Optically Guided Surgery John Black 4/6/10 Outline Overview I. - PDF document

Optically Guided Surgery John Black 4/6/10

Outline Overview I. How I came to love the laser I. Diagnostics – what can we do / what should we do? II. Case Study – Opportunities in Atrial Fibrillation II. Case Study – Peripheral and Coronary Artery Disease III. Conclusions IV. 2

Acknowledgements Professor Jennifer Barton, PhD • • Tissue Optics Lab – The University of Arizona, Tucson Roger Gammon, MD and Frank Zidar, MD. • • Austin Heart, Austin TX Horst Sievert, MD • • Sankt Katharinen Krankenhaus Frankfurt John B Simpson, MD, PhD • • And the staff at Avinger 3

4 Background

2010 – 50 th anniversary of the laser (CLEO (San Jose – May)) • Introduced as a surgical therapeutic in the 1960’s • Ophthalmology • Surgery • • Prostate reduction in BPH • OB/GYN Dermatology • 5

6 Ophthalmology Healthy retina •

Drexler – Radial view of a porcine retina. Ophthalmology http://www.iovs.org/cgi/content/full/48/12/5340 Optic Nerve Head Macula http://en.wikipedia.org/wiki/Retina 7

Diseases of the Retina Macular edema, Age-related Macular Degeneration • Diabetic retinopathy, Retinopathy of prematurity … • All conspire to rob you of vision at some rate. • 8

Treatment 9 http://www.optimedica.com/PASCAL-Method/fundus_images.aspx

Surgery Benign Prostatic Hyperplasia • • Chances you get this over 50 y/o = your age • Trans-urethral resection – HoLEP, PVP • Holmium laser, Green Laser 10

Dermatology – Skin Anatomy Stratum Corneum Epidermis Rete Ridges Papillary Dermis Reticular Dermis Pilo-sebaceous Unit Sebaceous Gland Hair Follicle Sweat Gland Feeder vessel / Vascular Plexus Muscle / Fat

Port Wine Stain

• Treatment • 532 nm laser • Strong absorption in hemoglobin

• One treatment 6 week follow-up. • Improvement rated as “Good 50 – 89% Clearance” • Mark M. Hamilton, MD. Perkins-Hamilton Facial Plastic Surgery P.C., Indianapolis, IN •

Optical Diagnostic Overview What do we need to “see” to guide a procedure • • Aside from the visual surgical field • http://www.ted.com/talks/catherine_mohr_surgery_s_past_pre sent_and_robotic_future.html 15

Why Optical Sensing? Bandwidth – GBs • Immunity • • Fiber optic signals are insensitive to EM interference Physical / Mechanical Impact • • Small 2 mm OD Catheter 100 micron OD Fiber 16

Pick up on “non-visual” surgical cues Atrial Fibrillation • Contraction of heart chambers becomes unsynchronized • • Especially left atrium • Serious condition http://en.wikipedia.org/wiki/Heart 17

Treatment – Pre-Catheter Surgical Maze Procedure • • Series of incisions to block impulse conduction pathways • Full sternotomy http://www.stopafib.org/surgical-ablation.cfm 18

Treatment – RF / Microwave Catheter Femoral access, inferior vena cava to RA • Trans-septal puncture to LA • Full wall thickness coagulation around pulmonary vein. • • Interrupt nerve conduction pathways 19

Clinical Procedure X-ray fluoroscopy • Problems • • X-ray dose • Surgeon and Patient • Contrast agent • Iodinated compound • Nephrotoxin • Limits procedure time • Especially in renally compromised patients http://www.healthcare.philips.com/de_de/products/interventional_xray/Solutions/Cli nicalSpecialties/xper_swing/index.wpd 20

Loss of Dimensionality 3-D structure is flattened to 2D • plane when image is captured Horst Sievert, MD Sankt Katharinen Krankenhaus Frankfurt 21

What would you like to know / see? CLINICAL RELEVANCE • • Anything that can improve the outcome for the patient • Shorten procedure time • Improve long-term efficacy • Reduce X-ray or contrast burden • … Is the catheter in contact with the heart wall? • Am I applying too much force? • What is the temperature of the coagulation zone? • Have I made a full-thickness lesion? • 22

Am I in contact with my target? Apposition • • Not just a question of pushing and feeling resistance • Catheter length can contribute to sensed resistance • No contact – no wall coagulation 23

Am I in contact with my target? Rotate catheter in the vessel • • Sub-mm resolution (wall approach and contact) Up Down Wall Reflection Poor Apposition Well Apposed (Blood in Field) 24 Roger Gammon (Austin Heart) – New Horizons 2007

Am I applying too much force? Tearing of trans-septal puncture area • Danger of perforation • 25

Fiber Bragg Gratings (FBG) • Periodic refractive index step functions in fiber core 5 microns 21 microns

Bragg Gratings • Reflect or eject very specific wavelengths • Performance is very sensitive to stress on FBG • Stress imparted by bending, torsion or tension • Submarine hulls, bridges, buildings, oil wells use FGBs • Hansen Medical • Distributed force sensing on catheter.

Am I applying too much force on the tip? Honeywell O-RIMS Technology • • Silicon microstructure on the end of a fiber 28

What is the temperature of the target? Clinical end point – Coagulation • Under-treat – potentially a sub-optimal outcome • Over-treat – charring • Stuart J. Loui, Honors Thesis, Electrical Engineering Department, U. Of Arizona 29 2002

Optical Temperature Measurement Based on Refraction • Happens when light goes from one medium to another • 30

Archer Fish Nature solved refraction • • A long time ago!

Learned (not inherited trait) Archer Fish •

Refraction • Critical Angle • Where light is no-longer refracted, but is reflected at the interface.

Temperature Measurement Refractive index can be sensitive to temperature. • Very! • n 1 n 2 Strength of the beam at point C ( ) • − − θ 2 2 2 θ 2 sin ( ) cos n n n n θ = 2 1 2 1 ( ) , r n 2 θ + − θ 2 2 2 2 cos sin n n n n 2 1 2 1 34 IEEE JSTQE, 7 , p 936 – 943 (2001) .

Simple Experiment IEEE JSTQE, 7 , p 936 – 943 (2001) . 35

Results IEEE JSTQE, 7 , p 936 – 943 (2001) . 36

Results Non-perturbative, real time interface T measurement • Can be insensitive to the heating method • • RF interferes with thermocouples No fitting parameters • • Know refractive index behavior wrt T – know temperature • Can be measured off-line Bandwidth determined by detector and probe laser power • Select AOI and polarization to set sensitivity • • On-off at a critical temperature • Feedback loop to heater power Usefulness? • • Confirm FEM model of heating 37

Comparison to Finite Element Model Use the measurement to refine the model • 38 http://www.ece.arizona.edu/~bmeoptics/publications.html

Have I made a full-thickness burn? Depth-resolved Measurement • IVUS Xray OCT Optical Coherence Tomography • 39

Depth / Resolution trade-offs with optical methods 1 cm Optical Diffuse Tomography 1 mm Laser- MRI CT Induced Resolution Fluorescence Photo- 100 µm Ultrasound Acoustic Tomography 10 µm Optical Coherence Tomography 1 µm Confocal Micro- Microscopy scopy 0.1 µm 10 µm 100 µm 1 mm 1 cm 10 cm Depth of Penetration http://www.ece.arizona.edu/~bmeoptics/publications.html

Which one should I use? What are your resolution needs? • • Cellular level? Are you potentially limited by penetration depth? • Progressively harder to implement as resolution ▲ • • Need a good excuse to do OCT, confocal microscopy! • Retinal imaging, cancer (cervical, lung), arterial disease OCT, confocal can be implemented fiber-optically • • Endoscope / catheter compatible DOT and microscopy mainly “free-space” techniques • 41

Optical Coherence Tomography Optical analog of 10x better resolution • • ultrasound 1 – 1.5 mm penetration Minimal crossing profile Preferable for therapeutic • • impact device incorporation COTS telecom Straightforward fiber optic • • components implementation Image quality allows for Reduced training • • intuitive pattern requirements and time-of- recognition procedure Optical bandwidths Microsecond time resolution • • 42

Experimental Geometry Pump Laser Beam OCT Probe Beam “Hot” Mirror Heated Blood Volume Cuvette Blood Sample (200 microns) http://www.ece.arizona.edu/~bmeoptics/publications.html

OCT Data M-Mode OCT Data • • Depth vs Time image • 1.25 ms time steps, 15 micron axial resolution. http://www.ece.arizona.edu/~bmeoptics/publications.html Time Coagulum formation Cuvette Wall Sample Depth 200 um Cuvette Wall

OCT comparison to FEM Cuvette Wall FEM • • Shows peak temperature is just inside cuvette wall • Shows lower part of cuvette does not get irradiated Good agreement between OCT and FEM • http://www.ece.arizona.edu/~bmeoptics/publications.html

Intra-operative parameters � Apposition • � Force • � Temperature • • Function and Structure • See beneath the surface • Tissue organization • Molecular content (Endogenous contrast) Clinical Need • • Retinal function / structure • Cancer • ARTERIAL DISEASE 46