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Biomedical subjects

R D Tien

Publications and source records attributed to R D Tien.

At least 73 records · Page 4Linked to original sources
PubMed1992

Sequence of enhancement of various portions of the pituitary gland on gadolinium-enhanced MR images: correlation with regional blood supply.

In an effort to study the blood supply of the pituitary gland, we determined the sequence in which various portions of the gland enhanced on MR images obtained after administration of gadopentetate dimeglumine in seven healthy volunteers. The pituitary gland has a unique blood supply: the pars nervosa is supplied by the inferior hypophyseal arteries; the infundibular stem is supplied by the superior hypophyseal arteries, which are more distal than the inferior hypophyseal arteries; and the pars distalis is supplied indirectly by portal systems from the infundibular stem. Therefore, the expected sequence of contrast enhancement of the pituitary gland is: the pars nervosa first, the infundibular stem second, and the pars distalis last. However, it is difficult to evaluate the temporal sequence of contrast enhancement with "slow" conventional MR techniques, such as routine enhanced images acquired minutes after contrast administration. Accordingly, we used rapid enhanced gradient-echo sequences (14 sec/image) and the region-of-interest method to determine contrast enhancement for various portions of the gland. Enhancement-time curves were then plotted for each portion and compared to determine the sequence of enhancement. Our results show that the timing of contrast enhancement of various parts of the pituitary gland as demonstrated on MR imaging correlates closely with the expected perfusion sequence based on knowledge of regional vascular anatomy. Normal enhancement-time curves of different portions of the pituitary gland were established. This technique and baseline data can be used to evaluate patients with hypopituitarism caused by ischemia.

Adult↗
PubMed1992

MR imaging of the pituitary gland in infants and children: changes in size, shape, and MR signal with growth and development.

It has been reported that on MR images of the brain in neonates the entire pituitary gland is hyperintense. This is quite different from the well-established observation that portion is isointense. To better understand the development of the neonatal pituitary gland, we studied the timing and magnitude of changes in the size, shape, and MR signal of the pituitary gland in early childhood and infancy. The study included 76 infants and children ages 3 days to 4 years old. In each MR study, the signal intensity of the pituitary gland on T1-weighted coronal (n = 24) and sagittal (n = 76) images was compared with the signal intensity of the pons by using region-of-interest methods. The size and shape of the pituitary glands were recorded. Statistical comparisons were made for signal intensity and size of the pituitary gland between boys and girls and among age groups. The results showed that the MR signal of the posterior lobe remained hyperintense relative to the pons for all age groups represented in our study (through 4 years). However, the signal intensity of the anterior lobe gradually diminished and by approximately age 2 months was isointense with the pons. Thus, by approximately age 2 months the MR signal intensity of the infant's pituitary gland has changed from being entirely hyperintense (as seen in neonates) to isointense in the anterior lobe and hyperintense in the posterior lobe (as seen in adults). In the first 2 months of life the pituitary gland is bulbous in shape; later it has a flatter upper surface. We found no significant changes in the length or signal intensity of the pituitary gland; no differences among sexes in size, shape, or signal intensity were demonstrated. Findings of a bulbous pituitary gland and high MR signal of the entire pituitary are normal in neonates up to 2 months of age. After that, the gland gradually flattens and the MR signal of the anterior lobe decreases until it has characteristics similar to the adult pituitary. Lack of high signal or discovery of a small pituitary gland in a neonate should alert the radiologist to the possibility of pituitary malformation or dysfunction.

Child, Preschool↗
PubMed1992

Crossed cerebellar diaschisis and crossed cerebellar atrophy: correlation of MR findings, clinical symptoms, and supratentorial diseases in 26 patients.

Crossed cerebellar diaschisis is a condition in which cerebellar hypometabolism is ascribed to functional disconnection of the contralateral hemisphere from the cerebral cortex. Interruption of the cerebropontine-cerebellar pathway is thought to be the most likely mechanism of this remote transneuronal metabolic depression. This phenomenon can be diagnosed by positron emission tomography, as there is hypometabolism in the affected cerebellar hemisphere. The morphologic features of the affected cerebellar hemisphere in patients with the diagnosis of crossed cerebellar diaschisis have not previously been studied by MR imaging. We retrospectively reviewed 26 patients in whom the diagnosis of crossed cerebellar diaschisis was suggested by positron emission tomography; these patients also had MR studies. In all 26 patients, supratentorial diseases were documented by MR imaging. Twenty-four of the 26 patients had a pathologic diagnosis. Detailed clinical history was also obtained for all patients. MR findings of morphologic change in the affected cerebellum were correlated with the patient's clinical symptoms and supratentorial disease. Of the 26 patients, eight had cerebellar atrophy; the remaining 18 patients showed no MR abnormality of the affected cerebellum. In the 18 in whom no atrophy was seen on MR imaging, the majority of the supratentorial lesions were tumors. The eight patients in whom cerebellar atrophy was demonstrated usually had significant contralateral supratentorial hemispheric atrophy. The patients with atrophy were also generally younger (average age, 14 years) than the 18 patients without cerebellar atrophy (average age, 42 years). Our experience shows that a significant number of patients with crossed cerebellar diaschisis have morphologic changes of cerebellar atrophy shown by MR imaging. These patients usually have significant contralateral supratentorial hemispheric atrophy.

Adult↗
PubMed1992

Neurosyphilis in HIV carriers: MR findings in six patients.

Neurosyphilis, a sexually transmitted disease that can cause neurologic damage, has become increasingly prevalent in the AIDS era. HIV carriers can contract neurosyphilis without the presence of other concurrent opportunistic infections. Because MR findings of neurosyphilis are seldom reported, we retrospectively reviewed and evaluated contrast-enhanced MR images of six young (average age, 33 years) HIV-positive men with high serum and CSF VDRL titers indicative of neurosyphilis. All six patients tested negative for concurrent opportunistic infections. Five patients had acute or subacute strokelike symptoms involving the basal ganglia or middle cerebral arteries; one had a parietal convexity mass mimicking meningioma with headache and ataxia. Contrast-enhanced MR images showed patchy enhancement involving the basal ganglia and middle cerebral artery territories in the first five patients and the convexity mass in the sixth patient. On the basis of brain biopsy, a convexity mass was diagnosed in the patient with syphilitic gumma. The imaging findings of the remaining five patients represented ischemic infarct caused by meningovascular syphilis. After penicillin treatment, serum and CSF VDRL titers decreased, and neurologic signs and symptoms improved in all six patients. A follow-up MR study in the patient with the gumma showed that the lesion resolved almost completely. In young HIV patients with stroke symptoms or a convexity mass, neurosyphilis should be considered. Contrast-enhanced MR can reveal the extent of involvement by neurosyphilis and should be used to facilitate diagnosis and proper treatment.

Adult↗
PubMed1992

Rasmussen's encephalitis: neuroimaging findings in four patients.

Rasmussen's encephalitis is a devastating disease of childhood causing progressive neurologic deficits and intractable seizure activity. Patients frequently have episodes of epilepsia partialis continua and, much less frequently, generalized status epilepticus. The seizures are intractable despite aggressive medical management. In advanced cases, hemispherectomy appears to be the only option to control the seizures. Permanent physical and mental impairments are inevitable. The cause of this disease is unknown, although pathologic specimens demonstrate nonspecific changes that are compatible with viral encephalitis. The progressive brain damage is typically so insidious in onset and gradual in course that it is difficult to make an accurate diagnosis on the basis of clinical evidence. We retrospectively evaluated the CT, xenon CT, positron emission tomographic, and MR neuroimaging findings in four young patients with pathologically suspected Rasmussen's encephalitis (three patients had CT scans, two had xenon CT scans, two had MR scans, and one had a positron emission tomogram). All studies showed abnormalities of the involved cerebral hemisphere: CT and MR revealed nonspecific atrophy, xenon CT showed decreased cerebral blood flow, and positron emission tomography revealed a hypometabolic state. Rasmussen's encephalitis is a diagnosis of exclusion; however, the information obtained from neuroimaging studies in combination with the clinical course should suggest this disorder.

Adolescent↗
PubMed1992

Diseases of the lumbar spine: findings on fat-suppression MR imaging.

Fat-suppression MR techniques have been useful in imaging both the head and neck and the orbit. The lumbar spine is not as complex as the head and neck and does not contain as much fat as the orbit. Nevertheless, high signal from epidural and marrow fat in the lumbar spine can make it difficult to detect and define pathologic processes. In addition, the administration of gadopentetate dimeglumine can cause some infectious and neoplastic lesions of the spine to become isointense with fat on T1-weighted images. Compared with conventional MR imaging without fat suppression, contrast-enhanced fat-suppression MR imaging can better differentiate these enhancing lesions from surrounding fat. In this essay, we illustrate the findings of fat-suppression MR imaging in a variety of diseases of the lumbar spine.

Female↗
PubMed1992

Fast spin-echo high-resolution MR imaging of the inner ear.

Advances in MR imaging continue to improve our ability to evaluate temporal bone anatomy and disease. CT remains the procedure of choice for fine-detail imaging of bone structures such as ossicular anatomy, but it is not the ideal imaging technique for soft-tissue structures (e.g., the membranous labyrinth and neural structures). Conventional spin-echo MR techniques used to image these structures cannot yield excellent contrast and spatial resolution in clinically acceptable time frames. Conventional spin-echo T1-weighted images lack tissue contrast between fluid (e.g., CSF, endolymph, perilymph), neural tissue, otic capsule septa, and surrounding temporal bone. Conventional T2-weighted imaging of the inner ear is needed to reveal the natural contrast between fluid, neural structures, and bone; unfortunately, the use of conventional T2-weighted images is limited by time constraints when large-matrix, thin-section techniques with more than one excitation are used. Fast spin-echo imaging is a recently developed technique that can provide T2-weighted, thin-section (2-mm) high-resolution images with excellent contrast in a fraction of the time needed for conventional spin-echo techniques. This speed advantage allows us to obtain high-resolution images in clinically acceptable time frames. Images produced by this technique are a useful addition, in conjunction with routine T1- and T2-weighted spin-echo images, in the diagnosis of disorders of the inner ear.

Adult↗
PubMed1992

Evaluation of complex cystic masses of the brain: value of steady-state free-precession MR imaging.

OBJECTIVE: This study evaluated the effectiveness of steady-state free-precession (SSFP) MR imaging of complex cystic masses of the brain compared with that of conventional T1- and T2-weighted spin-echo imaging. Our hypothesis is that SSFP MR images provide better characterization of these masses and facilitate more appropriate preoperative diagnoses and planning. SUBJECT AND METHODS: Axial T1-weighted and SSFP MR images and specimens for pathologic examination were obtained in seven consecutive patients, 9-81 years old, with cystic mass lesions of the brain and neurologic symptoms and signs directly related to the masses. Axial contrast-enhanced T1-weighted images were obtained in six patients, surgical exploration was done in five patients, and stereotaxic biopsy was done in two. After examination of the routine spin-echo and SSFP images, the usefulness of SSFP images was determined by how well they facilitated correct preoperative diagnosis. RESULTS: On SSFP MR images, the solid or inhomogeneous components of a cystic mass had extremely low signals in contrast to the high signal of surrounding fluid. On routine spin-echo images, however, the signals of these components were masked by the signal of the surrounding fluid. SSFP MR images helped markedly in diagnosis of hemorrhagic, epidermoid, and arachnoid cysts. In cases of enhancing brain tumors, SSFP MR images provided the same information that contrast-enhanced images did. Overall, when SSFP MR imaging was used, more information about the texture and constituents of the cystic mass was obtained, and a more useful diagnosis was made. CONCLUSION: Initial results show that SSFP MR imaging is a more useful technique than conventional spin-echo imaging for characterizing complex cystic masses of the brain. SSFP MR imaging (1) allows distinction of edema from tumor, (2) helps establish where biopsy has the best chance of providing tissue that will show pathologic changes, and (3) helps distinguish simple cysts from tumors, tumor-cyst, or multicompartmental cyst and may be particularly helpful in detecting the contents of hemorrhagic cysts.

Adult↗
PubMed1992

Pleomorphic xanthoastrocytoma of the brain: MR findings in six patients.

OBJECTIVE: Pleomorphic xanthoastrocytoma is a rare, usually benign brain tumor. This pleomorphic supratentorial tumor involves the leptomeninges and superficial cortex in young patients with seizures. The MR imaging features of this distinct tumor have not been reported. We describe the MR imaging findings in six patients with pathologically proved pleomorphic xanthoastrocytoma. MATERIALS AND METHODS: We retrospectively reviewed the MR images of six patients with pathologically proved pleomorphic xanthoastrocytoma. MR images were reviewed by two neuroradiologists. The pathologic slides of the tumors were reviewed by two neuropathologists. We also analyzed the patients' clinical features. RESULTS: Most of the tumors were cortical based and isointense with gray matter on T1-weighted images and mildly hyperintense on T2-weighted images. All the masses enhanced with contrast material. Cystic components and gyriform and leptomeningeal enhancement were seen occasionally. The tumors occurred in the temporal lobes in four of the six patients. Three patients had seizures, and the other three had headaches. CONCLUSION: Pleomorphic xanthoastrocytoma is a rare, usually benign, cortical-based mass that often enhances intensely with contrast material. The most common location is in the temporal lobes. Seizures and headaches are common clinical features. Familiarity with this lesion is important in the differential diagnosis of enhancing cortical-based masses.

Adolescent↗
PubMed1992

Normal anatomy of the hippocampus and adjacent temporal lobe: high-resolution fast spin-echo MR images in volunteers correlated with cadaveric histologic sections.

This essay illustrates the appearances of sections of the normal hippocampus and adjacent temporal lobe on high-resolution heavily T2-weighted fast spin-echo MR images and correlates them with histologic sections. We found that this MR examination showed the detailed anatomy of the normal hippocampus in a much shorter time than is possible with conventional spin-echo techniques. The information provided in this essay can be used as a baseline for distinguishing between normal and abnormal hippocampi in a variety of disease states.

Adult↗
PubMed1991

Unilateral hydrocephalus in adults.

The authors report 14 cases of unilateral hydrocephalus in adults. Headache was the most common presenting symptom. Unilateral hydrocephalus was documented in each patient with computed tomography scans; magnetic resonance imaging was also used in seven patients in the latter part of the series. Unilateral hydrocephalus was caused by tumor (seven patients), venous angioma (one patient), ependymal cyst (one patient), postinflammatory gliosis (one patient), and was idiopathic in four patients. The primary surgical treatment was craniotomy with fenestration of the septum pellucidum, which relieved symptoms in eight of nine patients for whom long-term follow-up data were available.

Adolescent↗
PubMed1991

Magnetic resonance imaging of AIDS-related polyradiculopathy.

AIDS-related polyradiculopathy is a syndrome associated with cytomegalovirus infection. We report two cases of AIDS-related polyradiculopathy in which spinal T1-weighted MRI with gadolinium-DTPA showed enhancement of the pial lining of the conus medullaris, cauda equina, and lumbar nerve roots. Both patients clinically improved with ganciclovir treatment.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Intraventricular mass lesions of the brain: CT and MR findings.

One tenth of all CNS neoplasms involve the ventricles of the brain. These mass lesions are located in areas that are difficult to reach surgically, and because they are intraventricular, spread via the CSF is common. CT and MR imaging have been useful in demonstrating these masses, but imaging characteristics are usually nonspecific. The location of the mass and the patient's age provide the most helpful information in the differential diagnosis.

Adolescent↗
PubMed1991

Concomitant occurrence of subchondral cyst and ruptured anterior crucial ligament at knee joint: new findings by MRI.

The magnetic resonance imaging (MRI) in 4 cases of subchondral cyst at the knee joint region, were acquired from a 1.5 Tesla imager. We found a high incidence of concomitant occurrence of subchondral cysts with a ruptured anterior cruciate ligament (ACL) in all of these cases. The 2 men and 2 women, had an average age of 35. Clinically, they complained of dull knee pain and mild instability. Conventional radiography detected subchondral cysts in 3 of them, while MRI disclosed that all of the subchondral cysts were at the tibial plateau, close to the intercondyloid eminence. To date, MRI is the only imaging modality which can depict the concomitant occurrence of a subchondral cyst and a ruptured anterior cruciate ligament at the knee joint. Whether these subchondral cysts were the consequences of the ruptured anterior cruciate ligaments as one of the causes in addition to synovial fluid intrusion and bony contusion, need further clinical observation and investigation.

Adult↗
PubMed1990

Loculated intracranial leptomeningeal metastases: CT and MR characteristics.

Studies of twenty-five patients with loculated leptomeningeal tumor metastases diagnosed by CT and/or MR were analyzed retrospectively. Medulloblastoma was the most frequent primary tumor (8/25, 32%). Four subgroups of loculated patterns were identified. Type A included mass(es) limited to the subarachnoid space without obvious direct parenchymal infiltration; this pattern occurred in 12 patients, of whom five had associated diffuse pattern. Type B was characterized by mass(es) still predominantly in the subarachnoid space but with minor transpinal parenchymal infiltration; this pattern was found in five patients. Type C comprised subarachnoid mass(es) with marked transpinal extension mimicking parenchymal lesion; this pattern was observed in three patients. Type D consisted of subarachnoid mass(es) growing along the perineural CSF space; this pattern was noted in two patients. Additionally, two patients presented with combined A and C patterns, and one patient had a combined B and C pattern. More than half the patients (14/25, 56%) presented with a single lesion. The most frequent locations were the suprasellar cistern, ventricular walls, and lateral recesses of the fourth ventricle, Gd-DTPA-enhanced T1-weighted MR images appeared best for demonstrating the site and extent of disease. Recognition of the loculated patterns of leptomeningeal metastases, which are less common than the diffuse pattern, is important to radiologists and clinicians for correct diagnosis and proper management of patients with this disease.

Carcinoma, Squamous Cell↗
PubMed1990

MR imaging of pineal tumors.

MR images of pineal region tumors were analyzed in 26 patients with histologically proved tumors: seven germ-cell tumors, six astrocytomas, five teratomas, three pineoblastomas, two meningiomas, one dermoid, one epidermoid, and one metastasis. In an attempt to identify specific MR characteristics of these lesions, Gd-DTPA was administered to six patients. CSF and blood serum were assayed for alpha-fetoprotein (AFP) and human chorionic gonadotropin-beta subunit (HCG-beta) in 18 patients. MR findings were correlated with age, sex, the presence of biochemical tumor markers, and surgical outcome. We found that the most important factors in the determination of tumor type were the patient's age and the tumor markers. Increased levels of both HCG-beta and AFP were specific for patients with malignant teratomas and undifferentiated germ-cell tumors. HCG-beta alone was elevated in the patient with choriocarcinoma; only AFP was elevated in the patient with an endodermal sinus tumor. Tumor markers were not present in other patients in this series. The tumor size and the presence of fat were also helpful in determining tumor type. Hemorrhage was rare, seen only in the patient with a choriocarcinoma. Gd-DTPA did not enhance diagnostic specificity but aided in the detection of tumor seeding through CSF. We conclude that, although MR is sensitive in the detection of pineal region tumors and provides superb anatomic detail, MR signal characteristics are usually nonspecific. Correlation with the patient's age and the tumor markers significantly improves diagnostic accuracy.

Adolescent↗
PubMed1989

Cerebral Erdheim-Chester disease: persistent enhancement with Gd-DTPA on MR images.

A case of Erdheim-Chester disease with intracerebral masses containing characteristic lipid-laden histiocytes is presented. These unusual lesions remained enhanced on magnetic resonance images obtained 8 days after injection of gadolinium diethylenetriaminepentaacetic acid (DTPA) dimeglumine. Chemical analysis of a biopsy specimen revealed a high concentration of gadolinium. Findings suggest that the Gd-DTPA complex or possibly a gadolinium-containing metabolite may be retained for extended periods in this unusual type of histiocytic lesion.

Brain↗