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Everything you need to know about Computed Tomography (CT) & CT Scanning

Wrist Pathology

CT has always been an important though at times under utilized imaging modality for the evaluation of the wrist. Although there are a range of applications for CT of the wrist, the most common to date has been the patient with trauma. Typical clinical applications have included detection of fractures where plane films were indeterminate, to determine healing of fractures particularly with possible non-union, as well as to look at the relationship of the carpal and metacarpals in cases of suspected dislocation. The introduction of 16 slice CT with isotropic datasets provides new opportunities for evaluation of the wrist. The ability to provide detailed evaluation in any plane or perspective with a single scan acquisition is critical. Applications including evaluation of arthritis, degenerative disease in addition to trauma becomes of increased interest in this new paradigm of isotropic , resolution of high-resolution datasets. In this exhibit, we review the current stateñof-the-art CT of the wrist by focusing on clinical applications. The value of CT is defined through extensive and detailed discussions as well as representative cases.

Evaluation of the wrist with 16 slice multidetector CT is a fairly straightforward protocol. The key is to position the patient comfortably in the scanner gantry. The positioning is not as critical to us as it was with single or four slice CT as we can obtain isotropic resolution. What is critical of course is the lack of motion on the study. Although a typical CT scan of the hand and wrist will take between 4 and 8 seconds even in that short period of time, motion can occur which would limit the quality of the resultant images and interpretative ability. When examining the wrist we use the thinnest collimation possible which on a Siemens Somatom Sensation 16 scanner is .75 mm and we can reconstruct data at .5 mm intervals. We routinely will reconstruct the images using a high-resolution bone kernel as well as a standard soft tissue kernel. All images once generated are then sent to the workstation for post processing. We use InSpace software on a Leonardo workstation. Using interactive rendering, we look at a series of images through a wide range of displays, which include coronal, sagittal, and oblique views as well as real-time three-dimensional imaging. We routinely will visualize structures with volume rendering using both a high degree of opacity and high degree of transparency. Please note that in most cases IV contrast is not used. Recently we have been using IV contrast in cases of soft tissue inflammation and suspected abscess. With fast scanning, and with an increasing population in patients with musculoskeletal pathology of the hand and wrist, we are being requested to examine more patients with soft tissue abnormalities. In these cases, we routinely inject IV contrast at 3 cc/sec and use a delay of approximately 35 seconds we are then able to create CT angiograms of the wrist. Although to date the role of CT angiography has not been addressed it is an important option, and we believe will be increasing importance in the future. This section presents a series of cases demonstrating pathology in the wrist and the corresponding scanning protocol.

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