PURPOSE To correct for attenuation in two-photon fluorescence (TPF) measurements of riboflavin absorption in porcine corneas. METHODS Two-photon fluorescence imaging of riboflavin was performed using excitation at a wavelength of 890 nm, with fluorescence signal detected between 525 and 650 nm. TPF signal attenuation was demonstrated by imaging from either side of a uniformly soaked corneoscl...

For activity quantification based on planar scintillation camera measurements, photon attenuation is an important factor that needs to be corrected for in a patient- and organ-specific manner. One possibility for obtaining attenuation correction maps is to use X-ray CT scout images. Since the intensity of scout images is in relative numbers, their image values need to be multiplied by a factor ...

Attenuation correction is necessary for quantification in micro-single-photon emission computed tomography (micro-SPECT). In general, this is done based on micro-computed tomographic (micro-CT) images. Derivation of the attenuation map from magnetic resonance (MR) images is difficult because bone and lung are invisible in conventional MR images and hence indistinguishable from air. An ultrashor...

Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy’s cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy’s condition was derived for an attenuation-free situation, we hypot...

This paper explores the fundamentals and applications of single and entangled photon sources. These sources are the ground works for advances in quantum communications, ranging from quantum cryptography to topics as peculiar as quantum teleportation. Single Photon Sources I. What is a Single Photon Source? A single photon source is an emitter of light that has all of its photons separated in ti...

Photon dose calculation algorithms (such as the pencil beam and collapsed cone, CC) model the attenuation of a primary photon beam in media other than water, by using pathlength scaling based on the relative mass density of the media to water. In this study, we assess if differences in the electron density between the water and media, with different atomic composition, can influence the accurac...

UNLABELLED The purpose of this study was to investigate whether a correction for annihilation photon attenuation in small objects such as mice is necessary. The attenuation recovery for specific organs and subcutaneous tumors was investigated. A comparison between different attenuation correction methods was performed. METHODS Ten NMRI nude mice with subcutaneous implantation of human breast ...

background: in radiation therapy, water is the phantom material of choice, both for reference and for relative dosimetry measurements. solid phantoms, however, are more useful for routine measurements because they tend to be more robust and easier to set up than water phantoms. materials and methods: fluka input data cards have been arranged in sequential order. a simple cylindrical geometry wi...

introduction: scattered photon is one of the main defects that degrade the quality and quantitative accuracy of nuclear medicine images. accurate estimation of scatter in projection data of spect is computationally extremely demanding for activity distribution in uniform and non-uniform dense media. methods: the objective of this paper is to develop and validate a scatter correction technique t...