Abstract/Video opens by clicking at the talk title.
Abstract/Video opens by clicking at the talk title.
A new method for the quantification of PET radiotracer Arterial Input Function in the Rat Carotid Artery (#457)
Mailyn Perez-Liva1, Thulaciga Yoganathan1, 2, Mariana Aramburo1, Jacobo Cal4, Mickael Tanter3, Jean Provost3, Thomas Viel1, Bertrand Tavitian1, 2
1 Paris-Cardiovascular Research Center at HEGP, INSERM U970, Paris, France
Assessment of the arterial input function (AIF) in the carotid artery would be ideal for radiotracer modeling of cerebral PET. This is highly challenging in rodents as the internal diameter of the carotid artery is smaller than the spatial resolution of preclinical PET scanners . Here, we used co-registration of Ultrafast ultrasound Doppler of the rat carotid artery with PET dynamic acquisition to enable segmentation-based correction of motion and partial volume effect for improved image radiotracer quantification.
Animal experiments were performed under ethical approval N°18-146. Measurements were performed using our hybrid imaging system PETRUS that combines an Ultrafast Ultrasound Imaging (UUI) scanner with a small animal PET/CT [2,3]. PET and UUI volumes were acquired simultaneously and precisely registered in the same spatial coordinates . Adult male rats (n=4) were injected IV with 55 MBq of [18F]FDG and imaged during 60 minutes. Radioactivity concentration counted in serial blood samples drawn from the left common carotid were compared with image-derived AIF of the right common carotid, segmented from the Doppler volume using isodata unsupervised classification . A local projection method  with motion deconvolution was applied to the dynamic PET sequences.
The maximum longitudinal and axial displacements of the carotid artery estimated with ultrasound were 2.1 and 0.7 mm, respectively. The maximal difference between ground-truth (i.e. obtained from blood sampling) values of the AIF and uncorrected image-derived AIF was 72%. Visually, both the peak value, amplitude and shape of the two AIFs differed considerably. After correction for PVE, maximum difference was reduced to 16 %, and after motion and PVE correction, it was reduced to 7 %. The fit in shape and amplitude between the two curves were also considerably improved.
Ultrafast Doppler co-registration with dynamic PET can be used for motion and PVE correction of small moving structures in preclinical PET. This allows for increased accuracy of image-derived AIF quantification in the rat carotid artery. Better quantification of the AIF should benefit PET radiotracer quantification in rodent brain.
AcknowledgmentThis project was funded in part by Plan Cancer (ASC16026HSA-C16026HS) and by LABEX WIFI (Laboratory of Excellence ANR-10-LABX-24) within the French program “Investments for the Future” under reference ANR-10-IDEX-0001-02 PSL In vivo imaging was performed at the Life Imaging Facility of Paris Descartes University (Plateforme Imageries du Vivant - PIV), supported by France Life Imaging (grant ANR-11-INBS-0006) and Infrastructures Biologie-Santé (IBISA). It was also funded in part by a CARPEM Siric grant (to BT)
 Moses, W. W. (2011). Fundamental limits of spatial resolution in PET. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 648, S236-S240.
 Provost J, et al., (2018). Simultaneous Positron Emission Tomography and Ultrafast Ultrasound for Hybrid Molecular, Anatomical, and Functional Imaging. Nature Biomed Eng., 2(2):85-94.
 Pérez-Liva M, et al., (2018). Performance evaluation of the PET component of a hybrid PET/CT-ultrafast ultrasound imaging instrument. Phys Med Biol. 2018 doi: 10.1088/1361-6560/aad946. PubMed PMID: 30091723.
 Magid, A., Rotman, S. R., & Weiss, A. M. (1990). Comments on Picture thresholding using an iterative selection method. IEEE transactions on systems, man, and cybernetics, 20(5), 1238-1239.
 Cal-González, et al, (2017). Impact of motion compensation and partial volume correction for 18F-NaF PET/CT imaging of coronary plaque. Physics in Medicine & Biology, 63(1), 015005.
Keywords: simultaneous PET/CT-UUI system, Image Derive Arterial Input Function, carotid artery, partial volume effect correction, motion correction
Hybrid Optical and CT Imaging reveals pulmonary fibrosis and perfusion defects in progeroid ercc1 mice (#249)
Alex KleinJan1, Yanto Ridwan1, Nicole van Vliet1, Anton Roks1, Ingrid van der Pluijm1, Jeroen Essers1
1 Erasmus MC, Molecular Genetics, Rotterdam, Netherlands
Idiopathic pulmonary fibrosis (IPF) is an aging-related progressive fatal lung disorder with unknown etiology. Accumulation of unrepaired DNA damage over time is one of the driving forces of age-related diseases. Ercc1 is involved in important DNA repair pathways. Hence, Ercc1 mutations cause accelerated aging phenotypes in humans and mice. We hypothesized that unrepaired DNA damage contributes to IPF and that alveolar macrophages contribute age-related fibrosis.
Lung density and perfusion were analyzed in hypomorfic Ercc1 mice (Ercc1-/D7) and endothelial cell specific Ercc1 deficient (Tie2-Cre- Ercc1) using microCT. After acquisition of a pre-contrast scan, the EXia160 contrast agent was infused and pre-contrast image was subtracted from the post-contrast image to determine perfusion. Mice were scanned using cardio-respiratory gating at parameters: 90kv, 160µA, field of view 20mm, 40 um resolution. We used a NIRF labeled bicyclic octapeptide, recognizing the PDGF-BB binding pocket of the homo-dimeric PDGFRb to monitor and quantify fibrosis in animals using a fluorescence mediated tomographic (FMT) imaging system. Histological analysis was performed for signs of fibrosis. In depth analysis for airway inflammation was done by FACS.
Ercc1-/D7showed structural airway abnormalities with a broad variety and consistent age-dependent progressive airway fibrosis (Ashcroft score) and inflammation. Alveolar compartment showed elevated numbers of alveolar macrophages (F4/80+ Siglec F+), T cells (CD3, CD4 and CD8) and Dendritic Cells (CD11c+MHCII+). Alveolar macrophages showed a pronounced activated CD11b+ phenotype in Ercc1-/D7 mice. An increase in PDGFRb staining could be quantitated and localized in vivo using CT-FMT. Macroscopic ex-vivo analysis showed that the Cy7 labeled PDGFRb probe accumulated in aorta, heart and lungs. Microscopic analysis highlighted cellular labeling, both in the medial layers of the aorta but also in heart and lungs. Lung perfusion measurement showed significantly decreased lung perfusion in Tie2-Cre- Ercc1 mice.
We demonstrate that accelerated aging ercc1 Ercc1-/7 mutant mice are a valuable model for IPF with age-related progressive fibrosis.
Keywords: MicroCT, optical, Lung imaging, Fibrosis
Time-domain Near Infrared Optical Tomography Guided Fluorescence Molecular Tomography (#223)
Wuwei Ren1, 2, Jingjing Jiang2, Aldo M. Di Costanzo2, Edoardo Charbon3, Alexander Kalyanov2, Martin Wolf2
1 ETH and University Zurich, Institute of Biomedical Engineering, Zurich, Switzerland
Fluorescence molecular tomography (FMT) copes with the scattering nature of living tissues and resolves fluorescence signal at a depth of several centimetres, making it a powerful tool for preclinical studies . A challenge associated with FMT reconstruction is that its accuracy depends largely on the assumed optical properties . A common strategy is by assuming a homogeneous setting of optical properties, which in principle mimics the average optical values of tissue in-vivo. However, this method can cause inaccuracy, especially when encountering a high degree of optical heterogeneity.
We improved the accuracy of the initial optical properties required for FMT by using a novel time-domain (TD) near-infrared optical tomography (NIROT). Phantom experiments were performed on a heterogeneous phantom containing a fluorescent inclusion. The NIROT system uses a pulsed laser as the illumination source, connected to a fibre switch with 11 fibres . These fibres are integrated into a customized ring, on which a 32 x 32-pixel SPAD camera is mounted. Both absorption and scattering coefficients were reconstructed using NIRFAST . Then we performed FMT by illuminating the bottom of the phantom with 8 x 8 laser points and acquired the paired excitation and emission images from the top surface for each laser point. We used STIFT for FMT reconstruction .
The imaged phantom (Fig.1) has a radius of 30 mm and a height of 20 mm, with a dark block featuring higher absorption and similar scattering properties compared with the surrounding material. The block is also cylindrical (radius, 10 mm; height, 10 mm) and centred 8.5 mm below the top surface. There is a tube passing through the centre of the block, allowing the injection of fluorescence dye (we used Cy5.5 in this experiment). Firstly, we have successfully decoupled absorption and scattering maps of the phantom (Fig.2). The reconstructed values of both coefficients agree well with the calibrated ones, localizing the dark block inside the phantom. Secondly, we utilized the NIROT-derived optical values as the prior information for FMT reconstruction, and correctly generated fluorescence signal seated 8.5 mm below the surface. On the other hand, the FMT reconstruction using a homogeneous setting (μa, 0.06 mm−1; μs, 2 mm−1) failed to localize the injected Cy5.5.
We propose a multimodal method combining TD-NIROT and CW-FMT, which provides complementary functional and molecular information in the tissue. The pilot experiment on a heterogeneous phantom indicates that the decoupled scattering and absorption parameters obtained from NIROT significantly improved the reconstruction quality of FMT. In the future, we expect more complicated phantom studies and in vivo imaging.
This work is supported by the BRIDGE grant No.178262 from the Swiss National Science Foundation and Swiss Innovation Agent. We thank Prof. Jorge Ripoll, Prof. Markus Rudin, and Prof. Daniel Razansky for helpful discussion.
 V. Ntziachristos, C. H. Tung, C. Bremer, and R. Weissleder, “Fluorescence molecular tomography resolves protease activity in vivo,” Nat Med, vol. 8, no. 7, pp. 757–60, 2002.
 J. F. P.J. Abascal, J. Aguirre, J. Chamorro-Servent, M. Schweiger, S. Arridge, J. Ripoll, J. J. Vaquero, and M. Desco, “Influence of absorption and scattering on the quantification of fluorescence diffuse optical tomography using normalized data,” Journal of Biomedical Optics, vol. 17, no. 3, 2012.
 A. Kalyanov, J. Jiang, S. Lindner, L. Ahnen, A. Costanzo, J. Pavia, S. Majos, and M. Wolf, “Time-domain near-infrared optical tomography with time-of-flight spad camera: The new generation,” in Optical Tomography and Spectroscopy, Optical Society of America, 2018.
 H. Dehghani, M. E. Eames, P. K. Yalavarthy, S. C. Davis, S. Srinivasan, C. M. Carpenter, B. W. Pogue, and K. D. Paulsen, “Near infrared optical tomography using nirfast: Algorithm for numerical model and image reconstruction,” Commun Numer Methods Eng, vol. 25, no. 6, pp. 711–732, 2008.
 W. Ren, H. Isler, M. Wolf, J. Ripoll, and M. Rudin, “Smart toolkit for fluorescence tomography: simulation, reconstruction, and validation,” IEEE Trans Biomed Eng, 2019.
Keywords: Near Infrared Optical Tomography, Fluorescence Molecular Tomography, Image reconstruction, Multimodal imaging
Tissue optical clearing monitoring by fluorescence and magnetic resonance imaging in vivo (#329)
Victoria V. Zherdeva1, Natalia I. Kazachkina1, Irina G. Meerovich2, Daria K. Tuchina3, 1, Valery V. Tuchin3, 1, Alexander P. Savitsky2, Alexei A. Bogdanov1, 4
1 Research Center of Biotechnology of the Russian Academy of Sciences, Bach Institute of Biochemistry,Laboratory of Molecular Imaging, Moscow, Russian Federation
Optical clearing is considered as an efficient strategy for increasing the depth of light penetration into the non-transparent media and improving the quality of the data for the optical diffusion tomography, multiphoton imaging and Raman spectroscopy [1,2]. The goal of our study was in investigating a correlation between the effects resulting from optical clearing (OC) with the changes in T2-weighted (T2w) magnetic resonance (MR) signal measured over the matched area in vivo.
OC/MRI experiments were performed in nude mice (n=4) carrying subcutaneous tumor xenografts expressing TagRFP marker protein at 2-3 weeks after tumor inoculation . To investigate the effect of OC induced by a mixture of 70%glycerol, 5%DMSO, 25%water, we performed measurements of TagRFP fluorescence intensity (FI) and lifetime (FL) before and after OC using a confocal system equipped with a supercontinuum laser with the acousto-optic tunable filter and a time-correlated single photon-counting (TCSPC) detector. The OC effect was achieved by applying the OC mixture onto the skin over the tumor area for 10 min followed by mixture removal from the skin. T2w fast spin-echo (FSE) MRI pulse sequences were used before and after OC mixture application in the same animals on non-consecutive days.
TCSPC experiments showed that after OC application FL of TagRFP was higher with median difference of 51 ps (p<0.05, Wilcoxon matched-pairs test, Figure 1A). Average FI increased by 33% after OC resulting in the higher frequency of fluorescence intensity increase observations (n=19 vs. n=3, Figure 1B). The analysis of obtained T2w FSE MR images showed significant quantitative differences (p=0.03) between Gaussian noise-normalized MR signal intensities of the 0.7-mm-thick axial peripheral tissue/skin slices before and after OC mixture applications in 3 animals, in one animal those differences were statistically insignificant (Figure 1C,D). The comparison of T2w MR signal intensities measured in OC mixture phantoms prepared at various dilutions and pure water showed that the observed differences in T2w MR signal intensity were not due to the application of OC mixture alone but is a consequence of OC mixture interaction with the skin and peripheral tissue.
The obtained results point to the potential mechanism of OC clearing as it relates to a transient change of microenvironment affecting the layer of TagRFP-expressing cells and resulting in FL increase and T2w MR hypointensity increase. T2w 1T MRI showed promise for detecting small longitudinal changes of the MR signal under the conditions of OC, which benefits in vivo imaging of marker protein expression in animal tumor models.
This work was supported in part by the Ministry of Science and Higher Education of the Russian Federation (project 14.W03.31.0023).
 Tuchin, VV, "Tissue optics: Light scattering methods and instruments for medical diagnosis", 2015, PM 254, 3rd ed, SPIE Press, Bellingham, WA, USA.
 Sdobnov, AY, Darvin, ME, Genina, E A, Bashkatov, AN. Lademann, J and Tuchin, VV, "Recent progress in tissue optical clearing for spectroscopic application", Spectrochim Acta A Mol. Biomol. Spectrosc., 2015, 197: 216-229.
 Savitsky AP, Rusanov AL, Zherdeva VV, Gorodnicheva TV, Khrenova MG, Nemukhin AV, "FLIM-FRET Imaging of caspase-3 activity in live cells using pair of red fluorescent proteins", Theranostics, 2012, 2: 215-26.
Magnetic resonance imaging (MRI), fluorescence intensity (FL) and fluorescence lifetime (FL) effect
A - The increase of FL (ps) of TagRFP-expressing tumor measured before and after OC (n=12 ROI); B - the number of observation of FI increase (FI/Fo>1) indicating optical clearing effect in 19 cases out of 22 total (n=3 animals); C - T2w SE (TR/TE=4000/40 ms, 7NEX, 0.7 mm slice thickness) of TagRFP-expressing tumor at 1T, bofore, during and after OC with ROI used to calculate tissue MR signal intensity and SD of noise shown in red; D - The change of normalized T2w MR signal intensity in n=10 slices over time before, during and after OC solution application onto the skin.
Keywords: Optical clearing, MRI, subcutaneous tumor xenografts, fluorescence life-time imaging, tumor microenviroment
Hybrid photoacoustic and fluorescence microscopy for the label-free investigation of melanin accumulation in fish scales (#314)
George Tserevelakis1, Adamantia-Ilianna Mantouka2, Michail Pavlidis2, Konstantina Evangelia Gleni3, Giannis Zacharakis1
1 Foundation for Research and Technology - Hellas (FORTH), Institute of Electronic Structure and Laser, Heraklion, Greece
Chromatophores are pigment-containing and light-reflecting cells that are responsible for the manifestation of skin coloration patterns. Their pigments are of high importance for enhancing vision and protection from UV exposure and metabolic oxidation [1,2]. In farmed fish species, skin coloration is related to animal health, welfare and quality . Herewith, we present the application of a hybrid photoacoustic and fluorescence microscope [3,4] on the investigation of melanin accumulation in fish scales, towards the development of a non-invasive bioassay for the assessment of fish welfare.
Scales were dissected from anaesthetized red sea breams. The hybrid system is built around a modified inverted optical microscope serving as a platform for the imaging apparatus. Two laser beams at 532 nm (pulsed; rep. rate: 5 KHz; pulse width: 10 ns) and 450 nm (continuous wave) are simultaneously focused on the specimen for the excitation of photoacoustic and autofluorescence signals respectively. The sample is raster scanned over the confocal beams using high precision XY motorized stages to form two complementary images. The recording of generated photoacoustic waves is achieved by an integrated spherically focused piezoelectric transducer at 20 MHz, whereas the emitted autofluorescence is detected by a photomultiplier tube, following its spatial filtering through a 100 μm pinhole.
The acquired photoacoustic images provided the spatial distribution of melanocytes with high specificity and resolution as a result of the strong optical absorption of the incident irradiation wavelength. On the other hand, autofluorescence imaging was able to delineate scales’ surface through the detection of a rather homogeneous signal background. The quantification of melanin’s accumulation was performed by employing a custom-developed algorithm, and the obtained results were further compared to independent measurements using conventional optical imaging and chemical methods. We have discovered a high level of agreement between the developed hybrid imaging methodology and the standard techniques, highlighting thus the potential of the followed approach towards the extraction of quantitative information as regards to melanin’s content and distribution in fish scales.
We validated the capabilities of the hybrid microscope as regards to the accurate detection of melanocytes’ accumulation in fish scales, demonstrating the application potential of the proposed technique in studies involving fish wellness and health. Further development of the method may provide a new bioassay for the evaluation of environmental hazards, managerial practices and procedures, life-history stress and physiological condition of fish.
AcknowledgmentThis work was supported by the projects BIOIMAGING-GR (MIS5002755) and HELLAS-CH (MIS5002735), funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" and co-financed by Greece and the European Union. Furthermore, we would like to acknowledge financial support from KRIPIS ΙΙ-VITAD (MIS 5002469), H2020 Laserlab Europe (EC-GA 654148), SNF (ARCHERS), HFRI / GSRT (GA. no. 130178/I2/31-7-2017) and MIS 5010684, ESPA 2014-2020.
 Fujii, R, 1993, 'Coloration and chromatophore', In Evans, D.H. (Ed.), The Physiology of Fishes, CRC Press, pp. 535-562, Boca Raton, FL, USA
 Pavlidis, M, Papandroulakis, N, Divanach, P, 2006, 'A method for the comparison of chromaticity parameters in fish skin: Preliminary data on the coloration pattern of red skin Sparidae (“red porgies”)', Aquaculture, 258, 211-219
 Tserevelakis, GJ, Tsagkaraki, M, Zacharakis, G, 2016, 'Hybrid photoacoustic and optical imaging of pigments in vegetative tissues', J. Microsc., 263 (3), pp. 300-306
 Tserevelakis, GJ, Avtzi, S, Tsilimbaris, MK, Zacharakis, G, 2017, 'Delineating the anatomy of the ciliary body using hybrid optical and photoacoustic imaging', Journal of Biomedical Optics, 22(6):60501
Keywords: photoacoustic, microscopy, hybrid, fish, melanin
Setup and implementation of an imaging chamber for 3D in-vivo monitoring of dwarf shrimp Neocardina davidi (#367)
Diego Díaz1, María Revuelta1, María del Carmen Prieto1, Manuel Desco Menéndez1, 2, 3, Roberto Fernández1, 4, Jorge Ripoll1, 2
1 Universidad Carlos III de Madrid, Bioengineering and Aerospace engineering, Leganés, Spain
Neocardina davidi is a dwarf shrimp that has received very little attention in research. The small size and social behavior of this invertebrate make it interesting, while its transparency shows great potential for in vivo research with optical imaging techniques such as Selective Plane Illumination Microscopy. Nevertheless, the understanding and tracking of this species activity has not been previously recorded. In this experiment, two cameras were placed perpendicularly to monitor the untethered activity of individuals and observe its behaviors while developing under an observational volume.
Three different shrimp tanks were mounted in a breadboard; one observational, one for females and one for males. Two cameras were installed at the top and side of the observational aquarium, to record the whole view of shrimp environment (Fig.1). Temperature and pH were measured with a specific sensor controlled by an Arduino, which also controls a LED to monitor shrimps at night without disturbing their circadian rhythms. Daylight illumination was provided in the indicated hours (7–20h) by a lamp connected to a timer plug. A feeding mechanism was designed and developed with a 3D printer, used to automatically administrate two different types of food to the three aquariums. Conditions of the aquariums were strictly prepared and controlled for the proper care of shrimps.
The cameras were fixed in the breadboard, one getting the x-z plane of the tank from a lateral view and the other getting the x-y plane from the top of the aquarium. The images obtained by both cameras were saved and segmented with Labview. The 3D volume of the tank was then reconstructed using Matlab, correcting the perspective errors introduced by the cameras and being able of detecting the position of the shrimps to its further segmentation and swimming analysis (Fig.2). The perspective correction was implemented using the known dimensions of the aquarium and the segmentation used was based on a dynamic dependent segmentation program, introduced after a seed-growing segmentation applied in the first image of the video. Thus, at the end of the process, 3D space of the tank was recreated and the 3D location of each shrimp was recorded.
The protocol using two cameras allows to perform the proper tracking of the shrimps. Therefore, it was possible to obtain a video of one week, segment it and save the 3D positions of every individual with an age >1 month. This project will set the base for future promising research with dwarf shrimps where we will monitor their behavior and interaction.
AcknowledgmentThis project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 801347 SENSITIVE and Spanish Ministry of Economy and Competitiveness (MINECO) Grant FIS2016-77892-R. R.F acknowledges funding from Generalitat Valenciana and European Social Fund through postdoctoral grant APOSTD/2018/A/084. The CNIC is supported by the Ministerio de Ciencia, Innovación y Universidades and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505).
 Brown, A. E., Yemini, E. I., Grundy, L. J., Jucikas, T., & Schafer, W. R. (2013). A dictionary of behavioral motifs reveals clusters of genes affecting Caenorhabditis elegans locomotion. Proceedings of the National Academy of Sciences, 110(2), 791-796.
 Swierczek, N. A., Giles, A. C., Rankin, C. H., & Kerr, R. A. (2011). High-throughput behavioral analysis in C. elegans. Nature methods, 8(7), 592.
 Yemini, E., Jucikas, T., Grundy, L. J., Brown, A. E., & Schafer, W. R. (2013). A database of Caenorhabditis elegans behavioral phenotypes. Nature methods, 10(9), 877.
 Krutikova, O., Sisojevs, A., & Kovalovs, M. (2017). Creation of a depth map from stereo images of faces for 3D model reconstruction. Procedia Computer Science, 104, 452-459.
Keywords: Dwarf Shrimp, behavior, 3D live tracking.