C-arm system

Lewin JS, Petersilge CA, Hatem SF et al (1998) Interactive MR imaging-guided biopsy and aspiration with a modified clinical C-arm system. AJR Am J Roentgenol 170 1593-1601... 

C-arm CT requires state-of-the-art C-arm systems equipped with flat-panel detector (FD) devices. It is commercially available from various vendors, e.g., marketed as syngo DynaCT (Siemens AG, Healthcare Sector, Forchheim, Germany), XperCT (Philips Healthcare, Andover, MA), or Innova CT (GE Healthcare, Chalfont St. Giles, UK). 

The goal of this book chapter is to provide an overview of how 3D C-arm imaging works and for what it can be used. To this end, we focus on important C-arm system components first. Then we explain how X-ray input images are acquired and take a look at the resulting patient dose. In the next step, we cover three-dimensional image reconstruction and the correction methods needed to obtain low-contrast 3D results with CT-like image quality. After we explained how C-arm... 

Until the 1990s, C-arm systems for real-time angiographic imaging used to rely on X-ray image intensi-fiers (XRIIs). Although optimized over decades, this technology has a number of inherent disadvantages that... 

Table 3.1. Common high-contrast C-arm CT scan protocols for Artis Forchheim, Germany) and the resulting effective doses zee C-arm systems (Siemens AG, Healthcare Sector, ...

Unlike in MSCT systems, where detectors are usually wide enough to always capture a patient s full X-ray profile irrespective of view direction, FDs of today s C-arm systems may not be large enough to accomplish this in any case. As a result, it is possible that X-ray projections are truncated in some or even all views. Truncated projections can be problematic for tomographic reconstruction algorithms, because they may generate bright circular artifacts and result in incorrectly reconstructed density values as shown in Fig. 3.3b. 

With a properly selected image acquisition protocol, state-of-the-art C-arm CT systems such as syngo DynaCT (Siemens AG, Healthcare Sector, Forchheim, Germany) can at least resolve 5-mm (10-mm) diameter objects with a contrast difference of 10 HU (SHU) (Fahrig et al. 2006). Even better results are sometimes possible as demonstrated in Fig. 3.5. From a chnical point of view, the low-contrast imaging performance of today s C-arm systems not only can be expected to differentiate between fat and muscle tissue, but C-arm CT can also resolve smaller contrast differences and possibly even visuahze bleeds. 

Fig. 3.4. Spatial resolution experiment involving an axial slice through a spatial resolution phantom. The 3D spatial resolution from 2D X-ray projections acquired with a Trixell Pixium 4700 detector is about 2.0 LP/mm, if 2 x 2-pixel binning is applied. Projection data were acquired on an Artis zee C-arm system, and reconstruction was performed with syngo DynaCT (both Siemens AG, Healthcare Sector, Forchheim, Germany)...

Fahrig R, Fox AJ, Lownie S, et al. (1997) Use of a C-arm system to generate true three-dimensional computed rotational angiograms preliminary in vitro and in vivo results. Am J Neuroradiol 18 1507-1514... 

Timing is very different. Mechanically, a partial scan with a C-arm takes a minimum 5 s (and up to date 8 s to 20 s for the scans with the potential of soft tissue imaging), but on a CT scarmer it takes 1 to 0.33 s only for a 360° scan. The frame rates on a C-arm system are 30 to 60 frames s, whereas the readout frequency of a CT detector is much higher (several... 

The geometry of a C-arm system is not as well defined as the geometry for a CT gantry. Therefore, calibration of a rotational C-arm is a technical challenge. 

Wiesent K, Barth K, Durlak P etal. (2000) Enhanced 3-D reconstruction algorithm for C-arm systems suitable for interventional procedures. IEEE Trans Med Imaging 19 391 403... 

---