Post on 04-Jun-2018
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) Surface In tegral Exposure5
(SIE)
An alternate name that is sometimes
used for this quantity is Exposure
Area Product. When the exposure is not uniformly
distributed over the exposed area ,
like in the fluoroscopic examplecoming up, the SIE is the sum (or
integral) of the individual area and
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) Surface In tegral Exposure5
(SIE)
An alternate name that is sometimes
used for this quantity is Exposure
Area Product. When the exposure is not uniformly
distributed over the exposed area ,
like in the fluoroscopic examplecoming up, the SIE is the sum (or
integral) of the individual area and
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) Surface In tegral Exposure5
(SIE)
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) Dose Area6
)Product (DAP
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Dose Area Product (DAP) is
similar in concept to (SIE)and
exposure area product in that they
all express total radiation delivered
to a patient. The principle difference is in the
units used.
DAP is in dose units, such as Gy-
cm2.
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DAP
For a uniformly exposed area, the
DAP is just the product of the air
kerma , in Gy or mGy, and theexposed area in cm2.
DAP provides a good estimation of
the total radiation energy delivered toa patient during a procedure.
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DAP
Both radiographic and fluoroscopic
machines can be equipped with
devices (DAP meters) or computerprograms that measure or calculate
the DAP for each procedure.
It is the most practical quantity formonitoring the radiation delivered to
patients.
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) Absorbed Dose7
Dose values can be in the traditional unit of
the rad or the SI unit of the gray (Gy).
The rad is equivalent to 100 ergs of
energy absorbed in a gram of tissue andthe gray is one joule of energy absorbed
per kilogram of tissue.1 gray (Gy) = 100 rads
10 mGy = 1 rad
1 mGy = 100 m rad
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ompu e omograp y ose
Index(CTDI)
The Computed Tomography Dose
Index, CTDI, is the special dose
quantity that is used extensively to
express absorbed dose in CT.
CTDI is based on the assumption that
the scatter measured from a single
slice, is a good estimate of the scatterinto a slice from adjacent slices
in a multiple-slice scan.
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(CTDI) This procedure does provide a good
approximation of the actual dose, butsince it is not completely precise, it is
called a dose index.
The CTDI can bemeasured at
points other
than the center
of a slice, if that
information is
needed.
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) In tegral Dose9* Integral dose is the radiation quant i tythat is equal to the to tal energy
abso rbed by the body.
The SI unit for integral dose is the joule(the standard unit
of energy), and
the conventionalunit is the gram-
rad.
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11) EQUIVALENT DOSE
DEFINE EQUIVALENT DOSEAND EFFECTIVE DOSE???
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Equ ivalent Dose (EqD)in the unit ,
s ievert (Sv), is a quantity that
at tempts to take into accoun t the
variation in biologic harm that is
produced by different types of
radiation.
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Dose Equivalent, is a quantity that
expresses the relative biological
impact of the radiation by including a
radiation weighting factor (wR). The
relationship is:
Dose Equ ivalen t (Sv) = Dose (Gy)
x wR
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Effec tive Dose (EfD)
A quantity that attempts to summarize
the overall potential for biologic damage to
a human due to exposure to ionizing
radiation.
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