Multisection T1-weighted hybrid-rare: A pulse sequence for MR imaging of the entire liver during suspended respiration

It is shown that the maximum average-data-collection-speed (ADCS) of multisection 2D hybrid-RARE sequences is independent of TR and TE_eff, and a monotonically increasing function of echo-train-length (ETL). This result was used in the design of an optimized T₁-weighted hybrid-RARE sequence that produces 20 images of the abdomen in 31 s divided into four breath-hold periods. The resulting ADCS is 58 lines in k-space per second. Twenty-four subjects (2 healthy volunteers and 22 patients) were imaged with a protocol that also included: (a) breath-hold T₁-weighted FLASH which acquires data at 34 lines in k-space per second (49 s scan time), and (b) T₁-weighted conventional spin-echo (9:44 minutes scan time) with respiratory compensation. The experiments show that this T₁-weighted-hybrid-RARE sequence has: (1) a level of T₁ weighting that is comparable with the conventional sequences, (2) very low vulnerability to susceptibility artifacts, (3) high data acquisition efficiency, and (4) higher SNR than T₁-weighted-FLASH. In conclusion, the T₁-weighted-hybrid-RARE sequence described herein is an efficacious and reproducible technique for rapid imaging of the upper abdomen during suspended respiration.