tailieunhanh - Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 27

Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 27. Spinal disorders are among the most common medical conditions with significant impact on health related quality of life, use of health care resources and socio-economic costs. Spinal surgery is still one of the fastest growing areas in clinical medicine. | Imaging Studies Chapter 9 241 are often unable to stay motionless for the 20 min required for a standard examination. Hip flexion which might relieve the patient s pain is only possible to a limited degree in most magnet designs. Proper analgesic medication prior to the MR examination may be required in order to reduce patient discomfort and pain-related motion artifacts. Computed Tomography CT has developed with amazing speed during the last few years. Spiral CT with continuous data acquisition appeared in routine work in the mid-1990s and multi-detector row CT at the end of the 1990s. Initially four detector rows were employed which were quickly followed by 16 40 and 64 detector rows. At the time of writing this development has not yet come to an end. Compared to MR imaging CT has several advantages. CT shows bony details with a high spatial resolution. In plane spatial resolution of CT pixel size is approximately mm depending on the system geometry and on the reconstruction kernel selected by the user and is therefore better than in typical MR protocols. CT does not interfere with the function of pacemakers and other electronic devices. The metal-related artifacts present in CT are related to so-called beam-hardening which depends on the amount size of implants and the atomic number of the implant. Such artifacts may be less pronounced or in a different place when compared to MR imaging. Examinations in emergency room and intensive care patients are preferably performed using CT because imaging times are shorter patient access is easier and no specialized non-ferromagnetic shielded intensive care equipment is necessary as for MR imaging. On the other hand the contrast resolution of CT is much inferior to MR imaging in important structures such as the intervertebral discs cerebrospinal fluid and soft tissue. The radiation dose is considerable in CT . 28 of the medical radiation dose in Switzerland is generated by CT examinations 46 . CT examinations .