Positioning Unit 1

radiographer/technologist

the maker of radiographs

radiologist

MD specifically trained in interpreting and performing radiographic studies; diagnoses the images

radiologist assistant

technologist with specialty training in performing an advanced role in specific radiographic studies; masters level education

lead markers

the correct, legal way to document x-rays; placed directly on image receptor

soft markers

added after image is made, not an equal alternative to lead markers; potential to mismark correct side

image receptor (IR)

object recording the x-rays to help create images

types of image receptors

film, CR cassette, DR receptor, fluoroscopy image intensifier

film receptor

x-rays cause an effect on a piece of film that is then run through a processor to produce the image; film must be replaced to capture a new image

CR (computed tomography) cassette

x-rays cause an effect on a screen inside a cassette which is scanned to produce a digital image; no film to replace, ready to reuse after scanning

DR (direct/digital radiography) receptor

x-rays cause an effect on a screen inside a cassette which is automatically converted into a digital image; IR is connected to a control panel monitor, where the image is immediately available; DR receptors can be built into table or stand, or can be portable

image intensifier (II)

used in fluoroscopy and viewed on a monitor; can be videos, still images, or runs (rapid stills)

image archives

where images are stored

PACS

electronic image archive system, used for storage, retrieval, and distribution; stands for Picture Archiving & Communications System

radiation protection standard

As Low As Reasonably Achievable (ALARA); keep radiation exposure as low as possible while still providing good diagnostic images

lead aprons

protect tech from radiation scattering off of patients; protect radiation-sensitive parts on patients

which radiation-sensitive parts have shields?

gonads, thyroid, breasts

dosimetry badges

worn on collar to monitor occupational exposure (on outside of aprons)

3 cardinal rules of radiation protection

time, distance, shielding

anatomical position

upright, facing observer, palms and feet forward; standard position; all references are as if patient is in anatomical position

anterior (ventral)

to/toward the front half of patient

posterior (dorsal)

to/toward the back half of the patient

superior

above/higher (used for trunk of body)

inferior

below/lower (used for trunk of body)

proximal

closer to the root of the limb (where it attaches to the trunk of the body)

distal

further from the root of a limb (where it attaches to the trunk of the body)

what are the preferred terms for extremities?

proximal/distal

internal

toward the center/inward

external

away from the center/outward

what movements can have interchangeable terms?

medial/internal, lateral/external

what terms are used for relativity?

anterior-posterior, superior-inferior, medial-lateral, proximal-distal

cephalad

direction of the head (toward the head)

caudad

direction of the feet (toward the feet)

superficial

nearer the skin surface

deep

farther away from the surface

interior

inside or nearer to the center

exterior

situated on or near the outside

plantar

refers to the sole (bottom) of the foot

dorsum

refers to the top of the foot or the back of the hand

palmar

refers to the palm of the hand

recumbent

lying down in ANY position

supine

lying on the back

prone

lying face down

lateral

lying on side; name of position (L/R) is the side closest to IR

oblique

a position that is neither a straight-on AP/PA, prone/supine, or lateral-intentional rotation; named for the surfaces in contact with the IR

Trendelenburg

recumbent with head lower than feet

Fowler’s position

recumbent with head higher than feet

semi-Fowler’s

not as head-up as Fowler’s

Sim’s position

recumbent, LAO/oblique on left anterior side, right knee flexed; used for enema tip insertion

lithotomy position

recumbent (supine), knees and hips flexed, thighs abducted and rotated externally

PA

Posterior → Anterior; central ray (CR) enters the posterior and exits the anterior

AP

Anterior → Posterior; CR enters the anterior and exits the posterior

mediolateral

CR enters medial side and exits lateral side

lateromedial

CR enters lateral side and exits medial side

axial projection

angled CR; cephalic or caudal

tangential projection

CR skims the surface of desired anatomy

rotation of extremity from anatomic position

medial/internal rotation, lateral/external rotation

supination

rolling the hand toward palm forward/up

pronation

rolling the hand toward palm back/down

adduction

move together

abduction

move apart

flexion

bending

extension

stretching

dorsiflexion

toes up

plantarflexion

toes down (pointed)

eversion

foot rolled outward

inversion

foot rolled inward; “rolling the ankle”

planes

hypothetical 2D surface that passes through the body

sagittal plane

plane dividing the body into left and right parts

midsagittal plane

plane dividing the body into EQUAL left and right parts/halves

coronal plane

plane dividing the body into anterior and posterior parts

midcoronal plane

plane midway between anterior and posterior surfaces

axial/transverse plane

plane dividing the body into superior and inferior parts

kVp

kilovoltage peak

low kVp

high contrast (image is very black and white)

high kVp

low contrast (image has more shades of gray)

mAs

milliamperage seconds

automatic exposure control (AEC)/phototimer

only on Buckys; photocells in table/upright that stop exposure when enough x-rays have penetrated the patient; *controls the TIME of exposure*

photocells

cells can be turned on/off, cells measure appropriate exposure through the region of interest

mA

the amount of x-rays coming out of the machine at any moment; intensity/density of image; affects how long it will take to produce sufficient x-rays to make the image

high mA=

shorter exposure time; less motion/blurring

what controls the *quantity* of xrays?

mAs

seconds (s)

measurement of time; more time = more x-ray photons released; usually less than a second, and frequently shown in milliseconds (ms)

what will affect the amount of x-rays needed (mAs)?

the body part and patient size

density

adjust the amount of exiting x-rays (photons) needed to terminate the exposure

density +/-

AEC/phototimer ONLY; exposure will terminate when less or more than normal amount of x-rays reach the cells

small focal spot

for details (finger, wrist, nasal bones), lower mA, lower total output, longer exposures

large focal spot

for output (chest, abdomen, pelvis), large total exposure with low exposure time to minimize motion blurring; less detail compared to small focal spot

SID

Source to Image Distance (x-ray tube to IR); either 40” or 72”

collimation

limits size of area being exposed to only what is needed