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Thermal effects generated by high-intensity focused ultrasound beams at normal incidence to a bone surface
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10.1121/1.3257547
/content/asa/journal/jasa/127/1/10.1121/1.3257547
http://aip.metastore.ingenta.com/content/asa/journal/jasa/127/1/10.1121/1.3257547

Figures

Image of FIG. 1.
FIG. 1.

(a) Cortical bone specimen with grid points marked and thermocouples attached at selected locations on the grid. (b) Cylindrical fixture containing the bone specimen and thermocouples in (a). (c) Bone/soft-tissue phantom mounted in tank coaxially with HIFU transducer. Vertical rods on the phantom and transducer are connected to an positioning system.

Image of FIG. 2.
FIG. 2.

Computational geometry and boundary conditions.

Image of FIG. 3.
FIG. 3.

(a) Temperature traces on thermocouples T1, T4, and T5 for a sonication at 5 W power. Also shown are the finite-element predictions of temperature at the same locations. (b) Experimental temperature rise at thermocouple T5, computational temperature rise at T5, and the difference between the two, which is taken to be the thermocouple artifact. (c) Experimental temperature traces measured at T5 for a power of 5 W and for a power of 1 W scaled by a factor of 5.

Image of FIG. 4.
FIG. 4.

(a) Variation in transducer voltage as a function of standoff distance between the transducer and the bone surface. (b) Variation in transducer voltage as a function of standoff distance for expanded range of standoffs.

Image of FIG. 5.
FIG. 5.

Temperature rise measured at the bone surface as a function of distance between bone surface and transducer. Acoustic power is 1 W. Solid line is a polynomial fit through experimental data.

Image of FIG. 6.
FIG. 6.

Temperature rise measured at the bone surface as a function of distance between bone surface and transducer for three different trials. Also shown is the computational prediction of temperature for the same standoffs.

Image of FIG. 7.
FIG. 7.

Computations of thermal dose as a function of axial position for 100 and 200 W powers. Transducer focus is located 4 cm from bone surface. Thermal-dose values above the threshold of 240 equivalent min are truncated at the 240-min value.

Image of FIG. 8.
FIG. 8.

(a) Computations of thermal dose at the surface of the bone as a function of distance between the bone surface and the transducer for 100 and 200 W power levels. Sonication time is 30 s. Values predicted by both linear and nonlinear models are presented. (b) Computations of thermal dose at the sacral nerve as a function of distance between the bone surface and the transducer for 100 and 200 W power levels. Sonication time is 30 s. Values predicted by both linear and nonlinear models are presented.

Image of FIG. 9.
FIG. 9.

Computed temperature vs radial position, predicted by models accounting for shear waves in bone and ignoring shear waves. Axial location is point of maximum temperature rise in bone.

Image of FIG. 10.
FIG. 10.

(a) Thermal dose as a function of axial position with and without the influence of shear waves. Exposure duration is 10 s, and power level is 5 W. (b) Thermal dose as a function of radial position with and without the influence of shear waves. Depth into bone is 6 mm. Exposure duration is 10 s, and power level is 5 W.

Tables

Generic image for table
TABLE I.

Properties of bone (cortical; water-saturated).

Generic image for table
TABLE II.

Properties of TMM.

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/content/asa/journal/jasa/127/1/10.1121/1.3257547
2010-01-05
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Thermal effects generated by high-intensity focused ultrasound beams at normal incidence to a bone surface
http://aip.metastore.ingenta.com/content/asa/journal/jasa/127/1/10.1121/1.3257547
10.1121/1.3257547
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