Physical characteristics of a low-dose gas microstrip detector for orthopedic x-ray imaging

Authors

  • Després Philippe,

    1. Hôpital Notre-Dame du Centre Hospitalier de l’Université de Montréal, Département de Radiologie, 1560 rue Sherbrooke est, Montréal, Québec, Canada H2L 4M1
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  • Beaudoin Gilles,

    1. Hôpital Notre-Dame du Centre Hospitalier de l’Université de Montréal, Département de Radiologie, 1560 rue Sherbrooke est, Montréal, Québec, Canada H2L 4M1
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  • Gravel Pierre,

    1. Laboratoire de Recherche en Imagerie et Orthopédie, École de Technologie Supérieure, 1100 rue Notre-Dame ouest, Montréal, Québec, Canada H3C 1K3
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  • de Guise Jacques A.

    1. Laboratoire de Recherche en Imagerie et Orthopédie, École de Technologie Supérieure, 1100 rue Notre-Dame ouest, Montréal, Québec, Canada H3C 1K3
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Abstract

A new scanning slit gas detector dedicated to orthopedic x-ray imaging is presented and evaluated in terms of its fundamental imaging characteristics. The system is based on the micromesh gaseous structure detector and achieves primary signal amplification through electronic avalanche in the gas. This feature, together with high quantum detection efficiency and fan-beam geometry, allows for imaging at low radiation levels. The system is composed of 1764 channels spanning a width of 44.8cm and is capable of imaging an entire patient at speeds of up to 15cms. The resolution was found to be anisotropic and significantly affected by the beam quality in the horizontal direction, but otherwise sufficient for orthopedic studies. As a consequence of line-by-line acquisition, the images contain some ripple components due to mechanical vibrations combined with variations in the x-ray tube output power. The reported detective quantum efficiency (DQE) values are relatively low (0.14 to 0.20 at 0.5mm1) as a consequence of a suboptimal collimation geometry. The DQE values were found to be unaffected by the exposure down to 7μGy, suggesting that the system is quantum limited even for low radiation levels. A system composed of two orthogonal detectors is already in use and can produce dual-view full body scans at low doses. This device could contribute to reduce the risk of radiation induced cancer in sensitive clientele undergoing intensive x-ray procedures, like young scoliotic women.

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