Original Research Article
Interscan reproducibility of computer-aided epicardial and thoracic fat measurement from noncontrast cardiac CT

https://doi.org/10.1016/j.jcct.2011.03.009Get rights and content

Background

Epicardial fat volume (EFV) measured from noncontrast CT is associated with coronary atherosclerosis and increased risk of major adverse cardiovascular events. Interscan reproducibility of EFV quantification from noncontrast CT has not been reported.

Objective

We evaluated the interscan (intrascanner and interscanner) reproducibility of EFV and thoracic fat volume (TFV) measurements from noncontrast CT.

Methods

We studied 25 consecutive patients who were scanned twice with 4-slice multidetector CT (MDCT), with 120 kVp, 2.5-mm slice thickness (intrascanner) and 23 consecutive patients who were scanned with MDCT and electron beam CT (EBCT) with 3-mm slice thickness (interscanner). For each scan, EFV and TFV were measured from user-defined range of CT slices covering the heart by experienced imaging cardiologists. Voxels within −30 to −190 HU within the epicardial contours was quantified as EFV. TFV was quantified within the heart range automatically. Repeatability coefficient (RC), defined as 1.96 × SD of the differences between pairs of repeated measures, was determined.

Results

Correlations for interscan measurements of EFV and TFV were high for both intrascanner (MDCT-MDCT) and interscanner (EBCT-MDCT) data (correlation coefficient ≥0.98). RC values were lowest (4.3% for EFV and 5.4% for TFV) for intrascanner same-observer measurement. For intrascanner cross-observer measurement, RC values were 10.7% for EFV and 9.0% for TFV. For interscanner data, RC values ranged from 6.8% to 8.2%.

Conclusion

Epicardial and thoracic fat measurements with the use of either MDCT or EBCT are highly reproducible.

Introduction

Epicardial fat volume (EFV) and thoracic fat volume (TFV) can be routinely quantified from noncontrast computed tomography (CT) scans performed for coronary calcium scoring.1, 2 EFV measured from noncontrast CT is associated with a higher coronary calcium score, coronary artery disease severity, biochemical markers of systemic inflammation, and increased risk of future adverse cardiovascular events.1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 Direct measurement of EFV can be challenging because of reliance on detection of the thin pericardium. As more data support the clinical use of EFV, it is important to establish the reproducibility of quantifying epicardial adipose tissue.

Historically, coronary artery calcium scanning has been performed on electron beam CT (EBCT) scanners and currently is performed with multidetector CT (MDCT) scanners. While our previous results showed interobserver reproducibility of epicardial and thoracic fat from a single scan, interscan reproducibility (intrascanner [MDCT-MDCT] and interscanner [EBCT-MDCT]) of EFV quantification from noncontrast CT have not yet been determined.1, 14 Therefore, the aim of our current study was to determine the interscan reproducibility of epicardial and thoracic fat measurements from non-contrast CT.

Section snippets

Patient population

From a cohort of patients without known coronary artery disease enrolled in the EISNER (Early Identification of Subclinical Atherosclerosis using Non-invasivE Imaging Research) registry at Cedars-Sinai Medical Center, we retrospectively analyzed 48 consecutive patients who underwent 2 noncontrast CT scans for coronary calcium scan on the same day. Of these 48 patients, 25 had both scans obtained with the same 4-slice MDCT scanner (first scan with MDCT, second scan with MDCT; “Intrascanner”),

Results

Interobserver variability was similar for MDCT and EBCT. With MDCT, the interobserver variability was 8.8% ± 3.9% for EFV and 5.5% ± 4.3% for TFV. With EBCT, interobserver variability was 9.8% ± 4.2% for EFV and 2.3% ± 2.5% for TFV.

Table 2 summarizes the interscan reproducibility results. Correlations for interscan measurements of EFV and TFV were high for both intrascanner (MDCT-MDCT) and interscanner (EBCT-MDCT) data (all correlation coefficient values ≥0.98). RC values were lowest (4.3% for

Discussion

Our group previously showed high interobserver reproducibility of epicardial and thoracic fat from a single scan.1, 14 The present study shows a high degree of reproducibility of same and cross-observer measurements of epicardial and thoracic fat from noncontrast CT, including between EBCT and MDCT.

The volume of epicardial fat measured on noncontrast cardiac CT has been associated with coronary atherosclerosis and its pathophysiology, including associations to coronary artery disease severity,

Conclusion

We demonstrated a high degree of interscan reproducibility of epicardial and thoracic fat measurements for both when scans were performed only on MDCT and between EBCT and MDCT. The interscan reproducibility reported in our study will help in the establishment of a lower limit for significant changes in the CT measurement of epicardial fat, an emerging risk marker for coronary artery disease and future adverse cardiovascular events.

Acknowledgments

This study was supported by the National Institutes of Health (NIH) grant number R21EB006829-01A2 (principal investigator: Damini Dey) from the National Institute of Biomedical Imaging and Bioengineering (NIBIB), and also in part by a grant from the Glazer Foundation (IRB 6318). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIBIB or the NIH.

References (25)

  • G. Wheeler et al.

    Pericardial and visceral adipose tissues measured volumetrically with computed tomography are highly associated in type 2 diabetic families

    Invest Radiol

    (2005)
  • C. Fox et al.

    Abdominal visceral and subcutaneous adipose tissue compartments: Association with metabolic risk factors in the framingham heart study

    Circulation

    (2007)
  • Cited by (0)

    Conflict of interest: The authors report no conflicts of interest.

    View full text