what is digital radiographic imaging also referred to asdigital projection radiography

any imaging acquisition process that produces an electronic imagethat can be viewed and manipulated on a computerdigital radiographic imaging

how do you created radiographic images in digital radiographic imaging and how are they created for film screen imagesdigital (binary code)analog format for film screen images

what type of conventional radiograhy does digital radiographic imaging incorporate?1. RT selects the required exposure factors (mA, Time, kVp)2. Rt positions patient3. Accessory devices must be used such as grids, collimator, etc.)

What does digital radiographic imaging depend on to produce radiographic imagesdepends on computer technology to process, manipulate, and store)

what are the advantages of digital radiographic imaging?1. obtaining, processing, storing, and retrieving images in a more timely manner2. virtual elimination of repeat images due to technique error3. ability to record a wider range of tissuees with one exposure, provide quantitative data on the attenuation characteristics of tissue, and visualize anatomic area without overlying structures4. simplification of filing images(no hard copy,all electronically stored)5. post processing of images ( can enhance detail and contrast on computer)6. electronic transmission of images to remote sites (quick access by physicians over long distances)

how is a digital image formed?

by a matrix of picture elements (pixels)

this is a group of # or layout of cells arranged in rows and columnsmatrix

what does each cell correspond to in a matrix?a specific location in the image

what does the value of the cell in a matrix represent?the brightness and intensity at that location

what is the smallest component of the matrix or each cell?pixel (picture element)

what does the location of the pixel within the image matrix correspond to?an area within the patient

what is the size of the matrix described bythe number of pixels in the rows and columns

a small matrix has a ____ number of pixels and a large matrix has a ____ number of pixelssmalllarge

what does a greater number of smaller pixels do?improve the image quality

this describes how much of the patient is imaged in the matrixfield of view

what is the relationship of pixel size to matrix and field of viewthe size of the pixel is directly related to the field of view and inversely related to size of the matrix

what is the size of the pixel directly related to?the field of view

what is the size of the pixel inversely related to

the size of the matrix

what is the formula for the relationship of pixel size to matrix and field of viewfield of viewpixel size = ----------------matrix size

the number of shadows of gray that can be representeddynamic range

what can visualize the x-ray beam's dyanamic range and what cant?the computer canwe can not

what does larger (high) dynamic range mean? What does it represent?more gradual the gray scale, wide image latitude, and greater the contrast resolutionrepresenting max - min intensity

a system with a low dynamic range is ____ contrast but over ______ of the imagehighlimited portion of the image

what is dynamic range measure inbits

the numeric value representing a shade of gray stored in each pixelbits

bits are a numerical value that represents whata shade of gray stored in each pixel

what are 2 methods used to create digital images?1. indirect capture method2. direct capture method or direct readout digital radiography

what is the most commonly used digital systemcomputed radiogrphy CR

what is the CR work flow very similar tofilm/screen

what is the differences between film screen and CRthe way the latent image is caputed

what does film/screen use to capute the latent imagescintillators to transfer info

what does CR use to capute the latent imageuses the image receptor to store electrons in high energy traps

what are the advantages of CR vs. conventional radiograhy1. lower pt. dose2. lower repeat rate bc of improper tech. factors3. higher contrast resolution and wider exposure latitude4. IR response is linear (greater range of Rad densities)5. NO darkroom or film costs6. digital image can be easily manipulated 7. image storage is easier thru either hard copy or eldctronic storage8. easy interface with PACS or image management and communication system

what is the dynamic range of CR1000:1

what are the ways that the digital image can be easily manipulatedpost processing subtraction, contrast and edge enhanced

what are the disadvantages of CR vs. conventional radiography1. capital costs are higher for IR, CR reader, and workstation hardware and software2. lower spatial resolution3. collimation and centering of part are critical for optical density and contrast4. potential overexposure of pts.

how much can the computer compensate for overexposure?up to 2X the necessary amount of mAs

what vaires with different manufacturers of CRsensitivity or Exposure values vary

what is the percentage difference of the radiation dose to the patient for CR when compared to conventional radiography for the following exams?chestUGIExcretary urographypediatric examinationschest is 5% relative decrease in doseUGI is 5% relative decrease in doseExcretary urography is 10% relative decreasePeds exams is 15-30 relative decrease dose

a digital image acquisition and processing system for producing static imagesIndirect method CR

what was the indirect method of CR developed? By whom? When was the first clinical application?1981fugi corp1983

the indirect method of CR uses standard x-ray tubes and generators but what does it require that is differentspecialized image receptors and processing

what does the indirect method CR consist of1. image receptors or acquisition medium - photostimulable phosphor and CR cassettes (no film or screens)2. CR reader unit (scanner)3. QC workstation4. viewing station and printer

for indirect capture you create a _____ image and then convert the image to what? How is this accomplished?analogdigital format

laser scanning film digitizer and computerized radiography (CR) system

for cassette based digital radiography vs. conventional radiogaphy what is the film replaced with and what is the conventional processor replaced with?film replaced with a recording phosphorprocessor is replaced with a laser reader unit and workstation

what does cassette-based digital radiography use to capture the imagea photostimulable storage phosphor imaging plate

what is the photostimulable storeage phosphor imaging plate made of1. barium fluorohalides in a binder - bromides and iodides: (Eu)2. amorphus silicon

what percentage of charge is lost by the latent image in how long?latent image loses 25% of charge in 8 hours

what does the image plate do to the x-raysabsorbs the x-rays and converts them into light

what happens after the image plate changes the x-rays into light?light is detected by a CCd or thin film transistor and converted into an electrical signal that is sent to the computer for processing and viewing

what is the image plate made of for indirect capturemetal or plastic

what is the image plate for indirect capture coated with on one sidewith photostimulable phosphors in a layer less than 1 mm thick

what are the phosphor materials in the image plate of indirect capture?barium fluorohalide crystals doped with europium impurity (BaFb:Eu2+)

what are the halide crystals in the image plate for indirect capturebromide chlorineiodineBr and I are the most commonly used

what can also be used that is an excellent absorption of x-ray energyCsBr:Eu2+

what happens to phosphor crystals when they are exposed to x-raysthey are energized until they are exposed to light

what does the image plate dostores x-ray energy to form the latent image

what are the functions of the cassette for indirect capture CR1. protects image plate from damage2. providees a stable vehicle for transport and placement of the IP under the pt

what are the cassettes frame made of for CR indirect methodlight weight Aluminum, plastic or steel

what is the front pannel of the cassette made of for CR indirect methodlow-attenuation carbon fiber

what are the components of the cassettes back panel for CR indirect method1. lead foil to minimize backscatter fog2. memory chip in one corner 3. allows RT to match pt to cassette and IP and use the exam data to set appropriate image processing parameters

what is the inner surface of the front and back of the cassette in CR indirect capture lined with? What does the do?

lined with a felt-like material; prevents electrostatic charging of IP (prevention of dust collection), and protects plate from mechanical damage

what is the standard IP comparable with for film/screena 300 relative speed film/screen system

what is a high resolution IP comparable with for film/screena 100 relative speed film/screen system

for indirect method CR what happens when remnant x-rays strike the IRlatent image is created on the IPsome of the x-ray energy is absorbed and released in the form of visible light and the remaining remnant x-ray energy is absorbed by (photoelectric effect) and the ionizing event caused crystal electrons to be stored in empty latice sites called "F" centers (these are used to form the latent image)

how long can the latent image be stored? what happens during this time?can be stored for up to 24 hoursit will gradually weaken thru a process called fading (spontaneous phosphorescence)

what is it called when the latent image gradually weakens because of spontaneous phosphorescencefading

how much of the images stored energy is lost within 8 hours?25%

when must you process the latent image in indirect method CRwithin 1 hour of exposure (in a timely manner)

for indirect method CR what happens when the IR is placed in the CR reader unit?1. CR cassette is automatically opened and IP is removed2. Cr scanner scans IP with a laser light and reads the latent image from the Phosphor3. light is detected by a photomultiplier tube,

amplified, converted to an electrical signal and sent to a computer for interpretation

what happens to the IP before it is stored for later use by the CR reader unitit is scanned with an intense light to release (erase) any residual energy

what is it called when the Cr scanner scans IP with a laser light and reads the latent image from the phosphorreadout

how is stored energy released in the CR readerin the form of visible light

what is the analog image converted to in the CR readerto a digital image for computer processing

if the IP is not used within 48 hours what must you do before using itput it thru the erasure cycle on the CR reader

can photstimulable phosphors be reused?yes

what is the life expectancy of photostimulable phosphors before needing replacement10,000 readings before replacing

how is the latent image formed for CR indirect method1. x-rays strike the photostimulable phosphor plate2. some light is given off; some of the photon energy is deposited within the phosphor particles to create the latent image3. the phosphor plate is fed throught the CR reader

what happens for the CR indirect method to release the latent image?1. a focused laser light is scanned over the plate, causing the electrons to return to their original state of emitting light in the process2. the light is picked up by a photomultiplier tube and converted into an electrical signal

3. the electrical signal is the nsent through an analog-to digital converter to produce a digital image

How does the CR reader unit work when the IR is placed in it? What is this process called?1. it automatically opens the IR and removes the IP2. IP is fed thru transport rollers to scan/read section3. a helium-neon laser beam scans IP in a transverse pattern and stimulated phosphor crystals to release stored energy in the form of visible light energyprocess called photostimulated luminescence (PSL)

in the CR reader what scanns the IP and stimulated the phosphor crystals to release stored energy in the form of visible light energy?a helium neon (HeNe) laser beam

what type of pattern does the helium neon (HeNe) laser beam scan the IPin a transverse pattern

what is the HeNe laser light very efficient at?stimulating the release of light

what is the light emitted from the IP after laser light stimulizationa blue-purple (wavelegnth of 390-400 nm)

what is the intensity of the PSL phosostimulated luminescence directly proportional to?the amount of energy absorbed in each area of phosphor

what must the size of the laser spot on the IP match?the size of the pixels used to display the anatomical image on the monitor

why is the size of the laser spot on the IP matching the size of the pixels used to display the anatomical image on the monitor important?the image resolution partly depends on the laser dimensions but also depends on the PSL light divergence which may be high with phosphors used in CR

what acts as light guides to reduce the PSL divergenceneedle-shaped crystals

how is some laser light directed toward a referenceway of a beam splitter

why is some laser light directed toward a reference detector by a beam splitter?to monitor the intensity of laser light so hat adjustments can be made for any fluctuations that may occur

why is monitoring the intensity of the laser light imporant?intensity of visible light coming from the IP is partially dependent on the intensity of stimulating laser light.

what will happen if the laser light intensity is too lowstimulated visible light emission decreases

what happens if laser light intensity is too highvisible light emission will increase and spread out thereby causing decrease in the image resolution

what is the PSL collected byan optical collection system called a light channeling guide or light gate

what does a light channeling guide or light gate dochannels light to one or more photomultiplier tubes

what is the detection sensitivity of the PM tube matched to? Where is this electrical energy sent tothe spectral wavelegnth of the blue-purple PSL.sent to an analog-to digital converted (ADC) where it is digitized

what does it mean when it says the electrical energy is digitized?translated to a binary code thru algorithmic computations for a computer to then be able to process

once the computer process the digital signal where does it go?transferred to another part of the CR reader where the IP is uniformly exposed to either a high intensity sodium vapor lamp (discharge lamp) or high intensity fluorescent light for a short time to erase any residual image so that it can be reused. ( can be reused thousands of times)

what do the CR readers for indirect caputure vary invary in size and plate handling capacity

how many IP can CR readers process in up to an hour?What is the average of most per hour?150most about 115 per hour

what different types of CR scanners are availablemuliple cassettes vs. single cassette scanners are available

once processed what happens to the digital imageit is immediately displayed on the monitor

once the digital image is displayed on the monitor what can the RT check for?1. check for positioning or gross technical errors and detect any artifacts

if the digital image on the screen is acceptable the RT can thendownload image into computer where it can be manipulated and transferred to a PACS workstation

the linear relationship between exposure and densityCR c-curve

the ability to convert incoming x-rays to useful output signalswide quantum detection efficiency(QDE)

what can be done at the Indirect method CR workstations

has a computer console where manifest images can be manipulated, stored, displayed, or produce hard copies or edge-enhanced image option can be done

what does the system of indicating x-ray exposure vary withmanufacturers

what does each manufacturer specifya range of x-ray exposures sufficient to produce a quality imageex: sensitivity # or S#, exposure index, relative exposure index

what do exposure errors result inhigh or low electrical signals (density or brightness)

an x-ray exposure error of more or less than ____ will produce poor quality images50%

what are the indirect method CR workstations functions?1. gradational enhancement (contrast)2. spatial frequency enhancement (detail)3. subtraction/addition option4. image magnification5. region of interest (ROI) display6. statistical analysis used for calculating surface areas and estimating volumes or changes in tissue density7. database functions

what is the image created with for an indirect method CR reader4096 X 4096 matrix

what are hard copy images created witha laser camera

what does the direct capture method not havecassettes

what are 3 other names for direct capture

1. direct-to-digital radiographic (DDR) system2. direct readout digital radiography (DR) systems3. direct raqdiography (DR) systems

what does the Direct Capture method replace cassettes and reader witha flat panel (shield) detector/plate (FPD)

what does the FPD doreceives and directly converts incoming x-ray photons to an electronic signal and automatically sends the digital image to a computer for digital processing and temporary storage and then to the monitor for displaying

what do you have to install for the direct capture methodinstallation of the flat-panel detector or image receptor in the bucky of rad table or upright bucky or in dental sysems

what does the receptor in the direct capture method directly sendsend the elctronic signal directly to a digital image processor

what are the benefits of a flat panel system?1. faster by 3-5 seconds2. better resolution (no laser)

what are 2 types of detector systems used in DR1. direct digital radiography2. indirect digital radiography

this produces an analog signal that must be subsequently digitizedindirect digital radiography

what happens for indirect digital radiography?1. incoming x-rays interact with crystal and convert them to light photons2. the detector detects and stores the light in the form of an electrical charge proportional to the amount of light that struck it3. the electrical charge is collected and transmitted through TFT or CCD's to the computer for processing

what is the detector in indirect digital radiography made ofamorphous silicon

what are the crystals in the indirect digital radiography made ofscintillator -(CsI) crystals

what is the problem with indirect digital radiography?scattering of light which produces unsharpness

what reduces the unsharpness in indirect digital radiographyCsI

what is similar to crossover in intensifying screensthe scattering of light that produces unsharpness in indirect digital radiography

what is not widely used in direct capturea CCD

what is located at the site of interaction ofr direct capture digital radiographya fixed image receptor

what does direct capture digital radiography use to receive exit radiation and convert that radiation to varying light intensitiesa phosphor type screen (scintillator)

what happens after the exit radiation is converted to varying light intensities?light sensitive electrodes directly convert these light patterns to a digital signal, this signal is physically small

what is needed to image the light emitted by the CCDminification optics are required

what are TFT arrayed in?a matrix called an AMA (active matrix array)

what are TFT coated with?a-silicon

what cause light to be produced in the CsI of the TFTincident x-ray

in TFT what do the light photons causea signal to be produced

where is the signal that is produced in the TFT stored?in the TFT until read one pixel at a time

what type of TFT are there?direct vs. indirect TFT detectors

what does direct digital radiography systems givea direct digital readout

what type of crystals does the DDR use? What do they doamorphus seleniumdirectly converts the x-ray into an electrical charge that is stored in a capacitor

how is the electric charge that is stored in the capacitor collected and transmittedthrought a TFT to the computer for processing

how is the electric charge that is produced after x-ray interaction detected for DDRby an array of pixels that consist of an electrode and capacitor which store the charge until switched by a TFT, then directed amplifiers and an A/D converter and then processed to a computer

how is spatial resolution primarily determined? What is it also influenced by?by pixel sizefill factor

current pixel size is 100 um which yeilds spatial resolution of ____

5 lp/mm

percentage of pixel area that is sensitive to the image signalfill factor

current DDR systems have a fill factor of ___%. Why?80% some of the pixel area is devoted to electronic conductors and TFT