Phillip C. Bunch

Analysis of the detective quantum efficiency of a radiographic screen-film combination.

Detective quantum efficiency provides a useful measure of the imaging efficiency of imaging systems. Methods for measuring the exposure and the spatial-frequency dependence of the contrast transfer function, the noise power spectrum, and the detective quantum efficiency are developed for x-ray imaging systems. These are applied to a high-resolution screen-film combination exposed to a 30-kV-peak x-ray spectrum. The major component sources of screen-film noise in this system are identified and quantified. These are interpreted in terms of a simple model to predict the screen-film noise power spectrum and detective quantum efficiency. Reasonable agreement is found between model predictions and experimental measurements.

Standardization of NPS measurement: interim report of AAPM TG16

This article reviews the state of the Noise Power Standard being drafted by Task Group No. 16 for the American Association of Physicists in Medicine. The Standard is intended to represent a consensus on acceptable practices in the measurement and reporting of noise power spectra for digital radiographic imaging devices based on single projections and to contain informative sections which will be of use to those not completely familiar with the measurement and interpretation of noise power spectra. Several of the issues considered by the committee are reviewed, including issues of conditioning and windowing data, issues specific to several modalities, and various methods of data presentation. A note on the historical background of noise power measurements and a brief discussion of possible avenues for future research is included.

Advances in high-speed mammographic image quality

The objective imaging characteristics of a new high-speed mammographic screen-film combination is analyzed in detail. By combining a large reduction in film granularity with substantial improvements in screen technology, high-speed mammography can now be re-optimized to yield improvements in imaging system performance. Optimal use of the materials for reducing patient motion and for magnification techniques is potentially more effective than previous high-speed systems.

Performance characteristics of asymmetric zero-crossover screen-film systems

The development of specialized dyes that essentially prevent light from crossing the film base in duplitized screen-film systems has made it possible to design screen-film combinations with unusual performance characteristics. Specifically, by combining front and back screens with differing light emission and resolution properties with asymmetric films with differing front and back sensitometric characteristics, it is now possible to design screen-film systems that have some or all of the following features: (1) density-dependent image blur, (2) previously impractical sensitometric curve shapes, and (3) screen-dependent system contrast. Performance characteristics of two specific systems are summarized, including sensitometric data, contrast transfer functions, noise equivalent quanta, and detective quantum efficiency. Initial clinical applications of this technology are also described, with an emphasis on thoracic radiography.

Objective imaging characteristics of mammographic screen-film systems

The basic performance characteristics of a wide variety of mammographic screen-film combinations have been experimentally determined. The performance characteristics studied include absolutely calibrated sensitometry, modulation transfer functions, noise power spectra, noise equivalent quanta, and detective quantum efficiency. Specific advantages of various systems are discussed as well as their potential limitations.

Detective Quantum Efficiency Of Selected Mammographic Screen-Film Combinations

The experimentally determined performance characteristics of selected mammographic screen-film combinations are described and compared in detail, including absolute sensitometry, modulation transfer functions, noise equivalent quanta, and detective quantum efficiency. Advantages of each screen-film combination for various mammographic applications are also described.

Effects of reduced film granularity on mammographic image quality

The basic imaging characteristics of a new mammographic screen-film combination have been experimentally determined. These characteristics include absolutely calibrated sensitometry, modulation transfer functions, noise power spectra, noise equivalent quanta, and detective quantum efficiency. Specific image quality advantages of this new system are discussed, including a substantial reduction in film noise, and comparisons are made with an established mammography system.

Comparison of high-MTF and reduced-noise radiographic imaging systems

The objective imaging characteristics of a wide range of gandolinium oxysulfide-based, zero- crossover, screen-film combinations are presented and compared. It is shown that complex high-spatial frequency versus low-spatial frequency performance tradeoffs are found among these systems, when these systems are examined in terms of sensitometric response, modulation transfer function, noise equivalent quanta, and detective quantum efficiency.

Sources Of Noise In High-Resolution Screen-Film Radiography

The contrast transfer function (CTF), noise power spectrum (NPS), noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) of a high-resolution screen-film combination have been measured for exposure to a 30 kVp x-ray spectrum. In addition to these overall system characteristics, selected component sources of noise in the screen-film combination have been determined experimentally. These data are interpreted in terms of a simple model which is used to predict screen-film NPS, NEQ, and DQE. Reasonable agreement between model predictions and experimental measurements has been found.

Comparison Of Theory And Experiment For The Dqe Of A Radiographic Screen-Film System

Models have been developed for the DQE of a screen-film system that, although based on a number of simplifying assumptions, include most of the significant parameters. At the same time an increasing number of experimental measurements are available for the complete DQE characteristics as a function of exposure and spatial frequency for practical screen-film systems. A systematic set of DQE measurements is presented here, which we examine from the viewpoint of current models. This reveals both areas of agreement and aspects that require further theory and experimentation.