Breath-hold three-dimensional gadolinium-enhanced multiphasic abdominal magnetic resonance imaging is a widely available technique that can be used, with excellent results, in the detection and characterization of a wide variety of abdominal and pelvic diseases. Breath-hold imaging eliminates respiratory motion and improves anatomic sharpness. This article will introduce the reader to this technique, including its technical facets, and will illustrate several cases of its use.
At the time this article was written, all authors were with
the Department of Radiology, University of Washington School of
Medicine, Seattle, WA. Currently,
is a Radiologist with The Good Samaritan Regional Medical Center,
is a Radiologist with Inland Imaging Associates, Spokane, WA; and
is a Radiologist with Seattle Radiology Associates, Seattle,
Improvements in gradient performance have made the rapid
acquisition of three-dimensional (3D) volumetric gradient echo data
possible. Thin contiguous images of the abdominal organs can be
obtained with isotropic voxels in a single breath-hold with
resultant decrease in respiratory motion artifact and improved
The volumetric image data can then be viewed in any desired plane.
This technique results in higher signal-to-noise ratios (SNRs)
(related to the longer repetition time) compared with spin-echo
(SE) or fast-spin-echo (FSE) T2-weighted images or two-dimensional
(2D) gradient-echo images.
Contrast-to-noise levels for hepatic lesions are better than for
spin-echo T2 and comparable to fast-spin-echo T2-weighted images.
We have used this technique to obtain gadolinium-enhanced 3D
spoiled gradient-echo images of the abdominal organs in multiple
phases of enhancement (arterial, venous, delayed). This allows
improved lesion detection and characterization by allowing
assessment of lesion vascularity similar to that achieved with
contrast-enhanced computed tomography (CT). This technique provides
an alternative to conventional CT in cases in which iodinated
contrast is contraindicated. This article will introduce the reader
to this technique, including its technical facets, and to
illustrate several cases of its use.
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 20š,
which, in our experience, provides good tissue contrast. Others
advocate higher flip angles of 30š to 60š.
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
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.
This technique can be used in place of CT to evaluate many
abdominal and pelvic disease processes. The dynamic
gadolinium-enhanced sequence is an adjunct to standard T1- and
T2-weighted sequences and is helpful in characterizing renal masses
(Figures 1 and 2), primary and secondary liver tumors (Figures 3
and 4), hepatic vascular disease (Figure 5), periportal masses
(Figure 6), pancreatic masses (Figures 7 and 8), and rectal lesions
(Figures 9 and 10).
Breath-hold 3D gadolinium-enhanced multiphasic abdominal MR is a
widely available technique that can be used, with excellent
results, in the detection and characterization of a wide variety of
abdominal and pelvic diseases. Breath-hold imaging eliminates
respiratory motion and improves anatomic sharpness. The 3D data set
can, when needed, be viewed in other planes. Lesion vascularity can
be assessed similar to multiphasic CT. Its use is suggested when CT
with iodinated contrast is either contraindicated or equivocal.