Sarah Hughes, MS, DABR
Radiation Safety Officer
502-852-6146
[email protected]
Mo my back is burnin’ !!!
I got it …
MAG the cine!
Fluoroscopy
http://dccwww.bumc.bu.edu/f luoroscopy/Def
ault.htm
University Medical Campus online
Sumthin’s not Boston
right.
training
Where’s his heart?
July 1 and the new residents are just foolin’ around ...
Radiation Source
Natural: Cosmic
Terrestrial
Radon
Internal (K-40, C-14, etc.)
Manmade: Medical
Consumer Products
All others: Fallout, air travel,
occupational, etc.
Average annual total
Average Annual
Whole Body Dose
(millirem/year)
31
19
229
16
300
13
12
620 millirem/year
Tobacco (if you smoke, add ~280
millirem)
3
Rad – Rem
 EXPOSURE units
 Rad - Radiation Absorbed Dose
 mrad – millirad = 0.001 rad
 RAD and Gray are used for actually calculating the dose of radiation
to a patient
 Rem - Radiation Equivalent Man
 mrem – millirem = 0.001 rem
 REM and Sievert are use for radiation exposure in
air.
 SI Units:
 Gray (Gy)
 1 Gy = 100 rad
 Sievert (Sv)
 1 Sv = 100 rem
4
Exam
Effective Radiation Dose
In mrem (milliSievert)
Time for Equal Background
Radiation
Hand/Foot X-ray1
0
0 weeks
Dental: Bitewing and full
mouth survey1
0.5 (0.005) per image
<1 day per image
Dental Panoramic1
1.0 (0.01)
<1 day
Dental Cephalometric1
1.2 (0.012)
1.2 days
Dental i-CAT2
6.1 (0.061)
6 days
Chest X-ray1
10 (0.1)
2 weeks
Abdomen X-ray1
70 (0.7)
3 months
Head CT scan1
200 (2)
7 months
Abdomen/Pelvis CT scan1
1000 (10)
33 months
Nuclear Medicine Cardiac
Perfusion scan1
1770 (17.7)
69 months
Radiation Exposure from
fluoroscopy:
Can be from 0.5 rem – 10 rem
per minute!
 Stochastic
 Latent effects (cancer)
 Neoplasm, heritable changes, and changes in genetic
material
 IT IS “ASSUMED” THAT FOR EVERY 1 REM OF
EXPOSURE, YOUR CANCER RISK INCREASES 0.01%
 Deterministic
 Threshold – we know at certain levels of exposure effects
will start to happen
 Cataracts, epilation, erythema, and necrosis
Deterministic effect:
Cath lab – multiple
procedures in a
period of a few
weeks; this picture
was taken 1 year
after the last
procedure; skin
grafts were required.
Spinal arteriogram
October 10 – 30 min of
fluoro and 4.4 min of CINE
October 28 – approx 90 min
fluoro
Notice the collimation
Picture taken about 2
months after exposure
 Most radiation injuries are due to multiple radiation
procedures performed over a short period of time (i.e.
multiple cath lab procedures over a few weeks)
 Why is the injury on their skin?
 Because the highest exposure to the patient is where the
x-ray enters their skin – the Entrance Skin Exposure
 Only 5-10% of the original x-ray produces makes up
the image you see on the screen; the patient absorbs
and scatters most of the radiation
BE MINDFUL OF PRIOR
EXPOSURES THE PT HAS HAD.
EFFECT
DOSE
RAD / GRAY
200 / 2
TIME TO
ONSET
Temp epilation
300 / 3
3 weeks
Main erythema
600 / 6
10 days
Permanent epilation
700 / 7
3 weeks
1000 / 10
4 weeks
Transient erythema
Dry desquamation
Hours
 Wear your radiation badge!!
 If you don’t wear your badge, we
don’t know your exposure.
 If you have 1 badge ALWAYS wear
it on the outside of your lead
apron to get your most
conservative exposure
 If you have 2 badges the WB
(whole body) badge goes under
your lead, the CL (collar) badge
goes outside the lead
e
Whole body badge:
labeled WB, should
be worn inside the
lead apron at the
chest or waist level
ONLY wear the badge
assigned to you!
Collar badge:
labeled CL, should
be worn outside the
lead apron at the
collar
Ring badge
should be worn
with the label
towards the x-ray
tube
 Dosimetry reports? How
do you know your
exposure?
 The Radiation Safety
Officer monitors these
reports as they come in
and would contact you
if your exposure is out of
the normal range; each
department is sent a
report after they are
received.
These limits are set by the Nuclear Regulatory Committee.
 Whole Body limit:
5000 mrem / year (50 mSv)
 Extremity:
50000 mrem / year (500 mSv)
 Lens of eye:
15000 mrem / year (150 mSv)
 Fetus:
900 mrem / 9 months (9 mSv)
The RSO looks over all badges when they are received; these
are reviewed at the Radiation Safety Committee Meeting
If you receive a reading that is outside of your normal range,
the RSO will contact you.
14
 For personnel exposure, we want to keep everyone’s
exposure ALARA (As Low As Reasonably Achievable)
 TIME
 DISTANCE
 SHIELDING
The duration of exposure of the individual is directly proportional to the
occupationally received radiation dose. Therefore, personnel doses are
directly linked to patient doses.
DOSE FROM 30 mCi OF TC-99M AT 1 METER:
2.2 mR/hr
DOSE FROM I-131:
0.22 mR/hr PER mCi AT 1 METER
DOSE AT 1 METER FROM FLUORO PATIENT
1/1000 OF WHAT PATIENT RECEIVES
PATIENT RECEIVES ANWHERE FROM 0.5 – 10
R/min FOR NORMAL FLUORO, MORE FOR
CINE (or “runs”)
16
 Effective & Easy
 Inverse Square Law
 Doubling distance from the source of
exposure (the patient),decreases dose
by factor of four
 Tripling it decreases dose nine-fold
 More Distance = Less Radiation
Exposure
Radiation scatter
The primary source of radiation exposure to physicians and staff during
fluoroscopy is radiation scattered from the patient, NOT from the x-ray tube.
• At 1 m from where the center of the x-ray
beam enters the patient, the exposure rate
to the operator (above the table) is on the
order of 1/1000th the patient’s entrance
exposure rate.
e.g., If the patient is receiving 4 R/min,
then you are receiving ≈ 4 mR/min.
backscatter
• Scatter
between the x-ray tube and
the patient (called backscatter) is about
twice as intense as that above.
X-ray tube
1m
Richard H. Behrman, PhD
ALWAYS Stand Closer to
the Image Intensifier
Always stand further from the
X-Ray Tube
 Scatter radiation
intensity is less on the
image intensifier side
as compared to the xray tube side.
 For Lateral and
oblique projections:
position the x-ray tube
on the opposite side of
the patient from where
you are standing.
 Scatter radiation does not linger in the room. It is only
present when the x-ray beam is on. (i.e.. Someone is
standing on the beam-on foot pedal. ) TAKE YOUR FOOT
OFF THE PEDAL WHEN YOU DON’T NEED IT.
 The patient is the main source of scatter radiation during
radiographic and fluoroscopic procedures.
 Fluoroscopy is real time x-ray imaging captured on a TV
monitor, while radiography is a single image captured with
one radiation exposure.
The inverse square law (again)
1. Step as far back from the patient as is reasonably possible when holding down
the fluoro pedal. This is especially true for high dose rate modes such as cine
and DSA.
1/16
4x
1
1/4
relative exposure rate
By standing 2 m instead of
0.5 m from the center of the
table, you will reduce your
exposure by a factor of 16.
0.5 1mm0.5 m
1m
2.0 m
Richard H. Behrman, PhD
 REGULATION AND
POLICY: If you are in the
room during
fluoroscopy you must
wear a lead apron.
 Wear apron and t-shield
with no gap in between
 Do you need a thyroid
shield?
 If you have it, wear it! But it
is not a regulatory
requirement.
Lead aprons
2. It is a legal requirement that all personnel in the room either wear a lead apron
or stand behind a lead barrier when fluoroscopy is being performed.
Lead Apron Thickness
Percentage of x-rays blocked
kV
70
90
110
0.25mm
88%
78%
72%
0.5mm
98%
95%
92%
Richard H. Behrman, PhD
 Anywhere from 85-99%
 Depends on the thickness of the lead
 REGULATION – LEAD MUST BE AT LEAST 0.25 MM
LEAD EQUIVALENT; most that are purchased are at least
0.35 mm lead equivalent.
 Depends on the energy of the x-ray
 Lead gloves??? May reduce hand exposure by 15-30% if
OUTSIDE primary beam.
 All fluoro units have Automatic Exposure Control. If your
hands get in the field of view, it will increase the
exposure to get through them.
 If you place lead shielding on the patient, place it on the
side of the x-ray tube. (i.e. if the x-rays are generated in
the tube underneath the table, put the lead apron on the
table, then the patient on top of the apron).
 MAKE SURE the lead will not be in the field of view,
otherwise the unit will compensate to get through the
lead and give a higher dose to the patient.
Additional shielding
Place any additional lead shielding between your face / neck and the patient.
• The patient is the source of scatter
and the lead apron is already protecting
your trunk organs.
• Extremities - tissue below the elbows
and knees are the least radiosensitive
parts of the body.
If it’s there, use it!! Many times the pull down shields
are over in the corner and never used.
Richard H. Behrman, PhD
 The person holding the patient should be
protected with a lead apron.
 If you wear lead gloves, if your hands get in the
field of view, the radiation exposure will increase
exponentially to get through the lead in turn
increasing the exposure to the patient and
personnel in the room.
 Radiologic technologists shall not hold a patient
during a radiation exposure, except in a lifethreatening situation.
 No person under the age of 18 shall be asked to
hold a patient during radiographic procedures.
Do you know
which part is the xray tube and which
is the image
intensifier where
the image is
captured?
Image Intensifier
(II) (where the radiation
is “captured” to make the
image)
X-RAY TUBE
(where the radiation is
generated) The side
between the pt and x-ray
tube has the most scatter;
be mindful where you and
others stand when the xray tube is in
oblique/lateral positions.
 Training for operators of fluoro
 Anyone operating fluoroscopy equipment should have
proper training
 Patients be informed prior to the procedure
 Do you inform your patients that their procedure
involves radiation exposure? A lot of patient’s do not
know this.
 Documentation be recorded of dose
 Facilities should record the dose to the patient – most
machines do monitor this automatically, or at least
record the fluoroscopy time.
Fluoroscopy
• All fluoroscopy equipment transforms x-rays exiting the patient
into real-time visual images.
• This transformation is made possible by either an image intensifier
or a flat panel digital detector.
Image intensified
system
Digital flat panel system
(latest technology)
Richard H. Behrman, PhD
Automatic brightness control
The Image Intensifier (I.I.) entrance exposure rate (set by Vref in the ABC) affects
both the patient exposure rates and the image “noise” (image graininess). Noise
is determined primarily by the number of x-rays used to form the image. The
higher the dose rate the lower the noise and vice versa.
• If Vref is set too low ⇒ Dose rates will be low but images will be noisy.
• If Vref is set too high ⇒ Dose rates will be high and images will contain very
little noise.
• This requires Vref to be properly set (trade off between dose and noise).
It is therefore important that I.I. entrance exposure rates be set appropriately by
the installation/service engineer and checked at least annually by a qualified
medical physicist. It one of the key parameters affecting both patient dose and
image quality.
Many fluoro units have “low”, “medium”, and “high” dose-rate selections. Each
corresponds to a different Vref setting.
Richard H. Behrman, PhD
 Size of the patient
 Larger pt – decrease in image quality so the unit increases
the kV and mA to compensate. This means an increase in
dose to the pt and personnel.
 mA = the # of x-ray produced. Dose to the pt and
personnel are proportional to mA
 kV = increases the penetrability of the x-ray. High kV with
low mA = lower doses
 Magnification
 The use of CINE (or runs they are sometimes called)
 Electronic Magnification
 Changing the Field of View (FOV) to see smaller objects
 Brightness gain decreases as the mag mode increases so
it compensates with ABC; therefore increasing the x-ray
exposure rate
 Increase in exposure rate is = ration of FOVs
 From 12” to 9” = (12/9)2 = 1.8 increase in dose to pt.
 Normal fluoroscopy mode has a regulatory limit of
10 R/minute (0.1 Sv/min) to the patient at a level
where you measure the output a 30 cm from the
image intensifier (this means put the patient closer
to the image intensifier and farther from the x-ray
tube)
 There is no regulatory limit on CINE! CINE usually
gives around 10-60 times the dose of normal
fluoroscopy.
 Use CINE sparingly if you can.
 There is usually a dose reduction choice on the unit
 Larger patient require more radiation to give you a
good picture.
 Pulsed fluoro will give less radiation to the
patient.
 Less radiation to the patient means less scatter in
the room.
 Use Last Image Hold when you can
 Be aware of the fluoroscopy time!
 C-arm




10 R/minute (0.1 Sv/min)
Cine/Fluorography
10-60 x higher than
regular fluoroscopy.
Lateral L. Spine
500 mR (5 mSv)
Chest -PA
10 mR (0.1 mSv)
C.T. Scan (Abd.)
3 - 7 Rads (0.03 -0.07 Gray)
The ESE is calculated annually by a physicist and reports
should be posted in the room. MOST fluoroscopy
equipment at normal fluoro levels do not go over 5 R/min;
the regulatory LIMIT is 10 R/min.
Typical patient entrance exposure rates
For an average 70 kg (155 lb) adult, typical patient entrance exposure rates for
posterior-anterior or anterior-posterior projections are,
2- 3 R/min
Normal Fluoro
30cm
4 - 6 R/min
High Dose Fluoro
20 - 40 R/min
Fluorography
(cine, DA, DSA)
Richard H. Behrman, PhD
 Distance between x-ray tube and skin.
 The farther the x-ray tube from the patient, the less
exposure the patient receives
 Distance between the patient and II:
 The closer the II is to the patient the less scatter in the
room and less noise on the image
 Collimate to the area of interest
 ONLY radiate the portion of the patient you need to see
 Separator cone – use this if available.
The difference in the patient / II / x-ray tube:
Keep the patient close to the image intensifier and farther
away from the x-ray tube! Less Scatter all around
SCAN
EFFECTIVE DOSE in mSv (mrem)
Brain PET F-18
14.1 (1400)
Brain Tc HMPAO
6.9 (690)
Bone Tc MDP
6.3 (630)
Lung Perfusion/Vent
2.5 (250)
Cardiolite (stress/rest)
9.4 (940)
Various PET Studies F-18
14 (1400)
Barium Enema
7.0 (700)
CT Chest
7.0 (700)
CT Abdomen/Pelvis
10.0 (1000)
Coronary Angiography
20.0 (2000)
Cardiac Diagnostic & Intervention
30 (3000)
Lumbar Spine
1.5 (150)
 Use Shielding
 Normal work practices should
NOT keep you from working
in a radiation area.
 Can Declare pregnancy to the
Radiation Safety Office
 Use of radiation badge at
waist level
 Contact the Radiation Safety
Officer if you have questions.
852-5231
 Lead causes more exposure – wear your lead, it shields
 Radiation follows easiest path and comes out pt’s
mouth
 No – radiation scatter from where it enters the patient.
 Scatter radiation hits floor and bounces up to cause
hair on legs to fall off
 Wouldn’t that be nice? At least for women.
At this point, there is no regulatory
Limit for radiation exposure.
Monitor your dose and the dose
and the dose to the patient.
 Radiation Safety Officer
 Sarah Hughes
 502-852-6146
 502-552-5454
 [email protected]
 If you ever have any questions, please do not
hesitate to contact Sarah Hughes