An approach to photodynamic treatment of tumors is the interstitial implantation of fiber optic light sources. Dosimetry is critical in identifying regions of low light intensity in the tumor which may prevent tumor cure. We describe a numerical technique for calculating light distributions within tumors, from multiple fiber optic sources. The method was tested using four translucent plastic needles, which were placed in a 0.94 X 0.94 cm grid pattern within excised Dunning R3327-AT rat prostate tumors. A cylindrical diffusing fiber tip, illuminated by 630 nm dye laser light was placed within one needle and a miniature light detector was placed within another. The average penetration depth in the tumor region between the two needles was calculated from the optical power measured by the detector, using a modified diffusion theory. Repeating the procedure for each pair of needles revealed significant variations in penetration depth within individual tumors. Average values of penetration depth, absorption coefficient, scattering coefficient, and mean scattering cosine were 0.282 cm, 0.469 cm-1, 250 cm-1 and 0.964, respectively. Calculated light distributions from four cylindrical sources in tumors gave reasonable agreement with direct light measurements using fiber optic probes.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1118/1.596361 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
A simple cavity-enhanced laser-based heater for reflective samples.
Rev Sci Instrum
January 2025
Institute for Physical Chemistry, University of Göttingen, 37077 Göttingen, Germany.
Surface science instruments require excellent vacuum to ensure surface cleanliness; they also require control of sample temperature, both to clean the surface of contaminants and to control reaction rates at the surface, for example, for molecular beam epitaxy and studies of heterogeneous catalysis. Standard approaches to sample heating within high vacuum chambers involve passing current through filaments of refractory metals, which then heat the sample by convective, radiative, or electron bombardment induced heat transfer. Such hot filament methods lead to outgassing of molecules from neighboring materials that are inadvertently heated; they also produce electrons and ions that may interfere with other aspects of the surface science experiment.
View Article and Find Full Text PDFDevelopment of a novel high-frequency reciprocal structure fiber optical pulsed current sensor.
Rev Sci Instrum
January 2025
Department of Plasma Physics and Fusion Engineering, University of Science and Technology of China, Hefei 230026, China.
A novel all-fiber optic current sensor (FOCS) is designed specifically for the measurement of large transient currents based on the Faraday effect. A reciprocal symmetric structure is incorporated into the optical sensing loop, and the current dependent phase demodulation is achieved by using a passive optical fiber coupler and the homodyne detection scheme. This design offers several advantages, including structural simplicity, high voltage insulation, low noise, high linearity, and excellent frequency response, and is highly suitable for use in any system of high-voltage, high-power, and high-frequency in nature.
View Article and Find Full Text PDFFTW SERS probes with Ag NCs-GO composite structure excited by evanescent wave for in situ detection of permethrin.
Anal Chim Acta
March 2025
Zhejiang Key Laboratory of Advanced Optical Functional Materials and Devices, Ningbo University, Ningbo, 315211, China; Engineering Research Center for Advanced Infrared Photoelectric Materials and Devices of Zhejiang Province, Ningbo University, Ningbo, 315211, China. Electronic address:
Background: Permethrin is a pesticide used to kill insects, and once used in excess, it poses a great threat to the environment and human health, therefore, it is necessary to realize the rapid and accurate detection of permethrin. Fiber optic surface enhanced Raman scattering (SERS) probes have the advantages of small volume and can be used for remote monitoring, which have great potential for application in achieving in-situ detection of pesticide residues.
Results: Fiber taper waist (FTW) SERS probes modified by silver nanocubes-graphene oxide (Ag NCs-GO) composite structures were prepared for in situ detection of permethrin in lake water.
Retinal and Choroidal Circulation Impairments in Fanconi Anemia.
Am J Ophthalmol
January 2025
Hacettepe University School of Medicine, Department of Ophthalmology, Ankara, Turkey.
Objective: To evaluate the effects of Fanconi anemia (FA) on retinal and choroidal microvasculature using Optical Coherence Tomography (OCT) and Optical Coherence Tomography Angiography (OCTA).
Design: Cohort study with age-matched controls.
Subjects And Participants: This study included 11 eyes from 11 patients diagnosed with FA and 12 eyes from 12 age-matched healthy controls.
Prevalence and Clinical Associations of Peripapillary Hyperreflective Ovoid Mass-like Structures in Craniosynostosis.
J Neuroophthalmol
January 2025
Department of Ophthalmology (JGJ-C, TE, Y-HC, LRD, RAG), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts; Frank H. Netter Medical School (JGJ-C), North Haven, Connecticut; and Department of Anesthesiology (DZ), Critical Care and Pain Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts.
Background: Patients with craniosynostosis are at high risk of developing elevated intracranial pressure (ICP) causing papilledema and secondary optic atrophy. Diagnosing and monitoring optic neuropathy is challenging because of multiple causes of vision loss including exposure keratopathy, amblyopia, and cognitive delays that limit examination. Peripapillary hyperreflective ovoid mass-like structures (PHOMS) are an optical coherence tomography (OCT) finding reported in association with papilledema and optic neuropathy.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!