Jiang Du, Presenter: Grant, General Electric Company Research collaboration, General Electric Company

Won C Bae PhD, Abstract Co-Author: Nothing to Disclose

Reni Biswas, Abstract Co-Author: Nothing to Disclose

Hermida Juan, Abstract Co-Author: Nothing to Disclose

Christine B. Chung MD, Abstract Co-Author: Nothing to Disclose

Darryl D'Lima, Abstract Co-Author: Research funded, Stryker Corporation Research funded, Smith & Nephew plc Consultant, MAKO Surgical Corporation Consultant, Orthosensor, Inc Research funded, ConforMIS, Inc Research funded, OC Dynamics

Graeme M. Bydder MBChB, Abstract Co-Author: Research grant, General Electric Company

To evaluate the free and bound water fractions and absolute concentrations by volume in cortical bone using Ultrashort TE (UTE) imaging and bi-component analysis, and investigate their correlation with porosity determined by μCT.

Forty four cadaveric human femur and tibia cortical bone fragments (3-4 mm long, 1.5-3 mm thick, 3-4 mm wide) were prepared and imaged using the UTE technique (minimum TE of 8 μs) on a clinical 3T MR scanner. UTE T2* images were acquired with the following parameters: TR = 200 ms, FOV = 4 cm, slice thickness = 3 mm, matrix = 256Χ256, flip angle = 60°, bandwidth = 62.5 kHz, 20 TEs ranging from 8 μs to 10 ms, total scan time = 40 minutes. In-house developed bi-component fitting software was used to calculate T2* and fractions of the bound and free water components. Total bone water concentration was measured through comparison of UTE MR signal of bone with that of a calibration water phantom. Absolute free and bond water concentrations were calculated by multiplying the free/bound water fraction by the total bone water concentration. Finally the specimens were subject to μCT imaging with an isotropic resolution of 9Χ9Χ9 μm3 to calculate bone porosity.

Excellent bi-component fitting was achieved for 35 of the 44 cortical bone samples, among them 12 samples have minor fat/water oscillation and 5 samples have significant fat/water oscillation. Among the 44 samples total water concentration ranged from 27.8-58.8% by volume. Bound water fraction ranged from 48.4-88.2%, bound water concentration ranged from 21.2-34.2%, and free water concentration ranged from 3.9-25.1%. μCT porosity ranged from 0.5-17.7%. Correlation analysis shows that free water fraction (R=0.5711, P < 0.0001), free water concentration (R=0.6774, P < 0.0001) and total bone water concentration (R=0.6534, P < 0.0001) were positively correlated with μCT porosity. While bound water fraction (R=-0.5652, P < 0.0001) was negatively correlated with μCT porosity.

UTE imaging and bi-component analysis can quantify the free and bound water components of cortical bone. Free and bound water fractions and absolute concentrations are highly correlated with μCT porosity.

UTE imaging and bi-component analysis provide information on bone porosity, and may have significant application in osteoporosis.

Du, J, Bae, W, Biswas, R, Juan, H, Chung, C, D'Lima, D, Bydder, G, Ultrashort TE Imaging and Bi-component Analysis of the Free and Bound Water in Cortical Bone and the Correlation with μCT Porosity.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11010030.html