DOI:10.2214/AJR.07.2280
AJR 2007; 189:W184-W191
© American Roentgen Ray Society
CT Image Fusion for 3D Depiction of Anatomic Abnormalities of the Hepatic Hilum
Masafumi Uchida1,
Masatoshi Ishibashi,
Jun Sakoda,
Sanae Azuma,
Shuji Nagata and
Naofumi Hayabuchi
1 All authors: Department of Radiology, Kurume University School of Medicine, 67
Asahi-Machi, Kurume City, Fukuoka, 830-0011, Japan.
Received March 20, 2007;
accepted after revision May 18, 2007.
Address correspondence to M. Uchida
(krumf{at}med.kurume-u.ac.jp).
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Abstract
OBJECTIVE. The purpose of this article is to show how CT image
fusion with 3D reconstruction is used to depict in detail the anatomic
structures of the hepatic hilum in the presence of hepatobiliary
abnormalities.
CONCLUSION. CT image fusion is a comprehensive imaging technique for
preoperative evaluation of the blood vessels and bile ducts of the hepatic
hilum.
Keywords: CT • CT angiography • CT cholangiography • CT image fusion • hepatobiliary system
Introduction
The hepatic hilum is a complex structure composed of the hepatic artery,
portal vein, bile ducts, lymphatic vessels, nerves, and liver parenchyma.
Accurate knowledge of the 3D anatomy of the hepatic hilum is essential for
successful liver surgery, including liver transplantation, tumor resection,
and laparoscopic hepatobiliary surgery. Several reports have described the 2D
imaging features of the anatomic structures of hepatic hilar blood vessels and
bile ducts
[1–3].
Few reports, however, have defined in 3D the anatomic structures of the
hepatic hilum [4,
5]. It is crucial to understand
the 3D anatomic relations between the blood vessels and the bile ducts in the
hepatic hilum. The purpose of this article is to illustrate the anatomic
features of the hepatic hilum in 3D detail obtained by fusion of CT
angiographic and CT cholangiographic images in the assessment of hepatobiliary
abnormalities. The article is based on a limited study involving 17 patients
with hepatobiliary abnormalities who were referred for further assessment
because of findings on CT angiography or CT cholangiography and who underwent
prospective evaluation. The patient group included 10 men and seven women
(mean age, 58 years; range, 32–80 years). Informed consent for
participation in the study was obtained from each patient or guardian as part
of the protocol approved by the institutional clinical subpanel on human
studies at our university hospital.
Imaging Technique
CT images were acquired with a 16-MDCT system (LightSpeed Ultra, GE
Healthcare). Scanning was performed at a pitch of 1.375:1, 0.7-second scanning
time per rotation, table speed of 13.75–27.50 mm/rotation, and detector
configuration of 0.625–1.25 x 16 mm. The scanning parameters (120
kVp, 300–440 mA, 30- to 35-cm field of view, 512 x 512 matrix
size) varied slightly depending on patient size. During CT angiography, a
power injector was used to administer contrast medium (370 mg I/mL of
iopamidol, Iopamiron, Schering) through a 20-gauge high-pressure IV catheter
at a rate of 4 mL/s. The total volume was 2 mL/kg of body weight. With a
bolus-triggered technique in which the cursor was placed on the aorta and the
threshold set at 200 H, hepatic artery phase images were obtained in a
craniocaudal direction. Portal venous phase images were obtained with a
scanning delay of 50 seconds after initiation of contrast injection.
The biliary contrast enhancement study was performed 3–7 days after
CT angiography. The CT cholangiographic image set was acquired 30 minutes
after IV infusion of 100 mL of meglumine iotroxate (50 mg I/mL Biliscopin,
Schering) over 45 minutes. The CT data for each phase were retrospectively
reconstructed at an interval of 0.625–1.25 mm with a 0.625- to 1.25-mm
section thickness. The raw data were transferred automatically via Ethernet to
a workstation (Ziostation, Ziosoft) in a 512 x 512 pixel format. Image
fusion was performed with the fusion software associated with the workstation.
After data acquisition, the workstation software was used to fuse CT
angiographic and CT cholangiographic images to make 3D images. Shifts in
location of the x-, y-, and z-axes under
respiration were automatically corrected with the semiautomatic function of
the workstation. The location also was corrected manually by means of fine
adjustments made with the guidance of a reference set of axial, coronal, and
sagittal images on a monitor next to the workstation. Although approximately
10% (two of 17) of the patients in our study had imperfect breath-holding,
images were produced when the software was used for manual correction of the
anatomic structures. Approximately 30–60 minutes of user time was
required to generate the fusion images after image acquisition
[5]. In this limited
prospective study, findings on fused CT images were confirmed surgically in 14
(82%) of the 17 patients. The other three patients had benign disease that
precluded surgical resection.
Anatomy of the Hepatic Hilum
The hepatic artery usually courses along the dorsal aspect of the common
bile duct and branches into the right and left hepatic arteries. The right
hepatic artery runs behind the common bile duct or common hepatic duct and
divides into anterior and posterior segmental branches immediately before it
enters the liver [2]. The
portal vein usually courses along the dorsal aspect of the hepatic artery. The
branches of the right portal vein are dorsal to the artery and enter Glisson's
sheath. The left branch of the portal vein is dorsal to the artery
(Fig. 1). Anatomic variations
in the bile duct and blood vessel branches are most common in the hepatic
hilar area [1,
2,
6]. Variation rates of
24–49% for the hepatic artery and 28–41.5% for the hilar and right
hepatic bile ducts have been reported
[2,
6,
7].
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Fig. 1 —Schematic shows anatomic features of hepatic hilum. RHA =
right hepatic artery, LHA = left hepatic artery, GB = gallbladder, PHA =
proper hepatic artery, CBD = common bile duct, PV = portal vein, CHA = common
hepatic artery.
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CT Image Fusion
In hepatic surgery, preoperative understanding of the variation in the
vessels and bile duct of the hepatic hilum helps avoid complications and helps
achieve the most effective surgical technique
[4,
8]. CT angiographic–CT
cholangiographic image fusion makes it easy to understand the complex
structure of the vascular and bile duct components of the hepatic hilum.
Before laparoscopic cholecystectomy, one can easily assess the cystic duct and
the flow of the cystic artery on one image. Figure
2A,
2B shows a concise depiction of
the cystic artery, and Figure
3A,
3B,
3C shows an anomalous cystic
bile duct in the hepatic hilum. Figure
4A,
4B,
4C shows anomalous arteries and
the anatomic structures along the course of the cystic artery, portal vein,
and gallbladder. Before surgery for a hepatic or gallbladder tumor, CT image
fusion can provide surgeons with 3D data sets showing the relation of the
tumor to the bile duct, portal vein, hepatic artery, and branches of these
vessels in the hepatic hilum. Figures
5A,
5B,
5C and
6A,
6B,
6C,
6D are images of anomalous
hepatic arteries. The images clearly depict the artery between the tumor and
the biliary system. Figure 7A,
7B,
7C,
7D is a concise depiction of
an anomalous artery and an anomalous bile duct in the hepatic hilum. The
resulting image makes it easy to evaluate the surrounding structures.
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Fig. 2B —53-year-old woman with diffuse adenomyomatosis of
gallbladder. Fused CT angiographic–CT cholangiographic image shows
anatomic relations of portal vein, hepatic artery, and common hepatic duct in
hepatic hilum. Configurations of cystic artery (curved arrow), cystic
duct (arrowhead), and anomalous right posterior segmental duct
(straight arrow) are evident. Pink indicates artery; yellow,
bile duct; dark blue, portal vein; olive green, liver parenchyma.
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Fig. 3B —63-year-old woman with cholelithiasis. CT angiogram shows
cystic artery origin of right hepatic artery (arrow). Liver
parenchyma is 90% transparent. Pink indicates artery; dark blue, portal vein;
light blue, renal vein; olive green, liver parenchyma.
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Fig. 3C —63-year-old woman with cholelithiasis. Fused CT
angiographic–CT cholangiographic image shows anatomic relations of
anomalous cystic duct, hepatic bile duct, hepatic artery, and portal vein of
hepatic hilum. Pink indicates artery; yellow, bile duct; dark blue, portal
vein; light blue, renal vein; olive green, liver parenchyma, which is 90%
transparent.
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Fig. 4A —66-year-old woman with gallbladder polyps. CT angiogram shows
entire celiac trunk arising from superior mesenteric artery (curved white
arrow), cystic artery (arrowhead) origin of right hepatic artery
(straight white arrow), and left hepatic artery arising from
left gastric artery (black arrow). Pink indicates artery.
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Fig. 4B —66-year-old woman with gallbladder polyps. CT angiogram shows
right hepatic artery is anterior to portal vein and cystic artery is anterior
to right portal vein (arrowhead). Pink indicates artery; blue, portal
vein.
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Fig. 4C —66-year-old woman with gallbladder polyps. Fused CT
angiographic–CT cholangiographic image shows anatomic relations of
portal vein, right hepatic artery, cystic artery (arrowhead), and
cystic duct (arrow) in hepatic hilum. Pink indicates artery; yellow,
bile duct; blue, portal vein; olive green, liver parenchyma.
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Fig. 5A —62-year-old man with hepatocellular carcinoma. CT angiogram
shows anomalous origin of right hepatic artery from superior mesenteric artery
(arrows). Celiac and superior mesenteric arteries are joined and have
common trunk (arrowhead). Pink indicates artery.
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Fig. 5B —62-year-old man with hepatocellular carcinoma. CT angiogram
shows that right hepatic artery (arrows) is posterior to superior
mesenteric vein, runs along portal vein for short distance, and enters liver
parenchyma from left side of tumor (arrowheads). Pink indicates
artery; blue, portal vein; olive green, liver parenchyma; emerald green, liver
tumor.
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Fig. 5C —62-year-old man with hepatocellular carcinoma. Fused CT
angiographic–CT cholangiographic image shows anatomic relations of
portal vein, anomalous hepatic artery, liver tumor (segment V), and common
hepatic duct in hepatic hilum. Liver parenchyma is 90% transparent. Pink
indicates artery; yellow, bile duct; dark blue, portal vein; light blue, renal
and hepatic veins; olive green, liver parenchyma; emerald green, liver
tumor.
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Fig. 6B —67-year-old man with intrahepatic cholangiocarcinoma. CT
angiogram shows left hepatic artery runs into tumor (arrowheads).
Tumor is supplied by left hepatic artery. Pink indicates artery; green, liver
tumor.
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Fig. 6C —67-year-old man with intrahepatic cholangiocarcinoma. Fused
CT angiographic–CT cholangiographic image shows focal defect
(arrowheads) of left hepatic bile duct with proximal segmental
dilatation and occlusion of left portal vein (arrow). Yellow
indicates bile duct; blue, portal vein.
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Fig. 6D —67-year-old man with intrahepatic cholangiocarcinoma. Fused
image depicts relations of liver tumor, anomalous hepatic artery, hepatic bile
duct, and portal vein. Understanding of hilar anatomy and course of bile duct
and hepatic vessels is crucial. After studying images, surgeons planned left
hepatectomy. Pink indicates artery; yellow, bile duct; blue, portal vein;
olive green, liver parenchyma; emerald green, liver tumor.
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Fig. 7C —68-year-old woman with gallbladder carcinoma. Fused image
shows right hepatic artery (straight arrow) runs along right
side of portal vein in course partly dorsal to hepatic duct, configuration of
cystic duct (curved arrow), and anomalous right posterior segmental
duct (arrowhead). Pink indicates artery; yellow, bile duct; dark
blue, portal vein; light blue, renal and hepatic veins; olive green, liver
parenchyma.
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Fig. 7D —68-year-old woman with gallbladder carcinoma. Intraoperative
photograph shows findings concordant with those of image fusion. Straight
arrow indicates right hepatic artery; curved arrow, cystic duct; arrowhead,
right posterior duct.
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Conclusion
Understanding a surgeon's perspective on liver surgery is critical so that
accurate imaging information can be provided. CT angiography–CT
cholangiography image fusion is a complementary method that allows one-step,
comprehensive, noninvasive evaluation of the hepatic hilum. In addition, 3D
images from designated projections can show anatomic features to their best
advantage [9,
10]. The findings on CT fusion
images in 14 patients who underwent surgery had near one-to-one correlation
with the surgical findings. We believe that high-resolution 3D fusion images
will be extremely useful for evaluation of the hepatic hilar anatomy, as in
preoperative planning for hepatic and bile duct resection and for liver
transplantation.
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Abstract
Introduction
