Effects of Radiation on Bone
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OSTEOPOROSIS AND CANCER (P TAXEL, SECTION EDITOR)
Effects of Radiation on Bone Rafael Pacheco & Harlan Stock
Published online: 22 September 2013 # Springer Science+Business Media New York 2013
Abstract Ionizing radiation produces its deleterious biologic effects by both direct (DNA strand breaks) and indirect processes (formation of free oxygen radicals). Mitotically active cells are more susceptible to the detrimental effects of ionizing radiation. These effects are most severe locally within the treatment field but can also occur systemically, possibly reflecting hormonal influences and inflammatory cytokine mediators. Specific bone complications of radiation include osteopenia, growth arrest, fracture and malignancy. Some of these complications, such as osteopenia, are reversible and severity is dose dependent. Insufficiency fractures are a common complication after radiation therapy and generally affect those bones under most physiologic stress and with the highest ratio of trabecular to cortical bone. Familiarity with the radiographic appearance of irradiated bone, including computed tomography (CT) and magnetic resonance imaging (MRI), will improve image interpretation and facilitate accurate diagnosis. Keywords Ionizing radiation . Particle radiation . Bone metabolism . Hematopoesis . Cortical bone . Trabecular bone . Imaging . Radiography . Fracture risk
Introduction Electromagnetic, ie, ionizing, radiation is employed in both diagnostic radiography and radiation oncology. Particle radiation (α and β particles) is equally valuable for imaging and the treatment of certain types of cancers but has poor R. Pacheco : H. Stock (*) Department of Diagnostic Imaging and Therapeutics, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-2802, USA e-mail: [email protected]
penetrance. Given the high density of bone tissue and its deep location within the human body, particle radiation is not as commonly associated with radiation osteitis and generalized bone disease compared with ionizing radiation [1]. Electromagnetic radiation can cause direct and indirect cell death via DNA strand breaks and free radical formation. Free radical formation occurs when a photon strikes an atom, resulting in the excitation and emission of an electron from that atom. Frequently occurring in water, free radial formation generates a reactive, partially reduced oxygen species [2••]. These free oxygen radicals can damage and mutate cellular DNA, helping to explain the increased rate of malignancy with radiation exposure [1]. Also, free radicals can destroy supporting cellular structures, such as organelles and cell membranes, eventually resulting in programmed cell death (i.e., apoptosis). Ionizing radiation can directly produce cell death via DNA strand breaks. As rapidly dividing cells demonstrate greater mitotic activity, they are more susceptible to radiation induced cell death, a rationale for targeted radiation therapy [3]. The progression of radiation induced marrow suppression has been well researche
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