M M Tomiak | Search PubMed

PubMed1995

Variable-mode helical CT: imaging protocols.

Helical CT provides a rapidly acquired, accurately registered, two-dimensional data set during the phase of maximum vascular and parenchymal enhancement. The z-axis can be covered by using either a single acquisition, single breath-hold technique or by using multiple helical groups with intergroup delays for the patient's breathing. The latter approach, called variable-mode helical CT, allows large z-axis coverage of more than one anatomic region during injection of a single bolus of contrast material. We discuss helical scanning protocols, both single-acquisition and variable-mode, that we have developed for detection of disease involving major blood vessels (pulmonary arteries and aorta), perivascular tissue planes (neck, thorax, and pelvis), and abdominal viscera (liver, pancreas, and kidneys).

Humans↗

PubMed1994

Magnetization transfer: a potential method to determine the age of multiple sclerosis lesions.

PURPOSE: To determine whether magnetization transfer contrast can differentiate acute from chronic lesions in multiple sclerosis. METHODS: Thirteen patients with multiple sclerosis and eight healthy patients were studied with MR using a 0.1-T system. Relatively T2-weighted spin-echo images were obtained without and with magnetization transfer contrast. The magnetization transfer effect of multiple sclerosis lesions was calculated and compared with the ages of the lesions. The magnetization transfer effect of normal-appearing white matter in patients with multiple sclerosis was calculated and compared with the magnetization transfer effect of white matter in healthy volunteers. Statistical analysis was performed. RESULTS: White matter in the healthy volunteers had values from 0.40 to 0.45. Normal-appearing white matter in the patients with multiple sclerosis had magnetization transfer effect values ranging from 0.41 to 0.45. Multiple sclerosis plaques of less than 1 year's duration had magnetization transfer effect values ranging from 0.05 to 0.26; older plaques had values from 0.25 to 0.41. The difference in the distributions of these values for acute and chronic multiple sclerosis plaques is statistically significant. CONCLUSION: Current imaging modalities do not differentiate acute multiple sclerosis lesions from chronic ones. Our data on magnetization transfer show a statistically significant difference in magnetization transfer effect values between lesions of less than 1 year's duration and older lesions. The different values may correspond to the histologic changes of multiple sclerosis plaques over time. Magnetization transfer may be a reliable method for determining the age of multiple sclerosis lesions.

Acute Disease↗

PubMed1993

Use of CT for diagnosis of traumatic rupture of the thoracic aorta.

CT imaging of traumatic aortic rupture has been both advocated and disparaged in the current literature as a reliable diagnostic modality. In a retrospective review of blunt chest trauma patients at our institution evaluated by both thoracic CT and arteriography, we found a 17% false negative rate and a 39% false positive rate. Although we feel CT is not sufficiently sensitive at present to evaluate traumatic rupture of the aorta directly, it is an invaluable adjunctive imaging modality for stable blunt chest trauma patients with equivocal chest radiographs or arteriograms.

Adolescent↗