Cone Beam CT

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Cone beam CT generically refers to using a fluoroscopic machine to sweep around the patient and acquire a 3D data set to build cross sectional or volumetric reformats. All of the sweeps on the ICONO from the 4sDSA to the 14sDCT Head Micro are cone beam CT acquisitions. Often times in labs, 4sDSA are referred to as a "3D" whereas the longer acquisitions (14sDCT, 8sDCT, 9s Sine Spin, etc) are referred to as a "CT". However, these differences in name are really just a difference in perception; all of these acquisitions are different forms of cone beam CT imaging, each with their own advantages and disadvantages. Note that the ICONO offers a unique workflow for almost all cone beam CT acquisitions called "twin spin". This feature allows the user to keep the B plane in fluoroscopic position during the sweep, saving time between the 3D and additional planar imaging. Also, this allows for the capability of the B plane to be utilized for centering of the cone beam CT image.

This is the most commonly used cone beam CT image utilized on the Seimens ICONO system by far. The advantages are the speed of the acquisition (the shortest cone beam CT offered by Seimens), which results in both less radiation as well as less venous contamination and susceptibility to motion. 

Resolution: 3

Edge Detection: 3

Bone Subtraction: 5

Radiation: 4 (really 8s with the two spins)

Susceptibility to Motion: 5

Venous Contamination: 5

The 8s scan is noticeably higher resolution than the 4s DSA. As it comes standard on the machine, it is only available with a single spin and therefore not a DSA. The 8s spin comes in two different photon energy levels; 109 kev, which is designed for optimal absorption of intracerebral hematoma and 70 kev designed to optimize the absorption of contrast (therefore optimal for visualization while injecting contrast). While the longer acquisition DCTs aren't set up as a dual spin with resultant subtracted bone, the edge detection and contrast detection are substantially better and therefore bone can often be windowed out without impacting visualization of arteries.

Resolution: 4

Edge Detection: 4

Bone Subtraction: 3

Radiation: 4

Susceptibility to Motion: 4

Venous Contamination: 4

Comparable to the 8s in many ways. The biggest difference is the image intensifier sweeps caudally at the vertex which enables shooting through the skull from an optimal position and thereby reduces artifact in the posterior fossa. As a result, the sine spin is the scan most often used to replace a non-contrast head CT. Note that there are no magnifications available for this scan. On previous software generations, this was not a "twin spin" acquisition- the B plane would have to move out of imaging position, however, the latest updates have ensured that this no longer has to happen to perform the acquisition. 

Resolution: 4

Edge Detection: 4

Bone Subtraction: 3

Radiation: 4 

Susceptibility to Motion: 4

Venous Contamination: 4

The highest resolution of all cone beam CT acquisitions offered on the ICONO. Once you get used to the quality of this imaging, it is very difficult to go back. The extra resolution isn't always necessary clinically, however it can be difficult to know a priori whether the additional resolution will be of clinical value. As a longer acquisition, it is higher in radiation use, however the ICONO in general uses substantially less radiation across the board then previous generations. Therefore, even with the 14s DCT we have noticed that the total radiation dose is less than previous generations (grant supported research on this subject is currently underway). 

Resolution: 5

Edge Detection: 5

Bone Subtraction: 5

Radiation: 3 

Susceptibility to Motion: 2

Venous Contamination: 3

We should note that the MicroDyna CT is an add on option to the Seimens ICONO and therefore comes at an additional expense. This feature has higher resolution due to the post processing of the acquisition in the form of non binning. Binning is a form of data compression that is used in all non micro acquisitions to reduce the total amount of data at the cost of resolution.