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RT 244 / 328 REVIEW & REVISIONS
9.21.12RHB SYLLABUS on
Fluoroscopy & Radiation Protection
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RHB NOTIFICATION (revised 2012) (RP Syllabus – pg 68 Fluoro Syllabus pb 53)
IMMEDIATE reporting –TOTAL DOSE OF 25 rems• Eye dose – 75 rem• Extremity – 250 RADSWITHIN 24 HOURS• TOTAL DOSE OF 5 rems• Eye dose – 15 rem• Extremity - 50 REMSALL other OVEREXPOSURE – (received w/in 24
hrsMust be Reported WITHIN 30 DAYS
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Report at least every quarterPreserved for indefinitely - individuala minimum of 3 years (employer)*(“all other records” pg 52)
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Gonad shielding & dose• ♀ receive 3x more dose than• ♂ for pelvic x-rays• 1 mm lead will reduce exposure
(primary) by about 50% ♀• by about 90 – 95 % ♂(STAT)
Pg 13 RHB –RP:0.5 mm ↓ 92% (inc internal scatter)Pg 43 300 Rads 30 Rads -temp sterility♀ ♂
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MONITORING PG 75
• CONTROLLED AREA – Used by occupationaly exposed personnel (monitored)
• 100mrem / WEEK
• UNCONTROLLED AREA – PUBLIC• 2 mrem per week*
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• HIGH RADIATION AREA –• 100 mRem ( 0.1 rem / (1 msV)– @ 30 cm from the source of radiaton
• RADIATION AREA –• RHB: 5 mRem ( 0.005 rem / (.05 msV)– @ 30 cm from the source of radiation
• PUBLIC 2 mrem per week* (STAT)
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DOSE REGULATIONS
• Fluoroscopic tubes operate at currents that range from0.5 to 5 mA with 3ma the most common
• BEFORE 1974 - AT TABLETOP• 5R/MIN (WITHOUT AEC) Reg & Boost• After 1974 with AEC (1993 )• 10 R/MIN 20R/MIN BOOST– Some books ave is 4 R/min if not given
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Over vs under the table fluoro tubes
pg 116 dose to operator
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DOSE
• CINE - 2mR per frame (60f/sec)• 400 mr per “look”
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SSD – TUBE TO SKIN DISTANCE
• FIXED UNITS• 18” PREFERRED• 15 “ MINIMUMMOBILE UNITS ( C-ARMS)• 12’ MINIMUM• 5 min AUDIBLE ALARM
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KEEP I.I. CLOSE TO PATIENT
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Patient Protection
• Tabletop exposure rate– Maximum 10 R/min– Typically 1 – 3 R/min
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Patient Protection
• Minimum source-to-skin distance– 12” for mobile equipment– 15” for stationary systems
• Audible alarm at 5 mins.• Same rules for collimation
Shielding to Scatter
Pg 70 Fluoro RHB: ScatterRT: 0.25 = ↓ 97% 0.5 = ↓ 99.9%
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Lead curtain & dose reduction
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Units of Dose – App #3 pg 79
100 R = 1 C/kg1Rad = 1/100 Gray1 Rem = .01 Sievert
(Rad + QF = REM)1 REM = 10 mSv
1 Rem = 1000mRem
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Pregnancy & Embryo
Mother – occupational worker (5 rem)• Baby – (500 mRem)• .5 rem/ year .05 rem/month• 5 mSv .5 mSv / month
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10 – 25 RAD Rule and Pregnancy Bush p 545
• Below 10 RAD (100mgy) ther ab NOT indicated
• Above 25 RAD may justify TAB
• FETAL doses RARELY reach 5 RAD
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• The NCRP states that: the risk (to the embryo/fetus) is considered to be negligible at 5 rads or less when compared to the other risks of pregnancy • and the risk of malformation is
significantly increased above control levels only at doses above 15 rads
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Kell Factor• The ability to resolve objects spaced apart in a
vertical direction.• More dots = more scan lines = more/better
resolution• Kell factor for 525 line system is 0.7VERTICAL RESOLUTION = VER - TI- K- AL
• RATIO OF VERTICAL RESOLUITON• # OF SCAN LINES
more dots(globules) = more scan lines = more/better resolution
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Bandpass/Horizantal Resolution
• Horizontal resolution is determined by the bandpass.
• Bandpass is expressed in frequency (Hz) and describes the number of times per second the electron beam can be modulated.
• The higher the bandpass, the better the resolution