Digital Film Research Articles

A limited PACS dedicated to a research environment. Nine years' experience in Santiago de Compostela.

A digital image network has been installed at the Department of Radiology of the University of Santiago de Compostela, Spain, to create a "limited' Picture Archiving and Communication System (PACS). This experience is being dedicated to address problems associated with digital techniques in a research environment. The backbone of the system is a multiprotocol ethernet network. Attached to the network are a number of advanced devices such as DEC VAX and UNIX workstations. Currently, a high resolution film digitizer and a laser printer are under evaluation for radiologic image research. During a period of nine years, 1987 to 1995, experimental and clinical trials have been conducted on different film based digital radiography apparatus primarily dedicated to chest and breast imaging. Several research projects have been completed. In this paper we describe the results of these investigations and discuss the advantages and disadvantages of this digital technique. The results of the different completed studies will be presented separately. A description of the physical characteristics of the limited PACS system dedicated to a research environment will serve as background.

290Characteristics and application of a commercially availale film digitizer to quantitative film dosimetry

290Characteristics and application of a commercially availale film digitizer to quantitative film dosimetry

Recording, processing, and analysis of digital high-speed sequences in glottography

A new high-speed system for recording, processing, and analyzing vocal fold vibrations has been developed. Results obtained with this system are discussed from the technical and the medical points of view. Laryngeal movement can be recorded with a digital high-speed camera, at a maximum speed of about 5 600 frames/s and the sequence can contain as many as 8 192 single frames. Application specific software for adaptive, semiautomatic, motion analysis is used to calculate and plot the glottograms for selected points on each vocal cord. From the data obtained, we can calculate speed, acceleration rates, the fundamental frequency, amplitudes, and perturbation parameters. This approach to laryngeal examination, based on the digital films, motion plots and characteristic statistics, is a practicable method that promotes the possibilities of quantitative and graphic analysis of the moving vocal folds and overcomes the disadvantages of the currently common examination methods.

Technique for the Digital Imaging of Histopathologic Preparations of Eyes for Research and Publication

Although there are excellent techniques to photograph gross ocular pathology specimens, it is difficult to view or photograph the entire eye from a glass slide using equipment designed for photomicrography. This investigation was initiated to develop a technique to image the entire eye from a glass slide. The glass histopathologic slide, placed in a carrier intended for 35-mm film transparencies, is inserted into a 35-mm slide scanner. The glass slide is scanned, creating a digital color image which may be converted to black and white with enhancement of certain histologic features. One may use a digital film recorder to produce 35-mm photographic transparencies or a dye sublimation printer to produce high-resolution color or black and white prints. More than 400 ocular whole-mount preparations have been digitized in the authors' laboratory to generate illustrations suitable for publication or for analysis in morphologic research. Digital techniques provide easier control over density and contrast than conventional photographic methods. Digitized images are well-suited for morphologic analyses in research. These techniques allow one to publish black and white photographs for books or journals while retaining the original color image for potential CD-ROM editions.

Topographical evaluation of skin perfusion patterns in peripheral arterial occlusive disease by means of computer-assisted fluorescein perfusography

To evaluate the clinical impact of computer-assisted fluorescein perfusography in peripheral arterial occlusive disease (PAOD). Foot and calf skin perfusion was visualised by intravenous fluorescein injection. Fluorescein influx was recorded photographically and converted into functional images of fluorescein appearance times (AT) by means of digital film processing. Vascular Laboratory of Clinic for Vascular Disease. 249 patients with PAOD. Among 481 limbs studied, 83 legs presented with patent arteries, 70 with asymptomatic obstructions (Stage I), 170 with claudication (Stage II) and 158 with rest pain and skin lesions (Stage III/IV). Forefoot and calf mean ATs and standard deviations (SD) served as arbitrary measures of regional skin perfusion rates and their homogeneity, respectively. In the control legs, a homogeneous and fast fluorescence appearance was observed (medians at the foot: AT33.4 s, SD 3.6). In stage II disease, AT (39.9 s, SD 5.6) were slightly impaired as compared to limbs with patent arteries or stage I disease (p < 0.01). Ninety-seven out of the 158 legs in stage III/IV could be managed by conservative therapy. According to fluorescein-perfusography, they did not differ from stage II disease (AT 38.8 s, SD 6.1). Sixty-one limbs were clinically affected by critical ischaemia. They exhibited a markedly delayed and heterogenous fluorescein influx at the foot (AT 77.3 s, SD 26.5, p < 0.01 vs all other groups). Non-fluorescent areas occurred in 53% compared to only 1% of limbs with and without critical ischaemia, respectively. Retrospectively, predictive values of fluorescein perfusography in identifying a critical limb ischaemia (accuracy 93%) were superior to the ankle systolic arterial pressure determination (accuracy 80%). Fluorescein perfusography seems to be of diagnostic and prognostic use in PAOD in stage III/IV where inflammatory and ischaemic patterns of dye appearance can be distinguished.

Tests for evaluating laser film digitizers.

A number of tests to evaluate the image transfer characteristics of laser film digitizers have been developed and these tests have been used to evaluate the performance of a Konica KFDR-S laser film digitizer. These tests were designed to be simple in nature and to use materials readily available in clinical departments. The tests examined (i) the geometric accuracy of the laser film digitizer; (ii) the linearity of the digitizer's characteristic curve; (iii) the temporal/spatial response of the digitizer to abrupt changes in optical density; and (iv) the noise added by the digitizer to the digitized images. The tests were easy to use and could be performed in a short period of time. Results of the tests for the Konica laser film digitizer revealed several problems including minor geometric inaccuracies, structural noise added by a shading correction circuit in the digitizer, and spread of the laser beam before reaching the film plane, possibly caused by the f-theta lens of the digitizer. The light spread made the optical density of small, high density structures measured by the digitizer dependent upon the optical density of the surrounding regions. Therefore, under some circumstances, film digitization with the Konica laser film digitizer could lead to erroneous results. In addition, our measurements suggest that these problems are not unique to the Konica digitizer. Thus, the testing of laser film digitizers is recommended, especially if the digitizer is to be used for quantitative measurements.

Light photon equalization and its application to X-ray film digitization

The principle of light photon equalization (LPE) is to modulate the light source during X-ray film digitization so that the dynamic range of the transmitted light into a photo-detector can be precisely controlled to obtain improved signal-to-noise ratio (SNR). The modulation of the light source is derived from a smoothed image of the original digitized image. The final output digital image is reconstructed by convoluting the modulation function with the resultant LPE image. The LPE was implemented in a laser film digitizer as a prototype. The results shows that, although the dynamic range of X-ray films is about 10 4:1, the range of the transmission light into a photo detector was reduced to 10 2:1 with this technique. Also the SNR improved by a maximum factor of five in the lung area of a digitized chest radiograph.

A test pattern for quality control of laser scanner and charge-coupled device film digitizers.

Although clinical images provide the ultimate test of diagnostic performance for a film digitizer, such images are not generally suitable for daily quality control (QC) purposes. However, a well-designed test pattern will provide a rapid, comprehensive, objective and reproducible assessment of image quality. This pattern should evaluate various parameters of image quality, including high contrast resolution, low contrast discrimination, linearity of gray scale, geometric distortion, and noise. Furthermore, the pattern should detect light leak and film slippage, two problems commonly associated with film digitizers. The test pattern described in this manuscript was designed to provide quantitative measures of performance for a film digitizer. As part of a regular QC routine for a laser scanner or charge-coupled device digitizer, this pattern provides a simple method to identify and quantify changes in digital image quality.

Digital chest radiography at the University of Chicago: Present status and future plans

Storage-phosphor computed radiography and film digitization systems have been in routine clinical use at the University of Chicago for several years. During this time we have implemented numerous modifications including techniques for scatter reduction, image processing enhancements and display systems to improve the image quality and utility of these devices. We have also evaluated the image quality and functionality of digital systems relative to conventional screen-film radiography. In this paper, we review our experience and summarize our impressions. In addition, we summarize our plans for a rapid transition into picture archiving and communication systems, with hardcopy interpretation being phased out for most modalities over the next 2 to 5 years.

Dynamic compressive properties of composites at interior ballistic rates of loading—Experimental method

An experimental method has been developed to investigate the dynamic effects on material behavior in a gun launch environment. A test fixture with a designed crashing mechanism generates a loading condition resulting from gun pressure. Methods of data acquisition and reduction have also been developed using a streak camera and a film digitization technique. The system is calibrated and verified by testing aluminum samples and fairly good results are obtained. Finally, polymer composite laminates with layup constructions of interest are tested. Strain rate effects on the compressive strength are discovered at the interior ballistic rates of loading.

Digital archive system for radiologic images.

Use of a picture archiving and communication system (PACS) for clinical review requires rapid access to patient images. The authors have developed a second-generation archive system for a departmental PACS that optimizes access time for both current and historical images. The system is based on a composite staging mechanism that uses multiple storage media: magnetic disks, erasable magneto-optical disks, and write-once-read-many (WORM) disks. A two-tiered communication network composed of a standard Ethernet network and a gigabit bandwidth fiberoptic UltraNet network is used for distributing images to remote display stations. The system currently archives 1.5 Gbytes of radiologic images daily from three magnetic resonance imagers, two computed tomographic scanners, one computed radiographic system, and one laser film digitizer. The system features (a) multiple optical drives and robotic arms, which support concurrent archival and retrieval operations; (b) a stacking mechanism, which provides fast retrieval of current images; (c) a pre-fetch mechanism, which minimizes on-line image retrieval, hence relieving peak-hour workload of the optical disk library and the networks; (d) studies grouping and platter management, which optimize retrieval of a patient's images from multiple examinations; and (e) a job-prioritizing control, which minimizes waiting time for radiologists and referring physicians to review images at the display stations. This system is suitable for a large-scale PACS to serve the clinical and research staff.

Development of a digital duplication system for portable chest radiographs.

To provide high-quality duplicate chest images for the intensive care units, we have developed a digital duplication system in which film digitization is performed in conjunction with nonlinear density correction, contrast adjustment, and unsharp mask filtering. This system provides consistent image densities over a wide exposure range and enhancement of structures in the mediastinum and upper abdominal areas, improving visibility of catheters and tubes. The image quality is often superior to that of the original radiograph and is more consistent from day to day. Repeat rates for portable chest radiographs have been reduced by more than a factor of two since implementation of digitization in December 1991, and the number of repeat examinations caused by exposure errors have been substantially reduced.

Measurements of the electron dose distribution near inhomogeneities using a plastic scintillation detector

Purpose : Accurate measurement of the electron dose distribution near an inhomogeneity is difficult with traditional dosimeters which themselves perturb the electron field. We tested the performance of a new high resolution, water-equivalent plastic scintillation detector which has ideal properties for this application. Methods and Materials : A plastic scintillation detector with a 1 mm diameter, 3 mm long cylindrical sensitive volume was used to measure the dose distributions behind standard benchmark inhomogeneities in water phantoms. The plastic scintillator material is more water equivalent than polystyrene in terms of its mass collision stopping power and mass scattering power. Measurements were performed for beams of electrons having initial energies of 6 and 18 MeV at depths from 0.2–4.2 cm behind the inhomogeneities. Results : The detector reveals hot and cold spots behind heterogeneities at resolutions equivalent to typical film digitizer spot sizes. Plots of the dose distributions behind air, aluminum, lead, and formulations for cortical and inner bone-equivalent materials are presented. Conclusion : The plastic scintillation detector is suited for measuring the electron dose distribution near an inhomogeneity.

Film digitization aliasing artifacts caused by grid line patterns

Sampling a radiographic film containing grid line patterns during digitization may produce aliasing artifacts (Moire pattern). The authors propose a mathematical model based on the laser spot size of the digitizer, the distance and the angle between the grid line and the sampling direction to predict the amplitudes and the frequencies of aliasing artifacts. The predicted results are compared to the experimental results. Effective ways of avoiding or reducing aliasing artifacts without sacrificing too much image quality are proposed.

Digital Film Scanning and Recording: The Technology and Practice

This article reviews the design components of a CCD film scanner and laser film recorder. The key image-quality parameters are reviewed, including resolution, quantization, noise, and color. The subject of system calibration is explored. Issues that affect the exchange of images between facilities are described, including file format and image data storage. Some of the operational issues of digital film scanning and recording are also discussed.

536. フィルムデジタイザを利用した PET 画像と MRI および CT 画像の重ね合わせ(核医学 PET)

536. フィルムデジタイザを利用した PET 画像と MRI および CT 画像の重ね合わせ(核医学 PET)

SMPTE Tutorial: Gray-Scale Transformations of Digital Film Data for Display, Conversion, and Film Recording

SMPTE Tutorial: Gray-Scale Transformations of Digital Film Data for Display, Conversion, and Film Recording

Evaluation of an Enhanced Digital Film-Duplication System by Receiver Operating Characteristic Analysis

Over- or underexposure often results in poor quality radiographs. Using receiver operating characteristic analysis, the authors investigated the potential utility of a system that corrects densities in such images to improve the accuracy of lung nodule detection. Chest radiographs were digitized by a laser film digitizer. Simulated nodules were superimposed on 36 improperly exposed chest radiographs. All images, with and without nodules, were then processed by a nonlinear density-correction technique. Hard-copy images were produced by a laser film printer. Eight radiologists evaluated the corrected and uncorrected images for the presence or absence of lung nodules using a continuous (0-100) confidence-rating scale. The detectability of lung nodules improved significantly in the retrocardiac/retrodiaphragmatic regions of underexposed images and in the peripheral lung region of overexposed images. This system may increase diagnostic accuracy in detection of lung nodules in improperly exposed images.

Digital mammography—the comparative evaluation of film digitizers

To study the potential of the computer interpretation of digital mammograms it is necessary to use digitized conventional films because at the present time insufficient resolution may be achieved using computed radiography. For example, the automatic detection of very small subtle calcifications requires digitization at 50 μm or smaller with at least 8 bits of grey level (Chan et al, 1987; Dance, 1993). In this paper we present a simple and practical method to evaluate and compare the technical performance of three film digitizers. These all cost about £20 000 and are being assessed as possible methods for obtaining digital mammograms for a national database (Astley, 1993). The digitizers investigated are a drum scanning microdensitometer, a laser scanning densitometer and a CCD camera. According to manufacturers' specifications, each has a high resolution sampling pixel size (50 μm or less) and is capable of digitizing to a grey level of at least 8 bits over the complete range of diffuse optical densities (0–3 or higher) typically found in a mammogram. The digitizers have been compared by measuring the modulation transfer function (MTF), noise and linearity of each system at a pixel resolution of 50 μm with an 8 bit grey scale. Measurement of these properties provides a means of comparison of important parameters such as resolution and dynamic range. Yin et al (1992) have recently presented an evaluation of the imaging properties of a laser film digitizer using a different approach from that described in this paper.

35-mm film scanner as an intraoral dental radiograph digitizer: I: A quantitative evaluation

A 35-mm slide scanner digital imaging system was tested for its suitability in digitizing intraoral dental radiographic film for quantitative studies. The system (Nikon model LS-35 10AF Nikon Electronic Imaging, Nikon, Inc., Melville, N.Y.) uses a charge-coupled device linear photodiode array. The data content in the original film images was evaluated, and the system performance assessed objectively with the use of specially designed test films. Radiometric and geometric performances for the digitizing system were extracted from measurements and observations, and these were compared with published data for two other film digitizing systems (video camera DAGE MTI, Michigan City, Ind. and Barneyscan 35-mm film digitizer Barneyscan, Berkeley, Calif.). The techniques used to evaluate this system are easy and suitable for evaluation of any digitizing system. This scanner system (Nikon) was superior to previously evaluated systems in transforming and recording radiographic film densities across the range (0.3 to 2.0 optical density units) of clinically relevant optical densities. The scanner offers substantial advantage over the other digitizing systems for gray scale information from clinically important optical densities.