Research

Dr. Osman's main interests are in the area of medical image analysis. During his PhD, Dr. Osman initially work in the area of Vector Tomography with his advisor, Dr. Jerry Prince. After publishing his first journal paper in Vector Tomography, he started workin on an interesting area of measuring the motion of the heart using MRI. It happened that a unique method, called MR Tagging, has been developed by Drs. Elias Zerhouni and Leon Axel generating temorary markers inside the tissue, noninvasevly. These markers would show the deformation of the heart's wall muscle (myocardium) during the cardiac cycle and have the ptoential of making the quantification of motion possible. the latter objective was significant, but was challanging as well. Methods for analyzing the tagged images have been developed, but they required a lot of user interaction and long time to complete analysis that make MR tagging unsuitable for clinical usage.

Harmonic Phase (HARP)

A new technique, called harmonic phase (HARP), was developed by Drs. Osman and Prince that solved a number of the problems facing the analysis of the tagged MR images. The technique reduced teh analysis time from few hours to minutes (and seconds sometimes). The technique was based on the same concepts used in radio transmission with FM (frequency modulation). In FM, the signal is sent on a sinusiodal wave signal (called carrier) by changing the local frequency of the carrier by the signal. When received, the signal can be recovered by detecting the changes in local frequency of the FM wave. Similalry, in HARP, the tagging pattern is considered to be a carrier whose local frequency (spacing between tags) is changed by local contracction of the myocardium. The amount of contraction in this case is measured in the form of strain. By measuring the local frequency of the tag pattern in the wall, the local motion and contraction of the wall can be measured.

2D HARP

HARP by default analyzes images of short- or long-axis images to determine inplane motion; hence it is 2D motion. The majority of the developments so far were in this area.

3D HARP

This research intended to extend HARP from 2D image analysis to 3D. Specifically, the purpose is to determine the 3D motion of the heart from a limited number of views (short- and long-axes) with tagged MR images.

Strain-Encoding (SENC)

Based in a concept similar to that used in HARP, which is that measuring the change in local frequency of the tag reveals local function of the wall. Strain encoding (SENC) was later developed by Dr. Osman as a modification to the MR imaging pulse sequence so that the changes in local freqeuncy appears immediately on the MR images (no need for analysis of tagged images).

SENC in the heart

This specific topic uses SENC for determining regional function of the heart.

SENC in Elastography

Another application for SENC is to determine tissue stiffness in order to detect cancer. The technique, in a way, provides a quantitative form of palpation.