Cardiac thrombus

Benefits or pitfalls of dual-energy CT

Young female patient with retrosternal pain for four months; HR 89 BPM, arrhythmia; ECG showed arrhythmia and persistent atrial fibrillation. Echocardiography: 23x35mm irregular soft tissue abnormality located close to ascending aortic root.

One benefit of CCTA spectral imaging on the IQon Spectral CT is the ability to use the iodine measurement tool to differentiate thrombus from atrial slow flow; in this case, in the low attenuation area located in the left atrial appendage.

Key images

Findings

Axial and sagittal images

Conventional CT image with contrast showed low attenuation in the left atrial appendage (CT value 50.9 HU). However, differentiation between a soft tissue mass, thrombus, or atrial slow flow was not possible. Iodine density of the lesion was 0 mg/ml, indicating lack of iodine within the lesion.

The spectral attenuation curve of the lesion was flat, showing that the changes in the CT number of the lesion were not significant with an increasing energy. Based on that, the spectrum analysis finally suggested that the lesion in the left atrial appendage was a thrombus.

Discussion effective lesion was color coded in orange in Z effective map, corresponding to an abnormally low value.

CT value of left atrial appendage was 50.9 HU, which was close to soft tissue in conventional CCTA images; therefore, the lesion could not be clearly characterized. However, demonstration of lack of iodine (0 mg/ml) on iodine density images allowed the clinician to clearly rule out the possibility of atrial slow flow and soft tissue lesions.

Images 3b and 3c: The lesion visualization was improved at monoenergetic 40 keV (3b) compared to 90 keV (3c) images. Monoenergetic 40 keV image (3b) increased the CT value of the heart chambers allowing a larger contrast difference between left atrial appendage content and normal heart chambers, with only a minimal increase in noise.

Details of iodine density and Z effective numbers related to images 4 and

History