POI P2

41問 • 1年前

問題一覧

contribute to overall radiographic quality

Geometric Qualities

2 Geometric Qualities ______ - distinct representation of objects true borders, edges ______ - misinterpretation of true size or shape of an object

- Recorded detail - Distortion

degree of difference or ratio between

Radiographic Contrast

no differences in density

Homogenous Object

object with different absorption characteristics produces an image with varying densities

Differential Absorption

Evaluating radiographic quality in contrast is ______

Subjective

- controlling factor of contrast - difference in potential applied to x-ray tube - directly proportional to average x-ray spectrum or x-ray quality - plays role in adjusting amount of penetration in an acquisition - energy of x-rays (higher penetrability)

kVp

examples of: low subject contrast > high kVp > long scale contrast

Air/Fluid

examples of: high subject contrast > low kVp > short scale contrast >

Bone

properties that comprise visibility of detail. Appear Gray

Contrast

visible to human eye

Visibility of detail

difference between adjacent densities

Image Contrast

number of useful visible densities or shades of gray

Scale of Contrast

described by scale of contrast

Radiographic Images

conversion factor between exposure to ionizing radiation

Technique Conversion Factors

what to do To maintain exposure when increasing kVp:

- increase kVp by 15% - reduce mAs to half

what to do To maintain exposure when decreasing kVp:

- decrease kVp 15% - multiply mAs by 2

tissues that makeup the human body that attenuate the beam of radiation

Patient Factors

- device used to improve contrast of radiographic image - absorbs scattered radiation before it reaches image receptor - employed when body part thickness is greater than 10cm or kVp is 60 - used for obese patients

Grid

3 X-ray Interaction through the body PBI

- Pass through the body - Be absorbed by body - Interact & change direction

interaction that produces scatter radiation

Compton Interaction

3 Amount of Scatter Radiation increase with: ILD

- Increased patient thickness - Larger field sizes - Decrease in atomic number of tissue

account for lead content of grid

Grid Conversion Factor aka Bucky Grid

- placed in cassette close contact with film, function is to reinforce the action of x-rays - amplify the incoming x-ray beam - introduced by Thomas Edison in 1896

Intensifying Screens

2 TYPES OF INTENSIFYING SCREENS

- Calcium Tungstate: blue light - Rare Earth: green light

percent of x-rays that reach cassette

33%

invisible product of x-ray film

Latent Image

4 PARTS OF INTENSIFYING SCREEN BRPP

- Base Layer - Reflective Layer - Phosphor Layer - Protective Coat

layer of IS that is polyester or cardboard or metal

Base Layer

layer of IS that is made up of magnesium oxide or titanium dioxide

Reflective Layer

active layer of IS , absorbs energy

Phosphor Layer

protects phosphor layer from abrasions

Protective Coat

3 Types of Beam Restrictors ACC

- Aperture Diaphragms - Cones/Cylinder - Collimators

beam restrictor that is a flat sheet of metal

Aperture diaphragms

circular aperture diaphragms

Cones/Cylinder

commonly employed beam restriction

Collimators

purpose is to deposit enough metallic silver at latent image sites

Film Processing

4 Processing Steps

> Developing - silver is deposited at latent image > Fixing - clearing agent > Washing - water to remove developer solutions > Drying - hot air

critical part of archiving process

Storage

radiograph time or expiry

5-7 years

- visibility of anatomy and sign of pathology - affected by photographic and geometric quality

Image Quality

physiology of circulation academic weaponizer

E · 24問 · 2年前