MRI scanners

Although the technology of an MRI scanner is rather sophisticated it does what we have seen other NMR spectrometers do it detects protons Thus MRI IS especially sensitive to biological materials such as... 

Figure 6 Transverse MR images of axillary-subscapular lymph node area in the rabbit 4 min after s.c. administration of PEG (5 kDa) -phosphatidyl ethanolamine micelles containing coreincorporated Gd-loaded amphiphilic chelate DTPA-phosphatidyl ethanolamine. The dose was 0.5 pmol Gd per injection site. Fast and clear visualization of both lymph vessel (1) and lymph node (2) was achieved. Images were acquired by using a 1.5 Tesla GE Signa MRI scanner operated at fat suppression mode and Ti-weighted pulse sequence [20].

For these studies, standard MRI scanners can be used to target the brain structures and to verify the BBBD. The only requirements are that the system has adequate space for the sonication system and high enough resolution to image animal brain. 

Claustrophobia typically MRI scanners require the patient to he in a long narrow tube, placing them in the centre of the magnet. As MRI scanning can take some time, people with even mild claustrophobia can find it a difficult experience and sedation/general anaesthesia may be required. 

Noise levels MRI scanners used rapidly switching magnetic gradients and as the coils expand and contract, high auditory noises and vibrations, which can reach 130dB (the sound intensity of a jet engine), can be emitted, so appropriate ear protection is required. 

RF burns although very rare, exposure to the MRI scanner s powerful radio transmitter has been reported to cause bums, and the risk of hyperthermia is increased in children or the elderly. 

MRI is a versatile method and in addition to uses in diagnostic medicine, it is important to note that while MRI is best known as a medical tool, this technique has other useful scientific applications. As an example, geologists have used MRI to examine the composition of geological stmctures, and MRI has also been exploited in assessment of produce and timber quality. However, as noted earlier, MRI scanners cost millions to buy and thousands to run and maintain, so remain a luxury big-budget item. 

Lymphography is rarely required with the availability of modern CT and MRI scanners. However, intradermal injection of 2-4 ml (iodine 300 mg/ml) of iso-osmolar non-ionic dimers (iotrolan and iodixanol) at a rate of 0.1 ml/minute can be used to assess the lymphatics in limbs with lymphedema. The procedure is safe with no serious adverse effects, but idiosyncratic and allergic like reactions can occur. 

NMR has become an important tool in medical diagnosis because it allows physicians to probe internal organs and structures without invasive surgical methods or the harmful ionizing radiation of X-rays. When NMR was first introduced into clinical practice in 1981, the selection of an appropriate name was a matter of some debate. Because some members of the public associate nuclear processes with harmful radiation, the N was dropped from the medical application of NMR, now known as magnetic resonance imaging (MRI). The spectrometer is called an MRI scanner. 

A recently developed pinhole high-resolution SPECT system and a 1.5 T clinical MRI scanner with a specially developed surface coil were used for rats (n = 9) after injection of the dopamine transporter ligand I-FP-CIT. The SPECT images showed clear striatal uptake. On the MR images, cerebral and extra-cerebral structures could be easily delineated. 

An MRI scanner is an NMR machine large enough to accommodate a human being, has a powerful magnet, operates in the pulse-FT mode, and detects protons—usually the protons in water and, to a lesser extent, lipids. The principles are the same as those of conventional FT-NMR spectroscopy but, because the goal is different, the way the data are collected and analyzed differs too. Some key features of MRI include ... 

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