Hirshberg et al calculated the volume of a lung abscess based on measurements taken from AP and lateral chest X-rays. The authors are from Hadassah University Hospital, Hebrew University, and Rabin Medical Center in Israel.
Patient selection: lung abscess
Assumption: ellipsoid
Parameters:
(1) vertical diameter in AP chest-Xray
(2) horizontal diameter in the AP chest X-ray (lateral)
(3) horizontal diameter in lateral chest X-ray (anterior to posterior)
volume in mL =
= 4/3 * PI() * ((vertical diameter) / 2) * ((horizontal diameter) / 2) * ((AP diameter) / 2)
where:
• The volume uses semi-axis measurements, which are half of the diameter.
• The equation in the article uses only one semiaxis rather than 3 (so overestimates volume by 4-fold.
Since abscesses often have a necrotic center surrounded by an inflamed wall, 2 volumes may need to be calculated:
(1) volume of the necrotic core
(2) volume of the exterior of the abscess
In a CT scan the volume can be calculated by summing the cross-sectional areas.
