Excellence in Computed Tomography:  What’s new in CT?
From the Radiology Department Newsletter, Editor: Mary McAllister

SOMATOM Definition (Siemens) is the latest innovation in Multiple-row Detector CT (MDCT) available in our Department. Its new Dual Source CT (DSCT) technology, featuring two X-ray tubes that simultaneously revolve around the patient's body, promotes new clinical opportunities for clinical care and research. It allows imaging heart even without ß-blockers, scanning of arrhythmic patients, high accuracy of in-stent imaging, and image acquisition with shortest breath-hold. Technical advantages include high temporal resolution of the order of less than 100 milliseconds (ms) due to utilization of dual x-ray and detector system simultaneously and high spatial resolution of less than 0.6 mm (isotropic resolution) ¹.

SOMATOM Definition can use as much as half the radiation dose for cardiac applications without any compromise in image quality. In addition, this DSCT scanner yields 64 slices per gantry rotation, uses adaptive ECG-controlled x-ray dose modulation further lowering the radiation dose for cardiac CT applications.. Moreover, this scanner allows examination of uncooperative patients, patients short of breath or with high heart rates – quickly and without restriction.

With the simultaneous acquisition of two data sets at different tube voltages (kVp’s), it is possible to obtain dual-energy CT images during single scan period. Also, additional benefits include: direct subtraction of bone even in complicated anatomical regions, unenhanced liver imaging, evaluation of lung perfusion defects, visualization of cartilage, tendon, and ligament, kidney stone characterization, and differentiation between hard plaques and contrast agent.

In May 2009, we installed even a more powerful imaging platform, SOMATOM Definition Flash® (Siemens). This next generation DSCT scanner at the time of installation was the second scanner of its kind in the United States and one of the few handful of scanners installed around the world and is poised to set new standards regarding imaging speed and dose reduction. The new scanner similar to the DSCT has added advantage of increased field size which can now accommodate even more clinical applications using dual-source in addition to cardiac CT applications.

The SOMATOM Definition Flash is a new dual-source CT, with the fastest scanning speed in CT (i.e., 43 cm/s) and gantry rotation time of 0.3 seconds (fastest CT scanner currently available) enables to complete scans of the entire chest region in less than one second. Also the new scanner yields 128 CT slices per gantry rotation covering twice the anatomy of that of previous generation DSCT. Thus, patients are no longer required to hold their breath during the exams. At the same time, the SOMATOM Definition Flash can operate at an extremely reduced radiation dose.


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1. Mahesh M. MDCT Physics: The Basics – Technology, Image Quality and Radiation Dose. Lippincott Williams and Wilkins, Philadelphia, 2009.