Digital Radiography Digital Radiography 2121stst December 2016 December 2016

Santosh NeupaneSantosh NeupaneB.Sc. MIT 2013 batchB.Sc. MIT 2013 batch

BPKIHS ,Dharan , NepalBPKIHS ,Dharan , Nepal

Good afternoon Good afternoon everybodyeverybody

IntroductionIntroduction Today the world is moving in the guidance Today the world is moving in the guidance

of computer and its application . Now we of computer and its application . Now we can call it digital world.can call it digital world.

Computer applications in radiology also Computer applications in radiology also continue to grow. Large scale radiology continue to grow. Large scale radiology applications are CT ,MRI, USG, direct applications are CT ,MRI, USG, direct digital radiography, indirect digital digital radiography, indirect digital radiography, digital fluoroscopy, digital radiography, digital fluoroscopy, digital mammography ,computed radiography mammography ,computed radiography and teleradiology.and teleradiology.

Digital Vs Analog systemDigital Vs Analog system

Analog system - a variable is Analog system - a variable is measured on a continuous scale measured on a continuous scale with infinite number of possible with infinite number of possible

values .values .

Digital system -measurments can Digital system -measurments can have a limited value .have a limited value .

Analog to digital Analog to digital conversion conversion

Conventional radiograph is produced Conventional radiograph is produced by a series of analog signals, from x-by a series of analog signals, from x-ray formation and interaction with the ray formation and interaction with the patient, to capture of x-rays by the patient, to capture of x-rays by the intensifying screen, which converts to intensifying screen, which converts to light which produces image on the film.light which produces image on the film.

Digital x-ray converts the analog signal Digital x-ray converts the analog signal of the light to a digital signal. Converts of the light to a digital signal. Converts the waves to a digital signal.the waves to a digital signal.

Binary number systemBinary number system Computer operate on the simplest number Computer operate on the simplest number

system of all –the binary number system.It system of all –the binary number system.It has only two digit 0 and 1.has only two digit 0 and 1.

Counting in the binary number system Counting in the binary number system stars with 0 and ends in 1 and then counts stars with 0 and ends in 1 and then counts over again.over again.

The computer performs all operation by The computer performs all operation by converting alphabetic characters, decimal converting alphabetic characters, decimal values and logis functions to binary values,values and logis functions to binary values,

Digital images are made of discrete picture Digital images are made of discrete picture elements, pixels arranged in a matrix. The elements, pixels arranged in a matrix. The size of image is described in the binary size of image is described in the binary number system by power of 2 equivalents.number system by power of 2 equivalents.

Most images measure 256* 256(2^8) to Most images measure 256* 256(2^8) to 1024*1024(2^10) in CT and MRI.1024*1024(2^10) in CT and MRI.

Digital fluoroscopy-1024*1024Digital fluoroscopy-1024*1024

Digital radiography-2048*2048 or Digital radiography-2048*2048 or 4096*40964096*4096

Pixel- picture element; the cell of the Pixel- picture element; the cell of the digital image matrix or X-ray beam is digital image matrix or X-ray beam is converted into a electronic form that is converted into a electronic form that is digitized and converted to squares of digitized and converted to squares of information known as pixels.information known as pixels.

Matrix-Rows and columns of pixels Matrix-Rows and columns of pixels displayed on a digital image.displayed on a digital image.

Smaller the pixel size,higher the image Smaller the pixel size,higher the image resolution.resolution.

Digital radiographic systemDigital radiographic system The main difference between digital The main difference between digital

radiographic system and conventional radiographic system and conventional radiographic system is the use of radiographic system is the use of detector we use.detector we use.

Conventional CR Cassette DR Conventional CR Cassette DR detectordetector

Primary difference is that digital radiographs Primary difference is that digital radiographs are electronically captured, recorded and are electronically captured, recorded and viewed at a computer terminal which replaces viewed at a computer terminal which replaces the radiographic film and the view box.the radiographic film and the view box.

Screen and cassette is replaced by a reusable Screen and cassette is replaced by a reusable image receptor or detector.image receptor or detector.

Receptor receives x-rays and exposes a digital Receptor receives x-rays and exposes a digital plate that transforms light to an electrical plate that transforms light to an electrical image.image.

Hardware is essentially same (X-ray tube, Hardware is essentially same (X-ray tube, stand, etc). stand, etc).

Once digital radiographic image is Once digital radiographic image is made, it is transferred to a dedicated made, it is transferred to a dedicated digital radiography computer for digital radiography computer for “image processing”.“image processing”.

Image can then be adjusted, rotated, Image can then be adjusted, rotated, etc.etc.

Limitations of Conventional Limitations of Conventional Screen-film RadiographyScreen-film Radiography

Limitations:Limitations: Require fairly narrow exposure factors Require fairly narrow exposure factors

to produce a diagnostic quality to produce a diagnostic quality radiograph.radiograph.

Radiographic image can not be adjusted Radiographic image can not be adjusted once it is made.once it is made.

Requires physical handling and storage.Requires physical handling and storage.

Types of digital Types of digital radiographyradiography

Computed RadiographyComputed Radiography Screen/Film & dark room is replaced Screen/Film & dark room is replaced

by photo stimulable phosphor plate by photo stimulable phosphor plate (PSP) made up of BaFx; (x-Br, I) (PSP) made up of BaFx; (x-Br, I) (Europium Activated)(Europium Activated)

It is based upon Photostimulated It is based upon Photostimulated LuminescenceLuminescence

MechanismMechanismX-rayX-ray tube primary beam patient tube primary beam patient

secondary beamsecondary beam

Scanned by laser beam scanner Scanned by laser beam scanner PSP platePSP plate

Blue light emitted input of PMT Blue light emitted input of PMT ADCADC

Digital imageDigital image

Components of CRComponents of CR Different size of cassetteDifferent size of cassette !0*12 square inch!0*12 square inch 12*15 square inch12*15 square inch !4*17 square inch !4*17 square inch ReaderReader Display monitorDisplay monitor PrinterPrinter

Advantage and disadvantage of Advantage and disadvantage of CRCR

Compatible with the conventional X-ray Compatible with the conventional X-ray imaging system.imaging system.

Image produced are of constant image Image produced are of constant image density.density.

Due to wide dynamic range of PSP plate, Due to wide dynamic range of PSP plate, over and under exposure can be over and under exposure can be manipulated, so no repeat of radiograph.manipulated, so no repeat of radiograph.

Therefore patient dose is reduced.Therefore patient dose is reduced. Post-processing is possible.Post-processing is possible.

DisadvantageDisadvantage Error done in the selection of over Error done in the selection of over

exposure cant be judged. So, risk of exposure cant be judged. So, risk of high patient dose.high patient dose.

Processing time 2 to 4 minute, so Processing time 2 to 4 minute, so more time consumption than more time consumption than conventional system.conventional system.

Picture of optics and dynamic rangePicture of optics and dynamic range

CR in our departmentCR in our department Kodak(USA)- Carestream classic CR Kodak(USA)- Carestream classic CR

system(Room 1).system(Room 1).

Kodak(USA)-Carestream Dry View Vita Kodak(USA)-Carestream Dry View Vita CR system (room 3 and 4).CR system (room 3 and 4).

Konica Minolta CR system(Japan)-Konica Minolta CR system(Japan)-EmergencyEmergency

Scanned Projection Scanned Projection RadiographyRadiography

It is based on CT–Technology and is It is based on CT–Technology and is possible after introduction of 3possible after introduction of 3rdrd generation CT. generation CT.

This system is based on the well This system is based on the well collimated narrow fan beam collimated narrow fan beam coressponds to the detector array.coressponds to the detector array.

SPR use the CT-Gantry & Computer SPR use the CT-Gantry & Computer to produce an image that looks like to produce an image that looks like Conventional Radiography.Conventional Radiography.

Pic of sprPic of spr

Components of SPRComponents of SPR

Gantry- X-ray tubeGantry- X-ray tube Detector (NaI/CsI)Detector (NaI/CsI) Patient couchPatient couch Display monitorDisplay monitor

Advantages Advantages 1.1. High Image Contrast.High Image Contrast.2.2. wide Dynamic Range.wide Dynamic Range.3.3. Post processing.Post processing.

DisadvantagesDisadvantages1.1. Exposure time is long.Exposure time is long.2.2. Poor Spatial Resolution & Poor Spatial Resolution & 3.3. Radiation Dose is more.Radiation Dose is more.

Indirect DRIndirect DR Indirect digital radiography works on Indirect digital radiography works on

following system.following system.1.1. Scintillator(CsI) +Optical coupling + Scintillator(CsI) +Optical coupling +

CCDCCD2.2. Scintillator(CsI/GdOS)Scintillator(CsI/GdOS)

+photodiode(a:Silicon)+TF T+photodiode(a:Silicon)+TF T

CCD(charge coupled device)CCD(charge coupled device) CCD is a Silicon based semi conductor and it CCD is a Silicon based semi conductor and it

has three principle advantage.has three principle advantage. Sensitivity-High QDE and CESensitivity-High QDE and CE Dynamic range- Respond to wide range of light Dynamic range- Respond to wide range of light

intensityintensity Size- very smallSize- very small It converts light photon into electronic signal.It converts light photon into electronic signal. Cesium- 55Cesium- 55 Iodide- 53Iodide- 53 High QDE and CE.High QDE and CE.

Advantage of CsIAdvantage of CsI

1.1. It is manufactured in columnar It is manufactured in columnar shape(pipeline Structure) and spreading shape(pipeline Structure) and spreading of light is minimum. Due to which image of light is minimum. Due to which image resolution is increased.resolution is increased.

2.2. Packing density is very high.Packing density is very high.

3.3. High QDE and CE.High QDE and CE.

MechanismMechanism X-RayX-Ray

Scintillator (CsI)Scintillator (CsI) Light signalLight signal CCDCCD

Electronic signalElectronic signal

Direct DRDirect DR The most commonly used element is The most commonly used element is

Selenium (Z=34) which converts x-ray Selenium (Z=34) which converts x-ray signal into electronic signal.signal into electronic signal.

Wireless (Carestream) Wireless (Carestream) DDR system in our DDR system in our

emergency.emergency.

Indirect DR Indirect DR system(Philips Diagnose) system(Philips Diagnose)

in room No.1 in our in room No.1 in our departmentdepartment

Other modality of digital radiography Other modality of digital radiography are:are:

CT-scanCT-scan OPGOPG CephalometryCephalometry CBCTCBCT Digital mammographyDigital mammography Digital fluoroscopyDigital fluoroscopy DEXA scanDEXA scan Gamma camera.Gamma camera.

Advantage of DR over CRAdvantage of DR over CR1.1. Reduced scanning time, image is Reduced scanning time, image is

displayed immidately.displayed immidately.2.2. Slightly better resolution.Slightly better resolution.3.3. Decreased exposure, reduced patient Decreased exposure, reduced patient

dose.dose.

Advantage of DDR over IDRAdvantage of DDR over IDR1.1. The main advantage is the resolution is The main advantage is the resolution is

better as there is less chance of loss of better as there is less chance of loss of signal.signal.

Advantages of Digital Advantages of Digital RadiographyRadiography

The imageThe image1.1. Image can be adjusted after exposure.Image can be adjusted after exposure.2.2. Need for re-takes are minimized.Need for re-takes are minimized.3.3. Computer manipulation of the digital Computer manipulation of the digital

image is possible.image is possible.4.4. Able to see soft tissue and bony detail Able to see soft tissue and bony detail

in single image.in single image.

TimeTime1.1. Reduces time takes to produce image.Reduces time takes to produce image.2.2. Reduces processing time.Reduces processing time.

Image storage and TransportImage storage and Transport1.1. Stored in computer and no need of other Stored in computer and no need of other

storage.storage.2.2. Quick access to digital image.Quick access to digital image.3.3. Ease of transfer of image.Ease of transfer of image.4.4. Digital radiograph improves quality of Digital radiograph improves quality of

imaging studies, which leads to better imaging studies, which leads to better diagnosis.diagnosis.

5.5. Not worried about lost or misplaced Not worried about lost or misplaced radiographs.radiographs.

Image Management Image Management Software and Image Software and Image

ProcessingProcessing Some digital radiology machines Some digital radiology machines

have pre-set selections based on have pre-set selections based on species, body part of interest, and species, body part of interest, and radiographic view to further identify radiographic view to further identify the study type. the study type.

Images will be sent to workstation or Images will be sent to workstation or printed on transparent film for printed on transparent film for viewing.viewing.

Digital ComputersDigital Computers Digital waveform is represented Digital waveform is represented

numerically by binary numbers.numerically by binary numbers. Computer memory and storage Computer memory and storage

consist of bits (binary digits).consist of bits (binary digits). Eight bits become one byte.Eight bits become one byte.

Viewing Digital ImagesViewing Digital Images Display MonitorsDisplay Monitors

Consideration given to size and typeConsideration given to size and type

Film Film Should be printed on high-quality, Should be printed on high-quality,

transparent laser film and can be transparent laser film and can be viewed on viewbox.viewed on viewbox.

Pixel Size and Matrix SizePixel Size and Matrix Size

The amount of resolution in an image is The amount of resolution in an image is determined by the size of the pixels and the determined by the size of the pixels and the spacing between them, or pixel pitch. spacing between them, or pixel pitch. Larger matrices combined with small pixel Larger matrices combined with small pixel size will increase resolution, but it may not size will increase resolution, but it may not be practical to use large matrices. The be practical to use large matrices. The larger the matrix, the larger the size of the larger the matrix, the larger the size of the image, and the greater the space needed for image, and the greater the space needed for network transmission and picture archiving network transmission and picture archiving and communication system (PACS) storage. and communication system (PACS) storage. Typically, 2000 pixels/row are adequate for Typically, 2000 pixels/row are adequate for most diagnostic examinationsmost diagnostic examinations

PACSPACS And we cannot forget the role of PACS in And we cannot forget the role of PACS in

digital radiography.digital radiography. The Picture Archiving and Communication The Picture Archiving and Communication

System (PACS) is an integral part of the digital System (PACS) is an integral part of the digital radiology imaging departmentradiology imaging department

PACS is an electronic network for PACS is an electronic network for communication between the image acquisition communication between the image acquisition modalities, display stations, and storage. For modalities, display stations, and storage. For these different systems to communicate with these different systems to communicate with each other, a common language is necessary. each other, a common language is necessary. The Digital Imaging and Communications in The Digital Imaging and Communications in Medicine (DICOM) standard was first Medicine (DICOM) standard was first formulated in 1983 for this purpose.formulated in 1983 for this purpose.

P—Picture: the digital medical image(s)P—Picture: the digital medical image(s)

A—Archiving: the “electronic” storage of A—Archiving: the “electronic” storage of the imagesthe images

C—Communication: the routing C—Communication: the routing (retrieval/sending) and displaying of the (retrieval/sending) and displaying of the imagesimages

S—System: the specialized computer S—System: the specialized computer network that manages the complete network that manages the complete systemsystem

Thank You…….Thank You…….