1 / 40

Oversigt

Oversigt. Interferens Speckler og deres dynamik Optisk blanding og Dopplerskift Lidt matematik: Campbells teorem og Wiener- Kinchine teoremet Diffusionsmålinger Laser Doppler teknik evt. med OCT Medicinske anvendelser. Incident beam. Surface. Observation plane. r s. A. r coh. B. C.

ora
Download Presentation

Oversigt

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Oversigt • Interferens • Speckler og deres dynamik • Optisk blanding og Dopplerskift • Lidt matematik: Campbells teorem og Wiener- Kinchine teoremet • Diffusionsmålinger • Laser Doppler teknik evt. med OCT • Medicinske anvendelser

  2. Incident beam Surface Observation plane rs A rcoh B C srms • Observed field = Sjexp[-iK Lj] Speckle/FreePen

  3. If spot size is larger than the lateral scale and surface roughnes larger than the wavelength, then the field obeys circular complex Gaussian statistics Im A+B+C A B Re C Speckle/FreePen

  4. This means that the field distribution function is Speckle/FreePen

  5. and the intensity distribution function is Speckle/FreePen

  6. Speckle size given by L Speckle/FreePen

  7. Speckle translation Dpx R L Incident beam Dx R is the radius of curvature of the incident beam Speckle/FreePen

  8. feltstyrke intensitet Eksempel: en partikel med hastigheden 1 m/sec spredes fra en HeNe-laser. Dopplerskiftet bliver ca. 3 MHz sammenholdt med lysets frekvens på 5*1014Hz Light beating eller optisk blanding

  9. kin kout v Intet Doppler skift!

  10. kin kout v Maksimalt Doppler skift!

  11. Ksc Intet Dopplerskift v

  12. Ksc rimeligt Dopplerskift væv blodåre v

  13. Frekvensmoduleret signal detektor Ksc rimeligt Dopplerskift væv blodåre v

  14. LaserDopplerAnemometri

  15. Wiener -Kinchine teoremet: 1

  16. Wiener -Kinchine teoremet: 2

  17. Filter: w1, w Filter: w0, w Filter: w2, w Filter: wn, w Power spectrum S(t)

  18. Sum af identiske “bursts”: Korrelationsfunktionen: og dermed spektret: Campbells theorem

  19. Hvorfor er spektret interessant? • det giver en målelig og let målbar størrelse • måling af korrelationsfunktionen er mere kompliceret • hastighed er direkte relateret til frekvens

  20. diffusionsmålinger laser Ksc detektor

  21. Idet “random walk” betyder at Spektret for strømmen bliver derfor en Lorentz-kurve med en halv- værdi bredde på

  22. w2flux = k1ò w. P(w)dw - noise w1In • = k2 x Average Speed of blood cells x • Number Concentration of Blood Cells

  23. Lisca

  24. Lisca

  25. Lisca

  26. The images below show the increase in foot sole tissue perfusion following lumbar sympathetic blockade in a patient with peripheral vascular disease. The Laser Doppler Perfusion Imager has been used successfully for visualization of two-dimensional microvascular flow-maps in a number of clinical settings including investigations of for example peripheral vascular disease, skin irritants, diabetics, burns and organ transplants. Before injection of drug.2 minutes after injection.30 minutes after injection. Lisca

  27. Microdialysis guide and probe inserted in forearm skin.Perfusion directly after insertion of probe. The skin at point of insertion is anaesthetized.Perfusion at site of insertion and probe tip 30 min after introduction. Lisca

  28. The moorLDI-VR imager

  29. The moorLDI-VR imager An example of irritant reaction to two cutting fluids and water control is shown here (courtesy of Mr C Packham, EnvironDerm Services Ltd, UK). Volar forearm 10.6 ´ 4.1 cm2 Irritancy of metal working fluids 1& 2, compared with water control 3.

  30. The moorLDI-VR imager

  31. Moor Instruments Two moorLDI laser Doppler images below show plaques of psoriasis that have been treated with coal tar. Clinically treatment was considered to be complete. The active edge on the leg might explain why some plaques recur within a relatively short time of discontinuing treatment whereas others are resolved. In the first case (a,b), there is higher blood flow at edge indicating further treatment is required. In the second case (c,d), coal tar treatment is complete and blood flow within and outside the plaque are similar

  32. Two moorLDI laser Doppler images below show plaques of psoriasis that have been treated with coal tar. Clinically treatment was considered to be complete. The active edge on the leg might explain why some plaques recur within a relatively short time of discontinuing treatment whereas others are resolved. In the first case (a,b), there is higher blood flow at edge indicating further treatment is required. In the second case (c,d), coal tar treatment is complete and blood flow within and outside the plaque are similar

  33. A Laser Doppler Imager (LDI) can be used to show heart tissue blood flow (b) during and (c) after coronary artery bypass graft (CABG) surgery. The reperfusion is clearly seen and areas of poor perfusion could be identified.

  34. a previously treated 15 mins post treatment 20 mins post treatment b, c not previously treated LDI Applications

  35. Blood flow in the lower limbs improves when the legs are raised to the horizontal. Laser Doppler imager (LDI) images from the moorLDI show improvement in skin blood flow from (a) dependent to (b) raised. This type of procedure needs further research to investigate how test responses might be used to select patient treatment and predict its efficacy.

  36. Konklusion • Doppler-metoden giver en kvalitativ måling • En kvantitativ måling af blod flow er næppe mulig for væv • Kombination af CCD-kameraer og speckle metoder giver nye muligheder • Kombination af OCT og Doppler metoder kan give dybdeselektiv måling • Anvendelse af nære IR-kilder vil give mindre spredning • Simultan anvendelse af to bølgelængder vil være interessant

More Related