V/Q Scan - Jubilant Draximage

What is a Ventilation/Perfusion Scan?

A Functional Lung Imaging Scan, also known as a Ventilation/Perfusion (V/Q) scan, is a nuclear medicine procedure that uses radioactive material to assess the flow of air and blood in the lungs. It is used by physicians to detect PE, which is a blood clot in the lungs.

V/Q: Reduced Radiation Exposure

Compared with CTPA, the breast radiation dose from V/Q is approximately 40 times less in women and 90 times less in pregnant women.2 That’s why the American Thoracic Society recommends V/Q over CTPA in pregnant patients with a normal chest X-ray.3 The radiation from CTPA is particularly a concern for young women because the breast tissue is particularly radiosensitive due to its higher metabolic activity,4 which is why the Society for Nuclear Medicine and Molecular Imaging recommends avoiding CTPA in young women with a low-pretest probability of PE or a negative D-dimer.5

CTPA delivers a vastly higher radiation dose to the female breast than that delivered by V/Q2

* Estimated CTPA radiation exposure to gravid breast ranges from 1000–2000 mrad, compared to 22–28 mrad from V/Q scan.2

The Society for Academic Emergency Medicine has advocated for evidence-based clinical decision rules to optimize CT utilization, stating that, “Research is needed to refine the indications for CT and to identify the scenarios in which alternatives to traditional CT are most appropriate … and when CT can be avoided without adversely affecting patient-centered care.” 6

ED algorithm with V/Q reduces radiation exposure by 20% 1,2*

* Validated at one of the busiest emergency departments in the U.S. † Unstable patients undergo CTPA. ‡ For PE alone.

An algorithm that incorporates V/Q scans to evaluate patients for PE in the emergency department has been shown to reduce overall patient radiation exposure by 20%.1 This approach uses chest radiography as an initial step to triage all suspected PE cases. Patients with a normal X-ray result underwent a V/Q scan, and patients with abnormal results received a CTPA. In the same study involving more than 2,000 patients at one hospital that employed this algorithm showed that the false-negative rates were 0.5% and 0.6% for V/Q and CTPA respectively, demonstrating that there was no statistical difference inoutcomes for both procedures.1,2 The use of other preliminary diagnostic criteria/ triage variables, such as validated prediction rules for risk stratification and screening with D-dimer assay, can be effectively utilized as well to diagnose PE while minimizing risk of unnecessary radiation burden.7