comparison of superparamagnetic quantifier and …

COMPARISON OF SUPERPARAMAGNETIC QUANTIFIER AND MAGNETIC PARTICLE SPECTROSCOPYMelissa M. van de Loosdrecht a,*, Sebastian Draack b, Sebastiaan Waanders a, Hendrikus J.G. Krooshoop a, Frank Ludwig b, and Bennie ten Haken a a Magnetic Detection and Imaging group, Faculty of Science and Technology, University of Twente, Enschede, the Netherlands b Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik, TU Braunschweig, Braunschweig, Germany Correspondence to: m.m.vandeloosdrecht@utwente.nl

Sentinel nodes

Tumor

Tracer

BACKGROUND PURPOSESPIONs are used as a tracer material in sentinel node biopsies. To locate them in vivo it is important to characterize them. To do this, we developed the SuperParamagnetic Quantifier (SPaQ) and compared it with Magnetic Particle Spectroscopy (MPS) [2].

When a patient is diagnosed with cancer, it is important to know if the tumor has spread through the body. Sentinel node biopsies are used to determine if the tumor has spread via the lymphatic system (Figure 1) [1]. Consequently, patient care will be personalized.

METHODS

RESULTS

DISCUSSION CONCLUSION

SUPERPARAMAGNETIC QUANTIFIER MAGNETIC PARTICLE SPECTROSCOPY

AcknowledgementsFinancial support by the Netherlands Organization for Scientific Research (NWO), under the research program Magnetic Sensing for Laparoscopy (MagLap) with project number 14322, and by the German Research Foundation DFG via SPP1681 under grant no. SCHI-383/2-1 acknowledged.

SPaQ MPSExcitation sequence Small AC amplitude (1.3 mT) Large AC amplitude (25 mT)

DC offset (up to 13.3 mT) No DC offsetMeasurement time 5 seconds 0.5 secondsMeasurement Quasi-static DynamicMagnetization curve Minor hysteresis Hysteresis

FIGURE 1 Sentinel node biopsy. A tracer is injected inside the tumor and will accumulate in the first lymph nodes it reaches. A dedicated probe [3] is used to detect these sentinel nodes followed by surgical removal.

FIGURE 2 Schematic overview of SPaQ measurements. (a) A continuous AC magnetic field and changing DC offset are applied to the nanoparticles. (b) The response of the particles is given by their magnetization curve. (c) The resulting magnetization of the particles over time. (d) The resulting signal is the changing magnetization. (e) The envelope of the signal is found by phase-sensitive detection; this is the derivative of the magnetization curve in two directions (which are almost identical). (f) Integration yields the magnetization curve. The blue and red colors indicate the direction in which the curve is measured.

FIGURE 3 Schematic overview of MPS measurements. (a) A continuous AC magnetic field is applied to the nanoparticles. (b) The response of the particles is given by their magnetization curve. (c) The resulting magnetization of the particles over time. (d) The resulting signal is the changing magnetization. (e) Averaging gives the derivative of the magnetization curve. (f) Integration leads to the magnetization curve. The blue and red colors indicate the direction in which the curve is measured.

TABLE 1 Differences between SPaQ and MPS.

FIGURE 4 SPaQ results, measured on ResovistTM and SHP-25 samples containing 750 µg iron in a total volume of 150 µl. b is a numerical integration of a.

FIGURE 5 MPS results, measured on ResovistTM and SHP-25 samples containing 750 µg iron in a total volume of 150 µl. b is a numerical integration of a.

The main difference between SPaQ and MPS measurements is that MPS measurements are more dynamic and therefore more sensitive to particle dynamics. However, which technique is superior depends on the application.

Both SPaQ and MPS provide proper measurements to characterize SPIONs, resulting in invaluable information on particle properties for many applications. Sentinel node biopsies will be improved by characterizing particles in the SPaQ.

References[1] A. E. Giuliano and A. Gangi, Breast J., vol. 21, no. 1, 2015. [2] S. Draack et al. Int. J. Magn. Part. Imaging; Vol 3, No 1, Mar. 2017. [3] S. Waanders et al. Phys. Med. Biol., vol. 61, no. 22, pp. 8120–8134, Nov. 2016.

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