Tomographic Imaging Group, Philips Technologie GmbH Innovative Technologies, Research Laboratories, Röntgenstraße 24-26, 22335 Hamburg, Germany.
BMC Med Imaging. 2011 Jun 29;11:16. doi: 10.1186/1471-2342-11-16.
Magnetic Particle Imaging is a novel method for medical imaging. It can be used to measure the local concentration of a tracer material based on iron oxide nanoparticles. While the resulting images show the distribution of the tracer material in phantoms or anatomic structures of subjects under examination, no information about the tissue is being acquired. To expand Magnetic Particle Imaging into the detection of soft tissue properties, a new method is proposed, which detects acoustic emissions caused by magnetization changes in superparamagnetic iron oxide.
Starting from an introduction to the theory of acoustically detected Magnetic Particle Imaging, a comparison to magnetically detected Magnetic Particle Imaging is presented. Furthermore, an experimental setup for the detection of acoustic emissions is described, which consists of the necessary field generating components, i.e. coils and permanent magnets, as well as a calibrated microphone to perform the detection.
The estimated detection limit of acoustic Magnetic Particle Imaging is comparable to the detection limit of magnetic resonance imaging for iron oxide nanoparticles, whereas both are inferior to the theoretical detection limit for magnetically detected Magnetic Particle Imaging. Sufficient data was acquired to perform a comparison to the simulated data. The experimental results are in agreement with the simulations. The remaining differences can be well explained.
It was possible to demonstrate the detection of acoustic emissions of magnetic tracer materials in Magnetic Particle Imaging. The processing of acoustic emission in addition to the tracer distribution acquired by magnetic detection might allow for the extraction of mechanical tissue parameters. Such parameters, like for example the velocity of sound and the attenuation caused by the tissue, might also be used to support and improve ultrasound imaging. However, the method can also be used to perform imaging on its own.
磁共振粒子成像是一种用于医学成像的新方法。它可以用来测量基于氧化铁纳米颗粒的示踪剂材料的局部浓度。虽然得到的图像显示了示踪剂材料在幻影或被检查对象的解剖结构中的分布，但没有获取关于组织的信息。为了将磁共振粒子成像扩展到软组织性质的检测中，提出了一种新的方法，该方法检测超顺磁性氧化铁的磁化变化引起的声发射。
从声学检测磁共振粒子成像的理论介绍开始，对其与磁共振检测磁共振粒子成像进行了比较。此外，还描述了用于检测声发射的实验设置，该设置包括必要的场生成组件，即线圈和永磁体，以及用于执行检测的校准麦克风。
声学磁共振粒子成像的估计检测限与氧化铁纳米颗粒的磁共振成像检测限相当，而两者均低于磁共振检测磁共振粒子成像的理论检测限。获取了足够的数据来与模拟数据进行比较。实验结果与模拟结果一致。其余差异可以很好地解释。
已经证明可以在磁共振粒子成像中检测到磁性示踪剂材料的声发射。除了磁性检测获得的示踪剂分布之外，对声发射的处理可能允许提取机械组织参数。这些参数，例如声速和组织引起的衰减，也可用于支持和改善超声成像。但是，该方法也可以单独用于成像。
