Multislice CT angiography of the plantar arch
Department of Imaging and Applied Physics, Curtin University of Technology, Perth, Australia
The aim of this case report is to present a multislice
computed tomography angiography (CTA) procedure for viewing the plantar arch.�
A CTA was requested to determine the vascular sufficiency of the plantar arch
of a 64-year-old patient with necrotic and gangrenous toes. The patient had
recently undergone a proximal wedge osteotomy procedure for correction of a
hallux valgus deformity. A 16-detector row CT scanner with 1.25 mm slice thickness
and 0.625 mm reconstruction interval was used to reconstruct multiplanar
reformats, maximum intensity projections and three-dimensional volume rendered
images of the foot in question in both arterial and venous phases to determine
if pathology of the plantar arch was present. The 3D reconstructed images of
CTA demonstrated a loss of continuity of the plantar arch between the first and
third metatarsals. This case report shows the diagnostic value of multislice
CTA, especially 3D visualisation in the assessment of peripheral vascular
branches. � 2010 Biomedical Imaging and Intervention Journal. All rights
Keywords: plantar arch, computed tomography angiography, 3D
visualisation, hallux valgus, peripheral arteries
Hallux valgus is a common joint deformity involving the
first metatarsophalangeal joint resulting in a change in the cosmetic
appearance of the foot and abnormal presentations such as pain and discomfort,
depending on the degree of abnormality [1-3]. Blood supply to the lower
extremity is extremely important, especially in patients with hallux valgus as
the peripheral artery branches could be involved. The small plantar arch artery
is very clinically significant in this abnormality because the necrotic toes
are an indication of the death of cells and tissues as a consequence of reduced
blood flow to that area. Traditionally, peripheral angiography is performed to
investigate the main arteries of the lower limb and their branches; however, it
is not only an invasive procedure but also associated with complications. With
the advent of multislice computed tomography (MSCT), especially the 16- and
64-slice CT, large anatomic coverage can be easily achieved in a short time
with high resolution images [4, 5].
Submillimetre CT scanning allows acquisition of nearly
isotropic volume data with 16-slice CT (0.5�0.5�0.6 mm) and isotropic
volume data with 64‑slice CT (0.4�0.4�0.4 mm) [5, 6]. Thus, anatomic
details such as peripheral blood vessels can be clearly demonstrated with MSCT angiography.
In addition to the 2D axial images, high-resolution volume data permits
generation of a series of 2D and 3D reconstruction images to enhance diagnostic
value of MSCT for assessment of both normal vascular branches and abnormal
changes [7, 8]. Of these reconstructions, multiplanar reformation (MPR),
maximum-intensity projection (MIP) and volume rendering (VR) are most commonly
used in clinical practice.
In this case report, the authors present an interesting
patient with hallux valgus with necrotising toes. MSCT angiography images in 2D
and 3D reconstructions were generated to demonstrate the diagnostic value of
these images in the assessment of vascular supply to the peripheral arteries.
A 64-year-old man presented to the radiology department 8
days post hallux valgus corrective surgery. Due to the severity of the
patient�s hallux valgus deformity, the surgery involved a proximal osteotomy of
the first metatarsal with three k-wires, as well as pins inserted through the
second, third and fourth metatarsophalangeal joints to maintain the bony
alignment of these areas. After the surgery, the second and possibly third toe
on the patient�s right foot had become necrotic and gangrenous. The medical
team was querying the possibility of insufficiency of the plantar arch of the
right foot, and requested an MRI to be performed on this foot. After examining
the request form, a radiologist determined that a CTA procedure for the plantar
arch would be more advisable in this situation due to the large amount of
orthopaedic hardware present in the foot, but that an MRI would also be helpful
to view the soft tissue areas of the foot after the CTA examination was
Imaging generation and visualization
The imaging examination was performed on a 16‑detector
row CT scanner (GE Lightspeed CT, GE Healthcare, Milwaukee, WI, USA) with
the scanning protocol as follows: 120 kVp, 200-250 mAs, beam collimation 16 x
0.625 mm, gantry rotation time 500 ms, section thickness of 1.25 mm, pitch
1.375 and reconstruction interval of 0.625 mm. The area of scan coverage ranged
from the lower third of tibia to the feet. During the procedure, 100 mL of a
contrast medium (Isovue 370) was infused with 50 mL of saline and injected via
a double power injector into the patient�s antecubital vein at a rate of 4 mL/s
to visualise the vessels in and around the foot. A bolus tracking technique
(Smart prep) of the thoracic abdominal aorta threshold of 100 HU over baseline
was used to ensure maximum enhancement of the peripheral vessels. A scan delay
of 60-70 seconds was used to demonstrate the venous supply to the lower
In addition to 2D axial views, a number of 3D
reconstructions were generated to demonstrate the peripheral arteries. These
reconstructions included multi-planar reformation (MPR), maximum-intensity
projection (MIP) and three-dimensional volume rendered (3D VR) reconstructions
of the foot. These particular reconstructions were used to effectively answer
the clinical question and allow the plantar arch to be viewed as clearly as
possible. Arterial and venous phase images were also produced to determine if
the problem was due to arterial or venous insufficiency.
Figure 1 is a sagittal MPR view of the plantar arch, while
Figure 2 is a series of MIP images showing the disruption of the plantar arch
artery along its distal segment based on coronal and sagittal views.
3D VR images shade and colour pixels depending on their
level of attenuation . The VR reconstruction reveals surface and
internal features, and allows the 3D images to be rotated in real time .
Figure 3 demonstrates 3D VR images of the vascular supply through the area of
interest with and without bony components.
All of the above images demonstrate a loss of continuity
of the plantar arch between the first and third metatarsal.� The presence of
the k-wires can also be seen by the metallic artifacts present on the images,
particularly along the first metatarsal (Figs 2D, 3D).
Discussion and Conclusion
Hallux valgus is a bony deformity that affects the first
metatarsophalangeal joint. It involves a valgus movement of the proximal
phalanx of the first metatarsal with an associated varus drift of the
metatarsal head which can cause bursitis over the medial eminence of the first
metatarsal with associated pain and discomfort . Schweitzer et al
 reported that the presence of an eminence, commonly referred to as a
bunion, is seen in 95% of hallux valgus sufferers, while bursitis of the first
metatarsal head is experienced in 70% of cases.
Radiographically, hallux valgus is assessed using weight-
or load-bearing views of the affected foot, in order to determine the extent of
loss of the transverse arch of the foot . There is little to no
use for multislice CT or MRI in diagnosing this disorder.� Dorsi-plantar (DP),
DP oblique and lateral weight-bearing radiographs are obtained, and
measurements are taken off these radiographs to determine the severity of the
disorder . These measurements include the angle made between the
first metatarsal and phalanges known as the hallux valgus angle, and the
intermetatarsal angle, or the angle between the first and second metatarsals
. The main limitation of these measurements is the lack of providing
vascular details in patients with suspected ischemic or necrotic changes.
MSCT allows acquisition of images much faster and with
better quality and resolution than single-slice CT [4, 5, 13]. These technical
improvements have significantly advanced the applications of MSCT, especially
CT angiography (CTA) procedures. Schoepf et al  stated that MSCT
allows CTA procedures to be used quickly and accurately for diagnosis of
suspected vascular diseases in all organ systems.� Clinical CTA applications
are vast, and include examinations for the aorta, coronary arteries, carotid
arteries, pulmonary vessels, vessels throughout the abdomen, brain and
peripheral arteries [6-9, 14].
CTA of the peripheral arteries of the lower limb is an
application that has been significantly enhanced with the development of MSCT technique
as longer anatomic coverage is required to be obtained in a single breath-hold
scan. Traditionally, examinations of this area required the use of invasive
angiography to examine the run-off of the iliac and femoral arteries throughout
the lower limb with the aim of assessing the presence of thrombus and
atherosclerotic formations within the arteries branching directly from the
iliac arteries . However, the application of this technique in
viewing the plantar arch is limited in the literature. Due to the invasiveness
of conventional angiography, MSCT has become widely used in clinical practice
as an effective alternative to invasive angiography for visualisation of
vascular disease , including the peripheral artery branches, as
shown in this case report.
While 2D axial CT images are routinely used in clinical
practice, some kind of 2D or 3D reconstructions are required to provide
information which is not available with 2D axial views, but still necessary for
clinical requirements. MPR is the most commonly used complementary
visualisation to 2D axial images as it allows quick demonstration of the
relationship between anatomical structures. However, a number of MPR images are
required to demonstrate the entire course of arteries and their branches, since
not all of the vascular segments can be displayed in a single MPR view. This
was observed in this case report (Fig 1), thus, application of MPR views in
assessment of distal vascular territory, such as plantar arch is limited.
MIP has been widely recognized as the most useful
visualisation tool in CT angiography as it provides angiographic-like images
less invasively.� The principle of MIP images is the demonstration of only
maximum CT number encountered in each ray.� The differentiation between contrast-enhanced
blood vessels and background is good, thus high-density structures such as
contrast-enhanced vessels and calcification can be clearly depicted and
displayed on MIP images.� MIP was found very useful in this case as it clearly
shows the main arteries and their peripheral branches (Fig 2).�� However, MIP
images do not provide depth information which is the main drawback for
visualisation of complex anatomy.
3D VR provides a 3D representation of the anatomical
structures based on a volume dataset, since it utilises all of the information
contained in the data. A voxel-based intensity histogram is generated, and
several parameters such as colour, brightness and opacity are assigned to each
voxel according to its CT attenuation value. Therefore, 3D relationship between
different structures can be easily displayed and appreciated on VR, as shown in
Figure 3. VR allows demonstration of both vascular branches and bony components
in a single image, thus it significantly enhances understanding of the complex
anatomic structures. VR requires extensive user interaction for accurate
evaluation of complex anatomical structures. Currently, advanced 3D
post-processing software packages are available in most of the recent MSCT
scanners, so the VR display of these complex structures including peripheral
arteries becomes feasible without further segmentation. VR image quality is
determined by the resolution of original source data.
In this case study, radiologists were specifically looking
for evidence to confirm the lack of presence of the plantar arch, a relatively
small artery located deep within the foot.� While MIP images provide necessary
information about the patency of the plantar arch arteries, the use of 3D VR
reconstructions through the plantar arch were extremely important to diagnose
and confirm that the continuity of the plantar arch had indeed been lost and
blood flow to the digits of the foot had been compromised. These
reconstructions allowed both internal and surface features to be seen and allowed
all images to be rotated in real time. Without using 3D VR reconstructions,
determining the sufficiency of the plantar arch in this case would have been
almost impossible and the patient�s long-term health and quality of life would
have been significantly affected.
In conclusion, the authors have demonstrated the
application and usefulness of MSCT angiography in the assessment of vascular
supplies to the small plantar artery in a patient diagnosed with hallux valgus.
A combination of 2D and 3D reconstructions of MSCT angiography (a combination
of MIP and VR) proved to be valuable in confirming the perfusion of peripheral
Figure 1 MPR view of the right plantar arch. Sagittal MPR images (A, B) demonstrate the plantar arch with apparent artifacts arising from the metal k- wires.
Figure 2 MIP visualisation of the plantar arch arteries. Coronal (A-D) and sagittal (E-H) MIP images show that the distal plantar arteries are occluded due to necrosis and occlusion in the location between 1st and 3rd metatarsal bones.
Figure 3 3D VR of the plantar arch arteries. VR images demonstrate the bony components and peripheral artery branches in the right foot (A-C), and the artery branches only (D, E). The distal plantar arteries between 1st and 3rd metatarsal bones are occluded.
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|Received 21 August 2009; received in revised form 29 October
2009, accepted 1 November 2009
Correspondence: Discipline of Medical Imaging, Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box, U1987, Perth, Western Australia 6845, Australia. Tel.: +61-8-9266 7509; Fax: +61-8-9266 4344; E-mail: firstname.lastname@example.org (Zhonghua Sun).
Please cite as: Field L, Sun Z,
Multislice CT angiography of the plantar arch, Biomed Imaging Interv J 2010; 6(1):e10