The use of focused ultrasound thermal ablation to treat hepatocarcinoma and other liver tumors produces promising clinical results. However, one of the major drawbacks is the high absorption of ultrasonic energy by the rib, making partial rib removal necessary in many cases. This study numerically investigated the feasibility of using a spherical ultrasound phased array for transrib liver-tumor thermal ablation. An independently array-element activitation scheme, which switches off the transducer elements obstructed by the ribs based on feedback anatomical medical imaging, was proposed to reduce the rib-overheating problem. The numerical results showed that the proposed treatment planning strategy can effectively reduce the specific energy absorbed by the rib while maintaining the energy at the target position, which both reduces the rib-overheating problem and increases the possibility of treating a target lesion under an intact rib. The analysis also demonstrated that the target position and the ultrasound frequency play key roles in the treatment. Patients with diverse characteristics were also tested to show the generality of the proposed strategy. The proposed treatment planning strategy also provides useful information for evaluating the treatment effectiveness prior to clinically performing transrib ultrasound liver-tumor thermal ablation.

Choosing an appropriate bias field correction method is a very important preprocessing step to allow an accurate segmentation of fibroglandular tissues based on breast MRI for quantitative measurement of breast density. The proposed algorithm combining N3+FCM and CLIC both yield satisfactory results.

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The aim of this study is to evaluate the effect of pulsatile blood flow in thermally significant blood vessels on the thermal lesion region during thermal therapy of tumor. A sinusoidally pulsatile velocity profile for blood flow was employed to simulate the cyclic effect of the heart beat on the blood flow. The evolution of temperature field was governed by the energy transport equation for blood flow together with Pennes' bioheat equation for perfused tissue encircling the blood vessel. The governing equations were numerically solved by a novel multi-block Chebyshev pseudospectral method and the accumulated thermal dose in tissue was computed. Numerical results show that pulsatile velocity profile, with various combinations of pulsatile amplitude and frequency, has little difference in effect on the thermal lesion region of tissue compared with uniform or parabolic velocity profile. However, some minor differences on the thermal lesion region of blood vessel is observed for middle-sized blood vessel. This consequence suggests that, in this kind of problem, we may as well do the simulation simply by a steady uniform velocity profile for blood flow.