AC Biosusceptometry is a non-invasive technique originally proposed to monitoring pharmaceutical dosage forms orally administered and to image the disintegration process.

The ACB results showed that this study provided a new approach for in vitro investigation of controlled-release dosage forms. Moreover, using automated ACB will also be possible to test these parameters in humans allowing to establish an in vitro.in vivo correlation (IVIVC).

A novel instrumentation using anisotropic magnetoresistive (AMR) sensors associated with magnetic coils excitation was developed to evaluate gastrointestinal tract motility parameters. The susceptometer has four sensors that were used to measure the gastric activity contractions (GAC) in anaesthetized dogs, its performance was evaluated by manometry with good results.

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.

Anisotropic Magnetoresistive (AMR) sensors shows a new possibility to detect magnetic fields produced by magnetic particles present in the gastrointestinal (GI) tract. A system that uses excitation and detection of magnetic field was developed using AMR sensor. A magnetic flux concentrator was also studied to increase the sensitivity of AMR in this work.

The association between anisotropic magnetoresistive (AMR) sensor and AC biosusceptometry (ACB) to evaluate gastrointestinal motility is presented. The AMR-ACB system was successfully characterized in a bench-top study, and in vivo results were compared with those obtained by means of simultaneous manometry. Both AMR-ACB and manometry techniques presented high temporal cross correlation between the two periodicals signals . The contraction frequencies using AMR-ACB were 73.9 ± 7.6 mHz and using manometry were 73.8 ± 7.9 mHz during the baseline . The amplitude of contraction using AMR-ACB was 396 ± 108 μT·s and using manometry were 540 ± 198 mmHg·s during the baseline. The amplitudes of signals for AMR-ACB and manometric recordings were similarly increased to 86.4% and 89.3% by neostigmine, and also decreased to 27.2% and 21.4% by hyoscine butylbromide in all animals, respectively. The AMR-ACB array is nonexpensive, portable, and has high-spatiotemporal resolution to provide helpful information about gastrointestinal tract.

The alternate current biosusceptometry (ACB) is a biomagnetic technique used to study some physiological parameters associated with gastrointestinal (GI) tract. For this purpose it applies an AC magnetic field and measures the response originating from magnetic marks or tracers. This paper presents an equipment based on the ACB which uses anisotropic magnetoresistive (AMR) sensors and an inexpensive electronic support. The ACB-AMR developed consists of a square array of 6×6 sensors arranged in a first-order gradiometer configuration with one reference sensor. The equipment was applied to capture magnetic images of different phantoms and to acquire gastric contraction activity of healthy rats. The results show a reasonable sensitivity and spatial-temporal resolution, so that it may be applied for imaging of phantoms and signal acquisition of the GI tract of small animals.

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