PET/MR Synchronization by Detection of Switching Gradients

Abstract

The full potential of simultaneous Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) acquisition, such as dynamic studies or motion compensation, can only be explored if the data of both modalities is temporally synchronized. As such hybrid imaging systems are commonly realized as custom-made PET inserts for commercially available MRI scanner, a synchronization solution has to be implemented (depending on the vendor of the MRI system). In contrast, we demonstrate a simple method for temporal synchronization, which does not require a connection to the MRI. It uses the normally undesired effect of induced voltages on the PET electronics from switching MRI gradients. The electronic circuit needs very few components and the gradient pick-up coils are made from PCB traces and vias on the PET detector boards. Neither programming the MRI nor any physical connection to the MR scanner is needed, thus avoiding electromagnetic compatibility problems. This method works inherently with most MRI sequences and is a vendor-independent solution. A characterization of the sensors in an MRI scanner showed that the MRI gradients are detected with a precision of s (with the current implementation). Using different trigger thresholds, it is possible to trigger selectively on certain MRI sequences, depending on their gradient slew rate settings. Timings and pulse diagrams of MRI sequences can be recognized from the generated Manuscript

Synergistic motion compensation strategies for positron emission tomography when acquired simultaneously with magnetic resonance imaging

“…Thus, it is challenging to acquire data within such sort time frames especially for some MRI sequences. During regular mouse breathing, diaphragm motion is about 1 mm and the rib cage expansion is at 0.7 mm, consequently appropriate motion management is essential to improve PET resolution beyond the state of the art, as demonstrated by Weissler et al [89]. Compensation using MRI was applied for respiratory motion on non-human primates [90] and for cardiac and respiratory motion of swine models [91][92][93] and around one-year-old dogs [94] showing clear improvements in image quality as illustratively demonstrated in figure 6.…”

Adaptive and Wireless Recordings of Electrophysiological Signals during Concurrent Magnetic Resonance Imaging

“…The device was designed to utilize the existing MR-hardware and the EM environment to trigger EP recording and wirelessly transmit digitized data. The device recorded the EP signal based on the input it received from the gradient detection system which monitored changes in the magnetic field inside the MRI bore [35]- [37]. The device amplified and filtered the EP signal and transmitted it wirelessly to the MR-receiver coil during MRI acquisition.…”

A Digital Preclinical PET/MRI Insert and Initial Results

“…Further available are: two Analog to Digital Converters (ADCs) (e.g., to sample respiratory information for PET motion correction [33]), three PT100 temperature sensor ports (e.g., to monitor animal heating devices), and an input for an MRI gradient switching detection coil (for temporal synchronization [34]). The housing of the synchronization unit also contains the conversion from POF to glass fiber communication, needed to connect to the standard optical gigabit Ethernet adaptors (Intel) in the DAPS.…”