PDF(Pubmed)
Abstract：
UNASSIGNED: Agar-based phantoms are popular in high intensity focused ultrasound (HIFU) studies, with magnetic resonance imaging (MRI) preferred for guidance since it provides temperature monitoring by proton resonance frequency (PRF) shift magnetic resonance (MR) thermometry. MR thermometry monitoring depends on several factors, thus, herein, the PRF coefficient of agar phantoms was estimated.
UNASSIGNED: Seven phantoms were developed with varied agar (2, 4, or 6% w/v) or constant agar (6% w/v) and varied silica concentrations (2, 4, 6, or 8% w/v) to assess the effect of the concentration on the PRF coefficient. Each phantom was sonicated using varied acoustical power for a 30 s duration in both a laboratory setting and inside a 3T MRI scanner. PRF coefficients were estimated through linear trends between phase shift acquired using gradient sequences and thermocouple-based temperatures changes.
UNASSIGNED: Linear regression (R 2 = 0.9707-0.9991) demonstrated a proportional dependency of phase shift with temperature change, resulting in PRF coefficients between -0.00336 ± 0.00029 and -0.00934 ± 0.00050 ppm/°C for the various phantom recipes. Weak negative linear correlations of the PRF coefficient were observed with increased agar. With silica concentrations, the negative linear correlation was strong. For all phantoms, calibrated PRF coefficients resulted in 1.01-3.01-fold higher temperature changes compared to the values calculated using a literature PRF coefficient.
UNASSIGNED: Phantoms developed with a 6% w/v agar concentration and doped with 0%-8% w/v silica best resemble tissue PRF coefficients and should be preferred in HIFU studies. The estimated PRF coefficients can result in enhanced MR thermometry monitoring and evaluation of HIFU protocols.
UNASSIGNED: Seven phantoms were developed with varied agar (2, 4, or 6% w/v) or constant agar (6% w/v) and varied silica concentrations (2, 4, 6, or 8% w/v) to assess the effect of the concentration on the PRF coefficient. Each phantom was sonicated using varied acoustical power for a 30 s duration in both a laboratory setting and inside a 3T MRI scanner. PRF coefficients were estimated through linear trends between phase shift acquired using gradient sequences and thermocouple-based temperatures changes.
UNASSIGNED: Linear regression (R 2 = 0.9707-0.9991) demonstrated a proportional dependency of phase shift with temperature change, resulting in PRF coefficients between -0.00336 ± 0.00029 and -0.00934 ± 0.00050 ppm/°C for the various phantom recipes. Weak negative linear correlations of the PRF coefficient were observed with increased agar. With silica concentrations, the negative linear correlation was strong. For all phantoms, calibrated PRF coefficients resulted in 1.01-3.01-fold higher temperature changes compared to the values calculated using a literature PRF coefficient.
UNASSIGNED: Phantoms developed with a 6% w/v agar concentration and doped with 0%-8% w/v silica best resemble tissue PRF coefficients and should be preferred in HIFU studies. The estimated PRF coefficients can result in enhanced MR thermometry monitoring and evaluation of HIFU protocols.
摘要：
■基于琼脂的体模在高强度聚焦超声（HIFU）研究中很受欢迎，优选使用磁共振成像（MRI）作为指导，因为它通过质子共振频率（PRF）移位磁共振（MR）测温法提供温度监测。MR测温监测取决于几个因素，因此，在这里，估计了琼脂体模的PRF系数。
■用不同的琼脂（2、4或6％w/v）或恒定琼脂（6％w/v）和不同的二氧化硅浓度（2、4、6或8％w/v）开发了七个体模，以评估浓度对PRF系数的影响。在实验室环境和3TMRI扫描仪内，使用不同的声功率对每个体模进行了30s的超声处理。通过使用梯度序列获得的相移和基于热电偶的温度变化之间的线性趋势来估计PRF系数。
■线性回归（R2=0.9707-0.9991）证明了相移随温度变化的比例依赖性，对于各种体模配方，导致PRF系数在-0.00336±0.00029和-0.00934±0.00050ppm/°C之间。随着琼脂的增加，观察到PRF系数的线性负相关。使用二氧化硅浓度，负线性相关较强。对于所有的幻影，与使用文献PRF系数计算的值相比，校准的PRF系数导致温度变化高1.01-3.01倍。
■用6％w/v琼脂浓度和0％-8％w/v二氧化硅掺杂开发的幻影最类似于组织PRF系数，应在HIFU研究中首选。估计的PRF系数可以导致增强的MR测温监测和HIFU协议的评估。
■用不同的琼脂（2、4或6％w/v）或恒定琼脂（6％w/v）和不同的二氧化硅浓度（2、4、6或8％w/v）开发了七个体模，以评估浓度对PRF系数的影响。在实验室环境和3TMRI扫描仪内，使用不同的声功率对每个体模进行了30s的超声处理。通过使用梯度序列获得的相移和基于热电偶的温度变化之间的线性趋势来估计PRF系数。
■线性回归（R2=0.9707-0.9991）证明了相移随温度变化的比例依赖性，对于各种体模配方，导致PRF系数在-0.00336±0.00029和-0.00934±0.00050ppm/°C之间。随着琼脂的增加，观察到PRF系数的线性负相关。使用二氧化硅浓度，负线性相关较强。对于所有的幻影，与使用文献PRF系数计算的值相比，校准的PRF系数导致温度变化高1.01-3.01倍。
■用6％w/v琼脂浓度和0％-8％w/v二氧化硅掺杂开发的幻影最类似于组织PRF系数，应在HIFU研究中首选。估计的PRF系数可以导致增强的MR测温监测和HIFU协议的评估。
