Fluoroscopy Components and Configuration Flashcards
1
Q
Image Intensifier
A
- electronic device which receives the image forming xray beam and intensifies and converts it into visibler light for an image
- being replaced by flat panel detector (FPD)
2
Q
Xray tube/generator
A
- very similar to general radiography tubes
- designed to operate for longer exposures with lower mA than xray
- generators are high frequency
- higher heat capacity that gen rad (fluoro: 500,00 HU, xray: 300,000)
3
Q
Video Monitoring System
A
- high resolution
- used for viewing images during exam
- receives electronic signal and converts it into a visible image
4
Q
Stationary Configuration with Tube Under the Table
A
- advantage of allowing operator to be close to the patient for better communication, reassurance and palpation during the exam
- controls are located on the carriage (near the II or FPD)
- good switch controls radiation so it can
4
Q
Stationary Configuration with Tube Over the Table
A
- advantages of allowing a greater distance between the tube and the patient and the II which improves image quality (reduces geometric unsharpness) and reduces the radiation skin dose to the patient
- operator at greater risk of radiation hazards mainly from scatter from the patient and from the primary beam so this configuration typically is remote controlled to reduce this risk
- disadvantage that the tech and the patient are separated during an exposure
- can be converted into room for general radiography (dual uses)
5
Q
Mobile C-arm Configuration
A
- mobile/portable so it can be moved through out the facility
- tube can be positioned under or over the table
- commonly used in the OR
- operator must be vigilant of source to skin distances because the tube can be positioned in many different ways around the patient, possibly unsafely irradiating them if not careful
- minimum source to skin distance is 30cm
6
Q
Angiography Fluoroscopy Suites
A
- larger diameter and thicker anodes which allows the tube to tolerate higher heat loads
- high power rating for rapid sequence serial radiography needed in angio imaging
- c-arms are floor/ceiling mounted and the table floats to where it is needed
- small focal spot (0.3mm) because very detailed images of small vessels needed
7
Q
Image Intensifier Housing
A
- metal construction, lead lined to absorb off-focus radiation (II is primary barrier)
- provides structural support and protection from rough handling
- protects the vacuum tube
8
Q
Image Intensifier Glass Envelope
A
vacuum tube that allows free flow of electrons form the photocathode to the anode
- can experience up to 1 ton of outside force
9
Q
Image Intensifier Input Phosphor Screen
A
- receives xray photons and emits light proportional to the absorption of the xray photon (receives X-rays, emits light)
- concave surface to improve spacial resolution by maintaining the distance between each point on the input screen and its corresponding location on the output phosphor
- coated with sodium activated caesium iodine phosphor which emits light
- ranges in diameter (6 inches to 23 inches)
10
Q
Image Intensifier Photocathode
A
- directly connected to the input screen
- receives light and releases electrons by photoemission (directly proportional)
- made of caesium antimony
- an extremely thin protective coating is applied between the input screen and the photocathode
11
Q
Image Intensifier Electrostatic Focusing Lens
A
- accelerates, converges and focuses the electrons onto the centre of the ring shaped anode (focus electrons onto the anode)
-charged electrons (25-35kV) located inside the glass envelope - electrons are focused to a point called the focal point (reverses the image)
12
Q
Image Intensifier Anode
A
- accelerates the electrons from the photocathode to the output phosphor
- circular plate with a hole int he middle for electrons to pass through
- the anode is positively charged and located directly in front of the output screen
- voltage difference between photocathode and anode is 25-35 kV
13
Q
Image Intensifier Output Phosphor
A
- receives electrons form the anode and converts them to light
- made of a thin layer of zinc cadmium sulphide, 1 inch diameter
- image becomes much brighter due to smaller size and additional energy throughout acceleration
- an opaque aluminum filter is placed along the inside of the output screen to prevent light from returning to input screen (not 100% effective)
14
Q
Flat Panel Detectors (FPD)
A
- slowly replacing the II
- utilizes indirect capture detector and direct capture detector like general radiography
