Magnetic stereotaxis

Abstract

Advances in imaging techniques and computer software over the past decade now define brain abnormalities such as tumors in precise, three-dimensional images. We have taken advantage of these technological improvements in designing a system capable of performing magnetic manipulation of an object in a nonlinear trajectory and able to deliver hyperthermia to highly specific targets within the brain. This device relies on external magnets to pull a small metal pellet (thermoceptor) through the brain, and on biplane fluoroscopy to localize the thermoceptor with respect to previously obtained magnetic resonance images. A radiofrequency tuned circuit serves as the hyperthermia applicator and selectively heats the thermoceptor. This paper describes experiments conducted in a series of dogs showing that all three components of the system (magnetic drive, stereotactic real time imaging, and hyperthermia) can be achieved. Integration of the system was accomplished in one animal. These encouraging results need further detailed substantiation in each of the components, yet demonstrate the feasibility of such a device.

Magnetization directions and geometries of helical microswimmers for linear velocity-frequency response

“…Biomedical applications include drug delivery [1,2], tissue manipulation [3][4][5], and in vivo diagnos tics and sensing [6][7][8][9]. A number of types of microrobots em ploying different propulsion techniques have been developed, including chemically powered microrobots dependent on external fuels to create phoretic flows [10][11][12][13][14][15][16][17][18], externally con trolled biotic systems [19], dielectrophoretically manipulated robots [20], and magnetically actuated robots, including those that require a nearby surface [21][22][23][24] and those that can swim in bulk fluids [25][26][27][28][29][30][31][32][33][34][35].…”

Fabrication and Characterization of Magnetic Microrobots for Three‐Dimensional Cell Culture and Targeted Transportation

“… 1 These operations can be carried out with microrobots that offer a minimally invasive, accurately targeted, localized therapy via wireless intervention, such as magnetic fields. 2 Numerous studies have examined the biomedical applications of magnetic actuation. Magnetic tubes and rotors have been developed for sensitive engines and fluid mixers driven by magnetic actuation.…”

Image‐Guided Magnetic Thermoseed Navigation and Tumor Ablation Using a Magnetic Resonance Imaging System

“…In terms of clinical relevance, 3 mm thermoseeds are comparable to standard brain biopsy needles and smaller than 5 mm thermoseeds that showed no evidence of gross hemorrhaging when navigated through the canine brain. [ 23 ]…”

“…Navigation of a ferromagnetic thermoseed through the canine brain has previously been demonstrated, although necessitating purpose‐built electromagnets that can generate gradients of up to 2 T m −1 . [ 23 , 24 ] A technique that could benefit from MRN is magnetic hyperthermia or thermoablation, which aims to induce cell death through the heating of ferromagnetic nanoparticles [ 25 , 26 ] or thermoseeds. [ 27 , 28 , 29 ] A major disadvantage of this established technique is the inability to manipulate the particles once inserted into the body, which can result in imprecise treatment delivery and impede its success as a cancer therapy.…”