Limits...
Spatial and Temporal Control of Hyperthermia Using Real Time Ultrasonic Thermal Strain Imaging with Motion Compensation, Phantom Study.

Foiret J, Ferrara KW - PLoS ONE (2015)

Bottom Line: However, combined ultrasound imaging and therapy systems offer the benefits of simple, low-cost devices that can be broadly applied.Here, we propose a motion compensation method based on the acquisition of multiple reference frames prior to treatment.The technique was tested in the presence of 2-D and 3-D physiological-scale motion and was found to provide effective real-time temperature monitoring.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, University of California Davis, Davis, CA, United States of America.

ABSTRACT
Mild hyperthermia has been successfully employed to induce reversible physiological changes that can directly treat cancer and enhance local drug delivery. In this approach, temperature monitoring is essential to avoid undesirable biological effects that result from thermal damage. For thermal therapies, Magnetic Resonance Imaging (MRI) has been employed to control real-time Focused Ultrasound (FUS) therapies. However, combined ultrasound imaging and therapy systems offer the benefits of simple, low-cost devices that can be broadly applied. To facilitate such technology, ultrasound thermometry has potential to reliably monitor temperature. Control of mild hyperthermia was previously achieved using a proportional-integral-derivative (PID) controller based on thermocouple measurements. Despite accurate temporal control of heating, this method is limited by the single position at which the temperature is measured. Ultrasound thermometry techniques based on exploiting the thermal dependence of acoustic parameters (such as longitudinal velocity) can be extended to create thermal maps and allow an accurate monitoring of temperature with good spatial resolution. However, in vivo applications of this technique have not been fully developed due to the high sensitivity to tissue motion. Here, we propose a motion compensation method based on the acquisition of multiple reference frames prior to treatment. The technique was tested in the presence of 2-D and 3-D physiological-scale motion and was found to provide effective real-time temperature monitoring. PID control of mild hyperthermia in presence of motion was then tested with ultrasound thermometry as feedback and temperature was maintained within 0.3°C of the requested value.

No MeSH data available.


Related in: MedlinePlus

Calibration measurement for the tissue-mimicking phantom.(A) Calibration of the material dependent k value for the tissue-mimicking phantom by comparing temperature elevation measured by the thermocouple and corresponding thermal strain. (B) Comparison between temperature changes estimated from thermal strain after calibration and thermocouple measurement.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4526517&req=5

pone.0134938.g004: Calibration measurement for the tissue-mimicking phantom.(A) Calibration of the material dependent k value for the tissue-mimicking phantom by comparing temperature elevation measured by the thermocouple and corresponding thermal strain. (B) Comparison between temperature changes estimated from thermal strain after calibration and thermocouple measurement.

Mentions: To evaluate the accuracy of the strain-based temperature without motion, thermal strain was estimated on the phantom and compared to thermocouple measurements. Thermal strain was averaged over a ROI of 3λ×3λ (0.9×0.9 mm2) centered on the heated region. The parameter k = 1/(α-β) was estimated to be -1220 ± 20°C for the phantom material with high correlation (R2 = 0.99) between estimated thermal strain and thermocouple measurements (Fig 4A). This value is similar to reported values for ex vivo muscle [25, 33]. The maximum temperature elevation after 30 s of heating was 3.8°C as measured by the thermocouple. After calibration, the strain-based temperature estimation matched the thermocouple measurement with an absolute error less than 0.1°C, as shown in Fig 4B. The temperature estimation without motion was thus considered as the reference temperature in the following sections due to its high correlation with thermocouple readings.


Spatial and Temporal Control of Hyperthermia Using Real Time Ultrasonic Thermal Strain Imaging with Motion Compensation, Phantom Study.

Foiret J, Ferrara KW - PLoS ONE (2015)

Calibration measurement for the tissue-mimicking phantom.(A) Calibration of the material dependent k value for the tissue-mimicking phantom by comparing temperature elevation measured by the thermocouple and corresponding thermal strain. (B) Comparison between temperature changes estimated from thermal strain after calibration and thermocouple measurement.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526517&req=5

pone.0134938.g004: Calibration measurement for the tissue-mimicking phantom.(A) Calibration of the material dependent k value for the tissue-mimicking phantom by comparing temperature elevation measured by the thermocouple and corresponding thermal strain. (B) Comparison between temperature changes estimated from thermal strain after calibration and thermocouple measurement.
Mentions: To evaluate the accuracy of the strain-based temperature without motion, thermal strain was estimated on the phantom and compared to thermocouple measurements. Thermal strain was averaged over a ROI of 3λ×3λ (0.9×0.9 mm2) centered on the heated region. The parameter k = 1/(α-β) was estimated to be -1220 ± 20°C for the phantom material with high correlation (R2 = 0.99) between estimated thermal strain and thermocouple measurements (Fig 4A). This value is similar to reported values for ex vivo muscle [25, 33]. The maximum temperature elevation after 30 s of heating was 3.8°C as measured by the thermocouple. After calibration, the strain-based temperature estimation matched the thermocouple measurement with an absolute error less than 0.1°C, as shown in Fig 4B. The temperature estimation without motion was thus considered as the reference temperature in the following sections due to its high correlation with thermocouple readings.

Bottom Line: However, combined ultrasound imaging and therapy systems offer the benefits of simple, low-cost devices that can be broadly applied.Here, we propose a motion compensation method based on the acquisition of multiple reference frames prior to treatment.The technique was tested in the presence of 2-D and 3-D physiological-scale motion and was found to provide effective real-time temperature monitoring.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, University of California Davis, Davis, CA, United States of America.

ABSTRACT
Mild hyperthermia has been successfully employed to induce reversible physiological changes that can directly treat cancer and enhance local drug delivery. In this approach, temperature monitoring is essential to avoid undesirable biological effects that result from thermal damage. For thermal therapies, Magnetic Resonance Imaging (MRI) has been employed to control real-time Focused Ultrasound (FUS) therapies. However, combined ultrasound imaging and therapy systems offer the benefits of simple, low-cost devices that can be broadly applied. To facilitate such technology, ultrasound thermometry has potential to reliably monitor temperature. Control of mild hyperthermia was previously achieved using a proportional-integral-derivative (PID) controller based on thermocouple measurements. Despite accurate temporal control of heating, this method is limited by the single position at which the temperature is measured. Ultrasound thermometry techniques based on exploiting the thermal dependence of acoustic parameters (such as longitudinal velocity) can be extended to create thermal maps and allow an accurate monitoring of temperature with good spatial resolution. However, in vivo applications of this technique have not been fully developed due to the high sensitivity to tissue motion. Here, we propose a motion compensation method based on the acquisition of multiple reference frames prior to treatment. The technique was tested in the presence of 2-D and 3-D physiological-scale motion and was found to provide effective real-time temperature monitoring. PID control of mild hyperthermia in presence of motion was then tested with ultrasound thermometry as feedback and temperature was maintained within 0.3°C of the requested value.

No MeSH data available.


Related in: MedlinePlus