Precise Prediction of Right Atrium Position within Expiratory Phase Thorax

Fifteen patients who underwent CT during both the inspiratory and expiratory phases were retrospectively reviewed. The anterior posterior (AP) diameter of the thorax, the largest vertical distance from the uppermost RA level to the back surface (RA height), and the ratio of RA height to AP diameter of the thorax (RA thorax ratio) were determined. We then attempted to predict the expiratory RA height using the following 2 methods. Formula 1: Predicted expiratory RA height = Average inspiratory RA thorax ratio × Expiratory AP diameter of thorax. Formula 2: Predicted expiratory RA height = Each inspiratory RA thorax ratio × Expiratory AP diameter of thorax. In a Bland-Altman plot with Formula 1, the bias was –0.34 mm and limit of agreement ranged from –19.44 to 18.75 mm, whereas those were –1.31 mm and –9.72 to 7.10 mm with Formula 2. Our findings indicate that inspiratory CT imaging and expiratory phase thorax diameter can be used to precisely predict expiratory phase RA height in individual patients.