Biologic and anatomic problems of lung shielding in whole-body irradiation.

Lung shielding by lead blocks for reducing the dose to the lungs in whole-body irradiation results in relative protection of the leukemia cell population. The consequence is acceptable if the dose reduction is moderate (from 10 to 8 Gy) and if the shielded volume amounts to a small fraction (5%) of the body weight. The suggestion was made that certain limits should be put on the extent of shielding, so that the shielded lung fraction represents only 60% of the total lung volume.