Technique Of Coronary CT Angiography [For Atherosclerosis Risk Assessment] With Links To Additional Resources

In addition to the article reviewed in this post, please carefully review:

What is the most current version of CAD-RADS (Google Search):

AI Overview

The most current version of the Coronary Artery Disease-Reporting and Data System is 

CAD-RADS 2.0, published in 2022. This expert consensus document was a collaborative effort by major cardiology and radiology societies to standardize the reporting of coronary CT angiography (CCTA) findings and guide patient management.

CAD-RADS™ 2.0 – 2022 Coronary Artery Disease-Reporting and Data System-An Expert Consensus Document of the Society of Cardiovascular Computed Tomography (SCCT), the American College of Cardiology (ACC), the American College of Radiology (ACR), and the North America Society of Cardiovascular Imaging (NASCI) [Full-Text HTML] [Full-Text PDF]. Journal Of Cardiovascular Computed  Tomography (JCCT), Volume 16, Issue 6p536-557November-December, 2022

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The following are two articles on the technique of coronary CT angiography.

In today’s post, I review, and excerpt from reference 2: Society of Cardiovascular Computed Tomography/North American Society of Cardiovascular Imaging—expert consensus document on coronary CT imaging of atherosclerotic plaque. J Cardiovasc Comput Tomogr. 2021;15:93–109. Link is to the PDF.

All that follows is from the above resource.

Abstract

Coronary computed tomographic angiography (CCTA) provides a wealth of clinically meaningful information beyond anatomic stenosis alone, including the presence or absence of nonobstructive atherosclerosis and high-risk plaque features as precursors for incident coronary events. There is, however, no
uniform agreement on how to identify and quantify these features or their use in evidence-based clinical
decision-making. This statement from the Society of Cardiovascular Computed Tomography and North
American Society of Cardiovascular Imaging addresses this gap and provides a comprehensive review of
the available evidence on imaging of coronary atherosclerosis. In this statement, we provide standardized definitions for high-risk plaque (HRP) features and distill the evidence on the effectiveness of risk stratification into usable practice points. This statement outlines how this information should be communicated to referring physicians and patients by identifying critical elements to include in a structured CCTA report – the presence and severity of atherosclerotic plaque (descriptive statements, CAD-RADS™ categories), the segment involvement score, HRP features (e.g., low attenuation plaque, positive remodeling), and the coronary artery calcium score (when performed). Rigorous documentation of atherosclerosis on CCTA provides a vital opportunity to make recommendations for preventive care and to initiate and guide an effective care strategy for at-risk patients.
© 2020 Published by Elsevier Inc. on behalf of Society of Cardiovascular Computed Tomography.

The traditional approach to imaging of coronary anatomy with
coronary computed tomographic angiography (CCTA) has been
oriented toward the detection of obstructive coronary artery disease (CAD). Over the past decade, evidence has accumulated concerning the prognostic significance of nonobstructive and
obstructive atherosclerotic plaque including specific features that are associated with an elevated risk of major adverse CAD events (MACE). This evidence now supports that imaging of atherosclerotic plaque is important for estimating patient risk and guiding preventive care. This link between initiation and intensification of prevention with atherosclerotic imaging using CCTA is vital to improving patient outcome. In this statement from the Society of Cardiovascular CT (SCCT) and North American Society of Cardiovascular Imaging (NASCI), we provide a synthesis of evidence concerning CCTA imaging of atherosclerosis and propose data elements that radiologists and cardiologists can integrate into their CCTA interpretation. One vital part of this statement is to acknowledge the advantages and limitations of current methods used to assess atherosclerotic plaque and to identify future research in this area. In this SCCT/NASCI statement, we enlist thought leaders in the field of CCTA including experts from the field of radiology and cardiology who bring unparalleled experience to this subject of atherosclerotic imaging. This field is rapidly evolving and
further advancements, including fully automated quantification of atherosclerotic plaque will necessitate future updates to this
statement.

This statement focuses on the following principal issues that will influence how we think about imaging coronary atherosclerotic plaque:

1. CT Imaging of Atherosclerotic Plaque: Risk prediction in stable and unstable chest pain syndromes
2. Evidence Gaps in Coronary Atherosclerotic Plaque Imaging and Future Research Needs
3. CT Plaque Imaging to Direct Risk-Reducing Preventive or Disease-Modifying Therapies: Observational evidence on CCTA guided preventive strategies
4. Minimum Data Elements for Structured Reporting For Coronary Atherosclerotic Plaque
5. Consensus Summary and Recommendations

1. Coronary atherosclerosis is the primary disease process
Imaging has traditionally focused on detecting flow limiting
stenosis or its surrogates. Detection of the presence and severity of
obstructive CAD by CCTA guide clinical decision making for secondary prevention including consideration of coronary revascularization. However, atherosclerosis is the primary disease process that mediates risk and stenosis is just one of its many subsets. Importantly, for risk assessment, patients with more extensive, multivessel CAD are at highest risk while those without any plaqueor stenosis comprise those at lowest risk (Central Illustration).

This document focuses on the presence and extent of atherosclerotic plaque that elevates risk above that of patients
without any documented plaque. This ranking of disease presence and severity remains vital to providing a comprehensive assessment of patient risk.

The evolving paradigm for CCTA imaging represented in this
document expands this viewpoint beyond detecting obstructive
lesions to imaging coronary vessel pathology itself: characterizing and providing measurement of the burden of atherosclerosis, identifying how its composition influences risk and outcomes, and potentially modifying risk with initiation or intensification of therapy. We propose that imaging of atherosclerotic plaque in order to target effective preventive care strategies reinforces the concept that early detection and intervention has the greatest potential for improved event-free life years for at-risk patients. However, current randomized trials are lacking and do not proscribe a detailed evaluation and treatment pathway. In this statement, we synthesize the observational evidence and patterns as they unfold about
the impact of treatment on atherosclerotic plaque.

2. Targeting the appropriate patient population
This guideline will focus discussion on the use of imaging of
atherosclerosis with CCTA for symptomatic patients. Although evidence does exist with regards to the role of imaging in asymptomatic individuals, there are separate guidance documents from SCCT on the clinical indications for coronary artery calcium (CAC) scoring in asymptomatic patients1 and the CAC data and reporting system statement (CAC-DRS™).2

3. Methodologic considerations in atherosclerotic plaque imaging
This document will highlight evidence on both qualitative as
well as quantitative atherosclerotic plaque assessment. However, at present, in the absence of validated tools for quantitative assessment, we recommend integration only of semi-quantitative measures of atherosclerotic plaque into clinical reporting and propose data elements that radiologists and cardiologists can integrate into their CCTA interpretations today. While they remain incompletely defined at present, the field is evolving rapidly. The current quality standards for evidence are detailed in Table 1.

Provided limitations in spatial resolution and image quality,
plaque analysis should be restricted to epicardial vessels 2.0 mm in size and greater. Moreover, prior SCCT guidelines make recommendations for initial setting the window width and window levels (initial window width: 800 Hounsfield Unites [HU] and level: 300 HU) for accurate gray-scale differentiation between vessel wall and calcified and noncalified plaque.3,4 More recently, reports have applied varied approaches including: a) initial settings starting at a window width of 700 HU and window level of 200 HU; with subsequent changes determined by the imager,5 b) employing a fixed HU setting of 740/220, including a fixed 0.3 mm gap between vessel wall and lumen,6 and c) vessel wall thresholds adjusted to the lumen using a 155%/65% window width/level of the luminal intensity.5,7 Plaque analysis has been validated across recommended target heart rate (60e80 beats per minute) and standard tube voltage (100e120 kV).8 Whether or not to employ low kVp imaging is guided by the specific clinical question being evaluated as well as whether radiation saving techniques are desirable (e.g., young age). Lower tube voltage would impact HU ranges for plaque measurements.

4. Importance of nonobstructive CAD and CAD event risk
An emerging message from the published literature, over the
past decade, is that patients with nonobstructive CAD (i.e., 1-49% stenosis) have worse prognosis when compared to those without any stenosis or plaque (i.e., normal CCTA). Fig. 1 provides a synthesis of available evidence, noting that nearly 1 in 3 patients referred for CCTA for suspected CAD will have nonobstructive CAD.3,9e23 One-third of patients referred to CCTA have nonobstructive CAD while ~10-15% of patients have obstructive CAD.24 The annualized event rate for patients with nonobstructive CAD is ~1.6% as compared to 0.2% for those with a normal CCTA. The adjusted hazard for MACE for nonobstructive CAD as compared to a normal CCTA ranged from 1.5 to 7.2; when controlling for CAD risk factors or a risk score.3,9-23

Thus, a first step for all CT imagers to comprehend that identification of nonobstructive plaque is an important aspect of identifying at-risk patients. One commonly reported measure is the semiquantitative assessment of the number of coronary segments with plaque, independent of the stenosis severity, using the segment involvement score (SIS).25 The SIS provides an assessment of the extent of atherosclerosis and has higher reproducibility than descriptive terms. An SIS score >5 has been associated with an elevated event risk (p < 0.0001).26

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What is the most current version of CAD-RADS (Google Search):

AI Overview

The most current version of the Coronary Artery Disease-Reporting and Data System is 

CAD-RADS 2.0, published in 2022. This expert consensus document was a collaborative effort by major cardiology and radiology societies to standardize the reporting of coronary CT angiography (CCTA) findings and guide patient management.

CAD-RADS™ 2.0 – 2022 Coronary Artery Disease-Reporting and Data System-An Expert Consensus Document of the Society of Cardiovascular Computed Tomography (SCCT), the American College of Cardiology (ACC), the American College of Radiology (ACR), and the North America Society of Cardiovascular Imaging (NASCI) [Full-Text HTML] [Full-Text PDF]. Journal Of Cardiovascular Computed  Tomography (JCCT), Volume 16, Issue 6p536-557November-December, 2022