Untitled

Abstract

The objective imaging characteristics of three systems that use charge coupled devices (CCD) for small-field digital mammography (SFDM) have been compared in terms of spatial resolution and signal to noise ratio. The results indicate that although they are designed for nominally the same tasks of stereotactic localization and spot imaging these detectors have significantly differing physical imaging properties. Imaging system design parameters such as the phosphor screen type and thickness, screen configuration and method of optically coupling the phosphor to the CCD have significant effects on the imaging performance of the detectors.

Techniques to improve the accuracy of noise power spectrum measurements in digital x‐ray imaging based on background trends removal

“…The NPS measurement for digital x-ray imaging systems has been studied extensively. [1][2][3][4][5][6][7] The goal of the NPS measurement is to use the limited amount of image data acquired to get a smooth and accurate NPS estimation with the finest frequency resolution. 8,9 The measurement and interpretation of the noise power spectrum with digital systems pose particular complications due to two principal difficulties.…”

Conversion of mammographic images to appear with the noise and sharpness characteristics of a different detector and x‐ray system

“…It was assumed that there are three sources that contribute to the noise in an image: electronic, quantum, and structure noise. Each has a different dependence on dose and spatial frequency [16][17][18] and it was convenient to express the total NPS (W) as a sum of three terms which show explicitly the dependence on air kerma (K) and spatial frequency…”

Characterization of noise sources for two generations of computed radiography systems using powder and crystalline photostimulable phosphors

“…Noise has a number of sources in a digital radiograph image: primary quantum noise, secondary quantum noise, Poisson excess noise, structure noise, additive electronic noise, and aliasing. 19 This section briefly describes the noise sources and how to quantify them. The primary quantum noise source is related to the Poisson distribution of the number of x-ray photons absorbed by the phosphor.…”

“…To understand the NNPS, it is useful to examine the individual sources of noise in an image and their relationship with air kerma and spatial frequency. 5,[19][20][21] According to Poisson statistics, the primary quantum ͑W Q ͒ NNPS at zero spatial frequency is equal to the inverse number of absorbed x-ray photons. A frequency-based primary quantum noise ͓W Q ͑u͔͒ can be estimated by applying the square of the MTF to the primary quantum noise for each frequency.…”

“…The NPS due to additive electronic noise is independent of the signal. When the NPS is normalized to give W e ͑u͒, it is related to the inverse square of detector air kerma 19 and so this noise source is most significant at low detector air kerma levels.…”