Measurement of bound and pore water T₁relaxation times in cortical bone using three-dimensional ultrashort echo time cones sequences

Abstract

Purpose We present three dimensional ultrashort echo time Cones (3D UTE Cones) techniques for quantification of total water T1s (T1TW), bound water T1s (T1BW) and pore water T1s (T1PW) in vitro and in vivo using a 3T scanner. Methods T1TW, T1BW and T1PW were measured with 3D Cones and adiabatic inversion recovery Cones (IR-Cones) sequences. 2D non-selective UTE techniques, including saturation recovery, variable TRs, and IR preparation approaches were compared with 3D-Cones techniques on bovine cortical bone samples (n=8). The 3D Cones sequences were used to measure T1TW, T1BW and T1PW in the tibial midshaft of healthy volunteers (n=8). Results Comparable T1s were achieved for cortical bone between 3D Cones and 2D UTE techniques as well as those published in the literature. The 3D Cones sequences showed a mean T1TW of 208±22 ms, a mean T1PW of 545±28 ms and a mean T1BW of 131±12 ms for bovine cortical bone, and a mean T1TW of 246±32 ms, a mean T1PW of 524±46 ms and a mean T1BW of 134±11 ms for the tibial midshaft of healthy volunteers. Conclusions The 3D Cones sequences can be used for fast volumetric assessment of bound and pore water T1s in vitro and in vivo.

Three-dimensional adiabatic inversion recovery prepared ultrashort echo time cones (3D IR-UTE-Cones) imaging of cortical bone in the hip

“…Although direct imaging of cortical bone has previously been presented at different locations such as the midshaft of the tibia [28,[32][33][34], direct imaging of the hip is considered of higher clinical significance since fractures at this location are more devastating [3]. In addition, imaging at this location is considered more technically challenging.…”

“…Previous studies employing the UTE sequence have shown that both bound water (short T 2 ⁎ component) and pore water (long T 2 ⁎ component) in cortical bone can be quantified using a bi-component T 2 ⁎ analysis technique [18,[25][26][27][28]. Moreover, T 2 ⁎ decay time for bound water in cortical bone can be measured with the IR-UTE technique by suppressing the signal from the pore water and then using a single component analysis of the remaining signal [27,29,38].…”

“…When followed by an adiabatic inversion recovery preparation pulse, the 3D UTE-Cones sequence can be utilized to acquire signal from cortical bone with high contrast [27,28]. This is done by inverting the longitudinal magnetization of the long T 2 signal components (i.e., muscle and bone marrow fat) while saturating the signal from cortical bone [27][28][29][30][31].…”

“…This is done by inverting the longitudinal magnetization of the long T 2 signal components (i.e., muscle and bone marrow fat) while saturating the signal from cortical bone [27][28][29][30][31]. The Cones acquisition starts after an inversion time (TI) delay, which is used to null the long T 2 ⁎ components while permitting detection of recovered cortical bone signal (Fig.…”

“…An adiabatic inversion pulse (duration = 8.64 ms) was used for robust inversion and suppression of the longitudinal magnetizations of long T2 water and fat. Four healthy volunteers (28,31,34, and 43 years old, male) were scanned by using a torso phased-array coil. The following scan parameters were used: TR = 116.7 ms, TI = 50 ms, four TEs (0.032, 0.2, 0.4, and 0.8 ms), BW = 250 kHz, FOV = 340 × 340 mm 2 , slice thickness = 3 mm, matrix = 128 × 128, flip angle = 18°, acquired voxel size = 2.6 × 2.6 × 3 mm 3 , and scan time = 4.5 min for each dataset.…”