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RADT 465-Image Eval

ARRT registry review covering Image Acquisition and Evaluation

QuestionAnswer
What can cause magnification in imaging? Magnification is effected by both OID and SID. If OID is too large or if SID is too short than the object being imaged will appear magnified. (Lange Q&A, 10th ed, Pg. 215)
What does pixel depth relate too? Pixel depth is directly related to the number of gray shades that can be represented in an image. It also can be referred to as dynamic range. (Lange Q&A, 10th ed, Pg. 215)
(T/F) As matrix size increases the resolution of an image decreases. False: As the matrix size increase the resolution will also increase due to an increase in the number (and decrease in the size) of pixels. (Lange Q&A, 10th ed, Pg. 215)
What causes Moire artifacts? A Moire artifact (AKA aliasing artifact) is seen in computed radiography when using stationary grids and results when the grid's lead strip pattern matches up with the scanning/sampling pattern in the image reader. (Lange Q&A, 10th ed, Pg. 215)
What is the inverse square law equation? The inverse square law is represented by the equation: (Starting intensity divided by ending intensity) = (ending distance squared divided by starting distance 1 squared) (Lange Q&A, 10th ed, Pg. 216)
What is attenuation? Attenuation is the reduction of x-ray intensity as it passes through matter. (Lange Q&A, 10th ed, Pg. 216)
(T/F) Increased kVp results in increased scatter radiation. True: An increase in kVp will result in more Compton interactions and as a result, more scatter radiation/image "fog" (Lange Q&A, 10th ed, Pg. 216)
What is HVL and what is its role in radiography? HVL or Half-Value Layer refers to the thickness of a material that will reduce the x-ray beam intensity by half it's original value (Lange Q&A, 10th ed, Pg. 217)
What is MTF and what is its role in radiography? MTF or Modulation Transfer Function is responsible for measuring the amount of information lost between the object being imaged and the image receptor (Lange Q&A, 10th ed, Pg. 218)
What does window width manipulate? Window width manipulates the contrast scale/ contrast resolution of the image. Alters the number of grays displayed in the image (Lange Q&A, 10th ed, Pg. 218)
What does window level manipulate? Window level manipulates the image brightness (Lange Q&A, 10th ed, Pg. 218)
What does DQE refer to? DQE or Detective quantum efficiency refers to how efficient the phosphors are at detecting and interacting with x-ray photons. (Lange Q&A, 10th ed, Pg. 220)
(T/F) PSP phosphor size has a direct relationship to resolution. False: Phosphor size is inversely related to resolution. This means that as phosphor size decreases, resolution increases.(Lange Q&A, 10th ed, Pg. 220)
How is pixel size calculated in digital imaging? Pixel size is calculated by dividing the FOV by the matrix. It is measured in mm/pixel (Lange Q&A, 10th ed, Pg. 220)
How is grid ratio calculated? Grid ratio is the height of the lead strips divided by the the width of the interspace material (Lange Q&A, 10th ed, Pg. 221)
What causes phantom image artifacts in PSP systems? Phantom image artifacts are caused by incomplete erasure of the previous image from the PSP cassette. The resulting artifact resembles a double exposure (Lange Q&A, 10th ed, Pg. 222)
What steps are involved in indirect image capture systems? Indirect image systems use a scintillator to convert x-ray photons to light. That light is then picked up by a photodectector and converted to an electrical signal that is transferred to the ADC (analogue-to-digital converter)(Lange Q&A, 10th ed, Pg. 223)
What steps are involved in direct image capture systems? Direct image systems convert captured x-ray photons directly to an electrical signal that is then sent to the ADC (Lange Q&A, 10th ed, Pg. 223)
What is the density maintenance formula? [(Old mAs / New mAs) = (Old Distance ^2 / New Distance ^2)](Lange Q&A, 10th ed, Pg. 225)
List the grid factors used to manipulate mAs? No Grid = 1 x original mAs, 5:1 grid = 2 x mAs, 6:1 grid = 3 x mAs, 8:1 grid = 4 x mAs, 12:1 grid = 5 x mAs, and 16:1 grid = 6 x mAs (Lange Q&A, 10th ed, Pg. 225)
How is mAs calculated? Milliamperage x time in seconds. [mA x seconds] Milliseconds must be converted to seconds and can be done by dividing the milliseconds by 1000 (Lange Q&A, 10th ed, Pg. 225)
How would exposure factors change for a disease such as emphysema? Would they increase or decrease? Since a disease like emphysema causes the lungs to be filled with an abnormal amount of air, the exposure factors would have to be decreased to avoid overexposure (Lange Q&A, 10th ed, Pg. 227)
How would exposure factors change for a disease such as pleural effusion? Would they increase or decrease? Since a disease like pleural effusion causes an abnormal accumulation of fluid in the chest, the exposure factors would have to be increased to help penetrate the additional material (Lange Q&A, 10th ed, Pg. 227)
What are some examples of exposure artifacts? Motion, Double Exposure, and Patient Clothing/Jewelry (Lange Q&A, 10th ed, Pg. 228)
(T/F) Histograms are unique to their respective body part. True (Lange Q&A, 10th ed, Pg. 228)
What are the developing steps/stages for radiographic film? (In order) Developer, Fixer, Wash, and Dryer (Lange Q&A, 10th ed, Pg. 228)
What is the job of the developer during film processing? The developer changes the silver bromide crystals in the emulsion on the film into black metallic silver which forms the image. (Lange Q&A, 10th ed, Pg. 228)
What is the job of the fixer during film processing? The fixer removes any unexposed silver bromide crystals left on the film emulsion (Lange Q&A, 10th ed, Pg. 228)
What is the job of the wash portion of film processing? The wash stage of film processing removes the remaining chemicals on the film (Lange Q&A, 10th ed, Pg. 228)
What is are compensating filters used for? A compensating filter is used on parts that have differences in density. The filter helps balance the uneven density by adding thickness to the part. Prevents the thin portion from being "burnt out" during exposure (Lange Q&A, 10th ed, Pg. 229-230)
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