High-energy x-ray Talbot-Lau radiography of a human knee.

We report on a radiographic measurement of an ex vivo human knee using a grating-based phase-contrast imaging setup and a medical x-ray tube at a tube voltage of 70 kV. The measurement has been carried out using a Talbot-Lau setup that is suitable to achieve a high visibility in the energy regime of medical imaging. In a medical reading by an experienced trauma surgeon signatures of chondrocalcinosis in the medial meniscus have been identified more evidently using the dark-field image in comparison to the conventional attenuation image. The analysis has been carried out at various dose levels down to 0.14 mGy measured as air kerma, which is a dose comparable to clinically used radiographic devices. The diagnosis has been confirmed by a histological analysis of the meniscus tissue. In the introduced high-frequency filtered phase-contrast image the anterior and posterior horn of the medial meniscus and the posterior cruciate ligament have also been visible. Furthermore, atherosclerotic plaque is visible in both imaging modalities, attenuation and dark-field, despite the presence of overlaying bone. This measurement, for the first time, proves the feasibility of Talbot-Lau x-ray imaging at high-energy spectra above 40 kVp and reasonable dose levels with regard to spacious and dense objects.

Optimisation of image reconstruction for phase-contrast x-ray Talbot-Lau imaging with regard to mechanical robustness.

X-ray grating-based phase-contrast imaging opens new opportunities, inter alia, in medical imaging and non-destructive testing. Because, information about the attenuation properties and about the refractive properties of an object are gained simultaneously. Talbot-Lau imaging requires the knowledge of a reference or free-field image. The long-term stability of a Talbot-Lau interferometer is related to the time span of the validity of a measured reference image. It would be desirable to keep the validity of the reference image for a day or longer to improve feasibility of Talbot-Lau imaging. However, for example thermal and other long-term external influences result in drifting effects of the phase images. Therefore, phases are shifting over time and the reference image is not valid for long-term measurements. Thus, artifacts occur in differential phase-contrast images. We developed an algorithm to determine the differential phase-contrast image with the help of just one calibration image, which is valid for a long time-period. With the help of this algorithm, called phase-plane-fit method, it is possible to save measurement-time, as it is not necessary to take a reference image for each measurement. Additionally, transferring the interferometer technique from laboratory setups to conventional imaging systems the necessary rigidity of the system is difficult to achieve. Therefore, short-term effects like vibrations or distortions of the system lead to imperfections within the phase-stepping procedure. Consequently, artifacts occur in all three image modalities (differential phase-contrast image, attenuation image and dark-field image) of Talbot-Lau imaging. This is a problem with regard to the intended use of phase-contrast imaging for example in clinical routine or non-destructive testing. In this publication an algorithm of Vargas et al is applied and complemented to correct inaccurate phase-step positions with the help of a principal component analysis (PCA). Thus, it is possible to calculate the artifact free images. Subsequently, the whole algorithm is called PCA minimization algorithm.

Solutions to challenges facing a university digital library and press.

During the creation of a university digital library and press intended to serve as a medical reference and education tool for health care providers and their patients, six distinct and complex digital publishing challenges were encountered. Over nine years, through a multidisciplinary approach, solutions were devised to the challenges of digital content ownership, management, mirroring, translation, interactions with users, and archiving. The result is a unique, author-owned, internationally mirrored, university digital library and press that serves as an authoritative medical reference and education tool for users around the world. The purpose of this paper is to share the valuable digital publishing lessons learned and outline the challenges facing university digital libraries and presses.

Identification and characterization of 19-nortestosterone in urine of meat-producing animals.

To monitor the illegal use of 19-nortestosterone as an anabolizing agent in meat-production, the Belgian Institute of Veterinary Expertise applies a strategy of urine control by radioimmunoassay, positive samples being confirmed by thin-layer chromatography. We have evaluated this control strategy, using gas chromatography-mass spectrometry to confirm the presence of 19-nortestosterone, or its metabolite oestrane-diol, in positive samples from radioimmunoassay. Our results show that the effective way of proceeding remains reliable in cattle, for mature and immature males as well as non-pregnant females, and in pigs, for pregnant and non-pregnant sows. The possible presence of endogenous 19-nortestosterone in cattle, in pregnant cows urine, and in pigs, in boars and in cryptorchid pigs, impedes the control of the use of 19-nortestosterone on these samples. False-positive (not confirmed by gas chromatography-mass spectrometry) results were produced by radioimmunoassay in the urine of castrated pigs and sheep.

Anabolics: the situation in Belgium.

The illegal use of anabolics in 1989-1990 and its control in Belgium are reviewed. After a short presentation of the Belgian legislation and EEC directives, a recent hormone scandal published by a consumer magazine is related and the composition of 17 hormone cocktails found on the black market is given. The strategy of control involves screening of the main artificial anabolics in urine by radioimmunoassay (RIA) and confirmation by thin-layer chromatography (TLC). Samples of fat and injection sites are also examined by TLC. In the future, RIA will probably be replaced by enzyme immunoassay and TLC by mass spectrometry.

Elimination of antithrombin III concentrate in healthy pregnant and preeclamptic women with an acquired antithrombin III deficiency.

The activity elimination half-life of heat-treated antithrombin III (AT III) concentrate was studied in 5 healthy pregnant and 5 preeclamptic women with a documented AT III deficiency. Healthy pregnant women received 1500 units over 20 minutes. Serial blood specimens were obtained over the next 12 hours. The mean (+/- SEM) activity elimination half-life of AT III was 29.4h +/- 3.4h. Preeclamptic subjects had a mean baseline AT III activity of 70.5 +/- 2% (range 61 to 75%). Their activity eliminator half-life after 3000 units of AT III concentrate was 8.5 +/- 1.2h. There was a direct relationship between the pre-concentrate AT III activity level and the AT III activity elimination half-life (r = 0.79, p = 0.01) for all subjects. Based upon parameters calculated from the first infusion, the AT III activity of preeclamptic subjects was maintained by a constant infusion at approximately 100% for 96h. At the conclusion of the infusion, the activity elimination half-life was again measured. A dramatic increase in the activity elimination half-life was demonstrated (433.6h). We conclude that the activity elimination half-life of AT III concentrate is increased during normal pregnancy and further increased in preeclamptic women with an acquired deficiency.

The effect of intravascular transfusion on umbilical venous pressure in anemic fetuses with and without hydrops.

Human fetal umbilical venous pressure was measured during 20 intravascular transfusions performed for treatment of hemolytic anemia. The mean (+/- 1 SEM) gestational age at the time of transfusion was 29.3 +/- 1 weeks and the mean beginning hematocrit was 27% +/- 2%. The mean volume of infused packed red blood cells (70% hematocrit) was 90.3 +/- 7 ml. The mean hematocrit at completion of the procedure was 48% +/- 1%. In nonhydropic fetuses umbilical venous pressure rose progressively from 6.7 +/- 1 mm Hg at the start of transfusion to 10.9 +/- 1 mm Hg at the completion of transfusion (p less than 0.002). However, most fetuses who began the infusion with a normal umbilical venous pressure ended the transfusion with a normal umbilical venous pressure (less than 10 mm Hg). Fetuses with immune hydrops (n = 2) had elevated umbilical venous pressure values before the initiation of transfusion therapy when compared with the first transfusion of nonhydropic fetuses (12.5 +/- 0.5 vs. 5.7 +/- 1 mm Hg, p = 0.01). However, the umbilical venous pressure measurements declined into the normal range within 24 hours of the first transfusion; this normalization was too rapid to be explained by the reversal of liver hypertrophy or portal hypertension. There was no demonstrable relationship between the rise in umbilical venous pressure and either the gestational age, the volume transfused, or the rise in hematocrit. This study demonstrated: (1) In terms of the umbilical venous pressure, direct intravenous infusion of the human anemic fetus is well tolerated; (2) the elevated umbilical venous pressure associated with immune hydrops can correct rapidly with red blood cell replacement.

Normal values for human umbilical venous and amniotic fluid pressures and their alteration by fetal disease.

Umbilical venous and amniotic fluid pressures were measured in 68 human pregnancies at the time that cordocentesis was performed. Normal umbilical venous pressure was unrelated to gestational age and remained within a tight range (5.3 +/- 2.3 mm Hg, mean +/- SD). Fetuses with an elevated umbilical venous pressure had disorders consistent with either hepatomegaly or congestive heart failure. Umbilical venous pressure was significantly increased before treatment in two fetuses with immune hydrops; it rapidly declined with treatment. Neither gestational age nor umbilical venous pressure was significantly different in the groups that received and did not receive pancuronium. There was a strong relationship between amniotic fluid pressure and gestational age in normal pregnancy (r = 0.54, p less than 0.0001). Women with hydramnios had amniotic fluid pressures greater than control subjects (p = 0.0007). This investigation documents normal human amniotic fluid and fetal umbilical venous pressures. These measurements are altered by disease and may prove to be of diagnostic and therapeutic value in the future.

On the influence of hydrophobicity in the SIMS spectra of amino acids in glycerol matrix.

Mass spectrometry is becoming an important method in structure determination of biopolymers. Determination of the nature and the number of the various monomers is an important information for the elucidation of fragmentation patterns. We present here a matrix designed to allow both identification and semi-quantitative measurement of amino acids residues in peptides.