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ORIGINAL ARTICLE
Three-dimensional fast imaging employing steady-stateacquisition MRI and its diagnostic value for lumbarforaminal stenosis
Osamu Nemoto • Akira Fujikawa • Atsuko Tachibana
Received: 27 July 2013 / Accepted: 16 November 2013
� Springer-Verlag France 2013
Abstract The aim of this study was to evaluate the use-
fulness of three-dimensional (3D) fast imaging employing
steady-state acquisition (3D FIESTA) in the diagnosis of
lumbar foraminal stenosis (LFS). Fifteen patients with LFS
and 10 healthy volunteers were studied. All patients met the
following criteria: (1) single L5 radiculopathy without
compressive lesion in the spinal canal, (2) pain reproduction
during provocative radiculography, and (3) improvement of
symptoms after surgery. We retrospectively compared the
symptomatic nerve roots to the asymptomatic nerve roots on
fast spin-echo (FSE) T1 sagittal, FSE T2 axial and recon-
stituted 3D FIESTA images. The j values for interobserver
agreement in determining the presence of LFS were 0.525 for
FSE T1 sagittal images, 0.735 for FSE T2 axial images,
0.750 for 3D FIESTA sagittal, 0.733 for axial images, and
0.953 for coronal images. The sensitivities and specificities
were 60 and 86 % for FSE T1 sagittal images, 27 and 91 %
for FSE T2 axial images, 60 and 97 % for 3D FIESTA sag-
ittal images, 60 and 94 % for 3D FIESTA axial images, and
100 and 97 % for 3D FIESTA coronal images, respectively.
3D FIESTA can provide more reliable and additional
information for the running course of lumbar nerve root,
compared with conventional magnetic resonance imaging.
Particularly, use of 3D FIESTA coronal images enables
accurate diagnosis for LFS.
Keywords Three-dimensional fast imaging
employing steady-state acquisition � Lumbar
foraminal stenosis � Magnetic resonance imaging
Introduction
Lumbar foraminal stenosis (LFS) unfortunately results in
failed back surgery syndrome and is the cause of continued
postoperative pain. Magnetic resonance imaging (MRI)
evaluation of lumbar nerve root is routinely performed with
fast spin-echo (FSE) T1 sagittal and FSE T2 axial images,
but inattentive evaluation may fail to discover pathologic
foraminal lesions since it may not clearly demonstrate
nerve root entrapment in the foraminal zone. Several
methods to prevent overlooking a diagnosis of LFS have
been proposed [1–3]. Among them, provocative radicu-
lography and nerve root block have been useful as golden
standard. However, it is invasive and difficult to examine
several levels simultaneously. Therefore, new diagnostic
imaging technique to detect lumbar nerve root entrapment
in the foraminal zone is urgently required.
With recent advantages of MRI in gradient system and
power amplifier technology leading to higher gradient
amplitude and higher slew rates, gradient-echo (GRE)
sequences have become fast and robust. One type of fast
GRE sequence is a steady-state sequence, in which longi-
tudinal magnetization and transverse magnetization are
kept constant with each cycle. Steady-state sequences have
proved to be useful in a variety of applications, including
imaging of the heart and vessels. First described in 1986 as
fast imaging employing steady-state precession, steady-
state-free precession sequences are currently known by
various synonyms: true FISP, balanced fast field echo and
fast imaging employing steady-state acquisition (FIESTA)
[4–7]. Recently, it has been reported that three-dimensional
(3D) FIESTA is useful for demonstrating the anatomy and
pathology of cranial nerves and spinal cord [8, 9]. How-
ever, application of 3D FIESTA to peripheral nerve such as
lumbar nerve root to improve visualization has not been
O. Nemoto (&) � A. Fujikawa � A. Tachibana
Department of Orthopaedic Surgery, Japanese Self Defense
Forces Central Hospital, 1-2-24, Ikejiri, Setagaya-ku,
Tokyo, Japan
e-mail: drsamusio@world.ocn.ne.jp
123
Eur J Orthop Surg Traumatol
DOI 10.1007/s00590-013-1377-9
investigated. The purpose of our study was to evaluate the
efficacy of 3D FIESTA for depicting lumbar nerve root
entrapment in the foraminal zone by comparing to the
conventional MRI sequences.
Materials and methods
From 2009 to 2011, a total of 24 consecutive patients, who
underwent surgical exploration for LFS refractory to con-
servative treatment, were screened for this study. The diag-
nosis was based on the neurological symptoms and a
combination of diagnostic images including radiographs,
computerized tomography, and MRI. Only those patients
who met the following criteria were included—(1) unilateral
single-level L5 radiculopathy without compressive lesions
in the spinal canal, (2) pain reproduction during provocative
radiculography and transient pain relief after nerve root
block for agreement of side and level, and (3) improvement
of symptoms after surgery. Of the 24 patients screened, 15
patients were suitable for inclusion. They consisted of 15
males, with an average age of 51.9 years (range
41–70 years). Transforaminal lumbar interbody fusion with
pedicle screwing system was performed, and the nerve root
entrapment in the foraminal zone was observed at surgery in
all patients. A total of 10 normal volunteers (8 men and 2
women) with a mean age of 49.8 years (range 37–66 years)
were included as controls. At the screening interview, these
normal volunteers did not report leg symptoms that sug-
gested LFS, and they did not show evidence of leg signs
during physical examination.
All volunteers and patients underwent two-dimensional
(2D) MRI with a 1.5-T scanner (Signa infinity Excite; GE
Medical Systems, Milwaukee, WI, USA) using a spine
array coil. Conventional axial, and sagittal MRI used FSE
T1-weighted (TR/TE 550/7.9 ms) and T2-weighted (TR/
TE 4,000/102 ms) sequences with the following parame-
ters: slice thickness 4 mm; slice gap 1 mm; field of view
32 cm for sagittal images and 15 cm for axial images;
matrix 320 9 224; flip angle 90�; excitations 3. Additional
3D FIESTA images were acquired with following acqui-
sition parameters: TR = 6 ms, TE = 1.3 ms, flip
angle = 45�, no intersection gap, slice thickness = 1 mm,
FOV = 18 9 18 cm, matrix = 320 9 320. Multiplanar
image reconstruction was performed using an advantage
workstation (AW 4.3; GE Medical Systems, Milwaukee,
WI, USA), and all 3D images were reconstructed in the 3
planes (sagittal, axial, and coronal). The additional time
taken for the 3D FIESTA acquisition was 5 min. On con-
ventional 2D MRI, LFS] grade 2 was defined as positive,
according to the classification reported by Lee et al. [10].
The evaluation by 3D FIESTA was performed by tracing
the entire running course of the nerve root from intracanal
to extraforaminal on consecutive sliced images. The
marked entrapment of the nerve root with running course
abnormality and surrounding fat obliteration was judged as
positive. The symptomatic L5 nerve roots of the patients
(n = 15) and the asymptomatic L5 nerve roots (contralat-
eral asymptomatic L5 nerve roots in the patients, n = 15;
bilateral L5 nerve roots in the normal volunteers, n = 20)
were evaluated on FSE T1 sagittal, FSE T2 axial, and
reconstituted 3 planes of 3D FIESTA images. The MRI
images were reviewed randomly and independently by an
experienced neuroradiologist and senior spinal surgeon
who did not participate in the care of the patients. They
were aware that images were obtained for the evaluation of
the lumbosacral spinal disorders but were blinded to any
clinical, diagnostic, or treatment-related information and
only asked to decide whether the patients were positive or
negative for LFS. After this independent evaluation was
performed, discrepancies were resolved through discus-
sion, and observations agreed on were used to analyze the
data. The reliability of the evaluation was estimated using
the j statistics for interobserver reliability. The agreement
was calculated using SPSS (ver. 13.0; SPSS Inc., Chicago,
IL, USA) and rated as follows: poor, j = 0–0.2; fair,
j = 0.21–0.4; moderate, j = 0.41–0.6; substantial
j = 0.61–0.8; and excellent, j[ 0.81.
Results
Interobserver reliability in the detection of nerve root
entrapment by MRI is summarized in Table 1. All sequences
except FSE T1 showed optimal reliability. Among them,
excellent agreement was demonstrated on 3D FIESTA
coronal images. Both on conventional 2D MRI and 3D
FIESTA images, exiting nerve root shown as low signal
intensity is normally surrounded by fat tissue and runs
obliquely downward from intracanal to foraminal and ex-
traforaminal zone without angulation. Because of the slice
gap, conventional sagittal and axial MRI images cannot
demonstrate the entire running course of the nerve root
(Fig. 1). In contrast, due to the thin slice thickness without
Table 1 Interobserver agreement in evaluating L5 nerve entrapment
Sequences j value
FSE T1 sagittal 0.525
FSE T2 axial 0.735
3D FIESTA sagittal 0.750
3D FIESTA axial 0.733
3D FIESTA coronal 0.953
FSE indicates fast spin-echo
FIESTA indicates fast imaging employing steady-state acquisition
Eur J Orthop Surg Traumatol
123
slice gap and the high signal-to-noise ratio, 3D FIESTA
sequences can reveal an excellent full view of the nerve root
from foraminal to extraforaminal continuously (Fig. 2).
Diagnostic performance in evaluating L5 nerve root
entrapment using conventional 2D MRI and 3D FIESTA is
presented in Table 2. The sensitivity of FSE T2 axial images
was poor. Although the specificities were high, the sensi-
tivities of 3D FIESTA sagittal, axial, and FSE T1 sagittal
images were suboptimal. Among them, 3D FIESTA coronal
images revealed excellent diagnostic performance of LFS
(Fig. 3).
Discussion
LFS is defined as the narrowing of the bony exit of the
nerve root, and its incidence is reported to be between 8
and 11 % [11]. In general, common and important findings
on MRI images related to the diagnosis of LFS have been
type of stenosis, amount of fat obliteration, and presence of
Fig. 1 Sagittal T1 (a) and axial T2 (b) images of conventional MRI
with a 48-year-old normal volunteer show asymptomatic bilateral L5
nerve roots from intracanal to foraminal zone. Because of the slice
gap, entire running course of L5 nerve root is not clearly
demonstrated
Fig. 2 Consecutive 3D FIESTA coronal images of a 51-year-old
normal volunteer can depict the entire fine view of bilateral L5 nerve
roots (arrow) from intracanal to foraminal zone
Table 2 Detection of L5 nerve root entrapment in the foraminal zone
FSE 3D FIESTA
T1
Sagittal
T2
Axial
Sagittal Axial Coronal
Normal volunteers 3/20 1/20 0/20 0/20 0/20
Patients
Asymptomatic
nerve root
2/15 2/15 1/15 2/15 1/15
Symptomatic
nerve root
9/15 4/15 9/15 9/15 15/15
Sensitivity (%) 60 26 60 60 100
Specificity (%) 86 91 97 94 97
Positive predictive
value
64 57 90 82 94
Negative predictive
value
83 74 85 85 100
FSE indicates fast spin-echo
FIESTA indicates fast imaging employing steady-state acquisition
Eur J Orthop Surg Traumatol
123
nerve root entrapment. However, these findings are occa-
sionally missed since conventional sagittal and axial MRI
images cannot depict the entire running course of the nerve
root because of the slice gap and its poor resolution.
Oblique MRI has been reported to be useful in detecting
LFS [12]. However, oblique images along intervertebral
foramina as well as several MR findings mentioned by Lee
et al. [13] have not been helpful in patients with spinal
deformities such as scoliosis or severe lordosis. Addition-
ally, it takes much time so as to perform bilateral oblique
images in each patient. On the contrary, some authors
reported that conventional MRI images do not detect LFS
with any certainty because false-positive findings may be
frequently observed [14, 15]. There is a possibility that in
cases in which the acquisition of images has not been
parallel or perpendicular to the disc, different sizes of nerve
roots, or an asymmetric position of the nerve roots in cases
without nerve root entrapment might be diagnosed as LFS.
Thus, there are many conflicting reports as to the sensi-
tivity and specificity of the conventional MRI sequences
for the diagnosis of LFS.
Recently, usefulness of MR myelography (MRM) and
diffusion tensor imaging (DTI) as diagnostic tool for LFS
has been reported. MRM was developed in late 1980s and
has become one of popular auxiliary diagnostic methods
used in brain and spinal lesion. MRM has several merits
Fig. 3 Conventional FSE T1 sagittal (a) and FSE T2 axial (b) images
cannot prove definite L5 nerve root entrapment of a 53-year-old male
with left L5/S foraminal stenosis. Coronal 3D FIESTA images
(c) clearly depict the entrapment of left L5 nerve root by bony spur
and bulged disc in the foraminal zone
Eur J Orthop Surg Traumatol
123
over conventional contrast media using myelography: non-
invasiveness, no drug adverse reaction, and so on. In the
evaluation of lumbar nerve root, study results by Kim et al.
[16] and Aota et al. [15] showed that MRM is helpful in
differentiating symptomatic nerve root from asymptomatic
nerve root. Although high specificity was observed in these
reports, the sensitivity of running course abnormality was
65.5 %. Accordingly, Kim et al. [16] described that MRM
alone was not good enough as diagnostic modality for LFS.
Diffusion-weighted imaging has been widely used clini-
cally in the evaluation of the central nervous system.
Several studies have shown that DTI is useful for the
evaluation and visualization of peripheral nerves [17–19].
Eguchi et al. [20] reported that DTI can clearly show
tractograms of lumbar nerves and determine fractional
anisotropy values of the nerve roots in patients and healthy
volunteers. However, that tracts might be apparently
missing in tractograms does not necessarily indicate loss of
nerve fibers. Accordingly, significance of nerve root dis-
ruption on the tractograms is not clearly understood. In
addition, there exist other limitations such as directional
information loss as a result of the partial volume effect,
indefinite relationship between the number of tracts visu-
alized by DTI and actual volume of nerve fiber trajectories,
and so on. Considering these shortcomings, simple and
practical diagnostic modality to evaluate the entrapment of
lumbar nerve root is needed.
Recently, several studies have shown that 3D FIESTA
can provide an excellent visualization of neurovascular
tissues [8, 21, 22]. 3D FIESTA sequence is a fully balanced
steady coherent imaging pulse sequence, and perfectly
balanced gradient at the end of each TR interval of hori-
zontal magnetic realignment phase, which results in neural
structures returning low signal intensity. Attenuation of
transverse magnetization re-gathered at the end of each TR
time creates good T2 contrast in the 3D FIESTA sequence,
and slowly flowing liquid generates high signal intensity.
Additionally, 3D FIESTA has a good signal-to-noise ratio
that allows the evaluation of small structures or lesions. In
this study, to visualize L5 nerve root entrapment, conven-
tional 2D MRI and 3D FIESTA sequences were performed
on 15 surgically treated patients with definite LFS and 10
normal volunteers. Our results show that compared with
conventional 2D MRI, 3D FIESTA imaging could provide
more precise information of the lumbar nerve root
entrapment in the foraminal zone. A key reason for the
difference between conventional 2D MRI and 3D FIESTA
might be distinction in MRI imaging techniques. Using
reconstituted images without slice gap and high spatial
resolution, 3D FIESTA can visualize the continuous full
view of the lumbar nerve root. Particularly, 3D FIESTA
coronal images offer excellent diagnostic performance
compared to sagittal or axial images. Kim et al. [16] also
described the usefulness of coronal views for detecting
foraminal L5 root entrapment in their report with 3D
MRM. Since craniocaudal compression-type LFS is better
visualized on coronal images, it might be affected by its
prevalence in our patient population. Another possibility
may be selection bias of the patient in this retrospective
study. With respect to avoid misdiagnosis of symptomatic
nerve root, provocative radiculography is still valuable. In
patients with multiple involvements of nerve roots on the
different levels, 3D FIESTA cannot identify the symp-
tomatic nerve roots and we have to perform the provocative
radiculography. However, this method is invasive, and it is
often difficult to evaluate the accurate localization of nerve
root entrapment by the leak of contrast media. Therefore, in
case with unilateral single-level radiculopathy, 3D FIESTA
can be an excellent modality for replacing invasive pro-
vocative radiculography.
To strengthen the superiority of the 3D FIESTA coronal
images, further investigations involving larger patient
cohorts are needed. There are several limitations in the
present study. The first limitation is the small sample size
of 15 patients with symptomatic LFS, but the LFS that
meets the criteria in this study is much less common.
Second, we could not repeat the 3D FIESTA following
surgery because of spinal instrumentation artifacts.
In conclusion, 3D FIESTA imaging revealed an excel-
lent full view of the lumbar nerve roots, compared with
conventional MRI. Particularly, 3D FIESTA coronal ima-
ges can provide more reliable information in the diagnosis
of LFS, in addition to helping with surgical treatment
planning. Considering the results of this study, we suggest
that 3D FIESTA should be included in the routine MRI
protocol for the investigation into LFS.
Conflicts of interest None.
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