Effect of acute experimental pulmonary arterial occlusion on the deposition and clearance of technetium-99m-DTPA radioaerosols.

UNLABELLED

Canine models of autologous PE and balloon occlusion of the pulmonary vasculature were used to evaluate radioaerosol deposition and to quantify radioaerosol clearance in the immediate postembolic period.

METHODS

A total of 28 animals were anesthetized, intubated and studied (central balloon occlusion = 4, peripheral balloon occlusion = 7, autologous PE = 5, various control groups = 12). A gamma camera computer system was used to monitor the distribution and clearance rate of inhaled DTPA radioaerosol. The perfusion defect distribution was determined after the radioaerosol study using 99mTc-MAA.

RESULTS

A new radioaerosol deposition defect was seen in 3 of 16 animals in a zone of acute vascular occlusion by a balloon (n = 2) or PE (n = 1). In addition, radioaerosol clearance rates were altered substantially. Peripheral vascular occlusion and PE caused radioaerosol clearance rates to accelerate significantly (control clearance half-time = 33.6 +/- 4.6 min, post-balloon occlusion = 19.0 +/- 8.3 min, post-PE = 12.4 +/_ 3.7 min, both p < 0.05). In only one case did these clearance rate changes create a visible abnormality in the aerosol images.

CONCLUSIONS

The pulmonary deposition patterns and clearance rates of 99mTc-DTPA radioaerosol can be altered by acute vascular occlusion or PE. These findings should be considered when interpreting radioaerosol images in patients with suspected PE.