Total Body Irradiation, Late Effects of Radiation, and Risk Estimates

Total body irradiation

• This refers to the exposure of the entire body to ionizing

radiation.

• The overall response of the body depends on how

different organ systems react to radiation exposure.

most radiosensitive system

The body's response is mainly determined by the ... affected.

1. Radiation accidents

2. Nuclear incidents

3. Radiation therapy preparation

Total body irradiation is usually discussed in:

Radiation accidents

Occurs after accidental exposure to high doses of radiation

Radiation sickness

Symptoms of nausea, vomitting, and fatigue

- External radiation

- Internal contamination

Nuclear incident, these exposures may involve:

Nuclear incidents

Large populations may be affected because of the scale of exposure

Radiation therapy preparation

This is carefully planned to minimize damage to normal tissues

o Bone marrow transplantation

o Stem cell transplantation

Radiation therapy preparation, TBI is intentionally used in medicine before:

o Destroy diseased bone marrow cells

o Suppress the immune system

o Prevent transplant rejection

Purpose of radiation therapy preparation:

• Radiation dose

• Dose rate

• Type of radiation

• Age and health of patient

• Radiosensitivity of tissues involved

Total body response, Severity of response depends on:

Dose rate

How quickly the radiation is delivered

Acute radiation syndrome

is a group of serious health effects

that occur after exposure to a high dose of ionizing radiation

delivered to the whole body or a large portion of the body within a short period of time.

• Radiation sickness

• Radiation toxicity

Acute radiation syndrome is also called:

The body receives a large radiation dose rapidly

Acute radiation syndrome occurs when ...

o Nuclear accidents

o Radiation emergencies

o Atomic bomb exposure

o Severe radiation therapy accidents

ARS usually from:

Whole-body exposure

Acute radiation syndrome usually develops after ...

Minutes, hours, days

Symptoms of ARS may appear within:

1. Prodromal stage

2. Latent stage

3. Manifest illness stage

4. Recovery or death

Phases of Acute radiation syndrome:

Prodromal stage

ARS phase: Early symptoms occurring within hours.

Prodromal stage

ARS phase:

Common manifestations:

o Nausea

o Vomiting

o Fatigue

o Diarrhea

o Loss of appetite

Latent stage

ARS phase: Temporary period where the patient

may appear normal.

Latent stage

ARS phase:

• Symptoms temporarily

improve

• Duration depends on

radiation dose

Manifest illness stage

ARS phase: Severe symptoms appear depending on the affected organ

system.

o Hematopoietic syndrome

o Gastrointestinal syndrome

o Cerebrovascular/CNS syndrome

Major syndromes in Manifest Illness stage:

o Radiation dose received

o Medical treatment

o Extent of tissue damage

Recovery or death, Outcome depends on:

Lethal dose

LD means ...

Lethal dose

This represents the radiation dose

expected to kill a certain percentage of

the population within a specific time.

LD50/30

The radiation dose that kills:

• 50% of the population

• Within 30 days

LD50/60

The radiation dose that kills:

• 50% of the population

• Within 60 days

250 - 450 rads

For humans, LD50/60 is approximately ... - ... rads

Survival time decreases,

Mortality increases

As radiation dose increase,

Survival time ...,

Mortality ...

Hematopoietic syndrome

an acute radiation syndrome caused by whole-body

exposure to ionizing radiation that damages the bone

marrow and blood-forming tissues.

Bone marrow syndrome or hematologic syndrome

Hematopoietic syndrome is also known as:

100 - 1000 R

Hematopoietic syndrome commonly occurs at radiation doses of approximately ... - ...

Bone marrow

Main target organ of hematopoietic syndrome

Several days up to 3 weeks

Hematopoietic syndrome: Latent stage occurs from ... up to ...

3-5 weeks

Hematopoietic syndrome: manifest illness stage occurs approximately ...-... after exposure

Cytopenia

Decrease in all blood cells

100-300 R

Hematopoietic syndrome: Recovery

- Many patients survive

- Bone marrow may recover

- Recovery may occur within weeks to

months

400-600 R

Hematopoietic syndrome: Recovery

- Lower survival rate

- Severe marrow destruction

500-1000 R

Hematopoietic syndrome: Recovery

- Death usually occurs within about 2

weeks

≥1000 R

Hematopoietic syndrome: Recovery

- No documented survival without

extraordinary intervention

o Severe infection (due to low WBC count)

o Hemorrhage (due to low platelet count)

o Anemia and circulatory failure

Hematopoietic syndrome:

Death usually results from:

Gastrointestinal syndrome

is an acute radiation

syndrome caused by very high doses of whole-body

radiation that severely damage the gastrointestinal

tract

1000-10000 R

Gastrointestinal syndrome commonly occurs at radiation doses of approximately ...-...

600 R

Gastrointestinal Syndrome:

In humans, symptoms may begin around ...

1000 R

In humans, full GI syndrome usually appears at about ...

o Small intestine

o Intestinal mucosa and villi

o Crypts of Lieberkühn (rapidly dividing

intestinal stem cells)

Main target organ of GI syndrome:

Prodromal stage of GI syndrome

o Occurs within hours after exposure.

o Symptoms:

- Nausea

- Vomiting

- Abdominal cramps

- Diarrhea

Fifth day

GI syndrome, Latent stage usually lasts until about the ...

Day 5 to day 10

GI syndrome, manifest illness stage occurs approximately from ... to ...

Manifest illness stage of GI syndrome

Symptoms

▪ Severe diarrhea

▪ Persistent vomiting

▪ Fever

▪ Severe dehydration

▪ Electrolyte imbalance

▪ Infection/sepsis

o Severe dehydration

o Electrolyte imbalance

o Infection and sepsis

o Bone marrow failure

GI syndrome, Death commonly occurs because of:

3-10 days

GI syndrome, without treatment, death occurs within ... - ...

2 weeks

GI syndrome, with medical intervention, survival may extend to approximately ...

Central Nervous System Syndrome

is the most severe

form of acute radiation syndrome caused by extremely high

whole-body radiation exposure

Cerebrovascular syndrome

Central Nervous System Syndrome also called ...

5000 R

CNS syndrome occurs at radiation doses greater than ...

Central Nervous system syndrome

This syndrome is rapidly fatal.

o Brain

o Spinal cord

o Blood vessels supplying the CNS

Main target organs of CNS syndrome:

o Severe damage to cerebral blood vessels

o Increased vascular permeability

o Cerebral edema (brain swelling)

o Increased intracranial pressure

CNS syndrome, Extremely high radiation doses cause:

o Vasculitis (inflammation of blood vessels)

o Meningitis-like inflammation

o Breakdown of blood-brain barrier

CNS syndrome, Possible associated conditions:

Cerebral edema

brain swelling

Vasculitis

inflammation of blood vessels

Prodromal stage of CNS syndrome

o Occurs within minutes to hours after exposure.

o Symptoms

▪ Nervousness

▪ Confusion

▪ Nausea and vomiting

▪ Burning sensation of the skin

▪ Loss of consciousness

Only a few hours

CNS syndrome, latent stage may last ...

Latent stage of CNS syndrome

Characteristics

▪ Temporary partial improvement

▪ Rapid progression follows

5-6 hours

CNS syndrome, manifest illness stage Usually develops within ...-... after exposure.

Manifest illness stage of CNS syndrome

Symptoms

▪ Severe diarrhea

▪ Convulsions/seizures

▪ Ataxia

▪ Respiratory distress

▪ Coma

• Severe cerebral edema

• Increased intracranial pressure

• Cardiovascular collapse

• Respiratory failure

CNS syndrome, Death is believed to result mainly from:

• Usually within hours

• Sometimes within 2-3 days after exposure

Survival time of CNS syndrome

Late effects of radiation

... are harmful biological effects that

appear months, years, or even decades after radiation

exposure

Somatic effects

are radiation effects that occur in the exposed

individual only and are not inherited.

• Cataract Formation

• Fibrosis

• Sterility

• Organ Atrophy

• Radiation Dermatitis

• Cancer Induction

Examples of Somatic effects:

• Sperm cells

• Egg cells (gametes)

Genetic effects occur when radiation damages:

Genetic effects

These effects may appear in future generations.

1. Mutations

2. Congenital abnormalities

3. Hereditary disorders

Examples of genetic effects:

Mutations

Permanent changes in genetic material.

Congenital abnormalities

Structural or functional defects

present at birth.

Hereditary disorders

Inherited genetic diseases passed to

offspring.

Carcinogenesis

refers to radiation-induced cancer

formation

Leukemia

Cancer type for bone marrow exposure

Thyroid cancer

Cancer type for radioactive iodine exposure

Breast cancer

Cancer type for chest irradiation

lung cancer

Cancer type for radon or radiation exposure

Skin cancer

Cancer type for chronic skin exposure

Bone cancer

Cancer type for internal radionuclide deposition

Prenatal effects

occur when an embryo or fetus is exposed to

radiation during pregnancy.

• Radiation dose

• Gestational age

• Stage of fetal development

Prenatal radiation effects severity depends on:

1. Growth retardation

2. Congenital malformations

3. Mental retardation/ cognitive impairment

4. Childhood cancer

5. Fetal death

Possible prenatal effects:

Growth Retardation

Poor fetal growth and low birth

weight.

Congenital malformations

Structural abnormalities

developing during organ formation.

Mental retardation/Cognitive impairment

Especially

after exposure during sensitive brain development

periods.

Childhood cancer

risk of leukemia and

other cancers later in life.

Fetal death

High-dose exposure may result in

spontaneous abortion or stillbirth.

0-2 weeks

When is preimplantation stage?

2-8 weeks

When is organogenesis stage?

8 weeks to birth

When is the fetal stage?

Organogenesis stage

This is the most radiosensitive stage for structural

abnormalities.