Radiology - Week 1

Front 1

Cathode

Back 1

Negatively charged side of x-ray tube that produces electrons from a metal filament when heated.

Contains:

Focusing cup, filament(s)
Filament wiring

Front 2

Anode

Back 2

Positively charged side of x-ray tube. Recieves electroms from cathode

Contains:

Anode disk
Focal spot (actual focal spot)
Induction motor
Rotor
Rotor bearings
Stators/coils

Front 3

Actual focal spot

Back 3

Beam from cathode to anode

Front 4

Effective focal spot

Back 4

Focal spot from anode to object being radiographed

Front 5

Heel effect

Back 5

x-ray beam produced through interactions with anode has spectrum of x-ray energies. x-ray beam stronger on cathode and weaker on anode side.

Can take advantage of this by placing chest/abdomen on weaker anode side and limbs on stronger cathode side to get a more balanced radiograph

Front 6

radiographic density

Back 6

mA. How black the black areas are and overall blackness of film

Front 7

radiographic contrast

Back 7

kVp. Long scale - many shades of gray (chest/ abdomen). Short scale - black and white with a few shades of gray (extremities)

Front 8

kVp

Back 8

Kilovoltage peak. Controls speed of electron acceleration and penetrability of adjacent areas. Controls how fast electrons go through an object

HIGH VOLTAGE and controls CONTRAST (differences in radiographic densitty between adjacent areas - organ wall or inside organs)

Average setting is 40 - 120 kVp

Front 9

mA

Back 9

Milliamperage. Controls the number of electrons produced. Setting on x-ray that controls the4 quantity of electrons boiled off filament on x-ray tube. Affects DENSITY - overall blackness of film. Controls how many electrons are made

Average setting is 100 - 300 mA

Front 10

Focal film distance

Back 10

distance from x-ray tube to film. AKA source image distance (SID)

Front 11

Object film distance

Back 11

Distance frrom objec that is being imaged to the film. Penumbra is decreased by ensuring object film distance is as short as possibble

Front 12

Dosimetry

Back 12

Monitor the amount of radiation one receives. Worn when radiographs are taken and sent to a lab to be processed. Allows cumulative radiation dose to be recorded for each individual for a lifetime.

Front 13

Maximum permissibble dose

Back 13

Recommendation off maximum dose by NCRP. Recommends that the max dose per year not to exceed 5 rem (0.05Sv), individual organs not to exceed 50 rem (5 Sv), and eye lenses not to exceed 1.5 rem (0.15 Sv)

Front 14

Scatter radiation

Back 14

Low energy x-ray photons that have undergone a change in direction after interactingg with structures in the patients body. Decreases the film quality and increases radiation exposure

Front 15

rem

Back 15

Roentgen equivelent man. Amount of ionizing radiation exposure taking into account eifferent sources and biological effects

-rem = 1 rad

-Sievert (Sv) used to define a rem - 1 Sv = 100 rem

NCRP recommends 5 rem/yr max

-The amt used to express the dose equivalant that results from exposure to ionizing radiation.

Front 16

X-rays are a form of what? What are 3 other forms of this type of radiation?

Back 16

Electromagnetic radiation.

gamma rays, radio waves and visible light are also a form of electromagnetic radiation

Front 17

What is a wavelength

Back 17

The distance a wave can move in the time it takes to complete one cycle

Front 18

What are wavelengths measured in?

Back 18

Nanometers. X-rays are typically 0.05 to 0.01 nm

Front 19

What is quanta?

Back 19

Small packets of energy

Front 20

How are x-rays generated in the x-ray tube

Back 20

Uses stream of electrons directed to a metal target. Energy of electrons interacting with the target atoms converted to heat (99%) and x-ray (1%)

Front 21

Small effective focal spots vs large focal spots

Back 21

Small effective focal spots produce better detail, but lack the ability to dissipate heat.

Large focal spots are used for images that need to be larger. Lack less detail as a small, but dissipates heat better.

Front 22

Difference between rotating and stationary anode?

Back 22

Rotating - used in higher output machines (100-1200 mA) Anode rotates at very high speeds to disipate heat.

Stationary - used in low output/low mA machines

Front 23

What is tube overload?

Back 23

Combined kVp and mA are too high for the machine. Too much heat created, causing anode to crack.

Front 24

What is tube saturation?

Back 24

When positive potential/voltage between cathode and anode is not enought to pull all electrons across tube. These electrons build up on glass envelope and causes it to be almost as attractive to electrons as anode during high kVp exposure and cause it to crack

Front 25

What are the three basic macine controls that a user must adjust on machine?

Back 25

kVp, mA, and exposure time

Front 26

What are the big 3 of radiation safety?

Back 26

Time, distance, and sheilding

Front 27

Radionuclides

Back 27

Technetium 99m is administered IV. Patient is radioactive for 6 hour half life and exreted mostly in urine and some in feces

Front 28

Computed Tomography

Back 28

CT or CAT scan. Electromagnetic enerrgy sent transaxially through the patients body and takes several thin slice images. Computer processes data onto a 2-D or 3-D image

-Commonly used for head/spinal for neurological disease
equine lameness

Front 29

Magnetic Resonance Imging

Back 29

MRI. Uses non-ionizing elecromagentic field.

2 types (measured in Tesla - T)

~Low field strength open magnents - 0.4 T or less

~High field sttrength (superconductive) magnents - 0.6T or above

Creates thin slice images that are superior in quality to CT scan

Common in brain and spinal exams

Front 30

Endoscopy

Back 30

The visual examination of interior structures of the body with an endoscope used for diagnostic and treatment procedures

Front 31

ultrasonography

Back 31

Nonivasive method of imaging soft tissue by sending low-intensity, high frequency sound waves into tissues and then listening for the returning echoes that have been reflected

Front 32

Radiology

Back 32

Form of diagnostic imaging that uses ionizing electromagnetic radiation to image bone and softt ttissue

Front 33

X-ray

Back 33

Conversion of electron energy to electrmagnetic radiation and transported through space by wavelengths and frequency

Front 34

Inverse square law

Back 34

The intensity of the x-ray beam is inversely proportional to the square of the distance from the source of the x-ray

Front 35

Transformers

Back 35

2 types: Step-up transformers and Step down transformers.

Step up: Increases incoming voltage to kilovolts. High voltage potentials needed to accelerate electrons from cathode to anode

Step down transformers: Decreases incoming voltage. Lower voltage requred by filamentt on the cathode side

Front 36

Rectification

Back 36

The process of converting alternating current to direct current - Limit the electron flow to one direction from the cathode to the anode

3 Types of rectifications:

Half wave, single phase (60 pulses/sec)

Full wave, single phase (120 pulses/sec) MOST OFTEN USED FOR RADIOGRAPHS!!!

Full wave, three phase (almost continuous pulses)

Front 37

Fluoroscopy

Back 37

Tube under table and consantly moving image on monitor. Radiation risk is GREATLY increased - continuous pulse

Front 38

Cleaning and maintinence of the x-ray machine

Back 38

Can wipe witth soft cloth NO CLEANSER! (rubbing alcohol ok)

Table wiped down with mild disinffectent NOT BLEACH

Floor of radiology should be bleached or disinfected

THE ONLY SELF SERVICABLE ITEM IS THE BULB IN THE COLLIMATOR

Front 39

Exposure time

Back 39

The amount of time the beam is penetrating.

Shorter time setting = less radiation exposure to patient bbut detail quality is reduced.

Average is between 1/120 to 1/10 of a second

mA x seconds = mAs

Average mAs setting between 2-10 mAs

Front 40

Penumbra effect

Back 40

Loss of detail. Excessive penumbra causes blurring at the edges of the shadows cast by the x-ray exposure. Changes to Size of focal spot (Larger the focal spot, the more pronounced penumbra effect, smaller focal spot size will help), Focal film distance (Distance from target to film, increasing the distance can decrease penumbra effect), and Object film distance (The distance from the object that is being imaged to the film, Penumbra decreased by keeping this as short as possible)

Front 41

Roentgen (R)

Back 41

A measure of radiation exposure or x-ray machine output

Front 42

rad

Back 42

Radiation absorbed dose - Amount of ionizing radiation by x-rays only

Gray (Gy) is used to define rad: 1 Gy = 100 rad

Front 43

ALARA

Back 43

As low as reasonably achievable - workplace principle

Front 44

Potter buckey

Back 44

Device that sets the grid in motion, blurring the white lines on the finished radiographs that are produced by the grid

Front 45

Focusing cup

Back 45

Part of cathode that restricts the diameter of accelerating electrons to the focal spot on anode

Front 46

Focal spot

Back 46

Site on anode where electrons are focused

Front 47

Tungsten filament

Back 47

Tightly coiled wire at the focusing cup on cathode