Biomedical subjects
Publications and source records attributed to C L Truwit.
Although much remains to be learned about the embryology of the intracranial vasculature, much of the developmental pathways of the intracranial vascular system are now apparent. Understanding these pathways offers the potential to appreciate the nature of such arterial anomalies as the azygos anterior cerebral artery and the trigeminal artery and such venous anomalies as the vein of Galen malformation and the venous angioma.
In this article, cerebral arterial and venous anatomy are reviewed. Although angiographic anatomy remains pertinent to neurosurgery and neurointerventional radiology, much of the previous concerns about vascular displacements (i.e., shifts) are no longer relevant in the age of MR imaging. Today, the MR anatomy of intracranial vessels is much more important.
PURPOSE: To describe 11 cases of posterior fossa venous angiomas with drainage through the brain stem. METHODS: Eleven cases of posterior fossa venous angioma with drainage through the brain stem were evaluated using MR. Correlation with known routes of venous drainage for the cerebellum and brain stem is made. RESULTS: Six of the 11 venous angiomas were found in the cerebellum, four in the brain stem; one involved both the cerebellum and brain stem. The cerebellar venous angiomas drained to subependymal veins about the fourth ventricle and dorsal pons. These then connected with an enlarged transmesencephalic or transpontine vein, to drain anteriorly to the anterior pontine veins. The brain stem angiomas had variable drainage depending on location. Evidence of hemorrhage was seen in five cases. CONCLUSION: Cerebellar and brain stem venous angiomas have several potential routes of drainage, including an enlarged vein traversing the pons, midbrain, or medulla. A knowledge of the normal venous anatomy of this region helps to understand the occurrence of these uncommon routes of venous drainage.
The abducens nerve, the sixth cranial nerve, innervates the lateral rectus muscle of the eye and is responsible for lateral horizontal ocular movement. A wide variety of abnormalities, both primary to the nerve itself and secondarily involving the nerve, can paralyze the abducens nerve. MR imaging offers the best opportunity to detect the underlying abnormality causing abducens nerve palsy. In this pictorial essay, we illustrate the MR imaging features of numerous conditions that cause isolated abducens nerve palsy.
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Magnetic resonance imaging with fat saturation after the administration of gadolinium-DTPA can detect and demarcate meningioma of the optic nerve sheath with a precision not attainable with any other current imaging technique. This article describes some of the clinical implications of this technique and illustrates the appearance of this tumor on magnetic resonance images.
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Eighty-four intubated, mechanically ventilated patients were prospectively evaluated for incidences of colonization and nosocomial pneumonias dependent on whether they received endotracheal suctioning by an "open" suction method vs. "closed" suction (Trach Care Closed Suction System) method. Results show that closed suctioning is associated with a significant (67% vs. 39% p less than .02) increase in colonization compared with open suctioning. However, difference in the incidence of nosocomial pneumonia was not significantly (26% vs. 29%) different between closed and open suctioning. Differences in severity of illness (Acute Physiology and Chronic Health Evaluation II and Therapeutic Intervention Scoring System), age, sex, presence of NG tubes, use of H2 antagonists or antacids, use of antibiotics, and history of smoking were all nonsignificant. Survival analysis demonstrated that the probability of survival without developing nosocomial pneumonia was greater among closed-suctioning patients vs. open-suctioned patients (p less than .03). This study shows that suctioning performed via the Trach Care closed-suction system increases the incidence of colonization but not the incidence of nosocomial pneumonia, and may actually decrease mortality when compared with open-suction systems.
Although computed tomography (CT) remains the most frequently used imaging examination in acute cerebral infarction, its sensitivity for early detection of strokes remains limited. In middle cerebral artery (MCA) strokes less than 6 hours old, loss of definition of the gray-white interface in the lateral margins of the insula ("insular ribbon") was observed. The acute and subacute CT findings in 11 retrospective and 16 prospective patients are presented. Loss of the insular ribbon was detected in 12 of the prospective cases and in all 11 retrospective cases. The insular ribbon is supplied by the insular segment of the MCA and its claustral branches. With cessation of MCA flow, the insular ribbon becomes the region most distal from the anterior and posterior cerebral collateral circulations. Consequently, the insular ribbon effectively becomes a watershed arterial zone. Loss of the insular ribbon is thus a reflection of acute edema due to infarction. Loss of the insular ribbon appears to be another frequent and reliable finding in acute MCA stroke.
Intracranial lipomas are uncommon lesions whose development remains poorly understood. To clarify the anatomic and embryologic features of intracranial lipomas, we retrospectively reviewed the MR scans of 42 patients with 44 intracranial lipomas. Interhemispheric lipomas were the most common, accounting for 45% of cases. The remainder of the lesions were clustered in the quadrigeminal/superior cerebellar (25%), suprasellar/interpeduncular (14%), cerebellopontine angle (9%), and sylvian (5%) cisterns. Fifty-five percent of the lesions were associated with brain malformations of varying degrees. Intracranial vessels and nerves were noted to course through 16 (36%) of the lesions. The relative frequencies of the locations of the lipomas correspond to the temporal sequence of dissolution of the meninx primitiva, the mesenchymal anlage of the meninges. This finding supports the concept of lipoma formation as a result of abnormal persistence and maldifferentiation of the meninx. This embryologic concept of the development of intracranial lipomas explains the high frequency of callosal and other brain hypoplasias. Intracranial lipomas are neither hamartomas nor true neoplasms; rather, they are congenital malformations.
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The typical appearance of subcutaneous ossification on a single photon emission computed tomography (SPECT) bone image is reminiscent of the patterns discovered by radiographs and computerized tomography. A case demonstrates the advantage of SPECT imaging to clarify the actual location of soft tissue Tc-99m methylene diphosphonate in this condition.
A categorical course curriculum was introduced at Brooke Army Medical Center to focus the content of daily conferences and lectures according to radiology subspecialties. Our goal was to improve the traditional uncoordinated conferences and apprenticeship approach to resident learning. After one-year's experience, resident performance has improved, and residents and staff greatly prefer this style of teaching. The format has been adopted.
A better understanding of the appearance of a biopsy needle as well as its interaction with various sequence parameters in MRI is beneficial for its application in interventional MRI. As an extension of previous researchers' contributions, we investigate the specific characteristics of MR image artifacts associated with the tip of a biopsy needle when it is approximately parallel to the main magnetic field. The origin of the needle tip artifact, which exhibits as a blooming ball, was studied using MRI techniques and numerical simulation using the finite element method (FEM). Satisfactory agreement between theory and experiment has been achieved. Results showed that the image artifacts associated with biopsy needle are present and dependent on imaging parameters, but the artifacts can be reduced if optimal imaging parameters were used. Images of actual human brain tumor biopsies performed using the same needle under MRI guidance and monitoring demonstrated this artifact.