Magnetic resonance imaging (MRI) is experiencing remarkable innovation. From better images, faster scans, and automated workflows to more powerful applications that will transform clinical imaging, MRI is getting smarter.
A new technique shows cancerous tissue glowing in medical images, allowing doctors to identify it and track its progression over time. It could also help with tumor treatment planning.
Coil Design
MRI is a diagnostic imaging technique that uses magnetic fields to visualize and assess the structure and function of tissues. Its noninvasive nature makes it ideal for a wide range of neuroscience studies and clinical diagnoses of neurological disorders, such as multiple sclerosis and Alzheimer’s disease.
Using a powerful magnet, MRI scanners create images by temporarily magnetizing the body, then detecting the radiofrequency signals that hydrogen atoms in tissue molecules excite and then return. Computers process the information to make detailed pictures of internal structures.
Magnetic resonance imaging (MRI) scans can reveal the presence of tumors, vascular problems, spinal cord injuries and more. However, the ability to detect these problems depends on how much detail the MRI can capture. New MRI technology, such as 7T and 10T systems, increases the image resolution and signal-to-noise ratio for more accurate diagnosis.
To improve the quality of MRI results, some imaging techniques use special coils designed to target specific body parts and enhance image contrast. The type of coil used can affect the image brightness, signal-to-noise ratio (SNR) and spatial resolution.
Conventional fat saturation with spectral selection of the fat peak based on CHESS (chemical shift selective) sequences may produce poor results in dorsal spine imaging, so researchers developed a new MRI preparation called SPAIR (spectral attenuated inversion recovery) that eliminates the fat signal without affecting image brightness and SNR.
In order to achieve high SNR and good spatial resolution in ex vivo brain samples, radiofrequency coils need to have maximized filling factors that are difficult to obtain in ultrahigh field whole-body scanners. RF solenoids are a potential solution because they can be constructed from a single transmitter and receive coil.
Intraoperative MRI
Unlike X-rays, MRI uses powerful magnets and radio waves to capture images of the body’s soft tissue and bone structures without exposing patients to radiation. It can be used to examine the brain and spinal cord, blood vessels, joints, muscles and other organs. It can also capture images of brain activity related to thinking and consciousness (functional magnetic resonance imaging).
MRI is often the first choice for examining a brain tumor, stroke, seizure disorder or other neurological condition because it provides detailed information about the location and type of a disease. It can help doctors decide whether surgery or another treatment is best for the patient. It can also be used to place brain stimulators to treat epilepsy, essential tremor, dystonia and Parkinson’s disease.
One of the biggest advancements in MRI has been making scans faster while maintaining image quality. A new technique called compressed sensing reduces scan time by a factor of four, which makes it much more convenient for people who can’t lie still for long periods of time.
Another way to improve MRI is to make it more sensitive, which can help doctors diagnose cancer and other diseases earlier. Another innovation, known as radial fMRI, makes it easier to locate cancerous cells within tissues.
Other MRI techniques include Diffusion Tensor Imaging (DTI) and Magnetic Resonance Spectroscopy (MRS). DTI measures the diffusion of water molecules to provide information about the anatomy of nerve fiber connections in the brain and spinal cord. It can help identify areas of demyelination, which occurs in conditions like multiple sclerosis and traumatic brain injury. MRS can detect the presence of certain chemicals in the brain, such as glucose and amino acids, which may play a role in dementia, Alzheimer’s disease and depression.
Functional MRI
A magnetic field and radio waves pass through the body, and a computer then makes images of tissue structures based on the resulting signal that’s returned to the magnet. The MRI technique allows physicians to visualize organs and soft tissues without using radiation (as in X-ray or ultrasound) and is used throughout biomedicine.
For example, the blood-oxygen level-dependent functional MRI (fMRI) technique detects brain activity by tracking changes in blood flow as the brain works. When your brain is working hard, certain parts use more oxygen, and this results in a larger fMRI signal that shows up on the scan. MRI imaging technology allows doctors to see this brain activity in a noninvasive way, helping them identify and diagnose disorders like multiple myeloma and Parkinson’s disease.
MRI is also an excellent tool to monitor patients’ recovery after surgery or injury and to assess the effectiveness of treatment. A recent innovation in MRI technology, called compressed sensing, allows for high-resolution scans to be completed in less time. This is a major advance in MRI that could lead to better patient care by speeding up the diagnostic process.
During an MRI scan, you will lie down on your back and remain completely still. Because an MRI machine is a large, powerful magnet, you must remove all metal items including jewelry, piercings, credit cards and cell phones, as they can interfere with the quality of the image. Your healthcare provider will give you specific instructions about preparing for your scan. If you are nervous or anxious about an MRI or have trouble lying down, your healthcare provider can discuss sedatives and other ways to help you relax during the procedure.
Diffusion Tensor Imaging (DTI)
Diffusion tensor imaging is an MRI technique that measures diffusion of water molecules within tissues. It allows direct in vivo examination of the directional distribution of complex tissue network, such as white matter tracts of the brain. It also provides substantial insight into the status of axon myelination and its relation to neuropathological conditions such as multiple sclerosis.
DTI can visualize the structural connectivity of the brain, a powerful tool for studying traumatic brain injury and neurological disorders like multiple sclerosis and Alzheimer’s disease. Advanced DTI techniques such as high-angular-resolution diffusion imaging improve nerve fiber mapping and help doctors understand how structures in the brain interact.
Researchers have recently developed a new technology called synthetic correlated diffusion imaging that highlights differences between cancerous and noncancerous tissue. It works by capturing, synthesizing and mixing MR signals at different gradient pulse strengths and timings. This approach, which is similar to functional MRI in its ability to highlight changes in blood flow, shows abnormalities that would not otherwise be apparent.
MRI technology is constantly being improved. In the future, we may see scanners that are smaller and more portable, with a lower price tag. The newest open-bore 3T MRI machine, for example, is being delivered to Texas A&M this spring and will be a standout for orthopedic imaging, particularly in the hands and feet. It can also be used for prostate exams and has a more comfortable setup that alleviates claustrophobia and makes it easier for patients with limb disabilities to lie down.
MRI is a safe, noninvasive technology that uses magnetic fields and radio waves to detect changes in tissue composition and structure. It can detect a wide range of diseases, from heart attacks and stroke to multiple sclerosis and cancer, and it can help guide surgical procedures. It can also pinpoint tumors that might be missed by other tests, such as a biopsy or CT scan.
Magnetic Resonance Spectroscopy (MRS)
Magnetic resonance spectroscopy (MRS) is an imaging technique that allows doctors to analyze the chemical composition of the body tissue. This allows doctors to detect changes in the brain and other organs resulting from disease or injury. In addition to producing 3D images, MRS produces a spectrum that displays the types and amounts of chemicals being detected. The three main peaks seen in MRS are N-acetyl-L-aspartate (NAA), creatine-phosphocreatine (Cr) and choline-containing compounds. This analysis has been used in the evaluation of a variety of neurological disorders such as Alzheimer’s disease, seizures, and strokes, as well as cancer and other diseases affecting the liver, kidneys and heart.
A recent meta-analysis of MRS in breast cancer showed variable sensitivity and high specificity. However, significant publication bias may have contributed to the heterogeneity of results. The authors recommend that future MRS studies incorporate multimodality techniques and use more standard methods of data acquisition, which can improve diagnostic accuracy and sensitivity.
MRS can be performed using most commercially available MRI scanners. However, a probe accessory is required. The accessory has received 510(k) clearance from the FDA.
A recent study by Beadle and Frenneaux found that 31-phosphorous MRS is useful for noninvasive assessment of cardiac metabolism and characterization of the myocardium without the need for radioactive tracers. This technique can also be used in conjunction with intraoperative MRI.
