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Biomedical subjects

H L Baker

Publications and source records attributed to H L Baker.

At least 37 records · Page 2Linked to original sources
PubMed1986

The application of magnetic resonance imaging in otolaryngology.

Magnetic resonance imaging is a new diagnostic technique that is being applied to study disease processes that involve the upper aerodigestive tract and cranial nerves of interest to otolaryngologists. As with all imaging techniques, an in-depth knowledge of the normal anatomy of a region is a prerequisite for the appreciation of disease states. In addition, magnetic resonance imaging requires a familiarity with the signal intensity produced by the different structures and the relationship of that signal to various radiofrequency pulse sequences that may be used. This report briefly reviews the techniques of magnetic resonance imaging and the normal anatomy of the cervical region and presents examples of pathologic processes that have been studied with this powerful diagnostic technique.

Ear↗
PubMed1986

Correlation of radiological features to failure of lumbar intervertebral disc chemonucleolysis.

Chemonucleolysis was performed in 103 patients for lumbar disc prolapse. Multiple (two) interspaces were injected in only seven patients. Radiographically, all patients had myelographic or computerized tomography evidence of disc prolapse. Eighty-seven of 100 patients who were available for follow-up review had improved. Ten of 13 patients with persistent symptoms required a laminectomy. Altered spinal alignment was evident in five of the 13 patients with persistent symptoms: retrolisthesis in three and myelographic disc defect on the convex aspect of the scoliosis in two. Review of radiographic studies was carried out in an attempt to establish guidelines for patient selection so as to decrease the rate of failure in chymopapain treatment.

Adolescent↗
PubMed1985

Magnetic resonance imaging in a routine clinical setting.

The results of magnetic resonance imaging (MRI) examinations in the first 1,000 consecutive patients who were studied by this technique at our institution were reviewed to determine the disease states encountered, the sensitivity and accuracy of results, and the value of the examination as compared with computed tomography and other imaging procedures. The MRI device was a 0.15-tesla resistive magnet that used a variety of saturation recovery, spin echo, and inversion recovery pulse sequences to produce images. MRI was found equal to or superior to other imaging techniques in most cases. Exceptions included organs or body regions that are prone to excessive respiratory or vascular motion, lesions that necessitate exquisite spatial resolution for diagnosis, and lesions in which angulation of the viewing plane is necessary for optimal depiction. Fresh blood and calcification within a lesion were also difficult to detect with use of MRI.

Adolescent↗
PubMed1985

Magnetic resonance imaging in syringomyelia.

Myelography and myelography assisted with computed tomography have been the most commonly used radiographic methods in the study of syringomyelia. These studies have never been entirely reliable in demonstrating the syrinx cavity and its relationship to other intracranial structures. During the 1st year of operation of the magnetic resonance imaging facility, the syringomyelic cavity was demonstrated in 15 patients who all had typical clinical signs and symptoms associated with syringomyelia. Nine cases were syringomyelia with Chiari malformation. One case showed additional hydrocephalus. Four cases were idiopathic, and 1 case was remotely posttraumatic. Magnetic resonance imaging, although it is in its infancy, already promises to be the most important radiographic technique for syringomyelia because it provides an anatomically truthful visualization of the sagittal plane of the cervical cord and can demonstrate the syrinx cavity and its relationship with the cerebellar tonsils, the 4th ventricle, and other related structures.

Adolescent↗
PubMed1985

CT of the sella turcica after transsphenoidal resection of pituitary adenomas.

A retrospective review of 120 patients undergoing transsphenoidal surgery for pituitary adenomas revealed that computed tomography (CT) was less sensitive and less specific than hormonal methods in identifying residual functioning adenomas. However, CT was the only useful method of evaluating nonfunctioning tumors, including pseudo-prolactinomas. Enlargement of the pituitary stalk, when seen on preoperative CT, was 100% predictive of "cure" if the enlargement returned to normal size on a remote follow-up scan (n = 8) and was 100% predictive of residual tumor if the enlargement persisted or evolved (n = 8). Resolution of stalk displacement was the next most reliable predictor of cure (91%, n = 11), but persistent displacement was less reliable than abnormal intrasellar enhancement in predicting the presence of residual tumor (71%, n = 28, vs. 81%, n = 26). Enhancement in the postoperative sella by other than normal pituitary gland was presumed to be due to inflammation in 19% of patients. Inflammatory enhancement was observed in the presence of autograft and homograft muscle plugs and, unlike enhancement due to untreated tumors, was observed to decrease in size and intensity with time. Intrasellar enhancement was an unreliable criterion of success or failure in cases of microadenoma. All 14 patients with functioning adenomas and preoperative parasellar tumor extension had persistent tumor at postoperative evaluation. Of the 47 patients with resected functioning adenomas who had CT scans showing empty or partly empty sellas after operation, 22 (47%) had hormonally detectable residual tumor.

Adenoma↗
PubMed1985

Lumbar spinal stenosis. Clinical features, diagnostic procedures, and results of surgical treatment in 68 patients.

Our experience with 68 patients with strictly defined, myelographically proven, surgically confirmed lumbar spinal stenosis seen over a 30-month period was reviewed. Pseudoclaudication was the commonest symptom (94%) and was described by patients as pain (93%), numbness (63%), or weakness (43%). Symptoms were frequently bilateral (68%) and generally relieved by flexing the lumbosacral spine. Neurologic abnormalities were found in a minority of patients and were usually mild. Electromyography showed one or more lumbosacral radiculopathies in 34 of 37 patients examined. Radiographic evidence of degenerative disk or joint disease was found in 63 patients. All patients had stenosis on myelography, with narrowing at L2, L3, and L4 being the commonest; 30% had multi-level stenosis. Two of ten computed tomograms were normal. Surgery was extensive; 72% of patients had three or more laminae removed. At a mean of 4 years after surgery, 84% of patients reported that surgery had yielded good to excellent results.

Adult↗
PubMed1985

Magnetic resonance imaging vs. computed tomography: advantages and disadvantages.

Magnetic resonance imaging (MRI) of the head and spine exceeds the sensitivity of computed tomography (CT) in detecting parenchymal lesions of the brain and spinal cord. MRI should be employed as a screening examination, particularly in patients suspected of having demyelinating diseases. CT continues to be the imaging technique of choice in evaluation of trauma, accurately depicting bony abnormalities and intracranial hemorrhage in evaluation of the spinal column and suspected disc herniation and in uncooperative patients.

Astrocytoma↗
PubMed1982

Radiologic evaluation of ischemic cerebrovascular syndromes with emphasis on computed tomography.

In patients with stroke syndromes, the extent and sequence of investigations are based upon clinical probabilities and take into account the age, general condition, and wishes of the patient. There is no doubt that the evaluation of such patients has been changed and improved by CT. The incidence of intraparenchymal bleeding is higher, but its mortality is lower than previously believed. The incidence of hemorrhagic infarction is probably not as great as previously suspected, but the hazards of anticoagulant therapy in a patient with a hemorrhagic infarct are easily obviated if a CT scan is obtained before anticoagulant therapy is started. The initial evaluation of the patient has been improved by CT, but in addition, following the course of the patient is easier by obtaining serial scans when satisfactory recovery does not take place or continue at the expected rate. Parenchymal changes such as hemorrhagic change, mass effect, or obstruction of the ventricular system can be detected early, and approached rationally.

Brain Edema↗
PubMed1982

Nuclear magnetic resonance imaging.

Nuclear magnetic resonance scanning provides the potential for measurement of new properties of tissue which may permit better pathologic differentiation. NMR will be less affected by bone, and so neurologic studies in which bone artifacts are a problem in CT may be facilitated. Direct sagittal and coronal imaging are possible. As far as we know, the biologic hazards are expected to be minimal but cannot be definitely ruled out at this time. At present, the relaxation times that are most frequently measured are such that clinically acceptable spatial resolution (2 to 3mm) requires scan times on the order of two minutes or more. Whether chemical cross-sections that are acceptable to clinical demands can be obtained remains to be demonstrated.

Electromagnetic Fields↗
PubMed1981

Screening for brain lesions with digital radiography of the head using a CT scanner.

Digital radiography was tested in a clinical setting as a screening device for detecting brain lesions and for following the response of known enhancing cranial masses to therapy. A concurrent phantom study was conducted to determine the low contrast sensitivity of the system. Contrast resolution was superior to that of film -- screen systems but suffered at a density level of 2 to 4% because of system noise. This noise appeared to be nonquantum in nature, related to electronic and mechanical inconsistencies of the computed tomographic instrument. System noise and patient motion combined to nullify the advantages of digital radiography for screening and monitoring intracranial masses.

Adolescent↗
PubMed1981

The clinical usefulness of routine coronal and sagittal reconstructions in cranial computed tomography.

In order to test a hypothesis that the routine use of one midsagittal and four preselected coronal reconstruction images would disclose lesions unsuspected on standard cranial computed tomography (CT) scans, 204 patient examinations were subjected to such multiplanar reconstruction manipulation; the original CT diagnoses, reconstruction diagnoses, and final clinical diagnoses were compared. The two CT diagnoses agreed in 144 cases. Lesions well shown on the standard CT examination were not seen on the reconstruction images in 23 cases (11% of the total), and reconstruction revealed brainstem or cerebellar atrophy not detected on standard CT in 37 cases (18% of the total). Applications of these findings to daily neuroradiologic practice are suggested.

Adolescent↗
PubMed1981

Dynamic sequential scanning with table incrementation.

Dynamic sequential scanning with table incrementation is a method of rapid computed tomographic head scanning in which a complete 10-section scan can be made in 2 minutes 40 seconds or less. Although some measurable and visible loss of low-contrast resolution occurs, there is no loss of high-contrast resolution. Monthly throughput of patients has been increased by about 30% since this technique was instituted.

Brain↗
PubMed1980

National Cancer Institute study: evaluation of computed tomography in the diagnosis of intracranial neoplasms. I. Overall results.

A cooperative study by five university centers assessed the relative usefulness of computed tomography (CT) of the head and compared with with plain head radiography, radionuclide brain scanning, and neuroangiography for the detection and diagnosis of masses in the brain. CT with and without contrast enhancement was the most accurate neurodiagnostic method employed in 2,928 patients, 1,071 of whom were found to harbor intracranial tumors. Angiography was as accurate as CT, whereas radionuclide studies and plain radiography were much less accurate and were seldom found to be positive if CT and angiography were negative.

Adult↗
PubMed1980

Long-term prognosis after carotid artery occlusion.

One hundred thirty eight patients with angiographically proved carotid artery occlusion and minimal or no neurologic deficit were followed up for an average of 5 years. For patients 35 years old or over, the observed 5-year survival rate on an actuarial basis was 77% compared with an expected rate of 85% in a matched normal population. For patients 35 years old or over, the subsequent stroke rate was 3% per year, and two-thirds of the strokes were ipsilateral to the carotid artery occlusion. The observed stroke rate for all patients 35 years old or over was eight times the expected rate for a matched normal population. The relative risk of stroke was much greater in the younger patients with atherosclerotic carotid artery occlusion than in the older patients.

Adolescent↗
PubMed1980

Pituitary and parapituitary tumours on computed tomography. A review article based on 230 cases.

This paper is based on a retrospective study of 230 tumours in the sellar area. All, except a few, were examined with the EMI 160 x 160 matrix and verified histologically. The main features of each pathological entity are described and most of the previous literature is reviewed. The degree of resolution of the scanner used precludes its reliability for detecting tumours less than one centimetre in diameter. Out of 30 microadenomas, only two were detectable on CT. This reflects an incidence of false negative results in 93% of microadenomas or 22% of all adenomas in the series. CT was also negative in 6% of craniopharyngiomas and 30% of chordomas. These findings emphasize the need for further neuroradiological tests in patients with clinically evident disease in the pituitary area. Many CT appearances are shared by more than one pathological entity; few are specific. However, if the CT findings are viewed in the light of the clinical presentation, a pathological diagnosis is possible in a large proportion of cases. Angiography is valuable; not only to exclude lesions of vascular origin, or show neovascularity, but also to demonstrate the relationship of the internal carotid arteries to the sphenoidal sinus prior to transsphenoidal surgery.

Adenoma↗