Forward-looking MRI Coils with Metal-backing

Unmet Need
Magnetic Resonance Imaging (MRI) uses radio-frequency coils to transmit and receive signals from material such as human tissue. Currently, there exist forward-looking coils that can image the tissue that is in front of the coil. Forward-looking coils for imaging the cervix gland, which is 20-30 mm from the coil’s end, are easy to build with current coil technology. However, it is much more difficult with current conventional-coil geometries to build a coil that can image further above the cervix into the endometrium. Thus, there exists unmet need for forward-looking radio frequency coil technology that can image further above the cervix to determine the extent of tumors found in advanced cervical-cancer patients. In advanced cervical cancer, the cancer has spread from its primary location in the cervix and is found also in the vagina and endometrium, so an extended visualization region is required in order to visualize the entire tumor.
 
Technology Overview
Johns Hopkins researchers have designed effective extended forward-looking coils. Image fields can be demonstrated by placing a loop of wire at a certain distance above the surface of a metal, oriented so it is parallel to the plane of the surface. When a radio frequency current runs through the loop, a primary magnetic field is created. These magnetic fields induce a transient magnetic field in the metal. The metal then builds a surface current, which induces an opposing-directionality magnetic field, called an image magnetic field, which exactly cancels the primary field on the metal surface. As a result, there are now have two fields, the primary magnetic field and an image magnetic field. In the region between the location of the loop and the metal, these two fields are in opposing directions and create a smaller net field, while above the loop, they are oriented in the same direction and therefore reinforce the primary field, creating a larger net field. This larger field therefore contributes to a larger magnetic field at locations above coil, leading to an extended field.

Stage of Development
Several simulations have been conducted with prototypes that have been built for the 1.5 Tesla Siemens scanner. A final prototype is being built and tested.
 
Publications
None.
 

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