Assessment of Gold Nanoparticle-Mediated-Enhanced Hyperthermia Using MR-Guided High-Intensity Focused Ultrasound Ablation Procedure

High-intensity focused ultrasound (HIFU) has gained increasing popularity as a noninvasive therapeutic procedure to treat solid tumors. However, collateral damage due to the use of high acoustic powers during HIFU procedures remains a challenge. The objective of this study is to assess the utility of using gold nanoparticles (gNPs) during HIFU procedures to locally enhance heating at low powers, thereby reducing the likelihood of collateral damage. Phantoms containing tissue-mimicking material (TMM) and physiologically relevant concentrations (0%, 0.0625%, and 0.125%) of gNPs were fabricated. Sonications at acoustic powers of 10, 15, and 20 W were performed for a duration of 16 s using an MR-HIFU system. Temperature rises and lesion volumes were calculated and compared for phantoms with and without gNPs. For an acoustic power of 10 W, the maximum temperature rise increased by 32% and 43% for gNPs concentrations of 0.0625% and 0.125%, respectively, when compared to the 0% gNPs concentration. For the power of 15 W, a lesion volume of 0, 44.5 ± 7, and 63.4 ± 32 mm³ was calculated for the gNPs concentration of 0%, 0.0625%, and 0.125%, respectively. For a power of 20 W, it was found that the lesion volume doubled and tripled for concentrations of 0.0625% and 0.125% gNPs, respectively, when compared to the concentration of 0% gNPs. We conclude that gNPs have the potential to locally enhance the heating and reduce damage to healthy tissue during tumor ablation using HIFU.

Enhanced Heat Transfer and Thermal Dose Using Magnetic Nanoparticles During HIFU Thermal Ablation—An In-Vitro Study

Avoiding collateral damage to healthy tissues during the high intensity focused ultrasound (HIFU) ablation of malignant tumors is one of the major challenges for effective thermal therapy. Such collateral damage can originate out of the need for using higher acoustic powers to treat deep seated or highly vascularized tumors. The objective of this study is to assess the utility of using magnetic nanoparticles (mNPs) during HIFU procedures to locally enhance heating at low powers, thereby reducing the likelihood of collateral thermal damage and undesired destruction due to cavitation. Tissue phantoms with 0% (control), 1% and 3% mNPs concentrations by volume were fabricated. Each tissue phantom was embedded with four thermocouples (TCs) and sonicated using transducer acoustic powers of 5.15 W, 9.17 W, and 14.26 W. The temperature profiles during the heating and cooling periods were recorded for each embedded TC. The measured transient temperature profiles were used for thermal-dose calculations. The increase in the concentration of mNPs in the tissue phantoms, from 0% to 3%, resulted in the rise in the peak temperatures for all the TCs for each acoustic power. The thermal dose also increased with the rise in the concentration of mNPs in the tissue phantoms. For the highest applied acoustic power (14.26 W), the peak temperature at TC 1 (T1) in tissue phantoms with 1% and 3% mNPs concentrations increased (with respect to tissue phantom with 0% (control) mNPs concentration) by 1.59× and 2.09×, respectively. For an acoustic power of 14.26 W, the time required to achieve cellular necrosis as defined by a 240 equivalent min thermal dose was approximately 75 s in the absence of mNPs, 14 s for the 1% concentration, and 8 s for the 3% concentration. Magnetic nanoparticles have the potential to significantly reduce the time for HIFU thermal-ablation procedures. They can also decrease the likelihood of collateral damage by the propagating beam in HIFU procedures by reducing the intensity required to achieve cellular necrosis.