Study Guide 2 - Radiographic and Fluoroscopic Equipment

efficacy

capacity for producing a desired result or effect; effectiveness

yield

the quantity or amount given forth or produced

diagnostic efficacy

•the accuracy with which a diagnostic study reveals the patient’s medical condition

diagnostic yield

the amount of clinically useful medical information about the patient

Why is it important for you to develop skills in equipment manipulation?

will maximize diagnostic yield (and efficacy) yet keeping patient risks as low as possible

What are the basic design features of all x-ray systems?

–X-ray tube and support system

–Collimator assembly

–X-ray table

–X-ray generator

–Control console

- Upright image receptor holder device

Describe the x-ray tube. What is its function? What is it made of? What are the

major components?

–Produces x-rays

–Made of Pyrex glass encased in a lead-lined, metal housing

–Major components:

•Cathode –

–mA is applied to tungsten filament causing thermionic emission; kV is applied to move electrons from anode to cathode

•Anode +

–Electrons strike rotating tungsten anode and produce x-rays (1%) and heat (99%)

Describe the collimator assembly. What is its function?

–Houses collimator

–Allows for manipulation of the x-ray tube

•Includes:

–Source-to-image distance (SID) indicator; either digital or tape measure or both

–Angulation scale (goniometer)

–Tube locks

–Misc. controls (i.e. bucky selector, kVp, mAs, etc.)

What is the tape measure for under the collimator assembly?

SID indicator

What does SID stand for? What is it? What are some common SID’s?

–Source-to-image distance (SID) indicator; either digital or tape measure or both

Describe the collimator. What is its function? What are the major components?

–Controls the size and shape of the x-ray field coming out of the x-ray tube

•Two controls on the front/side, one for length and one for width

–Increasing collimation or “coning down” refers to making the the light field/radiation field smaller

•Includes a high-intensity light bulb and a mirror that projects a light field onto the patient representative of the x-ray field exposure area

–Light bulb can get hot

–A Plexiglas “shadow shield” on the underside projects cross hairs onto the patient indicating the beam’s central point; may also project position of AEC chambers

•Some units include positive beam limitation (PBL)

–A sensor that allows the x-ray unit to detect the size of the image receptor and automatic collimation to that size

What is the purpose of the light field produced by the collimator assembly? What

is the purpose of the cross hairs projected from the collimator?

•that projects a light field onto the patient representative of the x-ray field exposure area

–cross hairs onto the patient indicating the beam’s central point; may also project position of AEC chambers

What does PBL stand for and what is it?

•include positive beam limitation (PBL)

–A sensor that allows the x-ray unit to detect the size of the image receptor and automatic collimation to that size

Describe the radiographic table. What is its function? What is it made of?

–Holds the patient

–Tabletops are made of radiolucent materials

–Several different types:

•Tilting/nontilting

–90-90; 90-45

•Free-floating/stationary

–Releasing locks allows for movement; direction of movement is determined by which lock is released

–Tops may also be motorized

–Must verify that patient’s hands are on the tabletop and not gripping the table

•Adjustable height/nonadjustable height

–Will include Bucky mechanism beneath tabletop

•Holds image receptor and houses reciprocating grid

•Must be locked into place in the center of the table; tube must be aligned

•Can move the length of the table

What is a stationary/fixed vs. floating tabletop? How does a floating tabletop

work?

•Free-floating/stationary

–Releasing locks allows for movement; direction of movement is determined by which lock is released

–Tops may also be motorized

–Must verify that patient’s hands are on the tabletop and not gripping the table

Describe the Bucky tray. What is its function?

•Holds image receptor and houses reciprocating grid

•Must be locked into place in the center of the table; tube must be aligned

•Can move the length of the table

Describe anti-scatter grid. What is its function? What is it made of? Where is it

located in the table and the wall stand?

designed to limit the amount of scattered radiation that reaches the x-ray detector. Lead and radiolucent materials. between the patient and the x-ray detector or film.

What does AEC stand for and what is it?

•Automatic exposure controls - automatically adjusts the exposure of radiation to the patient

Describe the control panel. What is its function?

–Electrical interface between the operator and the equipment

–Key features of control consoles:

•On and off

•Selection of x-ray exposure factors

–kVp

–mA

–Timer

•Initiate and terminate exposure

–Rotor/exposure switch

Audible and visual indication of x-ray exposure

What are the five generic controls on all control panel?

•On and off

•Selection of x-ray exposure factors

–kVp

–mA

–Timer

•Initiate and terminate exposure

–Rotor/exposure switch

•Audible and visual indication of x-ray exposure

What elements comprise “technique selection”?

AEC, kVp, mA, timer

What is the purpose of the “power switch”?

control the flow of current to the x-ray tube

What does kVp stand for and what does it control?

peak kilovoltage - control image quality and patient dose

What does mA stand for and what does it control?

milliamperes - the current used to generate x-rays in the x-ray tube

Describe the rotor-exposure switch?

one of the key features of the control console. Initiate and terminate exposure

Compare and contrast the various x-ray tube support designs. What is the most

versatile type?

•Floor-mounted tubestands

–Typically found in clinical settings

–Consists of a vertical column that runs along a longitudinal rail mounted to the floor

–Somewhat limited in movement

•Ceiling-suspended overhead tubecranes (OTC)

–Standard of care in hospitals and large clinics

–Most sophisticated design but are costly

–Consists of a rigid rail in the ceiling attached to overhead x-ray tube suspension

Very versatile

Describe something that is radiolucent. Describe something that is radiopaqe.

x-ray table

bones

Describe the different types of x-ray tube movement; longitudinal,

transverse/lateral, vertical, angulation.

–Longitudinal- the length of the patient (head to foot)

–Transverse/lateral- across the patient (right to left)

–Vertical- up and down

–Angulation- rotation of the tube

–Pivot- movement of the tube around an axis

Describe the wall stand. What is its function?

–Allows technologist to obtain upright images of the patient

–Usually a wall-mounted Bucky, however can also be a simple wall-mounted cassette holder

–Can move the length of the rail system to adjust for differing patient heights

What are three things that must be in alignment for any radiographic study?

–X-ray tube

–Patient/body part

–Image receptor

What is a detent?

lock in the ceiling that locks in place when tube and bucky are aligned

Historically, what has been the medium of choice for recording radiographic

images?

•Film-Screen Systems (cassette-based)

Computed radiography (CR) uses what type of medium to record radiographic

images?

•Uses a reusable imaging plate coated with a photostimulable phosphor (barium fluorohalide) encased in a light-tight cassette

What are the two major types of digital radiography (DR) and what is the major

difference?

–Indirect

•Uses scintillator (cesium iodide or gadolinium oxysulfide) and a semiconductor material (amorphous silicon)

•Process

–X-rays strike scintillator which emits light

–Light is absorbed by semiconductor which converts the light into electrons and eventually electronic signal

–Direct

•Uses a semiconductor material (amorphous selenium)

–X-rays strike semiconductor which converts x-rays directly into electrons and eventually electronic signal

What kind of image does fluoroscopy produce

dynamic action of the human body in real time

During fluoroscopy, where and how are images viewed?

image intensifier or flat panel detector attached to a carriage platform and a fluoroscopic tube; a fluoroscopic drape for radiation protection purposes; and a flat-screen t.v. monitor

Why are mobile units necessary?

allows for mobile radiography in all departments (ER, OR, ICU, etc.) when patients aren’t stable enough to travel to the radiology department

What are two main types of mobile radiographic units?

radiographic or fluoroscopic

Why is the exposure control on a mobile unit on the end of a coiled wire?

to allow for maximum distance during exposure

What is a “C-arm”?

radiography option used mainly for surgeries that is shaped like a C