Tissue Characterization

1346326 - Adiabatic dark-blood T1ρ mapping for blood signal suppression in myocardial tissue characterization at 3T.

Saturday, January 28, 2023

9:40 AM – 9:55 AM

Location: Silver Pearl 1

Presenting Author(s)

CC

Chiara Coletti, MSc

PhD student
TU Delft
Delft, Zuid-Holland, Netherlands

Primary Author(s)

CC

Chiara Coletti, MSc

PhD student
TU Delft
Delft, Zuid-Holland, Netherlands

Co-Author(s)

MB

Maša Bozic-Iven

PhD student
Heidelberg University, Germany
JT

Joao Tourais, MSc

Researcher
Delft University of Technology
Delft, Netherlands
Cv

Christal van de Steeg-Henzen

Senior MBB’er MRI
HollandPTC, Delft, the Netherlands
Delft, Zuid-Holland, Netherlands
Mehmet Akcakaya, PhD

Associate Professor
University of Minnesota
Minneapolis, Minnesota, United States
KC

Kelvin Chow, PhD

Staff Scientist
Siemens Healthineers
Chicago, Illinois, United States
Sebastian Weingartner, PhD

Assistant Professor
Delft University of Technology
Delft, Zuid-Holland, Netherlands

Disclosure(s):

Sebastian Weingartner, PhD: No financial relationships to disclose

Background: T1ρ mapping is increasingly gaining interest as a promising candidate for contrast-free assessment of scar and fibrosis in the myocardium1. However, long T1ρ times in the blood pool cause partial-voluming at the blood-myocardium interface. Dark-blood (DB) LGE has recently been proposed for its superior depiction of endocardial scar2. In this study, we propose a novel adiabatic spin-lock (SL) preparation to enable the use of DB contrast in T1ρ mapping.

Methods: Adiabatic T1ρ mapping was performed on a 3T scanner (Ingenia, Philips) with a 14s breath-hold cardiac-triggered single-shot bSSFP sequence (Fig1). Three T1ρ-prepared images (𝜏SL=60, 120, 180ms), interleaved with 4s rest-period, were acquired, followed by a saturation-prepared image. Bright-blood adiabatic T1ρ mapping was acquired as reference (RefT1ρ), concatenating 2, 4, and 6 hyperbolic secant (HS) adiabatic full passage (AFP) pulses (τHS=30ms, β=6.9, fmax=450Hz)3. DB contrast was achieved by playing a slice selective gradient during the last HS pulse. This way, an even number of AFPs is applied to the labeling slab, achieving T1ρ decay only. Outside the slab, an odd number of AFPs is effective, leading to magnetization inversion. Other sequence parameters were: resolution=2x2x8mm3, FOV=220x220mm2, TE/TR=0.76/1.90ms, preparation delay=440ms. Ten repetitions were acquired for phantom scans and three for in-vivo scans. All T1ρ maps were generated using a 3-parameter model4. Bloch simulations and phantom imaging with preparation delays varying from 0 to 500ms were performed to assess the influence of the delay on the measured T1ρ variance. In -vivo Ref and DBT1ρ maps were obtained in 1 healthy subject (m, 26y). Precision (CVp) and repeatability (CVr) were investigated in phantom and in the segmented myocardium.

Results: In a representative phantom vial (Fig2), DBT1ρ maps (169.8±39.7ms) yielded similar values to RefT1ρ (164.2±18.9ms). Comparable precision and repeatability were measured in phantom maps acquired with no preparation delay (DBT1ρ CVp=11.3±2.2%, CVr=2.7% vs RefT1ρ CVp=11.4±1.4%, CVr=1.6%) but decreased when using the 440ms delay (DBT1ρ CVp=27.6±3.5%, CVr=2.9%). Increasing preparation delays, in fact, yielded constant T1ρ values but higher variance (Fig2). In vivo DBT1ρ maps retained image quality compared with RefT1ρ maps, while presenting suppressed blood signal (Fig3). Myocardial DBT1ρ values were in agreement with the reference (DBT1ρ=152.8±103.9ms, RefT1ρ=152.1±65.4ms), while precision and repeatability were compromised (DBT1ρ CVp=33.0±0.8%, CVr=14.3% vs RefT1ρ CVp=19.1±1.6%, CVr=4.3%).

Conclusion: In this work, we introduce dark-blood T1ρ preparations. Phantom and in-vivo preliminary results indicate that these preparations enable thorough blood suppression for the trade-off against a moderate loss in precision. Thus, DB T1ρ mapping may be an excellent candidate for improved visualization of the blood-myocardium interface and the non-contrast depiction of epicardial scar.