The inherent mathematical error factors in the radiological determination of heart volume.

When heart volume is calculated from two X-ray projections, part of the error is due to the fact that the formulas employed are not mathematically exact. This error was calculated for a variety of shapes and positions of the heart. The results indicate that this error may reach about 30% for hearts of fairly ordinary shape. When the standard projections are used, horizontally positioned hearts are particularly liable to give rise to large errors of this kind.