ARRS 2022 Abstracts

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E1486. Patterns, Pearls, and Pitfalls of Lung Perfusion SPECT/CT In Pulmonary Embolism Evaluation: Clinical Application and Added Value
Authors
  1. Nafisa Reya; Temple University Hospital
  2. Jee Moon; Temple University Hospital
  3. Joseph Wise; Lewis Katz School of Medicine at Temple University
  4. Bhishak Kamat; Temple University Hospital
  5. Simindokht Dadparvar ; Temple University Hospital
  6. Yi Li ; Temple University Hospital
Background
Since the emergence of the COVID-19 as global pandemic, many institutions have opted out of performing the ventilation portion of a lung ventilation/perfusion (V/Q) scan for the diagnosis of acute pulmonary embolism (PE) in patients with contraindications to iodinated contrast. Q scan interpretation criteria have been proposed for planar imaging, such as the PISAPED and revised PIOPED II, but there are a number of nonspecific findings that lead to indeterminate results. Recent data have shown that perfusion SPECT/CT demonstrates increased sensitivity and improved diagnostic accuracy compared to V/Q or Q only scans in diagnosis of PE. Lung perfusion SPECT/CT imaging helps to overcome the limitations of planar imaging in lung V/Q perfusion scans, especially being useful in cases of intermediate or low probability results by providing a more accurate perfusion distribution matched to lung anatomy. Multiple studies recently proposed diagnostic algorithms for evaluation of PE without ventilation studies and addition of SPECT/CT due to concern for exposure of COVID-19 to patients and staff members through aerosolization. Many of the patient cases in our institution support the concomitant use of SPECT/CT and Q scan, especially in the setting of COVID-19, instead of using planar imaging only. Currently, there are no standard interpretation guidelines for reporting Q-SPECT CT findings. In our institution, we adopted the previously published Memorial Sloan Kettering Cancer Center (MSKCC) Q-SPECT/CT criteria for diagnostic interpretation of Q-SPECT/CT.

Educational Goals / Teaching Points
This educational exhibit will discuss imaging characteristics of perfusion defects on Q scan and SPECT/CT. We will provide a brief overview of the role of perfusion scintigraphy with the PISAPED and revised PIOPED II criteria. We will also review utilization of SPECT/CT using MSKCC Q-SPECT/CT diagnosis criteria for evaluation of PE. We will discuss normal anatomy of the lung and identify common imaging characteristics of perfusion defects and their respective SPECT/CT correspondence. We will highlight recent cases from our practice with concomitant use of lung perfusion SPECT/CT instead of planar imaging only.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
PE is a crucial diagnosis to guide appropriate therapy, with lung perfusion SPECT/CT being a valuable tool that provides higher accuracy in diagnosis of PE compared to using planar imaging only. There are many methods of evaluating for PE in perfusion-only scans, including PISAPED and revised PIOPED II for planar imaging and MSKCC Q-SPECT/CT for lung perfusion. Given SPECT/CTs grouped with a low-dose CT scan of the chest, we will demonstrate the combination of the chest x-ray, planar perfusion images, and SPECT/CT to evaluate the best underlying cause for a perfusion defect seen on planar images. Knowing the patterns and pitfalls of lung perfusion SPECT/CT are useful for interpretation of PE imaging in daily practice.

Conclusion
Lung perfusion with SPECT/CT is a simple but informative technique that aims to improve diagnostic interpretation accuracy of pulmonary embolism.