Dark-Blood Adiabatic T_1ρ Mapping of the Heart Using Combined Non-Selective and Slice-Selective RF Pulses at 3T

T1ρ mapping is emerging as a potential, contrast-free alternative to late gadolinium enhancement (LGE) for assessment of myocardial viability. However, strong signal contributions from the blood pool can impede quantitative evaluation at the (sub)endocardium. In this work, we study the effectiveness of dark-blood (DB) contrast in adiabatic T1ρ (T1ρ,adiab) mapping at 3T, using slice-selective and non-selective adiabatic spin-lock pulses. Adiabatic DB-T1ρ,adiab preparations consisted of an odd number of slice-selective adiabatic full passage (AFP) pulses, followed by a final, non-selective AFP pulse. This preparation induces T1ρ,adiab decay within the imaging slice while inverting the magnetization outside. A delay (δ) between preparation and imaging allowed for relaxation and inflow of the inverted blood to achieve DB contrast. Bias and precision of DB- and bright-blood (BB)-T1ρ,adiab were compared in phantom and in healthy subjects (n = 10). Blood suppression efficacy and apparent myocardial thickness in DB imaging were investigated in simulations, phantom, and in vivo. The clinical feasibility of DB-T1ρ,adiab mapping was evaluated in a small cohort of patients (n = 7) with suspected cardiovascular diseases. DB-T1ρ,adiab values were in agreement with reference BB-T1ρ,adiab values in phantom (myocardium-like vial BB: 219.27 ± 4.80 ms, DB: 218.09 ± 8.22 ms) and in healthy subjects (BB: 182.32 ± 28.27 ms, DB: 183.49 ± 45.54 ms). A moderate increase in intra-(wCVi,r) and inter-scan variability (wCVi¯) was observed in the DB method, compared with conventional BB imaging, for phantom and healthy subjects (in vivo wCVi,r BB: 15.51 ± 2.65%, DB: 24.82 ± 4.18%; in vivo wCVi¯ BB: 3.38 ± 0.86%, DB: 7.24 ± 2.55%). Longer delay times improved blood suppression in vivo for DB-T1ρ,adiab, albeit at increased intra-scan variability in phantom and in vivo (DB wCVi,r for δ = 0 ms: 4.90 ± 0.83% in phantom, 13.44 ± 2.91% in vivo, for δ = 600 ms: 8.14 ± 1.88% in phantom, 26.25 ± 5.19% in vivo). Average apparent myocardial thickness was slightly higher when using DB-T1ρ,adiab compared with BB-T1ρ,adiab (BB: 7.33 ± 2.05 mm, DB: 7.99 ± 2.46 mm). DB-T1ρ,adiab maps yielded comparable image quality to BB-T1ρ,adiab maps in patients. DB-T1ρ,adiab mapping represents an alternative to BB-T1ρ,adiab for myocardial assessment with the potential for improved visualization of the (sub-)endocardium.