Measuring lung volumes from chest films using equations derived from computed tomography

Area of Science:

• Radiology
• Pulmonary Medicine
• Medical Imaging

Background:

• Accurate lung volume measurement is crucial for diagnosing and managing respiratory diseases.
• Computed tomographic (CT) scans provide precise cross-sectional lung area but are resource-intensive.
• Estimating lung volume from conventional chest radiography remains a clinical challenge.

Purpose of the Study:

• To derive and validate equations for predicting regional and total lung volumes using measurements from standard posteroanterior (PA) and lateral chest films.
• To establish a non-invasive method for lung volume estimation that correlates well with CT-derived volumes.

Main Methods:

• Utilized CT scans from 26 cases to measure true cross-sectional lung areas at multiple levels.
• Derived regression equations correlating lung dimensions (width, anteroposterior diameter, relative scan level) with geometrically calculated lung volumes.
• Validated equations for predicting volumes of lung slices above and below the diaphragm, and total lung volume.

Main Results:

• Equations incorporating lung width, anteroposterior (AP) diameter, maximum AP lung diameter, and relative scan level demonstrated high accuracy.
• Predicted individual slice volumes with correlation coefficients (r) up to 0.99 (right lung, above diaphragm) and 0.92 (left lung, below diaphragm).
• Total lung volume was predicted with r values of 0.98 (right) and 0.97 (left), with small standard errors.

Conclusions:

• Developed a reliable method to estimate regional and total lung volumes from plain chest films.
• This technique offers a practical, non-invasive alternative to CT for lung volume assessment in clinical settings.
• The derived equations provide accurate lung volume estimations, comparable or superior to existing methods.