PubMed Health⌕ Search

Biomedical subjects

K W Pojunas

Publications and source records attributed to K W Pojunas.

17 recordsLinked to original sources
PubMed1993

Are both color-flow duplex scanning and cerebral arteriography required prior to carotid endarterectomy?

In an attempt to eliminate the morbidity, mortality, and cost associated with arteriography, surgeons are relying increasingly on duplex scanning of the extracranial arteries as the primary preoperative evaluation prior to carotid endarterectomy (CEA). This study was initiated to evaluate the need for cerebral arteriography in the preoperative evaluation of patients for CEA. One hundred five patients undergoing 114 CEA procedures are included in a retrospective review to determine whether the addition of cerebral arteriography changed the operative management of these patients. In 58 of 105 patients (55%), color-flow duplex scanning and cerebral arteriography were performed in the workup prior to CEA. In four patients a discrepancy was found between the duplex results and the arteriogram, leading to a change in the operative approach in two. The remaining 47 patients (45%) underwent color-flow duplex scanning as the definitive preoperative study; the surgical management was altered because of the operative findings in one patient. Although color-flow duplex scanning does not provide absolute concordance with cerebral arteriography, in most instances it can be used as the definitive preoperative study prior to CEA. We define the indications for cerebral arteriography in patients undergoing CEA.

Adult↗
PubMed1988

The effect of patient positioning on MR imaging of the internal auditory canal.

Identification of individual cranial nerves and complete exclusion of tumor in the internal auditory canal may be difficult with MR, especially in imperfectly positioned patients. MR studies of the temporal bones in patients and in normal volunteers positioned non-rotated or canted were correlated with corresponding cryomicrotomic sections. Especially in axial images, oblique sectioning of cranial nerves VII and VIII may cause difficulty in identifying individual nerves. A combination of axial and coronal short TR and TE images can be used to confidently exclude intracanalicular tumor in most cases.

Facial Nerve↗
PubMed1987

Benign extraaxial tumors: contrast enhancement with Gd-DTPA.

Meningiomas, acoustic neuromas, and other benign extraaxial tumors have little contrast with adjacent brain tissue on conventional magnetic resonance (MR) images. The contrast enhancement produced by intravenous administration of 0.1 mmol/kg of gadolinium-DTPA in these tumors was measured on T1 MR images. Acoustic neuromas showed the greatest enhancement (average, 310%), meningiomas the next greatest (average, 180%), and neurofibromas, glomus tumors, and pituitary microadenomas the least enhancement. The degree of enhancement was almost always greater at 3 minutes than at 25 or 55 minutes. Contrast between the tumor and adjacent tissue resulted from tumor enhancement in neuromas, meningiomas, and neurofibromas and from enhancement of the surrounding tissue in pituitary microadenomas.

Adenoma↗
PubMed1987

Cranial magnetic resonance imaging in the evaluation of myelopathy of undetermined etiology.

The spinal form of MS is a clinical conundrum, the solution of which may yield many answers; to be certain that it is MS and not another disease causing the myelopathy is often difficult. We evaluated 20 patients with myelopathy of undetermined etiology (clinical findings limited to the spinal cord) using T2-weighted cranial magnetic resonance imaging (T2 MRI) and cranial computerized tomography (CT). Some patients were also studied with flash visual evoked responses (FVER) and spinal fluid analysis for myelin basic protein (MBP) and oligoclonal banding (OCB). Thirteen patients had T2 MRIs consistent with demyelinating disease (two or more areas of increased signal intensity, of appropriate size, in periventricular/subcortical white matter), while only one CT showed focal lesions. FVER were abnormal in 8 of 15 patients tested; spinal fluid OCB was present in 12 of 16 patients tested, only 1 of whom had elevated MBP. T2 MRI showed lesions typical of demyelination in the majority of study patients, was much more sensitive than CT, and was well correlated with evidence of demyelination by other tests. Although the specificity of T2 MRI in MS is unknown, it may be very high in this clinical setting.

Adult↗
PubMed1987

MR detection of tumor in the internal auditory canal.

The MR appearance of 15 tumors within or near the internal auditory canal was analyzed in detail and compared with the subsequent surgical observations. In most cases, nonenhanced MR showed the precise extent of the intracanalicular and extracanalicular tumor despite minor variations in appearance. In a case of facial nerve neurinoma, the extent to which the tumor invaded the canal was underestimated by MR. Gadolinium-DTPA enhancement is expected to eliminate uncertainties in MR imaging of the internal auditory canal.

Cerebellar Neoplasms↗
PubMed1987

Differentiation of intramedullary neoplasms and cysts by MR.

To determine the MR criteria that are effective for differentiating intramedullary neoplasms from syringo- or hydromyelia, we reviewed MR scans made on prototype and commercial imagers of 33 patients with surgically confirmed cord abnormalities, including nine intramedullary neoplasms and 20 cysts (syringo- or hydromyelia). Two radiologists who did not know the clinical and radiologic diagnoses were asked to evaluate the scans with respect to cord expansion, distinctness of the disease margin, homogeneity, and signal intensity. These observations were correlated with the proved diagnoses. The combination of distinct margins and uniform signal intensity equal to that of CSF correlated consistently (88%) with spinal cord cysts. Other combinations were less reliable for diagnosing a cyst or tumor.

Diagnosis, Differential↗
PubMed1986

Trigeminal nerve: anatomic correlation with MR imaging.

Through correlation with cryomicrotic sections, the appearance of the trigeminal nerve and its branches on magnetic resonance images is described in healthy individuals and in patients with tumors involving this nerve. Coronal images are best for defining the different parts of the nerve and for making a side-to-side comparison. Sagittal images are useful to demonstrate tumors involving the gasserian ganglion.

Cavernous Sinus↗
PubMed1986

Cranial tissues: normal MR appearance after intravenous injection of Gd-DTPA.

The effect of intravenously administered gadolinium DTPA on signal intensity of normal intracranial structures was analyzed in 25 patients. Magnetic resonance (MR) image enhancement with Gd-DTPA differs from image enhancement on computed tomography with aqueous iodinated contrast media. Marked contrast enhancement owing to Gd-DTPA was observed in the pituitary gland, infundibulum, cavernous sinus, cranial nerves, choroid plexus, and nasal mucosa. Enhancement was not visible routinely in the falx cerebri, tentorium cerebelli, dura, or rapidly flowing blood. The efficacy of Gd-DTPA in any individual MR study may be assessed by observing the signal intensity of the pituitary gland, pituitary stalk, or nasal mucosa.

Arcuate Nucleus of Hypothalamus↗
PubMed1986

Pituitary and adrenal CT of Cushing syndrome.

Determination of the site of excessive hormone production in Cushing syndrome is possible with biochemical tests in 80% of cases. High-resolution CT of both the pituitary and adrenal glands was used to evaluate eight patients with surgically verified ACTH-secreting pituitary microadenomas and one patient with ectopic Cushing syndrome. Three ACTH-secreting microadenomas were demonstrated by CT. Adrenal CT was normal in six of the eight patients with pituitary tumors. The patient with ectopic ACTH production had mild unilateral adrenal gland enlargement and a normal pituitary CT scan. Normal adrenal or pituitary CT scans do not exclude Cushing syndrome.

Adenocarcinoma↗
PubMed1985

Cervical spinal fractures: CT detection.

Although computed tomography (CT) is commonly used in addition to plain radiographs to evaluate cervical spinal fractures, it may fail to detect some clinically significant fractures. Cervical spinal fractures were produced in cadavers, studied with CT, and documented by cryomicrotomy. The CT scans were interpreted independent of the anatomic sections. Pedicle and lateral mass fractures were regularly unrecognized on CT scans. In these cases, widening and hemarthrosis of the adjacent facet joints were evident. A widened facet joint is an indirect sign of an occult cervical spinal fracture.

Cadaver↗
PubMedDate not supplied

MR imaging of prolactin-secreting microadenomas.

Eight proven and three presumed prolactin-secreting microadenomas were studied with magnetic resonance (MR) imaging. All 11 cases had CT evidence of a tumor. Technical factors for MR included use of 1.3-1.5 T MR systems, 3 mm slice thickness, short repetition time (TR) (T1-weighted) and long TR (T2-weighted) spin-echo pulse sequences. Six microadenomas were demonstrated with MR. Four tumors had a long T1 and long T2, one had a long T1 and short T2, and one bromocriptine-treated tumor had a short T1 and short T2. MR failed to delineate the focal mass within the pituitary gland in the other five patients. The cause of the MR failures was not determined; however, tumor size did not appear to be a factor. MR signals arising from microadenomas are variable and possibly related to the activity of the prolactin-secreting cells. Correlation of findings from MR imaging, spectroscopy, and electron microscopy may lead to an understanding of the variable MR appearance of microadenomas.

Adenoma↗
PubMedDate not supplied

MR imaging of the optic nerve and sheath: correcting the chemical shift misregistration effect.

The interface between soft-tissue structures and adipose tissue may be obscured by the chemical shift misregistration effect on MR images. In the orbit, this effect occurs at the edges at the optic nerve, even on high-resolution local coil images. In both phantom and clinical studies with a 1.5 T local coil imaging system, it was found that the chemical shift misregistration effect can be minimized by positioning the patient so that the optic nerve is parallel to the frequency encoding gradient. Alternatively, the effect can be corrected by using a computer program to combine "lipid" and "water" proton images. The sensitivity of MR for optic nerve lesions should be improved by these technical modifications.

Child↗
PubMedDate not supplied

MR of the diaphragma sellae.

The appearance of the diaphragma sellae is described in cryomicrotomic sections and on MR in patients with and without intra- and suprasellar masses. On MR, it appears as a thin band of negligible signal that is best shown when adjacent CSF or a mass has greater signal intensity. Its position or absence can be used to differentiate intrasellar masses with suprasellar components from suprasellar masses.

Adenoma↗
PubMedDate not supplied

Facial nerve enhancement in MR imaging.

The significance of facial nerve enhancement after IV gadolinium administration has not been determined. We evaluated the MR appearance of facial nerves (nonenhanced and enhanced) in patients without and with masses involving the temporal bone, internal auditory canal, or cerebellopontine angle. In patients without such masses, no facial nerve enhancement was seen. In the other group, four of 11 patients showed facial nerve enhancement and geniculate ganglion masses. Three of these four patients had neurofibromatosis; one had surgical verification of a facial nerve neurofibroma. Enhanced MR facilitates identification of abnormal facial nerves.

Brain Neoplasms↗
PubMedDate not supplied

Neuroepithelial cysts of the lateral ventricles: MR appearance.

The MR imaging appearance of neuroepithelial cysts in the lateral ventricle is reported. Two cases of proven and two of presumed intraventricular neuroepithelial cysts are presented. In one case, MR observations documented spontaneous regression of a large intraventricular cyst. Theories regarding the origin of neuroepithelial cysts are briefly reviewed. Standard T1- and T2-weighted spin-echo pulse sequences were used to study cysts in the lateral ventricles in axial, coronal, and sagittal planes. The cyst wall can be demonstrated reliably with MR images, eliminating the need for CT and/or contrast ventriculography. MR may also be useful in monitoring cyst size on serial examinations.

Adult↗
PubMedDate not supplied

"Truncation" artifact in MR images of the internal auditory canal.

Dry skulls and a phantom were studied to determine whether an intracanalicular dark band in MR images of some acoustic neuromas could be artifactual. A "truncation" artifact was detected in the internal auditory canals of the dry skulls and in a simulated internal auditory canal of the phantom when the width of the canal approximately equaled 4 X (field of view) /N, where N equals 128 or 256, depending on the number of gradient steps chosen. The "truncation" artifact should not be confused with CSF between normal nerves when a canal contains tumor.

Humans↗