P. Mani Joseph

Learn More
It is often desired to calculate line integrals through a field of reconstructed CT density pixels for the purpose of improving CT image quality. Two algorithms widely published and discussed in the past are known to either degrade spatial resolution or generate errors in the results due to the discontinuous "square pixel" modeling of the reconstructed(More)
Apparent diffusion coefficients (ADC) were measured in a rat spinal cord weight-drop injury model. After sacrifice, the spinal cords were fixed in situ and excised for MR imaging and ADC measurement. Diffusion is anisotropic in normal gray and white matter. There were significant decreases in ADCs measured along the longitudinal axis of the injured cord and(More)
A method that corrects for artifacts in X-ray transmission scanners created by the alteration of the energy spectrum by bone is described. The method involves two reconstructions of the pictures: the first establishes the approximate distribution of bone and the second enables the artifacts to be eliminated. The first reconstruction is needed to establish(More)
Zero-mean noise introduced into quadrature detected MRI signals is generally rectified by the reconstruction algorithm to give a nonzero background intensity in the displayed image. In low signal-to-noise ratio (SNR) images, this background will inflate region of interest (ROI) signal measurements, leading to improper T2 and diffusion fits. A method is(More)
A method is described capable of correcting artifacts in x-ray computer tomography (CT) images due to beam hardening in an arbitrary number of substances. The method works with reconstructed image data and does not require the original raw data. It is necessary to have an estimate of the spectrum of the incident x-ray beam. The method is similar to(More)
To study the conventional and chemical-shift MR images of fatty, hemopoietic, and ischemic bone marrow, four normal femurs from autopsies and six femoral heads from total hip replacement done for avascular necrosis (AVN) were imaged with a small-bore 1.4-T MR unit. T1- and T2-weighted spin-echo images, fat- and water-selective spin-echo images, and(More)
Human and rat cervical spinal cords were imaged with high-resolution spin-echo and inversion-recovery pulse sequences in an experimental 1.9-T MR system. The gross morphology of the cord was easily discernible in fresh and fixed specimens, including the white and gray commissures, dorsal and ventral horns, and lateral and posterior funiculi. The T1, T2, and(More)
Dual energy CT scanning (tomochemistry) has been proposed as a method for determining various parameters relating to the elemental composition of the tissues. In this paper, our aim is to study the relative noise inherent in two proposed techniques for dual energy scanning; a "two crystal" technique and a "two kV" technique. In the two crystal technique, a(More)
Phantoms for evaluation of nuclear magnetic resonance (NMR) imaging systems were made from water-based agarose gels, according to a standard procedure herein described. Copper sulfate (CuSO4) was included in the gels to further affect their proton relaxation characteristics. The proton relaxation rates of each batch of gel are dependent on the(More)
Six freshly enucleated, unfixed human eyes with choroidal melanomas were imaged on a 1.4-T superconducting magnetic resonance (MR) imaging system. Immediately thereafter the eyes were sectioned, and tumor samples were removed for study on a variable-field (0.19-1.4 T) nuclear MR spectroscopy unit. Shorter T1 and T2 relaxation times were observed in those(More)