Koutsiaris 2013_b_ΜRI BLADE_Lumbar Spine

Elimination of motion, pulsatile flow and cross-talk artifacts using blade sequences
in lumbar spine MR imaging
Eleftherios Lavdas a
, Panayiotis Mavroidis b,c,
⁎, Spiros Kostopoulos d
, Dimitrios Glotsos d
, Violeta Roka e
,
Aristotle G. Koutsiaris f
, Georgios Batsikas g
, Georgios K. Sakkas h
, Antonios Tsagkalis i
, Ioannis Notaras i
,
Sotirios Stathakis b
, Nikos Papanikolaou b
, Katerina Vassiou j
a
Department of Medical Radiological Technologists, Technological Education Institute of Athens, Greece
b
Department of Radiological Sciences, University of Texas Health Sciences Center at San Antonio, San Antonio, TX, USA
c
Department of Medical Radiation Physics, Karolinska Institutet & Stockholm University, Stockholm, Sweden
d
Department of Medical Instruments Technology, Technological Education Institute of Athens, Greece
e
Health Center of Farkadona, Trikala, Greece
f
Bioinformatics Laboratory, Department of Medical Laboratories, School of Health Sciences, Technological Educational Institute of Larissa, Larissa, Greece
g
Department of Medical Imaging, IASO Thessalias Hospital, Larissa, Greece
h
Center for Research and Technology Thessaly Trikala
i
Department of Orthopaedic Surgery, IASO Thessalias Hospital, Larissa, Greece
j
Department of Radiology, Medical School, University of Thessaly, Larissa, Greece
a b s t r a c ta r t i c l e i n f o
Article history:
Received 24 October 2012
Revised 28 January 2013
Accepted 8 March 2013
Available online xxxx
Keywords:
1.5 T MRI
Motion
Pulsatile flow and cross-talk artifacts
BLADE sequences
Lumbar spine examination
The purpose of this study is to evaluate the ability of T2 turbo spin echo (TSE) axial and sagittal BLADE
sequences in reducing or even eliminating motion, pulsatile flow and cross-talk artifacts in lumbar spine
MRI examinations. Forty four patients, who had routinely undergone a lumbar spine examination,
participated in the study. The following pairs of sequences with and without BLADE were compared: a) T2
TSE Sagittal (SAG) in thirty two cases, and b) T2 TSE Axial (AX) also in thirty two cases. Both quantitative
and qualitative analyses were performed based on measurements in different normal anatomical
structures and examination of seven characteristics, respectively. The qualitative analysis was performed
by experienced radiologists. Also, the presence of image motion, pulsatile flow and cross-talk artifacts was
evaluated. Based on the results of the qualitative analysis for the different sequences and anatomical
structures, the BLADE sequences were found to be significantly superior to the conventional ones in all the
cases. The BLADE sequences eliminated the motion artifacts in all the cases. In our results, it was found that
in the examined sequences (sagittal and axial) the differences between the BLADE and conventional
sequences regarding the elimination of motion, pulsatile flow and cross-talk artifacts were statistically
significant. In all the comparisons, the T2 TSE BLADE sequences were significantly superior to the
corresponding conventional sequences regarding the classification of their image quality. In conclusion,
this technique appears to be capable of potentially eliminating motion, pulsatile flow and cross-talk
artifacts in lumbar spine MR images and producing high quality images in collaborative and non-
collaborative patients.
© 2013 Elsevier Inc. All rights reserved.
1. Introduction
Magnetic resonance imaging (MRI) is the imaging technique of
choice for the investigation of patients with documented primary
tumours and suspected malignant infiltration of the spine [1].
Extradural compression of the spinal cord or cauda equina from
vertebral metastases has been widely reported in the literature
[2–4]. Intradural extramedullary metastases are uncommon [5]
although their incidence is felt to be increasing, possibly as a result of
the longer survival times in patients with systemic metastatic
diseases [6]. Degenerative disc disease of the spine is one of the most
common clinical entities and the lumbar spine region is among the
most commonly involved sites in severe primary spinal degenerative
changes [7].
In all the above clinical cases, especially when the diseases are in
a more advanced stage (primary tumor, matastasis, degeneration
Magnetic Resonance Imaging xxx (2013) xxx–xxx
⁎ Corresponding author. Division of Medical Physics, Department of Radiological
Sciences, Cancer Therapy and Research Center, University of Texas Health Sciences
Center San Antonio, MC 7889, San Antonio TX 78229–4427, USA. Tel.: +1 210 450
1027; fax: +1 210 478 9703.
E-mail address: mavroidis@uthscsa.edu (P. Mavroidis).
0730-725X/$ – see front matter © 2013 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.mri.2013.03.006
Contents lists available at SciVerse ScienceDirect
Magnetic Resonance Imaging
journal homepage: www.mrijournal.com
Please cite this article as: Lavdas E, et al, Elimination of motion, pulsatile flow and cross-talk artifacts using blade sequences in lumbar
spine MR imaging, Magn Reson Imaging (2013), http://dx.doi.org/10.1016/j.mri.2013.03.006

etc.) the patient may often undergo MR examination under pain,
which may result in lack of patient collaboration and undesirable
patient movements during the course of the examination. The use of
sagittal T2-weighted and axial T2-weighted sequences is a basic
starting point in the imaging of spinal discogenic diseases [8]. MR of
the spine based on T2-weighted images can be performed with
conventional spin echo (SE) or, preferably with fast spin echo (FSE)
techniques [9–12]. FSE MR imaging sequences have a shorter
acquisition time than the conventional SE imaging sequences.
MR imaging with BLADE, which is a PROPELLER-equivalent
implementation of the Siemens Medical System (Erlangen, Germa-
ny), have been shown to effectively reduce motion and pulsatile flow
artifacts [12–17]. The term BLADE is the product name of a brand’s
TSE sequence that uses the PROPELLER (periodically rotated over-
lapping parallel lines with enhanced reconstruction) k-space
trajectory. The BLADE method acquires N blades (N number of
blades) that are rotated around the center of the k space. Each blade
consists of L lowest phase encoding lines (i.e., echo train length
[ETL]) of a conventional rectilinear k-space trajectory that are
acquired after a single radiofrequency excitation. In brain MR
imaging, it has been reported that the BLADE sequences reduce
motion artifacts and improve image quality [18–22]. Recently, the
BLADE technique was also used in examinations of the cervical spine,
neck, upper abdomen, knee, kidneys and breast [23–29]. The BLADE
technique has the advantage of central k-space oversampling, so that
image artifacts are greatly reduced [18,23–30]. On the other hand, it
is not yet confirmed how much motion and streak artifacts
[21,23,31], which appear in radial scans [32], are reduced when
different BLADE parameters are employed [33].
In this study, T2 TSE AX and T2 TSE SAG BLADE sequences were
employed in order to assess their ability to significantly reduce or
even eliminate motion artifacts and improve image quality in lumbar
spine MRI examinations.
2. Materials and methods
2.1. Patients
From March 2010 to April 2012, forty four patients (19 females,
25 males; mean age 41 years, range 16–81 years), who had been
routinely scanned for lumbar spine examination using four different
image acquisition techniques, participated in the study. More
specifically, the following pairs of sequences with and without
BLADE were applied: a) T2 TSE SAG in thirty two patients, and b) T2
TSE AXIAL in thirty two patients. This study was approved by the
local institutional review board and written informed consent was
obtained from all the subjects participating in the study protocol.
Due to practical limitations, both pairs of sequences were acquired in
20 of the patients. Of the remaining group of 24 patients, one half
was scanned using the TSE SAG BLADE sequence, whereas the other
half was scanned using the TSE AXIAL BLADE sequence.
2.2. MR imaging techniques
On all the patients, the lumbar spine MRI examinations were
performed using a 1.5 T scanner (Magneton Avanto, Siemens
Healthcare Sector, Erlangen, Germany) and a synergy body
phased-array surface coil. The parameters of the different sequences
are presented in Table 1.
2.3. Quantitative analysis
A quantitative analysis was performed for the examined four
sequences. In the quantitative analysis the following items were
analyzed: (a) the signal-to-noise ratio (SNR) in spinal cord (SC),
normal bone marrow (BM), neural root (NR), fatty tissue (FT),
cerebrospinal fluid (CSF) and vertebral disk (VD) (b) the contrast-to-
noise ratio (CNR) between the CSF and spinal cord, normal bone
marrow and vertebral disc, neural root and its surrounding fatty
tissue, CSF and normal bone marrow, CSF and vertebral disc,
vertebral disk and neural root, and finally vertebral disk and fatty
tissue. For calculating these values, the signal intensity (SI) of the
spinal cord, CSF, normal bone marrow, vertebral disc, neural root,
fatty tissue and standard deviation (SD) of background noise were
measured by placing regions of interest (ROIs). For each patient, the
ROIs were identical and were place in the same position in the two
sequences under comparison. The SD of the background noise was
measured in the largest possible ROI positioned in the phase-
encoding direction outside the abdominal wall (air) to account for
any motion artifacts. When in some cases the positions of the ROIs of
one sequence were shifted due to patient motion, the ROIs were
manually placed based on their relative position to adjacent tissues.
The SNR was calculated as:
SNRA ¼
SIA
N
ð1Þ
where A represents the tissue of interest, the SIA is the signal
intensity of A measured by an elliptical region-of-interest (ROI) on
the system console. SI is taken as the mean value throughout the ROI.
N is the background noise, which was defined as the standard
deviation of a measurement.
The CNR was calculated as:
CNRAB ¼
SIA−SIB
N
ð2Þ
where SIA and SIB define the SI of the tissues A and B, respectively.
A fundamental requirement for any comparison of SNR or CNR
between two different sequences is that the resolution should be
made equivalent between the two methods. For this reason, the SNR
and CNR values of the examined sequences were normalized by the
corresponding voxel sizes in order to account for the differences in
voxel size.
The quantitative evaluation was performed by means of the
Kolmogorov-Smirnov non parametric test.
2.4. Qualitative analysis
All the images of the examined four MR sequences with and
without BLADE were visually evaluated and compared indepen-
dently at two separate examination sessions with 3 weeks interval
Table 1
Summary of the sequences that were applied for lumbar spine MR examination.
Sequences T2-TSE-SAG T2-TSE-SAG
BLADE
T2 TSE-AX T2 TSE-AX
BLADE
TR (ms) 3500 6000 3610 6000
TE (ms) 92 103 108 103
Matrix (Freq/Phase) 384/288 256/256 384/288 256/256
BW (Hz/pixel) 161 383 171 383
Acquisition time (min) 4:03 3:08 4:25 3:08
Thickness (mm) 4 4 4 4
Space (%) 10 10 10 10
ETL 34 35 24 30
FOV (mm) 280/280 280/280 240/240 280/280
Echo spacing (ms) 11.05 5.74 12 5.74
Proportion of coverage - 130.4 - 130.4
Number of signal
averages (NSA)
2.0 1.0 3.0 1.0
2 E. Lavdas et al. / Magnetic Resonance Imaging xxx (2013) xxx–xxx

by two experienced on MR imaging radiologists and the results of the
blinded evaluations were used in the analysis.
The images from the corresponding sequences were filmed at
optimal window and level settings. It should be stated that window
settings have a dynamic width in MRI examinations and those
window and level settings are decided by the system itself. The
radiologists graded on a 5-point scale (0: non-visualization; 1: poor;
2: average; 3: good; 4: excellent) each of the following image
Table 2
Summary of the results of the quantitative comparison between the BLADE and conventional sequences.
SNR T2-TSE-SAG T2-TSE-SAG BLADE p T2 TSE-AX T2 TSE-AX BLADE p
BM 55.7 ± 19.4 203.5 ± 57.5 b0.01 43.2 ± 18.1 235.8 ± 75.5 b0.01
VD 29.1 ± 16.5 130.9 ± 82.2 b0.01 13.0 ± 5.6 86.2 ± 34.4 b0.01
NR 53.3 ± 20.1 181.4 ± 59.0 b0.01 38.5 ± 43.9 177.1 ± 121.0 b0.01
SC 63.8 ± 15.2 155.8 ± 33.4 b0.01 - - -
CSF 133.8 ± 39.2 436.6 ± 113.3 b0.01 85.9 ± 36.4 406.0 ± 109.8 b0.01
FT 55.7 ± 19.4 203.5 ± 57.5 b0.01 43.2 ± 18.1 235.8 ± 75.5 b0.01
NS 166.1 ± 50.8 424.6 ± 113.2 b0.01 118.9 ± 43.4 441.7 ± 154.9 b0.01
CNR T2-TSE-SAG T2-TSE-SAG BLADE p T2 TSE-AX T2 TSE-AX BLADE p
BM/VD 29.2 ± 18.8 85.6 ± 47.1 b0.01 30.3 ± 17.3 151.7 ± 76.4 b0.01
CSF/SC 102.3 ± 38.1 268.8 ± 87.6 b0.01 - - -
NR/FT 80.6 ± 28.5 255.2 ± 91.8 b0.01 54.7 ± 26.6 229.2 ± 120.4 b0.01
CSF/BM 110.4 ± 34.3 221.1 ± 85.9 b0.01 75.7 ± 35.4 205.9 ± 101.3 b0.01
CSF/VD 137.0 ± 47.5 293.7 ± 111.2 b0.01 106.0 ± 41.1 355.5 ± 148.5 b0.01
VD/NR 26.9 ± 18.7 81.3 ± 45.3 b0.01 25.8 ± 44.1 93.3 ± 123.7 b0.01
VD/FT 104.7 ± 37.3 305.7 ± 108.7 b0.01 73.0 ± 34.1 319.8 ± 98.5 b0.01
The analysis of the signal to noise ratio (SNR) and contrast to noise ratio (CNR) results was performed using the Kolmogorov-Smirnov non parametric test.
BM: bone marrow, VD: vertebral disc, NR: neural root, SC: spinal cord, NS: noise, CSF: cerebrospinal fluid, FT: fatty tissue.
Fig. 1. Sagittal T2 TSE (upper left), Sagittal T2 TSE BLADE (upper right), Axial T2 TSE (lower left) and Axial T2 TSE BLADE (lower right) images of the spine. It is shown that the
motion artifacts that are seen in the T2 TSE sequences are eliminated in the T2 TSE BLADE sequences improving significantly the overall image quality.
3E. Lavdas et al. / Magnetic Resonance Imaging xxx (2013) xxx–xxx

Fig. 2. Sagittal T2 TSE (left) and sagittal T2 TSE BLADE (right) images of the lumbar spine. It is shown that the motion artifacts that are seen in the T2 TSE sequence are eliminated
in the T2 TSE BLADE sequence improving signiﬁcantly the overall image quality.
Fig. 3. Axial T2 TSE (upper left), Axial T2 TSE BLADE (upper right), Axial T2 TSE (lower left) and Axial T2 TSE BLADE (lower right) images of the spine. It is shown that the BLADE
sequences manage to minimize or even eliminate the initially observed cross-talk (lateral arrows) and pulsatile ﬂow (central arrows) artifacts.

characteristics: (1) overall image quality, (2) conspicuousness of the
morphologic abnormalities in the discovertebral junction, (3)
conspicuousness of the nerve roots in the neural foramen, (4)
contrast at the vertebral disc–CSF interface, (5) contrast at the
vertebral disc–spinal cord (cauda equina) interface, (6) contrast at
the lesion of the vertebral body–bone marrow and (7) contrast at the
spinal cord (cauda equina)–CSF interface. The evaluators (radiolo-
gists) also evaluated the presence of image motion, pulsatile flow
and cross-talk artifacts using a separate scoring scale (0, maximum;
1, severe; 2, moderate; 3, slight; 4, minimum).
3. Results
3.1. Quantitative results
The results of the quantitative analysis obtained from all the
patients are presented in Table 2.
It is observed that the BLADE sequences are superior to the
corresponding conventional ones in all the cases. Moreover, the
results of the SNR and CNR comparisons show remarkable
statistically significant differences between the BLADE and the
conventional sequences, especially in the SNR comparisons of T2
TSE SAG for bone marrow, neural root, CSF, fatty tissue and those of
T2 TSE AX for bone marrow, vertebral disc, CSF and fatty tissue.
Similarly, large statistically significant differences were found in
the CNR comparisons between CSF/spinal cord, neural root/fatty
tissue, vertebral disc/fatty tissue in T2 TSE SAG and bone marrow/
vertebral disc, neural root/ fatty tissue, CSF/vertebral disc in T2 TSE
AX between the BLADE and conventional sequences. Also, statis-
tically significant differences were found in the SD in air results
between the BLADE and conventional sequences.
3.2. Qualitative analysis
The results of the qualitative analysis obtained from all
the patients indicate that BLADE sequences were superior to the
corresponding conventional sequences in all the cases. The
statistical significance of the qualitative data was determined by
Fig. 4. Axial T2 TSE (upper left), Axial T2 TSE BLADE (upper right), Sagittal T2 TSE (lower left) and Sagittal T2 TSE BLADE (lower right) images of the spine. It is shown that a better
visualization of the intervertebral discs is achieved by the BLADE sequences. Especially, the herniated disc that exists between the spinal sac and the normal vertebral disc can be
better identified in the Axial BLADE sequence. Furthermore, in the Sagittal T2 TSE BLADE sequence a better visualization of the annular tear in the inter-vertebral disc between L5–
S1, is achieved.

the Kruskal–Wallis non-parametric test. More specifically,
the qualitative analysis of motion artifacts based on the evaluation
of the two experts gave a scoring of 2.70 ± 1.03 for the T2 TSE
SAG sequence against 3.56 ± 0.56 for the T2 TSE SAG BLADE
sequence. Similarly, the score of the T2 TSE AX was 2.72 ± 1.05,
whereas that of the T2 TSE AX BLADE was 3.69 ± 0.47. In both
comparisons the differences were found to be statistically signif-
icant (p b 0.01).
The T2 TSE SAG BLADE sequence was significantly superior than
the corresponding conventional sequence in terms of: (1) overall
image quality (p b 0.01), (2) conspicuousness of the morphologic
abnormalities in the discovertebral junction (p b 0.01), (3)
conspicuousness of the nerve roots in the neural foramen
(p b 0.01), (4) contrast at the vertebral disc–CSF interface
(p b 0.01) and (5) contrast at the lesion of the vertebral body–
bone marrow (p b 0.01).
Similarly, the results of the qualitative analysis indicate that the
T2 TSE AX BLADE sequence was superior than the corresponding
conventional sequence in all the examined factors. Specifically, (1)
overall image quality (p b 0.01), (2) conspicuousness of the
morphologic abnormalities in the discovertebral junction
(p b 0.01), (3) conspicuousness of the nerve roots in the neural
foramen (p b 0.01), (4) contrast at the vertebral disc–spinal cord
(cauda equina) interface (p b 0.01), and (5) contrast at the lesion of
the vertebral body–bone marrow (p b 0.01) were in favour of the T2
TSE AX BLADE sequence.
Motion artifacts were shown in: a) seven T2 TSE SAG (Figs. 1 and
2), and b) six T2 TSE AXIAL (Fig. 1) cases, respectively. Four of these
sequences were of no diagnostic value. However, when BLADE
sequences were used, motion artifacts were eliminated.
Of the eleven patients, where pulsatile flow artifacts were
observed, the T2 TSE AXIAL BLADE sequence managed to eliminate
them in six cases, whereas of the eleven patients, where cross-talk
artifacts were observed, the T2 TSE AXIAL BLADE sequence managed
to eliminate them in all the cases (Fig. 3).
The pathologies that were found in the conventional sequences
were also found in the corresponding BLADE sequences. More
specifically, a better visualization of the herniated disc between the
spinal sac and the normal vertebral disc as well as of the annular dear
in the inter-vertebral disc could be achieved (Figs. 4 and 5). A better
distinction between the neural roots, the fatty tissue and the joints
were observed in the BLADE sequences (Fig. 5). Furthermore, the
Modic and in general the degenerative changes could be better
visualized by the BLADE sequences (Fig. 6) [34,35].
However, the evaluators (radiologists) observed that in some
cases where the T2 TSE AX conventional sequence was applied the
neural roots in spinal canal were visualized more clearly compared
with the T2 TSE AX BLADE sequence.
Fig. 5. Axial T2 TSE (upper left), Axial T2 TSE BLADE (upper right), Axial T2 TSE (lower left) and Axial T2 TSE BLADE (lower right) images of the lumbar spine. It is shown that by
using the BLADE sequences a better distinction between the neural roots, the fatty tissue (large arrow) and the joints (small arrow), is achieved. Furthermore, in the Axial T2 TSE
BLADE (lower right) sequence a better visualization of the annular tear in the inter-vertebral disc between, is achieved (small arrow) compared to Axial T2 TSE (lower left).

4. Discussion
The diagnostic value of T2-weighted TSE SAGITAL and AXIAL
images has been established in lumbar spine examination. However,
in severe cases of primary tumor, matastasis, spine fractures and
degeneration, which cause compression of the spinal cord, cauda
equina or peripheral nerves, there is presence of patient movements
producing motion artifacts, which have as a consequence a
degradation of image quality. Furthermore, motion artifacts can
also be observed in non-cooperative patients such as patients with
Parkinson’s disease, patients with brain damages (tumor, metastasis,
ischemic lesions etc.), small children, bone fractures etc. In brain MR
imaging, it has been reported that the BLADE sequences reduce
motion artifacts and improve image quality [16–20].
Motion artifacts appear as hypo-intense lines in the central tissue
in the phase encoding direction thereby reducing image quality to
levels that are often characterized by radiologists as being of non-
diagnostic value.
The artifacts cross-talk is very common in the examination of
lumbar spine. Selective RF pulses yield imperfect slice profiles,
whose edges are not clearly cut. In multislice techniques with
contiguous slices, a selective RF pulse can thus partially excite the
adjacent slices. Likewise, if several interlacing slice stacks cross, the
zone of intersection will be partially excited. This will cause a
modification in contrast and/or a loss of signal through partial
saturation in the slice or zone of intersection. These phenomena are
even more pronounced when pulses of 180° are used (inversion
recovery, fast spin echo or turbo spin echo).
The solution consists in spacing the slices by adding an interval
between them: the slices are no longer contiguous. It is also possible to
interlace multislice acquisition to avoid imaging the adjacent slices
with the same repetition time. In the cases where it is vital to visualize
the whole volume with no wasted time, it is preferable to use 3D
sequences. In lumbar spine examinations, T2 TSE AXIAL sequence
commonly covers only the intervertebral space so it is not possible to
increase the interval between the slices because this would cause loss
of valuable information. Furthermore, 3D sequences are not practical
to be applied for imaging each intervertebral space. The effective
reduction of the cross-talk artifacts is a feature of the BLADE technique.
This is based on the fact that although the reduction of those artifacts
stems from the use of long TR values, these long TR values are possible
to be applied due to the characteristics of the BLADE technique.
Otherwise, the overall acquisition time would be significantly larger
leading to a deterioration of image quality.
BLADE technique has been found to reduce motion artifacts in
examinations of the brain, cervical spine, neck, upper abdomen, knee,
Fig. 6. Sagittal T2 TSE (upper left), Sagittal T2 TSE BLADE (upper right), Sagittal T2 TSE (lower left) and Sagittal T2 TSE BLADE (lower right) images of the spine. It is shown that the
BLADE sequences achieve better visualization of the degenerative changes. More specifically, in the upper images it is shown that the Modic-II (arrows) in the inter-vertebral disc
between L5–S1, is better visualized by the BLADE sequence. Also, in the lower images, the degenerative changes (such as that shown by the arrows) are better distinguished from
their environment by the BLADE sequence.

kidneys and breast [22–29]. Due to the fact that in lumbar spine
examinations motion artifacts were often observed, we decided to use
BLADE sequences in order to examine whether they can eliminate
those motion as well as pulsatile flow and cross-talk artifacts and if
they have any impact in the visualization of the nearby tissues.
Siemens Healthcare Sector has not yet prepared BLADE se-
quences for lumbar spine to provide during the installation of their
systems. In this study, the T2 TSE SAG BLADE sequence from cervical
spine protocol of Siemens Healthcare Sector was employed, in which
the values of FOV, Slice Thickness and Space were modified in order
to match those of the T2 TSE SAG sequence from lumbar spine
protocol. For producing the T2 TSE AX BLADE sequence, the
previously described T2 TSE SAG BLADE sequence was used as a
basis, in which the values of Slice Thickness and Space were modified
to match those of the T2 TSE AX sequence from lumbar spine
protocol. In the BLADE sequences, the FOV was set to
280 mm × 280 mm, whereas in the T2 TSE sequences it was
240 mm × 240 mm. This was done in order to visualize a larger
area of the soft tissue, aorta and kidney and because in this way a
better SNR (lower noise) could be achieved. For this reason, the SNR
and CNR values of the examined sequences were normalized by the
corresponding voxel sizes in order to account for the differences in
voxel size and make the relevant comparisons compatible.
The BLADE sequences are commonly applied with higher echo
training length compared with conventional sequences. In one of our
previous studies, it was found that the T2 TSE AXIAL BLADE
sequence, which was applied in brain imaging with a lower echo
training length compared with the conventional T2 TSE AXIAL,
managed to eliminate motion and pulsatile flow artifacts without
decreasing image quality [22]. The same approach was applied in the
examined lumbar spine examinations where the T2 TSE SAG BLADE
sequence has an ETL of 35, whereas the T2 TSE SAG conversional
sequence has an ETL equal to 34. The ETL is significant factor because
it directly affects the acquisition time.
In the BLADE sequences, the acquisition time is normally
increased compared with the conventional sequences. However,
the T2 TSE AX BLADE sequence which is applied in this study has a
decreased acquisition time (3:08 min:sec) compared with the
corresponding conventional sequence (4:25). Similarly, the T2 TSE
SAG BLADE sequence has an acquisition time of 3:08, whereas the T2
TSE SAG conversional sequence has 4:03. This is a great advantage
because it allows us to increase the matrix and the blade coverage,
which results in a further enhancement of image quality. Also, by
increasing the size of the matrix it is possible to reduce the only
disadvantage that was found in the T2 TSE AX BLADE sequences in
the visualization of neural roots in spinal canal.
3 T MR imaging has a double SNR compared with 1.5 T. However,
more artifacts are commonly observed in 3 T compared with 1.5 T
systems. In 3 T MRI systems, the possibility of increasing the size of
the matrix without causing a SNR decrease and scan time increase
(compared with the values applied in the 1.5 T systems) is exploited
leading to a two-fold gain since: a) BLADE sequences can eliminate
the artifacts (which is significant problem in 3 T), and b) the
increased SNR can provide high image quality.
In our results, it was found that BLADE sequences eliminated
motion artifacts in all the cases. More specifically, the motion
artifacts that were observed in seven T2 TSE SAG and six T2 TSE
AXIAL cases, respectively were eliminated by the corresponding
BLADE sequences improving significantly the overall image quality
(Figs. 1 and 2). It is important to mention that although four of these
cases were of no diagnostic value when the conventional sequence
was used, the necessary diagnostic information was possible to be
acquired when the BLADE sequences were applied.
Regarding pulsatile flow and cross-talk artifacts it is shown that
the BLADE sequences manage to minimize or even eliminate them.
More specifically, in eleven cases where pulsatile flow artifacts were
observed, the T2 TSE AXIAL BLADE sequence managed to eliminate
them in six of those cases. On the other hand, the T2 TSE AXIAL
BLADE sequence managed to eliminate the cross-talk artifacts in all
the cases where those artifacts were observed (Fig. 3).
Another good achievement of the BLADE sequences is the better
visualization of the intervertebral discs. Especially, the herniated disc
and the normal vertebral disc can be better identified in the Axial
BLADE sequence. Additionally, the Sagittal T2 TSE BLADE sequence
achieved a better visualization of the annular tear in the inter-
vertebral disc (Figs. 4 and 5). The BLADE sequences provided a better
distinction between the neural roots, the fatty tissue and the joints
too (Fig. 5). Finally, by using the BLADE sequences, the Modic is
better visualized and the degenerative changes are better distin-
guished from their environment (Fig. 6).
Apart from the fact that BLADE sequences eliminate motion
artifacts, they are associated with a higher SNR in bone marrow,
vertebral disk, neural roots and fatty tissue. Also, image quality is
higher in BLADE sequences and one of the reasons is because
they use a larger bandwidth than the conventional sequences,
which may have as a consequence the reduction of chemical shift
artifacts [36].
Another significant finding of this study is the lower SD in air,
which was observed in all the patients. In two of our previous studies
it had been found that in brain and knee MRI examinations, the
BLADE sequences could achieve a lower SD only in uncooperative
groups of patients [22,27]. This finding of the present study stems
from the fact that the anterior abdominal wall moves due to
breathing and it produces motion artifacts, which are not eliminated
by the Rest slabs (Regional Saturation Technique) that are
commonly used in lumbar spine examinations. In Table 2, it is
shown that the noise (N) (which is the standard deviation) of the
BLADE and conventional sequences differ statistically significant. The
motion artifacts in the background of the conventional sequences are
larger than those in the BLADE sequences and this is a significant
factor contributing to the larger SNR values of the latter sequences.
Since these artifacts are shown in the background they will affect the
overall image quality.
Also this finding agrees with the findings of Bayramoglu et al.
[23], who found that the SNR values of BLADE sequences that were
applied in liver and gallbladder examinations were significantly
lower than those of the corresponding TSE sequences that used
breath-hold and free-breathing navigator-triggered techniques. The
mean background noise was not significantly lower in all the
examined sequences perhaps due to the breath-hold and free-
breathing navigator-triggered techniques, which also reduce motion
artifacts and consequently the mean background noise. However,
these breath-hold and free-breathing navigator-triggered tech-
niques cannot be applied in lumbar spine examinations.
However, regarding the SNR and CNR comparisons between the
BLADE and the conventional sequences, it should be clarified that
they are not compatible. The much higher SNR and CNR values of the
BLADE sequences compared to the conventional ones mainly stem
from the ability of the BLADE sequences to significantly reduce or
eliminate the motion and flow artifacts. This means that the reported
SNR and CNR values of the BLADE sequences do not stem solely from
their intrinsic characteristics. The noise in a magnitude MRI image is
Rician distributed. Its mean and standard deviation should not
substantially change regardless of where in the air the ROI is drawn
[37]. However, artifacts will vary in amplitude and composition
across the image. This will result in a very different standard
deviation value depending on where the ROI is drawn. Although the
method that has been employed in the present study to estimate the
SNR and CNR values is commonly used, it is only valid in the absence
of artifacts.

The combination of longer scan time and signal averaging
together with the other reported parameters of the conventional
sequences should normally yield higher SNR values compared to the
BLADE sequences. However, the BLADE sequences produce signifi-
cantly fewer motion and flow artifacts than the conventional
sequences and this is reflected in the SNR and CNR measurements.
So, the SNR and CNR findings of this study should be treated more as
another way of expressing the ability of the BLADE sequences to
reduce or eliminate the motion and flow artifacts rather than as a
mean to perform absolute comparisons with the conventional
sequences. In line with this analysis, it would be very interesting
to study the relationship of the SNR and CNR values as a function of
artifact reduction.
In clinical practice, this is considered to be very important
because in two cases annular tear was observed (Fig. 4). Also, in most
of the cases we could distinguish better the borders of the nerve from
the fatty tissue in the region of spinal foramen. Especially in one case,
the conventional sequences showed that the two nerves were in
contact with the disk, whereas the BLADE sequences showed that the
disk were in contact only with the right nerve and this finding was
verified by the clinical symptoms of the patient (Fig. 4).
Based on the findings of the present study, it is expected that the
use of BLADE sequences also in thoracic spine examinations could
improve image quality due to the extensive breathing motions in
this anatomical site.
It was observed that in the T2 TSE AX BLADE sequence the neural
root is shown as being smaller in size compared with the
conventional sequence. This finding is explained by the fact that
the BLADE sequence can distinguish the neural root from the root
vessel. This finding agrees with findings from previous studies in
knee and brain MR examinations [14], where it was observed that a
better visualization of the vessels could be achieved by BLADE
sequences, which led us to propose the use of BLADE-based
techniques in angiographies.
In conclusion, the use of BLADE sequences in lumbar spine MR
examinations appears to be capable of potentially eliminating
motion, pulsatile flow and cross-talk artifacts. However, the values
of the different parameters (ETL, bandwidth, matrix size, blade
coverage) have to be examined in order to optimize even more
image quality and image acquisition time. Furthermore, we propose
the use of BLADE sequences in the standard examination protocols
based on the fact that a significantly improved image quality could
be achieved.
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