Myocardial ischemia 1

Benefits or pitfalls of dual-energy CT

Key images

Findings

Patient presented with intermittent chest pain and congestion for one month. ECG showed a QS segment or Q-wave in leads V1-V2. Echocardiography showed a decline of left ventricular diastolic function.

Low monoenergetic, iodine density, and effective atomic number (Z effective) spectral image reconstructions improve visualization of the myocardial perfusion defect compared to conventional CT.

Axial images

The conventional images showed low attenuation of second diagonal branch, but there was no obvious myocardial density abnormality in conventional short axis images. Z effective map, iodine density map, and fusion images clearly showed the ischemic myocardial area. No iodine uptake was found given the iodine density in the region of interest (0 mg/ml). Effective atomic number (7.2) was significantly lower than that of the surrounding normal myocardium (8.7).

Discussion

Conventional CCTA enables detection of coronary artery stenosis and coronary artery plaque, but cannot evaluate myocardial ischemia. Spectral CT analysis can assist in the diagnosis of myocardial ischemia downstream to coronary stenoses and is more sensitive compared to using HU values for this purpose.

Conventional CT VR image: shows mixed plaque, calcifications, and tapering of the distal part of the left coronary artery system and interruption of the second diagonal branch (D2) (arrow).

Conventional MIP image: shows absence of contrast medium in the distal D2 branch (arrow).

Corresponding invasive digital subtraction angiography: confirms distal D2 occlusion (arrow).

Conventional CT image in midventricular short axis orientation: Shows homogeneous left ventricular wall thickness without obvious attenuation differences.

Fusion of conventional CT with spectral Z effective image: Shows abnormally low Z effective values in the left ventricular anteroseptal myocardium (color coded in purple, arrow).

Spectral Iodine no Water image: Shows lack of iodine uptake in the left ventricular anteroseptal myocardium (0.0 mg/ml, arrow) compared to remote normal appearing myocardium (2.2-2.3 mg/ml).

Spectral Z effective image: Shows abnormally lower effective atomic number (7.2, arrow) in left ventricular anteroseptal myocardium compared to normal appearing myocardium (8.7).

History

Benefits or pitfalls of dual-energy CT

Key images