Quantitative imaging of bound and pore water concentrations in cortical bone using UTE MRI has shown potential for evaluating fracture risk ^1–3, and several groups have developed methods to acquire these measures in clinically practical scans. ^4–6 In radius and tibia scans, the Double Adiabatic Full Passage (DAFP) and Adiabatic Inversion Recovery (AIR) sequences have been demonstrated in vivo with 3D UTE to acquire maps of cortical bone pore water and bound water concentrations, respectively.⁵ These 3D methods require a relatively long scan time, around 30 minutes total for both AIR and DAFP acquisitions. This long scan time is due to the 3D isotropic field of view and resolution that is used and the long TR that is necessary because of SAR constraints. One way to overcome these limitations is to use 2D UTE, especially in areas where a large 3D volume would otherwise be required. In this study, AIR and DAFP sequences were implemented with half-pulse 2D UTE and compared to corresponding 3D UTE methods in ex vivo cadaver radii and in vivo volunteers. DAFP and AIR sequences were implemented on a 3T Philips scanner using 2D UTE sequences. The 2D UTE scans used two half-pulses⁷ with an optimized slice select gradient and 550 μs RF waveform.⁸ The sequences were evaluated on four cadaver radii and two volunteer tibia (26 y.o. M, 36 y.o. F) with a FOV = 200 mm, in-plane resolution =1.5 mm, and slice thickness =5 mm. A total of 256 spokes acquired with TR = 400 ms resulted in a scan time ≈14 seconds for each protocol. Similar to the previous 3D implementation⁹: 16 spokes were acquired every TR, a variable flip angle schedule was used to generate constant signal amplitude for each spoke, and absolute bound and pore water concentrations were computed using reference marker in the FOV. Equivalent 3D scans were also acquired on the same subject using previously described methods¹⁰ and similar scan parameters with a scan time of 14 minutes each. Mean differences between 2D and 3D bound/pore water concentration in cadaver radii were 0.7/2.4 mol ¹H/L_bone (8.2%/9.8%). Figure 1 shows 2D bound and pore water maps on tibia and corresponding 3D bound and pore water maps in the same slice. The mean differences in bound/pore water concentration between 2D and 3D between both volunteers were 2.1/1.2 mol ¹H/L_bone (7.8/7.1 %). When using 8 averages in 2D (2 min scan time), the difference between bound/pore water concentration between 2D and 3D decreased to 3.9/1.9%. The average SNR of the bound water scans were ~ 23/5 in 3D/2D and the average SNR of the pore water scans were ~8/2 in 3D/2D. These values agree with expected relative SNR of 2D and 3D UTE. These results show promising methods for decreasing scan time of bound and pore water MRI of bone. The differences in bound and pore water between 2D and 3D scans is small and is within the expected variation. Averaging of 2D scans to get higher SNR could help in getting more precise maps, especially in the low signal of the DAFP images that results from healthy individuals having low pore water. Applying these fast DAFP and AIR sequences in 2D has the potential to greatly increase the utility of these methods in clinical settings for evaluating fracture risk in patient populations. The 2D UTE method could also be applied in other bones that are difficult to image with 3D UTE, such as the vertebrae or femoral neck.