## 6 CT Pre-Processing Core Implementation and Integration
### Open-Interface CT  
Before describing the integration of the CT pre-processing core within the DAS, we introduce our open-interface CT architecture, as well as the DAS architecture, which is the central control unit of the system, the flow of data from the DMS to the reconstruction system.  
Our open-interface CT, as shown in Figure 7, consists of the following components: a 64 row DMS and an X-ray tube system, a gantry module from Schleifring [40], a patient table, and a reconstruction system. As shown in Figure 8, all these components are controlled by the DAS, which is fixed in the rotating side and is implemented on the XC7Z045 MPSoC-FPGA.  
From the hardware designer prospective, the design of the open-interface CT is based on the system architecture shown in Figure 8, where the the DAS and the reconstruction  
Figure 8: System architecture of the open-interface CT, Reprinted with permission from Ref. [41]. Copyright 2020, IEEE.  
Figure 7: Components of our open-interface CT system. (**a**) Complete experimental CT system with (1) X-ray tube, (2) cooling system, (3) generator, (4) gantry subsystem with bore, (5) multiline DMS, (6) patient table. (**b**) Detailed view of the DMS and CCU implemented on the Xilinx ZC706 Evaluation Kit.  
systems are the components responsible for controlling and reconstructing tasks, respectively. The DAS has three main modules on the FPGA part of the MPSoC-FPGA and has a software stack on the PS part for controlling them [41].  
The DAS system has the following modules, which are implemented in the FPGA part and controlled by the PS part:  
* **Control-synchronization module**: This module is responsible for controlling and synchronizing all the external components on the stationary and the rotating sides. It is scalable, allowing an easy integration of other components in the open-interface CT, such as additional DMSs, X-ray tube systems and other sensors for multi-modality CT.
* **Data-flow module**: This module is responsible for collecting projections from the DMS, to manage eventually transmitting errors and to forward them to the _image pre-processing module_. After the pre-processing steps, it sends all the pre-processed data to the reconstruction system. It is implemented with a pipelined datapath that collects and forwards data in real time, without buffering them in external memory [42].
* **Image pre-processing module**: This module represents the proposed CT pre-processing core.  
During the acquisition, the DMS acquires the raw sensor data and forwards them to the DAS over the gigabit interface. The raw sensor data are collected in the data-flow module of the DAS, which properly merges them and forwards to the image pre-processing module, where our CT pre-processing core is implemented. Here, the raw sensor data are converted to the selected pre-processing data format, pre-processed from raw sensor data to attenuation data and converted to the selected reconstruction data format. After that, the pre-processed attenuation data are forwarded to the reconstruction system, through the data flow module, over the gigabit slip ring connection. In the reconstruction system, the 3D volume is reconstructed.