Comparison of different camera calibration approaches for underwater applications.

The purpose of this study was to compare three camera calibration approaches applied to underwater applications: (1) static control points with nonlinear DLT; (2) moving wand with nonlinear camera model and bundle adjustment; (3) moving plate with nonlinear camera model. The DVideo kinematic analysis system was used for underwater data acquisition. The system consisted of two gen-locked Basler cameras working at 100 Hz, with wide angle lenses that were enclosed in housings. The accuracy of the methods was compared in a dynamic rigid bar test (acquisition volume-4.5×1×1.5 m(3)). The mean absolute errors were 6.19 mm for the nonlinear DLT, 1.16 mm for the wand calibration, 1.20 mm for the 2D plate calibration using 8 control points and 0.73 mm for the 2D plane calibration using 16 control points. The results of the wand and 2D plate camera calibration methods were less associated to the rigid body position in the working volume and provided better accuracy than the nonlinear DLT. Wand and 2D plate camera calibration methods presented similar and highly accurate results, being alternatives for underwater 3D motion analysis.

Influence of compact disk recording protocols on reliability and comparability of speech audiometry outcomes: acoustic analysis.

OBJECTIVE: To assess whether different compact disk recording protocols, used to prepare speech test material, affect the reliability and comparability of speech audiometry testing. MATERIAL AND METHODS: We conducted acoustic analysis of compact disks used in clinical practice, to determine whether speech material had been recorded using similar procedures. To assess the impact of different recording procedures on speech test outcomes, normal hearing subjects were tested using differently prepared compact disks, and their psychometric curves compared. RESULTS: Acoustic analysis revealed that speech material had been recorded using different protocols. The major difference was the gain between the levels at which the speech material and the calibration signal had been recorded. Although correct calibration of the audiometer was performed for each compact disk before testing, speech recognition thresholds and maximum intelligibility thresholds differed significantly between compact disks (p < 0.05), and were influenced by the gain between the recording level of the speech material and the calibration signal. CONCLUSION: To ensure the reliability and comparability of speech test outcomes obtained using different compact disks, it is recommended to check for possible differences in the recording gains used to prepare the compact disks, and then to compensate for any differences before testing.

Security of patient and study data associated with DICOM images when transferred using compact disc media.

The transmission of patient and imaging data between imaging centers and other interested individuals is increasingly achieved by means of compact disc digital media (CD). These CDs typically contain, in addition to the patient images, a DICOM reader and information about the origin of the data. While equipment manufacturers attach disclaimers to these discs and specify the intended use of such media, they are often the only practical means of transmitting data for small medical, dental, or veterinary medical centers. Images transmitted by these means are used for clinical diagnosis. This has lead to a heavy reliance on the integrity of the data. This report describes attempts to alter significant patient and study data on CD media and their outcome. The results show that data files are extremely vulnerable to alteration, and alterations are not detectable without detailed analysis of file structure. No alterations to the DICOM readers were required to achieve this; changes were applied only to the data files. CDs with altered data can be readily prepared, and from the point of view of individuals viewing the images, function identically to the original manufacturer's CD. Such media should be considered unsafe where there is a potential for financial or other gain to be had from altering the data, and the copy cannot be cross-checked with the original data.

[The DICOM-CD-Project of the German Radiology Association--an overview of the content and results of a pilot study in 2006]. / Das DICOM-CD-Projekt der Deutschen Röntgengesellschaft--eine Ubersicht über die Inhalte und Ergebnisse des Pilottests 2006.

DICOM-CDs are frequently used for medical image data transfer. Many different potential advantages are known, such as improved image quality, handling simplification, and cost optimization. However, there are numerous restrictions in the daily routine. While testing DICOM-CDs at the 2006 German Radiology Congress, we found that more than 70 % of CDs have discrepancies with respect to data structure or content. The German Radiological Association and OFFIS started an initiative to improve the quality of DICOM-CDs. There are three main objectives: To provide requirements for vendors of CD-writing systems, to establish user guidelines for the handling of DICOM-CDs, and to develop a test procedure for DICOM-CDs. Radiologists using such systems should be aware of these developments and use them for RFP's.

Perception of music performance on historical and modern commercial recordings.

Performing styles as well as recording styles have changed considerably within the 20th century. To what extent do the age of a recording, the unfamiliarity with performing style, and the quality of a reproduction of a recording systematically influence how we perceive performances on record? Four exploratory experiments were run to formulate an answer to this question. Each experiment examined a different aspect of the perception of performance, including judgments of quality, perceived emotion, and dynamics. Fragments from Die junge Nonne sung by famous singers from the start, middle, and second half of the 20th century were presented in a noisy and clean version to musically trained participants. The results show independence of perception of emotional activity from recording date, strong dependence of perceived quality and emotional impact on recording date, and only limited effects of reproduction quality. Standards have clearly changed, which influence judgments of quality and age. Additionally, changes restrict the communication between early recorded performers and modern listeners to some extent as shown by systematically smaller variations in communicated dynamics and emotional valence for older recordings.

Cell analysis system based on compact disk technology.

BACKGROUND: A cell analysis system was developed to enumerate and differentiate magnetically aligned cells selected from whole blood. The cellular information extracted is similar to the readout of musical information from a compact disk (CD). Here we describe the optical design and data processing of the system. The performance of the system is demonstrated using fluorescent-labeled cells and beads. Materials and Methods System performance was demonstrated with 6-microm polystyrene beads labeled with magnetic nanoparticles and allophycocyanin (APC) and immunomagnetically aligned leukocytes, fluorescently labeled with Oxazine750 and CD4-APC, CD8-Cy5.5, and CD14-APC/Cy7 in whole blood. RESULTS: The sensitivity of the system was demonstrated using APC-labeled beads. With this system, beads containing 333 APC molecules could easily be resolved from the background. This level of sensitivity was not achievable with a commercial flow cytometer. A maximum of 20,000 immunomagnetically labeled cells could be aligned and analyzed in between 0.6 m of Ni lines, distributed over a surface area of 18 mm(2) and extracted from a blood volume that depended on the height of the chamber. The utility of the system was demonstrated by performing a three-color CD4-CD8-CD14 assay. CONCLUSIONS: We built a cell analysis system based on immunomagnetic cell selection and alignment and analysis of fluorescent signals employing CD-technology that is as good or better than current commercial analyzers. The cell analysis can be performed in whole blood or any other type of cell suspension without extensive sample preparation.

The DICOM review stations: are they truly different?

Digital acquisition systems are widely used nowadays. The digitization of the cath lab environment is now directed towards the change in the exchange media from an analog (i.e. cinefilm) to a digital (i.e. CD-R) medium. An important consequence of this development is the need for another type of review system. This article focuses on the replacement of the cineprojector by a digital equivalent: the DICOM review station. Since the technologies differ fundamentally, the DICOM review station has very little in common with its analog predecessor. This article explains the basics of DICOM review stations. Different approaches, both in hardware and in software, are possible, each showing their advantages and drawbacks. The impact of choices made by the industry will be illustrated by a number of commercially available DICOM review stations. Further, the article discusses the topics of diagnostic image quality and performance. In our opinion, these are the major topics when it comes to an objective comparison of the capabilities of DICOM review stations. The relation of these subjects with design choices in terms of hardware and software are discussed.

The Kodak approach to digital cardiovascular imaging laboratories.

Cine film had been a global standard in the cardiac catheterization lab for the acquisition, archive, review and exchange for decades. The advent of digital imaging in the cath lab heightened the desire to store cath procedure images in a digital format. The issues related to the development of a digital exchange standard, the data capacities and data rates, lossless and lossy compression, and techniques to obtain digital image data from the lab are discussed. In addition, Kodak's approach to cine film replacement with digital systems is described.

A comparison of the currency of secondary information sources in the biomedical literature. I. Weekly current awareness services.

Three biomedical current awareness products which are distributed on floppy disc, were studied over a period of 3 months. They were monitored for the speed with which primary journal issues were indexed, and for the coverage of the journals which were selected for study. Data on issues of 72 monthly journals (38 North American and 34 European) and nine weekly titles (four from North America and five from Europe) were recorded. The time to elapse between publication date and arrival of hard copy in the British libraries and appearance in secondary sources varied enormously. The findings suggest that monthly journal issues appear in the secondary sources on average 6-7 weeks after publication date and weekly journals appear after approximately 4 weeks. Indexing of North American monthly journals is 1 week ahead of European titles in the two products from the US, but the European service indexed European publications sooner. One product, Current Contents on Diskette, contained all issues included in the 3-month period covered by the study, but Reference Update omitted 9.1% of the issues and Medical Science Weekly 1.6%, including leading biomedical journals.