Magnetic resonance (MR) imaging was performed on 40 patients with intracranial tumors, before and after intravenous administration of gadolinium-DTPA (Gd-DTPA). Precontrast studies included a comprehensive protocol of spin-echo sequences. Tumors were visualized on precontrast images either directly or indirectly by anatomic distortion caused by the mass. However, differentiation of the tumor from adjacent tissues was possible in only 17 of 40 cases. Delineation of the tumor was best on precontrast, T2-weighted images. After administration of Gd-DTPA (0.1 mmol/kg), increased signal intensity from the tumor was observed in all patients. The localized increase in signal intensity in the tumor considerably improved the tumor delineation in 36 of 40 patients. Whereas most of the meningiomas, neuromas, and adenomas could be delineated prior to administration of contrast material if appropriate pulse sequences were applied, glioblastomas and intracranial metastases required Gd-DTPA administration for diagnostically sufficient tumor display.
To investigate the safety, patient tolerance, and efficacy with 0.3 mmol/kg gadopentetate dimeglumine in magnetic resonance (MR) imaging of the central nervous system (CNS), a phase 3 trial was conducted in 199 patients with suspected CNS lesions. Patients received either 0.1 or 0.3 mmol/kg gadopentate dimeglumine (injection time, 15 seconds and 45 seconds, respectively). T1- and T2-weighted spin-echo sequences were performed at either 0.5 T or 1.5 T. In 80 patients with enhancing brain lesions, contrast-to-noise ratios (C/Ns) were calculated, and lesion-to-brain contrast was evaluated visually. Six patients (6%) in each dose group reported adverse events. Eight adverse events occurred with 0.1 mmol/kg and seven with 0.3 mmol/kg. Vital signs and laboratory values did not change significantly. C/N (P < .05) and visual assessment ratings were higher with 0.3 mmol/kg than with 0.1 mmol/kg. According to these preliminary results, 0.3 mmol/kg gadopentetate dimeglumine is safe and well tolerated when administered at approximately 1 mL/sec.
Studies of contrast medium bolus geometry and dynamics were carried out to provide data for optimizing the use of contrast medium in digital subtraction angiography (DSA) and dynamic CT. Apparatus for fast digital recording of x-ray attenuation profiles was used; this is a new digital imaging mode (Chronogram) available on a CT scanner. Variables studied were injection site, injection speed, contrast medium volume, and subsequent saline injection; peak time, full width at half maximum, and maximum contrast enhancement were recorded. Positioning of the catheter in the vena cava reduced peak time and increased enhancement. High injection speeds led to shorter peak times. An increase in speed from 4 to 8 ml/s caused markedly higher enhancement, while further increase did not add significantly to enhancement. For a given injection speed, enhancement was increased and the peak time delayed by using larger injection volumes. Injection of saline solution after intravenous contrast medium did not change results significantly. There was a statistically significant correlation between pulse rate and peak time; the faster the pulse rate the shorter the peak time.
Thirty-nine patients with Graves ophthalmopathy were examined with magnetic resonance (MR) imaging at 0.5 T with use of a surface coil. T1- and T2-weighted spin-echo images were obtained, and T2 relaxation times of eye muscles and retrobulbar fat were calculated from a multiecho sequence. Normal values for T2 relaxation times of eye muscle were obtained by examining nine control subjects. MR imaging demonstrated eye muscle enlargement in 23 patients. Visual examination of T2-weighted and calculated T2 images showed areas of high signal intensity in enlarged eye muscles of 12 of 23 patients. Calculated T2 relaxation times of eye muscles differed significantly between control subjects and patients with stage III and IV disease. Signal intensity characteristics of these changes, as well as their correlation with well-known histologic findings, suggested their interpretation as edema caused by acute inflammation. Since computed tomography is not able to depict eye muscle edema, the MR findings of structural changes within enlarged eye muscles might have an impact on therapeutic decisions concerning the application of anti-inflammatory drugs.
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