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SD Chang
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Correlation of magnetic resonance characteristics and histopathological type of angiographically occult vascular malformations
OBJECTIVE: Histological and radiological classification of vascular malformations has previously been attempted in an effort to understand their nature and predict their biological behavior. There exists a subgroup of vascular malformations that are angiographically occult and share a common magnetic resonance imaging (MRI) appearance but may differ in their behavior. We sought to determine any correlation between MRI features and final histopathological diagnosis. METHODS: We reviewed our series of 72 patients with angiographically occult vascular malformations operated on at Stanford University Medical Center between 1988 and 1993. Radiographic magnetic resonance images and histopathological specimens were retrospectively evaluated for various diagnostic features. RESULTS: Our data indicate that lesions exhibiting a ring of hemosiderin are associated with the presence of a cavernous malformation (CM) component (86% of CMs versus 33% of non-CM lesions). A lesion associated with edema, mass effect, or a single prominent blood product on MRI correlates with the presence of an arteriovenous malformation (AVM) component. Sixty-three percent of AVMs and 80% of lesions with partial AVM components showed edema, compared with 8% of CMs and 0% of venous malformations. Sixty percent of AVMs and 63% of lesions with partial AVM components showed a single prominent blood product, compared with 8% of CMs and 0% of venous malformations. Finally, 60% of AVMs exhibited mass effect, compared with 20% of CMs. Additionally, an expansile hemorrhage is suggestive of an AVM. CONCLUSION: This study is the first to demonstrate that a particular MRI appearance of an angiographically occult vascular malformation is suggestive of an AVM component. This may have important implications with regard to the behavior of the lesion and planning of future treatment.
Image-guided robotic radiosurgery
PURPOSE: To describe the design and performance of a novel frameless system for radiosurgery. This technology, called image-guided radiosurgery (IGR), eliminates the need for stereotactic frame fixation by relating the identified lesion to radiographic landmarks. CONCEPT: IGR uses a lightweight x-band linear accelerator, computer-controlled robotic arm (Fanuc manipulator [Fanuc Robotics North America, Inc., Rochester Hills, MI]), paired orthogonal x-ray imagers, and a computer workstation that performs rapid image-to-image registration. During radiosurgery, the x-ray imaging system determines the location of the lesion and communicates these coordinates to the robot, which adjusts the pointing of the linear accelerator beam to maintain alignment with the target. RATIONALE: Existing stereotactic techniques require rigid cranial fixation to establish and maintain a system of reference for targeting. Such frames cause pain for the patient, limit the use of fractionation, and necessitate a prolonged period of general anesthesia if children are to be treated. Furthermore, skeletal or any other type of rigid fixation is difficult to achieve beyond the cranium. IGR was designed to overcome these limitations, which are inherent to nearly all current radiosurgical methods. DISCUSSION: Preliminary testing and early clinical experience have demonstrated the practicality and potential of the IGR concept and have identified the most important directions for improvement. For example, an IGR prototype accurately tracked target displacements in three dimensions but showed reduced accuracy when confronted by rotational movements. This observation led to development of a new generation of tracking algorithm that promises to improve tracking in all six dimensions. Further experience indicated that improvements in the quality of the x-ray images were needed to allow the system to locate and treat target sites outside the cranium. Consequently, a new x-ray imaging technology with superior resolution and increased sensitivity has been added to the system. These improvements should make it possible to apply IGR techniques to a variety of targets located throughout the body. This article describes and critiques the components of the IGR and summarizes our preliminary clinical experience.
Measurement of the relative branching fraction Gamma (D0-->K micro nu )/ Gamma (D0--> microX).
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Diffractive excitation of 14.6-, 60-, and 200-GeV/nucleon 16O and 14.6-GeV/nucleon 28Si nuclei in nuclear emulsion.
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