Magnetic resonance imaging (MRI) scans are often prohibited for patients with an

Question

Magnetic resonance imaging (MRI) scans are often prohibited for patients with an implanted device, such as a pacemaker. There are multiple reasons for this prohibition. One reason is the physical torque on the device due to the MRIs magnetic field. Suppose a paticent's pacemaker implant requires -1.6 mA of current to function. The leads of the devicetravel close together until they reach the heart and then split off to touch the top and bottom of the heart, such that size of the current loop is approximately half the cross-sectional area of the heart. Suppose the MRI machine uses a magnetic field of B 1.0T. Treating the heart as a box that is L = 12.0 cm long and W = 10.0 cm wide, calculate the magnitude of the maximum torque ? on the current loop.

Explanation / Answer

Area of the heart

A=LW/2 =0.12*0.1/2

A=6*10-3 m2

Maximum torque acting on the current loop is

Tmax=NIAB =1*(1.6*10-3)*(6*10-3)*1

Tmax=9.6*10-6 N-m

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