RAD141 – Chap2c – Digital Technology Applications

Question Answer
What are 4 types of digital imaging technologies in use today? computed tomography (CT), digital fluoroscopy (DF) (2 types), computed radiography (CR), and direct digital radiography (DR)
When was CT developed? in the late 1970s and early 1980s; one of the 1st applications of coputers to radiologic technology
How does CT work? it acquires sectional anatomic images primarily in the axial plane; a portion of the radiation for each CT slice is attenuated by the patient; remnant radiation is measured by detectors
How can CT images be displayed? data can be reconstructed in the sagittal and coronal planes, and into 3-D images
Which type of body structures attenuate most of the x-ray beam? higher-density structures, such as bones, contrast media; low-density structures (lungs, air-filled structures), attenuate little of the x-ray beam
In CT, how is the attenuation information used? attenuation information exits the detectors in analog form -> analog signal is converted to a digital signal -> a computer performs a series of algorithms to reconstruct the image based on attenuation values
What are 3 advantages of CT over conventional radiography? contrast resolution is superior; structures are visualized without superimposition; acquired data may be viewed in alternative planes
How does fluoroscopy differ from radiography? fluoroscopy provides dynamic imaging of structures; radiography -> static images
Where is fluoroscopy used? gastrointestinal p[rocedures, intra-operative imaging, and angiography/interventional procedures
What are the 2 types of fluoroscopy technology? most common -> analog-to-digital conversion (uses image intensifier -> produces visible, analog image -> converted to digital); directal digital (aka "flat detectors")
Where is direct digital conversion primarily used? cardiac and vascular applications
What are the advantages of flat detector technology? improved image quality (smaller pixel size & higher detection quantum efficiency (DQE)), contrast resolution is greater, smaller size allows more maneuverability
What is the primary disadvantage of flat panel x-ray detectors more expensive than image intensification technology
Can fluoroscopy product static images? yes, it can also produced still images
What is the difference in equipment between the direct digital conversion and analog-to-digital conversion systems? direct digital system uses a digital detector in place of the image intensifier, video camera, and digital conversion system required by the analog-to-digital conversion system
What is computed radiography? CR is a method of digital image acquisition for general diagnostic radiography
What are the main components of a CR system? image plates (IP), IP reader, and technologist workstation
What is an image plate? an IP replaces teh film-screen cassette and records an invisible (latent) image; the image plates are composed of photostimulable phosphors
How is an IP different from film? it can be used repeatedly, does not need to be "light tight", and can even be opened briefly in light w/o loss of the latent image
How is patient info linked to the CR image? electronically using a bar code reader, or by manual input; the usual lead blocker found on conventional film cassettes is not present
What happens after an exposure is made on an IP? the patient ID is linked and then the plate is placed into the IP reader which removes the IP from the cassette and reads the recorded image line by line by the laser scanner
How does the laser scanner work? IP phosphors release electrons that emit light equal to their stored energy; the light output is converted to an electrical signal, then to a digital format for manipulation, enhancement, viewing, and printing
How can an IP be reused? the image plate reader has a bright light which erases the IP; then the reader reloads the IP into the cassette
How long does it take for an IP to be processed? about 20 seconds
What does the CR technologist workstation contain? an optional bar code reader, a monitor for image display, and a keyboard with a mouse or trackball; technologist verifies the patient position and checks the exposure index at this workstation
What happens to a CR image after it has been processed? after the image quality has been verified and any adjustments have been made, the image can then be transmitted to the digital archive for viewing and reading
What are additional details which must be considered in CR? (7) collimation, 30% rule, accurate centering of part and IR, use of lead masks, use of grids, exposure factors, evaluation of exposure index values
What are collimation considerations for CR? collimation s/b closely restricted to part being examined; software considers entire x-ray field as data set; if un-attenuated beam is included in brightness & contrast calculations, exposure index will be misrepresented & image may exhibit lower contrast
What is the 30% rule for CR? a minimum of 30% of the IR must be exposed for an eaccurate exposure index; if colimation is less than 30% of the IR, exposure index is no longer accurate
When should lead masks be used in CR? lead masks are lead blockers and s/b used for multiple images in one IR, due to the hypersensitivity of the image plate phosphors to lower energy scatter radiation
When should grids be used in CR? for parts over 10 cm; especially important in CR because of the hypersensitivity of the image plate phosphors to scatter radiation
What exposure factor considerations s/b used in CR? ALARA -> lowest exposure factors required to obtain a diagnostic image
How should exposure index values to evaluated in CR? once image is available for viewing at the workstation, it is critiqued for positioning & exposure accuracy; then exposure index is checked to verify that exposure factors used were in correct range for optimum quality w/lowest radiation dose to patient
What is direct digital radiography? DR involves direct conversion; a digital detector detects radiation intensities transmitted thru patient & converts it to a digital format; data processed, image is displayed; digital detector replaces IP/cassette & image reader used in CR
What are the advantages of DR? DR eliminates the handling of cassettes -> significant timesaving feature; DR systems increase efficiency due to decreased image processing time (seconds); exposure factors may be reduced due to higher DQE of the detector
What is DQE? detection quantum efficiency; a higher DQE indicates that more x-ray are converted into visible light
Is a grid needed for DR? no, but the grid is expensive and fragile and is usually not removed; the increased exposure is not an issues except for pediatric examinations
How is chest imaging different with DR? there are dedicated DR systems available for chest imaging; detectors sizes for DR chest units are 16×16 or 17×17
What is the significance of digital processing in mammograms? digital acquisition is high-contrast resolution with possible reductions in patients dose, especially important for mammography; post-processing capabilities provide the opportunity for image manipulation to improve visibility of fine microcalcifications
What are special considerations when using DR? accurate positioning, careful collimation (but 30% rules does not apply), correct use of grids, careful attention to exposure factors and evaluation of exposure index values (ALARA); very similar to CR
What is PACS? a complex computer network for image management, similar to a "virtual film library"; Picture Archiving Communication (routing (retrieval/sending) and displaying of images) System
What standards are employed in PACS? DICOM and HL7 are used to ensure that all manufactures and types of equipment are able to communicate and effectively transmit images and information; standards allow for resolution of connectivity problems
What are DICOM and HL7? standards used in PACS; DICOM -> Digital Imaging Communications in Medicine; HL7 -> Health care Level 7
How is PACS integrated? ideally with the RIS (radiology Information System) or HIS (Hospital Information System)
What are some advantages of PACS? elimination of physical space requirements for film, easy search/retrieval, rapid transfer of images w/in hospital, teleradiology, simultaneous viewing, no misplaced/damaged films, incr in reporting exams efficiency; elimination of chemicals (environment)
What new careers are found in PACS? PACS administrator and Diagnostic Imaging Information Technologist
What is telemedicine? delivery of health care using telecommunications and computer technology
What are the advantages of telemedicine? use of remote specialists (incr efficiency/effectiveness), lower health care costs (reduces # of physicians on-site), hard-copies do not get lost in the mail
What is teleradiology? the electronic transmission of diagnostic imaging studies from one locations to another for the purposes of interpretation and/or consultation
What are the applications of teleradiology? on-call systems (transmission of images after hours to on-call radiologist); off-site systems – coverage for remote areas with no radiologist on site; in-hospital systems (transmission of images w/in hospital)
What is CAD? computer-assisted detection provides a "second look" at the radiographic image using computerized detection algorithms, pattern recognition, neural networks, and AI to analyze digital images for various suspicious lesions
Where is CAD used? in mammography and chest radiographs
How is CAD utilized? the radiologist performs the initial read and then the image is interpreted by the CAD device; if image was not acquired digitally, hard-copy image must be digitized first
How much improvement does CAD provide? some published studies have shown that CAD increases a radiologist's performance by 10%
What are benefits of CAD? improved detection, lack of intra-observer variation (computer detection is reproducible), computers not subject to distraction, fatique, or effects of a heavy workload
What is IHE? integrated health care enterprise; broader health care management integration, integrating all patient medical records into an EPR (electronic patient record); radiology, pathology, laboratory results, and medical records exist in single digital file
What are the challenges of creating an IHE? lack of standard communication/transmission standards between medical depts, lack of technical infrastructure, training of health professionals, cost, user acceptance, privacy
What is IMAC? image and information management and communication; a possible replacement term for PACS, which more accurately reflects the future of a totally integrated health-care enterprise