Radiation protection

Radiation ProtectionDr. Muhammad Bin Zulfiqar

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Why are x-rays harmful?

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Permissible Occupational Dose

• Annual dose:• 5 rem / year 50 mSv / year• Cumulative Dose• 1rem x age 10mSv X age

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Occupational DoseANNUAL LIMITS

•WHOLE BODY = 5 rem / 5000 mRem• LENS OF THE EYE = 15 rem• EXTREMITIES = 50 rem

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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

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OCCUPATIONAL EXPOSURES

• 5 rem / YEAR BUT NOT TO EXCEED 1.25 rem/QUARTER

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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!

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ALARA• ALWAYS KEEP RADIATION EXPOSURES AS LOW

AS REASONABLY ACHIEVABLE

• Can you think of ways to do this?

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CARDINAL RULESOF RADIATION PROTECTION

• TIME•DISTANCE • SHIELDING

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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

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DISTANCE

• Distance from the radiation source should be kept as great as possible

• Physical Law: – Inverse Square

Law

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INTENSITY IS SPREAD OUT…

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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.

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Holding patients

• STUDENT RADIOGRAPHERS ARE NOT PREMITED TO HOLD PATIENTS FOR PROPER POSITIONG DURING EXPOSURES

• Mechanical devices should be used

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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

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If holding a patient is required…

• Use shielding–Apron, gloves, thyroid shield, glasses

• Avoid exposing assisting person to the primary beam.

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SHEILDING

• A lead protective shield is placed between the x-ray tube and the individuals exposed, absorbing unnecessary radiation

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Wall Shielding

Often unnecessary for labsHowever, same principles employed for X-ray

rooms should be applied to assess requirements for Radiochemical Laboratories

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Primary Barriers

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SHEILDING

TECHNOLOGIST . 25 mm LEAD• LEAD APRON, GLOVES • THYROID SHIELD, GLASSESPATIENT – GONAD SHEILDING . 5 mm LEAD

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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

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TYPES OF SHEILDING

•FLAT /CONTACT •SHAPED•SHADOW

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Flat/Contact

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Shadow Shield

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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

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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!

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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

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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

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Pregnancy & Embryo

Mother – occupational worker (5 rem)• Baby – (500 mrem)• .5 rem/ year .05 rem/month• 5 mSv/ year 0.5 mSv/month

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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

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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

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Reduction of unnecessary patient dose

• TIME•DISTANCE • SHIELDING

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Reduction of unnecessary patient dose

• Unnecessary exam– If the order is unclear…clarify– If the order is wrong.. Fix it

• Repeat exams

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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

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Minimizing radiation exposure

• Is easy the equipment is designed to !• Filtration• Protective barrier

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Filtration REDUCES PATIENT EXPOSURES

• REMOVES LOW ENERGY PHOTONS

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Thank you…………..….Questions?

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