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Biomedical subjects

T H Newton

Publications and source records attributed to T H Newton.

At least 19 recordsLinked to original sources
PubMed1996

Development of the pineal gland: measurement with MR.

PURPOSE: To use MR imaging in the analysis of the size of the normal pineal gland in infants, children, and adolescents. METHODS: We retrospectively analyzed the size of the pineal gland in 249 patients (129 male and 120 female) aged 2 weeks to 20 years old. The maximum length (L), height (H), and width (W) of the gland were determined from a combination of sagittal, coronal, and axial MR images obtained on a 1.5-T scanner. The volume was calculated by using the formula 1/2 x L x H x W. RESULTS: The size of the pineal gland was significantly smaller in patients younger than 2 years old than in older patients. The size of the pineal gland increased until 2 years of age and remained stationary between the ages of 2 and 20 years. We found a large variation in size among all age groups. No difference in size was noted between males and females. CONCLUSION: This study establishes norms for pineal gland size in infants younger than 2 years old and in children and adolescents 2 to 20 years old as detected with MR imaging. Knowledge of the size of the normal pineal gland is important in the detection of abnormalities of the pineal gland, particularly neoplasms.

Adolescent↗
PubMed1993

Hypothalamic and pituitary pathology.

This article details the intricate anatomy and elegant physiology of the hypothalamic-pituitary axis. The discussion is meant to confer an understanding of the principles of neuroendocrinology appropriate for the radiologist interpreting imaging studies of this region. The clinical presentations of the diseases that occur in this area of the central nervous system are unique and therefore are discussed in some detail. The radiologic features of the diseases affecting the hypothalamic-pituitary axis are described and correlated with the relevant pathology.

Adenoma↗
PubMed1990

Three-dimensional gradient-recalled MR imaging as a screening tool for the diagnosis of cervical radiculopathy.

The purpose of the study was to implement and assess a fast-screening, three-dimensional Fourier transformation (3DFT) MR sequence for the cervical spine. This sequence maintains adequate signal-to-noise and image contrast similar to gradient-recalled echo two-dimensional Fourier transformation (2DFT) imaging. Thirty patients with radiculopathy were examined with 3DFT gradient-recalled echo imaging. The data set consisted of 60 contiguous 1.5- to 2.0-mm-thick axial slices with a total coverage of 9 to 12 cm. In 10 patients, comparison was made with 4-mm-thick axial T1-weighted spin-echo 2DFT or gradient-recalled echo 2DFT studies. With the use of a volume acquisition, adequate signal-to-noise and image contrast similar to T2-weighted gradient-recalled echo 2DFT acquisitions were obtainable. Coverage was improved despite the use of thinner sections without interslice gap. Thin-section 3DFT provided superior detail of acquired foraminal and spinal canal stenosis and disk morphology. Limitations included increased sensitivity to patient motion and "wraparound" artifact in the slice-select direction. Overall, diagnostic confidence was improved with 3DFT owing to the reduction of partial volume artifact. We have adopted this technique as the primary screening method for diagnosing cervical radiculopathy.

Cervical Vertebrae↗
PubMed1989

Intradural spinal cord lesions: Gd-DTPA-enhanced MR imaging.

Twenty-five patients with suspected spinal cord neoplasms were studied with high-field-strength magnetic resonance (MR) imaging (1.5 T) before and after administration of gadolinium diethylenetriamine-pentaacetic acid (DTPA) (gadopentetate dimeglumine). Five patients had enhancing, nonneoplastic lesions, including spinal dural arteriovenous fistulas (AVFs), cord infarction, and chronic arachnoiditis. Fifteen patients had proved spinal cord neoplasms, 13 intramedullary and two extramedullary. Four of the intramedullary tumors were detected only after Gd-DTPA administration; in five others, contrast material enhancement improved observer confidence. Gd-DTPA also demonstrated one dural AVF not detected on precontrast images. Regions of cord ischemia or infarction related to spinal dural AVF also enhanced in three patients. Advantages of Gd-DTPA include the demonstration of small isointense intramedullary tumors and the ability to permit differentiation of tumor from adjacent cord syrinx and solid tumor from postoperative gliosis and arachnoid scarring. Gd-DTPA enhancement is a useful adjunct to high-resolution MR imaging of the spinal cord.

Adult↗
PubMed1989

Posterior fossa hemangioblastomas: MR imaging.

The magnetic resonance (MR) imaging findings of 18 surgically proved posterior fossa hemangioblastomas (15 patients) were retrospectively analyzed and correlated with computed tomographic (ten patients) and angiographic (eight patients) findings. Thirteen tumors were located in the cerebellar hemisphere, three in the vermis, and two in the medulla with associated syrinxes. Three patients had von Hippel-Lindau disease, two of whom had multiple cerebellar hemangioblastomas. Seven hemangioblastomas appeared as solid tumors, six as solid masses with central cysts, and five as cysts with mural nodules. Abnormal tumor vessels, with characteristic signal void, were demonstrated in 13 tumors. Associated hemorrhage was present in four tumors. Although angiography is usually required for the diagnosis and preoperative assessment of this tumor, MR imaging demonstration of a posterior fossa mass with abnormal vessels should suggest the diagnosis of hemangioblastoma. Moreover, the combination of a peripheral posterior fossa cyst with a mural nodule supplied by enlarged vessels may be pathognomonic.

Adult↗
PubMed1989

High-resolution MR imaging of pituitary microadenomas at 1.5 T: experience with Cushing disease.

The MR images of 27 patients with clinically and biochemically suspected Cushing disease were evaluated retrospectively in a blinded fashion. The MR interpretation was compared with detailed operative diagrams and operative and pathologic reports. The examinations were performed on a 1.5-T MR system with thin-section sagittal and coronal T1-weighted (short TR/TE) images. Each pituitary half was considered separately (54 "halves"). Twenty-one pituitary halves were considered to have glandular abnormalities on MR. Compared with surgical findings, 17 MR findings were true positives and four were false positives (one pars intermedia cyst, three normal tissue). Of the 33 pituitary halves considered normal on MR, 26 were true negatives and seven were false negatives. MR had an overall sensitivity of 71% and a specificity of 87% for these adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas. A focal glandular hypointensity identified on coronal images was the most sensitive predictor of adenoma location. Sagittal images were not useful in either detection or localization. Upward convexity of the gland and deviation of the stalk were less useful indicators. Abnormalities of the sellar floor were the least reliable. In comparison with the capabilities of CT detection of microadenomas described in the current literature, it appears that high-field thin-section MR of the sella is the most sensitive imaging method for preoperative localization of ACTH-secreting adenomas in patients with Cushing disease.

Adenoma↗
PubMed1989

Histochemical characterization and functional significance of the hyperintense signal on MR images of the posterior pituitary.

MR imaging of the pituitary fossa characteristically shows a well-circumscribed area of high signal intensity in the posterior lobe on T1-weighted images. We used a combination of high-field MR, electron microscopy, and histologic techniques in experimental animals to determine whether the hyperintensity of the posterior lobe might be functionally related to hormone neurosecretory processes, and to attempt to establish its chemical nature. Histologic sections of a dog's pituitary gland processed with lipid-specific markers showed intense staining in the posterior lobe but not in the anterior lobe, thus documenting the location of fat in the posterior pituitary. Administration of vasoactive drugs known to influence vasopressin secretion to anesthetized cats produced changes in the volume of high-intensity signal in the posterior pituitary. Subsequent electron microscopy showed a significant increase in posterior lobe glial cell lipid droplets and neurosecretory granules in dehydration-stimulated cats. The data suggest that the pituitary hyperintensity represents intracellular lipid signal in the glial cell pituicytes of the posterior lobe or neurosecretory granules containing vasopressin. The volume of the signal may, in turn, reflect the functional state of hormonal release from the neurohypophysis.

Animals↗
PubMed1988

Chordomas: MR imaging.

Twenty histologically verified intracranial and upper cervical chordomas were retrospectively studied with both magnetic resonance (MR) imaging and computed tomography (CT), and the advantages of each modality were compared with regard to three criteria: detection of tumor, delineation of extent of tumor, and characterization of tumor. MR imaging and CT were equivalent in permitting the detection of chordomas. MR imaging was considerably better in delineating the full extent of the tumor, which would influence establishment of treatment. MR imaging also provided a degree of histologic specificity that would be useful in prognosis.

Adult↗
PubMed1988

MR imaging of cavernous sinus involvement by pituitary adenomas.

The ability of high-resolution MR imaging (1.5 T) to detect invasion of the cavernous sinuses by pituitary adenoma was determined through a retrospective review of 74 patients. These patients were divided into three groups: 25 normal subjects, 24 subjects with invasive pituitary adenomas, and 25 subjects with noninvasive pituitary adenomas. A fourth group of 30 patients, who subsequently underwent surgery for pituitary adenoma, was evaluated prospectively by MR for the presence or absence of cavernous sinus invasion. Several features were analyzed: (1) the detectability of the medial and lateral dural margins of the cavernous sinus (2) the size and variation in intensity of compartments within the cavernous sinus (3) the relationship of endocrine function to the surgical and MR appearance of the cavernous sinus and (4) carotid artery displacement or encasement by tumor. The normal cavernous sinuses were usually symmetric, but their sizes varied. The lateral dural margin of the cavernous sinus was always recognized on MR as a linear, discrete, low-intensity area. The medial dural margin (pituitary capsule) was seen on MR in only two of the 25 normal patients. In all 24 patients with cavernous sinus invasion involvement was unilateral and was most common with laterally positioned prolactin or adrenocorticotropic hormone secretory adenomas. Invasion of the cavernous sinus was suspected by MR in only two of the 13 invasive microadenomas and was questionable in three. In 10 of the 11 macroadenomas with surgically proved dural invasion, MR demonstrated an asymmetric increase in size and intensity of the superior and inferior cavernous sinus compartments. Noninvasive macroadenomas compressed and displaced the cavernous sinus bilaterally. The prospective MR evaluation of 30 patients undergoing surgery for pituitary tumor revealed a sensitivity for predicting cavernous sinus invasion of 55%, a specificity of 85.7%, a positive predictive value of 62.5%, and a negative predictive value of 81.8%. No feature permitted certain distinction between invasive and noninvasive microadenomas, as the medial dural wall of the cavernous sinus could not be reliably identified. The most specific sign of cavernous sinus invasion was carotid artery encasement.

Adenoma↗
PubMed1987

Giant intracranial aneurysms: MR imaging.

Fifteen patients with giant intracranial aneurysms were examined with magnetic resonance (MR) imaging, computed tomography (CT), and angiography. MR imaging revealed a rounded extraaxial mass with evidence of intraluminal blood flow in 12 of the 15 cases. Signal void within the lumen was seen in all 12 of these cases. Other flow effects, such as even-echo rephasing, were seen in some cases. Complete thrombosis was seen in three giant aneurysms in which high signal intensity on T1- and T2-weighted images filled the lumen, and no flow effects were seen. Partial thrombosis was detected in four aneurysms as persistent areas of medium to high signal intensity within the lumen on T1- and T2-weighted images. In five cases, the cause of the intraluminal signal that was present was difficult to determine. The ability of MR to indicate flow within the lumen in 12 of 15 cases provided for greater diagnostic confidence than with CT, which was strongly suggestive of an extraaxial tumor in nine patients. Calcification of the wall of the aneurysm was better detected with CT.

Adult↗
PubMed1987

Dural fistulas involving the cavernous sinus: results of treatment in 30 patients.

Thirty symptomatic indirect carotid cavernous fistulas were treated between 1978 and 1986 with a variety of treatment modalities. Combined carotid artery and jugular vein compression resulted in a complete cure in seven of 23 patients (30%) and improvement in one additional patient. There were no complications from this treatment, which is performed by the patient on an outpatient basis. Patients in whom carotid jugular compression therapy failed or who demonstrated cortical venous drainage or visual decline were treated with intravascular embolization. Embolization resulted in complete cure in 17 of 22 (77%) and improvement in four of 22 (18%). One patient required surgical excision of the involved dura after embolization to achieve complete cure. There was one permanent complication (stroke), which resulted in mild weakness caused by clot formation on a catheter.

Adult↗
PubMed1987

Dural fistulas involving the transverse and sigmoid sinuses: results of treatment in 28 patients.

Twenty-eight symptomatic dural fistulas involving the transverse and sigmoid sinuses were treated between 1978 and 1986 with a variety of treatment modalities. Occipital artery compression therapy resulted in a complete cure in two of nine patients (22%) and improvement in three of nine (33%). There were no complications from this treatment. Patients who were excluded or in whom compression therapy failed were treated with embolization alone or in conjunction with surgery. Of the 17 patients who underwent embolization alone, ten were cured and six were improved. Six patients had a combination of embolization and surgery; four patients were cured and two improved. There were three complications in this series, one related to surgery and two related to embolization.

Adult↗
PubMed1987

Posterior pituitary gland: appearance on MR images in normal and pathologic states.

T1-weighted magnetic resonance (MR) images of the pituitary gland and sella turcica routinely demonstrate a region of high signal intensity in the neurohypophysis. High-resolution MR imaging studies of the sella turcica in 200 subjects with a normal or abnormal sella were analyzed. The hyperintensity was found in the images of about 90% of healthy subjects and patients with microadenoma, in only 43% of patients with macroadenoma, and in 12% of patients with empty sellae. The signal was absent in several patients with functional or anatomic abnormalities of the hypothalamic-hypophyseal axis. It is concluded that the high signal intensity in the posterior lobe of the pituitary gland is present in most healthy individuals and that its absence in many patients with large intrasellar masses and empty sellae is due to compression of posterior lobe tissue. Its absence in diabetes insipidus further suggests a relationship between hyperintensity and the functional status of the hypothalamic-hypophyseal axis.

Adenoma↗
PubMed1987

Rathke cleft cysts: CT, MR imaging, and pathologic features.

The authors retrospectively reviewed the clinical, computed tomography (CT), and magnetic resonance (MR) imaging findings in seven patients with pathologically proved Rathke cleft cysts. All the cysts were located in the anterior sella turcica or the anterior suprasellar cistern. Five cysts had both intra- and suprasellar components, one was entirely intrasellar, and the other was predominantly suprasellar in location. The size of the cysts ranged from 8 to 20 mm. CT scans demonstrated low-density homogeneous lesions in four cases. On MR images of three of these four cases, the cysts had the same intensity as cerebrospinal fluid on T1- and T2-weighted images, while in the fourth case, the cyst was hyperintense on the T1-weighted images. In the remaining three cases, CT showed slight hyperdensity relative to brain parenchyma, suggestive of contrast enhancement. MR showed signal heterogeneity of these lesions with focal components of diminished signal intensity of T2-weighted images. These same foci appeared iso- to slightly hyperintense on T1-weighted images.

Adult↗
PubMed1987

MR imaging of paragangliomas.

MR imaging of 15 paragangliomas in 10 patients was compared with CT of 13 of the lesions in eight patients. All lesions were confirmed with angiography. All lesions were detected by MR and CT with the exception of one small glomus tympanicum tumor that was seen only in retrospect with MR. CT better demonstrated subtle osseous changes of the skull base and the relation of the tumor to the middle ear structures. MR better demonstrated the relation of the tumor to the adjacent internal jugular vein and carotid artery. The paragangliomas had a characteristic MR appearance based on their vascularity. Serpiginous areas of signal void representing high vascular flow were interspersed among areas of high signal intensity caused by slowly flowing blood and tumor cells. This "salt-and-pepper" pattern was seen in all lesions greater than 2 cm in maximal dimension. MR was therefore able to accurately characterize the tumors as highly vascular. Multiplanar imaging and good tissue contrast and anatomic detail permitted display of the relations of these neoplasms to surrounding carotid sheath vessels and to intracranial structures better than did CT. In this experience, the MR appearance of paragangliomas was quite characteristic and differed markedly from meningiomas, neuromas, and metastatic disease of the skull base.

Carotid Body Tumor↗
PubMed1987

MR imaging of intracranial tuberous sclerosis.

The role of MR in evaluating tuberous sclerosis is reviewed in 15 patients. These studies were compared with CT scans, which were available in 14 patients. Four characteristic findings were noted on the MR images obtained. Subependymal nodules projecting into the lateral ventricles were seen in 12 of 15 patients on T1-weighted images. This was the most specific finding. Distortion of the normal cortical architecture was seen in 10 of 11 patients in whom T1-weighted images were obtained using a 256 X 256 matrix. These foci corresponded to multiple cortical areas of increased signal on T2-weighted images. Dilated ventricles were seen in five patients. In one patient, a known astrocytoma showed increased signal on the T2-weighted images, allowing differentiation from a benign subependymal nodule. MR depicted the cortical hamartomas more completely than did CT. The MR scans were abnormal in all cases, and a diagnosis could be confidently made in all 11 cases scanned using a 256 X 256 matrix. Our preliminary experience suggests that MR will at least equal and probably exceed CT, both for sensitivity and specificity, given the use of a 256 X 256 matrix.

Adolescent↗