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[Spiral CT of the abdomen: weight-adjusted dose reduction]
E Coppenrath1, C Schmid, R Brandl
1Institut für Radiologische Diagnostik, Ludwig-Maximilians-Universität München, Klinikum Innenstadt. Eva.Coppenrath@radin.med.uni-muenchen.de
Aim Of The Study:
The influence of weight-adjusted current application in spiral CT of the abdomen on noise was investigated in a clinical study.
Patients And Methods:
In 77 routine abdominal CT investigations (120 kV, 8 mm, pitch 1.5) the patients were divided into three body-weight groups A (< 60 kg), B (60-80 kg), and C (> 80 kg). The tube current was randomized prospectively in low weight group A, either 125 mA or 150 mA, in middle and high weight groups B and C, 150, 175 or 200 mA, with a tube revolution time of one second. The noise was measured in liver, skeleton muscle, fat tissue, and bladder content for evaluation of image quality.
Results:
The bodyweight groups differ significantly in noise, e.g., in the liver (150 mA): group A: 15.8 HU, group B: 18.9 HU, group C: 21.5 HU. The increase of tube current (150, 175, 200 mA) within a body weight group resulted in a minor decrease of noise (18.9 HU, 17.6 HU, 17.5 HU, respectively, in group B). There is a good correlation of noise with body weight, body mass index and body cross section, but not with body size.
Conclusion:
A body weight adjusted reduction of tube current is possible without an increase of noise.