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Technical Aspects of SPECT Imaging

Coronary Arterial Territory Segments: Standard 17-Segment Model

The 17-segment model was developed in conjunction with, and is endorsed by, many professional associations, including the American Heart Association, the American Society of Nuclear Cardiology, the North American Society of Cardiac Imaging, and the American Society of Echocardiography.1 It has replaced the older 20-segment model as the standard.

 

Figure 1. Bull’s-Eye Display Showing the 17 Segments of the Coronary Arterial Territories.


Adapted from the American Society of Nuclear Cardiology. J Nucl Cardiol.1999;6:G47-G84.

Figure 2. Standard Model Showing the 17 Segments of the Coronary Arterial Territories Corresponding to the Left Anterior Descending Artery (LAD), Right Coronary Artery (RCA), and Left Circumflex Coronary Artery (LCX).


Adapted from the American Society of Nuclear Cardiology. J Nucl Cardiol.1999;6:G47-G84.

 

 

Summed Stress Scores

The summed stress score (SSS ) is obtained by adding the individual scores derived from the 17 segments during stress. Each segment is scored on a 5-point scale: 0 = normal perfusion, 1 = mild reduction of tracer uptake (not definitely abnormal), 2 = moderate reduction of uptake (definitely abnormal), 3 = severe reduction of uptake, and 4 = absence of uptake.2

 

Summed Stress Score

Indication3

<4

Normal

4-8

Mildly abnormal

9-13

Moderately abnormal

>13

Severely abnormal
  • The summed rest score (SRS) is the sum of the individual scores during rest
  • Summed difference score (SDS) = SSS – SRS

Bull’s-Eye Display

In a bull’s-eye display, perfusion image data are projected onto a single plane.

Figure 3. Regions and Coronary Artery Territories as Displayed in the Bull’s-Eye Format.


Image courtesy of Diwakar Jain, MD.

 

The color scale below indicates the severity of perfusion abnormality—the darker the color, the more severe the abnormality.

 

Figure 4. Bull’s-Eye Scans Obtained With Pharmacologic Stress SPECT MPI Showing Normal Perfusion (A), Mild Ischemia (B), Severe Ischemia (C), and Scarring (D).

A. Normal Bull’s-Eye Scan

Stress and rest images showing no perfusion abnormalities.

B. Mildly Ischemic Bull’s-Eye Scan

Stress and rest images showing a small area of ischemia involving the anterolateral segment. SSS = 4.

C. Severely Ischemic Bull’s-Eye Scan

Stress and rest images showing a large, reversible perfusion abnormality involving the anterior wall, lateral wall, and apex. SSS = 14.

D. Scarring

Stress and rest images demonstrating a large, dense scar involving the inferior wall, lateral wall, and apex.

Images courtesy of Diwakar Jain, MD.

 

References

  1. Cerqueira MD, Weissman NJ, Dilsizian V, et al. Standardized myocardial segmentation and nomenclature for tomographic imaging of the heart: a statement for healthcare professionals from the Cardiac Imaging Committee of the Council on Clinical Cardiology of the American Heart Association. Circulation. 2002;105:539-542.

  2. American Society of Nuclear Cardiology. Imaging guidelines for nuclear cardiology procedures: part 2. J Nucl Cardiol.1999;6:G47-G84.

  3. Hachamovitch R, Berman DS, Shaw LJ, et al. Incremental prognostic value of myocardial perfusion single photon emission computed tomography for the prediction of cardiac death: differential stratification for risk of cardiac death and myocardial infarction. Circulation. 1998;97:535-543.