Screening test for detection of metallic foreign objects in the orbit before magnetic resonance imaging.

RATIONALE AND OBJECTIVES: A study was designed to determine whether plain films, used as a screening modality for magnetic resonance imaging (MRI), could reliably detect intraorbital metallic foreign objects. METHODS: In the first experiment, 20 metal particles were placed in five human cadaver orbits. Routine orbital plain film series and computed tomography (CT) were obtained, randomized, and interpreted blinded by three experienced radiologists. RESULTS: The threshold size of particle detection for CT (0.07 mm3) was lower than for plain films (0.12 mm3). Placing metal particles in artificial and true vitreous demonstrated that all particles moved under a magnetic field at 1.5 T. When human globes were exposed to industrial tools (grinder, bandsaw, air hose, etc.), no metal objects penetrated the sclera. CONCLUSIONS: Plain films can be used as a low-cost, low-radiation screening procedure for high-risk patients with occupations involving metal work. CT should be used for patients with a history of eye trauma from other causes.

Research resources in academic radiology.

Research resources in academic radiology were investigated by analyzing the responses to a survey from 72 North American institutions. The questionnaire addressed five general areas: department size, departmental resources committed to research, availability of research training, research quality control, and research productivity. The highest correlates of grant productivity included measures of departmental resources committed to research, for example, space devoted to research, size of research budget, and full-time employee support for engineers, physicists, and chemists. In a regression model, measures of the number of engineers employed by a department, the number of attending staff, and the number of training lectures given by engineers were found to be most highly associated with dollar value of grant support. The average level of research resources available at responding institutions was generally low, despite a seemingly strong desire to do quality research. This is evidenced by a strong sentiment among respondents in favor of research training and quality control of research.

A study of optimization of the complex hyperbolic secant inversion pulses.

The conjugate gradient method is used to optimize the inversion slice profile produced by complex hyperbolic secant selective pulses. An improved quality is obtained for the inversion slice profile at a price, however, of a lower immunity to the amplitude variation of radiofrequency pulses.

Magnetic resonance imaging of spinal intradural granulocytic sarcoma.

We report the case of a young black male with a spinal intradural granulocytic sarcoma proved by needle aspiration. The tumor was evaluated by myelography, computed tomography, and magnetic resonance imaging (MRI). Other than its rarity, the "dripping candle wax" appearance on MR T1-weighted images and the lack of enhancement with Gd-DTPA makes this case unique. Progressive changes of the tumor following chemo- and radiotherapy were successfully demonstrated by MR.

Brain ischemia.

The sensitivity of MRI to changes in water state and volume makes it the most desirable modality for imaging early brain ischemia. Its sensitivity is reflected in the ability to show ischemic changes in the white matter of the asymptomatic elderly, which are attributed to axonal loss, demyelination, and gliosis. In large infarcts, however, contrast enhancement with Gd-DTPA can be used to add specificity, should doubt exist as to the proper diagnosis. The ability of MR to image flow is a valuable adjunct, and MR angiography has the potential partially to replace invasive angiography. Applications of MR such as diffusion-perfusion studies, sodium imaging, and spectroscopy could all prove to be useful in the future.

Low-risk large-needle biopsy of chest lesions.

There were 210 chest lesions biopsied with large-bore cutting needles (14.5 to 18.0 gauge). The patients ranged in age from 13 to 84 years with a heavy preponderance of males (99 percent). Most of the lesions were pleural based lung masses (133). In the majority (140) only one pass was required for diagnosis. Certain technical considerations were employed which resulted in a low complication rate of 4.8 percent. Pneumothorax occurred in only eight cases (4 percent). There were eight false-negative biopsies and no false-positives. The key advantage of large needle biopsy (LNB) over skinny needle biopsy (SNB) is that a large tissue core is obtained that allows for more specific histologic diagnosis. With proper technique and careful patient and lesion selection, LNB can be performed as safely as thin-needle biopsy.

Spinal subarachnoid hematoma complicating lumbar puncture: diagnosis and management.

Two patients with altered hemostatic mechanisms developed spinal subarachnoid hemorrhage after difficult lumbar punctures. One patient had received anticoagulation therapy soon after lumbar puncture and the other had a low platelet count (63,000/mm3) at the time of lumbar puncture. In both patients a hematoma evolved, producing blockage of cerebrospinal fluid flow. Clinical manifestations consisted of severe back and radicular pain with sphincteric disturbances followed by rapidly developing severe paraparesis. Of the methods of radiographic evaluation that were used, including computed tomography (CT) without contrast enhancement, myelography, CT with intrathecally administered contrast medium, and magnetic resonance imaging, we found the best study to be myelography via lateral cervical puncture followed by CT. Unfortunately, diagnosis was delayed, and surgical evacuation of the hematomas did not substantially improve the patients' conditions. The salient clinical and radiographic features of this disorder and its pathophysiology are reviewed. Prompt recognition of these lesions is necessary so that surgical intervention may maximize chances of recovery.

Computed tomography of combined right upper and middle lobe collapse.

We report two patients with combined right upper and middle lobe collapse and present the CT findings. The CT appearance is different from isolated right upper or middle lobe collapse, but similar to left upper lobe collapse. As with other types of lobar collapse, the diagnosis can usually be made from frontal and lateral chest radiography. However, occasionally the exact type of lung collapse may be unclear prior to CT, and thus CT may be useful in making the correct diagnosis.

The empty delta sign: frequency and significance in 76 cases of dural sinus thrombosis.

The presence of the empty delta sign on contrast material-enhanced computed tomographic (CT) scans of the brain is considered pathognomonic of sagittal sinus thrombosis (SST); however, a valid explanation for its appearance is lacking, despite several hypotheses. To determine the frequency of the sign and its prognostic significance, 76 reported cases (112 CT manifestations) of SST and SST-related intracranial sinovenous occlusive disease were reviewed. Ten CT signs related to both disease processes were reported; the empty delta sign was the most frequently reported sign (28.6%) of SST. Patients with hemorrhagic infarction and/or the empty delta sign on CT scans had the poorest prognosis. A case illustrative of the empty delta sign is described in which there was engorgement of endothelial- and nonendothelial-lined spaces in the dura mater with hemorrhagic rupture into the dural leaf. The empty delta sign can probably be explained on the basis of the rich dural venous collateral circulation, consisting primarily of lateral lacunae, a vascular mesh (dural cavernous spaces), and meningeal venous tributaries.

Setting up a quality-assurance program: issues with impact on patient care.

We developed a simplified approach to the setting up of a radiology quality-assurance program based on the standards of the Joint Commission on Accreditation of Hospitals. This approach gives priority to the little-discussed issues that have maximum impact on patient care: the monitoring of the radiologic service as a whole and personnel performance. Quality control of equipment and radiation protection have been extensively dealt with in the literature and are omitted.

Human brain infarcts: Gd-DTPA-enhanced MR imaging.

During Food and Drug Administration phase II and III clinical trials for gadolinium DTPA, the paramagnetic agent was used to study 11 patients with 20 subacute and chronic cerebral infarcts. Five patients had numerous periventricular and deep white-matter lesions, probably due to chronic ischemic disease. Magnetic resonance (MR) imaging was performed 4-30 days after the ictus, preceded by computed tomography (CT) in all but one case. In most cases, the nonenhanced spin-echo (SE) images, obtained at 500-msec repetition times and 30-msec echo times, failed to demonstrate the infarct, and in general the gadolinium-enhanced SE 500/30 images matched the contrast material-enhanced CT scans in pattern. Periventricular lesions and small, deep, white-matter infarcts that were chronic and asymptomatic were not enhanced by gadolinium MR. However, three small, symptomatic capsular and brain-stem infarcts showed definite enhancement. Usually the enhancement was visible at 3 minutes, increasing to a peak at 30 minutes. At 55 minutes, the enhancement increased in the medium-aged infarcts (8-14 days), while it decreased in the late infarcts (15-30 days). The T2 relaxation time-weighted pulse sequences were most sensitive for demonstrating all infarcts, but without the aid of a contrast agent, they were frequently poor in specificity.

Reactive gliosis simulating butterfly glioma: a neuroradiological case study.

Reactive gliosis was found in a 40-year-old man who presented with intractable seizures thought to be due to a malignant neoplasm. Although two separate lesions located bilaterally in the frontal lobes were evident on the computed tomographic scan, a connection between these lesions along the fibers of the corpus callosum was clearly demonstrated on T2-weighted magnetic resonance images. The unusual radiological appearance of this gliosis, which simulated a malignant butterfly glioma on magnetic resonance imaging (MRI), is reported. Because MRI is still a new modality, its images should be interpreted with judicious caution.

Primary intraspinal fibrosarcoma.

Fibrosarcomas of dura mater are very rare tumors representing only 0.5% of all central nervous system sarcomas. A higher incidence of dural fibrosarcomas has been reported in patients with neurofibromatosis. We present a case of spinal dura mater fibrosarcoma in a patient without neurofibromatosis. The diagnostic and therapeutic strategy in the clinical management is discussed.

The spine in 3D. Computed tomographic reformation from 2D axial sections.

A new program (3D83, General Electric) was used to reformat three-dimensional (3D) images from two-dimensional (2D) computed tomographic axial scans in 18 patients who had routine scans of the spine. The 3D spine images were extremely true to life and could be rotated around all three principle axes (constituting a movie), so that an illusion of head-motion parallax was created. The benefit of 3D reformation with this program is primarily for preoperative planning. It appears that 3D can also effectively determine the patency of foraminal stenosis by reformatting in hemisections. Currently this program is subject to several drawbacks that require user interaction and long reconstruction time. With further improvement, 3D reformation will find increasing clinical applicability.

Value of magnetic resonance imaging in assessing bone destruction in head and neck lesions.

We utilized low-field magnetic resonance imaging (MRI) to evaluate 12 patients with head and neck lesions and suspected skull base or facial bone destruction. All except one had high resolution computed tomography (CT). MRI was performed on a 0.15 tesla (low-field) resistive unit, with routinely good resolution due mainly to the use of specially designed rf receiver coils (surface coils). T1 and T2 weighted spin echo images were performed in all cases. In three instances axial, coronal, and sagittal images were done. All CTs were done with high resolution techniques on state-of-the-art equipment. Comparison of the CT and MR images (at low-field strength) showed that MRI's main strength lies in its freedom to perform images in any plane and to visualize intracranial lesions with early brain involvement. Otherwise, the two modalities are comparable. Bone destruction seen on CT was always detectable on MRI, although CT is clearly superior in resolving bone detail. MRI is recommended when direct coronal CT scans are not obtainable to evaluate superiad tumor extension. The improved visualization of nasopharyngeal soft tissue and cavernous sinus region is likely to make MRI the examination of first choice in evaluating lesions of the nasopharynx, skull base, and cavernous sinus.