Chiari II malformation: MR imaging evaluation

The purpose of this study was to explore the value of high-detail MR imaging in the diagnosis of the Chiari II malformation. Twenty-four patients with known Chiari II malformation as diagnosed by CT scanning were evaluated with cranial MR scans. Two patients also had spine scans. The sagittal-plane images were the most informative, and abnormalities of the telencephalon, diencephalon, mesencephalon, rhomboencephalon, upper spinal cord, and mesencephalon were shown extremely well. We found MR to be an easy and accurate method for demonstrating the abnormalities of the Chiari II malformation, and it is our procedure of choice.     

Gadoteridol dose dependence in MR imaging of a liver abscess model

A necrotic liver abscess model was studied with magnetic resonance (MR) imaging at 1.5 T before and after intravenous administration of gadoteridol at doses of 0.1, 0.25, and 0.5 mmol/kg in 24 rabbits. Enhancement characteristics and lesion delineation were assessed with both breath-hold and non-breath-hold imaging techniques. Lesion delineation, as assessed both by signal intensity measurements and evaluations by two image readers blinded to imaging technique, was greatest on high-dose (0.5 mmol/kg) breath-hold images. Lesion rim enhancement was seen consistently only on postcontrast images obtained at a dose of 0.5 mmol/kg and progressed with time after injection of contrast material.     

High-dose gadoteridol in MR imaging of intracranial neoplasms.

Twelve patients with a high suspicion of brain metastases by previous clinical or radiologic examinations were studied in a phase III investigation with magnetic resonance (MR) imaging at 1.5 T after a bolus intravenous injection of 0.1 mmol/kg gadoteridol followed at 30 minutes by a second bolus injection of 0.2 mmol/kg gadoteridol. All lesions were best demonstrated (showed greatest enhancement) at the 0.3-mmol/kg (cumulative) dose, with image analysis confirming signal intensity enhancement in the majority of cases after the second gadoteridol injection. More lesions were detected with the 0.3-mmol/kg dose than with the 0.1-mmol/kg dose, and more lesions were detected with the 0.1-mmol/kg dose than on precontrast images. In this limited clinical trial, high-dose gadoteridol injection (0.3-mmol/kg cumulative dose) provided improved lesion detection on MR images specifically in intracranial metastatic disease.     

Expression of an oncofetal protein (OFP) in rat and human leukemia cells.

A unique oncofetal protein (OFP) previously identified in rat fetal tissue and rat and human solid tumors, is now shown to be present in rat and human leukemia cells by use of a monoclonal antibody-based assay. Using a highly specific anti-rat OFP monoclonal antibody OFP has been unquivocally immunolocalized to the cytoplasm of the rat leukemia cells. The factor is rapidly released to the circulation as 50 and 55 kD species which share the immunological determinants. When leukemia cells are transplanted to normal rats, OFP increases in the circulation in a biphasic manner which may be due to immune clearance since circulating anti-OFP antibodies have been demonstrated. Induction of differentiation in the human HL-60 leukemia cell line by 13-cis-retinoic acid caused a down regulation of OFP synthesis, both intra- and extra-cellular levels dropping to essentially zero. Induction of differentiation with dibutyryl cyclic AMP caused a cessation of secretion of OFP, with a marked increase in its intracellular concentration, a condition resembling the retention in fetal cells. Leukemia cells add to a growing list of tumors previously shown to produce OFP, suggesting that OFP is intimately involved in some facet of tumorigenesis.     

Heart rate fluctuations in diabetic patients with cardiac vagal dysfunction: a spectral analysis

The autonomic nervous control of cardiac function during active orthostatic load has been studied by measuring the power spectrum of heart rate fluctuations in 16 insulin-dependent diabetic patients and 14 age-matched control subjects. The patients were subdivided into two groups: 8 with normal respiratory sinus dysrhythmia (RSA+) and 8 with reduced respiratory sinus dysrhythmia (RSA-). In RSA- patients the total power (0.01-0.50 Hz) was significantly reduced compared with control subjects (4.7 versus 15.5 min-2, 2p less than 0.05) and the pattern of heart rate fluctuations was characterized by a relative increase in the low-frequency component (0.01-0.05 Hz) as compared with RSA+ patients and control subjects (45% versus 24% and 27%, both 2p less than 0.01). There was also a significant reduction in the high-frequency component (0.15-0.50 Hz) as compared with RSA+ patients and control subjects (17% versus 36% and 33%, both 2p less than 0.05). During standing, a significant increase in total power was found only in control subjects (2p less than 0.01) and the difference between control subjects, and RSA+ and RSA- patients reached significance (32.2 versus 15.1 and 12.7 min-2, 2p less than 0.02 and 2p less than 0.01). The pattern of heart rate fluctuations in RSA- patients showed no significant change on standing. These results suggest that the reduced overall heart rate variability in diabetic patients with cardiac autonomic neuropathy is associated with a typical heart rate fluctuation pattern.     

Gd DTPA. Future applications with advanced imaging techniques

In this admittedly preliminary view of the future, the authors present a number of new concepts in MR imaging and consider their possible advantages and limitations.     

The bright pituitary gland--a normal MR appearance in infancy

Signal intensities of the pituitary gland were measured on T1-weighted sagittal MR images of 25 patients younger than 20 years old. We found that the signal intensities in the eight patients who were 8 weeks old or younger were higher (shorter T1) than those in the 17 older patients. We also noted a difference in the signal intensities across the pituitary gland, the signal being higher in the posterior part of the gland than in the anterior part. We attribute the high signal intensities to the rapid intrauterine pituitary growth, so that at term pituitary protein synthetic activity is at a maximum. Possibly, an increase in the bound fraction of the water molecules of the gland may also be present in the neonatal pituitary as compared with the older gland, but this remains to be proved. The higher signal in the posterior pituitary gland may be due to lipid in the pituicyte cells of the posterior pituitary gland.     

Contrast media research

This selective review highlights research in contrast media development and application in the field of diagnostic radiology in 1998 and 1999. The focus is on research published in Investigative Radiology, supplemented with work from other publications in the few areas not extensively covered by the journal. Studies continue to be performed, although at a low level, examining safety issues. Most preclinical investigations have focused on MR and ultrasound agents. In MR, the research effort is concentrated on the development of targeted agents; in ultrasound, work is focused on the characterization of basic contrast mechanisms. The demonstration of clinical applications is still dominated by work with MR, both in disease models and human investigations. The use of extracellular gadolinium chelates to enhance visualization of blood vessels (the field of contrast-enhanced MR angiography) is the largest single new clinical application of contrast media to emerge in several years. New clinical applications continue to be pursued with contrast media in CT, ultrasound, and x-ray angiography. As intravenously injected ultrasound contrast agents come to market, trials demonstrating clinical applications and subsequent scientific publications will increase in number.