Further Alternative Imaging Tests
Dual-energy CTPA distinguishes different absorption characteristics of different tissue types. It visualizes blood clots in the pulmonary arteries and will also give information of perfusion defects without additional radiation exposure compared with CTPA. Sensitivity of CTPA might improve using dual energy CTPA but needs further validation in outcome trials.
Electrocardiographically gated CTPA can differentiate between cardiac events and PE and may be of use in patients presenting with thoracic pain and suspected PE, cardiac events, or aorta dissection. However, more contrast material is needed, and the radiation dose is higher compared with CTPA.
Three-dimensional images acquired by single-photon emission computed tomography (SPECT) using a gamma-emitting radioisotope may improve V/Q scintigraphy and has a lower radiation dose. A few accuracy studies are published. Miles et al reported a 95% agreement between SPECT V/Q scintigraphy and CTPA data for the diagnosis of PE and a sensitivity of 83% with specificity of 98% for SPECT V/Q. Another study showed a superior diagnostic performance of V/Q SPECT to planar V/Q scintigraphy with a sensitivity of 100% and specificity of 87% for SPECT V/Q. But formal outcome studies in acute PE are lacking.