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RAD 354 Chapt . 26 Digital Fluoro

RAD 354 Chapt . 26 Digital Fluoro. Terms to remember DSA – digital subtraction angiography Registration Interrogation time Hybrid subtraction CCD = charge coupled device ROI = region of interest PACS = picture archival and communication system. Advantages of DF.

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RAD 354 Chapt . 26 Digital Fluoro

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  1. RAD 354 Chapt. 26 Digital Fluoro • Terms to remember • DSA – digital subtraction angiography • Registration • Interrogation time • Hybrid subtraction • CCD = charge coupled device • ROI = region of interest • PACS = picture archival and communication system

  2. Advantages of DF • Speed of image acquisition • Post processing “tweaking” of the image(s) • Spatial resolution is determined by the matrix size (usually 1024 X 1024) and the size of the image intensifier) • DF operates at “conventional mAs” (hundreds of mA rather than less than 5 mA as conventional fluoro) • BUT – DF operates in “pulsed, progressive” fluoro!

  3. “Pulsing” Terms • Interrogation time = time for unit to be switched on and reach the mA and kVp level • Extinction time = time for the tube to be switched off (usually times less than 1 ms)

  4. Receptor • The “receptor” is usually a “charge coupled device” (CCD) • CCD’s are VERY sensitive to light and have a much LOWER level of noise than a TV camera • This results in much HIGHER SNR than conventional TV cameras/systems • They also have NO lag time or “blooming” and require NO maintenance • CCD’s may be “docked” directly to the II’s output phosphor

  5. Advantages of CCD’s • High spatial resolution • High SNR • High Detective Quantum Efficiency (DQE) • No warm up required No lag/blooming • No spatial distortion/maintenance • Unlimited life • Unaffected by magnetic fields • Lower pt. dose

  6. CCD

  7. DR SubtrationTWO Primary Types • Temporal subtraction • Single kVp setting • Normal filtration • Good contrast resolution (1% @ 1 mm) • Simple arithmetic image subtraction used • Motion artifacts are a problem (misrepresentation) • Total subtraction is able to be achieved • Subtraction limited by number of images

  8. Energy Subtraction • Rapid voltage switching is used • Filter switching is preferred • Higher x-ray energy used for + contrast resol. • Complex image subtraction is required • Motion artifacts (misrepresentation) are reduced • Some residual bone is survived (shows) • More types of subtraction are possible • IF BOTH ARE COMBINED = HYBRID SUBTRACTION

  9. DF/D Subtraction RAD Dose • DF & D Subtraction usually result in much higher pt. dose and PULSED imaging is required to lower the dose! • Storage and image distribution are used as already discussed in class

  10. Images

  11. Lateral Cerebral DSA

  12. DSA Hand

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