Reproducibility of CT signs of right ventricular dysfunction in acute pulmonary embolism.
ABSTRACT The purpose of our study was to determine the interobserver reproducibility of CT findings of right ventricular (RV) dysfunction in pulmonary embolism (PE).
Two experienced observers independently and retrospectively evaluated pulmonary CT angiography (CTA) studies of 50 patients with acute PE for the following signs: bowing of the interventricular septum, inferior vena cava (IVC) contrast medium reflux, RV diameter (RVD)/left ventricular diameter (LVD) ratio on axial sections and four-chamber (4-CH) views, and RV volume (RVV)/left ventricular volume (LVV) ratio. Analysis used kappa statistics, Spearman's rank correlation, and Bland-Altman statistics.
The two observers had fair to moderate agreement (kappa = 0.32-0.44) for septal bowing and moderate to good agreement (kappa = 0.57-0.68) for diagnosing IVC reflux. The Spearman's rank correlation coefficients for RVD(axial)/LVD(axial) ratio and RVD(4-CH)/LVD(4-CH) ratio between the two observers were 0.88 (p < 0.001) and 0.85 (p < 0.001), respectively. On Bland-Altman analysis, the mean differences for RVD(axial)/LVD(axial) ratio and RVD(4-CH)/LVD(4-CH) ratio were 0.014 (+/- 0.195) and 0.001 (+/- 0.242), respectively. The correlation coefficient for RVV/LVV ratio was 0.93 (p < 0.001), and the mean difference was 0.033 (+/- 0.229).
Considerable differences exist in the interobserver reproducibility of CT findings of RV dysfunction on pulmonary CTA in patients with acute PE. Cardiac chamber measurements are more reproducible than septal bowing and IVC reflux. Volumetric determination of the RVV/LVV ratio is the least user dependent and most reproducible.
- SourceAvailable from: link.springer.comThe international journal of cardiovascular imaging 06/2011; 28(4):975-7. · 2.15 Impact Factor
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Conference Proceeding: A study on the PAPR using variable code sets (VCS) in multi-user MC-CDMA system[show abstract] [hide abstract]
ABSTRACT: Because an MC-CDMA system raises the high peak-to-average power ratio (PAPR), it has some disadvantages, such as nonlinear distortion at a high power amplifier (HPA), a significant power efficiency penalty and the degradation of the bit error rate (BER). Various methods for reducing PAPR have been proposed for the MC-CDMA system, such as partial transmit sequence (PTS), selected mapping (SLM), etc. However, these schemes require some side information bits which result in some losses of transmission efficiency. We do not use any side information bits. We decide a threshold to combine all of the code sets. The code set which exceeds the threshold is fed back. As a result, the transmitted symbols have a PAPR less than that required of the system. The basic idea of the proposed scheme is to generate a signal based on variable code sets (VCS), and to choose, before the transmission, the signal which has a smaller PAPR than the threshold.Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th; 10/2004