1. Ultrasonic Thermometry
Hirad Karimi
MBP1028

2. Outline Introduction US thermometry Summary and Discussions
Current methods
US thermometry
Physics
Different techniques
Summary and Discussions

3. Thermometry 3D distribution of temperature Different techniques
Crucial for the extent of damage
Controlling heat delivery
Protecting healthy tissues from thermal exposure
Ensuring adequate thermal dosimetry
Different techniques
Magnetic Resonance Imaging
Impedance Tomography
Microwave Radiometry
Backscattered Ultrasound techniques

4. Ultrasound Thermometry
Why US Thermometry?
Non-invasive
Relatively low cost
Real-time data collection and signal processing
Deep penetration
Good spatial and temporal localization
Compatibility with US therapeutic technologies

5. Physical and Biological effects
When a region of tissue heated:
Speed of sound
Thermal expansion
Changes in tissue stiffness
Tissue US attenuation
Leads to time-shifts between backscattered US RF-echoes

6. Speed Vs Temperature
Nasoni et al Techavipoo et al

7. Attenuation Coef. Vs Temperature
Techavipoo et al

8. Techniques Frequency dependent attenuation (Ueno et al)
Tracking changes in acoustic properties before and after heating

9. Techniques (cont’d) Backscattered power (Straube et al)
Measuring backscattered power differences between power measured before and after heating

10. Techniques (cont’d) Speed of sound and Thermal expansion (Simon et al)
1D: tracking frequency variation of the echo components in the spectral domain
2D: tracking echo time-shifts in the time domain

11. Techniques (cont’d) Optical-flow (Mehrabani et al)
Detecting shifts in speckle pattern location of ultrasound B-Mode digital images from a region of tissue undergoing thermal therapy

12. Limitations Signal-to-noise ratio Time-consuming process
Low spatial resolution
Time-consuming process
Low temporal resolution
Motion artifacts
Compromises time-shift estimations

13. References
Mehrabani, Bahram M., Tavakoli, Vahid, Abolhassani, Mohammad D., Alirezaie, Javad and Ahmadian, Alireza. An efficient temperature estimation using optical-flow in ultrasound B-mode digital images 2008
Nasoni, R. L., Bowen, T., Connor, W. G. and Sholes, R. R. In vivo temperature dependence of ultrasound speed in tissue and its application to noninvasive temperature monitoring 1979
Simon, C., VanBaren, P. and Ebbini, E. S. Two-dimensional temperature estimation using diagnostic ultrasound 1998
Straube, W. L., Arthur, R. M. Theoretical estimation of the temperature dependence of backscattered ultrasonic power for noninvasive thermometry 1994
Ueno, S., Hashimoto, M., Fukukita, H. and Yano, T. Ultrasound thermometry in hyperthermia 1990
Vaezy, Shahram, Shi, Xuegong, Martin, Roy W., et al. Real-time visualization of high-intensity focused ultrasound treatment using ultrasound imaging 2001
Techavipoo U, Varghese T, Chen Q, Stiles TA, Zagzebski JA, Frank GR. Temperature dependence of ultrasonic propagation speed and attenuation in excised canine liver tissue measured using transmitted and reflected pulses. Journal of the Acoustical Society of America 2004;115:2859–2865.