1 / 13

Photothermal Therapy

Photothermal Therapy. Nicholas Ellens MBP1028 28 September 2010. Outline. Context Photothermal mechanisms and delivery Absorption and power deposition in tissue. Context • Delivery • Absorption and Power Deposition. Hyperthermia has been used for thousands of years

donar
Télécharger la présentation

Photothermal Therapy

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. Photothermal Therapy Nicholas Ellens MBP1028 28 September 2010

  2. Outline • Context • Photothermal mechanisms and delivery • Absorption and power deposition in tissue

  3. Context• Delivery • Absorption and Power Deposition • Hyperthermia has been used for thousands of years • Photothermal therapy emerged shortly after the invention of the laser • Laser treatments range in orders of magnitude in both treatment time and intensity

  4. Context• Delivery • Absorption and Power Deposition Boulnois, J-L, “Photophysical Processes in Recent Medical Laser Developments: a Review” in Lasers in Medical Science, 1986.

  5. Context• Delivery • Absorption and Power Deposition • Driving limitation in phototherapy is the absorption, is quantified by a, the absorption coefficient (units of cm-1) • Depends on medium and frequency • Penetration depth, a-1, ranges from fractions of mm (UV) to a few mm (near IR) • As such, therapy is suitable for topical applications or deeper via fibres delivered an endoscope or percutaneously

  6. Context• Delivery • Absorption and Power Deposition • Further control provided by pulsing the light • If the pulse length is less than the thermal relaxation time, the treatment can be made more localised • Feedback usually involves direct observation • Smoke, blanching • Where this is not achieved, other methods are required

  7. Context• Delivery • Absorption and Power Deposition Boulnois, J-L, “Photophysical Processes in Recent Medical Laser Developments: a Review” in Lasers in Medical Science, 1986.

  8. Context• Delivery • Absorption and Power Deposition • Thermal treatment is a three stage process: • Conversion of heat to light • Thermal transfer • Tissue Response

  9. Context• Delivery • Absorption and Power Deposition Brunetaud, J et al., “Non-PDT Uses of Lasers in Oncology” in Laesrs in Medical Science, 1995. Covered elsewhere in course

  10. Context• Delivery • Absorption and Power Deposition • Reflection: • An air-tissue (n≈1.41) interface causes substantial internal reflection, further depositing energy • Scattering: • Scattering length is typically 100-1000 times less than absorption length • Upon entering tissue, photons are scattered many times before being absorbed • Effectively, this increasesthe light intensity close tothe tissue surface Burgholzer, P. “Photoacoustic tomography: Sounding out fluorescent proteins” in Nature Photonics 3, 2009.

  11. Context• Delivery • Absorption and Power Deposition • Conversion of light to heat • Absorption: • A + hu A* • Deactivation: • A* + B(E)  A + B’(E+DE) • Efficacy depends on high probability of collision and high number of accessible vibrational states • Though sensitive to wavelength, less so than chemical processes

  12. Context• Delivery • Absorption and Power Deposition • Heat diffusion • As per the bioheat transfer equation • Affected by thermal properties of tissue, timescale, blood perfusion • Thermal effects • Hyperthermia • Coagulation • Vaporisation

  13. fini

More Related