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Safety |
| As you strive each day to make a difference
in the lives of your patients, you are also
accepting the risks associated with handling
radioactive materials. DMS Imaging is committed
to supporting our customers in this important
work, and is proud to provide ongoing education
and products, such as Cardinal Health's PETPig™,
to promote safe and responsible
practices in the fields of PET and nuclear
medicine. |
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| Important Considerations
of PET Radioactivity and Shielding |
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PET has a 511 keV gamma
ray energy that is more than 3 times
greater than the 140 keV gamma ray energy
of Technetium 99m. |
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Technologist exposure rates
from high energy positron emitting radionuclides
are nearly 6 times greater than that
from lower energy radionuclides typically
used in nuclear medicine.
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Due to the higher energy,
16 times more lead is required to obtain
the same stopping effect for 511 keV
photons as compared to 140 keV photons. |
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Tungsten shielding has become the absorber
of choice for positron emitting radionuclides.
Tungsten provides about 1.4 times the
shielding capabilities for the same thickness
of lead. |
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| The Distance Factor |
 The
amount of radiation exposure varies with distance
by the “inverse square law”. In other
words, if you double your distance from the
source, your exposure is reduced by a factor
of four (1/4th). If you increase your distance
by a factor of 3, your exposure will reduce
to 1/9th, and so on.
By using the side handle the radiation exposure rate is reduced by about
75% compared to the surface exposure rate. As a result, every effort should
be made to maximize distance from the syringe during unit dose handling.
In addition to the benefits of tungsten, the unique ThermosŪ style design
of the PETPig™ reduces hand exposure during dose handling based on
distance. The top handle increases distance when removing the PETPig™ from
the delivery container, and the side handle increases distance when transporting
the dose to and from the dose calibration area, and then to the dose administration
area. |
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| The Shielding
Factor |
 Radiation
exposure can also be reduced by maximizing
shielding. The density of a material is related
to its radiation stopping ability. Higher density
means better stopping power and shielding.
Due to a higher density, tungsten has a much
higher stopping power than lead. The ability
to stop or attenuate photons is described as
the Half Value Layer (HVL). The HVL of a material
is the thickness required to reduce the incident
radiation by 50%. In the case of 511 keV, 4.1
mm of lead are required to reduce the photon
flux by 50%, while only 2.9 mm of tungsten
can accomplish the same degree of shielding.
The tungsten PETPig™ has an optimum stopping
power to mass ratio that results in the double
benefit of enhancing regulatory compliance
of ALARA practices while diminishing the lifting
requirements of workers compared to heavier
lead based shielding systems. |
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| Important Dose
Administration Considerations |
 Commercially
available PET syringe shields may provide a
false sense of protection due to the thin layer
of material provided. The wall thickness of
the PETPig™ is 21 mm of solid tungsten
(> 7 Half Value Layers) which is significantly
greater than other commercially available PET
syringe shields.
The uniquely designed PETPig™ transforms into
a semi-remote, thick, tungsten syringe shield for dose administration.
The syringe shield rests in the PETPig™ cradle making it unnecessary
to hand hold the shield during dose administration.
The difference is clear. The PETPig™ reduces hand dose exposure by
more than a factor of 6 resulting in a significant reduction in occupational
radiation exposure. |
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