Evaluation of imaging properties of a laser film digitizer.

In this paper we provide a quantitative assessment of the basic imaging properties of a laser film digitizer. The characteristic curve of the digitizer was determined in terms of the relationship between input optical density and output pixel value. Spatial resolution of the laser digitizer was characterized using the presampling modulation transfer function (MTF), which was measured using a curve fitting technique with an angulated slit. For the noise analysis, we compared the Wiener spectra of uniformly exposed film samples before and after digitization. The effects of different sampling distances and scanning directions were investigated. Our results show that the characteristic curve of the laser digitizer was linear. The presampling MTFs of the digitizer were similar at different sampling distances and were substantially greater in the vertical scanning direction than in the horizontal direction. The noise of the digitized film sample was mainly affected by the presampling MTF and structure noise of the digitizer.     

Contrast information of digital imaging in laser film digitizer and display monitor

A 10-bit or 12-bit gray scale is provided in commercial laser film digitizers. The true contrast resolution on the digitized image within a laser spot area of 200 microns in diameter is limited by both the quantum mottle and instrumentation noise. In this report, we investigated the mean value, standard deviation, and adjacent pixel correlation coefficient on a calibrated step wedge film with two laser digitizers. The results were disappointing, because we found that the evaluated contrast information is inferior to the manufacturers' specifications. On the output side, the brightnesses of different gray levels from a clinical monitor were measured with a narrow angle luminance probe and evaluated by a brief human perception study. In addition, the implications for teleradiology applications are discussed.     

Radioimmunoassay and bioassay data processing using a logistic curve fitting routine adapted to a desk top computer

The four parameter logistic curve fitting routine of Rodbard and Hutt [5] was adapted for use on a desk top computer and found to be an appropriate manner to process data from radioimmunoassays and bioassays.     

A new computer memory for biology and medicine using the laser card

A new computer memory using a laser beam to impress dimples on a standard credit card has been devised which contains about 2 million bytes (700 typed pages) and which has been formatted with software to permit access to a complete medical record which can be carried by the patient and updated at each encounter with the health care system. The system has been tested in an outpatient clinic with considerable success.     

Clinical laboratory data processing with a central hospital computer

A system for storing, retrieving and organizing laboratory test request and result information within the biochemistry, hematology, immunology, microbiology and urinalysis sections of a large clinical laboratory is described. All data files are maintained in a central hospital computer system separate from the laboratory. Specific items of information as well as various groupings of data can be retrieved in real-time by laboratory technologists and clinicians. Schedules, batch processing routines are used to produce more complex reports which are not required at a moments notice. Critical factors in the design of such an information handling system are discussed.     

Coronary atherosclerosis among Hong Kong Chinese--a histological and morphometric study using electronic digitizer

In order to document the prevalence of atherosclerosis of the major coronary arteries among Hong Kong Chinese, a study on material from autopsies done during the year 1981 in Queen Mary Hospital was carried out. The narrowest part of the proximal coronary arteries was studied by light microscopy and morphometrically by electronic digitizer. We found an onset of atherosclerosis in young adult males and a linear progression with age. Females had a delayed onset with a sharp rise after menopause. We were surprised to find an incidence of atherosclerosis among Hong Kong Chinese comparable with that in western populations, as distinct from Chinese in Mainland China. However, mortality due to ischemic heart disease remained relatively low. Racial factors may contribute to this partial dissociation between coronary atherosclerosis and ischemic heart disease.     

An intercomparison of computer assisted data processing and display methods in radioisotope scintigraphy using mathematical tumours

Several computer assisted processing and display methods are evaluated using a series of 100 normal brain scintigrams, 50 of which have had single 'mathematical tumours' superimposed. Using a standard rating system, or in some cases quantitative estimation, LROC curves are generated for each method and compared.     

Antibiotic combinations and serum concentrations: a study using a computer program

An original computer program developed to study antibiotic combinations is presented. In vitro combination effects were determined by broth microtiter checkerboard method. Inhibitory and bactericidal concentrations for each antibiotic alone and in combination were registered on a microcomputer (Apple Lisa). The program (Pascal UCSD) allowed to determine FIC and FBC index and a therapeutical index (IFT) based on reduction of concentrations under mean serum levels for the two antibiotics. An IFT less than 1 correlated to a combination of antibiotics with achievable therapeutic levels. More the IFT was low more the combination was effective. This therapeutical index was calculated for various combinations of antibiotic concentrations.     

Use of a computer for producing microbiological reports and for data storage and processing.

A simple 'fail-safe' system is described that produces microbiology reports on a computer teleprinter and stores results on the magnetic tapes and discs of a computer for instant retrieval and epidemiological analysis. The system, which has been in operation for over a year, involves the use of a modified conventional NCR request form. The top portion, which is completed manually by the laboratory staff, is coded by writing numbers in hatched boxes. The data thus written on to the bottom portion are transcribed by punch operators on to paper tape and this data input is verified by double punching. The reports are normally produced automatically by the computer terminal telprinter, but in case of mechanical failure the manually completed request forms can be returned to wards and outpatient departments. The system permits a wide choice of options for epidemiological analysis, and six programmes are described, one of which produces a digest of the overall percentage antibiotic sensitivities of organisms from various sites.     

Technical note: Signal resolution increase and noise reduction in a CCD digitizer

Increasing output resolution is assumed to improve noise characteristics of a CCD digitizer. In this work, however, we have found that as the quantization step becomes lower than the analog noise (present in the signal before its conversion to digital) the noise reduction becomes significantly lower than expected. That is the case for values of sigma(an)/delta larger than 0.6, where sigma(an) is the standard deviation of the analog noise and delta is the quantization step. The procedure is applied to a commercially available CCD digitizer, and noise reduction by means of signal resolution increase is compared to that obtained by low pass filtering.     

A multi-purpose voice recording and encoding device using a micro computer

A device for recording and encoding voice stimuli was developed with the NEC-PC 9801 micro computer. Sampling times are 100 microseconds (10 kHz), and one recording time can be lasted up to 15 s. The sound stimuli are monitored on the computer display. These stimuli could be edited directly by the cursor and saved onto a floppy disk. A multi purpose program was also developed for this apparatus. This program allows the user to manipulate the stimuli for various auditory experiments such as dichotic listening tests etc.     

Postmortem time estimation using body temperature and a finite-element computer model

In the Netherlands most murder victims are found 2–24 h after the crime. During this period, body temperature decrease is the most reliable method to estimate the postmortem time (PMT). Recently, two murder cases were analysed in which currently available methods did not provide a sufficiently reliable estimate of the PMT. In both cases a study was performed to verify the statements of suspects. For this purpose a finite-element computer model was developed that simulates a human torso and its clothing. With this model, changes to the body and the environment can also be modelled; this was very relevant in one of the cases, as the body had been in the presence of a small fire. In both cases it was possible to falsify the statements of the suspects by improving the accuracy of the PMT estimate. The estimated PMT in both cases was within the range of Henssges model. The standard deviation of the PMT estimate was 35 min in the first case and 45 min in the second case, compared to 168 min (2.8 h) in Henssges model. In conclusion, the model as presented here can have additional value for improving the accuracy of the PMT estimate. In contrast to the simple model of Henssge, the current model allows for increased accuracy when more detailed information is available. Moreover, the sensitivity of the predicted PMT for uncertainty in the circumstances can be studied, which is crucial to the confidence of the judge in the results.This work is based on the confidential reports TNO-TM-98-M57 and TNO-TM-00-C032 (in Dutch) to the specific forensic forces of the Dutch police     

Precise radiochromic film dosimetry using a flat-bed document scanner

In this study, a measurement protocol is presented that improves the precision of dose measurements using a flat-bed document scanner in conjunction with two new GafChromic film models, HS and Prototype A EBT exposed to 6 MV photon beams. We established two sources of uncertainties in dose measurements, governed by measurement and calibration curve fit parameters contributions. We have quantitatively assessed the influence of different steps in the protocol on the overall dose measurement uncertainty. Applying the protocol described in this paper on the Agfa Arcus II flat-bed document scanner, the overall one-sigma dose measurement uncertainty for an uniform field amounts to 2% or less for doses above around 0.4 Gy in the case of the EBT (Prototype A), and for doses above 5 Gy in the case of the HS model GafChromic film using a region of interest 2 X 2 mm2 in size.     

The teaching of computer programming and digital image processing in radiography

The increased use of digital processing techniques in Medical Radiations imaging modalities, along with the rapid advance in information technology has resulted in a significant change in the delivery of radiographic teaching programs. This paper details a methodology used to concurrently educate radiographers in both computer programming and image processing. The students learn to program in visual basic applications (VBA), and the programming skills are contextualised by requiring the students to write a digital subtraction angiography (DSA) package. Program code generation and image presentation interface is undertaken by the spreadsheet Microsoft Excel. The user-friendly nature of this common interface enables all students to readily begin program creation. The teaching of programming and image processing skills by this method may be readily generalised to other vocational fields where digital image manipulation is a professional requirement.