Questions and Answers
Match the following terms with their corresponding descriptions:
Control Panel = Adjustment Technique Lock = Exposure Adjustments High Dose Image = Pulsed Fluoroscopy Continuous Fluoroscopy = Increased mA Magnification = Mirror Image + Flip Superior/Inferior = Reduce Motion Blur Iris Collimator Adjustment = Rotate Paired Filters
What is fluoroscopy?
What are two advantages of fixed systems over mobile systems in fluoroscopic imaging?
More reliable x-ray generators and often better radiation protection
Digital Subtraction Angiography (DSA) can only work on anatomy that is not moving.
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Contrast media that has a higher atomic number than surrounding tissues and attenuates more x-rays is known as ____________.
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Match the following types of contrast media with their descriptions:
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Study Notes
Fluoroscopic Imaging
- Fluoroscopy is a type of medical imaging that shows a continuous X-ray image on a monitor, similar to an X-ray movie.
Applications of Fluoroscopy
- Orthopaedic: Arthrograms, theatre procedures
- Angiography: Cardiac, cerebral, peripheral
- GI Tract: Barium swallows, meals, and enemas
- Endoscopy: ERCP, OGD
- Urology: Ureteroscopy, nephrostomy insertions, PCNL
- Interventional Radiology: Line insertions, Embolisations, PTC
Fixed Systems
- Installed in a specific room or suite
- Typically used for longer screening cases
- Variety of styles: floor mounted, ceiling mounted, biplane
Mobile Systems
- Portable
- Used to support theatre cases and shorter or less complex interventions
- Can be moved between theatres
Comparison of System Advantages
- Mobile Systems: Does not require custom room design, can be moved between theatres, often better radiation protection
- Fixed Systems: More reliable x-ray generators, often more features, room is designed to allow uninhibited movement of c-arm
X-ray Generation
- Mechanism similar to conventional x-ray systems
- Modes: Continuous fluoroscopy, Pulsed fluoroscopy, High-Dose “Acquisitions”, Single high-dose image
Anode Heat Dissipation
- High-speed rotational anodes
- Oil or water cooled systems
- Range of focal spot sizes to balance detail with anode heating depending on application
Image Intensifier
- X-rays pass through the patient and reach the input phosphor
- Input phosphor emits light, which reaches the photoemissive layer, emitting electrons towards the anode
- Electrons reach the output phosphor, producing an amplified light signal
- Light signal is recorded by a camera
Flat Panel Detectors (FPDs)
- Similar to plain film direct digital receptors
- Input x-rays converted into electric via a Selenium photoconductor
- Charge transmitted to a thin-film transistor (TFT) array
- Array arranged in a matrix with each transistor mapped to a pixel
Comparison of Image Intensifier and Flat Panel Detectors
- Advantages of FPDs: Lower dose, greater field of view, higher image quality
- Disadvantages of FPDs: Higher initial cost, size of receptor can impact maneuverability
Contrast Media
- Positive Media: Radiopaque, higher atomic number, attenuates more x-rays, appears “Hyperdense” on image
- Negative Media: Radiolucent, lower atomic number, attenuates less x-rays, appears “Hypodense” on image
Double-Contrast Imaging
- Uses both positive and negative contrast together
- Can be used in Barium meal and Barium Enema investigations
Digital Subtraction Angiography (DSA)
- Process used in angiography to remove distracting detail and anatomical structures from the image
- Operator acquires images before injecting contrast, and computer system creates a “mask” demonstrating the background anatomy
- Subsequent images are subtracted from the mask, leaving only the new information visible on the screen
Biplane Systems
- Digital fluoroscopy systems with multiple c-arms
- Allow simultaneous images in multiple planes
Radiation Protection
- Room designated as a “Controlled Area”
- Warning signs, local radiation rules, and workers wear lead PPE
- Methods to reduce dose: Low dose fluoroscopy setting, collimation, reduce exposure factors, reduce SID, staff stand further from primary beam, reduce pulse/frame rate, use shallow angles, lead shielding, staging the procedure
Exposure Factor Control
- Automatic Brightness Control (ABC): Adjusts kVp and mAs to maintain a present brightness level
- Automatic Dose Rate Control (ADRC): Algorithmically controls exposure factors based on anatomical thickness and applies initial setting based on the program selected
Image Quality – Further Considerations
- Screen position, cleanliness of screens, lighting of the room, display settings
- Collimation: Reduces irradiation of unnecessary anatomy, reduces scatter, and affects the full circumference of the image
- Filtration: Reduces skin dose, reduces “flare” on the image, improves visibility
- Exposure Lock: Locks the exposure at a previously used level or overrides and sets manual parameters to prevent unnecessary compensation for high-density objects
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Description
Understand the physical principles of fluoroscopic imaging, radiation protection, and image generation. Learn about fixed and mobile fluoroscopic imaging and its applications in medical imaging.