Exam 1 - study guides 1-2

What are x-rays?

Invisible electromagnetic radiations similar to visible light and radio and television signals, but have shorter wavelengths

Shorter wavelengths = ?

The shorter the wavelengths, the greater the energy of the x-ray beam

The greater the energy of the x-ray beam = ?

the greater its penetration into body tissues

What are the two types of damage that can occur from overexposure to radiation?

Stochastic Effects and Deterministic effects.

Deterministic effects

Noticible short term effects

Stochastic effects

Long/ Late term effects

What is the purpose of the tungsten filament?

It is heated to “boil” off the electrons.

How are x-rays produced?

The cathode heats and boils off the electrons which are then directed by the focusing cup and since the cathode is negative and so are the electrons they are pushed away from the cathode and towards the positive anode. The electrons crash into the anode. This spot is the focal spot. Then they crash and energy is released. 99% is heat 1% is x-rays. Because of the angle of the anode the x-rays are shot down towards the window and out onto the patient and onto the film/plate/etc.

What type of x-ray machine will have a stationary anode and what type will have a rotating
anode? Why?

Dental and small portable units will have stationary anodes because they usually use less power and don’t need to withstand as much heat. Bigger machines and usually tabletops will have a rotating anode because the heat is going to be much more and a stationary anode cannot withstand the same amount of heat.

what is the heel effect?

Because of the angle of the anode the x-ray beam is more intense at the cathode side. Thicker part of patient should be towards cathode.

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

overheating

Basic properties of x-rays

Invisible, electrically neutral, have no mass, travel at the speed of light, travel in straight lines, can cause chemical and biological damage to living tissue.

What does the collimator do?

It reduces the x-ray beam to a specific area wanted, minimizing radiation exposure to the patient and surrounding areas.

What are 6 things that should be included in the radiation safety program at a veterinary
clinic?

Time, distance, shielding. ?

What are the three ways people are exposed to radiation?

Exposure to the primary beam, exposure from “scatter” radiation, and exposure from “leakage” radiation from the housing of the x-ray tube itself

What kinds of cells are most vulnerable to x-ray radiation?

Rapidly dividing cells.

How often should aprons, gloves and thyroid shields be x-rayed?

At least once a year.

What are some things that can be done to decrease the amount of exposure of personnel
when taking x-rays?

Shielding, distance, time. Reducing the time of exposure, increasing the distance between the source of radiation, and placing a shield or barrier between the personnel and radiation. Monitoring how much radiation one has received.

What is the mA?

The mA measures the amount of current used to heat the filament. This affects the
number of electrons that are made which affects how many x-rays are made. The
higher the mA, the more electrons used, the more x-rays will be made. This will make a
more intense x-ray beam.

What is the exposure time and how does it relate to mA?

How long the film will be exposed to the x-rays. mA and exposure time are related because by changing the mA you can change the amount of exposure time needed. Higher mA (more x-rays) will allow for a shorter exposure time because more x-rays were able to hit the film. Lower mA would need a longer exposure time to ensure enough x-rays hit the film.

How are mAs and kVp related?

mA controls concentration and kVp controls energy and penetrating power. You can adjust them to get different exposures.

What is Santes Rule? What does it tell you? What does the 40
represent?

It is an equation that tells you what kVp setting you should use based on the thickness of the animal’s body part. (2 x thickness) + 40 = kVp setting. 40 = the FFD/SID.

Does Santes Rule give you a value for table top or bucky?

Table top.

When should Sante’s rule be used?

When trying to make a technique chart/ Getting the kVp setting for a unique animal.

What is a caliper?

A measuring tool with two sliding peices used to determine the thickness of a body part being X-rayed

What is the SID (FFD)? What will happen to the image when the SID(FFD) is increased? What
will happen to the image when the SID (FFD) is decreased?

The SID/FFD is the distance from the focal spot to the image receptor. The closer the focal spot is the the image receptor, the more intense the x-ray beam. The further the distance, the less intense and worse quality.

What is the usualy SID/FFD?

36-40 inches

What is radiographic quality?

How easily details can be perceived on a radiograph. Determined by density, contrast, and geometric factors.

What is radiographic density? What factors and exposure factors will affect film density?

The degree of darkness on the x-ray film. mA and kVp affect density. So does the thickness of the tissue, and the developing/ processing.

What is a low contrast film?

A film with many shades of grey and not much black and white. Long scale of contrast.

What is a high contrast film?

A film with lots of black and white and not much grey. Short scale of contrast.

What is radiographic contrast? Films of what part of the body should be high contrast? Films
of what part of the body should be low contrast?

The density difference between two adjacent area on a radiograph. Bone radiographs should be high contrast. Organs and tissue should be low contrast.

From lightest to darkest what shows up in the x-ray in which order. Gas, bone, metal, fat, and water.

Metal, bone, water, fat, gas.

What will happen to an x-ray if you increase the kVP? What will happen if you decrease the
kVp?

If you increase kVp you will get a lower contrast photo. If the kVp is decreased you will get a higher contrast photo.

What is scatter radiation? Why should we worry about it? What setting will increase the
amount of scatter radiation?

It is the amount of radiation that scatters beyond the primary x-ray beam. Because it is still radiation that can harm us. mAs, kVp, and size of the x-ray beam will increase the amount of scatter radiation.

What is a grid? Where is it located? What does it do?

It is alternating strips of leads in a grid designed to block excess scatter radiation. It is located above the image receptor.

What causes grid cutoff?

When the x-ray primary beam is unintentionally absorbed by grid lines leading to a decrease in image density, exposure, and quality.

What is the main type of grid used?

The Potter-Bucky diaphragm.

What is the Potter-Bucky diaphragm (aka the “bucky”)?

It is a moving grid that travels rapidly back and forth during x-ray exposure. Filters scatter radiation while blurring grid lines.

What is Geometric Distortion?

Usually caused by patient motion. When the patient is positioned incorrectly and the x-ray beam hits the patient at a weird angle or too far from the plate. To avoid, keep the patient as close to the plate as possible, centered directly below the focal spot.

What is radiographic detail?

The definition of the edge of an anatomic structure on the film.