Publications by authors named "Maurice C Aalders"

72 Publications

Late Gadolinium Enhancement Cardiovascular Magnetic Resonance Assessment of Substrate for Ventricular Tachycardia With Hemodynamic Compromise.

Front Cardiovasc Med 2021 26;8:744779. Epub 2021 Oct 26.

School of Biomedical Engineering and Imaging Sciences, King's College, London, United Kingdom.

The majority of data regarding tissue substrate for post myocardial infarction (MI) VT has been collected during hemodynamically tolerated VT, which may be distinct from the substrate responsible for VT with hemodynamic compromise (VT-HC). This study aimed to characterize tissue at diastolic locations of VT-HC in a porcine model. Late Gadolinium Enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging was performed in eight pigs with healed antero-septal infarcts. Seven pigs underwent electrophysiology study with venous arterial-extra corporeal membrane oxygenation (VA-ECMO) support. Tissue thickness, scar and heterogeneous tissue (HT) transmurality were calculated at the location of the diastolic electrograms of mapped VT-HC. Diastolic locations had median scar transmurality of 33.1% and a median HT transmurality 7.6%. Diastolic activation was found within areas of non-transmural scar in 80.1% of cases. Tissue activated during the diastolic component of VT circuits was thinner than healthy tissue (median thickness: 5.5 mm vs. 8.2 mm healthy tissue, < 0.0001) and closer to HT (median distance diastolic tissue: 2.8 mm vs. 11.4 mm healthy tissue, < 0.0001). Non-scarred regions with diastolic activation were closer to steep gradients in thickness than non-scarred locations with normal EGMs (diastolic locations distance = 1.19 mm vs. 9.67 mm for non-diastolic locations, < 0.0001). Sites activated late in diastole were closest to steep gradients in tissue thickness. Non-transmural scar, mildly decreased tissue thickness, and steep gradients in tissue thickness represent the structural characteristics of the diastolic component of reentrant circuits in VT-HC in this porcine model and could form the basis for imaging criteria to define ablation targets in future trials.
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http://dx.doi.org/10.3389/fcvm.2021.744779DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8576410PMC
October 2021

Correction to: A literature review and novel theoretical approach on the optical properties of whole blood.

Lasers Med Sci 2021 Oct 25. Epub 2021 Oct 25.

Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE, Amsterdam, The Netherlands.

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http://dx.doi.org/10.1007/s10103-021-03361-7DOI Listing
October 2021

Individualised and non-contact post-mortem interval determination of human bodies using visible and thermal 3D imaging.

Nat Commun 2021 10 14;12(1):5997. Epub 2021 Oct 14.

Department of Biomedical Engineering and Physics, Amsterdam UMC Location AMC, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.

Determining the time since death, i.e., post-mortem interval (PMI), often plays a key role in forensic investigations. The current standard PMI-estimation method empirically correlates rectal temperatures and PMIs, frequently necessitating subjective correction factors. To overcome this, we previously developed a thermodynamic finite-difference (TFD) algorithm, providing a rigorous method to simulate post-mortem temperatures of bodies assuming a straight posture. However, in forensic practice, bodies are often found in non-straight postures, potentially limiting applicability of this algorithm in these cases. Here, we develop an individualised approach, enabling PMI reconstruction for bodies in arbitrary postures, by combining photogrammetry and TFD modelling. Utilising thermal photogrammetry, this approach also represents the first non-contact method for PMI reconstruction. The performed lab and crime scene validations reveal PMI reconstruction accuracies of 0.26 h ± 1.38 h for true PMIs between 2 h and 35 h and total procedural durations of ~15 min. Together, these findings broaden the potential applicability of TFD-based PMI reconstruction.
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http://dx.doi.org/10.1038/s41467-021-26318-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8517003PMC
October 2021

Improving the visualization of fingermarks using multi-target immunolabeling.

Forensic Sci Int 2021 Jul 8;324:110804. Epub 2021 May 8.

Department of Biomedical Engineering and Physics, University of Amsterdam, Amsterdam Medical Centers, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; Co van Ledden Hulsebosch Center (CLHC), University of Amsterdam, 1098 XH Amsterdam, The Netherlands.

The development of fingermarks is an important step in visualizing ridge patterns for individualization purposes. Immunolabeling can be applied to fingermarks to selectively and sensitively detect antigens in fingermarks, and can be used as a developing method to visualize fingermarks. In this study we investigated single (the detection of one antigen) and multiple targeting approaches (the detection of multiple antigens simultaneously) to improve fingermark development. The detection of dermcidin, an antimicrobial peptide, was used as the gold standard to compare single and multi-target detection of keratins, albumin and/or dermcidin. Single detection of dermcidin and albumin mostly resulted in clear ridge details and/or pore detection, whereas the single keratin detection resulted in a poor visualization of the fingermarks. The multi-target approach in which both dermcidin and albumin were targeted, resulted in improved fingermark development compared to single dermcidin detection. Therefore, we recommend the use of multi-target detection consisting of anti-dermcidin and anti-albumin when using immunolabeling as fingermark development technique. Additionally, the optimized multi-target approach was tested as a pre- and post-development technique in combination with powder dusting and cyanoacrylate fuming. Immunolabeling has not been implemented yet in forensic case work, however we expect that immunolabeling can be used to redevelop poorly developed and/or smudged fingermarks in the nearby future. Currently, an ongoing pilot-study is being conducted in collaboration with the Dutch police.
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http://dx.doi.org/10.1016/j.forsciint.2021.110804DOI Listing
July 2021

The compatibility of immunolabeling with STR profiling.

Forensic Sci Int Genet 2021 05 15;52:102485. Epub 2021 Feb 15.

Amsterdam UMC, University of Amsterdam, Biomedical Engineering & Physics, Meibergdreef 9, Amsterdam, The Netherlands.. Electronic address:

Immunolabeling is a technique, which has recently been introduced to enhance the quality of developed fingermarks and subsequently strengthen the evidential value. The effect of this method on subsequent DNA analysis, however, has not been explored yet. Therefore, the current pilot study aimed to determine whether STR profiling is possible after immunolabeling. Since immunolabeling involves washing steps which could reduce DNA quantities, the use of different fixatives including methanol, formaldehyde and universal molecular fixative (UMFIX) were investigated. STR profiles from the (immunolabeled) fingermarks were generated after four days and four weeks by a direct PCR method to enable comparison of relatively fresh and old fingermarks. The fingermarks were deposited on diverse forensically relevant substrates, including glass, metal and tile. STR profiles could be recovered for all tested fixatives with no significant difference in performance. However, the mean number of detected alleles was the highest when methanol was used for fixation. Furthermore, immunolabeling on aged fingermarks (4 weeks) was also possible, but the number of detected alleles showed a non-significant decrease. DNA could be recovered from deposits on all substrates, of which glass showed the highest mean number of detected alleles followed by metal and tile.
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http://dx.doi.org/10.1016/j.fsigen.2021.102485DOI Listing
May 2021

Bayesian analysis of depth resolved OCT attenuation coefficients.

Sci Rep 2021 01 26;11(1):2263. Epub 2021 Jan 26.

Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

Optical coherence tomography (OCT) is an optical technique which allows for volumetric visualization of the internal structures of translucent materials. Additional information can be gained by measuring the rate of signal attenuation in depth. Techniques have been developed to estimate the rate of attenuation on a voxel by voxel basis. This depth resolved attenuation analysis gives insight into tissue structure and organization in a spatially resolved way. However, the presence of speckle in the OCT measurement causes the attenuation coefficient image to contain unrealistic fluctuations and makes the reliability of these images at the voxel level poor. While the distribution of speckle in OCT images has appeared in literature, the resulting voxelwise corruption of the attenuation analysis has not. In this work, the estimated depth resolved attenuation coefficient from OCT data with speckle is shown to be approximately exponentially distributed. After this, a prior distribution for the depth resolved attenuation coefficient is derived for a simple system using statistical mechanics. Finally, given a set of depth resolved estimates which were made from OCT data in the presence of speckle, a posterior probability distribution for the true voxelwise attenuation coefficient is derived and a Bayesian voxelwise estimator for the coefficient is given. These results are demonstrated in simulation and validated experimentally.
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http://dx.doi.org/10.1038/s41598-021-81713-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7838413PMC
January 2021

The applicability of forensic time since death estimation methods for buried bodies in advanced decomposition stages.

PLoS One 2020 9;15(12):e0243395. Epub 2020 Dec 9.

Institute of Legal Medicine, Goethe-University Frankfurt, Frankfurt, Germany.

Estimation of the postmortem interval in advanced postmortem stages is a challenging task. Although there are several approaches available for addressing postmortem changes of a (human) body or its environment (ecologically and/or biochemically), most are restricted to specific timeframes and/or individual and environmental conditions. It is well known, for instance, that buried bodies decompose in a remarkably different manner than on the ground surface. However, data on how established methods for PMI estimation perform under these conditions are scarce. It is important to understand whether and how postmortem changes are affected under burial conditions, if corrective factors could be conceived, or if methods have to be excluded for respective cases. We present the first multi-methodological assessment of human postmortem decomposition carried out on buried body donors in Europe, at the Amsterdam Research Initiative for Sub-surface Taphonomy and Anthropology (ARISTA) in the Netherlands. We used a multidisciplinary approach to investigate postmortem changes of morphology, skeletal muscle protein decomposition, presence of insects and other necrophilous animals as well as microbial communities (i.e., microbiomes) from August to November 2018 associated with two complete body exhumations and eight partial exhumations. Our results clearly display the current possibilities and limitations of methods for PMI estimation in buried remains and provide a baseline for future research and application.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0243395PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7725292PMC
January 2021

Phosphorescence of thermally altered human bone.

Int J Legal Med 2021 May 19;135(3):1025-1034. Epub 2020 Nov 19.

Maastricht University, Maastricht, The Netherlands.

Bone has photoluminescent characteristics that can aid the analysis of thermally altered human skeletal remains as part of the forensic anthropological investigation. Photoluminescence stands collectively for fluorescence and phosphorescence. Because the difference in lifetime between fluorescence and phosphorescence is usually in the range of nano- to microseconds, it is only possible to visually determine whether bone phosphoresces when the lifetime is long enough to be observed. For this study, a distinction was made between long-decay and short-decay phosphorescence. So far, it was unknown whether (thermally altered) human bone emits long-decay phosphorescence after being illuminated and, thus, whether phosphorescence contributes to the observed photoluminescence. If so, whether the observable phosphorescence is dependent on temperature, exposure duration, surrounding medium, bone type, skeletal element, and excitation light and could aid the temperature estimation of heated bone fragments. In this study, bone samples were subjected to heat in the range of from room temperature to 900 °C for various durations in either air or adipose as surrounding medium. In addition, different skeletal elements of a human cadaver were recollected after cremation in a crematorium. Both sample collections were illuminated with light of different bandwidths and visually inspected for phosphorescence and photoluminescence. The samples were scored by means of a scoring index for the intensity of long-decay phosphorescence and photographically documented. The results show that thermally altered human bone fragments do phosphoresce. The observed phosphorescence is more dependent on temperature than on exposure duration, surrounding medium or skeletal element. Of the used wavelength bands, ultraviolet light provided the most temperature-related information, showing changes in both phosphorescence intensity and emission spectrum. Long-decay phosphorescence and fluorescence with short-decay phosphorescence coincide; however, there are also temperature-dependent differences. It is therefore concluded that phosphorescence contributes to the observable photoluminescence and that the visibly observable phosphorescent characteristics can aid the temperature estimation of cremated human skeletal fragments.
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http://dx.doi.org/10.1007/s00414-020-02455-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8036218PMC
May 2021

Amsterdam Research Initiative for Sub-surface Taphonomy and Anthropology (ARISTA) - A taphonomic research facility in the Netherlands for the study of human remains.

Forensic Sci Int 2020 Dec 6;317:110483. Epub 2020 Sep 6.

Dept. of Biomedical Engineering and Physics, Amsterdam University Medical Centers - location Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, P.O.Box 22660, 1100 DD, Amsterdam, the Netherlands; CLHC-Amsterdam Center for Forensic Science and Medicine, Science Park - Building 904 (Room C2.243), 1098 XH, Amsterdam, the Netherlands. Electronic address:

A taphonomic research facility for the study of human remains was recently realized in Amsterdam, the Netherlands, to systematically investigate the decomposition of the human body under known conditions. Governmental authorization was obtained to make use of the body donation program of the Amsterdam University Medical Centers, location Academic Medical Center, for this specific purpose. In contrast to the small number of comparable initiatives elsewhere, this facility specifically allows for the study of buried bodies e.g. with the use of telemetry and remote sensing. Here, we discuss the concept of body donation in the Netherlands, its role in taphonomic research, and the sequence of events that preceded the realization of this facility, which is the first of its kind in Europe. In addition to offering novel research options to the scientific community, we hope that it will also pave the way for the successful realization of similar initiatives in other locations.
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http://dx.doi.org/10.1016/j.forsciint.2020.110483DOI Listing
December 2020

Reconstructing the time since death using noninvasive thermometry and numerical analysis.

Sci Adv 2020 May 29;6(22):eaba4243. Epub 2020 May 29.

Department of Biomedical Engineering and Physics, Amsterdam UMC, location AMC, University of Amsterdam, Meibergdreef 9, 1105AZ Amsterdam, Netherlands.

The early postmortem interval (PMI), i.e., the time shortly after death, can aid in the temporal reconstruction of a suspected crime and therefore provides crucial information in forensic investigations. Currently, this information is often derived from an empirical model (Henssge's nomogram) describing posthumous body cooling under standard conditions. However, nonstandard conditions necessitate the use of subjective correction factors or preclude the use of Henssge's nomogram altogether. To address this, we developed a powerful method for early PMI reconstruction using skin thermometry in conjunction with a comprehensive thermodynamic finite-difference model, which we validated using deceased human bodies. PMIs reconstructed using this approach, on average, deviated no more than ±38 minutes from their corresponding true PMIs (which ranged from 5 to 50 hours), significantly improving on the ±3 to ±7 hours uncertainty of the gold standard. Together, these aspects render this approach a widely applicable, i.e., forensically relevant, method for thermometric early PMI reconstruction.
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http://dx.doi.org/10.1126/sciadv.aba4243DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7259946PMC
May 2020

Erratum to "The use of crime scene detection dogs to locate semen stains on different types of fabric" [Forensic Sci. Int. 302C (2020) 109907].

Forensic Sci Int 2020 04 5;309:110201. Epub 2020 Mar 5.

University of Amsterdam, Biomedical Engineering and Physics, Amsterdam University Medical Centers, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands; Co van Ledden Hulsebosch Center (CLHC), University of Amsterdam, 1098 XH Amsterdam, the Netherlands.

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http://dx.doi.org/10.1016/j.forsciint.2020.110201DOI Listing
April 2020

Pilot feasibility study of in vivo intraoperative quantitative optical coherence tomography of human brain tissue during glioma resection.

J Biophotonics 2019 10 15;12(10):e201900037. Epub 2019 Jul 15.

Department of Biomedical Engineering & Physics, Amsterdam UMC, University of Amsterdam, Amsterdam Cardiovascular Sciences, Cancer Center Amsterdam, Amsterdam, The Netherlands.

This study investigates the feasibility of in vivo quantitative optical coherence tomography (OCT) of human brain tissue during glioma resection surgery in six patients. High-resolution detection of glioma tissue may allow precise and thorough tumor resection while preserving functional brain areas, and improving overall survival. In this study, in vivo 3D OCT datasets were collected during standard surgical procedure, before and after partial resection of the tumor, both from glioma tissue and normal parenchyma. Subsequently, the attenuation coefficient was extracted from the OCT datasets using an automated and validated algorithm. The cortical measurements yield a mean attenuation coefficient of 3.8 ± 1.2 mm for normal brain tissue and 3.6 ± 1.1 mm for glioma tissue. The subcortical measurements yield a mean attenuation coefficient of 5.7 ± 2.1 and 4.5 ± 1.6 mm for, respectively, normal brain tissue and glioma. Although the results are inconclusive with respect to trends in attenuation coefficient between normal and glioma tissue due to the small sample size, the results are in the range of previously reported values. Therefore, we conclude that the proposed method for quantitative in vivo OCT of human brain tissue is feasible during glioma resection surgery.
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http://dx.doi.org/10.1002/jbio.201900037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7065626PMC
October 2019

Colourimetric analysis of thermally altered human bone samples.

Sci Rep 2019 06 20;9(1):8923. Epub 2019 Jun 20.

Maastricht University, Maastricht, The Netherlands.

At this moment, no method is available to objectively estimate the temperature to which skeletal remains have been exposed during a fire. Estimating this temperature can provide crucial information in a legal investigation. Exposure of bone to heat results in observable and measurable changes, including a change in colour. To determine the exposure temperature of experimental bone samples, heat related changes in colour were systemically studied by means of image analysis. In total 1138 samples of fresh human long bone diaphysis and epiphysis, varying in size, were subjected to heat ranging from room temperature to 900 °C for various durations and in different media. The samples were scanned with a calibrated flatbed scanner and photographed with a Digital Single Lens Reflex camera. Red, Green, Blue values and Lightness, A-, and B-coordinates were collected for statistical analysis. Cluster analysis showed that discriminating thresholds for Lightness and B-coordinate could be defined and used to construct a model of decision rules. This model enables the user to differentiate between seven different temperature clusters with relatively high precision and accuracy. The proposed decision model provides an objective, robust and non-destructive method for estimating the exposure temperature of heated bone samples.
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http://dx.doi.org/10.1038/s41598-019-45420-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6586926PMC
June 2019

Estimating the Time of Deposition of Semen Traces using Fluorescence Protein-Lipid Oxidation Signatures.

Anal Chem 2019 03 14;91(5):3204-3208. Epub 2019 Feb 14.

Department of Biomedical Engineering and Physics, Amsterdam University Medical Centers , University of Amsterdam , Meibergdreef 9 , 1105 AZ Amsterdam , The Netherlands.

In the forensic field, knowledge about the time of deposition of semen traces is extremely valuable to law enforcement agencies to assess the relevance of the traces and the validity of witness testimonies. However, currently, no method exists that is able to estimate the time of deposition of semen stains, due to the complex chemistry of the constituents and variation in degradation patterns. Here, we demonstrate a non-contact age estimation method to assess the time of deposition of semen stains using fluorescence spectroscopy. Protein-lipid oxidation reactions were monitored in semen stains over time using protein fluorescence and fluorescent oxidation product signatures to reveal distinctive aging patterns. On the basis of the relative amounts of these fluorescent products and the rate at which they are converted, successful age estimation was achieved up to a value of 16 days, with a median absolute error of 1.7 days. We demonstrate here a new tool that can fill the current gap in intelligence about the age of semen traces that has been challenging the forensic community worldwide.
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http://dx.doi.org/10.1021/acs.analchem.8b05625DOI Listing
March 2019

Prediction of DNA concentration in fingermarks using autofluorescence properties.

Forensic Sci Int 2019 Feb 14;295:128-136. Epub 2018 Dec 14.

University of Amsterdam, Biomedical Engineering and Physics, Amsterdam University Medical Centers, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address:

During criminal investigations trace DNA samples, including fingermarks, are submitted to laboratories for short tandem repeat (STR) analysis. For most common STR analysis systems a minimum amount of input DNA is required. Upon intake by the forensic laboratory the DNA concentration is estimated using quantitative polymerase chain reaction (qPCR) analysis after which most fingermarks are excluded. To tackle the problem of unnecessary processing in the lab, our study aimed to develop a method, which is able to predict the DNA content in fingermarks directly at the crime scene. Upon excitation with a UV Crime-lite, fingermark residues have autofluorescent properties. We hypothesize that the intensity of the autofluorescence signal of the fingermark content correlates to the DNA concentration in fingermarks. In this study, 164 fingermarks were examined on their autofluorescence intensity when excited at 365nm, the number of nucleated cells, their DNA concentration and the completeness of the STR profiles. No significant correlation was observed between the DNA concentration in fingermarks and the autofluorescence signal, indicating that a high amount of autofluorescence, thus a high amount of biomaterial, does not necessarily guarantee a higher amount of DNA. In addition, the completeness of the STR profiles did not correlate to the autofluorescence signal of fingermarks. A moderate correlation was found between the predicted DNA quantity, based on the number of nucleated cells and the DNA quantity. In summary, the autofluorescence signal of fingermarks cannot directly be used as a guide to select fingermarks for DNA analysis directly at the crime scene. However, predicting the amount of DNA using a sensitive and specific DNA staining method can probably be used to estimate the DNA concentration in touch samples.
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http://dx.doi.org/10.1016/j.forsciint.2018.12.005DOI Listing
February 2019

Identification and detection of protein markers to differentiate between forensically relevant body fluids.

Forensic Sci Int 2018 Sep 24;290:196-206. Epub 2018 Jul 24.

University of Amsterdam, Biomedical Engineering and Physics, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands. Electronic address:

The identification of body fluids at a crime scene is an important aspect of forensic casework analysis, being a source for investigative leads and contributing to case evidence. Yet, current methods for the forensic identification of body fluids suffer from several limitations, ranging from poor sensitivity and specificity, to sample destruction and interference with subsequent DNA analysis. Moreover, current identification assays target only one body fluid at the time. Besides being inefficient in terms of time, money and sample consumption, poor identification methods can also negatively influence the outcome of a (court) case. In this study, eleven potential protein biomarkers and antibodies were selected and assessed on their suitability for serving as identification markers, as a first step towards the development of a new multiplex protein-based body fluid identification assay relying on antigen-antibody interactions. Performing antibody-based dot blot assays, the specificity of the biomarkers for their target body fluids was evaluated, and biomarker detection was studied in diluted, mixed, aged and simulated casework samples. Hereby, nine out of eleven markers were identified as promising biomarkers to identify blood, semen, saliva, urine and sweat. With the identification of these targets and detection antibodies, a major step forward has been taken towards the development of a highly sensitive and specific, fast and non-labour-intensive protein-based body fluid identification assay, suitable for on-site analysis and able to test for multiple body fluids in a single reaction.
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http://dx.doi.org/10.1016/j.forsciint.2018.07.013DOI Listing
September 2018

Correction for the Hematocrit Bias in Dried Blood Spot Analysis Using a Nondestructive, Single-Wavelength Reflectance-Based Hematocrit Prediction Method.

Anal Chem 2018 02 17;90(3):1795-1804. Epub 2018 Jan 17.

Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University , Ottergemse-steenweg 460, Ghent 9000, Belgium.

The hematocrit (Hct) effect is one of the most important hurdles currently preventing more widespread implementation of quantitative dried blood spot (DBS) analysis in a routine context. Indeed, the Hct may affect both the accuracy of DBS methods as well as the interpretation of DBS-based results. We previously developed a method to determine the Hct of a DBS based on its hemoglobin content using noncontact diffuse reflectance spectroscopy. Despite the ease with which the analysis can be performed (i.e., mere scanning of the DBS) and the good results that were obtained, the method did require a complicated algorithm to derive the total hemoglobin content from the DBS's reflectance spectrum. As the total hemoglobin was calculated as the sum of oxyhemoglobin, methemoglobin, and hemichrome, the three main hemoglobin derivatives formed in DBS upon aging, the reflectance spectrum needed to be unmixed to determine the quantity of each of these derivatives. We now simplified the method by only using the reflectance at a single wavelength, located at a quasi-isosbestic point in the reflectance curve. At this wavelength, assuming 1-to-1 stoichiometry of the aging reaction, the reflectance is insensitive to the hemoglobin degradation and only scales with the total amount of hemoglobin and, hence, the Hct. This simplified method was successfully validated. At each quality control level as well as at the limits of quantitation (i.e., 0.20 and 0.67) bias, intra- and interday imprecision were within 10%. Method reproducibility was excellent based on incurred sample reanalysis and surpassed the reproducibility of the original method. Furthermore, the influence of the volume spotted, the measurement location within the spot, as well as storage time and temperature were evaluated, showing no relevant impact of these parameters. Application to 233 patient samples revealed a good correlation between the Hct determined on whole blood and the predicted Hct determined on venous DBS. The bias obtained with Bland and Altman analysis was -0.015 and the limits of agreement were -0.061 and 0.031, indicating that the simplified, noncontact Hct prediction method even outperforms the original method. In addition, using caffeine as a model compound, it was demonstrated that this simplified Hct prediction method can effectively be used to implement a Hct-dependent correction factor to DBS-based results to alleviate the Hct bias.
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http://dx.doi.org/10.1021/acs.analchem.7b03784DOI Listing
February 2018

A Novel, Nondestructive, Dried Blood Spot-Based Hematocrit Prediction Method Using Noncontact Diffuse Reflectance Spectroscopy.

Anal Chem 2016 06 3;88(12):6538-46. Epub 2016 Jun 3.

Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, Ghent University , Ottergemsesteenweg 460, 9000 Ghent, Belgium.

Dried blood spot (DBS) sampling is recognized as a valuable alternative sampling strategy both in research and in clinical routine. Although many advantages are associated with DBS sampling, its more widespread use is hampered by several issues, of which the hematocrit effect on DBS-based quantitation remains undoubtedly the most widely discussed one. Previously, we developed a method to derive the approximate hematocrit from a nonvolumetrically applied DBS based on its potassium content. Although this method yielded good results and was straightforward to perform, it was also destructive and required sample preparation. Therefore, we now developed a nondestructive method which allows to predict the hematocrit of a DBS based on its hemoglobin content, measured via noncontact diffuse reflectance spectroscopy. The developed method was thoroughly validated. A linear calibration curve was established after log/log transformation. The bias, intraday and interday imprecision of quality controls at three hematocrit levels and at the lower and upper limit of quantitation (0.20 and 0.67, respectively) were less than 11%. In addition, the influence of storage and the volume spotted was evaluated, as well as DBS homogeneity. Application of the method to venous DBSs prepared from whole blood patient samples (n = 233) revealed a good correlation between the actual and the predicted hematocrit. Limits of agreement obtained after Bland and Altman analysis were -0.076 and +0.018. Incurred sample reanalysis demonstrated good method reproducibility. In conclusion, mere scanning of a DBS suffices to derive its approximate hematocrit, one of the most important variables in DBS analysis.
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http://dx.doi.org/10.1021/acs.analchem.6b01321DOI Listing
June 2016

Techniques that acquire donor profiling information from fingermarks - A review.

Sci Justice 2016 Mar 5;56(2):143-54. Epub 2016 Jan 5.

Department of Biomedical Engineering and Physics, University of Amsterdam, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.

Fingermarks are among the most important types of evidence that can be encountered at the scene of a crime since the unique ridge pattern of a fingerprint can be used for individualization. But fingermarks contain more than the characteristic pattern of ridges and furrows, they are composed of a wide variety of different components that originate from endogenous and exogenous sources. The chemical composition can be used to obtain additional information from the donor of the fingermark, which in turn can be used to create a donor profile. Donor profiling can serve at least two purposes i) to enhance the evidential value of fingermarks and ii) to provide valuable tactical information during the crime scene investigation. Retrieving this additional information is not limited to fingermarks that have been used for individualization, but can also be applied on partial and/or distorted fingermarks. In this review we have summarized the types of information that can be obtained from fingermarks. Additionally, an overview is given of the techniques that are available addressing their unique characteristics and limitations. We expect that in the nearby future, donor profiling from contact traces, including fingermarks will be possible.
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http://dx.doi.org/10.1016/j.scijus.2015.12.002DOI Listing
March 2016

On the autofluorescence of aged fingermarks.

Forensic Sci Int 2016 Jan 14;258:19-25. Epub 2015 Nov 14.

Department of Biomedical Engineering and Physics University of Amsterdam, Academic Medical Center Meibergdreef 9, 1105, AZ Amsterdam, The Netherlands. Electronic address:

Fingermark autofluorescence changes with time, both spectrally and in total intensity. In this study we investigate which components in the aged fingermarks cause this change in autofluorescent signal. Thin layer chromatography combined with fluorescence spectroscopy was used to identify fluorescent aging products. Based on our results, tryptophan derivatives, including indoleacetic acid, (nor)harman and xanthurenic acid are indicated as important contributors to the autofluorescence of aged fingermarks. Knowledge about which fluorescent aging products are present in fingermarks might be useful in the development of fingermark age estimation methods. This work is part of a larger project of which the major goal is to develop a method to estimate the time of deposition of fingermarks. Additionally, by selective targeting of aging products the development of aged fingermarks might be improved.
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http://dx.doi.org/10.1016/j.forsciint.2015.11.002DOI Listing
January 2016

Fluorescence characteristics of human Barrett tissue specimens grafted on chick chorioallantoic membrane.

Lasers Med Sci 2016 Jan 4;31(1):137-44. Epub 2015 Dec 4.

Department of Biomedical Engineering and Physics, Academic Medical Center, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.

To improve (pre)malignant lesion identification in Barrett's esophagus (BE), recent research focuses on new developments in fluorescence imaging and spectroscopy to enhance tissue contrast. Our aim was to validate the chorioallantoic membrane (CAM) model as a preclinical tool to study the fluorescence characteristics such as autofluorescence and exogenously induced fluorescence of human Barrett's tissue. Therefore, esophageal biopsy specimens from Barrett's patients were freshly grafted onto the CAM of fertilized hen's eggs to simulate the in vivo situation. The BE biopsy specimens stayed between 1 and 9 days on the CAM to study the persistence of vitality. Fluorescence spectroscopy was performed using six excitation wavelengths (369, 395, 400, 405, 410, 416 nm). Obtained autofluorescence spectra were compared with in vivo spectra of an earlier study. Exogenous administration of 5-aminolevulinic-acid to the biopsy specimens was followed by fluorescence spectroscopy at several time points. Afterwards, the biopsy specimens were harvested and histologically evaluated. In total, 128 biopsy specimens obtained from 34 patients were grafted on the CAM. Biopsy specimens which stayed on average 1.7 days on the CAM were still vital. Autofluorescence spectra of the specimens correlated well with in vivo spectra. Administered 5-aminolevulinic-acid to the biopsy specimens showed conversion into protoporphyrin-IX. In conclusion, we showed that grafting freshly collected human BE biopsy specimens on the CAM is feasible. Our results suggest that the CAM model might be used to study the fluorescence behavior of human tissue specimens. Therefore, the CAM model might be a preclinical research tool for new photosensitizers.
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http://dx.doi.org/10.1007/s10103-015-1839-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4701780PMC
January 2016

Interplay between Static and Dynamic Energy Transfer in Biofunctional Upconversion Nanoplatforms.

J Phys Chem Lett 2015 Jul 17;6(13):2518-23. Epub 2015 Jun 17.

§State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, People's Republic of China.

Clarification of the energy-transfer (ET) mechanism is of vital importance for constructing efficient upconversion nanoplatforms for biological/biomedical applications. Yet, most strategies of optimizing these nanoplatforms were casually based on a dynamic ET assumption. In this work, we have modeled quantitatively the shell-thickness-dependent interplay between dynamic and static ET in nanosystems and validated the model in a typical biofunctional upconversion nanoplatform composed of NaYF4:Er, Yb/NaYF4 upconversion nanoparticles (UCNPs), and energy-acceptor photosensitizing molecule Rose Bengal (RB). It was determined that with a proper thickness shell, the energy transferred via dynamic ET as well as static ET in this case could be significantly improved by ∼4 and ∼9 fold, respectively, compared with the total energy transferred from bare core UCNPs. Our results shall form the bedrock in designing highly efficient ET-based biofunctional nanoplatforms.
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http://dx.doi.org/10.1021/acs.jpclett.5b00999DOI Listing
July 2015

Targeted labeling of an early-stage tumor spheroid in a chorioallantoic membrane model with upconversion nanoparticles.

Nanoscale 2015 Feb;7(5):1596-600

State Key Laboratory of Luminescence and Application, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science, Changchun 130033, P. R. China.

In vivo detection of cancer at an early-stage, i.e. smaller than 2 mm, is a challenge in biomedicine. In this work target labeling of an early-stage tumor spheroid (∼500 μm) is realized for the first time in a chick embryo chorioallantoic membrane (CAM) model with monoclonal antibody functionalized upconversion nanoparticles (UCNPs-mAb).
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http://dx.doi.org/10.1039/c4nr05638hDOI Listing
February 2015

Quantitative comparison of analysis methods for spectroscopic optical coherence tomography: reply to comment.

Biomed Opt Express 2014 Sep 12;5(9):3034-5. Epub 2014 Aug 12.

Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands.

We reply to the comment by Kraszewski et al on "Quantitative comparison of analysis methods for spectroscopic optical coherence tomography." We present additional simulations evaluating the proposed window function. We conclude that our simulations show good qualitative agreement with the results of Kraszewski, in support of their conclusion that SOCT optimization should include window shape, next to choice of window size and analysis algorithm.
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http://dx.doi.org/10.1364/BOE.5.003034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4230362PMC
September 2014

Visualization of latent blood stains using visible reflectance hyperspectral imaging and chemometrics.

J Forensic Sci 2015 Jan 7;60 Suppl 1:S188-92. Epub 2014 Nov 7.

Department of Biomedical Engineering & Physics, Academic Medical Center, University of Amsterdam, PO Box 22700, 1100 DE, Amsterdam, The Netherlands.

The detection of latent traces is an important aspect of crime scene investigation. Blood stains on black backgrounds can be visualized using chemiluminescence, which is invasive and requires a darkened room, or near-infrared photography, for which investigators need to change filters manually to optimize contrast. We demonstrated the performance of visible reflectance hyperspectral imaging (400-720 nm) for this purpose. Several processing methods were evaluated: single wavelength bands, ratio images, principal component analysis (PCA), and "SIMPLe-to-use Interactive Self-modeling Mixture Analysis" (SIMPLISMA). Using these methods, we were able to enhance the contrast between blood stains and 12 different fabrics. On black cotton, blood dilutions were visible with a minimal concentration of 25% of whole blood. The hyperspectral camera system used in this study is portable and wireless, which makes it suitable for crime scene use. The described technique is noncontact and nondestructive, so all traces are preserved for further analysis.
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http://dx.doi.org/10.1111/1556-4029.12591DOI Listing
January 2015

Immunolabeling and the compatibility with a variety of fingermark development techniques.

Sci Justice 2014 Sep 2;54(5):356-62. Epub 2014 Jul 2.

University of Amsterdam, Biomedical Engineering and Physics, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands.

Much information can be obtained from the chemical composition of a fingermark, which can be helpful in crime scene investigation. Immunolabeling can be used to extract information about the donor of the fingermark and it can also act as a fingermark development tool in sequence with the standard fingermark development techniques. However, before immunolabeling can be used in forensic practice more information on the possibilities and limitations of this technique is required. In this study, our aim was to investigate if immunolabeling is compatible with standard development protocols (indanedione-zinc, indanedione-zinc followed by ninhydrin spraying, physical developer, cyanoacrylate fuming, cyanoacrylate followed by basic yellow staining, lumicyanoacrylate fuming and polycyanoacrylate fuming). Immunolabeling was carried out successfully on all developed fingermarks, whereby dermcidin was selected as antigen of interest. We can conclude that immunolabeling is compatible with a wide variety of different fingermark developers. This finding in combination with previous findings, makes immunolabeling an interesting technique, which can be of great value in the forensic field.
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http://dx.doi.org/10.1016/j.scijus.2014.06.005DOI Listing
September 2014

Oxygenation measurement by multi-wavelength oxygen-dependent phosphorescence and delayed fluorescence: catchment depth and application in intact heart.

J Biophotonics 2015 Aug 22;8(8):615-28. Epub 2014 Sep 22.

Department of Anesthesiology, Laboratory of Experimental Anesthesiology, Erasmus MC - University Medical Center Rotterdam, Rotterdam, The Netherlands.

Oxygen delivery and metabolism represent key factors for organ function in health and disease. We describe the optical key characteristics of a technique to comprehensively measure oxygen tension (PO(2)) in myocardium, using oxygen-dependent quenching of phosphorescence and delayed fluorescence of porphyrins, by means of Monte Carlo simulations and ex vivo experiments. Oxyphor G2 (microvascular PO(2)) was excited at 442 nm and 632 nm and protoporphyrin IX (mitochondrial PO(2)) at 510 nm. This resulted in catchment depths of 161 (86) µm, 350 (307) µm and 262 (255) µm respectively, as estimated by Monte Carlo simulations and ex vivo experiments (brackets). The feasibility to detect changes in oxygenation within separate anatomical compartments is demonstrated in rat heart in vivo. Schematic of ex vivo measurements.
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http://dx.doi.org/10.1002/jbio.201400054DOI Listing
August 2015

Multispectral upconversion luminescence intensity ratios for ascertaining the tissue imaging depth.

Nanoscale 2014 Aug;6(15):9257-63

State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, P. R. China.

Upconversion nanoparticles (UCNPs) have in recent years emerged as excellent contrast agents for in vivo luminescence imaging of deep tissues. But information abstracted from these images is in most cases restricted to 2-dimensions, without the depth information. In this work, a simple method has been developed to accurately ascertain the tissue imaging depth based on the relative luminescence intensity ratio of multispectral NaYF4:Yb(3+),Er(3+) UCNPs. A theoretical mode was set up, where the parameters in the quantitative relation between the relative intensities of the upconversion luminescence spectra and the depth of the UCNPs were determined using tissue mimicking liquid phantoms. The 540 nm and 650 nm luminescence intensity ratios (G/R ratio) of NaYF4:Yb(3+),Er(3+) UCNPs were monitored following excitation path (Ex mode) and emission path (Em mode) schemes, respectively. The model was validated by embedding NaYF4:Yb(3+),Er(3+) UCNPs in layered pork muscles, which demonstrated a very high accuracy of measurement in the thickness up to centimeter. This approach shall promote significantly the power of nanotechnology in medical optical imaging by expanding the imaging information from 2-dimensional to real 3-dimensional.
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http://dx.doi.org/10.1039/c4nr02090aDOI Listing
August 2014

Fluorescence imaging for the detection of early neoplasia in Barrett's esophagus: old looks or new vision?

Eur J Gastroenterol Hepatol 2014 Jul;26(7):691-8

aDepartment of Gastroenterology and Hepatology bDepartment of Biomedical Engineering and Physics, Academic Medical Centre, Amsterdam, The Netherlands cMRC Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, UK.

Early neoplasia arising from Barrett's esophagus is often small, focally distributed and endoscopically poorly visible, and random four-quandrant biopsies may easily miss early lesions. Advanced imaging techniques, such as (auto)fluorescence-based modalities, aim to increase the detection rate of early lesions or the yield of random biopsies. Fluorescence-based light-tissue interaction has been designed successfully in point-probe differentiating spectroscopy systems or integrated into wide-field endoscopic systems such as autofluorescence imaging (AFI). In this review, we discuss the most recent advances in fluorescence spectroscopy and imaging for detecting early Barrett's neoplasia. A spectroscopy probe, integrated into regular biopsy forceps, was shown to offer decent discriminatory capabilities, while ensuring spot-on correlation between the measured area and the corresponding histology. With this tool, surveillance endoscopy with random biopsies may become more efficient and sensitive. AFI was shown to increase the targeted detection of early neoplasia. However, random biopsies could compensate for this effect. The clinical impact of AFI on the diagnosis and the treatment of early neoplasia is limited, and yet AFI may offer a novel approach in biomarker-based risk-stratification models. Moreover, in combination with new, readily available contrast agents such as fluorescent lectins, fluorescence imaging may receive renewed interest.
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http://dx.doi.org/10.1097/MEG.0000000000000101DOI Listing
July 2014

Oxidation monitoring by fluorescence spectroscopy reveals the age of fingermarks.

Angew Chem Int Ed Engl 2014 Jun 21;53(24):6272-5. Epub 2014 May 21.

Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam (The Netherlands).

No forensic method exists that can reliably estimate the age of fingermarks found at a crime scene. Information on time passed since fingermark deposition is desired as it can be used to distinguish between crime related and unrelated fingermarks and to support or refute statements made by the fingermark donors. We introduce a non-contact method that can estimate the age of fingermarks. Fingermarks were approached as protein-lipid mixtures and an age-estimation model was build based on the expected protein and lipid oxidation reactions. Two measures of oxidation are required from the fingermark to estimate its age: 1) the relative amount of fluorescent oxidation products 2) the rate at which these products are formed. Fluorescence spectroscopy was used to obtain these measures. We tested the method on 44 fingermarks and were able to estimate the age of 55% of the male fingermarks, up to three weeks old with an uncertainty of 1.9 days.
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http://dx.doi.org/10.1002/anie.201402740DOI Listing
June 2014
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