MRI Equipment
Generating Radio Waves from Water Molecules
Combined modalities and targeted contrast media are on the clinical horizon, but they will become a reality for specialist referral centers in the coming years.
MRI imaging has become the preferred diagnostic imaging method for imaging the central nervous system, particularly for detecting brain tumors, spine lesions, imaging blood vessels, and stroke-affected areas of the brain. Generating radio waves from water molecules in the body using a very powerful magnetic field, this technology has gained impetus from the keen interest shown by technology developers and manufacturers that wish to make it more patient friendly.
A 1.5T system continues to remain as the preferred choice for many of the diagnostic centers and smaller hospital setups to cover most of their clinical needs. Widespread use of 3T scanners is already becoming a reality and future developments in coil technology and new image contrasts will continue to provide new tools for clinical diagnosis.
The future holds good for MRI with ultra-high-field systems with 7T and 9.4T systems currently being evaluated. Combined modalities and targeted contrast media are further on the clinical horizon, but will become a reality for specialist referral centers in the coming years.
Research Updates
A substitute for serial biopsies in active prostate cancer surveillance. MRI may help monitor men with prostate cancer who are under active surveillance, according to a study published in the American Journal of Roentgenology. Researchers from Winthrop University Hospital, Mineola, N.Y., performed a study to report the multi-parametric MRI characteristics of prostate cancer patients who discontinued active surveillance after repeat imaging revealed possible evidence of tumor upgrading.
Two hundred patients with prostate cancer were being monitored with active surveillance; 114 patients had undergone an initial multi-parametric MRI study before active surveillance started and at least one follow-up multi-parametric MRI study performed after active surveillance began. The MRI findings were evaluated and correlated with pathology results, if available.
The results showed that 14 patients discontinued active surveillance because changes on follow-up MRI suggested progression of cancer. Seven of the 14 (50 percent) patients had a biopsy after follow-up multi-parametric MRI, and biopsy results led to tumor upgrading in six of the 14 (43 percent) patients. The duration of active surveillance ranged from 4 to 110 months. All patients received definitive treatment.
The researchers concluded the small number of patients with follow-up multi-parametric MRI findings showing worsening disease supports the role of MRI in patients with early stage prostate cancer. Multi-parametric MRI is useful in monitoring patients on active surveillance and may identify patients with clinically significant cancer amenable to definitive treatment.
Safe even for patients with non-MRI-conditional pacemakers or ICDs. Non-MRI-conditional pacemaker or ICD may not be a contraindication for MRI, according to a study published in The New England Journal of Medicine. Researchers from several states sought to determine the risks associated with MRI at a magnetic field strength of 1.5T for patients who had a pacemaker or ICD that was not approved by the Food and Drug Administration for MRI scanning, thereby considered to be non-MRI-conditional.
One thousand patients with pacemakers and 500 with ICDs were included in the study. The results showed that no deaths, lead failures, losses of capture, or ventricular arrhythmias occurred during MRI.
The researchers concluded that in their study, device or lead failure did not occur in any patient with a non-MRI-conditional pacemaker or ICD who underwent clinically indicated nonthoracic MRI at 1.5T, was appropriately screened, and had the device reprogrammed in accordance with the pre-specified protocol.
MRI detects breast cancer sooner than mammography. MRI screening improves early diagnosis of breast cancer among women who are at average risk for developing breast cancer, according to a study published in Radiology. Researchers from Germany performed a prospective observational study to investigate the utility and accuracy of breast MR imaging as a supplemental screening tool in women at average risk for breast cancer, as well as the types of cancer detected with MR imaging screening. The study included 2120 women who underwent 3861 screening MR imaging studies. The women, aged 40 to 70, had no breast cancer-associated risk factors. The study covered an observation period of 7007 women-years.
According to researchers, the results suggest that MRI can serve as a useful supplemental screening tool for women at average risk, especially those with dense mammographic tissue, and MRI is superior to supplemental ultrasound for this purpose. The results also highlight the ability of MRI in the detection of more aggressive types of cancer.
“The faster a cancer grows and the better it is in seeding metastases, the better will it be picked up early by MRI,” lead author Christiane Kuhl, MD, chair of the Department of Radiology at RWTH Aachen University in Aachen, Germany, said in a release, “In our cohort, cancers found by MRI alone exhibited features of rapid growth at pathology.”
Brain MRI may help diagnose cognitive disorder. Diffusion tensor imaging suggests subcortical disconnection within large-scale cognitive neural networks is a key mechanism of vascular cognitive disorder, according to a study in Radiology. Researchers from the United Kingdom investigated associations between neuroimaging markers of cerebrovascular disease, including lesion topography and extent and severity of strategic and global cerebral tissue injury, and cognition in carotid artery disease.
A total of 108 patients with symptomatic CAD participated in the study – 53 were cognitively impaired. All underwent MRI and the Addenbrooke’s Cognitive Examination–Revised. The results showed that the 53 cognitively impaired patients, classified as having probable vascular cognitive disorder, were older than nonimpaired patients. Lesion volumes did not correlate with global cognitive performance (lacunar infarctions, acute lesions, and chronic subcortical ischemic lesions). In contrast, cognitive performance correlated with presence of chronic ischemic lesions within the interhemispheric tracts and thalamic radiation. Skeleton mean diffusivity showed the closest correlation with cognition and promising diagnostic accuracy for vascular cognitive disorder. Findings were confirmed in subjects with a low risk of preclinical Alzheimer disease indexed by the absence of MTA (n=85).
The researchers concluded that subcortical white matter ischemic lesion locations and severity of ultrastructural tract damage contribute to cognitive impairment in symptomatic CAD, which suggests that subcortical disconnection within large-scale cognitive neural networks is a key mechanism of vascular cognitive disorder.
Way Forward
MRI systems have developed into the workhorse of high-quality diagnostic imaging and the applications of MRI have widened significantly toward functional imaging, real-time treatment monitoring for minimal invasive procedures using the unique contrast features of the method. As the use of MRI grows, physicians can expect to see an increase in the type of scans done with MRI. This phenomenon is also being driven by decreasing budgets. As radiology budgets get smaller, many healthcare providers are looking for equipment that gives them a variety of use cases for the price. MRI is expanding to different areas of medicine and the advantages of the technology continue to be realized, manufacturers and physicians can expect the market to grow around the world. New challenges are arising with significant changes and productivity pressure in healthcare delivery in the developed markets while the need for simplicity and ease of use is growing in the emerging markets.
Industry Speak
First Time Right Imaging with MRI
Raveendran Gandhi
Senior Director, Radiology, Health Systems, India,
Philips Healthcare
Recent developments in MRI are focused on addressing the challenges of MR imaging in a holistic way by delivering first time right imaging with superb patient experience. In fact, with time, patient experience inside the MRI magnet bore has become an active area of development to ensure high-quality motion-free images as well as reduced repeat scans. Many patients are anxious as they undergo an imaging exam. Anxiety can cause them to move unexpectedly or fail to comply with proper scan protocols, increasing the likelihood that they will need to repeat the entire process all over again. Reducing patient – and staff – anxiety during that initial scan, therefore, goes hand-in-hand with getting the right image the first time.
Portions of MRI examinations are very sensitive to patient motion and require the patient to be absolutely still. Any motion can distort the exam, making it very difficult to obtain and read high-quality images with MRI. This can be challenging for claustrophobic patients and young children. An exciting new innovation is the ambient experience patient in-bore solution. This new solution is designed to help patients relax and hold still during the MRI examination. Through an immersive video experience that distracts and entertains patients while they are in the bore, you can enhance patient cooperation and workflow, and deliver an experience that elevates patient comfort.
For many patients, gradient noise is one of the most uncomfortable parts of an MRI exam. New techniques such as ComforTone automatically provide up to 80 percent noise reduction within the same time and virtually the same image quality and contrast.
Another technological advancement is dStream digital broadband architecture. It digitizes the signal right in the coil, eliminating noise influences typical of analog pathways, to capture the MR signal without pre-distortion or compression. A fiber-optic connection from the coil to the image reconstructor enables lossless broadband data transmission. This technology enables high-quality images with remarkable speed as it provides 40 percent more signal-to-noise ratio and enhances patient comfort by completing the exam in a much shorter time.
Industry Speak
Workstations in Medical Imaging
Dr TBS Buxi
Chairman CT & MRI Departments,
Sir Ganga Ram Hospital, New Delhi
With advances in computers, radiology has transformed from films to digital. It has been possible to make this switch by the use of workstations, which are capable of handling a lot of data and allow viewing in any plane with ability to do multi-planar and three-dimensional reconstructions. The evolution of DICOM has standardized medical images and made them compatible between different modalities. Various types of workstations are available but generically these can be divided into two types, the thin client and the thick client. Thick clients are developed in a manner similar to the X Box gaming consoles and Play stations. Computer graphics hardware and the software with high-performance capabilities is the basis of their workstations. On the other hand, thin clients are web enabled and also provide computing resources using a remote set of host computers. The thin client workstations are just networked computers without a hard disk drive and are hence cheaper. They are simple terminals to the server and require constant communication with it at all times. They are easy to install as they do not require any specialized software, and run exactly as specified by the server.
Technology has had a significant impact on clinical practice, and special image-guided therapy workstations have been developed. Model-based therapies have come into practice wherein imaging information from various sources can be used to construct an abstract integrated model. These are more practical than just achieved films. Radiotherapy workstations offer virtual simulation, dosimetry, and treatment planning for optimizing the therapy delivered. Similarly, surgical navigation systems help plan minimally invasive surgeries with liver fluoroscopic images. Robotic surgeries and high-intensity focused ultrasound surgeries (HIFU) are only some of the advancements witnessed.
The latest workstations offer a broad set of applications covering multiple clinical domains, a multifaceted view with a single multimodality solution, work consistently and efficiently, integrate with the hospital PACS and information system, easy access from any computer, and integrate datasets from multiple vendors resulting in saving valuable time of the radiologist. These offer new measurement and interpretation tools with enhanced segmentation support confident diagnosis and clinical depth. The faster transfer and enhancements with automatic creation of MPR and volume-based images streamline workflow, and combine MR, CT, and PET images of tumor tracking. VNA and HL 7 integrations tie the workstations to the hospital network with advanced analysis – beyond the reading room. Newer post-processing software like CT Liver Analysis perform faster liver segmentation and volumetry resulting in quicker planning for resections and RF Ablations. Zero-click bone removal helps focus on vascular structures with MPR and volume images even before the study is opened. Fully automated segmentation tool can transform the heart in MR cardiac study into individual segments within seconds.
Multimodality viewer with multimodality tumor tracking can help share bookmarks, transfer studies, and collaborate in real time. Newer applications on the block like CT TAVI planning, CT comprehensive cardiac analysis, MR Q Flow, CT EP planning, CT-MI cardiac fusion, CT dynamic myocardial perfusion, CT myocardial defect assessing, MR cardiac temporal enhancement, and NM Astonish Reconstruction lower evaluation time. Comprehensive neurology applications like iMR and BOLD allow visualization of brain activation maps, fiber tracking with user-defined tracts, and overlay with functional maps. CT Brain perfusion to salvage brain tissue with fast time-critical decisions. Newer tools help analyze and automatically calculate FDG and amyloid PET uptake differences in two PET scans for interpretation of neurological degenerative diseases. Newer oncology tools include CT lung nodule assessment, MR Snoface permeability, US Microvascular Imaging, US Elastography analysis, and Quantification. Complicated orthopedic applications offered are CT-Acute multifunctional review, CT Bone mineral analysis, MR cartilage assessment, and MR-Echo accumulation. Advanced CT COPD helps track diffuse lung disease, localize specific areas, determine total and segmented lung volumes, measure airway parameters, and CT pulmonary artery analysis to visualize lungs and calculate heart chamber volumes in patients of pulmonary embolism. To exploit full potential of advanced visualization and analysis by a server-based, single-license, managed solution is desired. These can be scaled up at any time by networking to multiple servers and are the order of the day.
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