ABSTRACT
Accuracy in microarray technology requires new approaches to microarray reader development. A microarray reader system (optical scanning array or OSA reader) based on automated microscopy with large field of view, high speed 3 axis scanning at multiple narrow-band spectra of excitation light has been developed. It allows fast capture of high-resolution, multi-fluorescence images and is characterized by a linear dynamic range and sensitivity comparable to commonly used photo-multiplier tube (PMT)-based laser scanner. Controlled by high performance software, the instrument can be used for scanning and quantitative analysis of any type of dry microarray. Studies implying temperature-controlled hybridization chamber containing a microarray can also be performed. This enables the registration of kinetics and melting curves. This feature is required in a wide range of on-chip chemical and enzymatic reactions including on-chip PCR amplification. We used the OSA reader for the characterization of hybridization and melting behaviour of oligonucleotide:oligonucleotide duplexes on three-dimensional Code Link slides.
Subject(s)
Image Processing, Computer-Assisted/instrumentation , Oligonucleotide Array Sequence Analysis/instrumentation , Oligonucleotides/chemistry , Kinetics , Microscopy, Fluorescence/instrumentation , Nucleic Acid Hybridization/methods , Oligonucleotide Array Sequence Analysis/methods , SoftwareABSTRACT
The problem of transverse plane reconstruction from an ensemble of projections is considered in its general formulation and an analytically exact solution to the attenuated tomographic operator is proposed. Such a technique, called the regularizing iterative method (RIM), allows the introduction of a priori knowledge on the size and shape of the activity distribution and in principle on the exact attenuation distribution. The relaxation factor used is so named because it provides noise filtering for a small number of iterations. The effectiveness of RIM was studied in the single photon emission computed tomography (SPECT) problem with the aim of correcting for attenuation before quantitative study. Its application involves the use of a rotating scintillation camera connected to a mini-computer system. Various mathematical and physical phantoms were studied, and a satisfactory attenuation correction was always obtained in the final image with an improvement in the contrast and signal-to-noise ratio. Preliminary clinical studies on liver transverse sections seems to indicate an improvement in deep lesion detectability, compared with images obtained by the filtered (Ramp) back projection technique.
Subject(s)
Tomography, Emission-Computed/methods , Models, Structural , Models, Theoretical , Technology, RadiologicABSTRACT
A whole-body single-photon emission computed tomography system has been evaluated in terms of its physical performance. It consists of a standard GE 400 T maxi camera rotating on a ring stand, coupled to an Informatek Simis 3 computer system. In its standard mode of operation, 64 or 128 successive views of 64 X 64 or 128 X 64 matrices are collected at regular angular samples. The reconstruction of up to 64 possible adjacent transverse sections, sorted into coronal, sagittal, and oblique sections, is obtained by filtered backprojection. A conventional parallel-hole collimator is used. The uniformity of the camera field of view is corrected by the GE hardware module. The resolution in the transverse plane is typically of 15.5 mm in a 20 cm Lucite phantom, and independent of radial distance. The physical slice thickness is 19 mm (full width at half maximum of the longitudinal response using a point source) with only slight variations along the diameter of the image. The sensitivity is approximately 7,000 cps mCi-1 as measured using a 99m Tc thin source, enabling images of reasonable signal-to-noise ratio to be obtained in 10 min. The effect of the energy window, the number of angular samples, and the linear sampling modes on the transverse resolution and contrast is measured and discussed.
