Biomedical subjects

G J Puppels

Publications and source records attributed to G J Puppels.

At least 19 recordsLinked to original sources

PubMed2007

Raman spectroscopic characterization of porcine brain tissue using a single fiber-optic probe.

Accurate targeting of diseased and healthy tissue has significantly been improved by MRI/CT-based navigation systems. Recently, intraoperative MRI navigation systems have proven to be powerful tools for the guidance of the neurosurgical operations. However, the widespread use of such systems is held back by the costs, the time consumption during operation, and the need for MR-compatible surgical devices. Raman spectroscopy is a nondestructive optical technique that enables real-time tissue identification and classification and has proved to be a powerful diagnostic tool in a large number of studies. In the present report, we have investigated the possibility of distinguishing different brain structures by using a single fiber-optic probe to collect Raman scattered light in the high-wavenumber region of the spectrum. For the Raman measurements, 7 pig brains were sliced in the coronal plain and Raman spectra were obtained of 11-19 anatomical structures. Adjacent brain structures could be distinguished based on their Raman spectra, reflecting the differences in their biochemical composition and illustrating the potential Raman spectroscopy holds as a guidance tool during neurosurgical procedures.

Animals↗

PubMed2005

Design and validation of an analyser to measure sulphur hexafluoride gas during respiration.

The study presents the results of the development of an analyser to measure sulphur hexafluoride (SF6) gas in breathing circuits, for application is studies of lung function. The analyser consists of an in-line breathing circuit measurement transducer and a compact unit for signal treatment. The detector unit of the analyser consists of a near-infrared light source, a bandpass filter and a pyro-electrical detector. When incremental steps of SF6 gas between 0 and 2% were presented to the analyser, the maximum deviation from the theoretical calibration curve was calculated to be 0.01% SF6. The step response of the analyser (10-90%) was 250 ms. The sensitivity of the analyser to ambient temperature was 0.01% SF6 degrees C(-1) in the range between 0 and 2% SF6. It is concluded that the analyser presented is accurate, and has a sufficient response speed to be used in clinical measurement settings. Furthermore, the analyser is resistant to changes in temperature, gas flow, orientation and movement, which are likely to occur in clinical measurement settings.

Breath Tests↗

PubMed2005

Rapid identification of Candida spp. in peritonitis patients by Raman spectroscopy.

This prospective study evaluated Raman spectroscopy for the identification of clinically relevant Candida spp. in peritonitis patients. A Raman database was developed by measuring spectra from 93 reference strains belonging to ten different Candida spp. Clinical samples were obtained from the surgical department and intensive care unit of a tertiary university hospital. In total, 88 peritoneal specimens from 45 patients with primary, secondary or tertiary peritonitis were included. Specimens were cultured initially on a selective Sabouraud medium that contained gentamicin to suppress bacterial growth. For conventional identification, a chromogenic medium was used for presumptive identification, followed by use of the Vitek 2 system for definitive identification (requiring a total time of 48-96 h). Raman measurements were taken on overnight cultures from Sabouraud-gentamicin medium. Thirty-one samples were positive for Candida by culture. Using multivariate statistical analyses, a prediction accuracy of 90% was obtained for Raman spectroscopy, which appears to offer an accurate and rapid (12-24 h) alternative for the identification of Candida spp. in peritonitis patients. The reduced turn-around time is of great clinical importance for the treatment of critically ill patients with invasive candidiasis in intensive care units.

Candida↗

PubMed2004

Effect of culture conditions on the achievable taxonomic resolution of Raman spectroscopy disclosed by three Bacillus species.

Confocal micro-Raman spectroscopy requires a minimum of sample handling and no reagents and allows fast identification of microorganisms. Since it reflects the overall molecular composition of the cells, it provides much more information than classical, microbial analyses. However, since the molecular makeup of a cell depends on culture conditions, it can be argued that this will affect the reproducibility and discrimination ability of Raman spectroscopy. We used Bacillus cereus, Bacillus pumilus, and Bacillus licheniformis, which are known to be clearly distinct from each other and each displaying important phenotypic heterogeneity, in a wide variety of culture conditions to analyze this. It is illustrated that the influence of culture conditions on the identification accuracy and taxonomic resolution of Raman spectroscopy is important though the effect on the final identification is limited within the set of stains studied. Furthermore, some conditions even allow for better discrimination than others. From a practical point of view, it is especially important that differences in culturing time (and culturing temperature) can be accommodated.

Bacillus↗

PubMed2004

Raman spectroscopic analysis identifies testicular microlithiasis as intratubular hydroxyapatite.

PURPOSE: As diagnosed by ultrasonography, testicular microlithiasis is associated with various benign and malignant conditions. The molecular constitution of these microliths is largely unknown. Raman spectroscopy provides detailed in situ information about the molecular composition of tissues and to our knowledge it has not been applied to gonadal microliths. We analyzed the molecular composition of gonadal microlithiasis and its surrounding region using Raman spectroscopy in malignant and benign conditions. MATERIALS AND METHODS: Multiple microliths from 6 independent samples diagnosed with gonadal microlithiasis by ultrasound and histologically confirmed were investigated by Raman spectroscopy. The samples included 4 testicular parenchyma samples adjacent to a germ cell tumor (4 seminomas), a gonadoblastoma of a dysgenetic gonad and testicular biopsy of a subfertile male without malignancy. RESULTS: Raman spectroscopic mapping demonstrated that testicular microliths were located within the seminiferous tubule. Glycogen surrounded all microliths in the samples associated with germ cell neoplasm but not in the benign case. The molecular composition of the 26 microliths in all 6 conditions was pure hydroxyapatite. CONCLUSIONS: Microliths in the testis are located in the seminiferous tubules and composed of hydroxyapatite. In cases of germ cell neoplasm they co-localize with glycogen deposits.

Calculi↗

PubMed2003

Combined in vivo confocal Raman spectroscopy and confocal microscopy of human skin.

In vivo confocal Raman spectroscopy is a noninvasive optical method to obtain detailed information about the molecular composition of the skin with high spatial resolution. In vivo confocal scanning laser microscopy is an imaging modality that provides optical sections of the skin without physically dissecting the tissue. A combination of both techniques in a single instrument is described. This combination allows the skin morphology to be visualized and (subsurface) structures in the skin to be targeted for Raman measurements. Novel results are presented that show detailed in vivo concentration profiles of water and of natural moisturizing factor for the stratum corneum that are directly related to the skin architecture by in vivo cross-sectional images of the skin. Targeting of skin structures is demonstrated by recording in vivo Raman spectra of sweat ducts and sebaceous glands in situ. In vivo measurements on dermal capillaries yielded high-quality Raman spectra of blood in a completely noninvasive manner. From the results of this exploratory study we conclude that the technique presented has great potential for fundamental skin research, pharmacology (percutaneous transport), clinical dermatology, and cosmetic research, as well as for noninvasive analysis of blood analytes, including glucose.

Arm↗

PubMed2003

A fast, digitally controlled flow proportional gas injection system for studies in lung function.

The aim of this paper is to describe a device for flow proportional injection of tracer gas in the lungs of mechanically ventilated patients. This device may then be used for the study of the multiple breath indicator gas washout technique to determine the end-expiratory lung volume. Such a tracer gas injection device may also be used in the study of other techniques that rely on uptake and elimination of tracer gas by the lungs. In this paper, an injector is described which enables injection of indicator gas at a predetermined concentration in a breathing circuit independent of the type of breathing. The presented setup uses a control computer to produce steering signals to a multivalve array in proportion to the input breathing signals. The multivalve array consists of ten circular valves, each with a different diameter, which can be opened or closed individually according to the input signal of the array. By opening of a certain combination of valves an amount of sulphur hexafluoride gas proportional to the inspiratory breathing signal is released. The rate of transmission between the components of the injection system was 80 Hz. The injector has a full flow range between 0-10 L/min. The delay time between the breathing signal and the flow response was 70 ms. The aimed washin gas concentration of 1% SF6 was achieved after 0.5 s. The study describes the results of tests to determine valve-flow ratios, step response and dynamic response of the injector. The flow output response of the injector system was shown to increase in input frequencies above 3 Hz. The valve flow ratios showed the largest relative deviation in the two smallest valves of the 10 valve array, respectively 0.005 L/min (25%) and 0.002 L/min (20%). We conclude that the injector can achieve a stable concentration of indicator gas in a breathing system with an accuracy of 0.005 L/min to execute the multiple breath indicator washout test in human subjects. The results of the study indicate that the injector may be of use in other application fields in respiratory physiology in which breathing circuit injection of indicator gas is required.

Algorithms↗

PubMed2003

Prospective study of the performance of vibrational spectroscopies for rapid identification of bacterial and fungal pathogens recovered from blood cultures.

Rapid identification of microbial pathogens reduces infection-related morbidity and mortality of hospitalized patients. Raman spectra and Fourier transform infrared (IR) spectra constitute highly specific spectroscopic fingerprints of microorganisms by which they can be identified. Little biomass is required, so that spectra of microcolonies can be obtained. A prospective clinical study was carried out in which the causative pathogens of bloodstream infections in hospitalized patients were identified. Reference libraries of Raman and IR spectra of bacterial and yeast pathogens highly prevalent in bloodstream infections were created. They were used to develop identification models based on linear discriminant analysis and artificial neural networks. These models were tested by carrying out vibrational spectroscopic identification in parallel with routine diagnostic phenotypic identification. Whereas routine identification has a typical turnaround time of 1 to 2 days, Raman and IR spectra of microcolonies were collected 6 to 8 h after microbial growth was detected by an automated blood culture system. One hundred fifteen samples were analyzed by Raman spectroscopy, of which 109 contained bacteria and 6 contained yeasts. One hundred twenty-one samples were analyzed by IR spectroscopy. Of these, 114 yielded bacteria and 7 were positive for yeasts. High identification accuracy was achieved in both the Raman (92.2%, 106 of 115) and IR (98.3%, 119 of 121) studies. Vibrational spectroscopic techniques enable simple, rapid, and accurate microbial identification. These advantages can be easily transferred to other applications in diagnostic microbiology, e.g., to accelerate identification of fastidious microorganisms.

Bacteria↗

PubMed2003

On-line detection of cholesterol and calcification by catheter based Raman spectroscopy in human atherosclerotic plaque ex vivo.

BACKGROUND: Raman spectroscopy has the unique potential to detect and quantify cholesterol and calcification in an atherosclerotic plaque in vivo. OBJECTIVE: To evaluate the sensitivity and specificity of this technique for detecting cholesterol or calcification in human coronary artery and aorta specimens ex vivo, using a compact clinical fibreoptic based Raman system developed for in vivo applications. DESIGN: From nine coronary arteries and four aorta specimens, 114 sites were evaluated for the presence of cholesterol and calcification by Raman spectroscopy and standard histology. Raman spectra were acquired and evaluated on-line in around five seconds. RESULTS: The correlation between Raman spectroscopy and histology was r = 0.68 for cholesterol and r = 0.71 calcification in the plaque (p < 0.0001). Sensitivity and specificity for detecting cholesterol and calcification were excellent: receiver operating characteristic (ROC) analysis for each of the components revealed areas under the curves of > 0.92 (p < 0.0001). At the optimal cut-off values determined by ROC analysis, positive predictive values of > 80% and negative predictive values of > 90% were obtained. CONCLUSIONS: On-line real time catheter based Raman spectroscopy detects accumulation of cholesterol and calcification in atherosclerotic plaque with high sensitivity and specificity.

Calcinosis↗

PubMed2002

Medical applications of Raman spectroscopy: from proof of principle to clinical implementation.

Raman spectroscopy has recently been applied ex vivo and in vivo to address various biomedical issues such as the early detection of cancers, monitoring of the effect of various agents on the skin, determination of atherosclerotic plaque composition, and rapid identification of pathogenic microorganisms. This leap in the number of applications and the number of groups active in this field has been facilitated by several technological advancements in lasers, CCD detectors, and fiber-optic probes. However, most of the studies are still at the proof of concept stage. We present a discussion on the status of the field today, as well as the problems and issues that still need to be resolved to bring this technology to hospital settings (i.e., the medical laboratory, surgical suites, or clinics). Taken from the viewpoint of clinicians and medical analysts, the potential of Raman spectroscopic techniques as new tools for biomedical applications is discussed and a path is proposed for the clinical implementation of these techniques.

Arteriosclerosis↗

PubMed2002

Influence of Ca2+ cations on low pH-induced DNA structural transitions.

A confocal Raman microspectrometer was used to investigate the influence of Ca2+ cations on low pH-induced DNA structural changes. The effects of Ca2+ cations on the protonation mechanism of opening AT and changing the protonation of GC base pairs in DNA are discussed. Based on the observation that the midpoint of the transition of Watson-Crick GC base pairs to protonated GC base pairs lies at around pH 3 (analyzing the 681 cm(-1) line), measurements were carried out on calf thymus DNA at neutral pH and pH 3 in the presence of low and high concentrations of Ca2+ cations. Raman spectra show that low concentrations of Ca2+ cations partially protect DNA against protonation of cytosine (characteristic line at 1262 cm(-1)) and do not protect adenine (characteristic line at 1304 cm(-1)) and the N(7) of guanine (line at 1488 cm(-1)) against binding of H+. High Ca2+ concentrations can prevent protonation of cytosine and protonation of adenine (little disruption of AT pairs). Analyzing the line at 1488 cm(-1), which obtains most of its intensity from a guanine vibration, high salt was also found to protect the N(7) of guanine against protonation.

Animals↗

PubMed2002

Identification of medically relevant microorganisms by vibrational spectroscopy.

In the recent years, vibrational spectroscopies (infrared and Raman spectroscopy) have been developed for all sorts of analyses in microbiology. Important features of these methods are the relative ease with which measurements can be performed. Furthermore, in order to obtain infrared or Raman spectra, there is only a limited amount of sample handling involved without the need for expensive chemicals, labels or dyes. Here, we review the potential application of vibrational spectroscopies for the use in medical microbiology. After describing some of the basics of the techniques, considerations on reproducibility and standardisation are presented. Finally, the use of infrared and Raman spectroscopy for the (rapid) identification of medically relevant microorganisms is discussed. It can be concluded that vibrational spectroscopies show high potential as novel methods in medical microbiology.

Bacterial Infections↗

PubMed2002

Identification of bladder wall layers by Raman spectroscopy.

PURPOSE: We explored the applicability of Raman spectroscopy to in situ investigation of bladder wall tissue. MATERIALS AND METHODS: Bladder wall tissue was obtained from a guinea pig model and frozen sections were used for Raman spectroscopic investigations. From each section 500 to 700 spectra were obtained in a 2-dimensional grid spanning the urothelium, lamina propria and muscle layer. The data set of spectra was subdivided into groups of similar spectra by a cluster analysis algorithm. With each group assigned a different color Raman maps of frozen sections were constructed based on group membership of measured spectra. These maps were then compared with histological and histochemical data obtained from hematoxylin and eosin and immunohistochemical staining for collagen I and III and for smooth muscle actin to correlate Raman spectral features with bladder wall structure and molecular composition. RESULTS: Urothelium, lamina propria and muscle layers could be clearly distinguished based on Raman spectra. Lamina propria spectra were dominated by signal contributions of collagen and the smooth muscle layer showed strong signal contributions of actin. The urothelium had a relatively strong lipid signal contribution. CONCLUSIONS: These results and the fact that Raman spectroscopy is rapidly evolving into a technology that can be applied in vivo by thin, flexible fiberoptic catheters indicate that prospects are good for in vivo analysis of the molecular composition of the normal and pathological bladder without biopsies.

Actins↗

PubMed2002

Rapid identification of Candida species by confocal Raman microspectroscopy.

Candida species are important nosocomial pathogens associated with high mortality rates. Rapid detection and identification of Candida species can guide a clinician at an early stage to prescribe antifungal drugs or to adjust empirical therapy when resistant species are isolated. Confocal Raman microspectroscopy is highly suitable for the rapid identification of Candida species, since Raman spectra can be directly obtained from microcolonies on a solid culture medium after only 6 h of culturing. In this study, we have used a set of 42 Candida strains comprising five species that are frequently encountered in clinical microbiology to test the feasibility of the technique for the rapid identification of Candida species. The procedure was started either from a culture on Sabouraud medium or from a positive vial of an automated blood culture system. Prior to Raman measurements, strains were subcultured on Sabouraud medium for 6 h to form microcolonies. Using multivariate statistical analyses, a high prediction accuracy (97 to 100%) was obtained with the Raman method. Identification with Raman microspectroscopy may therefore be significantly faster than identification with commercial identification systems that allow various species to be identified and that often require 24 to 48 h before a reliable identification is obtained. We conclude that confocal Raman microspectroscopy offers a rapid, accurate, and easy-to-use alternative for the identification of clinically relevant Candida species.

Algorithms↗

PubMed2001

Determination of water concentration in brain tissue by Raman spectroscopy.

Brain edema is one of the most common morbidity factors in patients with intracranial neoplasms and cerebrovascular pathology. Monitoring of intracranial pressure gives only an indirect and global measure of brain swelling. We have made an assessment of the applicability of Raman spectroscopy as an alternative method for assessing brain edema, which measures the water concentration in the tissue directly. Partial least-squares models were developed on the basis of Raman spectra measured in the 2600-3800-cm(-1) region, which predict the water fraction of brain tissue in the 0.75-0.95 range, with an accuracy better than 0.01.

Animals↗

PubMed2001

Vibrational spectroscopic characterization of wild growing mushrooms and toadstools.

Recently, there has been increase of general interest in fungi because of the possible medical applications of their polysaccharide constituents called glucans, some of which are reported to have immunomodulatory properties. Since an extraction method can change the chemical composition of a substance, especially a delicate one such as fungal thallus, it is necessary and useful to know more about the studied matter in advance in order to choose the chemical procedure properly. We demonstrated the usefulness of vibrational spectroscopy in identifying different glucan types in various parts of intact fruiting bodies of Asco- and Basidiomycetes. Fourier transform-infrared (FT-IR) spectroscopy was used for obtaining vibrational spectra of spores and fruiting bodies of more than 70 species belonging to 37 different genera of wild growing mushrooms. The list of the bands in 750-950 cm(-1) interval, assigned to alpha- and beta-glucans, is provided for all species studied. Vibrational spectra in the interval 1000-1200 cm(-1) could serve as an indicator of mushroom genus, although particular species cannot be identified spectroscopically. Great similarities in spectra of spores of the same genus, but different species, e.g. Tricholoma album and Trichloma sulphureum, were observed. On the other hand, spectra of cap, stalk and spores of the same mushroom show great differences, indicating variety in the chemical composition of different parts of the same fruiting body.

Ascomycota↗

PubMed2001

In vivo confocal Raman microspectroscopy of the skin: noninvasive determination of molecular concentration profiles.

Confocal Raman spectroscopy is introduced as a noninvasive in vivo optical method to measure molecular concentration profiles in the skin. It is shown how it can be applied to determine the water concentration in the stratum corneum as a function of distance to the skin surface, with a depth resolution of 5 microm. The resulting in vivo concentration profiles are in qualitative and quantitative agreement with published data, obtained by in vitro X-ray microanalysis of skin samples. Semi-quantitative concentration profiles were determined for the major constituents of natural moisturizing factor (serine, glycine, pyrrolidone-5-carboxylic acid, arginine, ornithine, citrulline, alanine, histidine, urocanic acid) and for the sweat constituents lactate and urea. A detailed description is given of the signal analysis methodology that enables the extraction of this information from the skin Raman spectra. No other noninvasive in vivo method exists that enables an analysis of skin molecular composition as a function of distance to the skin surface with similar detail and spatial resolution. Therefore, it may be expected that in vivo confocal Raman spectroscopy will find many applications in basic and applied dermatologic research.

Adult↗

PubMed2001

Investigating microbial (micro)colony heterogeneity by vibrational spectroscopy.

Fourier transform infrared and Raman microspectroscopy are currently being developed as new methods for the rapid identification of clinically relevant microorganisms. These methods involve measuring spectra from microcolonies which have been cultured for as little as 6 h, followed by the nonsubjective identification of microorganisms through the use of multivariate statistical analyses. To examine the biological heterogeneity of microorganism growth which is reflected in the spectra, measurements were acquired from various positions within (micro)colonies cultured for 6, 12, and 24 h. The studies reveal that there is little spectral variance in 6-h microcolonies. In contrast, the 12- and 24-h cultures exhibited a significant amount of heterogeneity. Hierarchical cluster analysis of the spectra from the various positions and depths reveals the presence of different layers in the colonies. Further analysis indicates that spectra acquired from the surface of the colonies exhibit higher levels of glycogen than do the deeper layers of the colony. Additionally, the spectra from the deeper layers present with higher RNA levels than the surface layers. Therefore, the 6-h colonies with their limited heterogeneity are more suitable for inclusion in a spectral database to be used for classification purposes. These results also demonstrate that vibrational spectroscopic techniques can be useful tools for studying the nature of colony development and biofilm formation.

Candida albicans↗