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What is the formula for mAs?
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RADT465- Image Prod.
ARRT registry review covering Image Production Equip. Op. & QC and Acq. & Eval.
| Question | Answer |
|---|---|
| What are the grid conversion ratios? | -No grid=1 -5:1=2 -6:1=3 **Equivalent to air gap technique -8:1=4 -10:1/12:1=5 -16:1=6 (Williams Math Review, 2021) |
| What is the formula for mAs? | mA x Seconds= mAs (Williams Math Review, 2021) |
| What is the 15% rule? | ***Applies only to 60-100 kVp range ONLY -Increase kVp 15%, divide mAs by 2 -Decrease kVp by 15%, multiply mAs by 2 (Williams Math Review, 2021) |
| What are the relationships of SID, SOD, and OID? | -SOD+OID=SID -SID-OID=SOD -SID-SOD=OID (Williams Math Review, 2021) |
| What is the Inverse square law? | (I1)/(I2)=(d2)^2/(d1)^2 (Williams Math Review, 2021) |
| What is the Direct square law? | "old" mAs1/"new"mAs2=(d1)^2/(d2)^2 (Williams Math Review, 2021) |
| What is the Unsharpness formula? | Filament size X OID/SOD=Unsharpness (Williams Math Review, 2021) |
| How do you figure out the Grid Ratio? (formula) | Height of Grid material/ Width of Interspace= Grid Ratio (Williams Math Review, 2021) |
| What is the Grid conversion formula? | mAs1/mAs2=Conversion Factor 1/Conversion Factor 2 (Williams Math Review, 2021) |
| What are the field size multipliers? | mAs1/mAs2=From/To 14"x17= 1 10"x12"= 1.25 8"x10" OR 9"x9"= 1.40 (Williams Math Review, 2021) |
| What is the magnification formula? | SID/SOD=MF Image size/Object size= MF ***Fluoro Old input screen size/New input screen size= Fluoro MF (Williams Math Review, 2021) |
| What is the percentage of magnification factor formula? | Image size- Object size/ Object size X 100= % (Williams Math Review, 2021) |
| What is the formula for patient dose increase in fluoro? | Input phosphor #1^2/ Input phosphor #2^2= Pt dose increase (Williams Math Review, 2021) |
| What is the formula for minification gain? | Input Phosphor Diameter^2/Output Phosphor Diameter^2= Mini. Gain (Williams Math Review, 2021) |
| What is the formula for brightness gain? | Magnification gain X Flux gain= brightness gain (Williams Math Review, 2021) |
| What is the formula for Heat Units? | # of exposures X kVp X mA X seconds X GENERATOR= Heat Untis (Williams Math Review, 2021) |
| What is the multiplication factors for the heat unit formula based on generator? | Single Phase= 1 3 Phase, 6 Pulse= 1.35 3 Phase, 12 Pulse/High Frequency= 1.41 (Williams Math Review, 2021) |
| As DQE goes _______, patient dose goes _______? | Up, Down (Image Acquisition Worksheet Day 2, 2021) |
| EI is ______________ to the exposure of the image receptor? | Directly proportional (Image Acquisition Worksheet Day 2, 2021) |
| S-number is _________________ to the exposure of the image receptor? | Inversely proportional (Image Acquisition Worksheet Day 2, 2021) |
| What is contrast resolution? | Ability of a digital imaging system to display changes in gray values; bit depth (Image Acquisition Worksheet Day 2, 2021) |
| What is spatial resolution? | Ability of a system to record adjacent small structures; measured in line pairs/mm (Image Acquisition Worksheet Day 2, 2021) |
| What is MTF? | Describes the contribution of all system components (Image Acquisition Worksheet Day 2, 2021) |
| What are the technique considerations for casts? | -Wet/Plaster= 100% mAs/8-10 kVp -Dry= 5-7 kVP -Fiberglass= 3-4 kVp (Image Acquisition Worksheet Day 2, 2021) |
| What is DICOM? | Digital Imaging and Communications in Medicine interconnects medical digital imaging devices (Image Acquisition Worksheet Day 2, 2021) |
| What is PACS? | Picture Archival Communication System Where all digital images are stored (Image Acquisition Worksheet Day 2, 2021) |
| What is RIS? | Radiology Information System Order entry, pt demographic information (Image Acquisition Worksheet Day 2, 2021) |
| What is HIS? | Hospital Information System Pt demographic information, billing, supplies, order entry for testing (Image Acquisition Worksheet Day 2, 2021) |
| What is EMR/EHR? | Electronic Medical/Health Record Pt medical charts, Medication administration record, supply chain (Image Acquisition Worksheet Day 2, 2021) |
| What is the single greatest source of acute radiation exposure in diagnostic imaging? | Fluoroscopy (Equipment Operation and Quality Control 2, 2021) |
| How is image quality evaluated? | According to image brightness, grayscale, spatial resolution, and distortion (Radiography Prep, pg. 313) |
| What are the visibility factors? | Brightness and grayscale (Radiography Prep, pg. 313) |
| What are the geometric factors? | Spatial resolution and distortion (Radiography Prep, pg. 313) |
| What are the prime exposure/technical factors used to create an image? | milliamperage (mA), exposure time (s), kilovoltage (kV), and SID (Radiography Prep, pg. 313) |
| What do digital radiographic images require? | Large amount of digital storage space High-bandwidth in PACS High-resolution display monitors (Radiography Prep, pg. 313) |
| In Digital Imaging, what does kV affect? | Penetration (Radiography Prep, pg. 313) |
| In Digital Imaging, mAs determines what? | Dose/receptor exposure (Radiography Prep, pg. 313) |
| How are brightness and contrast determined in digital imaging? | By computer software and monitor controls (Radiography Prep, pg. 313) |
| State 3 advantages of digital imaging. | Image manipulation permits visualization of structures not seen in analog imaging. Digital IRs respond to a wide range of exposures; provide a wide dynamic range Digital images can be shared and/or sent to distant locations (Radiography Prep, pg. 313) |
| Define long-scale and short-scale contrast. | Long-scale: Low contrast; lots grays Short-scale: High contrast; few grays (Radiography Prep, pg. 314) |
| What is the function of contrast? | To make details visible (Radiography Prep, pg. 314) |
| What does brightness refer to? | Principally to the amount of light transmitted by the display monitor (Radiography Prep, pg. 314) |
| What does subject contrast refer to? | Various body tissue densities and thicknesses, which result in differential absorption of the x-ray beam and signal differences within the remnant beam (Radiography Prep, pg. 314) |
| What is the Reciprocity Law? | Any combination of mA and exposure time that will produce a particular "mAs" will produce identical receptor exposure (Radiography Prep, pg. 315) |
| What are 3 factors that determine production of scattered radiation? | 1. Field size/beam restriction 2. Kilovoltage 3. Thickness/volume and density of tissues (Radiography Prep, pg. 318) |
| A 6 inch Air-gap is the equivalent to which grid ratio? | 8:1 grid (Radiography Prep, pg. 320) |
| X-ray photons can do what 3 things? | 1. Penetrate through the part 2. Scatter within the part 3. Be absorbed by the part (Radiography Prep, pg. 321) |
| When should a grid be used? | When the body part is thicker than 10 cm (Radiography Prep, pg. 321) |
| Grids can be what? | 1. Parallel or focused 2. Stationary or moving (Radiography Prep, pg. 323) |
| What are the 5 Grid errors? | 1. Angulation error: angled against lead strips 2. Off-level error: grid surface must be perpendicular to the CR 3. Off-focus error: if the SID is outside lower OR upper limits 4. Off-center error 5. Upside-down grid (Radiography Prep, pg. 323-324) |
| What is the minimum filtration requirement for x-ray tubes operated above 70 kVp? | 2.5 mm Al equivalent (Radiography Prep, pg.328) |
| Name a few additive pathologic conditions. | Ascites R.A. Paget's disease Pneumonia Atelectasis CHF Edematous tissue (Radiography Prep, pg. 331) |
| Name a few destructive pathologic conditions. | Osteoporosis Osteomalacia Pneumoperitoneum Emphysema Degenerative arthritis Atrophic and necrotic conditions (Radiography Prep, pg. 331) |
| Name 3 Anode heel effect conditions. | At short SID With large-size Its With small anode angle x-ray tubes (Radiography Prep, pg. 332) |
| State the % ripple for each generator. -Single phase -3 Phase, 6 pulse -3 Phase, 12 pulse -High Frequency | Single phase: 100% 3 phase, 6 pulse: 13% 3 phase, 12 pulse: 3-4% High Frequency: <1% (Radiography Prep, pg. 333) |
| What is the smallest unit of computer data? | Bit (Radiography Prep, pg. 334) |
| What is bit depth? | Number of bits per pixel (Radiography Prep, pg. 334) |
| What do window width and window level correspond to? | Width: controls shades of gray Level: controls brightness (Radiography Prep, pg. 334-335) |
| What are causes for image graininess? | Underexposure Incorrect processing algorithm/LUT Excess scattered radiation Inadequate beam restriction Grid misalignment; cutoff (Radiography Prep, pg. 337) |
| What are the 2 types of AEC? | Phototimer Ionization Chamber (Radiography Prep, pg. 337) |
| Digital image resolution improves with what? | Smaller pixel size Smaller pixel pitch Larger image matrix Greater pixel density (Radiography Prep, pg. 348) |
| What is Detective Quantum Efficiency (DQE)? | Describes the percentage of incoming x-ray photons that are detected and absorbed by the detector for transformation to the x-ray image (Radiography Prep, pg. 349) |
| What is quantum mottle? | Insufficient number of x-ray photons resulting in noise appearing as graininess (Radiography Prep, pg. 350) |
| What are factors that affect resolution? | -OID (magnification) -SID (magnification) -Focal Spot Size (F.S. blur) -Patient factors (shape/position) -Motion (motion blur) (Radiography Prep, pg. 350) |
| What are 2 types of image distortion? | -Size (magnification) -Shape (elongation/foreshortening) (Radiography Prep, pg. 350) |
| What is the information required on each x-ray image? | -Patient name/ ID number -Side marker, R or L -Examination date -Institution's name (Radiography Prep, pg. 368) |
| When is shielding evident? | When reproductive organs are in the collimated primary beam OR within 5 cm of it (Radiography Prep, pg. 368) |
| What is aliasing "Moire effect"? | If the direction of the lead strips and the grid lines per inch match the scan frequency of the scanner/reader (Radiography Prep, pg. 373) |
| With PSP plates, if they have been inactive for more than 48 hours, what needs to happen? | Should be erased prior to use (Radiography Prep, pg. 374) |
| What is the Nyquist theorem? | When the electric signals are sampled for conversion to a digital image, the sampling frequency must be more than twice the frequency of the input signal in order to best duplicate that original signal (Radiography Prep, pg. 375) |
| Digital imaging has what type of dynamic range/latitude? | Wide (Radiography Prep, pg. 380) |
| What is shuttering used for? | To remove the bright unexposed areas outside of the collimated field that contribute to veil glare (Radiography Prep, pg. 380) |
| Which detector systems have the highest DQE? | a-Se TFT's used in direct-capture systems (Radiography Prep, pg. 382) |
| Bremsstrahlung "braking" radiation comprise _______ % of the x-ray beam? | 70-90% (Radiography Prep, pg. 388) |
| Characteristic radiation occurs at the minimum keV and comprises how much of the x-ray beam? | 70 keV 10-30% (Radiography Prep, pg. 388) |
| What is the velocity of an x-ray? | 186,000 miles a second (3 x 10^8 m/s) (Radiography Prep, pg. 389) |
| When is the photoelectric effect most likely to occur? | In absorbers with a high atomic number (Radiography Prep, pg. 391) |
| What does Compton scatter contribute to an image and pose to personnel? | Image fog Radiation hazards (in Fluoro procedures) (Radiography Prep, pg. 391) |
| Do X-rays have an electrical charge? | No, they are electrically neutral (Radiography Prep, pg. 391) |
| What effect do x-rays have on the air? | Ionizing effect (Radiography Prep, pg. 391) |
| Classical scatter is also known as and occurs with what? | Coherent, unmodified, Rayleigh scatter With very-low energies, scatters other ways, no ionization occurs (Radiography Prep, pg. 392) |
| What is the function of a generator? | To change mechanical energy to electrical energy (Radiography Prep, pg. 394) |
| What are X-ray transformers used for? | To increase the incoming voltage to the more useful kilovoltage required for x-ray production (Radiography Prep, pg. 397) |
| Autotransformers operation on the principle of? | Self-Induction (Radiography Prep, pg. 398) |
| What do transformers & autotransformers require for operation? | AC (alternating current) (Radiography Prep, pg. 399) |
| What principle do transformers operate on? | Mutual induction (Radiography Prep, pg. 399) |
| What is the X-ray tube comprised of? | Anode (+) Cathode (-) Glass envelope (vacuum) (Radiography Prep, pg. 408) |
| What does the anode consist of? | Graphite/molybdenium disk with beveled edge Tungsten/rhenium alloy focal track (0.6-1.2 mm) Molybdenium stem (support for anode disk (Radiography Prep, pg. 408) |
| The induction motor does what? and is composed of what 2 things? | Rotates anode Stator (outside glass envelope) Rotor (inside glass envelope) (Radiography Prep, pg. 408 |
| What are 3 characteristics of Tungsten (W)? | High atomic # Z=74 High melting point= 3410 Celsius Thermal conductivity for heat dissipation (Radiography Prep, pg. 408) |
| The filament is heated with what required A and V? | 3-5 A 10-12 V (Radiography Prep, pg. 408) |
| During the production of x-rays, how much of the kinetic energy is converted to x-rays? | 0.2% the rest is converted to heat (Radiography Prep, pg. 410) |
| What is the line focus principle? | The effective focal spot is always smaller than the actual focal spot (Radiography Prep, pg. 411) |
| What % must collimators be accurate of the SID? | 2% (Radiography Prep, pg. 413) |
| What are 4 causes of X-ray tube failure? | 1. Vaporized Tungsten 2. Pitted Anode 3. Cracked Anode 4. Gassy Tube (Radiography Prep, pg. 415-416) |
| What are the types of X-ray timers? | Mechanical Synchronous Impulse Electronic mAs AEC (Radiography Prep, pg. 422) |
| What are the components of the Primary/Low-Voltage circuit? | Main Switch/Circuit breaker Autotransformer kV selector switch Line voltage compensator Timer Primary coil of high voltage transformer Exposure switch (Radiography Prep, pg. 424) |
| What are the components of the Secondary/High-Voltage circuit? | Secondary coil of the high-voltage transformer mA meter (grounded at midpoint of the secondary coil) Rectifiers X-ray tube (Radiography Prep, pg. 425) |
| What are some advantages of Flat Panel Fluoroscopy? | Pulsed x-ray beam Decreased patient dose Increased sensitivity to x-rays (DQE) Increased temporal resolution; decreased motion unsharpness Improved contrast resolution (Radiography Prep, pg. 451) |
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