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Biomedical subjects

G J Alker

Publications and source records attributed to G J Alker.

At least 19 recordsLinked to original sources
PubMed1994

Radiology in survivors of traumatic atlanto-occipital dislocation.

Traumatic atlanto-occipital dislocation is fatal, but survivals are reported. Six cases of survival after atlanto-occipital dislocation are presented. Lateral cervical spine radiographs demonstrated retropharyngeal swelling in all patients, and Powers' ratio was abnormal in five of six patients. Reformatted computed tomography (CT) images or three-dimensional CT were useful in confirming the diagnosis. Initial treatment consisted of immobilization with halo or collar, and, in one patient, Crutchfield tongs. Reduction of the dislocation was associated with decreasing Powers' ratio in five long-term survivors. Residual neurologic deficits, however, were seen in these patients. Atlanto-occipital dislocation should be suspected in trauma patients with findings of brain stem injury--especially agonal respirations, irregular heart rate, lower cranial nerve abnormality, and asymmetrical motor deficits.

Accidents, Traffic↗
PubMed1988

Focal cortical dysplasia. Case report.

A histologically confirmed case of focal dysplasia of the cerebral cortex is presented. The computerized tomographic, electroencephalographic, pathological, and angiographic findings are discussed with respect to this rare developmental disorder. A review of the literature is presented with a possible etiology for this condition.

Adult↗
PubMed1988

Fractures of the atlas vertebra. The two-part burst fracture of Jefferson.

Burst fractures of the atlas are usually diagnosed and treated as four-part fractures as described by Jefferson in 1920. Review of the literature, roentgenogram, computed axial tomography (CAT) scans, and laboratory studies, indicates that the burst fracture is usually, if not always, a two-part fracture. These findings are contrary to the accepted concept of burst fractures, and indicate that routine roentgenograms are not adequate for proper diagnosis. Also, with disclosure of the true nature of these injuries, there is indication for further consideration and study relating to treatment of these injuries.

Cervical Atlas↗
PubMed1985

An effective surrogate for impact studies.

Nineteen unembalmed (fresh) cadavers were used in 21 experiments to test restraint systems in automobile impact studies. Some were mounted in a rearward firing sled; others were placed in standard cars during collisions. Prior to and after testing, each cadaver was evaluated. After each experiment a postmortem examination was performed. High-speed registering cameras (1,000 to 2,000 frames per second) were used and multiple telemetric recordings were made. The radiographic and pathologic changes were similar to those seen in patients following high-velocity accidents. Results were compared with those of car accident victims admitted dead on arrival to one of our hospitals. This study is a progress report. The results are being used to improve existing restraint systems and to evaluate experimental models.

Accidents, Traffic↗
PubMed1984

Method of computed tomography-based stereotactic biopsy with arteriographic control.

A method for computed tomography (CT)-based stereotactic biopsy of intracranial neoplasms with arteriographic control is described. Stereotactic CT and digitized stereotactic arteriographic data are input to a three-dimensional computer matrix that corresponds to the coordinate system of a stereotactic frame located in the operating room. A site for biopsy is selected by cursor from the CT display screen. The computer calculates and outputs the mechanical adjustments of the stereotactic frame necessary to place the target point into the focal point of the frame. Horizontal and vertical approach angles are determined from the digitized arteriogram and are displayed as settings on the stereotactic frame that represent an avascular trajectory along which the lesion may be biopsied safely. This procedure has been used successfully in 86 patients, with no morbidity or mortality.

Biopsy↗
PubMed1983

Precision resection of intra-axial CNS lesions by CT-based stereotactic craniotomy and computer monitored CO2 laser.

This report describes an open stereotactic technique by which a tumour volume reconstructed in stereotactic space from CT data is removed by stereotactic CO2 laser vaporization. The position of the laser beam in relation to the tumour outlines is monitored by computer and displayed to the surgeon on a graphics display terminal in the operating room. Twenty-six (26) of these procedures have been performed on twenty-four (24) patients with deep-seated intra-axial neoplasms (23) and arteriovenous malformation (1). Post-operative CT scanning revealed no evidence of contrast enhancing lesions in nineteen (19) patients while a small amount of residual tumour was noted in five (5) patients post-operatively. This method has proven itself valuable for maintaining three-dimensional surgical orientation for the resection of intra-axial neoplasms from neurologically important areas.

Adult↗
PubMed1982

Computer-assisted stereotactic microsurgery for the treatment of intracranial neoplasms.

This paper describes a stereotactic CO2 laser system for the removal of intra-axial, intracranial neoplasms. The volume of the neoplasm is transferred into stereotactic space by computer reconstruction of data derived by computed tomography (CT) performed under stereotactic conditions. The tumor volume is sliced in a plane orthogonal to the surgical approach, and slices at specific distances from the focal point of the stereotactic frame are displayed on a graphics monitor in the operating suite along with a cursor representing the position of the surgical laser. Laser vaporization of sequential slices of the tumor results in a cavity, the formation of which is monitored by anteroposterior and lateral roentgenograms. Fifteen stereotactic laser procedures have been performed on 13 patients, and the results are discussed. By this method, it is theoretically possible to remove all of an intracranial neoplasm detected by CT scanning.

Adolescent↗
PubMed1982

A computed tomographic stereotactic adaptation system.

An adaptation to render an existing popular stereotactic apparatus compatible with computed tomography (CT) is described. A localization system attaches to the stereotactic head holder and a simple computer program allows considerable accuracy in the translation of CT data into stereotactic space in the operating room.

Computers↗
PubMed1981

False positive dynamic imaging of the cerebral circulation due to a congenital anomaly.

False positive dynamic imaging of the cerebral circulation simulating vascular occlusive disease resulted from a clinically insignificant congenital variation in several patients at our institutions. The anomaly consisted of the asymmetrical caliber of the internal carotid and proximal anterior cerebral arteries. The 1 mm difference in the diameter of the internal carotid arteries was sufficient to be appreciated on dynamic imaging. The frequency of this anomaly was found to be 5% in a series of 200 bilateral carotid angiograms.

Adult↗
PubMed1981

Computed tomography of the orbit.

In less than a decade computed tomography (CT scanning) had a profound impact on diagnostic radiology. Radiology of the orbit is no exception. As early as 1973, reports published in the radiological literature indicated that this new noninvasive imaging method was a highly effective way of demonstrating intraorbital mass lesions. As CT scanners became widely available, computed tomography became a significant adjunct to ophthalmological diagnosis. Today the main indications for CT scanning of the orbit are (1) suspected mass lesions, most frequently presenting as exophthalmos, (2) orbital trauma, including foreign bodies, (3) some congenital anomalies, and (4) suspicion of extension into the orbit of extraorbital disease processes. Along with ultrasonography, another new noninvasive imaging technique, CT has replaced a number of more invasive and often less effective diagnostic methods, such as orbital pneumography, venography, and arteriography as major imaging techniques in orbital pathology. The paper discusses current practices in the technique of CT scanning of the orbit including the important aspect of radiation dosimetry and the clinical applications, using a number of cases to illustrate its use.

Eye Foreign Bodies↗
PubMed1980

A method for stereotactic laser microsurgery in the treatment of deep-seated CNS neoplasms.

Intracranial tumors are reconstructed in stereotactic space by means of computerized axial tomographic data. The intracranial tumor is operated on with the patient in the stereotactic frame using a carbon dioxide laser to approach the lesion and vaporize it. Ultimately, a gas-filled cavity results which can be monitored on AP and lateral radiographs. Vaporization continues until the cavity produced is superimposable on the coronal and sagittal CT reconstruction. 2 cases treated by this method are presented.

Adenocarcinoma↗
PubMed1980

Computed tomography of the abdomen.

In a few short years, computed tomography has become an important diagnostic procedure in the examination of the abdomen and pelvis. Its forte lies in its ability to provide cross-sectional views of excellent anatomical detail. Imaging of deep-seated structures such as the pancreas, adrenal glands, and enlarged retroperitoneal lymph nodes is now possible. The ability to distinguish small variations in tissue density enables the radiologist to evaluate the texture of solid structures, and to differentiate them from cysts or abscesses. The addition of contrast enhancement makes it possible to determine the vascularity of a lesson. The major limitation of CT is poorer delineation of structures in thin patients, and in patients in whom voluntary and involuntary motion cannot be interrupted. Computed tomography is compared with other complementary imaging procedures to include sonography, radionuclide imaging, and conventional radiograph procedures. It has replaced invasive diagnostic procedures in many instances. In a given situation, one or more imaging modalities may be appropriate.

Adrenal Glands↗
PubMed1979

Radiology of a large cisterna magna cyst. A case report.

A case of a large cisterna magna cyst presented a problem in differential diagnosis. Characteristic changes were shown on plain skull roentgenograms and on radionuclide brain scan. The diagnosis was established on the basis of pneumoencephalography and isotope cisternography. The lesion responded well to surgical management.

Adolescent↗
PubMed1978

Efficacy of computed tomography of the abdomen--early results.

Our experience with 153 CT scans of the abdomen and pelvis over the first eight months of availability at our institution has been analyzed. The efficacy in terms of contribution to the diagnosis in each patient was assessed and accuracy determined. CT was found to have made a significant contribution to the diagnosis in patients with diseases of the pancreas, aorta, retroperitoneal structures, and in cases of abdominal and pelvic masses and abcesses. It has been somewhat less helpful in evaluation of liver and renal diseases. Overall, CT scanning appears to be a significant new diagnostic modality in the evaluation of patients with abdominal and pelvic diseases.

Abdominal Neoplasms↗
PubMed1978

Lithopedion: case report and ultrastructural study of the skeletal muscle.

A case of lithopedion (lythokelyphopedion) is reported in a 69 year old woman who had carried a nearly full term dead fetus for at least 20 years. The fine structure of the skeletal muscle was in an astonishingly good state of preservation with contractile elements and myosin molecules identifiable. The conditions and modifying factors that may play a role in the development of a lithopedion are discussed, and x-ray, histologic, and electron microscopic studies are described.

Aged↗