(4) Radiation Physics - Late Effects of Radiation

When can late effects of radiation occur in individuals?

 After surviving acute high-dose exposure or following chronic/repetitive low dose exposures 

All or nothing effect is associated with what kind of effect?

Stochastic effects 

What happens to the probability of stochastic effects as dose increases?

 It increases

What are the two categories of stochastic effects?

 Somatic and genetic (hereditary).

Effects that occur above a threshold dose and whose severity increases with dose are termed?

 deterministic effects

What happens to the probability of deterministic effects above the threshold?

 It increases rapidly with dose, approaching 100%.

Which effect is dose related?

 Deterministic effect

What type of dose-response relationship do deterministic effects follow?

Nonlinear threshold

What is the late radiation effect involving the skin called?

Radiodermatitis

In what layer of the skin do radiation-induced changes occur?

 Basal layer

What can chronic, long-term radiation exposure cause to the skin?

Serious skin injuries, including weathering and brittleness.

What procedures are associated with increased risk of radiodermatitis?

Cardiovascular and interventional procedures.

What type of dose-response relationship does radiodermatitis follow?

 Nonlinear threshold (sigmoidal curve) 

Radiotermatitis is considered as what kind of effect?

 Late deterministic effect

Can chromosome damage occur as both an early and late radiation response?

Yes

Why can late chromosomal effects occur?

Radiation damage to lymphocytic stem cells.

Are the eyes generally radiosensitive or radioresistant?

Radioresistant, except for the lens.

Is radiation-induced cataract formation age-dependent?

Yes

What is the estimated latent period for radiation-induced cataracts?

 Approximately 15 years

What type of dose-response relationship do radiation-induced cataracts follow?

 Nonlinear threshold

Are cataracts stochastic or deterministic late effects?

Deterministic

What is the cataract threshold for a single acute exposure according to the lecture?

Approximately 200 rad (2 Gy)

What is the estimated cataract threshold for fractionated radiation exposure?

Approximately 1,000 rad (10 Gy)

What is radiation-induced life-span shortening?

Accelerated premature aging and death.

Is radiation-induced life-span shortening specific to a particular disease?

No

Does the definition of life-span shortening include late malignant effects?

No

How much shorter was the life span of early radiologists compared with other physicians?

5 years

According to the lecture, was life-span shortening observed in atomic bomb survivors, radium dial painters, or diagnostic imaging patients?

No

What is the minimum latent period seen in children for radiation-induced leukemia?

 2-3 years

What is the latent period seen in adults for  radiation-induced leukemia?

 4–7 years

What is the approximate at-risk period for leukemia?

 20 years

What type of dose-response relationship does radiation-induced leukemia follow?

 Linear nonthreshold

What is the relative risk of leukemia in the atomic bomb survivor study?

 3:1

Why did early radiologists experience increased leukemia incidence?

 They worked without adequate radiation protection and sometimes received high occupational doses.

What annual dose did some early radiologists reportedly receive?

 More than 100 rad (1 Gy) per year

In the ankylosing spondylitis study, how many patients were examined?

 14,554

How many leukemia cases occurred compared with the number expected?

 52 observed versus 5.5 expected

Which populations provided evidence of radiation-induced thyroid cancer?

Children treated for enlarged thymus glands and children exposed to nuclear fallout on Rongelap Atoll.

What dose was used historically to treat enlarged thymus glands?

500 rad (5 Gy)

What was the reported increase in thyroid cancer after these treatments?

 100-fold

What is the latent period for radiation-induced thyroid cancer?

10–20 years

What dose was reported for the Rongelap Atoll exposure study?

1,200 rad (12 Gy)

What dose-response model is used for radiation-induced thyroid cancer?

Linear nonthreshold

Which occupational group provided evidence of radiation-induced bone cancer?

Radium watch-dial painters

What radioactive material did watch-dial painters use?

 Radium sulfate paint

Why does radium cause bone cancer?

Radium is a bone-seeking radioactive element.

What is the half-life of radium listed in the lecture?

1,620 years

What types of radiation does radium emit according to the lecture?

Alpha and beta

What was the estimated bone dose in the dial-painter studies?

 Up to 50,000 rad

What is the relative risk of bone cancer in the lecture?

 122:1

What dose-response model does bone cancer appear to follow?

 Linear quadratic 

What types of x-ray treatments were associated with radiation-induced skin cancer?

Orthovoltage and superficial x-ray treatments.

What is the latent period for radiation-induced skin cancer?

Approximately 5–10 years

What dose-response relationship does radiation-induced skin cancer follow according to the lecture?

Threshold

What skin condition may precede radiation-induced skin cancer?

Radiodermatitis

What populations were studied for radiation-induced breast cancer?

 Patients treated for tuberculosis, atomic bomb survivors, and women treated with x-rays for postpartum mastitis.

What concern does the lecture identify for younger women undergoing numerous mammograms?

Increased radiation-related breast cancer risk

What are the recommendations for mammography patients?

1. only 2 views

2. Women under 40 shouldn’t receive imaging unless symptoms, above age 55 get mammo every other year

3. family history of breast cancer, mammo should be done every 1-2 yrs from 40-50

What occupational group provided evidence of radiation-induced lung cancer?

Uranium miners

What caused increased lung cancer incidence among uranium miners?

 Inhalation of radon and its daughter products.

What was the estimated lung dose in some American uranium miners?

Up to 3,000 rad

What is the relative risk of lung cancer in nonsmoking uranium miners?

 8:1

What is the relative risk in smoking uranium miners?

 20:1

What dose-response model is assumed for radiation-induced lung cancer?

 Linear nonthreshold

Can a single radiation exposure increase cancer incidence years later?

Yes

Is there a type of cancer unique to radiation exposure?

No

Does irradiation increase the incidence of most cancers?

Yes

What is the minimum latent period for solid tumors according to the lecture?

At least 10 years

What factors affect radiation-induced cancer incidence?

 Age at exposure, organ irradiated, and type of cancer.

What dose-response model is generally assumed for radiation protection?

 Linear nonthreshold

What is the natural lifetime risk of malignancy stated in the lecture?

 33%

How much does the lecture estimate malignancy risk increases for every 100 mGy of total-body exposure

1%

Is the overall cancer risk for radiographers and radiologists statistically different from that of the general public according to the lecture?

No

Does chronic low-dose radiation exposure impair fertility according to the lecture?

No

What determines the radiation-related risks throughout pregnancy?

The stage of pregnancy and the absorbed dose.

What is the preimplantation period?

The first two weeks after fertilization.

What can high radiation doses during preimplantation cause?

Prenatal death or spontaneous abortion.

What is the estimated additional spontaneous abortion risk after 100 mGy according to the lecture?

0.1%

What happens if the embryo survives radiation exposure during preimplantation?

The pregnancy generally continues without radiation-induced developmental abnormalities (NO ill effects)

What type of effect occurs during preimplantation?

All-or-nothing

The period when cells differentiate and organs begin forming is called?

organogenesis

During what weeks does organogenesis occur?

Weeks 2–8

What abnormalities are associated with irradiation during weeks 2–5?

Skeletal abnormalities

What are examples of skeletal abnormalities?

Stunted limbs, missing fingers, or extra fingers.

What abnormalities are associated with irradiation during weeks 6–8?

entral nervous system and neurological deformities.

When is the earlt fetal period?

8-12 Weeks

What is the major radiation concern during the early fetal period (weeks 8–12) of pregnancy?

Intellectual disability and abnormalities such as microcephaly (mental retardation)

What is microcephaly?

Abnormally small head size.

What is the most radiosensitive stage of pregnancy?

First trimester

What is the main radiation risk after the first trimester according to the lecture?

Latent carcinogenic effects, including adolescent leukemia.

What types of diagnostic procedures are identified as potential concerns for the fetus?

Fluoroscopy, angiographic/cardiac catheterization, barium enema, upper GI studies, and multiexposure urograms.

Are radiation therapy procedures considered high risk for the fetus?

Yes

At what dose does the lecture report increased evidence of CNS abnormalities and tumors?

50 mGy

At what dose does the lecture report microcephaly and intellectual disability?

500 mGy

Neonatal death is most likely to occur during?

Orgenogenesis

prenatal death is most likely to occur during?

Preimplantation