US 12,449,494 B2
Chemical exchange saturation transfer (CEST) magnetic resonance imaging using an ASEF or AROSE system
Tao Jin, Wexford, PA (US); and Julius Chung, Pittsburgh, PA (US)
Assigned to University Of Pittsburgh—Of the Commonwealth System of Higher Education, Pittsburgh, PA (US)
Appl. No. 18/561,126
Filed by UNIVERSITY OF PITTSBURGH—OF THE COMMONWEALTH SYSTEM OF HIGHER EDUCATION, Pittsburgh, PA (US)
PCT Filed Jun. 6, 2022, PCT No. PCT/US2022/032317
§ 371(c)(1), (2) Date Nov. 15, 2023,
PCT Pub. No. WO2023/022778, PCT Pub. Date Feb. 23, 2023.
Claims priority of provisional application 63/234,464, filed on Aug. 18, 2021.
Prior Publication US 2024/0230809 A1, Jul. 11, 2024
Int. Cl. G01R 33/56 (2006.01); G01R 33/48 (2006.01); G01R 33/485 (2006.01)
CPC G01R 33/5605 (2013.01) [G01R 33/4828 (2013.01); G01R 33/485 (2013.01)] 44 Claims
OG exemplary drawing
 
1. A method for chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) of a target structure using an average saturation efficiency filter (ASEF) executed on an MR device, comprising:
a. applying a first radio frequency (RF) pulse train with a high duty cycle (DCh) and a first average irradiation power (B1, avg), wherein
i. the target structure comprises target molecules including exchangeable protons and a water pool including free water protons and semi-solid macromolecules, the first RF pulse train being applied at a resonant frequency of the exchangeable protons of the target molecules for a first predefined period,
ii. the exchangeable protons in the target molecules are saturated based on the application of the first RF pulse train,
iii. a first saturation transfer of the target molecules to the water pool based on chemical exchange processes exchanging the saturated exchangeable protons with a set of the free water protons is made, and the first RF pulse train also causes direct water saturation and a magnetization transfer contrast (MTC) between the semi-solid macromolecules and another set of the free water protons; and
iv. an MR signal of the water pool exhibits a first attenuation based at least in part on the first saturation transfer, the MTC and direct water saturation;
b. discontinuing the application of the first RF pulse train upon a lapse of the first predefined period;
c. acquiring a first water MR signal of the water pool from the MR device, the first water MR signal representing the first attenuation, the target molecules and the water pool returning to thermal equilibrium after the acquisition of the first water MR signal and the discontinuance;
d. applying, to the exchangeable protons of the target molecules for a second predefined period, a second RF pulse train with a low duty cycle (DCl) and a second average irradiation power, the second RF pulse train comprising a plurality of pairs of bipolar or composite pulses having a pulse duration (tP), separated by a period of wait (td), wherein
i. the second RF pulse train is applied at the same resonant frequency as the first RF pulse train, causing the exchangeable protons of the target molecules to be saturated as well as direct water saturation and MTC;
ii. a second saturation transfer of the target molecules to the water pool is made based on the chemical exchange processes affected by the low duty cycle of the second RF pulse train,
iii. the MR signal of the water pool exhibits a second attenuation based at least in part on the second saturation transfer, the MTC, and the direct water saturation;
e. discontinuing the application of the second RF pulse train upon a lapse of the second predefined period;
f. acquiring a second water MR signal of the water pool from the MR device, the second water MR signal representing the second attenuation; and
g. generating an ASEF signal representing a difference between the first water MR signal and the second water MR signal.