Biomedical subjects
Publications and source records attributed to P Pech.
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.
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The CT appearance of the cervical neural foramina and contents is described in detail. Nineteen cervical spine specimens were studied with CT and corresponding cryomicrotomy in direct axial, sagittal, coronal, and oblique planes. Both ventral and dorsal nerve roots can be identified in the foramen's lower portion at or below the disk level. The dorsal nerve roots and ganglion contact the superior facet. The ventral nerve roots contact the uncinate process and bottom of the neural foramen. The ventral nerve roots, dorsal nerve roots and ganglion, and vertebral artery are resolved with current high-resolution CT.
Exactly corresponding magnetic resonance (MR) images and anatomic sections were obtained of cadaveric lumbar intervertebral disks. MR differentiated two major components of the intervertebral disk, one corresponding to the collagenous fibers in the periphery of the disk, the other corresponding to the combination of nucleus and annulus. The vertebral osseous end plate appears to be faintly resolved, but may be simulated by a chemical shift artifact. More correlative studies and development of additional techniques are needed to characterize completely the MR appearance of the intervertebral disks.
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.
The magnetic resonance (MR) appearance of the cavernous sinus was studied by correlating the MR images of normal volunteers and cryomicrotomic sections from six cadavers. In addition, MR images of patients with parasellar masses were compared with corresponding intravenously enhanced computed tomographic (CT) scans. The MR appearance of the cranial nerves in the cavernous sinuses is demonstrated, as well as MR signs of a parasellar mass, including obliteration of intracavernous venous spaces, displacement of the intracavernous internal carotid artery, and bulging of the lateral wall of the cavernous sinus. MR proved to be more effective than CT in delineating the parts of the cavernous sinus.
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Computed tomography is effective for detecting acoustic neuromas, but not for resolving individual nerves in the internal auditory canal. Surface-coil magnetic resonance (MR) images of the internal auditory canal were obtained using a 1.5 T superconducting magnet, a 13.5-cm-diameter surface coil, 3- and 5-mm-thick slices, and partial-saturation pulse sequences. Cranial nerves VII and VIII (three branches) were identified on MR images in volunteers and on corresponding cryomicrotomic sections. The nerves were obscured in one patient with an acoustic neuroma. Because high-resolution surface-coil images can demonstrate specific nerves in the internal auditory canal, MR should be a sensitive study to evaluate cranial nerves VII and VIII in patients with facial paralysis and neurosensory hearing loss that is congenital or caused by small acoustic neuromas.
A detailed analysis of the coronal anatomic and CT appearances of the orbital apex is presented. In cadavers, coronal CT 9800 scans of the orbital apex and precisely corresponding cryomicrotomic sections were obtained. The CT appearance of the optic nerve, anulus of Zinn, and cranial nerves III-VI at the superior orbital fissure and orbital apex were determined. These anatomic structures were also demonstrated in clinical CT studies. Practical applications of the anatomic landmarks in evaluating orbital apex tumors are illustrated.
Diagnostic value of radiologic examinations was assessed in a homogeneous series of 130 cases of neurinoma of acoustic nerve seen over the last 10 years. Radiologic exploration is conceived and used at the present time for two purposes. Firstly, it enables selection of patients with suspected acoustic nerve neurinoma. Radiotomography appears to be currently an accessory examination because of the discriminative performance of early auditory evoked potentials tests on the brain stem. Secondly, radiology is necessary for confirmation of diagnosis. Visualization of the tumoral syndrome can be obtained only by a scan or possibly opaque or gas meatocisternography.
This study characterizes the normal appearance of the pituitary fossa in partial saturation magnetic resonance (MR) images. In sagittal images, the pituitary fossa appears inhomogeneous. Correlation of sagittal MR images in normal subjects with sagittal cryomicrotomic images in cadavers suggests that the highest intensity signal from the posterior-inferior pituitary fossa is due to a fat pad. This conclusion was supported by MR images and postmortem cryotome sections obtained in normal subhuman primates. The cause of the less constant, low intensity signal was less certain. The height of the pituitary gland in sagittal images was usually less than 8 mm, and the upper surface was flat or concave.
To produce accurate correlating anatomical reference material, fresh frozen craniospinal cadaver specimens were examined in a computed tomography (CT) scanner and sectioned through on a large-format cryomicrotome in the identical plane. Macrophotography of the surface of the specimen during the course of trimming rendered undistorted sectional--anatomical images showing in great detail the morphological structures of the corresponding CT scan.
Correlation of direct coronal CT with observations at surgery demonstrates that direct coronal CT is a highly useful guide to planning surgical resection of posterior fossa tumors. Computed tomography performed in this plane displays all significant anatomic relationships in the exact orientation found during surgical dissection.
A test method with use of a biologic phantom--a deep-frozen specimen of a human cadaver--was developed in an attempt to simulate the clinical setting in CT of the spine. The quality of both soft tissue and bone images in the absence of motion artifacts was evaluated for seven scanner models. Special attention was paid to identification of the pattern and extent of artifacts. The phantom consisted of a spine with surrounding muscles. The images were evaluated subjectively and comparisons were made between the different scanners. Examples of these results are presented. A biologic phantom is a valuable supplement to artificial phantoms and increases the ability to evaluate and compare the performance of CT scanners.
Ten patients who had undergone leg lengthening were monitored with plain radiographs and computed tomography (CT) scans at 3-month intervals. Four of them were examined with magnetic resonance imaging (MRI) scans. When the external fixator was removed, MRI scans could not demonstrate any continuous fat signals in the lengthened region, suggesting the lack of medullary cavity. CT scans disclosed double cortex in three patients and irregular new bone formation in seven. At 6 months, a medullary cavity could be detected. Other aberrations were less evident. Remodeling of new bone material required at least 1 year.
To study the appearance of gray and white matter in the cervicomedullary region, six fresh cadavers were imaged with a 1.5-T MR scanner and then sectioned with a cryomicrotome. The pyramidal tracts, fasciculus cuneatus and gracilis, inferior olivary nuclei, supraspinal nuclei, spinal trigeminal nuclei, and medial lemnisci were identified by MR in the cervicomedullary region.
Freezing of animal and human tissue may change their shape, size and other physical properties such as attenuation of roentgen rays. In correlative radiologic-anatomic studies such artifacts are potential sources of inaccuracy. In fluid phantoms changes of computed tomography (CT) numbers and volume were measured before and after freezing. Frozen saline decreased in attenuation by 80 Hounsfield units (HU) and increased in volume by 9 per cent. Pure soy oil increased in attenuation by 40 HU after freezing and shrank in volume by 4 per cent. Emulsions of 10, 20 and 30 per cent lipid expanded in inverse relationship to the changes in attenuation. In animal and human tissue, changes in CT number of -80 to +55 HU were measured and changes in volume of -6 to +9 per cent were calculated. The attenuation of the vitreous body in the eye decreased by 80 HU and its volume was calculated to increase by 8 to 9 per cent. In the muscle and spinal cord the attenuation decreased by 40 to 60 HU, corresponding to the increase in volume of 4 to 6 per cent. Attenuation of fat was increased by 55 HU after freezing and a decrease in volume of 5 to 6 per cent was calculated. Deformation of soft tissue and herniation of the cerebellar tonsils into the foramen magnum were observed. Most anatomic, freezing artifacts can be avoided by careful preparation.
A detailed study of the magnetic resonance (MR) appearance of the cervical nerves and neural foramina is presented. Using a "butterfly" local coil and a 1.5-T GE Signa MR system, the authors obtained 3-mm-thick axial, parasagittal, and 45 degrees oblique MR images of the cervical neural foramina in four normal volunteers. For the oblique images, subjects were rotated 45 degrees toward the right posterior oblique. Neural and vascular structures in the foramina were identified by correlation of the MR images with corresponding cryomicrotomic sections from four cadavers. The 45 degrees oblique images were more useful than axial or parasagittal images for demonstrating anatomic relations in the neural foramina. MR imaging with local coils demonstrates the complex anatomy of cervical neural foramina in various planes.