Clinical Update: Breath-Hold 3D Gadolinium-Enhanced Multiphasic Abdominal MR

Matthew P. Evitts, DO, Scott B. Hoefer, MD, Udo P. Schmiedl, MD, PhD

Appl Radiol. 2003;32(1) 

In This Article

Technique

Images were obtained on a 1.5 T scanner (Signa, GE Medical Systems, Waukesha, WI) with a phased-array torso coil. Three plane-localizer images are first obtained. The patient is then timed to see how long he or she can maintain a breath-hold. Slice thickness and coverage area are adjusted based on the patient's ability to hold a breath. Single breath-hold imaging of the organ of interest is achievable in the majority of patients imaged.

Our standard scan parameters include an echo time (TE) of 3 msec, representing a compromise between fat-water phase cancellation (occurring at 2.1 msec at 1.5 T) and signal loss due to T2* decay with longer TE times. Repetition time (TR) is set at minimum (usually approximately 7.6 to 7.7 msec) to reduce flow and susceptibility artifacts. Bandwidth is set to 31.25 kHz and is related indirectly to the other parameters. A wide bandwidth allows for a shorter TR and TE and therefore faster scanning but at the expense of lower SNR. A narrow bandwidth is preferred, resulting in longer scan times but higher SNR. We use a flip angle of 20°, which, in our experience, provides good tissue contrast. Others advocate higher flip angles of 30° to 60°.

Acquisition time is further reduced by using 0.5 number of excitations (NEX [fractional NEX]), which takes advantage of k-space symmetry, allowing sampling of just over half of k-space with mathematical reconstruction of the remaining data, resulting in a decrease in scan time by one-half.

Apparent spatial resolution is increased by using Zerofill Interpolation Processing (ZIP, GE Medical Systems). This post-processing technique improves scan resolution without increasing scan time. The trade-off is an increase in reconstruction time. When applied in the slice direction (Slice ZIP), there is no decrease in SNR. When applied in the x and y directions (512 ZIP), there is a small decrease in SNR. This technique improves the quality of reformations and maximum intensity projection (MIP) images and decreases volume- averaging artifacts. Gibbs ringing and truncation artifacts are increased with ZIP.

Noncontrast images are obtained first. Gadolinium contrast (20 mL) is administered through a ≥ 20-gauge needle placed in an antecubital vein at a rate of 1 to 1.5 mL/sec. The technologist instructs the patient on breathing while injecting the first 10 mL of contrast. The patient takes two deep breaths, then takes one deep breath and holds it. The first postcontrast scan is initiated and the remaining 10 mL of contrast is injected. This is followed by a 20-mL saline flush. Following the first scan, the patient takes a few breaths and then breath-holds for the venous phase and 5 minutes later for the delayed phase.

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