Exposure & Techniques

which Image Receptor (IR) is used in computer radiography?

Photostimuable Phosphor

This IR uses an imaging plate (IP) to trap electrons in higher energy states that give off light that is then converted into an xray image

Photostimuable Phosphor

Which IR still requires 2 steps?

Photostimuable Phosphor

this IR converts xray beams into an electronic signal and produces an xray image made by a matrix of pixels?

Digital Detector

IR that uses an image intensifier to convert xray energy into an electron beam that is then converted into visible light and recorded by a video camera.

Fluoroscopic Screen

what do grids help to capture when taking an xray?

scatter radiation

what is scatter radiation

parts of the primary beam that bounce off body tissue, bone, and room surfaces in different directions

what are grids made of?

lead and plastic

in the context of xray imaging, what is milliampere in mAs?

amount of electrons in the xray tube current

in the context of xray imaging, what is seconds in mAs?

exposure time

the number of xray photons is directionally proportional to ____?

the product of tube current and time

in the context of xray imaging, what is kilovolts?

the force acting on electrons in the xray tube

in the context of xray imaging, what is peak?

the amount of forces pulling on the electrons (voltage)

what is used to control how much the beam spreads when taking an xray?

collimation

what does collimation mean?

trim

Source to Image Receptro Distance is defined as ____?

the distance from the anode inside the xray tube to the IR

What can cause your xray beam to spread out?

Increased SID

Increased SID can ____ the intensity of your xray beam

decrease

which factor best counteracts SID’s affect on the intensity of the xray beam?

mAs

how does mAs help counteract SIDs affect on xray beam density?

it increases the amount of xray photons sent from the xray tube meaning there are more photons to cover a larger surface area

SID and the Inverse Square Law

the intensity of an X-ray beam is inversely proportional to the square of the source-to-image distance (SID)

in the context of xray, what is brightness?

the appearance of the image on a display montior

what primarily controls the brightness of the image?

system software

what does window width on the system software control?

contrast

increased window width with means _____

more shades of grey

decrease window width means ____

less shades of grey

window level on the system software controls what?

brightness and darkness

increased window level mean ___?

darker image

decrease window level means __?

brighter image

what is contrast?

the range of the gray scale on an xray image

contrast helps with seeing anatomical structures because?

if they are not a different color gray from what is surrounding them, we are unable to see them

if an image has low contrast then there is a _____ grey scale meaning there are ______ present

longer, more shades of grey

if an image his high contrast then there is a _____ grey scale, meaning there are _____ present

shorter, less shades of grey

it’s easier to the see the differences in anatomical structures when an image has _____ contrast

high contrast

is high contrast inherently better than low contrast in an xray image?

no, it depends on what body part/tissue is being examined

what is signal?

remnant beam strength

what is remnant beam?

the part of the primary beam that makes it through the patient and is captured by the IR

if you increase mAs, ____ and ____ increases

signal, dose

if you increase kVp, _____, _____, and ______ increases

signal, penetration, scatter

signal and dose are ________ to each other

directly proportional

signal, penetration, scatter, are to each other

directly proportional

what can increase noise/randomness in the image and cause it to look muddy/grainy?

scatter

which factor affects the amount of radiation exposure a patient receives the most?

mAs

What factor automatically terminates the exposure whenit’s hit by a certain number of photons?

Automatic Exposure Control (AEC)

which factor is inversely proportional to intensity?

SID

which factor is used by tech to absorb scatter xray protons (and sometimes primary photons)

grid

the most consistent/accurate way to measure part thickness is by ____

using a caliper

which factor must be increased for thicker objects?

kVp

whether body parts are made up of muscle, bone, fat, or air refers to_____

part composition

body parts that are composed mostly of bone require more _____ than those composed of air

mAs

since pneumothorax creates thinner tissue because it collapses the lung, a(n) _______ in technique is required

decrease

since there is more air in a emphysema lung than a health lung, a(n) ______ in technique is required

decrease

since emaciation is thinning due to starving, a(n) ______ in technique is required

decrease

since atrophy is when muscles lose size from not being used enough, a(n) _____ in technique is required

decrease

if a patient has pneumonia that means the air in the lungs is replaced by fluid, so a(n) _______ in technique is required

increase

a patient with pleural effusion has fluid build up in the lungs, so a(n) ______ in technique is required

increase

hydrocephalus is when fluid builds up in the brain, so a(n) ______ in technique is required

increase

edema involves soft tissue swelling and fluid build up, so a(n) _____ in technique is required

increase

if a patient has ascites, fluid has gathered in their peritoneal cavity, so a(n) _______ in technique is required

increase

what is the key to quality in digital imaging?

attention to detail

______ kVp yield better image than ______ kVp

higher, lower

______ and ______ work to lessen the effects of scatter on the final image in digital imaging

grid, software

in digital imaging, one the exposure is taken the xray images goes from being ______ to _______

photons, data(pixels)

what’s the optimal technique that will produce the lowest dose for patients?

high kVp, low mAs

why is it better to increase kVp over mAs?

kVp doesn’t directly increase the dose to patient, but mAs does

if your kVp is too low it will _______ and cause your xray image to be a white silhouette

under penetrate

if your mAs is too low that will cause ______

quantum mottle

quantum mottle occurs when random pixels don’t receive enough _____ so the image doesn’t know what to broadcast

photons

since the computer in digital systems constantly manipulates the image, there is no guarantee that _____ nor _____ is due to radiographic technique

brightness, contrast

why are radiographers unable to receive obvious feedback that excessive technique is used for an image?

computer manipulation of image contrast and brightness

What’s the lowest % you can come in at, according to the manufacturer's technique recommendations, without seeing quantum mottle?

75%

At what % of under-exposure will quantum mottle definitely show?

near 50%

if a radiographer was to over expose the patient, the software is able to ____ pixel intensities

rescale

the software’s ability to _________ pixels is why radiographer are unable to tell when they overexpose the image

automatically rescale

exposure indicators do not report _____

patient dose

exposure indicators report the strength of your

remnant beam signal

if the exposure indicator shows that your remnant beam strength is higher than recommended that means ____

your patient dose was also higher than recommended

this is caused by insufficent techniques that result in low exposure indicatiors

mottle noise

mottle noise is present the same as ____ but is caused by ______

scatter, insufficient technique

on this graph, exposure indicator is the ___

midpoint between C-B and represents anatomic exposure

on this graph, point C represents ___

prosthetics, bright white metallic objects

on this graph, point B represents ___

primary radiation, is jet black

in this graph, most anatomy falls _____

in between point C and B, is a range of grays