Abstract

Purpose: To develop and characterize a tissue-mimicking phantom that enables the direct comparison of magnetic resonance (MR) and ultrasound (US) imaging techniques useful for monitoring high-intensity focused ultrasound (HIFU) treatments. With no additions, gelatin phantoms produce little if any scattering required for US imaging. This study characterizes the MR and US image characteristics as a function of psyllium husk concentration, which was added to increase US scattering.

Methods: Gelatin phantoms were constructed with varying concentrations of psyllium husk. The effects of psyllium husk concentration on US B-mode and MR imaging were evaluated at nine different concentrations. T1, T2, and T2* MR maps were acquired. Acoustic properties (attenuation and speed of sound) were measured at frequencies of 0.6, 1.0, 1.8, and 3.0 MHz using a through-transmission technique. Phantom elastic properties were evaluated for both time and temperature dependence.

Results: Ultrasound image echogenicity increased with increasing psyllium husk concentration while quality of gradient-recalled echo MR images decreased with increasing concentration. For all phantoms, the measured speed of sound ranged between 1567–1569 m/s and the attenuation ranged between 0.42–0.44 dB/(cm·MHz). Measured T1 ranged from 974–1051 ms. The T2 and T2* values ranged from 97–108 ms and 48–88 ms, respectively, with both showing a decreasing trend with increased psyllium husk concentration. Phantom stiffness, measured using US shear-wave speed measurements, increased with age and decreased with increasing temperature.

Conclusions: The presented dual-use tissue-mimicking phantom is easy to manufacture and can be used to compare and evaluate US-guided and MR-guided HIFU imaging protocols.

摘要

目的：开发和表征模仿组织的模型，从而可以直接比较磁共振（MR）和超声（US）成像技术，这些技术可用于监测高强度聚焦超声（HIFU）治疗。没有添加，明胶体模几乎不会产生US成像所需的散射。这项研究将MR和US图像特征表征为车前草壳浓度的函数，并增加了US散射。

方法：用不同浓度的车前草壳构建明胶体模。在九种不同浓度下评估了车前子壳浓度对US B模式和MR成像的影响。采集了T1，T2和T2 * MR图。使用穿透传输技术在0.6、1.0、1.8和3.0 MHz的频率下测量声学特性（衰减和声音速度）。对于时间和温度依赖性，评估了幻影的弹性特性。

结果：超声图像的回声性随着车前子壳浓度的增加而增加，而梯度回波MR图像的质量则随着浓度的增加而降低。对于所有体模，测得的声速范围为1567-1569 m / s，衰减范围为0.42-0.44 dB /（cm·MHz）。T1的测量范围为974–1051 ms。T2和T2 *值的范围分别为97-108 ms和48-88 ms，二者均显示出随车前草壳浓度增加而降低的趋势。使用美国剪切波速度测量值测量的幻像刚度随年龄增加而随温度升高而降低。

结论：提出的双重用途组织模仿体模易于制造，可用于比较和评估US制导和MR制导的HIFU成像方案。