Martin H. K. Hoffmann

Multislice CT imaging of anomalous coronary arteries

The purpose of the present study was to evaluate the role of 16 multislice computed tomography (MSCT) to identify the origin of anomalous coronary arteries and to confirm their anatomic course in relation to the great vessels. Accuracy of coronary artery disease (CAD) detection was a secondary aim and was tested with conventional angiograms (CA) serving as standard of reference. Two hundred and forty-two consecutive patients referred for noninvasive coronary CT imaging were reviewed for the study. Sixteen patients (6.6%) with anomalous coronary arteries were detected and included as the study group. MSCT and CA images were analyzed in a blinded fashion for accuracy of anomalous artery origin and path detection. Results were compared in a secondary consensus evaluation. Accuracy ratios to detect CAD with MSCT in all vessels were calculated. Coronary anomalies for all 16 patients were correctly displayed on MSCT. CA alone achieved correct identification of the abnormality in only 53% (P=0.016). Sensitivity and specificity of MSCT to detect significantly stenosed vessels was 90 and 92%. 16-MSCT is accurate to delineate abnormally branching coronary arteries and allows sufficiently accurate detection of obstructive coronary artery disease in distal branches. It should therefore be considered as a prime non-invasive imaging tool for suspected coronary anomalies.

Multienergy Photon-counting K-edge Imaging: Potential for Improved Luminal Depiction in Vascular Imaging

The purpose of this study was to investigate whether spectral computed tomography (CT) has the potential to improve luminal depiction by differentiating among intravascular gadolinium-based contrast agent, calcified plaque, and stent material by using the characteristic k edge of gadolinium. A preclinical spectral CT scanner with a photon-counting detector and six energy threshold levels was used to scan a phantom vessel. A partially occluded stent was simulated by using a calcified plaque isoattenuated to a surrounding gadolinium chelate solution. The reconstructed images showed an effective isolation of the gadolinium with subsequent clear depiction of the perfused vessel lumen. The calcified plaque and the stent material are suppressed.

Detection and localization of acute upper and lower gastrointestinal (GI) bleeding with arterial phase multi-detector row helical CT

The purpose of this study was to evaluate the accuracy of multi-detector row helical CT (MDCT) for detection and localization of acute upper and lower gastrointestinal (GI) hemorrhage or intraperitoneal bleeding. Thirty-six consecutive patients with clinical signs of acute bleeding underwent biphasic (16- or 40-channel) MDCT. MDCT findings were correlated with endoscopy, angiography or surgery. Among the 36 patients evaluated, 26 were examined for GI bleeding and 10 for intraperitoneal hemorrhage. Confirmed sites of GI bleeding were the stomach (n = 5), duodenum (n = 5), small bowel (n = 6), large bowel (n = 8) and rectum (n = 2). The correct site of bleeding was identifiable on MDCT in 24/26 patients with GI bleeding. In 20 of these 24 patients, active CM extravasation was apparent during the exam. Among the ten patients with intraperitoneal hemorrhage, MDCT correctly identified the bleeding source in nine patients. Our findings suggest that fast and accurate localization of acute gastrointestinal and intraperitoneal bleeding is achievable on MDCT.

Pitfalls in Abdominal Diffusion-Weighted Imaging: How Predictive is Restricted Water Diffusion for Malignancy

OBJECTIVE As diffusion-weighted imaging is increasingly implemented into routine protocols of abdominal MRI, abnormal findings in expected and unexpected locations become more common. The aim of our retrospective study was to investigate the specificity of restricted diffusion in differentiation of benign from malignant abdominal disease. MATERIALS AND METHODS Two hundred thirty consecutively registered patients underwent abdominal MRI including diffusion-weighted imaging (single-shot spin-echo echo-planar sequence) with b values of 0, 150, 500, and 1,000 s/mm(2). Lesions were detected by two blinded readers using only the images with a b value of 1,000 s/mm(2), and representative apparent diffusion coefficients were measured. Lymph nodes were not documented. RESULTS Fifty-two of the 230 patients had a total of 55 lesions with restricted diffusion (23.9%). The mean apparent diffusion coefficient was 809 mm(2)/s. Forty-three lesions (78.2%) were malignant. The 12 benign lesions were liver hemangioma, liver adenoma, autoimmune pancreatitis, pancreatic teratoma, two abscesses, three cases of inflammatory bowel wall thickening due to Crohns disease, Bartholin cyst, hemorrhagic ovarian cyst, and renal Rosai-Dorfman disease. CONCLUSION Restricted diffusion is generally considered to be associated with malignant tumors because of the high cellularity of these tumors. However, in interpretation of diffusion-weighted images, it should be kept in mind that a number of benign lesions, as many as 22% in our cohort, can exhibit restricted diffusion on images with high b values, thus mimicking malignant lesions.

Automatic determination of minimal cardiac motion phases for computed tomography imaging: initial experience

Low motion phases for cardiac computed tomography reconstructions are currently detected manually in a user-dependent selection process which is often time consuming and suboptimal. The concept of motion maps was recently introduced to achieve automatic phase selection. This pilot study compared the accuracy of motion-map phase selection to that with manual iterative selection. The study included 20 patients, consisting of one group with low and one with high heart rate. The technique automatically derives a motion strength function between multiple low-resolution reconstructions through the cardiac cycle, with periods of lowest difference between neighboring phases indicating minimal cardiac motion. A high level of agreement was found for phase selection achieved with the motion map approach compared with the manual iterative selection process. The motion maps allowed automated quiescent phase detection of the cardiac cycle in 85% of cases, with best results at low heart rates and for the left coronary artery. They can also provide additional information such as the presence of breathing artifacts. Motion maps show promise as a rapid off-line tool to automatically detect quiescent cardiac phases in a variety of patients.

Spectral coronary multidetector computed tomography angiography: dual benefit by facilitating plaque characterization and enhancing lumen depiction.

Objective: To assess ex vivo specimens of atherosclerotic coronary arteries by dual energy (DE) multidetector computed tomography (MDCT) imaging, and to correlate depicted vessel lumen morphology and detected tissue characteristics with histopathologic analysis. Methods: Coronary arteries were imaged on a 16-slice MDCT using a DE protocol consisting of a 90- and 140-kV scan. Coronary arteries were perfused with iodine- and gadolinium-based contrast agents. The DE K-edge subtractions were performed. Regions-of-interest were placed on histopathologically/radiographically-matched vascular lumen and wall, fibromuscular and calcified plaque, and fat tissues. Vascular/tissue contrast-to-noise ratios (CNR) were calculated, and their dependence on tissue type and contrast agent type was statistically evaluated. Results: Tissue CNR analysis confirmed that all tissue types were successfully distinguished. Vascular wall and fibromuscular plaque achieved a significant increase in CNR ratios when DE techniques were used compared with 140 kV protocols. Conclusions: Spectral DE MDCT imaging of ex vivo atherosclerotic coronary arteries allows successful tissue characterization and enhances depiction of coronary lumen.

Coronary plaque imaging with 256-slice multidetector computed tomography: interobserver variability of volumetric lesion parameters with semiautomatic plaque analysis software

The purpose of this study was to evaluate the potential clinical value of coronary plaque imaging with a new generation CT scanner and the interobserver variability of coronary plaque assessment with a new semiautomatic plaque analysis application. Thirty-five isolated plaques of the left anterior descending coronary artery from 35 patients were evaluated with a new semiautomatic plaque analysis application. All patients were scanned with a 256-slice MDCT scanner (Brilliance iCT, Philips Healthcare, Cleveland OH, USA). Two independent observers evaluated lesion volume, maximum plaque burden, lesion CT number mean and standard deviation, and relative lesion composition. We found 10 noncalcified, 16 mixed, and 9 calcified lesions in our study cohort. Relative interobserver bias and variability for lesion volume were −37%, −13%, −49%, −44% and 28%, 16%, 37%, and 90% for all, noncalcified, mixed, and calcified lesions, respectively. Absolute interobserver bias and variability for relative lesion composition were 1.2%, 0.5%, 1.5%, 1.3% and 3.3%, 4.5%, 7.0%, and 4.4% for all, noncalcified, mixed, and calcified lesions, respectively. While mixed and calcified lesions demonstrated a high degree of lesion volume interobserver variability, noncalcified lesions had a lower degree of lesion volume interobserver variability. In addition, relative noncalcified lesion composition had a very low interobserver variability. Therefore, there may a role for MDCT in serial noncalcified plaque assessment with semiautomatic analysis software.

Comparison of aortic neck dilatation after open and endovascular repair of abdominal aortic aneurysm.

OBJECTIVE This study evaluated the changes of the aortic diameter at the suprarenal and infrarenal segment after open repair (OR) and endovascular repair (EVAR) of abdominal aortic aneurysms (AAAs). METHODS This was a retrospective analysis of all patients undergoing AAA repair between 1997 and 2008. Inclusion criteria were at least 3 months of follow-up at our institution, elective aneurysm repair, and absence of false, mycotic, or inflammatory aneurysms. For EVAR, standard computed tomography (CT) scans from follow-up were used; in the OR group, CT scans performed for unrelated nonvascular indications were used. Diameters of the aorta were measured at the first slice below the lowest renal artery and at the first slice above the highest renal artery. A 2-mm change was defined as measurable aortic neck dilatation. RESULTS Inclusion criteria were met by 46 patients in the OR group and 103 in the EVAR group. After a follow-up of 34.1 months (range, 5.5-131.7 months) in the OR group and 39.4 months (range, 3-108.9 months) in the EVAR group, the mean changes were 1.75 ± 3.50 mm (OR) and 0.9 ± 2.3 mm (EVAR; P = .305) in the suprarenal diameters and 0.8 ± 2.9 mm (OR) and 1.2 ± 2.5 mm (EVAR; P = .311) in the infrarenal diameters. The absolute suprarenal vs infrarenal sizes were 29.7 ± 7.1 and 28.7 ± 6.8 mm in the OR group and 28.7 ± 3.2 and 28.5 ± 3.6 mm, respectively, in the EVAR group (suprarenal, P = .749; infrarenal, P = .273). Increase of the aortic diameter >2 mm, defined as aortic neck dilatation, was found in 23 of 103 EVAR patients (22.3% ± 0.862%), and in nine of 46 OR patients (19.57% ± 0.484%; P = .870). Increase in the suprarenal change >2 mm occurred in 21 of 103 EVAR patients (20.39% ± 1.04%) and in 14 of 46 OR patients (30.4% ± 0.446%; P = .260). Reintervention rate of patients with an increase >2 mm was 31% (seven of 23) in EVAR and 11.1% (one of nine) in the OR group (P = .386). CONCLUSIONS The AAA groups treated with EVAR or OR demonstrated similar increases of aneurysmal neck diameters. This suggests that aortic neck dilatation may be caused by a natural progression of the disease rather than by deviating therapeutic strategies.

Quantification of aortic valve area at 256-slice computed tomography: Comparison with transesophageal echocardiography and cardiac catheterization in subjects with high-grade aortic valve stenosis prior to percutaneous valve replacement

PURPOSE The purpose of this study was to compare planimetric aortic valve area (AVA) measurements from 256-slice CT to those derived from transesophageal echocardiography (TEE) and cardiac catheterization in high-risk subjects with known high-grade calcified aortic stenosis. METHODS AND MATERIALS The study included 26 subjects (10 males, mean age: 79±6; range, 61-88 years). All subjects were clinically referred for aortic valve imaging prior to percutaneous aortic valve replacement from April 2008 to March 2009. Two radiologists, blinded to the results of TEE and cardiac catheterization, independently selected the systolic cardiac phase of maximum aortic valve area and independently performed manual CT AVA planimetry for all subjects. Repeated AVA measurements were made to establish CT intra- and interobserver repeatability. In addition, the image quality of the aortic valve was rated by both observers. Aortic valve calcification was also quantified. RESULTS All 26 subjects had a high-grade aortic valve stenosis (systolic opening area <1.0 cm(2)) via CT-based planimetry, with a mean AVA of 0.62±0.18. In four subjects, TEE planimetry was precluded due to severe aortic valve calcification, but CT-planimetry was successfully performed with a mean AVA of 0.46±0.23 cm(2). Mean aortic valve calcium mass score was 563.8±526.2 mg. Aortic valve area by CT was not correlated with aortic valve calcium mass score. A bias and limits of agreement among CT and TEE, CT and cardiac catheterization, and TEE and cardiac catheterization were -0.07 [-0.37 to 0.24], 0.03 [-0.49 to 0.55], 0.12 [-0.39 to 0.63]cm(2), respectively. Differences in AVA among CT and TEE or cardiac catheterization did not differ systematically over the range of measurements and were not correlated with aortic valve calcium mass score. CONCLUSION Planimetric aortic valve area measurements from 256-slice CT agree well with those derived from TEE and cardiac catheterization in high-risk subjects with known high-grade calcified aortic stenosis.

Evaluation of Accordance of Magnetic Resonance Volumetric and Flow Measurements in Determining Ventricular Stroke Volume in Cardiac Patients

Background: Cardiovascular magnetic resonance imaging (CMR) has become an established noninvasive method for evaluating ventricular function utilizing three-dimensional volumetry. Postprocessing of volumetric measurements is still tedious and time consuming. Stroke volumes obtained by flow quantification across the aortic root or pulmonary trunk could be utilized to increase both speed of workflow and accuracy. Purpose: To assess accuracy of stroke volume quantification using MR volumetric imaging compared to flow quantification in patients with various cardiac diseases. Strategies for the augmentation of accuracy in clinical routine were deduced. Material and Methods: 78 patients with various cardiac diseases—excluding intra- or extracardiac shunts, regurgitant valvular defects, or heart rhythm disturbance—underwent cardiac function analysis with flow measurements across the aortic root and cine imaging of the left ventricle. Forty-six patients additionally underwent flow measurements in the pulmonary trunk and cine imaging of the right ventricle. Results: Left ventricular stroke volume (LVSV) and stroke volume of the aortic root (SVAo) correlated with r=0.97, and Bland-Altman analysis showed a mean difference of 0.11 ml and a standard error of estimation (SEE) of 4.31 ml. Ninety-two percent of the data were within the 95% limits of agreement. Right ventricular stroke volume (RVSV) and stroke volume of the pulmonary trunk (SVP) correlated with a factor of r=0.86, and mean difference in the Bland-Altman analysis was fixed at –2.62 ml (SEE 8.47 ml). For RVSV and SVP, we calculated r=0.82, and Bland-Altman analysis revealed a mean difference of 1.27 ml (SEE 9.89 ml). LVSV and RVSV correlated closely, with r=0.91 and a mean difference of 2.79 ml (SEE 7.17 ml). SVAo and SVP correlated with r=0.95 and a mean difference of 0.50 ml (SEE 5.56 ml). Conclusion: Flow quantification can be used as a guidance tool, providing accurate and reproducible stroke volumes of both ventricles. Combining both offers a highly accurate tool to gauge ventricular function in a routine clinical setting, increasing workflow speed.