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[Computerized tomography volumetry of the cerebrospinal fluid by semiautomatic contour recognition and gray value
A Tschammler1, C Middendorf, M von Lüdinghausen
1Institut für Röntgendiagnostik, Universität Würzburg.
Purpose:
A program (VAC, Siemens) using self-made, anthropomorphous phantoms to measure semiautomatically the volume of the cerebral liquor in CT scans of the whole skull was tested.
Material And Methods:
Cerebral tissue was simulated by ellipsoid bodies made from Agar and NaI which were placed in a human skull. Volumes of the ventricular and subarachnoidal liquor could be defined arbitrarily.
Results:
A correlation coefficient of r > = 0.9 using a slice thickness of 1-5 mm was found (thickness 8 mm: r = 0.75). The volume of the cerebral liquor was underestimated by 25-68%. Separate measurements of the ventricular and subarachnoidal liquor spaces showed a high accuracy of the measurements done in the ventricles (r = 0.997, y = 0.996 x -1). The volume of the subarachnoidal liquor was not detected completely due to partial volume effects which were seen especially in the basal and apical scans.
Conclusion:
The program VAC is useful for the semiautomatic measurement of the volume of the ventricles. The assessment of the subarachnoidal liquor is limited to semiquantitative results which may, however, be useful for follow-up studies.