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Automated calculation of the right ventricle to left ventricle ratio on CT for the risk stratification of patients with acute pulmonary embolism



To assess the feasibility and reliability of the use of artificial intelligence post-processing to calculate the RV:LV diameter ratio on computed tomography pulmonary angiography (CTPA) and to investigate its prognostic value in patients with acute PE.


Single-centre, retrospective study of 101 consecutive patients with CTPA-proven acute PE. RV and LV volumes were segmented on 1-mm contrast-enhanced axial slices and maximal ventricular diameters were derived for RV:LV ratio using automated post-processing software (IMBIO LLC, USA) and compared to manual analysis in two observers, via intraclass coefficient correlation analysis. Each CTPA report was analysed for mention of the RV:LV ratio and compared to the automated RV:LV ratio. Thirty-day all-cause mortality post-CTPA was recorded.


Automated RV:LV analysis was feasible in 87% (n = 88). RV:LV ratios ranged from 0.67 to 2.43, with 64% (n = 65) > 1.0. There was very strong agreement between manual and automated RV:LV ratios (ICC = 0.83, 0.77–0.88). The use of automated analysis led to a change in risk stratification in 45% of patients (n = 40). The AUC of the automated measurement for the prediction of all-cause 30-day mortality was 0.77 (95% CI: 0.62–0.99).


The RV:LV ratio on CTPA can be reliably measured automatically in the majority of real-world cases of acute PE, with perfect reproducibility. The routine use of this automated analysis in clinical practice would add important prognostic information in patients with acute PE.

Key Points

Automated calculation of the right ventricle to left ventricle ratio was feasible in the majority of patients and demonstrated perfect intraobserver variability.

Automated analysis would have added important prognostic information and altered risk stratification in the majority of patients.

The optimal cut-off value for the automated right ventricle to left ventricle ratio was 1.18, with a sensitivity of 100% and specificity of 54% for the prediction of 30-day mortality.

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Computed tomography pulmonary angiography


Hounsfield unit


Intraclass coefficient correlation


Interquartile range


Left ventricle


Pulmonary embolism


Right ventricle


Right ventricle to left ventricle


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Correspondence to Jonathan C. L. Rodrigues.

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The scientific guarantor of this publication is Jonathan CL Rodrigues.

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The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.

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Institutional Review Board approval was not required because approval was obtained from our Institutional Audit Committee.


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• Observational

• Performed at one institution

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Supplementary file

Bland-Altman plots showing agreement analysis for intra-observer measurements for rater 1, rater 2 and automated software and for inter-observer measurements between rater 1 / rater 2, automated software / rater 1 and automated software / rater 2. (PDF 344 kb)

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Foley, R.W., Glenn-Cox, S., Rossdale, J. et al. Automated calculation of the right ventricle to left ventricle ratio on CT for the risk stratification of patients with acute pulmonary embolism. Eur Radiol 31, 6013–6020 (2021).

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  • Artificial intelligence
  • Pulmonary embolism
  • Computed tomography pulmonary angiography
  • Prognosis
  • Right ventricle to left ventricle ratio