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62 Cards in this Set
- Front
- Back
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typical kVp for angio
typical kVp for Ba |
75 for angio to maximize the vasculature
110 for ba to penetrate the Ba |
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highest skin dose in FLX
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500 µGy
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how does minification gain affect the brightness of an image
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if you take a lot of light and squeeze it into a smaller area makes the image brighter
the increased brightness = minification gain |
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when are del's used
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FPD
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binning
what is it how does it affect imges |
tak e4 pixels and add them together -> 1 pixel
decreases QM |
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how does collimation affect resoluton
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it doesn't
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how does collimating affect air kerma
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it doesn't
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how does electronic magnification affect KAP
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it doesn't
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how does electronic mag affect resolution
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increases resolution
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how does electronic mag affect air kerma
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increases it
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how does collimation affect KAP
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decreases it
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how does eletronic mag affect tube current
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increases it
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which gives more dose to pt:
FPD analog II digital II |
all the same
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air kerma in AXR
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5 µGy
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air kerma in FLX spot
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1 µGy
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air kerma in last image hold
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0.01 µGy
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which improves with collimation: contrast or resolution
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contrast (b/c less scatteR)
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grid ratio in FLX
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10:1
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how does electronic mag affect resolution
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increases it
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spatial resolution of II
spatial resolution in standard TV |
4-6 lp/min
1 lp/min |
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halving the FOB will change the spatial resolution by how much
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2x
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resolution for FPD
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3 lp/mm
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FLX of a larger pt would best reduce dose by increasing what
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kVp (to a more penetrating beam)
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what causes S distortion
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magnetic feilds
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maximum entrance air kerma rate in standard FLX
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100 mGy/min
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how many XR = 1 min of FLX for same FOV and kV
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10 XR = 1 min FLX
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XR absorption by I is maximized by using an avg energy of:
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35 keV (just above the k-edge)
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typical tube current for pulm angio
typical pulse duration for pulm angio |
300 mA
50 ms |
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ideal skin dose for IR studies (abdomen)
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25 mGy/min
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skin dose for extremity or peds IR
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4mGy/min + grid (or half that with grid removed)
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scatter:primary ratio i nIR in neonates and extremities
in bariatric pts? |
1:1
7:1 |
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at what thickness is a grid essential
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>12 cm
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when should you use geometric magnification in IR
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NEVER!!!!! (-> focal spot blur, increased scatter, increased skin dose)
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how does angling the XR tube affect dose
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can triple the dose b/c you are going through more of the pt
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why is skin entrance dose so impt
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1/2 dose dielivered to the first 3-5 cm of tissue
83% of the dose is delivered to the first half of the pt entrance dose is 100X the exit dose |
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what are the only 2 dose limits in radiology
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100 mGy/min in FLX (not DSA)
<3mGy/image to a phantom in mammo |
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how long does it take for skin burns to appear after IR procedure
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10 days
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minimum focus to skin distance in a fixed and mobile unit
how is this insured |
38cm
30 cm this is insured with a spacer cone |
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sentinel event for skin dose
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15 Gy
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when converting KAP to effective dose, must account for what
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beam quality
pt size and age region and projection |
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what will effective dose tell you
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cancer risk
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how to convert KAP to effective dose (rule of thumb)
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x0.1
1 Gy-cm^2 (KAP) = 0.1 mSv |
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approx skin doses in IR
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2 Gy
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KAP in IR are ~
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300 Gy-cm^2
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maximum operator dose in IR
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can't exceed 1mGy/hr at 1 m
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air kerma rates at 1m during IR
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~30 µGy/min
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at 1m, how much dose is the operator getting
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0.1% of skin entrance dose
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type of filtration that is most commonly used in IR
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Cu (reduces dose more than Al)
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dose above hte lead apron best estimates what dose
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eye lens
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use of Pb apron reduces operator effective dose by how much
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90%
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for IR sworker, conceptus dose limit =
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0.5 mSv/monht
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legal max lifetime extremity dose
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20 Gy
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what is the problem with ambient lighting when looking at images
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too much lighting, wont' see low contrast lesions
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what is the point of adding Cu (not Al) to the beam in IR
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that + adjusting kVp and mAs will maimize hte fraction of photons just above the i k edge
(Al doesn't have much photo-electric absorption in this region) just decreasing kVp will increase pt dose |
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why won't only using iodine k-edge characteristic photons help to see iodinated contrast
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I will be transparent to its own k characteristic photons b/c their energies are below the k-absorption edge
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coning in during IR will have what effects
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decreased DAP
decreased scatter improved contrast |
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how does coning in during FLX affect spatial res
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doesn't
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end result of ABC
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maintains contrast image brightness reaching TV camera
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where are scatter levels near a pt greatest in FLX/IR
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on the beam entrance side
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best place to stand to receive lowest dose when doing intracranial aneurysm embo in lateral positioin
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next to image receptor
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IR procedure that delivers highest pt dose
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neuroIR
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what happens to dose area product if you increase the source to skin distance
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stays the same
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