AJR 2004; 182:161-165
© American Roentgen Ray Society
MDCT of Tendon Abnormalities Using Volume-Rendered Images
K. Ohashi1,
G. Y. El-Khoury and
D. L. Bennett
1 All authors: Department of Radiology, University of Iowa Hospitals and
Clinics, 200 Hawkins Dr., Iowa City, IA 52242.
Received April 14, 2003;
accepted after revision July 8, 2003.
Address correspondence to K. Ohashi
(kenjirou-ohashi{at}uiowa.edu).
Abstract
OBJECTIVE. Our objectives were to report tendon abnormalities
diagnosed on 3D volume-rendered images from MDCT data and to validate the
clinical usefulness of this technique.
CONCLUSION. We present 18 tendon abnormalities from 16 patients that
were diagnosed on 3D volume-rendered MDCT images generated by commercially
available software. Certain abnormalities such as avulsions, partial tears,
and dislocations of tendons are clearly shown by this technique. This
technique may prove useful in the evaluation of tendon abnormalities when MRI
or sonography cannot be used.
Introduction
Imaging of tendons has been the domain of MRI and sonography. The
effectiveness of both techniques has been well validated
[1,
2]. However, sonography is
limited in that it is not widely accepted by orthopedic surgeons and some
radiologists are not skilled in musculoskeletal sonography. Also, these
techniques cannot be used in some patients because of metal hardware, surgical
wounds, and open lacerations in the area of interest. MRI is contraindicated
in patients who are claustrophobic or who have a pacemaker or metal in the
orbits.
MDCT has had a significant impact on musculoskeletal imaging, especially in
trauma. Detectors are aligned in the longitudinal (z-axis) direction
that simultaneously collect four to 16 CT slices with each tube rotation. The
advantages of MDCT over its predecessor, single-slice helical CT, are
increased speed and coverage, isotropic imaging capability, reduced metallic
artifacts, and ease of interpretation. MDCT can acquire isotropic or
near-isotropic data sets from which high-quality 3D images can be
reconstructed [3]. In a recent
study, Pelc and Beaulieu [4]
performed postprocessing on CT data sets using commercially available
workstations to quantify differences in attenuation values among bone, tendon,
and muscle to display 3D volume-rendered images of normal tendons. The ease
with which 3D images of tendons can be acquired is the result of the
availability of independent workstations that are capable of displaying 3D
volume-rendered images quickly
[3]. When the ever-increasing
number of images generated by MDCT are viewed, acquired data are now looked at
as a volume to be explored rather than as individual images. Three-dimensional
images are often the key images.
To our knowledge, no report yet shows the clinical use of 3D
volume-rendered images from MDCT data for visualizing tendon abnormalities. In
this article, we present 18 tendon abnormalities from 16 patients diagnosed on
3D volume-rendered MDCT images. In six patients (seven tendon abnormalities),
the abnormalities were surgically proven. In one patient, the CT findings were
confirmed by MRI.
Subjects and Methods
Eighteen tendon abnormalities from 16 patients (10 male and six female,
12–80 years old; average age, 43 years) were prospectively diagnosed on
3D volume-rendered images generated by MDCT. Imaging diagnoses were made in
consensus by three musculoskeletal radiologists. Clinical correlations were
obtained from the medical records. This investigation was performed before
implementation of the federal Health Insurance Portability and Accountability
Act, and our institutional review board did not require its approval or
informed consent for this type of study.
MDCT studies were obtained by a four–detector row CT scanner
(Aquilion, Toshiba American Medical Systems, Tustin, CA) using the following
parameters: 120–135 kVp, 75–130 mAs (0.5-sec gantry rotation
period), 2-mm slice thickness (x 4), 7- to 9-mm table travel per
rotation, 512 x 512 matrix, and a 180- to 240-mm field of view. Axial
images were reconstructed with 2-mm slice thickness at every 0.5-mm interval
using a 136- to 200-mm reconstruction field of view (0.3- to 0.4-mm in-plane
pixel dimension). Raw data were processed into axial images using a standard
soft-tissue kernel (algorithm).
Multiplanar reformatted images and 3D volume-rendered images were generated
on a Vitrea 2 computer workstation (version 3.0.1, Vital Images, Plymouth,
MN). These images were reconstructed from axial image data sets that were
transferred over an intradepartmental network, Kodak PACS (Eastman Kodak,
Rochester, NY), using the DICOM (Digital Imaging and Communications in
Medicine) protocol.
Results
The CT and clinical findings for 16 patients diagnosed as having tendon
abnormalities on MDCT 3D volume-rendered images are summarized in
Table 1. The indication for all
the CT studies was to evaluate osseous abnormalities. Six patients had acute
fractures; the rest complained of chronic symptoms associated with chronic
fractures, tarsal coalition, lateral ankle impingement, and peroneal tubercle
hypertrophy. Four patients had orthopedic hardware in the region of interest:
one patient each had an external fixator, knee prosthesis, ankle prosthesis,
or surgical screws.
Abnormalities were found in three Achilles tendons, 12 peroneal tendons,
one posterior tibial tendon, one biceps femoris tendon, and one quadriceps
tendon. Tendon abnormalities included 11 peroneal tendon dislocations (Fig.
1A,
1B), three partial tears (two
Achilles and one quadriceps) (Figs.
2 and
3A,
3B), two tendons (peroneus
longus and posterior tibial tendons) with tendinopathy (Fig.
4A,
4B,
4C), two anomalous tendons
(biceps femoris and Achilles tendon) (Fig.
5A,
5B), and one Achilles tendon
avulsion (Fig. 3A,
3B). One patient had both a
partial tear and an avulsion of the Achilles tendon. Seven tendon
abnormalities from six patients were surgically confirmed. One tendon
abnormality (tendinopathy) was confirmed on MRI (Fig.
4A,
4B,
4C).
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Fig. 1A. —18-year-old woman with bilateral anterior dislocation of
peroneus brevis tendons and bilateral calcaneal fractures. Axial CT image of
left ankle shows anterolateral dislocation of peroneus brevis tendon
(short arrow) and small avulsed bone fragment from lateral malleolus
(long arrow).
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Fig. 1B. —18-year-old woman with bilateral anterior dislocation of
peroneus brevis tendons and bilateral calcaneal fractures. Volume-rendered 3D
CT image viewed from lateral aspect of left ankle shows anteriorly dislocated
peroneus brevis tendon (short arrow). Avulsed bone fragment (long
arrow) from fibula is also visualized. Similar findings were seen on
right (not shown). Dislocated peroneal tendons were surgically reduced
bilaterally.
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Fig. 2. —46-year-old man with partial tear of Achilles tendon.
Volume-rendered image from helical CT data shows eccentric defect
(arrow) of Achilles tendon that is consistent with partial tear.
Achilles tendon thickening may reflect underlying tendinopathy.
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Fig. 3A. —21-year-old man with avulsion of Achilles tendon from
calcaneal tuberosity and partial tear of Achilles tendon. Sagittally
reconstructed CT image shows avulsed bone fragment (white arrow) from
calcaneus (black arrow). Achilles tendon (arrowheads) is
retracted superiorly.
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Fig. 3B. —21-year-old man with avulsion of Achilles tendon from
calcaneal tuberosity and partial tear of Achilles tendon. Volume-rendered CT
image viewed from posterior aspect of ankle shows eccentric defect (long
arrow) in substance of Achilles tendon, which is seen inserting onto
avulsed bone fragment (short arrow). These findings were surgically
confirmed.
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Fig. 4A. —45-year-old man with tendinopathy of peroneus longus tendon.
Volume-rendered CT image of lateral aspect of ankle shows markedly
hypertrophied peroneal tubercle (long arrow). Note thickening of
peroneus longus tendon (short arrow) distal and inferior to peroneal
tubercle.
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Fig. 4C. —45-year-old man with tendinopathy of peroneus longus tendon.
Sagittal T1-weighted image (TR/TE, 440/21) shows thickening of peroneus longus
tendon (short arrow) with increased signal at peroneal tubercle
(long arrow). MRI findings confirm presence of tendinopathy.
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Fig. 5A. —46-year-old man with incidental finding of anomalous tibial
insertion of biceps femoris tendon. Volume-rendered 3D CT image viewed from
lateral aspect of knee shows biceps tendon (short arrows) inserting
onto lateral aspect of proximal tibia. Lateral collateral ligament (long
arrow) is partially visualized and is seen to insert on head of
fibula.
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Fig. 5B. —46-year-old man with incidental finding of anomalous tibial
insertion of biceps femoris tendon. Sagittally reconstructed CT image through
fibular head shows tibial insertion of biceps tendon (arrows).
Lateral collateral ligament is also seen (arrowheads) between lateral
femoral condyle and fibular head.
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Peroneus tendon dislocations were readily recognized on the 3D
volume-rendered images (Fig.
1A,
1B) and are commonly associated
with calcaneal fractures. Partial tears of the Achilles tendon were seen as
eccentric defects (Figs. 2 and
3A,
3B). In one patient, an avulsed
Achilles tendon was associated with a bone fragment from the calcaneal
tuberosity (Fig. 3A,
3B). In another patient, severe
attenuation of the quadriceps tendon was diagnosed as a partial tear that was
confirmed at surgery. Diagnosis of tendinopathy was based on focal or diffuse
thickening of the tendon and associated symptoms and physical findings (Fig.
4A,
4B,
4C). Anomalous insertion of the
biceps femoris tendon onto the tibia (Fig.
5A,
5B) and an accessory soleus
were incidentally found on the 3D volume-rendered images.
Discussion
In addition to its increased speed and volume coverage, MDCT has a definite
advantage with enhanced resolution in the longitudinal axis (z-axis),
which is essential for obtaining isotropic or near-isotropic data sets. With
isotropic or near-isotropic imaging, 2D multiplanar images in any arbitrary
plane and 3D images can be reconstructed from the volumetric data. With
postprocessing workstations and fast rendering speed, one can navigate through
the data set interactively, creating a variety of 2D and 3D reformatted images
almost instantaneously. The display of spatial relationships on 3D images can
aid in diagnosis and surgical planning, especially in patients with complex
musculoskeletal injuries. Some authors have reported a change in management
for 30% of patients with acetabular fractures when 3D imaging is used
[5]. The 2D multiplanar
reconstructions, in any arbitrary plane, and 3D volume rendering are
frequently more helpful than axial images in reaching a diagnosis. With volume
rendering, the CT voxel values are assigned an opacity level that varies from
total transparency to total opacity. Lighting effects and various levels of
transparency are displayed simultaneously. It is more effective to view
volume-rendered images of soft tissues in color than in black-and-white
[3,
6].
Before the advent of MDCT, several attempts were made at imaging tendons
using conventional CT; the technique, however, had some drawbacks that limited
its widespread use
[7–11].
The multiplanar reconstructions showed poor spatial resolution and the
reconstructed 3D images invariably produced stairstep artifacts
[12]. In addition, the
step–shoot action necessary for table translation was too slow, and the
section-by-section acquisition produced misregistration artifacts as a result
of involuntary motion.
The technique described in this article is simple and uses widely available
technology. As with MRI, CT is not operator-dependent, although both
techniques require strong knowledge of the technology. Image processing
methods vary among scanners. However, a standard soft-tissue kernel
(algorithm) for postprocessing produces better soft-tissue contrast
[4]. Optimal peak kilovoltage
and tube current settings further improve soft-tissue contrast, although these
have not been thoroughly investigated. With such technique parameters, the
integrity of tendons can be routinely inspected on MDCT studies of the joints
and extremities performed for a variety of indications, including trauma.
Metal artifacts from orthopedic hardware are less pronounced with MDCT
scanners than with earlier CT scanners
[13]. Three-dimensional
volume-rendered imaging can illustrate metal hardware clearly (Fig.
3A,
3B).
Abnormalities such as tendon avulsion (Fig.
3A,
3B), partial tear (Figs.
2 and
3A,
3B), anomalous tendon insertion
(Fig. 5A,
5B), and dislocation (Fig.
1A,
1B) of superficial tendons can
be easily detected on 3D volume-rendered MDCT images. Peroneal tendon
dislocation, especially, is easily recognized with this technique. Peroneal
tendon dislocation is considered a rare injury
[14], but it is commonly
associated with calcaneal fractures because of lateral displacement of the
major fracture fragments [15].
Using this technique, the integrity of the peroneal tendons and their
relationship to fracture fragments can be easily assessed.
Some limitations of this technique include the fact that MDCT has not been
validated for the evaluation of tendinosis (tendinopathy) or longitudinal
splitting of tendons. We have also observed that deep tendons such as the
hamstring tendons and rotator cuff are difficult to visualize on 3D
volume-rendered MDCT images.
In conclusion, we report 18 tendon abnormalities in 16 patients that were
diagnosed on 3D volume-rendered images generated from MDCT data sets. Seven
tendon abnormalities were confirmed surgically and one by MRI. Avulsions,
partial tears, anomalous insertions, and dislocations of superficial tendons
were easily detected on 3D volume-rendered MDCT images. To assess the accuracy
of this technique and how it compares with MRI and sonography, larger studies
are needed in which results from all three techniques are correlated with
surgical or pathologic findings.
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Abstract
Introduction
