Biomedical subjects

Erin M Simon

Publications and source records attributed to Erin M Simon.

6 recordsLinked to original sources

PubMed2003

High-resolution 3D T2-weighted fast spin echo: new applications in the orbit.

Recent developments have made available for ophthalmologic MR imaging a very high-resolution 3D fast spin echo T2 (3D FSE T2) sequence, which runs in a standard head coil. A modification of this technique, 3D FSEz T2, uses a zero-filled slice interpolation method during post-processing to further improve spatial resolution. We describe the technique and share our early clinical observations in patients with ocular masses. Briefly, the additional information from the 3D FSEz T2 resulted in a change in diagnosis from the conventional imaging series in 11 of (41%) 27 studies, usually through the identification of previously treated retinoblastoma lesions. The new sequence significantly increased diagnostic confidence in six (38%) of the remaining 16 cases, usually through better anatomical detail and lesion conspicuity, and did not change interpretation in 10 cases. Such an approach improves diagnostic confidence and may eliminate the need for a dedicated surface coil examination.

Fourier Analysis↗

PubMed2003

In vivo pyruvate detected by MR spectroscopy in neonatal pyruvate dehydrogenase deficiency.

We present a unique finding of an elevated level of pyruvate at 2.37 ppm revealed by in vivo MR spectroscopy of a female neonate. Low fibroblast pyruvate dehydrogenase (PDH) complex activity subsequently confirmed a diagnosis of PDH deficiency. Abnormalities of brain development consistent with PDH deficiency were also evident on fetal and postnatal MR images. To our knowledge, this is the first report of pyruvate being shown in vivo in a child and the first report of MR spectroscopy aiding in the diagnosis of inborn error in pyruvate metabolism before confirmation by conventional enzymatic testing. This finding has potential implications for earlier diagnosis in patients with defects in mitochondrial metabolism.

Abnormalities, Multiple↗

PubMed2002

Three-dimensional high-resolution magnetic resonance imaging of ocular and orbital malignancies.

BACKGROUND: Ultrathin-section 3-dimensional fast spin-echo (3-D FSE) T2-weighted imaging is a new magnetic resonance imaging (MRI) technique that we used in the evaluation of ocular and orbital malignancies. We evaluated the usefulness of this new technique compared with conventional MRI. METHODS: Imaging data from 26 consecutive patients seen in the Ocular Oncology Unit at the University of California-San Francisco were retrospectively reviewed by physicians from the ocular oncology and neuroradiology units. For all patients, 3-D FSE T2-weighted images (27 scans) were compared with results of conventional MRI and correlated with results of computed tomography (CT), A- and B-scan ultrasonography, ultrasound biomicroscopy, clinical examinations, and histopathology, when available. RESULTS: The 3-D FSE T2-weighted imaging sequence resulted in an overall improvement in accuracy of imaging findings in 17 (63%) of our 27 cases compared with the standard MRI protocol. The increased resolution led to the radiographic detection of additional lesions in 11 (41%) of 27 cases and to an increase in confidence in radiographic diagnosis in 6 (22%) of the remaining cases. The improved resolution of the 3-D FSE T2-weighted sequence resulted in a change of disease management in 3 (60%) of the 5 patients with nonretinoblastoma lesions. One hundred percent of active retinoblastoma lesions could be detected by means of 3-D FSE and conventional imaging; however, inactive lesions were not always detected using conventional imaging. CONCLUSIONS: The 3-D FSE T2-weighted sequence offers superior resolution of intraocular and orbital structures compared with conventional MRI. It is particularly useful in the evaluation of intraocular tumors and the nerve-sheath complex. This new technique contributes significantly to improved diagnosis and management in patients with ocular and orbital malignancies.

Eye Neoplasms↗

PubMed2002

Fetal imaging.

Presently, MRI is an adjunct to prenatal sonography. It provides information that can aid in the diagnosis of fetal anomalies, affect prenatal counseling and management of the pregnancy, and guide prenatal intervention and delivery planning. With further advances in technology, particularly shorter scan times and better image resolution, the applications for fetal imaging are likely to increase.

Congenital Abnormalities↗

PubMed2002

Analysis of the cerebral cortex in holoprosencephaly with attention to the sylvian fissures.

BACKGROUND AND PURPOSE: Analysis of specific features in the brain of patients with holoprosencephaly (HPE) may clarify normal and abnormal brain development and help predict outcomes for specific children. We assessed sulcal and gyral patterns of cerebral cortex in patients with HPE and developed a method of grading brain development. METHODS: Neuroimaging studies (75 MR imaging, 21 CT) of 96 patients with HPE were retrospectively reviewed, with specific attention paid to the cerebral cortex. Thickness of cortex, width of gyri, and depth of sulci were assessed subjectively and by measurement. The angle between lines drawn tangential to the sylvian fissures ("sylvian angle") was measured in each patient with HPE and in 20 control patients. RESULTS: Thickness of cortex was normal in all 96 patients. Gyral shape and width and sulcal depth were normal in 80 patients. Twelve patients, all with very severe HPE and microcephaly, had reduced sulcal depth, diffusely in eight and limited to the anteromedial cortex in four with lobar HPE. Four patients had subcortical heterotopia, located anterior to the interhemispheric fissure, associated with shallow sulci in the overlying cortex. Sylvian fissures were displaced further anteriorly and medially as HPE became more severe, until, in the most severe cases, no sylvian fissures could be identified. Sylvian angle measurements corresponded closely with severity of HPE, being largest in the most severe and smallest in the least severe cases. All patients with HPE had sylvian angles significantly larger than the mean of 15 degrees measured in the control patients. CONCLUSION: The only true malformations of cortical development were subcortical heterotopia. However, diffuse and focal abnormal sulci were observed. We propose our sylvian angle measurement of extent of frontal lobe development as an objective means of quantifying the severity of HPE.

Cerebral Cortex↗

PubMed2002

The middle interhemispheric variant of holoprosencephaly.

BACKGROUND AND PURPOSE: The middle interhemispheric variant of holoprosencephaly (MIH) is a rare malformation in which the cerebral hemispheres fail to divide in the posterior frontal and parietal regions. We herein describe the structural abnormalities of the brain in a large group of patients with MIH, compare these features with those of classic holoprosencephaly (HPE), and propose a developmental mechanism, based on current knowledge of developmental neurogenetics, by which MIH develops. METHODS: Brain images obtained in 21 patients with MIH (MR images in 16 patients and high-quality X-ray CT scans in five patients) were retrospectively reviewed to classify cerebral abnormalities. The cerebral parenchyma, hypothalami, caudate nuclei, lentiform nuclei, thalami, and mesencephalon were examined for the degree of midline separation (cleavage) of the two hemispheres. The orbits, olfactory apparati, and presence or absence of a dorsal cyst were also assessed. RESULTS: In all patients, by definition, midportions of the cerebral hemispheres were continuous across the midline, with an intervening interhemispheric fissure. The sylvian fissures were abnormally connected across the midline over the vertex in 18 (86%) of 21 patients. Two patients had relatively normal-appearing sylvian fissures; one had unilateral absence of a sylvian fissure owing to substantial subcortical heterotopia. Heterotopic gray matter or dysplastic cerebral cortex was also seen in 18 (86%) of 21 patients. MIH differed from classic HPE as follows. 1) In all subjects, the midline third ventricle separated the hypothalamus and lentiform nuclei. 2) The caudate nuclei were separated by the cerebral ventricles in 17 (89%) of the 19 [corrected] patients in whom they could be assessed. 3) The most commonly affected basal nucleus was the thalamus (non-cleavage in seven [33%] of 21 cases, abnormal alignment in 1 [5%]). 4) Three (18%) of the 17 [corrected] patients in whom the mesencephalon could be assessed showed some degree of mesencephalic non-cleavage. 5) No patients had hypotelorism (four had hypertelorism, the remainder manifested normal intraocular distances). Dorsal cysts were present in five (25%) of the 20 patients in whom they could be assessed (dorsal cysts could not be assessed after shunt surgery), and as in classic HPE, were associated with severe thalamic non-cleavage in three of these five patients. CONCLUSION: MIH appears to cause non-cleavage of midline structures in a completely different pattern than does classic HPE. In MIH, impaired induction or expression of genetic factors appears to influence the embryonic roof plate, whereas in classic HPE, induction or expression of the embryonic floor plate seems to be affected.

Brain↗