Scintigraphic evaluation of pulmonary embolism after total hip replacement, using a dry 99mTc-microaerosol for regional ventilation.

A new 99mTc-microaerosol was used for ventilation scintigraphy in combination with perfusion scintigraphy for studying the incidence of pulmonary embolism (PE) from 189 consecutive investigations in patients undergoing total hip replacement. Diagnostic criteria are presented. Perfusion defects of triangular shape were significantly more frequent in combination with ventilation mismatch (PE) than with ventilation match (not PE) (P less than 0.001). Reevaluation of the scintigrams more than 2 months later gave identical results in more than 90% of patients and as regards the diagnosis of PE, in 93%. Attacks of sudden chest pain were more frequent in patients with pulmonary embolism (P less than 0.01), but measurement of arterial blood gases did not discriminate between patients with and without PE. The 99mTc-microaerosol provides a high resolution and images that are directly comparable to perfusion studies using the same, easily available isotope. In many aspects this new microaerosol seems to be superior to previously described radioaerosols and to 133Xe for ventilation studies.