Date post: | 07-May-2015 |
Category: |
Education |
Upload: | muhammad-bin-zulfiqar |
View: | 257 times |
Download: | 0 times |
Radiation ProtectionDr. Muhammad Bin Zulfiqar
PGR 1
Why are x-rays harmful?
2
13
Permissible Occupational Dose
• Annual dose:• 5 rem / year 50 mSv / year• Cumulative Dose• 1rem x age 10mSv X age
14
Occupational DoseANNUAL LIMITS
•WHOLE BODY = 5 rem / 5000 mRem• LENS OF THE EYE = 15 rem• EXTREMITIES = 50 rem
15
PUBLIC EXPOSURE• 10 % OF OCCUPATIONAL• (MUST BE MONITORED IF ABOVE 10%)
• NON MEDICAL EXPOSURE• .1 rem OR 100 mrem OR 1 mSv (Freq)
• .5 rem OR 500 mrem OR 5 mSv (Infreq)
• UNDER AGE 18 & STUDENTS• .1 rem OR 1 mSv
• Pg 116 RTA BOOK
16
OCCUPATIONAL EXPOSURES
• 5 rem / YEAR BUT NOT TO EXCEED 1.25 rem/QUARTER
17
18
Reduction of Occupational Radiation Exposure
• Radiography as a profession is very safe .. if you follow the ALARA rules
• Most technologist exposure occurs from fluoroscopy exams and mobile exams– During all fluoroscopy and mobile exams
technologists should wear a protective apron– The primary beam should never be pointed at the
tech or other staff… primary at the patient!
19
ALARA• ALWAYS KEEP RADIATION EXPOSURES AS LOW
AS REASONABLY ACHIEVABLE
• Can you think of ways to do this?
20
CARDINAL RULESOF RADIATION PROTECTION
• TIME•DISTANCE • SHIELDING
21
22
TIME
• The exposure is to be kept as short as possible because the exposure is directly proportional to time.
• 20 rem = 2min• 10 rem = 1min
23
DISTANCE
• Distance from the radiation source should be kept as great as possible
• Physical Law: – Inverse Square
Law
24
INTENSITY IS SPREAD OUT…
25
Position
• When primary beam is on.. Your distance should be kept as great as possible
• The closer you are to the patient or primary beam the more exposure you are receiving.
26
Holding patients
• STUDENT RADIOGRAPHERS ARE NOT PREMITED TO HOLD PATIENTS FOR PROPER POSITIONG DURING EXPOSURES
• Mechanical devices should be used
27
Holding patients
• Otherwise, a relative or friend accompanying the patient should be asked to help
• Occasionally, other hospital employees such as nurses and orderlies may be asked to help
• Radiology staff should never hold patients
28
If holding a patient is required…
• Use shielding–Apron, gloves, thyroid shield, glasses
• Avoid exposing assisting person to the primary beam.
29
SHEILDING
• A lead protective shield is placed between the x-ray tube and the individuals exposed, absorbing unnecessary radiation
30
Wall Shielding
Often unnecessary for labsHowever, same principles employed for X-ray
rooms should be applied to assess requirements for Radiochemical Laboratories
32
Primary Barriers
33
SHEILDING
TECHNOLOGIST . 25 mm LEAD• LEAD APRON, GLOVES • THYROID SHIELD, GLASSESPATIENT – GONAD SHEILDING . 5 mm LEAD
34
GONAD SHIELDING
• MUST BE . 5 MM OF LEAD• MUST BE USED WHEN GONADS WILL LIE
WITHIN 5 CM OF THE COLLIMATED AREA
• KUB. Lumbar Spine Pelvis • male vs. female shielding
35
TYPES OF SHEILDING
•FLAT /CONTACT •SHAPED•SHADOW
36
Flat/Contact
37
38
Shadow Shield
39
Local Shielding 1
Vial Shielding– b emitters - Perspex Vial shields & Storage– g emitters - Tungsten Vial shields &
lead-lined box for Storage
Local Shielding 2
Nuclear Medicine Syringes– g emitters - Tungsten syringe shields
lead-lined box for Storage
Perspex L Bench b emitters
Minimizing radiation exposure
• Is easy when technologist and student technologist are informed!
• Collimation
• Protective apparel/Gonadal shielding
43
Personnel Dosimeters
• Desirable characteristics – Should be lightweight, durable, and reliable– Should be inexpensive
• Types of personnel dosimeters– Film badge– Pocket ionization chambers– Thermo luminescent dosimeters (TLD)
Film Badge• Most widely used and most economical• Consists of three parts:
– Plastic film holder– Metal filters– Film packet
• Can read x, gamma, and beta radiation• Accurate from 10mrem - 500rem• Developed and read by densitometer• A certain density value equals a certain level of radiation• Read with a control badge• Results generally sent as a printout
Advantages And Disadvantages Of The Film Badge
• Lightweight, durable, portable• Cost efficient• Permanent legal record• Can differentiate between scatter and primary beam• Can discriminate between x, gamma, and beta radiation• Can indicate direction from where radiation came from• Control badge can indicate if exposed in transit
• Only records exposure where it’s worn• Not effective if not worn• Can be affected by heat and humidity• Sensitivity is decreased above and below 50 keV• Exposure cannot be determined on day of exposure• Accuracy limited to + or - 20%
Pocket Dosimeter
• The most sensitive personnel dosimeter
• Two types– Self-reading– Non self-reading
• Can only be read once• Detects gamma or x-radiation
Advantages And Disadvantages Of The Pocket Dosimeter
• Small, compact, easy to use• Reasonably accurate and sensitive• Provides immediate reading
• Expensive• Readings can be lost• Must be read each day• No permanent record• Susceptible to false readout if dropped or
jarred
Thermo luminescent Dosimeters
• Looks like a film badge• Contains a lithium fluoride crystal• Responds to radiation similarly to skin• Measured by a TLD analyzer• Crystal will luminescence if exposed to radiation, then
heated• More accurate than a film badge
Advantages And Disadvantages Of The Thermoluminescent Dosimeter
• Crystals contained in TLD interact with ionizing radiation as tissue does
• Determines dose more accurately
• The initial cost is greater than that of a film badge
• Can only be read once• Records exposure only where worn
Occupational radiation monitor does NOT protect against radiation exposure!
51
Occupational radiation monitor
• Should be a life time dose record
• Should NOT be worn when YOU are the patient
• Should be left at the hospital for safe keeping
• Should be stored in a radiation free area
52
Radiation Survey Instruments
• Area monitoring devices• Detect and measure radiation• Measures either quantity or rate• Generally gas filled• Major types of survey instruments– Ionization chamber - cutie pie– Proportional counter– Geiger-Müller detector– Calibration instruments
Ionization Chamber (Cutie Pie)
• Measures x or gamma radiation generally - can be equipped to measure beta
• Measures intensity from 1mR/hr to several thousand R/hr• Most commonly used to measure patients receiving
brachytherapy or diagnostic isotopes
Proportional Counter
• Generally used in laboratories to measure beta or alpha radiation
• Can discriminate between these particles• Operator must hold the counter close to the
object being surveyed to obtain accurate reading
Geiger-Müller Detector
• Generally used for nuclear medicine facilities• Unit is sensitive enough to detect individual particles• Can be used to locate a lost radioactive source• Has an audible sound system• Alerts to presence of radiation• Meter readings are generally displayed in mR/hr
57
Pregnancy & Embryo
Mother – occupational worker (5 rem)• Baby – (500 mrem)• .5 rem/ year .05 rem/month• 5 mSv/ year 0.5 mSv/month
58
Declared Pregnant Worker• Must declare pregnancy – 2 badges
provided• 1 worn at collar (Mother’s exposure)• 1 worn inside apron at waist levelUnder 5 rad – negligible riskRisk increases above 15 radRecommend abortion (spontaneous) 25 rad
59
Fetal Exposure
• (“Baby exposure” approx 1/1000 of ESE)
• ALWAYS ASK LMP before exposure made … any females that could be exposed to primary or scatter
60
Reduction of unnecessary patient dose
• TIME•DISTANCE • SHIELDING
61
Reduction of unnecessary patient dose
• Unnecessary exam– If the order is unclear…clarify– If the order is wrong.. Fix it
• Repeat exams
62
Patient Positioning
• When ever possible primary exposure to the gonads, breasts, lenses of the eyes and thyroid should be avoided.
• Especially female patients… perform exams PA as apposed to AP– PA = posterior anterior– AP = anterior posterior
63
Minimizing radiation exposure
• Is easy the equipment is designed to !• Filtration• Protective barrier
64
Filtration REDUCES PATIENT EXPOSURES
• REMOVES LOW ENERGY PHOTONS
65
Thank you…………..….Questions?
66