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KETT: Image Prod. 1
Image Acquisition &Technical Evaluation
| Question | Answer |
|---|---|
| How does INC mAs affect: receptor exposure, spatial resolution, distortion | INC, no change, no change (more photons) |
| How does INC kVp affect: receptor exposure, spatial resolution, distortion | INC, no change, no change (more photons, higher penetrability, more scatter) |
| How does INC OID affect: receptor exposure, spatial resolution, distortion | DEC, DEC, INC (size) (increase magnification) |
| How does INC SID affect: receptor exposure, spatial resolution, distortion | DEC, INC, DEC (size) (inverse square law, less magnification) |
| How does INC FSS affect: receptor exposure, spatial resolution, distortion | no change, DEC, no change (increases penumbra) |
| How does INC Grids (grid ratio) affect: receptor exposure, spatial resolution, distortion | DEC, no change, no change (decrease scatter) |
| How does INC tube filtration affect: receptor exposure, spatial resolution, distortion | DEC, no change, no change (decreases overall intensity, removes low E xrays) |
| How does INC beam restriction affect: receptor exposure, spatial resolution, distortion | DEC, no change, no change (decreases FOV, decreases scatter) |
| How does INC motion affect: receptor exposure, spatial resolution, distortion | No change, DEC, no change (Blur) |
| How does INC anode heel effect affect: receptor exposure, spatial resolution, distortion | DEC, no change, no change ("evens out exposure", less intensity under anode side) |
| How does INC patient size affect: receptor exposure, spatial resolution, distortion | DEC, DEC, INC (size) (more absorption, increases OID) |
| How does INC pathology (additive) affect: receptor exposure, spatial resolution, distortion | DEC, no change, no change (more absorption) |
| How does INC angle (tube, part, receptor) affect: receptor exposure, spatial resolution, distortion | No change, DEC, INC (shape) (elongation and foreshortening) |
| How does INC pixel size affect: receptor exposure, spatial resolution, distortion | No change, DEC, no change (lose detail) |
| How does INC pixel pitch affect: receptor exposure, spatial resolution, distortion | No change, DEC, no change (bigger pixels) |
| How does INC DEL fill factor affect: receptor exposure, spatial resolution, distortion | INC, INC, no change (increases sensing area) |
| How does INC sampling frequency (CR) affect: receptor exposure, spatial resolution, distortion | No change, INC, no change (samples more pixel/ more info) |
| How does INC matrix size affect: receptor exposure, spatial resolution, distortion | No change, INC, no change (smaller matrix = more pixels) |
| How does INC FOV (not beam restriction) affect: receptor exposure, spatial resolution, distortion | No change, DEC, no change (changing FOV with a fixed matrix gives bigger pixels) |
| How does INC MTF affect: receptor exposure, spatial resolution, distortion | No change, INC, no change (increases fidelity) MTF = trueness of image |
| How does INC DQE affect: receptor exposure, spatial resolution, distortion | INC, no change, no change (more conversion of xrays to signal) |
| How does INC DEL size affect: receptor exposure, spatial resolution, distortion | No change, DEC, no change (increases pixel size) |
| Contrast is MOST affected/determine by the _______ | LUT |
| Geometric factors definition | Factors that affect the degree of divergence of x-ray beam and the the information recorded on the radiographic image |
| Radiographic factors (2) | Receptor Exposure & Contrast |
| Radiographic receptor exposure definition | the overall amount of xrays/radiation that reaches the IR |
| Radiographic contrast definition | the difference in densities on adjacent areas of the radiographic image |
| A high contrast image will have | mostly blacks and whites with few shades of gray (i.e. extremities) |
| A low contrast image will have | many shades of gray (chest/abdomen) |
| mAs (milliampere seconds) | the direct controlling factor of radiographic receptor exposure |
| As mAs increases, radiographic receptor exposure _______ | increases proportionally |
| Reciprocity Law Principle: | the receptor exposure on a radiograph is proportional only to the total energy imparted to the radiographic image receptor mAs1 = mAs2 |
| Radiographic exposure varies ____ with changes in distance | Indirectly |
| As the SID increases, radiographic exposure will _________ | Decrease |
| Direct square law formula is used for | adjusting mAs to compensate for changes in SID to keep radiographic receptor exposure constant; MAINTAINS CONTSTANT RECEPTOR EXPOSURE |
| Inverse square law formula used to | calculate the change in beam intensity that results from a change in distance |
| Inverse Square Law Formula: | I1/I2 = (SID2)^2 / (SID1)^2 |
| Direct Square Law Formula: | mAs1/mAs2 = (SID1)^2 / (SID2)^2 |
| kVp (kilovoltage peak) | an influencing factor of radiographic receptor exposure |
| Increasing kVp will ____ receptor exposure until 100% of the beam is successful in reaching the IR | Increase |
| 15% Rule | Increasing or decreasing the kVp by 15% will DOUBLE or HALVE the receptor exposure (when between 60-90kV) |
| Grid Ratio = | height / distance |
| Grids are | beam attenuators |
| If no adjustment is made, increasing the grid ratio will _____ receptor exposure | Decrease |
| Grids decrease _______ prior to interacting with the image receptor; reduces fog effect | scatter radiation |
| To maintain the desired amount of receptor exposure, changes in _____ must be made to compensate for the presence of a grid | mAs |
| A decrease in scatter will _____ contrast | Increase/improve |
| Grid Ratio & mAs Multiplication Factors (table) | No grid = 1 5:1 = 2 6:1 = 3 8:1 = 4 10:1/12:1 = 5 16:1 = 6 |
| Grid conversion formula | mAs1 / mAs2 = conversion factor1 (from)/conversion factor2 (to) |
| Grid frequency is | a measure of the number of grid lines per unit distance |
| True/False: Grids affect patient dose | FALSE; grids do NOT affect pt. dose but mAs does |
| Filters ___ skin exposure to patients | Decrease |
| Increasing filtration will _____ the amount of radiation available to expose the IR | decrease (will dec receptor exposure) |
| Factors that contribute to the absorbing ability of a body part incldue: | Thickness, Atomic Number, Specific Gravity |
| As thickness increases, beam attenuation ____ and receptor exposure will ____ | Increases; decreases |
| As the atomic # of an object increases, attenuation will _____, yielding a _____ in receptor exposure | Increase; decrease |
| As specific gravity increases, attenuation will _____ yielding a ____ in receptor exposure | Increase; decrease |
| Additive diseases _____ the amount of beam attenuation | increase; this results in a decrease in receptor exposure |
| Destructive diseases ____ the amount of beam attenuation | decrease; yielding an increase in receptor exposure |
| Beam restriction means | increasing collimation |
| Beam restriction will ______ the field size, which ______ receptor exposure and ____ the amount of scatter reaching the IR | decrease; decreases; decreases |
| True/False: Filtration does not affect scatter | TRUE |
| True/False: Beam restriction does not affect scatter | FALSE |
| Additive diseases increase ________ and decrease ______ | Subject exposure; receptor exposure |
| Examples of additive diseases (main) | Edema, tumors, atelectasis, cardiomegaly, CHF, emphysema, pleural effusion, pneumonia, tuberculosis, ascites, hydrocephalus |
| Examples of additive diseases (extra) | Abcess, bronchiectasis, pneumoconiosis, pneumonectomy, aortic aneurysm, cirrhosis, calcified stones, acromegaly, chronic osteomyelitis, osteochondroma, Paget's disease, sclerosis, osteopetrosis |
| Destructive diseases decrease _______ and increase _________ | Subject contrast, receptor exposure |
| Examples of destructive diseases (main) | Atrophy, emphysema, pneumothorax, bowel obstruction, carcinoma, degenerative arthritis, gout, multiple myeloma, osteomalacia, osteoporosis |
| Examples of destructive diseases (extra) | Anorexia nervous, emaciation, aerophagia, active osteomyelitis, aseptic necrosis, fibrosarcoma, hyperparathyroidism, osteolytic mets |
| Technique adjustment for additive diseases | Increase kVp 15% |
| Technique adjustment for destructive diseases | Decrease mAs 50% |
| Anode Heel Effect definition | A variation in xray beam intensity with an INC in beam intensity toward the cathode end of the beam and a DEC in intensity toward the anode end of the beam. |
| Anode heel effect is most prominent when | imaging with a long field size in line with the long axis of the tube combined with a body part of varying part thickness at its extremities (AP T-spine/ AP Femur) |
| Anode heel effect is overcome with | adjustments in part positioning (FAT CAT) or through the use of a compensating filter (wedge filter with thicker end toward cathode end of the beam) |
| Radiographic contrast is the product of ______ and ______ | Subject contrast and image receptor contrast |
| Subject contrast definition | The variations in absorbing ability of objects within part of interest (in the patient; inherent. FACTORS: body habitus, prosthetics, pathology) |
| Image receptor contrast definition | Ability of the image receptor to respond to variations in exposure (radiation) resulting in variations in receptor exposure |
| Exposure Latitude definition | The range of exposure factors that will produce a radiograph of diagnostic quality |
| Narrow width (High Contrast) | There is a large difference in measured opacity (receptor exposure) between two points on a image receptor Hint: image receptor is snappy/crisp (i.e. extremities) |
| Wide width (Low Contrast) | There is a small difference in measured opacity (receptor exposure) between two points on the image receptor. Hint: Image receptor has uniform level of opacity, bland. (i.e. chest or abdomen images) |
| SHALL | S = short (low kVp) (black & whites) (narrow exposure latitude) H = High A L = Long L = Low (high kVp) (grays) (wide exposure latitude) |
| kVp is | the primary controlling factor for subject contrast |
| Scales of contrast definition | the range of receptor exposure differences present in an image |
| Short scale contrast | the image receptor exhibits few variations in opacity (receptor exposure) with great differences between opacities |
| Long scale contrast | the image receptor exhibits many variations in opacity (receptor exposure) with small differences between opacities |
| Contrast varies _________ with kVp | indirectly |
| As kVp INC, contrast will _________ | Decrease (longer scale, more grays) |
| As you INC filtration, penetrability _______ and contrast ______ | INC, DEC |
| Spatial resolution definition | The ability to perceive structures on the radiographic image receptor as being separate and distinct. Depends on how well the edges of objects are recorded on the image receptor. |
| Umbra | area of image sharpness |
| Penumbra/Blur | area of unsharpness surrounding the image |
| Penumbra is ______ toward the cathode side | greater |
| OID is the | Object to Image Distance |
| OID effects | RECORDED DETAIL and MAGNIFICATION by allowing an increase in divergence of the remnant beam prior to reaching the IR |
| As OID INC, recorded detail _______________ | DECREASES |
| Equation to calculate magnification | Image Size / Object Size = SID / SOD |
| SID = _____ + ______ | SOD + OID |
| SOD = ____ - _____ | SID - OID |
| OID = _____ - ______ | SID -SOD |
| SID is the | Source to Image Distance |
| SID effects | the recorded detail and magnification (size distortion) |
| As SID INC, recorded detail _________ while magnification _______ | Increases, decreases |
| T/F: Every exposure has some magnification | TRUE (inherent OID from part thickness) |
| Two types of patient motion | Voluntary (respiration) and involuntary (peristalsis, heartbeat) |
| 5 projections that need breathing motion (orthostatic breathing technique) | Lateral T-Spine AP Scapula RAO Sternum Lateral Soft Tissue Neck Lateral Transthoracic (shoulder/proximal humerus) aka Lawrence method |
| Ways to reduce patient motion | Proper pt instructions/communication Adjustments in exposure time (decrease using reciprocity law) |
| Motion causes | overall blurring of details in the image |
| As focal spot size INC, recorded detail ______ | DEC |
| Actual focal spot | On the anode; measured at right angles to the surface of the ANODE Reflects the size of the filament used for the exposure |
| Effective Focal Spot / Projected Focal Spot (Useful FS) | Measured at right angles to the long axis of the xray tube (coming toward the patient) |
| The effective FS size is always ______ than the actual FS size | SMALLER |
| As the angle of the anode DEC, the effective FS ___________ | DEC |
| Line Focus Principle | the relationship between actual and effective focal spot; the actual focal spot is always larger than the effective focal spot |
| A smaller FS results in ______ penumbra and _____ spatial resolution | DEC ; INC |
| Distortion | deals with the degree of perversion or "untrueness" of the image recorded on the IR |
| Types of distortion | Size distortion (magnification) Shape distortion (elongation and foreshortening) |
| Factors affecting size distortion | ONLY OID and SID |
| Factors affecting shape distortion | ONLY tube angle, part angle, angle of the IR, and motion |
| Elongation results from | increase in tube angle |
| Foreshortening results from | angle/tilt of the part or IR |
| Technique charts are | pre-programmed techniques - anatomically programmed radiography (APR) programmed into the control unit |
| Fixed kVp/ Variable mAs Chart | has a pre-established kVp value used for each body part per patient body habitus (sthenic, hypo, hyper) with mAs values applied to each category |
| Value of fixed kVp/variable mAs chart | more consistent radiographic contrast |
| Disadvantage of fixed kVp/variable mAs chart | Requires higher mAs settings for larger pts/body parts, which increases exposure times & INC risk of repeats due to pt motion |
| Fixed kVp technique system is similar to the basic principle of _____ | phototiming |
| Variable kVp / Fixed mAs Chart | Uses a pre-established mAs for each body part kVp determined by using calipers to measure thickness of part |
| Operating at 80 kVp, a _____ change is made for each centimeter in part thickness | 2 kV |
| Operating above 80 kVp, a _____ change is made for each centimeter in part thickness | 3 kV |
| Value of Variable kVp / Fixed mAs Chart | Assures penetration of the objects of interest |
| Disadvantage of Variable kVp / Fixed mAs Chart | radiographic contrast is prone to unacceptable variations |
| Wet plaster casts usually require | doubling of exposure factors 100% INC in mAs or +8-10 kV |
| Dry plaster casts usually require | 50-60% INC mAs or +5-7 kV |
| Fiberglass casts usually require | 25-30% INC mAs or +3-4 kV |
| Tissue receptor exposure (effects of aging process) | As the amount of tissue mass to water content in a volume of tissue decreases, the amount of exposure needed will DEC |
| Part thickness | parts measuring 10cm or greater require the use of a grid to offset secondary and scatter radiation produced |
| Tissue abnormalities | attenuation of the beam will vary greatly between a normal body region and one suffering from some abnormality |
| Age and receptor exposure | Pediatric and geriatric pts are more sensitive to radiation exposure, thus need LESS dose |
| How does contrast media affect receptor exposure | Contrast media artificially alters the receptor exposure (subject contrast) of internal structures |
| what may occur with AEC techniques if the required mAs is too low | quantum mottle (this can be prevented by decreasing kVp which will increase the mAs) |
| Detector selection (AEC) | phototiming cell or field that is selected depends on body part being imaged |
| Anatomic alignment using AEC | the amount of radiation required to produce a quality, diagnostic image depends on the cell that is selected *must use careful positioning and correct CR centering when using AEC* |
| Exposure adjustments using AEC | +1 for very large patients to prevent underexposure -1 for very thin patients to prevent overexposure (1 = a 25% change in exposure) |
| Spatial resolution in digital imaging | is the ability of the system to record adjacent small structures, equipment related; "sharpness" of the structural edges recorded; measured in line pairs per mm |
| Pixel | smallest area depicted in an image 2D square that contains discrete gray shade |
| Pixel size is | measured end to end; as pixel size INC, spatial resolution DEC |
| Pixel pitch is | measured center of one pixel to the center of another pixel as pitch INC, spatial resolution DEC |
| Pixel units | measured in microns 1 micron = 0.001 mm |
| DEL (detector element) | used with direct capture radiography (cassetteless); uses a flat panel detector |
| Fill factor is | the ratio of a pixels light sensitive area versus a pixels total area |
| As DEL increases, spatial resolution _____ | DECREASES |
| We want a ________ DEL size with a ___________ DEL fill factor | small; large |
| Matrix | 2D array of pixels (x & y); the total number of pixels matrix size is dependent on FOV and pixel density |
| INC in IR size results in _____ of matrix size | INC |
| DEC pixel size results in ______ matrix size and _____ spatial resolution | INC; INC |
| DEC pixel size ____ visibility of small structures and ______ spatial resolution | INC; INC |
| T/F: spatial resolution is related to exposure amount | FALSE Spatial resolution is NOT related to exposure amount |
| Sampling frequency definition | the number of pixels sampled per mm as the laser scans each line of the imaging plate |
| The more pixels sampled per mm, the _____ the sampling frequency | greater |
| Increasing the sampling frequency results in | the laser moving a SMALLER distance and an INC in spatial resolution; but also a longer processing time due to more info being collected |
| CR uses | sampling frequency |
| Contrast resolution | the ability to detect subtle changes in the grayscale |
| Bit depth | the amount of grays available in a pixel |
| Detective Quantum Efficiency (DQE) | how efficient a system is at converting xrays into signal |
| Dynamic range/contrast resolution | range of values over which a digital image receptor will respond greater dynamic range will yield greater contrast resolution |
| Signal | results from xray deposition of energy in a detector (image data) |
| Noise | results from extraneous info (interference); limits the ability to visualize objects |
| Types of noise | Quantum mottle (too few xrays reach IR - underexpdosure) Scatter Electronic |
| Dynamic range | series of expected values used to produce acceptable image; what we should use |
| Exposure latitude | room for error; ability of a system to under or over expose and still produce an acceptable image EVERYTHING we can use |
| Signal to Noise Ratio (SNR) | radio btwn signal or meaningful info and noise or background info |
| As noise increases | it is more difficult to visualize small objects |
| We want a ________ SNR | high |
| INC signal will _______ visibility of spatial resolution | INC |
| Noise will _____ an image | degrade it decreases our ability to see all spatial and contrast resolution |
| Types of image identification | 1. Radiographic - lead markers (placed pre-exposure) 2. Electronic - on digital image (post-exposure) |
| Legal data required for a radiograph | Patient data - name and ID # Exam data - postural and side markers Exam date Institutional data - hospital name where exam was performed |
| A minimum of _____ kVp change is necessary to yield a noticeable receptor exposure difference within the image | 10% |
| A minimum of ____ mAs change is necessary to yield a noticeable receptor exposure difference within the image | 30% |
| Usually a radiograph that needs to be repeated due to over or underexposure requires a ________ or ______ of the exposure factors | Doubling or Halving |
| Receptor exposure increases and decreases _______ with mAs (reciprocity law principle) | directly/proportionally |
| Receptor exposure _________ as SID increases | decreases exponentially |
| The Inverse Square Law | will determine the amount of receptor exposure as SID is changed |
| The Direct Square Law | will determine the change in mAs required to obtain an image of similar receptor exposure if SID is changed |
| Exposure indicator is | a numeric value that represents the amount of exposure the image recepter received |
| Sensitivity (s) number is ________ related to the amount of exposure received by the IR | inversely |
| Exposure index is _______ proportional to the exposure received by the IR | directly |
| Digital imaging systems have a ______ exposure latitude | wide images with S# or exposure index outside of recommended range may still appear diagnostically acceptable |
| Digital IR should be exposed to ______ of radiation at 80 kVp | 1mR (0.01 mGy) |
| The acceptable range of exposure is determined by the __________ and the ___________ desired to produce a diagnostic radiograph | part under examination; level of spatial resolution |
| Underexposure can result in a ________ image and loss of _________ | mottled; spatial resolution |
| Overexposure can result in a loss of ___________ and an _________ violation | contrast resolution; ALARA |
| Quantum noise / Quantum mottle | insufficient quantity of xray photons; mAs is too low and insufficient light is produced by the phosphor |
| Contrast decreases ________ as kVp ___________ | proportionally; increases |
| Scatter reaching the IR _______ as kVp increases | increases |
| Optimal kVp range for adults is | 60-120 kVp |
| Optimal range for children weighing less than 100lb is | 50-90 kVp |
| Increasing kVp for digital imaging will have a __________ impact on image contrast, but will reduce patient dose | minimal |
| Filtration __________ the effective energy level of the beam by hardening the beam removing low energy, non-diagnostic photons from the beam | increases |
| Image contrast _________ as filtration increases | decreases (INC filtration INC penetrability DEC contrast) |
| Increasing kVp will _______ contrast, ______ noise, _______ scatter | decrease; increase; increase |
| Grids are used to | control scatter reaching the IR |
| Contrast ________ as the grid ratio increases | increases more scatter is absorbed prior to interacting with the IR |
| As grid ratio increases, exposure factors must _____ to account for the loss of receptor exposure resulting from the elimination of scatter | increase |
| Off Distance/ Off Focus grids happens when | using a grid outside the established focal range; exhibits uniform cutoff along the lateral edges of the image; can be near or far focus decentering (wrong SID) |
| Lateral decentering / Off center | Lateral off centering will exhibit the presence of lead strips of more frequency on one side of the image than the other; uniform exposure loss |
| Stopped grid | a reciprocating grid that stopped at some point during exposure will exhibit a uniform appearance of lead strips across the entire image |
| Upside down grid | will exhibit normal receptor exposure in the center with complete cutoff toward both lateral ends of the image |
| Off level grid / tilted grid | results in decreased receptor exposure across the entire image |
| Moire Pattern | wave-like or water appearance on an image occurs when two linear grids are placed on top of one another to make a crosshatched grid but the lead lines are not aligned at right angles |
| Grid frequency is | the number of lead strips per inch or cm the "lead content" |
| Moire Pattern/ Aliasing artifact with digital subtraction | there is a misalignment of pixels of the digital mask and a second digitized image; caused with short dimensional (SD) grids |
| Use a ______ frequency grid to decrease moire | high |
| Recorded detail _______ as patient motion increases | decreases |
| a ______ exposure time will help minimize the effects of voluntary and involuntary motion | short |
| Size distortion is | magnification |
| Magnification is increased with | long OID or short SID |
| Best way to minimize magnification is to use a | short OID (longer SID will result in greater entrance exposure to pt) |
| Shape distortion is affected by | angulation of the tube, part, and IR AND motion |
| Images of anatomical structures are best represented if the structure is positioned ____________ to the IR | parallel |
| the CR should be directed ___________ to the anatomical structure to best demonstrate that structure | perpendicular |
| Identification markers include | anatomical side, patient information, date of exam |
| Additive pathologies ________ the receptor exposure of anatomical structures and require an _________ in exposure factors | increase; increase |
| Destructuive pathologies ________ the receptor exposure of anatomical structures and require an _________ in exposure factors | decrease; decrease |
| Static appears as a ____________________ artifact on an image | black spider-like |
| Static is the result of _________ when the IR is exposed to open air | static electricity discharge |
| Pressure image artifact | results from improper/rough handling; from CR IR being stacked too high in storage |
| Grid lines image artifact results from | using a stationary grid or improper use of a reciprocating grid; appears as parallel opaque lines on the radiograph |
| Moire Effect/Aliasing image artifacts | a wavy artifact in digital imaging caused when grid lines are projected onto the imaging plate and are parallel with the scanning laser |
| System malfunctions: ghosting | there is insufficient erasure of an image and a ghost image is seen on the new image |
| System malfunctions: dead pixels | occur when there is no response to the light input by the pixel; when there is a dead pixel the system averages the good pixels surrounding the bad ones and replaces the value of the bad ones |
| Radiation Fog (CR) | unintentional exposure to radiation; true fog; does not display patient information |
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SavHoffman25
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