Flouroscopy Flashcards
Main function of fluoroscopy is:
to provide real-time or dynamic studies of the internal organs.
Dynamic refers to:
structures or organs in motion.
How does the radiologist highlight the internal organs?
With the aid of contrast material (such as barium).
Still photos taken during fluoro are called:
“Spot” images.
Who invented fluoroscopy and when?
Thomas Edison in 1896.
How did radiologists view fluoro screens at first?
By directly exposing their eyes to the X-ray beam.
How was the original fluoro design altered to improve safety to the radiologist?
An arrangement of mirrors permitted an indirect way to view the image & the primary beam was shielded into a lead enclosure.
How did the original fluoro screen need to be viewed and what did the radiologist have to do to prepare to view the screen?
Had to be viewed in a darkened room & the radiologist would need 15 minutes of dark adaptation.
What was invented that overcame the need for the radiologist to have to adapt to the dark before viewing a fluoro screen?
Image Intensification Tubes in 1948.
Why was the invention of image intensification tubes so significant?
They raised the illumination of the fluoro screen to the level that the human eye can perceive it and where the visual acuity is the greatest.
Though the invention of image intensifiers increased safety to the radiologist and improved brightness of the image, the downside was:
loss of detail.
Where is the X-ray tube located on a fluoroscopy table and where is the image intensifier located?
The tube is under the table and the I.I. is above the patient. (Though there are some that are designed exactly opposite.)
Why are the tube and I.I. usually mounted on a c-arm?
To maintain their alignment. The c-arm permits the IR to be raised and lowered and permits scanning over the length and width of the table.
What is the carriage on the fluoroscopy machine?
The arm the supports the equipment which is suspended over the table.
What does the carriage hold within it?
It holds the I.I. tube, controls for power drive to the table, brightness control, spot image selection, tube shutters, spot imaging/cine camera and video input tube.
The carriage can be disengaged & pushed away from the table to gain access to pt, however:
an exposure cannot commence until carriage is returned to full beam intercept position.
What allows the radiologist to have their hands free to position the pt or operate the carriage?
The foot switch. Care must be taken not to unintentionally step on the switch once the fluoro unit is engaged.
What mA is the tube operated at during fluoro?
less than 5 mA (0.5 - 5.0 mA). However, the dose is still higher than conventional X-ray since the beam is on for a much longer time.
The brightness of a fluoro exam depends on:
Anatomy
kVp
mA
What type of technique is preferred for fluoro (High or low kVp and high or low mA?)?
High kVp and low mA.
What is the Automatic Brightness Control (ABC)?
A function of the fluoro unit that maintains the overall appearance of the image (its contrast and density) by automatically adjusting the kVp, mA or both.
How does the ABC work?
It either monitors the current throughout the I.I. or the output phosphor intensity and adjusts the exposure factor if the monitored value falls below preset levels.
What other names is the ABC referred to?
Automatic Dose Control (ADC) or Automatic Brightness Stabilization (ABS).
The input phosphor is made of
cesium iodide and is bonded to the curved surface of the tube itself