A Simple, robust hardware device for passive or active respiratory gating in MRI and MRS experiments

The synchronization of MR data collection with respiration is essential for collecting high-quality, in vivo magnetic resonance images and spectra of rodents. In this article, we describe the design and operation of a simple, robust device for respiratory gating. Inexpensive and easy to construct, the device operates in either free-breathing or actively driven (ventilator) modes. Respiration is monitored either by a pressure transducer connected to the nosecone used to deliver anesthesia to the animal or by a fiber-optic detector of the animal's motion. The device generates a TTL signal that can be used to trigger the MR scanner to enable respiratory-synchronized data acquisition. A variety of different MR imaging sequences can be easily modified to incorporate respiratory gating. We present respiratory-synchronized imaging and spectroscopy results obtained using this device, including ¹H MR images of mouse lung, liver, and spinal cord and localized ¹H spectra of mouse liver.