THE USE OF99mTc RADIOAEROSOL VENTILATION AND MACROAGGREGATED ALBUMIN PERFUSION IMAGING FOR THE DETECTION OF PULMONARY EMBOLI IN THE DOG

Abstract

This study was undertaken to design protocol for use of radioaerosol of technetium‐99m‐labeled diethylenetriaminepentacetic acid (99mTc‐DTPA) for ventilation imaging as clinical tool in the dog and to evaluate imaging characteristics in both normal dogs and dogs with simulated pulmonary embolism. Clearance of the 99mTc‐DTPA radioaerosol from the lung was also evaluated. Six normal dogs were used in two phases: (1) as their own controls and (2) during pulmonary artery occlusion using Swan‐Ganz catheter. Radioaerosol ventilation images were obtained and rate of clearance from normal and occluded lungs determined. Perfusion studies using technetium‐99m‐macroaggregated albumin (99mTc‐MAA) immediately followed. Clearance half‐times (T1/2) were found to be significantly increased (p < 0.05) in acutely occluded lungs; however, the small magnitude of this change was visually difficult to detect on the ventilation images. Good quality initial ventilation and perfusion images were obtained and provided ready evaluation of ventilation (V), perfusion (Q), and induced V/Q mismatches. A clinical case of pulmonary thromboembolic disease was also evaluated with diagnostic result, indicating that this method of V/Q scintigraphy can provide useful information in those clinical cases in which pulmonary thromboembolism is suspected.