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This type of study should be reserved for instances in which the animal is severely obtunded by its medical condition or for the rare instances in which sedation would significantly alter the status of the tissues (such as an attempt to evaluate the effect of drug intervention in an asthmatic cat).
As with conventional radiography, the use of nonionic contrast agents can markedly improve the diagnostic accuracy and sensitivity of CT.
Metastatic lesions in the lung are far more evident at a smaller size on CT scans than on conventional radiographs.
If a CT scan is performed after detection of metastatic lesions on radiographs, the CT scan will almost always find more nodules than are evident on the radiographic images.
The image reconstruction time is short, and the entire study can be completed in less time than was required to acquire a single image 15 years ago.
Some veterinary practices now have 8- to 64-slice scanners installed, and the actual scan takes less time than it takes to position the animal on the scanning table.
By sequentially scanning a body area, the entire volume of interest can be imaged without any superimposition of structures.
CT also has much better contrast discrimination than standard radiographs, so structures such as individual parts of the brain or individual muscle bellies are seen as separate and distinct on the CT scan.
Together, all of the attenuation points make an image of the cross-section of the portion of the body through which the beam is passed.The number of x-rays reaching the detector changes as the beam passes through different tissues because of the tube movement.A computer mathematically evaluates the data and determines the most probable density of any point within the volume of tissue scanned.In addition to some of the imaging procedures unique to CT, this modality is replacing conventional radiography for evaluation of some structures and diseases traditionally assessed by radiography.CT scans of the skull in any species are far more informative and diagnostic than any conventional radiograph because the complex anatomy of the skull, which results in a pattern of overlying structures on a radiograph, is vastly simplified on a CT scan, making the diagnosis much more specific and accurate and improving treatment results.
This tomographic image is usually referred to as a slice, and each of the individual attenuation points in the image is referred to as a voxel (volume element).