Early Tissue Reactions and Their Effects on Organ Systems (2/20/2025 & 2/27/2025)

Rad to Gy

100 Rad = 1 Gy

What is the significance of organic damage?

radiation induced damage at the cellular level may lead to measurable somatic and genetic damage in the organism as a whole

Define threshold

the point at which a response or reaction first occurs

Define non-threshold

no radiation exposure is absolutely safe

Define linear

implies biologic response to radiation is directly proportional to dose received

Define non-linear

more of an “s-shaped” response on a graph

Explain somatic effects

• defined as biologic damage sustained by living organisms as a consequence of exposure to ionizing radiation

• effects upon the body that was irradiated

• classified as early (acute) or late

Explain early somatic tissue reactions

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

• as dose increases, so does the severity of early somatic tissue reactions

• they have a threshold

• reactions will appear within minutes, hours, days, or weeks

• (Dx usually doesn’t give high enough doses to cause early tissue reactions)

List some examples of early tissue reactions

• nausea

• fatigue

• erythema

• epilation

• blood disorders

• intestinal disorders

• fever

• dry and moist desquamation (ulceration and shedding of outer layer of skin)

• depression of sperm count

• temporary or permanent sterility

• injury to CNS

What are the 4 factors that affect the amount of damage done?

• quantity (amount)

• ability to ionize (LET or quality of radiation)

• amount of tissue (how much of the body)

• specific part (where radiation was received)

What is the worst case scenario (in terms of how much damage is done to the patient)?

large dose, highly ionizing (high LET) radiation to a large part of the body or a highly radiosensitive part of the body

When the whole body is exposed to a dose of ___ Gy_t, many manifestations of organic damage occur in succession. These early tissue reactions are then termed ___

6

acute radiation syndrome

Explain acute radiation syndrome (ARS)

• also known as radiation sickness

• occurs after whole body exposure to large doses of radiation delivered over a short period of time (hours to days)

What are 3 dose related syndromes or conditions that are forms of ARS?

• hematopoietic syndrome

• gastrointestinal syndrome

• cerebrovascular syndrome

What are the 4 stages of acute radiation syndrome?

1. prodromal stage

2. latent period stage

3. manifest illness stage

4. recovery or death

Explain the prodromal stage (as 1 of the 4 stages of acute radiation syndrome)

• “prodromal syndrome”

• occurs within hours after a whole body absorbed dose of 1 Gy_t or more

• length of this stage is dose dependent (a few hours to a few days)

  • the higher the dose, the shorter the course of the stage

• symptoms

  • nausea - anorexia

  • vomiting

  • diarrhea - cramping

  • fatigue - headache

  • leukopenia

  • the higher the dose, the more severe the symptoms

Explain the latent stage (as 1 of the 4 stages of acute radiation syndrome)

• approximately 1 week in which no visible symptoms occur

• time of “well-being”

  • often mistaken for early recovery

• during this period, either recovery or lethal effects begin

• the higher the dose, the shorter the period

Explain the manifest illness stage (as 1 of the 4 stages of acute radiation syndrome)

• towards the end of the first week of latent period

• symptoms become visible (manifest themselves)

• 3 possibilities:

  • hematologic, GI, or CVS

• symptoms

  • apathy, confusion

  • fluid loss, dehydration

  • epilation

  • headaches, exhaustion

  • vomiting, sever diarrhea

  • fever, infection

  • decrease in RBCs, WBCs, and platelets

  • hemorrhage

  • cardiovascular collapse

Explain the recovery or death stage (as 1 of the 4 stages of acute radiation syndrome)

• emaciated humans eventually die in days or weeks

• after sub-lethal dose (2-3 Gy_t) recovery may occur within 3-6 months

• those who recover may show signs of permanent radiation damage and experience late effects

Explain treatments for radiation exposure

• doses <1.5 Gy_t will probably survive with only comfort measures

• doses <6 Gy_t, antibiotics fight infection, sterile environment, bone marrow transplants may improve odds of survival

• doses >50 Gy_t will always result in death

Explain repair and recovery after radiation exposure

• repeated radiation injuries have a cumulative effect

• a percentage of rad induced damage becomes non-repairable

  • 10% is irreparable

  • 90% may be repaired over time

Explain hematopoietic syndrome

• “hematologic syndrome” or “bone marrow syndrome”

• doses from 1-10 Gy_t

• hematopoietic system is the most radiosensitive vital organ system in humans

• causes # of RBCs, WBCs, and platelets to decrease

• symptoms appear in a few hours and last for several days

• prodromal stage occurs in a few hours and consists of nausea and vomiting

• manifest stage begins 3-5 weeks after exposure as stem cells are dying

• survival time decreases as dose increases

  • recovery is dose dependent

  • many recover 1-6 months after exposure

  • when death occurs, it is a result of bone marrow destruction causing anemia and no resistance to infection

  • death may occur as late as 6-8 weeks after exposure

Explain gastrointestinal syndrome

• appears at a threshold of 6 Gy_t and peaks after 10 Gy_t

• prodromal stage begins within a few hours and persists for as long as 24 hours

• latent period may last 2-5 days

• manifest illness stage follows

  • severe nausea, vomiting, diarrhea, cramping

  • fever, fatigue, lethargy

  • loss of appetite and weight loss

  • anemia and leukopenia

  • hemorrhage (GI bleed)

  • infection

  • electrolyte imbalance

  • emaciation

• death within 3-10 days after exposure

  • survival time does not vary (there is no survival)

  • death due to damage to epithelial cells that line the GI tract (causes infection, fluid loss, electrolyte imbalance)

  • intestinal lining is stripped of functional cells

Explain cerebrovascular syndrome

• “CVS” or “CNS” syndrome

• dose of 50 Gy_t or more

• death within hours or a few days

• prodromal stage occurs quickly

  • nervousness, confusion

  • severe N/V/D

  • loss of vision and consciousness

  • burning feeling of skin

• latent period up to 12 hours

• manifest stage has increased severity of symptoms and more appear

  • shock, agitation, ataxia, edema, fatigue, lethargy, respiratory distress, vasculitis, coma

• injured blood vessels and capillaries permit fluids to leak into the brain causing increased intra-cranial pressure

  • failure of CNS and CV systems

  • death within minutes

Explain mean survival time (from Bushong book)

as body rad-dose increases, the average time between exposure and death decreases

Explain Chernobyl

• ARS due to nuclear power plant accident

• 4/26/1986 massive explosion that caused 7 tons of contaminants to burn with a 3-mile high radioactive plume

• workers doses of 6 Gy_t or more

• ARS hospitalized >203 people

Explain biologic dosimetry

• serial measurements of levels of lymphocytes and granulocytes in blood and quantitative analysis of dicentric chromosomes and hematopoietic cells coming from active bone marrow

• used to measure exposure after nuclear accidents and other radiation mishaps

Lethal dose

50/30 is defined as the whole body dose lethal to 50% of the population within 30 days

LD for >8 Gy_t

100/30

Explain repair and recovery after radiation

• can occur when cells are exposed to sublethal dose

• most cells regain ability to divide and repopulate

• oxygenated cells are more severely damaged but can recover

• hypoxic cells are less damaged but not good at recovering

What is it called when significant cell death leads to shrinkage of organs and tissues?

atrophy

Explain local tissue damage

• atrophied organs and tissues can lose ability to function partially or completely

• if they don’t recover, necrosis/death of the structure occurs

• organ/tissue response to radiation exposure depends on radiosensitivity, reproductive characteristics, growth rate

What is radiodermatitis?

significant reddening of the skin caused by exposure to radiation that eventually led to cancerous lesions on the hands and fingers of early radiologists

Who was William Herbert Rollins?

• dentist who became 1st known advocate for radiation protection

• experimented on guinea pigs and found 3 importances:

  • wear radiopaque eyewear

  • enclose x-ray tube in housing

  • cover area of interest

What are the 3 layers of the skin?

• epidermis - outer layer

• dermis - middle layer of connective tissue

• hypodermis - fat and connective tissues

skin and accessory organs are radiosensitive

What is skin erythema?

• a single absorbed dose of 2 Gy_t can cause erythema with 1-2 days after exposure

• diffused redness over an area of skin after irradiation

What is desquamation?

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

• begins as moist, and then may develop dry desquamation

Epilation

• “alopecia”

• moderate doses of radiation can cause temporary hair loss

• large doses of radiation can cause permanent hair loss

Historically, skin diseases were treated with ___, which are x-rays in the energy range of 10-20 kVp

grenz rays

Use of HLF for extended periods of time can cause ___

radiation burns

Doses as low as ___ Gy_t can depress the sperm population, delay or suppress menstruation, and cause genetic mutations in future generations

0.1

Explain the hematopoietic system

• consists of bone marrow, blood, and lymphoid organs

• cells develop from a single pluripotential stem cell

• multiple other cells originate from this one primary cell

What are cytogenetic effects?

the study of cell genetics with an emphasis on cell chromosomes

Explain karyotypes

• chromosome map of chromosomes paired with their sister chromosomes

• analysis and understanding of the influence of radiation on genetics

Explain chromosome aberrations

occur when irradiation occurs early in interphase, before DNA synthesis takes place

Explain chromatid aberrations

occur if irradiated later in interphase, after DNA synthesis