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M Dahleh

Publications and source records attributed to M Dahleh.

4 recordsLinked to original sources
PubMedDate not supplied

Control system for an MRI compatible intracavitary ultrasound array for thermal treatment of prostate disease.

A 16-channel ultrasound intracavitary array is currently being used in a clinical setting for localized hyperthermia treatment of prostate tumours. Currently, the individual power to each array element is adjusted based on the clinician's judgement of the temperature measured at the locations of invasive thermocouple probes. MRI-derived temperature measurements may be useful for a feedback control system that non-invasively regulates the temperature distribution by adjusting the power to the elements of the array. MRI has been shown to provide accurate, high resolution, non-invasive thermometry. A proportional-plus-integral, single-input, single-output controller was designed to evaluate the feasibility of MRI-derived temperature feedback with this applicator. Input parameters for the controller were determined by modelling the tissue response to the heating from the array. Ex vivo and in vivo experiments evaluated the ability of the MRI-based temperature feedback control system to achieve and maintain a target temperature for a sustained period similar to that of a clinical hyperthermia treatment. With the controller set to a reference temperature of 43 degrees C and a rise time of 6 min, the temperatures within the ex vivo tissue (n = 6) were 43.1 +/- 0.3 degrees C after reaching the reference temperature and had a rise time of 9.5 +/- 0.3 min. In vivo results using rabbit thigh muscle (n = 7) showed that the steady state temperatures were within +/- 1 degree C of their target temperatures. These results demonstrated the feasibility of a temperature feedback for controlling the heating from an intracavitary transrectal array based on temperature information from MR images.

Animals↗
PubMedDate not supplied

The feasibility of MRI feedback control for intracavitary phased array hyperthermia treatments.

Temperature feedback control has the potential to enhance hyperthermia treatments by providing more uniform heating of the target volume and improving the transient temperature response. A multivariable least squares batch algorithm was used to estimate system parameters for simulated prostate hyperthermia treatments. A multi-input, multi-output (MIMO) linear quadratic regulator (LQR) controller was designed for prostate hyperthermia treatments with an intracavitary phased array. A parametric study was performed for the one-dimensional control case, investigating factors relevant to magnetic resonance imaging (MRI) feedback control such as spatial resolution of temperature measurements (size of the averaging volume), sampling rate (image acquisition time), thermometry noise, control width, control depth, physiological parameter changes and reference input structure. Simulations utilizing the two dimensional (2-D) thermometry of MRI and the 2-D focusing capabilities of phased arrays demonstrated that near field heating can be controlled such that the size and shape of the heated volume can be tailored in 2-D. The control algorithms developed in this study show promising potential for incorporation into a non-invasive prostate hyperthermia system utilizing MRI feedback.

Acoustics↗