GE Healthcare's compact 3T MR
scanner at the Mayo Clinic
With the latest cutting-edge capabilities, MR enters new diagnostic frontiers
October 17, 2016
by Lauren Dubinsky
, Senior Reporter
More than 5 million people in the U.S. are living with Alzheimer’s disease and this year, along with other dementias, it will cost the nation $236 billion, according to the Alzheimer’s Association. It’s a challenge to diagnose the disease before the onset of symptoms, but researchers are investigating whether MR imaging can spot the signs of the disease earlier.
“MR has the best soft tissue contrast,” says Jonathan Furuyama, product manager of MR at Toshiba America Medical Systems. “In terms of being able to monitor brain matter volumes, it’s definitely superior to all other modalities. CT doesn’t have quite the soft tissue contrast that you would like if you’re looking at things like volumes.”
Members of COST Action, networks centered around nationally-funded research projects, recently brought 200 scientists together to develop an MR imaging tool that uses a noninvasive technology called Arterial Spin Labelling (ASL). It measures blood flow to the brain, which helps clinicians determine if brain cells are being properly nourished with oxygen and glucose.
“ASL is a big thing. They are trying to see if blood flow patterns are early indicators of some sort of cognitive decline,” says Furuyama. “If you were to do similar things on CT, you have to inject iodine and not everyone can.” ASL has been under development for 15 years, which has resulted in a variety of methodologies and techniques. The scientists had to rigorously analyze literature to find the best method for measuring blood flow. They then published a paper in January 2015 that serves as a reference.
Toshiba, Siemens Healthineers, GE Healthcare and Philips Healthcare offer ASL on their MR systems, and GE, Siemens and Philips are already using the ASL tool. COST Action is working with the Quantitative Imaging Biomarker Alliance to have ASL recognized around the world as a biomarker for dementia.
When PET data is used in conjunction with MR data, it can be useful for assessing dementia. Researchers from the Montreal Neurological Institute and Hospital analyzed a considerable amount of patient information, including MR and PET exams, and found that decreased blood flow in the brain is the earliest sign that a patient may have dementia.
The data was pooled from the Alzheimer’s Disease Neuroimaging Initiative database, which includes more than 30 institutions across Canada and the U.S. They analyzed more than 7,700 brain images from 1,171 patients with various stages of Alzheimer’s. The research, which was published in Nature Communications in July, also revealed that changes in a patient’s cognitive abilities start earlier than previously thought.
MR-guided focused ultrasound
“The beauty that MR brings to the table is that we can measure temperature,” says Jason Launders, director of operations in the health device group at ECRI. “That is what you’re trying to do with focused ultrasound. You are trying to ablate tissue with [heat].”MR-guided focused ultrasound (MRg-FUS) has FDA approval for the treatment of uterine fibroids, bone metastases and prostate cancer. Most recently, it received approval for essential tremor, and Siemens and GE have made sure to offer that to their customers.
InSightec’s Exablate Neuro MRgFUS can be used on GE’s 1.5T and 3T MR systems. In August, InSightec announced an agreement with Siemens to make the Exablate Neuro compatible with Siemens’ MAGNETOM Aera and Skyra MR systems. “The reason MR is used in focused ultrasound treatment is because temperature-sensitive scans can be acquired during the ultrasound treatment,” says Stuart Clarkson, zone business manager for MR at Siemens.
“This effectively shows the clinician where the treatment is being delivered.” Philips also has a presence in the market. In 2010, the company released its MR-guided, high-intensity focused ultrasound (HIFU) product called Sonalleve. It can be purchased as an upgrade to an existing MR system and can be used for uterine fibroids, pain management and bone metastases.
Cardiac MR isn’t so difficult anymore
“MR is very technologically demanding on the technologist,” says Launders. “Some technologists understand what’s going on to make those images, but they are few and far between.” In cardiac imaging, the technologist has to understand the physiology of the heart as well as be able to set up the right images and time them with contrast. There are many things that need to happen at the right time.
Some MR manufacturers offer tools to make cardiac MR exams easier for those who aren’t experts. Toshiba’s solution is called CardioLine and it works to simplify and standardize how cardiac exams are performed. CardioLine reconstructs a low-resolution, 3-D model of the heart and uses an atlas to determine the exact location of the heart. Usually when performing a valve shot, clinicians must go through different localizers and planes before they can visualize where the valve might be.
“It’s meant to speed things up. You don’t have to do so many localizers if you are letting a computer determine where the planes are,” says Furuyama. “Some technicians are not as proficient as others at cardiac MR and from what we’ve heard, doctors can tell which technician was doing the scan based on the quality of the exam.”
Many hospitals are interested in standardizing their MR protocols, but it’s a very difficult task depending on certain factors. In any given hospital there could be a mixture of 3T and 1.5T MR systems with different gradient strengths. “It’s not as easy as it sounds, but it’s something that people are trying to do because hospitals want to be able to put a patient in any scanner in their system and get the same image out, regardless of what scanner they put them in,” says Launders.
It’s easy to standardize protocols if all of the MR scanners are from the same manufacturer, but that’s usually not the case. To copy the protocol from a Siemens MR to a GE MR is complicated because the nomenclature is completely different. “A lot of our larger customers can sometimes have so many scanners in so many different locations, but are on different software platforms or different vendors,” says Siemens’ Clarkson. “It’s always been quite challenging.”
Siemens is hoping protocols can be delivered from a central location to all of the scanners in the hospital. That will help save money because the clinicians won’t have to travel to each of the remote facilities, which is the traditional approach. For example, if a radiologist switches from doing 3-millimeter slices to 2-millimeter slices, that can be centrally broadcast to all of the Siemens scanners without requiring someone to go to each individual scanner. “The idea for that centralization is to homogenize the imaging technology across the fleet of [Siemens’] MR scanners,” says Siemens’ Clarkson.
GE and the Mayo Clinic worked together to develop a compact MR system that’s about one-third the size of a conventional MR and only requires a fraction of the liquid helium to operate. Unlike conventional systems, the patient’s arms and torso can be completely out of the magnet. “The idea was to take some advanced technology that’s there and deliver a highly accessible, high-performance 3T system for brain imaging that would give us better image quality than what you currently get in a whole body system,” says Eric Stahre, president and CEO of GE Healthcare MR.
Since 30 percent of all procedure volumes are head and neck exams, Stahre felt it was worth pursuing a dedicated system that could take up that procedure volume and do it in a more effective way. The system is also intended to be used for small extremities such as wrists, feet and ankles. Early this year, it was installed at Mayo’s downtown campus in Rochester, Minnesota.
In February, the Mayo Clinic announced that the MR would be used in research involving 300 initial head scans. They hope to improve the diagnosis and treatment of focal diseases such as gliomas, meningiomas, stroke, aneurysm and congenital anomalies as well as Alzheimer’s disease, multiple sclerosis, psychiatric disorders, leukoaraiosis and hydrocephalus. Physicians at the Mayo Clinic who focus on pediatrics, musculoskeletal, deep-brain stimulation and Alzheimer’s disease are hoping that the compact MR can bring insight into their fields as well.
Helium-free 3T MR
Mitsubishi Electric, Kyoto University and Tohoku University in Japan have developed a helium-free 3T MR that uses a “high-temperature superconducting” (HTS) coil. HTS is a relative term. It means that the MR doesn’t need to be cooled to below 30K (-405.6° F) to operate. “Ordinary” superconducting MR magnets must be cooled below 30K to lose their electrical resistance and become superconducting. High-temperature superconductivity has been observed at temperatures as high as 138K (-211.2° F), but the Mitsubishi MR operates nearer the 30K level. HTS systems, therefore, still need to be very cold, but do not need liquid helium to work efficiently. Liquid nitrogen is sometimes used.
“In order to realize [the HTS effect] without helium cooling during operation of the magnet, we make use of a conduction cooling system [direct contact cooling] using a small refrigerator system and high-temperature superconducting wires, which enables us to realize a helium-free MRI system,” says Dr. Kazuo Yamamoto, senior manager of the magnetic application and the particle accelerator group at Mitsubishi.
Researchers at the universities have already used the system to successfully image a 25-millimeter mouse fetus. The developers have plans to increase the size of the system by one-half the size of a full-size MR by 2020. Yamamoto believes that helium-free MR systems will be launched in the next 10 years and that one day MR imaging will no longer require helium. His team is currently working toward commercializing the helium-free MR.
“The helium supply crisis five years ago, and a steep rise in costs, motivated us to realize a helium-free MRI,” says Yamamoto. “By providing helium-free superconducting magnets in MRIs, we want to realize MRI systems that do not depend on helium and contribute positively to society.”