• contrast
  • Exogenous contrast agents may be given to the person to make the image clearer. (wikipedia.org)
  • These are high resolution still images which in certain circumstances identify abnormal myocardium through differences in intrinsic contrast. (wikipedia.org)
  • Compare the image orientation (4 chamber) with the short axis view of the movie above Scar is best seen after giving a contrast agent, typically one containing gadolinium bound to DTPA. (wikipedia.org)
  • Contrast agents may also be directly injected into a joint in the case of arthrograms, MRI images of joints. (wikipedia.org)
  • Phase contrast magnetic resonance imaging (PC-MRI) is a specific type of magnetic resonance imaging used primarily to determine flow velocities. (wikipedia.org)
  • Conventional qualitative interpretation of Fourier Analysis asserts that low spatial frequencies (near the center of k-space) contain the signal to noise and contrast information of the image, whereas high spatial frequencies (outer peripheral regions of k-space) contain the information determining the image resolution. (wikipedia.org)
  • in this way, different contrast images can be acquired without the need of running full scans. (wikipedia.org)
  • A nice symmetry property exists in k-space if the image magnetization Mxy is prepared to be proportional simply to a contrast-weighted proton density and thus is a real quantity. (wikipedia.org)
  • Due to the high contrast between the blood pool and the myocardium it is common to get what looks like a thin subendocardial area of ischaemia called the Gibbs artifact, this however, is less common with newer technology allowing higher resolution imaging. (wikipedia.org)
  • The factors leading to image contrast (differences in tissue relaxation time values) had been described nearly 20 years earlier by Erik Odeblad (physician and scientist) and Gunnar Lindström. (wikipedia.org)
  • Next, endogenous contrast mechanisms were discovered by Detre, Koretsky, and colleagues was based on the net longitudinal magnetization within an organ, and a "second based on changes in the magnetic susceptibility induced by changing net tissue deoxyhemoglobin content", which has been labeled BOLD contrast by Siege Ogawa. (wikipedia.org)
  • selective
  • FLASH reduced the typical sequence interval to what is minimally required for imaging: a slice-selective radio-frequency pulse and gradient, a phase-encoding gradient, and a (reversed) frequency-encoding gradient generating the echo for data acquisition. (wikipedia.org)
  • reconstruction
  • In terms of MRI, signals with different spatial encodings that are required for the reconstruction of a full image need to be acquired by generating multiple signals - usually in a repetitive way using multiple radio-frequency excitations. (wikipedia.org)
  • Most recently, highly undersampled radial FLASH MRI acquisitions have been combined with an iterative image reconstruction by regularized nonlinear inversion to achieve real-time MRI at a temporal resolution of 20 to 30 milliseconds for images with a spatial resolution of 1.5 to 2.0 millimeters. (wikipedia.org)
  • excitation
  • An MR image is a complex-valued map of the spatial distribution of the transverse magnetization Mxy in the sample at a specific time point after an excitation. (wikipedia.org)
  • Only the combination of (i) a low-flip angle excitation which leaves unused longitudinal magnetization for an immediate next excitation with (ii) the acquisition of a gradient echo which does not need a further radio-frequency pulse that would affect the residual longitudinal magnetization, allows for the rapid repetition of the basic sequence interval and the resulting speed of the entire image acquisition. (wikipedia.org)
  • frequency
  • Certain atomic nuclei are able to absorb and emit radio frequency energy when placed in an external magnetic field. (wikipedia.org)
  • First, energy from an oscillating magnetic field temporarily is applied to the patient at the appropriate resonance frequency. (wikipedia.org)
  • When the radio frequency pulse is turned off, the transverse vector component produces an oscillating magnetic field which induces a small current in the receiver coil. (wikipedia.org)
  • Thus k-space information is somewhat redundant then, and an image can be reconstructed using only one half of the k-space, either in the PE (Phase Encode) direction saving scan time (such a technique is known as half Fourier or half scan) or in the FE (Frequency Encode) direction, allowing for lower sampling frequencies and/or shorter echo times (such a technique is known as half echo). (wikipedia.org)
  • Interaction of the magnetic and radio frequency fields with such objects may lead to heating or torque of the object during an MRI. (wikipedia.org)
  • coils
  • The radio signal may be made to encode position information by varying the main magnetic field using gradient coils. (wikipedia.org)
  • The major components of an MRI scanner are: the main magnet, which polarizes the sample, the shim coils for correcting shifts in the homogeneity of the main magnetic field, the gradient system which is used to localize the MR signal and the RF system, which excites the sample and detects the resulting NMR signal. (wikipedia.org)
  • Due to the magnetic Lorentz force from B0 on the current flowing in the gradient coils, the gradient coils will try to move. (wikipedia.org)
  • coil
  • this arrangement improves image quality by increasing radio signal strength, since the coil is located close to the tissue being examined. (britannica.com)
  • Endorectal coil magnetic resonance imaging or endorectal coil MRI is a type of medical imaging in which MRI is used in conjunction with a coil placed into the rectum in order to obtain high quality images of the area surrounding the rectum. (wikipedia.org)
  • nuclei
  • The nuclei absorb this energy and flip out of alignment with the magnetic field. (springer.com)
  • The brighter the area of the image, the more intense the signal which is related to the quantity of nuclei present in the sample and to their environment. (springer.com)
  • patient's
  • On 28 August 1980 they used this machine to obtain the first clinically useful image of a patient's internal tissues using MRI, which identified a primary tumour in the patient's chest, an abnormal liver, and secondary cancer in his bones. (wikipedia.org)
  • blood vessels
  • MRI is used to image every part of the body, and is particularly useful for neurological conditions, for disorders of the muscles and joints, for evaluating tumors, and for showing abnormalities in the heart and blood vessels. (wikipedia.org)
  • tissues
  • Different tissues respond to the added energy in different ways, and imaging parameters can be adjusted to highlight desired tissues. (wikipedia.org)
  • typically
  • Since modern PC-MRI is typically time-resolved, it provides a means of 4D imaging (three spatial dimensions plus time). (wikipedia.org)
  • Typically, k-space has the same number of rows and columns as the final image and is filled with raw data during the scan, usually one line per TR (Repetition Time). (wikipedia.org)
  • acquisition
  • In this system, a data acquisition section is operated under the control of a control section only while the patient stands still in response to the announcement of the announcement section, thereby intermittently acquiring magnetic resonance data in units of a predetermined volume. (google.de)
  • This can be described by: S N R v = π 2 v v e n c S N R {\displaystyle SNR_{v}={\frac {\pi }{\sqrt {2}}}{\frac {v}{v_{enc}}}SNR} where S N R {\displaystyle SNR} is the signal-to-noise ratio of the image (which depends on the magnetic field of the scanner, the voxel volume, and the acquisition time of the scan). (wikipedia.org)
  • In practice, k-space often refers to the temporary image space, usually a matrix, in which data from digitized MR signals are stored during data acquisition. (wikipedia.org)
  • The acquisition of the images is very sensitive to the rhythm of the heart and scans of patients with atrial fibrillation, bigeminy or trigeminy will sometimes be of low quality and may not be interpretable. (wikipedia.org)
  • One company, Cubresa, offers an MR-compatible preclinical PET scanner called NuPET™ for use in the bore of an existing MRI, enabling simultaneous PET/MR image acquisition. (wikipedia.org)
  • A preclinical PET-MRI system with sequential acquisition is commercially available from Mediso Medical Imaging Systems since 2011. (wikipedia.org)
  • In either case, repetition times are as short as 2 to 10 milliseconds, so that the use of 64 to 256 repetitions results in image acquisition times of about 0.1 to 2.5 seconds for a two-dimensional image. (wikipedia.org)
  • structures
  • the use of electromagnetic radiation to produce images of internal structures of the human body for the purpose of accurate diagnosis. (britannica.com)
  • signal
  • This difference leads to an improved MR signal since the diamagnetic blood interferes with the magnetic MR signal less. (wikipedia.org)
  • medical
  • How can somebody know so much about medical imaging and not know that mitosis occurs in animals? (conservapedia.com)
  • Medical devices and implants are categorized as MR Safe, MR Conditional or MR Unsafe: MR-Safe - The device or implant is completely non-magnetic, non-electrically conductive, and non-RF reactive, eliminating all of the primary potential threats during an MRI procedure. (wikipedia.org)
  • The Erwin L. Hahn Institute for Magnetic Resonance Imaging is a research institute which develops magnetic resonance imaging (MRI) for both cognitive neuroscience and medical diagnosis and treatment. (wikipedia.org)
  • technology
  • With the support of Pfizer, Diasonics, and later Toshiba America MRI, the lab developed new imaging technology and installed systems in the US and worldwide. (wikipedia.org)
  • interval
  • means for controlling said data collecting means to collect the magnetic resonance data while said movement of the object is halted, and to repeat said collection of data correlated with said halting of the movement a predetermined number of times in accordance with said predetermined interval, until the requisite resonance data for forming said magnetic resonance image is obtained. (google.de)
  • scanner
  • The aforementioned NuPET™ MR-compatible preclinical scanner from Cubresa is designed to fit into a variety of existing MRI magnets, including those originally used for clinical imaging. (wikipedia.org)
  • signals
  • These signals are converted into an image, and during a single session a doctor collects a series of images, often from several different angles. (britannica.com)
  • scan
  • In some cases, it can provide clear images of body parts that can't be seen as well with an X-ray, CAT scan, or ultrasound. (kidshealth.org)
  • This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow ( hemodynamic response ) related to energy use by brain cells. (wikipedia.org)
  • When k-space is full (at the end of the scan) the data are mathematically processed to produce a final image. (wikipedia.org)