Dual-Energy CT for the Detection of Portal Vein Thrombosis: Improved Diagnostic Performance Using Virtual Monoenergetic Reconstructions.

Purpose: To investigate the diagnostic performance of noise-optimized virtual monoenergetic images (VMI+) in dual-energy CT (DECT) of portal vein thrombosis (PVT) compared to standard reconstructions. Method: This retrospective, single-center study included 107 patients (68 men; mean age, 60.1 ± 10.7 years) with malignant or cirrhotic liver disease and suspected PVT who had undergone contrast-enhanced portal-phase DECT of the abdomen. Linearly blended (M_0.6) and virtual monoenergetic images were calculated using both standard VMI and noise-optimized VMI+ algorithms in 20 keV increments from 40 to 100 keV. Quantitative measurements were performed in the portal vein for objective contrast-to-noise ratio (CNR) calculation. The image series showing the greatest CNR were further assessed for subjective image quality and diagnostic accuracy of PVT detection by two blinded radiologists. Results: PVT was present in 38 subjects. VMI+ reconstructions at 40 keV revealed the best objective image quality (CNR, 9.6 ± 4.3) compared to all other image reconstructions (p < 0.01). In the standard VMI series, CNR peaked at 60 keV (CNR, 4.7 ± 2.1). Qualitative image parameters showed the highest image quality rating scores for the 60 keV VMI+ series (median, 4) (p ≤ 0.03). The greatest diagnostic accuracy for the diagnosis of PVT was found for the 40 keV VMI+ series (sensitivity, 96%; specificity, 96%) compared to M_0.6 images (sensitivity, 87%; specificity, 92%), 60 keV VMI (sensitivity, 87%; specificity, 97%), and 60 keV VMI+ reconstructions (sensitivity, 92%; specificity, 97%) (p ≤ 0.01). Conclusions: Low-keV VMI+ reconstructions resulted in significantly improved diagnostic performance for the detection of PVT compared to other DECT reconstruction algorithms.

Improved coronary artery contrast enhancement using noise-optimised virtual monoenergetic imaging from dual-source dual-energy computed tomography.

PURPOSE: To define optimal kiloelectron volt (keV) settings for virtual monoenergetic imaging (VMI) reconstruction at dual-energy coronary computed tomography angiography (DE-CCTA). METHOD: Fifty-one DE-CCTA data sets (33 men; mean age, 63.9 ±â€¯13.2 years) were reconstructed as standard linearly-blended images (F_0.6; 60% of 90 kVp, 40% of 150 kVpSn), and with traditional (VMI) and noise-optimised (VMI+) algorithms from 40 to 100 keV in 10-keV intervals. Objective image quality was assessed with signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements. Three observers subjectively evaluated vascular contrast, image sharpness, noise and delineation of coronary plaques. RESULTS: Median values for objective image analysis were highest in VMI + series at 40 keV (SNR, 44.5; CNR: 33.5), significantly superior (allp < 0.001) to the best VMI series at 70 keV (SNR, 28.1; CNR, 18.4) and standard F_0.6 images (SNR, 23.2; CNR, 15.6). Overall subjective metrics achieved higher scores at 40-keV VMI+ series in comparison to 70-keV VMI series and F_0.6 images (all p < 0.001), with optimal vascular contrast (5; ICC, 0.90), good image sharpness (4; 0.88), low noise (4; 0.82), and optimal plaque delineation (5; 0.89). CONCLUSIONS: DE-CCTA image reconstruction with 40-keV VMI + allows for significant improvement of both objective and subjective image quality.

Dual-energy CT-based iodine quantification to differentiate abdominal malignant lymphoma from lymph node metastasis.

PURPOSE: To investigate the value of dual-energy computed tomography (DECT)-derived iodine and fat quantification in differentiating malignant abdominal lymphoma from lymph node metastasis. MATERIALS AND METHODS: In this retrospective study, 59 patients (39 men; mean age, 62.7 years) with histopathologically-confirmed diagnosis of either malignant lymphoma or lymph node metastasis were included. For each lesion, contrast-enhanced attenuation, as well as DECT-derived iodine density and fat fraction measurements were recorded. Mean attenuation and material density values were compared between malignant lymphomas and lymph node metastases. The receiver operating characteristic (ROC) curve analysis was adopted to estimate the optimal threshold for discriminating between both entities. A control group (n = 60) was analyzed for comparison of attenuation and material density values of normal abdominal lymph nodes. RESULTS: Assessment of DECT-derived iodine density and fat fraction values revealed significant differences between lymph node metastases (1.7 ±â€¯0.4 mg/ml and 15.5 ±â€¯7.3%) and malignant lymphomas (2.5 ±â€¯0.5 mg/ml and 26.7 ±â€¯12.2%) as well as normal lymph nodes (2.4 ±â€¯0.8 mg/ml and 24.1 ±â€¯10.8%) (P ≤ 0.013). An iodine concentration of 2.0 mg/ml represented the optimal threshold to discriminate between lymphoma and lymph node metastasis (sensitivity, 87%; specificity, 89%). Moreover, a significant correlation was found between iodine concentration and fat fraction for both lymphomas and lymph node metastases (P = 0.001). CONCLUSION: DECT enables characterization of abdominal masses as derived iodine and fat fraction values differ significantly between malignant abdominal lymphomas and lymph node metastases.

Dual-energy CT in patients with colorectal cancer: Improved assessment of hypoattenuating liver metastases using noise-optimized virtual monoenergetic imaging.

PURPOSE: To assess the value of the noise-optimized virtual monoenergetic imaging (VMI+) technique on quantitative and qualitative image parameters in patients with hypoattenuating liver metastases from colorectal cancer (CRC) at abdominal dual-energy CT (DECT). MATERIALS AND METHODS: Fifty-three consecutive patients (mean age, 70.3 ± 11.4 years; range, 44-86 years) with histologically proven, hypoattenuating liver metastases from CRC were retrospectively included in this IRB-approved study. DECT datasets were reconstructed as standard linearly-blended M_0.6 image series, traditional virtual monoenergetic images (VMI), and noise-optimized VMI+ series. VMI and VMI+ reconstructions were obtained at energy levels ranging from 40 to 100-keV with 10-keV increments. Signal attenuation of liver parenchyma and liver metastases was measured to calculate signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Each image series was subjectively rated by three blinded radiologists with regard to image quality, lesion delineation, and image noise using a five-point Likert scale. RESULTS: Quantitative image quality parameters peaked at 40-keV VMI+ (SNR, 8.1 ± 3.4; CNR, 6.5 ± 2.6) with statistically significant differences in comparison with standard reconstructions and all traditional VMI series (P ≤ 0.001). Qualitative image analysis revealed best rating scores for 60-keV VMI+ series (median, 5) with significant differences compared to linearly-blended M_0.6 and all traditional VMI series (P ≤ 0.001). Lesion delineation showed significantly superior ratings for 40-keV VMI+ series compared to all other reconstructions (median, 5) (P ≤ 0.001). CONCLUSION: Low-keV VMI+ reconstructions demonstrate significantly increased quantitative and qualitative image quality parameters in patients with hypoattenuating liver metastases from CRC in comparison with standard reconstructions and traditional VMI series at abdominal DECT. Best lesion delineation can be achieved at 40-keV VMI+.

Iodine and Fat Quantification for Differentiation of Adrenal Gland Adenomas From Metastases Using Third-Generation Dual-Source Dual-Energy Computed Tomography.

OBJECTIVES: The aim of this study was to investigate the value of third-generation dual-source dual-energy computed tomography (DECT) iodine and fat quantification in differentiating adrenal gland adenomas from metastases. MATERIALS AND METHODS: Sixty-two patients (38 men and 24 women; mean age, 69.1 years) underwent clinically indicated DECT of the abdomen on a third-generation dual-source scanner. Examinations were retrospectively included due to detected adrenal masses. For each adrenal lesion, unenhanced and contrast-enhanced attenuation values, as well as dual-energy iodine density and fat fraction, were recorded. Additional magnetic resonance imaging data, positron emission tomography/computed tomography scans, interval imaging follow-up, and histopathological analysis were used as the reference standard for all adrenal lesions. Mean values of unenhanced and contrast-enhanced attenuation, as well as material densities, were compared between adenomas, metastases, and normal adrenal glands. Furthermore, the diagnostic accuracy of unenhanced, contrast-enhanced, and material density analysis was assessed between adrenal adenomas and metastases. RESULTS: Adrenal adenomas showed significant differences regarding iodine density and fat fraction values (1.3 ± 0.4 mg/mL and 34.2% ± 12.6%) in comparison with adrenal metastases (3.2 ± 1.4 mg/mL and 10.7% ± 7.8%) and normal adrenal glands (1.7 ± 0.6 mg/mL and 18.7% ± 12.0%) (all P ≤ 0.004). Analysis of unenhanced attenuation values revealed no significant differences between healthy adrenal parenchyma (19.1 ± 15.6 HU) and adrenal metastases (26.9 ± 16.2 HU) (P = 0.135). Iodine density and fat fraction analysis showed significantly higher diagnostic accuracy for the diagnosis of adenomas (sensitivity, 97% and 89%; specificity, 96% and 89%, respectively) compared with unenhanced and contrast-enhanced evaluation (sensitivity, 65% and 58%; specificity, 73% and 85%, respectively) (P ≤ 0.023). The combined diagnostic value of iodine density and fat fraction analysis revealed a sensitivity of 97% and a specificity of 100%. CONCLUSIONS: Third-generation dual-source DECT iodine and fat quantification allow for differentiation between adrenal adenomas and metastases with high diagnostic accuracy.

Multi-observer comparison study between unenhanced quiescent-interval single-shot magnetic resonance angiography and invasive carbon dioxide angiography in patients with peripheral arterial disease and chronic renal insufficiency.

OBJECTIVES: Non-contrast-enhanced quiescent-interval single-shot magnetic resonance angiography (QISS-MRA) and invasive carbon dioxide (CO2) angiography are suggested as nephroprotective methods for accurate staging of peripheral arterial disease (PAD) in patients with chronic renal insufficiency (CRI). The aim of our study was to compare the image quality of both examinations. METHODS: 16 consecutive PAD patients with highly impaired renal function (estimated glomerular filtration rate (eGFR) < 30 ml/min/1.73 m²) who underwent 3 T MRA with QISS and catheter angiography with CO2 within 90 days were retrospectively included. Subjective image quality was determined using a five-point Likert scale (1, non-diagnostic; 5, excellent) and presence of significant (≥50%) stenoses of pelvic and lower extremity arteries (21-segment-model) was evaluated per-region and per-segment, respectively, in random order by four independent readers with different levels of experience. CO2 angiography of an experienced interventional radiologist was considered the standard reference method. RESULTS: 167 segments were available for direct comparison with a prevalence of ≥50% stenoses of 28.1%. QISS-MRA yield was: sensitivity 91.5%, specificity 94.2%, positive predictive value 86.0% and negative predictive value 96.6%, with an intraclass correlation coeffcient (ICC) of 0.88. Median values of qualitative imaging parameters for QISS-MRA were as follows: arterial signal intensity: 4 (pelvis), 5 (thigh), 5 (calf); venous overlay: 4, 5, 5; susceptibility artifacts: 5, 5, 5; motion artifacts: 4, 5, 5; ECG-related artifacts: 5, 5, 5. ICC-values for image quality were 0.74, 0.73, 0.93, 0.69 and 0.79, respectively. Arterial opacification at CO2 angiography was rated 3, 4, 3, with an ICC of 0.63. CONCLUSIONS: Image quality of non-invasive unenhanced MR angiography with QISS was preferred over invasive CO2 angiography, whilst taking into account that it offers high diagnostic performance for the detection and ruling out of PAD.