Medical Ultrasound

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Medical Ultrasound

• Spring 2008

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Chapter 7. Therapeutic Ultrasound Systems
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Medical Ultrasound

• Medical Ultrasound Imaging
• OBGYN
• Cardiac Vascular Imaging
• Well known Therapeutic Ultrasound
• Liposuction
• Lithotripsy
• .

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Medical Ultrasound

• Unknown therapeutic ultrasound
• Ultrasound surgery HIFU
• Targeted drug delivery
• Trasndermal drug delivery
• Gene delivery
• Hypo-plastic Left Heart Syndrome
• .

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Lithotripsy

• A lithotriptor is a medical device used in the
  non-invasive treatment of kidney stones (urinary
  calculosis) and biliary calculi (stones in the
  gallbladder or in the liver).
• The scientific name of this procedure is
  Extracorporeal Shock Wave Lithotripsy (ESWL).
• Lithotripsy was developed in the early 1980s in
  Germany by Dornier Medizintechnik GmbH.

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Shock Waves
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Shock Waves
?
p
Sound
Shock Wave
100.000.000 Pa (1.000 Bar)
2,2 msec
p
10 Pa (0.0001 Bar)
t
t
lt 2 ?sec
E.g. big church organ playing concert pitch in 5
m distance
E.g. Lithotripter shock wave focus
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Lithotripsy
Characteristics of shock waves (in medical
applications)
Pressure
Velocity in water 1500 m/sec
Time
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Lithotripsy
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Electromagnetic Shock Wave
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Focus Size
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Shock Wave Applications
Tendinopathy Pseudarthrosis
Urinary Stones
Biliary Stones
Shock Wave Lithotripsy
Shock Wave Therapy
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Shock Wave ApplicationsKidney stone

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Shock wave source parameter
-6dB Focus size
approx. 100 mm
approx. 5 mm
Pressure 3 75 MPa
150 mm
Energy Flux Density 0.005 0.65 mJ/mm2
144 mm
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Established Orthopaedic Therapies with Shock
Waves - Chronic Pain associated with Tendon
Disorders - Pseudarthrosis (non-union) of bones

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Orthopaedic Therapy with Shock Waves(calicifying
tendinitis of the shoulder)
right shoulder
left shoulder
Pre-shock wave application
Enhanced blood flow and perfusion related to
shock wave application
Indication for possible application
in Cardiology
post-shock wave application
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Shock Wave Applications
Cardiac Shock Wave Therapy Shock Wave Treatment
of Angina Pectoris
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Angina Pectoris
European Heart Journal (1997) 18 394-413
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Angina Pectoris
Definition

• Angina Pectoris occurs when there is an
  imbalance between myocardial perfusion and
  the demand of the myocardium
• The pathological substrate of this is almost
  invariably narrowing of the coronary arteries
  (coronary atherosclerosis)
• It is usually considered that the coronary
  artery must be narrowed by at least 50 70 in
  luminal diameter before coronary artery blood
  flow is inadequate to meet the metabolic
  demands of the heart with exercise of stress

Epidemiology

• It is estimated that in countries with
  relatively high coronary heart disease rates,
  the total prevalent number of patients with
  angina pectoris may be as high as 30.000 to
  40.000 per 1 million total population

European Heart Journal (1997) 18 394-413
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Angina Pectoris
Classification of Angina Pectoris (CCS)

• Class I Ordinary physical exercise does not
  cause angina pectoris
• Class II Slight limitation of ordinary
  activities
• Class III Marked limitation of ordinary
  activities
• Class IV Inability to carry on any physical
  activity without discomfort

Aims of Treatment

• To improve prognosis by preventing myocardial
  infarction and death
• To minimise or abolish symptoms

Canadian Cardiovascular Society
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Angina Pectoris
Present Treatment Options

• Pharmacological treatment of patients with
  stable angina pectoris
• Percutaneous transluminal coronary angioplasty
  (PTCA) and implantation of stents
• Coronary artery bypass grafting (CABG)
• Other revascularisation techniques

Data on Recurrent Angina

• 24 of patients had recurrence of angina
  pectoris in the first year after coronary
  artery bypass surgery, 40 had recurrence after
  6 years¹
• After 2 years 31 of patients in the angioplasty
  group had angina pectoris, compared with 22
  in the surgical group²
• Restenosis occurs in 35 40 of cases with
  angiographic control

¹ Coronary Artery Surgery Study (CASS) ² Coronary
angioplasty versus coronary artery bypass
surgery RITA trail, Lancet 1993 341 573-90
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Angina Pectoris
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Angina Pectoris
Present Coronary Artery Disease Treatment Options
Blocked coronary arteries ? Necrosis ? Myocardial
Infarction
Atherosclerosis
Narrowed coronary arteries ? Ischemia ? Angina
Pectoris
Lyses Emergency Angioplasty/Stenting Coronary
Artery Bypass Surgery ? Multiple interventions
Pharmacological Treatment Angioplasty/Stenting Cor
onary Artery Bypass Surgery ? Multiple
interventions
Refractory Angina Pectoris unresponsive to both
maximal drug treatment and revascularisation
techniques and/or diffuse and distal coronary
artery disease
New alternative treatments
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Angina Pectoris
New alternative treatment options with various
degrees of invasiveness

• Pharmacological Treatment
• Neurostimulation (TENS SCS)
• Enhanced External Counter Pulsation (EECP)
• Laser Revascularisation (PTMR TMLR)
• Therapeutic Angiogenesis

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Coronary Arteriogram
Pre SW (4wks)
Post SW (8wks)
Number of visible Coronary arteries
Control
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SW
Control
10
5
SW
0
Pre treatment
Post treatment
Shimokawa et al. (Circulation Vol. 110, No. 19,
Nov. 9. 2004)
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Improved Left Ventricle Ejection Fraction (LVEF)
after the SW treatment
Pre (4wks)
Post (8wks)
Left Ventricle Ejection Fraction ()
80
Control
SW
Control
60
40
SW
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Pre treatment
Post Treatment
Shimokawa et al. (Circulation Vol. 110, No. 19,
Nov. 9. 2004)
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Cardiac Shock Wave Therapy (Inclusion Criteria)

• Refractory stable angina pectoris
• Guideline medication
• Canadian Cardiovascular Society (CCS)
  classification III IV CCS classification I
  II for patients refusing or not tolerating other
  therapies
• 18 years, both gender

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Liposuction

• Modern liposuction first burst on the scene in a
  presentation by the French surgeon, Dr
  Yves-Gerard Illouz, in 1982.
• Dr. Michele Zocchi invented a technique whereby a
  sound wave generator is attached to a sterile
  hand piece with a titanium rod which vibrates at
  a very high but slightly audible pitch. (UAL)
• External ultrasound-assisted liposuction (XUAL or
  EUAL)
• XUAL is a type of UAL where the ultrasonic energy
  is applied from outside the body, through the
  skin, making the specialized cannula of the UAL
  procedure unnecessary.
• Ultrashape
• No suction, just external ultrasound treatment
• 500cc / treatment

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Liposuction

• Type
• Tumescent Liposuction
• The word "tumescent" means swollen and firm. By
  injecting a large volume of very dilute lidocaine
  (local anesthetic) and epinephrine (capillary
  constrictor) into subcutaneous fat, the targeted
  tissue becomes swollen and firm, or tumescent.
  The tumescent technique is a method that provides
  local anesthesia to large volumes of subcutaneous
  fat and thus permits liposuction totally by local
  anesthesia.
• Dry liposuction
• The dry technique derived its name from the fact
  that it did not use injections of local
  anesthesia into the fat before liposuction. This
  technique was abandoned because of the excessive
  blood loss it caused. Blood composed
  approximately thirty percent (30) of the tissue
  that was removed by liposuction using the dry
  technique.

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Liposuction

• Type
• Wet Liposuction
• Wet Technique also required general anesthesia.
  The wet technique required the injection of
  approximately 100 milliliters of local anesthesia
  containing epinephrine. Although the wet
  technique caused less blood loss than the dry
  technique, blood loss with the wet technique was
  still excessive and dangerous. Blood composed
  approximately 15 to 20 of the tissue removed by
  liposuction using the wet technique.
• UAL liposuction
• Ultrasonic Assisted Liposuction (UAL) requires
  the use of a large volume of tumescent fluid and
  uses either a metal probe or metal paddle to
  deliver ultrasonic energy and heat into
  subcutaneous fat. Internal UAL is the term used
  to describe the technique where a long metal
  probe, which may be solid or hollow, is inserted
  into fat through a large incision. Among those
  surgeons who do internal UAL, most rely on the
  use of general anesthesia or heavy IV sedation.
  Internal UAL has largely been abandoned because
  of the risk of full-thickness skin burns and
  severe scaring. The initial reports of internal
  UAL were unrealistically enthusiastic. Some
  authors did not report their complications, and
  others have learned of major UAL complications
  after publishing their articles. External UAL
  requires the use of tumescent fluid and uses a
  metal paddle applied to the skin and directs
  ultrasonic energy into subcutaneous fat. External
  UAL does not improve liposuction results and can
  cause burns to the skin.

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Liposuction

• Type
• Powered Liposuction
• Power Assisted Liposuction (PAL) devices have
  recently become available. PAL devices use power
  supplied by an electric motor or compressed air
  to produce either a rapid in-and-out movement or
  a spinning rotation of an attached liposuction
  cannula. Advocates of PAL assert that it makes
  liposuction easier for the surgeon. While some
  liposuction surgeons have expressed enthusiasm
  about PAL, many others remain skeptical about any
  advantages of PAL.
• Ultrashape (no suction)
• UltraShape technology uses focused ultrasound
  waves which are directed at a specific target
  point on the body where they selectively break
  down unwanted fat cells without affecting
  surrounding structures.

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UAL
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Ultrashape
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Ultrasound Surgery
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Ultrasound Surgery
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Ultrasound Surgery

• Characteristics of ultrasound surgery

• Radiotherapy
• Particle wave
• Deliver high energy in the
• intervening tissue
• Adverse effect in the
• intervening tissue
• In order to avoid collateral
• damage focus size becomes
• order of 10x10x100 cm3 range

• ultrasound surgery
• Mechanical Wave
• Absorption less than 5
• Most energy propagates thru
• Non-toxicity in the
• intervening tissue
• Focus size is 1x1x10 mm3
• (Selectivity is much better)

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Ultrasound Surgery

• Frequency around 1MHz
• Wavelength around 1.54 mm
• Focus size 1 x 1 x 10 mm3

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Ultrasound Surgery

• Target organs
• Liver, prostate, kidney, brain, pancreas, uterus
• Problems in ultrasound surgery
• Noninvasive Evaluation tool
• Ultrasound Imaging
• MRI Imaging
• Long Surgery Period
• Aberration Correction
• Rib cage, Skull

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Physical mechanism of US

• What does cause the tissue damage?
• Thermal damage
• Even though very small amount of energy is
  absorbed the target area, if the focus is tight
  enough and the delivered energy is large enough,
  there will be heat accumulation.
• The accumulated heat can kill cells
• Caviational damage
• Mechanical rapid collapse of bubble(micro size)
  inside liquid(body) have highly localized (um
  range) high concentrated energy effect.
  Mechanically rupture and high temperature can be
  induced

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Thermal Dose

• Dose
• Concept from radiation dose
• Radiation dose
• Total absorbed energy from radiation
• Factor of attuenaution
• Thermal dose
• Acoustic energy absorbed thermally
• Hyperthermia
• Sensitization of tissue to enhance other
  treatment effect
• Less than 43C
• Ultrasound surgery/ tissue ablation
• Treatment method
• Usually more than 43C

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Thermal Dose

• Thermal dose
• Tref reference temperature 43C
• R 4 when T(t) 43C
• 2 when T(t) 43C
• Example
• At 43C 50-250 miniutes (usually assumed 240)
• At 44C 120 minute
• At 45C 60 minute
• At 55C 3.5 sec

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Thermal Dose

• Use of thermal dose
• Temperature rise estimation
• Tissue damage
• Surgery planning
• Temperature monitoring
• Tissue damage estimation
• Immediate feedback information
• Ultrasound guided Ultrasound surgery
• Thermal expansion
• MR guided Ultrasound surgery
• Proton chemical shift

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Thermal Dose

• Temperature estimation procedure
• Acoustic field calculation
• Acoustic intensity calculation
• Deposited power calculation
• Bioheat transfer function calculation
• 3D temporal -gt 4D partial differential equation
• Thermal dose calculation
• Usually the optimization requires repetition of
  above procedure

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Ultrasound Surgery Equipment

• Extracorporeal type

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Ultrasound Surgery Equipment

• Transrectal type

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Ultrasound Surgery
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Ultrasound Surgery
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Ultrasound Surgery
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Ultrasound Surgery
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Ultrasound Imaging Guidance Ultrasound Surgery
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Ultrasound Lesion Detection

• Step 5 Applying to 2nd set of data in 2D

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Imaging Modalities for US

• MR guided Ultrasound surgery

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Ultrasound guided Ultrasound surgery

• Characteristics
• easy to build
• Shielding
• System cross talk
• Fast imaging
• almost real time
• cheap
• low resolution
• 10 times worse than MRI
• speckles
• difficult in temperature measurement

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Ultrasound guided Ultrasound surgery

• Improvement
• Tissue characterization
• Evaluation tool for various soft tissues
  characteristics
• Elasticity
• Temperature
• Attenuation coefficient
• Reflectivity
• Blood perfusion rate

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MR guided Ultrasound surgery

• Characteristics
• High Resolution
• High sensitivity to temperature
• Large calculation time
• Difficulty to build
• System cross talk
• Static Magnetic field
• Slow imaging
• Reconstruction period
• Body motion problem

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MR guided Ultrasound surgery

• Improvement
• Temperature measurement
• Calculation period
• Body motion control
• Fast reconstruction
• Cost

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Ultrasound Induced Embolizationdroplet
vaporization

• Droplet micro-size bubble seed
• Becoming macro-size bubble by high frequency
  ultrasound

Canine Brain Occipital lobe
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Hypo-plastic Left Heart Syndrome

• Shunt Perforation on Septum
• Erosion induced by Focused Ultrasound
• Histotripsy
• Cavitation, micro-streaming

Porcine Atrial Wall
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Targeted Drug Delivery
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Targeted Drug Delivery
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Transdermal Drug Delivery

• Stratum Corneum
• Major resistance of transdermal transport
• Some drugs has high permeability
• Developed into a patches
• Ultrasound transdermal protein delivery
• FDA approval in 1995

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Bone Growth

• Low Intensity Pulse Ultrasound
• Bone tissue Piezo characteristic
• Equivalent with electromagnetic pulse
• Mechanical Shear stress effect on osteoblast
• Ultrasound field induced Micro-streaming

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Urinary Reflux

• Creation of Bubbles in Bladder
• Focused Ultrasound

Rabbit bladder