Dr. Lars Kasper is the MRI Physicist and Engineer for ToNI, responsible for overseeing the facility’s imaging operations and supporting MRI technical development. John Milne is the MRI Technologist, responsible for operating the MRI scanner, as well as facilitating booking and billing. The duties of the staff include maintaining and trouble-shooting equipment, training new users, providing help with experimental design and analysis (including stimulus timing, choice of pulse sequences and coils, and analysis implementation), MRI protocol development, backing up data to storage, quality assurance, and charging grants for use of the facilities.
Quality assurance (QA) on our MRI scanner is performed by Dr. Lars Kasper. The overall performance and data quality of the scanner are assessed weekly. Preventative maintenance on the MRI scanner is performed periodically by the Siemens field service engineers, per our service contract.
Siemens Prisma 3T Full-Body MRI Scanner
ToNI is home to a Siemens Prisma 3T MRI scanner installed in October of 2017. The Prisma was designed by Siemens with the research community in mind. With its gradient strength of 80 mT/m and slew rate of 200 T/m/s, it is the fastest whole-body 3T scanner commercially available, making it ideal for EPI imaging (both BOLD- and diffusion-weighted imaging). The actively shielded magnet has zero helium boil-off technology, reducing maintenance costs and downtime. The RF system has up to 128 channels in the magnet housing for increased SNR. The 20- and 32-channel head and 64-channel head/neck coils with integrated pre-amplifiers allows parallel acquisition techniques and image acceleration, reducing susceptibility distortion and image blurring in EPI while maintaining an excellent SNR. Our state-of-the-art scanner enables access to the most recently developed imaging technologies, including Simultaneous Multi-Slice acquisition for faster acquisition (shorter TR and/or increased resolution). In addition, we offer the Siemens Spectroscopy Package, which bundles Single Voxel Spectroscopy, 2D Chemical Shift Imaging, 3D Chemical Shift Imaging, and syngo Spectroscopy Evaluation. We also have access to work-in-progress packages, including multi-echo acquisition for better signal in brain regions prone to susceptibility artifacts, including frontal and temporal regions.
ToNI maintains a variety of ancillary systems for presenting stimuli and collecting a variety of behavioral and physiological signals. These systems include stimulus computers running both OSX and Windows platforms.
Visual display. To display visual stimuli to participants in the MRI scanner, we use a BOLDscreen display. Our BOLDscreen monitor is an MR compatible screen with high resolution (32”, 1920 x 1080, 100Hz or 120Hz refresh rate) and zero delay. The displays are calibrated to obtain high-fidelity psychophysical measurements in the MR scanner. For stimulus presentation, a PC running Windows is used for visual presentation. Matlab, PsychToolbox, E-Prime, Presentation, PsychoPy, and Inquisit are available. Additional information regarding the screen, including three potential screen positions and their corresponding visual angles, is available in this document.
Auditory stimulation. Auditory stimulation can be delivered to a subject in the MRI scanner in several ways. One option is the conventional Siemens air-driven headset. In addition, for auditory experiments requiring a very flat frequency response and fine control of low-level auditory characteristics, the center has a set of in-ear MRI-compatible headphones (Sensimetrics, model S14) that have been modified to provide excellent isolation from scanner noise. The earphones are small enough to fit within a small head coil, including our 32- and 64-channel head coils.
Button boxes, joystick. We routinely collect behavioral responses during fMRI experiments, using different button boxes and a joystick. The buttons emulate key presses on the computer. Our standard button box is a 4-button keypad that has been specially designed for use in an MR scanner (Current Designs, HHSC-1X4-CR). We also have a bimanual option in the form of two 4-button hand-held response pads (Current Designs, HHSC-2X4-N4), as well as a hand-held joystick response device (Current Designs, HHSC-JOY-5).
Eye movement monitoring. Eye-position is routinely monitored in the MRI scanner with an infrared videographic camera equipped with a telephoto lens, designed specially for use in the MRI scanner (SR Research, EyeLink 1000 Plus). The system consists of a camera, mirror system, and dedicated host computer. The camera that rests in the bore of the scanner is focused on either eye, first through a two-way coated ‘hot’ mirror that allows the camera to see the eye while appearing transparent to the subject, and then through the same mirror that subjects use to view the visual display. The specifications on this system are as follows:
- Sampling and output rates: 500/1000/2000 Hz
- System accuracy: 0.25 – 0.5 degrees of visual angle
- Visual angle resolution: less than 0.01 degrees of visual angle
- Tracking range: 32 degrees horizontally, 25 degrees vertically.
MR safe prescription glasses: MRI safe glasses allow the participants with refractive vision errors to see the visual stimuli during their scan. This provides corrective eyewear to participants inside the MRI scanner. The lens inserts are easily changed based on the needs of the participant. The kit includes 24 sets of prescription lenses from +6 to -6 in 0.5 diopter increments.
Biopac: Complex physiological signals in the MRI can be collected using the Biopac system available at ToNI. This system permits the acquisition of several physiological signals, including: Electrocardiogram (ECG), Electromyogram (EMG), Respiration, blood pressure, and Electrodermal activities such as Galvanic skin response (GSR). These signals can serve as valuable measures of nervous system function in different experimental designs. Electrical stimulation is also available for constant current and constant voltage electrical stimulation. Collected data can be analyzed using Acqknowledge software, which provides an environment to view, record, analyze, and transfer data.
Streamlined physiological monitoring and recording: Cardiac signal can also be recorded using Siemens Bluetooth-enabled pulse oximeter that clips to the index finger of the subject. Respiration can be recorded using a Siemens pneumatic respiratory belt. These physiological signals may be used to correct for artifacts, physiological alterations, induced field inhomogeneity, or interference with the experiment.
Shells of a previously active 1.5T Siemens Avanto scanner are used to build an MRI simulator or “mock” scanner. This allows participants to become acclimatized to the scanner environment before data is actually acquired. In addition, participants can be trained to keep their head still using behavioral feedback. Motion is detected by a Mo-Trak unit from Psychological Software Technologies (PST). While the participant lies in the mock scanner, a motion detector is placed on the participant’s head and motion-related feedback can be provided. Realistic MR scanner sounds are played during the session to further enhance the simulation.
The facility houses a file server, which currently includes 52 TB of shared disk space. The drives are configured for a combination of redundancy and performance. The server is located in a secure and climate-controlled location. Researchers can access their study data remotely through a secure connection, immediately following the completion of their scanning session.
To lacerovide researchers with a functional and productive environment, a number of amenities are available. To simplify access to the secure building, video intercoms facilitate the identification of and communication with participants on arrival. Secured lockers are available for participants’ belongings, and Wi-Fi is available in all areas. A limited number of locked drawers are also available to labs by request, to store study-related materials on-site.
Work and conference space
Between scans there is a quiet workspace available, which includes a large presentation screen and computer, and conference-style seating for up to seven people. One of the video intercom systems is also present in the room, making it a convenient location to wait for the next participant.
Behavioral testing room
For studies requiring behavioral data before or after scans, appropriate testing space is also available. There are two testing stations with space suitable to place laptops for one to two participants in a private and low-stimulus environment.
To facilitate obtaining informed consent, or other private communication with participants, ToNI offers an interview space with a table seating two.