Quality Control. HIGH QUALITY FILMS REPRODUCES ANATOMICAL IMAGE EXACTLY FILM HAS: CORRECT TECHNICAL...

Quality Control

HIGH QUALITY FILMS

REPRODUCES ANATOMICAL IMAGE EXACTLY

FILM HAS: CORRECT TECHNICAL FACTORS NO MOTION NO ARTIFACTS PROCESSED CORRECTLY

RESOLUTION

ABLE TO VISUALLY SEPARATE OBJECTS

BONE VS. TISSUE-- IE: SPATIAL RESOLUTION CR VS CONVENTIONAL FILM

DIFFERENCES BETWEEN DIFFERENT TISSUES-- IE: CONTRAST RESOLUTION CR VS. CONVENTIONAL FILM

NOISE

FILM GRAININESS (INHERENT) SIZE OF FILM CRYSTALS

STRUCTURE MOTTLE (INHERENT), PHOSPHOR IN SCREEN

QUANTUM MOTTLE

QUANTUM MOTTLE

LOW NUMBER OF X-RAY PHOTONS INTERACTING WITH SCREEN. INSUFFICIENT AMOUNT OF PHOTONS STRIKING INTENSIFYING SCREEN CAUSING AN INSUFFICIENT LIGHT TO EMIT FROM PHOSPHOR CRYSTALS.

How do we adjust technique for this? CR and Quantum Mottle

SPEED

FILM’S ABILITY TO RESPOND TO X-RAY EXPOSURE

IF FILM “A” RECORDS MORE DENSITY SOONER THAN FILM “B”, WHICH FILM HAS A HIGHER SPEED?

A

SENSITOMETRY

MEASUREMENT OF SENSITIVITY TO LIGHT AND THE FILM’S RESPONSE TO CHANGES IN TECHNIQUE AND PROCESSING.

DENSITOMETRY

MEASUREMENT OF THE DENSITY OF THE FILM BASED ON THE PERCENTAGE OF LIGHT TRANSMITTED THROUGH THE FILM.

ANATOMY OF A CHARACTERISTIC(H & D CURVE)

OVERHEADS!!!!!!!

RECIPROCITY LAW

OD REMAINS THE SAME NO MATTER THE LENGTH OF EXPOSURE

100 mA X 1 sec = 100 mAs ↓↓

200 mA X .5 sec= 100mAs ↓↓

400 mA X .25 sec =100mAs →→same OD 500 mA X .2 sec = 100mAs ↑↑ Applicable to direct screen exposures

RECIPROCITY LAW FAILURE

FILM/SCREEN RADIOGRAPHY EXPOSURE TIMES LESS THAT 10

MILLISECONDS EXPOSURE TIMES GREATER THAN

5 SECONDS INTERVENTIONAL STUDIES MAMMOGRAPHY

RADIOGRAPHIC CONTRAST

IMAGE RECEPTOR CONTRAST

PLUS

SUBJECT CONTRAST

IMAGE RECEPTOR CONTRAST

Formerly known as film contrast. Why the change in name?

Inherent to film Affected by processing

SUBJECT CONTRAST

SIZE SHAPE X-RAY ATTENUATION OF THE

ANATOMY AND ENERGY OF BEAM

REVIEW

L ATITUDE (REMEMBER THIS IN REFERENCE TO THE FILM)

W I D E LATITUDE = LOOOOONNNNG GRAY AKA LOW OR LONG SCALE CONTRAST

NARROW LATITUDE = SHORT SCALE =HIGH CONTRAST

WIDE LATITUDE FILM, BECAUSE OF LONG GRAY SCALE ALLOWS AS MUCH AT 15% ERROR BY RADIOLGRAPHER

MAGNIFICATION FACTORS

MOST IMAGES ARE LARGER ON RADIOGRAPH THEN IN ACTUALITY DUE TO SID AND SOD!

FOR EVERY 1” INCREASE IN OID, SID MUST BE INCREASED BY 7” TO COMPENSATE FOR MAGNIFICATION

SID AND SOD?

SID: SOURCE TO IMAGE DISTANCE

SOD: SOURCE TO OBJECT DISTANCE

MAG. FACTOR IMAGE SIZE OR SID OBJECT SIZE SOD

TO FIND SOD SUBTRACT THE OID FROM THE SID

IF YOU COULD MEASURE A HEART AND IT MEASURED 12.5 CM BUT ON THE RADIOGRAPH IT MEASURED 14.7 CM, THE MAGNIFICATION FACTOR WOULD BE CALCULATED AS 14.7 DIVIDED BY 12.5 WHICH EQUALS A MAGNIFICATION FACTOR OF 1.17.

WAYS TO DECREASE MAGNIFICATION

IF OID IS INCREASED? INCREASE SID! CHEST LATERAL AND OBLIQUE C-SPINE

DISTORTION

Foreshortening Object at an angle and CR is perpendicular

to the part that is angled-trauma elbow Spatial

Tube is angled to separate body parts Clavicle

Elongation object is parallel but tube is angled sigmoid

FOG LEVEL/CONTRAST AND THE PROCESSOR

As time extends in the developing process the fog level____(toe of the characteristic curve) and the contrast____

increases decreases

90 seconds is the optimal developer time

A variation of 5 seconds either way can affect quality of film.

Developer temperature

As the temperature increases the fog level______

increases optimum temperature is usually 90

degrees F.

SUBJECT CONTRAST

Review: Rad. Contrast=film contrast plus

subject contrast film contrast is controlled latitude of

film, and processing factors

Subject contrast

Patient (Size) Tissue (KUB) Atomic # ( higher

produces high contrast)

object shape

MOTION

PATIENT TUBE MOVEMENT

TOMOGRAPHY

MOTION

LARGE SID = LESS FOCAL SPOT BLUR

SMALL SID = MORE FOCAL SPOT BLUR

FOCAL SPOT BLUR

KVP

GIVES ELECTRONS ENERGY TO HIT THE ANODE

HIGH AMOUNT OF KINECTIC ENERGY IN AN ELECTRON PRODUCES A HIGHLY ENERGIZED X-RAY PHOTON

BETTER PENETRATION=LOTS OF GRAYS

KVP

LOW KVP PRODUCES A BLACK AND WHITE IMAGE.

TO PRODUCE AN ADEQUATE OD MUST USE HIGHER MAS

HIGHER MAS MEANS MORE EXPOSURE TO THE PATIENT

HIGH KVP HIGH MAS

+Greater margin of error

+Reduction in patient dose

+Wider latitude -increase scatter -increase fog

+Higher OD +Lower Rad noise -increased pt.

Exposure -less margin of

error

The Radiographer controls

kVp mAs focal spot size distance added filtration screen speed

REMEMBER

200 mA increased to 300mA is a 50% increase in electrons being produced

As mA increases, time must decrease to maintain same density

Distance Maintenance formula--New Sid over Old Sid Squared

REMEMBER

Small mA station uses smaller focal spot

smaller focal spot = more detail Inherent = .5 mm additional 2 mm of aluminum between

housing and collimator collimator adds 1 mm