 120 kVp scanning protocol with contrast dose at 0.6 gI/kg while group B ( n = 20) used dual-energy spectral imaging with reduced contrast dose at 0.3 gI/kg. The 120 kVp images in Group A and 50 keV images in Group B were reconstructed with 40% ASiR. The contrast-to-noise ratio of portal vein was calculated. The image quality and the numbers of intrahepatic portal vein branches were evaluated by two experienced radiologists using a 5-point scoring system.

RESULTS

Group B reduced iodine load by 52% compared to Group A (17.21 ± 3.30 gI vs 35.80 ± 6.18 gI, p < 0.001). All images in both groups were acceptable for diagnosis. CT values and standard deviations in portal veins of Group B were higher than Group A (all p < 0.05); There were no statistical differences in contrast-to-noise ratio, image quality score and the number of observed portal vein branches between the two groups (all p > 0.05), and the two observers had excellent agreement in image quality assessment (all κ > 0.75).

CONCLUSION

The use of 50 keV images in dual-energy spectral CTPV with ASiR reduces total iodine load by 52% while maintaining good image quality.

ADVANCES IN KNOWLEDGE

Spectral CT images combined with ASiR can be used in low contrast dose CTPV portal venography to maintain image quality and reduce contrast dose.

Effects of low-dose energy spectrum scanning combined with adaptive statistical iterative reconstruction on the quality of imaging in Budd-Chiari syndrome

OBJECTIVE

To assess the quality and diagnostic accuracy of monochromatic images combined with adaptive statistical iterative reconstruction (ASIR) performed via spectral computed tomography (CT) in patients with Budd-Chiari syndrome (BCS).

METHODS

Sixty-two patients with BCS underwent pectral CT with upper abdominal two-phase contrast-enhanced scanning to generate a 60keV monochromatic energy level combined with ASIR (ranging from 0% -100%) during the portal venous phase (PVP) and the hepatic venous phase (HVP). One-way ANOVA was used to compare vessel-to-liver contrast-to-noise ratio (CNR) for the portal vein (PV), hepatic vein (HV), and inferior vena cava (IVC). Subjective evaluations of the images in the three groups were conducted by image quality assessors and compared via Kruskal-Wallis H test.

RESULTS

The CNR values of the PV trunk, HV, IVC, liver parenchyma and pancreas were within ASIR (ranging from 0% - 100%) weight, and the difference were statistically significant (p <0.05). The highest overall image score was distributed at 50% ASIR weight value. Higher CNR values of HV, hepatic parenchyma and pancreas were obtained in the IVC type than in mixed and HV types (respective p values = 0.035, 0.019 and 0.042). Higher CNR values of the IVC were obtained in the HV type than in mixed and IVC types (p = 0.032). The CNR value of the IVC in the mixed type was less than that of the HV type (p = 0.028). The CNR values of the HV and liver parenchyma in mixed type were lower than those of the IVC type (p = 0.016 and 0.038, respectively). The CNR value of pancreas in IVC type was higher than that of the HV type (p = 0.037). The diagnostic value of CNR in patients with the IVC type was higher than that in patients with mixed and HV type, while the diagnostic value of CNR was found to be the lowest for the HV type (p = 0.043).

CONCLUSION

A monochromatic energy level of 60 keV with 50% ASIR can significantly improve image quality in cases of BCS.

Dual-Energy Spectral Computed Tomography With Adaptive Statistical Iterative Reconstruction for Improving Image Quality of Portal Venography

OBJECTIVE

The aim of the study was to investigate whether spectral computed tomography (CT) plus adaptive statistical iterative reconstruction (ASIR) could improve imaging quality of computed tomography portal venography (CTPV).

METHODS

Sixty-four patients underwent CTPV, with CT number of portal vein (PV) less than 150 HU in portal phase, were divided into 2 groups A (n = 31), using standard 120-kVp protocol. group B (n = 33), using spectral CT protocol. Standard 120-kVp images were reconstructed with 40% ASIR, and monochromatic images at 60 keV were reconstructed with the following 4 ASIR percentages: 0%, 20%, 40%, and 60%. The CT number, image noise, and contrast-to-noise ratio in main PV were measured. The maximum intensity projection and volume-rendering images were used for subjective evaluation. These 2 kinds of results were statistically analyzed.

RESULTS

The contrast-to-noise ratio and subjective scoring of PV increased gradually from 120-kVp images to 60% weight ASIR (3.44 ± 0.95, 4.58 ± 1. 59, 5.26 ± 1.85, 6.18 ± 2.18, and 7.39 ± 2.65 and 4.35 ± 1.17, 6.21 ± 1.29, 6.48 ± 1.35, 6.85 ± 1.28, and 7.00 ± 1.19). There were statistically different for the 5 groups (P < 0.001). The CT number of the PV in the 60-kiloelectron volt spectral images had higher than the 120-kVp images (P < 0.001). The noise of 120 kVp was significantly higher than those of 60% ASIR and significantly lower than those of 0% ASIR (both P < 0.001), and there were no significant differences between 120-kVp, 20% ASIR, and 40% ASIR (P = 0.107 and 1.000, respectively). The diagnostic acceptability was highest at 40% ASIR.

CONCLUSIONS

Forty-percent ASIR addition to the 60-kiloelectron volt monochromatic image could improve image quality of CTPV comparing with conventional 120-kVp images.

Gemstone spectral imaging in lung cancer: A preliminary study

The present study aimed to evaluate the application of gemstone spectral imaging (GSI) for multi-parameter quantitative measurement in lung cancer.The study retrospectively enrolled 30 patients with lung cancer who underwent chest contrast enhanced CT scan with GSI mode. The GSI viewer was used for image display and data analysis. Optimal energy value, CT values at 40 keV, 70 keV and optimal energy level, spectral curve slope, effective atomic number (Zeff), iodine concentration (IC), and water concentration (WC) at the region of interest were measured and analyzed by statistical methods.The optimal energy value for optimal contrast-to-noise ratio on plain scan, arterial phase and venous phase was 62.2 ± 5.38 keV, 50.63 ± 3.84 keV, and 52.5 ± 3.7 keV, respectively. There were significant differences in CT values at different energy levels on each scan phase (P = .033). The spectral curve slope values among 40 to 70 keV, 40 to 100 keV, and 40 to 140 keV were significantly different (P < .001). No significant difference with the slope between arterial phase and venous phase at each energy level interval was observed. Zeff on plain scan, arterial phase, and venous phase was 7.75 ± 0.15, 8.38 ± 0.37, and 8.38 ± 0.30, respectively. Positive correlation was observed among IC, normalized IC, and Zeff on enhanced scan.Multiparameter of GSI can be used for lung tumor lesion evaluation. Different parameters were correlated and provide multiple qualitative and quantitative information together.

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.

Subtraction CT angiography in head and neck with low radiation and contrast dose dual-energy spectral CT using rapid kV-switching technique

OBJECTIVE

To investigate the application of low radiation and contrast dose spectral CT angiology using rapid kV-switching technique in the head and neck with subtraction method for bone removal.

METHODS

This prospective study was approved by the local ethics committee. 64 cases for head and neck CT angiology were randomly divided into Groups A (n = 32) and B (n = 32). Group A underwent unenhanced CT with 100 kVp, 200 mA and contrast-enhanced CT with spectral CT mode with body mass index-dependent low dose protocols. Group B used conventional helical scanning with 120 kVp, auto mA for noise index of 12 HU (Hounsfield unit) for both the unenhanced and contrast-enhanced CT. Subtraction images were formed by subtracting the unenhanced images from enhanced images (with the 65 keV-enhanced spectral CT image in Group A). CT numbers and their standard deviations in aortic arch, carotid arteries, middle cerebral artery and air were measured in the subtraction images. The signal-to-noise ratio and contrast-to-noise ratio for the common and internal carotid arteries and middle cerebral artery were calculated. Image quality in terms of bone removal effect was evaluated by two experienced radiologists independently and blindly using a 4-point system. Radiation dose and total iodine load were recorded. Measurements were statistically compared between the two groups.

RESULTS

The two groups had same demographic results. There was no difference in the CT number, signal-to-noise and contrast-to-noise ratio values for carotid arteries and middle cerebral artery in the subtraction images between the two groups (p > 0.05). However, the bone removal effect score [median (min-max)] in Group A [4 (3-4)] was rated better than in Group B [3 (2-4)] (p < 0.001), with excellent agreement between the two observers (κ > 0.80). The radiation dose in Group A (average of 2.64 mSv) was 57% lower than the 6.18 mSv in Group B (p < 0.001). The total iodine intake in Group A was 13.5g, 36% lower than the 21g in Group B.

CONCLUSION

Spectral CT imaging with rapid kV-switching in the subtraction angiography in head and neck provides better bone removal with significantly reduced radiation and contrast dose compared with conventional subtraction method. Advances in knowledge: This novel method provides better bone removal with significant radiation and contrast dose reduction compared with the conventional subtraction CT, and maybe used clinically to protect the thyroid gland and ocular lenses from unnecessary high radiation.

Automatic spectral imaging protocol selection combined with iterative reconstruction can enhance image quality and decrease radiation and contrast dosage in abdominal CT angiography

PURPOSE

To investigate the effect of automatic spectral imaging protocol selection (ASIS) and adaptive statistical iterative reconstruction (ASIR) technology in reducing radiation and contrast dosage.

METHODS

Sixty-four patients were randomly divided into two groups for abdominal computed tomography (CT): the experiment group with ASIS plus 50% ASIR and the control with 120 kVp voltage.

RESULTS

The CT dose-index volume decreased by 23.68 and 23.57% and the dose-length product dropped by 25.59 and 18.45% in the arterial and portal venous phases, respectively, in the experiment than control group. The contrast dose was reduced by 16.86% in the experiment group. In the 55 keV + 50% ASIR group, the arterial contrast-to-noise ratio and scores were significantly (P < 0.05) higher than in the control group in the arterial phase while the portal contrast-to-noise ratio and scores were not significantly different between the two groups (P > 0.05).

CONCLUSION

The ASIS technique plus 50% ASIR can enhance image quality of the abdominal structures while decreasing the radiation and contrast dosage compared with the conventional scan mode.

Quantitative assessment of the degree of differentiation in colon cancer with dual-energy spectral CT

OBJECTIVE

To evaluate dual-energy spectral CT imaging in evaluating the degree of differentiation in colon cancer.

METHODS

Forty-seven colon cancer patients underwent spectral CT during arterial phase (AP) and portal venous phase (PP), and were characterized pathologically differentiated to well-differentiated (A, n = 18) and poorly differentiated or undifferentiated carcinoma group (B, n = 29). Lesion iodine concentration (IC) was measured and normalized to that of aorta (NIC). CT numbers were measured and the slope (λ _HU) of the spectral HU curve was calculated. These parameters were statistically compared between the two groups. ROC curves were used to evaluate their diagnostic efficacies.

RESULTS

There were significant differences in IC (1.01 ± 0.20 vs. 1.59 ± 0.57 mg/ml), NIC (0.12 ± 0.03 vs. 0.19 ± 0.09), λ _HU (1.41 ± 0.29 vs. 2.03 ± 0.85), and CT number at 70 keV (48.61 ± 9.03HU vs. 63.97 ± 15.86HU) between groups A and B in AP (p < 0.05), but no difference in PP. Using IC = 1.13 mg/ml in AP as the threshold, one obtained a sensitivity of 81.8% and a specificity of 71.4% for differentiating well-differentiated from poorly differentiated or undifferentiated carcinoma. These values were statistically higher than those (64.7% and 62.3%) using CT number at 70 keV.

CONCLUSION

Spectral CT imaging parameters (IC, NIC, and λ _HU) in AP provide improved accuracy for evaluating the degrees of differentiation in colon cancer than CT number at 70 keV.

Assessment of 70-keV virtual monoenergetic spectral images in abdominal CT imaging: A comparison study to conventional polychromatic 120-kVp images

PURPOSE

To evaluate the image quality of 70-keV virtual monoenergetic (monoE) abdominal CT images compared to 120-kVp polychromatic images generated from a spectral detector CT (SDCT) scanner.

METHODS

This prospective study included generation of a 120-kVp polychromatic dataset and a 70-keV virtual monoE dataset after a single contrast-enhanced CT acquisition on a SDCT scanner (Philips Healthcare) during portal venous phase. The attenuation values (HU), noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured in the liver, spleen, pancreas, kidney, aorta, portal vein, and muscle. The subjective image quality including noise, soft tissue contrast, sharpness, and overall image quality were graded on a 5-point Likert scale by two radiologists independently (1-worst image quality, 5-best image quality). Statistical analysis was performed using paired sample t test and Fleiss's Kappa.

RESULTS

Fifty-five patients (54.3 ± 16.8 y/o; 28 M, 27 F) were recruited. The noise of target organs was significantly lower in virtual monoE images in comparison to polychromatic images (p < 0.001). The SNR and CNR were significantly higher in virtual monoE images (p < 0.001 for both). Subjective image quality of 70-keV virtual monoE images was significantly better (p < 0.001) for all evaluated parameters. Median scores for all subjective parameters were 3.0 versus 4.0 for polychromatic vs virtual monoE images, respectively. The inter-reader agreement for overall image quality was good (Kappa were 0.767 and 0.762 for polychromatic and virtual monoE images, respectively).

CONCLUSION

In abdominal imaging, 70-keV virtual monoE CT images demonstrated significantly better noise, SNR, CNR, and subjective score compared to conventional 120-kVp polychromatic images.

Contrast Dose and Radiation Dose Reduction in Abdominal Enhanced Computerized Tomography Scans with Single-phase Dual-energy Spectral Computerized Tomography Mode for Children with Solid Tumors

Background:

Contrast dose and radiation dose reduction in computerized tomography (CT) scan for adult has been explored successfully, but there have been few studies on the application of low-concentration contrast in pediatric abdominal CT examinations. This was a feasibility study on the use of dual-energy spectral imaging and adaptive statistical iterative reconstruction (ASiR) for the reduction of radiation dose and iodine contrast dose in pediatric abdominal CT patients with solid tumors.

Methods:

Forty-five patients with solid tumors who had initial CT (Group B) and follow-up CT (Group A) after chemotherapy were enrolled. The initial diagnostic CT scan (Group B) was performed using the standard two-phase enhanced CT with 320 mgI/ml concentration contrast, and the follow-up scan (Group A) was performed using a single-phase enhanced CT at 45 s after the beginning of the 270 mgI/ml contrast injection using spectral mode. Forty percent ASiR was used for the images in Group B and monochromatic images with energy levels ≥60 keV in Group A. In addition, filtered back-projection (FBP) reconstruction was used for monochromatic images <60 keV in Group A. The total radiation dose, total iodine load, contrast injection speed, and maximum injection pressure were compared between the two groups. The 40 keV and 60 keV spectral CT images of Group A were compared with the images of Group B to evaluate overall image quality.

Results:

The total radiation dose, total iodine load, injection speed, and maximum injection pressure for Group A were decreased by 19%, 15%, 34.4%, and 18.3%, respectively. The optimal energy level in spectral CT for displaying the abdominal vessels was 40 keV. At this level, the CT values in the abdominal aorta and its three branches, the portal vein and its two branches, and the inferior vena cava were all greater than 340 hounsfield unit (HU). The abdominal organs of Groups A and B had similar degrees of absolute and relative enhancement (t = 0.36 and −1.716 for liver, −0.153 and −1.546 for pancreas, and 2.427 and 0.866 for renal cortex, all P > 0.05). Signal-to-noise ratio of the abdominal organs was significantly lower in Group A than in Group B (t = −8.11 for liver, −7.83 for pancreas, and −5.38 for renal cortex, all P < 0.05). However, the subjective scores for the 40 keV (FBP) and 60 keV (40% ASiR) spectral CT images determined by two radiologists were all >3, indicating clinically acceptable image quality.

Conclusions:

Single-phase, dual-energy spectral CT used for children with solid abdominal tumors can reduce contrast dose and radiation dose and can also maintain clinically acceptable image quality.

A Comparison of the Image Quality and Radiation Dose With Routine Computed Tomography and the Latest Gemstone Spectral Imaging Combination of Different Scanning Protocols in Computed Tomography Angiography of the Kidney

OBJECTIVE

The objective of our study was to compare the image quality and radiation dose of computed tomography angiography (CTA) of the kidney in patients with different body mass indexes using routine CT and the latest gemstone spectral imaging (GSI) combination of different scanning protocols with the adaptive statistical iterative reconstruction 2.0 algorithm.

METHODS

A total of 90 patients who had undergone a CTA of the kidney were divided into 3 groups (A, B, and C), with 30 patients in each group. Group A underwent a routine CT examination, whereas groups B and C underwent GSI with different scanning protocols. All images were restructured using the adaptive statistical iterative reconstruction 2.0. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated when the kidney CTA was completed. Each subjective image evaluation used a 5-point scoring method and was conducted by 2 independent radiologists. The CT dose index of volume and the dose-length product were recorded, and the mean value was calculated. The dose-length product was converted to the effective dose. All data were compared with a 1-way analysis of variance.

RESULTS

The SNR, CNR, and subjective image quality in group A were significantly lower than those in groups B and C (P < 0.01). There were no significant differences in SNR, CNR, and subjective image quality between groups B and C. The effective dose of group C decreased by 46.05% and 15.03% relative to those of groups A and B, respectively (P < 0.01).

CONCLUSIONS

The latest GSI with different scanning protocols can more effectively reduce the radiation dose than can the routine CT scan mode for a kidney CTA while still maintaining diagnostic image quality.

Dual-Energy Spectral CT: Various Clinical Vascular Applications

Single-source dual-energy (DE) computed tomography (CT) with fast switching of tube voltage allows projection-based image reconstruction, substantial reduction of beam-hardening effects, reconstruction of accurate monochromatic images and material decomposition images (MDIs), and detailing of material composition by using x-ray spectral information. In vascular applications, DE CT is expected to overcome limitations of standard single-energy CT angiography, including patient exposure to nephrotoxic contrast medium and carcinogenic radiation, insufficient contrast vascular enhancement, interference from metallic and beam-hardening artifacts and severe vessel calcification, and limited tissue characterization and perfusion assessment. Acquisition of low-energy monochromatic images and iodine/water MDIs can reasonably reduce contrast agent dose and improve vessel enhancement. Acquisition of virtual noncontrast images, such as water/iodine MDIs, can reduce overall radiation exposure by replacing true noncontrast CT in each examination. Acquisition of monochromatic images by using metal artifact reduction software or acquisition of iodine/water MDIs can reduce metal artifacts with preserved or increased vessel contrast, and subtraction of monochromatic images between two energy levels can subtract coils composed of dense metallic materials. Acquisition of iodine/calcium (ie, hydroxyapatite) MDIs permits subtraction of vessel calcification and improves vessel lumen delineation. Sensitive detection of lipid-rich plaque can be achieved by using fat/water MDIs, the spectral Hounsfield unit curve (energy level vs CT attenuation), and a histogram of effective atomic numbers included in an image. Various MDIs are useful for accurate differentiation among materials with high attenuation values, including contrast medium, calcification, and fresh hematoma. Iodine/water MDIs are used to assess organ perfusion, such as in the lungs and myocardium. Understanding these DE CT techniques enhances the value of CT for vascular applications. (©)RSNA, 2016.

The optimal monochromatic spectral computed tomographic imaging plus adaptive statistical iterative reconstruction algorithm can improve the superior mesenteric vessel image quality

OBJECTIVE

To investigate the effect of the optimal monochromatic spectral computed tomography (CT) plus adaptive statistical iterative reconstruction on the improvement of the image quality of the superior mesenteric artery and vein.

MATERIALS AND METHODS

The gemstone spectral CT angiographic data of 25 patients were reconstructed in the following three groups: 70KeV, the optimal monochromatic imaging, and the optimal monochromatic plus 40%iterative reconstruction mode. The CT value, image noises (IN), background CT value and noises, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and image scores of the vessels and surrounding tissues were analyzed.

RESULTS

In the 70KeV, the optimal monochromatic and the optimal monochromatic images plus 40% iterative reconstruction group, the mean scores of image quality were 3.86, 4.24 and 4.25 for the superior mesenteric artery and 3.46, 3.78 and 3.81 for the superior mesenteric vein, respectively. The image quality scores for the optimal monochromatic and the optimal monochromatic plus 40% iterative reconstruction groups were significantly greater than for the 70KeV group (P<0.05). The vascular CT value, image noise, background noise, CNR and SNR were significantly (P<0.001) greater in the optimal monochromatic and the optimal monochromatic images plus 40% iterative reconstruction group than in the 70KeV group. The optimal monochromatic plus 40% iterative reconstruction group had significantly (P<0.05) lower image and background noise but higher CNR and SNR than the other two groups.

CONCLUSION

The optimal monochromatic imaging combined with 40% iterative reconstruction using low-contrast agent dosage and low injection rate can significantly improve the image quality of the superior mesenteric artery and vein.

Single source dual energy CT: What is the optimal monochromatic energy level for the analysis of the lung parenchyma?

OBJECTIVE

To determine the optimal monochromatic energy level for lung parenchyma analysis in spectral CT.

METHODS

All 50 examinations (58% men, 64.8±16yo) from an IRB-approved prospective study on single-source dual energy chest CT were retrospectively included and analyzed. Monochromatic images in lung window reconstructed every 5keV from 40 to 140keV were independently assessed by two chest radiologists. Based on the overall image quality and the depiction/conspicuity of parenchymal lesions, each reader had to designate for every patient the keV level providing the best diagnostic and image quality.

RESULTS

72% of the examinations exhibited parenchymal lesions. Reader 1 picked the 55keV monochromatic reconstruction in 52% of cases, 50 in 30% and 60 in 18%. Reader 2 chose 50keV in 52% cases, 55 in 40%, 60 in 6% and 40 in 2%. The 50 and 55keV levels were chosen by at least one reader in 64% and 76% of all patients, respectively. Merging 50 and 55keV into one category results in an optimal setting selected by reader 1 in 82% of patients and by reader 2 in 92%, with a 74% concomitant agreement.

CONCLUSION

The best image quality for lung parenchyma in spectral CT is obtained with the 50-55keV monochromatic reconstructions.

Application of low concentration contrast medium in spectral CT imaging for CT portal venography

OBJECTIVE

To investigate the effect of low-concentration contrast medium on spectral computed tomography (CT) image quality for portal venography CT.

METHODS

150 patients with suspected portal diseases were divided into three groups and had spectral CT examination using a GE Discovery CT 750 HD scanner. The patients in three groups were injected with different concentrations of iodine (350 mgI/mL, 315 mgI/mL and 280 mgI/mL) at an injection rate of 4.0-5.0 mL/s with 1.2 mL/kg (body weight) of contrast medium, respectively. During the portal vein imaging phase, 0.625 mm-slice-thickness monochromatic images and optimal monochromatic images were obtained. Optimal keV mono-energy was achieved using the optimal contrast-to-noise ratio (CNR) in the portal vein relative to the erector spinae muscle. Volume rendering and maximum intensity projection methods were applied to generate portal venography. The CT values and standard deviations were measured at the portal vein, the erector spinae muscle, and the abdomen fat, respectively. These values were used to calculate the signal-to-noise ratio (SNR); while CNR was calculated using CT values of the portal vein and erector spinae muscle. The overall imaging quality was evaluated on a five-point scale by two radiologists with at least five years' experience. Comparisons among the three groups were performed using One-Way ANOVA test.

RESULTS

Monochromatic images at 50-53 keV demonstrated the best CNR for both the portal vein and erector spinae muscle. SNR and CNR of images with different contrast medium concentrations were similar (P > 0.05). The five-point scores were also similar (P > 0.05) for the three groups. The total iodine intake at 280 mgI/mL was 25.4% lower than that at 350 mgI/mL.

CONCLUSIONS

Spectral CT with monochromatic images at 50-53 keV allows significant reduction in iodine load while improving portal vein signal intensity and maintaining image quality.

CT pulmonary angiography using different noise index values with an iterative reconstruction algorithm and dual energy CT imaging using different body mass indices: Image quality and radiation dose

OBJECTIVE

To investigate the differences in imaging quality and radiation dose in CT pulmonary angiography (CTPA) by using fast-kV switching dual energy CT imaging and 3D Smart mA modulation at different body mass indices (BMIs) and at different noise index (NI) values with an adaptive statistical iterative reconstruction (ASIR) algorithm.

METHODS

Four hundred patients who underwent CTPA were equally divided into two groups: A (18.5 kg/m2 ≦ BMI <24.9 kg/m2) and B (24.9 kg/m2 ≦ BMI ≦ 4.9 kg/m2). The groups were randomly subdivided into four subgroups (n = 50): A1-A4 and B1-B4. The patients in subgroups A1 and B1 underwent fast-kV switching dual energy CT imaging. The other patients underwent 3D Smart mA modulation with the ASIR algorithm at NI values 26, 36, and 46 for A2/B2, A3/B3, and A4/B4, respectively. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated after CTPA. Images were then subjectively evaluated using a 5-point scale. The volume CT dose index and dose-length product (DLP) were recorded and their means calculated. The DLP was converted to the effective dose (ED).

RESULTS

In group A, the SNR, CNR, and subjective image scores showed no statistical differences (P > 0.05). The ED in subgroup A4 was 67.12% and 31.53% lower than that in A1 and A2, respectively. In group B, the variables showed no significant differences between the subgroups B3, B1, and B2 (P > 0.05). The ED in subgroup B3 was 50.12% and 35.95% lower than that in B1 and B2, respectively.

CONCLUSIONS

Setting different NI values according to BMIs and applying the ASIR algorithm can more effectively reduce the radiation dose in CTPA than in fast-kV switching dual energy CT, while maintaining image quality. Imaging may be performed at NI = 46 in patients with lower BMI (group A) and at NI = 36 in patients with higher BMI (group B).

Spectral CT Reconstruction with Image Sparsity and Spectral Mean

Photon-counting detectors can acquire x-ray intensity data in different energy bins. The signal to noise ratio of resultant raw data in each energy bin is generally low due to the narrow bin width and quantum noise. To address this problem, here we propose an image reconstruction approach for spectral CT to simultaneously reconstructs x-ray attenuation coefficients in all the energy bins. Because the measured spectral data are highly correlated among the x-ray energy bins, the intra-image sparsity and inter-image similarity are important prior acknowledge for image reconstruction. Inspired by this observation, the total variation (TV) and spectral mean (SM) measures are combined to improve the quality of reconstructed images. For this purpose, a linear mapping function is used to minimalize image differences between energy bins. The split Bregman technique is applied to perform image reconstruction. Our numerical and experimental results show that the proposed algorithms outperform competing iterative algorithms in this context.

Spectral CT imaging in cervical computed tomography angiography: comparison of spectral CT monochromatic imaging and conventional CT polychromatic imaging

OBJECTIVE

To compare the image quality of spectral CT monochromatic imaging and conventional CT polychromatic imaging for analysing CTAs in patients with cervical cancer.

METHODS

In this IRB approved prospective study, 60 patients who had been diagnosed with cervical cancer underwent pelvic arterial CTA between May 2013 and July 2013. They were randomly divided into two groups; one group (30 patients) received 120 kVp polychromatic imaging (conventional CT group) and the other group (30 patients) received spectral CT imaging (spectral CT group), while all patients in both the groups received injections of 1 ml/kg of contrast agent. A total of 101 sets of monochromatic images (40-140 keV) were obtained via data reconstruction in the spectral CT group, and the monochromatic images with the best contrast-to-noise ratio (CNR) between the common iliac artery and pelvic fat (i.e. the best monochromatic energy) were selected. The best monochromatic images for the spectral CT group and the polychromatic images for the conventional CT group were postprocessed and visualised in MIP, VR and CPR mode. The CT attenuation value, noise and CNR of bilateral common iliac arteries were measured with the best monochromatic energy, as well as with 70 keV, in the spectral CT group and in the conventional CT group. The quality of the CT images was evaluated with a 5-point scale. The CTDIvol and the dose-length product (DLP) of the two groups were measured, and the results were statistically analysed.

RESULTS

When images were at 50±1 keV, the common iliac artery and pelvic fat had the highest CNR, which was 72.00% higher than the images at 70 keV (P=.001) in the spectral group, and thus, the images at 50±1 keV were considered to have the best monochromatic energy. The average CT value of the internal iliac artery, which had the best monochromatic energy from the spectral CT group, was higher than that of the images from the conventional CT group (603.96±62.68 vs 251.24±28.77; P<.001), and the differences in the CNR (73.97±11.83 vs 45.21±16.63) and the subjective score (3.10±1.73 vs 2.80±1.63) were statistically significant (both P<.05). There were no significant differences in the CTDIvol (10.48±2.86 vs 12.38±1.88 mGy) or the DLP (317.76±95.50 vs 332.25±21.25 mGy cm) between the spectral and the conventional CT groups.

CONCLUSION

Monochromatic spectral CT imaging has excellent soft tissue contrast and good spatial resolution and can visualise the arteries and branches supplying the tumours more clearly in patients with cervical cancer. Compared with polychromatic images, monochromatic spectral CT images are higher quality, which helps the treatment of patients with cervical cancer.

Feasibility of spectral imaging with low-concentration contrast medium in abdominal CT angiography of obese patients

OBJECTIVE

To explore the application value of dual-energy spectral imaging scanning with low radiation dose and low-concentration contrast medium (270 mg I/mL) in abdominal CT angiography (CTA) of obese patients.

METHODS

A total of 127 obese patients (BMI≥25 kg/m(2) and waist circumference ≥900 mm) referred for abdominal CTA were prospectively enrolled in the study. The patients were divided into two groups; in group A (n=69), a spectral imaging scan mode and 270 mg I/mL iodine concentration contrast medium was used, and in group B (n=58), a conventional imaging scan mode using 120 kVp and 350 mg I/mL iodine concentration contrast medium was used. The image quality of the right renal artery in the two groups was evaluated by two observers using a 5-point scale, and the scores were compared using the Mann-Whitney U-test; the inter-observer agreement for the scores was analysed using the Kappa test. The CT values of the abdominal aorta, the superior mesenteric artery, the common hepatic artery and the splenic artery, and the CT value and standard deviation (SD) of the erector spinae at the level of the right renal hilum in groups A and B were measured by two observers; the inter-observer agreement of the measurement data was analysed using the inter-class correlation coefficient test. The following parameters were compared between the two groups using an independent sample t-test: the CT values of the abdominal aorta and its main branches; the image contrast-to-noise ratio (CNR) and figure of merit (FOM) of the abdominal aorta; the CT dose index (CTDIvol ); the dose length product (DLP); and the total iodine intake of the patients. P<.05 suggested a statistically significant difference.

RESULTS

The image scores of the right renal artery in groups A (4.59±0.60) and B (4.53±0.63) were the same (P=.57), with good inter-observer agreement. The CT values of the abdominal aorta, the superior mesenteric artery, the common hepatic artery and the splenic artery were >300 HU in both the groups; there was no statistically significant difference between the two groups (all P>.05), and inter-observer agreement was also good. Group A had significantly higher CNR and FOM values in the abdominal aorta than group B (all P<.001). Compared with group B, the CTDIvol and DLP values in group A were decreased by 46% and 35%, respectively. The total iodine intake for patients in group A was 27 g, 23% lower than the 35 g intake for patients in group B.

CONCLUSION

Compared with conventional CT, spectral CT imaging significantly reduces both radiation dose and contrast dose while maintaining image quality in abdominal CTA for patients with central obesity and high BMI.

Adrenal and nephrogenic hypertension: an image quality study of low tube voltage, low-concentration contrast media combined with adaptive statistical iterative reconstruction

PURPOSE

The aim of this study was to investigate the effect of using low tube voltage, low-concentration contrast media and adaptive statistical iterative reconstruction (ASIR) for reducing the radiation and iodine contrast doses in adrenal and nephrogenic hypertension patients.

METHODS AND MATERIALS

A total of 148 hypertension patients who were suspected for adrenal lesions or renal artery stenoses were assigned to two groups and. Group A (n=74) underwent a low tube voltage, low molecular weight dextran enhanced multi-detector row spiral CT (MDCT) (80 kVp, 270 mg I/mL contrast agent), and the raw data were reconstructed with standard filtered back projection (FBP) and ASIR at four different levels of blending (20%, 40%, 60% and 80%, respectively). The control group (Group B, n=74) underwent conventional MDCT (120 kVp, 370 mg I/mL contrast agent), and the data were reconstructed with FBP. The CT values, standard deviation (SD), signal-noise-ratio (SNR) and contrast-noise-ratio (CNR) were measured in the renal vessels, normal adrenal tissue, adrenal neoplasms and subcutaneous fat. The volume CT dose index (CTDIvol ) and dose length product (DLP) were recorded, and an effective dose (ED) was obtained. Two-tailed independent t-tests, paired Chi-square tests and Kappa consistency tests were used for statistical analysis of the data.

RESULTS

The CTDIvol , DLP and total iodine dose in group A were decreased by 47.8%, 49.0% and 26.07%, respectively, compared to group B (P<.001). In the qualitative quality analysis, the radiologists rated the 60% ASIR the highest. The mean value of noise (SD) was significantly lower in the 40%, 60% and 80% ASIR-A groups compared with FBP-B for all comparisons. Compared to FBP-B, CNR was significantly higher, with 40%, 60% and 80% ASIR in renal artery stems (P<.05). Compared with FBP-B, a significant increase in the SNR of 40%, 60%, or 80% ASIR was observed in all cases (P<.05).

CONCLUSIONS

Compared with conventional protocols, the use of low tube voltage, low-concentration contrast media and 60% ASIR provides similar enhancement and image quality with a reduced radiation dose and contrast iodine dose.

Improving Image Quality for Lung Cancer Imaging With Optimal Monochromatic Energy Level in Dual Energy Spectral Computed Tomography

OBJECTIVE

The aim of this study was to find optimal monochromatic spectral computed tomography (CT) level to improve image quality of lung cancer.

METHODS

Fifty patients with lung cancers were scanned by spectral CT; monochromatic images at 50, 60, 70 and 80 keV energy levels were generated; and objective analysis including image noise, lesion-to-lung contrast-to-noise ratio, and CT number difference between central and peripheral regions of tumor (dCT value) were measured and compared. Subjective assessment about the overall image quality and inhomogeneity enhancement was compared.

RESULTS

The highest contrast-to-noise ratio value and subjective score of image quality were obtained at 70 keV, which were superior to those of 50- and 80-keV series (all P < 0.05). The subjective score of the inhomogeneity evaluation was peaked at 60-keV series and significantly higher than other energy levels (all P < 0.05).

CONCLUSIONS

Both objective and subjective image analysis of lung cancers may be improved with the combined observation of 60 keV and 70 keV monochromatic images in spectral CT.

Dual Energy CT (DECT) Monochromatic Imaging: Added Value of Adaptive Statistical Iterative Reconstructions (ASIR) in Portal Venography

OBJECTIVE

To investigate the effect of the adaptive statistical iterative reconstructions (ASIR) on image quality in portal venography by dual energy CT (DECT) imaging.

MATERIALS AND METHODS

DECT scans of 45 cirrhotic patients obtained in the portal venous phase were analyzed. Monochromatic images at 70keV were reconstructed with the following 4 ASIR percentages: 0%, 30%, 50%, and 70%. The image noise (IN) (standard deviation, SD) of portal vein (PV), the contrast-to-noise-ratio (CNR), and the subjective score for the sharpness of PV boundaries, and the diagnostic acceptability (DA) were obtained. The IN, CNR, and the subjective scores were compared among the four ASIR groups.

RESULTS

The IN (in HU) of PV (10.05±3.14, 9.23±3.05, 8.44±2.95 and 7.83±2.90) decreased and CNR values of PV (8.04±3.32, 8.95±3.63, 9.80±4.12 and 10.74±4.73) increased with the increase in ASIR percentage (0%, 30%, 50%, and 70%, respectively), and were statistically different for the 4 ASIR groups (p<0.05). The subjective scores showed that the sharpness of portal vein boundaries (3.13±0.59, 2.82±0.44, 2.73±0.54 and 2.07±0.54) decreased with higher ASIR percentages (p<0.05). The subjective diagnostic acceptability was highest at 30% ASIR (p<0.05).

CONCLUSIONS

30% ASIR addition in DECT portal venography could improve the 70 keV monochromatic image quality.

Monochromatic Spectral Computed Tomography with Low Iodine Concentration Contrast Medium in a Rabbit VX2 Liver Model:: Investigation of Image Quality and Detection Rate

RATIONALE AND OBJECTIVES

This study aimed to validate the feasibility of using virtual monochromatic spectral computed tomography (CT) with isotonic low iodine concentration contrast medium for VX2 hepatic tumors.

MATERIALS AND METHODS

Sixty New Zealand white rabbits with implanted VX2 hepatic tumors underwent two-phase contrast-enhanced spectral CT imaging on the 14th day after tumor implantation. They were randomly divided into groups A, B, and C, with 20 rabbits each (group A: 270 mg I/mL, monochromatic spectral images; group B: 370 mg I/mL, conventional 120 kVp images, 100% filtered back projection [FBP]; group C: 270 mg I/mL, conventional 120 kVp images, 100% FBP). Group A was further divided into two subgroups (subgroup A1: 100% FBP; subgroup A2: 50% FBP + 50% adaptive statistical iterative reconstruction). Objective evaluation (signal-to-noise ratio [SNR], contrast-to-noise ratio [CNR], and image noise), subjective rating score (image noise score, anatomical details score, overall image quality score, and lesion conspicuity score), CT dose index volume, and dose length product were compared between groups during two-phase contrast enhancement. The detection rates of the four groups were calculated as percentages.

RESULTS

Image noise (SNR and CNR) among the four groups was statistically significant (P <0.05). The image noise in group A2 was lower than in group A1, but higher than that in groups B and C (P <0.05). SNR and CNR in group A2 were the highest, followed by group A1, and group C was the lowest (P <0.05 for all). The image noise score of group A2 was higher than that of the other three groups. In terms of the anatomic details score, the overall image quality score, and the lesion conspicuity score, the images of group A2 were superior to that of groups A1 and C. For hepatic tumor diameters more than or equal to 1.0 cm and less than 3.0 cm, group A achieved a higher detection rate than groups B and C. The CT dose index volume, dose length product, and effective dose in group A were significantly lower than that in groups B and C (P <0.05). On average, group A reduced the effective radiation dose by 27.2% compared to group B, whereas group B reduced the effective radiation dose by 28% compared to group C. Group A reduced the iodine load by 22.86% compared to group B.

CONCLUSIONS

The use of monochromatic images combined with 50% adaptive statistical iterative reconstruction with an isotonic low concentration contrast medium of 270 mg I/mL can optimize image quality, reduce image noise, increase detection rate for small tumors, and decrease radiation dose and iodine load in hepatic tumor CT examinations.

Clinical value of dual-energy spectral imaging with adaptive statistical iterative reconstruction for reducing contrast medium dose in CT portal venography: in comparison with standard 120-kVp imaging protocol

OBJECTIVE

To evaluate the clinical value of dual-energy spectral CT with adaptive statistical iterative reconstruction (ASiR) for reducing contrast medium dose in CT portal venography (CTPV).

METHODS

This prospective study was institutional review board-approved, and written informed consent was obtained from all patients. 50 patients undergoing abdominal CT were randomized to 2 groups: Group A (n = 25), using spectral CT and 350 mgI kg(-1) contrast injection protocol; Group B (n = 25), using standard 120 kVp and 500 mgI kg(-1) contrast. Spectral CT images at 60 keV and standard 120-kVp images were both reconstructed with 50% ASiR. CT number and contrast-to-noise ratio (CNR) for intrahepatic and extrahepatic portal veins were measured. The maximum intensity projection (MIP) and volume-rendering (VR) images were used for subjective evaluation. These two kinds of results were statistically analyzed.

RESULTS

CNR values for the intrahepatic portal vein of the 60-keV spectral images (4.2 ± 1.1) were higher than those of 120-kVp images (3.0 ± 2.1) (p = 0.03) and were the same for the extrahepatic portal vein (5.9 ± 1.4 vs 5.9 ± 1.6, p = 0.90). The portal vein and left and right branches in the 60-keV spectral images had higher CT number and lower standard deviation than the 120-kVp images (p < 0.05). Radiation dose (dose-length product and effective dose) and subjective image quality were similar for the two groups, while the spectral CT group required 25% less iodine dose (23.1 ± 3.2 g vs 30.5 ± 5.0 g).

CONCLUSION

The 60-keV spectral CT images with ASiR allow 25% reduction in the iodine dose while providing better or equal image quality as the standard 120-kVp images in portal venography with comparable radiation dose.

ADVANCES IN KNOWLEDGE

Compared with conventional 120-kVp CT, the use of 60-keV spectral CT images provides 25% contrast dose reduction with similar image quality in CTPV. Compared with conventional 120-kVp CT, the use of 60-keV spectral CT images with ASiR algorithm improves CNR values for the intrahepatic portal vein.

Application of gemstone spectral imaging for efficacy evaluation in hepatocellular carcinoma after transarterial chemoembolization

AIM: To assess the value of gemstone spectral imaging (GSI) in efficacy evaluation in hepatocellular cancer (HCC) after transcatheter arterial chemoembolization (TACE) treatment.

METHODS: Thirty patients with HCC underwent GSI, including nonenhanced, arterial, portalvenous and delayed phase scans, after TACE treatment. Arterial phase images were acquired with GSI for reconstruction of virtual nonenhanced images and color overlay images. Digital subtraction angiography (DSA) was performed in all these patients. Two blinded and independent readers evaluated the data in two reading sessions; standard nonenhanced, arterial, portalvenous, and delayed phase images were read in session A, and the optimal monochromatic images, iodine/water based images and spectrum features were read in session B. Sensitivity and specificity were calculated with the DSA data as the reference standard. The sensitivity and specificity were compared using the χ² test.

RESULTS: DSA revealed 154 lesions in 30 patients, and 100 of them had blood supply. Overall sensitivity and specificity were 72% (72/100) and 77.8% (42/54) for session A, and 97% (97/100) and 94.4% (51/54) for session B, respectively. The sensitivity and specificity of the two reading sessions were significantly different (χ² = 23.04, χ² = 7.11, P < 0.05).

CONCLUSION: Compared with conventional CT, GSI could significantly improve the detection of small and multiple lesions without increasing the radiation dose. Based on spectrum features, GSI could assess tumor homogeneity and more accurately identify residual tumors and recurrent or metastatic lesions during efficacy evaluation and follow-up in HCC after TACE treatment.

Improving Image Quality of Bronchial Arteries with Virtual Monochromatic Spectral CT Images

OBJECTIVE

To evaluate the clinical value of using monochromatic images in spectral CT pulmonary angiography to improve image quality of bronchial arteries.

METHODS

We retrospectively analyzed the chest CT images of 38 patients who underwent contrast-enhanced spectral CT. These images included a set of 140kVp polychromatic images and the default 70keV monochromatic images. Using the standard Gemstone Spectral Imaging (GSI) viewer on an advanced workstation (AW4.6,GE Healthcare), an optimal energy level (in keV) for obtaining the best contrast-to-noise ratio (CNR) for the artery could be automatically obtained. The signal-to-noise ratio (SNR), CNR and objective image quality score (1-5) for these 3 image sets (140kVp, 70keV and optimal energy level) were obtained and, statistically compared. The image quality score consistency between the two observers was also evaluated using Kappa test.

RESULTS

The optimal energy levels for obtaining the best CNR were 62.58±2.74keV.SNR and CNR from the 140kVp polychromatic, 70keV and optimal keV monochromatic images were (16.44±5.85, 13.24±5.52), (20.79±7.45, 16.69±6.27) and (24.9±9.91, 20.53±8.46), respectively. The corresponding subjective image quality scores were 1.97±0.82, 3.24±0.75, and 4.47±0.60. SNR, CNR and subjective scores had significant difference among groups (all p<0.001). The optimal keV monochromatic images were superior to the 70keV monochromatic and 140kVp polychromatic images, and there was high agreement between the two observers on image quality score (kappa>0.80).

CONCLUSIONS

Virtual monochromatic images at approximately 63keV in dual-energy spectral CT pulmonary angiography yielded the best CNR and highest diagnostic confidence for imaging bronchial arteries.

Multireader evaluation of lesion conspicuity in small pancreatic adenocarcinomas: complimentary value of iodine material density and low keV simulated monoenergetic images using multiphasic rapid kVp-switching dual energy CT

OBJECTIVE

Perform multireader analysis of objective and subjective lesion conspicuity for small pancreatic adenocarcinomas using rapid switching dual energy CT (rsDECT).

MATERIALS AND METHODS

With IRB approval, 51 abdominal multiphasic rsDECT scans in 46 subjects with small (<3 cm) pancreatic adenocarcinomas were retrospectively reviewed by three independent readers for objective and subjective lesion conspicuity. Measured variables during individual, blinded interpretive sessions of separate low (52) keV, PACS-equivalent (70) keV, and iodine material density (MD) image sets included Hounsfield units (HU) and mg/cc iodine for tumor, nontumoral pancreas, and subcutaneous fat. Objective measures included absolute lesion contrast (LC) and contrast to noise ratios (CNR). Subjective measures included image quality, lesion conspicuity, and reader confidence. Reader agreement was measured with kappa statistic; correlation with truth by Pearson coefficient, CNR with repeated mANOVA; subjective quality measures utilized Tukey-Cramer corrections for multiple testing, p < 0.05 considered significant.

RESULTS

Demographics: 26 F, 20 M, mean age 68 years, weight 75 kg, tumor size of 2.3 cm. LC was highest on 52 keV images for all three readers (mean 90.1 HU). Mean CNR for iodine MD images (4.87) was significantly higher than 52 keV (4.13) or 70 keV (3.9). Very high to near-perfect kappa values were observed for all individual measured objective variables but were best for 52 keV images (52 keV 0.89-0.95, 70 keV 0.76-0.83, iodine 0.87-0.92). 70 keV images scored best for subjective image quality; iodine MD images scored best for lesion conspicuity and reader confidence.

CONCLUSION

We observed very high reader agreement for independent objective rsDECT image variables and subjective rsDECT image scores in patients with small pancreatic adenocarcinomas. Maximal objective tumor to nontumoral LC was depicted on 52 keV and highest CNR on iodine MD images; readers scored the iodine MD images best for lesion conspicuity and confidence.