Wojciech Zbijewski PhD, Presenter: Research Grant, Carestream Health, Inc

Alejandro Sisniega PhD, Abstract Co-Author: Research Grant, Carestream Health, Inc

Joseph Webster Stayman PhD, Abstract Co-Author: Research Grant, Varian Medical Systems, Inc

Gaurav Kumar Thawait MD, Abstract Co-Author: Nothing to Disclose

Shadpour Demehri MD, Abstract Co-Author: Nothing to Disclose

Jan Fritz MD, Abstract Co-Author: Research Grant, Siemens AG Research Consultant, Siemens AG

Jeffrey H. Siewerdsen PhD, Abstract Co-Author: Research Grant, Siemens AG Consultant, Siemens AG Research Grant, Carestream Health, Inc Royalties, Elekta AB

Bone marrow edema (BME) is an important biomarker of arthritis and bone trauma. BME presents as increased fluid content and decreased fat content in the cancellous bone and is challenging to detect in x-ray CT due to trabecular structure. Virtual noncalcium (VNC) images obtained using Dual Energy (DE) enable visualization of BME in conventional CT. We investigate the feasibility of DE imaging of BME on a dedicated flat-panel detector extremities cone-beam CT (CBCT).      

DE CBCT imaging was performed at 0.278 mm pixel pitch and 480 projections over 240o using a low energy (LE) beam of 70 kVp, 120 mAs/scan (~9.6 mGy), and a high energy (HE) beam of 120 kVp, 48 mAs/scan (~19 mGy). Due to power limitations of the x-ray tube (max. 0.875 kW), no high-Z filtration could be applied to the HE beam to increase energy separation. Reconstructions were obtained at 0.5 mm voxels using FBP and penalized-likelihood with Huber penalty (PLH). Reconstruction-based three-material DE decomposition yielded volume fractions of soft tissue, fat, and bone. A computer simulation study with polyenergetic projections of a digital BME knee phantom was performed. Experimental studies involved a 12 cm water phantom with two bone inserts (50 mg/mL CaCO3) embedded in water and alcohol (simulating fat). Each insert contained a pattern of 1 mm - 4 mm cavities filled with the surrounding fluid to emulate the trabecular matrix. 

DE noncalcium soft-tissue images correctly identified 76% of the area of simulated BME at realistic levels of projection noise (corresponding to bare beam signal of 105-106 photons/pixel). The experimental studies show discrimination of water and fat even in the presence of partial volume effects and resolution blur in the vicinity of the cavities of bone inserts. PLH performed slightly better than FBP, reducing the error in estimation of the total fat area from 46% for FBP to 19% for PLH at similar noise levels in the VNC image.

Detection of BME and quantification of water and fat content using DE were demonstrated on the extremities CBCT, opening a broad range of diagnostic applications in e.g. detection and staging of arthritis. 

DE detects BME in extremities CBCT, overcoming a major limitation of single energy imaging and enabling novel diagnostic applications in rheumatoid arthritis, osteoarthritis and bone trauma.

Zbijewski, W, Sisniega, A, Stayman, J, Thawait, G, Demehri, S, Fritz, J, Siewerdsen, J, Dual-Energy Imaging of Bone Marrow Edema on a Dedicated Extremities Cone-Beam CT System.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017959.html