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Chris Xenos, Spiros Sgouros, Kalyan Natarajan, A. Richard Walsh, and Anthony Hockley

surrounding brain is to measure sequentially the reduction in ventricular volume caused by the shunt. A recent study of healthy volunteers conducted by our group provided normal reference values for comparisons. 22 Taking advantage of the fact that, within the same department, surgeons use two different shunt types, we embarked on a study of sequential measurement of ventricular and intracranial volume after shunt insertion, aiming to investigate the different function patterns of two shunt types and to obtain an indirect indication of the brain's response to shunt

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Lawrence B. Marks and David P. Spencer

D uring radiosurgery, a large dose of radiation (approximately 10 to 50 Gy) is delivered to a small volume of the brain in a single fraction. This procedure is usually well tolerated. Since large volumes of brain tissue generally do not tolerate single large doses of radiation, 5 the tolerance of the brain is clearly related to the volume of brain irradiated. This dose/volume/tolerance relationship is one of the cornerstones of radiosurgery. Despite the rapidly growing interest in radiosurgery, the influence of volume on the tolerance of the brain is not well

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Stefan-Nikolaus Kroppenstedt, Michael Kern, Ulrich-Wilhelm Thomale, Gerd-Helge Schneider, Wolfgang Reinhardt Lanksch, and Andreas Wilhelm Unterberg

critical threshold for exacerbation of primary brain damage has not been defined. Therefore, the effect of blood pressure reduction and elevation on contusion volume after controlled cortical impact injury (CCII) was studied. 11 Blood pressure was decreased by venous blood pooling in lower body portions by using hypobaric hypotension or elevated by administration of dopamine. 10, 15 Materials and Methods Controlled Cortical Impact Injury The experimental protocol was approved by the committee for animal research in Berlin, Germany. Sixty male Sprague—Dawley rats, each

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Christopher Reilly, Chris Amidei, Jocelyn Tolentino, Babak S. Jahromi, and R. Loch Macdonald

investigated the role of these factors in relation to vasospasm, there are no studies in which the relationships between vasospasm and initial clot volume, clearance, and density have been examined simultaneously and quantitatively. Because larger volumes of clot might clear more slowly, a multivariate analysis would be needed to determine whether clot volume and clearance are independent factors associated with vasospasm. Clinical Material and Methods Patient Characteristics and Clinical Variables After approval of the protocol by the Institutional Review Board

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Michael Kosteljanetz

A n analysis of the relationship between intracranial pressure (ICP) and volume is essential for a better understanding of ICP dynamics, under both normal and hypertensive conditions. Various methods have been employed to study this relationship, most of which demand a volume perturbation of the cerebrospinal fluid (CSF) space. 11–13, 27 In an attempt to avoid fluid manipulations of the CSF space, some authors have analyzed the ICP pulse amplitude, 2, 4, 5, 25 because it has been suggested that the pulse amplitude is a measure of intracranial compliance or

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David S. Ditor, Sunil John, Jason Cakiroglu, Colin Kittmer, Paula J. Foster, and Lynne C. Weaver

efficacy of neuroprotective or neuroregenerative strategies. Traditionally, many investigators have relied on histological techniques to estimate lesion size after experimental SCI, with the Cavalieri method being perhaps the most commonplace. 10–12 , 14 , 15 In brief, the Cavalieri method of lesion volume estimation involves serial sectioning of the injured spinal cord, either transversely or longitudinally, and then staining of the sections to differentiate the spared tissue from the lesion. The area of the lesion is then determined for each serial section, and the

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Letters to the Editor To The Editor Harold A. Wilkinson , M.D. Worcester, Massachusetts 804 805 In their article on intracranial volume-pressure relationships, Tans and Poortvliet state that “there is no general agreement on how to administer the bolus infusions…” for volume-pressure testing in the clinical situation (Tans JTJ, Poortvliet DCJ: Intracranial volume-pressure relationships in man. Part 2: Clinical significance of the pressure-volume index. J Neurosurg 59: 810–816, November, 1983). Their article

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Sung Huang Laurent Tsai, Anshit Goyal, Mohammed Ali Alvi, Panagiotis Kerezoudis, Yagiz Ugur Yolcu, Waseem Wahood, Elizabeth B. Habermann, Terry C. Burns, and Mohamad Bydon

T he volume-outcome relationship in trauma centers has been a subject of debate in the last 2 decades. Conflicting analyses have demonstrated that a higher case volume is associated with improved outcomes 5 , 10 , 12 , 14 , 16 , 22 or is not associated with any overall effect. 3 , 7 , 9 , 11 , 17 The American College of Surgeons (ACS) has developed guidelines outlining minimum volume standards for level I and level II trauma centers. 2 For example, according to the ACS, level I trauma centers are required to admit at least 1200 trauma patients yearly or to

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Fred G. Barker II, William E. Butler, Sue Lyons, Ethan Cascio, Christopher S. Ogilvy, Jay S. Loeffler, and Paul H. Chapman

designed to deliver 90% of the maximum dose at the arteriographically defined margins of the lesion. Dose inhomogeneities within the treatment volume were 10% or less. Doses were chosen according to the anticipated risk of brain necrosis, using Kjellberg's isocentile curves as the basis of predicted risk. 19 Definition of Variables and End Points Treatment dose is expressed as the maximum dose within the treatment volume, based on ionization chamber dosimetry. No correction has been made for relative biological effectiveness. Because the relative biological

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Victoria J. Williams, Jenifer Juranek, Karla K. Stuebing, Paul T. Cirino, Maureen Dennis, Robin M. Bowman, Susan Blaser, Larry A. Kramer, and Jack M. Fletcher

from those in patients who had enlarged ventricles due to neuronal atrophy and in whom the caudate FA matched that in healthy individuals. In patients with chronic hydrocephalus, caudate diffusion rapidly returns to normal immediately after shunting. 29 Few studies have quantified the relationship between diffusion metrics and a stabilized subacute ventricular volume in individuals who underwent shunting. The Evans ratio is a commonly used clinical indicator of ventricular dilation, but volumetric measurements of the lateral ventricles in experimental hydrocephalus