Flat-panel detector

Thin film transistor (TFT) arrays are produced inexpensively and in large numbers for use in modern computer monitors and televisions. This readout system can be combined with amorphous hydrated silicon or amorphous selenium which is deposited over the large surface of the TFT array and acts as the X-ray conversion layer. Having established themselves firmly as an X-ray detector for medical imaging already, they have until now failed to make an impact on the field of crystallography, their high noise level being the main drawback. It can be surmised with some confidence that this type of detector will become standard equipment in the near future. 

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Therefore it is reasonable to prepare already the data acquisition for a three dimensional evaluation in cone-beam-technique by means of two-dimensional detectors. The system is already prepared to integrate a second detector- system for this purpose. An array of up to four flat panel detectors is foreseen. The detector- elements are based on amorphous silicon. Because of the high photon energy and the high dose rates special attention was necessary to protect the read-out electronics. Details of the detector arrangement and the software for reconstruction, visualisation and comparison between the CT results and CAD data are part of a separate paper during this conference [2]. 

Phosphor flat panel detector systems (Fig. 2.9) are based on a large-area glass plate. Using solid-state manufacturing techniques, a rectangular array of light-sensitive photodiodes is deposited onto the plate. These... 

Fig. 2.9. Flat panel detector with Csl(Tl) absorber, (a) Detector with photodiode array. TFT readout element is shown in inset, (b) Structure of Csl Tl needle phosphor (Reprinted from Enhanced a-Si/Csl-based flat-panel X-ray detector for...

Fig. 2.10. Photo of flat-panel detector. (Courtesy, GE Global Research Center)...

Fig. 2.19. Dependence of DQE on exposure to detector for a screen-film system (Bunch 1999), a flat panel detector and a CR system (Data from Monnin 2007)...

Shaw C, Chen L, Altunbas M, et al (2005) Cone beam breast CT with a flat panel detector- simulation, implementation and demonstration. Conf Proc IEEE Eng Med Biol Soc 4 4461-4464... 

Hgure 4 Construction of the flat-panel detector. The X-ray sensitive layer consists of cesium iodide (Csl). The amorphous silicon sensor array comprises 3000 x 3000 pixels. (Reproduced with permission from Hamers S and Freyschmidt J (1998) Digital radiography with an electronic flat-panel detector First clinical experience in skeletal diagnostics. Medicamundi 42 2-6 Medicamundi.)... 

Akpek S, Brunner T, Benndorf G, Strother C (2005) Three-dimensional imaging and cone beam volume CT in C-arm angiography with flat panel detector. Diagn Interv Radiol 11(1) 10-13... 

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). 

With single-row detectors of third generation CT scarmers, scatter is almost negligible, because the irradiated patient volume is reduced to a small shce by coUimation near the X-ray source. However, when working with flat-panel detectors, the collimator at the X-ray source is usually opened much more widely, and a considerable amount of scattered radiation may be produced, ft can reach a multiple of the primary intensity in case of abdominal X-ray projections and up... 

Fig. 16.2a,b. In-stent lumen imaging, a Imaging of a stent phantom acquired on a conventional 16-detector-row scanner with a voxel size of 1 mm. A conventional cobalt-chromium alloy bare metal stent (Multi-Link Vision Rx Coronary Stent System, Boston Scientific, Gatwick, Mass.) with thin struts (0.08 mm) is used, b The same stent as in a is visualized with a fourfold-better spatial resolution (voxel size of 0.25 mm), utilizing a flat-panel detector. (Modified according to Mahnken et al. 2005)... 

S, Kuettner A, Wildberger JE, Gunther RW (2005) Flat-panel detector computed tomography for the assessment of coronary artery stents phantom study in comparison with 16-slice spiral computed tomography. Invest Radiol 40 8 13... 

Kalender WA (2003) The use of flat-panel detectors for CT imaging. Der Einsatz von Flachbilddetektoren fur die CT-Bildgebung. Der Radiologe 43 379-387... 

Molyneux A J. Kerr R S, Yu L M et al. (2005) International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2,143 patients with ruptured intracranial aneurysms a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet 3-9 366 809-917 Richter G, Engelhorn T, Struffert T et al. (2007) Flat panel detector angiographic CT for stent-assisted coil embolization of broad-based cerebral aneurysms. Am J Neurora-diol 28 1902-1908... 

Recently, a new kind of system has been introduced to the market, where the C-arm is mounted on a robot, allowing for faster, more precise and more flexible data acquisition. Because of these new features, this system is capable of performing a complex movement around the patients. After having completed the first rotation, the system shifts the C-arm to a more lateral position and rotates then immediately back again. If the flat panel detector is brought into portrait mode, this option for data acquisition allows covering a 47-cm field... 

Kakeda S, Korogi Y, Miyaguni Y et al. (2007) A cone-beam vol-irnie CT using a 3D angiography system with a flat panel detector of direct conversion type usefulness for super-selective intra-arterial chemotherapy for head and neck tumors. AJNR 28 1783-1788... 

Kakeda S, Korogi Y, Ohnari N et al. (2007) Usefulness of cone-beam volume CT with flat panel detectors in conjunction with catheter angiography for transcatheter arterial embolization. J Vase Interv Radiol 18 1508-1516... 

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