chapter 7: image production

what is the main function of filtration

to reduce low energy photons from reaching the patient

which type of radiation exits the patient and strikes the image receptor to form the radiographic image

rement radiation

what process describes the total reduction of x-ray photons in the primary beam as it passes through matter

attenuation

which exposure factor directly governs the total number of x-ray photons produced

milliamperage x time (mAs)

as patient subject density increases, what happened to the IR exposure/ signal value

IR exposure decreases

photostimulable phosphor plates containing barium flurohalide crystals are utilized in which IR system

computed radiography

which semiconductor material is used in direct conversion DR to convert x-rays directly into an electrical signal

amorphous selenium

an indirect conversion DR, what intermediate step occurs before generating an electrical digital signal

x-rays are converted to visible light

signal value is defined as

total accumulated electrical charge in the digital IR

what is the proposed new terminology for IR contrast

signal differences

spatial resolution in digital radiology is also know as

sharpness or recorded detail

which technical guideline is used to adjust kVp to maintain overall image exposure

15% rule

which physics law states that beam intensity changes inversely with the square of the distance from the source

inverse square law

which divice is positioned specifically between the patient and the IR to absorb scatter radiation

grid

what is the primary function of collimation in radiography

to restrict beam size and reduce scatter/fog

tissues or materials that absorb x-rays readily and appear light on a image receptor are called

radiopaque

an x-ray beam that contains photons of many different energy levels is described as

polqyenergentic or heterogenous

which system requires a external image reader to scam and extract latent image data from a phosphor plate

computed radiography

in indirect DR system, which material is used to convert visible light into an electrical digital signal

amorphous silicon

what system specification describes the number of gray shades each pixel is capable of displaying

grayscale bit depth

when changing distance (SID), which formula recalculates mAs to maintain consistent exposure to the IR

exposure maintenance formula

that active percentage os a detector element (del) area sensitive to x-ray photons is know as the

fill factor

which digital image processing feature adjusts displays brightness to present uniform visual quality despite minor exposure variations

automatic rescaling

patient factors that impact x-ray attenuation and Ir exposures include

size and thickness of anatomic part, atomic number of tissue and presence of pathological conditions

aluminum or an equivalent material is places in the tube assembly primarily to

remove low-energy photons before they reach the patient

what term refers to the quantum energy units composing an x-ray beam

photons

what is the proposed new term for image receptor exposure

signal value

kilo voltage peak primary controls which beam characteristic

relative strength and penetrating ability of x-ray photons

direct conversion DR systems convert x-ray photons energy directly into

an electrical signal via amorphous selenium

grid function

intercepts scattered photons exiting the patient while allowing primary, unscattered photons to pass through to the detector

exposure indecator

a numerical parameter representing the amount of radiation exposure is reaching the digital image receptor, also used to monitor patient dose and technique accuracy

automatic rescaling

shifts the pixel value histogram to match a target display standard, producing uniform brightness despite exposure variation

amount of irradiated material

increases patient thickness or tissue volume generates more scatter, decreasing image contrast

source to image receptor distance (SID)

distance from tube focal spot to image receptor; greater the distance- greater the resolution

object to image receptor distance (OID)

distance from the patient to the image receptor; minimizing OID reduces magnification and improves recorded detail

distortion

misrepresentation of actual anatomical size or shape on the radiograph

shape distortion

foreshortening caused by improper alignment of the central ray

contrast resolution

the ability of a digital imaging system to distinguish between small differences; the differences between different shades of gray

image receptor contrast

the ability to capture and display varying exposure levels; records the different shades of gray

what is the primary function of a x-ray grid

to absorb scatter radiation exiting the patient

which numerical factor provides feedback regarding the amount of radiation exposure reaching the digital image receptor

exposure indicator

the range of radiation exposures over which a digital image receptor can yield diagnostically acceptable images are called

exposure latitude

which digital image processing operation automatically normalizes display brightness despite exposure variances

automatic rescaling

post-processing adjustment of the window level on a digital display monitor alters image

brightness

the degree of differences between adjacent signal intensities on a digital monitor is defined as

digital image contrast

which primary exposure factor controls x-ray photons energy and penetrating power

kVp

how does a increase in the amount of irradiated martial affects scatter production

increase scatter production

tissues with higher atomic numbers absorb more radiation primarily through which interactions

photoelectric effect

barium and iodine are used as contrast media because they possess

high atomic numbers

what is the single greatest cause of geometric image unsharpness

motion

which focal spot size setting yields the highest spatial resolution

small focal spot

increasing the source to image receptor distance has what effect of geometric sharpness

increases sharpness

increasing the object to image receptor distance causes a increase in

image magnification

size distortion on a radiograph is strictly defined as

magnification

shape distortion caused by improper central ray angle or part alignment results in

elongation or foreshortening

the ability of a digital imaging system to distinguish between subtle differences in tissue densities is

contrast resolution

the inherent ability of a digital image receptor system to capture varying exposure levels is termed

image receptor contrast

fluoroscopic imaging is best defined as

real time dynamic evaluation of moving structures

if the central ray is angled perpendicular to the image receptor but angled relative to an inclined anatomical part, what occurs

foreshortening

which factor directly increases subject contrast within patient anatomy

administering high atomic number contrast media

what post- processing function adjusts the overall digital image contrast (grayscale range) on a monitor

window width

a high grid ratio absorbs more scatter radiation than a low grid ratio, which results in

increased image contrast

which technique modification minimizes shape distortion

aligning the tube, part, and IR perpendicular

the bit depth of a digital system directly determines its capability for

contrast resolution

what change increases magnification (size distortion)

increased OID

what type of motion can be controlled through clear patient communication and immobilization

voluntary motion

which interaction increases when higher kVp techniques are selected, leading to decreased subject contrast

Compton scattering

when OID cannot be reduced, which adjustment helps compensate for lost spatial resolution

increase SID

in real time fluoroscopy, the continuous production of dynamic images allows radiographers to observe

anatomical motion and physiological function

The production of x-radiation that occurs in an x-ray tube requires the movement of negatively charged particles traveling from one side of the tube to the other. This movement of charges must occur in:

a vacuum

The x-ray tube component that stops the stream of electrons and produces the x-ray beam is called the:

anode

what is the only way to tell if a digital image has been overexposed or underexposed.

exposure index value

what is a numeric representation of the quantity of exposure received by a digital image receptor.

El