6. Patient as a Beam Emitter Flashcards
Is the reduction in the total number of x-ray photons remaining in the beam after passing through a given thickness of material
Attenuation
As an x-ray beam passes through a patient, the beam is
attenuated
The thicker the body part being radiographed, the _____ the attenuation
greater
is also affected by the type of absorber
Attenuation
Higher atomic number materials (lead or barium)
attenuate a ______ percentage of the beam than low atomic number materials (oxygen, hydrogen and
carbon)
greater
Higher atomic number materials
lead or barium
low atomic number materials
oxygen, hydrogen and
carbon
Effective Atomic number of Fat
6.3
Effective Atomic number of Soft Tissue
7.4
Effective Atomic number of Lung
7.4
Effective Atomic number of Bone
13.8
Effective Atomic number of Air (Contrast Material)
7.6 / 7.78
Effective Atomic number of Iodine (Contrast Material)
53
Effective Atomic number of Barium (Contrast Material)
56
Effective Atomic number of Concrete
17
Effective Atomic number of Molybdenum
42
Effective Atomic number of Tungsten
74
Effective Atomic number of Lead
82
Density of the absorbing material also has an impact on
attenuation
is the quantity of matter per unit of volume
measured in kilograms per cubic meter.
Density
is the greatest variable the radiographer
faces when performing a radiographic procedure
Patient
At the atomic level, the body consists primarily of
hydrogen, carbon, nitrogen & oxygen
Hydrogen atomic no.
1
Carbon atomic no.
6
Nitrogen atomic no.
7
Oxygen atomic no.
8
found in concentrated amounts in bones &
teeth
Calcium
Calcium atomic no.
20
The composition of the human body determines its
radiographic appearance
Air has an effective atomic number of 7.78 which is
greater than either
fat or muscle
is naturally present in the lungs, the sinuses and in
small amounts, in the gastrointestinal tract
Air
is similar to muscle in that they are both among the soft-tissue structures in the body
Fat
has an effective atomic number which is slightly less than muscle’s.
Fat
Like fat, muscle is
soft tissue
is easily seen radiographically
because of the calcium content of bone
skeletal anatomy
also has the greatest tissue density and as a result,
absorbs radiation at a greater rate than any of the soft tissues or air-filled structures
Bone
The patient has an impact on all properties affecting
radiographic quality:
Density, Contrast, Recorded Detail
and Distortion
The relationships between these factors and the patient
(subject) are termed
subject density, subject contrast, subject detail & subject distortion
refers to the impact the subject (patient) has on the
resultant radiographic density
Subject Density
Patients body build
Habitus
Massive patient body build
Hypersthenic
Average patient body build
Sthenic
Slender patient body build
Hyposthenic
Very slender patient body build
Asthenic
is the difference in densities of a
recorded image
Radiographic contrast
is the degree of differential absorption
resulting from the differing absorption characteristics of
the tissues in the body
Subject contrast
When there is little difference in the absorption
characteristic of the given body tissues within a part
being examined (e.g. mammography) subject contrast
will be
low
One of the primary factors that affects the sharpness or detail of an image is the ______ between the structure of interest and the image receptor
distance
is dependent on
their position within the body and also on the body’s placement in relationship to the receptor
recorded detail of the structures
The _____ and _____ has a great impact on the
recorded detail
overall size,
placement
is the misrepresentation of the size or shape of
the structure of interest
Distortion
