Relative lung perfusion distribution in normal lung scans: observations and clinical implications

While relative lung perfusion distributions are cited in clinical decision making for congenital and acquired pulmonary vascular diseases, normal values and ranges have not been published for a large population of normally perfused lungs. These values of normal relative perfusion will be useful for establishing what is abnormal and for clinical decisions related to various pulmonary vascular diseases.

Relative perfusion distributions were quantified for the top, middle, and bottom thirds of the right and left lungs with a semiautomatic algorithm in 206 normal scintigraphy lung studies (45 +/- 18 years, 149 female, 57 male) acquired between January 1, 2000 and March 30, 2004 in the Nuclear Medicine Division at Stanford Hospital and Clinics.

The perfusion data were found to be highly non-Gaussian in nature (necessitating the use of Wilcoxon statistical comparisons), and the right/left perfusion ratio was found to be 52.5/47.5 (+/-2.1%) rather than the often quoted 55/45 split. While this right/left split was consistent between the genders, males had proportionally less perfusion in the lower left lung as compared with females (P < .05).

The long-standing 55/45 right/left perfusion ratio assumption was found to be more than 1 standard deviation greater than the mean, and the population variance is very small. Relative pulmonary perfusion distribution varies significantly with lung region, gender, and age, and should be considered when making clinical decisions based on pulmonary perfusion.