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Fluoro exam with 100% correct answers
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Fluoro exam with 100% correct answers
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Fluoro exam with 100% correct answersNote: Most modem image intensifiers are constructecl with 1 inch output
phosphor.
* brightness gain (B.G.) = minification gain x flux gain
Example: What is the brightness gain of an image intensifier that has 9" input
phosphor, 1" output phosphor, and has 50 gain flux?
B.G. = 81 x 50 =4050
* conversion factor =
intensity of output phosphor (measured in candelas or cd)
________________________________________
millirads/second
* f-number = focal length
___________________
lens diameter
100mm
f-number = ___________ = 6
15 mm
* Integral dose= When the beam of radiation enters the patient, energy is
absorbed by the tissue irradiated.
,The total energy absorbed from the beam by the patient is called the integral
dose.
The integral dose to a mass of tissue is the product of the mass of tissue and the
dose which it receives.
The unit of integral dose is the gram rad (1 gm rad =100 ergs).
For example:
- A 10 gram block of
tissue is given an absorbed dose of 3 rads, then the integral dose is 3 (rads) x 10
(grams) = 30 gram
rads.
- If the irradiated area is doubled, that is, 20 gram block of tissue is given an
absorbed dose of
3 rads, then the integral dose would be 3 (rads) x 20 (grams) = 60 gram rads.
* You are fluoroscoping a patient. The fluoroscope emits 1.
Filtration
* Radiation protection method that limits unnecessary exposure by reducing the
number of photons (low level) in the x-ray beam.
* A filter is defined as material placed in the useful (primary) X-ray beam to
preferentially absorb the
less penetrating radiations.
* It is usually made of aluminum or equivalent material and placed in the useful or
primary beam.
* The main purpose of a filter is
to reduce the number/amount of low-energy (long wavelength) X-rays from
,reaching the patient.
* Low energy X-rays cannot completely penetrate through a body to reach the
image intensifier and, therefore, contribute nothing to the diagnostic image.
* A large portion of these useless, "soft", long wavelength X-rays can be filtered
out of the X-ray beam if the X-ray tube aperture is intercepted with at least 2.5
mm of aluminum or equivalent material.
* Thus, appropriate amounts of filtration reduce patient dose.
* Appropriate filtration also accomplishes the following (these are subtle effects):
o Reduces scattered radiation
o Improves the image quality
* Filtration Regulatory Requirements.
* The total filtration of an X-ray beam includes inherent filter and added filter.
* Inherent filter: Inherent filtration includes the X-ray tube and its housing such as
the glass envelope
(window) through which the X-ray beam passes.
* Added filter: Added filtration includes sheets of metal (usually aluminum)
placed in the direct path
of the X-ray beam.
* Regulations require that the total filtration permanently in the useful X-ray
beam at normal operating
voltages may not be less than 2.5 mm aluminum equivalent for fluoroscopy.
* Since normal operating voltages for an average adult patient vary from 80 to
, 120 kV, this requirement may be assumed to have been met if the half-value layer
is not less than 3.0 millimeters aluminum.
Interspace material
Aluminum and carbon fiber
PACS vs. DICOM
* Picture Archiving and Communication System:
- image acquisition, storage, transmission and display
Functions:
- storage
- rapid retrieval of images
- access to images acquired with multiple modalities
- simultaneous access at multiple sites.
- Input to a PACS may come from digital or analog sources (when the latter have
been digitized).
* Digital Imaging and Communications in Medicine standard:
- A standard for handling, storing, printing, and transmitting information in
medical imaging
- Form and flow of the electronic messages that convey images and related
information between computers
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