Exam 1 review Radiology

What is the basic structure of atoms?

Protons and neutrons surrounded by electrons. Mostly space.

What is mass?

Anything that takes up space/ the amount of space that something takes up.

What is electromagnetic radiation?

It is energy in electrical and magnetic fields in the form of waves moving through space.

What % of electrons produced make up the x-rays and what % make up the heat.

1% makes up the x-rays and 99% makes up the heat.

What are the components of the x-ray machine?

Cathode, Anode, Tungsten filament, Focusing cup, Tungsten target,

What are you going to make sure to go do?

GO MEMORIZE THE X-RAY PARTS SHEET

What is the Cathode made of?

Tungsten.

What is the cathode?

It is the negative side of the x-ray tube, where the x-rays are produced.

What is the Anode?

The positive side of the x-ray tube where the electrons crash into and turn into heat and x-rays.

What is the anode made of?

Tungsten and often adhered to a copper filament to help absorb heat. A fixed anode cannot stand as much heat as a rotating anode.

What is the rotating anode and what is it made of.

It is an anode that rotates made of tungsten or tungsten alode. It’s rotating helps distribute the heat but still provides a small focal spot.

What is the focusing cup

It is the cup that is shaped to help focus the electrons to the target at the anode. Contains the wire tungsten filament.

What is the tungsten filament?

It is a coiled tungsten wire that heats up and “boils” off electrons on the cathode.

What is the Tungsten Target?

The target for the electrons to hit when coming from the cathode. It is made of tungsten and angled to direct the x-rays through the window.

What is the focal spot?

It is the area on the anode where the electrons crash into the target. Usually the focal spot is 1-2mm squared. The smaller the focal spot the more clear the film. But the smaller the focal spot, the hotter the area.

What is the glass housing?

A glass container around the x-ray tube that provides a vacuumed space for the tube.

What is the metal housing?

It is the metal housing that surrounds the glass housing.

What is the aluminum filter?

It is an aluminum filter that filters out the low-energy less penetrating x-ray beams. This makes the image clearer, and reduces patient exposure.

What is the window?

Where the x-ray beam leaves the x-ray tube.

How hot does the temperature get from the electrons?

Up to 1000 degrees Celsius.

What are the different rectifiers.

Single, full, 3-phase, and high-frequency.

Single rectification.

One single wave going up and down (positive and negative). So there is a pause between each.

Full rectification.

Waves going only one way, not up and down, just positive, or just negative. Like a pulse, closer together than the single.

3-phase rectification.

3 waves, alternating to make an almost constant current.

High-frequency rectification.

The waves are so close together that it gives a constant current.

What is an AC current?

Alternating current, positive, negative, up and down.

What is a DC current?

One current, not going from negative to positive. (Full?)

What do most houses and x-ray machines have? DC or SC?

Both have DC.

Why could an AC current be bad for an x-ray unit?

Because it is unpredictable.

What do x-ray machines use to make the electron currents predictable and constant?

Rectifiers.

What kind of rectification do most x-rays machines use?

3-phase used to be used but it was too expensive. Most new ones have a high-frequency.

Radiation age limit?

18

Protective gear for x-ray radiation.

Lead aprons, lead gloves, thyroid shields, glasses.

X-ray safety procedure synonym.

ALARA, which means as Low As Reasonably Achievable.

How is radiation measured and what is the limit?

It is measured with dosimeters. In Sev or REM. The recommended limit is 5 REM or 0.05 Sev.

What is the advantage vs disadvantage of a small focal spot on the anode?

Advantage: Sharper image. Disadvantage: increased heat production.

What is the advantage vs disadvantage of a larger focal spot on the anode?

Disadvantages: Less sharp image, more exposure. Advantages: Less heat.

What do FFD and SID stand for?

Focal Film Distance, Source Image Distance.

What is SID/FFD?

It is the distance between the focal spot and the film/plate.

Further vs Closer FFD/SID?

Think flashlight, shadow, and white board. The closer the image and the light, the sharper the image turns out. The further away the image and the light, the less sharp the image is.

What is the heel effect?

The heel effect is the x-ray beam being more intense or more concentrated on the cathode side. This is because the anode target is angled at about 20 degrees from vertical and causes the beams to hit it and have one side more concentrated than the other.

How should we always position a patient because of the heel effect?

We should always position the thickest part of the patient towards the cathode side to even out that effect.

What are the exposure factors?

kVp, mA, and S(econds)

What is mA?

Milliamperage. It is the QUANTITY of x-rays The amount of x-rays can change how long exposure is needed to get the image.

what is kVp.

Kilovoltage Peak/Potential. It is the speed/energy of the electrons accelerating. Affects the penetration power of the x-rays. Affects contrast.

How does the Seconds exposure factor mix with the mA?

mA plays into Seconds and becomes Milliamperages per Second (mA’s) And says depending on how many mA’s we need, that changes how long we need our exposure time to be, or vise versa.

mAs ex.

20mA X ½ a second (of exposure time) = 10 mAs. 200mA X 1/20sec = 10mAs. So the amount of mA changes how long we need exposure.

What role does positioning play in radiographic quality?

Patient motion is the #1 artifact in radiographs. Positioning can affect how good the image and detail are. Think shadow and flashlight again. You want to position the body part being radiographed to be as close to the plate/film as possible.

What is the purpose of a Potter-Bucky Diaphragm?

To reduce scatter radiation.

What is the grid device used to reduce scatter radiation?

A Potter-Bucky Diaphragm.

How is grid efficiency determined?

Grid efficiency is determined by the height and the distances between the lead strips. The ratio between those two factors. The larger the ratio the more efficient?

Grid efficiency example, what most machines are.

Most grids are 8 to 1, but 15 to 1 ratio is more efficient because the grid is taller and will filter scatter radiation better.

What is the downside to having a more efficient grid?

It takes more power to get through the grid to the plate/film, because it is thicker.

What is the collimator on the x-ray machine used for?

It is used to reduce the image size, which limits the size of exposure.

What are the 5 steps of developing film?

Developing, rinsing, fixing, washing, and drying.

What is Sante’s Law?

(2 x Thickness (body part in centimeters) + 40 (SID/FFD) = kVp setting.

What is the inverse square law?

It is describing how the intensity of the x-ray beam decreases as the distance from the source increases. The intensity is inversely proportional to the square of the distance. So if you double the distance from the X-ray source, the intensity of the beam reaching a point will be one-quarter of what it was at the original distance

What is absorption when it comes to x-rays?

The amount of x-rays that the body absorbs. Some tissue is more absorbent than others.

What is Density?

The number of x-rays that are going to hit our image receptor!!!! Milliamperage is one of the controls of density, and exposure time. SO mA’s control density!

What is Contrast?

kVp. It is the ability to see differences in adjacent tissues. The heart is easy to see because it is surrounded by gas (lungs) so high contrast. Guts and stuff have a lower contrast because they look more the same. 

What is Detail?

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

What is the relationship between crystal size of phosphor and/or silver halide crystals and film detail?

The bigger the crystals the less x-rays it takes, but it penetrates them faster, causing a grainer the image. The smaller the crystals the more x-rays it takes, and the more time it takes to hit all the crystals, but the sharper the image.

What is the caliper used for in film based radiology?

The caliper is used to measure the thickest part of the body you are radiographing, then the digital system adjusts the kVp and the mA’s appropriately.

When manipulating mAs settings on the radiology machine, what is directly affected?

The quantity of electrons available to hit the target, therefore how many x-rays are produced.

What are the common materials used to make the target, the filament, and the spindle of the rotating anode in the x-ray tube?

Tungsten Alode are used for the target and filament. The spindle of the rotating anode is made from molybdenum.