Assessment of left ventricular function – Comparative analysis using an integrated SPECT/CT device

Abstract

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Objectives: Gated single photon emission computed tomography (GSPECT) is an established method for assessing myocardial perfusion, left ventricle (LV) contractility and volume parameters. CT coronary angiography (CTCA) is an emerging technique for non-invasive cardiac imaging. The experimental Infinia LS SPECT/CT research device combining an Infinia gamma camera and a Light Speed16 CT Scanner (GE Healthcare Technologies) enables concurrent assessment of anatomic and functional cardiac parameters. Present study aims to compare parameters of LV function on GSPECT and CTCA acquired sequentially within a single imaging session.

Methods: Eighty five patients (72 M, 13 F, age 39 - 83) with chest pain underwent cardiac SPECT/CTCA. LV contractility and volumes parameters, including the ejection fraction (LVEF), end-diastolic (EDV) and end-systolic (ESV) volume, were calculated for both cardiac imaging modalities. GSPECT analysis was performed using Cedars-Sinai’s QGS automatic algorithm that calculates LV volume changes by identifying the endocardial and epicardial LV contours throughout the cardiac cycle. CTCA analysis was performed using a semi-automatic algorithm based on short axis reformations of the LV supplied by multi-phase CT, successive identification of end-diastolic and end-systolic phases, mitral valve plane and LV endocardial contours. The parameters provided by each modality were statistically compared using linear regression test.

Results: GSPECT based LVEF, EDV and ESV were calculated in all 85 patients. Six patients were excluded from CTCA analysis (3 due to inhomogeneous distribution of the contrast material within the LV and 3 due to motion or metal artifacts). Thus, 79 patients were available for comparison. LVEF, EDV and ESV measured by GSPECT and CTCA showed a good correlation, of r=0.74, 0.74 and 0.83 respectively (p<0.001). Differences in over 10 measured units between the two imaging modalities were observed in 19 patients (24%).

Conclusions: LV volumes and EF values measured sequentially during a single imaging session using a SPECT/CT device showed a good correlation in the majority of patients (76%). Discrepancy in measurements between the two modalities may be related to CTCA data acquisition using breath hold at full inspiration, to inclusion of trabeculations and papillary muscles in CTCA data processing, or to differences in gating methods and spatial resolution between the two modalities.