AJR 2005; 185:253-256
© American Roentgen Ray Society
Clinical Potentials for Dynamic Contrast-Enhanced Hepatic Volumetric Cine Imaging with the Prototype 256-MDCT Scanner
Shinichiro Mori1,2,
Takayuki Obata3,
Riwa Kishimoto4,
Hirotoshi Kato4,
Kenya Murase2,
Hideaki Fujiwara2,
Susumu Kandatsu4,
Shuji Tanada3,
Hirohiko Tsujii4 and
Masahiro Endo1
1 Department of Medical Physics, National Institute of Radiological Sciences,
Chiba, 4-9-1 Anagawa, Inage-ku, Chiba-shi, Chiba, 263-8555, Japan.
2 School of Allied Health Sciences, Faculty of Medicine, Osaka University,
Osaka, Japan.
3 Department of Medical Imaging, National Institute of Radiological Sciences,
Chiba, Japan.
4 Hospital, National Institute of Radiological Sciences, Chiba, Japan.
Received July 16, 2004;
accepted after revision October 15, 2004.
Address correspondence to S. Mori
(shinshin{at}nirs.go.jp).
Abstract
OBJECTIVE. To achieve dynamic contrast-enhanced hepatic volumetric
cine imaging, we developed a prototype 256-MDCT scanner. This study examined
the feasibility of the technique for human hepatic imaging in three
hepatocellular carcinoma patients.
CONCLUSION. Volumetric cine imaging successfully visualized dynamic
contrast enhancement of the hepatocellular carcinoma. It is helpful to
evaluate the phase of contrast enhancement or for functional studies of the
head, renal artery, coronary artery, and liver.
Introduction
Developments in CT technology have allowed applications of 3D images
in clinical fields such as diagnosis, surgical simulation, planning of
radiation therapy, and monitoring of interventional therapy. Multiphasic
images provide important information for the diagnosis and characterization of
liver neoplasms [1]. Arterial
phase imaging is useful for the detection and characterization of
hypervascular hepatic lesions. High spatial resolution can be helpful to
achieve a more accurate diagnosis
[1]. The development of the
latest 16-MDCT has made dynamic 3D imaging possible. However, the craniocaudal
coverage of the 16-MDCT scanner's detector, without gantry movement, is
typically only 20-32 mm, which imposes a limit on cine imaging, that is, the
capturing of images continuously (approximately 1 or more images per second)
during and immediately after completion of contrast agent injection. To make
cine imaging with a wider coverage in the craniocaudal direction (volumetric
cine imaging), we developed a prototype 256-MDCT. The purpose of our study is
to give a preliminary visualization of volumetric cine imaging during the
arterial phase. For this we used the 256-MDCT to evaluate three hepatocellular
carcinoma patients.
Subjects and Methods
Subjects
The subjects in this study were three male patients with hepatocellular
carcinoma, ages 63, 70, and 74 years, who were selected at random among the
hepatocellular carcinoma patients in our hospital. They gave their informed
consent to be included in the study, which was conducted in accordance with
the principles of the Declaration of Helsinki
[2]. All were inpatients of the
institute hospital and receiving radiation therapy with a carbon ion beam.
Prototype 256-MDCT
The prototype 256-MDCT used a wide-area cylindric 2D detector, designed on
the basis of present CT technology and mounted on the gantry frame of the
16-MDCT (Aquilion, Toshiba Medical Systems)
[3]. The number of detectors
was 912 (transverse) x 256 (craniocaudal), each approximately 0.58
x 0.50 mm at the center of rotation, resulting in a total of 233,472
elements. The rotation time of the gantry was 1.0 sec. Several collimation
sets (e.g., 1-256 x 0.5 mm, 1-128 x 1.0 mm, 1-64 x 2.0 mm)
could be set continuously to a 128-mm total beam width. The craniocaudal
coverage of the 256-MDCT was approximately 100 mm long with one rotation
[4,
5]. The data sampling rate was
900 views/sec, and dynamic range of the analog-digital converter was 16 bits.
The detector element consisted of a scintillator and photodiode. The
scintillator was Gd2O2S ceramic, and the photodiode was
made of single-crystal silicon; these were the same as for an MDCT.
Technique for Volumetric Cine Imaging
After we obtained an initial scout topogram of the abdomen, all patients
were scanned in a cine fashion with the gantry centered over the upper abdomen
after the onset of injection of 90 mL of nonionic iodinated contrast material
(Iopamiron 370 [iopamidol], Nihon Schering) using a power injector with a flow
rate of 3.5 mL/sec. The delay between the start of contrast material
administration and scanning was 30 sec. Scan parameters were 120 kV, 200 mA, 1
sec rotation time, 10 sec entire scanning time, and 256 x 0.5 mm beam
collimation. Effective dose was 27.7 mSv/10 sec
[6]. This dose was almost the
same as we routinely used for the liver multiphasic protocol. The scanning
time was conservatively limited to 10 sec less than the dose routinely used in
the institute [6] because the
256-MDCT scans continuously at the same position and the dose increases in
proportion to the scanning time. The patients held their breath at
end-expiratory during scanning. A Feldkamp-Davis-Kress algorithm was used for
reconstruction [7]. It took
less than 1 sec to reconstruct volume data of 512 x 512 x 256
voxels by a high-speed image processor with a field programmable
gate-array-based architecture. Its physical performance had been previously
identified as promising [5].
The reconstruction increment was 0.62 mm with a 0.1 sec time interval and
matrix size of 512 x 512 x 256. The reconstructed images were
transferred to a workstation (Dell) and software routines were run within the
PV-WAVE programming package (Visual Numerics) for image postprocessing.
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Fig. 1B —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1C —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1D —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1E —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1F —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1G —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1H —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1I —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Fig. 1J —74-year-old man with hepatocellular carcinoma. Coronal views
with 3D volume rendering every 1 sec after A. Note slightly enhanced
abdominal aorta (arrow, D) 33 sec after injection. Two iridium
beads (< 2 mm diameter) were implanted around hepatocellular carcinoma to
verify patient positioning with fluoroscopy before each section of radiation
therapy. Two bright points (arrows, F) show iridium markers
(also seen on other images). Slightly enhanced celiac artery (arrow,
G) 36 sec after injection. Note markedly enhanced arterial systems
(J) 39 sec after injection.
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Results
Dynamic hepatic CT satisfactorily obtained continuous enhancement in the
arterial phase. Contrast enhancement could be observed in coronal views with
3D volume rendering 30 sec after injection (74-year-old man,
Fig. 1A). This patient had
heart failure, and the backflow of contrast material to the inferior vena cava
(IVC) was clearly shown. The hepatic veins were best visualized on the images
obtained approximately 30-34 sec after the start of contrast agent injection
(Figs. 1A,
1B,
1C,
1D,
1E). The IVC was visualized in
contrast enhancement (arrow, Fig.
1A) and then enhancement was completely lost at 36 sec. After 34
sec, enhancement of the abdominal aorta increased gradually (Figs.
1D,
1E,
1F,
1G). The renal artery enhanced
gradually at 36 sec, and finally the arterial phase was best visualized on the
images with high contrast in the celiac, splenic, and hepatic arteries (Figs.
1I,
1J).
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Fig. 2A —63-year-old man with hepatocellular carcinoma. Axial view
shows hypervascular mass in right lobe of Couinaud's segment 6-7
(arrow). P and Q = orientation of images, MIP = maximum intensity
projection.
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Fig. 2B —63-year-old man with hepatocellular carcinoma. Coronal views
with MIP in 33° oblique plane 30-38 sec after injection show only arterial
phase. Hypervascular hepatocellular carcinoma and nutrient artery are clearly
visualized. Radiodense objects in all images were iridium beads (< 2 mm
diameter).
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Fig. 2C —63-year-old man with hepatocellular carcinoma. Coronal views
with MIP in 33° oblique plane 30-38 sec after injection show only arterial
phase. Hypervascular hepatocellular carcinoma and nutrient artery are clearly
visualized. Radiodense objects in all images were iridium beads (< 2 mm
diameter).
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Fig. 2D —63-year-old man with hepatocellular carcinoma. Coronal views
with MIP in 33° oblique plane 30-38 sec after injection show only arterial
phase. Hypervascular hepatocellular carcinoma and nutrient artery are clearly
visualized. Radiodense objects in all images were iridium beads (< 2 mm
diameter).
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Fig. 2E —63-year-old man with hepatocellular carcinoma. Coronal views
with MIP in 33° oblique plane 30-38 sec after injection show only arterial
phase. Hypervascular hepatocellular carcinoma and nutrient artery are clearly
visualized. Radiodense objects in all images were iridium beads (< 2 mm
diameter).
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Fig. 2F —63-year-old man with hepatocellular carcinoma. Coronal views
with MIP in 33° oblique plane 30-38 sec after injection show only arterial
phase. Hypervascular hepatocellular carcinoma and nutrient artery are clearly
visualized. Radiodense objects in all images were iridium beads (< 2 mm
diameter).
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An example of dynamic maximum-intensity-projection-reconstructed
contrast-enhanced CT from the arterial phase to the portal vein phase was
obtained in the oblique plane (63-year-old man, Figs.
2A,
2B,
2C,
2D,
2E, and
2F). Hepatocellular carcinoma
(50 x 40 mm) was observed in the right lobe of Couinaud's segment 6-7
(arrow, Fig. 2A). The
hepatocellular carcinoma showed a typical early enhancement, and the
well-enhanced hepatic artery supplying the hepatocellular carcinoma was
clearly visualized at 30 sec after injection. At 31-34 sec, the hepatic
arteries had less enhancement. At 38 sec, the hepatic arteries were not
visualized at all, and only the hepatic portal veins were revealed
(Fig. 2F).
Discussion
This 256-MDCT scanner was designed to allow cine imaging over a
craniocaudal distance of approximately 10 cm. The images created had a 0.5 mm
thickness, resulting in isotropic voxels that can be used to create images and
cine loops, in any plane, with any of several postprocessing techniques. The
scanner has the ability to provide useful information when examining 3D
structures, as illustrated in this article. A significant advantage appears in
examinations of the abdomen and chest since the major anatomic structures in
these regions run longitudinally. High spatial resolution improves evaluation
of the liver and its vascular system. The use of thin sections facilitates the
detection of small lesions since relatively thick slices result in a partial
volume artifact.
Cine images provide useful diagnostic information. In this study, the
thin-slice cine images can also be used to create cine loops in multiple
planes from the volumetric data acquired from a patient with hepatocellular
carcinoma (Figs. 2A,
2B,
2C,
2D,
2E, and
2F). This was not possible
before with conventional MDCT. Since imaging results can vary considerably
depending on differences in patient circulation
[8], appropriate timing of the
scan after the start of contrast material injection is essential to avoid
imaging for an excessively long period with the cine technique to reduce an
excessively high dose or to eliminate the need for an excessively long
breath-hold. Thus, a volumetric cine imaging with a test bolus is more useful
for acquisition of the phase of contrast enhancement study.
In conclusion, the craniocaudal coverage of the 256-MDCT is limited for
less than one whole organ such as the liver, and the effective dose is
increased in proportion to the scanning time. However, cine imaging in the
256-MDCT is helpful to evaluate the phase of contrast enhancement or
functional studies for the head, renal artery, coronary artery, and liver.
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Abstract
Introduction
