title: Electromagnetic Techniques to Minimize the Risk of Hazardous Local Heating around Medical Implant Electrodes during MRI Scanning

authors: McCabe, Steven Owen

abstract: Magnetic Resonance Imaging (MRI) scans are contraindicated for many patients with medical implants. We establish the circumstances that cause, and the resistances required to ameliorate and to eliminate dangerous levels of MRI-induced heating that occur at the exposed, distal end of an electrical lead implanted in tissue. Simulated predictions are compared with measurements made at 128 MHz in a 3-Tesla MRI machine. A low resistance at kilohertz frequencies is sought by implant makers, in contrast with the high resistance demanded for safety. The practicality of presently-developed strategies to prevent tissue damage is brought into question. We examine the extent to which skin-depth and transmission-line properties can be manipulated to improve safety.

text: Electromagnetic Techniques to Minimize the Risk of Hazardous Local Heating around Medical Implant Electrodes during MRI Scanning Magnetic Resonance Imaging (MRI) scans are contraindicated for many patients with medical implants. We establish the circumstances that cause, and the resistances required to ameliorate and to eliminate dangerous levels of MRI-induced heating that occur at the exposed, distal end of an electrical lead implanted in tissue. Simulated predictions are compared with measurements made at 128 MHz in a 3-Tesla MRI machine. A low resistance at kilohertz frequencies is sought by implant makers, in contrast with the high resistance demanded for safety. The practicality of presently-developed strategies to prevent tissue damage is brought into question. We examine the extent to which skin-depth and transmission-line properties can be manipulated to improve safety.

year: 2015

title: A similarity reduction of the Grad-Shafranov equation

authors: Litvinenko, Yuri E.

subjects: mathematics

abstract: A direct method for finding similarity reductions of partial differential equations is applied to a specific case of the Grad–Shafranov equation. As an illustration of the method, the frequently used Solov’ev equilibrium is derived. The method is employed to obtain a new family of exact analytical solutions, which contain both the classical and nonclassical group-invariant solutions of the Grad–Shafranov equation and thus greatly extends the range of the available analytical solutions. All the group-invariant solutions based on the classical Lie symmetries are shown to be particular cases in the new family of solutions.

text: A similarity reduction of the Grad-Shafranov equation A direct method for finding similarity reductions of partial differential equations is applied to a specific case of the Grad–Shafranov equation. As an illustration of the method, the frequently used Solov’ev equilibrium is derived. The method is employed to obtain a new family of exact analytical solutions, which contain both the classical and nonclassical group-invariant solutions of the Grad–Shafranov equation and thus greatly extends the range of the available analytical solutions. All the group-invariant solutions based on the classical Lie symmetries are shown to be particular cases in the new family of solutions.

year: 2010

title: Stemming the colonial environmental tide

authors: Joseph, Robert

subjects: human activities

abstract: Stemming the colonial environmental tide supports an Aotearoa New Zealand context that fundamentally acknowledges mātauranga and tikanga Māori law and shared co-governance and concurrent jurisdiction through 7 Aotearoa New Zealand EBM principles.

text: Stemming the colonial environmental tide Stemming the colonial environmental tide supports an Aotearoa New Zealand context that fundamentally acknowledges mātauranga and tikanga Māori law and shared co-governance and concurrent jurisdiction through 7 Aotearoa New Zealand EBM principles.

year: 2022-05