Comparison of the Detection of Subtle Changes in Myocardial Regional Systolic Function Using Qualitative and Semi-Quantitative Techniques

Purpose: To evaluate qualitative wall motion assessment vs. quantitative wall thickening for the assessment of subtle changes in myocardial systolic function using cine MRI. Methods: Cine MR images were obtained in 5 canines with a significant coronary artery stenosis and in 2 controls on a 1.5T scanner. Qualitative results were obtained using a numerical scoring system; quantitative analysis was performed using a semi-automatic segmentation program. The techniques were matched and compared using Spearman correlations. Results: All correlations in the experimental group revealed significant but weak to moderate relationships between the qualitative and quantitative results (e.g., at-risk tissue rho = 0.363, p < 0.0001; remote tissue rho = 0.275, p = 0.0002), with each identifying changes in regional function that ensued following creation of the stenosis. Intra-observer variability was reasonable in both methods when repeat analysis on a subset of the data was performed, with both techniques showing a significant correlation between the repeated measurements (quantitative − rho = 0.52, p < 0.0001; qualitative − rho = 0.54, p < 0.0001). Conclusion: Both methods were able to detect very limited wall motion abnormalities present in the canines with significant stenosis and either method gives comparable results

A 4D visualization tool for treatment planning of non-invasive radioablation in patients with ventricular tachycardia

Non-invasive cardiac radioablation is an emerging therapy for the treatment of ventricular tachycardia (VT). Electrophysiologic, anatomic and molecular imaging studies are used to localize the breakout region of the VT, but current therapy planning is tedious and prone to error due to a lack of data integration. In this work we present the design and development of a software platform and workflow to facilitate precision-targeted therapy planning, including affine non-rigid multimodality image registration and 2D-3D-4D visualization across modalities. Registration accuracy was measured using Dice Similarity and Hausdorff Distance of total left ventricle tissue volumes, which were 0.914 ± 0.013 and 2.65mm ± 0.34mm, respectively (average ± standard deviation). Electrocardiographic maps of VT parameters were registered temporally to surface electrode data to recreate familiar ECG tracings. 2D polar maps, 3D slice-views, and 4D cine-renderings were used for hybrid fusion displays of molecular and electroanatomic images. Segmentations of the cardiac-gated contrast CT blood-pool and molecular images of perfusion and glucose metabolism were used to identify regions of fibrotic scar tissue and hibernating myocardium in the 3D scene. Ablation targets were painted onto the 2D polar map, 3D slice or 4D-cine views, and exported as DICOM for import to radiotherapy planning software. We anticipate that the combination of accurate multimodality image registration and visualizations will enable more reliable therapy planning, expedite treatment and may improve understanding of the underlying pathophysiology of these lethal arrhythmias.</p

Cell Tracking and Therapy Evaluation of Bone Marrow Monocytes and Stromal Cells Using SPECT and CMR in a Canine Model of Myocardial Infarction

Background: The clinical application of stem cell therapy for myocardial infarction will require the development of methods to monitor treatment and pre-clinical assessment in a large animal model, to determine its effectiveness and the optimum cell population, route of delivery, timing, and flow milieu. Objectives: To establish a model for a) in vivo tracking to monitor cell engraftment after autologous transplantation and b) concurrent measurement of infarct evolution and remodeling. Methods: We evaluated 22 dogs (8 sham controls, 7 treated with autologous bone marrow monocytes, and 7 with stromal cells) using both imaging of 111Indium-tropolone labeled cells and late gadolinium enhancement CMR for up to12 weeks after a 3 hour coronary occlusion. Hearts were also examined using immunohistochemistry for capillary density and presence of PKH26 labeled cells. Results: In vivo Indium imaging demonstrated an effective biological clearance half-life from the injection site of ~5 days. CMR demonstrated a pattern of progressive infarct shrinkage over 12 weeks, ranging from 67-88% of baseline values with monocytes producing a significant treatment effect. Relative infarct shrinkage was similar through to 6 weeks in all groups, following which the treatment effect was manifest. There was a trend towards an increase in capillary density with cell treatment. Conclusion: This multi-modality approach will allow determination of the success and persistence of engraftment, and a correlation of this with infarct size shrinkage, regional function, and left ventricular remodeling. There were overall no major treatment effects with this particular model of transplantation immediately post-infarct