Optimization of SPIO Injection for Sentinel Lymph Node Dissection in a Rat Model

The magnetic technique, consisting of a magnetic tracer and a handheld magnetometer, is a promising alternative technique for sentinel lymph node dissection (SLND) and was shown to be non-inferior to the standard technique in terms of identification rates. In this study, injection characteristics (iron dose, dilution, time course and massaging) were evaluated to optimize magnetic tracer uptake in the sentinel lymph nodes (SLN) in a rat hindleg model. 202 successful SLNDs were performed. Iron uptake in the SLN is proportional (10% utilization rate) to the injection dose between 20 and 200 μg, showing a plateau uptake of 80 μg in the SLN around 1000 μg injection. Linear regression showed that time had a higher impact than dilution, on the SLN iron uptake. Massaging showed no significant change in iron uptake. The amount of residual iron at the injection site was also proportional to the injection dose without any plateau. Time was a significant factor for wash-out of residual iron. From these results, preoperative injection may be advantageous for SLN detection as well as reduction in residual iron at the injection site by potential decrease in required injection dose.

Magnetic nanoparticle technique versus radioisotope technique in detection of sentinel lymph node in early breast cancer: a systematic review and meta-analysis

Sentinel lymph node biopsy is the standard technique to stage the axilla in early breast cancer. The gold standard is the dual technique of radioisotope and blue dye injection. The drawbacks of dual technique include handling and disposal of radioactive material. Equally reliable, user and patient friendly, magnetic tracer super paramagnetic iron oxide, was compared with the radioisotope tracer in detection of Sentinel lymph node in a clinically node negative axilla in early breast cancer in this meta-analysis, with emphasis on the utility and safety of both techniques. PubMed, Medline were searched from April 2015 to October 2019. 1395 patients’ data was included from seven homogenous studies in this meta-analysis. A statistical analysis was performed using STATA 16.1 version for sentinel lymph node detection rate using standard technique, magnetic tracer technique and both techniques. Ratio of successes and failures of the outcomes was measured and analysed. A paired two sample ‘Z’ test was performed to compare between the standard technique and magnetic tracer techniques. The standardised mean difference of ratio of success rate between two techniques was; 1.013334 with a p value of 0.3136.The standardised mean difference of ratio of failure rate between two techniques was 1.016667, with a p value of 0.3132. Success and failure rate showed statistically no significant difference between the two techniques. This two-way analysis with paired two sample ‘Z’ test confirms that neither standard technique nor magnetic tracer techniques are superior or inferior to each other.

Detection of magnetic tracers with Mx atomic magnetometer for application to blood velocimetry

In the new generation of blood velocimeter systems, considerable attention has been paid to atomic magnetometers due to their high resolution and high sensitivity for detection of magnetic tracers. Passing the magnetic tracers adjacent to the atomic magnetometer produces a spike-like signal, the shape of which depends on the position of the tracer, as well as its velocity and orientation. The present study aimed to evaluate the effect of abrupt variations in the instantaneous velocity of the magnetic tracer on the magnetometer response compare to constant velocity. Modeling the magnetic tracer as a dipole moment indicated that the velocity dependence of the magnetic field and local magnetic field gradient associated with moving magnetic tracer cause the spike-like signal to go out of symmetry in the case of variable velocity. Based on the experimental results, any instantaneous variation in tracer velocity leads to shrinkage in the signal width. The behavior has been studied for both magnetic microwire with variable instantaneous velocity and magnetic droplets in stenosis artery phantom. In addition, the position of the tracer could be detected by following the shrinkage behavior which may occur on the peak, valley, or both. These advantageous outcomes can be applied for high sensitivity diagnosis of arterial stenosis.

An easy and low-cost biomagnetic methodology to study regional gastrointestinal transit in rats

The identification of gastrointestinal (GI) motility disorders requires the evaluation of regional GI transit, and the development of alternative methodologies in animals has a significant impact on translational approaches. Therefore, the purpose of this study was to validate an easy and low-cost methodology (alternate current biosusceptometry – ACB) for the assessment of regional GI transit in rats through images. Rats were fed a test meal containing magnetic tracer and phenol red, and GI segments (stomach, proximal, medial and distal small intestine, and cecum) were collected to assess tracer’s retention at distinct times after ingestion (0, 60, 120, 240, and 360 min). Images were obtained by scanning the segments, and phenol red concentration was determined by the sample’s absorbance. The temporal retention profile, geometric center, gastric emptying, and cecum arrival were evaluated. The correlation coefficient between methods was 0.802, and the temporal retention of each segment was successfully assessed. GI parameters yielded comparable results between methods, and ACB images presented advantages as the possibility to visualize intrasegmental tracer distribution and the automated scan of the segments. The imaging approach provided a reliable assessment of several parameters simultaneously and may serve as an accurate and sensitive approach for regional GI research in rats.