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W Kucharczyk

Publications and source records attributed to W Kucharczyk.

98 records · Page 6Linked to original sources
PubMedDate not supplied

Effect of multislice interference on image contrast in T2- and T1-weighted MR images.

Multislice imaging markedly degrades the contrast of T2-weighted MR images as the separation between slices is reduced. Image contrast was measured clinically at 1.5 T and experimentally at 0.15 T as a function of interslice gap width and shown to be in agreement with calculations based on known relaxation times and excitation profiles. Thus, the cause of T2 contrast degradation in multislice sequences is demonstrated. Contrast in T1-weighted sequences is shown to be minimally affected or even slightly enhanced. Selective excitation pulses with better spatial definition will diminish these contrast changes. Since perfect slice profiles can never be achieved, the clinical implications of these findings are discussed for MR imaging. The choice of slice gaps is an important operator-selected parameter in reducing contrast degradation in T2-weighted sequences.

Adult↗
PubMedDate not supplied

Posterior pituitary ectopia: an MR feature of pituitary dwarfism.

Using high-field-strength, 1.5-T, high-resolution MR, we identified the following complex of neurohypophyseal abnormalities in each of five pituitary dwarfs: (1) severe hypoplasia or total absence of the infundibulum; (2) absence of the posterior pituitary bright spot in its normal location; and (3) a 3-8-mm tissue nodule at the median eminence exhibiting lipidlike signal on T1-weighted images. On the basis of its signal features and the clinical absence of diabetes insipidus in these patients, the median eminence nodule appears to represent an ectopic and functional posterior pituitary gland. We propose that this anatomic derangement is the end result of a localized defect of developmental origin, possibly ischemic in nature, and involving principally the infundibular stem. Thus, human growth hormone deficiency could result from perinatal disruption of the peri-infundibular hypophyseal portal system, which in turn impairs anterior pituitary function through deprivation of direct delivery of crucial hypothalamic-releasing factors. Finally, we suggest that the trophic influence of continued axonal neurosecretion at the median eminence engages proliferation of rest cell pituicytes; a process that induces formation of an ectopic and functional posterior pituitary gland, complete with its characteristic bright spot.

Adolescent↗
PubMedDate not supplied

Neuroendocrine tumor (paraganglioma) of the cauda equina: MR and pathologic findings.

The MR and pathologic features of a case with neuroendocrine tumor (paraganglioma) of the cauda equina are presented. MR showed the tumor to be hyperintense on postcontrast examination and also showed serpiginous flow voids suggesting vessels capping the tumor. A neuroendocrine tumor should be considered in the differential diagnosis of tumors in this location.

Adult↗
PubMedDate not supplied

MR of human postmortem brain tissue: correlative study between T2 and assays of iron and ferritin in Parkinson and Huntington disease.

PURPOSE: To test the hypothesis that the T2 shortening observed on MR images of the brain in patients with Parkinson and Huntington diseases is due to tissue iron deposition. METHODS: Tissue iron and ferritin assays were performed on postmortem putamen and globus pallidus samples from subjects with Huntington and Parkinson disease. The assays were correlated with T2 measurements. Normal samples were included as controls. RESULTS: There were significant differences in T2 values, and iron and ferritin concentrations among the putamen samples. Compared with normal controls, subjects with Huntington disease had approximately a threefold increase in iron and a sixfold increase in ferritin concentrations; however, they also had the longest T2 values. Parkinson disease putamens had milder elevations of iron concentrations above that of controls (33%) and demonstrated slightly shorter T2 values. The globus pallidus samples demonstrated a similar trend in their T2s, iron, and ferritin levels, but there was a larger overlap in the T2 values. CONCLUSIONS: Our results indicate that tissue iron and ferritin concentrations are elevated in the brains of subjects with both Parkinson and Huntington disease but the elevated concentrations do not correlate with T2 shortening. Although iron and ferritin can shorten T2, we conclude that other factors must play a significant role in determining the T2 relaxation time and that iron or ferritin are not dominant in this regard.

Adult↗
PubMedDate not supplied

Unusual location of a shunt tube in the basal subarachnoid space.

The authors observed flow-void in a shunt tube in the basal cisterns of a 28-year-old man who had previously undergone surgery for a craniopharyngioma. They describe the appearance of a subarachnoid shunt catheter in the basal cisterns to caution against misinterpreting it as an aberrant vessel.

Adult↗
PubMedDate not supplied

The accuracy of magnetic resonance imaging in patients with suspected multiple sclerosis. The Rochester-Toronto Magnetic Resonance Imaging Study Group.

OBJECTIVE: To design and implement a methodologically rigorous study to examine the accuracy of magnetic resonance imaging (MRI) in a patient population clinically suspected of having multiple sclerosis (MS). DESIGN AND SETTING: Three hundred three patients, who were referred to two university medical centers because of the suspicion of MS, underwent MRI of the head and double-dose, contrast-enhanced computed tomography (CT) of the head. The images were read by two observers individually and without knowledge of the clinical course or final diagnosis. Patients were followed up for at least 6 months and reevaluated clinically with subsequent neurological examination. Final diagnosis (MS or not MS) was made by a panel of neurologists on the basis of the clinical findings at presentation, those that developed during follow-up, and other diagnostic tests. The results of the imaging procedures were excluded to avoid incorporation bias. Diagnostic accuracy was assessed using receiver-operating characteristic analysis and likelihood ratios. RESULTS: Magnetic resonance imaging of the head was considerably more accurate than CT in diagnosing MS. The area under the receiver-operating characteristic curve for MS was 0.82 (compared with 0.52 for CT) indicating that MRI was a good but not definitively accurate test for MS. A "definite MS" reading on an MRI of the head was specific for MS (likelihood ratio, 24.9) and essentially established the diagnosis, especially in patients clinically designated as "probable MS" before testing. However, MRI of the head was negative for MS in 25% and equivocal in 40% of the patients considered to have MS by the diagnostic review committee (sensitivity, 58%). CONCLUSIONS: Magnetic resonance imaging of the head provided assistance in the diagnosis of MS when lesions were visualized. Its ability far exceeded imaging with double-contrast CT. The sensitivity and, therefore, the predictive value of a negative MRI result for MS were, however, not sufficiently high for a normal MRI to be used to conclusively exclude the diagnosis of MS.

Adolescent↗
PubMedDate not supplied

Spontaneous regression of a tectal mass in neurofibromatosis 1.

MR images showed an enhancing, enlarging mass in the tectum of the midbrain in a child with neurofibromatosis type 1. The mass was presumed to be a tectal glioma, which initially enlarged then regressed in size over a 3-year period and ceased to enhance. Although a tissue diagnosis was not available, we believe the temporal evolution of this lesion is strong presumptive evidence of a hamartoma. This case argues for the conservative management of patients with neurofibromatosis type 1 when possible.

Adolescent↗