DOI:10.2214/AJR.08.1086
AJR 2008; 191:1401-1405
© American Roentgen Ray Society
Usefulness of Cone-Beam CT Before and After Percutaneous Vertebroplasty
Akio Hiwatashi1,
Takashi Yoshiura,
Tomoyuki Noguchi,
Osamu Togao,
Koji Yamashita,
Hironori Kamano and
Hiroshi Honda
1 All authors: Department of Clinical Radiology, Graduate School of Medical
Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582,
Japan.
Received April 18, 2008;
accepted after revision May 29, 2008.
Address correspondence to A. Hiwatashi.
This study was supported in part by research grants from the Ministry of
Education, Culture, Sports, Science and Technology (grant no. 19790879) and
the Japan Radiological Society (grant no. KJ-18-3).
Abstract
OBJECTIVE. The usefulness of cone-beam C-arm CT for percutaneous
vertebroplasty has not been fully evaluated. The purpose of this study was to
assess the feasibility of cone-beam CT for evaluation before and after
vertebroplasty.
SUBJECTS AND METHODS. This prospective study included 22 consecutive
patients (15 women and seven men) with osteoporotic compression fractures (51
vertebrae). Cone-beam CT and 64-MDCT were performed before and after
percutaneous vertebroplasty. Multiplanar reformations of the axial, sagittal,
and coronal planes were obtained. We evaluated the presence of cortical
defects, vacuum phenomena in adjacent disks, and cement leakage, and we
calculated the sensitivity, specificity, positive predictive value, negative
predictive value, and accuracy of cone-beam CT compared with MDCT.
RESULTS. All 75 cortical defects in 51 vertebrae seen on MDCT were
also observed on cone-beam CT (100% sensitivity and specificity). Vacuum
phenomena were detected in 33 of 86 (38.4%) adjacent disk spaces on MDCT and
in 29 on cone-beam CT (84.8% sensitivity, 98.1% specificity, and 93.0%
accuracy). Cement leakage was noted at 17 disk spaces, 15 paravertebral soft
tissues, and 12 veins on MDCT. All cement leakages were correctly identified
on cone-beam CT.
CONCLUSION. Cone-beam CT is able to correctly evaluate for vertebral
fractures and vacuum phenomena in adjacent disks before vertebroplasty and for
cement leakage after vertebroplasty.
Keywords: compression fractures • cone-beam CT • osteoporosis • percutaneous vertebroplasty • thoracolumbar junction • vertebral body
Introduction
Percutaneous vertebroplasty is a minimally invasive procedure that provides
pain relief and stability for osteoporotic compression fractures
[1–5].
The main goal of this technique is to relieve pain for patients in whom
conservative treatment has failed. In our clinical work with vertebroplasty,
we have often noticed cement leakage into the paraspinal soft tissues, disk
spaces, and spinal canal and have found that it is usually asymptomatic when
only a small amount of cement has leaked. However, cement leakage can cause
complications such as pulmonary embolism, spinal canal stenosis, and
subsequent fractures of adjacent vertebral bodies
[1–9].
Recently, cone-beam C-arm CT with a flat-panel detector became available
for use in the interventional suite
[10]. Although the usefulness
of MDCT for evaluation before and after vertebroplasty is well established,
little is known about the usefulness of cone-beam CT in this setting.
Therefore, the purpose of this study was to evaluate the usefulness of
cone-beam CT performed before and after percutaneous vertebroplasty.
Subjects and Methods
Our institutional review board approved this study, and written informed
consent was obtained from all participants before their enrollment in the
study.
Patients
The participants in this prospective study were 22 consecutive patients (15
women and seven men; age range, 54–88 years; mean age, 74 years) in whom
a total of 51 vertebral bodies were treated with vertebroplasty from July 2006
to January 2008 at our institution. All of these patients had back pain
refractory to conservative treatment with compression fractures on MRI. The
duration of the pain ranged from 1 to 9 months (median, 4 months).
Most of the fractured vertebrae were located around the thoracolumbar
junction. The mean height of the fractured vertebrae was 17.0 mm in anterior,
13.4 mm in central, and 22.8 mm in posterior portions in the midsagittal plane
on reformatted images of MDCT. The mean wedge angle was 10.0°. The
locations and numbers of the treated vertebrae were as follows: T5 (n
= 1), T6 (n = 2), T7 (n = 2), T8 (n = 1), T9
(n = 2), T10 (n = 1), T11 (n = 3), T12 (n
= 12), L1 (n = 14), L2 (n = 5), L3 (n = 4), and L4
(n = 4).
Vertebroplasty Technique
Vertebroplasty was performed using a bilateral transpedicular approach with
11-gauge bone biopsy needles placed into the anterior one fourth of the
vertebral body. The procedure was per formed under biplane fluoroscopic
control with the patient under conscious sedation and local anesthesia on an
inpatient basis.
Once the needles were placed in the vertebral body, liquid and powder
polymethylmethacrylate was mixed with 15 g of barium sulfate. The cement was
relatively difficult to inject through the 11-gauge needle using a 1-mL
syringe. Under biplane fluoroscopic guidance (primarily lateral), the cement
was injected alternately through the needles. Injection was continued until
the vertebral body was filled toward its posterior 25% or until there was
notable leakage. The amount of cement injected ranged from 1.5 to 15 mL (mean,
4.6 mL).
The patient was lying prone on the angio graphic table during the injection
and remained in that position until the cement had completely hardened (
15 minutes), at which point he or she was transferred to a regular bed. The
patients were routinely discharged from the hospital 3–5 days after the
treatment. There were no com pli cations in any patients at the time of
hospital discharge.
Imaging Technique
One day before vertebroplasty, 64-MDCT (Aquilion, Toshiba Medical Systems)
was performed, and 64-MDCT was repeated within 1 hour after the procedure with
the patient in the supine position. Typical imaging parameters were as
follows: collimation, 64 x 0.5 mm; gantry rotation time, 400
milliseconds; tube voltage, 120 kVp; tube current, 300 mA; field of view, 240
x 240 mm; and matrix, 512 x 512.
Cone-beam CT (DynaCT software, Axiom Artis dBA System, Siemens Medical
Solutions) was performed during vertebroplasty before the placement of needles
and immediately after cement injection with the patient in the prone position
using automatic exposure control. Typical imaging parameters were as follows:
flat-panel detector size, 380 x 300 mm; field of view, 225 x 225
mm; matrix, 1,024 x 1,024; flat-panel detec tor rotation time, 10
seconds; 200° rotation angle; 275 projections (30 projections per second);
tube voltage, 90–110 kVp; tube current, 180–250 mA; and standard
radiation dose, 1.2 µGy per pulse.
Multiplanar reformations of the axial, sagittal, and coronal planes with a
2-mm thickness and without a gap were obtained using workstations
(AquariusNet, TeraRecon; or Leonardo, Siemens Medical Solutions).
Image Assessment
All images were transferred to a PACS. CT images were shown with regular
clinical window settings. For bone windows, window width and window level were
3,000 and 600 HU, respectively, and for lung windows, 1,500 and –600 HU.
Qualitative analysis was based on consensus interpretations of two
board-certified neuroradiologists who had 19 and 11 years' experience in
diagnostic neuroradiology. One mainly performed the procedure, however, and
the other did not. Preoperative and postoperative CT images were evaluated
independently.
A cortical defect was defined as a discontinuation of the cortex on bone
windows on preoperative images. The presence of cortical defects in six
directions (anterior, posterior, superior, inferior, right, and left) in each
vertebra was evaluated. An intradiskal vacuum phenomenon was defined as air in
the disks on lung windows on preoperative images. The presence of vacuum
phenomena was evaluated in each disk adjacent to a treated verte bra. Cement
leakage was defined as extravasation of the cement from the treated vertebra
on bone windows of post-operative images. The location of leakage was divided
into paraspinal soft tissues, disk spaces, and veins (segmental or
basivertebral).
Statistical Analysis
The sensitivity, specificity, positive predictive value (PPV), negative
predictive value (NPV), and accuracy of cone-beam CT compared with MDCT were
calculated.
Results
All 75 cortical defects in 51 vertebrae seen on MDCT were also observed on
cone-beam CT (100% sensitivity and specificity) (Fig.
1A,
1B,
1C,
1D and
Table 1). These 75 defects were
seen in the anterior (n = 16), superior (n = 18), inferior
(n = 15), right (n = 13), and left (n = 13)
directions; no defects were observed in the posterior direction. Vacuum
phenomena were identified in 33 of 86 adjacent disk spaces on MDCT (Fig.
2A,
2B) and in 29 on cone-beam CT
(84.8% sensitivity, 98.1% specificity, 96.6% PPV, 91.2% NPV, and 93.0%
accuracy) (Table 2 and Fig.
3A,
3B).
View this table:
[in this window]
[in a new window]
|
TABLE 2: Number of Intervertebral Disks Adjacent to Treated Vertebral Bodies With
and Without Vacuum Phenomena on MDCT and Cone-Beam CT
|
|
View larger version (96K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3A —72-year-old woman with compression fracture at L1.
Preoperative MDCT with coronal reformation fails to reveal any vacuum
phenomena at L1–L2 disk space. Note intravertebral vacuum phenomenon in
L1 vertebral body.
|
|
Cement leakage was noted at 17 disk spaces, 15 paravertebral soft tissues,
and 12 veins. In these 12 veins, leakage into the segmental vein was seen in
nine (Fig. 4A,
4B) and into the basivertebral
vein in three (Fig. 5A,
5B). All three vertebral
bodies with epidural leakage via a basivertebral vein occurred at L1. The
volume of cement injected in these vertebrae ranged from 3.0 to 3.5 mL. All
cement leakages were correctly observed on cone-beam CT.
View larger version (78K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4B —77-year-old woman with compression fractures at L1 and L2.
Postoperative cone-beam CT with coronal reformation shows same cement leakage
into segmental vein at L2 on right side (arrow).
|
|
View larger version (79K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5A —79-year-old man with compression fractures at T12 and L1.
Axial postoperative MDCT shows minimal amount of cement leakage into spinal
canal via basivertebral vein at L1 (arrow). No neurologic symptoms
were noted in this patient after vertebroplasty.
|
|
Discussion
The results of the present study show that accurate evaluation of both
cortical defects in fractured vertebrae and cement leakage is possible on
cone-beam CT. In a previous study, Kobayashi et al. (presented at the 2006
annual meeting of the American Society of Neuroradiology) used C-arm 3D
rotational imaging for evaluation before percutaneous vertebroplasty,
reporting 93.9% sensitivity, 98.6% specificity, and 97.4% accuracy for the
detection of cortical defects. In the present study, we correctly diagnosed
all fractures on cone-beam CT with a flat-panel detector. One possible
explanation for the difference in detection between our results and those of
Kobayashi and colleagues might be advances in imaging techniques from the use
of an image intensifier in their study to the use of a flat-panel detector in
our study.
With respect to postoperative imaging, Hodek-Wuerz et al.
[11] reported 86% sensitivity
and 82% specificity for the detection of cement leakage on rotational imaging
after vertebroplasty. The results of the present study were superior to those
of Hodek-Wuerz and colleagues; however, because of the lack of detail
concerning imaging technique in their article, we were unable to identify the
reason for this difference. In addition, van de Kraats et al.
[12] used 3D rotational
imaging for needle insertion during vertebroplasty. They used 3D imaging only
for navigation and not for the evaluation of the vertebral bodies or adjacent
structures. During needle insertion and cement injection, we routinely use
biplane fluoroscopy guidance; therefore, we cannot comment on the usefulness
of cone-beam CT for the placement of the needles.
Cement leakage is common, occurring in 30–65% of patients with
osteoporosis who have undergone vertebroplasty for treatment of compression
fractures
[1–6].
Yeom et al. [6] divide cement
leakage into three types: cortical defect, segmental vein, and basivertebral
vein. Cement leakage into the paraspinal soft tissues via cortical defects is
usually asymptomatic. In the present study, we observed no immediate
complications related to cement leakage.
After learning the results of a previous study
[13], we regarded intradiskal
vacuum phenomena as indicators of degeneration as well as subsequent cement
leakage. We observed a discrepancy between cone-beam CT and MDCT in the
detection of vacuum phenomena, possibly because of differences in image
quality. Technically cone-beam CT with a flat-panel detector has a higher
spatial resolution than MDCT; however, cone-beam CT also has lower contrast
resolution and a smaller field of view than MDCT
[10]. Although we attempted to
calculate the contrast-to-noise ratio to verify the difference in contrast
resolution, our test failed because of the small field of view in cone-beam
CT. The difference between MDCT and cone-beam CT in detecting vacuum phenomena
may be related to the position of the patient during the examination. We
routinely perform spinal MDCT with the patient in the supine position;
however, we performed cone-beam CT with the patient in the prone position
during vertebroplasty. In a previous report, investigators found that a change
in the position of the patient has an effect on the detection of vacuum
phenomena [13].
IV cement leakage can cause complications. Padovani et al.
[7] reported pulmonary embolism
after vertebroplasty. In addition, a large amount of cement leakage into the
venous system can cause serious problems such as brain infarction
[8]. Ryu et al.
[9] reported that epidural
leakage is frequently seen in vertebrae above T7 and that this leakage is
dose-dependent. In the present study, we observed epidural cement leakage via
the basivertebral veins in three L1 vertebrae. The amount of cement injected
for our study was 3.0–3.5 mL. When cement was observed in the spinal
canal, cement injection was stopped immediately. We then waited for the cement
to harden and restarted the injection if there was no additional leakage. This
wait-and-see technique allows the prevention of a large amount of cement
leakage.
The primary limitation of the present study is the limited number of
subjects. This study is a preliminary study and we included all patients
treated during the study period. Nevertheless, we believe that our results
have verified the usefulness of cone-beam CT in this study population. In
addition, imaging the patient in the same position for cone-beam CT and MDCT
is preferable. Cone-beam CT performed with the patient in a supine position
during vertebroplasty is inevitable because of the treatment technique.
However, we do not perform MDCT with the patient in a prone position in our
clinical practice of spine imaging. Dedicated study with patients in the same
position during the two CT examinations might be preferred.
In conclusion, cone-beam CT is able to correctly evaluate vertebral
fractures and vacuum phenomena in adjacent disks before vertebroplasty and
cement leakage after vertebroplasty. Cone-beam CT can be used for both
preprocedural planning and postprocedural assessment of vertebroplasty.
References
- Jensen ME, Evans AJ, Mathis JM, Kallmes DF, Cloft HJ, Dion JE.
Percutaneous polymethylmethacrylate vertebroplasty in the treatment of
osteoporotic vertebral body compression fractures: technical aspects.
Am J Neuroradiol 1997;18
:1897
–1904[Abstract]
- Cortet B, Cotten A, Boutry N, et al. Percutaneous vertebroplasty in
the treatment of osteoporotic vertebral compression fractures: an open
prospective study. J Rheumatol 1999;26
:2222
–2228[Medline]
- Mathis JM. Percutaneous vertebroplasty: complication avoidance and
technique optimization. Am J Neuroradiol2003; 24:1697
–1706[Free Full Text]
- McGraw JK, Cardella J, Barr JD, et al.; Society of Interventional
Radiology Standards of Practice Committee. Society of Interventional Radiology
quality improvement guidelines for percutaneous vertebroplasty. J
Vasc Interv Radiol 2003;14
(9 Pt 2):S311
–S315[Medline]
- Laredo JD, Hamze B. Complications of percutaneous vertebroplasty
and their prevention. Skeletal Radiol2004; 33:493
–505[Medline]
- Yeom JS, Kim WJ, Choy WS, Lee CK, Chang BS, Kang JW. Leakage of
cement in percutaneous transpedicular vertebroplasty for painful osteoporotic
compression fractures. J Bone Joint Surg Br2003; 85:83
–89[CrossRef][Medline]
- Padovani B, Kasriel O, Brunner P, Peretti-Viton P. Pulmonary
embolism caused by acrylic cement: a rare complication of percutaneous
vertebroplasty. Am J Neuroradiol 1999;20
: 375–377[Abstract/Free Full Text]
- Scroop R, Eskridge J, Britz GW. Paradoxical cerebral arterial
embolization of cement during intraoperative vertebroplasty: case report.
Am J Neuroradiol 2002;23
: 868–870[Abstract/Free Full Text]
- Ryu KS, Park CK, Kim MC, Kang JK. Dose-dependent epidural leakage
of polymethylmethacrylate after percutaneous vertebroplasty in patients with
osteoporotic vertebral compression fractures. J
Neurosurg 2002; 96:56
–61[Medline]
- Kalender WA, Kyriakou Y. Flat-detector computed tomography (FD-CT).
Eur Radiol 2007;17
:2767
–2779[CrossRef][Medline]
- Hodek-Wuerz R, Martin JB, Wilhelm K, et al. Percutaneous
vertebroplasty: preliminary experiences with rotational acquisitions and 3D
reconstructions for therapy control. Cardiovasc Intervent
Radiol 2006; 29:862
–865[CrossRef][Medline]
- van de Kraats EB, van Walsum T, Verlaan JJ, Voormolen MH, Mali WP,
Niessen WJ. Three-dimensional rotational X-ray navigation for needle guidance
in percutaneous vertebroplasty: an accuracy study.
Spine 2006; 31:1359
–1364[CrossRef][Medline]
- Ford LT, Goodman FG. X-ray studies of the lumbosacral spine.
South Med J 1966;59
:1123
–1128[Medline]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Abstract
Introduction
