History
A 78-year-old female diabetic patient, with clinical symptoms of a suspected stable angina, came to the hospital for a check-up. A coronary CT angiography (CCTA) was requested to evaluate the coronary arteries and to rule out coronary stenosis. A prospectively ECG-triggered sequential mode was performed with a dual source photon-counting detector (PCD) CT, NAEOTOM Alpha®.
Diagnosis
CCTA images in a standard reconstruction showed calcified plaques in the proximal left anterior descending artery (LAD) with signs of suspicious stair-step artifacts. This was clearly identified in the TrueStack reconstruction, showing misalignment of image stacks most likely due to an incomplete patient breath-hold. The misalignment was corrected in the image reconstruction using the ZeeFree algorithm, which resulted in clear visualization of mild stenoses. A non-calcified plaque in the mid LAD, as well as multiple calcified plaques in the proximal right coronary artery (RCA), mid LAD and proximal circumflex (Cx), causing mild stenoses (<50%), were also seen. CT findings were classified as CAD-RADS 2/P2.
Based on CCTA findings, an interventional coronary angioplasty was obviated. The patient was recommended for pharmacotherapy.
Fig. 1: MPR images show a comparison of calcified plaques seen in the proximal LAD. Misalignment is observed in standard reconstruction (Fig. 1a), identified in the TrueStack reconstruction (Fig. 1b) and resolved in the ZeeFree reconstruction (Fig. 1c). Mild stenoses are clearly visualized (arrows).
Fig. 2: Two corresponding curved MPR images, using standard (Fig. 2a) and ZeeFree (Fig. 2b) reconstruction, demonstrate a clear visualization of mild stenoses in the proximal LAD, caused by calcified plaques, after the ZeeFree correction (Fig. 2b, arrows). A non-calcified plaque in the mid LAD is also seen (dotted arrows).
Comments
CCTA is considered a first-line test (Class I) for use in acute and chronic coronary syndromes by various cardiological societies and guidelines. [1] One of the remaining challenges in CCTA imaging is the occurrence of stair-step artifacts in the transition areas of an acquisition over multiple cardiac cycles, hampering diagnostic interpretability of the images. This can occur in prospectively ECG-triggered sequential scanning, as well as in retrospectively ECG-gated spiral scanning. Potential causes considered are insufficient patient breathhold or movement or irregular heart rate during the acquisition. [2] Images using TrueStack reconstruction can make the presence of misalignment clear, however, may be difficult to interpret, if analyzed as curved planar reformation (CPR). ZeeFree is a novel reconstruction technique, using a non-rigid registration in the reconstruction process between the transition of adjacent cardiac cycle acquisition to correct and reduce misalignment. This is a detector width-independent algorithm and can be applied to both prospectively ECG-triggered sequential and retrospectively ECG-gated spiral acquisitions. [3] A recent study has demonstrated significant reduction of non-diagnostic coronary segments using the ZeeFree algorithm. [2]
As shown in this case, the misalignment caused by stair-step artifacts, observed in the standard reconstruction and identified in the TrueStack reconstruction, is resolved in the ZeeFree reconstruction, enabling the morphology to be seen as intended. This helps the physician to make a confident assessment and confirmation on coronary atherosclerosis without significant stenoses, obviating further examinations.
Examination Protocol
