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RADIOFREQUENCY CORRECTION FOR HYPERPOLARIZED DYNAMIC METABOLIC IMAGING

IP.com Disclosure Number: IPCOM000241264D
Publication Date: 2015-Apr-10
Document File: 5 page(s) / 155K

Publishing Venue

The IP.com Prior Art Database

Abstract

The disclosed invention provides a technique for removal of radiofrequency (RF) sampling conditions from dynamic metabolic imaging. The technique is used to remove RF effects and allows for a meta-analysis of several dynamic metabolic images collected using a wide variety of RF sampling methods, in multiple studies, carried out at multiple numbers of independent sites. In the studies [1-13C] lactate response is compared across a variety of tissues and pathology. The build-up rate (apparent Kpl) and the decay rate (apparent lactate T1) are found to be tissue specific.

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RADIOFREQUENCY CORRECTION FOR HYPERPOLARIZED DYNAMIC METABOLIC IMAGING

BACKGROUND

The present invention relates generally to hyperpolarized dynamic metabolic imaging and more particularly to a technique to remove radiofrequency (RF) sampling conditions from dynamic metabolic imaging.

In present time there is a substantial increase in use of dynamically sampled metabolic images, especially for hyperpolarized [1-13C] pyruvate. Metabolic data are sampled under a wide variety of radiofrequency (RF) conditions, including use of variable flip angles and multiple-band excitation. Although dynamic spectra can be collected with minimal RF perturbation, the dynamic spectra typically are only from large volumes, and lack definitive anatomical resolution. In contrast, more heavily saturated conditions, necessary for full dynamic imaging, have substantial impact on shape of temporal response, calculation of apparent rate constants, and signal-to-noise ratio (SNR) averaged over the response. Each of SNR, shape and apparent rate constants contributes to ultimate contrast-to-noise in dynamic metabolic imaging. However, comparison of dynamic metabolic images collected under different conditions requires calculation and removal of RF sampling effects.

It would be desirable to have an efficient technique to remove RF sampling conditions from dynamic metabolic imaging.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 depicts a graph that illustrates a fit to a kidney dynamic metabolic image collected with an equivalent of a 45-degrees excitation of lactate and a 12-degrees excitation every 5 s TR.

Figure 2 depicts bar graphs that illustrate fitted values of apparent T1 and apparent Kpl for 4 of the tissues investigated.

DETAILED DESCRIPTION

The disclosed invention provides a technique for removal of radiofrequency (RF) sampling conditions from dynamic metabolic imaging. The technique is used to remove RF effects and allows for meta-analysis of several dynamic metabolic images collected using a wide variety of RF sampling methods in multiple studies carried out at multiple numbers of independent sites. In the studies [1-13C] lactate response is compared across a variety of tissues and pathology. The build-up rate (apparent Kpl) and the decay rate (apparent lactate T1) are found to be tissue specific.

In the studies, pyruvate signal is a function of injected concentration, injection rate(s), delivery technique, location, polarization, and losses due to T1, perfusion, flow, RF sampling and metabolism. Given an inherent complexity of pyruvate bolus, no pyruvate fitting is attempted, but rather impact of RF is calculated based on estimated lifetime of any spin within bandwidth of RF excitation, referred to as pyruvate transit time (PTT). Also it is assumed that observed pyruvate signal pyrraw,n is a mixtu...