Historical Evolution of Imaging Techniques for the Evaluation of Pulmonary Embolism:RSNA Centennial Article

Abstract

As we celebrate the 100th anniversary of the founding of the Radiological Society of North America (RSNA), it seems fitting to look back at the major accomplishments of the radiology community in the diagnosis of pulmonary embolism. Few diseases have so consistently captured the attention of the medical community. Since the first description of pulmonary embolism by Virchow in the 1850s, clinicians have struggled to reach a timely diagnosis of this common condition because of its nonspecific and often confusing clinical picture. As imaging tests started to gain importance in the 1900s, the approach to diagnosing pulmonary embolism also began to change. Rapid improvements in angiography, ventilation-perfusion imaging, and cross-sectional imaging modalities such as computed tomography (CT) and magnetic resonance imaging have constantly forced health care professionals to rethink how they diagnose pulmonary embolism. Needless to say, the way pulmonary embolism is diagnosed today is distinctly different from how it was diagnosed in Virchow's era; and imaging, particularly CT, now forms the cornerstone of diagnostic evaluation. Currently, radiology offers a variety of tests that are fast and accurate and can provide anatomic and functional information, thus allowing early diagnosis and triage of cases. This review provides a historical journey into the evolution of these imaging tests and highlights some of the major breakthroughs achieved by the radiology community and RSNA in this process. Also highlighted are areas of ongoing research and development in this field of imaging as radiologists seek to combat some of the newer challenges faced by modern medicine, such as rising health care costs and radiation dose hazards.

Do radiologists detect chronic thromboembolic disease on computed tomography?

“…In 1938 a first attempt was made to visualise the cardiovascular system by an intravenous injection of iodine, but it was not until the mid-1960s more extensive research was made, including both intravenous contrast administration and selective pulmonary arterial angiography (36). For a long period of time pulmonary angiography was considered the gold standard of APE imaging (6,37), although it recently has been replaced by CTPA (36,38). In CTEPH patients on the other hand, it remains the gold standard for confirming the diagnosis (39).…”

A review of imaging modalities in pulmonary hypertension

“…Signs of pulmonary embolism (PE), such as Westermark's sign (a wedge-shaped shadow indicating infarction) or Hampton's hump (a wedge-shaped opacification secondary to hemorrhage), may denote the need for further workup for CTEPH, since approximately 0.6%–3.8% of acute PE events lead to CTEPH. [20] In one study of 36 patients, characteristic CXR findings of focal areas of avascularity or enlarged right descending PA (diameter >20 mm) together with pleuritic changes, such as pleuritic scarring and pleuritic shadow due to prior pulmonary infarction, were found more commonly in CTEPH than in idiopathic pulmonary arterial hypertension (IPAH). [21]…”

Diagnosis of Deep Venous Thrombosis and Pulmonary Embolism

“…Combination of CT angiography with clinical probability criteria further increases predictive values as demonstrated by the PIOPED II study. 40-42 Thus, a negative CT in a non-high-risk patient is adequate to rule out PE. Additionally, once a diagnosis of PE has been established, the CT finding of increased RV:LV ratio may further aid in risk stratification and management.…”

“…67,68 Significant research has led to improvement of interpretation of V/Q scans and the data from PIOPED I study and the subsequent PIOPED II study have led to the modifications of PIOPED II guidelines for image interpretation. 40-42 …”