Radiation Effects in the Lung

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The National Institute of Environmental Health Sciences (NIEHS) and Brogan & Partners are collaborating with JSTOR to digitize, preserve and extend access to Environmental Health Perspectives. This article outlines the principles of radiobiology that can explain the time of onset, duration, and severity of the complex reactions of the lung to ionizing radiation. These reactions have been assayed biochemically, cell kinetically, physiologically, and pathologically. Clinical and experimental data are used to describe the acute and late reactions of the lung to both external and internal radiation including pneumonitis, fibrosis and carcinogenesis.Acute radiation pneumonitis, which can be fatal, develops in both humans and animals within 6 months of exposure to doses ^ 8 Gy of low LET radiation. It is divisible into a latent period lasting up to 4 weeks; an exudative phase (3-8 weeks) and with an acute pneumonitic phase between 2 and 6 months. The latter is an inflammatory reaction with intra-alveolar and septal edema accompanied by epithelial and endothelial desquamation. The critical role of type II pneumonocytes is discussed.One favored hypothesis suggests that the primary response of the lung is an increase in microvascular permeability. The plasma proteins overwhelm the lymphatic and other drainage mechanisms and this elicits the secondary response of type II cell hyperplasia. This, in its turn, produces an excess of surfactant that ultimately causes the fall in compliance, abnormal gas exchange values, and even respiratory failure.The inflammatory early reaction may progress to chronic fibrosis. There is much evidence to suggest that pneumonitis is an epithelial reaction and some evidence to suggest that this early damage may not be predictive of late fibrosis. However, despite detailed work on collagen metabolism, the pathogenesis of radiation fibrosis remains unknown.The data on radiation-induced pulmonary cancer, both in man and experimental animals from both external and internal irradiation following the inhalation of both soluble and insoluble alpha and beta emitting radionuclides are reviewed. Emphasis is placed on the data showing that alpha emitters are at least an order of magnitude more hazardous than beta/gamma radiation and on recent data showing that the more homogeneous the irradiation ofthe lung, the greater is the carcinogenic hazard which contradicts the so-called "hot particle" theory.

Three-dimensional computed tomography imaging in an animal model of emphysema

“…The data can be then reconstructed in another 2 min and further analysed for three-dimensional assessment using Amira1 imaging software in another 5 min. The present authors determined that the radiation dose of a 120-s scan is ,27 mGy, some 50 times less than values capable of significant lung damage [20]. The resolution of the scans is 115 mm 3 , which, although large compared with the finest micro-CT resolutions, shows significant and meaningful differences between animals with and without emphysema.…”

Mesenchymal Stem Cell Therapy Protects Lungs from Radiation-Induced Endothelial Cell Loss by Restoring Superoxide Dismutase 1 Expression

“…Herein, the high intrinsic sensitivity of normal tissues to ionizing radiation (IR) often precludes the application of curative radiation doses (32,76). In particular, thorax irradiation induces tissue inflammation (pneumonitis) and fibrosis within 12 weeks and 6-24 months after RT as dose-limiting side effects (12,22,37). The radiation-induced lung disease is a major obstacle to successful treatment of thorax-associated tumors (7,38).…”

Structural and functional alterations in the rat lung following whole thoracic irradiation with moderate doses: Injury and recovery

“…Two phases of functional injury to the lungs have been described in humans: an acute phase of radiation pneumonitis occurring 4-30 wks after exposure and a later phase of fibrosis appearing 6-12 months after irradiation (Coggle et al 1986). Inflammation is the predominant early histological and physiological finding.…”