Radiologic Physics, Maintenance, Radiobiology, and Radiation Protection

Flashcards covering essential concepts in radiologic physics, equipment maintenance, radiobiology, radiation protection, and QA/QC derived from lecture review materials.

What is the expected image on a radiograph exposed at $70\,\text{kVp}$, $100\,\text{mA}$, and $100\,\text{s}$ on a full 3-phase unit?

36 degree arc

Which technical factors increase the effective energy of the x-ray beam?

Increasing added filtration and increasing kilovoltage

What does a spinning top test result of 8 dots (dashes) indicate for an exposure set at $200\,\text{mA}$, $0.05\,\text{s}$, and $70\,\text{kVp}$?

The $0.05\text{-s}$ time station is inaccurate

Comparing mR output across $50\,\text{mA}$ @ $0.2\,\text{s}$, $100\,\text{mA}$ @ $0.1\,\text{s}$, and $200\,\text{mA}$ @ $0.05\,\text{s}$ tests which quality control parameter?

Linearity

In which portion of the x-ray circuit is the step-down transformer located?

Filament circuit

If a high-voltage generator has 100 primary turns and 35,000 secondary turns and is supplied by $220\,\text{V}$ and $75\,\text{A}$, what are the secondary voltage and current?

$220\,\text{mA}$ and $77\,\text{kVp}$

Which branch of physics describes large objects such as planets, universe, cars, and planes?

Classical Mechanics

How is the congruence of the x-ray beam with the light field tested?

Using radiopaque objects

An Automatic Exposure Control (AEC) device operates on which principles?

PMT charged by a fluorescent screen and parallel-plate ionization chamber charged by x-ray photons

What effect do Aluminium (Al), Copper (Cu), and Tin (Sn) filters have in the x-ray beam?

Low-energy x-rays are absorbed

Which principle states that no electron in the same atomic system may be assigned identical values?

Pauli's exclusion principle

If the exposure rate to a body $2\,\text{m}$ from a source of radiation is $28\,\text{R/hr}$, what distance from the source is necessary to decrease exposure to $7\,\text{R/hr}$?

$$4\,\text{m}$$

According to recommendations published in ICRP 60, the annual dose limit for radiation workers was reduced from $50\,\text{mSv}$ to what value?

$$20\,\text{mSv}$$

What unit results when a coulomb is divided by a second?

Ampere

What is the only difference between x-rays and gamma rays?

Their origin

What is the power loss in kW in a circuit where current flow is $100\,\text{A}$ and line resistance is $2\,\Omega$?

$$20\,\text{kW}$$

Which component corrects for variations in the power distribution supplied to the x-ray tube?

Voltage compensator

Which component is the first to receive power in the x-ray circuit?

Autotransformer

What percentage of voltage ripple is associated with a 3-phase, 6-pulse waveform?

$$14\%$$

What is the most common cause of x-ray tube failure?

Tungsten vaporization

What is the formula for heat units (Hounsfield units) for a 3-phase, 6-pulse x-ray generator?

$$1.35 \times \text{kVp} \times \text{mA} \times \text{seconds}$$

What is the effective energy of characteristic K-shell x-rays in a tungsten target?

$$69\,\text{keV}$$

The measurement of the half-value layer (HVL) of an x-ray beam determines which beam characteristic?

Quality

During which phase of cell division is chromosome damage caused by radiation best observed?

Metaphase

What is the total dose limit for the embryo and fetus during the gestation period?

$$0.5\,\text{rem}$$

In fluoroscopy, exposure to the collar under a protective apron is how many times greater than exposure to the trunk?

20 times

If the output intensity of an x-ray machine is $6.4\,\text{mR/mAs}$ at $80\,\text{kVp}$, what is the patient ESE for an exam done at $20\,\text{mAs}$ at $80\,\text{kVp}$?

$$128\,\text{mR}$$

What serves as the primary protective barrier of a fluoroscopy x-ray tube?

Image intensifier

What lead equivalent thickness is required for the Bucky slot opening cover during fluoroscopy?

$$0.25\,\text{mm Pb}$$

The intensity of scatter radiation $1\,\text{m}$ from the patient is approximately what percentage of the incident beam?

$$0.1\%$$

How is relative risk calculated in radiation epidemiological studies?

Observed cases / expected cases

What dose to a localized area of the body can cause skin erythema?

$$\ge 200\,\text{rads}$$

What is the approximate $\text{LD}_{50/60}$ value for humans in rads?

$$350\,\text{rad}$$

What is the principal biological effect mechanism of radiation on the human body?

Indirect effect

What is the minimum source-to-skin distance (SSD) for a portable fluoroscope?

$$30\,\text{cm}$$

What quantity reflects both radiation dose and the volume of tissue irradiated?

Dose Area Product (DAP)

What is the term for the minimum energy required to remove an electron from its orbit?

Ionization energy

Nucleons are made of which fundamental particles bounded by gluons?

Quark

How many half-value layers are required to reduce an x-ray beam intensity from $78\,\text{R/min}$ to less than $10\,\text{R/min}$?

3

What is the equation for Ohm's law?

$$I = \frac{V}{R}$$

What is the formula for mechanical work?

$$W = F \times D$$

What is the power consumption in kW for a fluoroscopy x-ray unit operating at $95\,\text{kVp}$ and $2\,\text{mA}$?

$$0.190\,\text{kW}$$

Which part of the image intensifier converts electron energy into visible light?

Output phosphor

A radiograph was produced at an SID of $100\,\text{cm}$ with an exposure of $100\,\text{mR}$. What will the exposure be if the SID is reduced to $50\,\text{cm}$?

$$400\,\text{mR}$$

What percentage of initial activity remains in a radioactive sample after three physical half-lives?

$$12.5\%$$

What is the SI unit used to describe absorbed dose ($D$), defined as energy absorbed per mass?

Joule per kilogram ($\text{J\,kg}^{-1}$)

Which law states that the radiosensitivity of biological tissue depends on cell maturity and metabolic rate?

Law of Bergonie and Tribondeau

What is the constant velocity of all electromagnetic radiation in a vacuum?

$$3 \times 10^8\,\text{m/s}$$

What percentage of projectile electron kinetic energy is converted into heat during x-ray production?

$$99\%$$

What is the significant material composition used in a Thermoluminescence Dosimeter (TLD)?

Lithium fluoride