Novel Handheld Magnetometer Probe Based on Magnetic Tunnelling Junction Sensors for Intraoperative Sentinel Lymph Node Identification

Abstract

Using magnetic tunnelling junction sensors, a novel magnetometer probe for the identification of the sentinel lymph node using magnetic tracers was developed. Probe performance was characterised in vitro and validated in a preclinical swine model. Compared to conventional gamma probes, the magnetometer probe showed excellent spatial resolution of 4.0 mm, and the potential to detect as few as 5 μg of magnetic tracer. Due to the high sensitivity of the magnetometer, all first-tier nodes were identified in the preclinical experiments, and there were no instances of false positive or false negative detection. Furthermore, these preliminary data encourage the application of the magnetometer probe for use in more complex lymphatic environments, such as in gastrointestinal cancers, where the sentinel node is often in close proximity to other non-sentinel nodes, and high spatial resolution detection is required.

Magnetic resonance sentinel lymph node imaging and magnetometer-guided intraoperative detection in prostate cancer using superparamagnetic iron oxide nanoparticles

“…The magnetometer probe is most effective when measuring nodes with tracer uptake concentrated close to the node surface where it can be measured at very close range. 28 However, in the present study, the SLNs showed a very heterogeneous SPION uptake. In vivo, adipose tissue surrounding SLNs can limit the distance of the probe to the node resulting in insufficient exposure of the node or not sufficient measurement of the magnetic signal.…”

Accuracy of Magnetometer-Guided Sentinel Lymphadenectomy after Intraprostatic Injection of Superparamagnetic Iron Oxide Nanoparticles in Prostate Cancer: The SentiMag Pro II Study

“…An insufficient measurement of the magnetic signal can be the result. Moreover, the presence of tissue in the vicinity of the probe tip of the magnetometer and the LN reduces the in vivo magnetic signal because of the negative magnetic susceptibility of surrounding tissue [20]. The limited spatial resolution of the SentiMag ® probe (~20 mm) could restrain the differentiation of SLN signals from the background signal from the injection site.…”

“…The limited spatial resolution of the SentiMag ® probe (~20 mm) could restrain the differentiation of SLN signals from the background signal from the injection site. In the near future, the higher resolution of novel probes using magnetic tunneling junction techniques (resolution~4 mm) could lead to a sustainable improvement in intracorporeally SLN identification [20]. In addition, the now available possibility of preoperative localization of magnetically marked SLNs using magnetic resonance imaging (MRI) could further improve intraoperative detectability [10].…”

Magnetic stability under magnetic cycling of MgO-based magnetic tunneling junctions with an exchange-biased synthetic antiferromagnetic pinned layer

“…Figure 1 shows such a magnetic transfer curve of a representative MTJ sample (MTJ-1). Within the field range of ±100 Oe, the magnetoresistance response is primarily from the free layer of 3-nm Co 40 Fe 40 B 20 . In our MTJ samples, the exchange-bias provides a pinning field of about 500 Oe for the SAF hard layer, which remains mostly inert within ±100 Oe.…”

“…[7][8][9][10][11][12][13][14][15][16][17][18][19] Applications of MTJs have extended beyond read heads in hard disk drives and MRAMs. MTJ sensors have been used for medical and biological devices, 20 high frequency oscillators, 24 non-destructive testing, 25 current sensors, 26 and ultra-low noise sensors. 27 MTJ sensors due to its high sensitivity and thermal performance have becoming an enabling technology in many areas of science and engineering.…”