Richard E. Latchaw

Thrombotic and hemorrhagic strokes complicating early therapy for childhood acute lymphoblastic leukemia

Sudden cerebrovascular insults occurred during or immediately following remission induction therapy in 4 children with acute lymphoblastic leukemia. In 3, cerebral infarction was due to thrombosis. In the fourth, an intracerebral hematoma developed representing either frank hemorrhaging or a hemorrhagic infarction. None of the patients had central nervous system leukemia or extreme leukocytosis at the time of diagnosis. Symptoms were obtundation, hemiparesis, seizures, and headache. The induction chemotherapy included L‐asparaginase which causes deficiencies of antithrombin, plasminogen, fibrinogen, and factors IX and XI. These hemostatic abnormalities may explain the thromboses and bleeding observed in these children.

Functional Magnetic Resonance Imaging as a Management Tool for Cerebral Arteriovenous Malformations

The location of eloquent cortex, such as the motor strip, the visual cortex, or Brocas area, may be difficult to predict even with multiprojectional magnetic resonance imaging (MRI). Distortion and displacement of this cortex may occur with a congenital lesion, such as an arteriovenous malformation, or by an acquired disease, such as a neoplasm. A desire to avoid damaging these eloquent areas by conventional surgery, radiosurgery, or endovascular surgery makes their accurate identification an important part of the pretherapeutic planning process. Blood oxygen level dependent functional MRI is a technique that uses the local increase of oxyhemoglobin concentration in the patient that occurs as a result of the increase in flow rate and blood volume in eloquent cortex undergoing stimulation from, for example, flashing lights, hand movements, or speech. We have used the blood oxygen level dependent technique to localize eloquent cortex relative to arteriovenous malformations and tumors. Using a 4.0-T magnetic resonance (MR) system, there is a sufficiently high degree of spatial resolution of the MR signal intensity changes during stimulation to allow the identification of eloquent cortex. Alternative, non-MR, invasive techniques for functional localization include electrocorticography and stimulation from subdural grids and strips. Noninvasive, non-MR technologies, such as positron emission tomography and magnetoencephalography, can also provide functional localization of eloquent cortex. However, the perfection of functional MRI at the 1.5-T field strength and the large number of such MR systems in operation mean that a highly accurate cerebral cortical localization technique can be available to most neuroscientists without the need to purchase alternative expensive technology.

Periventricular spread of tumor demonstrated by computed tomography.

Spread of intracranial neoplasms through the periventricular tissues of the brain is well known to neuropathologists, but is almost never recognized by the usual neuroradiologic techniques of angiography and pneumoencephalography. Periventricular tumor spread can, however, be readily dmonstrated by contrast-enhanced CT scanning. This report documents 4 cases of periventricular tumor diagnosed by CT scanning.

Imaging of perinatal hypoxic-ischemic brain injury

This article reviews some physiological parameters that influence the location and degree of injury from hypoxia-ischemia. The ability of various imaging tests, particularly magnetic resonance imaging, to detect tissue changes after hypoxia-ischemia is discussed. Most importantly, we evaluate the extent of our knowledge regarding the correlations between imaging, pathophysiological processes, and clinical medicine.

RADIOLOGIC DIAGNOSIS AND STAGING OF HEAD AND NECK SQUAMOUS CELL CARCINOMA

The predominant extracranial head and neck cancer in adults is squamous cell carcinoma. The purpose of this article is to discuss the radiographic evaluation of these patients with CT scans or MR imaging before therapeutic intervention. Specific focus is given to the efficacy of CT scans and MR imaging, as an adjunct to clinical staging for evaluation of the primary tumor, and metastatic adenopathy. MR imaging, because of its improved soft tissue contrast and multiplanar capability, is probably superior to CT scans for evaluation of the primary tumor in patients with squamous cell carcinoma. CT scans, however, remain the gold standard for identifying metastatic adenopathy and in most institutions remain the study of choice for evaluating this patient population.

The use of nonionic contrast agents in neuroangiography. A review of the literature and recommendations for clinical use.

RATIONALE AND OBJECTIVES. Several large studies have demonstrated the improved safety record of nonionic versus ionic contrast agents for intravenous administration. However, nonionic agents are much more expensive than ionic agents. The author addresses whether, given this large cost differential, nonionic contrast agents should always be used in neuroangiography (cerebral and spinal cord angiography and intravascular neurointerventional procedures). The answer could come from a closer examination of the effects of contrast agents on the brain.METHODS. There have been a number of animal experiments and clinical trials performed using a variety of available intravascular contrast agents. In an attempt to arrive at some reasonable conclusions regarding the use of contrast agents today, the author reviews several of these studies. In the human studies, three areas were analyzed: 1) cerebral angiography, 2) spinal cord angiography, and 3) intravascular neurointervention. The author explains why demonstrating the effect of a contrast agent on the brain or spinal cord in the clinical setting is more difficult than studying the effect of this agent on the liver, heart, or kidney. For example, obtaining objective measurements of altered cerebral physiology following intravascular injection of a contrast agent may itself alter the physiology. In lieu of objective measurements, investigators must rely on apparent changes in behavior, mentation, or the production of a focal neurologic deficit. However, it is extremely difficult, if not impossible, to separate the effect of the contrast agent from the effects of the arteriographic procedure, or from the disease process being evaluated.RESULTS. The neuronal environment is protected by the blood-brain barrier. A number of animal experiments have demonstrated that nonionic agents produce breakage of the blood-brain barrier less frequently than do ionic agents. In these studies, nonionic agents also produced fewer neurologic effects than did ionic agents. The human studies showed no statistically significant differences in neurologic effects when ionic and nonionic agents were compared. Cerebral: minor changes in heart rate were more common with ionic than with nonionic agents; there were no significant electroencephalogram changes in any of the patients studied. Spinal cord: the effects of intravascular injections of contrast material into the spinal cord of experimental animals have been rarely evaluated; direct comparisons of contrast agents in human spinal cord angiography have not been performed. Neurointervenlion: there have been no comparative studies of different contrast agents used during intravascular neurointerventional procedures in humans.CONCLUSIONS. Extensive animal data demonstrate that nonionic contrast agents are safer than ionic for cerebral angiography. Animals in the cited studies show less blood-brain barrier disruption, fewer direct neuronal effects, and fewer neurobehavioral deficits. However, the overwhelming conclusion from the human studies is that, while there is evidence in the experimental animal that nonionic agents produce fewer neurologic effects than do ionic agents, no study to date has been able to translate these findings into an apparent clinical difference in humans, mainly because its so difficult to detect and measure neurologic changes in human trials. In addition, differences in neurologic effects between contrast agents used in human studies may be relatively small. Thus, one must make an educated guess as to the appropriate use of contrast agents in the context of their apparent clinical safety and cost-benefit ratio.

Computerized tomography of the orbit in carotid-cavernous sinus fistulae

Abstract Orbital Computerized Tomography was utilized in seven cases of angiographically proven carotid-cavernous sinus fistulae. The findings were as follows: (A) proptosis (in all cases), (B) enlarged superior opthalmic vein (in six cases) and (C) introorbital muscle enlargement (in three cases). Carotid-cavernous sinus fistulae can usually be differentiated from other entities in the clinical differential diagnosis by the use of orbital CT.

Safety Efficacy of Gadodiamide Injection Administered Intravenously to Children for Contrast-Enhanced MR of the Central Nervous System

Rationale and Objectives. The lower osmolality of gadodiamide injection than gadopentetate dimeglumine (Gd-DTPA) contributes to gadodiamide having a higher median lethal dose in mice and rats. However, proof of safety and efficacy of gadodiamide has been derived largely from adult studies. To assess the performance of gadodiamide in pediatric central nervous system imaging, a study of 187 pediatric patients was performed. Methods. Part 1 of the study compared gadodiamide and Gd-DTPA in 174 children from 2 to 18 years of age. In part 2, 13 patients under the age of 2 were evaluated with gadodiamide alone. The majority of patients in both parts of the study were evaluated for possible neoplasm. Results. The difference in the incidence of adverse events between gadodiamide and Gd-DTPA showed an important trend. Three percent of gadodiamide-treated patients reported adverse events, whereas 9% did so in the Gd-DTPA group. Both agents were equally effective in terms of providing added diagnostic value: 76% for gadodiamide and 75% for Gd-DTPA. Conclusion. Gadodiamide and Gd-DTPA are equally effective in detecting lesions, and gadodiamide is at least equal in safety to Gd-DTPA at a dose of 0.1 mmol/kg in the pediatric population from birth to 18 years of age.

Temporal interpolation of low frame rate digital subtraction angiograms

Typical digital subtraction angiography (DSA) acquisition rates are often inadequate for visualizing and analyzing fast-moving flow patterns. Therefore, an interpolation method that captures the angiographic flow pattern was developed. The temporal change of gray value in each pixel along a blood vessel records the flow movement at that location. Thus, temporal interpolation was performed on a pixel-by-pixel basis. To generate each interpolated image, a polynomial interpolation was applied to six sequential images. To validate the interpolation technique, a flow phantom was imaged with a high acquisition frame rate, and interpolation was done in a lower frame rate and compared to the acquired data. The interpolated images were also compared to results from linear interpolation and cubic spline interpolation. Clinical utility was illustrated on DSA images of cerebral vasculature with aneurysms. Image sequences of 60 frame/s were generated from DSA images acquired at 7.5 frame/s. The results show improved flow pattern visualization, especially flow head locations in blood vessels. This interpolation method has also been applied to dynamic 3D reconstruction from biplane DSA projections. In this application, the method was used to offset temporal discrepancies between biplane projection pairs and contrast injections, making dynamic 3D reconstruction possible.

Three-dimensional reconstruction from limited biplane angiographic projections: a phantom study

A method for 3D cone beam reconstruction of cerebral vasculature (both morphology and grayscale) from a limited number (less than 10) of digital subtraction angiographic (DSA) projections obtained with a standard biplane C-arm x-ray system is described. The reconstruction method includes geometric calibration of the source and detector orientation, spatial image distortion correction, and algebraic reconstruction technique (ART) with non- negativity constraint. Accuracy of voxel gray scale values estimated by ART is enhanced by determination of weights based on the intersection volume between a pyramidal ray and cubic voxel. The reconstruction is accelerated by retaining only the vessel containing voxels and distributed computing. Reconstruction of a phantom containing fiducial markers at known 3D locations demonstrated that the reconstructed geometry is accurate to less than a pixel width. Reconstruction is also obtained from an anatomic skull phantom with an embedded cerebral vasculature reproduction that includes an aneurysm. Three dimensional reconstruction exhibited the necessary details, both structural and grayscale.