Rapid 3D‐T₁ mapping of cartilage with variable flip angle and parallel imaging at 3.0T

Abstract

Purpose: To rapidly acquire T 1 -weighted images using a three-dimensional fast low angle shot (3D FLASH) sequence in combination with generalized autocalibrating partially parallel acquisitions (GRAPPA) and variable flip angle (VFA) method at 3.0T. Materials and Methods:3D T 1 maps of model systems (gadolinium [Gd] and agarose phantoms), bovine cartilage, and human subjects were constructed on a 3.0T clinical whole-body MR scanner. The T 1 values of model systems measured using the 2D inversion-recovery fast-spin-echo (IR-FSE) sequence were considered as a reference method to validate the rapid 3D method for comparison. Results:The root mean square coefficient of variation percentage (RMS-CV%) of the median T 1 of agarose phantom across different acquisition methods was ϳ6.2%. The RMS-CV% of the median T 1 of bovine cartilage across different acquisition methods was ϳ4.1%. The RMS-CV% of median T 1 of the cartilages among the subjects was between ϳ7.3% to 11.1%. In our study, rapid 3D-T 1 mapping with VFA and parallel imaging with different acceleration factors (AFs) (AF ϭ 1, 2, 3, and 4) seems to have no obvious influence on the T 1 mapping (before and after contrast agent administration). Conclusion:The preliminary results demonstrate that it is possible to quantify 3D-T 1 mapping of the whole knee joint (with 0.7 mm 3 isotropic resolution) under approximately five minutes with excellent in vivo reproducibility at 3.0T.

Spatial variation inT1of healthy human articular cartilage of the knee joint

“…For T 1 mapping of the entire knee joint, a dual flipangle 3D GE sequence in combination with parallel imaging (acceleration factor 52) was performed in the sagittal plane [15,17]. The sequence parameters were repetition time, 13.2 ms; echo time, 5.4 ms; flip angle, 4.7å nd 26.2˚; effective section thickness, 3 mm; number of excitations, 3; field of view, 12 6 12 cm; and matrix, 256 6 256.…”

“…The sequence parameters were repetition time, 13.2 ms; echo time, 5.4 ms; flip angle, 4.7å nd 26.2˚; effective section thickness, 3 mm; number of excitations, 3; field of view, 12 6 12 cm; and matrix, 256 6 256. The 2 optimum flip angles were selected as those with signals that were 71% of the Ernst angle signal [15,23], which is the greatest signal for a given repetition time and T 1 . The acquisition time was 5.05 min.…”

“…* -IR-TSE 1.5 T Tiderius et al [18] Turbo-IR 952¡86 952¡86 ---1.5 T Williams et al [14] Turbo-IR ---1.5 T 916¡102 819¡86 3.0 T 1146¡133 1167¡79 Gold et al [19] Look-Locker ----1.5 T 1066¡155 3.0 T 1240¡107 Wang et al [15] 3D GE with VFA 1004¡72 * 1193¡108 3.0 T Trattnig et al [17] 3D GE with VFA 1013¡89 ----3.0 T Data are presented as the mean ¡ standard deviation. VFA, variable flip angle; GE, gradient echo; IR, inversion-recovery; IR-TSE, inversion-recovery turbo spin-echo; 3D, three-dimensional.…”

“…However, it is frequently assumed to be constant across cartilage [11][12][13]. A few studies have investigated the mean values of a single compartment (Table 1) [10, [14][15][16][17][18][19] but have not investigated the depth-dependent variation. To our knowledge, no study has systematically compared T 1 of unenhanced human knee cartilage in different cartilage layers and in different cartilage compartments in healthy volunteers.…”

Methodological developments and clinical applications of pharmacokinetic models in contrast-enhanced magnetic resonance perfusion studies

“…Most recent studies use multiple flip angle sequences to estimate pre-contrast T1 and its variation during contrast injection [82]. From this variation the concentration can be easily calculated with the linear relationship shown above.…”