2721 Early Tissue Reaction and Their Effects

Somatic Effects

• Effects upon the body that was irradiated (Soma means body)

• Classified as either

  • Early

  • Late

• Somatic Tissue Reactions

  • If the effects include cell killing and are directly related to the dose received

  • When radiation dose increases, the severity of the somatic tissue reaction increases

Early Effects

• Biologic effect of radiation that occur relatively soon after humans receive high doses of ionizing radiation

• Evidence of such effects comes from numerous laboratory animal studies and data from observation of some irradiated human populations

• Not common in diagnostic imaging

• Produced by a substantial dose of ionizing radiation

Early Tissue Reactions

• May appear within

  • Minutes

  • Hours

  • Days

  • Weeks

• Diagnostic imaging exams do not normally impose radiation doses sufficient to cause early tissue reactions

• Possible high radiation dose consequences include

  • Nausea, fatigue, erythema (diffuse redness over an area of skin after irradiation), epilation (loss of hair), blood disorders, intestinal disorders, fever, dry and moist desquamation (shedding of the outer layer of skin), depressed sperm count in the male, temporary or permanent sterility in the male and female, and injury to the central nervous system (at extremely high radiation doses)

• This succession of clinical signs and symptoms are referred to as the Acute Radiation Syndrome

• If dose in superleth (600 rad or 6 Gy) effects to organs will occur in succession and can lead to death within days

Acute Radiation Syndrome (ARS)

• Radiation sickness

• Occurs in human after whole body reception of large doses of ionizing radiation delivered over a short period (from several hours to a few days)

• Data fro epidemiologic studies of human population exposed to doses of ionizing radiation sufficient to cause the syndrome have been obtained from

  • Atomic bomb survivors of Hiroshima and Nagasaki

  • Marshall Islanders who were inadvertently subjected to high levels of fallout during an atomic bomb test in 1954

  • Nuclear radiation accident victims such as those injuring in the 1986 Chernobyl disaster

  • Patient who have undergone radiation therapy

ARS Presents in Four Major Response Stages

• Prodromal

• Latent Period

• Manifest Illness

• Recovery or Death

Prodromal Stage

• Also called Prodromal Syndrome

• Occurs within hours after a whole body absorbed dose of 1Gy or more

Latent Period

• After the prodromal stage

• Approximately 1 week follows during which no visible signs occur

Manifest Illness

• The period when signs and symptoms involving the hematopoietic, GI, and cerebrovascular systems become visible

Recovery or Death

• May occur in approximately 3 months

• Such person may show some signs of permanent radiation damage and experience late effects

Symptoms of acute radiation syndrome

• Three separate dose related syndromes or conditions occur as part of the total body syndrome

  • Hematopoietic syndrome

  • Gastrointestinal syndrome

  • Cerebrovascular syndrome

Hematopoietic Syndrome

• “Bone marrow syndrome”

• Occurs when people receive whole body doses of ionizing radiation ranging from 1-10 Gy

• The hematopoietic system manufactures the corpuscular elements of the blood and is the most radiosensitive vital organ system in humans

• Survival time shorten as the radiation dose increases

• The body becomes more susceptible to infection (mostly from its own intestinal bacteria) and more prone to hemorrhage

• Death may occur 6-8 weeks after irradiation. Death in some very sensitive human subjects who recieve a whole body dose just exceeding 2 Gy

• Survival probability of patient with hematopoietic syndrome is enhanced by intense supportive care and special hematologic procedures

Gastrointestinal Syndrome

• Appears at a threshold dose of approximately 6 Gyt and peaks after a dose of 10 Gyt

• May die 3-10 days after being exposed

• A few hours after the dose (prodromal or beginning stage) severe nausea, vomiting, and diarrhea persist for as long as 24 hours. Latent period could last as long as 5 day where symptoms disappear

• Once manifest illness stage begins subject experiences severe nausea, vomiting diarrhea

• Other signs and symptoms that may occur include

  • Fever (as in hematopoietic syndrome) fatigue, loss of appetite, lethargy, anemia, leukopenia (decrease in the number of WBC) hemorrhage (GI tract bleeding because of the body losing its blood clotting ability) infection, electrolyte imbalance, emaciation

• Death of the exposed person within 3-5 days from a combination of infection, fluid loss, and electrolytic imbalance

Cerebrovascular Syndrome

• Results when the central nervous system and cardiovascular system receive doses of 50 Gyt or more of ionizing radiation

• Can cause death within a few hours to 2 or 3 days after exposure

• Signs and symptoms in prodromal stage include: excessive nervousness, confusion, sever nausea, vomiting, diarrhea, loss of vision, burning sensation of the skin, loss of consciousness

• Latent period lasting up to 12 hours follows, then manifest stage occurs in which disorientation and shock, period of agitation alternating with stupor, ataxia (confusion and lack of muscular coordination), edema in the cranial vault, loss of equilibrium, fatigue, lethargy, convulsive seizures, electrolyte imbalance, meningitis, prostration, respiratory distress, vasculitis, coma

Prodromal Stage Snapshot

• Dose: 1 Gyt

• Symptoms: Nausea, vomiting, diarrhea, fatigue, leukopenia

Latent Stage Snapshot

• Dose: 1-100 Gyt

• Symptoms: None

Hematopoietic Stage Snapshot

• Dose: 1-10 Gyt

• Average survival time: 6-8 weeks (doses over 2 Gyt)

• Symptoms: nausea, vomiting, diarrhea, decrease in number of red blood cells, white blood cells, and platelets in the circulating bloods, hemorrhage, infection

Gastrointestinal Stage Snapshot

• Dose: 6-10 Gyt

• Average Survival Time: 3-10 days

• Symptoms: Severe nausea, vomiting, diarrhea, fever, fatigue, loss of appetite, lethargy, anemia, leukopenia, hemorrhage, infection, electrolytic imbalance, and emaciation

Cerebrovascular Stage Snapshot

• Dose: 50 and above

• Average survival time: Several hours to 2-3 days

• Symptoms: Same as hematopoietic and GI, plus excessive nervousness, confusion, lack of coordination, loss of vision, burning sensation of the skin, loss of consciousness, disorientation, shock, period of agitation alternating with stupor, edema, loss of equilibrium, meningitis, prostration, respiratory distress, vasculitis, coma

Lethal Dose

• 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

  • The LD 50/30 for adult humans is estimated to be 3-4 Gyt without medical support

  • Whole body doses greater than 6 Gyt will cause the death of the entire population in 30 days without medical support. With medical support some humans have survived doses as high as 8.5 Gyt

• LD 10/30, LD 50/60, and LD 100/60

  • All these measures refer to the percentage of subject who die after a certain number of days

Local Tissue Damage

• A destructive response in biologic tissue will likely occur when any part of the human body receives a high radiation dose

• Significant cell death usually results, leading to the shrinkage of organs and tissues, a process referred to as atrophy

• Organ and tissue response to radiation exposure depend on factors such as: radiosensitivity, reproductive characteristic, growth rate

• Some local tissues suffer immediate consequences from high radiation doses

  • Skin

  • Male and female reproductive organs

  • Bone marrow

Effects on the Skin

• Radiodermatitis, a significant reddening of the skin caused by excessive exposure to relatively low energy ionizing radiation that eventually led to cancerous lesions on the hands and fingers

• Because the skin function as an ongoing regeneration system, it is relatively radiosensitive

• A single absorbed dose of 2 Gy can cause radiation induced skin erythema within 24-48 hours after irradiation

• Desquamation or shedding of the outer layer of the skin occurs at higher radiation doses

• Epilation or hair loss (aka alopecia) can be caused from exposure to radiation because hair follicles are growing tissue. Moderate doses of radiation generally produce temporary hair loss whereas radiation large radiation doses can result in permanent hair loss

• Significant evidence of skin damage as a consequence of exposure to orthovoltage radiation therapy (x-rays in the range of 200-300 kVp) comes from oncology patients who underwent such treatments in earlier years for deep seated tumors

Effects on the Reproductive System

• Human germ cells are relatively radiosensitive

• Doses as low as 0.1 Gyt can depress the male sperm population and this same dose has the potential to cause genetic mutation in future generations. In girl and women, a gonadal dose of 0.1 Gyt may delay or suppress menstruation

Hematologic Effects

• A whole body dose as low as 0.25 Gyt would produce measurable hematologic depression

• This dose could cause enough of a decrease in the number of lymphocytes in the blood to leave the body vulnerable to infection by foreign invaders

• The hematopoietic system consists of

  • Bone marrow

  • Circulating blood

  • Lymphoid Organs (lymph nodes, spleen and thymus gland)

• Cells of this system all develop from a single precursor cell, the pluripotential stem cell. The following are other types of cells that originate from the one type of elementary cell: lymphocytes, granulocytes, thrombocytes or platelets, and erythrocytes

• *Pluripotential relating to or being a cell that is capable of differentiating into cells of any type of tissue except placental tissue

Cytogenetic Effects

• Cytogenetics may be defined as the study of cell genetic with and emphasis on cell chromosomes

• A cytogenetic analysis of chromosomes may be accomplished through the use of a chromosome map called a karyotype

• Metaphase is the phase of cell division in which chromosome damage caused by radiation exposure can be evaluated. Chromosome aberrations (deviation from normal development or growth) and chromatid aberrations have been observed at metaphase

• Both low and high radiation doses can cause chromosomal damage that may not be apparent immediately. Most chromosomal damage results from the process of indirect action of ionizing radiation on vital biologic macromolecules