Radiation Safety Board Practice Questions

Which pair of features defines a deterministic effect?

A threshold dose, with severity rising above it

For a stochastic effect, what increases as the dose increases?

The chance that it occurs

Two weeks after a long fluoroscopically guided procedure, a patient develops reddening of the skin at the beam entry site. How is this effect classified?

Deterministic

Which of the following is an example of a stochastic effect?

Leukemia

Two workers develop radiation-induced thyroid cancer; one had received three times the dose of the other. How does the severity of the two cancers compare?

Severity does not depend on dose

A physician who never wore leaded eyewear during years of fluoroscopy develops lens opacities. Which description fits this effect?

Deterministic, with a threshold

Which pairing of effect and classification is correct?

Cataract – deterministic

A worker loses scalp hair after a large localized dose, and a coworker with a smaller dose to the same area loses none. Which concept best explains the difference?

Only one dose crossed the threshold

Which dose-response model is used for stochastic effects and as the basis of radiation protection policy?

Linear, no-threshold

A dose-response graph shows no response at low doses, then an S-shaped rise once a certain dose is passed. Which effect does this curve best describe?

Cataract formation

A coworker skips a syringe shield, saying the small extra hand dose is harmless because it is below any threshold. Which concept contradicts this reasoning?

The LNT model assigns risk to any dose

A dose-response curve passes through the origin and rises as a straight line with dose. Which type of effect is it modeling?

Stochastic (linear no-threshold)

Acute radiation effects typically result from which pattern of exposure?

A high dose delivered over a short time

A worker develops a cataract eight years after an eye exposure. How is this effect classified on both axes?

Deterministic and late (chronic)

Which statement correctly relates the acute/chronic and deterministic/stochastic classifications?

They are separate; acute effects are usually deterministic

A technologist accumulates small occupational doses over a 30-year career. Which effect is of greatest concern from this pattern?

Delayed cancer

Which of the following is an acute radiation effect?

Acute radiation syndrome

Which radiation-induced cancer has the shortest latency period?

Leukemia

Survivors of a radiation accident are enrolled in long-term follow-up for solid tumors. Over roughly what latency would a radiation-induced solid tumor typically appear?

10–20 or more years

A worker diagnosed with lung cancer 15 years after a minor spill asks whether the spill caused it. Why is this hard to establish?

The risk is probabilistic and delayed

A radiation accident survivor develops leukemia three years after exposure. How does this timing compare with typical latency?

It fits leukemia's short 2–5 year latency

Most human radiation cancer-risk estimates are built largely on data from which source?

Atomic bomb survivors

Carcinogenesis is the prototype of which kind of radiation effect?

Stochastic

List the acute radiation syndromes in order of increasing dose threshold.

Hemopoietic, GI, CNS

Approximately what acute whole-body dose range produces the hemopoietic syndrome?

About 1–10 Gy

An accident victim receives an estimated 25 Gy whole-body dose and develops severe diarrhea and fluid and electrolyte loss. Which syndrome is present?

Gastrointestinal

A victim of a criticality accident with an estimated whole-body dose above 50 Gy becomes confused and collapses within hours. Which syndrome is this?

Cerebrovascular (CNS)

Which acute radiation syndrome is potentially survivable with medical treatment?

Hemopoietic

What is the correct order of the stages of acute radiation syndrome?

Prodromal, latent, manifest illness, recovery or death

An exposed worker vomits a few hours after an accident, then feels well for about two weeks before blood counts fall. What is the symptom-free interval called?

Latent stage

What is the approximate LD50 for humans exposed to an acute whole-body dose without treatment?

About 3.5–4 Gy

Responders estimate one untreated victim's whole-body dose at about 4 Gy. Which outcome is expected for a group at this dose?

Roughly half would die without treatment

Why does the hemopoietic syndrome appear at lower doses than the CNS syndrome?

Marrow stem cells divide rapidly

Genetic (heritable) radiation effects result from damage to which cells?

Germ cells

A man receives a significant gonadal dose, and years later his child is born with a mutation attributed to that exposure. How is this effect classified?

Genetic and stochastic

A woman's 6-week pregnancy is irradiated during an abdominal CT. How is any resulting effect on the embryo classified?

In-utero (embryo) effect

Somatic effects differ from genetic effects because somatic effects:

Affect only the exposed person

The doubling dose is defined as the dose that:

Doubles the natural mutation rate

What is the approximate doubling dose for heritable mutations in humans?

About 1 Gy

Which statement about heritable radiation effects in humans is most accurate?

Hard to show, yet still built into limits

Why are patient diagnostic doses not capped by the occupational dose limits?

The exposure is benefit-justified

Before a PET/CT, a patient worries the scan will push her past the 50 mSv annual dose limit she read about. Which response is accurate?

That limit is for workers, not patients

A technologist has her own myocardial perfusion study with Tc-99m sestamibi. How is this dose handled for occupational records?

It is excluded from her occupational dose

For patients, the ALARA principle is best described as:

Optimizing dose while keeping diagnostic quality

A technologist wears a dosimetry badge while the patient does not. What is the main reason?

Staff dose is cumulative and regulated

According to the law of Bergonié and Tribondeau, cells are most radiosensitive when they are:

Dividing often, undifferentiated, with a long mitotic future

Which cell is generally considered the most radiosensitive in the body?

Lymphocyte

Which tissue is the most radioresistant?

Adult nerve tissue

After an accidental whole-body exposure, serial blood counts are drawn. Which cell count is expected to fall first?

Lymphocytes

Which list is ordered from most to least radiosensitive?

Lymphocytes, skin basal cells, adult neurons

Why can radiation therapy destroy a tumor while sparing much of the surrounding normal tissue?

Tumor cells divide more rapidly

A patient receives incidental dose to the adult brain during a procedure. Why is this tissue relatively radioresistant?

Mature neurons rarely divide

A worker receives a moderate whole-body dose. Which tissue is expected to show damage at the lowest dose?

Intestinal crypt cells

A man's testes receive a significant dose. Which cells are most radiosensitive?

Spermatogonia

A patient's skin receives a high dose. Which skin layer is most radiosensitive?

Basal layer

Mature bone and skeletal muscle are radioresistant mainly because their cells are:

Differentiated, with slow turnover

Linear energy transfer (LET) describes:

Energy deposited per unit path length

In what units is LET usually expressed?

keV/µm

Which ranking lists radiation from highest to lowest LET?

Alpha, neutron, proton, beta, gamma

An alpha particle and a beta particle deliver the same absorbed dose to tissue. Which does more biological damage?

Alpha, because of its higher LET

Compared with low-LET radiation, high-LET radiation produces:

Dense damage over a short track

What reference radiation is typically used when determining RBE?

250 kVp x-rays

Relative biological effectiveness (RBE) is calculated as:

Reference dose ÷ test dose, same effect

In a cell study, a test radiation produces the same cell kill as 250 kVp x-rays with only one-fifth the dose. What does this indicate?

Its RBE is about 5

What is the approximate RBE of alpha particles?

About 20

Which radiation type has an approximate RBE of 10?

Neutrons

Ra-223 kills bone metastases while largely sparing nearby marrow. Which property explains this?

High LET with a very short range

An alpha-emitting source is handled in the hot lab. Which hazard is of greatest concern?

Internal contamination by intake

Which statement about LET and RBE is correct?

As LET rises, RBE generally rises

A technologist handles Tc-99m and administers I-131. What radiation weighting factor (wR) applies to both the gamma and the beta radiation?

1

Why is the embryo or fetus so radiosensitive?

Its cells divide rapidly and are undifferentiated

A patient learns she was about 10 days past conception when she had a bone scan. Which risk best applies to exposure at that stage?

All-or-nothing

During which gestational period is the risk of congenital malformations greatest?

2–8 weeks (organogenesis)

A pregnant patient was inadvertently exposed at 11 weeks of gestation. Which risk is most associated with this stage?

CNS effects and severe intellectual disability

An exposure occurs at 30 weeks of gestation. Which statement best describes the risk?

Growth restriction, with lower overall risk

Exposure during the pre-implantation stage (0–2 weeks) most often results in:

Loss of pregnancy or no lasting effect

A technologist declares her pregnancy during her third month. Over what period does the 5 mSv (0.5 rem) embryo/fetus limit apply?

The entire pregnancy

A technologist who has just declared her pregnancy is issued a second dosimeter for the fetus. Where should it be worn?

At waist level

A 28-year-old woman scheduled for an elective gallium scan mentions that her period is late. What is the best action?

Hold the study and notify the physician

The critical organ for a radiopharmaceutical is the organ that:

Receives the highest significant dose

The target organ for a radiopharmaceutical is the organ that:

The study aims to image or treat

A patient receives Sr-89 chloride for painful bone metastases. Which organ is the critical organ?

Red marrow

A patient has a Tc-99m DTPA renal scan. Which organ is typically the critical organ for this renally excreted agent?

Bladder wall

A patient receives I-131 sodium iodide for hyperthyroidism. How do the critical and target organs relate?

The thyroid is both

After a Tc-99m MAG3 renal study, what instruction best reduces the patient's bladder wall dose?

Drink fluids and void often

A 4-year-old and an adult receive the same dose to the same organ. Why is the child at greater risk?

More of their cells are actively dividing

Which statement about critical and target organs is correct?

They may be the same or different

The quantity called exposure measures:

Ionization in air

Which is the traditional unit of exposure?

Roentgen

What is the SI unit of exposure?

C/kg

Which pair are the SI and traditional units of absorbed dose?

Gray and rad

A dosimetry report lists 2 Gy to the red marrow. What quantity is being reported?

Absorbed dose

Absorbed dose describes:

Energy deposited per unit mass

An older dosimetry report lists a marrow dose of 300 rad. What is this dose in gray?

3 Gy

The sievert is the SI unit for which quantities?

Dose equivalent and effective dose

Which unit is the traditional unit of dose equivalent?

Rem

Dose equivalent is obtained by multiplying absorbed dose by:

The radiation weighting factor

Effective dose differs from dose equivalent because it also accounts for:

Which organs were exposed

Two organs receive the same dose equivalent, yet they contribute differently to the effective dose. What explains this?

Different tissue weighting factors

The radiation weighting factor (wR) is essentially a standardized form of:

RBE