Phthalocyanine derivatives are currently under investigation for use in photodynamic therapy, which is a promising cancer treatment. These materials, which display preferential uptake in cancerous cells, also exhibit high fluorescence yields and can be used for tumour detection. Problems with steady-state fluorescence techniques such as excitation scatter and background autofluorescence can be eliminated by using time-resolved imaging techniques without the need for filters. A tissue phantom was assembled to test a constructed time-gated imaging system by drilling 36 wells of varying diameter and depth (10 mm to 1 mm) into a block of polymethyl methacrylate (PMMA). The system was used to record images of chloroaluminium phthalocyanine tetrasulfonate (AlPcTS) at differing concentrations in neat aqueous solvent and cell suspensions within the wells. A mixture of Intralipid (to mimic tissue scatter) and Evan's blue (to mimic tissue absorption) of depths ranging from 1 mm to 10 mm was placed on top of the PMMA block. The ensuing images were analysed using signal-to-noise ratios and contrast-detail curves. The results indicate that the time-gated imaging system can prevent background excitation scatter from distorting the fluorescence signal from a longer-lived photosensitizer without the need for filters.

The use of fluorescence for cancer detection is currently under investigation. Presently, steady-state fluorescence detection methods are in use, but have limitations due to poor contrast between the fluorescence of the tumor and background autofluorescence. Improved contrast can be obtained with time-resolved techniques because of the differing lifetimes between autofluorescence and exogenous photosensitizers that selectively accumulate within tumor tissue. An imaging system is constructed using a fast-gated (200-ps) charge-coupled device (CCD) camera and a pulsed 635-nm laser diode. To characterize the ability of the system to transfer object contrast to an image, the modulation transfer function (MTF) of the system is acquired by employing an extended knife-edge technique. A knife-edge target is assembled by drilling a rectangular well into a block of polymethyl methacrylate (PMMA). The imaging system records images of the photosensitizer, chloroaluminum phthalocyanine tetrasulfonate (AlPcTS), within the well. AlPcTS was chosen to test the system because of its strong absorption of 635-nm, high fluorescence yield, and relatively long fluorescence lifetime (approximately 7.5 ns). The results show that the system is capable of resolving 10(-4) M AlPcTS fluorescence as small as 1 mm. The findings of this study contribute to the development of a time-gated imaging system using fluorescence lifetimes.

Porphycenes are currently under investigation for use in Photodynamic therapy, which is a promising treatment for cancer. These materials, which display preferential uptake in cancerous cells, also exhibit high fluorescence yields, and can be used for tumour detection. Problems with steady-state fluorescence techniques such as background autofluorescence can be eliminated by the use of time-reolved techniques. Improved contrast can be obtained with time-resolved techniques because of the differing fluorescence lifetimes between autofluorescence and longer-living exogenous photosensitisers. An imaging system was constructed using a fast (200 ps) gated CCD camera and a pulsed 635 nm laser diode. A tissue phantom composed of polymethyl methacrylate (PMMA) with thirty-six wells of varying diameter and depth (10 mm to 1 mm) was assembled to test the system. The system was used to record images of a porphycene derivative within the wells at differing concentrations in an organic solvent. A tissue imitator was placed on top of the PMMA block at varying thickness. 10(-4) M zinc phthalocyanine tetrasulfonate was also placed on top of the block to mimic autofluorescence. The results indicate that the time-gated imaging system can prevent background excitation scatter and fluorescence from a shorter-lived fluorophore from distorting the fluorescence signal from a longer-lived photosensitiser.

A new modular high time resolution imaging camera system with sub-microsecond timing accuracy has been built in the Physics Dept. of NUI, Galway. The system was designed to be mounted on large telescopes for observing the temporal, spectral and polarisation characteristics of faint astronomical objects, such as optical pulsars.The camera system developed allows simultaneous and independent observing of multiple wavebands of emission from the target objects. This is achieved using optics that split images into their different spectral or polarisation components. The system currently incorporates a multi-anode microchannel array (MAMA) photon detecting and imaging camera with a time resolution of up to 100ns. This is combined with three high quantum efficiency avalanche photodiodes (APDs) with count rates of up to 16 million photons per second. The high time resolution recording system can allow for the removal of telescope tracking inaccuracy and wind shear off-line. This yields better PSFs for bright objects such as crowded globular star clusters.This combination of different detectors allows the system to be operated as a multi purpose, high QE, high time resolution system. The modular nature of the design electronics also allows the addition and removal of detectors without limiting the performance of other elements within the system. The data path is also designed so that archiving integrity is maintained while the data path is simultaneously used for real-time analysis and display systems.Future applications in the bio-medical imaging sector are envisaged for high time resolution fluorescence imaging, and astronomical polarisation studies.

Phthalocyanine derivatives. are currently under investigation for use in Photodynamic Therapy, which is a promising treatment, for cancer. These materials, which display preferential uptake in cancerous cells, also exhibit high fluorescence yields; and can be used for tumour detection. Problems with steady-state fluorescence techniques such as background autofluorescence can be eliminated by the use of time-resolved techniques. Improved contrast can be obtained with time-resolved techniques because of the differing lifetimes between endogenous and exogenous photosensitisers. An imaging system was constructed using a fast (200 psec) gated CCD camera and a pulsed 635 rim laser diode. A tissue phantom was assembled to test the system by drilling thirty-six wells of varying diameter and depth (10 mm to 1 mm) into a block of polymethyl methacrylate (PMMA). The system was used to record images of chloroaluminum phthalocyanine tetrasulfonate within the-wells at differing concentrations in phosphate buffer. A mixture of 1) Intralipid to mimic tissue scatter, 2) Evans blue to mimic tissue absorption, and 3) zinc phthalocyanine tetrasulfonate to mimic-healthy tissue:autofluorescence of varying depth was placed on top of the PMMA block. These results contribute to the precision of a time-gated imaging system to image living organisms using fluorescence lifetimes.

The aim of this paper is to demonstrate that trailing wake vortices can be reliably detected from an axial point of view using Doppler lidar. Three-dimensional large eddy simulations of wake vortices are performed in order to investigate the performances of an airborne Doppler Lidar based wake vortex detection system, known as the MFLAME system. Three test cases were investigated: i) Crow instabilities, ii) wake vortex decay in isotropic homogeneous turbulence and iii) wake vortex collapse in convective atmospheric boundary layer. In all cases, the axial velocity is not initialized. Once the appropriate flowfield is computed, it is inputted into the MFLAME system simulator. The results indicate that a forward looking Doppler Lidar system is capable of detecting wake vortex signatures from several ages of the applied vortices.