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

Richard Znamirowski, Abstract Co-Author: Nothing to Disclose

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

Eric Y. Chang MD, Abstract Co-Author: Nothing to Disclose

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

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

To evaluate cortical bone structure in vitro and in vivo using ultrashort echo time (UTE) and fast spin echo (FSE) sequences on a clinical 3T scanner.

Eight cadaveric human femur and tibia cortical bone samples were prepared and imaged using the UTE techniques (minimum TE of 8 μs) as well as conventional 2D FSE sequences on a clinical 3T MR scanner. Five healthy volunteers were also recruited. The regular UTE sequence was performed to image both the short and long T2 water components in cortical bone. Additionally, an adiabatic inversion recovery (IR) prepared UTE (IR-UTE) sequence was performed to selectively image the shorter T2 component (bound water) by using a long adiabatic IR pulse to invert and null the longer T2 water component (free water). A clinical 2D FSE sequence was employed to selectively image the long T2 water residing in large pores and Haverisan canals. A 2.5 cm receive-only surface coil was used for signal reception with typical imaging parameters: field of view (FOV) = 4 cm for FSE and 10 cm for UTE, slice thickness = 3 mm with UTE, and 0.7 mm with FSE sequences, matrix = 512×512, TR = 300 ms for UTE and 3 sec for FSE, TI = 90 ms for IR-UTE, scan time = 6.5 minutes.

Our preliminary results show that bone water in large pores and canals can be imaged directly in vitro and in vivo using conventional 2D multi-slice FSE sequences. The use of small surface coils allows high spatial resolution imaging with voxe sizes down to 78×78×700 µm3, with adequate signal to noise ratio in a scan time of 6.5 minutes. Regular UTE sequences provide images of both bound and free water, but with limited contrast due to the high signal from surrounding muscle and fat which have much longer T2s and higher proton densities. The IR-UTE sequence provides selective imaging of water bound to the organic matrix, with free water inverted and nulled by the adiabatic preparation pulse.

Bone water residing in the large pores and Haversian canals can be imaged directly with high resolution 2D FSE sequences, while water bound to the organic matrix can be selectively imaged with the IR-UTE sequence. Both bound and free water can be detected simultaneously with UTE sequences.

The novel UTE and high resolution FSE imaging techniques allow clinical evaluation of water in different locations in cortical bone, and may have significant applications in osteoporosis.

Du, J, Znamirowski, R, Bae, W, Chang, E, Chung, C, Bydder, G, High Resolution Magnetic Resonance Imaging of Cortical Bone.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12026932.html