AJR 2005; 184:497-504
© American Roentgen Ray Society
Feasibility of Application of Sensitivity Encoding to the Breath-Hold T2-Weighted Turbo Spin-Echo Sequence for Evaluation of Focal Hepatic Tumors
Young Kon Kim1,
Chong Soo Kim1,
Gyung Ho Chung1,
Su Bin Jeon1 and
Jeong Min Lee2
1 Department of Diagnostic Radiology, Chonbuk National University Hospital and
Medical School, Jeonju, South Korea.
2 Department of Diagnostic Radiology, Seoul National University College of
Medicine and Institute of Radiation Medicine, Seoul National University
Medical School Research Center, Seoul, South Korea.
Received February 27, 2004;
accepted after revision July 14, 2004.
Address correspondence to J. M. Lee.
Abstract
OBJECTIVE. The purpose of this study is to assess the feasibility of
the application of sensitivity encoding (SENSE) to the T2-weighted breath-hold
turbo spin-echo (BHTSE) sequence for evaluating focal hepatic lesions.
MATERIALS AND METHODS. Thirty consecutive patients with 43 focal
liver lesions underwent BHTSE, BHTSE using SENSE with the conventional
parameters, and BHTSE using SENSE with increased matrix and reduced echo-train
length (ETL). There were 23 hepatocellular carcinomas in 21 patients, 10
hemangiomas in six, and 10 metastases in three. The images were compared
quantitatively by measuring the signal-to-noise ratio (SNR) of the liver and
the lesion and the lesion–liver contrast-to-noise ratio (CNR) and
qualitatively by evaluating image quality, lesion conspicuity, artifact, and
lesion detectability.
RESULTS. The SNR of lesions and the lesion–liver CNR were
highest on BHTSE using SENSE with increased matrix and reduced ETL, which were
significantly higher than conventional BHTSE (p < 0.05). In
qualitative analysis, the image quality and conspicuity of malignant lesions
with BHTSE using SENSE with increased matrix and reduced ETL were better than
with BHTSE and BHTSE using SENSE with the conventional parameter (p
< 0.05). The image artifacts were lower with two BHTSEs using SENSE than
with BHTSE (p < 0.05). Lesion conspicuity of malignancy on BHTSE
using SENSE with the conventional parameter was superior to those on BHTSE
(p < 0.05). Although there was no significant difference in the
lesion detectability among the three images, two malignant lesions were
clearly depicted on BHTSE using SENSE with increased matrix and reduced
ETL.
CONCLUSION. The application of SENSE to BHTSE can provide
high-quality liver imaging with decreased acquisition time compared with
conventional BHTSE.
Introduction
Despite the development of MRI contrast agents, including gadolinium-based
agents and liver-targeted agents, T2-weighted MR images still are considered
to be an important part of routine liver MRI for the detection and
characterization of focal liver lesions
[1–3].
Numerous comparative studies were performed to determine the best T2-weighted
images with a shorter image acquisition time and to preserve high image
quality with less artifact
[4–8].
Breath-hold turbo spin-echo (BHTSE) or fast spin-echo techniques are the usual
T2-weighted sequences as they offer high image quality with minimal artifact
in a shorter acquisition time compared with conventional spin-echo imaging
[5,
6]. However, even with the
rapid recent development of MRI technologies, to obtain T2-weighted images
covering the liver using BHTSE requires 25–30 sec, which is not easy for
a single breath-hold. Given that many patients who are referred for liver MRI
are elderly and/or cirrhotic patients with ascites, obtaining T2-weighted
liver images during one breath-hold is not possible. Therefore, limiting the
number of slices and section thickness by the length of the breath-hold period
offers lower-resolution imaging of the breath-hold T2-weighted sequence, which
might otherwise be a weak point in the detection of small liver lesions. There
have been several strategies to increase the speed of image acquisition for
T2-weighted turbo spin-echo (TSE) images, including the use of high echo-train
length (ETL), high bandwidth, and partial Fourier acquisition
[9–11].
However, those techniques have the trade-offs of decreased signal-to-noise
ratio (SNR) and/or increased magnetization transfer effect, both of which can
decrease the detection rates of malignant hepatic tumors
[12–14].
Recently, parallel acquisition techniques, such as sensitivity encoding
(SENSE) and the simultaneous acquisition of spatial harmonics (SMASH), were
introduced as methods to reduce scanning time with respect to standard Fourier
imaging by means of arrays of multiple receiver coils, with a resultant
decrease in the number of measured echoes
[15–18].
This increased speed of image acquisition by application of the parallel
acquisition technique has the potential for the acquisition of high-quality
liver imaging with reduced-motion artifact and can provide increased spatial
resolution and higher lesion conspicuity while maintaining reasonable imaging
times. In other words, the parallel acquisition technique can overcome the
drawbacks of routine liver MRI. There have been many studies regarding the
usefulness of SENSE and SMASH applied to real-time cardiac imaging
[19,
20], brain functional MRI
[21], and 3D-contrast-enhanced
MR angiography [22]. However,
application of the parallel acquisition technique to liver MRI has been
limited, and to our knowledge, there have been no comparative studies of a
T2-weighted fast spin-echo sequence with and without a parallel acquisition
technique.
In this study, we applied SENSE to the BHTSE T2-weighted sequence. To
assess the feasibility of the parallel acquisition technique in T2-weighted
liver imaging, we compared the BHTSE T2-weighted images with and without the
parallel acquisition technique, both quantitatively and qualitatively.
Materials and Methods
Between November 2002 and January 2004, 34 consecutive patients suspected
of having focal liver lesions from previously performed sonography or dynamic
helical CT were included in this study. Four patients were excluded from the
study for the following reasons: poor cooperation in breath-holding and motion
restriction during MRI examination in two patients who were aged and suffered
from dementia; and poor breath-holding and nonvisualization of focal liver
lesions on MRI examination in two patients with advanced liver cirrhosis and a
large amount of ascites. Therefore, in those four patients, acceptable quality
MR images could not be obtained. The remaining 30 patients (17 men, 13 women;
mean age, 55 years) were enrolled in this study. Written informed consent was
obtained from each patient before he or she was entered into the study, and
the study was approved by the institutional review board of our hospital.
A total of 43 lesions (size range, 0.5–7 cm; mean, 2.8 cm) in 30
patients was included in this study: 23 hepatocellular carcinomas in 21
patients (size range, 0.5–7 cm; mean, 3.2 cm); 10 hemangiomas in six
patients (size range, 0.8–5 cm; mean, 2.3 cm); and 10 metastases in
three patients (colon cancer, n = 2; breast cancer, n = 1)
(size range, 0.8–4.5 cm; mean, 2.3 cm). Confirmation of these
hepatocellular carcinomas was made by surgical biopsy in eight patients, and
by core needle biopsy in eight and was based in the remaining five patients on
a combination of the clinical and radiologic findings, including
characteristic findings of hepatocellular carcinomas on angiography and on
iodized oil–enhanced CT scans after transcatheter arterial
chemoembolization with 3 months or more of follow-up and from an elevated
serum 
-fetoprotein level. Metastases were confirmed by core needle
biopsy in all patients, but only one lesion was biopsied in patients with
multiple metastases. Confirmation of a hemangioma was based on the typical
imaging findings of hemangioma on dynamic MRI or dynamic CT scan: peripheral
globular enhancement with progressive partial or complete fill-in during
dynamic studies of the clinical and laboratory findings or no change on at
least the 6-month follow-up imaging.
Determination of the total number of malignant hepatic masses was made by
iodized oil–enhanced CT in 14 hepatocellular carcinomas in 12 patients
referred for transcatheter arterial chemoembolization, on intraoperative
sonography in eight hepatocellular carcinomas in eight patients referred for
surgery, and on follow-up contrast-enhanced CT for at least 5 months in the
other patients with hepatocellular carcinomas or metastases. Determination of
the total number of hemangiomas was based on the reviewers' consensus reading
of the MRI images, including the precontrast T1- and T2-weighted images, the
superpramagnetic oxide-enhanced T2-weighted images, and the
gadolinium-enhanced dynamic images.
MRI
All MRI was performed on a 1.5-T superconducting imager (Magnetom Symphony,
Siemens) with a phased-array body coil for signal reception. All images were
obtained in the axial plane. Three kinds of T2-weighted images were acquired
using the following techniques: conventional BHTSE image, BHTSE image with
application of the SENSE (factor 2) with the same imaging parameters (matrix
number and ETL) as conventional BHTSE, and BHTSE image with application of
SENSE with increased phase-encoding steps and reduced ETL relative to
conventional BHTSE. The three kinds of T2-weighted sequences were run in the
same order and were not randomized.
All images were acquired using the same field of view (32–33 cm),
with a 7-mm section thickness, and a 3-mm intersection gap. The parameters for
conventional BHTSE imaging were as follows: TR/TE, 4,200/102; ETL, 29;
receiver bandwidth, 254 Hz/pixel; matrix size, 256 (frequency) x 144
(phase); and 15 sections acquired in 25 sec. The parameters for BHTSE using
SENSE with conventional parameters were as follows: 3,180/102; ETL, 29;
receiver bandwidth, 254 Hz/pixel; matrix size, 256 (frequency) x 144
(phase); and 16-sec image acquisition time. The parameters for BHTSE using
SENSE with increased phase-encoding steps and reduced ETL compared with
conventional BHTSE were as follows: 2,700/102; ETL, 19; receiver bandwidth,
254 Hz/pixel; matrix size, 256 (frequency) x 173 (phase); and 19-sec
image acquisition time.
Image Analysis
Quantitative analysis.—Quantitative image analysis was
performed by measuring the liver signal intensity, tumor signal intensity, and
the SD of background noise using operator-defined regions of interest (ROIs)
for each image by an abdominal radiologist who did not participate in the
qualitative image analysis. For measurements within the lesion, the ROI was
positioned manually as much as possible to avoid the necrotic foci. For
hepatic lesions too small for placement of an ROI, the image was magnified as
much as three to four times. For signal intensities of the liver, ROIs were
drawn in the same location as each sequence, devoid of a large intrahepatic
vessel. The SD of background noise was measured along the phase-encoding
direction outside the body just ventral to the right anterior abdominal wall
and included respiratory- or motion-related artifacts. The shape and size of
the ROI were identical for all images as far as was possible. The SNR of the
liver and lesion and the liver–lesion contrast-to-noise ratio (CNR) were
calculated from the signal intensity of the liver and lesion, and the SD of
the background noise according to the following formulas:
 | (1) |
 | (2) |
Qualitative analysis.—All images were evaluated jointly by
two gastrointestinal radiologists experienced in interpreting MR liver imaging
in their daily clinical practice. Qualitative image analysis was performed
separately and independently with quantitative measurements. The two observers
did not have any other information about the patients' histories, laboratory
results, findings of other imaging techniques, or final diagnosis or regarding
the design of the present study. To minimize any learning bias, we set the
intervals of reviewing the three images—that is, conventional BHTSE,
BHTSE with SENSE, and BHTSE with SENSE using increased phase encoding steps
and reduced ETL—at 3 weeks. Discrepancies of interpretation were
resolved by means of a consensus reading. Two observers subjectively rated
each sequence for overall image quality, lesion conspicuity, and artifacts. To
avoid a learning bias, review of each image was done in a randomized, blinded
fashion. Overall image quality and lesion conspicuity were based on the
following five grading scales: unacceptable = 1; poor = 2; fair = 3; good = 4;
and excellent = 5. The presence of artifacts was rated using the following
four grading scales: 1, absent; 2, mild; 3, moderate; and 4, severe. For the
lesion detectability of each image, the true number and location of the
lesions on each image were evaluated by comparing them to the
standard-of-reference findings such as iodized oil CT, intraoperative
sonography findings, follow-up CT, and contrast-enhanced MRI. A matched-pair
analysis was performed to verify which of the lesions detected on one image
coincided with those observed on the other images.
Statistical analysis.—The statistical significance of the
quantitative data for SNR of the liver parenchyma and lesions and the
lesion–liver CNR were determined using the repeated measures analysis of
variance test, and the differences between the groups were compared using the
Tukey-Kramer multiple comparisons test. In addition, the statistical
significance of the qualitative data for image quality, lesion conspicuity,
and artifact was determined using the Friedman test. The lesion detectability
of each image was compared using the McNemar test. A p value of less
than 0.05 was considered statistically significant. The statistical analyses
were performed using SPSS 8.0 computer software (Statistical Package for the
Social Sciences).
Results
The quantitative results for the mean SNR of liver parenchyma and lesions
and the liver–lesion CNR with each image are shown in
Table 1. The SNR of the liver
parenchyma and lesions and lesion–liver CNR were highest with BHTSE
using SENSE with increased matrix and reduced ETL; they were lowest with
conventional BHTSE. The SNR of lesions and lesion–liver CNR on BHTSE
using SENSE with increased matrix and reduced ETL were usually significantly
higher than those of conventional BHTSE in both malignancy and hemangioma (SNR
of malignancy, 15.3 ± 4.9 [SD] vs 13.6 ± 5.2; SNR of hemangioma,
28.6 ± 5.8 vs 24.6 ± 7.5; lesion–liver CNR in malignancy,
7.2 ± 3.6 vs 5.7 ± 3.8; in hemangioma, 21.8 ± 7.4 vs 16.8
± 4.9) (p < 0.05). There was no statistical difference in
the quantitative results between BHTSE using SENSE with increased matrix and
reduced ETL and BHTSE using SENSE with conventional parameters, or between
conventional BHTSE and BHTSE using SENSE with conventional parameters.
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TABLE 1 Results of Quantitative Analysis of Breath-Hold Turbo Spin-Echo
T2-Weighted Sequence With and Without Sensivity Encoding (SENSE)
|
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The results of the qualitative analysis are shown in
Table 2. The image quality of
BHTSE using SENSE with increased matrix and reduced ETL was significantly
better than that on BHTSE using SENSE with conventional parameters and
conventional BHTSE (3.5 ± 0.5 vs 3.3 ± 0.5, 3.2 ± 0.5).
Although lesion conspicuity of liver malignancy was significantly better on
BHTSE using SENSE with increased matrix and reduced ETL (3.6 ± 0.5)
(p < 0.05) than on BHTSE using SENSE with conventional parameters
(3.4 ± 0.5) and conventional BHTSE (3.1 ± 0.6) (Fig.
1A,
1B,
1C), no significant difference
among the three images was found in cases of hemangiomas (Fig.
2A,
2B,
2C). In addition, a significant
difference in lesion conspicuity of malignancy was found between conventional
BHTSE and BHTSE using SENSE with conventional parameters (p <
0.05).
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TABLE 2 Results of Qualitative Analysis of Breath-Hold Turbo Spin-Echo
T2-Weighted Sequence With and Without Sensivity Encoding (SENSE)
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Fig. 1C. —52-year-old man with liver metastases. BHTSE T2-weighted
image with SENSE using increased matrix and reduced echotrain length shows
definitive mild increase in signal intensity of lesion (arrow).
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Fig. 2A. —40-year-old-woman with hepatic hemangioma. Breath-hold turbo
spin-echo (BHTSE) T2-weighted image shows bright high signal intensity of
lesion (arrow) in liver segment V. Motion artifact and marginal
blurring of liver lesion are noted.
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Fig. 2B. —40-year-old-woman with hepatic hemangioma. BHTSE T2-weighted
image with sensitivity encoding (SENSE) using same parameters as A
shows bright high signal intensity of the lesion (arrow) with similar
contrast as in A. Motion artifact and marginal blurring of lesion are
reduced compared with A.
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Fig. 2C. —40-year-old-woman with hepatic hemangioma. BHTSE T2-weighted
image with SENSE using increased matrix and reduced echotrain length shows
bright high signal intensity of lesion (arrow) with similar contrast
to A and B. Motion artifact and marginal blurring of lesion are
reduced compared with A.
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The image artifacts were lower with BHTSE using SENSE with conventional
parameters (2.1 ± 0.4) than on BHTSE using SENSE with increased matrix
and reduced ETL (2.2 ± 0.5) and BHTSE (2.6 ± 0.5) (p
< 0.05) (Fig. 3A,
3B,
3C). In four patients with
liver cirrhosis and hepatocellular carcinomas who had poor breath-holding
capability, severe image artifacts (rating scale 4) were noted on conventional
BHTSE, but these artifacts were markedly reduced on two kinds of BHTSE with
SENSE showing mild image artifacts (rating scale 1–2). There was no
significant difference in the lesion detectability among the three kinds of
images. However, there were two small hepatic masses—one hepatocellular
carcinoma and one metastasis in two patients—that were depicted clearly
only on BHTSE using SENSE with increased matrix and reduced ETL rather than on
the two other images (Fig. 4A,
4B,
4C).
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Fig. 3A. —61-year-old man with hepatocellular carcinoma. Breath-hold
turbo spin-echo (BHTSE) T2-weighted image shows heterogeneous mildly increased
signal intensity of mass (arrows) in the hepatic dome. Marked motion
artifacts are noted.
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Fig. 3B. —61-year-old man with hepatocellular carcinoma. BHTSE
T2-weighted image with sensitivity encoding (SENSE) using same parameters as
A shows increased resolution of hepatic mass (arrows) compared
with A. Motion artifacts are still present but reduced compared with
A.
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Fig. 3C. —61-year-old man with hepatocellular carcinoma. BHTSE
T2-weighted image with SENSE using increased matrix and reduced echo-train
length shows hepatic mass (arrows) with highest contrast among three
images. Motion artifacts are still present but are reduced compared with
A.
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Fig. 4A. —44-year-old man with multiple hepatocellular carcinomas.
Breath-hold turbo spin-echo (BHTSE) T2-weighted image shows multiple mildly
increased signal intensity of masses (arrows). But small masses are
not definitive because of lower contrast and motion artifact.
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Fig. 4B. —44-year-old man with multiple hepatocellular carcinomas.
BHTSE T2-weighted image with sensitivity encoding (SENSE) using same
parameters as A shows multiple mildly increased signal intensity of
masses (arrows). Small mass is shown more clearly than in A.
Motion artifacts are reduced compared with A.
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Fig. 4C. —44-year-old man with multiple hepatocellular carcinomas.
BHTSE T2-weighted image with SENSE using increased matrix and reduced
echotrain length shows multiple mildly increased signal intensity of masses
(arrows) with highest contrast and resolution of the three
images.
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Discussion
Although T2-weighted MRI plays an important role in the detection and
characterization of focal liver lesions
[1–3],
lengthy examination times relative to widely used CT and physiologic motion
artifact limits their use as an effective screening method for focal liver
lesions [5,
23]. On the basis of these
backgrounds, Coulam et al.
[24] suggested that routine
acquisition of unenhanced T1- and T2-weighted imaging could be eliminated
without substantially affecting the diagnostic accuracy for focal liver
lesions by using only contrast-enhanced dynamic MRI. A number of methods have
been proposed to overcome motion artifact and the long acquisition time of
T2-weighted images while preserving comparable image quality, but there is
still controversy regarding which technique is most appropriate for
T2-weighted imaging
[24–28].
BHTSE or fast spin-echo techniques are the most widely used T2-weighted
images because of their short acquisition time, comparable image quality, and
diagnostic performance to non–breath-hold techniques such as
conventional spin-echo or respiratory-triggered TSE
[5–9].
However, the relatively long breath-holding time of BHTSE frequently brings
about motion artifact that obscures hepatic lesions, whereas the use of
multiple refocusing pulses causes signal decrease in solid liver tumors
because of the magnetization transfer effect; the resulting low conspicuity of
malignant liver tumors is thus still problematic. Furthermore, limiting the
number of sections by multiple echo trains for short image acquisition times
may necessitate multiple acquisitions of BHTSE images.
In our study, we hypothesized that with application of SENSE to BHTSE, the
quality of BHTSE imaging could be improved in two ways. First, it can decrease
imaging acquisition time and thereby result in reduced motion artifacts.
Second, it can be used for improved spatial resolution with increasing matrix
number by trade of reduced scanning time and/or decreased ETL for improved
conspicuity of solid liver lesion while still maintaining reasonable imaging
times. To test this hypothesis, we acquired two kinds of BHTSE by applying the
parallel acquisition technique—that is, one kind by applying SENSE using
the same parameters as conventional BHTSE imaging and the other type by
applying SENSE with an increased matrix and reduced ETL for improvement of
image quality.
Theoretically, by reducing the number of measured echoes and the nonoptimum
weighting of the array coil elements, the SNR in SENSE or SMASH images is
decreased according to the square root of the acquisition time and is
inversely proportional to the square root of the reduction factor
[16]. However, our study
results showed that the mean SNR of liver and lesion and the mean
lesion–liver CNR in BHTSE using SENSE with the same parameters as the
conventional ones were slightly higher than in conventional BHTSE but with no
significant difference. Although we could not exactly explain the cause of the
unexpected results of our quantitative analysis, as our study results of image
artifact show, the increased mean SNR of the liver and the lesion could be
attributed to the decrease of image noise related to the lower motion artifact
by decreasing the image acquisition time (from 25 to 16 sec)
[29]. Particularly in four of
our study patients who were unable to achieve long breath-holds, acquiring
BHTSE images with SENSE offered better image quality with minimal motion
artifact than did conventional BHTSE imaging showing a severe motion artifact
that masked the liver lesions. These better results of the quantitative data
in terms of lesion–liver CNR and markedly reduced image artifact on
BHTSE using SENSE with conventional parameters relative to conventional BHTSE
enabled us to rate higher conspicuity of malignancy on BHTSE with SENSE than
on conventional BHTSE.
For evaluation of focal liver lesions, spatial resolution and tissue
contrast also are important factors along with the image artifacts. In this
regard, we acquired BHTSE with SENSE, having increased the phase-encoding
steps for spatial resolution and having decreased the ETL for decreasing
magnetization transfer in a shorter acquisition time (from 25 to 19 sec)
compared with conventional BHTSE. In this study, the quantitative results
showed that the SNR of the hepatic lesions and lesion–liver CNR in both
malignant lesions and hemangiomas, with BHTSE using SENSE with increased
phase-encoding steps and reduced ETL, were significantly better than those
with conventional BHTSE. In addition, the results of the qualitative analysis
regarding image quality and lesion conspicuity of malignancy on BHTSE using
SENSE with increased phase-encoding steps and reduced ETL were significantly
better than those of BHTSE using SENSE with conventional parameters and
conventional BHTSE. Improvement of image quality on BHTSE using the parallel
acquisition technique relative to conventional BHTSE is most likely due to the
decreased prominence of motion artifacts because of the decreased breath-hold
time and decreased blurring by the increased matrix. Furthermore, use of a
lower ETL decreases the magnetization transfer effects that lower the signal
intensity of malignant liver lesions and result in the achievement of higher
conspicuity in malignant liver lesions.
In our study, although there was no significant difference in lesion
detectability among the three imaging techniques, two small hepatic
masses—one hepatocellular carcinoma with a 0.9-cm diameter and one
metastasis with a 0.8-cm diameter—in two patients, were only clearly
depicted on BHTSE using SENSE with increased matrix and reduced ETL compared
with the other images. When we retrospectively analyzed the MR images of two
patients, missed small lesions were shown as faintly increased signal
intensities in both BHTSE using SENSE with conventional parameters and BHTSE
that were not definitive as in BHTSE using SENSE with increased matrix and
reduced ETL.
Our study had some limitations. First, histologic proofs were not acquired
in all lesions. Second, because the total number of tumors was small and the
majority of the tumors were relatively large (size range of detected lesions,
0.8–7 cm; mean, 2.9 cm in diameter), a precise comparison study of the
lesion detectability of each image technique was not made. Third, the
decreased image-acquisition time by application of the parallel acquisition
technique was only used for increased resolution of the in-plane and not the
through-plane for thinner slice thickness, which is an effective way to
improve the detection rate of focal liver lesions
[30]. Lastly, the order for
acquisition of the three types of BHTSE was the same in all of our study
subjects, and this might be biased because the ability to achieve a long
breath-hold might be improved by its repetition from the initial conventional
BHTSE to the last BHTSE using SENSE with increased matrix and reduced ETL.
Our study results indicate that the application of SENSE to BHTSE makes it
possible to acquire BHTSE imaging with better image quality with markedly
reduced motion artifact in a shorter imaging acquisition time. Furthermore,
BHTSE using SENSE with increased matrix and reduced ETL showed better results
in both quantitative and qualitative analysis compared with conventional BHTSE
and BHTSE using SENSE with conventional parameters. However, it is certain
that T2-weighted liver imaging alone without contrast-enhanced imaging, even
though high-quality images were acquired, is limited in accurate lesion
characterization and detection. The primary intent of this study is not to
show the potential of T2-weighted imaging to replace contrast-enhanced liver
imaging but only to show the technique for acquiring T2-weighted images with
better image quality than conventional images. Therefore, we recommend routine
use of SENSE for acquisition of BHTSE, especially in patients who cannot
tolerate gadolinium-enhanced dynamic liver imaging, because it might be
helpful for the accurate evaluation of focal liver lesions. To conclude, we
found the application of SENSE to BHTSE to be useful for acquiring
high-quality T2-weighted liver imaging compared with conventional BHTSE.
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Abstract
Introduction
