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John W. Rutland, Satish Govindaraj, Corey M. Gill, Michael Shohet, Alfred M. C. Iloreta Jr., Joshua B. Bederson, Raj K. Shrivastava and Bradley N. Delman

remains a clinical challenge. Disease features such as degree of CSF flow rate can complicate and compromise efficacy of surgical repair, with high-flow leaks increasing the likelihood of numerous adverse outcomes including postoperative leaks. 19 Prior studies have shown the importance of distinguishing high-flow from low-flow CSF leaks before surgery; 21 however, current clinical tools are limited for preoperatively predicting objective flow rate. An imaging biomarker for quantifying CSF leak flow rate may prove useful for surgical planning, 29 flap repair choice

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John L. Fox, David C. McCullough and Robert C. Green

F ew comparative studies have been done on flow rates in cerebrospinal fluid (CSF) shunts. Shunts are usually categorized according to the closing pressure value. This is a very nebulous concept at best because of the overlapping of reported or advertised pressure values (see Table 1 ). Values for extra low pressure (ELP) have ranged from 5 to 10 mm H 2 O, low pressure (LP) from 10 to 50 mm H 2 O, medium pressure (MP) from 20 to 100 mm H 2 O, high pressure (HP) from 50 to 125 mm H 2 O, and extra high pressure (EHP) from 100 to 200 mm H 2 O. TABLE 1

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Alexandra Lauric, James E. Hippelheuser and Adel M. Malek

, and we sought to explore the effect of individual daughter branch angulations, mother vessel geometry, and flow rate on spatial shear gradient direction in order to link known aneurysmogenic shear conditions to observed aneurysm colocation in wider bifurcations. Methods Parametric Models Three series of parametric models of the middle cerebral artery (MCA) bifurcation were constructed to account for the morphological configurations observed in patient data sets with respect to bifurcation angles and parent vessel geometry ( Fig. 1A ). All models were created using

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Sanford J. Larson and Leonard W. Worman

I n his monograph on carotid cavernous fistula, Hamby has thoroughly reviewed the pertinent publications and has described a definitive operation. 1 We have performed this operation in four patients with carotid cavernous fistula and have measured internal carotid artery flow rates at various stages of the operation. Case Reports Case 1 A 24-year-old man came to the hospital on July 7, 1965, complaining of pain in the left eye and double vision which had begun after a fall 3 weeks earlier. Two years previously the patient had sustained fractures of

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Robin Hartman, Salavat Aglyamov, Douglas J. Fox Jr.,  and Stanislav Emelianov

tissue are recorded to form an image. Ultrasound is a nonionizing and noninvasive imaging modality. In contrast-enhanced ultrasound, micrometer-sized bubbles of gas, which are characterized by a very high acoustic impedance mismatch relative to soft tissue, create a strong ultrasound backscatter signal. Previously, Doppler ultrasound imaging has been proposed as a method for measuring CSF flow rates in hydrocephalus shunts with and without added contrast agents. 17 , 22 Researchers developed an imaging system that could detect lower flow rates than previously

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Prem Venugopal, Daniel Valentino, Holger Schmitt, J. Pablo Villablanca, Fernando Viñuela and Gary Duckwiler

isolated from the rest of the arterial network. The wall boundary condition arises from the fact that the vascular walls are distensible. Unfortunately, patient-specific data for the imposition of boundary conditions are not always available. Thus, many assumptions have to be made while imposing these boundary conditions in numerical simulations. The variables about which assumptions are made include the heart and blood flow rates, the shape of the inlet velocity profile, distributions of flow rates in the inflow arteries (when the aneurysm is fed by more than one artery

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Sherman C. Stein and Stewart Apfel

CSF flow through the shunt tubing to the rate or degree of thermistor response have not been successful in vivo . The device reported herein uses two thermistors in series to determine velocity of flow, from which measurement of flow rate can be calculated. Although we obtained measurable responses in shunted patients, we had no means of safely and independently determining flow rates to confirm the technique's accuracy. We therefore undertook a series of animal experiments in which infusions at known rates through subcutaneously implanted shunt tubing served as a

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Hiroshi Yamada

. The ICP is measured at the proximal end of the tube, and the flow resistance of the intra-atrial or intraperitoneal distal valves is recorded. The distal VA or VP shunt is disconnected and the ends of the tubes are then reunited by means of an FRD connector. Experimental Studies Flow rates in the Pudenz shunts were measured with a technique similar to that described by Fox, et al. 1, 2 Fifteen Pudenz differential-pressure valves (five each for low-, medium-, and high-pressure flow), a ventricular catheter, and a flushing device were used. The flow rates of

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Yasuo Aihara, Ichiro Shoji and Yoshikazu Okada

to each of these situations. With regard to ICP, in vivo treatment involves not only setting the shunt's valve pressure but also taking into consideration the CSF flow rate, which is a very important parameter. 12 , 14 Even with antisiphon devices attached to some valves, despite their advantages, there is still no perfect valve system in neurosurgery. Devices with these attachments still fail to adequately control undesirable pressure deviations and CSF flow rates simultaneously. In clinical practice, we sometimes see a patient with an overdrainage problem even

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Mitsuhiro Hara, Chikafusa Kadowaki, Yoshifumi Konishi, Motohide Ogashiwa, Mitsuo Numoto and Kazuo Takeuchi

electrodes. Flow Calculation The bubbles thus created in the shunt tube are detected transcutaneously downstream by a pair of Doppler ultrasound probes ‡ placed 5 to 10 cm apart on the skin overlying the shunt tubing. The Doppler signals are registered on a two-channel pen-recording oscillograph. The CSF flow rate is calculated based on the distance between the two Doppler probes, the time required for the bubbles to travel between the two points, and the diameter of the tube. The rate is expressed in milliliters per minute using the following formula