IDL Speeds Assessment of Myocardial Perfusion

Medical interns, practicing physicians and patients at the Emory School of Medicine in Atlanta, Georgia are benefitting from faster, more informed diagnoses using an IDL application that provides accurate, quantified measurement of cardiac perfusion and function. This non-invasive diagnostic technique lets doctors, whose patients have experienced signs of heart attack, rapidly assess the relative blood flow through the cardiac arteries.

Developed by a team of researchers at Emory (Ernest Garcia, Ph.D., David Cooke, M.S.E.E., Tracy Faber, Ph.D., and Russ Folks, B.S.), the Emory Cardiac Toolbox™ has streamlined a physician';s reading of cardiac PET (positron emission tomography) and SPECT (single photon emission computed tomography) studies, into a single, effective software system. "Prior to the application we developed, physicians had to employ several different analysis tools to evaluate cardiac perfusion and function. Now, through a point and click GUI, they can analyze the data and process the images more quickly than ever-all in one computer environment," says Cooke.

Speed and Accuracy Are Critical

"Accurate processing and the ability to move from screen to screen quickly is critical," Cooke says. The application helps physicians estimate a heart's efficiency. Some of the telltale parameters assessed are the heart's blood flow, ejection fraction, endocardial chamber volume and estimated wall-thickening.

Ejection fraction represents the percentage of blood pumped with each contraction and is directly related to the chamber volume; the lower the ejection fraction, the lower the amount of blood pumped. Since the heart is a muscle, it gets bigger as it works harder to pump blood, just as one's bicep increases in size with exercise. When a heart gets too large, or its walls get too thick, it is less able to pump properly and it is more difficult for blood to diffuse into the heart muscle.

With the Emory Cardiac Toolbox, physicians can ascertain the probable source of chest pain or other signs of abnormal heart activity. Easily getting to the correct answer fast is important; lives are at stake.

The raw results from the nuclear medicine tests are accessed by querying the patient's file in the database. "All the physician or technician has to do is enter the patient's name and select "Go." The data is processed automatically. After that, it's so easy to work through the GUI and review the results that the doctor can just use the program straight out," says Cooke.

3D Display Gives Best Insight

Using three dimensional displays of the patient's heart, physicians can determine whether blood is flowing to all aspects of the myocardium. "IDL's shading, 3D graphics and support for OpenGL are some features that are very effective for our imaging," Cooke says. Emory's application also provides three "generic" sets of coronary arteries which can be overlaid on the 3D images to help the physician infer which coronary arteries may be diseased. "Physicians are able to view the fused data as never before," Cooke says.

Program Linking Tools, Cross-Platform Development

"All this began about five years ago when Emory bought a PET scanner. We needed a good cardiac package and the scanner included IDL-based applications. To prepare for the future, we began using IDL," Cooke says.

A lot of programming had been completed prior to when Emory started developing with IDL. They needed to be able to use the previously developed code (CEqual®), written in C, in addition to the new IDL programs. IDL's ability to link to existing code proved to be a big, labor-saving benefit. "Not having to rewrite the C code was great," says Cooke. "Currently, we have about fifteen thousand lines of IDL code and fifteen thousand lines of C code. The C code is called and executed when necessary, as the physician reviews and reads the study."

Emory developed the application on Sun® and Power Macintosh® platforms. Because IDL is a "platform-neutral" language, they have been able to distribute the application without rewriting the code. Because the majority of people who use the application are non-programmers, it's important that they can get good performance in a very user-friendly computer environment. "Performance on the Macintosh has been quite good. One of our external sites, with an older Power Macintosh, tells us they are impressed with the speed," Cooke remarks.

Multiple views of a patient-derived three-dimensional models of Stress Tc-99m and Rest TI-201 myocardial perfusion for an abnormal patient. Brighter colors show better blood flow and darker colors show poorer blood flow. An extensive stress-induced defect can be seen in the anterior, lateral, septal and apical portions of the myocardium that partially returns to normal at rest.