T2 Relaxometry with Indirect Echo Compensation from Highly Undersampled Data

This invention enables accurate T2 estimation from highly undersampled data with indirect echo contamination. The technique is based on an iterative algorithm where the signalmodel (which is derived from a model that takes into account the presence of indirect echoes) is linearized using principal component analysis. The goal of the proposed SlicE Resolved ExteNd phAse graph baseD rEconstruction of principal component coefficient maps (SERENADE) algorithm is to obtain accurate T2 estimates from data acquired in a short period of time (as short as a breath hold). Currently there are a few algorithms capable of performing T2 estimation from highly undersampled data. These algorithms ignore the indirect echo contamination which results in T2 overestimation especially when non-180° refocusing pulses are prescribed (as in athe case in high field magnets)

Background:
While MRI technical improvements have transformed this modality for clinical application over the past 15 years, there remains a number of pressing technical requirements for continued progress towards more extensive utilization in clinical applications. A major current aim in furthering MRI development and applications is the need to achieve shorter acquisition times, particularly for imaging tissues that move (as a result from physiological effects such as respiration) or in types of imaging (as is the case for parametric imaging) where obtaining the required information involves long acquisition times rendering the method impractical under clinical conditions.

The SEPG algorithm has been recently proposed for T2 estimation with indirect echo compensation, however, this algorithm is not capable of performing the estimation using highly undersampled data. Slice-resolve Extended Phase Graph (SEPG) signal model has been proposed to estimate decay curves that consider indirect echoes. The main problem of incorporating the SEPG approach into a model-based reconstruction (in order to obtain accurate T2 estimates from highly undersampled data) is that the signal model is highly non-linear.

Applications:

• The common denominator is to able to estimate a parameter called the T2 relaxation time in a very short period of time. Changes in T2 are Indicative of a wide variety of pathologies including inflammatory processes, tumor formation, iron deposition, etc. In the case of abdominal and cardiothoracic imaging the technique has a tremendous advantage because it allows for accurate T2 mapping (by compensating for the effects of indirect echoes) from data acquired in just a single breath hold. Currently, no other techniques are available to achieve this degree of acceleration when high temporal and spatial resolution is required for tissue characterization. Thus, the proposed technology could represent a considerable opportunity regarding commercial value, such as through licensing arrangements.
   

Advantages:

• New technique enables accurate T2 estimation from highly undersampled data with indirect echo contamination
• SERENADE enables fast T2 estimation for any anatomy in the body
• Enables T2 mapping with non-180° refocusing pulses which is essential when working at high magnetic fields (eg, 3 T) or for cardiac imaging when short refocusing pulses are needed to shorten the acquisition window
• Primarily useful for abdominal and cardiothoracic applications where the imaging time is limited to a breath hold