Roman Fischbach

Left ventricular function studied with MDCT

Accurate determination of left ventricular (LV) myocardial function is fundamental for clinical diagnosis, risk stratification, and estimation of prognosis in patients with ischemic and nonischemic cardiomyopathy. Primarily, multi-detector-row spiral CT (MDCT) of the heart aimed at detecting coronary artery obstruction and cardiac morphology. Multiple studies have demonstrated that retrospectively, ECG-gated MDCT determination of LV volumes and consequently global LV function parameters is feasible in good agreement with established imaging modalities such as cineventriculography, echocardiography, and cine magnetic resonance imaging (CMR). Post-processing tools allow fast and semi-automatic determination of LV function parameters from MDCT data in analogy to known CMR evaluation approaches. Although MDCT is not considered to be first-line modality for LV function assessment, this technique provides accessory dynamic information in patients undergoing MDCT coronary angiography, contributing to combined assessment of cardiac morphology and function without need of additional radiation exposure. MDCT regional LV wall motion analysis at rest is feasible, but further improvement in temporal resolution seems mandatory to match results obtained from competing modalities. This paper will discuss the diagnostic potential of MDCT for assessment of LV function with regards to accuracy and clinical applications, as well as limitations, particularly in comparison with CMR as modality of reference.

Evaluation of global left ventricular myocardial function with electrocardiogram-gated multidetector computed tomography: comparison with magnetic resonance imaging.

Rationale and Objectives:Electrocardiogram-gated 3D volume data from multidetector computed tomography coronary angiography (MDCT-CA) enable image reconstruction in any phase of the cardiac cycle. The objective was to determine left ventricular (LV) function parameters by MDCT in comparison to cine magnetic resonance imaging (MRI). Methods:Thirty patients with known or suspected coronary artery disease (CAD) underwent MDCT-CA. From multiplanar reformations in short axis orientation end-diastolic and end-systolic LV volumes (LVEDV, LVESV) were determined to calculate LV stroke volume and ejection fraction (LVSV, LVEF) and compared with MRI measurements. Results:LVEDV (147 ± 27 mL) and LVESV (65 ± 22 mL) determined by MDCT correlated well to the respective MRI measurements (LVEDV 133 ± 27 mL, r = 0.80, P < 0.001; LVESV 48 ± 19 mL, r = 0.89, P < 0.001). LVSV (MDCT 82 ± 15 mL; MRI 85 ± 17 mL; r = 0.77, P < 0.001) and LVEF (MDCT 56 ± 9%; MRI 65 ± 8%; r = 0.85, P < 0.001) showed a good correlation as well. LVEF was significantly underestimated by MDCT (−8.5 ± 4.7%, P < 0.001). Conclusions:Initial experience in patients evaluated for CAD shows that spiral MDCT studies may provide LV functional data in good correlation to Cine MRI.

64- Versus 16-slice CT angiography for coronary artery stent assessment: in vitro experience.

Objectives:We sought to assess the visualization of different coronary artery stents and the delineation of in-stent stenoses using 64- and 16-slice multidector computed tomography (MDCT). Materials and Methods:A total of 15 different coronary stents with a simulated in-stent stenosis were placed in a vascular phantom and scanned with a 16-slice and a 64-slice MDCT at orientations of 0°, 45°, and 90° relative to the scanners z-axis. Visible lumen diameter and attenuation in the stented and the unstented segment of the phantom were measured. Three readers assessed stenosis delineation and visualization of the residual lumen using a 5-point scale. Results:Artificial lumen narrowing (ALN) was significantly reduced with 64-slice CT compared with 16-slice CT. At an angle of 0°, 45°, and 90° relative to the scanners z-axis, the ALN for 16-slice CT was 42.2%, 39.8%, and 44.0% using a slice-thickness of 1.0 mm and 40.9%, 40.4%, and 41.6% using a slice thickness of 0.75 mm, respectively. With 64-slice CT, the ALN was 39.1%, 37.3%, and 36.0% at the respective angles. The differences between attenuation values in the stented and unstented segment of the tube were significantly lower for 64-slice CT. Mean visibility scores were significantly higher for 64-slice CT. Conclusion:Use of the 64-slice CT results in superior visualization of the stent lumen and in-stent stenosis compared with 16-slice CT, especially when the stent is orientated parallel to the x-ray beam.

Optimal Systolic and Diastolic Reconstruction Windows for Coronary CT Angiography Using Dual-Source CT

OBJECTIVE The purpose of this study was to determine the position of the optimal systolic and diastolic reconstruction intervals for coronary CT angiography using dual-source CT. SUBJECTS AND METHODS In 90 patients, coronary dual-source CT angiography was performed without beta-blocking agents. Data were reconstructed in 5% steps throughout the R-R interval. Two independent readers selected optimal systolic and diastolic reconstruction windows for each major coronary vessel--the right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex artery (LCX)--using a 3D viewer and volume-rendering displays. The motion score for each vessel was graded from 1 (no motion artifacts) to 5 (severe motion artifacts over entire vessel). RESULTS The average heart rate of all patients was 68.7 beats per minute (bpm) (range, 43-119 bpm). The median optimal systolic reconstruction windows were at 35%, 30%, and 35% for the RCA, LAD, and LCX, respectively. The median optimal diastolic reconstruction window was at 75% for all vessels. The mean motion scores (+/- SD) in the systolic reconstructions were 1.9 +/- 0.8 (RCA), 1.7 +/- 0.5 (LAD), and 2.0 +/- 0.6 (LCX). The mean motion scores for the diastolic reconstructions were 1.7 +/- 0.9, 1.5 +/- 0.6, and 1.6 +/- 0.7, respectively. In patients with a heart rate of < 70 bpm, motion scores were significantly lower in diastole versus systole (1.3 +/- 0.4 and 1.9 +/- 0.5, respectively; p < 0.01). In most patients with a heart rate of > 80 bpm, motion scores were lower in systolic than in diastolic reconstructions (2.1 +/- 0.6 and 2.6 +/- 0.8, respectively; p < 0.05). CONCLUSION Using dual-source CT, the overall optimal reconstruction window is at 75% of the R-R interval in patients with low or intermediate heart rates. In patients with heart rates of > 80 bpm, systolic reconstructions often yield superior image quality compared with diastolic reconstructions.

Safety, Efficacy, and Indications of β-Adrenergic Receptor Blockade to Reduce Heart Rate prior to Coronary CT Angiography

For selected indications, coronary computed tomographic (CT) angiography is an established clinical technology for evaluation in patients suspected of having or known to have coronary artery disease. In coronary CT angiography, image quality is highly dependent on heart rate, with heart rate reduction to less than 60 beats per minute being important for both image quality and radiation dose reduction, especially when single-source CT scanners are used. β-Blockers are the first-line option for short-term reduction of heart rate prior to coronary CT angiography. In recent years, multiple β-blocker administration protocols with oral and/or intravenous application have been proposed. This review article provides an overview of the indications, efficacy, and safety of β-blockade protocols prior to coronary CT angiography with respect to different scanner techniques. Moreover, implications for radiation exposure and left ventricular function analysis are discussed.

MRI examination of the TMJ and functional results after conservative and surgical treatment of mandibular condyle fractures

Thirty patients with healed condylar fractures were included in this study. Ten patients were conservatively treated while in 20 patients the fractures were treated surgically. All patients were assessed using: magnetic resonance imaging of both temporomandibular joints (TMJs) to evaluate the disc position and morphology; radiographs to evaluate the alignment of the bony fragments after consolidation; and clinical examination including the stomatognathic functional status and mechanical axiography. The study shows that anatomical reduction of a low, displaced or dislocated condylar fracture by surgical approach may be of benefit for the functional recovery of the TMJ.

High-resolution magnetic resonance imaging of the temporomandibular joint: image quality at 1.5 and 3.0 Tesla in volunteers.

Purpose:To assess the image quality of a high-resolution imaging protocol for the temporomandibular joint (TMJ) at 3.0 T and to compare it with our standard 1.5 T protocol. Materials and Methods:Fifteen volunteers without history of TMJ dysfunction underwent bilateral magnetic resonance imaging (MRI) of the TMJ with the jaw in closed and open position. MRI was performed with using a 1.5 T (standard TMJ coil) and 3.0 T (purpose build phased array coil) MR system (Gyroscan Intera 1.5 T and 3.0 T; Philips Medical Systems, Best, the Netherlands). Imaging protocols consisted of a parasagittal PDw-TSE sequence and a coronal PDw-TSE sequence in closed mouth position and a sagittal PDw-TSE sequence in open mouth position. Acquisition parameters were adjusted for 3.0 T and voxel size was reduced from 0.29 × 0.29 × 3.0 mm (1.5 T) to 0.15 × 0.15 × 1.5 mm (3.0 T). Total examination time (15 minutes) was similar for both systems. Two observers assessed in consensus delineation, image quality, and artifacts of anatomic landmarks (disk, bilaminar zone, capsular attachment, cortical bone) and ranked them qualitatively on a 5-point scale from 1 (optimal) to 5 (nondiagnostic). Disk position and motility was noted. For CNR analysis, signal intensity from disk and retrodiscal tissue was measured. Results:Disk position and mobility was identical at both field strengths. All anatomic landmarks were visualized significantly better at 3.0 T. In particular, the capsular attachment was depicted in more detail. Overall image quality was ranked significantly higher at 3.0 T, whereas artifact score was similar. Quantitative evaluation showed significantly higher CNR for 3.0 T (10.23 vs. 8.08, P < 0.0001). Conclusion:Depiction of the normal anatomy of the TMJ benefits significantly when investing the higher SNR at 3.0 T into better spatial resolution. We anticipate that this advantage of 3.0 T MRI will also permit a more detailed analysis of capsular and disk pathology.

Automated Threshold-Based 3D Segmentation Versus Short-Axis Planimetry for Assessment of Global Left Ventricular Function with Dual-Source MDCT

OBJECTIVE The purpose of this study was to evaluate software for threshold-based 3D segmentation of the left ventricle in comparison with traditional 2D short axis-based planimetry (Simpson method) for measurement of left ventricular (LV) volume and global function with state-of-the-art dual-source CT. SUBJECTS AND METHODS Fifty patients with known or suspected coronary artery disease underwent coronary CT angiography. LV end-diastolic, end-systolic, and stroke volumes and ejection fraction were determined from axial images to which 3D segmentation had been applied and from short-axis reformations from 2D planimetry. Interobserver variability was assessed for both approaches. RESULTS Threshold-based 3D LV segmentation had excellent correlation with 2D short-axis results (end-diastolic volume, R = 0.99; end-systolic volume, R = 0.99; stroke volume, R = 0.90; ejection fraction, R = 0.97; p < 0.0001). Bland-Altman analyses revealed systematic underestimation of LV end-diastolic volume (-7.4 +/- 8.9 mL) and LV end-systolic volume (-7.0 +/- 4.4 mL) with the 3D segmentation approach and 2.8 +/- 3.3% overestimation of LV ejection fraction. Interobserver variation with 3D segmentation analysis was significantly (p < 0.001) less (e.g., LV ejection fraction, 0.1 +/- 1.7%) than with the 2D technique, and mean analysis time was significantly shorter (172 +/- 20 vs 248 +/- 29 seconds; p < 0.05). CONCLUSION Automated threshold-based 3D segmentation enables accurate and reproducible dual-source CT assessment of LV volume and function with excellent correlation with results of 2D short-axis analysis. Exclusion of papillary muscles from LV volume results in small systematic differences in quantitative values.

Prospective Study of Access Site Complications of Automated Contrast Injection With Peripheral Venous Access in MDCT

OBJECTIVE The purpose of this article is to prospectively assess the frequency and type of IV injection site complications associated with high-flow power injection of nonionic contrast medium in MDCT. SUBJECTS AND METHODS Contrast-enhanced (300-370 mg iodine/mL) MDCT examinations with high flow rates (up to 8 mL/s) using automatic CT injectors were performed according to standardized MDCT protocols. The location, type, and size (16-24 gauge) of IV catheters and volumes, iodine concentration, and flow rates of contrast medium were documented. Patients were questioned about associated discomfort, IV catheter sites were checked, and adverse effects were recorded. RESULTS Prospectively, 4,457 patients were studied. The injection rate ranged from 1-2.9 mL/s (group 1; n = 1,140) to 3-4.9 mL/s (group 2; n = 2,536) to 5-8 mL/s (group 3; n = 781); 1.2% of the patients experienced extravasations (n = 52). Contrast medium iodine concentration, flow rates, and volumes were not related to the frequency of extravasation. The extravasation rate was highest with 22-gauge IV catheters (2.2%; p < 0.05) independently of the anatomic location. For 20-gauge IV catheters, extravasation rates were significantly higher in the dorsum of the hand than in the antecubital fossa (1.8% vs 0.8%; p = 0.018). Extravasation rates were higher in older patients (≥ 50 vs < 50 years, 0.6% vs 1.4%; p = 0.019). Different iodine concentrations did not trigger significant differences in contrast material reactions (p = 0.782). CONCLUSION Automated IV contrast injection applying high flow rates (i.e., up to 8 mL/s) is performed without increased risk of extravasation. The overall extravasation rate was 1.2% and showed no correlation with iodine concentration, flow rates, or contrast material reactions. Performing high flow rates with low-diameter IV catheters (e.g., 22-gauge catheters) and a location of IV catheter in the hand is associated with a higher extravasation rate.

Perfusion CT in acute stroke: prediction of vessel recanalization and clinical outcome in intravenous thrombolytic therapy

This study evaluated perfusion computed tomography (PCT) for the prediction of vessel recanalization and clinical outcome in patients undergoing intravenous thrombolysis. Thirty-nine patients with acute ischemic stroke of the middle cerebral artery territory underwent intravenous thrombolysis within 3 h of symptom onset. They all had non-enhanced CT (NECT), PCT, and CT angiography (CTA) before treatment. The Alberta Stroke Program Early Computed Tomography (ASPECT) score was applied to NECT and PCT maps to assess the extent of ischemia. CTA was assessed for the site of vessel occlusion. The National Institute of Health Stroke Scale (NIHSS) score was used for initial clinical assessment. Three-month clinical outcome was assessed using the modified Rankin scale. Vessel recanalization was determined by follow-up ultrasound. Of the PCT maps, a cerebral blood volume (CBV) ASPECT score of >6 versus ≤6 was the best predictor for clinical outcome (odds ratio, 31.43; 95% confidence interval, 3.41–289.58; P < 0.002), and was superior to NIHSS, NECT and CTA. No significant differences in ASPECT scores were found for the prediction of vessel recanalization. ASPECT score applied to PCT maps in acute stroke patients predicts the clinical outcome of intravenous thrombolysis and is superior to both early NECT and clinical parameters.