Mannudeep Karanvirsingh Kalra MD, Presenter: Nothing to Disclose

Bernhard Schmidt PhD, Abstract Co-Author: Nothing to Disclose

Christoph Suess PhD, Abstract Co-Author: Nothing to Disclose

Stefan Ulzheimer PhD, Abstract Co-Author: Nothing to Disclose

Michael Grasruck PhD, Abstract Co-Author: Nothing to Disclose

Thomas G. Flohr PhD, Abstract Co-Author: Nothing to Disclose

Sanjay Saini MD, Abstract Co-Author: Nothing to Disclose

B.S.,C.S.,S.U.,M.G.,T.G.F.: Employee of Siemens Medical Solutions, GermanyM.K.K.: Received a research grant from Siemens Medical Solutions, Germany

Purpose: CT scanning of large patients is a significant clinical problem due to weight limitations for gantry tables (350- 400 lbs), and inability to generate adequate x-ray beam with single x-ray source (80 kW) for obtaining optimum image quality. Thus, the purpose of our study was to compare single-source 64-channel MDCT and dual source MDCT scanners for evaluation of large patients with a phantom study. Material and Methods: A new MDCT system (Siemens Medical Solutions), with two x-ray tubes (both 80 kW), dual detector arrays (both with 32*0.6 mm, double z-sampling, 0.4 mm z-axis resolution) and wide bore gantry (78 cm) was developed. This system allows scanning of patients weighing up to 615 lbs with simultaneous exposure from two x-ray tubes (80+80=160 kW). Two PMA phantoms, measuring 32 cm (standard adult abdomen phantom) and 50 cm (simulating large patient’s abdomen) in diameter, were scanned on both single-source MDCT (Siemens Sensation 64) and dual source MDCTat 290 mAs (both phantoms, maximum of 580 mA at 0.5s rotation time) and at 500 mAs (only 50 cm phantom, maximum of 500 mA at 1s rotation time). Remaining parameters were held constant for both systems and included 120 kVp, 500 mm field of view, and soft/standard body kernels. Image noise was measured with a constant size and shape ROI in all image datasets. Results: Image noise in standard size phantom was 12.2 (290 mAs) with single source MDCT, and 6.2 (290 mAs) with dual source MDCT. Image noise in large phantom was 92.6 (290 mAs) and 68.0 (500 mAs) with single source MDCT, and 71.6 (290 mAs) and 49.2 (500 mAs) with dual source MDCT. Regardless of mAs, there was improvement in image noise for large phantom scanned with dual source MDCT compared to the single source MDCT (p< .01). Conclusions:  Compared to single source 64-slice MDCT, the dual source MDCT resulted in substantial improvement in image quality of the large phantom. Dual source MDCT scanners can help in obtaining optimum image quality in large patients due to their greater weight tolerance (up to 615 lbs), higher x-ray tube power (160 kW), and data over-sampling (from two detector arrays).

Kalra, M, Schmidt, B, Suess, C, Ulzheimer, S, Grasruck, M, Flohr, T, Saini, S, Hot Topic: Comparison of Single and Dual Source 64-Channel MDCT Scanners for Evaluation of Large Patients: A Phantom Study.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4425786.html