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Enhanced thermal effect using magnetic nano-particles during high-intensity focused ultrasound

View Article: PubMed Central - PubMed

ABSTRACT

Collateral damage and long sonication times occurring during high-intensity focused ultrasound (HIFU) ablation procedures limit clinical advancement. In this reserarch, we investigated whether the use of magnetic nano-particles (mNPs) can reduce the power required to ablate tissue or, for the same power, reduce the duration of the procedure. Tissue-mimicking phantoms containing embedded thermocouples and physiologically acceptable concentrations (0%, 0.0047%, and 0.047%) of mNPs were sonicated at acoustic powers of 5.2 W, 9.2 W, and 14.5 W, for 30 seconds. Lesion volumes were determined for the phantoms with and without mNPs. It was found that with the 0.047% mNP concentration, the power required to obtain a lesion volume of 13 mm3 can be halved, and the time required to achieve a 21 mm3 lesion decreased by a factor of 5. We conclude that mNPs have the potential to reduce damage to healthy tissue, and reduce the procedure time, during tumor ablation using HIFU.

No MeSH data available.


Flow chart to determine the z location with thermal dose of 240 equivalent minutes.
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pone.0175093.g006: Flow chart to determine the z location with thermal dose of 240 equivalent minutes.

Mentions: To quantify the lesion volume, the locations along the z and r axes where the thermal dose was equal to a minimum of 240 equivalent minutes were calculated for the end-of-sonication time of interest. Fig 6 presents the flow diagram of the steps involved in determining the axial extent of the lesion. In the algorithm, an initial guess z was made for the axial boundary of the lesion. At that axial location, the on-axis absorbed intensity αI0(z) relative to the value in the T1-T2 plane was determined from the axial intensity profile (Fig 5) for the transducer, as described above. The beam radius r0 was then determined from the conservation of energy relation. The temperature profile in the plane at axial location z was subsequently found from Eqs (1A) and (1B). The temperature was then used in Eq (2) to determine the thermal dose in the plane at location z. If the thermal dose was not within 3% of 240 equivalent minutes, the guess for z was updated and the procedure repeated. The radial coordinate of the 240-minute point was found using a similar iterative process.


Enhanced thermal effect using magnetic nano-particles during high-intensity focused ultrasound
Flow chart to determine the z location with thermal dose of 240 equivalent minutes.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383424&req=5

pone.0175093.g006: Flow chart to determine the z location with thermal dose of 240 equivalent minutes.
Mentions: To quantify the lesion volume, the locations along the z and r axes where the thermal dose was equal to a minimum of 240 equivalent minutes were calculated for the end-of-sonication time of interest. Fig 6 presents the flow diagram of the steps involved in determining the axial extent of the lesion. In the algorithm, an initial guess z was made for the axial boundary of the lesion. At that axial location, the on-axis absorbed intensity αI0(z) relative to the value in the T1-T2 plane was determined from the axial intensity profile (Fig 5) for the transducer, as described above. The beam radius r0 was then determined from the conservation of energy relation. The temperature profile in the plane at axial location z was subsequently found from Eqs (1A) and (1B). The temperature was then used in Eq (2) to determine the thermal dose in the plane at location z. If the thermal dose was not within 3% of 240 equivalent minutes, the guess for z was updated and the procedure repeated. The radial coordinate of the 240-minute point was found using a similar iterative process.

View Article: PubMed Central - PubMed

ABSTRACT

Collateral damage and long sonication times occurring during high-intensity focused ultrasound (HIFU) ablation procedures limit clinical advancement. In this reserarch, we investigated whether the use of magnetic nano-particles (mNPs) can reduce the power required to ablate tissue or, for the same power, reduce the duration of the procedure. Tissue-mimicking phantoms containing embedded thermocouples and physiologically acceptable concentrations (0%, 0.0047%, and 0.047%) of mNPs were sonicated at acoustic powers of 5.2 W, 9.2 W, and 14.5 W, for 30 seconds. Lesion volumes were determined for the phantoms with and without mNPs. It was found that with the 0.047% mNP concentration, the power required to obtain a lesion volume of 13 mm3 can be halved, and the time required to achieve a 21 mm3 lesion decreased by a factor of 5. We conclude that mNPs have the potential to reduce damage to healthy tissue, and reduce the procedure time, during tumor ablation using HIFU.

No MeSH data available.