USE OF SONOMICROMETRY AND MULTIDIMENSIONAL-SCALING TO DETERMINE THE 3-DIMENSIONAL COORDINATES OF MULTIPLE CARDIAC LOCATIONS - FEASIBILITY AND INITIAL IMPLEMENTATION

We describe a new method which uses sonomicrometry and the statistical technique of multidimensional scaling (MDS) to measure the three-dime nsional (3-D) coordinates of multiple cardiac locations, We refer to t his new method as sonomicrometry array localization (SAL). The new met hod differs from standard sonomicrometry in that each piezoelectric tr ansducer element is used as both transmitter and receiver and the set of intertransducer element distances is measured, MDS calculates the 3 -D coordinates of each sonomicrometry transducer element from the set of intertransducer element distances, The feasibility of this new meth od was tested with mathematical simulations which demonstrated the abi lity of MDS to compensate for signal error and missing intertransducer element distances, We describe the design elements of a modified digi tally controlled sonomicrometer in which a single transducer element c an sequentially broadcast to as many as eight receiver elements, That design is used to validate SAL in a water bath and in ex vivo and livi ng hearts, Correlation with caliper measurement in the water bath (y i nt. = 3.91 +/- 3.36 mm, slope = 1.04 +/- 0.05, r(2) = 0.969 +/- 0.027) and with radiography in ex vivo (y int. = -0.87 +/- 0.92 mm, slope = 0.97 +/- 0.02, r(2) = 0.960 +/- 0.023) and in vivo hearts (y int. = 2. 98 +/- 2.59 mm, slope = 1.01 +/- 0.06, r(2) = 0.953 +/- 0.031) was exc ellent. Sonomicrometry array localization is able to accurately measur e the 3-D coordinates of multiple cardiac locations. it can potentiall y measure myocardial deformation and remodeling after ischemic or valv ular injury.