Reed F. Busse PhD, Presenter: Nothing to Disclose

Jean H Brittain PhD, Abstract Co-Author: Nothing to Disclose

Jane W Johnson, Abstract Co-Author: Nothing to Disclose

Stefan Hura MD, Abstract Co-Author: Nothing to Disclose

Bruce L. Daniel MD, Abstract Co-Author: Nothing to Disclose

Robert John Herfkens MD, Abstract Co-Author: Nothing to Disclose

Long echo-train 3D-FSE has previously been demonstrated for MRCP. This 3D technique produces thin-slice images that may be reformatted into MIPs. However, individual slices can exhibit high spatial frequency artifacts. Furthermore, the very long TEs (600-1000 ms) cause complete suppression of any background, potentially obscuring contextual information. We sought to: (i) suppress the high-frequency artifacts, and (ii) reduce the TE in order to optimize CNR while retaining some background for context.

The 3D-FSE sequence acquired all y phase-encodes (PEs) for a particular slice (z) encode each repetition, requiring as many repetitions as prescribed slices. Partial-Fourier encoding in the y-direction was used. For the baseline method, the PEs were ordered linearly beginning with the highest spatial frequency; TE was determined by the time to acquire yres/2 echoes and signal modulation due to T2 decay was uncorrected. For the new method, the PE order was reversed; TE was determined by the time to acquire the PEs prior to DC, allowing for much greater flexibility (180ms in this case). Additionally, signal was corrected to reverse T2-decay of fluid. Modeling was performed to determine the effect of these variations on SNR and the point spread functions of fluid and soft tissues. Volunteers and patients were imaged with both methods.

The artifact noted in the baseline technique was caused by sampling high spatial frequencies while signal was still strong in shorter-T2 tissues. Compared to the baseline method, the new method suppressed the artifacts, produced some visible tissue background for context, and increased fluid signal and fluid-to-tissue contrast. While T2-reversal, which restored the PSF of fluid, increased noise somewhat, SNR of fluid nevertheless increased by 12%. In many human MRCP studies, the bile and pancreatic ducts were better visualized with the new method.

Altering the PE schedule and correcting for T2 decay suppress high-frequency artifacts seen in long echo-train FSE sequences, improve SNR, and allow for much greater flexibility in selecting TE. These developments can improve the image quality of MRCP studies.

R.F.B.,J.H.B.,J.W.J.: Employees of GE HealthcareR.F.B.,J.H.B.,J.W.J.,S.H.,B.L.D.,R.J.H.: No additional disclosuresS.H.: No disclosuresB.L.D.,R.J.H.: Receive grant support from GE Healthcare

Busse, R, Brittain, J, Johnson, J, Hura, S, Daniel, B, Herfkens, R, MRCP with 3D-FSE: How View Order and T2-Decay Signal Correction Affect Image Quality.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4405709.html