An accelerated photo-magnetic imaging reconstruction algorithm based on an analytical forward solution and a fast Jacobian assembly method.

We previously introduced photo-magnetic imaging (PMI), an imaging technique that illuminates the medium under investigation with near-infrared light and measures the induced temperature increase using magnetic resonance thermometry (MRT). Using a multiphysics solver combining photon migration and heat diffusion, PMI models the spatiotemporal distribution of temperature variation and recovers high resolution optical absorption images using these temperature maps. In this paper, we present a new fast non-iterative reconstruction algorithm for PMI. This new algorithm uses analytic methods during the resolution of the forward problem and the assembly of the sensitivity matrix. We validate our new analytic-based algorithm with the first generation finite element method (FEM) based reconstruction algorithm previously developed by our team. The validation is performed using, first synthetic data and afterwards, real MRT measured temperature maps. Our new method accelerates the reconstruction process 30-fold when compared to a single iteration of the FEM-based algorithm.

An extended analytical approach for diffuse optical imaging.

In this work, we introduce an analytical method to solve the diffusion equation in a cylindrical geometry. This method is based on an integral approach to derive the Green's function for specific boundary conditions. Using our approach, we obtain comprehensive analytical solutions with the Robin boundary condition for diffuse optical imaging in both two and three dimensions. The solutions are expressed in terms of the optical properties of tissue and the amplitude and position of the light source. Our method not only works well inside the tissue but provides very accurate results near the tissue boundaries as well. The results obtained by our method are first compared with those obtained by a conventional analytical method then validated using numerical simulations. Our new analytical method allows not only implementation of any boundary condition for a specific problem but also fast simulation of light propagation making it very suitable for iterative image reconstruction algorithms.

A photo-multiplier tube-based hybrid MRI and frequency domain fluorescence tomography system for small animal imaging.

Fluorescence tomography (FT) is a promising molecular imaging technique that can spatially resolve both fluorophore concentration and lifetime parameters. However, recovered fluorophore parameters highly depend on the size and depth of the object due to the ill-posedness of the FT inverse problem. Structural a priori information from another high spatial resolution imaging modality has been demonstrated to significantly improve FT reconstruction accuracy. In this study, we have constructed a combined magnetic resonance imaging (MRI) and FT system for small animal imaging. A photo-multiplier tube is used as the detector to acquire frequency domain FT measurements. This is the first MR-compatible time-resolved FT system that can reconstruct both fluorescence concentration and lifetime maps simultaneously. The performance of the hybrid system is evaluated with phantom studies. Two different fluorophores, indocyanine green and 3-3' diethylthiatricarbocyanine iodide, which have similar excitation and emission spectra but different lifetimes, are utilized. The fluorescence concentration and lifetime maps are both reconstructed with and without the structural a priori information obtained from MRI for comparison. We show that the hybrid system can accurately recover both fluorescence intensity and lifetime within 10% error for two 4.2 mm-diameter cylindrical objects embedded in a 38 mm-diameter cylindrical phantom when MRI structural a priori information is utilized.

Combined fluorescence and X-Ray tomography for quantitative in vivo detection of fluorophore.

Initial results from a novel dual modality preclinical imager which combines non-contact fluorescence tomography (FT) and x-ray computed tomography (CT) for preclinical functional and anatomical in vivo imaging are presented. The anatomical data from CT provides a priori information to the FT reconstruction to create overlaid functional and anatomical images with accurate localization and quantification of fluorophore distribution. Phantoms with inclusions containing Indocyanine-Green (ICG), and with heterogeneous backgrounds including iodine in compartments at different concentrations for CT contrast, have been imaged with the dual modality FT/CT system. Anatomical information from attenuation maps and optical morphological information from absorption and scattering maps are used as a priori information in the FT reconstruction. Although ICG inclusions can be located without the a priori information, the recovered ICG concentration shows 75% error. When the a priori information is utilized, the ICG concentration can be recovered with only 15% error. Developing the ability to accurately quantify fluorophore concentration in anatomical regions of interest may provide a powerful tool for in vivo small animal imaging.

Functional recovery of patients with brain tumor or acute stroke after rehabilitation: a comparative study.

The aim of this study was to compare the locomotor functional recovery of patients with brain tumor and patients with stroke. Each patient with a brain tumor was matched to a patient with stroke according to the lesion side. Twenty-one patients operated for intracranial tumors and 21 patients with stroke were studied. The mean ages (+/- standard deviation) of patients were 52.5+/-16 years for patients with brain tumor and 56.7+/-11 years for patients with stroke. For each patient, the age, gender, presence of aphasia, smoking habit, co-morbidities, lesion origin and lesion size (for the brain tumor group) were recorded. Locomotor and functional recovery were evaluated by using the Postural Assessment Scale for Stroke, the Berg Balance Scale, Motor Assessment Scale and the mobility section of the Functional Impairment Measure. There was no difference regarding demographic characteristics between the two groups. After rehabilitation both groups had significantly improved in terms of all parameters, but the extent of improvement did not differ between the two groups.

In vivo water state measurements in breast cancer using broadband diffuse optical spectroscopy.

Structural changes in water molecules are related to physiological, anatomical and pathological properties of tissues. Near infrared (NIR) optical absorption methods are sensitive to water; however, detailed characterization of water in thick tissues is difficult to achieve because subtle spectral shifts can be obscured by multiple light scattering. In the NIR, a water absorption peak is observed around 975 nm. The precise NIR peak's shape and position are highly sensitive to water molecular disposition. We introduce a bound water index (BWI) that quantifies shifts observed in tissue water absorption spectra measured by broadband diffuse optical spectroscopy (DOS). DOS quantitatively measures light absorption and scattering spectra and therefore reveals bound water spectral shifts. BWI as a water state index was validated by comparing broadband DOS to magnetic resonance spectroscopy, diffusion-weighted MRI and conductivity in bound water tissue phantoms. Non-invasive DOS measurements of malignant and normal breast tissues performed in 18 subjects showed a significantly higher fraction of free water in malignant tissues (p < 0.0001) compared to normal tissues. BWI of breast cancer tissues inversely correlated with Nottingham-Bloom-Richardson histopathology scores. These results highlight broadband DOS sensitivity to molecular disposition of water and demonstrate the potential of BWI as a non-invasive in vivo index that correlates with tissue pathology.

Fluorescence diffuse optical tomography with functional and anatomical a priori information: feasibility study.

Fluorescence diffuse optical tomography (FT) is an emerging molecular imaging technique that can spatially resolve both fluorophore concentration and lifetime parameters. In this study, we investigate the performance of a frequency-domain FT system for small inclusions that are embedded in a heterogeneous background. The results demonstrate that functional and structural a priori information is crucial to be able to recover both parameters with high accuracy. The functional a priori information is defined by the absorption and scattering maps at both excitation and emission wavelengths. Similarly, the boundaries of the small inclusion and different regions in the background are utilized as the structural a priori information. Without a priori information, the fluorophore concentration of a 5 mm inclusion in a 40 mm medium is recovered with 50% error, while the lifetime cannot be recovered at all. On the other hand, when both functional and structural information are available, the true lifetime can be recovered and the fluorophore concentration can be estimated only with 5% error. This study shows that a hybrid system that can acquire diffuse optical absorption tomography (DOT), FT and anatomical images in the same setting is essential to be able to recover the fluorophore concentration and lifetime accurately in vivo.

The use of hydrotherapy for the management of spasticity.

INTRODUCTION: Spasticity is a major problem for the rehabilitation team. Physiotherapy is a vital component of therapy. Oral medication and other modalities such as heat, cold, ultrasound, electrical stimulation, and surgery (neuro-surgical or orthopedic) can also be used. The aim of this study was to compare the effects of hydrotherapy on spasticity and Functional Independence Measure (FIM) scores of patients with spinal cord injury (SCI). MATERIALS AND METHODS: This is a control case matched study. Twenty SCI patients were divided into 2 groups and matched for age, gender, injury time, Ashworth scores, oral baclofen intake, American Spinal Injury Association, and FIM scores. The control group received passive range of motion exercise twice a day and oral baclofen for 10 weeks. The study group also received passive range of motion and oral baclofen, as well as 20 min of water exercises (at 71 degrees F, full immersion) 3 times per week. The authors evaluated spasm severity, FIM scores, oral baclofen intake, and Ashworth scales, between groups at the beginning and at the end of the treatment period. RESULTS: Both groups demonstrated a significant increase in FIM scores. However, the hydrotherapy group demonstrated a larger increase (P < 0.0001) than the control group. There was a statistically significant decrease in oral baclofen intake in the hydrotherapy group (P < 0.01). There was no statistical change in the control group. Spasticity was evaluated by the Ashworth scale. There was a statistical improvement in each group (P < 0.01, P < 0.02). However, when compared to the control group, the use of hydrotherapy produced a significant decrease in spasm severity (P < 0.02). CONCLUSION: Side effects are often seen when using oral drug treatment for spasticity. Adding hydrotherapy to the rehabilitation program can be helpful in decreasing the amount of medication required. Future studies must evaluate benefits of hydrotherapy for rehabilitation.

Comparison of water and lipid content measurements using diffuse optical spectroscopy and MRI in emulsion phantoms.

We present a quantitative comparison of lipid and water signals obtained from broadband Diffuse Optical Spectroscopy (DOS) and Magnetic Resonance Imaging (MRI). DOS and MRI measurements were performed on an identical set of emulsion phantoms that were composed of different water/soybean oil fractions. Absolute concentrations of water and lipid ranging from 35-94% and 63-6%, respectively were calculated from quantitative broadband near-infrared (NIR) absorption spectra (650-1000 nm). MR images of fat and water were separated using the three-point Dixon technique. DOS and MRI measured water and lipid were highly correlated (R(2) = 0.98 and R(2) = 0.99, respectively) suggesting that these techniques are complementary over a broad range of physiologically relevant water and lipid values. In addition, comparison of DOS derived concentrations to the MRI "gold standard" technique validates our quantitation approach and permits estimation of DOS accuracy and sensitivity in vivo.