Estimation of the minimum dose required to measure ventricular width in follow-up cranial computed tomography (CCT) in children with hydrocephalus.
OBJECTIVE
To estimate the minimum dose needed at follow-up cranial computed tomography (CCT) to reliably determine ventricular width in children with hydrocephalus.


METHODS
For the study, a phantom was created using the calvarium of an infant which was filled with gelatin and the shaped inner cones of two carrots serving as lateral ventricles. The phantom was scanned ten times with two multi-slice CTs (LightSpeed Ultra, GE, and Somatom Sensation, Siemens), using a tube current of 400, 350, 300, 250, 200, 150, and 100 mA, and a tube voltage of 140, 120, 100, and 80 kV. The width of both lateral ventricles was measured at 4 sites. The values derived from scans performed at 380/400 mA and 140 kV (LightSpeed/Somatom) served as a reference. Measurements scored 1 point if they did not differ by more than 0.5 mm from the reference values.


RESULTS
The radiation dose can be reduced from 61.0 mGy to 9.2 mGy (15.1%) with LightSpeed and from 55.0 mGy to 8.0 mGy (14.6%) with Somatom without impairing the reliability of ventricular width measurements. However, in the case of both scanners, certain combinations of tube voltage and current yielded less reliable measurements although the dose was higher and the pixel noise was lower.


CONCLUSIONS
There is no single cut-off dose or setting for tube voltage and current which guarantees reliable ventricular width measurements with the least radiation exposure for both scanners. As a guideline, it is safe to use the standard protocols with a reduced tube current of 100 kV.
Institut und Poliklinik für Radiologische Diagnostik, Universitätsklinikum Carl Gustav Carus, Dresden, Germany. Klaus.Kirchhof@uniklinikumdresden.de
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Kirchhof
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Wohlgemuth
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Berlis
D014695:Cerebral Ventriculography / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D006849:Hydrocephalus / Q000000981:diagnostic imaging*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007223:Infant; D020547:Lateral Ventricles / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011874:Radiometry; D012016:Reference Values; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed / Q000379:methods*