[Show abstract][Hide abstract] ABSTRACT: We have developed a model-based iterative image reconstruction scheme based on the equation of radiative transfer in the frequency domain for the applications in small animal optical tomographic imaging. To test the utility of such a code in small animal imaging we have furthermore developed a numerical phantom of a mouse. In simulation studies using this and other phantoms, we found that to make truly use of phase information in the reconstruction process modulation frequencies well above 100 MHz are necessary. Only at these higher frequencies the phase shifts introduced by the lesions of interest are large enough to be measured. For smaller frequencies no substantial improvements over steady-state systems are achieved in small geometries typical for small animal imaging.
Preview · Article · Apr 2005 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: To identify classifiers in images obtained with sagittal laser optical tomography (SLOT) that can be used to distinguish between joints affected and not affected by synovitis.
78 SLOT images of proximal interphalangeal joints II-IV from 13 patients with rheumatoid arthritis were compared with ultrasound (US) images and clinical examination (CE). SLOT images showing the spatial distribution of scattering and absorption coefficients within the joint cavity were generated. The means and standard errors for seven different classifiers (operator score and six quantitative measurements) were determined from SLOT images using CE and US as diagnostic references. For classifiers showing significant differences between affected and non-affected joints, sensitivities and specificities for various cut off parameters were obtained by receiver operating characteristic (ROC) analysis.
For five classifiers used to characterise SLOT images the mean between affected and unaffected joints was statistically significant using US as diagnostic reference, but statistically significant for only one classifier with CE as reference. In general, high absorption and scattering coefficients in and around the joint cavity are indicative of synovitis. ROC analysis showed that the minimal absorption classifier yields the largest area under the curve (0.777; sensitivity and specificity 0.705 each) with US as diagnostic reference.
Classifiers in SLOT images have been identified that show statistically significant differences between joints with and without synovitis. It is possible to classify a joint as inflamed with SLOT, without the need for a reference measurement. Furthermore, SLOT based diagnosis of synovitis agrees better with US diagnosis than CE.
Full-text · Article · Mar 2005 · Annals of the Rheumatic Diseases
[Show abstract][Hide abstract] ABSTRACT: Over the last decade the field of diffuse optical tomography (DOT) has seen considerable advances and is now close to becoming a clinically viable medical imaging modality. Imaging of dynamic changes in blood parameters, functional brain imaging, and breast imaging are the most advanced application areas of this novel technique. In this study we focus on difficulties that are encountered when DOT is employed for imaging small tissue volumes. These problems arise, for example, in studies involving small animals, such as rats or mice, or human finger joints. In these cases widely accepted image reconstruction schemes that rely on the diffusion approximation have limited applicability, and more advanced model-based iterative image reconstructions methods that make use of the equation of radiative transfer promise more accurate results.
[Show abstract][Hide abstract] ABSTRACT: We present a novel optical tomographic imaging system that was designed to determine two-dimensional spatial distribution of optical properties in a sagittal plane through finger joints. The system incorporates a single laser diode and a single silicon photodetector into a scanning device that records spatially resolved light intensities as they are transmitted through a finger. These data are input to a model-based iterative image reconstruction (MOBIIR) scheme, which uses the equation of radiative transfer (ERT) as a forward model for light propagation through tissue. We have used this system to obtain tomographic images of six proximal interphalangeal finger joints from two patients with rheumatoid arthritis. The optical images were compared to clinical symptoms and ultrasound images.
Full-text · Article · May 2004 · Physics in Medicine and Biology
[Show abstract][Hide abstract] ABSTRACT: We report on a clinical study involving measurements on 80 proximal interphalangeal joints of patients with rheumatoid arthritis. We evaluated the performance of a novel sagittal optical tomographic imager by comparing it to ultrasound imaging.