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Biomedical subjects

L R Gentry

Publications and source records attributed to L R Gentry.

At least 37 records · Page 2Linked to original sources
PubMed1998

Anatomy of the temporal bone.

High resolution computed tomography has proved to be invaluable in the evaluation of the temporal bone, and demonstrates its bony anatomy in exquisite detail. Furthermore, the role of magnetic resonance imaging, especially with improving high resolution techniques, has continued to expand in the past decade. A thorough understanding of normal temporal bone anatomy is a requisite for accurate radiologic evaluation. The ensuing discussion is an attempt to summarize the normal temporal bone anatomy with emphasis on clinically relevant structures, temporal bone pneumatization, and common anatomic variants.

Ear↗
PubMed1994

Blinded comparison of cranial CT and MR in closed head injury evaluation.

PURPOSE: To compare CT and MR in the evaluation of acute head injury. METHODS: One hundred seven consecutive patients who were referred to the emergency department and underwent both MR and CT cranial examinations within 48 hours were retrospectively reviewed. The films were interpreted by two neuroradiologists blinded to all patient information. RESULTS: The sensitivity of MR was significantly higher than that of CT for the detection of contusion, shearing injury, subdural and epidural hematoma, and sinus involvement. The sensitivity of CT was significantly higher than that of MR for the evaluation of fracture. The sensitivities of MR and CT were statistically equivalent for the detection of superficial soft-tissue injury. The overall sensitivity of MR for the detection of abnormalities in acute head trauma was 96.4%, and for CT was 63.4%. CONCLUSIONS: CT and MR are complementary studies in the evaluation of acute head trauma. MR is necessary to define or exclude contusions, deep shearing injury, and extraaxial fluid collections in acute head trauma.

Brain↗
PubMed1993

Disk-caused nerve compression in patients with acute low-back pain: diagnosis with MR, CT myelography, and plain CT.

Ninety-five patients with acute low-back and radicular pain underwent magnetic resonance (MR) imaging and either plain computed tomography (CT) (n = 32) or CT myelography (n = 63) for diagnosis of herniated nucleus pulposus-caused nerve compression (HNPNC). Patients were followed up for at least 6-12 months. Fifty-six patients underwent surgery, and 39 received conservative treatment. Receiver operating characteristic (ROC) analysis was performed on correlation of results of blinded image reading with "true" diagnoses determined by an expert panel [corrected]. Results in subgroup analysis for ROC curve areas were MR, 0.84, versus plain CT, 0.86; MR, 0.81, versus CT myelography, 0.83; and MR, 0.82, versus findings with both CT techniques, 0.85. Results indicate no statistically significant difference in diagnostic accuracy of HNPNC among the three modalities. Thus, factors of cost, radiation dose, and invasiveness influence selection of modality. On the basis of accuracy findings, the authors suggest that MR should replace CT myelography because of the invasiveness of myelography but that MR should not replace plain CT because plain CT is equally accurate and much less costly.

Acute Disease↗
PubMed1990

Magnetic resonance imaging and neurobehavioural outcome in traumatic brain injury.

Magnetic resonance (MR) imaging is a sensitive means of detecting haemorrhagic and nonhaemorrhagic forms of brain injury. This study correlates the neurobehavioural (NB) deficits in 49 adult patients with lesions detected by MR imaging. MR imaging was performed 2-19 days following trauma, analyzed for the injury type and graded for severity. A battery of NB tests was performed prior to hospital discharge or at the time of initial follow-up visit (31 patients). 15 patients were so severely impaired that testing could not be done and 3 died prior to discharge. The NB test scores were grouped into 3 levels of impairment. The overall NB scores were compared with MR lesion severity ratings and a positive correlation found (r = 0.47). In addition, lesion severity, type and location resulted in specific NB deficits. We conclude that the lesion location and severity can be accurately identified by acute phase MR are associated with specific types of neurobehavioural deficits in a high percentage of testable patients.

Adolescent↗
PubMed1990

Sphenoid fractures: prevalence, sites, and significance.

The computed tomographic (CT) scans of the head of 490 blunt trauma victims were reviewed to establish the frequency of sphenoid fractures. There were 111 patients with craniofacial fractures, 78 of whom had fractures of the sphenoid bone. In 51 of the 78 patients these were associated with complex facial fractures, and in the 27 remaining patients they represented primarily fractures of the skull base. The number of sphenoid fractures not only exceeded those that involved the other bones of the base of the skull, including the temporal bone, but also exceeded the number of fractures of the cranial vault that could be identified with CT. All available charts were reviewed for the patients with sphenoid fractures in order to determine the presence of potentially related injuries. In 21 patients there were complications that included damage to the internal carotid artery, cerebrospinal fluid rhinorrhea, optic nerve damage, superior orbital fissure syndrome, and posttraumatic diabetes insipidus.

Accidents, Traffic↗
PubMed1989

Magnetic resonance imaging of the orbit. Part I. Physical principles.

Magnetic resonance has twin capabilities. It can provide anatomical (magnetic resonance imaging, MRI) and physiochemical (magnetic resonance spectroscopy) information. Nuclei with an odd mass number, particularly hydrogen in free water, have electromagnetic properties. When placed in a strong static magnetic field and excited by radiofrequency waves of a specific wavelength, these nuclei emit a signal. The MR signal can then be digitized, stored in a computer, and subsequently converted into an image. Factors that affect these images are tissue parameters (T1 and T2 time constants, proton density, and flow) and radiofrequency pulse sequences. Surface coils are useful for improving images of the orbit. The magnet can have a major and potentially dangerous influence on the surrounding environment, and access to the MRI area must be carefully controlled. Shielding of the MRI room prevents external factors from adversely affecting the MRI unit and the images produced.

Equipment Design↗
PubMed1989

Magnetic resonance imaging of the orbit. Part II. Clinical applications.

Imaging of the orbit with magnetic resonance imaging (MRI) provides better anatomic detail with T1-weighted sequences and superior visualization of pathologic conditions with T2-weighted sequences. Compared with computerized tomography (CT), MRI has the following advantages: lack of ionizing radiation, direct multiplanar imaging, better contrast resolution, lack of bone artifacts, visualization of bone marrow, superior study of certain neurological disorders, and spectroscopy. Compared with CT, MRI has the following disadvantages: prolonged examination, poorer ability to detect orbital calcifications and cortical bone destruction, poorer spatial resolution, fewer suitable patients, certain image artifacts, high cost of MRI units, and higher cost of MRI examinations.

Humans↗
PubMed1989

Traumatic brain stem injury: MR imaging.

Eighty-seven patients with acute (n = 70) or chronic (n = 17) head injuries were prospectively studied with magnetic resonance (MR) imaging and computed tomography (CT) to characterize the frequency and nature of traumatic brain stem injury (BSI). Forty-eight traumatic lesions were identified in 36 patients. Of 36 patients, 35 had neurologic findings that corroborated the radiographic impression of BSI. T1- and T2-weighted MR images demonstrated a significantly higher number of lesions than did CT. Patients with BSI had a significantly higher frequency of corpus callosum and diffuse axonal "shear" lesions. The number of cortical contusions and extraaxial hematomas was similar in both groups. The mean Glasgow Coma Scale (GCS) scores at admission were significantly lower in patients with evidence of BSI on MR images. Patients with primary BSI had lower initial GCS scores, a longer duration of coma, more diffuse axonal "shear" lesions, and a higher frequency of corpus callosum injury than patients with secondary BSI. The location of primary and secondary lesions was significantly different. Overall, MR imaging was more helpful than CT in detecting, localizing, and characterizing BSI.

Acute Disease↗
PubMed1989

Posterior ischemic optic neuropathy due to Aspergillus fumigatus.

A 35-year-old woman with metastatic breast cancer experienced acute monocular visual loss. Her fundus examination was normal. The patient died 48 h later, and autopsy demonstrated hematogenously disseminated aspergillosis. The retrobulbar optic nerve of the affected eye showed infarction due to massive embolization with Aspergillus fumigatus. Although the retrobulbar optic nerve is relatively resistant to ischemia, its meningeal derived blood supply may be occluded by massive showers of emboli.

Adult↗
PubMed1989

Facial trauma and associated brain damage.

CT continues to be the most important diagnostic study for detection and classification of maxillofacial injury. MR has a complementary role in specific situations because of its multiplanar imaging capabilities and exquisite soft tissue contrast resolution. MR is particularly useful for evaluation of orbital "blow-out" fractures, intraorbital and intraocular hemorrhage, traumatic vascular injuries, and associated intracranial damage.

Brain Injuries↗
PubMed1988

MR imaging of head trauma: review of the distribution and radiopathologic features of traumatic lesions.

The distribution and extent of traumatic lesions were prospectively evaluated with MR imaging in 40 patients with closed head injuries. Primary intraaxial lesions were classified according to their distinctive topographical distribution within the brain and were of four main types: (1) diffuse axonal injury (48.2%), (2) cortical contusion (43.7%), (3) subcortical gray-matter injury (4.5%), and (4) primary brainstem injury (3.6%). Diffuse axonal injury most commonly involved the white matter of the frontal and temporal lobes, the body and splenium of the corpus callosum, and the corona radiata. Cortical contusions most frequently involved the inferior, lateral, and anterior aspects of the frontal and temporal lobes. Primary brainstem lesions were most commonly seen in the dorsolateral aspects of the rostral brainstem. The pattern and distribution of primary lesions seen by MR were compared with those expected from previous pathologic studies and found to be quite similar. Our data and review of the literature would also indicate that MR detects a more complete spectrum of traumatic lesions than does CT. Secondary forms of injury (territorial arterial infarction, pressure necrosis from increased intracranial pressure, cerebral herniation, secondary brainstem injury) were also visible by MR in some cases. The level of consciousness was most impaired in patients with primary brainstem injury, followed by those with widespread diffuse axonal injury and subcortical gray-matter injury. The best MR imaging planes, pulse sequences, and imaging strategies for evaluating and classifying traumatic lesions were evaluated, and the mechanisms by which traumatic stresses result in injury were reviewed. MR was found to be superior to CT and to be very effective in the detection of traumatic head lesions and some secondary forms of injury. While T2-weighted images were most useful for lesion detection, T1-weighted images proved to be most useful for anatomic localization and classification.

Adolescent↗
PubMed1988

Prospective comparative study of intermediate-field MR and CT in the evaluation of closed head trauma.

Forty patients with closed head trauma were evaluated prospectively with CT and intermediate-field-strength MR imaging to compare the diagnostic efficacies of the two techniques. Traumatic lesions were detected in 38 patients. The severity of injury, as determined by the Glascow Coma Scale, ranged from 3 to 14. The sensitivities of CT and MR were calculated for all subgroups of lesions: (1) hemorrhagic and nonhemorrhagic intraaxial lesions (diffuse axonal injury, cortical contusion, subcortical gray-matter injury, primary brainstem injury); (2) extraaxial hematomas (subdural, epidural); and (3) diffuse hemorrhage (subarachnoid, intraventricular). CT and MR (T1- and T2-weighted) studies were both highly and comparably sensitive in the detection of hemorrhagic intraaxial lesions. MR scans, however, were much more sensitive in detecting nonhemorrhagic lesions. cortical contusions and diffuse axonal injury constituted 91.9% of all intraaxial lesions. The sensitivities of the imaging techniques for this combined group of lesions were (1) nonhemorrhagic lesions (CT = 17.7%, T1-weighted MR = 67.6%, T2-weighted MR = 93.3%); (2) hemorrhagic lesions (CT = 89.8%, T1-weighted MR = 87.1%, T2-weighted MR = 92.5%). MR was also significantly better in detecting brainstem lesions (CT = 9.1%, T1-weighted MR = 81.8%, T2-weighted MR = 72.7%). The sensitivities of the diagnostic studies in the detection of extraaxial hematomas were CT = 73.2%, T1-weighted MR = 97.6%, T2-weighted MR = 90.5%). Intraventricular hemorrhage was consistently seen with all three imaging studies, but subarachnoid hemorrhage was detected much more frequently with CT. In summary, MR has clear advantages over CT in evaluating closed head trauma. Although its sensitivity in detecting hemorrhagic lesions is similar to that of CT, it is much better than CT in detecting nonhemorrhagic lesions, which are more prevalent. MR is more useful than CT in classifying primary and secondary forms of injury and directing treatment. CT's one advantage over MR is its ability to more rapidly assess unstable patients who may need surgery.

Adolescent↗
PubMed1987

Cerebellopontine angle-petromastoid mass lesions: comparative study of diagnosis with MR imaging and CT.

Capabilities of computed tomography (CT) and magnetic resonance (MR) imaging in the diagnosis of cerebellopontine angle-petromastoid (CPA-PM) lesions were compared in 75 patients. CT and MR demonstrated 95.8% and 98.7% of the lesions, respectively. MR was often more helpful for characterization of neuromas, epidermoid cysts, exophytic gliomas, and vascular lesions, while CT was usually more informative for meningiomas, metastases, and tympanomastoid cholesteatomas. A specific diagnosis could be made with MR for most types of lesions through use of relaxation parameters and characteristic morphologic changes. Size, shape, location, and contour of the lesions, however, were generally more helpful for differential diagnosis than relaxation times. With the exception of metastatic lesions, cholesteatomas, and some meningiomas, MR was usually more helpful than CT in defining the full extent of the lesions and their relationships to contiguous structures. MR, because of its high accuracy in lesion detection, characterization, and localization, is a suitable primary diagnostic modality for evaluating patients with suspected CPA-PM lesions.

Brain↗
PubMed1986

The spectrum of multiple sclerosis lesions using a multiple spin echo pulse sequence and a high field strength.

Seventy-one patients having clinical laboratory findings consistent with multiple sclerosis (MS) were imaged with a 1.5 tesla MR instrument using multiple spin echo sequences (TR = 2,000 ms and TE = 30, 60, 90, 120 ms). Multiple spin echo is a sensitive method for detecting MS lesions. Sixty-seven patients (94%) demonstrated lesions consistent with MS. With the exception of those located in the cortex, optic nerve and chiasm the lesions detected correlated with pathologic data. Lesions of the cerebral hemispheres, corpus callosum and cerebellum were generally multiple while lesions of the brain stem and optic tracts were generally singular. The majority of the lesions were associated with the white matter tracts of the cerebral hemispheres and brain stem.

Brain↗
PubMed1985

Chymopapain chemonucleolysis: correlation of diagnostic radiographic factors and clinical outcome.

The therapeutic response to treatment of lumbar disk herniation with chymopapain chemonucleolysis is significantly influenced by the criteria used for patient selection. Although careful clinical selection of patients reduces the frequency of treatment failure, some patients do not achieve satisfactory relief of pain with chemonucleolysis. In an attempt to identify objective pretreatment radiographic findings that might refine selection criteria and further reduce the failure rate of chemonucleolysis, a retrospective correlation of pretreatment radiographs and clinical responses was made of 200 consecutive chemonucleolysis patients. Marked improvement in sciatica occurred in 79.9% and 79.3% of patients at early and late follow-up, respectively. There was a significantly higher response rate, however, in patients who had definite radiographic evidence of focal disk herniation and in those patients with definite radiographic evidence of nerve-root compression (marked nerve-root deviation, nerve-root flattening or edema, root-sleeve amputation) by disk material. Those patients with a preinjection disk height greater than the mean had a slightly better response rate (91.1%) than those whose disk height was smaller than the mean (80.0%). Most cases of treatment failure could be attributed to an incorrect radiographic diagnosis, treatment of patients with equivocal diagnostic studies, the presence of "free" disk fragments, and causes of nerve-root compression unresponsive to chymopapain.

Adult↗