Amy Davis MBBS, MRCP, Presenter: Nothing to Disclose

Arjun Nair MBCHB, FRCR, Abstract Co-Author: Nothing to Disclose

Anisha Patel MBCHB, Abstract Co-Author: Nothing to Disclose

Ioannis Vlahos MBBS, Abstract Co-Author: Researcher, Siemens AG Consultant, Siemens AG Consultant, General Electric Company Consultant, Medicsight, Inc

Anand Devaraj MBBS, Abstract Co-Author: Nothing to Disclose

To evaluate the reliability of cardiac ventricular measurements on non ECG-gated conventional thoracic CT.

This retrospective study had institutional review board approval and patient consent was not required.  24 patients (14 males, median age (and range)  55 years (29-79)) who had undergone both ECG-gated cardiac CT and non ECG-gated thoracic CT (64 detector x 0.6mm) were identified by review of the Radiology Information System. Using a four chamber reformatted view, two radiologists measured maximum left and right ventricular diameters (LVDiam and RVDiam) on ECG-gated cardiac CTs at end-diastole.  After 4 weeks, the radiologists measured LVDiam and RVDiam on axial non ECG-gated thoracic CTs of the same patients.  Spearmans correlation and Bland Altman Plots were used to compare cardiac chamber measurements obtained on gated and non gated CT. Interobserver agreement for cardiac chamber measurements on ECG-gated and non ECG-gated CT were evaluated with the intraclass correlation co-efficient (Rco).  

Non ECG-gated LVDiam correlated strongly with ECG-gated LVDiam (r=0.66, p=0.002) and there was no significant difference between the measurements (-0.8mm +/-12.1mm, p=0.53). However, there was a significant underestimation of RVDiam on non gated CT compared to gated CT (-3.5mm +/- 13.2mm, p=(0.01), and a weaker correlation between the measurements (r=0.45, p=0.03). Concordance between observers for ECG-gated RVdiam and non ECG-gated RVdiam was satisfactory (Rco=0.73, (0.48,0.87) and Rco=.0.56 (0.23, 0.77) respectively); but was inferior to that for ECG-gated LVDiam and non ECG-gated LVDiam (Rco=0.89 (0.80, 0.94) and Rco= 0.76 (0.3, 0.88) respectively).  

Left ventricular diameter on axial non ECG-gated thoracic CT correlates well with measurements obtained on reformatted ECG-gated cardiac CT, and can be used to provide information on cardiac size and hence function. However, measurements for right ventricular diameter obtained on non ECG-gated thoracic CT are less reliable and are prone to greater interobserver variation.

Left ventricular diameter on conventional axial thoracic CT can be reliably used to estimate left ventricular size, but caution should be used when interpreting right ventricular dimensions.

Davis, A, Nair, A, Patel, A, Vlahos, I, Devaraj, A, Cardiac Ventricular Measurements on Non-ECG-gated Thoracic CT: Are They Reliable?.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034460.html