[Experimental and clinical studies on the diagnostic value of CT-myelography using a water-soluble contrast medium, metrizamide]

Abstract

A basic and clinical study on the diagnostic value of computed tomographic myelography (CTM) with metrizamide was performed using the GE. CT/T. X-2. A basic study: using the fourth lumbar spine taken from a fresh cadaver and the phantom containing a test tube filled with metrizamide, the optimum window level (W. L.) and window width (W. W.) of the spinal CT and the optimum metrizamide concentration for the CTM were investigated. A clinical study: the relation between the concentration and volume of metrizamide and the timing for performing the CTM after intrathecal injection of metrizamide were examined, then CTM was performed in 82 cases with spinal and spinal cord disorders and 4 cases with normal spinal cords.

Results: 1) Observing the spinal CT and CTM, the optimum W. L. is 50-150 and W. W. is 1,000. 2) The optimum metrizamide concentration of the subarachnoid space for CTM is 6-12 mgI/ml and its CT number is 150-300. This concentration is difficult to recognize in the conventional myelography. 3) It was confirmed that there were two methods to obtain the optimum concentration. One is the CTM after conventional myelography by lumbar puncture; at the cervical or thoracic level CT is performed 1-2 hours after metrizamide myelography with 230-250 mgI/ml and 7-10 ml, and at the lumbar level CT is performed 3-6 hours after myelography with 190-200 mgI/ml and 6-7 ml. The other is the CTM without conventional myelography; at each level, metrizamide with 100 mgI/ml is injected by lumbar puncture and CT is performed 15-40 minutes after injection of 10-15 ml for the cervical or thoracic level, and 3-5 ml for the lumbar level. The CTM obtained under these conditions provides the accurate information about intraspinal canal lesions and, therefore, it is very useful not only for the diagnosis of the lesion but also for the selection of the approach when a surgical treatment is indicated.