1. Assessment of cerebral venous return by a novel plethysmography method
Paolo Zamboni, MD, Erica Menegatti, PhD, Paolo Conforti, MD, Simon Shepherd, PhD, Mirko Tessari, VT, Clive Beggs, PhD 
Journal of Vascular Surgery 
Volume 56, Issue 3, Pages e1 (September 2012)
DOI: /j.jvs
Copyright © 2012 Society for Vascular Surgery Terms and Conditions

2. Fig 1
B-mode evaluation of internal jugular veins in longitudinal plane showing: (A) tiny and hyperechoic intraluminal obstacle (septum), and (B) wall stenosis leading to well-apparent reduction of the jugular lumen.
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3. Fig 2
The operator places the strain gauge around the neck of the subject and rapidly tilts the chair backward from 90° to 0° (<1.8 seconds). When the blood volume curve reaches a plateau, the subject is again tilted forward to the upright position (<1.8 seconds).
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4. Fig 3
The plethysmographic trace is represented by the solid line, with the gravitational gradient (measured by the sensor positioned on the tilt chair) represented by the dotted line. For each experimental run, the following key parameters were recorded: the venous volume (VV); the filling time (FT) required to achieve 90% of VV (90% VV); the residual volume (RV); and the emptying time (ET) required to achieve 90% of emptying volume (90% EV), where EV = VV − RV.
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5. Fig 4
Representative plethysmography plots for a healthy individual and a patient with chronic cerebrospinal venous insufficiency (CCSVI).
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6. Fig 5
A considerable overlap area between controls (cross) and patients with chronic cerebrospinal venous insufficiency (CCSVI; circles) is clearly visible by plotting the filling gradient (FG) with emptying gradient (EG) values, respectively.
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7. Fig 6
The result of principal component (PC) analysis. Left panel, comparison of the correlation between the first PC and emptying gradient (EG) found in controls (cross; R2 = 1.000) vs chronic cerebrospinal venous insufficiency (CCSVI; circles) (R2 = 0.781). Right panel, comparison plotting the second PC against filling gradient (FG), again stronger in controls (cross; R2 = 1.000) than in CCSVI (circles; R2 = 0.515).
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8. Fig 7
Plot of the first and second principal components (PCs) for chronic cerebrospinal venous insufficiency (CCSVI) and healthy controls (HCs).
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9. Fig 8
Receiver operating characteristic (ROC) analysis comparing one variable model (emptying time [ET], dashed line) with three-variables model (ET, filling gradient [FG], and emptying volume [EV], interrupted line). The area under the curve in the latter (ROC area, ) seems not to significantly increase the diagnostic accuracy (ROC area, ).
Journal of Vascular Surgery  , e1DOI: ( /j.jvs )
Copyright © 2012 Society for Vascular Surgery Terms and Conditions