Ryoko Iwata

Chiba-East National Hospital, Tiba, Chiba, Japan

Are you Ryoko Iwata?

Claim your profile

Publications (34)79.33 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: To evaluate the clinical usefulness of dual-energy computed tomography (CT) with weighted-average (WA) images and iodine overlay (IO) images in the evaluation of laryngeal cartilage invasion in patients with laryngeal and hypopharyngeal squamous cell carcinoma (SCC). Materials and Methods: The institutional review board approved this retrospective study, and written comprehensive consent was obtained from all patients. Seventy-two consecutive patients underwent 128-section dual-source dual-energy CT to stage laryngeal (n = 27) or hypopharyngeal (n = 45) cancer. Three observers who were blinded to the patients' clinical histories and histopathologic findings evaluated cartilage invasion on WA images alone or in combination with IO images (nonossified cartilages were selectively evaluated on IO images) by using a five-point scale. Thirty of the 72 patients (42%) underwent surgery, and findings from histopathologic examination in those patients were used as the standard of reference for the evaluation of diagnostic performance with receiver operating characteristic (ROC) curve analysis and in terms of sensitivity and specificity. Interobserver reproducibility was calculated with κ statistics. Results: For thyroid cartilage, the area under the ROC curve (AUC) of the WA plus IO images was marginally larger than that for WA images alone (AUC = 0.957 vs 0.870, respectively; P = .075). The specificity of WA plus IO images was significantly superior to that of WA images alone (96% vs 70%, respectively; P = .031), with no compromise to the sensitivity (86% for both). For thyroid and cricoid cartilages, the interobserver reproducibility was higher for diagnoses made with WA plus IO images (κ = 0.68-0.72 and 0.64-0.79, respectively) than for those made with WA images alone (κ = 0.29-0.56 and 0.20-0.64, respectively). Conclusion: Combined analysis of WA and IO images obtained with dual-energy CT improves the diagnostic performance and interobserver reproducibility of evaluations of laryngeal cartilage invasion by SCC. © RSNA, 2012.
    Radiology 09/2012; 265(2):488-496. DOI:10.1148/radiol.12111719 · 6.21 Impact Factor
  • Kanzo 01/2008; 49(10):461-469. DOI:10.2957/kanzo.49.461
  • [Show abstract] [Hide abstract]
    ABSTRACT: A 69-year-old woman was referred to our hospital due to a liver tumor that was incidentally noted on ultrasound (US). US revealed a pedunculated mass of 5 cm in diameter, with a heterogeneous echo pattern. On arterial phase dynamic contrast-enhanced computed tomography (CT), a tiny enhancing dot in the upper aspect of the mass was seen; whereas, the main portion of the lesion appeared as hypoattenuating. The tumor was of low intensity on T1-weighted magnetic resonance (MR) images, and showed slightly heterogeneous high intensity on T2-weighted MR images. The most characteristic feature of the tumor was its exophytic appearance. On post-gadolinium hepatic arterial dominant-phase MR images, the tumor showed nodular enhancement centrally, with progressive spread of enhancement on later images. Angiography showed dilatation of the right posterior inferior branch of the hepatic artery and C-shaped opacification. Since we could not rule out malignancy for these nonspecific radiologic findings, a partial resection of the liver was carried out, resulting in a pathological diagnosis of hepatic hemangioma. This hemangioma had marked hyalinization and fibrosis, causing a heterogeneous appearance on MR images. The tumor presented an exophytic appearance, which caused some diagnostic confusion.
    Radiation Medicine 09/2005; 23(5):371-5.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Transcatheter arterial embolization induces marked antitumor response in patients with hepatocellular carcinoma, but the survival benefit of transcatheter arterial embolization remains to be determined. This study investigated prognostic factors in patients with advanced hepatocellular carcinoma treated by transcatheter arterial embolization. A total of 128 consecutive patients with non-resectable hepatocellular carcinoma, who had undergone transcatheter arterial embolization between May 1990 and August 1998, were analyzed to investigate prognostic factors. Median survival time and survival proportions at 1, 3 and 5 years were 3.3 years, 92.0, 54.6 and 23.4%, respectively. By multivariate analysis using the accelerated failure time model, age <60 years, hepatitis C virus antibody positivity, serum albumin >3.5 g/dl, absence of portal vein invasion and serum alpha-fetoprotein level <400 ng/ml were significantly associated with favorable survival. For clinical application, we also propose a prognostic equation with combination of specific prognostic factors, by which survival curves of each patient could be predicted directly. The findings of the current study may be helpful in predicting the life expectancy of hepatocellular carcinoma patients treated by transcatheter arterial embolization and in designing future clinical trials of transcatheter arterial embolization for hepatocellular carcinoma.
    Japanese Journal of Clinical Oncology 11/2002; 32(11):455-60. · 1.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To study the clinicopathologic characteristics of hepatic nodular lesions with high attenuation (increased portal blood flow) compared with surrounding hepatic parenchyma on computed tomography (CT) during arterial portography (CTAP). For six lesions found in six patients demonstrated as a high-attenuated mass by CTAP, CT during hepatic arteriography (CTHA; n = 3 patients), digital subtraction hepatic arteriography (n = 6) and conventional helical CT (n = 6) were evaluated retrospectively and compared with histopathologic findings (n = 4). Pathologic diagnosis was atypical adenomatous hyperplasia, nodule-in-nodule hepatocellular carcinoma (HCC) in one resected lesion each and overt HCC in two biopsied lesions. Two patients did not undergo any therapy and were followed up. The average size of lesions was 2.2 cm (range 1.2-3.5 cm). The CTAP revealed high attenuation in all six lesions; entirely within the lesion (n = 4 lesions) or peripherally with a central low attenuation (n = 2). In contrast, CTHA showed low attenuated lesions; entirely within the mass (n = 2) or peripherally with a central high-attenuated spot (n = 1). Hepatic arteriogram revealed only two hypervascular lesions; entirely and partially in one each. In the arterial phase of helical CT, all but one lesion were iso- or hypo-attenuated. In two patients who were followed up to 39 and 55 months without therapy, neither tumor growth nor hemodynamic change of the lesion was recognized on CT. Even though the incidence of hepatic nodular lesions demonstrated as high attenuating on CTAP is low, all but one lesion in the current series showed iso- or hypo-attenuation on CTHA and/or helical CT, suggesting the hemodynamics are reciprocal between CTAP and CTHA. One exceptional lesion that showed high attenuation on both CTAP and conventional CT was pathologically advanced HCC. Based on the follow-up study of two untreated patients, this kind of lesion with high attenuation on CTAP seems to grow slowly.
    Journal of Gastroenterology and Hepatology 08/2002; 17(7):779-84. DOI:10.1046/j.1440-1746.2002.02808.x · 3.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To obtain successful arterial chemoembolization for hepatocellular carcinoma (HCC), we evaluated the sensitivity of proximal arteriography, superselective (subsegmental or more distal branch) arteriography and computed tomography (CT) during superselective arteriography and assessed the method for the injection of contrast medium. Thirty-two patients with 38 HCCs (< or = 5 cm) with a mean diameter of 2.2 cm underwent digital subtraction arteriography of proximal and superselective arteriography. In addition, they also had helical CT during superselective arteriography. The contrast medium was injected with a mechanical injector (n = 6 lesions) or by hand (n = 32) for superselective arteriography and CT during superselective arteriography. The amount of contrast medium used for superselective arteriography and CT during superselective arteriography with the mechanical injector was 3.5 times and 9 times that with manual injection, respectively. Overall, 31 lesions (81.6%) were detected by proximal arteriography, 25 (65.8%) by superselective arteriography and 35 (92.1%) by CT during superselective arteriography. CT during superselective arteriography was significantly superior to superselective arteriography (P = 0.005). In both studies, manual injection of contrast medium had a significantly higher sensitivity than mechanical injection (P = 0.013). To detect small HCC, CT during superselective arteriography showed significantly higher sensitivity than superselective arteriography. Manual injection of contrast medium was significantly superior to mechanical injection. Therefore, manual injection CT during superselective arteriography is recommended for accurately targeted, transarterial chemoembolization therapy.
    Japanese Journal of Clinical Oncology 06/2002; 32(6):191-5. · 1.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Zinostatin stimalamer (SMANCS) is a lipophilic intra-arterial chemotherapeutic agent for hepatocellular carcinoma (HCC). In our previous study, transcatheter arterial infusion chemotherapy using SMANCS for HCC showed a response rate of 20%. In an effort to obtain a superior anti-tumor effect against HCC, we conducted a phase II study of transcatheter arterial embolization (TAE) using SMANCS and gelatin sponge in 50 chemotherapy-naive patients with HCC. Four milligrams SMANCS plus 4 ml lipiodol emulsion was injected into the hepatic artery, followed by an injection of gelatin sponge. The responses were evaluated by computed tomography (CT) 1 month after treatment and thereafter every 3-4 months. One patient (2%) showed complete response and 15 patients (30%) had partial response resulting in an overall response rate of 32% (16/50; 95% confidence interval 19-45%). In 33 patients (66%), the disease remained stable, and 1 patient (2%) showed progressive disease. In 35 patients (70%), the rate of necrotic area to whole tumor was more than 50% according to the evaluation method using lipiodol accumulation in CT. The 1-, 3- and 5-year survival rates were 90, 55 and 19%, respectively. Grade 3 hematological toxicity was observed as thrombocytopenia in 2 patients (4%). Grade 3 and 4 non-hematological toxicity (liver dysfunction) occurred in 17 (34%) and 7 patients (14%), respectively. TAE using SMANCS, which was well tolerated, may be an effective treatment for advanced HCC.
    Oncology 02/2002; 62(3):228-33. DOI:10.1159/000059570 · 2.61 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A better understanding of the growth rate of pancreatic carcinoma is important in determining its natural course and in evaluating the effects of treatment or prognosis. The authors studied the growth rate of pancreatic carcinoma and the relation between its tumor volume doubling time (TVDT) and host survival. Nine patients with pancreatic carcinoma who underwent serial examinations by helical computed tomography but no anticancer treatment during the observation period were included. The TVDTs were calculated by measuring the tumor size on the helical computed tomograms. The mean TVDT of the nine primary lesions of pancreatic carcinoma was 159 +/- 67 days (median, 144 days), and the range was 64 to 255 days. The correlation between TVDT and survival time was positive and significant (r = 0.793, p = 0.011). This preliminary study suggests that examination of TVDT may be useful in the clinical evaluation of prognosis for patients with pancreatic carcinoma in certain situations.
    Pancreas 06/2001; 22(4):366-9. DOI:10.1097/00006676-200105000-00005 · 3.01 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We evaluated computed tomography during arterial portography (CTAP) for the preoperative evaluation of liver metastases from pancreatic carcinoma. Thirty-one patients with invasive ductal carcinoma of the pancreas underwent CTAP for evaluation of liver metastasis. Diagnostic accuracy of CTAP was compared with that of intravenous contrast-enhanced CT (IVCT). In this series, both CTAP and IVCT showed the same diagnostic accuracy for the patients. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of both CT examinations for detecting liver metastases were 60% (three of five), 100% (26 of 26), 100% (three of three), 93% (26 of 28), and 94% (29 of 31), respectively. CTAP did not confer any advantage over IVCT for the preoperative evaluation of liver metastases from pancreatic carcinoma.
    Pancreas 04/2001; 22(2):200-2. DOI:10.1097/00006676-200103000-00015 · 3.01 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We assessed the local recurrence rate after a single targeted transarterial oily chemoembolization for small hepatocellular carcinoma with the unified helical CT and angiography system and analyzed the factors affecting the local recurrence rate and survival rate with Cox proportional hazards model. For 54 consecutive patients with 71 small hepatocellular carcinomas (< or = 5 cm) with no more than two associated lesions, targeted oily chemoembolization was performed with an emulsion of doxorubicin hydrochloride mixed with iodized oil or a suspension of zinostatin stimalamer followed by gelatin sponge particles. When local recurrence or a new lesion appeared, follow-up targeted oily chemoembolization was performed. For 52 of 71 lesions, the catheterization to a subsegmental or more distal feeding artery could be performed. Local recurrence was recognized in 33.2% at 1 year and 37.8% at 2 and 3 years. The significant factors that affected local recurrence were tumor size (p = 0.005) and degree of deposition of iodized oil within the lesion (p = 0.049). The survival rates at 1, 2, and 3 years were 93.3%, 77.1%, and 77.1%, respectively. The significant factors affecting survival rate were tumor thrombus in large vessels (p = 0.0001), appearing after the first chemoembolization, and maximum tumor size (p = 0.022). Single targeted transarterial oily chemoembolization with the unified helical CT and angiography system had a low local recurrence rate for small hepatocellular carcinoma, and follow-up embolization resulted in a good survival rate. Tumor size along with degree of intratumoral iodized oil deposition and tumor thrombus along with maximum tumor size were significant factors affecting local recurrence and survival rate, respectively.
    American Journal of Roentgenology 04/2001; 176(3):681-8. · 2.74 Impact Factor
  • American Journal of Roentgenology 03/2001; 176(3):681-688. DOI:10.2214/ajr.176.3.1760681 · 2.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the usefulness of right anterior oblique (RAO) arteriography for evaluating encasement of the right hepatic artery (RHA) by hilar cholangiocarcinoma. Celiac arteriography was performed in both the antero-posterior (AP) and RAO projection in ten patients with cholangiocarcinoma. The lengths of the arteries between the bifurcation of the anterior and posterior branch of the liver and the following points were measured: (a) the bifurcation of the left and right hepatic artery (AP-LR), (b) the bifurcation of the proper hepatic artery and the gastroduodenal artery (AP-PG). Additionally, image quality in investigating the invasion of the RHA was evaluated. On the AP images, the average lengths of AP-LR and AP-PG were 24.5 +/- 5.1 mm and 30.0 +/- 4.9 mm, respectively. On RAO images, the lengths were 28.2 +/- 4.6 mm and 32.7 +/- 4.8 mm, respectively. Every length was different between the two projections (p < 0.01). In 6 of 10 patients with hilar cholangiocarcinoma, images in RAO projections were superior to AP images for evaluation of encasement. We conclude that angiography obtained in the RAO projection yields images that are superior to those obtained in the conventional AP projection for assessment of RHA encasement.
    CardioVascular and Interventional Radiology 01/2001; 24(1):37-41. DOI:10.1007/s002700000392 · 1.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to compare CT with selective intraarterial contrast enhancement with IV contrast-enhanced CT for diagnostic usefulness in the detection of tumors in the pancreaticoduodenal region. intraarterial contrast enhanced CT was performed in 36 patients with tumors of the pancreaticoduodenal region. Feeding arteries of the tumors and distribution of hyperattenuating areas on intraarterial contrast-enhanced CT were analyzed with various routes of contrast material injections. The intraarterial contrast-enhanced CT scans were compared with the IV contrast-enhanced CT scans. In all 29 patients with standard vascular anatomy, the right cephalic portion of the pancreatic head was enhanced on CT during common hepatic or gastroduodenal arteriography and the left caudal portion was enhanced on CT during superior mesenteric arteriography. The enhanced areas were complementary to each other in the whole pancreatic head, including the tumor. Tumor conspicuity from the surrounding pancreatic tissue on intraarterial contrast-enhanced CT was not superior to that on IV contrast-enhanced CT in all but four patients with cystic tumors. After intraarterial contrast-enhanced CT, three patients with tumors less invasive than pancreatic ductal carcinoma underwent local resection of their lesions. Intraarterial contrast-enhanced CT for pancreaticoduodenal tumors has potential technical problems and is not valuable in improving the detectability of tumors other than cystic lesions because the enhancement of the wall and septa of the tumor is emphasized. However, the feeding artery of the tumor and its surrounding tissue were clearly depicted.
    American Journal of Roentgenology 08/2000; 175(1):91-7. · 2.74 Impact Factor
  • Surgery 07/2000; 127(6):711-2. DOI:10.1067/msy.2000.104485 · 3.11 Impact Factor
  • American Journal of Roentgenology 07/2000; 175(1):91-97. DOI:10.2214/ajr.175.1.1750091 · 2.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Transcatheter arterial embolization (TAE) has been widely performed for patients with hepatocellular carcinoma (HCC). However, the method of evaluating the therapeutic effect of TAE has not been established. We examined the rate of necrotic area to whole tumor (TN) by CT, the tumor regression rate (TR) and the reduction rate in serum alpha-fetoprotein (AFP) levels in patients with HCC who received hepatic resection within 3 months after TAE. In the evaluation of TN, the lipiodol accumulation in tumor was regarded as being necrotic. Rates of necrotic area, which were also examined pathologically (PN) in resected tumors, were compared with TN, TR and AFP reduction rates, respectively. Eighty-eight patients were enrolled in this study, and there was a significant positive correlation between TN and PN (r = 0.80, p < 0.001). Although TR significantly correlated to PN (p = 0.001), the correlation coefficient between them was low (r = 0.34). The correlation coefficients between AFP reduction rate and PN was 0.76 (p < 0.001) in 26 patients (30%) with an AFP level >/=200 ng/ml before TAE. The evaluation method using lipiodol accumulation in CT is the most useful for assessing the therapeutic effect of TAE, particularly when a sufficiently long interval exists between TAE and the evaluation, because of the highest correlation coefficient between TN and PN, and the availability of TN for all patients. The reduction rate in serum AFP levels was also useful in patients with AFP levels >200 ng/ml before treatment.
    Oncology 06/2000; 58(4):293-9. DOI:10.1159/000012115 · 2.61 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Blood supply to the peripancreatic region is derived from the celiac and superior mesenteric arteries, complementary to each other. Cohort analytic study. Tertiary care public hospital. Computed tomography (CT) during superior mesenteric artery arteriography (SMAA-CT) and during celiac artery arteriography (CEAA-CT), in which a catheter tip was inserted into the common hepatic or gastroduodenal artery, was performed in 25 patients. Distribution and correlation of these areas of marked enhancement on SMAA-CT and CEAA-CT were analyzed. The right cephalic part of the pancreatic head that is derived from the dorsal bud was enhanced on CEAA-CT, and the left caudal part of the pancreatic head that is derived from the ventral bud was enhanced on SMAA-CT. Blood supply to the intrapancreatic bile duct, including the ampulla of Vater, is derived from the CEA. The boundary between the areas of the duodenum supplied from the CEA and SMA was in the second or third portion. The pancreatic head can be separated into 2 segments by the arterial supply, and each segment may be removed separately.
    Archives of Surgery 11/1999; 134(10):1086-90. · 4.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate haemodynamic and vascular changes in non-alcoholic (viral) cirrhosis on conventional computed tomography (CT), CT arteriography (CTA) and CT arterial portography (CTAP), and to determine the cause of the observed reticular stain on angiography. Using surgically resected liver specimens from 31 patients with viral hepatitis associated hepatocellular carcinoma, images of conventional CT, CTA, CTAP and the sinusoidal phase of hepatic arteriography were retrospectively analysed and compared with pathology of the non-cancerous portion of the liver. Computed tomography arteriography showed inhomogeneous enhancement (diffuse, low-density nodules) in a total of 16 samples (52%); in eight of 10 (80%) cirrhotic livers, three of six (50%) precirrhotic livers, five of 12 (42%) livers with chronic active hepatitis and none of three with no active liver disease. The frequency of inhomogeneous enhancement became significantly higher with increasing severity of parenchymal damage (P < 0.05). In contrast, conventional CT and CTAP showed homogeneous enhancement in all 31 (100%) patients. There was no correlation between inhomogeneous enhancement on CTA and reticular staining on sinusoidal-phase hepatic angiograms. Inhomogeneous enhancement was frequently seen in patients with hepatitis B surface antigen and/or anti-hepatitis C virus antibody compared with those without them (P < 0.05). The CTA was much more sensitive in detecting haemodynamic changes in the cirrhotic liver than CTAP, conventional CT and sinusoidal-phased hepatic angiography. Further study is required to clarify the mechanism of inhomogeneous enhancement on CTA and homogeneous enhancement on CTAP seen in cirrhosis.
    Journal of Gastroenterology and Hepatology 10/1999; 14(9):908-14. DOI:10.1046/j.1440-1746.1999.01957.x · 3.63 Impact Factor
  • Source
    American Journal of Roentgenology 04/1999; 172(3):659-60. DOI:10.2214/ajr.172.3.10063855 · 2.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To demonstrate the helical computed tomographic (CT) features of small polypoid lesions of the gallbladder and to establish a clinical strategy based on CT findings for the treatment of such lesions. Validation cohort study. Tertiary care public hospital. Thirty-one patients with polypoid lesions of the gallbladder (< or = 3 cm) underwent CT followed by resection. The detectability of the lesions on both unenhanced and enhanced CT and the configuration of the lesions on enhanced CT were prospectively evaluated in comparison with the histopathological findings. Unenhanced CT detected 14 (45%) of the 31 lesions, whereas enhanced CT detected all of the lesions. The detection rates of the neoplastic lesions (adenoma, adenocarcinoma, and metastatic tumor) and cholesterol polyps were 81% (13/16) and 7% (1/15), respectively (P<.001). Among the 20 lesions demonstrated as pedunculated, 6 (30%) were neoplastic, whereas 10 (91%) of the 11 lesions demonstrated as sessile were neoplastic (P<.001). When a lesion was demonstrated on unenhanced CT or its shape was sessile on enhanced CT, the case was diagnosed as a neoplastic lesion. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of the CT diagnosis of the neoplastic lesions were 88% (14/16), 87% (13/15), 88% (14/16), 87% (13/15), and 87% (27/31), respectively. Computed tomography can differentiate neoplastic and nonneoplastic small polypoid lesions of the gallbladder and reliably identify the presence of neoplastic lesions that should be resected.
    Archives of Surgery 07/1998; 133(7):735-9. DOI:10.1001/archsurg.133.7.735 · 4.30 Impact Factor