Optimizing techniques in screen-film mammography

This article provides a practical approach to the steps needed to optimize mammography techniques. Those steps consist of a series of activities that begin with the choice of mammography film, then choosing the optimum film processing for that film type, selecting the appropriate technique factors for exposure, and the proper viewing of processed mammography films. In each area, the basic physics underlying film and film processing, mammography equipment performance, image contrast, and image display, are used to determine optimized mammography techniques.     

DR、CR、屏-胶系统在胸部摄影中的价值比较

随着计算机技术和图像处理技术的飞速发展,医学影像设备不断更新换代,近几年X线摄影已由普通屏-胶摄影到CR(computed radiography,CR)再到DR(Direct Digitized Radiography,DR)而进入数字化时代.     

Recent advances in screen-film mammography

Today there are many dedicated mammographic x-ray units available that are capable of providing high-quality screen-film mammograms. Likewise, screen-film combinations designed for mammography are capable of providing images with appropriate contrast, resolution, and noise levels. Proper film processing is most important in order to obtain the appropriate film speed and contrast. A higher-speed screen-film combination designed for mammography can provide mammograms with significantly lower radiation dose, especially for grid and magnification techniques. Designing x-ray units and techniques as well as screen-film combinations with the singular goal of reducing radiation dose will always involve compromises and trade-offs. The key is to always consider optimizing all of the factors that affect image quality: (1) appropriate beam quality, (2) breast compression, (3) consideration of the use of grids, (4) good geometry, (5) selection of an appropriate screen-film combination, and (6) proper film processing. Optimization of all appropriate imaging factors will produce high-quality mammograms at the lowest radiation dose to the patient.     

Patient discomfort during screen-film mammography

Vigorous compression is required to minimize radiation dose and maximize image quality for screen-film mammography. Of 356 women who adequately completed a questionnaire following mammography, 171 (48%) reported mammography to be comfortable, 135 (38%) uncomfortable but tolerable, 39 (11%) very uncomfortable, and only 11 (3%) found the examination to be intolerable. Only 14 women (4%) indicated that they would not return for mammography at our facility in the future. Because of this high level of acceptance of compression by women, technologists and radiologists should not hesitate to use vigorous compression to optimize image quality and decrease radiation dose to the patient.     

Clinical evaluation of wavelet-compressed digitized screen-film mammography

RATIONALE AND OBJECTIVES: The authors compared diagnostic accuracy and callback rates with conventional screen-film mammograms and wavelet-compressed digitized images. MATERIALS AND METHODS: Sixty sets of mammograms (four views per case) were digitized at a spatial resolution of 100 microm. The images were wavelet compressed to a mean compression ratio of 8:1 and reviewed by three mammographers. Five regions were evaluated in each breast. Suspicion of malignancy was graded on a scale of 0% to 100%, and receiver operating characteristic (ROC) analysis was performed. Callback rates were calculated by using the American College of Radiology's Breast Imaging Reporting and Data System lexicon scale. RESULTS: The mean diagnostic accuracy with compressed and conventional images was 0.832 and 0.860, respectively. The upper 95% confidence bound for the difference in ROC areas was 0.061. The mean false-positive rate at a fixed sensitivity of 0.90 was 0.041 for compressed images and 0.059 for conventional images. The mean callback rates for normal, benign, and malignant regions were 0.023, 0.305, and 0.677, respectively, for compressed images and 0.036, 0.447, and 0.750, respectively, for conventional images. The upper 95% confidence bound for the (absolute) differences in callback rates was 0.012 for normal regions, 0.163 for benign regions, and 0.138 for malignant regions. CONCLUSION: Diagnostic accuracies were equivalent for both compressed and conventional images. The mean false-positive rate at fixed sensitivity was much better with the compressed images. However, the callback rates for malignant lesions were lower when the compressed images were used.     

A protocol for evaluating screen-film systems]

When a competition is made for the supply of sensitive photographic material, each USL is asked, in a time scan of one or more years, to evaluate the characteristics of the screen-film systems proposed by the various companies. In the last years the authors had several opportunities to check different screen-film systems for many Friuli-Venezia Giulia hospitals. For this reason they have set an evaluation form tested after following changes and recently employed in its final version. The check form is reported on in this paper with some personal considerations originated by the authors' experience. The technical parameters which must be evaluated are reported, together with the instrumentation needed to perform the technical examination, the examination modality, and the score-attributing criteria. The evaluation form is very flexible for it allows each Radiology Department to evaluate each parameter in a personal way and to fit it to its own needs.     

A comparison of mammography screen-film combinations.

A comparison study was performed to evaluate the image quality and radiation dose of six mammographic screen-film combinations: a Min-R screen with OM-1, SO-155, and SO-177 films (Eastman Kodak); a Min-R medium screen (Eastman Kodak) with OM-1 film; an HR Mammo medium screen (Fuji Medical Systems USA) with OM-1 film; and a Min-R fast screen with T-Mat M II film (Eastman Kodak). SO-177 films were processed with an extended cycle. Exposures of an acrylic test object with embedded masses, fibers, and specks and of a preserved breast specimen were made, for two paired image comparison tests in which the visibility of diagnostic features, contrast, and noise were judged. In most areas of image quality evaluated, a Min-R screen with OM-1, SO-155, and SO-177 films was superior. These three screen-film combinations had similar imaging characteristics, even though OM-1 film requires a higher radiation exposure. Images produced with a Min-R fast screen and T-Mat M II film were significantly lower in quality.     

增感屏-胶片组合体系的威纳频谱测试探讨

目的　通过实验测试增感屏-胶片组合体系的威纳频谱(Wienerspectrum,WS),评价X线照片的粒状性。方法　制作CaWO4屏-Kodak片、BaFClEu屏-Kodak片、T颗粒技术3种增感屏-胶片组合体系的10cm×10cm粒状性抽样照片,用显微密度计扫描,获得10万个密度值,作为离散随机信号来处理,用快速傅立叶变换（fastFouriertransform,FFT）计算WS。结果　（1）BaFClEu屏-Kodak片的WS值当空间频率为0.1LP/mm时,WS值为8.26×10     

An evaluation of screen-film speed characteristics.

The relative speeds of six commercially available screen-film combinations were evaluated. There is a nonlinear relationship throughout the kVp range between the calcium tungstate, barium strontium sulfate, and rare earth screens. The speed of the last two types falls off considerably at lower kVp levels.     

Simple test pattern for mammographic screen-film contact measurement

Test patterns to measure mammographic screen-film contact require the use of a much finer screen-wire mesh than can be used in test patterns for other diagnostic cassettes. The author has found that a radiographic grid of any line spacing equal to or exceeding 40 lines per inch can be used to test mammographic screen-film contact, making it unnecessary to purchase a special dedicated fine-mesh mammographic test pattern. However, the use of a magnification technique will often be required, since modern grids have mesh frequencies in excess of 100 lines per inch.     

Exposure factors and screen-film combinations in temporomandibular joint radiography

Exposure factors and screen-film combinations providing optimal quality are identified for transcranial and transpharyngeal temporomandibular joint views, using conventional intra-oral radiographic equipment without grids. Standardized transcranial and transpharyngeal views, using a fixed whole cadaver head, were performed. Ten readily available screen-film combinations, ranging in nominal speed 20-600, were exposed over 40-100 kV. Films were blindly and independently order ranked by three observers on the basis of sharpness and contrast of cortical outline, trabecular detail, and visualization of adjacent bony structures. Preferred screen-film combinations as a function of kV, preferred kV levels for each screen-film combination, and overall ranking irrespective of kV or screen-film combination, were established. Accepting the use of the lowest radiation dose possible for diagnostically useful radiographs but imposing arbitrarily an upper limit of 20 mGy, it was found that exposures between 50 kV and 70 kV gave the optimal result for both techniques. The amount of scattered radiation in the emergent beam differs greatly between the two techniques. The most favoured combinations for the transpharyngeal technique used screens of fine resolution. Min-r/ortho M screen and film with nominal speed 40 at 60 kV gave 8.0 mGy skin dosage at 0.8 seconds exposure; the same combination at 50 kV was the most favoured, but with skin dosage calculated at 16.7 mGy for 3.0 seconds exposure. For the transcranial technique, medium speed screens providing better differentiation of scattered radiation beams and increased speeds were preferred. Most favoured for image quality was the Lanex Fine/T-Mat G combination at 60 kV giving 17.5 mGy skin radiation dose at 1.75 seconds exposure.(ABSTRACT TRUNCATED AT 250 WORDS)