Myocardial deformation imaging based on ultrasonic pixel tracking to identify reversible myocardial dysfunction.

OBJECTIVES: This study evaluated the predictive value of myocardial deformation imaging for improvement in cardiac function after revascularization therapy in comparison with contrast-enhanced cardiac magnetic resonance imaging (ceMRI). BACKGROUND: Myocardial deformation imaging allows analysis of myocardial viability in ischemic left ventricular dysfunction. METHODS: In 53 patients with ischemic left ventricular dysfunction, myocardial viability was assessed using pixel-tracking-derived myocardial deformation imaging and ceMRI to predict recovery of function at 9 +/- 2 months follow-up. For each left ventricular segment in a 16-segment model, peak systolic radial strain was determined from parasternal 2-dimensional echocardiographic views using an automatic frame-by-frame tracking system of natural acoustic echocardiographic markers (EchoPAC, GE Ultrasound, Horton, Norway), and the relative extent of hyperenhancement using ceMRI. RESULTS: Of 463 segments with abnormal baseline function, 227 showed regional recovery. Compared with segments showing functional improvement, those that failed to recover had lower peak radial strain (15.2 +/- 7.5% vs. 22.6 +/- 6.3%; p < 0.001) and a greater extent of hyperenhancement (56 +/- 29% vs. 14 +/- 17%; p < 0.001). Using a cutoff of 17.2% for peak systolic radial strain, functional recovery could be predicted with high accuracy (sensitivity 70.2%, specificity 85.1%, area under the curve 0.859, 95% confidence interval 0.825 to 0.893). The predictive value was similar to that of hyperenhancement by ceMRI (sensitivity 71.6%, specificity 92.1%, area under the curve 0.874, 95% confidence interval 0.840 to 0.901, at a cutoff of 43% hyperenhancement). CONCLUSIONS: Myocardial deformation imaging based on frame-to-frame tracking of acoustic markers in 2-dimensional echocardiographic images is a powerful novel modality to identify reversible myocardial dysfunction.

Automated volumetry of solid pulmonary nodules in a phantom: accuracy across different CT scanner technologies.

OBJECTIVES: The accuracy of automated volumetry for pulmonary nodules in a phantom using different CT scanner technologies from single-slice spiral CT (SSCT) to 64-slice multidetector-row CT (MDCT) was compared. MATERIALS AND METHODS: A lung phantom with 5 different categories of pulmonary nodules was scanned using a single-slice spiral CT, a 4-slice MDCT, a 16-slice MDCT and a 64-slice MDCT. Each category comprised of 7-9 nodules each (total n = 40) with different known volumes. Standard dose and low dose protocols were performed using thin and thick collimation. Image data were reconstructed at the thinnest slice thickness. Data sets were analyzed with a dedicated volumetry software. Volumes of all nodules were calculated and compared. RESULTS: Mean absolute percentage error (APE) for all nodules was 8.65% (+/-7.29%) for the SSCT, 10.26% (+/-8.25%) for the 4-slice MDCT, 8.19% (+/-7.57%) for the 16-slice MDCT and 7.89% (+/-7.39%) for the 64-slice MDCT. There was statistically significant influence of the scanner type, protocol, anatomic location, and nodule volume on APE, but overall, APEs were comparable. CONCLUSION: Computer-aided volumetry showed accurate measurements in all tested scanner types. This finding has important implications for nodule assessment and follow-up.

Molecular MRI of cerebral venous sinus thrombosis using a new fibrin-specific MR contrast agent.

BACKGROUND AND PURPOSE: Imaging of cerebral vein thrombosis is still challenging. Currently, diagnosis is based on CT venography and MRI including MRA and conventional digital subtraction angiography. However, especially in chronic cases, each method has shown its limitations. Newer strategies for MRI are found on molecular imaging using targeted contrast agents. The aim of this study was to prove the feasibility of a novel fibrin-targeted MR contrast agent (EP-2104R; EPIX Pharmaceuticals) for selective imaging of sinus venous thrombosis in an animal model. METHODS: Thrombosis of the superior sagittal sinus with human blood was induced in 6 pigs using a combined microsurgical and interventional approach. MRI was then performed before and up to 120 minutes after injection of 4 micromol/kg body weight EP-2104R. Molecular imaging was performed with a 3-dimensional high-resolution T1-weighted gradient echo sequence. Time courses of signal-to-noise ratio and contrast-to-noise ratio were analyzed. Thrombi were then surgically removed and the Gadolinium concentration was assessed. RESULTS: In all cases the thrombosis could be successfully induced; the complete MR protocol could be performed in 5 animals. In these cases the thrombi showed selective enhancement after injection of the molecular contrast agent. However, a continuous contrast-to-noise ratio increase was seen up to 120 minutes after contrast administration, achieving a contrast-to-noise ratio of 14.2+/-0.7 between clot and the blood pool. CONCLUSIONS: The novel fibrin-targeted molecular MR contrast EP-2104R allows selective and high-contrast imaging of cerebral sinus vein thrombosis in an animal model.

Accuracy of automated volumetry of pulmonary nodules across different multislice CT scanners.

The purpose of this study was to compare the accuracy of an automated volumetry software for phantom pulmonary nodules across various 16-slice multislice spiral CT (MSCT) scanners from different vendors. A lung phantom containing five different nodule categories (intraparenchymal, around a vessel, vessel attached, pleural, and attached to the pleura), with each category comprised of 7-9 nodules (total, n = 40) of varying sizes (diameter 3-10 mm; volume 6.62 mm(3)-525 mm(3)), was scanned with four different 16-slice MSCT scanners (Siemens, GE, Philips, Toshiba). Routine and low-dose chest protocols with thin and thick collimations were applied. The data from all scanners were used for further analysis using a dedicated prototype volumetry software. Absolute percentage volume errors (APE) were calculated and compared. The mean APE for all nodules was 8.4% (+/-7.7%) for data acquired with the 16-slice Siemens scanner, 14.3% (+/-11.1%) for the GE scanner, 9.7% (+/-9.6%) for the Philips scanner and 7.5% (+/-7.2%) for the Toshiba scanner, respectively. The lowest APEs were found within the diameter size range of 5-10 mm and volumes >66 mm(3). Nodule volumetry is accurate with a reasonable volume error in data from different scanner vendors. This may have an important impact for intraindividual follow-up studies.

Analysis of myocardial deformation based on ultrasonic pixel tracking to determine transmurality in chronic myocardial infarction.

AIMS: Pixel tracking-derived myocardial deformation imaging is a new echocardiographic modality which allows quantitative analysis of segmental myocardial function on the basis of tracking of natural acoustic markers in 2D echocardiography. This study evaluated whether myocardial deformation parameters calculated from 2D echocardiography allow assessment of transmurality of myocardial infarction as defined by contrast-enhanced cardiac magnetic resonance imaging (ceMRI). Methods In 47 patients with ischaemic left ventricular dysfunction, transmurality of myocardial infarction was assessed using pixel-tracking-derived myocardial deformation imaging and ceMRI. For each left ventricular segment in a 16-segment model, peak systolic radial strain, circumferential strain, radial strain rate, and circumferential strain rate were calculated from parasternal 2D echocardiographic views using an automatic frame-by-frame tracking system of natural acoustic echocardiographic markers (EchoPAC, GE Ultrasound). Myocardial deformation parameters were related to the segmental extent of hyperenhancement by ceMRI. The relative amount of contrast-enhanced myocardial tissue per segment was used to define no infarction (0% hyperenhancement), non-transmural infarction (1-50% hyperenhancement), or transmural infarction (51-100% hyperenhancement). Results Analysis of myocardial deformation parameters was possible in 659 segments (88%). Systolic strain and strain rate parameters decreased with increasing relative hyperenhancement defined by ceMRI. Radial strain was 27.7+/-8.0, 20.5+/-9.7, and 11.6+/-8.5% for segments with no infarction (n=422), non-transmural infarction (n=106), and transmural infarction (n=131), respectively (P<0.0001). Radial strain allowed distinction of non-transmural infarction from transmural infarction with a sensitivity of 70.0% and a specificity of 71.2% (cut-off value for radial strain 16.5%). CONCLUSION: Frame-to-frame tracking of acoustic markers in 2D echocardiographic images for the analysis of myocardial deformation allows discrimination between different transmurality states of myocardial infarction.

MR-guided percutaneous intramyocardial injection with an MR-compatible catheter: feasibility and changes in T1 values after injection of extracellular contrast medium in pigs.

PURPOSE: To assess the feasibility of percutaneous magnetic resonance (MR)-guided intramyocardial injection of gadodiamide by using real-time imaging and to quantify T1 values and the size of the enhanced region for different concentrations of contrast agent for 30 minutes after injection. MATERIALS AND METHODS: Animal care committee approval was obtained. A catheter with a needle tip was advanced into the left ventricle in seven pigs by using real-time imaging with radial steady-state free precession. After intramyocardial injection of 2 mL of solution at concentrations of 0.05 or 0.10 mmol/mL gadodiamide, local changes in T1 values and size of the contrast material-enhanced region were sequentially measured at 3, 15, and 30 minutes after injection by using the Look-Locker sequence. Two-tailed paired Student t tests were used for statistical analysis. RESULTS: Catheter guidance and visualization of contrast agent distribution were feasible in all animals. Regional changes in T1 values were significantly different for different contrast agent concentrations (for 0.05 mmol/mL, 456 msec +/- 5 [+/- standard error of the mean]; for 0.10 mmol/mL, 228 msec +/- 4; P < .001) measured 3 minutes after injection. T1 values increased significantly (P < .05) to 720 msec +/- 7 for 0.05 mmol/mL gadodiamide and 445 msec +/- 6 for 0.10 mmol/mL gadodiamide 30 minutes after injection but remained significantly lower than those of remote myocardium (879 msec +/- 8). The size of the contrast-enhanced region increased from 13 mm(2) +/- 2 at 3 minutes to 30 mm(2) +/- 3 at 30 minutes (P < .05). CONCLUSION: Catheter MR-guided percutaneous intramyocardial injection is feasible; after intramyocardial injection of gadodiamide at concentrations of 0.05 and 0.10 mmol/mL, T1 values decreased over the observation time.

High-resolution transthoracic real-time three-dimensional echocardiography: quantitation of cardiac volumes and function using semi-automatic border detection and comparison with cardiac magnetic resonance imaging.

OBJECTIVES: We sought to validate high-resolution transthoracic real-time (RT) three-dimensional echocardiography (3DE), in combination with a novel semi-automatic contour detection algorithm, for the assessment of left ventricular (LV) volumes and function in patients. BACKGROUND: Quantitative RT-3DE has been limited by impaired image quality and time-consuming manual data analysis. METHODS: Twenty-four subjects with abnormal (n = 14) or normal (n = 10) LVs were investigated. The results for end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) obtained by manual tracing were compared with the results determined by the semi-automatic border detection algorithm. Moreover, the results of the semi-automatic method were compared with volumes and EF obtained by cardiac magnetic resonance imaging (CMRI). RESULTS: Excellent correlation coefficients (r = 0.98 to 0.99) and low variability (EDV -1.3 +/- 8.6 ml; ESV -0.2 +/- 5.4 ml; EF -0.1 +/- 2.7%; p = NS) were observed between the semi-automatically and manually assessed data. The RT-3DE data correlated highly with CMRI (r = 0.98). However, LV volumes were underestimated by RT-3DE compared with CMRI (EDV -13.6 +/- 18.9 ml, p = 0.002; ESV -12.8 +/- 20.5 ml, p = 0.005). The difference for EF was not significant between the two methods (EF 0.9 +/- 4.4%, p = NS). Observer variability was acceptable, and repeatability of the method was excellent. CONCLUSIONS: The RT-3DE, in combination with a semi-automatic contour tracing algorithm, allows accurate determination of cardiac volumes and function compared with both manual tracing and CMRI. High repeatability suggests applicability of the method for the serial follow-up of patients with cardiac disease.