16. PUBLIC EXPOSURE
• 10 % OF OCCUPATIONAL
•
(MUST BE MONITORED IF ABOVE 10%)
• NON MEDICAL EXPOSURE
• .1 rem OR 100 mrem OR 1 mSv
• .5 rem OR 500 mrem OR 5 mSv
(Freq)
(Infreq)
• UNDER AGE 18 & STUDENTS
• .1 rem OR 1 mSv
• Pg 116 RTA BOOK
16
19. 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
20. ALARA
• ALWAYS KEEP RADIATION EXPOSURES AS LOW
AS REASONABLY ACHIEVABLE
• Can you think
of ways to do this?
20
26. 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
27. Holding patients
• STUDENT RADIOGRAPHERS ARE NOT
PREMITED TO HOLD PATIENTS FOR PROPER
POSITIONG DURING EXPOSURES
• Mechanical devices should be used
27
28. 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
29. If holding a patient is required…
• Use shielding
– Apron, gloves, thyroid shield, glasses
• Avoid exposing assisting person to the primary
beam.
29
30. SHEILDING
• A lead protective
shield is placed
between the x-ray
tube and the
individuals exposed,
absorbing
unnecessary
radiation
30
31. Wall Shielding
Often unnecessary for labs
However, same principles employed for X-ray
rooms should be applied to assess
requirements for Radiochemical Laboratories
34. SHEILDING
TECHNOLOGIST . 25 mm LEAD
• LEAD APRON, GLOVES
• THYROID SHIELD, GLASSES
PATIENT –
GONAD SHEILDING
. 5 mm LEAD
34
35. 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
43. Minimizing radiation exposure
• Is easy when technologist and student
technologist are informed!
• Collimation
• Protective apparel/Gonadal shielding
43
44. 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)
45. 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
46. 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%
47. Pocket Dosimeter
• The most sensitive personnel
dosimeter
• Two types
– Self-reading
– Non self-reading
• Can only be read once
• Detects gamma or x-radiation
48. 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
49. 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
50. 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
52. 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
53. 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
54. 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
55. 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
56. 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
59. Declared Pregnant Worker
• Must declare pregnancy – 2 badges
provided
• 1 worn at collar (Mother’s exposure)
• 1 worn inside apron at waist level
Under 5 rad – negligible risk
Risk increases above 15 rad
Recommend abortion (spontaneous)
25 rad
59
60. 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
62. Reduction of unnecessary patient dose
• Unnecessary exam
– If the order is unclear…clarify
– If the order is wrong.. Fix it
• Repeat exams
62
63. 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
