Biological Effects of Alpha Particles in Lung Tissue

Abstract

Allowing for concomitant cellular inactivation, the tumour incidence function can be written as the product of two probabilities, for malignant transformation and for not being killed. While cell survival of mammalian cells in culture after heavy ion irradiation has been described successfully by the formalism of track structure theory for cellular inactivation, we seek to derive a transformation function by extracting cellular radiosensitivity parameters from experimental data on mutation to thioguanine resistance. For defined conditions of radon daughter inhalation, we are able to calculate the fraction of inhaled radionuclides deposited and retained on broncial airway surfaces. The LET distribution in sensitive bronchial stem cells hit by alpha particles depends on initial alpha particle energy, airway diameter, and stem cell depth. Applying the methodology of track structure theory and using cellular radiosensitivity parameters for cell killing and mutation, we express the radiation risk at a given stem cell depth by the probabilities for cellular survival, for mutation or transformation, and the joint probability for cancer induction.