2108. Opportunistic Detection of Coronary Calcium on Dual Energy, Dual Exposure Lateral Chest Radiograph (DE Lateral CXR)
Authors * Denotes Presenting Author
  1. Gilbert Boswell *; Naval Medical Center San Diego
  2. Brandon Dugar; Naval Medical Center San Diego
  3. Sarah Ludington; Stanford University
Heart disease remains the leading cause of death in the United States, resulting in approximately 24% of all deaths. It is estimated that 180,000 to 250,000 Americans succumb to sudden cardiac death. Approximately 80% of cardiac death can be attributed to coronary atherosclerosis. Chest radiography is one of the most commonly performed medical procedures in the US. In the last two decades, dual energy chest radiography has increased in utilization, made possible by developments in digital radiography, and computer processing creating subtraction images with water "Lung" images, and Calcium "Bone" images. This technique has largely been utilized in the frontal projection to evaluate for calcification in pulmonary nodules, and better visualize the lungs following bone subtraction. On the frontal projection the sternum, and spine obscure the coronary arteries. Also, rib end calcification confuse identification of the coronary arteries. In this study, we apply a Dual Energy and Dual Exposure technique in the lateral projection specifically to demonstrate coronary artery calcified atherosclerotic plaque. We have created an atlas of dual energy lateral CXR images with CT correlation, many with Agatston calcium scores. In this presentation we teach the "Where to look" to find the coronary arteries. We teach how a useful motion subtraction artifact from the beating heart creates a specific appearance "black line with adjacent white line" demonstrates that the calcium is on the heart. We also show how fat in the atrio-ventricular grooves, and surrounding left main coronary artery, and the proximal left anterior descending coronary artery, can be identified in subtraction images. We also show how the motion of the aorta results in being able to better outline the aorta compared with standard views.

Materials and Methods:
We present an educational review of the physics behind dual energy chest radiography. We demonstrate examples from retrospectively gated CT in the lateral projection to simulate the lateral chest radiograph, to show how motion can be helpful in identifying coronary artery, and fat plane location. We present an atlas of cases we have collected, with CT scan correlation. The greatest use is detection of coronary calcium greater than expected for patient gender and age. We illustrate examples where we have detected coronary calcium in patients in their 30's 40's and 50's. We do not claim that this is a screening test, or a substitute for a CT calcium score.

This is being presented as a new twist on an imaging procedure that is already accepted. We are not claiming that this is a screening test, or a substitute for a CT calcium score. This is an opportunity to incidentally detect coronary calcium, on CXR's ordered for other indications. If we then qualitatively estimate the amount of calcium in context of patient age and gender, we can then lead this patient down a path of diagnosis and preventive health management.

This presents a means to identify a coronary risk factor in asymptomatic patients as an important incidental finding on CXR.