Early detection of cancer through medical imaging has a critical impact on patient survival rates. There are many efforts for detecting early cancer in situ using modalities other than traditional medical optical imaging, which contain additional information over conventional micrographs of surface morphology acquired without staining. We analyzed the Mueller matrix components of human colon tissue obtained with an imaging polarimeter microscope at an illumination wavelength of 442 nm by principal components analysis in order to separate the traditional non-polarized gray image and to investigate the structure of the parameter space of polarization transformation by tissue. We also analyzed Mueller matrix by mapping it to a coherent matrix and performed eigenvalue analysis. The 1st to 4th principal components contain 99% of the information present in the images; polarization information contributes less than 10% of the information in the Mueller matrix. In one individual, 80% of the cancer was detected, without the first components which contains traditional non-polarized gray image for traditional diagnosis. Microscopic fine structures were observed, particularly in the 3rd and 4th principal components’ score images. The entropy image of corrugated cancer tissue was smoother than that of the traditional gray image. There were several abnormal regions identified in adjacent regions of cancer, whose residues exceeded the noise level of the instrument used.
Mueller polarimetric imaging in dark-field observation shows a contrast enhancement between healthy and cancerous human colon tissue in some reports. We have developed a Mueller-matrix microscope system that combines a dark-field polarization illuminator with an imaging polarimeter to measure the polarization characteristics of scattered light from human colon tissue samples. A multichannel light source permits the acquisition of multispectral Mueller matrices of the sample. The wavelength and polarization state selections are automated, as is the Mueller matrix measurement. The imaging polarimeter permits the system to perform fast, stable measurements. Calibration allows us to reduce the error associated with the illumination and imaging optics in the microscope system. Our system indicates a clear difference between the average Mueller matrix measurements of healthy and cancerous human colon tissue, which agrees well with previously reported results.
Preclinical single-photon emission computed tomography (SPECT) is an essential tool for studying the pro-gression, response to treatment, and physiological changes in small animal models of human disease. The wide range of imaging applications is often limited by the static design of many preclinical SPECT systems. We have developed a prototype imaging system that replaces the standard static pinhole aperture with two sets of movable, keel-edged copper-tungsten blades configured as crossed (skewed) slits. These apertures can be positioned independently between the object and detector, producing a continuum of imaging configurations in which the axial and transaxial magnifications are not constrained to be equal. We incorporated a megapixel silicon double-sided strip detector to permit ultrahigh-resolution imaging. We describe the configuration of the adjustable slit aperture imaging system and discuss its application toward adaptive imaging, and reconstruction techniques using an accurate imaging forward model, a novel geometric calibration technique, and a GPU-based ultra-high-resolution reconstruction code.
We are developing a prototype gamma-ray imaging system that consists of two sets of movable, keel-edged
copper-tungsten blades configured as crossed slits. These apertures can be positioned independently between the
object and detector, producing an anamorphic image in which the axial and transaxial magnifications are not
constrained to be equal. The detector is a 60 mm x 60 mm, millimeter thick, one-megapixel silicon double-sided
strip detector. The flexible nature of this system allows the application of adaptive imaging techniques. We
will discuss system details, calibration and acquisition methods, and our progress towards biological imaging
An inexpensive, portable digital radiography (DR) detector system for use in remote regions has been built and
evaluated. The system utilizes a large-format digital single-lens reflex (DSLR) camera to capture the image from a
standard fluorescent screen. The large sensor area allows relatively small demagnification factors and hence minimizes
the light loss. The system has been used for initial phantom tests in urban hospitals and Himalayan clinics in Nepal, and
it has been evaluated in the laboratory at the University of Arizona by additional phantom studies. Typical phantom images are presented in this paper, and a simplified discussion of the detective quantum efficiency of the detector is given.