Feasibility of coronary calcium and stent image subtraction using 320-detector row CT angiography

Abstract

Background: The reader confidence and diagnostic accuracy of coronary CT angiography (CCTA) can be compromised by the presence of calcified plaques and stents causing blooming artifacts. Compared to conventional invasive coronary angiography (ICA), this may cause an overestimation of stenosis severity leading to false-positive results. In a pilot study, we tested the feasibility of a new coronary calcium image subtraction algorithm in relation to reader confidence and diagnostic accuracy.

Methods: Forty-three patients underwent clinically indicated ICA and CCTA using a 320-detector row CT. Median Agatston score was 510. Two data sets were reconstructed: a conventional CCTA (CCTAconv) and a subtracted CCTA (CCTAsub), where calcifications detected on noncontrast images were subtracted from the CCTA. Reader confidence and concordance with ICA for identification of >50% stenosis were recorded. We defined target segments on CCTAconv as motion-free coronary segments with calcification or stent and low reader confidence. The effect of CCTAsub was assessed. No approval from the ethics committee was required according to Danish law.

Results: A total of 76 target segments were identified. The use of coronary calcium image subtraction improved the reader confidence in 66% of these segments. In target segments, specificity (86% vs 65%; P < .01) and positive predictive value (71% vs 51%, P = .03) were improved using CCTAsub compared to CCTAconv without loss in negative predictive value.

Conclusions: Our initial experience with coronary calcium image subtraction suggests that it is feasible and could lead to an improvement in reader confidence and diagnostic accuracy for identification of significant coronary artery disease.

Keywords: Angiography; CCTA; CT; Coronary; Subtraction.

Conflict of interest statement

Disclosures of Potential Conflicts of Interest: A.E.A. Activities related to this article: none to disclose. K.F.K. Activities related to this article: none to disclose. For the remaining authors no conflicts of interests to disclose.

Copyright © 2015 Society of Cardiovascular Computed Tomography. All rights reserved.

Figures

Figure 1

Step #1: Non-rigid registration between contrast and non-contrast image. Step #2: Registered non-contrast image is subtracted from registered contrast image, resulting in a subtracted image.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 2

In panel A a severely calcified right coronary artery can be seen. After performing subtraction (using the contrast and non-contrast image in panel A and B), a diagnostic image is obtained (Panel C), which closely resembles the invasive coronary angiogram (panel D). Panel E–H illustrate the corresponding subtraction process for a stented left anterior descending coronary artery. Similar to panel A-D, the non-diagnostic stent became interpretable after subtraction. Arrows indicate position of calcium and subtraction.

Figure 3

Shows example of misregistration artifact. Calcium in contrast (A) and non-contrast (B) images is not identical. Therefore misregistration artifacts ocur in the resulting subtraction image (C). Calcium and artifacts are indicated by arrows.

Figure 3

Shows example of misregistration artifact. Calcium in contrast (A) and non-contrast (B) images is not identical. Therefore misregistration artifacts ocur in the resulting subtraction image (C). Calcium and artifacts are indicated by arrows.

Figure 3

Shows example of misregistration artifact. Calcium in contrast (A) and non-contrast (B) images is not identical. Therefore misregistration artifacts ocur in the resulting subtraction image (C). Calcium and artifacts are indicated by arrows.