James Goldfarb, Presenter: Nothing to Disclose

Sunil T Mathew MD, Abstract Co-Author: Nothing to Disclose

Nathaniel Reichek, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to 1) develop the pulse sequence and post-processing software for retrospective fat/water separation using CINE SSFP imaging of the heart 2)determine the necessary phase corrections and 3) assess the accuracy of the method.

Eleven subjects (4 male/7 female; mean age=63; range=37-74; ten healthy volunteers and one subject with a history of MI) were studied on a 1.5T Siemens Sonata scanner using a four-element phased array coil. An ECG-gated SSFP breath-hold protocol was implemented that allowed the complex k-space data to be written to disk. Anatomical orientations included the heart’s horizontal and vertical long axis, short axis and along the heart’s left ventricular outflow tract. Images in the same orientations were also collected using a FLASH pulse sequence with and without a chemically selective fat saturation pre-pulse. Fat and water images were created from sum-of-squares magnitude pixels based on the sign of the real part of the complex summation image. If the real part of the complex image was determined to be less than zero, the signal in that pixel was placed in the fat image. Three image domain phase corrections were used: constant and linear in the read and phase encoding dimensions. The phase corrections were tabulated and analyzed for any trends. SSFP fat and water images were compared to FLASH images with and without fat saturation.

Significant constant, linear read and linear phases-encode phase corrections were needed in 30%, 76% and 80% of the images, respectively. Signals from the anterior coils were often 180 degrees out-of–phase with the posterior coils. No pattern was evident leading us to believe that phase corrections were needed to offset patient specific field inhomogenieties. When compared to the FLASH acquisition, accurate fat/water separation was achieved in most cases. Fat/water separation could not be accurately achieved in areas of intense field inhomogenieties.

Fat/water SSFP imaging of the heart may find uses in characterization of structures with signal intensities close to fat (e.g. fluid and blood). Results of this study show that linear and constant phase corrections are sufficient.

Goldfarb, J, Mathew, S, Reichek, N, Fat/Water Separation with Continuously Pulsed CINE SSFP Imaging of the Heart.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4409606.html