2. PHYSICS
the emission of energy as electromagnetic
waves or as moving subatomic
particles,especially high-energy particles that
cause ionization
BIOLOGY
divergence out from a central point,in
particular evolution from an ancestral animal or
plant group into a variety of new forms
5. The amount of ionizing radiation a person is
exposed to
Expressed as roentgens(R)
Can be directly measured and is expressed as
R/min or milli R/hour
6. The amount of energy deposited in tissue(the
amount of radiation needed to transfer a
certain amount of energy ie,1J/Kg)
Expressed as gray(Gy) or rad (1Gy=100rad)
Absorbed dose varies with type of tissue
ie,bone=5.0,soft tissue=0.95
7. The absorbed dose multiplied a quality factor
allowing for different tissue sensitivities
Expressed as Sievert(Sv) or rem (1Sv=100rem)
Used to account for different biological
effects of radiation
Rad,rem and roentgen have approximate
numerical equivalence in the x-ray energy
range used in the cardiac catheterization lab
8. Production
Current is applied to a filament electrons are
released and accelerated towards a target by a
high voltage electrical potential
X-rays are produced when electrons collide
and are completely stopped by the
target(charecteristic x-rays)
Electrons are rapidly decelerated after striking
the target(breaking x-rays)
9.
10. Fluroscopy-type of x-ray examination used for
dynamic imaging
Image intensifier-amplify the brightness of the
image to improve visibility
X-ray transmitted through patient,enter the input
phophor which emits light that is then converted
to electrical energy
The electrical energy is amplified and converted
back into light at the output phosphor
Output phosphor of the image intensifier is
coupled to a television pickup tube which
converts the light pattern into an electrical signal
which forms the image on the monitor
11.
12.
13. Light exiting the output phosphor is divided,
diverting part of the beam to television
monitor and the rest to the cine camera lens-
refocuses light onto cine film
Standard cameras use 35 mm film at frame
rates of 15-60 frames/sec(15-30 fps for
angiography and 60 fps for ventriculography)
14. Limit of 10 R/minute
Patient radiation dependent on several factors
1.x-ray tube factors
2.Image intensifier factors
3.Distance factors
4.Patient factors
15. Operator independent
kVp- voltage across the x-ray tube, the energy
that accelerates the electrons
intensity of x-ray and image brightness directly
related to the current passing through the filament
increasing the kVp produces higher energy
x-rays which have greater penetrating power for
large patients
optimal setting for adult70-80kVp
copper or aluminium filters placed between x-ray
tube and patient to absorb low energy x-rays that
are inadequate for imaging purposes
16. Automatic brightness control-automatically
adjusted to maintain brightness
Collimation
restrict the size of the x-ray field
Field size and magnification
field size decreases with magnification,
therefore the local patient radiation dose must
increase to compensate for the loss of brightness
low magnification(9-11inch)
intermediate magnification(6-7inch)
high magnification(4-5inch)
17. Skin exposure
1-2R/min in 9 inch mode
2-5R/min for smaller magnification modes
for 10 minutes of fluroscopy, patients skin
exposure is 10-50R(10-50rads)
18. Skin radiation increases with decreasing
distance
Table height affects patient dose
Standard is to maintain 18” between x-ray
tube and patient
Image intensifier should be as close to
patient as possible
19. Prolonged or repeated cine runs
Longer fluroscopy times
Higher frame rates
All increase radiation exposure to the patient
22. Injury produced by large amounts of energy
transferred to individual molecule
Cause ejection of electrons
Initiates physical and chemical effects on
tissues especially DNA
Failure of repair mechanism leads to cell
death or mutation
23. Effects to tissue depend on:
> Amount of energy imparted
> Location and extent of region of body
exposed
> Time interval over which energy is
imparted
24. Deterministic effects-those in which the
number of cells lost in an organ or tissue is
so great that there is a loss of tissue function
>IE skin erythema and ulceration
Stochastic effects-occur if an irradiated cell is
modified rather than killed and then goes on
to reproduce
>Do not appear to have a threshold and
the probability of the effect occurring is
related to the radiation dose
25. * Observed early (days to week)
>Early effects develop in proliferating cell
systems (most radiosensitive skin,ocular lens,
testes,intestine,esophagus)
OR
*Observed late (months to year)
>Carcinogenesis is the most important delayed
somatic effect
>Delayed effects often seen in nerves,muscles
and other radioresistant tissues
26. Five groups of patients known to have genetic
or chromosomal defects and an increased
sensitivity to various types of ionizing
radiation:
-Xeroderma pigmentosum
-Ataxia-telangiectasia
-Fanconi’s anemia
-Bloom syndrome
-Cockayne’s syndrome
27. Determined by dose
-Bone marrow depression with whole body
radiation>500 rad
Skin erythema occurs if a single dose of
6-8 Gy(600-800 rad) is given,and it is not
identified until 1-2 days after irradiation
The higher the irradiation dose,the more
quickly the erythema may be identified
28. Characterized by a blue or mauve
discoloration of the skin
Increases during the first week
Usually fades during the second week
May return 2-3 weeks after the initial insult
and last for 20-30 days
Acute doses in excess of 8Gy will produce
exudative and erosive changes in the skin
Penetrating doses in excess of 20Gy: there is
usually a nonhealing ulceration
29. May appear in a few hours or a few weeks
The higher the dose,the shorter the period
for appearance
30. Type 1 injury-damage limited to the
epidermis and dermis without much damage
to the subcutaneous tissue
-Initial erythema
-A 3wk latency period
-A secondary erythema followed by
-An exudative epidermatitis and recovery in
3-6 months
31. Type II Injury
- A vascular endothelitis
- At least 6-8 months post exposure the acute
reactions are renewed with necrosis and
ulceration usually requiring surgery
- A result of damage below the basal layer of
the epidermis
35. Time
Radiation dose is proportional to exposure
duration
Distance
Radiation dose is inversely proportional
to the square root of the distance from the
patient
36. Shielding
- Lead is the most common material used
- A lead apron with an equivalent of 0.5mm of
lead in front panel is mandatory
- Lead in the back panel provides additional
protection
- Thyroid shield (0.5mm equivalence) is
recommended to shield the sternum,upper
breast and thyroid gland
37.
38. Shielding continued
- Leaded eyeglasses with the side shields
reduce the exposure to the eyes and may
improve visual acuity
- Recommended for staff with collar-badge
doses approaching 15rem per year and for
interventionalist’s training
39.
40. Shielding continued
- Hands receive the highest radiation dose,but
are relatively insensitive to radiation
- Supplemental lead shielding to reduce
exposure to scatter is available in the form of
table mounted lead drapes,ceiling mounted
lead acrylic shields and rolling lead acrylic
shields
41.
42. Interventionalists commonly assigned 2
radiation badges
- One on collar
- Second underneath lead apron
Lead apron reduces the radiation dose at the
waist to 10% of dose at collar at 75kVp
Effective dose equivalent best estimated by
averaging the 2 dosimeters
- Mean dose equivalent per procedure
4+/-2 millirem,highest doses were delivered
to physicians in training
43. Women of child-bearing age should receive a
pregnancy test prior to procedure
Current regulations restrict radiation dose to
the embryo and fetus to 500millirem for the
entire gestation and a monthly dose
<50millirem
Pregnancy does not exclude working in the
cardiac catheterization lab
Highest danger of fetal abnormalities is in the
first trimester
44. Maturity lead aprons provide an additional
1mm of lead equivalence
Use of properly fitting wrap-around apron
provides same protection to the fetus
Fetal radiation badge should be worn on the
abdomen under the apron to record monthly
fetal exposure
