Chapter 15: Image Acquistion (Test 2)

Basic Imaging Principles for Technique chart basics. By CJ quizlet.

mA, time (sec), kVp, SID

What are the prime factors?

IR exposure

What is mAs the controlling factor of?

- mAs

- mA

- Sec

- mA x sec = ?

- mAs / sec = ?

- mAs / mA = ?

Increase intensity / quantity

Increase mAs = ?

X-ray beam energy/quality, contrast, magnification, spatial resolution, distortion

What does mAs not affect?

Controls X-ray beam energy/quality and influences intensity/quantity

What does kVp control, and what does it influence?

Increased brems energy

If the kinetic energy of the electrons in the tube increases, what happens?

Photoelectric absorption decreases

If kVp or the penetration of the X-ray beam increases, what happens to photoelectric absorption in the patient?

Patient absorbed dose decreases

If kvp or the penetration of the X-ray beam increases, what happens to the patient's absorbed dose?

Patient ESE increases

If the kVp increases, what happens to the patient's entrance skin exposure?

Differential absorption decreases and subject contrast decreases

If the kVp increases, what happens to the differential absorption in the patient? What happens to subject contrast?

Compton Scatter

When kVp increases, what patient interaction is predominant?

Image contrast decreases

If the kVp increases, what happens to image contrast?

- Increase kVp by 15% = 2x IR exposure unless 1/2 mAs

- Decrease kVp by 15% = 1/2 IR exposure unless 2x mAs

What are the kVp 15% rules?

IR exposure decreases

If you increase your distance (SID), what happens to IR exposure?

Intensity/quantity decreases

If you increase your distance (SID), what happens to intensity/quantity?

- Intensity is inversly proportional to the square of the distance

- i 1 / i 2 = d2^2 / d1^2

- What is the inverse square law?

- What is the inverse square law formula?

mGya, Gya, mR, R

What units is intensity measured in?

Contrast or beam energy/quality

What does intensity/quantity not affect?

0.5 - 1.0 mm; In diagnostic X-ray

What is the measurement for a small focal spot, and where is it used?

1.0 - 2.0 mm; In diagnostic x-ray `

What is the measurement for a large focal spot, and where is it used?

0.3 - 1.0 mm; In interventional and cath lab

What is the measurement for a fractional focal spot, and where is it used?

0.1 - 0.3; In mammo

What is the measurement for a microfocus focal spot, and where is it used?

smaller / higher

____________ focal spot = ___________ spatial resolution

0.5 mm AL

What is the inherent filtration aluminum equivalent?

Glass envelope, insulating oil, tungsten vaporization, mirrors near the collimator

What are parts of the X-ray tube that are also considered inherent filtration?

1.0 mm AL

What is the adjustable collimator aluminum equivalent?

Inherent filtration

What type of filtration is the adjustable collimator considered to be?

1.0 mm AL

What is the amount of aluminum needed for added filtration?

2.5 mm AL

What is the total filtration for a machine that operates above 70kVp and is required by the National Council on Radiation Protection (NCRP)?

Increases beam energy/quality; Decreases intensity/quantity

If filtration is increased, what happens to the beam energy/quality? What happens to the intensity/quantity?

Penetration and scatter increase

If filtration is increased, what happens to penetration and scatter?

Image contrast decreases

If filtration is increased, what happens to image contrast?

Full wave and half wave

What are the two types of rectification that single phase machines produce?

The negative part of the cycle is made positive

What happens to the negative part of the cycle in full-wave rectification?

The negative part of the cycle is suppressed

What happens to the negative part of the cycle in half-wave rectification?

100%

What is the voltage ripple for half-wave and full-wave (single-phase) rectification?

No change in quality

What is the quality change from half-wave to full-wave rectification?

Increased quantity

What is the quantity change from half-wave to full-wave rectification?

Increased quality and quantity

What is the quality and quantity change from single phase to three-phase, six pulse, three-phase, twelve pulse, or high frequency rectification?

- 13-14%

- 3-4%

- 1%

- What is the voltage ripple for three-phase, six pulse?

- What is the voltage ripple for three-phase, twelve pulse?

- What is the voltage ripple for high-frequency?

Half wave

Full wave

Three phase, six pulse

Three phase, twelve pulse

High frequency (most efficient)

What are the machine phases from least efficient to most efficient?

1/2 the mAs to maintain IR exposure

What is the technical adjustment when going from a single-phase machine to a three-phase machine?

2x the mAs to maintain IR exposure

What is the technical adjustment when going from a three-phase machine to a single-phase machine?

Patient dose stays the same

After proper technical adjustments, what happens to the patient's dose when going from single-phase to three-phase or vice versa?

Magnification Radiography

What refers to the intentional increase in OID to increase the image size?

Interventional and mammography

What imaging modalities intentionally cause size distortion to magnify specific anatomy?

Anatomically Programmed Units

What is a feature on modern X-ray machines that uses preprogrammed exposure settings (kVp and mAs) based on the specific anatomical area being imaged and works with AECs?

Microprocessors

In an anatomically programmed unit, what sets the kVp and mAs?

Icons for body part and body habitus

What do anatomically programmed units include?

Positioning is critical

When using an automatic exposure control, what is critical?

Careful with collimation

When using an automatic exposure control, what should a technologist be careful with?

600 mAs

Automatic Exposure Controls has a safety override at what level?

Pathology not patient size (+2, +1, N, -1, -2)

What is the IR exposure selector set for?

25 - 50% exposure adjustment

When using the IR exposure, what percentage is the exposure adjustment?

Technique Charts

What refers to charts that determine the correct X-ray exposure settings, such as kVp and mAs, for specific anatomical parts, patient sizes, and views?

consistently / updated

Technique charts should be used _______________ and ____________ often

different

There are ____________ technique charts for each radiographic room

Variable kVp chart and Fixed kVp chart

What are the two types of technique charts?

- 2 x cm + 30 = kVp

- Measurements (callipers)

- Lower kVp; Higher patient absorbed dose

- High contrast (short gray scale and narrow latitude)

- What is the formula used for variable kVp charts?

- What must variable kVp charts be very accurate in?

- What kind of kVp do variable kVp charts use? What does this result in?

- What is the image contrast like with variable kVp charts?

- Most often used

- Higher kVp; Lower patient absorbed dose

- Low contrast (long gray scale and wide latitude)

- 2x mAs for every 4cm thickness added

- Small, medium, large

- Fixed kVp charts are what?

- What kind of kVp do kixed kVp charts use? What does this result in?

- What is the image contrast like with fixed kVp charts?

- When using fixed kVp charts, what are the mAs changes for part thickness?

- What are the size groups with fixed kVp charts?

- Barium and chest exams

- Lowers patient absorbed dose

- 100 / greater

- What exams are high kVp charts used for?

- What do high kVp charts do to the patient absorbed dose?

- High kVp charts are used with ______ kVp or __________