Presentation on theme: "CR/QA RADCHEX. History of digital imaging Early, crude digital detectors were developed in the 1970’s Image quality was problematic Processing time of."— Presentation transcript:
History of digital imaging Early, crude digital detectors were developed in the 1970’s Image quality was problematic Processing time of digital images was untenable Viewing, transfer and storage of digital data was not ready for clinical application Digital radiography was first marketed in the 1980’s Based on a way to improve image quality Used post processing to extract maximum information from each image Potential for reduced dose with fewer repeat images Early commercialization slowed by detector cost CR (Computed Radiography) using photostimulable plate hit its stride in the early 90’s CR can be used with existing x-ray system and deployed like film/screen cassettes- big economic benefit CR plagued by marginal image quality at first when used at film/screen dose levels
History of digital imaging (cont.) CR vendors refine CR systems for better imaging quality New phosphor science and system improvements bring wide acceptance PACS developments enable filmless conventional radiography Dose creep Direct Digital Radiography (DDR) finds increased acceptance today but CR is still preferred by many The lines between CR and DR are beginning to blur as both technologies evolve CR companies begin marketing CR systems with on-board plate readers and self contained x-ray system Digital mammography expands with both DDR and CR technology employed MQSA will refine QA requirements for FFDM applications CR and DR system use is global and will eventually replace all film/screen applications
How a CR system operates Photo Stimulated Phosphor (PSP) is exposed to x-ray X-rays cause phosphor to store invisible light image Image Plate (IP) removed and placed into reader and exposed to laser light IP then releases visible light which is fed to a computer for image processing CR operates in a similar manner for all OEM suppliers
How a CR system operates (cont.) Plate reader has a light sensor that detects and measures light given off by IP (light value) Every OEM provides a different value for this light and calls it by different names –Fuji, Konica/Minolta and Philips = S# –Afga = LgM –Kodak = El Bottom line: it is x-ray produced light!
Each OEM calibrates its plate reader differently Different because each OEM needs to link their light exposure index value back to the x-rays that produce the image because each system differs in its speed (conversion efficiency) Technologists use the light exposure index value to confirm the right amount of light was produced –For the particular type of exam –To ensure the patient has been appropriately exposed to x-rays OEMs give technologists a range of acceptable light exposure index values, appropriate for various types of exams –Fuji, Konica/Minolta, Philips = S# ~200 –Agfa = LgM ~2.2 –Kodak = EL ~2000
Let’s look at this x-ray/light relationship closely Plate reader light sensor is downstream of image production Plate reader only looks at light to construct image Upstream is where the plate is exposed to x-rays CR OEMs calibrate each plate reader using one factory x-ray machine & tube with same Al filtration, and measure using a single well-calibrated dosimeter so each plate reader is perfectly calibrated & each reader produced is balanced or matched to every other reader –Eg: for a dosimeter value of 1 mR, the Fuji S# or Light Exposure Index # is 200 Bottom line: the conversion efficiency of the PSP is linked to a single light output value for a given x-ray input value and everything is perfect…right?
Wrong! Plate readers are mis-calibrated when they get to the field The perfectly calibrated factory plate readers are mis- calibrated when they are installed due to variations in: –Service staff (x-ray and CR OEM disharmony) –Many different x-ray machines – Dosimeters are in different states of calibration –Hospital x-ray tubes with different x-ray beams & conditions Instead of factory-matched and balanced readers, each reader re-calibration now maintains its memory of the x-ray beam condition and dosimeter variation used to calibrate it in the field! Bottom line: the variation between and among plate readers in a single hospital department can be as much as 80%
Magnitude of mis-calibration Conversion efficiency values change with small change in x-ray beam condition For the same one mR x-ray exposure, the light output from the IP can vary by as much as 80% as the x-ray beam filtration changes
Variation in field plate readers Variation among four field plate readers’ calibration in a single department over 45 days The four Fuji readers should have the same S#, if well calibrated Need for traceable plate reader calibration to identify abnormal readings on day 16 Daily QC on x-ray and CR system would have caught abnormality Bottom line: CR RADCHEX would have easily detected the abnormality
How CR RADCHEX works CR RADCHEX is a chameleon Configured to mimic any of the available CR OEM plate readers using interactive software Calibrated at the Fluke Biomedical Global Calibration Lab A calibrated, traceable, portable plate reader
How CR RADCHEX works (cont.)
CR RADCHEX is a downstream meter compared to a dosimeter since it, like the reader, measures x-ray-produced light CR RADCHEX has the same energy dependence to x-rays as a CR plate & the same x-ray to light conversion efficiency so it can be used to calibrate other plate readers as well as all CR AEC systems CR RADCHEX doesn’t need to travel upstream or up the waterfall to the x-ray side of the imaging plate Bottom Line: use a traceable, calibrated light meter (CR RADCHEX) to calibrate another light meter (CR plate reader). After all, one wouldn’t use a light meter to calibrate a dosimeter!
How CR RADCHEX works (cont.) The CR RADCHEX need not be exposed to a laser to give up its light image CR RADCHEX measures light immediately upon exposure to x- rays Using a dosimeter, one waits minutes for imaging plate to stabilize before processing CR RADCHEX can calibrate the AEC to produce the same light signal for any patient thickness or kVp without waiting minutes and without using a plate reader Bottom line: CR RADCHEX can calibrate radiographic AEC systems in under an hour and mammography AEC systems in about two hours, resulting in tremendous time and cost savings in addition to accuracy.
How CR RADCHEX works (cont.) The CR RADCHEX x- ray to light converter physically fits into any place a CR imaging plate fits Of benefit when placing the converter into the X- ray machine’s IP holder (Bucky) during AEC calibration Bottom line: CR RADCHEX is a chameleon
How CR RADCHEX works (cont.) The CR RADCHEX is immune to upstream field x-ray machine, dosimeter and tube filtration variations –Therefore it can be used to re-establish the ‘perfect’ calibration the plate reader had from the CR OEM factory –The light measurement value (CRLU, CR Light Units) is traceable back to the Fluke Biomedical Global Calibration Lab calibration condition and OEM calibration specifications –Not to upstream x-ray machine, dosimeter and x-ray tube filtration conditions
How CR RADCHEX works (cont.) CR RADCHEX is supplied with a 1.5 mm copper reference filter –Strapped to exit side of x-ray tube collimator during plate reader assessment & calibration X-ray beam is heavily filtered by copper filter & gives meter a source of consistent x-rays from one x-ray tube to another
How CR RADCHEX works (cont.) CR RADCHEX software looks at the x-ray-produced light from the stable x-ray beam & converts the light output to any OEM light exposure index value CR RADCHEX software also converts any light signal to all OEM-specified calibration conditions & hence reads out in S#, LgM, and EI values as well as a generic CRLU value for any and all x-ray exposures CR RADCHEX also provides an estimated mR value for radiation exposing the imaging plate at the calibration point
How CR RADCHEX works (cont.) Bottom line: Any and all plate readers can once again be re-calibrated to the perfect OEM factory calibration specifications Hence, all plate readers are once again balanced and matched to each other In addition, each plate reader calibration can be verified since each CR RADCHEX meter is calibrated and traceable to the GCL, PTB or NIST defined x- ray technique
Implications for well-calibrated CR systems Implications for well-calibrated AEC systems and plate readers are extreme Medical imaging QA standpoint –If images from four mis-calibrated plate readers in a department are sent to a PACS, the images will have different signal-to-noise values, even though technologists have used what they thought were the same S# –The image processing software may or may not correct for the various signal to noise variations leading to radiologist frustration and possible diagnostic deficiencies –Patients in this situation are exposed to varying x-ray doses for the same exam from these four different mis-calibrated plate readers Not imaging or ALARA friendly
QA RADCHEX option QA RADCHEX is a cost effective alternative to the CR RADCHEX QA RADCHEX –Performs the same basic functions as the CR RADCHEX without the need for a laptop computer –The QA RADCHEX cassette contains a LCD readout and displays CRLU and speed values (compared to film/screen) –Data can be manually entered on a template with the software supplied if desired –QA RADCHEX is ideal for QA personnel to conduct periodic assessment of CR system function –Both the CR RADCHEX and QA RADCHEX can be used to assess Plate Reader and x-ray System AEC calibration QA and CR RADCHEX are QA timesavers
How do CR and QA RADCHEX benefit customers? Who are the customers? What are their issues? DX Service OEM (CR RADCHEX) Productivity/calibration integrity CR OEM (CR RADCHEX) Productivity/image quality ISO Service OEM (CR RADCHEX) Productivity/service integrity Biomedical Engineers/Technicians (CR RADCHEX) Productivity/service integrity Radiology Administrators (QA RADCHEX) System uptime/image quality Radiology QA Technologists (QA RADCHEX) Image quality/consistency DX Medical Physicists (CR or QA RADCHEX) Image quality/dose Health Physicists (CR or QA RADCHEX) Dose Economic justification-OEM service example Calibrating AEC for CR site using conventional methods (CR plate/reader/dosimeter) will consume 8 hours of service time worth $3, Calibrating AEC using CR RADCHEX in place of CR Plate/reader/dosimeter will consume less than 2 hours. The difference (6 hours) will pay for a CR RADCHEX in just over one application That 6 hour savings pertains to the productivity of the OEM or the cost for service to the site CR RADCHEX
Frequently asked questions FAQS 1.What does this device gain for me as a technologist? A.The ability to quickly verify the correct performance of AEC before calling in expensive service. 2.How does my job as a service engineer/biomedical engineer benefit? A. Save significant time increasing productivity and provide high integrity results 3.How can the system help me in a multiple CR system environment? A. A standardized, traceable QA tool to balance all systems for consistent dose/image quality 4.How can I justify the purchase? A.The time saved in a single calibration application could pay for the device 5.What are my alternatives? A.Use a dosimeter/plate/reader method and try to balance radiation and light energies (difficult) 6.What happens as image-recording media advances? Obsolescence? A CR System speed and calibration routine changes can be accommodated by software upgrades CR RADCHEX
Frequently asked questions (cont.) FAQS 7. Why can’t I just use a dosimeter to do the same thing? A.Dosimeters measure x-ray dose and plate readers measure light – two different energies leaving room for errors. The CR RADCHEX is a radiation stimulated light meter traceable to the Global Calibration Lab 8. Who else sells this technology? A. No one. It is exclusive to Fluke Biomedical 9. What about mammography? A. A special version of the CR RADCHEX called CR MAMCHEX (and QA MAMCHEX) will be introduced for CR mammography applications 10. Can I use the CR RADCHEX with my screen/film systems for AEC Calibration and tracking? A.The AEC 6 system is available for screen/film systems and provides the same time saving advantages for calibrating and QA of AEC CR/QA RADCHEX
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