HIGH INTENSITY FOCUSED ULTRASOUND

1. HIGH INTENSITY FOCUSED ULTRASOUND CESO Conference April 29, 2004 Jason Smale Clinical Engineering Student, University of Toronto

2. A PRIMTIVE ANALOGY ANALOGY FROM: Gail R. ter Haar, Royal Marsden Hospital:United Kingdom PICTURE FROM: http://wmuma.com/tracker/skills/fire/magnifier/

3. ADVANTAGES OF HIFU • Non-Invasive • Preserve tissue integrity • Relatively Infection Free • Non-Ionizing Treatment • Minimal or no anesthesia required • Shorter recovery period • Shorter treatment time • 10-15 sec/treatment point • 60-600 sec/treatment point for other hyperthermia treatments • laser, RF or water

4. LIMITATIONS OF HIFU • Controlling of the Focal Spot • Patient shift or tissue motion • Cannot adequately control shape, size or location • Beam dosimetry • Unknown tissue temperatures • Possibility of acoustic cavitation • Local tissue thermal conductivity and perfusion • Tissue specific • Patient specific (Skin thickness, proportion of fat and muscle) • Growth specific (Malignant, Benign, and Healthy)

5. SOLUTIONS? • Couple With Diagnostic Ultrasound • Can monitor focal point position • Could not measure tissue temperature • Couple With Diagnostic MRI • Easily monitor soft tissue focal point • Can calculate tissue temperature • Proton resonant frequency is dependent of temperature • Must use a MRI compatible focused ultrasound system

6. MR GUIDED HIFU SYSTEM UPPER PICTURE SOURCE: http://www.insightec.com LEFT PICTURE SOURCE: http://www.surgeons.org/asernip-s/net-s/information/mri_guided_focused_ultrasound.htm RIGHT PICTURE SOURCE: MRI Guided Focused Ultrasound Surgery of Fibroadenomas in the Breast: A Feasibility Study, Hynynen et al.

7. MR GUIDED TEMP CONTROL UPPER PICTURE SOURCE: http://www.dkfz-heidelberg.de/mrphys/temperature/temperature.html LEFT PICTURE SOURCE: MR Imaging–guided Focused Ultrasound Surgery of Uterine Leiomyomas: A Feasibility Study, Tempany et al. RIGHT PICTURE SOURCE: MRI Guided Focused Ultrasound Surgery of Fibroadenomas in the Breast: A Feasibility Study, Hynynen et al.

8. HIFU’S TREATMENT TREND • 1960s – Proved to be an effective treatment for Parkinson’s Disease • Outdone by L-Dopa treatment • 1980s and 90s – Proved to be an effective eye treatment • Outdone by eye-laser treatment • 1990s and 2000s– Tumor ablation treatment • Hoping to be outdone by a cure for cancer?

9. HIFU’S TUMOR ABLATION EFFECTIVENESS • Proven effective treatment for prostate tumors • Uses a trans-rectal transducer • Investigations are being performed to test safety and efficacy: • 9 centers are performing clinical investigations worldwide • Phase III Benign Fibroadenomas • Paper published Hynynen (BWH) • Phase III Benign Uterine Fibroids • Paper published by Tempany (BWH) • Phase II Breast Cancer • Paper published by Gianfelice (St. Luc) • General Investigation into Brain Tumor ablation • Investigations underway at BWH

10. IMPORTANT POINTS FROM RESEARCH • Patients are released same day • Some patients suffered from • Skin burns, Abdominal Blistering, Scar Tissue burns • Approximately 17% of patients received 2nd degree burns • Mild discomfort as tumor site for 24-36 hours following ablation • 30% patients rated pain more severe than mild discomfort

11. TRANS-SKULL HIFU • Problems with using HIFU on the brain • Heterogeneous thickness and density of the skull • Very diverse acoustic velocities of the skull and brain tissue • Impedance matching • Results in Signal attenuation, overheating of tissue near the skull and requires a high number of transducers • Uses CT instead of MR • Able to measure heterogeneous internal density of skull • The magic of time reversal • Virtual source sends “acoustical wave” from focal point and amplitude and delay are calculated at HIFU transducer points • Measured signal is sent into the brain to create focal point

12. HIFU EFFECTS ON THE CLINICAL ENGINEER • Future roll of MR Guided HIFU is relatively unknown • Similar to lasers – “The solution without a problem” • Since reporting on Phase 3 trials for benign tumors, implementation might be just over the horizon for some of the larger hospitals • “Its better to lead the technology trend than to follow it.” – A. Dolan, University of Toronto

13. REFERENCES • MR Imaging-guided Focused Ultrasound Surgery of Uterine Leiomyomas, Tempany et al., Radiology (226), March 2003 • MR Imaging-guided Focused Ultrasound Surgery of Fibroadenomas in the Breast, Hynynen et al., Radiology (219), April 2001 • MR Imaging-guided Focused US Ablation of Breast Cancer: Histopathologic Assessment of Effectiveness—Initial Experience, Gianfelice et al., Radiology (227), June 2003 • High Intensity Focused Ultrasound for the Treatment of Tumors, Ter Haar, Echocardiography, Volume 18, No. 4, May 2001 • Newand Emerging Techniques – Surgical Procedure Brief MRI-Guided Focused Ultrasound for Uterine Fibroids, Royal Australasian College of Surgeons, August 2003 • Tissue Thermal Conductivity by Magnetic Resonance Thermometry and Focused Ultrasound Heating,Cheng et al.,JOURNAL OF MAGNETIC RESONANCE IMAGING (16), 2002 • Experimental demonstration of noninvasive transskull adaptive focusing based on prior computed tomography scans, Aubry et al., Journal of Acoustical Society of America, January 2003 • Poster: MR Guided Focused Ultrasound Surgery, R. Newman, Vice President, InSightec TxSonics • InSightec Website: www.insightec.com • In-vivo MR Temperature Monitoring of Focused Ultrasound (HIFU) in Rabbit Muscle, Rademaker et al., http://www.dkfz-heidelberg.de/mrphys/temperature/temperature.html QUESTIONS OR COMMENTS: jason.smale@utoronto.ca