Flat Detector Research

Flat Detectors

What are they?

Solid state x-ray image detectors, (flat-panel detectors) are under development by a number of manufacturers. These systems potentially offer a number of advantages over existing detector technologies, such as improved image quality under a wide range of imaging conditions.

These devices are of muti-layer construction, incorporating an x-ray detector layer and a integral sensor layer in a relatively compact design- hence the name flat panel. The detector layer is either a x-ray photoconductor or a scintillator and the sensor is an amorphous silicon thin film transistor array.

FD construction

History of FD research in Leeds

First installation - 1997

LXi have been involved in FD research since 1997, when a FD system capable of both static (single-shot) and dynamic (fluoroscopy/fluorography) acquisition was installed into the General Infirmary at Leeds. The joint project between Philips Medical Systems, The General Infirmary at Leeds and ourselves aimed to assess the technical and clinical performance of the new x-ray detector technology.

The original installation, installed in the Clarendon Wing x-ray department, is pictured on the left (the patient table is removed, so that the detector is visible). The system was given a number of upgrades to allow a wide range of examinations to be conducted.

Original FD installation

Ethical approval was granted for initial work to begin on the imaging of patients. However the range of applications that could be carried out given the operational and physical limitations of the FD system was restricted. The detector itself had a 20 cm x 20 cm field of coverage. The x-ray tube was mounted in a fixed position above a moving patient table. The picture to the left shows the tube and plate mountings with the patient table removed. Despite the limitations the system had a wide range of exposure settings, automatic dose control via the image data in fluoroscopy and via an amplimat sensor for exposures. An x-ray anti-scatter grid could also be used if required.

Upgraded installation

The limitations of the system as was in 1997 had limited the clinical work that could be done on the system. To improve the range of clinical applications that could be carried out on the FD system, a new installation in the main x-ray department was undertaken in the spring of 2000.

The FD system was installed in a room with an multi-field 35 cm Image Intensifier (II) fluoroscopy system, allowing a patient to be imaged on both the FD and II system. The large area and flexible projections available in the II allowed the examinations requiring these to be use the II for the bulk of the exam, and the FD where praticable. This joint installation also facilitated the comparison of the image quality of the II and FD systems, and significant effort was placed into comparing the two systems in fluoroscopy.

A summary of the work undertaken on the flat detector systems at this time was shown as a poster presentation at RSNA 2000, and is also available online.

Current work

Moving away from the mixed mode radiography/fluorography applications of previous years, our main focus is now cardiac imaging. A new fully operational Catheterisation laboratory was installed in June 2001. The system is certainly an advance on the original FD installation in Leeds. Operationally it is virtually identical to the state-of-the-art Philips H5000 Image Intensifier (II) system installed nearby.

Once FD cardio system is a fully specified cath. lab, and has all of the features one would expect including the full range of pulsed fluoroscopy and digital cine acquisition, MRC high output x-ray tube, dual progressive scan monitors, rapid C-arm movement with BodyGuard collision detection and the SpectraBeam dose management system.

The H5000 system in the nearby lab allows direct comparison of the quality of FD images with that of the II system. The H5000 has a CDD TV camera and high efficiency intensifier, and represents the gold standard of image quality for IITV cardiac imaging.

Our efforts have been focussed on the relative performance of the FD system when compared to the image intensifier based system, and in exploiting the imaging performance of the FD system to reduce x-ray dose to the staff and patients.

LXi's FD Publications

Cowen AR, Kengyelics SM and Davies AG "Solid-state, flat-panel, digital radiography detectors and their physical imaging characteristics," Clinical Radiology, Volume 63, pages 487-498, 2008. [detail]

Davies AG, Cowen AR, Kengyelics SM, Moore J and Sivananthan UM "Do flat detector cardiac X-ray systems convey advantages over image-intensifier-based systems? Study comparing X-ray dose and image quality," European Radiology, Volume 17, pages 1787-1794, 2007. [detail]

Davies AG, Cowen AR, Kengyelics SM, Moore J, Pepper C, Cowan C and Sivananthan MU "X-ray dose reduction in fluoroscopically guided electrophysiology proceedures," PACE, Volume 29(3), pages 262-271, 2006. [detail]

Bruijns AJC, Bastiaens R, Hoornaert B, von Reth E, Busse F, Heer VK, Ducourant T, Cowen AR, Davies AG and Terrier F "Image quality of a large-area dynamic flat detector: comparison with a state-of-the-art II/TV system," In: Medical Imaging 2002: Physics of Medical Imaging, Eds. Antonuk LE and Yaffe MJ, pages 332-343, 2003, Publisher: Soc. Photo-optical Instrumentation Engineers (Bellingham WA). [detail]

Ducourant T, Couder D, Wirth T, Trochet JC, Bastiaens R, Bruijns AJC, Luijendijk H, Sandkamp B, Davies AG, Didier D, Gonzalez A, Terraz S and Ruefenacht D "Image quality of digital radiography using flat detector technology," In: Medical Imaging 2003: Physics of Medical Imaging, Eds. Yaffe MJ and Antonuk LE, pages 203-214, 2003, Publisher: Soc. Photo-optical Instrumentation Engineers (Bellingham WA). [detail]

Davies AG, Cowen AR, Kengyelics SM, Bury RF and Bruijns AJC "Threshold contrast detail detectability (TCDD) evaluation of the Image quality of a flat-panel dynamic digital X-ray image detector," Medical Physics, Volume 28(1), pages 11-15, 2001. [detail]

Bruijns AJC, Adriaansz T, Cowen AR, Davies AG, Kengyelics SM, Kiani K, Kroon H and Luijendijk H "Simulation of the image quality of an a-Si flat panel imaging system in low dose fluoroscopic applications," In: Medical Imaging 2000: Physics of Medical Imaging, Eds. Street RA, pages 117-127, 2000, Publisher: Soc. Photo-optical Instrumentation Engineers (Bellingham WA). [detail]

Bury RF, Cowen AR, Davies AG, Baker EL, Hawkridge P, Bruijns AJC and von Reth E "Clinical and technical experiences with an experimental solid-state universal digital X-ray image detector," European Radiology, Volume 10(12), pages 1983-1987, 2000. [detail]

Davies AG, Cowen AR and Bruijns AJC "Psychophysical evaluation of the image quality of a dynamic flat-panel digital X-ray image detector," In: Medical Imaging 99: Physics of Medical Imaging, Eds. Krupinski EA, pages 170-179, 1999, Publisher: Soc. Photo-optical Instrumentation Engineers (Bellingham WA). [detail]

Bruijns AJC, Bury RF, Busse F, Davies AG, Cowen AR, Rutten W and Reitsma H "Technical and clinical assessments of an experimental flat dynamic X-ray image detector system," In: Medical Imaging 99: Physics of Medical Imaging, Eds. Boone JM and Dobbins JT III, pages 324-335, 1999, Publisher: Soc. Photo-optical Instrumentation Engineers (Bellingham WA). [detail]

Bury RF, Cowen AR, Davies AG, Baker EL, Hawkridge P, Bruijns AJC and Reitsma H "Technical report: Initial experiences with an experimental solid-state universal digital X-ray image," Clinical Radiology, Volume 53(12), pages 923-928, 1998. [detail]

Bruijns AJC, Alving L, Luijendijk H, Meulenbrugge HJ, Stouten HJ, Jung N, Baker EL, Bury RF and Cowen AR "Technical and clinical results of an experimental flat dynamic X-ray detector based system with on-line corrections," In: Medical Imaging 98: Physics of Medical Imaging, Eds. Dobbins JT III and Boone JM, pages 33-44, 1998, Publisher: Soc. Photo-optical Instrumentation Engineers (Bellingham WA). [detail]