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HIGH INTENSITY FOCUSED ULTRASOUND. CESO Conference April 29, 2004 Jason Smale Clinical Engineering Student, University of Toronto. A PRIMTIVE ANALOGY. ANALOGY FROM: Gail R. ter Haar, Royal Marsden Hospital:United Kingdom PICTURE FROM: http://wmuma.com/tracker/skills/fire/magnifier/.

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high intensity focused ultrasound
HIGH INTENSITY FOCUSED ULTRASOUND

CESO Conference

April 29, 2004

Jason Smale

Clinical Engineering Student,

University of Toronto

a primtive analogy
A PRIMTIVE ANALOGY

ANALOGY FROM: Gail R. ter Haar, Royal Marsden Hospital:United Kingdom

PICTURE FROM: http://wmuma.com/tracker/skills/fire/magnifier/

advantages of hifu
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
limitations of hifu
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)
solutions
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
mr guided hifu system
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.

mr guided temp control
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.

hifu s treatment trend
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?
hifu s tumor ablation effectiveness
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
important points from research
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
trans skull hifu
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
hifu effects on the clinical engineer
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
references
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: [email protected]

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