Use of different magnification factors to calculate radiological lung volumes.

In previous papers from this laboratory, Pierce et al described a method of measuring lung volumes from routine chest radiographs. The images on the film are magnified, and this was taken into account in their calculations. Their findings have recently been confirmed by Rodenstein et al. It is important to measure magnification accurately because errors in linear dimensions are cubed when volume is calculated. This paper describes two simple methods of improving the accuracy of the calculation of magnification.