論文ID: 2017-04
Endoscopic ultrasonography (EUS) plays a major role in diagnosing gallbladder (GB) cancer and pancreatic cancer (PC). In cases of GB cancer, EUS allows for precise observations of morphology and wall layers. However, proficiency is required for the morphologic diagnosis of GB tumors. Therefore, contrast-enhanced harmonic EUS (CH-EUS) began to be performed to diagnose GB lesions. CH-EUS enables real-time observation of the hemodynamics of GB tumors. The enhanced patterns generated by CH-EUS improve precision in the diagnosis of such tumors.PC appears as a hypoechoic mass on EUS. However, distinguishing between PC and mass-forming pancreatitis or focal autoimmune pancreatitis (AIP) is difficult via conventional EUS. CH-EUS allows for differentiating among these diseases (PC is hypoenhanced and heterogeneously enhanced, pancreatitis is isoenhanced, and a pancreatic neuroendocrine tumor is hyperenhanced). EUS-guided fine needle aspiration (EUS-FNA) also contributes to pathological diagnoses of pancreatic lesions. However, certain PC patients cannot be diagnosed via EUS-FNA. PC is heterogeneously enhanced on CH-EUS, and unenhanced regions have been reported to be areas of fibrosis or necrosis. CH-EUS-guided fine needle aspiration (CH-EUS-FNA) permits puncturing of the enhanced area while avoiding necrotic and fibrotic regions. Moreover, as CH-EUS findings have been quantitatively analyzed, a time-intensity curve (TIC) has become usable for diagnosing solid pancreatic lesions. CH-EUS-related techniques have been developed and increasingly utilized in the pancreaticobiliary area.
Biliary tract cancer and pancreatic cancer (PC) have poor prognoses. More precise methods for diagnosing these diseases were desired. Endoscopic ultrasonography (EUS) has played an important role in diagnosing gallbladder (GB) cancer and PC1-5). However, when EUS is used, GB cancer must be diagnosed morphologically, and it is difficult to differentiate between pancreatic inflammatory tumor-like lesions and PC6,7).
Recently, contrast-enhanced harmonic EUS (CH-EUS) was reported to be useful in diagnosing pancreaticobiliary diseases8-27). In this report, we describe the efficacy of CH-EUS in diagnosing GB cancer and PC, including in experiments at our institution.
Ultrasound contrast agents have been classified based on their ability to cross the pulmonary arterial bed and their motion under an ultrasound beam with a low mechanical index (MI) (Table 1)28).
Historically, Levovist (Schering, Berlin, Germany) was widely used for contrast-enhanced abdominal ultrasonography. Levovist features air surrounded by a galactose shell. When Levovist is used, enhanced images are created from harmonic signals received when microbubbles are destroyed by high MI ultrasound. Therefore, for continued observation, contrast agents must be repeatedly injected and destroyed.
However, second-generation contrast agents are used today. In particular, SonoVue (Bracco, Milan, Italy) and Sonazoid (GE Healthcare, Little Chalfont, United Kingdom) have been used for pancreaticobiliary CH-EUS. These microbubbles of contrast agents resonate under low MI ultrasound without being destroyed. Thus, second-generation contrast agents have allowed for the prolonged observation of enhancement effects.
Ultrasound contrast agents
MI, Mechanical index
In our hospital, the endoscopes and ultrasonic equipment used for CH-EUS are GF-UCT260 and GF-UE260 ultrasound gastrovideoscopes (Olympus Medical Systems, Tokyo, Japan), the ProSound α-10 ultrasound system (Aloka, Tokyo, Japan), and the EU-ME2 ultrasound processor (Olympus Medical Systems, Tokyo, Japan). Ideally, patients are adequately sedated with midazolam or another agent prior to endoscope insertion. After target lesions are visualized on the monitor in the B and extended pure harmonic detection (ExPHD) modes, 0.015 mL/kg of the contrast medium (16 µg of Sonazoid in 2 mL of distilled water) is injected. Subsequently, the target lesions are evaluated in the arterial and early venous phases that occur approximately 90 seconds after these lesions are enhanced15,29).
Several investigators have previously described the superiority of EUS relative to abdominal ultrasonography (US) for diagnosing neoplastic GB lesions (adenomas and adenocarcinomas)1,2,30,31). However, these reports did not intend to imply that EUS can only be used to diagnose GB adenocarcinomas. The efficacy of CH-EUS for diagnosing GB malignant lesions has also been reported. In 1997 and 1998, Hirooka et al.8,10) observed that the visualization of GB adenocarcinoma was enhanced by the contrast medium Albunex, a first-generation enhancing agent (Table 1). In those studies, 11 GB adenocarcinoma patients (91.7%) exhibited enhancement effects, but such effects were not observed for patients with adenosquamous carcinoma or cholesterol polyps.
Recently, the differentiation of GB lesions via CH-EUS with second-generation enhancing agents (SonoVue or Sonazoid) has been reported. In these reports, GB polyps were diagnosed based on enhanced patterns.
Choi et al.13) and Park et al.14) described the efficacy of CH-EUS with the contrast medium SonoVue. Choi et al.13) reported that irregular vessels observed via CH-EUS were useful in the diagnosis of malignant polyps, with a sensitivity and a specificity of 90.3% and 96.6%, respectively. Furthermore, perfusion defects observed via CH-EUS could be used to efficiently diagnose malignant polyps, with a sensitivity and a specificity of 90.3% and 94.9%, respectively. In addition, when using SonoVue and the same procedures, Park et al.14) found that 80% (8/10) of GB adenocarcinomas were heterogeneously enhanced and that 75% of GB adenomas (6/8) were homogeneously enhanced.
In Japan, Sonazoid is used as the second-generation contrast agent for EUS for pancreaticobiliary or other abdominal diseases11,15,24-26,32-35). Imazu et al. performed CH-EUS with Sonazoid and reported finding inhomogeneously enhanced patterns that indicated malignant GB wall thickening. In that report, the sensitivity, specificity and accuracy for conventional EUS vs CH-EUS for diagnosing malignant GB wall thickening were 83.3% vs 89.6%, 65.0% vs 98.0% (p<0.001) and 73.1% vs 94.4% (p<0.001), respectively. Specificity and accuracy for GB wall thickening were significantly higher for CH-EUS than for conventional EUS. We retrospectively reviewed the efficacy of CH-EUS for diagnosing large (>10 mm) malignant and benign GB-protruding lesions17). In that review, the sensitivity, specificity, and malignant accuracy of CH-EUS were 100% (7/7), 94.1%, (16/17) and 95.8% (23/24), respectively. Cases treated at our hospital are presented in Figure 1.
Enhanced pattern of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) for gallbladder (GB) lesions.
A. GB cancer was detected in a B-mode image.
B. After contrast agent (Sonazoid) injection, GB cancer was enhanced heterogeneously in an extended pure harmonic detection (ExPHD)-mode image.
C. GB adenoma was detected in a B-mode image.
D. After contrast agent (Sonazoid) injection, GB adenoma was enhanced homogeneously in an ExPHD mode image.
E. GB cyst was detected in a B-mode image.
F. After contrast agent (Sonazoid) injection, a GB cyst was not enhanced in an ExPHD-mode image.
CH-EUS using SonoVue or Sonazoid has been used to diagnose solid pancreatic lesions (SPLs)18,19,21,24,26,27,36). CH-EUS can be utilized to clearly visualize SPL microvasculature and blood flow of the pancreatic parenchyma. PC has been observed as a hypoenhanced heterogeneous tumor on CH-EUS18,19,24,26,27) (Figure 2).
In 2008, Kitano et al. reported that on CH-EUS with SonoVue, hypovascular and heterogeneous images were observed for 80% (4/5) of malignant pancreatic lesions and isovascular images were observed for 100% (3/3) of pancreatitis lesions18). In 2010, Fusaroli et al. stated that hypoenhanced and inhomogeneous images on CH-EUS with Sono-Vue were a good identifier for diagnosing pancreatic adenocarcinoma. In 2014, Park et al. found that 57 out of 62 pancreatic adenocarcinomas produced hypoenhanced images on CH-EUS with Sono-Vue, which had a sensitivity of 92%, a specificity of 68% and an accuracy of 82%27).
In 2012, Kitano et al. described findings obtained when using CH-EUS with Sonazoid to assess small (≤2 cm in diameter) SPLs26). In this report, small pancreatic ductal carcinomas (n=67) appeared as hypoenhanced lesions, and the sensitivity and specificity of the tested imaging approach were 91.2% and 94.4%, respectively. This approach was superior to multidetector-row computed tomography (which had a sensitivity of 70.6% and a specificity of 91.9%). Furthermore, these researchers reported sensitivities of 90.6% and 92.2% for CH-EUS and EUS-guided fine needle aspiration (EUS-FNA), respectively, in patients who underwent surgical resection of tumors (n=91), although sensitivity increased to 100% if findings for both procedures were considered.
EUS-FNA is used to collect biopsy samples from many organs throughout the digestive tract and is useful for diagnosing SPLs37-40). The reported diagnostic accuracy, sensitivity, and specificity of EUS-FNA for SPLs are 85-89.4%, 82-94.7%, and 100%, respectively41-43). However, certain SPL patients could not be diagnosed via EUS-FNA. In 2015, Hou et al. described findings obtained using CH-EUS-FNA with Sono-Vue44). They punctured SPLs after they had confirmed these lesions’ enhanced patterns and retrospectively analyzed 58 cases involving CH-EUS-FNA and 105 cases involving EUS-FNA. Sufficient biopsy specimens were more frequently obtained in the CH-EUS group (96.6%) than in the EUS-FNA group (86.7%).
As mentioned above, PC appears as hypoenhanced heterogeneous tumors on CH-EUS. Unenhanced areas reportedly reflect necrosis and fibrosis45). Therefore, we performed CH-EUS-FNA by puncturing the enhanced region of SPLs33) (Figure 2). In our report, sufficient biopsy samples were obtained with a single needle pass for 60% (12/20) of the CH-EUS-FNA group compared with 25% (5/20) of the conventional EUS-FNA group (P=0.027). In many cases, when EUS-FNA is performed, four needle passes are needed to obtain sufficient biopsy samples46). In all reports about pancreatic tumor seeding associated with EUS-FNA, multiple needle punctures were performed47-51). CH-EUS-FNA is expected to require a minimal number of needle passes.
Enhanced pattern of pancreatic cancer (PC) on contrast-enhanced harmonic EUS (CH-EUS) and CH-EUS-guided fine needle aspiration (CH-EUS-FNA).
A. PC was imaged using B mode.
B. (Left: B mode; right: extended pure harmonic detection (ExPHD) mode) CH-EUS was performed and visualized using ExPHD mode. PC was hypoenhanced and enhanced heterogeneously on CH-EUS.
C. (Left: B mode; right: ExPHD mode) Fine needle aspiration was performed in the enhanced region of PC.
In the reports described above, enhanced patterns were judged subjectively. However, as CH-EUS findings for SPLs have been subjected to objective quantitative analyses, a time-intensity curve (TIC) has been determined.
In 2011, Matsubara et al. observed that the rate of echo intensity reduction from the peak at one minute was greatest for PC, followed by mass-forming pancreatitis, autoimmune pancreatitis (AIP), and pancreatic neuroendocrine tumors24). The reported sensitivity, specificity, and accuracy of EUS with a TIC were 95.8%, 92.6%, and 94.7%, respectively. In 2012, Imazu et al. reported that peak intensity and maximum intensity gain were significantly higher for AIP than for PC25).
In 2015, Saftoiu et al. described TIC analysis with an artificial neural network classification model for diagnosing PC and chronic pancreatitis52). The sensitivity, specificity, positive predictive value, and negative predictive value for this approach were 94.64%, 94.44%, 97.24%, and 89.4%, respectively.
CH-EUS has been reported to be extremely effective in the diagnosis of pancreaticobiliary diseases. The combination of CH-EUS with EUS-FNA recently began being utilized; furthermore, techniques to quantitatively evaluate enhancement effects, such as determination of a TIC, have been performed. Procedures related to CH-EUS play a major role in the pancreaticobiliary field.
