oct.2013 c.r

Digital RadiographyDigital Radiography

Understanding Digital Understanding Digital Radiography PrinciplesRadiography Principles

Dr. Hussein Ahmed Hassan

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Original

Purpose: Basic AnswersPurpose: Basic Answers

What is digital radiography?What is digital radiography? What components are required?What components are required? What types of digital radiography work best in What types of digital radiography work best in

practice?practice? How do we choose the right solution for our How do we choose the right solution for our

program?program? What are the computer and networking What are the computer and networking

requirements to support our digital solution? requirements to support our digital solution?

What is Digital Radiography?What is Digital Radiography?

Sensors or phosphor plates Sensors or phosphor plates take the place of traditional take the place of traditional film.film.

Radiographic images are Radiographic images are acquired almost instantly acquired almost instantly and stored electronically.and stored electronically.

They can be manipulated, They can be manipulated, viewed, and transferred with viewed, and transferred with a software program.a software program.

What Components are required for What Components are required for Digital Radiography?Digital Radiography?

Sensors or phosphor plates to replace x-ray film.Sensors or phosphor plates to replace x-ray film. Imaging software that allows image storage and Imaging software that allows image storage and

management.management. Computer system to run imaging software.Computer system to run imaging software. Optional: Practice management software –for Optional: Practice management software –for

completely paperless patient records completely paperless patient records management.management.

Digital RadiographyDigital Radiography Is a form of x-ray imaging, where digitalIs a form of x-ray imaging, where digital

X-ray sensors are used instead of traditional sensors are used instead of traditional photographic film.photographic film.

Advantages include;Advantages include;

1.1. Time efficiency through bypassing chemical Time efficiency through bypassing chemical processing processing

2.2.The ability to digitally transfer and enhance images. The ability to digitally transfer and enhance images.

3.3.Less radiation can be used to produce an image of Less radiation can be used to produce an image of similar contrast to conventional radiography.similar contrast to conventional radiography.

http://en.wikipedia.org/wiki/X-ray

Digital methods for processing and displaying x-ray images Digital methods for processing and displaying x-ray images were first introduced with the advent of computed tomography were first introduced with the advent of computed tomography (CT) in 1972. (CT) in 1972.

Digital Imaging Technology

Continuing advances in computer technology have promoted the general development of image acquisition in digital form (CCD cameras), most commonly from image intensifiers (digital fluoroscopy) or from storage phosphor plates (computed radiography).

Other detector systems such as ‘flat-panel’ technology for indirect or direct digital radiography are now available for general purpose equipment.

Capture technologies used today:

• Screen/film (S/F) combination system

• Computed radiography (CR) with storage phosphors

• Image intensifiers

• Direct Digital radiography (DDR)

Image AcquisitionImage Acquisition

Conventional X-rayConventional X-ray

fixer water

water

developer

Drying

X-ray

Image Acquisition in Digital ImagingImage Acquisition in Digital Imaging There are a number of technologies used for There are a number of technologies used for

digital imaging in planar radiography these are;digital imaging in planar radiography these are;

1. Computed radiography (CR), 1. Computed radiography (CR), CRCR in first in first appearance, similar to the used of film/screen appearance, similar to the used of film/screen system. The CR plate is in a cassette, which system. The CR plate is in a cassette, which will fit the table and vertical Backy trays and will fit the table and vertical Backy trays and can be used with mobile equipment. The plate can be used with mobile equipment. The plate is then scanned in a reading system, this make is then scanned in a reading system, this make the change to the change to computed radiography (CR) computed radiography (CR) easier. easier.

Image Acquisition Image Acquisition CRCR

X-ray TubeLatent image Readout Photomultiplie

r

Workstation

Erasure

Fluorescent Lamp

IP Ready

ADC

2.Direct Digital 2.Direct Digital Means, instead of using x-ray film, a Means, instead of using x-ray film, a

sensor connects directly to your sensor connects directly to your computer - the x-ray image displays computer - the x-ray image displays almost immediately after taking it.almost immediately after taking it.

Sensors use either a Sensors use either a Charge Coupled Charge Coupled DeviceDevice (CCD (CCD), or a ), or a Complementary Complementary Metal Oxide SemiconductorMetal Oxide Semiconductor (CMOS) (CMOS) or or thin-film transistor (TFT) thin-film transistor (TFT) to convert to convert light into electrons. These are light into electrons. These are collected & turned into pixels that collected & turned into pixels that show brightness and contrast - that’s show brightness and contrast - that’s what makes a digital x-ray image. what makes a digital x-ray image.

You still use your regular x-ray You still use your regular x-ray machine to take the exposure. machine to take the exposure.

Both CCD sensors, CMOS sensors Both CCD sensors, CMOS sensors and TFTwork extremely well.and TFTwork extremely well.

Direct Digital Radiography --cot----Direct Digital Radiography --cot----

Direct Digital Radiography (DDR), Direct Digital Radiography (DDR), DDR DDR system needs more changes in x-ray couch system needs more changes in x-ray couch and vertical backy design and often and vertical backy design and often changes to x-ray tube assembly, DR changes to x-ray tube assembly, DR detector is fully integrated into exposure detector is fully integrated into exposure equipment. The patient is radiographed and equipment. The patient is radiographed and the image appears on workstation in few the image appears on workstation in few seconds. Here image optimized and then seconds. Here image optimized and then sent for reporting or repeated if necessary.sent for reporting or repeated if necessary.

Image Acquisition DRImage Acquisition DR

X-ray Tube

Workstation

Detectors (TFT)

1.X-ray scintillator bonded to readout ray, thin-film transistor (TFT)

• Absolutely nothing !!!!

• Still the “gold standard” to which all new projection radiography systems are measured against

• The choice of technology depends on clinical, technical, operational and economic factors

Why do we need a new technology, what is wrong with film/screen?

• On many accounts (e.g.: mammography) , S/F is still superior than some new technologies (e.g.: CR)

Uses Digital RadiographyUses Digital Radiography CR is used in all areas where film/screen systems CR is used in all areas where film/screen systems

are currently used, including mammography.are currently used, including mammography. Direct Digital Radiography (DDR) can be used in Direct Digital Radiography (DDR) can be used in

general radiography and mobile radiography.general radiography and mobile radiography. DDR is very popular in small-field mammography DDR is very popular in small-field mammography

and being introduced into full-field mammography.and being introduced into full-field mammography. DDR detectors are now being used instead of DDR detectors are now being used instead of

image intensifiers in fluoroscopy. image intensifiers in fluoroscopy.

Computed RadiographyComputed Radiography What is it?What is it?

Computed Radiography, commonly known as CR, is a Computed Radiography, commonly known as CR, is a

digital radiography process that is designed to replace digital radiography process that is designed to replace

industrial radiographic filmindustrial radiographic film

The CR process is very similar to the process associated The CR process is very similar to the process associated

with film … mainly because of the film-like digital detector with film … mainly because of the film-like digital detector

that is used to capture the radiographic imagethat is used to capture the radiographic image

The CR film-like digital detector is a flexible phosphor The CR film-like digital detector is a flexible phosphor

screen that looks and feels a lot like filmscreen that looks and feels a lot like film

CR Cassettes

Storage phosphor (SP) screens are similar in structure to conventional intensifying screens

Computed RadiographyComputed Radiography

Storage Phosphor Storage Phosphor Digital X-ray Imaging SystemsDigital X-ray Imaging Systems

Computed RadiographyComputed RadiographyHow does it work?How does it work?

Step 1:Step 1: The phosphor screen is inserted into a The phosphor screen is inserted into a

soft or hard cassette (with or without lead)soft or hard cassette (with or without lead)

Step 2:Step 2: A radiation pattern is exposed on the phosphor screen A radiation pattern is exposed on the phosphor screen

creating a latent imagecreating a latent image

Step 3:Step 3: The phosphor screen is then inserted The phosphor screen is then inserted

into a phosphor scanner to be readinto a phosphor scanner to be read

Step 4:Step 4: The phosphor screen is scanned and the digital The phosphor screen is scanned and the digital

image is displayed on the workstation image is displayed on the workstation

monitor for review and evaluationmonitor for review and evaluation

Step 5:Step 5: The phosphor screen is then erased and ready to The phosphor screen is then erased and ready to

be reusedbe reused

Computed Radiography System ProcessComputed Radiography System Process

DifferencesDifferences between Phosphor & Filmbetween Phosphor & Film

Step 1:Step 1: The phosphor screen is inserted into a soft or hard The phosphor screen is inserted into a soft or hard

cassette (with or without lead screens)cassette (with or without lead screens)

Do not need a light-tight darkroom for phosphor imagingDo not need a light-tight darkroom for phosphor imaging



Phosphor is faster and much more forgiving (wide latitude)Phosphor is faster and much more forgiving (wide latitude)

Step 3:Step 3: The phosphor screen is then inserted into a phosphor The phosphor screen is then inserted into a phosphor

scanner to be read scanner to be read No chemical.No chemical.

Film processor (8 minutes) vs. Phosphor (1 to 2 minutes)Film processor (8 minutes) vs. Phosphor (1 to 2 minutes)

Step 4:Step 4: The phosphor screen is scanned and the digital image is The phosphor screen is scanned and the digital image is

displayed on the workstation monitor for reviewdisplayed on the workstation monitor for review

Digital image can be enhanced increasing ODDigital image can be enhanced increasing OD

Step 5:Step 5: The phosphor screen is then erased and ready to be reused The phosphor screen is then erased and ready to be reused

The phosphor screens are reusableThe phosphor screens are reusable

Computed Radiography System ProcessComputed Radiography System Process

SimilaritiesSimilarities between Phosphor & Filmbetween Phosphor & Film

Step 1:Step 1: The phosphor screen is inserted into a soft or hard The phosphor screen is inserted into a soft or hard

cassette (with or without lead screens)cassette (with or without lead screens)

Just like filmJust like film



Shot set-up and technique are basically the same Shot set-up and technique are basically the same

Step 3:Step 3: The phosphor screen is then inserted into a phosphor The phosphor screen is then inserted into a phosphor

scanner to be readscanner to be read

Very similar to film being put into a film processorVery similar to film being put into a film processor

Step 4:Step 4: The phosphor screen is scanned and the digital image The phosphor screen is scanned and the digital image

is displayed on the workstation monitor for reviewis displayed on the workstation monitor for review

Film is put on a lightbox to view Film is put on a lightbox to view

Step 5:Step 5: The phosphor screen is then erased and ready to be The phosphor screen is then erased and ready to be

reusedreused

Computed Radiography SystemComputed Radiography SystemComponents OverviewComponents Overview

Computed Radiography SystemComputed Radiography Systemconsists of the following components:consists of the following components:

WORKSTATION PHOSPHOR PHOSPHOR WORKSTATION PHOSPHOR PHOSPHOR

& SOFTWARE SCANNER SCREENS& SOFTWARE SCANNER SCREENS

& ERASER& ERASER

Computed Radiography SystemComputed Radiography System

Workstation and SoftwareWorkstation and Software

Computed Radiography SystemComputed Radiography SystemWorkstation andWorkstation and SoftwareSoftware

Operates the Phosphor ScannerOperates the Phosphor Scanner Manages your images and Manages your images and

associated data: associated data: drawings, worddrawings, word

documents, digital photos, procedures,documents, digital photos, procedures,

reference images, techniques, etc.reference images, techniques, etc.

Image enhancement capabilities:Image enhancement capabilities:

zoom, gray-scale manipulation, pan & scroll,zoom, gray-scale manipulation, pan & scroll,

density & measurements tools (histograms, point profiles, line density & measurements tools (histograms, point profiles, line profiles, line and area measurements), image processing, profiles, line and area measurements), image processing, annotation, etc.annotation, etc.

Ability to save and archive your digital images and Ability to save and archive your digital images and associated dataassociated data


Phosphor ScannersPhosphor Scanners

Two different types of Phosphor ScannersTwo different types of Phosphor Scanners

CR TowerCR Tower

Table-top Table-top CR100 CR100

Computed Radiography SystemsComputed Radiography Systems

Computed Radiography SystemComputed Radiography System(Table-top Unit)(Table-top Unit)

consists of the following components:consists of the following components:


& SOFTWARE SCANNER SCREENS& SOFTWARE SCANNER SCREENS Phosphor Screen is placedPhosphor Screen is placed

directly into the scannerdirectly into the scanner

Computed Radiography SystemComputed Radiography System(CR Tower Free-Standing Unit)(CR Tower Free-Standing Unit)

consists of the following components:consists of the following components:


& SOFTWARE SCANNER SCREENS& SOFTWARE SCANNER SCREENS

Hard-cassetteHard-cassette

based systembased system

rotating mirror

PMT

light-guide

He-Ne laser

storage phosphor plate

Phosphor ScannersPhosphor Scanners How is the phosphorHow is the phosphor screen scanned?screen scanned?

Overall mechanism


Phosphor Imaging ScreensPhosphor Imaging Screens

and customized Cassettesand customized Cassettes

Computed RadiographyComputed Radiography

Phosphor ScreensPhosphor Screens Manufactured in similar sizes as filmManufactured in similar sizes as film Utilizes the same cassettes as film Utilizes the same cassettes as film Utilizes the same x-ray sources as film Utilizes the same x-ray sources as film Set-up in the field is the same as filmSet-up in the field is the same as film Typically faster exposures than filmTypically faster exposures than film Very wide latitude which makes it much Very wide latitude which makes it much

more forgiving than film / less reshotsmore forgiving than film / less reshots No chemicals required for processingNo chemicals required for processing Image quality good match for aircraft Image quality good match for aircraft

applicationsapplications

PSP- PhotoStimulated PhosphorPSP- PhotoStimulated Phosphor

Reusable plastic plate Reusable plastic plate coated with phosphorcoated with phosphor

It stores the energy of It stores the energy of the remnant x-ray - x-the remnant x-ray - x-ray photons excites the ray photons excites the electrons in the electrons in the phosphor. phosphor.

Laser scanning - the Laser scanning - the trapped electrons are trapped electrons are released - released - photostimulated photostimulated luminescenceluminescence

The emitted light is The emitted light is detected by detected by photomultiplier tube, photomultiplier tube, and is digitized to form and is digitized to form an imagean image

Computed Radiography How is the phosphor screenmanufactured (very similar to film)?

phosphorlayer

protectivelayer

substratephosphorgrains

Computed Radiography Technology The active phosphor layer of a CR plate usually comprises a layer of europium-doped barium fluorobromide, which is coated on to a semi-rigid or flexible polyester base.

phosphorlayer

protectivelayer

substratephosphorgrains

X-ray photons are absorbed by the phosphor layer, the phosphor electron become excited and raised to high energy level, where they can stay trapped in semi-stable high energy state.The trapped electron represent a latent image in the phosphor plate in form of stored energy. The stored energy is released by adding energy to the trapped electrons.This done by stimulation with laser beam, the trap electrons then escapefrom the traps to fall back to their equilibrium state.

As the electrons fall back, the electrons release energy in form of light.This phenomenon is known as photostimulable luminescence (PSL).The emitted light intensity is proportional to original x-ray intensity.The light energy detected and signal is digitized and processed digitally to produce a visible diagnostic radiograph on a monitor.The phosphor plate is then erased with a bright white light to remove any remaining trapped electrons, and the plate is then ready for the next examination.

Computed Radiography Technology---cot----

DDirected irected DDigital igital RRadiographyadiography

(DDR)(DDR)

Directed digital radiography, aDirected digital radiography, a

term used to describe totalterm used to describe total

electronic imaging capturing.electronic imaging capturing.

Eliminates the need for an Eliminates the need for an image plate altogether.image plate altogether.

Amorphous Selenium detector technology for DR Direct Radiography

IMAGE CAPTUREIMAGE CAPTURE

CRCR– PSP – photostimulable phosphor platePSP – photostimulable phosphor plate– REPLACES FILM IN THE CASSETTEREPLACES FILM IN THE CASSETTE

DR – NO CASSETTE – PHOTONSDR – NO CASSETTE – PHOTONS– CAPTURED DIRECTLY CAPTURED DIRECTLY – ONTO A TRANSISTOR ONTO A TRANSISTOR – SENT DIRECTLY TO A MONITORSENT DIRECTLY TO A MONITOR

Densities of the IMAGEDensities of the IMAGE

The light is proportional to The light is proportional to amount of light received amount of light received

digital values are then equivalent digital values are then equivalent (not exactly the same) to a value (not exactly the same) to a value of optical density (OD) from a of optical density (OD) from a film, at that location of the imagefilm, at that location of the image

CR VS DRCR VS DR

– CR -CR -Indirect captureIndirect capture where the image where the image is first captured on plate and stored = is first captured on plate and stored = then converted to digital signalthen converted to digital signal

– DDRDDR -Direct capture -Direct capture where the image is where the image is acquired immediately as a matrix of acquired immediately as a matrix of pixels – sent to a monitorpixels – sent to a monitor

DIRECT RADIOGRAPHYDIRECT RADIOGRAPHY

uses a transistor receiver (like bucky)uses a transistor receiver (like bucky) that captures and converts x-ray energythat captures and converts x-ray energy directly into digital signal directly into digital signal seen immediately on monitor seen immediately on monitor then sent to PACS/ printer/ other then sent to PACS/ printer/ other

workstations FOR VIEWINGworkstations FOR VIEWING

CR vs DRCR vs DRCR CR imaging plate imaging plate

processed in a Digital processed in a Digital Reader Reader

Signal sent to computerSignal sent to computer

Viewed on a monitorViewed on a monitor

DRDR transistor receiver (like transistor receiver (like

bucky)bucky)

directly into digital directly into digital signal signal

seen immediately on seen immediately on monitor – monitor –

ADVANTAGE OF CR/DRADVANTAGE OF CR/DR

Can optimize image quality Can optimize image quality by by manipulatingmanipulating digital data digital data to improve visualization of anatomy to improve visualization of anatomy

and pathologyand pathology AFTER EXPOSURE TO PATIENTAFTER EXPOSURE TO PATIENT

ADVANTAGE OF CR/DRADVANTAGE OF CR/DR

CHANGES MADE TO IMAGECHANGES MADE TO IMAGE

AFTER THE EXPOSUREAFTER THE EXPOSURE

CAN ELIMINATE THE NEED TO CAN ELIMINATE THE NEED TO REPEAT THE EXPOSUREREPEAT THE EXPOSURE

ADVANTAGE OF CR/DR vs FSADVANTAGE OF CR/DR vs FS

Rapid storageRapid storage retrieval of images NO LOST FILMS!retrieval of images NO LOST FILMS! PAC (storage management)PAC (storage management) Teleradiology - long distance transmission Teleradiology - long distance transmission

of image informationof image information Economic advantage - at least in the long Economic advantage - at least in the long

run?run?

CR/DR VS FILM/SCREENCR/DR VS FILM/SCREEN

FILM these can not be modified FILM these can not be modified once processedonce processed

If copied – lose qualityIf copied – lose quality DR/CR – print from file – no loss DR/CR – print from file – no loss

of qualityof quality

““no fault” TECHNIQUESno fault” TECHNIQUES

F/S: RT must choose technical factors F/S: RT must choose technical factors

(mAs & kvp) to optimally visualize anatomic detail(mAs & kvp) to optimally visualize anatomic detail

CR: the selection of processing algorithms and CR: the selection of processing algorithms and anatomical regions controls how the acquired anatomical regions controls how the acquired latent image is presented for display latent image is presented for display

HOW THE IMAGE LOOKS CAN BE ALTERED BY HOW THE IMAGE LOOKS CAN BE ALTERED BY THE COMPUTER – EVEN WHEN “BAD” THE COMPUTER – EVEN WHEN “BAD” TECHNIQUES ARE SETTECHNIQUES ARE SET

DRDR

Initial expense highInitial expense high very low dose to pt –very low dose to pt – image quality of 100s using a 400s image quality of 100s using a 400s

techniquetechnique Therfore ¼ the dose needed to make the Therfore ¼ the dose needed to make the

imageimage

Storage /ArchivingStorage /ArchivingFILM/SCREENFILM/SCREEN films: bulkyfilms: bulky deteriorates over timedeteriorates over time requires large storage requires large storage

& expense& expense environmental environmental

concernsconcerns

CR & DRCR & DR 8000 images stored 8000 images stored

on CD-Ron CD-R Jukebox CD storageJukebox CD storage no deterioration of no deterioration of

imagesimages easy accesseasy access


Compatibility & Growth OpportunitiesCompatibility & Growth Opportunities

Most of the CR Workstations also have the ability to Most of the CR Workstations also have the ability to

operate a wide variety of: operate a wide variety of:

- printers - printers - document scanners - document scanners - archiving hardware - archiving hardware

- film digitizers - film digitizers - flat panel arrays - flat panel arrays - and other digital - and other digital

detectorsdetectors

Transmission of ImagesTransmission of Images

PACS PACS - Picture Archiving & - Picture Archiving & CommunicationsCommunications

SystemSystem DICOMDICOM - Digital Images & Communication - Digital Images & Communication in Medicinein Medicine TELERADIOGRAPHYTELERADIOGRAPHY -Remote -Remote

Transmission of ImagesTransmission of Images

Digital imaging technology (cont)

The technique of digital subtraction angiography (DSA), based on digital image processing, allows enhanced visualization of blood vessels by electronically subtracting unwanted parts of the image.

Digital subtraction angiography. (a) Mask ,immediately prior to contrast injection a preliminary digitized image known as the “mask” is performed. Note pelvic bone, bowel gas and arterial catheter. (b) Contrast image. Contrast is injected through the catheter producing opacification of arteries.(c) Subtracted image. The computer subtract the mask from the contrast image leaving an image of contrast fill blood vessels unobscured by overlying bone and bowel.Note a tight localized stenosis of the right common illiac artery (arrow)

At this time,At this time, there is no consensus on the best there is no consensus on the best technology for balancing dose and image quality. technology for balancing dose and image quality. Digital Digital imaging potentially can provide lower doses than the imaging potentially can provide lower doses than the film-intensifying screen method.film-intensifying screen method.

However, through post-exposure manipulation of the data, satisfactory diagnostic images can be produced even when unnecessarily high patient radiation doses are used. Proper quality assurance procedures are essential.

Digital imaging technology

The selection of an imaging system should involve a thorough evaluation and analysis of its complete characteristics together with consideration of the technical and human environment in which the system will be used.

Main Characteristics of an Image Receptor

The main characteristics to be considered when selecting an image receptor are:-

spatial resolution; contrast resolution; dose efficiency; Modulation Transfer Function; detector size; possibilities of image storage and transfer; and qualities such as weight, robustness, fast image access, etc).

CR - ? Which shows CR - ? Which shows “better detail” Why/how?“better detail” Why/how?

8 x 10 cassette 14 x 17 cassette

To Produce Quality ImagesTo Produce Quality Images

For Conventional ProjectionFor Conventional Projection or CR Radiography:or CR Radiography:

The same rules, theories, and laws still apply The same rules, theories, and laws still apply and can not be overlookedand can not be overlooked FFD/OFD (SID/SOD) FFD/OFD (SID/SOD) Inverse Square Law Inverse Square Law Beam Alignment Beam Alignment Tube- Tube-Part-Film AlignmentPart-Film Alignment Collimation Collimation Grids Grids

Exposure Factors: KVP, MaSExposure Factors: KVP, MaS

Patient PositioningPatient Positioning

GE DRGE DR90 KVP

BURNING

0˚ Angle 30˚ Angle 50˚ Angle

NEW IMAGENEW IMAGE towel that was used towel that was used to help in to help in positioning a childpositioning a child

CR is MORE CR is MORE sensitive to sensitive to

ARTIFACTSARTIFACTS

CR image – CR image – NEW IMAGENEW IMAGE

Line caused Line caused from dirt from dirt collected in a collected in a CR ReaderCR Reader

Double Double exposureexposure

ChildChild

Fuji CRFuji CR

120 KVP

??

Hands over upper abdomen

High resolution with digital High resolution with digital imagingimaging

Vertical patterns of hyperintense signalVertical patterns of hyperintense signal usually represent foreign materials usually represent foreign materials

that are stuck to the light path that are stuck to the light path assembly that acquires the assembly that acquires the photostimulated luminescence photostimulated luminescence signal from the CR imaging plate as signal from the CR imaging plate as it is being scanned by a laser beam. it is being scanned by a laser beam. As the light is blocked at the same As the light is blocked at the same spot as the plate translated through spot as the plate translated through the optical stage, the artifact occurs the optical stage, the artifact occurs perpendicular to the laser beam perpendicular to the laser beam readout, in the plate translation readout, in the plate translation (slow-scan) direction. The stripe (slow-scan) direction. The stripe appears bright, since the image appears bright, since the image undergoes a reverse grayscale undergoes a reverse grayscale transformation to make the image transformation to make the image appear similar to a screen-film appear similar to a screen-film image with processing.image with processing.

A lateral chest image with an unusual A lateral chest image with an unusual superimposed pattern on the anatomy.superimposed pattern on the anatomy.

This is an example of a CR This is an example of a CR image obtained with image obtained with cassette reversed, where cassette reversed, where the the tube side of cassette tube side of cassette is is pointed away from the pointed away from the x-ray x-ray tube source and toward the tube source and toward the

patient. Cassette patient. Cassette plastic plastic structural patterns are structural patterns are projected onto the imaging projected onto the imaging plate (particularly plate (particularly noticeable in the arms and noticeable in the arms and anterior part of the patient. anterior part of the patient.

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