DQE of direct and indirect digital radiography systems

Ehsan Samei; Michael J. Flynn; Harrell G. Chotas; James T. Dobbins III

doi:10.1117/12.430953

28 June 2001 DQE of direct and indirect digital radiography systems

Ehsan Samei, Michael J. Flynn, Harrell G. Chotas, James T. Dobbins III

Proceedings Volume 4320, Medical Imaging 2001: Physics of Medical Imaging; (2001) https://doi.org/10.1117/12.430953
Event: Medical Imaging 2001, 2001, San Diego, CA, United States

Abstract

Current flat-panel detectors either directly convert x-ray energy to electronic charge or use indirect conversion with an intermediate optical process. The purpose of this work was to compare direct and indirect detectors in terms of their modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Measurements were made on three flat-panel detectors, Philips Digital Diagnost, GE Revolution XQ/i, and Hologic Direct-Ray DR1000 using the IEC-defined RQA5 (approximately 75 kVp, 21 mm Al) and RQA9 (approximately 120 kVp, 40 mm Al) radiographic techniques. The presampled MTF of the systems was measured using an edge method (Samei et al., Med Phys 25:102, 1998). The NPS of the systems was determined for a range of exposure levels by 2D Fourier analysis of uniformly exposed radiographs (Flynn and Samei, Med Phys 26:1612, 1999). The ideal signal-to-noise ratio per exposure for each system was estimated using a semi-empirical x-ray model. The DQE, reported only at the RQA5 technique, was assessed from the measured MTF, NPS, exposure, and the ideal signal-to-noise ratio. For the direct system, the MTF was found to be significantly higher than that for the indirect systems and very close to an ideal function associated with the detector pixel size. The NPS for the direct system was found to be constant in relation to frequency. The DQE results reflected expected differences based on the absorption efficiency of the different detector materials. Using RQA5 and 0.3 mR exposure, the measured DQE values at spatial frequencies of 0.15 mm-1 and 2.5 mm-1 were 64% and 14% for the XQ/i system and 35% and 19% for DR-1000. Using RQA5 and the averages at all exposures, the corresponding values were 58% and 13% for the XQ/i system and 36% and 19% for DR-1000.

Citation Download Citation

Ehsan Samei, Michael J. Flynn, Harrell G. Chotas, and James T. Dobbins III "DQE of direct and indirect digital radiography systems", Proc. SPIE 4320, Medical Imaging 2001: Physics of Medical Imaging, (28 June 2001); https://doi.org/10.1117/12.430953

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available