TEST #1 MANUAL REVIEW QUESTIONS

What is the heel effect? (TEST QUESTION)

→ variation in x-ray beam intensity

→ the beam is more intense on the cathode side of the tube head

→ place the thicker part of the anatomy under the cathode side to use the greater intensity

What is the penumbra effect? (TEST QUESTION)

→ burring of the radiographic image

→ focal spot

• lrg: more blurring

• sm: sharper image

What are the 5 requirements needed to produce an X-ray? (TEST QUESTION)

1. source of electrons

2. method of accelerating electrons

3. obstacle free path

4. traget

5. vacuum tube/envelope

How does the 15% rule help adjust radiographic density and contrast?

increase kVp by 15% = x2 exposure

decrease kVp by 15% = ½ exposure

→ if image is too light/underexposed increase mAs or kVp by 15% (ONE @ a time)

→ if the image is too dark/overexposed decrease mAs or kVp by 15%

→ increasing mAs increases density WITHOUT changing contrast

→ increasing kVp increases density AND decreases contrast

→ choose a kVp that allows penetration while preserving useful diff in absorption btw tissues

What are x-rays?

→ electromagnetic radiation w very short wavelengths that originate from the extra nuclear part of an atom

What is radiograph?

→ A photographic image produced by a beam of penetrating ionizing radiation after passing through an object

When radiation encounters living cells what 4 events may occur?

1) radiation passes through cell = no effect

2) radiation damages cells = damage can be repaired

3) radiation damages cells = damage is NOT repairable

4) radiation kills the cell = cell death

What are the four sources of radiation exposure listed int he lec notes?

1) primary beam

2) scatter radiation

3) x-ray tube head

4) fluoroscopy (live time imaging)

T or F: Radiation dose is directly related to the duration of exposure?

TRUE

What are 2 ways to minimize exposure time?

→ prevent retakes by using correct settings and positioning

→ use the fastest exposure time possible w mAs as low as possible

What are the 8 ways to maximize distance or reduce radiation exposure during radiography?

1) use non manual restraint

2) stay out of rm if possible

3) rotate personnel

4) do not touch the tube head or cassette during exposure

5) do not take x-rays if prego

6) do not take x-rays if <18yrs old

7) avoid retakes by using technique charts and proper positioning

8) do not direct the beam @ adjacent occupied rms

What are 6 ways to maximize shielding?

→ lead aprons: 0.50 mm lead equivalent

→ lead gloves: 0.25mm lead equivalent

→ thyroid protectors

→ goggles

→ lead screens

→ store equipment properly to prevent damage

T or F: some body parts are allowed to be in the primary beam

→ False (keep hands and all body parts out of the primary beam)

When and where should a dosimeter be worn?

→ always wear the personal radiation monitor when taking X-rays

→ attach it to the outside of the thyroid protector, outside the apron

When should mechanical restraint devices be used, and what are 3 examples?

→ use non manual restraint whenever possible to help hold the patient and allow proper positioning

examples of positioning aids:

• sandbags

• foam blocks

• socks

→ GA or sedation can allow the technician to leave the rm or stand behind a lead wall

How should the collimation beam be positioned?

→ collimate to the smallest field needed to include the area being radiographed

→ this decreases patient exposure and scatter production, reduces technician exposure, and increases image detail

What are the rules for X-ray equipment?

→ use only equipment in good working order

→ check equipment regularly

→ calibrate annually

→ keep an exposure log

→ equipment must also be maintained and inspected @ < q 2yrs

What % of energy becomes X-rays, and what % becomes heat when electrons interact w the target?

1% becomes roentgen radiation (x-rays)

99% is released as heat

What two factors determine whether an X-ray beam penetrates a subject?

1) atomic #

2) density of subject

note: absorption depends on x-ray energy

What is the variation in x-ray penetration and absorption caused by diff in tissue thickness, density and atomic # called?

→ differential absorption

What is the atomic # of a subject and what are some examples?

→ the atomic # is the # of protons in the atoms nucleus

→ examples:

• tungsten - 74

• lead - 87

• bone - 14 (higher atomic # than soft tissue therefore will absorb more x-ray beams)

• calcium - 20

• soft tissue - 6

What are some examples of radiopaque materials?

→ lead, water, sandbags, bones

What are some examples of radiolucent materials?

→ air, foam wedges, wood, cartilage, lungs, tape

What 7 factors influence radiographic contrast?

→ kVp

→ mAs

→ FFD/SID

→ film/screen combinations

→ processing factors

→ grid/filters

→ collimation

What 4 things influence subject contrast?

→ patient

→ part being x-rayed

→ bone to muscle ratio to fluid ratio

→ contrast media (high contrast = low setting)

What is the 15% rule?

→ used to adjust exposure by changing kVp

• increase kVp by 15% x2 exposure

• decrease kVp by 15% ½ exposure

• if the image is too light, increase mAs or kVp by 15%

• if the image is too dark, decrease mAs or kVp by 15%

REMEMBER: increasing kVp increases radiographic density and decreases contrast increasing mAs increases density WITHOUT changing contrast

What happens when you increase mAs?

→ radiographic density increases WITHOUT changing contrast

What happens when you increase kVp?

→ radiographic density increases

→ radiographic contrast decreases

→ the beam’s penetrating power increases

What are 3 things you should remember to reduce geometric distortion?

→ keep the object parallel to the image receptor

→ center the object

→ keep the object as close to the cassette/image receptor as possible to reduce object film distance (OFD)