Virtual nonenhanced abdominal dual-energy MDCT:Analysis of image characteristics

AIM: To evaluate abdominal and pelvic image characteristics and artifacts on virtual nonenhanced (VNE) images generated from contrast-enhanced dual-energy multidetector computed tomography (MDCT) studies. METHODS: Hadassah-Hebrew University Medical Institutional Review Board approval was obtained; 22 patients underwent clinically-indicated abdominal and pelvic single-source dual-energy MDCT (Philips Healthcare, Cleveland, OH, USA), pre- and post-IV administration of Omnipaque 300 contrast (100 cc). Various solid and vascular structures were evaluated. VNE images were generated from the portal contrast-enhanced phase using probabilistic separation. Contrast-enhanced-, regular nonenhanced (RNE)-, and VNE images were evaluated with a total of 1494 density measurements. The ratio of iodine contrast deletion was calculated. Visualization of calcifications, urinary tract stones, and image artifacts in VNE images were assessed. RESULTS: VNE images were successfully generated in all patients. Significant portal-phase iodine contrast deletion was seen in the kidney (61.7%), adrenal gland (55.3%), iliac artery (55.0%), aorta (51.6%), and spleen (34.5%). Contrast deletion was also significant in the right atrium (RA) (51.5%) and portal vein (39.3%), but insignificant in the iliac vein and inferior vena cava (IVC). Average post contrast-to-VNE HU differences were significant (P < 0.05) in the: RA -135.3 (SD 121.8), aorta -114.1 (SD 48.5), iliac artery -104.6 (SD 53.7), kidney -30.3 (SD 34.9), spleen -9.2 (SD 8.8), and portal vein -7.7 (SD 13.2). Average VNE-to-RNE HU differences were significant in all organs but the prostate and subcutaneous fat: aorta 38.0 (SD 9.3), RA 37.8 (SD 16.1), portal vein 21.8 (SD 12.0), IVC 12.2 (SD 11.6), muscle 3.3 (SD 4.9), liver 5.7 (SD 6.4), spleen 22.3 (SD 9.8), kidney 40.5 (SD 6.8), and adrenal 20.7 (SD 13.5). On VNE images, 196/213 calcifications (92%) and 5/6 renal stones (84%) were visualized. Lytic-like artifacts in the vertebral bodies were seen in all studies. CONCLUSION: Iodine deletion in VNE images is most significant in arteries, and less significant in solid organs and veins. Most vascular and intra-abdominal organ calcifications are preserved.

Determinants of Detection of Stones and Calcifications in the Hepatobiliary System on Virtual Nonenhanced Dual-energy CT

Objective To retrospectively determine the features of stones and calcifications in hepatobiliary system on virtual nonenhanced (VNE) dual-energy computed tomography (CT), and to evaluate the possibility of VNE images in diagnosis for those lesions. Methods A total of 128 gall stones and calcifications of the liver found in 110 patients were examined with triple phase abdominal CT scan from July 2007 to December 2011, in which true nonenhanced (TNE) phase and arterial phase were performed with single-energy CT (120 kVp) and portal venous phase was performed with dual-energy CT (100 kVp and 140 kVp). VNE images were generated from the portal venous phase dual-energy CT data sets by using commercially VNC software. The mean CT values for the stone, liver, bile and paraspinal muscle, mean lesion density and size in area dimension, contrast-to-noise ratio (CNR) of lesion to the liver or bile, and image noise were assessed and compared between VNE and TNE images. The effective dose and size-specific dose estimate (SSDE) were also calculated. Results The mean CT values of the lesions measured on VNE images declined significantly compared with those measured on TNE images (164.51±102.13vs. 290.72±197.80 HU,P<0.001), so did the lesion-to-liver CNR (10.80±11.82vs.18.81±17.06,P<0.001) and the lesion-to-bile CNR (17.24±14.41 vs. 21.32±17.31,P<0.001). There was no significant difference in size of lesions area between VNE and TNE images (0.69±0.88vs.0.72±0.85 cm2,P=0.062). Compared to the 128 lesions found in TNE images, VNE images showed the same density in 30 (23.4%) lesions, lighter density in 88 (68.8%) lesions, while failed to show 10 (7.8%) lesions, and showed the same size in 61 (47.7%) lesions and smaller size in 57 (44.5%)&nbsp;lesions. The CT cutoff values of lesion and size were 229.21 HU and 0.15 cm2, respectively. The total effective dose for triple phase scan protocol with TNE images was 19.51±7.03 mSv, and the SSDE was 39.84±11.10 mGy. The effective dose for dual phase scan protocol with VNE images instead of TNE images was 13.29±4.89 mSv, and the SSDE was 27.83±9.99 mGy. Compared with TNE images, the effective dose and SSDE of VNE images were down by 32.05%±3.69 % and 30.63%±2.34 %, respectively. Conclusions Although the CT values and CNR of the lesions decreased in VNE images, the lesions of which attenuation greater than 229.21 HU and size larger than 0.15 cm2could be detected with good reliability and obvious dose reduction. There was good consistency in the size of stones and calcifications in hepatobiliary system between VNE images and TNE images, which ensured the possibility of the clinical application of VNE images.

Value of dual-energy CT virtual noncalcium in the diagnosis of sacroiliac joint bone marrow edema

Objective:To explore the clinical value of dual energy CT(DECT)virtual noncalcium(VNCa)in the diagnosis of sacroiliac joint bone marrow edema(BME).Methods:A collection of 45 patients(21 males,24 females,and an average age of 34 years)who underwent MRI and DECT(Siemens Somatom definition force)examinations for the sacroiliac joints in our hospital from January 2019 to August 2020.After the DECT scan,the bone marrow pseudo-color map was obtained after VNCa processing.The bone marrow pseudo-color map was evaluated by two physicians.Take MRI test results as the gold standard,the application value of DECT VNCa technology in the diagnosis of sacroiliac joint BME was analyzed.Results:The positive predictive value(PPV),negative predictive value(NPV),sensitivity(Sen),specificity(Spe)and accuracy(Acc)of the qualitative diagnosis of iliac bone and sacral BME with DECT VNCa technology was:80.6%,85.2%,78.4%,86.8%,83.3%and 100%,64.9%,32.5%,100%,70.0%,respectively.The area of edema displayed by quantitative measurement of DECT VNCa image is smaller than the area measured by MRI image.The VNCa CT value(-71.66±72.97Hu)of the iliac edema area was higher than that of the non-edema area(-90.27±65.85Hu),and the VNCa CT value of the sacral edema area(-62.90±46.87Hu)was higher than that of the non-edema area(-101.08±134.02Hu),the best cut-off values(Cut-off values)for the quantitative diagnosis of iliac bone and sacral BME by VNCa are-66.40Hu and-50.60Hu,respectively.The curve of the receiver operating characteristic(ROC)of the iliac bone and sacrum area under the cure(AUC)is 0.720 and 0.706 respectively.There is a moderate negative correlation between the VNCa CT values of the ilium and sacrum in the edema area and the conventional CT values.Conclusion:The DECT VNCa technique has certain effectiveness in the diagnosis of sacroiliac joint BME,and its effectiveness in the diagnosis of ilium BME is better than sacrum.

Feasibility of Improved Attenuation Correction for SPECT Reconstruction in the Presence of Dense Materials Using Dual-Energy Virtual Monochromatic CT: A Phantom Study

Objective: Computed tomography (CT)-based attenuation correction (CTAC) offers the clear benefit of reliable reconstruction of single-photon emission computed tomography (SPECT) images through its ability to achieve object-specific attenuation maps, but artifacts from dense materials often deteriorate CTAC performance. Therefore, we investigate the feasibility of CTAC in the presence of dense materials using dual-energy virtual monochromatic CT data. Methods: A sodium pertechnetate-filled cylindrical uniform phantom, with a pair of undiluted iodine syringes attached, is scanned with a dual-source CT scanner to obtain both single-energy (120 kVp) polychromatic and dual-energy (80 kVp/140 kVp with tin filtering) virtual monochromatic CT images. The single-energy and the dual-energy CT images are then converted to attenuation maps at 141 keV. SPECT images are reconstructed from 99mTc emission data of the phantom using each single-energy and dual-energy attenuation map and incorporating CTAC procedure. A region-of-in- terest analysis is performed to quantitatively compare the attenuation maps between the single-energy and the dual-energy techniques, each at an iodine-free position and a position adjacent to the iodine solutions. Results: At the iodine-free position, the phantom provides a uniform distribution of attenuation maps in both the single-energy and the dual-energy techniques. In the presence of adjacent iodine solutions, however, severe artifacts appeare in the single-energy CT images. These artifacts make attenuation values fluctuate, resulting in erroneous pixel values in the CTAC SPECT images. In contrast, dual-energy CT strongly suppresses the artifacts and hence improves the uniformity of the attenuation maps and the resultant SPECT images. Conclusions: Dual-energy CT with virtual monochromatic reconstruction has the potential to substantially reduce artifacts arising from dense materials. It has the potential to improve the accuracy of attenuation maps and the resultant CTAC SPECT images.

Application of an Advanced Image-Based Virtual Monoenergetic Reconstruction of Dual Source Dual-Energy CT Data at Low keV Increases Image Quality for Esophageal Cancer Patients Imaging

Purpose: To explore the significance of dual-source computed tomography (DECT) virtual monoenergetic reconstructions technology in improving the imaging quality of esophageal cancer patients. Materials and methods: 68 patients with clinically suspected esophageal cancer (all confirmed by pathology) were collected. Routine plain scan was performed with SIEMENS Force dual-energy CT and then dual-phase scans were performed. The venous phase images were respectively subjected to traditional virtual monoenergetic reconstructions (Mono_E) and new generation virtual monoenergetic reconstructions (Mono+). Mono_E 55 keV and Mono+ 55 keV virtual single-energy images were obtained respectively. The signal-to-noise ratio (SNR) of normal esophageal tissue and esophageal cancer lesions, noise and contrast noise ratio (CNR tumor) of normal esophageal tissue and esophageal cancer lesions were compared among 100 kV images, Mono_E images and Mono+ images. At the same time, two imaging physicians read the films and scored the images of each group by using a 5-point scoring method. Results: Mono+ 55 keV images, SNR, SNRtumor, noise and CNRtumor were statistically different from those of 100 kV images and Mono_E images (P < 0.05). And Mono+ 55 keV images also had the highest subjective score, with statistical significance (P 55 keV images had the best quality. Conclusion: The new generation of virtual monoenergetic reconstructions post-processing (Mono+) could reduce image noise and improve the contrast between esophageal cancer lesions and normal esophageal tissues, which was of great significance to improve the imaging quality of esophageal cancer patients and improve the early detection rate of esophageal cancer.

Characteristics of the imaging diagnosis of alveolar echinococcosis

Alveolar echinococcosis(AE)primarily manifests in the liver and exhibits charac-teristics resembling those of slow-growing malignant tumours.Untreated Echino-coccus multilocularis infection can be lethal.By infiltrating the vascular systems,biliary tracts,and the hilum of the liver,it might lead to various problems.Due to its ability to infiltrate neighbouring tissues or metastasize to distant organs,AE can often be mistaken for malignancies.We present a concise overview of the epi-demiological and pathophysiological characteristics of AE,as well as the clinical manifestations of the disease.This article primarily examines the imaging charac-teristics of AE using various imaging techniques such as ultrasonography,com-puted tomography(CT),magnetic resonance imaging,diffusion-weighted ima-ging,and virtual non-enhanced dual-energy CT.We additionally examined the contribution of radiography in the diagnosis,treatment,and monitoring of the condition.

Gadolinium Enhances Dual-energy Computed Tomography Scan of Pulmonary Artery

Objective To evaluate the feasibility of using gadopentetate dimeglumine(Gd-DTPA)for dual-energy computed tomography pulmonary angiography(CTPA).Methods Sixty-six patients were randomly divided into three groups and underwent CTPA.Group A had a turbo flash scan using an iohexol injection,Group B had a turbo flash scan using Gd-DTPA,and Group C had a dual-energy scan using Gd-DTPA.The original images of Group C were linearly blended with a blending factor of 0.5 or reconstructed at 40,50,60,70,80,90,100,and 110 keV,respectively.The groups were compared in terms of pulmonary artery CT value,image quality,and radiation dose.Results The pulmonary artery CT values were significantly higher in Group C40keV than in Groups B and C,but lower than in Group A.There was no significant difference in the image noise of Groups C40keV,B,and C.Moreover,Group A had the largest beam hardening artifacts of the superior vena cava(SVC),followed by Groups B and C.Group C40keV showed better vascular branching than the other three groups,among which Group B was superior to Group A.The subjective score of the image quality of Groups A,B,and C showed no significant difference,but the score was significantly higher in Group C40keV than in Groups A and B.The radiation dose was significantly lower in Group B than in Groups A and C.Conclusion Gd-CTPA is recommended to patients who are unsuitable for receiving an iodine-based CTPA.Furthermore,a turbo flash scan could surpass a dual-energy scan without consideration for virtual monoenergetic imaging.

Image Processing Tool Promoting Decision-Making in Liver Surgery of Patients with Chronic Kidney Disease

Preoperative assessment of the liver volume and function of the remnant liver is a mandatory prerequisite before performing major hepatectomy. The aim of this work is to develop and test a software application for evaluation of the residual function of the liver prior to the intervention of the surgeons. For this purpose, a complete software platform consisting of three basic modules: liver volume segmentation, visualization, and virtual cutting, was developed and tested. Liver volume segmentation is based on a patient examination with non-contrast abdominal Computed Tomography (CT). The basis of the segmentation is a multiple seeded region growing algorithm adapted for use with CT images without contrast-enhancement. Virtual tumor resection is performed interactively by outlining the liver region on the CT images. The software application then processes the results to produce a three-dimensional (3D) image of the “resected” region. Finally, 3D rendering module provides possibility for easy and fast interpretation of the segmentation results. The visual outputs are accompanied with quantitative measures that further provide estimation of the residual liver function and based on them the surgeons could make a better decision. The developed system was tested and verified with twenty abdominal CT patient sets consisting of different numbers of tomographic images. Volumes, obtained by manual tracing of two surgeon experts, showed a mean relative difference of 4.5%. The application was used in a study that demonstrates the need and the added value of such a tool in practice and in education.