Radiography Flashcards
(28 cards)
Compare and contrast the advantages and disadvantages of direct and indrect digital imaging systems in dental radiography.
Advantages of DDI: highlight the immediate image acquisition with solid-state sensors (e.g., CCD/CMOS), reduced radiation dose compare to indirect system, superior resolution with 256 shades of gray, and elimination of processing error due to real-timie capture.
Disadvantages of DDI: discuss the high cost and fragility of solid-state sensors, patient discomfort due to rigid and bulky sensors, smaller viewable surface area, and inability to withstand heat sterilisation, requiring disposable sleeves.
Advantages of IDI: Note the lower initial cost of the PSP plates, flexibility with various plate sizes (0~4), compatibility with existing X-ray units, and ease of positioning in complex anatomical areas.
Disadvantages of IDI: Explain the slower processing time due to laser scanning, potential for lower resolution compared to direct systems, shorter lifespan of PSP plates, and risk of incorrect plate orientation (E.g., blue active surface errors)
Explain the role of position indicating device (PIDs) and film holders in achieving accurate periapical radiographs using the paralleling technique.
PIDs for beam alignment, Film holder for stability, Reduction of errors (minimises retakes by maintaining angulation, and minimises exposure), system-specific design (holders are tailored for solid-state sensors or PSP plate, accomodating different detector types while ensuring precise positioning in the oral cavity.
Discuss the technical challenges of using solid-state sensors in direct digital imaging and propose solutions to mitigate these issues.
Challenge: Patient Discomfort: Solid-state sensors are rigid, bulky, and can cause gagging or discomfort, particularly in patients with small mouths or sensitive gag reflexes.
Solution: Sensor Design: Use smaller sensor sizes or wireless sensors to reduce bulk, and employ specialized holders to improve intraoral positioning and patient comfort.
Challenge: Fragility and Cost: Sensors are expensive and easily damaged if dropped or mishandled, increasing replacement costs.
Solution: Handling Protocols: Implement strict handling and storage protocols, use protective covers, and train staff to minimize careless damage, extending sensor lifespan.
Evaluate the impact of incorrect PSP plate placement in indirect digital imaging and its consequences for diagnostic quality.
horizontal&vertical detector positioning
horizontal&vertical beam angulation
central beam positioning
collimator rotational angulation
impact on workflow
Describe the process of image acquisition in indirect digital imaging using PSP plates and identify potential sources of error in this workflow.
Process Overview: X-rays strike the PSP plate, exciting phosphor crystals to store a latent image; the plate is scanned by a laser, emitting light that is converted into a digital signal, after which the plate is erased for reuse.
Error: Plate Misplacement: Incorrect orientation (e.g., blue active surface visible or “P” misaligned) results in no image capture, requiring re-exposure.
Error: Scanner Issues: Dust or scratches on the plate or scanner can introduce artifacts, degrading image quality and affecting diagnostic accuracy.
Error: Plate Wear: Over time, PSP plates degrade, reducing their ability to store latent images, leading to lower resolution or incomplete images if not replaced timely.
Explain how anatomical restrictions can complicate the paralleling technique in periapical radiography and suggest modifications to address these challenges.
Restriction: Shallow Palatal Vault: A shallow palate makes it difficult to position the detector parallel to the tooth, potentially causing patient discomfort or image distortion.
Restriction: Large Tori: Mandibular or palatal tori obstruct detector placement, preventing proper alignment with the tooth’s long axis.
Modification: Smaller Detectors: Use smaller film sizes (e.g., size 0 or 1) or pediatric sensors to fit constrained spaces while maintaining parallelism.
Modification: Alternative Technique: If paralleling is infeasible, switch to the bisected angle technique (taught in BDS3) for patients with severe anatomical limitations, though this may compromise image accuracy.
What are the two types of digital imaging?
- Solid state (detector) detector
- Photostimulable phosphor plate (indirect) detector
-> both utilise same X-ray source
What are the equipment required for a PA?
- Standard dental X-ray tube
- Detector: solid-state sensor / storage plate
- Computer with large hard drive, high resolution monitor, software, storage and external drive / offsite back-up
- printer
What are the advantages of Digital Radiography?
- Reduced patient radiation dose: -> analogue (chemical processed, most radiation) > indirect (PSP) plate > direct (solid state sensor, least radiation)
- No ongoing purchase / storage of films, processing solution
- Workplace Health Safety (WHS) issues reduced: chemical hazards
- large dynamic range -> less sensitive to exposure settings
- darkroom not needed
- decreased processing time: film (longest processing time taken) > indirect > direct (fasted)
- Elimination of processing errors
- Electronic storage & transmission of images
- linkage of images to patient electronic files
- Superior resolution: 256 shades of gray
- Software allows image enhancement
- Inversion is possible
What is inversion and what does it do?
Inversion in radiographs refers to a digital image processing technique where the grayscale values of the image are reversed, transforming light areas to dark and vice versa, to enhance diagnostic visualization.
Allowing you to observe additional detail
What are the disadvantages of digital radiography of direct (solid state) sensors?
- Expensive, easily damaged if careless
- Require specialised holders
- Rigid & bulky
- Patient discomfort and/or gagging
- Viewable surface area is smaller than size of the sensor
- Not universal & not interchangeable between different systems
- Can’t withstand heat sterialisation -> require coverage with disposable plastic sleeves
- Initial purchase cost and set up
- possible medical-legal issues from image enhancement
What are PIDs?
Position Indicating Device
What are the different types of Direct Digital Imaging?
- Cabled / wired or cordless / wireless sensor
- acquisition with minimal delay or in real time
Wireless Vs Wired sensors
Wireless:
- Thicker and requires a battery
- Image quality not affected
- roughly 1.5 X more expensive
- easier to lose or drop the sensor
What are the characteristics of Indirect Digital Imaging?
- Detector needs to be read by laser scanner
- Plates of various size: 0, 1, 2, 3, 4
- Less expensive than solid-state sensors
- Possible shorter life than solid-state sensors
Does digital technology compensate for poor radiographic technique?
If information isn’t recorded correctly, no amount of manipulation can produce a good image on the monitor
What is a P.A. radiograph & How to explain to a patient?
- An intra-oral radiograph used to show individual teeth and the structures around their apices.
- Paralleling technique requires use of a dedicated detector holder.
What are the indications for P.A.?
- Detection of apical pathology
- Periodontal assessment
- Endodontics
- Assessment of tooth and alveolar bone following trauma
- Pre/post extraction assessment
- Pre/post implant evaluation
What are the advantages of paralleling technique?
- Relatively simple
- Minimal elongation / shortening of image
- Bone levels well presented
- film holders (e.g., Rinn) used
- use of long cone
What does the Rinn System ensure?
- image fairly reproducible at different appointments and with different operators
- Stable: film holders secured by bite force, steady position
- Reduced cone cutting
- Correct vertical and horizontal positioning and angulation
What does long cone ensure?
- Minimal magnification
- Minimises exposure
What are the advantages of using film holders?
- Improves diagnostic quality of intra-oral radiographs
- reduced number of retakes
- assist us to position film
- allows us to align the beam correctly horizontally and vertically
- essential for accurate, reproducable alignment with the intra-oral film, especailly when using rectangular collimation
