Lecture_4.pptx

Radiobiology & Protection RMI 212 Lecture 4 Total body irradiation Slide 1 fchs.ac.ae  Objectives:  The main goal of this unit is to Explain briefly the effects of radiation to human and to the body as a whole and the factors affecting radiation res...

Radiobiology & Protection RMI 212 Lecture 4 Total body irradiation Slide 1 fchs.ac.ae  Objectives:  The main goal of this unit is to Explain briefly the effects of radiation to human and to the body as a whole and the factors affecting radiation response. Including: 1.early effect of radiation (radiation sickness). 2.late effect of radiation. 3. Irradiation of Fetus(developmental effect). (Discuss the effects of radiation on a fetus ) 4. heritable effect and cancer fchs.ac.ae  The three principles methods used to control radiation exposure are:  Time  Distance  Shielding fchs.ac.ae 4 fchs.ac.ae 5 fchs.ac.ae WHOLE BODY RADIATION SYNDROMES fchs.ac.ae  Acute radiation syndrome  Syndrome is the medical term that means a collection of symptoms.  ARS is a collection of symptoms associated with high-level radiation exposure. fchs.ac.ae  Acute radiation syndrome  ARS, or radiation sickness, occurs in humans after whole-body reception of large doses of ionizing radiation delivered over a short period of time.  Causes of acute radiation syndrome  Data from epidemiologic studies of human populations exposed to doses of ionizing radiation sufficient to cause this syndrome have been obtained from atomic bomb survivors of Hiroshima and Nagasaki who were subjected to high levels of effect during an atomic bomb test in 1954, nuclear radiation accident victims such as those injured in the 1986 Chernobyl disaster, and radiation therapy patients. fchs.ac.ae Required conditions for ARS are: 1. High level radiation dose. 2. Delivered to the whole body. 3. Short period of time (not protracted). fchs.ac.ae Former Russian spy, Alexander Litvinenko, 43, is the first known victim to be poisoned with polonium-210 and to die from the resulting radiation sickness. He died on Nov. 23, three weeks after he fell ill in London. fchs.ac.ae About a third of Hiroshima's population was killed within a week of the bombing. Many more have since died through radiation sickness fchs.ac.ae Nuclear bomb and power plant incidents. fchs.ac.ae Whole Body Radiation Syndromes stages  ARS demonstrates itself in three major response stages: prodromal, latent period and manifest illness. 1. Prodromal (initial stage) 2. Latent period 3. Manifest illness stage fchs.ac.ae Course: FRD1011 Radiologic Physics & Radiation Protection Lecture 1: Essential Concepts of Radiologic Slide 14 fchs.ac.ae Physics - 1  Prodromal stage  Occurs within hours after a whole-body absorbed dose of 1 Gy (100 rads) or more.  Nausea, vomiting, diarrhea, fatigue, and leukopenia (an abnormal decrease in white blood) characterize this initial stage.  The length of time involved for this stage to run its course may be hours or a few days fchs.ac.ae  Latent period  It occurs within 1 week, during which no visible symptoms occur.  Actually, it is during this period that either recovery or fatal effects begin.  Toward the end of the first week, the next stage started. fchs.ac.ae  Manifest illness stage  It is the period when symptoms that affect the hematopoietic, gastrointestinal, and cerebrovascular systems become visible.  Some of these symptoms are decrease in the number of red and white blood cells and platelets in the circulating blood, fluid loss, dehydration, epilation, exhaustion, vomiting, severe diarrhea, fever, headaches and infection.  In severe high-dose cases, emaciated human (weakly) beings eventually die. fchs.ac.ae Total Body Irradiation syndromes  Three separate dose-related syndromes occur as part of the total-body syndrome: 1. Bone Marrow Syndrome 2. Gastrointestinal Syndrome 3. Central Nervous System Syndrome fchs.ac.ae  Bone Marrow Syndrome  The hematopoietic form of ARS, or “bone marrow syndrome,” occurs when human beings receive whole-body doses of ionizing radiation ranging from 1 to 10 Gy (100 to 1000 rads).  Radiation exposure causes the number of red blood cells, white blood cells and platelets, in the circulating blood to decrease.  The patient initially experiences mild symptoms of the prodromal syndrome, which appear in a matter of a few hours and may persist for several days. fchs.ac.ae  Bone Marrow Syndrome  For example, radiation doses ranging from 1 to 10 Gy (100 to 1000 rads) produce a decrease in the number of bone marrow stem cells.  When the cells of the lymphatic system are damaged, the body loses some of its ability to combat infection.  Because the number of platelets also decreases with loss of bone marrow function, the body loses a corresponding amount of its blood-clotting ability. This makes the body more susceptible to hemorrhage. fchs.ac.ae  Bone Marrow Syndrome  For persons affected with hematopoietic syndrome, “survival time shortens as the radiation dose increases” radiation dose escalates  additional bone marrow cells are destroyed. the body becomes more susceptible to infection (mostly from its own intestinal bacteria) and more prone to hemorrhage.  When death occurs, it is a consequence of bone marrow destruction fchs.ac.ae  Gastrointestinal Syndrome  In human beings the gastrointestinal form of ARS appears at a threshold dose of approximately 6 Gy (600 rads) and peaks after a dose of 10 Gy (1000 rads).  A few hours after the dose required to cause the gastrointestinal syndrome has been received, the prodromal stage occurs. Severe nausea, vomiting, and diarrhea persist for as long as 24 hours. fchs.ac.ae  The manifest illness stage follows this period. Again, the human subject experiences severe nausea, vomiting, and diarrhea.  Other symptoms that may occur include fever (as in hematopoietic syndrome), anemia, leukopenia (decrease in the number of white blood cells), hemorrhage (gastrointestinal tract bleeding occurs because the body loses its blood-clotting ability) and infection. fchs.ac.ae  Gastrointestinal Syndrome  Death occurs primarily because of catastrophic damage to the epithelial cells that line the gastrointestinal tract. Such severe damage to these cells results in the death of the exposed person within 3 to 5 days of irradiation, as a result of infection, fluid loss, or electrolytic imbalance.  The small intestine is the most severely affected part of the gastrointestinal tract. fchs.ac.ae  Gastrointestinal Syndrome  Because epithelial cells function as an essential biologic barrier, their breakdown leaves the body susceptible to infection (mostly from its own intestinal bacteria), dehydration, and severe diarrhea.  Some epithelial cells regenerate before death occurs. However, because of the large number of epithelial cells damaged by the radiation, death may occur before cell regeneration is accomplished.  The workers and firefighters at Chernobyl are examples of humans who died as a result of gastrointestinal syndrome. fchs.ac.ae  Central Nervous System Syndrome  The cerebrovascular form of the ARS results when the central nervous system and cardiovascular system receive doses of 50 Gy (5000 rads) or more of ionizing radiation.  A dose of this magnitude can cause death within a few hours to 2 or 3 days after exposure.  After irradiation the prodromal stage begins. Symptoms include excessive nervousness, confusion, severe nausea, vomiting, diarrhea, loss of vision and a burning sensation of the skin. fchs.ac.ae  Central Nervous System Syndrome  During this period the prodromal syndrome recurs with increased severity, and other symptoms appear, including disorientation and shock,, loss of equilibrium, respiratory distress and coma.  Damaged blood vessels and permeable capillaries permit fluid to leak into the brain, causing an increase in fluid content.  The final result of this damage is failure of the central nervous and cardiovascular systems, which causes death in a matter of minutes. fchs.ac.ae fchs.ac.ae  Stage Dose—Gy (Rads) Average Survival Time Symptoms Nausea, vomiting, diarrhea, Prodromal 1 (100) — fatigue, leukopenia Latent 1–100 (100–10000) — None Nausea; vomiting; diarrhea; decrease in number of red Hematopoietic 1–10 (100–1000) 6 to 8wk (doses over 2Gy) blood cells, white blood cells, and platelets in the circulating blood; hemorrhage; infection Severe nausea, vomiting, diarrhea, fever, fatigue, loss of Gastrointestinal 6–10 (600–1000) 3–10 days appetite, anemia, leukopenia, hemorrhage and infection Same as hematopoietic and gastrointestinal, plus excessive nervousness, confusion, lack of coordination, loss of vision, a Cerebrovascular 5 and above (5000 and above) Several hours to 2 or 3 days burning sensation of the skin, disorientation, shock, loss of equilibrium, respiratory distress and coma. fchs.ac.ae  Lethal Dose (LD)  LD 50/30: The term LD 50/30 signifies the whole-body dose of radiation that can be lethal to 50% of the exposed population within 30 days.  LD 50/60: The term LD 50/60 signifies the whole-body dose of radiation that can be lethal to 50% of the exposed population within 60 days. fchs.ac.ae  Lethal Dose (LD) LD 50/30: Approximately occurred in the range of 250 – 450 rad ( 2.5 – 4.5 Gy) LD 50/60: Approximately occurred in the range of 250 – 300 rad(2.5-3Gy) fchs.ac.ae