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RHB Rad Prot & Fluoro Syllabus. RT 244 FALL 2007. measurement. 100 R = 1 C/kg 1Rad = 1/100 Gray 1 Rem = .01 Sievert (Rad + QF = REM) 1 REM = 10 mSv 1 Rem = 1000mRem.
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RHB Rad Prot& Fluoro Syllabus RT 244 FALL 2007
measurement 100 R = 1 C/kg 1Rad = 1/100 Gray 1 Rem = .01 Sievert (Rad + QF = REM) 1 REM = 10 mSv 1 Rem = 1000mRem
The average person in the United States receives about 360 mrem every year whole body equivalent dose. This is mostly from natural sources of radiation, such as radon
PUBLIC EXPOSURE • 10 % OF OCCUPATIONAL • NON MEDICAL EXPOSURE • .5 RAD OR 500 MRAD • UNDER AGE 18 AND STUDENT • .1 rem 1 mSv • Pg 98 RTA BOOK
COLLIMATION • The PATIENT’S SKIN SURFACE • SHOULD NOT BE CLOSER THAN • ___________ CM BELOW THE COLLIMATOR? • ____________ INCHES? 15 cm / 6.5 inches
IMAGE INTENSIFIER • FUNCTION: • CHANGE XRAY PHOTONS TO • LIGHT PHOTONS (INPUT PHOSPHOR) • TO ELECTONS (PHOTOCATHODE) • ACCERATES ELECTRONS ACROSS TUBE AT 25,000 VOLT POTIENTAL • CHANGED BACK TO LIGHT AT OUTPUT PHOSPHOR
The ratio of the number of light photons striking the output screen to the ratio of the number of x-ray photons striking the input screen is called fluxgain
IMAGE INTENSIFIER • INPUT PHOSPHOR – CESIUM IODIDE • PHOTOCATHODE (LIGHT TO E’S) • ELECTOSTATIC LENSES – • FOCUSES AND ACCELERATES THE E • INTENSIFIES LIGHT = BRIGHTNESS GAIN (BG) • BG = MG X FG • ENCASED IN A LEAD HOUSING • = 2MM PB (PRIMARY BARRIER)
MAG USED TO ENLARGE SMALL STRUCTURE OR TO PENETRATE THROUGH LARGER PARTS FORMULA: PATIENT DOSE IS INCREASED IN THE MAG MODE – DEPENDANT ON SIZE OF INPUT PHOSPHOR MAG MODE VS PT DOSE
MAG MODE FORMULA IP OLD SIZE IP NEW SIZE = MAG
MORE FORMULASBG = MG X FG • BG = MINIFICATION GAIN X FLUX GAIN • MINIFICATION GAIN – same # e at input condensed to output phosphor – ratio of surface area on input screen over surface area of output screen IP SIZE 2 OP SIZE 2
BG = MG X FG • FLUX GAIN – increase of light brightness due to the conversion efficiency of the output screen • 1 electron = 50 light photons is 50FG • Can decrease as II ages • Output phosphor almost always 1 inch • Zinc cadnium phosphot • Flux gain is almost always 50
BG = MG X FG • Brightness gain BG • = MINIFICATION GAIN X FLUX GAIN • (old Patterson B-2 fluoro –obsolete) • Brightness gain is a measure of the conversion factor that is the ratio of the intensity of the output phosphor to the input phosphor • conversion factor = intensity of OP Ø • mR/sec
VERTICAL RESOLUTION ABILITY TO RESOLVE OBJECTS SPACED APART IN A VERTICAL DIRECTION MORE DOTS(GLOBULES) = MORE SCAN LINES = MORE/BETTER RESOLUTION RATIO OF VERTICAL RESOLUITON # OF SCAN LINES KELL FACTOR FOR 525 LINE SYSTEM IS 0.7 KELL FACTOR
ESE FOR FLUORO • TLD PLACED AT SKIN ENTRACE POINT • 1 – 5 R/MINUTE AVE IS 4 R/MIN • INTERGRAL DOSE – • 100 ERGS OF TISSUE = 1 RAD EXPOSURE • OR 1 GM RAD = 100 ERGS
SSD – TUBE TO SKIN DISTANCE • FIXED UNITS • 18” PREFERRED • 15 “ MINIMUM MOBILE UNITS ( C-ARMS) • 12’ MINIMUM
PATIENT PROTECTION • LIMIT SIZE OF BEAM • BEAM ON TIME • DISTANCE OF SOURCE TO SKIN • PBL • FILTRATION (2.5 mm Al eq) @ 70 • SHEILDING • SCREEN/FILM COMBO
GONAD SHIELDING • MUST BE . 5 MM OF LEAD • MUST BE USED WHEN GONADS WILL LIE WITHING 5 CM OF THE COLLIMATED AREA (RHB) • KUB. Lumbar Spine Pelvis • male vs female shielding
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 % ♂
Framing and patient dosesyll = Pg 31 • The use of the available film area to control the image as seen from the output phosphor. • Underframing • Exact Framing, (58 % lost film surface) • Overframing,(part of image is lost) • Total overframing
EXPOSURE RATES FLUORO • MA IS 0.5 MA TO 5 MA PER MIN • AVE DOSE IS 4 R / MIN • IF MACHINE OUTPUT IS 2 R/MA/MIN = WHAT IS PT DOSE AT 1.5 MA FOR 5 MIN STUDY? • 15R
EXPOSURE RATES FOR FLUORO • CURRENT STANDARD • 10 R/MIN (INTENSIFIED UNITS) • HLC: BOOST MODE 20 R/MIN • OLD (1974) NO ABC NON IMAGE INTES • 5 R/MIN
DOSE REGULATIONS • BEFORE 1974 - AT TABLETOP • 5R/MIN (WITHOUT AEC) • 5R/MIN (WITHOUT AEC) – BOOST MODE • After 1974 with AEC • 10 R/MIN 20R/MIN BOOST
RADIATION PROTECTIONThe Patient is the largest scattering object • Lower at a 90 DEGREE ANGLE from the patient + PRIMARY BEAM AT 1 METER DISTANCE - • 1/1000 OF INTENSITY PRIMARY XRAY or 0.1%
BUCKY SLOT COVER .25 MM LEAD
SCATTER FROM THE PATIENT TABLE TOP, COLLIMATOR, TUBE HOUSING, BUCKY STRAY RADIATION – LEAKAGE OR SCATTER RADIATION PERSONNEL PROTECTION
TOWER CURTAIN .25 MM LEAD EQ
PERSONNEL PROTECTION • STANDING BEHIND A PROTECTIVE PRIMARY (1/16TH pb) BARRIER: • PRIMARY RADIATION EXPOSURE – 99.87% REDUCED • PORTABLE BARRIER = 99 % REDUCTION
PERSONNEL PROTECTION • PROTECTIVE APRONS – • 0.25 PB = 97% ↓ TO SCATTER • 0.5 PB = 99.9% ↓ TO SCATTER • THYROID SHEILDS (0.25 & 0.5) • GLOVES (0.25 & 0.5)
FILM BADGE TLD POSL POCKET DOSIMETER RING BADGE PERSONNEL PROTECTIONMONITORING
PERSONNEL PROTECTIONMONITORING • DOSE LIMITS • WHOLE BODY • EYES • EXTREMITIES (BELOW ELBOW/KNEES)
Occupational DoseANNUAL LIMITS • WHOLE BODY = 5 REMS / 5000mRem • LENS OF THE EYE = 15 REMS • EXTREMITIES = 50 REMS
Report at least every quarterPreserved for a minimum of 3 years
RHB NOTIFICATION (EXP IN 24 HOURS) • IMMEDIATE – WITHIN 24 HOURS • TOTAL DOSE OF 25 rems • Eye dose – 75 rem • Extremity – 250 RADS • OVEREXPOSURE – WITHIN 30 DAYS • TOTAL DOSE OF 5 rems • Eye dose – 15 rem • Extremity - 50 REMS
LICENSE RENEWAL • WITHIN 30 DAYS OF EXPRIATION • NOTIFICATION OF CHANGE OF ADDRESS
HIGH RADIAITON AREA – • 100 mRem ( 0.1 rem / (1 msV) • @ 30 cm from the source of radiaton • RADIAITON AREA – • RHB: 5 mRem ( 0.005 rem / (.05 msV) • @ 30 cm from the source of radiation • PUBLIC 2 mrem per week* (STAT)
RHB “RULES” RHB RP PG61 • LICENTIATES OF THE HEALING ARTS (MD, DO, DC, DPM) • MUST HAVE A • RADIOLOGY SUPERVISOR & OPERATORS PERMIT & CERTIFICATE • TO OPERATE OR SUPERVISE THE USE OF X-RAYS ON HUMANS • SUPEVISORS MUST POST THEIR LICENSES