Seo-Youn Choi

Shear-Wave Elastography: A Noninvasive Tool for Monitoring Changing Hepatic Venous Pressure Gradients in Patients with Cirrhosis

PURPOSE To investigate whether liver stiffness ( LS liver stiffness ) and change in LS liver stiffness measurements ( ΔLS change in LS ) at shear-wave elastography ( SWE shear-wave elastography ) correlates with the hepatic venous pressure gradient ( HVPG hepatic venous pressure gradient ) and to assess the feasibility of using SWE shear-wave elastography to estimate the change in HVPG hepatic venous pressure gradient ( ΔHVPG change in HVPG ) in patients with portal hypertension. MATERIALS AND METHODS Institutional review board approval was obtained, with waiver of informed consent. Between September 2010 and October 2012, 97 consecutive patients who were given a diagnosis of portal hypertension on the basis of HVPG hepatic venous pressure gradient measurement were included. Among these patients, 23 who underwent follow-up HVPG hepatic venous pressure gradient measurement to evaluate response to treatment were included in the follow-up group. The correlation between HVPG hepatic venous pressure gradient and LS liver stiffness was analyzed by using the Pearson correlation test. In the follow-up group, whether ΔHVPG change in HVPG was correlated with ΔLS change in LS was also evaluated. Thereafter, the areas under the receiver operating characteristic curves ( AUC area under the ROC curve s) were calculated to determine the diagnostic performances of ΔLS change in LS and the second LS liver stiffness measurement after medical treatment and to compare their performances in association with clinical improvement and aggravation of portal hypertension. RESULTS LS liver stiffness was moderately correlated with HVPG hepatic venous pressure gradient (r = 0.593) in the single-measurement group. There was also a strong correlation between ΔLS change in LS and ΔHVPG change in HVPG (r = 0.863). At comparison of the second LS liver stiffness measurement, ΔLS change in LS showed no significant difference in AUC area under the ROC curve in patients with improvement (0.627 vs 0.794, P = .201) but showed higher AUC area under the ROC curve in association with aggravation of portal hypertension (0.925 vs 0.611, P = .026). CONCLUSION Estimating ΔHVPG change in HVPG by using SWE shear-wave elastography may be useful in patients with cirrhosis and portal hypertension.

Radiofrequency ablation of very-early-stage hepatocellular carcinoma inconspicuous on fusion imaging with B-mode US: value of fusion imaging with contrast-enhanced US

Background/Aims To determine the value of fusion imaging with contrast-enhanced ultrasonography (CEUS) and computed tomography (CT)/magnetic resonance (MR) images for percutaneous radiofrequency ablation (RFA) of very-early-stage hepatocellular carcinomas (HCCs) that are inconspicuous on fusion imaging with B-mode ultrasound (US) and CT/MR images. Methods This retrospective study was approved by our institutional review board and the requirement for informed consent was waived. Fusion imaging with CEUS using Sonazoid contrast agent and CT/MR imaging was performed on HCCs (<2 cm) that were inconspicuous on fusion imaging with B-mode US. We evaluated the number of cases that became conspicuous on fusion imaging with CEUS. Percutaneous RFA was performed under the guidance of fusion imaging with CEUS. Technical success and major complication rates were assessed. Results In total, 30 patients with 30 HCCs (mean, 1.2 cm; range, 0.6-1.7 cm) were included, among which 25 (83.3%) became conspicuous on fusion imaging with CEUS at the time of the planning US and/or RFA procedure. Of those 25 HCCs, RFA was considered feasible for 23 (92.0%), which were thus treated. The technical success and major complication rates were 91.3% (21/23) and 4.3% (1/23), respectively. Conclusions Fusion imaging with CEUS and CT/MR imaging is highly effective for percutaneous RFA of very-early-stage HCCs inconspicuous on fusion imaging with B-mode US and CT/MR imaging.

Preoperative Detection of Small Pancreatic Carcinoma: Value of Adding Diffusion-weighted Imaging to Conventional MR Imaging for Improving Confidence Level

PURPOSE To evaluate the benefit of adding diffusion-weighted ( DW diffusion weighted ) imaging to conventional magnetic resonance (MR) imaging in the preoperative detection of small pancreatic adenocarcinoma (≤ 3.0 cm). MATERIALS AND METHODS The institutional review board approved this retrospective study and waived the requirement for informed consent. This study included 83 patients (56 men, 27 women) with surgically confirmed pancreatic adenocarcinoma of 3.0 cm or smaller and 12 patients (nine men, three women) with histologically proven focal pancreatitis who underwent gadoxetic acid-enhanced MR imaging and DW diffusion weighted imaging at 3.0 T. Two observers reviewed the two image sets, a conventional MR image set and a combined image set including DW diffusion weighted images, to evaluate tumor conspicuity using receiver operating characteristic curve analysis. Contrast ratios between the tumor and proximal or distal pancreas on T1- and T2-weighted images, arterial and portal phase images, and DW diffusion weighted images obtained with a b value of 800 sec/mm(2) were compared by using one-way analysis of variance or Kruskal-Wallis test. RESULTS On DW diffusion weighted images, all tumors but two were delineated as completely (32 of 83, 39%) or partially (49 of 83, 59%) hyperintense. Area under the receiver operating characteristic curve values for the two observers were 0.890 and 0.884 for the conventional image set and 0.976 and 0.978 for the combined image set (P = .01 and P = .04), respectively. In regard to tumor detection, the combined image set (98%, 81 of 83 [observer 1]; 96%, 80 of 83 [observer 2]) yielded better sensitivity than the conventional image set (75%, 62 of 83 [observer 1]; 76%, 63 of 83 [observer 2]) (P < .001). Contrast ratios of tumor to proximal or distal pancreas were significantly higher with DW diffusion weighted images than with other images (P < .001). CONCLUSION In preoperative evaluation of small pancreatic adenocarcinoma, the addition of DW diffusion weighted imaging to conventional MR imaging improves the sensitivity of cancer detection.

Mistargeting after Fusion Imaging–Guided Percutaneous Radiofrequency Ablation of Hepatocellular Carcinomas

PURPOSE To evaluate the incidence and causes of mistargeting after fusion imaging-guided percutaneous radiofrequency (RF) ablation of hepatocellular carcinomas (HCCs). MATERIALS AND METHODS Between September 2011 and March 2013, 955 HCCs in 732 patients were treated with percutaneous RF ablation. Among them, ablation of 551 HCCs was accomplished under fusion imaging guidance, and seven mistargetings were noted in seven patients (male-to-female ratio = 6:1; mean age, 60.1 y; range, 47-73 y). The incidence of mistargeting and the cause of liver disease in the patients with mistargeting were evaluated. The causes of mistargeting were assessed according to the following classification: small size of HCC, subcapsular location, subphrenic location, confusion with pseudolesions, poor conspicuity of HCC, poor sonographic window, and poor electrode path. RESULTS The incidence of mistargeting after fusion imaging-guided RF ablation was 1.3% (7 of 551). All patients with mistargeting were hepatitis B virus carriers. The most common cause of mistargeting was the small size of HCC (100%; 7 of 7), followed by confusion with surrounding pseudolesions (85.7%; 6 of 7), subcapsular (71.4%; 5 of 7) and subphrenic locations (71.4%; 5 of 7), poor conspicuity of the HCC (71.4%; 6 of 7), poor sonographic window (28.6%; 2 of 7), and poor electrode path (28.6%; 2 of 7). CONCLUSIONS The incidence of mistargeting after fusion imaging-guided RF ablation was 1.3%. The most common cause of mistargeting was the small size of HCC, followed by confusion with surrounding pseudolesions, subcapsular and subphrenic locations, and poor conspicuity of the HCC.

A novel electrode with electromagnetic tip tracking in ultrasonography-guided radiofrequency ablation: a phantom, ex vivo, and in vivo experimental study.

ObjectivesThe objective of this study was to compare the targeting and ablation performance between a newly developed radiofrequency (RF) electrode embedded with an electromagnetic position sensor (EMPS) at the electrode tip and a conventional RF electrode. Materials and MethodsThe institutional animal care and use committee approved this study. The targeting of paint balls within phantoms was performed under ultrasonography guidance by 2 radiologists (beginner vs expert) with an “in-plane” and “out-of-plane” approaches using the new RF electrode and a conventional RF electrode (n = 20 for each method). To evaluate the targeting performance, the electrode placement time and the number of electrode pullbacks for redirection were compared between the 2 electrodes. The ablation performance was also compared by analyzing the ablation volumes in ex vivo bovine and in vivo porcine livers (n = 30 and n = 24, respectively) and the cellular viability of the ablation zone in in vivo specimens. ResultsIn the phantom study, the RF electrode embedded with an EMPS showed a significantly shorter electrode placement time compared with the conventional RF electrode in both the in-plane and out-of-plane approaches by both radiologists (P < 0.05). The electrode pullback rate for both radiologists was lower in the new RF electrode than in the conventional RF electrode, but it did not reach statistical significance in the in-plane approach by the expert (P = 0.059). The ablation volumes analyzed with and without cellular viability in the ex vivo and in vivo studies were not significantly different between the 2 electrodes (P > 0.05). ConclusionsThe RF electrode embedded with an EMPS is faster than the conventional electrode in the electrode placement into the target lesions. The ablation performance is not significantly different between the 2 electrodes.

Local tumour progression after loco-regional therapy of hepatocellular carcinomas: Value of fusion imaging-guided radiofrequency ablation

AIM To assess the value of fusion imaging of real-time ultrasonography (US) with liver computed tomography (CT)/magnetic resonance imaging (MRI) images for planning US of radiofrequency ablation (RFA) in improving conspicuity of the lesions and reducing false-positive detection of local tumour progression (LTP) found after transcatheter arterial chemoembolization (TACE) or RFA of hepatocellular carcinoma (HCC). MATERIALS AND METHODS This study was approved by the institutional review board and informed consent was waived. Fifty patients with LTP (mean ± SD, 1.5 ± 0.6 cm; range 0.5-3 cm) detected at follow-up CT or MRI were included. Planning US was performed by two radiologists using conventional US first and fusion imaging later in the same session. False-positive detection rates were assessed using conventional US based on the results of fusion imaging. The number cases of initially invisible tumours on conventional US that became visible after image fusion were also evaluated. The true-positive detection rate and conspicuity scores of the index tumours were compared between conventional US and fusion imaging. RESULTS On conventional US, 40 (80%) out of 50 HCCs with LTP were identified. However, the false-positive detection rate of conventional US was 12.5% (5/40). Out of 10 initially invisible HCCs with LTP on conventional US, six (60%) became visible after image fusion. The true-positive detection rate on conventional US was 70% (35/50), whereas it was increased to 92% (46/50) after image fusion (p = 0.0026). CONCLUSION Fusion imaging can improve the conspicuity of lesions and reduce the false-positive detection of LTP after TACE or RFA.

Imaging Features of Gadoxetic Acid–enhanced and Diffusion-weighted MR Imaging for Identifying Cytokeratin 19-positive Hepatocellular Carcinoma: A Retrospective Observational Study

Purpose To determine the preoperative magnetic resonance (MR) imaging findings potentially most useful for predicting cytokeratin 19 (CK19)-positive hepatocellular carcinoma (HCC) and to evaluate the prognosis after curative resection in patients with a single HCC lesion positive for CK19 compared with patients with HCC who are negative for CK19. Materials and Methods The institutional review board approved this study and waived the requirement for informed consent. Two hundred four patients with CK19-negative HCC and 38 with CK19-positive HCC who underwent curative resection after gadoxetic acid-enhanced and diffusion-weighted MR imaging were retrospectively evaluated in a single institution. Two radiologists evaluated preoperative findings at MR imaging. Significant findings for differentiating the two groups were identified at univariate and multivariate analyses. By using receiver operating characteristic analysis, the optimal cut-off values for quantitative variables were determined. Recurrence-free survival rates after surgery were also compared between groups. Results At multivariate analysis, irregular tumor margin (P = .024), arterial rim enhancement (P < .001), lower tumor-to-liver signal intensity (SI) ratio on hepatobiliary phase (HBP) images (≤0.522; P = .01), and lower tumor-to-liver apparent diffusion coefficient (ADC) ratio (≤0.820; P < .001) were independent significant factors to predict CK19-positive HCC. When three of these four criteria were combined, 63.2% (24 of 38; 95% confidence interval: 46.0%, 78.2%) of CK19-positive HCCs were identified with a specificity of 90.7% (185 of 204; 95% confidence interval: 46.0%, 78.2%). When all four criteria were satisfied, specificity was 99.5% (203 of 204; 95% confidence interval: 97.3%, 100%). Recurrence-free survival rates were significantly lower in patients with CK19-positive HCCs compared with those with CK19-negative HCCs after curative resection (63.9% vs 90.0% at 1 year, 63.9% vs 79.9% at 2 years, and 54.8% vs 70.2% at 3 years, P = .001 by log-rank test). Conclusion At gadoxetic acid-enhanced and diffusion-weighted MR imaging, irregular margin, arterial phase rim enhancement, lower tumor-to-liver ADC ratio, and lower tumor-to-liver SI ratio at HBP imaging may be helpful to predict CK19-positive HCC with early recurrence (<2 years) after curative resection.

Iterative reconstruction: comparison of techniques for reduced-dose liver computed tomography following transarterial chemoembolization for hepatocellular carcinoma

Background Adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) algorithms have the potential to reduce dose while maintaining image quality. Purpose To compare computed tomography (CT) image quality and diagnostic performance among three reconstruction techniques – ASIR, MBIR, and filtered back projection (FBP) – after transcatheter arterial chemoembolization (TACE) of hepatocellular carcinomas (HCC). Material and Methods Of 60 patients that underwent initial TACE for HCCs, half underwent dynamic liver CT with conventional scanning protocol, and the other half with dose reduction to approximately 60% of conventional exposure. All images were reconstructed using three algorithms: FBP, ASIR, and MBIR. For objective analysis, image noise and signal-to-noise ratio (SNR) were compared. For subjective analysis, three radiologists independently assessed image quality. Ability to detect viable HCCs was also evaluated. Results MBIR and ASIR produced images with less noise and higher SNR compared with FBP regardless of radiation dosage (P < 0.017). However, in terms of subjective parameters, such as image blotchiness, artifacts, and overall quality, MBIR was inferior to FBP and ASIR (P < 0.001). Regarding diagnostic performance, there were no significant differences among reviewers in the detection of viable HCCs depending on the reconstruction algorithm, regardless of the dose reduction protocol (P > 0.017). Conclusion Although subjective evaluations suggest that MBIR images are of lower quality compared with FBP and ASIR regardless of radiation dosage, there were no significant differences among reconstruction algorithms in diagnosis of viable HCC after TACE.

The value of contrast-enhanced dynamic and diffusion-weighted MR imaging for distinguishing benign and malignant splenic masses

OBJECTIVE To assess the value of contrast-enhanced dynamic and diffusion-weighted (DW) MR imaging for differentiating malignant from benign splenic lesions. METHODS This retrospective study included 51 patients with 35 benign and 16 malignant focal splenic lesions. All patients underwent contrast-enhanced dynamic and DW MR imaging. Two radiologists evaluated the MR images in consensus. Significant imaging findings on univariate and multivariate analyses were identified and their diagnostic performance for predicting the malignant splenic lesion was analyzed. Using receiver-operating characteristic analysis, the optimal cut-off of the apparent diffusion coefficient (ADC) value corresponding to the maximal Youdens index (J) for differentiating the two groups was determined. RESULTS In univariate analysis, low signal intensity (SI) on the arterial, portal and 3-min delayed-phase images, high or iso SI on the DW image, iso or low SI on the ADC map, the presence of diffusion restriction and arterial hypovascularity with a progressive enhancement pattern were more frequently observed (p < 0.05) in malignant splenic lesions. The ADC value was significantly lower for malignancy than for benignancy (0.78 ± 0.24 vs 1.16 ± 0.53 × 10(-3) mm(2) s(-1); p < 0.001). The optimal cut-off ADC value for differentiating the two groups was 0.995 × 10(-3) mm(2) s(-1). In multivariate analysis, findings that differentiated malignant from benign splenic lesions were low SI on the 3-min delayed-phase image [odds ratio (OR), 27.68; p = 0.006] and the presence of diffusion restriction (OR, 48.01; p = 0.002). When two of these criteria were combined, 12 (75.0%) of 16 malignant splenic masses were identified with a specificity of 100%. CONCLUSION Contrast-enhanced dynamic and DW MR imaging may be helpful for differentiating malignant from benign splenic lesions. A low SI on the 3-min delayed phase and diffusion restriction are the most reliable findings for the differentiation of malignant from benign splenic lesions. ADVANCES IN KNOWLEDGE Dynamic and DW MR imaging help in distinguishing malignant from benign splenic lesions. A low SI on the 3-min delayed phase and diffusion restriction are the most reliable findings for the differentiation of malignant from benign splenic lesions.