Unit 4 Radiographic Techniques Part 1

Radiography

Is both an art and a science?

-technology produced radiographs by way of operating equipment that produce x-rays

-must be skilled in the use of technique factors are considerably produced good radiographs

Technique

The systematic procedure to produce a high quality radiograph. Includes ability to select appropriate factors to produce an x-ray beam that will accurately penetrate the body body parts and provide the appropriate level of blackening(density) and subject contrast on the image

-knowledge and understanding of how these factors and combined to produce a diagnostic radiograph is the science

Exposure factor

Factors governing density

-Kilovoltage (kV)

-milliampereseconds (mAs)

distances

Kilovoltage (kV)

-the force that accelerates the electrons from cat to android

-the energy or quality of the x-ray beam is determined by the kV selected

-x-rays travel through matter in a wavelike fashion

-mass controls density KV controls contrast

-KV is not the primary choice for controlling density on the image

-however it does control contrast

-It is a factor of the production of scatter radiation

Wavelength

Is the distance from crest to the wave to the crest of the next wave?

-an increase in KV will produce x-ray photons of shorter wavelength

-In increase in KV produces more x-ray photons having higher energy levels

-low frequency, low energy

-high frequency, high energy

high kV

long scale (shades of grey) , low contrast bigger body

-Ask, KV increases Stobo, the penetration ability which increases the amount of radiation, reaching the image receptor

-this will produce more density on the image

Remember

KV does not produce more x-ray futons. It is the increase in energy that allows more x-rays to penetrate the body part producing increase blackening (density) of the image.

15% rule

An increase in KV only by 15% will result in doubling the amount of overall blackening or density on the image

15%=0.15

0.15(70) kV=10.5

70kV + 10.5+80.5~ 81 kV

Increase KV

Double density

Larger scale, gray shades

Two times as dark

Increase in 15% rule add

Decreased in 15% rule subtract

-increase a production of scatter radiation

-increased chances of scatter radiation to reach image receptor

-increase

-fog

-Decreased quality resolution detail

-increase exposure

Decrease kV

Shorter scale (black and white)

half density

Small body

-A decrease in KB for 10% will reduce the overall test density of the image by 1/2

ex:

p.15(70)kV=10.5

70kV -10.5=59.5 ~60 kV

15% rule continued

-It is a non-linear and non-proportional relationship

-however, it serves a technologies well as a practical tool when changes in KV are necessary in order to control the amount of exposure to the image

-caution must be used when using KV to decrease

-A significant reduction in KV mirror result in x-ray energy in adequate to patriate the body parts of

-the selected KB must be adequate to penetrate the part

Penetration of the part

Means the x-ray futons have significantly energy to pass through the part and emerge as a remnant radiation -selection below six KV may not be adequate for part penetration

KV selection

KV selected base on average body thickness

-Chest 110 KV

-abdominal 70 KV

-Upper extremity 60 KV

KV scatter radiation

- KV is a factor of the production

-as x-ray photo strike the body parts, especially with higher KV the x-ray photos undergo a change in interaction

-Occurs in the atomic level

-x-ray photos travel any direction it's original straight line path

Scatter radiation

-Exit the body traveling in many directions with different energy levels

-Scatter radiation is a danger to the patient on the tech technologies

-It is detriment to image quantity

Higher KV

Increase scatter radiation, increase fog unwanted density on image

Lower KV

Not enough penetration, and most of the radiation is absorbed by the patient

-therefore OPTIMUMKV is necessary, where the adequate amount of x-ray photos reaches the image of for adequate dens

-KV selection has been standardized based on body parts thickness

-KV is primary used to control radiographic contrast

milliamperes

Control the current flow of the cat filament at the time of exposure

-As Emmy is increased figment temperature rises, increasing the number of electrons released through the automatic admission

-And increase an MA will increase the number of x-ray photos in the emergency beam

Doubling

A doubling of mAm double radiographic density

-the relationship of MMA selected an overall image density is proportional

-if the Emmy is doubled from 200 to 400 that amount of density is also

30 to 35% a minimal change in MA of 30 to 35% is then needed to visualize the change in density

-Emmy has no relationship to the penetration ability of the x-ray four times therefore does not affect scatter radiation

-And increase an MA however w will increase the amount of exposure absorbed by the patient

Time

Is the factor that controls the length of the exposure?

Milliamperage (mA)

Manipulators and time are combined and recognized as a single quantitative factor

-and increase an MA increases the number of protons exposure the image receptor

Decrease KV by 15%

-half flight density

-more black and white

-double mass

-short scale

Increase KV by 15

Long scale, more gray

-2 density

- decrease by half

-longer scale

kV and mAs relationship

-a decrease in KV by 15% may be compensated for doubling the mAs

an increase in KV by 15% may be compensated for the decreasing the mA by half

Examples of kV and mAs

A reader graph is made using 80 KV @ 100 MAS. A request was made to make a second exposure with the lower KV, but to maintain the same density.

Step one; change KV by 15%

0.15×80 KV = 12

80 KB -12 equals 68

Step 2 double the MAS

100mAs (2)=0.485 µrads 200 mAs

Final: new technique is 68KV @ 200 MAS

mA and time relationship

the mA and time relationship is inverse property because MAs is considered as what value

-an increase or decrease in one will require a decrease or increase in the other to maintain the same radiographic density

formual

original / new MAs = new/ original S

Example

A radiograph is made using 200 mA. (old) 0.3 S (old) and 90 kV. A second exposure is needed with the same MAs and kV but using 500 MA(new). What is the. Ew exposure

spent 1

200/500=x/0.3

spet 2

500x+60 all divide by 60

x=0.12 sec

step 4 60/500=0.3

200(0.3)=t0 New factors is 90kV 500 mA and 0.12 S

Reciprocity law

Indicates the blackening of the image will remain constant as long as the total energy, exposing the image receptor is constant

Time like MMA has no effect on the penetrating ability of the x-ray four

-short exposure times are necessary to prevent patient's motion during exposure, which is determining an image quantity

-short exposure is their motion

Distant

Represent the length of the distance between the x-ray resource to the image receptor the intensify of the x-ray beam is affected by changes in the source of the image distance

Source the image distant SID

inverse square laws

Old/ new = new /old

Example inverse square law

And exposure is drawn at 40 SID at 40 and idolize chamber measurements the radiation exposure of or which will have new reading show if the same technique technical Are used at 45 Sid

5R/x=45^2/40^2

5R/x= 2025/1600

x=3.95

-only works when measure intensify or exposure rate coming from an x-ray source

The direct square kaw

SSID increases so much MAS to maintain adequate radiographic density

Example

A technologist performs a chest x-ray using 3MAS and 75KV at 72 SID. A second radiograph is required, but a result of the patient's condition must be done at 54 SID. What is the new MA for the second exposure?

X divided by three equals 74^2/72^2

X /3 + 2916/5184

5184x=8748

'divided 5184 from both side

X= 1.69