Three-dimensional sensitivity mapping of a handheld magnetic probe for sentinel lymph node biopsy

Abstract

An experimental apparatus for three-dimensional sensitivity mapping of a handheld magnetic probe with a permanent magnet and a Hall sensor was developed. To optimize the shapes and sizes of the magnets, the sensitivity mappings of two types of magnets, column- and cone-type magnets, were evaluated by the experimental apparatus. The longitudinal sensitivities of column and cone types are 8 and 9 mm, respectively, for 5 μL of magnetic nanoparticles. The measured longitudinal sensitivities agree well with the sensitivities calculated by the finite element method. Furthermore, the maximum lateral resolutions of column and cone types are 4.1 and 3.7 mm, respectively. In terms of the directionality, the sensitivities of column and cone types of the angle of 90° with respect to the probe axis fall approximately to 72% and 50% at 6 mm distance from the probe head, indicating that the cone type has high directionality due to its sharp shape. The measurement of sensitivity mapping revealed that the characteristics of the cone-type magnet are superior to that of the column-type magnet for the identification of sentinel lymph nodes.

Magnetometer with nitrogen-vacancy center in a bulk diamond for detecting magnetic nanoparticles in biomedical applications

“…3, the minimal magnetic sensitivity η is inversely proportional to the square root of the intensity. In the case of a hundredfold I 0 , the magnetic sensitivity increases up to approximately 0.9 nT, indicating that the detectable distance could reach >10 mm, resulting in the application of the MNP detection in clinical trials for breast cancer patients 35,36 . The second method would be to optimize the coil system for magnetizing the MNPs.…”

“…For example, the detection of MNPs accumulating into sentinel lymph nodes is useful for the diagnosis of cancer metastasis in breast cancer patients. Recent advanced clinical/engineering studies for breast cancer patients have described the detection of MNPs using a magnetometer with a conventional magnetic sensor, such as a Hall sensor or pickup coil, as a promising technique that offers an alternative to harmful radioactive particles [31][32][33][34][35][36][37] . The detectable distance is approximately 10 mm for 140 μg of MNPs.…”

Moving a neodymium magnet promotes the migration of a magnetic tracer and increases the monitoring counts on the skin surface of sentinel lymph nodes in breast cancer

“…The magnetometer developed by Tokyo University contains a small neodymium magnet in its tip (Fig. 1) [11,12]. After skin incision, if the removed node had a measurable RI count or a value exceeding 1 μT on the magnetometer, it was considered an SLN.…”

Detection techniques of biological and chemical Hall sensors

“…For instance, Ookubo et al and Kuwahata et al have implemented a Hall sensor (NHE520) to detect magnetic uid containing MNPs for sentinel lymph node biopsy. 84,85 3 Performance development The Hall effect was rst discovered in 1897, but the rst application did not appear until aer 1950, and the device cost was very high. Since 1965, Hall sensors have become the rst choice for solid-state magneto-sensitive devices due to their advantages of being fully integrated into silicon chips.…”