CAD evaluation using IQ•SPECT, an ultrafast cardiac imaging solution
Author: Guillame Bouchard, MD
Case study data provided by Hôpital de la Cité-de-la-Santé de Laval, Quebec, Canada
A 65-year-old female with progressive history of chest pain on exertion and hypertension was referred for a stress/rest myocardial perfusion study to evaluate for inducible ischemia. A technetium-99 (99mTc) sestamibi (MIBI) ultrafast myocardial perfusion study was performed using IQ•SPECT at rest and with pharmacological stress. Total acquisition time for each study, stress and rest, was only 4 minutes.
Scanner: Symbia T
Parameters: 17 frames, 9 sec/frame, 4 min total
Scan Mode: IQ•SPECT
CT: 130 kV, 25 mAs, 5 mm slice
Diagnosis IQ•SPECT study (Figure 1) shows reversible ischemia in the inferolateral wall (white arrow) suggestive of ischemia in the left circumflex artery territory. The rest of the left ventricular (LV) myocardium showed normal perfusion. LV cavity size in the stress study is slightly larger than in the rest study, although the dilatation is not clinically significant. (TID: 1.07)
The patient subsequently underwent coronary angiography.
Coronary angiograms (Figure 2) for the same patient show single 95% stenosis of the mid-left circumflex artery (black arrow), which correlates well with IQ•SPECT findings. The patient underwent stenting of the lesion. Coronary flow was completely restored after the successful placement of two stents (small white arrows).
A follow-up IQ•SPECT myocardial perfusion study was performed for atypical chest pain after revascularization, which shows normalization of the reversible defect of the inferolateral wall (Figure 3). Attenuation corrected pre- and post-stenting studies (6-month interval between MPI studies) shows significant improvement in the inferolateral defect with normal perfusion throughout the rest of the LV myocardium. Note the prominent apical thinning in the post-stent study, which is a common post-attenuation correction finding in IQ•SPECT studies.
Comments IQ•SPECT provides high-quality myocardial perfusion SPECT acquisition at high acquisition speed. In this case example, the IQ•SPECT 4-minute scan provided the same image quality as more conventional imaging methods, which require longer acquisition times. The inferolateral perfusion defect seen on stress images and clear evidence of reversibility seen in the rest images was conclusive enough for the prediction of a predominantly left circumflex artery territory ischemia. LV cavity size delineation was visually appropriate for appreciation of mild post-stress dilation, which did not appear to be clinically significant. The angiographic correlation of a single vessel disease involving the left circumflex artery correlated well with the IQ•SPECT evaluation. CT attenuation correction using an integrated diagnostic CT on the Symbia T system along with IQ•SPECT, provided improved sensitivity through attenuation correction combined with fast cardiac SPECT acquisition.