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

Correlation magnitude between frames acquired during the thermometry sequence and the matching reference frames for 3-D motion measurements as calculated over the entire ROI.(A) With a single reference frame and (B) with the proposed multi-reference frame method. With a single reference frame, only a fraction of the sequence shows high correlation and can be processed for temperature estimation. With the proposed method, correlation is maintained during the whole sequence.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0134938.g008: Correlation magnitude between frames acquired during the thermometry sequence and the matching reference frames for 3-D motion measurements as calculated over the entire ROI.(A) With a single reference frame and (B) with the proposed multi-reference frame method. With a single reference frame, only a fraction of the sequence shows high correlation and can be processed for temperature estimation. With the proposed method, correlation is maintained during the whole sequence.

Mentions: To reflect this result, the magnitude of the correlation over the ROI is shown at each time point for the 3-D motion measurements in Fig 8. If a single reference frame is used, the correlation magnitude between the current and reference frame approaches zero and thermal strain cannot be calculated (Fig 8A). With the multi-reference frame method (Fig 8B), the correlation magnitude exceeded 0.85 and the mean temperature elevation estimate acquired over time was similar to the experimental results without motion, even for experiments in which the probe was translated by 8.7 mm. This result is consistent with decorrelation measurements performed with the L7-4 imaging array (see S2 Fig) where complete decorrelation (correlation value <0.1) between two frames was measured for a 1.8 mm separation in elevation. However, significant artifacts in the temperature maps were observed above a separation of 0.7 mm due to localized decorrelation.


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)

Correlation magnitude between frames acquired during the thermometry sequence and the matching reference frames for 3-D motion measurements as calculated over the entire ROI.(A) With a single reference frame and (B) with the proposed multi-reference frame method. With a single reference frame, only a fraction of the sequence shows high correlation and can be processed for temperature estimation. With the proposed method, correlation is maintained during the whole sequence.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0134938.g008: Correlation magnitude between frames acquired during the thermometry sequence and the matching reference frames for 3-D motion measurements as calculated over the entire ROI.(A) With a single reference frame and (B) with the proposed multi-reference frame method. With a single reference frame, only a fraction of the sequence shows high correlation and can be processed for temperature estimation. With the proposed method, correlation is maintained during the whole sequence.
Mentions: To reflect this result, the magnitude of the correlation over the ROI is shown at each time point for the 3-D motion measurements in Fig 8. If a single reference frame is used, the correlation magnitude between the current and reference frame approaches zero and thermal strain cannot be calculated (Fig 8A). With the multi-reference frame method (Fig 8B), the correlation magnitude exceeded 0.85 and the mean temperature elevation estimate acquired over time was similar to the experimental results without motion, even for experiments in which the probe was translated by 8.7 mm. This result is consistent with decorrelation measurements performed with the L7-4 imaging array (see S2 Fig) where complete decorrelation (correlation value <0.1) between two frames was measured for a 1.8 mm separation in elevation. However, significant artifacts in the temperature maps were observed above a separation of 0.7 mm due to localized decorrelation.

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