Thomas Helzel

The rf coil as a sensitive motion detector for magnetic resonance imaging

A new sensor principle for detection of patient movement in magnetic resonance imaging has been successfully applied for the reduction of motion artifacts. It uses a device that is already present in every MRI system, namely the rf coil. Patient movement within the coil causes changes in the rf impedance match of the coil, which can be measured as variations in the reflected rf power. The principle used for the detection of respiratory and cardiac motion is described, and experimental results measured with several coil arrangements are given. Images are presented which were acquired with respiratory gating derived from the rf body coil of a 2 Tesla whole body MRI system.

Optical Detection Of Respiration Motion And Heart Beats For Magnetic Resonance Imaging (MRI) Applications

A fiber optical strain gauge sensor for detection of respiration motion and heart beat rhythm has been developed in order to suppress motion artifacts in magnetic resonance images (MRI) by gating and triggering procedures. A photoelastic sensing principle has been used in this sensor. It has been adapted to optical fibers to achieve a remote evaluation of the optical signals. The sensor properties are discussed and first results on image quality improvements by the application of this optical sensor are presented for the case of 2 Tesla magnetic resonance imaging of the beating human heart.

Optical Detection Of Pulse Beats For Magnetic Resonance Imaging Applications

Two different types of fiber optic sensors for the detection of human heart beats in the harsh electro magnetic environment of a Magnetic Resonance (MR) scanner have been developed. The first type is a photo elastic strain gauge belt sensor, which originally has been developed for the detection of respiratory motion. This sensor has been applied around the thigh in order to detect the pulse of the thigh artery. The second type is a fiberoptic version of a photo plethysmograph detecting the optical transmission of human tissue. A transmissive and a reflective type of this sensor have been tested by application to ear lobes, finger and toe tips respectively.