Molecular Imaging is a new diagnostic discipline to visualize biological processes.
Molecular magnetic resonance imaging (mMRI) offers the potential to image tissues at the cellular and subcellular level. Targeted MR contrast agents enhance the diagnostic specificity and range of molecular magnetic resonance imaging.
Other modalities that can be used for noninvasive molecular imaging:

See also Nanoparticle, Monocrystalline Iron Oxide Nanoparticle, Polycrystalline Iron Oxide Nanoparticles, Liposomes, Monoclonal Antibodies, Bimodal Imaging, Tumor Specific Agents, and Intracellular Contrast Agents.

(LE) Myocardial late enhancement in contrast enhanced cardiac MRI has the ability to precisely delineate myocardial scar associated with coronary artery disease. Viability imaging implies evaluating infarcted myocardium to see whether there is enough viable tissue available for revascularization. The reversal of myocardial dysfunction is particularly relevant in patients with depressed ventricular function because revascularization improves long-term survival. In comparison to SPECT and PET imaging, myocardial late enhancement MRI demonstrates areas of delayed enhancement exactly in correlation with the infarcted region.
Viability on cardiac MRI (CMR) is based on the fact that all infarcts enhance vividly 10-15 minutes after the administration of intravenous paramagnetic contrast agents. This enhancement represents the accumulation of gadolinium in the extracellular space, due to the loss of membrane integrity in the infarcted tissue. This phenomenon of delayed hyperenhancement has been proven to correlate with the actual extent of the infarct.
MRI myocardial late enhancement can quantify the size, location and transmural extent of the infarct. If the transmural extent of the infarct (region of enhancement on MRI) is less than 50% of the wall thickness, there will be improved contractility in that segment following revascularization. In areas of hypokinesia, if there is a rim of "black" or non-infarcted myocardium that is not contracting well, it indicates the presence of hibernating myocardium, which is likely to improve after revascularization of the artery supplying that particular territory.
The total duration of a myocardial late enhancement MR imaging protocol for viability is approximately 30 minutes, including scout images, first-pass images, cine images in two planes, and delayed myocardial enhancement images. In order to assess viable myocardium, the gadolinium contrast agent is injected at a dose of 0.15 to 0.2 mmol/kg. After about 10 minutes, short axis and long axis views (see cardiac axes) of the heart are obtained using an inversion prepared ECG gated gradient echo sequence. The inversion pulse is adjusted to suppress normal myocardium. Areas of nonviable myocardium retain extremely high signal intensity, black areas show normal tissue.

For Ultrasound Imaging (USI) see Myocardial Contrast Echocardiography at Medical-Ultrasound-Imaging.com.

Quadrature detection is used in magnetic resonance imaging as well as in Doppler ultrasound and is also called quadrature demodulation or phase quadrature technique.
With this phase sensitive demodulation technique the complex demodulated signal is separated into two components. One is called the real channel; the second part is called the imaginary channel and is located 90° away from the real channel. The signals from both channels are combined to produce a single set of quadrature detected real and imaginary spectra. In MRI, the parts of the demodulated MR signal are further processed by Fourier transformation analysis. All information on the MR signal components e.g. amplitude, phase, and frequency is given by this quadrature detection combined with Fourier analysis.

MRI of the shoulder with its excellent soft tissue discrimination, and high spatial resolution offers the best noninvasive way to study the shoulder. MRI images of the bone, muscles and tendons of the glenohumeral joint can be obtained in any oblique planes and projections. MRI gives excellent depiction of rotator cuff tears, injuries to the biceps tendon and damage to the glenoid labrum. Shoulder MRI is better than ultrasound imaging at depicting structural changes such as osteophytic spurs, ligament thickening, and acromial shape that may have predisposed to tendon degeneration.
A dedicated shoulder coil and careful patient positioning in external rotation with the shoulder as close as reasonably possible to the center of the magnet is necessary for a good image quality. If possible, the opposite shoulder should be lifted up, so that the patient lies on the imaged shoulder in order to rotate and fix this shoulder to reduce motion during breathing.
Axial, coronal oblique, and sagittal oblique proton density with fat suppression, T2 and T1 provide an assessment of the rotator cuff, biceps, deltoid, acromio-clavicular joint, the glenohumeral joint and surrounding large structures. If a labral injury is suspected, a Fat Sat gradient echo sequence is recommended. In some cases, a direct MR shoulder arthrogram with intra-articular injection of dilute gadolinium or an indirect arthrogram with imaging 20 min. after intravenous injection may be helpful.

See also Imaging of the Extremities.

The range of diagnostics and imaging systems of Siemens Medical Systems covers ultrasound, nuclear medicine, angiography, magnetic resonance, computer tomography and patient monitoring. Siemens is one of the three leading MRI manufacturers, which together account for approximately 80 percent of the MRI machines installed worldwide. Siemens currently offers the Allegra 3T MRI, which is for head scanning only, but the company will also be launching the Trio MRI, a 3T whole body scanner.
Siemens has formed partnerships with more than ten research institutions and private practitioners to define a comprehensive MRI examination and compare MR to currently established cardiovascular modalities, thereby defining optimal diagnosis and treatment.

MRI Scanners:

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