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Selected Topics in Biophotonics: Diffuse Optics and Optical Molecular Imaging

Andersson-Engels, Stefan; Andersen, Peter

Published in:Journal of Biomedical Optics

DOI:10.1117/1.2965438

2008

Link to publication

Citation for published version (APA):Andersson-Engels, S., & Andersen, P. (2008). Selected Topics in Biophotonics: Diffuse Optics and OpticalMolecular Imaging. Journal of Biomedical Optics, 13(4), [041301]. https://doi.org/10.1117/1.2965438

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PECIAL SECTION GUEST EDITORIALelected Topics in Biophotonics: Diffuse Optics and Optical Molecular Imaging

The present special section entitled “Selected Topics iniophotonics: Diffuse Optics and Optical Molecular Imaging”omprises invited review papers and contributed papers fromhe summer school Biophotonics ’07 as well as contributedapers within the main scope of this section, i.e., within dif-use optics and optical molecular imaging.

otivation and Purpose of Biophotonics Graduatechoolsver the past decade, lasers, optical methods, and instrumentsased on light interaction with tissues have emerged as pow-rful techniques for medical diagnostics, monitoring widepectra of tissue function and pathology together with therapy.n biophysics and biology, optical sensing and manipulationf cells have furthered understanding of basic cell function.cross the world, major research centers are highly active in

his field that in a broad sense may be labeled biophotonics.herefore, education within this area is becoming increasingly

mportant.Around 2000, we realized the increasing need for educa-

ion for graduate students and postdoctoral fellows. Accord-ngly, we developed a series of graduate summer schools aim-ng at filling this void, the first school being held in 2003 andvery second year since then. Our main purpose with the bi-nnial graduate summer school is to provide education withiniophotonics for students and young scientists at the highestnternational level. Our aim is to attract internationally re-owned researchers as lecturers who would attract the mostalented young researchers in the field of biophotonics.

ormat of the Biophotonics Graduate Summer Schoolhe format of the school is a combination of lectures andtudent poster presentations—with time between lectures foriscussions and the exchange of new scientific ideas. The lec-urers cover one topic in one full session comprising fourectures. Thereby both the basics of each topic and the state ofhe art are thoroughly covered. On one hand, this choice limitshe number of topics taught at each school. On the other hand,he topics selected for the schools are covered in detail. There-ore, the range of topics taught will change from school tochool.

The school targets graduate students and postdoctoral fel-ows with a limit of approximately of 50 participants. Appli-ants must submit a three-page summary of their research andesults or planned research project. After the application dead-ine, the organizers conduct a peer review of the summariesnd applicants are admitted based on the outcome of the re-iew process. It is our experience that this procedure ensureshe highest scientific level among the students admitted intohe school. An important feature of the school format is thattudents and lecturers spend the entire week together provid-ng excellent opportunities for the exchange of scientificdeas, networking, and socializing.

The 3rd International Graduate Summer School Biophoto-ics ’07 �www.biop.dk/biophotonics07/� covered the basics of

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lasers and their application in medicine, tissue optics, photo-dynamic therapy, optical tweezers and their applications inbiophotonics, optical biosensors, molecular imaging based onoptical methods, and optical coherence tomography.

Special Section in the Journal of Biomedical Optics

We are pleased to introduce the contributions to this specialsection on “Selected Topics in Biophotonics: Diffuse Opticsand Optical Molecular Imaging” comprising two invited re-view papers as well as 17 contributed papers, mainly from theparticipants of the school but also from other researchers inthe field.

The two invited review papers are entitled “Tutorial ondiffuse light transport” by Jacques and Pogue, and “Molecularimaging with optics: a primer and case for near-infrared fluo-rescence techniques in personalized medicine” by Sevick-Muraca and Rasmussen. These papers of tutorial characterfrom lecturers at the school provide an excellent backgroundto the fields of diffuse optics and molecular imaging, respec-tively. The two invited review papers are the first ones in aplanned series of tutorial review papers following each school�biennially� providing high-level educational material to thebenefit of the scientific community and, in addition, fulfillingour own motivation for creating the school in the first place.

Following the two invited review papers, we have orga-nized the contributed papers according to their main topic,starting with papers categorized as contributions within dif-fuse optics, including measurements of absorption and scat-tering properties, and followed by molecular imaging andfluorescence spectroscopy articles, first on a macroscopicscale, followed by cellular studies. The section ends with twocontributions from areas other than the two main topics of thesection. All of the contributions, however, reflect the core top-ics of the school and span the fields of biomedical optics andbiophotonics.

The first article within the diffuse optics category is writtenby Alerstam et al. describing a scalable white Monte Carlotechnique providing the possibility for fast and accurateanalysis of time-of-flight recordings in situations when theconventionally used diffusion approximation fails to provideaccurate results. This is typically the case for prostate cancer.Wang et al. then show that multispectral frequency domainmeasurements on breast tissue provide more accurate and ro-bust data as compared to the broadband continuous wavetechnique. More wavelengths in the frequency domain resultin less noise and higher accuracy in the evaluated chrompo-hore concentrations. They evaluated this interesting approachin region-guided spectroscopy of breast tissue using informa-tion obtained from magnetic resonance imaging. Mallia et al.then present a clinical study of diffuse reflectance spectros-copy for oral pre-cancer diagnostics, followed by a paper byVacas-Jacques et al. describing a technique using ballisticphotons in a low-coherence interferometric transilluminationsetup for biomedical analysis. Next is a paper by Pop andNeamtu describing an investigation of light scattering of the

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ggregation process of red blood cells. Ending this part, Sa-atham et al. present a novel technique to measure the scat-

ering coefficient �s and anisotropy factor g of tissue. Thisuggested approach is based on confocal microscopy, measur-ng the epi-reflectance as a function of depth in the tissue. The

ethod seems to exhibit great potential and its simplicity sug-ests a straightforward adoption to in vivo measurements oncehe technique is further developed and evaluated.

The next set of articles is more focused towards molecularmaging and fluorescence spectroscopy of tissues and cells.he first three papers consider subsurface fluorescence imag-

ng in animals. First Turchin et al. describe a robust systemor multispectral noncontact fluorescence tomography. Theyllustrate the potential of the system in vivo by imaging cellsransfected with red fluorescence proteins and then injectednto mice. Next, Bourayou et al. present a fluorescence to-

ography technique optimized for mouse brain imaging.ampath et al. then demonstrate how fluorescence imagingan be used to track the path of the lymph drainage from aegion of a malignant tumor, to be able to locate and resectymph nodes for histopathological examination of tumorpread. They illustrate the developed technique with convinc-ng evidence that this may have the potential to become clini-ally important in the future. Following that comes two papersrom Mermut et al., using liposomes as simplified models forell membranes to study interactions with photosensitizers forhotodynamic therapy. In the development of new photosen-itizers it is critical to understand the photophysical propertiesn the cellular environment. These papers suggest using well-ontrolled liposomes for such studies. In these papers theyresent fluorescence studies both with spectral and time-esolved techniques to investigate how the confinement of theiposomes affect the fluorescence properties of various photo-ensitizers. Then follows four articles by Heikal, Bednark-ewicz, Bruns, and Prent et al., respectively, dealing with vari-us techniques for microscopy tools for cellular imaging andpectroscopy. The article by Bruns et al. describes a very el-

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egant system based on total internal reflections for high con-tent screening of plasma membranes utilizing fluorescencelifetimes and anisotropies. Prent et al. show how second-harmonic generation microscopy can be used to assess struc-tures and dynamics in 100-nm scales. The special section thenends with an article by Tkaczyk et al. concerning flow cytom-etry and a report by Fischer et al. on risk estimation for skindamage of femtosecond pulses. This is a very interesting areain order to provide an improved understanding and thereby, inthe future, better norms for laser safety for such short pulses.

AcknowledgmentsThe editors would first like to thank all lecturers and partici-pants of the summer school Biophotonics ’07 for making theschool a very fruitful and positive experience, the authors ofall papers in this special section for their excellent contribu-tions, as well as many reviewers around the world who pro-vided high-quality reviews of the manuscripts. Your dedicatedefforts have made this special section possible with such highquality. The editors would also like to thank the JBO publica-tion staff, Rita Davis and Karolyn Labes in particular, for theirinvaluable support and prompt assistance in helping meet theJBO standards. Finally, the editors would like to thank Prof.Bruce Tromberg, Editor-in-Chief, for his never-ending sup-port and stimulating encouragements during the entire processof producing this special section.

Stefan Andersson-Engels, Ph.D.Lund University

Peter E. Andersen, Ph.D.Technical University of Denmark

Special Section Guest Editors

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