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Published on: December 16, 2022
Left ventricular mass from gated SPECT myocardial perfusion imaging: comparison with cardiac computed tomography
Tochi M Okwuosa1, Chetan V Hampole, Javid Ali
1Department of Medicine, Section of Cardiology, University of Chicago, Chicago, IL 60637, USA.
Insights
Gated SPECT myocardial perfusion imaging (MPI) software provides reproducible left ventricular mass (LVM) measurements, but these values are not directly substitutable for CT angiography (CTA) due to systematic over/underestimations.
Area of Science:
- Cardiology
- Medical Imaging
- Quantitative Analysis
Background:
- Increased left ventricular mass (LVM) is linked to adverse cardiac events.
- Quantitation of LVM using gated SPECT MPI software lacks extensive validation and clinical application.
- Current gated SPECT software requires comparison against a reference standard for accurate LVM assessment.
Purpose of the Study:
- To compare Left Ventricular Mass (LVM) measurements from two gated SPECT software packages (4D-MSPECT and QPS) against CT angiography (CTA) as a 3D reference standard.
- To evaluate the clinical utility and accuracy of SPECT-derived LVM in comparison to CTA.
- To determine the reproducibility and agreement between LVM quantitation methods.
Main Methods:
- 56 patients referred for MPI and cardiac CTA underwent LVM measurement by two blinded observers.
- Dual-isotope or low-dose/high-dose Tc-99m-tetrofosmin rest/stress MPI and cardiac CTA were utilized.
- Interobserver reproducibility and correlation analyses, including Bland-Altman analysis, were performed.
Main Results:
- Post-stress MPI values showed better correlation with CTA than rest values.
- Both 4DM and QPS demonstrated high reproducibility (r = 0.99).
- SPECT LVM values showed moderate correlation with CTA (r = 0.74 for 4DM, r = 0.72 for QPS), but Bland-Altman analysis revealed significant overestimation of lower LVM and underestimation of higher LVM values compared to CTA.
Conclusions:
- Gated SPECT and CTA provide reproducible LVM measurements.
- While mean SPECT LVM values are comparable to CTA, systematic biases necessitate caution.
- SPECT LVM values require mathematical correction for accurate substitution of CTA-derived values.
Background:
Increased left ventricular mass (LVM) has been correlated with adverse cardiac events, such as sudden cardiac death. However, LVM quantitation with widely utilized gated SPECT myocardial perfusion imaging (MPI) software, has little validation and clinical application. Thus, we compared LVM from two commonly employed gated SPECT packages [4D-MSPECT (4DM) and Quantitative Perfusion SPECT (QPS)] with the 3-dimensional reference standard, CT angiography (CTA).
Methods:
Comparisons were made in 56 patients (mean age 61.4 +/- 14.6; 32% female) referred for dual-isotope or low-dose/high-dose Tc-99m-tetrofosmin rest/stress MPI and cardiac CTA (mean 1.5 +/-4.5 months apart). LVM measurement was performed for both CTA and MPI by two independent observers blinded to clinical information.
Results:
Correlation with CTA was best for post-stress MPI than at rest; thus, post-stress values are reported. Values obtained with each of the techniques were very highly reproducible (interobserver correlation r = 0.99 for each technique). The mean LVM values were 142 g by CTA, 145 g by 4DM, and 135 g by QPS (P = NS for CTA vs SPECT, but P < .001 for 4DM vs QPS). There was moderately good correlation between CTA and SPECT LVM data (r = 0.74 and 0.72 for 4DM and QPS, respectively; both P < .001). However, on Bland-Altman analysis there was significant overestimation of lower values and underestimation of higher CT LVM values by both QPS and 4DM (both r = 0.68 and 0.69, P < .001). The limits of agreement relative to CT LVM were wide (-52.1 g to 64.1 g for QPS; and -60.0 g to 53.5 g for 4DM).
Conclusions:
SPECT and CTA give reproducible measures of LVM. Using CTA as the reference standard, the mean SPECT LVM values are similar, but lower values are overestimated and higher values are underestimated. Thus, the SPECT values are not substitutable for CTA without mathematical correction.
