CT-based SPECT attenuation correction and assessment of infarct size: results from a cardiac phantom study

Ann Nucl Med. 2017 Dec;31(10):764-772. doi: 10.1007/s12149-017-1211-2. Epub 2017 Sep 21.


Rationale: Myocardial perfusion SPECT is a commonly performed, well established, clinically useful procedure for the management of patients with coronary artery disease. However, the attenuation of photons from myocardium impacts the quantification of infarct sizes. CT-Attenuation Correction (AC) potentially resolves this problem. This contention was investigated by analyzing various parameters for infarct size delineation in a cardiac phantom model.

Methods: A thorax phantom with a left ventricle (LV), fillable defects, lungs, spine and liver was used. The defects were combined to simulate 6 infarct sizes (5-20% LV). The LV walls were filled with 100120 kBq/ml 99mTc and the liver with 10-12 kBq/ml 99mTc. The defects were filled with water of 50% LV activity to simulate transmural and non-transmural infarction, respectively. Imaging of the phantom was repeated for each configuration in a SPECT/CT system. The defects were positioned in the anterior as well as in the inferior wall. Data were acquired in two modes: 32 views, 30 s/view, 180° and 64 views, 15 s/view, 360° orbit. Images were reconstructed iteratively with scatter correction and resolution recovery. Polar maps were generated and defect sizes were calculated with variable thresholds (40-60%, in 5% steps). The threshold yielding the best correlation and the lowest mean deviation from the true extents was considered optimal.

Results: AC data showed accurate estimation of transmural defect extents with an optimal threshold of 50% [non attenuation correction (NAC): 40%]. For the simulation of non-transmural defects, a threshold of 55% for AC was found to yield the best results (NAC: 45%). The variability in defect size due to the location (anterior versus inferior) of the defect was reduced by 50% when using AC data indicating the benefit from using AC. No difference in the optimal threshold was observed between the different orbits.

Conclusion: Cardiac SPECT/CT shows an improved capability for quantitative defect size assessment in phantom studies due to the positive effects of attenuation correction.

Keywords: Attenuation correction; Cardiac SPECT; Infarct size; SPECT/CT.

MeSH terms

  • Heart / diagnostic imaging*
  • Humans
  • Image Processing, Computer-Assisted / instrumentation*
  • Myocardial Infarction / diagnostic imaging*
  • Myocardial Infarction / pathology
  • Phantoms, Imaging*
  • Single Photon Emission Computed Tomography Computed Tomography*