EARLY EFFECTS OF - Montgomery College

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Transcript EARLY EFFECTS OF - Montgomery College

EARLY NONSTOCHASTIC EFFECTS/LATE STOCHASTIC EFFECTS Sherer Chapter 6, Reference: Bushong, Chapter 36 and 37

Review of Dose response curves

• Threshold • Non threshold • Linear quadratic non threshold curve • Non linear (s-shaped or sigmoid)

Early, Nonstochastic Effects:

• Soon after Rad. Exposure • minutes • hours • days • weeks • “x-ray burns”

ACUTE RADIATION SYNDROMES

• Total body exposure • acute exposure in a matter of minutes • 100’s or 1000’s of rads

RADIATION AND MAMMALS

• 200-1000 rads • Survive a few weeks • 1000-10,000 rads • 3-4 days • 10,000 + • few minutes

FOUR STAGES TOTAL BODY IRRADIATION

1) PRODROMAL (NVD SYNDROME) 2)LATENT 3) MANIFEST ILLNESS 4) RECOVERY OR DEATH

1)Prodromal

• Initial • can occur as low as 100 rads • within minutes with exposure to 1000 rads • nausea, vomiting, diarrhea (NVD)

2) Latent period

• Weeks in low dose • Hours in high dose • pt appears symptom free • lethal effects or recovery is beginning

3) Manifest Illness

A) Hematologic • Bone Marrow B) Gastrointestinal C) Cardiovascular D) Cerebrovascular/ CNS

A) HEMATOLOGIC

• AKA: bone marrow or hemotopoietic syndrome • Rad exposure-low • Stages: • Prodromal (NVD) • Latent Mitotic stem cells are sterilized pancytopenia-diminished supply of blood cells Death due to dehydration, electrolyte imbalance infection

B) GI syndrome

• 600 rads(6 gy)-1000 rads (10 gy) • prodromal - one day • latent 3-5 days-deterioration of the lining of the GI tract has begun • manifest of illness • death ( dehydration, anorexia ) 3-4 days • cannot prevent progression of syndrome

CARDIOVASCULAR

• Not a syndrome • Decreased BP • Increased pulse rate • Acute myocardial insufficiency

C) Cerebrovascular/CNS

• 5000 RADS • Prodromal (nausea and vomiting) • latent period 6-12 hours • Death occurs within hours- to several days • GI and Hemopoietic syndrome occurring simultaneously

L/D

• LD 50/30 (Sherer), LD 50/60 (Bushong) – used in animals – humans tend to survive longer (Chernobyl) – see curve (figure 36-1) on page 519 of Bushong or LD curve on page 120 Sherer

REPAIR?

• Can occur with sublethal doses but dependent on cell or organ’s potential for recovery.

• 10% of radiation induced damage irreparable

LOCAL TISSUE DAMAGE

• High doses • atrophy of organ • Skin-many x-ray pioneers suffered x-ray burns to skin

Skin layers

• Subcutaneous • middle layer • outer layer (epidermis) • accessory structures – sensory – hair – sebaceous – sweat

Erythema

• 100-300 rad - mild within 1-2 days • Q:Dose Response curve?

• A: Non-linear, threshold • Hair loss –epilation • Q:Dose Response curve?

• • A: For high dose - Non-linear, threshold low dose – linear, threshold • severe necrosis rare

Late somatic effects

Months or years after whole or partial ARS OR Low doses sustained over a couple of years

WHAT ARE THE THREE MAJOR TYPES OF LATE SOMATIC EFFECTS?

RISK ESTIMATES

• Low doses (below 10 rem) effect must be estimated • Risk still exists –controversial concept • Absolute risk –specific # of excess cancers will result due to exposure • Relative risk - # of excess cancers will increase as the natural incidence of cancer increases in the population with age

Carcinogenesis

• Distinguishing radiation induced cancer from low doses difficult. Why?

• Epidemiologic studies from high doses are used. Examples include: – Radium watch dial painters – Uranium miners – Early Radiation workers – Infants treated with radiation for enlarged thymus – Children of Marshall Island – Japanese atomic bomb survivors – Evacuees from Chernobyl

Match the pathology (can use more than once) • Radium dial workers • Uranium miners • Early Medical radiation workers • Infants treated for enlarged thymus • Children of Marshall Islands • Japanese atomic bomb survivors • Chernobyl • Thyroid • Leukemia • Breast cancer • Bone cancer • Skin cancer • Lung cancer

EXTREMITIES

• Amputations • radiodermatitis • shoe fluoroscopy • nuc med. techs

• LIFE SPAN SHORTENING • CATARCTOGENESIS • GENETIC EFFECTS

American RT’s

• Ongoing study of 146,000 RT’s • Higher risk of dying?

• Higher risk of dying from leukemia?

• Higher risk of dying from breast cancer?

• When did these risks become less?

GONADS

• Highly sensitive • can pass on effects to future generations • animal studies/radiotherapy patients, radiation accident victims, convicts • oogonia • spermatogonia

• 10 rad • 200-250 rads

TESTES

effect?

• 500-600 rads effect?

OVARIES

• 10 rad • more sensitive in fetus /small children • 200 rad • 500-625 rads effect?

why?