RAD 111 UNIT 4- DIGITAL IMAGE

LATENT IMAGE

DIGITAL DATA THAT MUST BE PROCESSED BY A COMPUTER FOR VIEWING ON A DISPLAY MONITOR (UNPROCESSED)

MATRIX

COMBINATION OF ROWS AND COLUMNS OF PIXELS

PIXEL

SMALLEST COMPONENT OF THE MATRIX

MICRONS

MEASUREMENT OF PIXELS

.01 MM

100 MICRONS = _ MM

Voxel

Volume element of area of tissue on a patient

Pixels (2)

Single numerical value representing a brightness level on a display monitor is recorded as

Location of pixels in the matrix

What corresponds to an area within the patient or volume of tissue

COMPUTED AND DIGITAL RADIOGRAPHY

TYPES OF RADIOGRAPHIC SYSTEMS

INCREASED MATRIX, DECREASED PIXEL SIZE, AND INCREASE NUMBER OF PIXELS (VICE-VERSA)

RELATIONSHIP BETWEEN MATRIX, PIXEL SIZE, # OF PIXELS FOR A FIXED FOV

LARGER MATRIX SIZE WITH GREATER NUMBER OF SMALLER PIXELS

IMPROVED DIGITAL IMAGE QUALITY WITH (MATRIX/PIXELS)

INCREASED (DIRECT)

IF FOV IS INCREASED FOR FIXED MATRIX SIZE, THEN PIXEL SIZE IS _

DECREASED (INVERSE RELATIONSHIP)

IF MATIX SIZE INCREASED FOR FIXED FOV THEN PIXEL SIZE IS

PIXEL SIZE= FOV/ MATRIX SIZE

FORMULA FOR PIXEL SIZE

DECREASED FOV, DECREASED PIXEL SIZE, SAME # OF PIXELS (VICE-VERSA)

RELATIONSHIP BETWEEN FOV, PIXEL SIZE, AND #OF PIXELS IN A FIXED MATRIX SIZE

DIRECT RELATIONSHIP

RELATIONSHIP BETWEEN PIXEL SIZE AND FOV

INVERSE RELATIONSHIP

RELATIONSHIP BETWEEN PIXEL SIZE AND MATRIX SIZE

INCREASE; DECREASE

INCREASING THE FOV FOR THE SAME MATRIX SIZE DOES WHAT TO THE PIXEL SIZE AND SPATIAL RESOLUTION

DECREASE; INCREASE

INCREASING THE MATRIX SIZE FOR THE SAME FOV WILL DO WHAT TO PIXEL SIZE AND SPATIAL RESOLUTION

PIXEL BIT DEPTH

NUMBER OF SHADES OF GRAY THAT CAN BE DISPLAYED BY A PIXEL DUE TO EXIT RADIATION BEING RECORDED AND CONTROLS PIXEL BRIGHTNESS

2^N (N= NUMBER OF PIXELS)

FORMULA FOR NUMBER OF BIT/PIXEL BIT DEPTH

LARGER BIT DEPTH

A BIT DEPTH IS LARGER OR SMALLER IF IT HAS GREATER NUMBER OF SHADES OF GRAY

GREATER (GREATER OIXEL BIT DEPTH)

A _ NUMBER SHADES OF GRAY HAS BETTER CONTRAST RESOLUTION

VISIBILITY OF ANATOMIC DETAILS AND SPATIAL RESOLUTION

AN INCREASED CONTRAST IMAGE HAS GOOD

PIXEL DENSITY

NUMBER OF PIXEL PER UNIT AREA (MM)

PIXEL PITCH

DISTANCE FROM THE CENTER OF A PIXEL TO ANOTHER PIXEL

SMALLER; SMALLER; BIGGER

WHAT PIXEL SIZE, PITCH, & DENSITY CREATES BETTER SPATIAL RESOLUTION

SIZE OF THE PIXEL

SPATIAL RESOLUTION IS LIMITED TO THE

SPATIAL FREQUENCY

WHAT IS MEASURED IN LINE PAIRS PER MILLIMETER (LP/MM)

LINE PAIR

HIGH CONTRAST LINE SEPARATED BY A LINE OF EQUAL WIDTH

DIRECT RELATIONSHIP (INCREASED SPATIAL RESOLUTION AND FREQUENCY)

RELATIONSHIP BETWEEN SPATIAL FREQUENCY AND SPATIAL RESOLUTION

SMALLER, GREATER, GREATER, (VICE-VERSA)

RELATIONSHIP BETWEEN PIXEL SIZE, SPATIAL FREQUENCY, AND SPATIAL RESOUTION

DYNAMIC RANGE

ABILITY OF DETECTOR TO ACCURATELY CAPTURE THE RANGE OF PHOTON INTENSITIES THAT EXIT THE PATIENT

WIDE

A DIGITAL IR HAS A _ DYNAMIC RANGE

WIDE/ MORE GRAYSCALE

WIDE DYNAMIC RANGE IS A _ GRAYSCALE

EXPOSURE LATITUDE

RANGE OF EXPOSURES TECNIQUES THAT SHOULD BE USED TO PRODUCE A DIAGNOSTIC IMAGE WITHOUT UNDER OR OVEREXPOSURE

AIR KERMA

INTENSITY OF X-RAYS AT A GIVEN POINT IN THE IR AT A DISTANCE FROM FOCAL SPOT

KINETIC ENERGY RELEASED IN MATTER

KERMA STANDS FOR

DOSE- AREA PRODUCT (DAP)

MEASURE OF EXPOSURE IN AIR AND ALSO ESTIMATES ABSORBED DOSE TO THE PATIENT

COLLIMATING AND FOV

WHAT FACTORS AFFECT DAP

KERMA AREA PRODUCT

KAP STANDS FOR

KERMA AREA PRODUCT (KAP)

TOTAL AIR KERMA AND THE AREA OF THE X-RAY BEAM AT THE ENTRANCE OF THE PATIENT

DIRECT (SAME THING)

RELATIONSHIP BETWEEN KAP AND DAP

MICRO-MILLI- OR CENTIGRAY PER AREA ^2

DAP AND KAP ARE MEASURED IN WHAT UNITS

MODULATION TRANSFER FUNCTION

WHAT DOES MTF STAND FOR

MODULATION TRANSFER FUNCTION (MTF)

MEASURE OF THE IMAGING SYSTEMS ABILITY TO DISPLAY THE CONTRAST OF ANATOMIC OBJECTS VARYING IN SIZE

MTF= (MAX. INTENSITY- MIN. INTENSITY)/(MAX. INTENSITY+MINIMM INTENSITY)

FORMULA FOR MODULATION TRANSFER FUNCTION

RANGE 0-1; BEST CLOSER TO 1

HOW IS MTF MEASURED; WHATS THE BEST MTF VALUE

LARGE OBJECTS WITH LOW SPATIAL FREQUENCY

A MODULAR TRANSFER FUNCTION IS EASIER TO ACHIEVE WITH

DETECTIVE QUANTUM EFFICIENCY

WHAT DOES DQE MEAN

DETECTIVE QUANTUM EFFICIENCY (DQE)

MEASUREMENT OF THE EFFICIENCY OF AN IMAGE RECEPTOR IN CONVERTING X-RAY EXPOSURE TO A QUALITY RADIOGRAPHIC IMAGE

LOWER; DECREASING

THE HIGHER THE DQE; THE *RAD. EXPOSURE AND* _ PT EXPOSURE

1\.0

100% EFFICIENCY IN DQE OR MTF. IS REPRESENTED A WHAT VALUE

MATERIAL OF IR AND ENERGY OF BEAM

THE FACTORS THAT INFLUENCE THE DETECTIVE QUANTUM EFFICIENCY INCLUDES

DIRECT RELATIONSHIP

RELATIONSHIP BETWEEN DETECTIVE QUANTUM EFFICIENCY AND MODULAR TRANSFER FUNCTION

DIGITAL RADIOGRAPHY

DQE IS HIGHER FOR WHAT RADIOGRAPHY

SIGNAL TO NOISE RATIO

WHAT DOES SNR STAND FOR

SIGNAL TO NOISE RATIO (SNR)

METHOD OF DESCRIBING THE STRENGTH OF RAD. EXPOSURE IN COMPARISON TO THE AMOUNT OF “QUANTUM MOTTLE” APPARENT IN THE DIGITAL IMAGE

SIGNAL

STRENGTH OR AMOUNT OF RAD EXPOSURE CAPTURED BY THE IR TO CREATE AN IMAGE

QUANTUM NOISE

RESULT OF TOO FEW X-RAY PHOTONS CAPTURED BY IR TO CREATE LATENT IMAGE

STRONGER SIGNAL; LESS QUANTUM NOISE (VICE-VERSA FOR LOW)

A HIGH SNR MEANS

Improve; increase (VICE-VERSA)

INCREASING THE SNR WILL *THE QUALITY OF THE DIGITAL IMAGE AND* _ VISIBILITY OF ANATOMIC DETAILS

CONTRAST TO NOISE RATIO (CNR)

METHOD OF DESCRIBING CONTRAST RESOLUTION COMPARED WITH AMOUNT OF “QUANTUM MOTTLE” APPARENT IN A DIGITAL IMAGE

BETTER; INCREASE (VICE-VERSA)

HIGH CNR *_* VISUALIZES TISSUES WITH SIMILAR BEAM ATTENUATION AND _ THE VISIBILITY OF ANATOMIC DETAILS

Image capture and image readout

Two step process for image acquisition

Photostimulable phosphor

What is the iMAGING plate for a CR MADE OF

Computed radiography

A IMAGING PLATE CAN BE FOUND IN

Digital radiography

A flat panel detector can be found in

Digital; computed

What type combines both image capture and readout , what type separates both

LUMINESCENCE

EMISSION OF LIGHT WHEN STIMULATED BY RADIATION

CASSETTE

WHAT HOUSES AN IMAGING PLATE

RADIATION EXITS PT AND INTERACTS WITH IP

First step of CR

Photons absorbed by the phosphor layer of IP

Second step of CR

Energy is released as luminescence and some stored in phosphor for the latent image

Third step of CR

Five

HOW MANY LAYERS IS THE IMAGING PLATE COMPOSED OF

Support layer

STURDY MATERIAL THAT GIVES THE IP SOME RIGIDITY

Conductive layer

Layer that reduces and conducts away static electricity

Reflective layer

Reflects light released during the reading phase toward the photodetector

Soft back-protective layer

Protects back of IP preventing backscatter from fogging the plate during exposure

Barium fluorohalide crystals doped with europium (photostimulable phosphor PSP)

Phosphor layer composed of

Photostimulable luminescence

Visible light stimulated by high-intensity laser beam

Turbid (random) or Structured

Phosphor layer can be

Conduction band

Excited electrons are trapped in the

Released as luminance, create the latent image, releases during laser beam scan

What happens to the electrons that are in an excited stage

SCANNING

First step of digitization

HELIUM-NEON LASER BEAM

WHAT RELEASES STORED ENERGY AS VISIBLE LIGHT ON THE IP

PHOTOMULTIPLIER TUBE (PMT)

WHAT COLLECTS, AMPLIFIES, AND CONVERTS VISIBLE LIGHT INTO AN ELECTRICAL SIGNAL

ANALOG TO DIGITAL CONVERTER THROUGH SAMPLING

SIGNAL FROM PMT IS DIGITIZED BY

MAJOR COMPONENTS OF THE CR READER UNIT

DRIVE MECHANISM, OPTICAL STSTEM, PMT AND ADC ARE ALL COMPONENTS OF

ANALOG TO DIGITAL CONVERTER

WHATS ADC

SAMPLING

CONVERTING ANALOG DATA TO DIGITAL DATA

SAMPLING FREQUENCY

HOW OFTEN ANALOG SIGNAL IS REPRODUCED INTO A DIGITIZED/NUMERICAL FORM

NYQUIST FREQUENCY

FORMULA FOR CONVERTING ANALOG DATA INTO UNITS PRESENTING ANALOG SIGNAL

2X HIGHEST SPATIAL FREQUENCY

SAMPLING RATE FROM ANALOG TO DIGITAL MUST BE MINIMAL _ IN XRAY SIGNAL

ALIASING WAVEFORMS, FORM OF IMAGE ARTIFACT

iF SAMPLING FREQUENCY IS TOO LOW, THEN WHAT IS CREATED

FIXED SAMPLING FREQUENCY

SET __PIXEL SIZE__ DESPITE IR SIZE FOR MAINTAINED SPATIAL RESOLUTION

LARGER MATRIX→ MORE PIXELS

A LARGER IP HAS A _ TO MAINTAIN SAME PIXEL SIZE

FIXED MATRIX SIZE

SAME NUMBER OF PIXELS DESPITE IR SIZE

SMALLEST

WITH A FIXED MATRIX SIZE, THE BEST POSSIBLE SPATIAL RESOLUTION HAS THE _ IR

Quantization

Each pixel is assigned a numerical value controlling the number of shades of gray