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Ch11. Equipment
RAD protection/Biology. Chap 11. Equipment Design
| Question | Answer |
|---|---|
| Leakage radiation at 1 m from source cannot exceed _______ when the tube is operated at its highest voltage at the highest current | 1mGya/hr (100 mR/hr) |
| Distance and centering indicators must be accurate to within ____ % and ____% of the source-to-image receptor distance (SID). | 2 and 1 |
| When the size of the x-ray field is restricted, dose is significantly reduced because... | a smaller field size produces less scatter. |
| What is the most common type of collimator? | light localizing variable-aperture rectangular collimator. |
| light localizing variable-aperture rectangular collimator consists of what 3 things? | 2 sets of lead shutters, light source to illuminate the x-ray field, mirror to deflect the light beam toward the patient. |
| To minimize skin exposure, the patients surface should be at least _____ below the collimator. | 15 cm. |
| Simplest of all beam limitation devices? | aperture diaphragm |
| 2 benefits of extending the SID? | Less magnification (better recorded detail) and can also decrease pt dose. |
| Inherent filtration includes the: _____, ____, and _____. Which these 3 things amounts to approx _____ mm aluminum equivalent. | glass envelope, insulating oil, glass window in tube housing. 0.5 mm. |
| The light localizing variable aperture rectangular collimator provides an additional _______ mm aluminum equivalent to the 0.5 of inherent filtration. | 1.0 mm |
| Total filtration of _____mm aluminum equivalent for fixed units operating above ______kVp, ______mm aluminum equiv for operating from ____ to ___ kVp, and ____ mm aluminum equiv below ____ kVp. | Above 70 = 2.5. Between 50-70 = 1.5. Below 50= 0.5. |
| Mammo uses ___ to ___ keV(approx) | 17-20 |
| When the tube target for mammo is made of ______, either a 0.03 mm molybdenum or a 0.025 mm rhodium filter can be used. | molybdenum |
| When the tube target for mammo is made of ______, the rhodium filters are used. | rhodium |
| _____ filters allow a lower energy window, therefore they are better for small and average breast thickness. | Molybdenum |
| rhodium filters, used with either anode, are better for ____ or ____ breasts because they will produce a beam with higher energy. | large or dense |
| ____ is defined as the thickness of an absorber required to decrease the intensity of the beam by 50% of its initial value. | Half Value Layer (HVL) |
| When should the HVL be checked? | At least once a year and after each tube is replaced or repaired. |
| Consistency in output in intensity for identical generator settings form one exposure to subsequent exposures is termed _____. (unit must be able to duplicate exposures for any given combo of kVp and mAs) | exposure reproducibility |
| A variance of ____% is acceptable for exposure reproducibility | 5 |
| ____ refers to a consistency in output radiation intensity at any kVp when generator settings are changed from one mA and time to another. | exposure linearity |
| exposure linearity must be less than ____. (L cannot exceed ____%) | .1 (10%) |
| What is the standard film screen speed for general radiography? | 400 |
| When the speed of screen film systems doubles, the patients exposure... | is reduced by approx half. |
| Increase grid ratio what happens to pt dose? | increase. Need to use more mAs. |
| __________ is the ratio of the height of the lead strips to the distance between them | grid ratio |
| ______, such as amorphous silicon, converts the x-ray energy into visible light. | Scintillators (in indirect).... (photoconductor of A-se in direct changes x-rays to electric right away) |
| The sensitivity of the phosphor used in CR has been described as approx equal to a 200 speed screen film combination. What does this imply? | that CR technique factors are generally somewhat greater than those used in conventional radiography, in which 400 speed is typically used. |
| 3 significant benefits of image intensification fluoroscopy | Increased image brightness, saving time for the radiologist, patient dose reduction (less mAs is required now) |
| Why use magnification mode? | Even though it increases tube mA increasing pt dose, the overall quality of the image is better because of improved contrast, so tissues can be distinguished more easily. |
| 2 benefits of pulsed fluoro? | decreases pt dose, helps extend life of tube |
| In accordance to NCRP regulations, SSD must be no less than ____cm for stationary fluoroscopes, and no less than ___ for mobile fluoroscopes. | 38 cm (15 inches), 30 cm (12 inches) |
| A _______ timer must be provided and used with each fluoro unit. What does this device do? | cumulative timer. Sounds at 5 minutes. |
| Current standards limit the ESE rates of general intensified fluoro to a max of ________ mGya per minute (_____ R/min) | 100 (10 R/ min) |
| During C-arm procedures, the II distance should be as _____ as possible to reduce pt dose. | short |
| To reduce pt dose, the tube should always be above or below the table? | below. (scatter is more intense when tube is above) |
| ____ can result in the highest pt doses of all diagnostic procedures. | cinefluorography |
| How can pt dose be reduced when using cinefluoro? | intermitten activation to locate the catheter, limit the time of the cine, use the last image hold feature |
| If skin dose is received in the rang of ______ to ____, the FDA requires that a notation be placed in the pt's record. | 1-2 Gyt |
| Rad skin injuries may not appear for approx ..... | 10 days |
| High level control fluoro is used when? What is the SSD and maximum entrance exposure rate? | in IR. SSD is 30 cm (same as mobile fluoro... stationary is 38) and entrance is 200 mGya (normal is 100) |
| In II systems, pt exposure increases when a smaller viewing mode (15 cm compared to 23 cm) or a ____ speed cine film is used. | lower |
| Switching from 23cm to a 15 cm field of view has approximately what effect on pt dose? | nearly doubles the tabletop exposure rate. |
| Increasing the frames per second from 30 to 60 would do what to pt dose? | double it. |
Created by:
Zoest35
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