Technetium 99M-MIBI regional myocardial wall imaging.

Abnormalities in left ventricular (LV) function and perfusion occur on exercise in patients with coronary artery disease. Both are used for diagnosis as well as evaluation after interventions and are important in prognosis. The myocardial imaging agent technetium methoxy-isobutylisonitrile (MIBI) has improved imaging characteristics over thallium. This thesis has investigated MIBI to measure both perfusion and function in patients with CAD. A new method was devised to quantify regional and global LV function by measuring fractional shortening (FS) of the gated perfusion image in 4 axes. A close correlation was shown between resting FS and ejection fraction measured by radionuclide ventriculography (RNV) and cineangiography. On exercise a good correlation persisted and for the first time a method of FS accurately determined changes from rest to exercise and differentiated normals from those with CAD comparable to the results of exercise RNV. This work identified an improvement in detection of regional defects, especially with the use quantitative measurements, using the end diastolic frame of the gated images as compared to the site of stenoses on coronary angiography. A close association between the perfusion defects found and the regional abnormalities detected on FS analysis was also demonstrated. The use of combined perfusion and function imaging was found to have a sensitivity of 100% for CAD. Patients were, therefore, studied who were undergoing PTCA. Abnormalities in perfusion and/or function were detected in all patients pre PTCA. Post successful PTCA combined imaging was able to differentiate restenosis from new disease and was able to demonstrate a good medium term result. Gated MIBI imaging is a sensitive detector of CAD, is of value in those with an equivocal exercise test and is useful in the long term follow up of patients undergoing PTCA. MIBI is, therefore, a step forward in radionuclide imaging of the heart.