Richard Alan Johnson

Improved quantification of myocardial mass by three-dimensional echocardiography using a deposit contrast agent

The aim of the study was to assess the usefulness of a novel contrast agent in combination with three-dimensional echocardiography for improved mass quantification. Three-dimensional reconstruction of left ventricular myocardium was performed from images obtained with rotational epicardial acquisition in eight open-chested pigs, before and after injection of a deposit contrast agent, Quantison Depot. Three-dimensional echocardiographic myocardial mass values were in excellent agreement with weighted mass (differences -1.6 +/- 5.0 g for end-diastolic frame, -2.8 +/- 4.5 g for end-systolic, 1.0 +/- 1.0 g for end-diastolic with contrast and 0.6 +/- 2.0 g for end-systolic with contrast, p = NS). Left ventricular mass measurements after contrast injection were more accurate and had less measurement variability. In conclusion, myocardial contrast enhancement improves left ventricular mass calculation with three-dimensional echocardiography.

Visualization and quantification of myocardial mass at risk using three-dimensional contrast echocardiography

OBJECTIVE Three-dimensional echocardiographic assessment of myocardial ischemia using contrast echocardiography has been hampered by limitations of available contrast agents and analytic software. In the study presented, a three-dimensional perfusion imaging method was evaluated in the porcine model of myocardial ischemia using a novel contrast agent. METHODS Three-dimensional echocardiography was performed in eight open-chested pigs before, during and after left anterior descending (six animals) or circumflex (two animals) coronary artery occlusion. The intramyocardial contrast effect was obtained by left atrial injection of Myomap, a deposit contrast agent. RESULTS Myocardial opacification was visible in all studies and retained in all three-dimensional datasets. Three-dimensional intensity analysis demonstrated a significant difference, exceeding 20 intensity units in every animal (in 127-level scale), between perfused and non-perfused myocardium. Reperfusion followed by contrast reinjection resulted in homogenous myocardial enhancement. Myocardial mass at risk was clearly delineated in all studies and measured with a mean error of -0.1 +/- 2.0 g against real mass (p = non-significant). Spatial extent of ischemia could be displayed in volume-rendered reconstruction of separate perfusion territories. CONCLUSIONS Quantitative analysis of myocardial contrast enhancement from three-dimensional datasets is feasible and allows accurate measurement of myocardial mass at risk.

Evaluation of rHA labeled with Gd-DTPA for blood pool imaging and targeted contrast delivery.

A new contrast agent was developed by linking Gd-DTPA chelate to recombinant human albumin in the laboratory. The molar relaxivity of the new agent was tested in aqueous solution at B(0) 1.5 T and temperature 20 degrees C. The soluble compound had a higher molar longitudinal relaxivity and molar transverse relaxivity in water (r(1) = 7.2 s(-1) mM(-1), r(2) = 18.4 s(-1) mM(-1)) than those measured for Gd-DTPA solution (r(1) = 3.5 s(-1) mM(-1), r(2) = 5.5 s(-1) mM(-1)). The performance of the compound as a blood pool agent was investigated with soluble and microparticulate forms of the compound and comparisons were made with Gd-DTPA and the polymeric blood-pool agent, Gadomer. T(1)-weighted imaging experiments show that the soluble compound acts as a highly effective blood pool agent with hyperintensity in the vasculature persisting beyond 2 h post administration, compared with free Gd-DTPA, which was cleared from the blood pool after approximately 10 min. The clearance kinetics of the new agents were examined, due to the incomplete elimination within 14 days post injection; both rHA labeled compounds are probably not suitable for development as routine blood pool contrast media. However, with free sites on the Gd-loaded rHA molecule, there are possibilities for binding the agent to antibodies in the laboratory, which was demonstrated, and thus there exist potential applications for in vivo molecular imaging with this agent.