Ultrasound Therapeutics

Transcription

1 4 th International Summer School on Emerging Technologies in Biomedicine Brain Molecular Imaging and Molecular Delivery Through the Blood-Brain Barrier Ultrasound Therapeutics Elisa Konofagou, PhD Columbia University Ultrasound Therapeutics High intensity focused ultrasound (HIFU) Focused Ultrasound Surgery (FUS) Ultrasound Surgery Ultrasound Therapy FUS applications Treatment of neurological diseases (Lynn 1944, Fry and Fry 196) Ocular treatment FDA approved (Lizzi et al. 1978) Treatment of benign prostatic hyperplasia (Gelet et al. 1993) and prostate cancer (Chapelon et al. 1999, Feleppa et al. 1) Hemostasis (Delon et al. 1995, Vaezy et al. 1998) Lithotripsy (Vallancien et al. 1993) Tumor ablation (Hughes et al. 1988, ter Haar 1998) Uterine Fibroid treatment (Tempany et al. 1) FDA approved Blood-brain barrier opening (Hynynen et al. 1, Choi et al. 5) HIFU bioeffects Heating (Thermal Index) Hyperthermia Protein-denaturing lesions (PDL) Vaporization Mechanical effects (Mechanical Index) Radiation force Streaming Cavitation Definition of Thermal Index TI is defined as the ratio of the acoustical power produced by the transducer to the power required to raise the temperature in tissue by 1 C. A long exposure time is assumed. TI is estimated using theoretical models taking into account the acoustical power, frequency and beam area. And also, assumptions are made on the conditions of tissue attenuation, tissue perfusion and thermal properties.

2 TIS, TIB, TIC TIS: TI for soft tissue path. TIB: TI for the acoustical path with bone at or near the focus of the transducer and a non-scanning operating mode is selected. Bone has much greater absorption than soft tissue; thus it can result in much higher TI. This is often seen during scans of fetal bones. TIC: TI for transcranial studies in which the acoustical path has cranial bones at or near the skin surface. Thermal Dose -Accumulated dose at a reference temperature under different temperature profiles and temperature histories. t= final 43 = T t43 R t t= t 43 = equivalent time at 43 o C T = average temperature during t R =.5 when T> 43 o C, R =.5 when T< 4 o C Sarapeto and Dewey, Int. J. Radiation Oncology Biol. Phys, 787-8, 1994 Figure 8.4 in Ultrasonic Bioinstrumentation, D.A. Christensen, 1988 CAVITATION Refers to the generation, growth and interaction of small gas bubbles in a sound field. Bubbles are more easily compressed than tissues; leads to greater stresses on cells. Ultrasound in Med. & Biol., Vol. 4, Supplement 1, pp. S11-S1, 1998 CAVITATION Peak pressure amplitudes and peak intensities are most closely associated with the risk of cavitation. Not sure of its likelihood in diagnostic exposures, but it cannot be ruled out: -lithotripsy and HIFU systems induce cavitation. -pressure values from diagnostic instruments above pressures where effects in animals were reported. Definition of MI The Mechanical Index is an attempt to indicate the probability that mechanical damage by nonthermal processes, in particular cavitation, might occur within tissue. The MI is computed from the peak rarefactional pressure and the frequency using relations between these parameters and cavitation thresholds established by researchers. MI ~ P derated / f

3 Key parameters: F.I.T. Therapeutic methods Frequency resonant transducer frequency resonant transducer frequency typically several MHz typically several MHz Intensity maximum area power density in focal plane typically several hundred W/cm Time duration of exposure duration of exposure typically few seconds Nonlinear Propagation Transducers Ultrasound transducer: piezoelectric material that converts electrical signal to mechanical vibration. Transducer shape and size: Linear transducer dimensional change piezoelectric material Focused transducer surface electrodes Riverside Research Institute, New York, NY Frequency (MHz) V Laboratoire d Ondes et Acoustique, ESPCI, Paris, France Large focused ultrasound transducers Focused transducers Therapeutic transducer Focal zone Focal zone dimensions: 1 x 1 x 1 mm 3 D F 7λ(F/D) F λ D λ mm Laboratoire d Ondes et Acoustique, ESPCI, Paris, France Riverside Research Institute, New York, NY

4 Advanced transducers Multielement ultrasonic array Electronical beamsteering of the focus Focused transducer for generation of the acoustic radiation force Linear array for ultrasonic imaging Focused Ultrasound Ultrasound energy is localized to a specific region. To induce damage. To stimulate the tissue. High intensity relative to diagnostic ultrasound. FUS is also known as High-Intensity Focused Ultrasound (HIFU). FUS Beam Dimension at the Focus Depends on transducer geometry and operating frequency. At 1.55 MHz Cigar shaped Diameter (-6 db):. mm Length (-6 db): 1 mm Intensity= power/area = 1-1 kw/cm X (mm) Lateral Beam Profile at Focus Y (mm) 5 X (mm) Axial Beam Profile at Focus Z (mm) Commercial HIFU systems Riverside Sonocare CST1 FDA approved Chongqing Haifu Technology Co., Ltd. Model JC Focus Surgery -Sonablate 5 U Wash CIMU -Acoustic Hemostasis Device Insightec - FDA approved etc. The Blood-Brain Barrier The blood-brain barrier (BBB) is a specialized vascular system in the brain. Tight junctions connect endothelial cells. Membranes are highly selective. Only 5% of the drugs developed treat Central Nervous System (CNS) diseases. This 5% can only treat four main disorders: depression, schizophrenia, epilepsy, and chronic pain. The BBB is the rate-limiting factor in brain drug delivery. Riverside Research Institute, New York, NY *Abbott NJ et al., Nature Reviews Neuroscience 6 The Blood-Brain Barrier Current Brain Drug Delivery Methods Method Noninvasive Localized Lipidization: Add lipid groups to drug to increase permeability. X Transcranial Brain Drug Delivery: Insert needle through brain tissue. X Solvents and Adjuvants: Mix drug with molecules to cause contraction or dilation. X Autoradiogram of a mouse injected with radiolabeled histamine (sacrificed 3 min after IV injection).* Endogenous Transporters: Chemically modify drugs to travel through transporters endogenous to the cell membranes. X ** Pardridge WM The blood-brain barrier: bottleneck in brain drug development. NeuroRx. 5 Jan;(1): Focused Ultrasound (FUS)*: Apply FUS after injection of microbubbles to open the BBB. *Hynynen et al., Radiology, 1. 4

5 FUS-induced BBB Opening Mouse as the animal model Transgenic models of neurodegenerative disease* Transcranial ultrasound on hippocampus Microbubble: Optison or Sonovue Clinically used diagnostically as ultrasound contrast agent Readily available Monitoring of BBB opening with MRI Qualitative and quantitative analysis of BBB opening/closure** Temporal/Spatial analysis using T1/T-weighted MRI Molecular diffusion of Magnevist (568 Da> 5 Da BBB limit) *Faber et al., Magnetic Resonance in Medicine 57:696 73, 7. **Choi JJ et al. Ultrasound in Med. Biol. 33: 95-14, 7. 5 Mattson and Magnus, Nature Reviews Neuroscience 7, 78-94, 6. 6 Typical Acoustic Pressure Clinical Ultrasound Imaging Ultrasound Contrast Agents (1-1 µm diameter; FDA approved) Operating Mode B-Scan M-Mode Pulsed Doppler Color Doppler Peak Pressure Amplitude 1.68 MPa 1.68 MPa.48 MPa.59 MPa

6 General BBB Opening Procedure FUS transducer Steps: 1. Target a specific region of the brain.. Inject microbubbles intravenously (IV). 3. Apply focused ultrasound. 4. The BBB opens. 5. Inject the molecule of interest intravenously. 6. The molecule deposits through the BBB opened regions. Focused Ultrasound in Mice Mouse BBB opening is noninvasive, localized, and transient [1] [1] Choi et al., Phys Med Biol 7 31 Choi JJ et al. Phys. Med. Biol. 5: , 7. 3 Trans-skull propagation - Simulation Maps of the acoustic properties were placed into a finite element wave propagation simulation program. Simulations Beam was well formed. Diameter: ~. mm (approximately the same as without the skull present). Direction of Wave Propagation 33 1 mm Transcranial Beam Characterization in Mice (1.5 MHz) Pressure fields were measured using a needle hydrophone. Beam Profile of a 1.5 MHz FUS transducer at its focus Intensity (db) Intensity (db) No skull Beamwidth: 1.3 mm y y (mm) x 5 (mm) y y (mm) x (mm) 5 x (mm) y (mm) Intensity (db) (db) Through Ex Vivo Skull (1) Attenuation of intensity: ~33% () Change in beamwidth: ~1% (3) Focus displacement: < spatial sensitivity of the needle hydrophone Choi JJ et al. Ultrasound in Med. Biol. 33: 95-14, 7. ~ Transcranial Beam Characterization in Humans (.5 MHz) Ex vivo human skull experiment Setup Beam profile x MRI Experimental Timeline Day 1 Day BBB Opening Monitoring of the BBB Opening Anesthesia Targeting Microbubble IV injection Sonication MRI MRI Gadolinium IP injection Gadolinium IP injection MRI MRI Time Monitoring of the BBB Closing Time 35 36

7 Magnetic Resonance Imaging Bruker System Magnet Field Strength: 9.4 Tesla Slice orientation: Horizontal Resolution: 75 x 84 µm in-plane Slice thickness:.6 mm Number of averages: 5 and 15 Number of mice: 3 MR Contrast Agents (gadolinium): Omniscan Amount:.75 ml Method: Intraperitoneally (IP) Molecular weight: 574 Da Omniscan does not normally traverse the BBB FUS-induced BBB Opening Settings Pulsed Focused Ultrasound [1] Frequency: 1.55 MHz Pressure:.64 MPa Peak to peak Duty Cycle: % Repetition rate: 1 Hz Pulse length: ms Duration: 1 minute [1] Choi et al., Ultrasound Med Biol 7 Microbubbles Optison TM SonoVue In-house lipid-shelled Amount: 5-3 µl Method: Intravenous MPa 5 µl Optison -9 min post-opening FUS-induced BBB opening Hippocampus Spatio-temporal analysis after BBB opening Normalized MRI signal 8.5 intensity rise Target Hippocampus Control Hippocampus Sequential T1-weighted MRI to 9 min after IP gadolinium injection Every image is thresholded at different standard deviations above the averaged right hippocampus. Choi JJ et al. Phys. Med. Biol. 5: , Choi JJ et al. Phys. Med. Biol. 5: , 7. Bar indicates 1 mm 4 Temporal Analysis.67 MPa and 5 ul Optison 9 minutes after sonication Normalized MRI BBB Closure.67 MPa and 5 ul Optison 8 hours after sonication pre-gadolinium 13 min 39 min 65 min 159 min pre-gadolinium 13 min 39 min 65 min IP gadolinium injection Choi JJ et al. Phys. Med. Biol. 5: , IP gadolinium injection Choi JJ et al. Phys. Med. Biol., 7 (submitted) 4

8 T 1 -Weighted MR Images Day 1 9 min Day 9 min 3D Mapping of BBB opening BBB Opening BBB Closure Quantitative Analysis BBB closure Haematoxylin and Eosin Staining Normalized change in MRI signal intensity (%) Left striatum Right striatum Left hippocampus Right hippocampus Left Hippocampus (Sonicated) 5 µm Right Hippocampus (Control) Time after gadolinium injection (min) Choi JJ et al. Phys. Med. Biol., 7 (submitted) Choi JJ et al. Phys. Med. Biol., 7 (submitted) pre-gd PS/APP (AD) Mouse Model.67 MPa and 5 ul Sonovue 13 min post-gd 39 min post-gd 65 min post-gd T 65 min post-gd Delivery of 7, Da fluorescent dextran through the BBB and to the entire left hippocampus (Coronal slice) BBB Closure BBB Opening 47 H SNR H: hippocampus SNR: substantia nigra 48 Choi JJ et al. Stroke, 8 (submitted).

9 Area of Contrast Enhancement Day 1 - Spatio-Temporal Analysis Left hippocampus Right hippocampus Normalized signal intensity increase 49 5 Spatial Contour Maps Day 1 9 min Day 9 min Normalized MRI signal intensity increase BBB opening Alzheimer s (PS1-APP) model mice min 15 min 3 min 9 min BBB closing 51 Choi et al., Phys. Med. Biol., 8 (submitted). Fluorescent Dextran Fluorescent Dextran: Sugar polymers at different molecular weights tagged with a fluorescent marker 3, Da (.33±.38 nm) tagged with Texas Red 7, Da (1.±1.4 nm) tagged with Texas Red,, Da (.±.6 nm) tagged with Tetramethlyrhodamine Histology Sectioning: Cryostat Slice thickness: 3 µm Number of mice studied = 1 Horizontal Coronal 3, Da 7, Da 1 Dextran is normally BBB impermeable,, Da 1 Control 1: No FUS 3, DX 1 Control : FUS No DX 1 DX Experimental Timeline Anesthesia BBB Opening Targeting Microbubble IV injection Sonication Fluorescent Dextran IV injection Perfusion and Fixation Time 53 54

10 Texas Red - 3, Da Slice thickness: 3 µm Slide#: 7; Slice#: 1; Magnification: 4x Texas Red (Exposure time: 5 ms) Bright Field (Exposure time: 3 ms) Texas Red - 7, Da Slice thickness: 3 µm Slide#: 16; Slice#: 1; Magnification: 4x Bright Field (Exposure time: 3 ms) Texas Red (Exposure time: 5 ms) TMR,, Da Slice thickness: 3 µm Magnification: 4x Bright Field (Exposure time: 3 ms) Texas Red (Exposure time: 5 ms) Control No Dextran Horizontal sections Left hippocampus Right hippocampus 1 mm , Da (Texas Red ) Horizontal sections 7, Da (Texas Red ) Horizontal sections Left hippocampus Right hippocampus Left hippocampus Right hippocampus 1 mm 1 mm 59 6

11 ,, Da (Tetramethyrhodamine) Horizontal sections Coronal - 7, Da (Texas Red ) Left hippocampus Right hippocampus Left hippocampus Right hippocampus 61 6 Texas Red - 7, Da - coronal Slice thickness: 3 µm Magnification: 4x Bright Field (Exposure time: 3 ms) Texas Red (Exposure time: 5 ms) Fluorescence imaging (MW=7 kda) Left Hippocampus (sonicated) Right Hippocampus (control) 63 Statistical analysis of Dextran results MR and Fluorescence imaging Opening (59 Da) Closure (59 Da) Opening (3 Da) 65

12 Thermal effect Mechanism and localization of opening Temperature Change ( C) Time (s) Choi et al., Phys. Med. Biol. 5: , MPa.86 MPa.53 MPa Fluorescence microscopy Olympus IX Excitation: 595 nm Emittion:615 nm Microbubble type and size effect Microbubble type and size effect mpeg 1-5 µ m PC 1- µm.33 MPa DTPA - Gd(III ) ~3 n m 4-5 µm.33 MPa Borden et al. IEEE Trans Ultrason Ferroelect Freq Contr. 5;5(11):199-. Mark Borden, Ph.D. Truman Brown, Ph.D. James Choi, M.S. Kevin Costa, Ph.D. Karen Duff, Ph.D. Kana Fujikura, M.D., Ph.D. Brian Garra, M.D. Jeff Holmes, M.D., Ph.D. Shunichi Homma, M.D. Wei-Ning Lee, M.S. Thomas Ludwig, Ph.D. Jianwen Luo, Ph.D. Caroline Maleke, M.S. Dimitris Metaxas, Ph.D. Jonathan Ophir, Ph.D. Scott Small, M.D. Shougang Wang, Ph.D. Acknowledgments NIH R1 EB64 NSF CAREER NIH R1 EY1855 NIH R1 EB851 NIH KL RR4157 American Heart Association American Society of Echocardiography Brigham Research and Education Council Kinetics Foundation Radiological Society of North America Wallace H. Coulter Foundation Whitaker Foundation Contact information Elisa E. Konofagou, Ph.D. Department of Biomedical Engineering Columbia University Tel: Fax: ek191@columbia.edu URL: