The Athinoula A. Martinos Center for Biomedical Imaging is part of the Department of Radiology at Massachusetts General Hospital, Harvard Medical School. It is one of the world’s largest and most comprehensive academic biomedical imaging research enterprises, with over 150 investigators, 8 human MRI scanners, combined PET/MR, M/EEG, Optical Imaging, and ultrahigh field MRI facilities for small animal imaging.
The Martinos Center is one of the birthplaces of functional MRI (fMRI), and continues to be a resource for novel pain neuroimaging discoveries. Many of the imaging equipment is from Siemens Healthineers and delegates will be able to tour the facilities and view the latest in imaging technology. The following areas of the center will be toured:
Detailed information regarding the stations at Martinos Center:
The Pain Imaging Tour of the latest imaging technology used in research and clinical use will provide participants with a clear understanding of new innovations available to them and their uses.
The key strategies are:
- To increase the knowledge of participants on imaging technologies: clinicians and researchers working in the field of pain management.
- Increase participant knowledge and skills in state-of-the-art devices for use in pain management for acute, chronic and cancer pain.
- To share relevant research with peer and discuss with experts working at the center.
The learning objectives upon completion of this activity are that participants will able to:
- Enhance their skills and knowledge on imaging in pain management for acute, chronic and cancer pain.
- Discuss the latest and current research and developments in these areas.
- Translate learning experiences into their clinical practice.
Each station will have a general demonstration and discussion on the specific imaging equipment and their uses and applications to pain neuroimaging. An overall description of the technology presented at each station is outlined below:
STATION 1: Magnetoencephalography (MEG) and Electroencephalography (EEG)
Magnetoencephalography (MEG) is a noninvasive technique used to measure magnetic fields generated by small intracellular electrical currents in neurons of the brain. In this way MEG can provide direct information about the dynamics of evoked and spontaneous neural activity and the location of their sources in the brain. MEG and EEG are closely related, the latter detecting the electric potentials generated by neural currents instead of the corresponding magnetic fields. However, it turns out that the task of inferring the sites of brain activation is often more straightforward with MEG than with EEG. This is due to the electric and magnetic properties of the tissues in the cranium as well as to the fact that MEG is selectively sensitive to currents flowing tangential to the scalp, corresponding to sulcal activations. In contrast, the interpretation of EEG is often complicated by the simultaneous presense of both sulcal and gyral sources, the latter corresponding to radial currents.
Clinically, MEG is used to detect and localize epileptiform spiking activity in patients with epilepsy. Also, when planning for removal of brain tumors, surgeons will use it to localize brain areas important for speech that should be avoided.
At the Martinos Center, researchers use MEG – often in conjunction with EEG, MRI, fMRI and optical imaging – to obtain maps of brain activity in cognitive neuroscience studies carefully designed to investigate the workings of the normal and damaged brain.
STATION 2: Positron emission tomography (PET)
Positron emission tomography (PET) is a noninvasive imaging method used to obtain quantitative molecular and biochemical information about physiological processes in the body. PET imaging can show the chemical functioning of organs and tissues in the living object. PET can help to advance a range of applications. It can be a powerful tool in drug discovery and development, for example, as it can noninvasively assess drug distribution and action at the molecular level. Preliminary studies indicate that dynamic PET imaging – using repeated images over time – can be a valuable technique for defining the time course of uptake and retention of radiolabeled anticancer drugs in tumors and in the surrounding normal tissue in patients. These drugs are designed to inhibit key processes in cancer initiation and progression: angiogenesis, proliferation, avoidance of cell death or apoptosis, invasion and metastasis, and transduction of signals that modulate these processes. In the clinical environment PET has established its efficacy in cancer studies, though these studies have only begun to utilize the full potential of PET imaging
STATION 3: 3T, 7T and 9.4T Magnetic resonance imaging (MRI)
Bay 4: 3T MRI
This is a 3T Siemens Prisma fit. The system features the Siemens XR200 gradient system. Bay 4 is equipped with a full assortment of body imaging coils as well as Siemens 32-channel and 64-channel head-neck coils. Bay 4 is also multi-nuclear capable and an MGH-built 8-channel 31P head array is available. In addition, it contains an assortment of audio, visual, and sensory stimulus equipment for fMRI studies including rear projection, audio stimulation, a subject response device, and an eye tracking setup. Bay 4 has also been configured to allow simultaneous TMS stimulation as well as recording of simultaneous EEG.
Bay 5: 7T MRI Laboratory
This laboratory supports an ultrahigh-field 7 Tesla whole-body MRI. The 7T whole body magnet (90 cm magnet ID) was built by Magnex Scientific (Oxford, UK). Siemens provided the conventional MRI console, the gradient and gradient drivers, and the patient table. The system has been upgraded by Siemens to contain 8 independent 1kW transmit channels capable of simultaneous parallel excitation with different RF pulse shapes for B1 shimming and/or parallel transmit methods such as transmit SENSE. The 7T scanner environment includes a visual display system and a button box for acquiring subject responses in the scanner. A MedRad power injector is installed in the Bay for the injection of gadolinium contrast agents.
Bay 9: Small-bore MRI Systems – 9.4T Laboratory
The 9.4T (400 MHz proton frequency) 21-cm diameter horizontal bore magnet (Magnex Scientific) uses a Bruker Avance console, and is capable of multinuclear imaging and spectroscopy of small animals (rats and mice). Capabilities include high-quality high-resolution anatomical and functional imaging, using a wide variety of contrast mechanisms (T1, T2, diffusion, perfusion), together with multi-shot 2D and 3D sequences, single shot EPI, localized spectroscopy and spectroscopic imaging. The dual gradient system comprises a Bruker gradient coil capable of 44 G/cm, and a Resonance Research (Billerica, MA) gradient insert capable of 150 G/cm.
STATION 4: Large-bore MRI Systems Bays 1, 3 3T MRI Trio 1, 2, 3 and 3T Skyra
Bay 3: 3T MRI 1
This is a 32-channel Siemens Tim Trio 3T whole-body MRI scanner. The whole-body gradient system uses the same gradients as the 1.5T Avanto (45 mT/m strength, 200T/m/s slew rate). It has 32 independent RF receive channels for phased array coils, including a Siemens 32-channel head coil and a home-built 32-channel head coil for the gradient insert. Bay 3 further features an insertable asymmetric head gradient coil (Siemens AC88) that is capable of 60 mT/m and slew rates in excess of 600 T/m/s at a duty cycle of 70%, allowing single-shot 3mm resolution EPI with an echo spacing of 300 µs at a sustained rate of 14 images/second. Bay 3 also contains an assortment of audio, visual, and sensory stimulus equipment for fMRI studies including rear projection, audio stimulation, a subject response device, and an eye tracking setup.
Bay 1: Siemens 3T Skyra
This is a Siemens 3T Skyra with 128-channel receive capabilities and 2-channel parallel transmit. The system comes with 128 RF channels, 40mT/m gradients and a 70cm patient bore for improved subject comfort (and mandatory for fetal imaging) and stimulus access. The scanner provides Siemens 32- and 64-channel head coils as well as an assortment of body arrays. Bay 1 also contains an assortment of audio, visual, and sensory stimuli equipment for fMRI studies, including digital high-definition rear projection, audio stimulation, and a subject response device. The stimulus equipment is set up to be run from a PC, a Macintosh, or the user’s laptop computer. Stimuli can trigger or be triggered by the scanner. Bay 1 is also equipped with a state-of-the-art power injector. Furthermore, the system is configured for simultaneous TMS/MRI operation, including a video navigation system for the TMS stimulator.
STATION 5: Connectome Imaging at LF-MRI Building 75
Bay 8: 3T Laboratory
Connectome imaging techniques provide the opportunity of mapping the human brain pathways in vivo at unprecedented resolution.
Siemens Skyra 3T platform is the “Connectome” scanner, which is based on a Siemens Skyra 3T with the 300mT/m SR=200T/m/s “connectome” gradients. The full gradient strength is available for maximum duty-cycle on diffusion images. Since the diffusion pulses and EPI readout have different needs (diffusion pulses need high Gmax and modest slew rate while EPI needs only a ~50mT/m at 200T/m/s slew rate), the combination of 300mT/m and SR=200T/m/s is potent and usable for diffusion imaging without peripheral nerve stimulation. This gradient strength is useful for achieving high b value diffusion imaging in a short echo time (TE). For example, a b =15,000s/mm2 diffusion weighting can be acquired with a TE of about 55ms, compared to 120ms for a conventional 40mT/m scanner. This improves the diffusion images in two ways: First, it shortens the diffusion time and thus reduces blurring of the water PDF. Second, it increases SNR by about 3.5 fold by reducing loss to T2 decay. The system comes with 64 RF channels and a home-built 32- and 64-channel brain arrays available. The bore is reduced to 56 cm to accommodate the bigger gradients and the gradients have a linear region (to 5%) of 20 cm. Bay 8 also contains visual (rear projection) and auditory stimulation setups as well as a triggering interface.
STATION 6: Functional near-infrared spectroscopy (fNIRS) at Optics Division
Near Infrared Spectroscopy and Diffuse Optical Tomography
Using fNIRS, brain activity is measured through hemodynamic responses associated with neuronal activity. The use of fNIRS as a functional imaging method relies on the principle of neuro-vascular coupling also known as the haemodynamic response or blood-oxygen-level dependent (BOLD) response. This principle also forms the core of fMRI techniques. fNIRS includes the use of diffuse optical tomography (DOT/NIRDOT) for functional assessment. Multiplexing fNIRS channels can allow 2D topographic functional maps of brain activity while using multiple emitter spacings, and may be used to build 3D tomographic maps.
The Optics division offers two CW-DOT imaging systems (CW6), each with 32 lasers and 32 detectors (manufactured by TechEn) and One CW-DOT (CW5) + multiplexer with 26 continuous lasers and 6 lasers multiplexed to 200 output fibers, Three supplemental source extensions boxes for CW6 systems, each with 32 lasers, One frequency-domain 2 wavelength spectrometer, 40 switched output fibers, 8 APD detectors and two CW-NIRS systems, each with 16 lasers and 8 detectors (manufactured by TechEn). There is also three ISS frequency domain systems, one with 32 laser diodes and 4 photomultiplier detectors (Imagent™ functional brain imaging), two with 16 laser diodes and 2 photomultiplier detectors (OxiTS), a time-domain diffuse optical tomography (TD-DOT) imaging system, with an image intensified CCD detector and optically multiplexed sources, a time-domain fluorescence diffuse optical tomography (TD-DOT) imaging system, with an image intensified CCD detector and motorized source positioning system and a 3D camera system for surface acquisition for small animal optical tomography (Technest Holdings Inc.,). A supercontinuum laser system consisting of Photonic Crystal Fiber (PCF, NL-PM-750, Thorlabs) fiber coupling system consisting of a 2 axis translation stages to hold an aspheric lens and PCF (Newport) Electrostrictive actuators (AD-100, Newport) and controller for precision micrometer positioning. Two diffuse correlation spectroscopy systems with 785 nm diode pumped solid state lasers, 4 photon counting APD detectors and 256-tau 8 channel correlators.