The difference between sequential imaging and going beyond visualization?
Spiral Dual Energy.

It has always been an aim to collect as much information as possible for differentiation of tissues. Providing spiral dual energy scanning, SOMATOM Definition opens the door to a new world of characterization, visualizing the chemical composition of material.

The idea of dual energy is not new to the CT community. Earlier approaches, including two subsequent scans at different tube voltages or two subsequent scans at the same position, failed to seamlessly align the imaged anatomy. SOMATOM Definition overcomes this limitation by permitting the use of two sources at two different kV levels simultaneously. The result are two spiral data sets acquired in a single scan providing diverse information, which allows you to differentiate, characterize, isolate, and distinguish the imaged tissue and material.

The X-ray tube’s kilo voltage (kV) determines the average energy level of the X-ray beam. Changing the kV setting results in an alteration of photon energy and a corresponding attenuation modification of the materials scanned. In other words, X-ray absorption is energydependent, e.g. scanning an object with 80 kV results in a different attenuation than with 140 kV.

In addition, this attenuation depends also on the type of tissue scanned. Iodine, for instance, has its maximum attenuation at low energy, while its CT-value is only about half in high-energy scans. The attenuation of bones, on the other hand, changes much less when exposed to low-energy scans compared to high-energy voltage examinations.

Spiral Dual Energy exploits this effect:
Two X-ray sources running simultaneously at different energies acquire two data sets showing different attenuation levels. In the resulting images, the material-specific difference in attenuation enables an easy classification of the elementary chemical composition of the scanned tissue. In addition, a fused image is provided for initial diagnosis.