PowerPoint Q and A
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| What is the goal of imaging? | show 🗑
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| What are the principles of digital exposure? | show 🗑
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| Why does digital imaging give a successful image even when under/over exposed? | show 🗑
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| What is over exposure during digital imaging called? | show 🗑
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| show | overdosing patient during exposure due to wide exposure range
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| Where does risk of failure occur during imaging? | show 🗑
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| show | S# - 200 (inverse)
EI# - 2000 (DIRECT)
LgM - 2.2 (DIRECT)
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| show | PRE - The ability to manipulate image before display on monitor (automatic)
POST - The ability to manipulate the image after display on monitor (tech can adjust)
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| show | Deflective pixel;
Image lag;
Line noise;
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| What can be done to correct common defects in FPD? | show 🗑
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| Describe potential DR image problems. | show 🗑
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| How are problems with DR image addressed? | show 🗑
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| show | Signal averaging over the detector aperture width; 1/2 number of pixels/mm; sampling data points 2x per cycle;
DETERMINED by pixel pitch;
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| show | sampling frequency for cassette based PSP systems and by DEL (detector element) size in flat panel systems
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| How to ensure optimal image with lowest patient exposure before exposure? | show 🗑
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| show | -Automatic exposure field recognition (collimation);
-Histogram analysis (describes exposure indicator value);
-Automatic rescaling (normalization, mapping grayscale VOI to achieve specific display levels) ;
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| What is another way to describe auto rescaling? | show 🗑
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| show | system chooses which pixel values are valid for image; eliminates signals outside collimated margins (4 edges preferred)
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| What is histogram analysis? | show 🗑
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| show | mapping grayscale VOI to achieve specific display levels; specifically, provides images that have uniform display brightness over wide exposure range
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| Define data manipulation. | show 🗑
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| show | up to four images per plate, must be symmetrical; 1, 2 or 4 images per plate,
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| CR - Describe collimated edges for successful and unsuccessful exposure field recognition. | show 🗑
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| CR - what is important in collimating? | show 🗑
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| show | failure to accurately identify collimated borders;
UNEXPECTED ARTIFACTS (PROSTHESIS, SHIELD...);
WRONG HISTOGRAM ASSIGNED
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| show | system needs a defined collimated border with minimum 2 symmetrical/centered borders, 3 or 4 preferred
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| What is image plate saturation? | show 🗑
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| show | LOSS of contrast (this is not the same as LOW CONTRAST)
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| show | BRIGHTNESS and CONTRAST
-Window Level - adjust brightness;
-Window Width - INVERSELY related to contrast;
CHANGING PROCESSING CODE
-alters histogram
-limits data sent to radiologists
-potential legal ramifications
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| show | number of values that are included in contrast;
INVERSE - wider width, less contrast
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| Describe function of WINDOW LEVEL | show 🗑
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| show | image noise
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| show | because CR plates are EXTREMELY sensitive to background radiation which will compromise image quality
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| Why are CR plates so sensitive to background radiation? | show 🗑
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| Which is more intense - scatter or background radiation? | show 🗑
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| What is the best method to control scatter? | show 🗑
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| show | ZEBRA PATTERN artifact - double set of grid lines appear on image (2 grids used);
CR reader and grid have similar frequencies or are aligned parallel to CR reader scan lines
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| show | VIOLATION of NYQUIST FREQUENCY;
loss of info and fluctuating signal is produced (aliasing); creates wraparound image that appears as 2 superimposed, slightly out of alignment images (Moire effect)
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| Describe Nyquist Frequency relationship to sampling. | show 🗑
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| What are the causes of aliasing/Moire effect? | show 🗑
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| How do you identify the causes of zebra lines? | show 🗑
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| show | 1. multiple conversions result in loss during transitions;
2. light spread - loss of data;
3. distance (between capture/collection) light spread - loss of data;
4. time - must be read within 1hr (charges escaping)
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| Describe loss of info in DR systems. | show 🗑
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| show | AEC - automatic exposure control;
preceded by phototimer
AEC is designed to terminate exposure when appropriate amount of radiation is received at receptor
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| show | eliminates need for radiographer to set mAs; lower patient dose
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| What are tech responsibilities using AEC? | show 🗑
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| Describe AEC. | show 🗑
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| show | CENTERING anatomy over chamber
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| show | image will be underexposed, exposure indicators will be affected, possibly requiring a repeat
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| What affects receptor exposure when using AEC? | show 🗑
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| show | incorrect bucky selected;
exp time < min response time;
incorrect density selected;
AEC malfunction;
Incorrect chamber selection;
prosthesis;
artifact (sandbag/lead strip over AEC)
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| show | backup timer too short;
incorrect density selected;
lack of collimation;
incorrect chamber selection;
incorrect positioning of anatomy (peripheral to detector, too small (hand), not centered)
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| What is backup timer? | show 🗑
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| show | behind IR
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| show | in front of IR
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| Describe PHOTODIODE | show 🗑
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| show | Ionization chamber;
between patient and IR, ionization within the chambers occur to predetermined charge, then terminates exposure
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| show | AEC is a part of x-ray circuitry
minimum response time;
back up timer;
density controls;
detector configuration
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| What is the maximum time the backup timer can continue? | show 🗑
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| show | radiant energy that strikes or crosses surface per unit of time or radiant energy emitted by a source per unit time
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| What is PHOTOMETRY? | show 🗑
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| What is LUMINOUS FLUX? | show 🗑
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| What is ILLUMINANCE? | show 🗑
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| What is LUMINANCE INTENSITY? | show 🗑
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| show | Similar to luminance intensity / another measure of brightness;
the amount of luminous intensity emitted by a source of light;
-candela per sq/m
-nit
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| show | when ambient or room lighting reflects off the surface of the monitor or display screen
minimize this by turning down the room lights (using LCD instead of CRT)
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| show | Orth p326/Papp p183
-light scatering in display that induces a diffuse luminance veils intended image
-internal glare (inside CRT) caused by electron backscatter, lateral leakage of light from phosphor, and other scattered light
**degrades CONTRAST**
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| show | type of monitor used to display images; consists of vacuum tube, electron gun (cathode) w/focusing and accelerating grids and a deflecting coil for steering electron beam. Anode is reflective phosphor coating on inside of front screen; raster pattern scan
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| show | emits a stream of electrons, which go through three modifications to control the shape, direction and quality of the electron streem
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| What is the electron beam? | show 🗑
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| What is the Aluminum reflector? | show 🗑
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| show | spot pixel is round (CRT, electron);
picture element is square (LCD)
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| How does SNR affect CRT displays? | show 🗑
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| show | MONITOR
LCD - liquid crystal display
CRT - cathode ray tube
AMLCD - plasma display
MONITOR=weakest link in dig sys (resolution)
DIGITAL FILM PRINT
DIGITAL COMMUNICATION NETWORKS
PACS, RIS, HIS, DICOM, Teleradiology, HL7
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| show | flat panel monitor using liquid crystals that consist of liquid crystal cells, polarizer filters, and a backlight ;
Crystals change molecular orientation when electrical field is applied
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| what are the advantages of LCD over CRT? | show 🗑
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| show | light is emitted at 90' angle to faceplate and there are lower black levels (min luminance)
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| show | *limited viewing angle (40' either side) called angular dependence
*subject to dead pixels
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| show | flat panel plasma displays consist of active matrix of tiny fluorescent bulbs emit light from each pixel. Thin yet have a high luminance output, wide angle of viewing
EXPENSIVE and short lifespan
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| What are the advantages of CRT? | show 🗑
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| show | *large size/weight
*prone to geometric distortions
*high power consumption/high heat
*susceptible to screen burn
*flicker at refresh rates <85Hz
*sensitive to mag interference
*blurred edges
*glass envelopes contain lead/barium (shielding)
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| Describe digital communication networks | show 🗑
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| show | *picture archiving and communication system;
*divided into acquisition, display, and storage system;
*Communication btwn modalities
*Use common language DICOM
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| Describe DICOM | show 🗑
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| Describe RIS | show 🗑
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| show | hospital info system (EPIC in this area)
contains the patient's full medical info from billing to inpatient ordering; any possible service to patient
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| show | Electronic Medical record
houses the patient's private health records including prior imaging or medical procedures, lab results, pathology reports, notes from Drs/Nurses, etc; allows interface with ancillary services to view reports in common format
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| show | communication standard configured for info systems PACS, RIS, HIS, and EMR can exch alphanumeric data. integrates textual data with patient demographics, admission, and discharge orders, types of procedures, radiology reports, admin info, clinical data
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| show | liquid crystals are linearly arranged by electrical current to dipole state
2 thin glass plates with liquid crystals between, one glass has rows, the other columns
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| What is contained in a DICOM header? | show 🗑
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| What are important concepts in medical imaging? | show 🗑
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Created by:
Larobbins
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