CHAPTER 33 - DETERMINISTIC EFFECTS OF RADIATION

death

_______, of course, is the most devastating human response to radiation exposure.

stochastic effects

No cases of death after diagnostic x-ray exposure have ever been recorded, although some early x-ray pioneers died from the ___________ of x-ray exposure.

intense enough nor large enough

Diagnostic x-ray beams are neither ____________ to cause death.

Diagnostic x-ray beams

_____________ always result in partial body exposure, which is less harmful than whole-body exposure.

power industry

Employment in the nuclear ________ is a safe occupation.

acute radiation syndrome.

The sequence of events that follow high-level radiation exposure leading to death within days or weeks is called the ________.

• hematologic death

• gastrointestinal (GI) death

• central nervous system (CNS) death

These syndromes are (3):

Hematologic death and GI death

________ and __________follow lower exposures and require a longer time for death to occur.

two periods

In addition to the three lethal syndromes,_________ are associated with acute radiation lethality.

prodromal period

The __________ consists of acute clinical symptoms that occur within hours of exposure and continue for up to a day or two.

latent period

After the prodromal period has ended, there may be a _______, during which the subject is free of visible effects.

1 Gyt (100 rad)

At radiation doses above approximately__________ delivered to the total body, signs and symptoms of radiation sickness may appear within minutes to hours.

minutes to hours

At radiation doses above approximately 1 Gyt (100 rad) delivered to the total body, signs and symptoms of radiation sickness may appear within ______________.

• nausea

• vomiting

• diarrhea

• a reduction in the white blood cells of the peripheral blood (leukopenia).

The symptoms of early radiation sickness most often take the form of:

prodromal period

This immediate response of radiation sickness is the ____________.

few hours to a couple of days.

The prodromal period may last from a ____________

dose related

The severity of the symptoms in prodromal period is __________, at doses in excess of 10 Gyt (1000 rad), symptoms can be violent.

higher doses

At still ___________, the duration of the prodromal syndrome becomes shorter until it is difficult to separate the prodromal syndrome from the period of manifest illness.

latent period

After the period of initial radiation sickness, a period of apparent well-being occurs, which is called the _______

latent period

The__________ extends from hours or less (at doses in excess of 50 Gyt) to weeks (at doses from 1 to 5 Gyt).

latent period

The __________ is the time after exposure during which there is no sign of radiation sickness.

latent period

The _________ is sometimes mistakenly thought to indicate an early recovery from a moderate radiation dose.

latent period

It may be misleading, however, because it gives no indication of the extensive radiation response yet to follow.

latent period

At very high radiation doses, the __________ disappears altogether

prodromal period

At very low radiation doses, there may be no __________ at all.

hematologic syndrome

Radiation doses in the range of approximately 2 to 10 Gyt (200–1000 rad) produce the ___________.

latent period

In hematologic syndrome, the __________ that follows can extend as long as 4 weeks and is characterized by a general feeling of wellness.

Latent Period - Hematologic Syndrome

There are no obvious signs of illness, although the number of cells in the peripheral blood declines during this time.

hematologic syndrome

The ____________ is characterized by a reduction in white blood cells, red blood cells, and platelets.

Manifest Illness - Hematologic Syndrome

The period of __________ is characterized by possible vomiting, mild diarrhea, malaise, lethargy, and fever

2 to 4 weeks

If the dose is not lethal in hematologic syndrome, recovery begins in _________, but as long as 6 months may be required for full recovery

6 months

If the dose is not lethal in hematologic syndrome, recovery begins in 2 to 4 weeks, but as long as ________ may be required for full recovery

hemorrhage and dehydration (Hematologic Syndrome)

Just before death,_____________may be pronounced.

(Hematologic Syndrome)

Death occurs because of generalized infection, electrolyte imbalance, and dehydration.

gastrointestinal (GI) syndrome

Radiation doses of approximately 10 to 50 Gyt (1000–5000 rad) result in ____________

vomiting and diarrhea

The prodromal symptoms of gastrointestinal syndrome includes ___________ occur within hours of exposure and persist for hours to as long as a day.

3 to 5 days (Gastrointestinal Syndrome)

A latent period of _______ follows, during which no symptoms are present.

manifest illness

The __________ period begins with a second wave of nausea and vomiting followed by diarrhea.

Manifest Illness (Gastrointestinal Syndrome)

The victim experiences a loss of appetite (anorexia) and may become lethargic.

4 to 10 days (Gastrointestinal Syndrome)

Supportive therapy cannot prevent the rapid progression of symptoms that ultimately leads to death within__________ of exposure.

GI death

________ occurs principally because of severe damage to the cells lining the intestines.

Intestinal cells

________ are normally in a rapid state of proliferation and are continuously being replaced by new cells.

3 to 5 days

Intestinal cells are normally in a rapid state of proliferation and are continuously being replaced by new cells. The turnover time for this cell renewal system is normally _________

stem cells

Radiation exposure kills the most sensitive cells— _______; this controls the length of time until death.

central nervous system (CNS) syndrome.

After a radiation dose in excess of approximately 50 Gyt (5000 rad) or higher is received, a series of signs and symptoms occur that lead to death within a matter of hours to days. This is the ___________

Prodromal stage - CNS

During this initial onset, the patient may become extremely nervous and confused, may describe a burning sensation in the skin, may lose vision, and can even lose consciousness within the first hour.

12 hours - CNS

This may be followed by a latent period that lasts up to __________, during which earlier symptoms subside or disappear.

latent period - CNS

The__________ is followed by the period of manifest illness, during which symptoms of the prodromal stage return but are more severe

Latent Period - CNS

The person becomes disoriented; loses muscle coordination; has difficulty breathing; may go into convulsive seizures; experiences loss of equilibrium, ataxia, and lethargy; lapses into a coma; and dies.

manifest illness

Regardless of the medical attention given the patient, the symptoms of ______________ appear rather suddenly and always with extreme severity.

CNS effects

At radiation doses high enough to produce _________, the outcome is always death within a few days of exposure.

elevated fluid content of the brain

The ultimate cause of death in CNS syndrome is ____________

CNS syndrome

__________ is characterized by increased intracranial pressure, inflammatory changes in the blood vessels of the brain (vasculitis), and inflammation of the meninges (meningitis).

equally severe

At doses sufficient to produce CNS damage, damage to all other organs of the body is __________

GI tract and the hematologic system

The classic radiation-induced changes in the ________ and _________ cannot occur, because there is insufficient time between exposure and death for them to appear

LD50/60

The ________ is the whole body radiation dose that causes 50% of irradiated subjects to die within 60 days.

1 Gyt (100 rad)

At the lower dose of approximately __________, no one is expected to die.

6 Gyt (600 rad)

Above approximately ________, all those irradiated die unless vigorous medical support is available.

10 Gyt (1000 rad

Above _________, even vigorous medical support does not prevent death.

nonlinear, threshold dose-response relationship

Acute radiation lethality follows a ________________.

LD50/60

If death is to occur, it usually happens within 60 days of exposure.

Acute radiation lethality

____________ is measured quantitatively by the LD50/60

3.5 Gyt (350 rad)

Acute radiation lethality is measured quantitatively by the LD50/60, which is approximately ____________ for humans

8.5 Gyt (850 rad)

With clinical support, humans can tolerate much higher doses; the maximum is reported to be ____________

mean survival time

As the whole-body radiation dose increases, the average time between exposure and death decreases. This time is known as the ____________.

60 to 4 days

As the radiation dose increases from 2 to 10 Gyt (200–1000 rad), the mean survival time decreases from approximately ________; this region is consistent with death resulting from the hematologic syndrome

hematologic syndrome

As the radiation dose increases from 2 to 10 Gyt (200–1000 rad), the mean survival time decreases from approximately 60 to 4 days; this region is consistent with death resulting from the ___________

dose dependent

Mean survival time is ___________ with the hematologic syndrome.

4 days

In the dose range associated with GI syndrome, however, the mean survival time remains relatively constant, at _________

dose dependent

With larger doses, those associated with CNS syndrome, the mean survival time is again ___________, varying from approximately 3 days to a matter of hours.

3 days to a matter of hours.

With larger doses, those associated with CNS syndrome, the mean survival time is again dose dependent, varying from approximately ______________

higher

When only part of the body is irradiated, in contrast to whole-body irradiation, a ______ dose is required to produce a response.

partial-body irradiation

Every organ and tissue of the body can be affected by ____________.

shrinkage

The effect is cell death, which results in The effect is cell death, which results in shrinkage of the organ or tissue ________of the organ or tissue.

Atrophy

_________ is the shrinkage of an organ or tissue caused by cell death.

intrinsic radiosensitivity and the kinetics of cell proliferation and maturation

The manner in which local tissues respond depends on their________________ and ________________.

• skin

• gonads

• bone marrow.

Examples of local tissues that can be affected immediately are the _______, ________ and _________.

threshold-type dose-response relationship.

All deterministic radiation responses—local tissue damage is a good example—follow a ______________

minimum dose

A _____________ is necessary to produce a deterministic response.

nonlinear fashion.

A minimum dose is necessary to produce a deterministic response. When that threshold dose has been exceeded, the severity of the response increases with increasing dose in a ___________.

Skin

The tissue with which we have had the most experience is the _______

• an outer layer (the epidermis)

• an intermediate layer of connective tissue (the dermis)

• a subcutaneous layer of fat and connective tissue.

Normal skin consists of three layers:

• hair follicles

• sweat glands

• sensory receptors

The skin has additional accessory structures, such as __________, ___________, and __________.

radiation exposure

All cell layers and accessory structures participate in the response to ______________.

slower rate

The skin, similar to the lining of the intestine, represents a continuing cell renewal system, only with a much __________ than that experienced by intestinal cells

every day

Almost 50% of the cells lining the intestine are replaced ______, but skin cells are replaced at the rate of only approximately 2% per day.

2% per day

Almost 50% of the cells lining the intestine are replaced every day, but skin cells are replaced at the rate of only approximately ________.

basal cells

The outer skin layer, the epidermis, consists of several layers of cells; the lowest layer consists of ________

Basal cells

_________ are the stem cells that mature as they migrate to the surface of the epidermis.

basal cells

Damage to ___________ results in the earliest manifestation of radiation injury to the skin.

orthovoltage x-rays (200–300 kVp x-rays)

In earlier times the tolerance of the patient’s skin determined the limitations of radiation oncology with ____________

x-ray therapy

The object of __________ was to deposit energy in the tumor while sparing the surrounding normal tissue.

erythema

The resultant skin damage was seen as ___________ (a sunburn-like reddening of the skin)

desquamation

The resultant skin damage was seen as erythema (a sunburn-like reddening of the skin) followed by ___________ (ulceration and denudation of the skin), which often required interruption of treatment.

3 to 10 Gyt (300–1000 rad)

After a single dose of _____________, an initial mild erythema may occur within the first or second day.

2 weeks

After a single dose of 3 to 10 Gyt (300–1000 rad), an initial mild erythema may occur within the first or second day. This first wave of erythema then subsides, only to be followed by a second wave that reaches maximum intensity in about _________

moist desquamation

At higher doses, this second wave of erythema is followed by a ___________, which in turn may lead to a dry desquamation.

Moist desquamation

_________ is known as clinical tolerance for radiation therapy

fractionated scheme,

During radiation therapy, the skin is exposed according to a___________ usually approximately 2 Gyt/day (200 rad/day, 5 days a week).

Erythema

____________ was perhaps the first observed biologic response to radiation exposure.