MAGNETIC RESONANCE


 

The high-field MR release a very scenic examination in a short time (a few minutes), often avoiding the anesthesia, and particularly by providing accurate and useful diagnostic material for the clinic. The functional MR is an example of how the high-field MR is distinguished by wealth of information obtainable in a short time.



DIFFUSION  The MR is a method very sensitive in recognizing the minimum spontaneous movements of the water molecules (about 1 mm/minute/37 ° C). The movement of water across cell membranes is determined by passive (simple diffusion) and active (ion transporters) factors. A reduction in the efficiency of the mechanisms of cellular active transport occurs in vascular disease and in neoplastic disease due to, respectively, hypoperfusion hypoxia or abnormal cell density. In these conditions the reduced diffusion of water explains as an early and marked increase of involved structure signal. The acquisition of MR images dependent on the diffusion of the whole body, completed in 3-6 minutes depending on the size of a patient, can be used in extention balance of neoplasia as well as in searching of possible hidden neoplasia (for example in the course of suspected paraneoplastic syndrome).

 


PERFUSION Through MR it is possible to obtain information about organ perfusion like those obtained by nuclear medicine methods, using though as a marker of contrast medium usually used in diagnostic morphology (Gadolinium chelates). Since the paramagnetic contrast agent causes a shortening of the relaxation time T2 *, using GRE-EPI sequences to bolus way in normally perfused tissues we can see the physiological reduction of signal, reduced or absent in those ischemic or infarcted.

 


TRACTOGRAPHY The DTI (diffusion tensor imaging) sequence is an MRI technique based on the movement of water molecules in the extra-cellular compartment inherent in the space between the fibers of the white matter. Thanks to the three-dimensional reconstruction software we can show the path of spinal or cranial nerve tracts (pictography or tractography).

 



SPECTROSCOPY The signal that is the basis of image formation in morphological MRI was costituited by the set of differentiable signals depending on the nube elettronica electron cloud surrounding the protons or of different chemical compounds. 


 

A Section of Radiology has recently been expanded to contain the new 1,5T Magnetic Resonance. Equipment, the summary of the most modern technology acquisitions, opens so far little explored perspectives in Veterinary Medicine such as:

  • the high magnetic field, the speed of the gradients, the data processing systems and the combined use of multiple receiving antennas which allow to make fast tests;
  • the possibility to conduct investigation even more in simple sedation than to extend the methodology to the cardio-thoracic, vascular and abdominal organs in movement (MRA, cardio MR) with a field of view up to 183 cm, particularly useful in patients of large size (up to 160 kg), the use of 1024×1024matrix capture, layer thicknesses up to 200 microns (MR microscopy) provides high sensitivity in the detection of lesions, even in patients with very small size alongside morphological examination;
  • functional MR allows to study the organ perfusion, cerebrospinal fluid dynamics, the map of the nerve fibers, spectroscopy. The availability of functions dedicated to oncology expands the use of MRI in already consolidated extention balance and therapeutic monitoring in the course of neoplastic disease.

The unique in Italy high-field MRI and Linear particle accelerator with micro multilamellar collimator in clinical veterinary, our Centre provides its service referring both to the Vet exam (first level test) structures with low-field MRI equipment exam (consulting).

MORPHOLOGICAL MRI

HEAD, NECK, OPTIC PATHWAY. The survey provides a package of contiguous scans of 3 mm thick in sequence TSE T2-dip, followed by contiguous scans of 1 mm thickness with several other sequences (IR, FLAIR, FFE 3D base and  after intravenous contrast) supplying with images qualitatively equal to the anatomical shape on the fixed organ in a total time of 20 minutes-examination. In cases where it is better to use a simple sedation rather narcosis can be made a quick basic test and contrast with a total duration of two minutes. The use of sub-millimetric layers of 200-300 micron thickness is particularly useful for demonstrating cortical dysplasias, in the examination of pituitary or of the inner ear. Through spectroscopy it is possible to draw conclusions about the nature of the injury both focal and spread. Nasal and ear exams are usually conducted combined with CT, MR and endoscopy.

RHACHIS. The complete examination of the rhachis requires 8-20 minutes. The use of thin layer thicknesses allows good visualization of anatomical details of the different longitudinal bundles in the spinal cord white matter. The use of the 53 cm field of view with a matrix 1024 allows with a single acquisition scenic quality and details, especially useful in diseases characterized by polyfocal lesions, such as discospondylitis, osteochondromatosis or in neoplastic diseases. The combined use of more receiving coils is particularly valuable in the brachial plexus study.

CARDIO-THORACIC. With Thoracic MR it is possibile to make multiplanar scanning (packets of 40 images with 3-5 mm of thickness) in 9 seconds of entire thorax in patients with spontaneous respiration. Through Cardio MRI and MR angiography, examination of the length variable from 30 to 120 seconds conducted in deep sedation or anesthesia in spontaneous respiration, are obtained images of the moving heart and blood vessels. These tests are considered as a second level referring to ultrasound; however, they differ due to higher spatial resolution and contrast, the ability to obtain scans of the whole body according to any plan, the extension of the study with no limits to the thoracic great vessels, visualization of parenchymal lesions (myocarditis), the assessment of 'activities of outbreaks of endocarditis by intravenous administration of contrast medium.

ADRENAL. In the diagnostic practice of suspected hyperadrenocorticism or in case of highlighting ultrasound of adrenal nodule, the high-field MR can show clear indications. The possibility of studying both hypothalamic-pituitary and adrenal sections can be useful in patients of large dimensions with uncertain laboratory findings. The test takes about 20 minutes. Since it is possible to differentiate easily the cortical adrenal through MR, the MRI finding of adreno cortical thickness increase it is useful to confirm a state of hyperadrenocorticism in case of intermediate response to stimulation test and / or in patients with compatible case history but echographycally within standart limits. The difference between nodular adenoma-hypertrophy, carcinoma-metastasis, pheochromocytoma is facilitated by MR. The semiologic criteria are: the morphology (number, size, margins, signal intensity, presence of calcifications), the concentration of water and lipids, the vasculature, the presence of catecholamines. Through spectroscopy it is possible to diagnose or exclude a pheochromocytoma, from the moment that the highlight of a spectroscopic peak at 6.8 ppm, tipico delle catecolamine, typical of catecholamines, is indicative of this neoplasia.

KIDNEY, PROSTATE, CIRCULATORY SYSTEM. Using abdominal MRI it is possible to perform multiplanar scans of the entire abdomen in 10-30 seconds (packets of 30-60 images with 5 mm thickness). Using CT angiography and MRA is possible to study the morphology of the blood vessels and kidneys in any district in terms of morphological and functional. These surveys can be useful in the diagnosis of cerebral vascular and abdominal-pelvic diseases. Nevertheless, the measurement of renal perfusion and excretion provide superimposable feedback to those obtained by scintigraphy rapidly without the use of radioactive isotopes. In the prostate, using functional imaging-dependent diffusion and perfusion, it is possible to obtain very accurate information about the nature of the lesions present.

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