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Biomedical subjects

D W Shaw

Publications and source records attributed to D W Shaw.

62 records · Page 4Linked to original sources
PubMedDate not supplied

Cranial MR in phenylketonuria.

Phenylketonuria (PKU) is an autosomal recessive disease in which defects in phenylalanine metabolism result in hyperphenylalaninemia. Untreated patients generally have poor motor function and are profoundly retarded. We report a patient with PKU whose cranial magnetic resonance abnormalities correlate with known histopathologic changes. The ability to image the pathologic changes in PKU may have important implications regarding treatment and prognosis of these patients.

Adult↗
PubMedDate not supplied

Discoid menisci in children: MR features.

OBJECTIVE: To define the MR appearance of discoid meniscus in children. MATERIALS AND METHODS: In 22 children (15 girls and 7 boys; age range 5-17 years; median age 9 years) who were referred for evaluation of painful knees 27 discoid lateral menisci were identified. Meniscal shape and signal intensity and abnormalities of the surrounding structures were evaluated and compared with adult standards. Clinical (11 knees) or surgical (10 knees) follow-up was available on 16 patients (21 knees). RESULTS: The menisci were classified as slab type (no. 20) or wedge type (no. 7). Transverse diameter at the midbody was 22.4 mm (range 10.5-36.7 mm) for discoid lateral menisci and 6 mm (range 5.1-28.3 mm) for medial menisci. Of 27 menisci, 23 had a central band of diffusely increased signal. Extension of intrameniscal signal to the joint space was noted in 16 of 23 menisci. Of 9 patients with intrameniscal signal who underwent surgery, only 7 had tears. Associated popliteal cysts occurred in 3 knees. No medial meniscal injury was observed. CONCLUSION: The characteristic MRI appearance of symptomatic discoid meniscus in children is that of a diffusely thick meniscus with a slab configuration and diffusely increased intrameniscal signal that may or may not extend to the joint surface.

Child↗
PubMedDate not supplied

Three-dimensional fast spin echo T1-weighted imaging of the pediatric spine.

OBJECTIVE: We evaluated the feasibility of using a three-dimensional (3D) fast SE (FSE) pulse sequence to acquire T1-weighted (T1W) images of the pediatric spine. MATERIALS AND METHODS: The 3D FSE T1W images were acquired in nine pediatric patients undergoing spine MRI for different clinical indications. The 3D FSE images were compared with our standard 2D SE T1W images. RESULTS: Image contrast was comparable between the two sequences. The 3D FSE sequence produced contiguous thin sections that allowed multiplanar reformations not possible with the 2D SE sequence. CONCLUSION: 3D T1W spine imaging with conventional SE-like contrast is feasible with 3D FSE.

Cerebrospinal Fluid↗
PubMedDate not supplied

Quantitative comparison of conventional spin echo and fast spin echo during brain myelination.

PURPOSE: Fast SE (FSE) sequences have largely replaced conventional SE (CSE) T2-weighted sequences in the brain and have been generally accepted as qualitatively comparable. The purpose of the present study was to subject these sequences to a quantitative comparative analysis in the brain. METHOD: A quantitative analysis of relative signal intensities of white and gray matter was performed comparing CSE and FSE T2-weighted sequences in brains of 20 children at varying stages of myelination. RESULTS AND CONCLUSION: At all ages in individual patients, white matter had less signal intensity (SI) relative to gray matter on FSE than CSE, though the relative difference in SI was small. This resulted in white matter appearing slightly more myelinated on FSE than CSE. This difference is attributed to differences in magnetization transfer. In myelinated brain (white matter hypointense to gray matter), contrast-to-noise was greater with FSE, while in unmyelinated brain, contrast-to-noise was greater with CSE.

Brain↗
PubMedDate not supplied

Diabetes insipidus as a presenting symptom of acute myelogenous leukemia.

This report describes a case of diabetes insipidus associated with acute myelogenous leukemia. An 11-year-old boy presented with fatigue, polydipsia and polyuria. His evaluation revealed a diagnosis of acute myelogenous leukemia FAB-M2, and a water deprivation test confirmed the diagnosis of central diabetes insipidus. His brain magnetic resonance imaging (MRI) showed a thickened, enhancing pituitary stalk with absence of the normal hyperintense signal in the posterior pituitary. He was treated with systemic chemotherapy, intensive intrathecal therapy, and 1,000 cGy to the pituitary. The patient achieved a remission but continued to need desmopressin therapy to control his diabetes insipidus. Diabetes insipidus is a rare complication of acute myelogenous leukemia that can be caused by leukemic infiltration of the pituitary. The diabetes insipidus is irreversible despite intensive systemic and central nervous system chemotherapy and radiation.

Child↗
PubMedDate not supplied

Binding of the hypoxia tracer [3H]misonidazole in cerebral ischemia.

Radiolabelled misonidazole, a radiosensitizing drug that binds to viable hypoxic tumor cells, may be useful in identifying hypoxic cells in cerebrovascular disease. Its potential was investigated in the gerbil stroke model. Biodistribution of [3H]misonidazole was measured in normal gerbils and animals that had been subjected to right common carotid artery ligation to produce cerebral ischemia. The uptake of [3H]misonidazole in the right cerebral hemisphere and right/left hemispheral uptake ratios correlated positively with the severity of the stroke when measured 6-9 hours after carotid ligation. Histologic studies in symptomatic ligated animals showed ipsilateral widespread but patchy acute ischemic changes as well as areas that showed no morphological changes. Microscopic autoradiography in these animals showed diffuse heavy labelling only in the ipsilateral hemisphere. This was over areas that had histological damage as well as in adjacent areas that appeared intact. Studies comparing blood flow measured with [14C]iodoantipyrine and [3H]misonidazole retention in gerbils with carotid artery ligations indicated that flow is not a major determinant of retention of this hypoxia tracer. We conclude that a misonidazole congener labelled with a gamma- or positron-emitting isotope may be useful in nuclear imaging of the degree and regional distribution of hypoxic tissue in cerebrovascular disease.

Animals↗
PubMedDate not supplied

MR imaging of phenylketonuria.

Cranial MR imaging was performed on nine patients (13-27 years old) with classical phenylketonuria in order to define the spectrum of abnormal findings and to determine if these could be related to clinical or biochemical findings. MR abnormalities consistent with demyelination were found in varying degrees in a distribution corresponding to previous histopathologic studies. Specifically, increased signal was seen on T2-weighted sequences, most marked in the periventricular deep cerebral white matter. These changes were more prominent posteriorly, especially about the optic radiations. Comparison with clinical history and MR findings in this small series revealed that patients with adequate dietary control of phenylalanine levels had less severe white matter abnormalities than did patients with poorly controlled phenylalanine intake.

Adolescent↗