Development of robust/predictive control strategies for image-guided ablative treatments using a minimally invasive ultrasound applicator

Figures & data

Figure 1. (A) The concept of MRI-controlled transurethral ultrasound therapy with multiple collimated high-intensity ultrasound beams. (B) Photograph of an MRI-compatible transurethral ultrasound applicator used to deliver high-intensity ultrasound energy to the prostate gland. (C) Photograph of the experimental system used in this study attached to the patient table of a clinical 3-T MR imager.

Table 1. Physical parameters used in acoustic calculation and bio-thermal simulation [10].

Parameter	Value
Density, ρ	1000 kg m^−3
Specific heat capacity, cb = ct	3700 J kg^−1° C^−1
Blood perfusion, wb	5.3 kg m^−3 s^−1
Thermal conductivity, kt	0.5 W m^−1° C^−1
Attenuation, μatt	5.76 Npm^−1MHz^−1
Ultrasound absorption, αabs	7.4 Npm^−1MHz^−1
Speed of sound, c	1500 m s^−1

Figure 2. Typical temperature profile along the direction of heating of an ultrasound transducer element.

Figure 3. Geometrical description of the proposed algorithm.

Figure 4. The mean value as well as the standard deviation of the error for different values of α across all patients.

Figure 5. The mean value as well as the standard deviation of the error for different values of window size, n, across all patients.

Figure 6. The pattern of conformal thermal heating for one element of ultrasound transducer with different value of α and the angle window of 15°.

Table 2. The mean value as well as the standard deviation of the error across all patients.

	Binary	Adaptive PI	MRAC
Without prediction	−2.8 ± 0.94 mm	−2.7 ± 1 mm	−2.8 ± 0.89 mm
With prediction	−0.8 ± 1 mm	−0.5 ± 0.5 mm	−0.5 ± 0.7 mm

Figure 7. The pattern of conformal thermal heating for two elements using different controllers (experimental results).

Figure 8. The difference between targeted and treated boundaries for two elements using different controllers.

Figure 9. The pattern of conformal thermal heating for values of α using binary controller (experimental results).

Goharrizi A, N’djin W, Kwong R, Chopra R. Development of a new control strategy for 3D MRI-controlled interstitial ultrasound cancer therapy. Medical Physics 2013;40:33301–13

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