Magnetic Oculomotor Prosthetics for Acquired Nystagmus

Stability and in vivo safety of gold, titanium nitride and parylene C coatings on NdFeB magnets implanted in muscles towards a new generation of myokinetic prosthetic limbs

Rare earth magnets are the elective choice when high magnetic field density is required and they are particularly intriguing for inclusion in implantable devices. A safe implantation of NdFeB magnets in muscles would enable the control of limb prostheses using a myokinetic interface i.e., direct control of artificial limb movements by means of magnetic tracking of residual muscle contractions. However, myokinetic prosthesis control is prevented by NdFeB magnets poor biocompatibility, at present. Here we investigated three biocompatible materials as NdFeB magnet coating candidates, namely gold, titanium nitride and parylene C, which have not been analyzed in a systematic way for this purpose, so far. In vitro testing in a tissue-mimicking environment and upon contact with C2C12 myoblasts enabled assessment of the superiority of parylene C coated magnets in terms of corrosion prevention and lack of cytotoxicity. In addition, parylene C coated magnets implanted in rabbit muscles for 28 days confirmed, both locally and systemically, their biocompatibility, with a lack of irritation and toxicity associated with the implant. These findings pave the way towards the development of implantable devices based on permanent magnets and of a new generation of limb prostheses.

Mathematical models and human disease

Mathematical models of brain function are built from data covering anatomy, physiology, biophysics and behavior. In almost all cases, many possible models could fit the available data. Theoreticians make assumptions that allow them to constrain the number of possible model structures. However, a model that was more useful clinically would result if the constraints came from lesion studies in animals or clinical disorders. Here, we show a few examples of how clinical disorders have led to improvements in models. We also show a few examples of how models could lead to neural prostheses for patients. The best outcomes result when clinicians, basic scientists and theoreticians work together to understand brain function.

Evaluation of a Ferromagnetic Marker Technology for Intraoperative Localization of Nonpalpable Breast Lesions

OBJECTIVE

The purpose of this study was to evaluate the magnetic occult lesion localization instrument (MOLLI) system that involves implantation of a small, ferromagnetic marker to guide surgical excision of nonpalpable breast lesions. Characterization of the system was undertaken as part of what is, to our knowledge, the first study to assess the MOLLI system.

MATERIALS AND METHODS

The MOLLI system consists of a handheld probe that can detect the position and distance of an implanted magnetic marker. The system presents the surgeon with an accurate assessment of lesion location and depth measurement for precise 3D localization. The marker is implanted under ultrasound or mammographic guidance at any time before the surgical procedure and requires no special precautions. Experimental analysis focused on characterization of the following aspects of the MOLLI system: visualization of the marker under imaging, 3D detection of the magnetic marker, spatial resolution of the probe to detect markers placed in close proximity, and the effect of signal interference on system performance.

RESULTS

The MOLLI system can reliably detect mean (± SD) marker depths up to 53 ± 8.56 mm from the probe. Bracketing large lesions or localizing multiple lesions can be accomplished by placing markers as close as 10 mm apart, at depths of up to 42 mm. The biologically inert MOLLI marker is readily visible under ultrasound and mammographic guidance, and it is differentiable from radiologic clips. The effect of surgical instruments on MOLLI functioning is minimal and does not impact system accuracy or reliability.

CONCLUSION

The MOLLI system offers an accurate and efficient alternative lesion localization method for nonpalpable breast lesions.