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Original Research |
1 Department of Radiology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki
City, Osaka 569-8686, Japan.
2 Department of General and Gastroenterological Surgery, Osaka Medical College,
Takatsuki City, Osaka 569-8686, Japan.
Received May 7, 2004;
accepted after revision February 21, 2005.
Address correspondence to M. Matsuki
(rad053{at}poh.osaka-med.ac.jp).
Abstract
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MATERIALS AND METHODS. The study involved 20 consecutive patients (10 men, 10 women; mean age, 59 years) scheduled for laparoscopic gastrectomy for the treatment of early gastric cancer. A dual-phase contrast-enhanced CT scan using 16-MDCT was obtained before laparoscopic gastrectomy. After rapid infusion of a nonionic contrast agent, arterial and venous phase scans were obtained serially with an interval of 15 sec during a single breath-hold of 31 sec. Three-dimensional CTA images in the arterial phase (3D CT arteriography) and venous phase (3D CT venography) were individually reconstructed using the volume-rendering technique, and then the images were fused together. We evaluated the detectability of the celiac trunk, left gastric artery (LGA), right gastric artery (RGA), left gastric coronary vein (LCV), Henle's gastrocolic trunk, right gastroepiploic vein (RGEV), and accessory right colic vein on 3D CTA to compare with surgical findings.
RESULTS. In all 20 patients, 3D CT arteriography and venography clearly showed the celiac trunk, LGA, RGA, Henle's gastrocolic trunk, RGEV, and accessory right colic vein, which were correctly identified during surgery. The branching pattern of the celiac trunk was classified as Michels type I in 19 patients and Michels type II in one patient. Imaging showed the RGA originating from the proper hepatic artery (PHA) in nine patients; from the gastroduodenal artery (GDA) in seven patients; and from the left hepatic artery (LHA) in four patients. In 12 patients, the LCV joined the portal vein (PV) and in eight, the splenic vein (SV). In all patients, the accessory right colic vein joined the RGEV, and Henle's gastrocolic trunk proximal to the joining point flowed to the superior mesenteric vein (SMV). In all 20 patients, the fused image simultaneously showed arteries and veins around the stomach, with no mismatch between the arterial and venous phase images. In 10 patients, the LCV joined the PV after running along the dorsal side of the PHA, common hepatic artery (CHA), or splenic artery (SA). In eight patients, the LCV joined the SV after running along the ventral side of the PHA, CHA, or SA. In two patients, the LCV joined the PV after running along the ventral side of the CHA, which correlated with the surgical findings. Both the sensitivity and positive predictive values of 3D CTA revealed 100% correct identification of the celiac trunk, LGA, RGA, LCV, Henle's gastrocolic trunk, RGEV, and accessory right colic vein.
CONCLUSION. Dual-phase 3D CTA using 16-MDCT clearly revealed individual arteries and veins around the stomach before laparoscopic gastrectomy. The fused image of 3D CT arteriography and venography during a single breath-hold enabled the simultaneous assessment of arteries and veins before laparoscopic gastrectomy.
Keywords: CT • CT angiography • gastric cancer • laparoscopic surgery • MDCT • vascular anatomy
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Previously, we reported the utilization of 3D CTA in the arterial phase using 4-MDCT for the assessment of the vascular anatomy around the stomach before laparoscopic gastrectomy [6-8]. However, the disadvantage of this method is that the arterial phase is too early for visualization of the veins around the stomach [6-8]. Moreover, reconstructing the 3D CTA images of the veins in the arterial phase is time-consuming because of poor contrast enhancement of the veins [6-8].
We attempted to obtain arterial and venous phase images at 15-sec intervals during a single breath-hold with a total duration of 31 sec using 16-MDCT [9]. Three-dimensional CTA images of the arteries in the arterial phase (3D CT arteriography) and veins in the venous phase (3D CT venography) around the stomach were individually reconstructed and developed into fused images for simultaneous evaluation of the gastric arteries and veins [9]. In this study, we discuss the use of dual-phase 3D CTA during a single breath-hold for safe and rapid performance of laparoscopic gastrectomy and examine the ability of 3D CTA to allow visualization and identification of pertinent gastric vascular anatomy.
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Local lymph node dissection involved the perigastric lymph nodes (lymph nodes 1 and 3-6 in Fig. 1) together with the lymph nodes around the left gastric artery (LGA) trunk (7), in the anterosuperior region of the common hepatic artery (CHA) (8a), and around the celiac artery (9), according to the Japanese classification of gastric cancer [11] (Fig. 1). None of the patients had any comorbid condition for which undergoing laparoscopic distal gastrectomy was contraindicated, and all gave written informed consent to have the procedure performed. A CT examination was performed at a mean of 8 days and a range of 2-15 days before laparoscopic distal gastrectomy.
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To enable a breath-hold to be performed during the CT examination with ease, 100% oxygen was administered to the patient at 3 L/min under a mask. The contrast-enhanced CT examination was set to cover the area ranging from the dome of the liver to the lower border of the stomach and was referred to as the scout image. Imaging was performed using the following parameters: 120 kVp, 300 mA, 0.5-sec gantry rotation speed, 15 helical pitch, 1-mm slice thickness, table speed of 15 mm per rotation, and reconstruction intervals of 0.5 mm. For contrast-enhanced CT examination, a nonionic contrast agent (300 mg I/mL gadodiamide [Omnipaque, Daiichi Pharmaceutical]) was infused rapidly at 5 mL/sec using an automated injector (Autoenhance A-250, Nemotokyorindou) in a total volume of 100 mL for patients weighing less than 40 kg, in a total volume equivalent to body weight (in kilograms) x 2.5 mL for patients weighing between 40 and 60 kg, and in a total volume of 150 mL for patients weighing more than 60 kg. The volume of contrast medium administered ranged from 100 to 150 mL (mean, 133 mL).
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Arterial phase images were obtained using computer-assisted bolus-tracking technology (referred to as the "Real Prepare Method" and developed by Toshiba Medical Systems), which sets a region of interest (ROI) in the aorta at the level of bifurcation of the celiac artery and is designed so that imaging begins when the attenuation value of the ROI is 50 H higher than that of the ROI on unenhanced imaging [7-9, 13]. The average scanning delay for the arterial phase after the start of injection was 20 sec (range, 18-23 sec) (Fig. 2). After arterial phase images were obtained during a single breath-hold with a total duration of 31 sec, which is considered commonly possible to perform, we obtained venous phase images (scan timing after the start of injection: mean, 43 sec; range, 41-46 sec) at 15-sec intervals after the arterial phase (Fig. 2). All of the patients were able to perform the respiratory hold continuously from the arterial to venous phase.
Reconstruction
The slice data obtained from the arterial and venous phases were
transferred to a workstation (M900QUADRA, Zio Software Co.) in which the data
at the individual phase were converted into a multiplanar reconstruction (MPR)
and a 3D reconstruction using the volume-rendering technique.
To confirm that a single breath-hold had been performed and the stomach had not assumed a different shape because of peristalsis between the arterial and venous phases, one radiologist prepared and examined the MPR image at the venous phase fused with that of the selective air-filled stomach at the arterial phase from axial, coronal, and sagittal views at 1-mm slice thicknesses and 1-mm intervals (Figs. 3 and 4).
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A 3D CTA image of the arteries in the arterial phase (3D CT arteriography) and a 3D CTA image of the air-filled stomach in the arterial phase were individually prepared and fused together (Fig. 2A). A 3D CTA image of the veins in the venous phase (3D CT venography) was prepared next (Fig. 2B). Between 12 and 28 min (mean, 18 min) was required to obtain both 3D CT arteriography and venography images on the workstation. These dual-phase 3D CTA images were then fused using commercial software (Fusion Technique, Zio Software Co.) (Fig. 3). All 3D CTA images were reconstructed by one radiologist. On the basis of the 3D CTA images, laparoscopic gastrectomy was preoperatively planned by the surgeons.
Image Analysis
All 3D CTA examinations were prospectively evaluated by one radiologist and
one surgeon at the same time, and visualization of the arteries and veins
around the stomach was determined with a consensus agreement. The branching
patterns of the celiac trunk in individual cases were evaluated on 3D CT
arteriography, which were divided into six types (I through VI), according to
Michels classification [13].
The right gastric artery (RGA) was evaluated on 3D CT arteriography. The
inflows of the left gastric coronary vein (LCV), Henle's gastrocolic trunk,
right gastroepiploic vein (RGEV), and accessory right colic vein were
evaluated on 3D CT venography and the fused images. The surgeon mentioned
earlier performed the operation and correlated the 3D CTA findings with the
surgical findings. The sensitivity and positive predictive values of 3D CTA
for determining the arterial origin and venous inflow were computed using the
surgical findings as the standard of reference.
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In all 20 patients, the branching pattern was correctly identified on 3D CT arteriography, as confirmed later by comparison with the surgical findings. The branching pattern of the celiac trunk was classified as type I (hepatosplenogastric trunk: the LGA, CHA, and splenic artery [SA] originate from the celiac trunk) in 19 patients (Fig. 5A) and type II (hepatosplenic trunk: the CHA and SA originate from the celiac trunk, whereas the LGA originates from the aorta) in one patient. In all 20 patients, the RGA was correctly identified on 3D CT arteriography, as determined by comparison with the surgical findings. Imaging showed the RGA originating from the proper hepatic artery (PHA) in nine patients; from the gastroduodenal artery (GDA) (Fig. 5A) in seven patients; and from the left hepatic artery (LHA) (Fig. 6A) in four patients.
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In all 20 patients, the fused image simultaneously showed the arteries and veins surrounding the stomach, which correlated to the surgical findings. In 10 of the 20 patients, the LCV joined the PV after running along the dorsal side of the PHA, CHA, or SA. In eight of the 20 patients, the LCV joined the SV after running along the ventral side of the PHA, CHA, or SA (Figs. 5A and 5B). In the other two patients, the LCV joined the PV after running along the ventral side of the CHA.
Both the sensitivity and positive predictive values of 3D CTA were 100% in terms of correctly identifying the LGA, RGA, LCV, Henle's gastrocolic trunk, RGEV, and accessory right colic vein. All 20 patients underwent successful laparoscopic distal gastrectomy as determined on the basis of the 3D CTA images. None of the patients had to undergo conversion from laparoscopic distal gastrectomy to open surgery because of uncontrolled bleeding. Pathologic study revealed no metastasis in the dissected lymph nodes.
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Generally, distal gastrectomy is performed for cancer of the body or antrum of the stomach. Local lymphadenectomy involves dissection of the perigastric lymph nodes (1-6) and the lymph nodes around the LGA trunk (7), in the anterosuperior region of the CHA (8a), and around the celiac artery (9), according to the Japanese classification of gastric cancer [11] (Fig. 1). Despite the advantages of this procedure, it is difficult to obtain an image of the entire view of the operative field under a laparoscope; and the lesion, organs, and vessels cannot be manipulated directly. For these reasons, a great deal of time is required to manipulate the origins of the arteries and the inflow of the veins, the patterns of which vary among patients [2]. The veins around the stomach run along or across the arteries (Fig. 1); thus, the veins are sometimes injured during ligation of the arterial origins and dissection of the lymph nodes along the arteries using laparoscopic guidance, which leads to heavy bleeding that prevents the surgeon from having access to a good view of the operative field [3, 5].
The following technical points are important to consider during laparoscopic distal gastrectomy [8]: First, the area facing the greater curvature must be approached, the left and right gastroepiploic arteries (RGEAs) and veins (RGEVs) must be ligated, and the lymph nodes along the greater curvature (2, 4) must be dissected. In cases in which the accessory right colic vein joins the RGEV and Henle's gastrocolic trunk proximal to the joining point inflows to the superior mesenteric vein (SMV), Henle's gastrocolic trunk can be erroneously dissected under laparoscopic guidance, although the RGEV distal to Henle's gastrocolic trunk should be ligated while preserving the accessory right colic vein (Fig. 7B). Moreover, the accessory right colic vein can be erroneously injured during subpyloric lymph node dissection (6) along the RGEA (Fig. 7B). Second, the origin of the RGA should be ligated after dissecting the first portion of the duodenum or everting the greater curvature. Then, the area facing the lesser curvature should be manipulated. The dissection of the lymph nodes in the anterosuperior region of the CHA (8a) proceeds in the proximal direction.
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It is essential that the LCV be confirmed first and be ligated before dissecting the lymph nodes (8a). If the LCV ligation is not performed in advance, the LCV can be erroneously injured during the dissection of the lymph nodes (8a), leading to massive bleeding that will prevent the surgeon from having a good view of the operative field [3] (Fig. 7A). The dissection en bloc of the lymph nodes around the celiac trunk (9) will expose the LGA; then, the origin of the LGA must be ligated and the lymph nodes along the lesser curvature (3) must be dissected. Therefore, to safely ligate the arterial origins and veins and to dissect the lymph nodes under laparoscopic guidance, simultaneous assessment of the arteries and veins around the stomach using 3D CTA before laparoscopic gastrectomy is considered to be useful [5-8].
Previously, we reported the usefulness of 3D CTA in the arterial phase using 4-MDCT in the assessment of vascular anatomy before laparoscopic gastrectomy [6-8]. We found that 3D CTA images clearly depicted the arteries around the stomach and were useful for assessing the arterial origins before laparoscopic gastrectomy. However, the arterial phase is too early for simultaneous visualization of the veins around the stomach, especially the RGEV, accessory right colic vein, Henle's gastrocolic trunk, and the other veins that flow to the SMV [6-8]. Moreover, for 3D CT venography in the arterial phase, the original 3D CTA image was subtracted by 3D CT arteriography and the surrounding organs and structures were manually removed. Because of this procedure, preparing the fused image took a long time, a mean of 35 min [8].
To simultaneously obtain images of the arteries and veins around the stomach, we obtained serial arterial and venous phase images during a single breath-hold and fused the dual-phase CTA images. If the images had not been obtained during an individual breath-hold, a mismatch between the arterial and venous phase images could have occurred [9]. In our previous study, using 4-MDCT with a 0.5-sec gantry rotation speed, 5.5 helical pitch, and 1-mm slice thickness, it took 20 sec to scan the area from the point below the dome of the liver to the lower border of the stomach (200-250 mm) [6-8]. Therefore, most patients could not hold their breath for 40 sec serially from the arterial phase (20 sec) to the venous phase (20 sec). However, using 16-MDCT with a 0.5-sec gantry rotation speed, 15 helical pitch, and 1-mm slice thickness, it took only 8 sec to scan the same area [9].
Takahashi et al. [12] reported that serial scanning of the dual-arterial phase of the liver during a single breath-hold and the early arterial phase using the test injection method (mean, 20 sec after the start of injection) was useful for CT arteriography and that the delayed arterial phase at 5 sec after the early arterial phase (mean, 38 sec after the start of injection) was useful for CT portography. However, scanning performed at the delayed arterial phase is a little too early to show the veins around the stomach (especially the RGEV, accessory right colic vein, and Henle's gastrocolic trunk, and so on that flow to the SMV) [12].
We considered that the venous phase may fall between the delayed arterial phase and the hepatic parenchymal phase (50-60 sec). Therefore, we attempted to obtain venous phase images (scan timing: 43 sec [range, 41-46 sec] after the start of injection) at 15-sec intervals after early arterial phase imaging during a single breath-hold (duration, 31 sec), which is commonly considered to be possible to perform [9]. All 20 patients were able to perform the respiratory hold continuously from the arterial phase to the venous phase. In addition, in all 20 patients, 3D CT venography clearly revealed the veins around the stomach, including the LCV, RGEV, Henle's gastrocolic trunk, and accessory right colic vein. The fused images of 3D CT arteriography and venography with no mismatch in the dual phase clearly showed the vascular anatomy around the stomach. This approach proved to be useful for allowing safe manipulation of the arterial origins and veins and dissection of the lymph nodes under laparoscopic guidance without incurring injury to the involved arteries and veins.
In conclusion, dual-phase 3D CTA using 16-MDCT clearly revealed individual arteries and veins around the stomach. Moreover, the fused images of the arteries and veins, which were obtained during a single breath-hold, enabled us to simultaneously assess the arteries and veins around the stomach before laparoscopic gastrectomy.
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