Moritz H. Albrecht

Comprehensive Comparison of Virtual Monoenergetic and Linearly Blended Reconstruction Techniques in Third-Generation Dual-Source Dual-Energy Computed Tomography Angiography of the Thorax and Abdomen.

ObjectivesThe aim of this study was to perform an objective and subjective image analysis of traditional and advanced noise-optimized virtual monoenergetic imaging (VMI) algorithms and standard linearly blended images in third-generation dual-source dual-energy computed tomography angiography (DE-CTA) of the thorax and abdomen. Materials and MethodsThoracoabdominal DE-CTA examinations of 55 patients (36 male; mean age, 64.2 ± 12.7 years) were included in this retrospective institutional review board–approved study. Dual-energy computed tomography angiography data were reconstructed using standard linearly blended M_0.6 (merging 60% low kiloelectron volt [90 kV] with 40% high kiloelectron volt [150 kV] spectrum), traditional (VMI), and advanced VMI (VMI+) algorithms. Monoenergetic series were calculated ranging from 40 to 120 keV with 10 keV increments. Attenuation and standard deviation of 8 arteries and various anatomical landmarks of the thorax and abdomen were measured to calculate contrast-to-noise ratio values. Two radiologists subjectively assessed image quality, contrast conditions, noise, and visualization of small arterial branches using 5-point Likert scales. ResultsVascular attenuation of VMI and VMI+ series showed a gradual increase from high to low kiloelectron volt levels without significant differences between both algorithms (P < 0.894). VMI+ 40-keV series showed the highest contrast-to-noise ratio for both thoracic and abdominal DE-CTA (P < 0.001), albeit revealing higher noise than M_0.6 images (objectively and subjectively, P < 0.001) and were rated best for visualization of small arterial branches in the subjective analysis (P < 0.109). Substantially increased noise was found for VMI 40 and 50 keV series compared with all other reconstructions (objectively and subjectively, P < 0.001). VMI+ images at 100 keV+ were rated best regarding image noise (P < 0.843), whereas VMI+ reconstructions at 70 keV were found to have superior subjective image quality (P < 0.031) compared with other series except for 60 and 80 keV VMI+ series (P < 0.587). Contrast conditions at 50 keV VMI+ were rated superior compared with 60 to 100 keV VMI and VMI+ reconstructions (P < 0.012). ConclusionsGeneral image quality of DE-CTA examinations can be substantially improved using the VMI+ algorithm with observer preference of 70 keV, while 40 to 50 keV series provide superior contrast and improved visualization of small arterial branches compared with traditional VMI and standard linearly blended series.

Dual-Energy CT–based Display of Bone Marrow Edema in Osteoporotic Vertebral Compression Fractures: Impact on Diagnostic Accuracy of Radiologists with Varying Levels of Experience in Correlation to MR Imaging

Purpose To evaluate whether a dual-energy (DE) computed tomographic (CT) virtual noncalcium technique can improve the detection rate of acute thoracolumbar vertebral compression fractures in patients with osteoporosis compared with that at magnetic resonance (MR) imaging depending on the level of experience of the reading radiologist. Materials and Methods This retrospective study was approved by the institutional ethics committee. Informed consent was obtained from all patients. Forty-nine patients with osteoporosis who were suspected of having acute vertebral fracture underwent DE CT and MR imaging. Conventional linear-blended CT scans and corresponding virtual noncalcium reconstructions were obtained. Five radiologists with varying levels of experience evaluated gray-scale CT scans for the presence of fractures and their suspected age. Then, virtual noncalcium images were evaluated to detect bone marrow edema. Findings were compared with those from MR imaging (the standard of reference). Sensitivity and specificity analyses for diagnostic performance and matched pair analyses were performed on vertebral fracture and patient levels. Results Sixty-two fractures were classified as fresh and 52 as old at MR imaging. The diagnostic performance of all readers in the detection of fresh fractures improved with the addition of virtual noncalcium reconstructions compared with that with conventional CT alone. Although the diagnostic accuracy of the least experienced reader with virtual noncalcium CT (accuracy with CT alone, 61%; accuracy with virtual noncalcium technique, 83%) was within the range of that of the most experienced reader with CT alone, the latter improved his accuracy with the noncalcium technique (from 81% to 95%), coming close to that with MR imaging. The number of vertebrae rated as unclear decreased by 59%-90% or from 15-53 to 2-13 in absolute numbers across readers. The number of patients potentially referred to MR imaging decreased by 36%-87% (from 11-23 to 2-10 patients). Considering the gain in true decisions with the virtual noncalcium technique on a patient level, between 12 (most experienced reader) and 17 (least experienced reader) MR examinations could have been avoided. Conclusion The DE CT-based virtual noncalcium technique may enable depiction of bone marrow edema in thoracolumbar vertebral compression fractures in patients with osteoporosis, with good accordance with MR imaging when images are read by experienced radiologists. Although less experienced readers improved their diagnostic performance to some degree, the experienced readers diagnostic performance approached that with MR imaging. (©) RSNA, 2016.

Cinematic Rendering in CT: A Novel, Lifelike 3D Visualization Technique

OBJECTIVE The purpose of this article is to present an overview of cinematic rendering, illustrating its potential advantages and applications. CONCLUSION Volume-rendered reconstruction, obtaining 3D visualization from original CT datasets, is increasingly used by physicians and medical educators in various clinical and educational scenarios. Cinematic rendering is a novel 3D rendering algorithm that simulates the propagation and interaction of light rays as they pass through the volumetric data, showing a more photorealistic representation of 3D images than achieved with standard volume rendering.

Noise-optimized advanced image-based virtual monoenergetic imaging for improved visualization of lung cancer: Comparison with traditional virtual monoenergetic imaging

PURPOSE To assess the effect of a noise-optimized image-based virtual monoenergetic imaging (VMI+) algorithm in direct comparison with the traditional VMI technique and standard linearly-blended images emulating 120-kVp acquisition (M_0.3) on image quality at dual-energy CT in patients with lung cancer. MATERIALS AND METHODS Dual-source dual-energy CT examinations of 48 patients with biopsy-proven primary (n=31) or recurrent (n=20) lung cancer were evaluated. Images were reconstructed as M_0.3, and VMI+ and traditional VMI series at 40, 55, and 70keV. Attenuation of tumor, descending aorta, pulmonary trunk, latissimus muscle, and noise were measured. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Five-point scales were used by three observers to subjectively evaluate general image impression, tumor delineation, image sharpness, and image noise. RESULTS Background noise was consistently lower with VMI+ compared to VMI at all keV levels (all p<0.0001) and M_0.3 (all p≤0.0004). Tumor SNR and CNR peaked in the 40keV VMI+ series, significantly higher compared to all VMI and M_0.3 series (all p<0.0008). Observers preferred the 55keV VMI+ series regarding general image impression and tumor delineation compared to all other series (all p<0.0001). Image sharpness and image noise ratings were highest in the 55keV VMI+ and 70keV VMI and VMI+ reconstructions. CONCLUSIONS Tumor CNR peaked at 40keV VMI+ while observers preferred 55keV VMI+ series overall other series for dual-energy CT of lung cancer. The noise-optimized VMI+ technique showed significantly lower background noise and higher SNR and CNR compared to the traditional VMI technique at matching keV levels.

State-of-the-Art Pulmonary CT Angiography for Acute Pulmonary Embolism.

OBJECTIVE Pulmonary CT angiography (CTA) is the imaging modality of choice in suspected acute pulmonary embolism (PE). Current pulmonary CTA techniques involve ever lower doses of contrast medium and radiation along with advanced postprocessing applications to enhance image quality, diagnostic accuracy, and provide added value in patient management. The objective of this article is to summarize these current developments and discuss the appropriate use of state-of-the-art pulmonary CTA. CONCLUSION Pulmonary CTA is well established as a fast and reliable means of excluding or diagnosing PE. Continued developments in CT system hardware and postprocessing techniques will allow incremental reductions in radiation and contrast material requirements while improving image quality. Advances in risk stratification and prognostication from pulmonary CTA examinations should further refine its clinical value while minimizing the potential harm from overutilization and overdiagnosis.

Evaluation of image quality and dose reduction of 80 kVp neck computed tomography in patients with suspected peritonsillar abscess

AIM To evaluate neck computed tomography (CT) with a reduced tube voltage of 80 kVp in patients with suspected peritonsillar abscess (PTA) regarding objective and subjective image quality, and the potential for dose reduction. MATERIALS AND METHODS Forty-seven patients with clinically suspected PTA were retrospectively analysed. Patients were examined using dual-source CT in dual-energy mode. The objective and subjective image quality of 80 kVp images were compared with linearly blended 120 kVp images (M_0.3; 30% of 80 kV, 70% of 140 kV spectrum). Attenuation of abscess rim enhancement, central necrosis, and several other anatomical landmarks were measured. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and rim-to-abscess CNR (raCNR) were calculated. Radiation dose was assessed as size-specific dose estimates (SSDE). Subjective image quality was assessed according to the European guidelines on quality criteria for CT. Interobserver agreement was calculated using the intraclass correlation coefficient (ICC). RESULTS Attenuation of inflamed soft tissue (141.7 ± 16.3 versus 93.7 ± 9.3 HU, p < 0.001), CNR (9.6 ± 4.8 versus 5.6 ± 3.8, p = 0.001), raCNR (14.3 ± 5.9 versus 12.4 ± 4.4, p = 0.02), and subjective image sharpness (3.6 ± 0.6 versus 2.8 ± 0.7, p < 0.001) were significantly increased in the 80 kVp compared to 120 kVp, whereas subjective and objective image noise were significantly increased with 80 kVp acquisition (p < 0.001). Overall interobserver agreement was almost perfect (ICC, 0.87). Calculated SSDE of 80 kVp acquisition was decreased by 49.7% compared to 120 kVp (10.58 ± 0.76 versus 21.04 ± 1.43 mGy, p < 0.001). CONCLUSION Low-tube-voltage 80 kVp neck CT provides increased enhancement of soft-tissue inflammation, CNR, raCNR, and improved abscess delineation in patients with PTA compared to standard 120 kVp acquisition while resulting in a significant reduction of radiation exposure.

Dual-Energy Computed Tomography Virtual Monoenergetic Imaging of Lung Cancer: Assessment of Optimal Energy Levels.

Objective The aim of the study was to evaluate objective and subjective image qualities of virtual monoenergetic imaging (VMI) in dual-source dual-energy computed tomography (DECT) and optimal kiloelectron-volt (keV) levels for lung cancer. Methods Fifty-nine lung cancer patients underwent chest DECT. Images were reconstructed as VMI series at energy levels of 40, 60, 80, and 100 keV and standard linear blending (M_0.3) for comparison. Objective and subjective image qualities were assessed. Results Lesion contrast peaked in 40-keV VMI reconstructions (2.5 ± 2.9) and 60 keV (1.9 ± 3.0), which was superior to M_0.3 (0.5 ± 2.7) for both comparisons (P < 0.001). Compared with M_0.3, subjective ratings were highest for 60-keV VMI series regarding general image quality (4.48 vs 4.52; P = 0.74) and increased for lesion demarcation (4.07 vs 4.84; P < 0.001), superior to all other VMI series (P < 0.001). Image sharpness was similar between both series. Image noise was rated superior in the 80-keV and M_0.3 series, followed by 60 keV. Conclusions Virtual monoenergetic imaging reconstructions at 60-keV provided the best combination of subjective and objective image qualities in DECT of lung cancer.

Comparative evaluation of non-contrast CAIPIRINHA-VIBE 3T-MRI and multidetector CT for detection of pulmonary nodules: In vivo evaluation of diagnostic accuracy and image quality

PURPOSE To evaluate the diagnostic accuracy, subjective image quality, and interobserver agreement of non-contrast Controlled Aliasing In Parallel Imaging Results In Higher Acceleration (CAIPIRINHA) volumetric interpolated breath-hold examination (VIBE) 3T magnetic resonance imaging (MRI) for the detection of pulmonary nodules with intra-individual comparison to computed tomography (CT). MATERIALS AND METHODS We evaluated 54 patients (27 male, 27 female; mean age, 60.8 ± 11.5 years) who prospectively underwent thoracic 3T-MRI using CAIPIRINHA-VIBE sequences and chest CT. Diagnostic accuracy for the detection of lung nodules on CAIPIRINHA-VIBE MRI by three independent observers were compared to the reference standard CT. Subjective image quality was rated using a 5-point grading scale. Diagnostic accuracy was calculated and interobserver agreement was assessed using intraclass correlation coefficient (ICC). RESULTS Sensitivity of 3T-MRI for the detection of pulmonary lesions compared to CT was 88.1% (95% confidence interval [CI]: 0.81-0.93) and specifity was 79.1% (95% CI: 0.50-0.95). Sensitivity for lesions <5mm was 77.2% (95% CI: 0.59-0.90) and for lesions from 5 to 10mm was 87.2% (95% CI: 0.76-0.94). Sensitivity for lesions >10mm was 100%. Observer ratings regarding subjective image quality were good to excellent for 3T-MRI (1.54) and CT (1.14) with almost perfect interobserver agreement for 3T-MRI and CT (ICC=0.83, 95% CI: 0.78-0.89; ICC=0.89, 95% CI: 0.85-0.94). CONCLUSIONS Non-contrast CAIPIRINHA-VIBE 3T-MRI allows for the reliable detection of pulmonary lesions with a diameter >5mm in comparison with chest CT with high diagnostic accuracy, subjective image quality, and interobserver agreement.

Assessment of colorectal liver metastases using MRI and CT: Impact of observer experience on diagnostic performance and inter-observer reproducibility with histopathological correlation

INTRODUCTION To compare the diagnostic performance and inter-observer reproducibility of CT and MRI in detecting colorectal liver metastases (CRLM) of observers with different levels of experience. MATERIALS AND METHODS Data from 51 CT and 54 MRI examinations of 105 patients with CRLM were analysed. Intraoperative and histopathological findings served as the reference standard. Analyses were performed by four observers with varying levels of experience regarding imaging of CRLM (reviewers A, B, C and D with respectively >20, >5, <1 and 0 years of experience). Per-segment sensitivity, specificity, Cohens kappa (κ) for diagnosed segments and Intra-class Correlation Coefficients (ICC) for reported number of lesions were calculated. RESULTS CT sensitivity and specificity was for reviewer A 89.71%/94.41%, B 78.50%/88.37%, C 63.55%/85.58%, D 84.11%/78.60% and regarding MRI A 90.40%/95.43%, B 74.40%/90.04%, C 60.00%/85.89% and D 65.60%/75.90%. The overall inter-observer agreement was higher for CT (κ=0.43, p<0.001; ICC=0.75, p<0.001) than MRI (κ=0.38, p<0.001; ICC=0.65, p<0.001). The experienced reviewers A and B achieved better agreement for MRI (κ=0.54, p<0.001; ICC=0.77, p<0.001) than CT (κ=0.52, p<0.00; ICC=0.76, p<0.001) unlike the less experienced C and D (MRI κ=0.38, ICC=0.63 and CT κ=0.41, ICC=0.74, respectively, p<0.001). CONCLUSIONS The proficiency in detection of CRLM is significantly influenced by observer experience, although CT interpretation is less affected than MRI analysis.

Coronary CT Angiography–derived Fractional Flow Reserve

Invasive coronary angiography (ICA) with measurement of fractional flow reserve (FFR) by means of a pressure wire technique is the established reference standard for the functional assessment of coronary artery disease (CAD) ( 1 , 2 ). Coronary computed tomographic (CT) angiography has emerged as a noninvasive method for direct assessment of CAD and plaque characterization with high diagnostic accuracy compared with ICA ( 3 , 4 ). However, the solely anatomic assessment provided with both coronary CT angiography and ICA has poor discriminatory power for ischemia-inducing lesions. FFR derived from standard coronary CT angiography (FFRCT) data sets by using any of several advanced computational analytic approaches enables combined anatomic and hemodynamic assessment of a coronary lesion by a single noninvasive test. Current technical approaches to the calculation of FFRCT include algorithms based on full- and reduced-order computational fluid dynamic modeling, as well as artificial intelligence deep machine learning ( 5 , 6 ). A growing body of evidence has validated the diagnostic accuracy of FFRCT techniques compared with invasive FFR. Improved therapeutic guidance has been demonstrated, showing the potential of FFRCT to streamline and rationalize the care of patients suspected of having CAD and improve outcomes while reducing overall health care costs ( 7 , 8 ). The purpose of this review is to describe the scientific principles, clinical validation, and implementation of various FFRCT approaches, their precursors, and related imaging tests.