Bethel Road Open MRI  |  Services   |  Doctors

Committed to providing the latest advancement in MR scanning, Bethel Road High-Field Open MRI has installed Hitachi's Altaire MR imaging system. The Altaire is a high-field performance Open MR system that provides advanced magnetic resonance imaging capabilities with a number of unique features and benefits for both patients and physicians.

Focused on providing the ultimate in patient comfort, Bethel Road High-Field Open MRI's Altaire system uses a wide-open design offering a panoramic view out all four sides to create a relaxing environment. This open design alleviates claustrophobia and anxiety stress and allows a friend, loved one or healthcare professional to be seated at the patient's side during the exam.

---

Services

Magnetic resonance imaging (MRI) is a method of creating images of the inside of opaque organs in living organisms as well as detecting the amount of bound water in chemical structures. It is primarily used to visualise pathological or other physiological alterations of living tissues as well as to estimate the permability of rock to hydrocarbons. It is now a commonly used form of medical imaging.

Nomenclature

Magnetic resonance imaging was developed as an offshoot of nuclear magnetic resonance. The original name for the technology was nuclear magnetic resonance imaging (NMRI), but the term nuclear was dropped because it was thought that it carried negative connotations from its usage in other contexts (nuclear warfare, nuclear waste, nuclear winter, nuclear meltdown et cetera). Physicists in universities and such settings still speak of NMR when discussing non-medical devices operating on the same principles.

Principles

First, the spins of the atomic nuclei of the tissue molecules are aligned in a powerful magnetic field. Then, radio frequency pulses are applied in a plane perpendicular to the magnetic field lines so as to cause some of the hydrogen nuclei to change alignment. The frequency of the radio wave pulses used is governed by the Larmor Equation. Magnetic field gradients are then applied in the 3 dimensional planes to allow encoding of the position of the atoms. After this, the radio frequency is turned off and the nuclei go back to their original configuration but, as they do so, they release radio frequency energy which can be picked up by coils wrapped around the patient. These signals are recorded and the resulting data are processed by a computer to generate an image of the tissue. Thus, the examined tissue can be seen with its quite detailed anatomical features. In clinical practice, MRI is used to distinguish pathologic tissue such as a brain tumor from normal tissue.

The technique most frequently relies on the relaxation properties of magnetically-excited hydrogen nuclei in water. The sample is briefly exposed to a burst of radiofrequency energy, which in the presence of a magnetic field, puts the nuclei in an elevated energy state. As the molecules undergo their normal, microscopic tumbling, they shed this energy to their surroundings, in a process referred to as "relaxation." Molecules free to tumble more rapidly relax more rapidly.

T1-weighted MRI scans rely on relaxation in the longitudinal plane, and T2 weighted MRI scans rely on relaxation in the transverse plane. Differences in relaxation rates are the basis of MRI images--for example, the water molecules in blood are free to tumble more rapidly, and hence, relax at a different rate than water molecules in other tissues. Different scan sequences allow different tissue types and pathologies to be highlighted. A contrast agent is sometimes injected in the sample to augment these differences and improve sensitivity.

Advantages

One of the advantages of an MRI scan is that, according to current medical knowledge, it is harmless to the patient. It only utilizes strong magnetic fields and non-ionizing radiation in the radio frequency range. Compare this to CT scans and traditional X-rays which involve doses of ionizing radiation. It must be noted, however, that the presence of a ferromagnetic foreign body (say, shell fragments) in the patient, or a metallic implant (like surgical prostheses, or pacemakers) can present a (relative or absolute) contraindication towards MRI scanning: interaction of the magnetic and radiofrequency fields with such an object can lead to mechanical or thermal injury, or failure of an implanted device.

MRI allows to manipulate the spins in many different ways, each yielding a specific type of image contrast and information. With the same machine a variety of scans can be made and a typical MRI examination consists of several such scans.

Another advantage of MRI is that the contrast resolution of soft tissues is much better than in CT, leading to higher-quality images, especially in brain and spinal cord scans. The spatial resolution achieved per second of scanning time, however, is better in CT, giving this modality the advantage in assessing, e.g., bony abnormalities.

Nobel prize (2003)

Reflecting the fundamental importance and applicability of MRI in the medical field, Paul Lauterbur and Sir Peter Mansfield were awarded the 2003 Nobel Prize in Medicine for their discoveries concerning MRI. Lauterbur discovered that gradients in the magnetic field could be used to generate two-dimensional images. Mansfield analyzed the gradients mathematically. The Nobel Committee ignored Raymond V. Damadian, who demonstrated in 1971 that MRI can detect cancer and filed a patent for the first whole-body scanner, which he successfully defended against infringement by General Electric with an award of $129 million in 1997, and settling out of court for further millions from other MRI scanner manufacturers.

Specialised MRI scans

Magnetic resonance spectroscopy (MRS) is a technique which combines the spatially-addressable nature of MRI with the spectroscopically-rich information obtainable from nuclear magnetic resonance (NMR). That is to say, MRI allows one to study a particular region within an organism or sample, but gives relatively little information about the chemical or physical nature of that region--its chief value is in being able to distinguish the properties of that region relative to those of surrounding regions. MR spectroscopy, however, provides a wealth of chemical information about that region, as would an NMR spectrum of that region.

Functional MRI (fMRI) measures signal changes in the brain that are due to changing neural activity. The brain is scanned at low resolution but at a rapid rate (typically once every 2-3 seconds). Increases in neural activity cause changes in the MR signal via a mechanism called the BOLD (blood oxygen level-dependent) effect. Increased neural activity causes an increased demand for oxygen, and the vascular system actually overcompensates for this, increasing the amount of oxygenated hemoglobin relative to deoxygenated hemoglobin. Since deoxygenated hemoglobin reduces MR signal, the vascular response leads to a signal increase that is related to the neural activity. The precise nature of the relationship between neural activity and the BOLD signal is a subject of current research. The BOLD effect also allows to generate high resolution 3D maps of the venous vasculature of the human brain.

Diffusion MRI measures the diffusion of water molecules in biological tissues. In an isotropic medium (inside a glass of water for example) water molecules naturally move according to Brownian motion. In biological tissues however the diffusion is very often anisotropic. For example a molecule inside the axon of a neuron has a low probability to cross a myelin membrane. Therefore the molecule will move principally along the axis of the neural fiber. Conversely if we know that molecules locally diffuse principally in one direction we can make the assumption that this corresponds to a set of fibers. Diffusion MRI is a tool for scientists (and medical doctors) to study connections in the brain. Diffusion MRI is still at the research stage. The problem of finding a fiber from a Diffusion MRI image is called tractography.

Because of the lack of deleterious effects on the patient and the operator alike, MRI is well suited for interventional radiology, where the images produced by an MRI scanner are used to guide a minimally invasive procedure intraoperatively and/or interactively. The non-magnetic environment required by the scanner, and the strong magnetic radiofrequency and quasi-static fields generated by the scanner hardware necessitate the use of specialized instruments.

^ Top ^

---

Doctors

^ Top ^