Download Great Blood Vessels Anomalies at Thoracic Inlet with CT Scan

J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
Great Blood Vessels Anomalies at Thoracic Inlet with CT Scan
Hussein Ahmed Hassan 1and Tahir Osman Ali 2
1
2
College of Medical Radiological Science, Sudan University of Science and Technology
National Ribat University College of Graduate Studies and Scientific Research, Khartoum- Sudan
ABSTRACT: Over the past decade, faster computed tomography (CT) scan, thinner
collimation, and the development of multi detector computed tomography (MDCT), coupled
with the increasing capability of computers to process large amounts of data in short periods
of time, have lead to an expansion in the ability to create diagnostically useful twodimensional (2D) and three-dimensional (3D) images within the thoracic inlet. The objectives
of the present study were to identify the CT angiographic appearances of vascular system and
study the variable appearance of arterial and venous anatomy in thoracic inlet on contrastenhanced, upper chest CT. In four hundred thirty-five patients who underwent spiral CT scan
for either neck or thorax. The patients had different clinical symptoms. The cases included
patients examined both with dual detectors row helical CT scanner and scanners that have a
16 detectors row configuration. Interpretation of axial and reformatted coronal and sagigttal
images were done by experts.
The results revealed that normal pattern of the great blood vessels were observed in 85.1%
of study group and right internal thoracic vein draining into SVC were observed in 3.4% of
study group. Bovine aortic arch was observed in 8.5 %, while in 0.9 % the left vertebral
artery originated directly from the arch of the aorta. Aberrant right subclavian and
thyroideama were observed in 0.3 % for each.
Conclusion: CT imaging appeared helpful in demonstrating the great vessels anomalies.
KEYWORDS; Great blood vessel, Anomalies, Computed tomography, Spiral CT.
INTRODUCTION:
The vascular anomaly is insufficiently
demonstrated by conventional radiographic techniques, unless the vascular
anomaly is interfered with low attenuation
lung field, like aberrant right subclavian
artery which can be seen on chest x.rays
(CXR) as an edge along its interface with
the lung. It will be seen running from the
left side immediately above the aortic
knob, across the midline to the right
superior mediastinum. On lateral views,
there may be obscuration of the posterior
aspect of the aortic arch by the aberrant
vessel (1,2). CT is used because it clearly
demonstrates this area free from
superimposition, accurately depicts the
size, shape and abnormalities of the
thoracic inlet structures (2,3).
Vascular structures are usually readily
identified on (CT) scans of the chest with
intravenously
administered
contrast
medium. From a single helical scan,
vascular structures can be reformatted in
any plane or rendered in three dimensions
(3D), providing a simplified display of
even most complex vascular anatomy
(3,4,5)
. Helical images of thorax obtained
with 60 ml of 60 % iodinated contrast
material were judged to have superior
vascular contrast enhancement to that of
conventional CT images obtained with 120
ml of 60% contrast material (6, 7, and 8).
Objectives
To identify the CT angiographic
appearances of vascular system in thoracic
inlet and to study the variable appearances
of arterial and venous anatomy and
thoracic inlet structures on contrastenhanced, upper chest CT.
MATERIALS and METHODS
The study group consisted of 435 patients
who underwent spiral CT scan for either
neck or thorax, they had different clinical
symptoms. The cases included patients
71
J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
examined both with dual detectors row
helical CT scanner and scanners that have
a 16 detectors row configuration. All
patients were studied for clinical purposes
rather than research interest. One hundred
and seven patients were excluded from the
study due to marked deformities in their
thoracic inlet noted in the axial CT images.
Written consents were taken from all
patients included in this study.
For evaluation of images and to measure
the size, and relate the anatomic structures
in thorax inlet using the CT images the
following window setting was made, soft
tissue window for lymph nodes, blood
vessels and muscles, lungs window to
view lung parenchyma in apex area and
bone window to view ribs, clavicles
scapula and vertebrae.
Each of the anatomic structures in the
thoracic inlet was identified; this was
confirmed by comparing these images with
photographs of cryosections and drawings
of the thoracic inlet region from an atlas.
For accuracy, the identification was
carried out initially by using a set of axial
source images followed by images viewing
in the additional planes.
CT Protocol
All scans were acquired after the initiation
of an antecubital intravenous catheter. If
possible, the intravenous catheter should
be in place before the patient arrives in the
CT site. This reduces patient agitation that
otherwise would be associated with a
venipuncture injection of iodinated
contrast medium; (70-100 ml, approximately 300 mg iodine concentration) of nonionic contrast. The contrast was injected
with 25-35 sec delay time. This dose will
establish a bolus duration that is equivalent
to the scanning duration. The contrast
material was injected automatically at a
rate of 2-2.5 ml/ second.
Scan delay time for chest is 35 sec and for
the neck 25 sec. For some patients, the
contrast maximum enhancement was
determined by smart preparation technique
in which contrast enhancement of thoracic
inlet and neck structures is measured with
circular regions of interest during initial
fast scan, followed by the proper scan
when the contrast maximum enhancement
was reached in the region of interest.
The caudocranial helical acquisition was
planned on the basis of a lateral digital
scout view of the neck or frontal view of
the chest, which starts at the top of the
aortic arch and ends at the base of the skull
in case of neck and starts at upper
abdomen to the root of the neck in case of
thorax.
Image Interpretation
RESULTS
Normal pattern of the great blood vessels
were observed in 85.1% of the study
group. One hundred fifty one (87.4%) of
the 174 male patients had normal vascular
pattern. One hundred twenty seven
(82.5%) of 154 of the female patients had
normal vascular pattern. Right internal
thoracic vein draining into SVC were
observed in four (2.3%) of the 174 male
patient in study group. Seven (4.5%) of the
154 female patients. Thirteen (7.5 %) of
the 174 male cases and fifteen (9.7%) of
the 154 female cases had bovine aortic
arch. In three (1.7%) of the 174 male
cases, the left vertebral artery originated
directly from the arch of the aorta, and not
observed at all in female group. Aberrant
right subclavian and thyroideama were
observed in one (0.6 %) for each in male.
Four (2.6%) from female group has
aberrant right subclavian artery and none
of them had thyroideama.
Two brachiocephalic arteries were found
in one (0.6%) of the 154 female groups
(Table 2). These results are shown in
Tables 1, 2 and Figures 1-8.
Table 1 : Study group gender and age frequencies (years)
72
J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
Age groups
20 – 29
30 – 39
40 -49
50 -59
60 – 69
70 – 79
80 – 89
Male frequency
17
26
30
47
29
24
1
Female frequency
21
20
23
41
30
16
3
Total
38
46
53
88
59
40
4
50
Frequency
40
30
Male
20
Female
10
0
20 – 29 30 – 39 40 -49
50 -59 60 – 69 70 – 79 80 – 89
Age groups (years)
Figure1 . Study gender group age frequencies (years)
Table 2. Anatomical variations of blood vessels in study group.
Anatomical variant
Male
Female
No.
Normal
152
Right internal thoracic vein draining into SVC.
4
Bovine aortic arch
13
L.V.A.O Aortic arch*
3
Aberrant Rt. subclavian
1
Thyroideama
1
Two bachiocephalic arteries
Total
174
%
Male & Female
No.
87.4 127
2.3
7
7.5
15
1.7
0.6
4
0.6
1
100
154
%
No.
82.5 279
4.5
11
9.7
28
3
2.6
5
1
0.6
1
100
328
%
85.1
3.4
8.5
0.9
1.5
0.3
0.3
100
*Left vertebral artery originated from aortic arch.
12
10
8
6
4
2
0
Male
Female
Total
Figure 2. Anatomical variations of blood vessels in study group.
73
J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
Figure 3 . Internal thoracic vein. Axial contrast-enhanced CT scan shows internal thoracic
vein (arrow) draining into SVC, in a 79 years woman.
Figure 4 . Bovine aortic arch. Coronal reformatted contrast-enhanced CT scan shows bovine
aortic arch arrow (common origin of barchiocephalic artery and left common carotid artery, in a 58 years woman with left lobe of thyroid mass.
Figure 5 . Bovine aortic arch. axial contrast-enhanced CT scan of bovine aortic arch
(arrow), in a 33 years old man.
74
J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
Figure 6. Bovine aortic arch (arrow). Sagittal reformatted contrast-enhanced CT scan in a
50 years old woman.
Figure 7. Aberrant right subclavian artery. Axial contrast-enhanced CT scan shows the
artery (arrow) passing behind the esophagus, in a 36 years old man.
Figure 8 . Aberrant right subclavian artery. Axial contrast-enhanced CT scan shows the
artery (arrowhead) passing behind the esophagus, in a 76 years old woman.
brachicephalic trunk subsequently branches into right common carotid artery and
right subclavian artery) was found to be
the most common anatomical appearance
in the study. The incidence of this pattern
is found to be 85.1% in the study group,
with higher percentage in men (87.1%)
than women (82.5%) (Table 2). A study by
Troyer (9) showed a percentage less than
the above (70%), and this may be
DISCUSSION
An anomalous of blood vessel is rare.
With the widespread application of
noninvasive imaging techniques such as
sonography, CT, and MRI,
however, it is increasingly being
recognized. The most likely interpretation
is that the frequencies of the standard
aortic arch, (where there are three great
vessels that originate from the arch; the
75
J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
explained on ethnic group variations and
the technique used for the study.
Three types of anatomical variations of
aortic arch pattern were noted in this study
they include; common origin of
brachiocephalic artery and left common
carotid artery (bovine arch), in which there
were only 2 great vessels originating from
the arch, with an average of 8.5% in the
study group with 7.5% among men group
and 9.7% among women (Table 2). This
correlates with the findings of Layton (10)
in his study which revealed an average of
8%.
Variations in the origin of the vertebra
arteries usually occur on the left (11) and
anomalous origin of left vertebral artery
may be present in about 5% of individuals.
The artery may arise from the aorta, or
common carotid artery (12). In this study
variation of origin of left vertebral artery
was noted only in 0.9% of study
population and all were men. Left
vertebral artery originating from common
carotid artery was not seen at all. The
difference seen in the result may be due to
difficulty of demonstrating the exact origin
of the artery when its origin is from the
common carotid artery in thick slices of
axial CT images.
The right subclavian artery usually arises
as a branch of the brachicephalic trunk.
Aberrant right subclavian artery is a
congenital anomaly of the aortic arch. The
artery runs to the right posterior to
esophagus. This anomaly is present in
about 0.5% to 1% of population (13,14)
(Table 2). The affected people are
typically asymptomatic, but the condition
may cause dyphagia (dysphagia lusoria ).
In this study, this anomaly was found in
1.5% of the study population, (men 0.6%,
and women 2.6%) (Table 2). All the
affected people were asymptomatic, and
result conform to the findings of other
authors (11, 12)
Thyroidea ima is a small branch,
occasionally arises from the right
brachiocephalic, the aorta, the common
carotid, the right subclavian or the internal
thoracic artery. The
thyroidea ima
ascends in front of the trachea to the lower
part of thyroid gland, which it supplies (13)
. In this study thyreoidea ima variation
occurred in about 0.6% of cases. In other
studies variation were seen in 4 to
10%(16,17). The frequency is variable and it
can be as low as 0.4% (18) or as high as
10% (16, 17).
The brachicephalic artery is an artery of
themediastinum that supplies blood to the
right arm, neck and head. It is the first
branch of the aortic arch. Soon after it
emerges, the brachiocephalic artery
divides into the right common carotid
artery and right subclavian artery. There is
no brachiocephalic artery for the left side
of the body, the left common carotid, and
the subclavin artery, come directly from
the aortic arch, however there are two
brachiocephalic veins (13). In this study two
brachicephalic arteries were found in about
0.6% of cases. Such a variation was not
reported by CT images in other studies,
but absence of the brachiocephalic trunk
was noted in 0.44% by Bergman et al (11).
Knowledge of the internal thoracic vessel
anatomy is important to avoid hemorrhagic
complications when an anterior parasternal
approach is used for percutaneous
transthoracic procedures, such as CT
guided biopsy and empyema drainage,
because
their appearance can mimic
pathology when there is anomalies in their
pattern. These vessels have received
increased attention in recent clinical
literature, largely from the discovery of
their involvement in breast reconstruction,
reconstruction of complex thoracic wall
defect, their frequent use in cardiac
surgery and are generally accepted as
coronary artery bypass (19).
The most common venous variations noted
in this study was a right internal thoracic
vein (RITV), which drain drained into the
superior vena (SVC). This was in about
3.8%, of the study population, (2.3 % of
men and 4.5 % of women). However, on
the left side, the internal thoracic vein
termination was normal.
Standard
76
J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
anatomy textbooks show that the internal
thoracic veins (ITVs) are connected at the
point of manubriosternal joint. The RITV
and LITV receive the posterior intercostal
veins to form common trunks that ascend
and drain into the right and left
brachicephalic veins respectively (20).
Vollala et al (18) observed a rare variation
of right internal thoracic vein draining into
the extra-pericardial part of the superior
vena cava about 1.5 cm distal to the
junction of the right and left
brachiocephalic veins. Such a variation
was not observed in this study.
Superior vena cava anomalies are of rare
occurrence caused by variations in the
development of the embryonic venous
system. Persistent left superior vena cavae
are the most common congenital
aberrations in the thoracic venous system,
with an incidence of 0.3-0.5%. (21). in this
study no anomalies concerning SVC were
noted.
The clinical significance of anatomical
variants of thoracic inlet vasculature is
given less attention by radiologists. Most
of studies (22, 23) of this topic have been
made in normal individual or patients
suspected of having unrelated pathology.
One study found that most of patients had
dysphagia in case of aberrant subclivian
artery (23,).
angiography, be much more expensive
than CT.
Two effects facilitate the viewing of
thoracic inlet structures, the delineation of
the thoracic inlet muscles from the lymph
nodes, and the enhancement pattern of
blood vessels by contrast media in MDCT
compared to the appearance of these
structures with non enhancement study.
The contrast-enhanced CT imaging can
assess both the normal anatomy and
variations of thoracic inlet structures
accurately. Reformatted sagittal and
coronal CT sections may help to show the
origin, pathways the size and shape of
thoracic inlet structures. CT should be
used as a procedure of choice for diagnosis
of thoracic inlet blood vessel abnormallities, especially in patients suspected to
have vascular obstruction.
Clinicians and technologist should be
aware of the characteristic findings of noncontrast-enhanced as well as contrastenhanced images.
The wide spectrum of variations in
anatomical arrangements of aortic arch
branches in this study population was
similar to those of other studies. Although
anomalous origins of the aortic arch are
congenital, accurate knowledge of these
variations are vital for vascular surgery in
the thorax, and the neck region. The
present study findings may be useful in the
planning for thoracic inlet surgery and
may induce a change of surgical strategy.
It recommended that checking the vascular
variants and position of great blood vessels
and other structures should be done before
surgery.
There is a potential hazard from I.V.
administration of iodinated contrast
material, in CT compared to other images
modalities (MRI, US), in addition thoracic
inlet zone is prone to CT beam hardening
artifacts from the thickness of the
shoulders, often resulting in poor quality
images.
Acknowledgement
The authors would like to thank Modern
Medical Centre and The Ribat University
CONCLUSIONS
CT is superior to radiology for identification of normal anatomy, anatomic
variants and early abnormalities or
pathological processes. CT angiography is
promising method for both detection and
therapy planning of great vessels
anomalies. MDCT is a useful, less invasive technique for diagnosing most types of
vascular variations. It provides useful
information to differentiate lymph nodes
and small soft tissue lesions in thoracic
inlet from blood vessels. The combination
of MDCT and volume rendering (VRT)
provides higher quality data sets which
previously required two radiological
studies which may, in case of conventional
77
J.Sc. Tech ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬. 12(1) 2011
Hospital x-ray departments for the
valuable support with interesting CT
REFERENCES
1. Joans R, Yun L, Shawn D. T. 2003.
Fundamental
of
multichannel
CT,
Radiologic Clinic of North America.; 41:
P. 465-474.
2. Gosling J. A, Harris PF, Whitmore I,
Willan PL. 2002. Human Anatomy, fourth
edition, Mosby; P. 26-37.
3. Chiles C, Davis KW, Williams DW. 1999.
Navigating
the
Thoracic
Inlet.
Radigraphics; 19: 1161-1176.
4. Searm E. 2002. Computed Tomography;
physical principles, clinical application
and quality control. Second edition. W B
Saunders company, Philadelphia.; P.131151, 209-214.
5. Diego B, Nunez, JR, Mario TL, 2004.
Felipe M. Vascular injuries of the neck and
thoracic inlet: Helical CT- Angiographic
Correlation, Radio-graphics; 24: 10871098.
6. Meghal A, Anthony W, Bernard DC,
Douglas M C, Robert M K and Ziv J H.
2002. Thoracic Outlet Syndrome. e
medicine.
7. Rashad M. A. 2006. Value of CT and
MRI in the evaluation of thoracic inlet
syndrome. University of Cairo . P. 3.
8. Matthias H. 2005. CT Teaching Manual, A
systematic Approach to CT Reading.
Thieme. Second Edition: P.69-75.
9. Troyer, J. R. 1961. A multiple anomaly of
the human heart and great veins. Anat.
Rec. ; 139: P. 509-513.
10. Layton KF, Kallimes D. F., Cloft H. J.,
Lindell EP, Cox VS. 2006. Bovine aortic
variant in humans: clarification of
common misnomer. American Journal of
Neuroradiology; 27 P. 1541-1542.
11. Stuart E. M. 1998. Imaging diagnosis of
thoracic aorta and great vessel injury.
Radiology; 209: P. 335-348.
12. Bergman R. A, Afifi AK, Aorta Arch and
Thoracic part of descending Aorta. Peer
review. Anatomy Atlases A digital library
images.
of
anatomy
information
(www.anatomyatlases.org).
13. Neuhauser, E. B. D. 1946. Roentgen
diagnosis of double aortic arch and other
anomalies of the great vessels. Am. J.
Roentgenorphy (AJR).: P. 56:1-2.
14. Demos T. C., Posniak HV, Pierce KL,
Olson M. C., Muscato M. 2004. Venous
Anomalies of thorax. American Journal of
Roentgenology,; 182:1139-1150.
15. Raider, L. 1967. Aberrant right subclavian
artery. South. Med. J.; 60: P. 145-151.
16. Carrizo GJ, Marjani M. A. 2004.
Dysphagia Lusoria caused by an aberrant
right subclavian artery. Tex Heart Inst J.;
31(2): P. 168-171.
17. Tins B, Patel S. 2001. Comprasion of C. T.
angiography with conventional arterial
angiography in aortoilliac occlusive
disease. British Journal of Radiology
74,;219-223.
18. Vollala V. R., Pamidi N, Potu B K. 2008.
Internal thoracic vein draining into the
extrapericardial part of the superior vena
cava: a case report, Jornal Vascular
Brasileiro Print ISSN, . 7, (1) P; 1677-5449
19. Buxton, F. B., Ruengsa, Johkulrach P,
Fuller J, Rosalion A, Reid MC, Tatoulis J.
2000. The Right Internal of Thoracic
Artery Graft. European Journal of Cardiothoracic Surgery;18:255-261
20. Ronald A,Bergman R. A., Afifi AK.
Miyauchi R. 2008. Illustrated Encylopedia
of Human Anatomic Variation; Cardiovascular System; Arteries: head, neck, and
thorax. Brachiocephalic artery.
Peer
Reviewed. -10-70.
21. Strub WM, Leach J. L., Tomsick TA.
2008. Left Vertebral artery Origin from the
thyrocervical Trunk: A unique vascular
variant. American Journal of Neuroradiology
MAY; 27:1155-1156.
22. Boshong S. C. Radiologic Science for
Technologist. 7th Edition Mosby. 2001; P.393404.
23. Henolee WR, Ritenour E. R. 2002. Medical
imaging physics, fourth edition,
24. John Wiley and sons, Inc, Publication.; P.252259.
78