Abstract
Background: Pulmonary emboli (PE) have a significant incident rate of 112.3 per 100,000 adults. When age-weighted, the population over 75 has an incident rate of 1 out of 100. 90% of deaths from acute cases occur within two hours of the onset of symptoms. In pregnancy-related deaths, 20% are attributed to PE, and pregnancy increases the risk of the development of PE by 400 – 600%. Significant risk factors for PE include COPD, obesity, recent trauma or surgery, a history of deep vein thrombosis (DVT), a history of hormonal therapy, smoking, and pregnancy. Purpose: This literature review discusses how PE is evaluated by clinicians and the criteria determining a high or low risk of PE. Once a clinician has determined a significant risk of PE exists, medical imaging is used to determine if PE is present or should be ruled out as a diagnosis. The primary imaging modalities are computed tomography (CT) and nuclear medicine (NM). In addition to CT and NM, diagnostic X-ray, magnetic resonance imaging (MRI), and ultrasound (US) are used to a lesser degree. Understanding the conditions by which each modality is best used and the contraindications for each will aid any clinician, nurse, or allied health professional in their care for these patients. Methods: An extensive literature review was conducted using academic databases, Google Scholar, and direct searches of applicable journals. In most cases, peer-reviewed articles were limited to less than five years of age to ensure the information was current and relevant. In a few cases, older resources were used as primary sources. These resources included FDA drug labels, which have not changed in several years. Results: In most instances, computed tomography pulmonary angiography (CTPA) was the modality of choice. It has a high sensitivity (96-100%) and specificity (89-90%). The equipment is available at all accredited medical facilities and is usually staffed 24/7. CTPA allows for a highly accurate diagnosis in a short period of time, which can be critical in successfully treating acute PE. CTPA does have contraindications, including allergic reaction to the contrast media required and poor intravenous access. CTPA performance is being improved by emerging technologies such as photon counting and artificial intelligence. When CTPA is not possible, V/Q in the NM department is often the second choice. While V/Q has fewer contraindications, it has a lower sensitivity (93-97%) and specificity (80-85%) than CTPA. It also often takes longer to obtain the images because the NM department may not be staffed around the clock, and the radiopharmaceuticals used may have to be delivered to the facility. SPECT/CT, a hybrid of a V/Q and CT scan, has the highest sensitivity (97%) and specificity (100%) of any imaging modality but has the same time constraints as V/Q and higher equipment costs. SPECT/CT is not prevalent in the United States at the current time. Magnetic resonance pulmonary angiography (MRPA) is a non-ionizing radiation alternative to CTPA, V/Q, or SPECT/CT. However, the long scan times and required patient respiration suspensions result in many non-diagnostic quality studies, limiting the usefulness of the modality. Transthoracic lung ultrasound (LUS) is another non-ionizing radiation modality. However, its relatively low sensitivity (80%) and specificity (87%) limits its diagnostic viability.
Recommended Citation
Fisher RC, Onstott KL. The Current Status of Multi-Modality Imaging of Pulmonary Emboli. The Internet Journal of Allied Health Sciences and Practice. 2025 Jun 30;23(3), Article 9.
