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Bioengineering

Semi-Automatic Graphical Tool for Measuring Coronary Artery Spatially Weighted Calcium Score from Gated Cardiac Computed Tomography Images

Published: September 22nd, 2023

DOI:

10.3791/65458

1Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai

This video demonstrates the use of a novel graphical tool for measuring the spatially weighted calcium score (SWCS), an alternative to the Agatston score, for quantifying coronary artery calcification. The graphical tool computes SWCS based on image data from gated cardiac computed tomography and user-defined paths of the coronary arteries.

The current standard for measuring coronary artery calcification to determine the extent of atherosclerosis is by calculating the Agatston score from computed tomography (CT). However, the Agatston score disregards pixel values less than 130 Hounsfield Units (HU) and calcium regions less than 1 mm2. Due to this thresholding, the score is not sensitive to small, weakly attenuating regions of calcium deposition and may not detect nascent micro-calcification. A recently proposed metric called the spatially weighted calcium score (SWCS) also utilizes CT but does not include a threshold for HU and does not require elevated signals in contiguous pixels. Thus, the SWCS is sensitive to weakly attenuating, smaller calcium deposits and may improve the measurement of coronary heart disease risk. Currently, the SWCS is underutilized owing to the added computational complexity. To promote translation of the SWCS into clinical research and reliable, repeatable computation of the score, the aim of this study was to develop a semi-automatic graphical tool that calculates both the SWCS and the Agatston score. The program requires gated cardiac CT scans with a calcium hydroxyapatite phantom in the field of view. The phantom allows for deriving a weighting function, from which each pixel's weight is adjusted, allowing for the mitigation of signal variations and variability between scans. With all three anatomical views visible simultaneously, the user traces the course of the four main coronary arteries by placing points or regions of interest. Features such as scroll-to-zoom, double-click to delete, and brightness/contrast adjustment, along with written guidance at every step, make the program user-friendly and easy to use. Once tracing the arteries is complete, the program generates reports, which include the scores and snapshots of any visible calcium. The SWCS may reveal the presence of subclinical disease, which may be used for early intervention and lifestyle changes.

Measuring the amount of calcium within arteries using computed tomography (CT) is an established way to assess the severity of coronary atherosclerosis. Knowing and quantifying the extent of atherosclerosis is key to determining the risk of future coronary heart disease1,2,3,4. The most common way of measuring calcium in the coronary arteries is using the Agatston score5. However, part of the Agatston score calculation relies on the intensity of the chosen pixels, measured in Hounsfield Units (HU). Any pixels less tha....

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This study was conducted with approval of the Mount Sinai Institutional Review Board (HS-20-01011), and all subjects gave written informed consent.

1. Preparation before starting the protocol

  1. Appropriate folder structure is necessary for this program. Start by creating a main folder for the project anywhere on the computer by right-clicking and selecting the New Folder option in the files directory. All input DICOM files and results will be stored .......

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The representative results shown in this section display what successful use of the program entails. Here, a patient with an Agatston score greater than zero is used as an example. As discussed earlier, the results within a patient's metadata folder will have spreadsheets in the form of CSV files, images in the form of PNG files, and reports in the form of PDF files, as shown in Figure 5. The number of PNG files differs from case to case, since only snapshots of selected pixels with noti.......

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While the protocol for this program is relatively easy to follow, there are a few critical steps that are necessary for successful use and reliable results. Before starting, it is important to make sure the patient data that will be used in this program is anonymized to ensure patient confidentiality. The initial formatting and naming of the project's main folder must be correct for the program to recognize where to pull and place data. Incorrect naming and/or placement of folders, especially the Meta_Data folder, leads .......

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This work was supported by NIH grant R01ES029967.

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Name Company Catalog Number Comments
Calcium Hydroxyapatite Sigma-Aldrich 289396-100G Suspended in EpoxAcast 690 resin for phantom creation
Clinical Cardiac CT Scanner Siemens SOMATOM Force Dual Source CT Used for the source images; Any cardiac CT will be sufficient
EpoxAcast 690 Smooth-On 03641 Used for phantom creation
MATLAB Mathworks R2019a Requires Image Processing Toolbox and Statistics and Machine Learning Toolbox; Any version compatible with and able to run version R2019a scripts is sufficient
Standard Computer N/A N/A macOS or Windows operating system
syngo.via Siemens VB60A_HF04 Commercial software used for computing Agatston score for validation study

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