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Biomedical subjects

D B Hackney

Publications and source records attributed to D B Hackney.

At least 55 records · Page 3Linked to original sources
PubMed1992

Central nodal necrosis and extracapsular neoplastic spread in cervical lymph nodes: MR imaging versus CT.

Computed tomographic (CT) scans and magnetic resonance (MR) images obtained in 24 patients with cervical lymphadenopathy were retrospectively and blindly evaluated by two readers for the presence of central nodal necrosis (CNN) and extracapsular nodal spread (ENS). The CT studies were all enhanced, and the MR images were obtained with short repetition time (TR)/echo time (TE), long TR/double echo, and enhanced short TR/TE fat-suppressed sequences. Each MR imaging sequence was interpreted separately and then collectively. Sixty lymph nodes were identified with CT. Sensitivity for CNN was 16%-67% with the unenhanced MR pulse sequences, 50% with enhanced sequences, and 83%-100% with CT. The most accurate reading of MR images for CNN was with the unenhanced T1-weighted and T2-weighted images (86%-87%); the accuracy of CT was 91%-96%. The accuracy of MR imaging for detecting ENS was maximal with T1-weighted images (78%-90%). Gadolinium-enhanced, fat-suppressed images did not improve accuracy in evaluating CNN or ENS. CT is currently more accurate than unenhanced or enhanced MR imaging in detecting CNN or ENS.

Carcinoma, Squamous Cell↗
PubMed1992

Reversible arteriovenous malformation-induced venous hypertension as a cause of neurological deficits.

A case of a dural arteriovenous malformation with prominent localizing neurological deficits is reported. The venous drainage of the lesion and the lack of a significant pial supply implicate venous hypertension as the mechanism of neurological dysfunction. This mechanism is supported further by the angiographic changes and the prompt resolution of the deficits after endovascular treatment. This case illustrates the potential for this frequently postulated but rarely confirmed pathophysiological mechanism to cause reversible neurological dysfunction.

Cerebral Veins↗
PubMed1992

Magnetic resonance imaging of the spine. Normal anatomy.

Standard anatomy of the spine may be found in anatomy and radiology textbooks. However, there are aspects of spinal anatomy that are of particular importance to magnetic resonance imaging (MRI). The structure and orientation of the facet joints and their relationship to the neural foramina receive relatively little attention in standard anatomic works, but they are of great importance in evaluating nerve root compression syndromes. Similarly, the relationships between the cross-sectional diameters of the spinal canal, the subarachnoid space, and the spinal cord assume a great deal of significance when evaluating patients with signs or symptoms of spinal stenosis. Changes in the configurations and composition of the spinal cord will become increasingly important to the radiologists as it becomes possible to identify and distinguish spinal cord grey and white matter. Degenerative syndromes of the spinal cord may be more thoroughly evaluated once MRI permits identification of the specific regions or structures of the cord in which the tissue loss has been most severe.

Humans↗
PubMed1992

Degenerative disk disease.

Evaluation of degenerative disk disease is, by far, the most common indication for spinal magnetic resonance imaging (MRI). It is rare to identify a patient over the age of 40 whose spine does not demonstrate at least some of the imaging features of degenerative disease. In spite of the ubiquitous nature of degenerative changes in the spine and decades of intensive study of degenerative processes, many questions concerning degenerative disease, including its immediate etiology, remain unanswered. Radiologic evaluation of degenerative spine disease focuses on the anatomic relationships between the disk, vertebral endplates and facet joints with the subarachnoid space, nerve roots, and spinal cord. Although MRI lacks the detail of high resolution computed tomography for defining the anatomy of osteophytes, MRI appears to be the primary modality for evaluating degenerative spine disease, and in most cases, MRI may be definitive.

Humans↗
PubMed1992

Neoplasms and related disorders.

Spinal neoplasms may be primary or metastatic, benign or malignant. In adults, metastatic involvement of the spine will represent the most important neoplastic disease of this region. However, hemangiomas are the most common spinal neoplasms. The vast majority of intradural, extramedullary neoplasms that will be identified in the spine are meningiomas and neurofibromas. Both lesions may be sporadic or associated with phakomatoses. Intramedullary spinal cord and filum terminale tumors are relatively rare and are far less common than intramedullary brain tumors. As is the case in the brain, these are overwhelmingly glial neoplasms, with ependymomas and low-grade astrocytomas representing the majority of the lesions. Hemangioblastoma deserves mention because of its often characteristic imaging findings and its association with von Hippel-Lindau disease.

Humans↗
PubMed1992

Inflammation, infection, cavitary disorders, and ischemia.

Demyclinating lesions of the spinal cord, including multiple sclerosis as well as other less common diseases, probably represent the etiology of a substantial proportion of all idiopathic myelopathies. Magnetic resonance imaging (MRI) has made major advances in the diagnosis and characterization of demyclinating disease. Infections of the spine may have severe consequences and, if detected early, are usually treatable processes. Osteomyelitis and epidural abscesses have characteristic imaging findings. Poor outcomes are more often due to delays in clinical presentation or the debilitated condition of the patients than to limitations in the accuracy of MRI diagnosis. Cavitary lesions of the spinal cord were among the first applications in which MRI proved its superiority to previously available techniques. Accurate diagnosis of these lesions involves detecting characteristics findings and relating these observations to the clinical history. Spinal cord infarction is relatively rare due to the extensively collateralized blood supply to the spinal canal. However, aortic aneurysms and the surgery for these lesions places the blood supply of the distal spinal cord and conus at risk. The syndrome of postoperative spinal cord infarction has characteristic clinical findings. However, MRI may contribute to distinguishing transient ischemia from true infarction and to predicting the severity of the final deficit.

Demyelinating Diseases↗
PubMed1992

Magnetic resonance imaging of the spine. Technology and technique.

Perhaps in no other area of radiology is the appearance of the images as dependent on the technique used to obtain them as is the case in magnetic resonance imaging (MRI). In some instances, such as decreasing signal-to-noise ratios at the periphery of surface coils or obvious difficulties in localizing the level of an abnormality detected in spinal images, the technical dependence is obvious. There are many instances, however, in which the influence of technology may be more subtle, although no less important. It is far less of a problem to have difficulty localizing a level when this difficulty is recognized than it is when ambiguity concerning the level of an abnormality goes undetected. Obsessive attention to accurate localization of levels is necessary to avoid potentially dangerous mistakes. Terms such as "T1-weighted" rarely provide an accurate description of the contrast characteristics of an MRI image. Careful use of terminology, or at a minimum clear thinking concerning the determinants of image contrast will avoid confusion in image interpretation. The "weighting" of an image usually cannot be defined in terms of a single parameter, and attempts to do so often obfuscate more than they clarify. As technology evolves, a variety of different "T1-weighted" pulse sequences may be introduced. Each of these may display different contrast characteristics. It will be important to identify the specific pulse sequence, rather than "weighting" to understand the signal intensities observed on images.

Artifacts↗
PubMed1991

Skull radiography in the evaluation of acute head trauma: a survey of current practice.

A survey was conducted to determine the extent to which skull radiography continues to be used for the evaluation of head trauma. Of 53 hospitals with emergency departments and computed tomography (CT) available full time, only 6% (n = 3) reported that skull radiographs were never a part of the evaluation of acute head injuries. At more than half of the institutions, skull radiographs were obtained always or often in cases of head trauma. High usage rates occurred at teaching and nonteaching institutions and were not related to the availability of CT or the size of the hospitals. CT was always employed in cases of severe head trauma, and skull radiography was frequently used in cases of minor injuries. Magnetic resonance imaging was rarely, if ever, used for evaluating head trauma. Skull radiography continues to be employed at a high rate for the evaluation of head trauma long after it has been demonstrated to provide little or no useful information in such cases.

Acute Disease↗
PubMed1991

In vitro modeling of the magnetic resonance appearance of cerebral hemorrhage.

In vitro studies provide a framework for understanding the biophysical mechanisms in the evolution of the magnetic resonance (MR) appearance of cerebral hematomas. Varying concentrations of oxyhemoglobin, deoxyhemoglobin and methemoglobin in saline or in concentrated bovine serum albumin solutions were imaged at 1.5 T, allowing assessment of the relative relaxation effects of heme oxidation state, oxygenation, and protein concentration. The findings demonstrate the importance of susceptibility effects arising from local field heterogeneity in producing T2 shortening upon varying hemoglobin concentration for intracellular deoxyhemoglobin and methemoglobin. Correlation between the clinically observed MR appearance of acute and subacute hematomas with these in vitro models is presented.

Brain↗
PubMed1990

Pediatric brainstem glioma. Post-radiation clinical and MR follow-up.

Thirty-four pediatric patients, twenty with presumed and fourteen with biopsy or autopsy proven brainstem gliomas were imaged by CT and MR before radiation therapy. Twenty-eight patients received radiotherapy. Of these, eighteen fit the protocol for combined clinical and MR post-treatment evaluation. No cases of radionecrosis were seen at autopsy. This study shows that MR can demonstrate tumor response to radiation therapy, tumor progression prior to clinical deterioration, post-treatment cyst formation and hemorrhage. Although MR clinical correlation was not optimal on six week post-treatment evaluation, 4-10 month post-treatment MR scanning correlated well with clinical evaluation. MR appears useful in post-therapeutic monitoring of tumor response.

Adolescent↗
PubMed1990

Varied MR appearance of autism: fifty-three pediatric patients having the full autistic syndrome.

Fifty-three autism patients ranging in age from 2 to 22 yr with a mean age of 9 yr were evaluated by MR imaging over a 3-yr study period. Sagittal, axial, and coronal spin-echo and short TI inversion recovery scans were performed on a 0.5 Tesla (Picker Inc., Cleveland, OH) system. Results were compared to 32 control patients age range 1 to 17 yr, mean 8.5 yr. MR scans were evaluated by three neuroradiologists. Measurements of midsagittal vermian height and AP diameter were performed. Subjective estimates were made of ventricular size, amygdala size, fourth ventricular size, and vermian shape. Results were correlated with clinical presentation, course, and lab analyses by a pediatric neurologist. MR findings did not present a single pattern capable of predicting the presence or severity of autism. The constellation of MR findings in this group of 53 patients was highly variable, thus we advise caution in the interpretation of MR images in autistic patients. Autism is a heterogeneous disease entity containing different clinical subgroups, which do not manifest similar radiologic pictures.

Adolescent↗
PubMed1990

Pseudoatrophy of the cervical portion of the spinal cord on MR images: a manifestation of the truncation artifact?

Routine evaluation of axial MR images of the cervical spine with high-intensity CSF (long TR/TE spin-echo or gradient-echo images) revealed apparent narrowing of the cord's anteroposterior diameter when these images were compared with corresponding postmyelography CT scans. This discrepancy was believed to be due to the truncation artifact at the CSF-cord boundary. To examine the truncation effect, we compared cord diameters in 12 patients on postmyelography CT scans and MR images and then compared these with MR scans of normal volunteers and of an agar-saline spine phantom. There was an artifactual diminution of the cord diameter in the 128-step phase-encoding axis of the 128 x 256-matrix MR scan as compared with the diameter of the cord in the patients' postiohexol CT scans and in the 256 phase-encoded axis MR scan in the volunteer study. A similar discrepancy was noted in the spine phantom study, in which the cord diameter in the 256-step phase-encoded MR scan, the CT scan, and direct measurement exceeded that in the 128-step phase-encoded axis MR scan. The range of differences between the measurements was as large as 2.3 mm (patients), 1.7 mm (volunteers), and 1.8 mm (phantom) for the three studies. In all three studies, varying the photographic window width and level produced variation in the apparent cord diameter of up to 1.5 mm. To eliminate this effect, the cord diameters in the phantom and the normal control subjects were measured at identical window levels. The truncation artifact, coupled with standard window settings used in photography, may lead to inaccurate display of the diameter of the cervical spinal cord.

Atrophy↗
PubMed1989

MR imaging of Parkinson disease with spin-echo and gradient-echo sequences.

High-field MR with both spin-echo and gradient-echo sequences was performed in 21 patients with (idiopathic, drug-responsive) Parkinson disease. The use of gradient echoes allowed more sensitive detection than did spin echoes of susceptibility changes in the putamina and substantia nigra. No statistically significant difference in putaminal hypointensity on long TR/long TE spin-echo sequences or on T2*-weighted images using gradient-echo sequences was observed between Parkinson patients and controls. There was also no statistically significant difference in the frequency of restoration of the signal intensity of the substantia nigra between the two groups of patients. The width of the pars compacta of the substantia nigra in patients with Parkinson disease was 2.12 + 0.82 mm (mean +/- SD). This value in age- and gender-matched controls was 2.67 +/- 0.5. Comparing these two groups with an unpaired t test resulted in a p value less than or equal to .005. Our MR study with spin-echo and gradient-echo images in Parkinson and control patients was able to substantiate and elaborate on previously described MR features of Parkinson disease.

Adult↗
PubMed1989

MR characteristics of subdural hematomas and hygromas at 1.5 T.

MR images of 24 patients with 33 subdural collections were retrospectively reviewed to determine the spectrum of MR findings associated with such lesions. The lesions were dated by history, when available. Hematomas were grouped as follows: acute, four; early subacute, four; late subacute, four; chronic, 13. Six collections were classified as rehemorrhage; and two patients had CSF hygromas. Subdural hematomas evolved in a pattern similar to intracerebral hemorrhage with the exception of chronic subdural hematomas, in which isointensity of hypointensity relative to gray matter was observed on short TR/TE images compared with the persistent very high signal intensity noted in chronic parenchymal hematomas. Hemosiderin was rarely seen in chronic hematomas. These findings are most likely the result of the absence of a blood-brain barrier, which allowed clearance and dilution of blood products. Subdural hematomas with repeat hemorrhage demonstrated multiple phases of bleeding with layering phenomenon and more frequent hemosiderin deposition. It is possible that the clearance of blood products, as observed in chronic subdural hematomas, is impaired or poorly functional when rehemorrhage occurs. The persistence of high signal from methemoglobin in a hematoma that is expected to be in the chronic phase also suggests repeated hemorrhage. Acute CSF subdural hygromas had signal intensities identical to CSF without MR evidence of blood products. At surgery, clear fluid under pressure was found. MR imaging, with its unique ability to delineate the various phases of hemorrhage, is well suited to the evaluation of subdural hemorrhage.

Adolescent↗
PubMed1988

Focal cortical dysplasia on magnetic resonance imaging: a case report.

A case report of an 11 years old boy with new onset of a seizure disorder is presented. A computed tomography scan demonstrated a noncalcified, nonenhancing focal region of abnormal cortex. A magnetic resonance imaging scan delineated both an isointense area of abnormally thickened gyri and linear areas of abnormal high signal intensity in the subjacent white matter. A review of the radiologic and pathologic literature suggests that this lesion represents the entity focal cortical dysplasia as described by Taylor, et al. This abnormality is part of a spectrum of disorders including hamartomas (of tuberous sclerosis), focal cortical dysplasia and heterotopias.

Astrocytes↗
PubMed1988

MR imaging of hemorrhagic conditions of the head and neck.

1. There is a constant sequence of signal intensity patterns that characterize 1.5 T, spin echo MR images of hemorrhagic lesions. 2. The MRI appearance of intraparenchymal hemorrhage is determined by the sequential chemical degradation of Hb, by the paramagnetic properties of the degradation products and by certain biologic factors including pO2, edema formation, hematocrit and BBB. 3. Acute intraparenchymal hemorrhage is characterized by markedly diminished signal intensity centrally relative to surrounding white matter (hypointensity) on T2 weighted images and often by a moderately increased signal intensity (hyperintensity) of the adjacent white matter produced by surrounding edema on proton density and T2 weighted images. 4. Early subacute intraparenchymal hemorrhage is characterized centrally by moderate hypointensity on T2 weighted images, and peripherally, by moderate hyperintensity on T1 weighted and marked hypointensity on T2 weighted images. Hyperintensity on proton density and T2 weighted images of nearby white matter owing to edema may again be seen. 5. Late subacute intraparenchymal hemorrhage is characterized by marked peripheral and central hyperintensity on both T1 and T2 weighted images. Also, marked hypointensity of the adjacent brain rim on T2 weighted images owing to hemosiderin deposition may be seen. 6. Chronic intraparenchymal hemorrhage is characterized by marked hyperintensity both centrally and peripherally on both T1 and T2 weighted images and by marked hypointensity of the adjacent brain rim on T2 weighted images owing to hemosiderin deposition. Surrounding edema is no longer present. 7. The integrity of the blood-brain barrier appears to be important in determining whether or not hemosiderin accumulations consistently occur in subacute and chronic hemorrhage. 8. Hemorrhagic conditions in which the defined sequence of signal intensity patterns may be seen include: venous thrombosis, hemorrhagic infarction, occult vascular malformation and intracranial aneurysm.

Acute Disease↗
PubMed1988

Variable appearances of subacute intracranial hematomas on high-field spin-echo MR.

Subacute intracranial hematomas have variable appearances on high-field MR images. They are hyperintense on T1-weighted images owing to methemoglobin, but have variable intensities on T2-weighted images. Observation of the different high-field spin-echo MR intensity patterns of five subacute hematomas suggests that further subcategorization into different methemoglobin states may be possible. In particular, undiluted intracellular methemoglobin is hyperintense on T1-weighted images and markedly hypointense on T2-weighted images, undiluted free methemoglobin should be hyperintense on T1-weighted images and isointense or slightly hypointense on T2-weighted images, and dilute free methemoglobin is hyperintense on both T1- and T2-weighted images. However, it appears that certain regions of subacute hematomas may be difficult to differentiate, by intensity patterns alone, from melanotic melanomas or fat. We believe that, despite some limitations, MR is useful in dividing subacute intracranial hematomas into their respective methemoglobin states, and also that further subcategorization is possible.

Brain↗