It’s been more than 35 years since Dr. Raymond Damadian, a physician and scientist, scanned one of his students in what turned out to be the first ever MRI body scan on a human being. It took almost five hours to produce one image, and that original machine, named the “Indomitable,” is now owned by the Smithsonian Institution.
Today, magnetic resonance imaging (MRI) is commonly used in hospitals to scan patients and determine the severity of certain injuries or abnormalities. Unlike CT scanning or x-rays, no ionizing radiation is involved. MRI scanners noninvasively scan the body with the use of magnets. They can scan selected body parts in incredible detail, allowing doctors and clinicians to detect the early signs of cancer and help diagnose multiple sclerosis, brain tumors, torn ligaments, tendonitis, and strokes, amongst many others.
An MRI scanner uses a magnetic field and radio waves to create detailed images of the body. It generates a magnetic field by passing an electric current through wire loops in the machine. Another set of coils transmits radio frequency waves into the patient’s body. There are different coils for different parts of the body: knees, shoulders, wrists, head, neck and so on. These coils usually conform to the contour of the body part being imaged, or at least reside very close to it during the exam. The emitted radio waves force the protons in the patient’s body to align, at which point the radio waves are absorbed by the protons which are stimulated and start to spin. The energy released by excited molecules emits signals received by the coil which are then processed by a computer in order to generate a 3D image of the body part being analyzed.
Back in 1977, patients had to stay still for five hours to be scanned, but fortunately modern electronics have cut the waiting time down quite significantly. Even so, it can still be uncomfortable for patients who are forced to remain immobile for periods of up to 45 minutes or more depending on the number of body parts being examined. Even very slight movement of the part being scanned can cause a distorted image and require a repeat.
The market has evolved too, since that very first experiment, and according to MarketsandMarkets Global Forecast, the global MRI market was valued in the region of US$4.13 billion in 2013 and is estimated to rise to US$5.24 billion by the year 2018. Of this, the US market has a 40% share.
Scanner Selection Criteria
The manufacturers of MRI equipment are constantly focusing on offering higher levels of performance in terms of improved image quality and consistency, faster imaging and processing, and higher patient throughput. From the purchasing body’s perspective, there are a number of technical factors which are taken into account when selecting a product. The higher the strength of the main magnetic field, the better the image quality and the higher the number of applications for which the scanner can be used. At one end of the spectrum, advanced neurological imaging will require at least 1.5T equipment, while at the other end low field systems can produce images of good diagnostic quality for numerous applications. However image quality will be better with higher strength equipment because the higher the magnetic field, the higher the signal-to-noise ratio. This signal-to-noise ratio (SNR) is the most important parameter defining image quality in MRI. A high SNR provides more flexibility for finer detail or faster images through parallel imaging, which is useful in reducing the blurring effect caused by breathing. A low SNR on the other hand can cause the contrast between different tissues to be obscured by background noise.
The number of independent channels that can receive signals from the RF coils is another important factor. A higher number of channels improves the SNR and offers the option of parallel imaging. Also, higher gradient coil systems provide images in any desired plane and can provide a better spatial resolution in a shorter scan time. Finally, parallel imaging techniques help spatially encode the MR signal, and reduce the number of times that the gradient coils have to be switched on and off, which speeds up the imaging process. The parallel imaging factor describes the number of times by which the scan time is reduced.
Manufacturers are striving to improve the overall scan process in several key areas. Ultimately high SNR and enhanced image quality are probably the most important but there are other areas which also offer major advancements. For example, workflow simplification can be achieved when there are fewer coils to position and as a consequence patient positioning time can be accelerated. Patient throughput times are also an important factor, with the latest digital technologies performing quality scans for routine exams in less than 10 minutes. From a patient perspective, speedier scan times, reduced acoustic noise levels, and less confinement are critical considerations.
Typical System Architecture
A typical MRI system consists of a scanning element plus a processing and control element. The scanning element includes a main magnet, an RF transmit and receive unit, a number of RF coils, and the gradient coils which are carefully positioned around the person to be scanned. The processing element typically includes a control unit to control and acquire data from the gradient coils. A scanning processor sends commands to the control unit to activate gradient scanning and receives the measurement results. In addition, it controls and acquires data from the scanner’s RF module in order to process RF data and to build a scanned image. The system comprises an image display for displaying a processed scanned image, and a tracking output for the display and implementation of tracking information. Several manufactures design the tracking processor and control unit using readily available commercial hardware such as CompactPCI. Signals from the sensor are digitized by A/D converter boards and processed in real-time by DSP or Intel®-based processor cards which also provide a communication interface to a host computer.
To meet many of the performance and longevity needs, several medical equipment manufacturers had already selected the CompactPCI architecture in their earlier generation designs. With levels of reliability, modularity, and maintainability much higher than any other available commercial or industrial computing form factor, CompactPCI was an ideal choice. In addition, a broad ecosystem of suppliers for both CPU blades and I/O existed to ensure competitive pricing and dual source supply. The best way to adequately plan for the long-term is to design around an extensible and easily upgradeable architecture. This ensures that all elements have room to scale up, grow and expand, and guarantees the longest possible product lifecycles.
In one particular scanner design, Advantech was chosen as the supplier of the platform processing element. Advantech’s close relationship with Intel® and a proven commitment to following Intel®s embedded processor roadmap helped breed confidence at design and management level and reassured the customer of Advantech’s long-term supply capabilities. In addition, Advantech’s flexibility in modifying standard products as a part of its Customized COTS (C2OTS) program was a decisive factor, as not all CompactPCI manufacturers’ CPU blades are identical. So the ability to modify a standard product to meet the form, fit and function of the customer’s previous choice of CPU blade meant very little change was required to the original scanner design, and almost no disruption to the R&D or manufacturing process. It did however provide the opportunity to move to a multicore platform with significantly more parallel processing power that enhanced the performance of the current design.
MIC-3396 Advantech CompactPCI Blade -
Based on 4th Generation Intel® Core™ Technology
The MIC-3396 6U CompactPCI SBC offers a seamless upgrade path to OEMs with higher levels of performance and richer features. The board supports the latest Intel® Core™ i3, i5 and i7 processor SKUs in 22nm technology and an Intel® QM87 PCH with embedded graphics for up to 3 independent displays. It fits in a single 4HP slot with up to 8GB of on board ECC DDR3 memory expandable to 16GB via an SO-UDIMM module. I/O expansion is ensured by a PMC/XMC slot while mass storage is available with onboard 2.5” SATA-III and Cfast support. On-board flash and RTM-based SATA-III storage options are also available. Independent gigabit Ethernet ports cater to a wide range of integration options with dual GbE connectivity to front, rear and PICMG 2.16 ports.
Drop-in Replacement with Higher Performance and a Longer Lease on Life
The MIC-3396 blade was designed to fit a wide range of markets beyond just medical imaging, and represents a plug compatible upgrade path with 8 times the memory capacity and more than 14 times the performance of the original Intel® Pentium® M based blade which was formerly used. For many of Advantech’s customers this has provided a whole new lease of life for their installed base, enabling the potential for major performance improvements, new software capabilities and greater channel densities, all without the need to alter the fundamental platform designs.