China is a country that has strong market demand for magnetic resonance imaging (MRI) systems; it’s also the one that sees rapid growth in the sector of open MRI system manufacturing.

Compared with other imaging modalities, MRI has many advantages in the indices of imaging speed, spatial and dense resolution, slice thickness, etc. It’s comparable to CT in these technical indices. What’s more, its unique superiority in detecting soft tissue, the variety of parameters (proton density-weighted, T1, T2, T1-weighted scan, T2-weighted scan, T2*-weighted scan or multiple weighted scan, etc.), multiplicity and comparability in data accessing, as well as the openness of the magnets, are increasingly expanding its clinical application scope. It’s one of the imaging equipments that have received attentions worldwide.

1. Characteristics and Clinical Application of Low-field Permanent Magnet Open MR

At present, the MRI system is evolving into two directions - the high-field super conducting magnet type and the low-field permanent magnet open type. The former mainly refers to the magnetic field above 1.5T in the super conducting magnet, such as 3T, 4T, or even 7T and 9.4T. Developing high-field MRI system is in line with the industry’s long-term goal of pursuing ideal ratio of signal to noise. These types of systems can be the best choice for either fulfilling the clinical imaging task or conducting research on functional imaging. The high-field super conducting magnet MRI systems are currently mainly used in clinical study to detect the special diseases and unveil more "mysteries" of human body. So they are mostly found in large-scale hospitals and research units.

Low-field permanent magnet MRI system generally uses 0.2-0.5T magnets. And the open-type machines are prevalent in clinical field. The system has been widely installed and operated in China’s healthcare units at all levels. The prevalence of this system can be attributed to the following factors.

a. Economy

Generally speaking, the purchaser will cut a 50-60 percent’s cost in purchasing the middle- or low-field MRI systems rather than the high-field ones. This is the underlying reason why the low-field systems are much favored by healthcare purchasers. Another reason is that many countries (including China) are taking efforts to control the growth rate of high-field equipments in order to curb the soaring medical costs. This governmental behavior and policy will surely have a negative impact on the advance of super-high-field MRI systems, which in turn and facilitate the promotion of permanent open ones.

b. Performance

Recent years of consistent initiatives in optimizing the designs and integrating the cutting-edge technology of high-field systems in the hardware systems, including the major magnets and magnetic field gradient, greatly enhanced the performance of open MRI systems. At present, the diameter spherical volume (DSV) of the permanent 0.35 T magnets have reached the following levels: lower than 4.0ppm within the range of 36cm, lower than 0.4ppm within the range of 24cm and the general gradient strength is between 12-22mT/m, the gradient slew rate above 24mT/m/ms. The integrated phased array coils have been applied to radio-frequency (RF) coils. Other accessory special surface coils being used vary from one manufacture to another, with a wide spectrum which can be geared to clinical use, covering coils for head, neck, shoulder, chest, breast, spine, knee, limbs and multi-functional ones. And there are different coil styles such as orthogonal, planar and flexible style.

Similarly, in software, the manufacturers are vying with each other in earmarking more money to upgrade the pulse sequences and special examining software. Among the important technologies in the fast scanning sequences are: fast spin-echo (FSE), field echo and echo-planar imaging (EPI), which reduce the signal acquisition time of single-layer images to less than 100ms. At present, various fast imaging methods have been, or being and going to be adopted by the permanent low field open MRI system. Techniques such as eliminating motion artifacts, fat suppression, MR water imaging, will enhance imaging quality.

2. Open Examinations and Interventional Radiography

It’s well known that interventional radiography is one of the highlights of modern radiography. The fast growth of MRI technology has driven the modern radiography to the forefront of interventional radiography. X-ray guided interventional procedures have well known defects. Ultrasonography-guided interventional procedures fail to provide accurate anatomic information and location; in contrast, open MRI boasts the highest contrast resolution, 3D imaging capability at any direction. Besides anatomic information, open MRI can also provide multiple physical and functional parameters, such as spin density, relaxation time, blood flow, diffusion, temperature and chemical shift, which are significant in interventional diagnosis and treatment. As a result, the application of open MRI in interventional radiological diagnosis and treatment is on the rise and has favorable prospect.

To date, the clinical application of MR image-guided interventional procedures generally fall into two categories: diagnosis and therapy. The diagnostic techniques include: aspiration, biopsy and intra-articular injection, such as percutaneous abdomen and bone biopsy, in vivo breast biopsy location and head and neck biopsy, etc. The therapeutic techniques are mostly focused on the thermo- or chemical ablation of tumors under the guidance of MRI, which are expected to damage the local tumors in a precise and complete way.

Image-guided and computer-assisted neurosurgery is a substitute for stent stereostatic surgery and conventional surgery. It has been proved that perfect combination of complete image data, detailed surgery plan, interoperable image guidance and real-time interoperative guidance will play an important role in mini-invasive surgery and tele-surgeries.

3. Open MR Industry in China

China has the world’s richest source of permanent magnetic materials. There are currently a dozen of Chinese enterprises undertaking the production of MR, some of which have reached international advanced levels in terms of quality and technology.

Let’s take a few examples:

The Shenyang based Neusoft Digital Medical System Co., Ltd. is the China National Research Center for digital imaging devices and engineering project. Neusoft mainly provides CT, MR, X-ray apparatus and ultrasound scanner; its NAM-P023A and SUPEROPEN 0.35T opening MRI systems had obtained FDA and CE certificates. Shenzhen Anke High-tech Co., Ltd. specializes in the R&D of over 30 kinds of equipments and software systems covering four areas of medical imaging, medical information, medical electronics and medical treatment. The company unveiled China’s first MRI system in 1989 its major MRI products are the OPENMARK 3000C and OPENMARK 4000. Beijing Wandong Medical Equipment Co., Ltd. is committed to developing, manufacturing of medical X-ray diagnostic equipment, MR, dental unit as well as blood recovery technological products; its main MR product is the OPEN 0.36T system. XinAoMDT Technology Co., Ltd. was established in 2003. The company’s main product lines include flexible robotic manufacturing system, Open MRI System, early breast cancer diagnostic system and intelligent information application integration platform. XinAoMDT has the Centauri series of 0.45T open MRI system and MPF3000-I system. Founded in April 1998, Ningbo Xingaoyi Medical Instruments Co., Ltd. is one of China’s largest manufacturers of MRI systems. Its main products are OPER-0.2T, 0.3T, 0.35T and 0.4T open MRI systems. Xi’an Landcom Digital Medical Science & Technology Co., Ltd., founded in October 2000, is the provider of ambulance series, mobile C-arm X-ray apparatus and cardiac series products. It has EXPOTUS 0.35T open MRI system. The main MRI products of Shenzhen Basda Medical Apparatus Co., Ltd. are the BTI 0.35 open MRI system and BTX II Stereotactic Radiotherapy System (X-knife). Siemens Mindit Magnetic Resonance Ltd. provides NOVUS 0.35T MRI System.

The open MR products made in China have emulated its leading-edge overseas counterparts in the main magnet structure, gradient field coils, RF system, pulse sequences and other parameters and functions. These products have obtained international certificates and are well accepted in clinical units at various levels in China. In aspect of market prospect, the main purchasers are expanding from the hospitals at provincial and city levels to those at county levels. In clinical field, the application scope of MRI system is expanding from conventional imaging diagnosis to the rising image-guided interventional therapy - the construction of specialized, MRI-centered interventional radiotherapy departments is under way or in blueprint.