ABSTRACT
PURPOSE: To determine the possible mechanism by which an area of high signal intensity appears on T1-weighted MR images adjacent to a vacuum cleft in intervertebral disks. MATERIALS AND METHODS: We analyzed a total of 14 disks in nine patients in whom a vacuum cleft with T1-signal hyperintensity was observed. Lesions were present from T11-12 to L5-S1 using a 1.5-T whole-body imager, sagittal spine-echo T1-weighted and gradient-echo images (flip angle, 20 'and 60 ) were obtained. In order to identify the vacuum cleft, using plain radiographs in all patients and CT scans in two were also obtained. A 3% agar-gel block containing empty slits to form a magnetic susceptibility difference, a phantom was designed. The air spaces were 1.6 mm in thickness, 25 mm in width, and 20 to 25 mm in depth with 1.6-mm spacing. RESULTS: In all patients, vacuum clefts were confirmed by plain radiographs and CT scans. At the level containing air, T1-weighted images (both spin-echo and gradient-echo) showed a signal void resulting from the intervertebral disk vacuum cleft. A hyperintense band adjacent to the vacuum cleft was, however, observed. A gradient-echo image with a 60 'flip angle showed a brighter signal intensity than one with a 20 'angle. Our phantom study gave the same results. CONCLUSION: The magnetic susceptibility artifact may be responsible for the T1-signal hyperintensity observed adjacent to the vacuum cleft in intervertebral disks. In addition, in order to generate signal hyperintensity, the desiccating disk material must contain a certain amount of water molecules.
Subject(s)
Humans , Artifacts , Intervertebral Disc , Tomography, X-Ray Computed , VacuumABSTRACT
PURPOSE: To determine the possible mechanism by which an area of high signal intensity appears on T1-weighted MR images adjacent to a vacuum cleft in intervertebral disks. MATERIALS AND METHODS: We analyzed a total of 14 disks in nine patients in whom a vacuum cleft with T1-signal hyperintensity was observed. Lesions were present from T11-12 to L5-S1 using a 1.5-T whole-body imager, sagittal spine-echo T1-weighted and gradient-echo images (flip angle, 20 'and 60 ) were obtained. In order to identify the vacuum cleft, using plain radiographs in all patients and CT scans in two were also obtained. A 3% agar-gel block containing empty slits to form a magnetic susceptibility difference, a phantom was designed. The air spaces were 1.6 mm in thickness, 25 mm in width, and 20 to 25 mm in depth with 1.6-mm spacing. RESULTS: In all patients, vacuum clefts were confirmed by plain radiographs and CT scans. At the level containing air, T1-weighted images (both spin-echo and gradient-echo) showed a signal void resulting from the intervertebral disk vacuum cleft. A hyperintense band adjacent to the vacuum cleft was, however, observed. A gradient-echo image with a 60 'flip angle showed a brighter signal intensity than one with a 20 'angle. Our phantom study gave the same results. CONCLUSION: The magnetic susceptibility artifact may be responsible for the T1-signal hyperintensity observed adjacent to the vacuum cleft in intervertebral disks. In addition, in order to generate signal hyperintensity, the desiccating disk material must contain a certain amount of water molecules.
Subject(s)
Humans , Artifacts , Intervertebral Disc , Tomography, X-Ray Computed , VacuumABSTRACT
PURPOSE: To evaluate the accuracy and safety of ultrasound-guided biopsy of the thickened peritoneal reflections and to determine the efficacy and diagnostic role of this procedure in the differential diagnosis of peritoneal tuberculosis and peritoneal carcinomatosis. MATERIALS AND METHODS: Twenty-seven patients with only mildly thickened (25 mm or less) peritoneal reflections without apparent mass formations, and in whom imaging findings were not diagnostic, underwent ultra-sound-guided biopsy. Five-MHz linear or convex linear array transducers were used for ultrasound guidance,and an automated gun with 18-gauge (n = 23) or 20-gauge (n = 4) needles for tissue sampling. Biopsies were performed on the thickened parietal peritoneum (n = 9), greater omentum (n = 11), and small bowel mesentery (n = 7), and the results were compared with the final diagnosis determined by adiologic/clinical follow-up (n = 17) or laparoscopic biopsy (n = 10). Complications and changes in hemoglobin and hematocrit levels after the procedure were evaluated. RESULTS: Specimens adequate for pathologic examination were obtained in all 27 patients. The histopathologic results were metastatic carcinomatosis (n = 15), peritoneal tuberculosis (n = 8), and chronic granulomatous inflammation (n = 4). Specific pathologic diagnosis was obtained in all patients except the four with chronic granulomatous inflammation. Differentiation between benignancy and malignancy was possible in all patients and the histopathologic specific accuracy rate was 100%. No clinically significant complications were observed. In 24 patients with ascites at the site of the biopsy, transient bleeding was observed immediately after the procedure, but this stopped spontaneously within a few minutes. Post-procedural hemoglobin and hematocrit levels were only minimally lower (mean values of 0.9g/dL and 3.0%, respectively) than pre-procedurally. CONCLUSION: Ultrasound-guided biopsy of thickened peritoneal reflections is a safe and effective diagnostic procedure and is useful in the differential diagnosis of peritoneal tuberculosis and peritoneal carcinomatosis.