Fabian Eisa Dipl Eng, PhD, Presenter: Nothing to Disclose

Robert Brauweiler, Abstract Co-Author: Nothing to Disclose

Willi A. Kalender PhD, Abstract Co-Author: Consultant, Siemens AG Consultant, Bayer AG Founder, CT Imaging GmbH Scientific Advisor, CT Imaging GmbH Shareholder, CT Imaging GmbH Founder, Artemis Imaging GmbH CEO, Artemis Imaging GmbH Shareholder, Artemis Imaging GmbH

In dynamic CT applications an optimal timing of the CT scan with the bolus of contrast medium (CM) is required in order to reduce acquisition time and amount of CM. In this study two approaches are introduced to trigger the CT scan by detecting iodine or a clinical dye, respectively, in the peripheral anatomy, e.g. the finger tip.

A dedicated x-ray detection system consisting of a miniature x-ray tube (50 kV Magnum®, Moxtek, Orem, USA) and a CsI scintillator coupled to a photodiode was used to detect the iodine (Ultravist® 300, Bayer Schering Pharma AG, Berlin, Germany). As second method an optical densitometry detection system consisting of a signal and a reference laser diode which were coupled into a multimode dual fiber coupler and a photodiode was used to detect the dye (Cardiogreen®, Fluka Chemie AG, Buchs, Switzerland) which was injected simultaneously with the iodine. Static and dynamic in vitro measurements were performed to validate specification and sensitivity of both systems. At expected iodine and dye concentrations in the finger tip of 15 mg/ml and 15 mg/l, respectively, the percentage difference in signal regarding water and the influence of pre-filtration were investigated. The specified systems were cross-validated in phantom and animal studies by comparing the measured contrast-time curves of the x-ray system with the density-time curves of the optical system.  

At tube settings of 50 kV and 0.1 mA the in vitro measurements of the x-ray system provided a significant difference in signal of 4%. With 0.5 mm Al and 0.2 mm Cu pre-filtration the signal difference increased to 6% and 8%, respectively. The in vitro measurements of the optical detection system provided a difference in signal up to 9%. The bolus shapes of the contrast and density time curves measured with both systems in phantom and animal studies were in good agreement.

Two promising methods to trigger dynamic CT scans peripherally were specified, developed, and cross validated in phantom and animal studies. Since there is no radiation the optical densitometry detection system is preferable. The x-ray system is practical, but associated with a negligibly small dose.

Optimal timing of the CT scan with the injected contrast agent is required because arrival and form of the bolus may vary strongly in patients due to physiological and clinical conditions.

Eisa, F, Brauweiler, R, Kalender, W, Peripheral Recording of the Contrast Bolus to Trigger Dynamic CT Scans.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9007199.html