The feasibility of MR elastography with transpelvic vibration for localization of focal prostate lesion.

We aimed to evaluate the feasibility of MR elastography (MRE) using a transpelvic approach. Thirty-one patients who underwent prostate MRE and had a pathological diagnosis were included in this study. MRE was obtained using a passive driver placed at the umbilicus and iliac crests. The shear stiffness, clinical data, and conventional imaging findings of prostate cancer and benign prostatic hyperplasia (BPH) were compared. Inter-reader agreements were evaluated using the intraclass coefficient class (ICC). Prostate MRE was successfully performed for all patients (100% technical success rate). Nineteen cancer and 10 BPH lesions were visualized on MRE. The mean shear stiffness of cancer was significantly higher than that of BPH (5.99 ± 1.46 kPa vs. 4.67 ± 1.54 kPa, p = 0.045). One cancer was detected on MRE but not on conventional sequences. Six tiny cancer lesions were not visualized on MRE. The mean size of cancers that were not detected on MRE was smaller than that of cancers that were visible on MRE (0.8 ± 0.3 cm vs. 2.3 ± 1.8 cm, p = 0.001). The inter-reader agreement for interpreting MRE was excellent (ICC = 0.95). Prostate MRE with transpelvic vibration is feasible without intracavitary actuators. Transpelvic prostate MRE is reliable for detecting focal lesions, including clinically significant prostate cancer and BPH.

Ultrasound-guided percutaneous core needle biopsy of abdominal subcutaneous fat for diagnosing amyloidosis: comparison with bone marrow biopsy.

BACKGROUND: Patients with underlying hematologic malignancy have a higher risk of developing systemic amyloidosis, which worsens their prognosis. Histopathologic detection of amyloid deposits in tissue biopsy specimens is the only diagnostic method for amyloidosis. PURPOSE: To compare the efficacy of ultrasound-guided percutaneous core needle biopsy (USPCB) of abdominal subcutaneous fat with that of bone marrow biopsy (BMB) for diagnosing amyloidosis. MATERIAL AND METHODS: A total of 90 consecutive patients with underlying hematologic disorders who underwent both USPCB of abdominal subcutaneous fat and BMB for suspicion of amyloid deposition during a 10-year period were included in this retrospective study. RESULTS: The sensitivity and specificity of detecting amyloid deposition were 85.7% and 100%, respectively, with USPCB as opposed to 4.8% and 100%, respectively, with BMB, and the sensitivity was significantly higher with USPCB (P < 0.001). The mean number of times USPCB was performed was 3.3. There were no major complications associated with USPCB. The sensitivity of detecting amyloidosis was not different between the 18-G needle group and the 14-G group (100% vs. 80%; P = 0.623). Logistic regression analysis revealed that acquiring more cores from USPCB and thinner fat tissues were statistically significant factors that affected the diagnostic accuracy of USPCB for amyloid detection. CONCLUSION: The sensitivity of amyloid deposition was significantly higher with USPCB of abdominal subcutaneous fat than BMB. Acquiring more cores by multiple biopsies instead of using a larger bore needle and thin subcutaneous fat pad may be a favorable factor for the diagnostic accuracy of USPCB.

Ultra-low-dose hepatic multiphase CT using deep learning-based image reconstruction algorithm focused on arterial phase in chronic liver disease: A non-inferiority study.

PURPOSE: This study determined whether image quality and detectability of ultralow-dose hepatic multiphase CT (ULDCT, 33.3% dose) using a vendor-agnostic deep learning model(DLM) are noninferior to those of standard-dose CT (SDCT, 100% dose) using model-based iterative reconstruction(MBIR) in patients with chronic liver disease focusing on arterial phase. METHODS: Sixty-seven patients underwent hepatic multiphase CT using a dual-source scanner to obtain two different radiation dose CT scans (100%, SDCT and 33.3%, ULDCT). ULDCT using DLM and SDCT using MBIR were compared. A margin of -0.5 for the difference between the two protocols was pre-defined as noninferiority of the overall image quality of the arterial phase image. Quantitative image analysis (signal to noise ratio[SNR] and contrast to noise ratio[CNR]) was also conducted. The detectability of hepatic arterial focal lesions was compared using the Jackknife free-response receiver operating characteristic analysis. Non-inferiority was satisfied if the margin of the lower limit of 95%CI of the difference in figure-of-merit was less than -0.1. RESULTS: Mean overall arterial phase image quality scores with ULDCT using DLM and SDCT using MBIR were 4.35 ± 0.57 and 4.08 ± 0.58, showing noninferiority (difference: -0.269; 95 %CI, -0.374 to -0.164). ULDCT using DLM showed a significantly superior contrast-to-noise ratio of arterial enhancing lesion (p < 0.05). Figure-of-merit for detectability of arterial hepatic focal lesion was 0.986 for ULDCT using DLM and 0.963 for SDCT using MBIR, showing noninferiority (difference: -0.023, 95 %CI: -0.016 to 0.063). CONCLUSION: ULDCT using DLM with 66.7% dose reduction showed non-inferior overall image quality and detectability of arterial focal hepatic lesion compared to SDCT using MBIR.

Prospective evaluation of low-dose multiphase hepatic computed tomography for detecting and characterizing hepatocellular carcinoma in patients with chronic liver disease.

BACKGROUND: Knowing the lowest acceptable radiation dose of multiphase hepatic CT may allow us to reduce the radiation dose for detecting HCC. PURPOSE: To prospectively assess the image quality and diagnostic performance of low-dose and ultra-low-dose multiphase hepatic computed tomography using a dual-source CT scanner. METHODS: Three reconstructed different dose scan images (standard-dose, low-dose, and ultra-low-dose) of hepatic multiphase CT were obtained from 67 patients with a dual-source CT scanner. The image quality and the diagnostic performance of the three radiation dose CT scans of the hepatic focal lesion (≥ 0.5 cm) were analyzed by two independent readers using the Liver Imaging Reporting and Data System. RESULTS: Qualitative image quality and signal-to-noise ratio were significantly different among the radiation doses (p < 0.001). In total, 154 lesions comprising 32 hepatocellular carcinomas (HCC) and 122 non-HCC were included. The sensitivities of SDCT, LDCT, and ULDCT were 90.6%(29/32), 81.3%(26/32), and 56.2%(18/32), respectively. The accuracies of SDCT, LDCT, and ULDCT were 98.1%(151/154), 96.1%(148/154), and 89.6%(138/154), respectively. On per-lesion analysis, SDCT and LDCT did not show significantly different sensitivity and accuracy in diagnosing HCC (p = 0.250 and 0.250). CONCLUSIONS: The diagnostic performance of dynamic hepatic LDCT with 33% reduced radiation dose in comparison to SDCT would be acceptable even though its image quality was qualitatively and quantitatively inferior. However, few HCCs could be overlooked. Therefore, with caution, radiation dose reduction by one-third could be implemented for follow-up CT scans for patients suspected of having HCC with caution and further studies are needed in the future.

Imaging Findings of an Intraluminal Duodenal Diverticulum Associated with Adult Duodeno-Duodenal Intussusception and Recurrent Pancreatitis: A Case Report.

Intraluminal duodenal diverticulum (IDD) is a rare congenital abnormality, consisting of a sac-like mucosal lesion in the duodenum. Cases of IDD can present with gastrointestinal bleeding, duodenal obstruction, or pancreatitis. Here, we report a rare case of a 25-year-old female presenting with IDD complicated by duodeno-duodenal intussusception and recurrent pancreatitis. The diagnosis was based on findings from radiologic examinations (CT and MRI), upper gastrointestinal series (barium swallow), and gastroduodenofiberscopy. Laparoscopic excision of the presumed duodenal duplication was performed. The subsequent histopathologic evaluation of the excised sac revealed normal mucosa on both sides, but the absence of a proper muscle layer confirmed the diagnosis of IDD. Radiologic detection of a saccular structure in the second portion of the duodenum can indicate IDD with duodeno-duodenal intussusception as the lead point.

Direction of Tissue Contraction after Microwave Ablation: A Comparative Experimental Study in Ex Vivo Bovine Liver.

OBJECTIVE: This study aimed to investigate the direction of tissue contraction after microwave ablation in ex vivo bovine liver models. MATERIALS AND METHODS: Ablation procedures were conducted in a total of 90 sites in ex vivo bovine liver models, including the surface (n = 60) and parenchyma (n = 30), to examine the direction of contraction of the tissue in the peripheral and central regions from the microwave antenna. Three commercially available 2.45-GHz microwave systems (Emprint, Neuwave, and Surblate) were used. For surface ablation, the lengths of two overlapped square markers were measured after 2.5- and 5-minutes ablations (n = 10 ablations for each system for each ablation time). For parenchyma ablation, seven predetermined distances between the markers were measured on the cutting plane after 5- and 10-minutes ablations (n = 5 ablations for each system for each ablation time). The contraction in the radial and longitudinal directions and the sphericity index (SI) of the ablation zones were compared between the three systems using analysis of variance. RESULTS: In the surface ablation experiment, the mean longitudinal contraction ratio and SI from a 5-minutes ablation using the Emprint, Neuwave, and Surblate systems were 28.92% and 1.04, 20.10% and 0.53, and 24.90% and 0.45, respectively (p < 0.001). A positive correlation between longitudinal contraction and SI was noted, and a similar radial contraction was observed. In the parenchyma ablation experiment, the mean longitudinal contraction ratio and SI from a 10-minutes ablation using the three pieces of equipment were 38.60% and 1.06, 32.45% and 0.61, and 28.50% and 0.50, respectively (p < 0.001). There was a significant difference in the longitudinal contraction properties, whereas there was no significant difference in the radial contraction properties. CONCLUSION: The degree of longitudinal contraction showed significant differences depending on the microwave ablation equipment, which may affect the SI of the ablation zone.

Free-breathing contrast-enhanced multiphase MRI of the liver in patients with a high risk of breath-holding failure: comparison of compressed sensing-accelerated radial and Cartesian acquisition techniques.

BACKGROUND: Knowing the advantages and disadvantages of each magnetic resonance (MR) technique, would allow us to choose a sequence better suited in patients with a high risk of breath-holding failure. PURPOSE: To compare the image quality of free-breathing contrast-enhanced multiphase MR imaging (MRI) using incoherent Cartesian k-space sampling combined with a motion-resolved compressed sensing reconstruction (XD-VIBE) and Golden-Angle Radial Sparse Parallel MRI (GRASP). MATERIAL AND METHODS: A total of 67 patients were included. Overall image quality, motion artifacts, and liver edge sharpness on arterial and portal-venous phase were evaluated by two radiologists. We evaluated the signal intensity ratio between liver in the late arterial phase to aorta at peak enhancement and the detection rate of hypervascular lesions. RESULTS: Overall image quality, artifact, and liver edge sharpness scores of XD-VIBE and GRASP were not significantly different (P = 0.070-0.397). Four (reviewer 1, 12.1%) and seven patients (reviewer 2, 21.2%) received non-diagnostic quality in the XD-VIBE group whereas one patient (reviewer 2, 2.9%) received non-diagnostic quality in the GRASP group. The ratio between the aorta and liver signal for GRASP was significantly higher than that of XD-VIBE (0.32 ± 0.10 vs. 0.47 ± 0.13; P < 0.001). The hypervascular lesion detection rate of XD-VIBE (86.7%) was higher than that of GRASP (57.1%) in the arterial phase without a statistically significant difference (P = 0.081). CONCLUSION: Overall image quality of XD-VIBE and GRASP were not significantly different. More XD-VIBE examinations were rated non-diagnostic. On the other hand, the relative liver parenchymal enhancement to the aorta in the late arterial phase of GRASP was higher than that of XD-VIBE, which potentially leads to lower detectability of hypervascular lesions on arterial phase images.

Proposed nomogram predicting neoplastic ampullary obstruction in patients with a suspected ampulla of Vater lesion on CT.

PURPOSE: To stratify and weigh the computed tomography (CT) imaging and clinical features differentiating a neoplastic ampullary obstruction from a non-neoplastic ampullary obstruction and to develop a nomogram for estimating individualized risk of neoplastic potential in patients with a suspected ampulla of Vater (AOV) lesion on CT. METHODS: 135 patients (92 non-neoplastic and 43 neoplastic) with a suspected ampullary obstruction on a CT scan between February 2015 and May 2019 were included after the exclusion criteria were applied. Significant imaging and clinical findings of the neoplastic lesions were assessed using univariate and multivariate logistic regression analyses. Based on the significant variables in the multivariate analysis, a nomogram was developed to predict neoplastic potential in patients suspected of ampullary obstruction. The area under the receiver operating characteristic curve (AUC) was used to assess the diagnostic value in the external validation cohort (36 non-neoplastic and 13 neoplastic). RESULTS: The multivariate analysis revealed that the presence of an AOV mass (odds ratio (OR), 77.21; 95% confidence intervals (CI) 1.51-3950.38), AOV size > 12 mm (OR, 23.93; 95% CI 2.96-193.60), total bilirubin > 1.2 mg/dl (OR, 9.99; 95% CI 1.37-73.06) and age ≤ 63 years (OR, 7.52; 95% CI 1.33-42.48) were independent significant parameters that predicted a neoplastic lesion in the AOV. The AUC for the nomogram was 0.93 on the internal validation and 0.91 (95% CI 0.79-0.97) on the external validation. CONCLUSIONS: A nomogram using imaging and clinical findings was useful to estimate a neoplastic ampullary obstruction in patients with a suspected AOV lesion on CT and suggests a further evaluation.

A radiomics nomogram for predicting transcatheter arterial chemoembolization refractoriness of hepatocellular carcinoma without extrahepatic metastasis or macrovascular invasion.

OBJECTIVE: A radiomics nomogram for pretreatment prediction of TACE refractoriness was developed and validated for hepatocellular carcinoma (HCC) without extrahepatic metastasis or macrovascular invasion. MATERIALS AND METHODS: This study included 80 patients with HCC without extrahepatic metastasis or macrovascular involvement treated with TACE between July 2016 and November 2018. The datasets were divided into a training set (80%) and a test set (20%) for feature selection and tenfold cross-validation. Forty radiomic features were extracted from arterial-phase computed tomography (CT) using the Local Image Features Extraction software. The Lasso regression model was used for radiomics signature selection. The Lasso regression model was used for radiomics signature selection and the selected signatures were validated using the Mann-Whitney U-test. The radiomics nomogram was developed based on a multivariate logistic regression model incorporating the Rad-score, CT imaging factors, and clinical factors, and it was validated. RESULTS: The Rad-score, which consists of the Gray-Level Zone Length Matrix (GLZLM)-Long-Zone Low Gray-Level Emphasis (LZLGE) and GLZLM-Gray-Level Non-Uniformity (GLNU), T-stage, log α-fetoprotein (AFP), and bilobar distribution were significantly associated with TACE refractoriness (p < 0.05). Predictors in the radiomics nomogram were the Rad-score and T-stage (Rad-score + T-stage), Rad-score and bilobar distribution (Rad-score + bilobar distribution), or Rad-score and logAFP (Rad-score + logAFP). The multivariate logistic regression model showed a good predictive performance (Rad-score + T-stage, AUC, 0.95; Rad-score + bilobar distribution, AUC 0.91; and Rad-score + logAFP, AUC, 0.91). CONCLUSION: The radiomics nomogram could be used for the pretreatment prediction of TACE refractoriness.

Safety and Efficacy of Ultrasound-Guided Percutaneous Core Needle Biopsy of Pancreatic and Peripancreatic Lesions Adjacent to Critical Vessels.

Purpose: To evaluate the safety and efficacy of ultrasound-guided percutaneous core needle biopsy (USPCB) of pancreatic and peripancreatic lesions adjacent to critical vessels. Materials and Methods: Data were collected retrospectively from 162 patients who underwent USPCB of the pancreas (n = 98), the peripancreatic area adjacent to the portal vein, the paraaortic area adjacent to pancreatic uncinate (n = 34), and lesions on the third duodenal portion (n = 30) during a 10-year period. An automated biopsy gun with an 18-gauge needle was used for biopsies under US guidance. The USPCB results were compared with those of the final follow- up imaging performed postoperatively. The diagnostic accuracy and major complication rate of the USPCB were calculated. Multiple factors were evaluated for the prediction of successful biopsies using univariate and multivariate analyses. Results: The histopathologic diagnosis from USPCB was correct in 149 (92%) patients. The major complication rate was 3%. Four cases of mesenteric hematomas and one intramural hematoma of the duodenum occurred during the study period. The following factors were significantly associated with successful biopsies: a transmesenteric biopsy route rather than a transgastric or transenteric route; good visualization of targets; and evaluation of the entire US pathway. In addition, the number of biopsies required was less when the biopsy was successful. Conclusion: USPCB demonstrated high diagnostic accuracy and a low complication rate for the histopathologic diagnosis of pancreatic and peripancreatic lesions adjacent to critical vessels.

A differential risk assessment and decision model for Transarterial chemoembolization in hepatocellular carcinoma based on hepatic function.

BACKGROUND: The decision of transarterial chemoembolization (TACE) initiation and/or repetition remains challenging in patients with unresectable hepatocellular carcinoma (HCC). The aim was to develop a prognostic scoring system to guide TACE initiation/repetition. METHODS: A total of 597 consecutive patients who underwent TACE as their initial treatment for unresectable HCC were included. We derived a prediction model using independent risk factors for overall survival (OS), which was externally validated in an independent cohort (n = 739). RESULTS: Independent risk factors of OS included Albumin-bilirubin (ALBI) grade, maximal tumor size, alpha-fetoprotein, and tumor response to initial TACE, which were used to develop a scoring system ("ASAR"). C-index values for OS were 0.733 (95% confidence interval [CI] = 0.570-0.871) in the derivation, 0.700 (95% CI = 0.445-0.905) in the internal validation, and 0.680 (95% CI = 0.652-0.707) in the external validation, respectively. Patients with ASAR< 4 showed significantly longer OS than patients with ASAR≥4 in all three datasets (all P < 0.001). Among Child-Pugh class B patients, a modified model without TACE response, i.e., "ASA(R)", discriminated OS with a c-index of 0.788 (95% CI, 0.703-0.876) in the derivation, and 0.745 (95% CI, 0.646-0.862) in the internal validation, and 0.670 (95% CI, 0.605-0.725) in the external validation, respectively. Child-Pugh B patients with ASA(R) < 4 showed significantly longer OS than patients with ASA(R) ≥ 4 in all three datasets (all P < 0.001). CONCLUSIONS: ASAR provides refined prognostication for repetition of TACE in patients with unresectable HCC. For Child-Pugh class B patients, a modified model with baseline factors might guide TACE initiation.

Noninvasive indices for predicting nonalcoholic fatty liver disease in patients with chronic kidney disease.

BACKGROUND: Data on clinical characteristics of nonalcoholic fatty liver disease (NAFLD) in patients with chronic kidney disease (CKD) are scarce. We investigated the clinical features and risk factors of NAFLD using noninvasive serum markers in CKD patients and attempted the temporal validation of a predictive model for CKD based on NAFLD. METHODS: This retrospective cross-sectional study was conducted in a single tertiary center. We enrolled 819 CKD patients and evaluated the predictive performance of relevant clinical and laboratory markers for the presence of NAFLD in both derivation (data from 2011 to 2014, n = 567) and validation (data from 2015 to 2016, n = 252) groups. RESULTS: In the derivation group, NAFLD was observed in 89 patients (15.7%; mean body mass index (BMI), 24.6 kg/m2; median estimated glomerular filtration rate (eGFR), 28.0 ml/min). BMI, hemoglobin, serum alanine aminotransferase, eGFR, and triglyceride-glucose index were used to derive a prediction model for the presence of NAFLD. Using the cutoff value of 0.146, the area under the receiver operating characteristic curve (AUROC) for the prediction of NAFLD was 0.850. In the validation group, NAFLD was observed in 51 patients (20.2%; mean BMI, 25.4 kg/m2; median eGFR, 36.0 ml/min). Using the same prediction model and cutoff value, the AUROC was 0.842. NAFLD prevalence in CKD patients was comparable to that in the general population, increasing over time. CONCLUSIONS: Our model using BMI, renal function, triglyceride-glucose index, serum alanine aminotransferase, and hemoglobin accurately predicted the presence of NAFLD in CKD patients.

Diagnostic performance of a minimized protocol of non-contrast MRI for hepatocellular carcinoma surveillance.

PURPOSE: To evaluate the per-patient diagnostic performance of a minimized non-contrast MRI protocol for hepatocellular carcinoma (HCC) surveillance in cirrhotic liver, as well as factors affecting diagnostic sensitivity. METHODS: A total of 226 patients who underwent MRI for HCC surveillance over an 8 year period were included in this retrospective study. Set1 consisted of diffusion-weighted imaging and respiratory-triggered, fast-spin echo T2-weighted imaging with fat suppression. Set2 included T1-weighted in/opposed-phase images added to the images from Set1. Image sets were scored as positive or negative for HCC according to predetermined criteria by two readers independently. The diagnostic performance of the two sets in conjunction with α-fetoprotein (AFP) was assessed and compared using the McNemar test. Logistic regression was used to determine factors that affected sensitivity. RESULTS: The sensitivity, specificity, and accuracy of Set1 of readers 1 and 2 were 84.4%/87.3%, 86.8%/86.8%, and 85.0%/87.2%, respectively; and those for Set2 were 87.3%/89.6%, 81.1%/79.2%, and 85.8/87.2%, respectively. The sensitivities of the sets were not significantly different (p = 0.063). Sensitivities of both sets in conjunction with AFP were higher than those of MRI alone without statistical significance (87.3%/89.6%, p = 0.063/> 0.99; 89.6%/89.6%, p = 0.125/> 0.99). In very early-stage HCC, the sensitivities of Sets1 and 2 were 73.1%/76.9% and 76.9%/82.7%, respectively. Perihepatic ascites and size less than 2 cm were associated with sensitivity (p < 0.05). CONCLUSIONS: A minimized non-contrast MRI protocol consisting of Fat-sat T2WI and DWI is highly sensitive and may be a viable method for HCC surveillance of the cirrhotic liver. The inclusion of T1-weighted in/opposed-phase and AFP may increase this sensitivity.

Mapping of local recurrence after pancreaticoduodenectomy for distal extrahepatic cholangiocarcinoma: implications for adjuvant radiotherapy.

OBJECTIVE: To generate a map of local recurrences after pancreaticoduodenectomy (PD) for patients with distal extrahepatic cholangiocarcinoma (DEHC) and to evaluate the adequate target volume coverage encompassing the majority of local recurrences when the clinical target volume (CTV) for pancreatic cancer was applied. METHODS: We retrospectively reviewed the records of DEHC patients who underwent pancreaticoduodenectomy and had postoperative CT scans acquired between 1991 and 2015 available. The sites of local recurrence were delineated on individual CT scans, and then, mapping was manually performed onto template CT images. Coverage of each site of local recurrence was evaluated by applying the CTV defined according to Radiation Therapy Oncology Group (RTOG) consensus guidelines (CTVRTOG ) for target delineation in the postoperative treatment of pancreatic head cancer. RESULTS: Of the 99 patients, 36 patients had a total of 62 local relapses identifiable by postoperative CT scans; the relapses were the most frequent in the choledochojejunostomy (CJ) site, 11 sites (17.7%); para-aortic area, 10 sites (16.1%), superior mesenteric artery area, 10 sites (16.1%); and portal vein area, 9 sites (14.5%). 21 sites (33.9%) were not covered by the CTVRTOG, and the most common site of local recurrence outside the CTVRTOG was the CJ site. CONCLUSION: When mapping of local relapses was evaluated according to the CTVRTOG, the choledochojejunostomy site was identified as a high-risk area of local recurrence but was insufficiently covered within the CTVRTOG. These findings may help construct a target volume for postoperative radiotherapy in DEHC. ADVANCES IN KNOWLEDGE: Mapping local recurrences can aid in defining appropriate target volume for postoperative radiotherapy in DEHC.

Impact of Energy and Access Methods on Extrahepatic Tumor Spreading and the Ablation Zone: An Ex vivo Experiment Using a Subcapsular Tumor Model.

OBJECTIVE: To evaluate the impact of energy and access methods on extrahepatic tumor spreading and the ablation zone in an ex vivo subcapsular tumor mimic model with a risk of extrahepatic tumor spreading. MATERIALS AND METHODS: Forty-two tumor-mimics were created in bovine liver blocks by injecting a mixture of iodine contrast material just below the liver capsule. Radiofrequency (RF) ablations were performed using an electrode placed parallel or perpendicular to hepatic surface through the tumor mimic with low- and high-power protocols (groups 1 and 2, respectively). Computed tomography (CT) scans were performed before and after ablation. The presence of contrast leak on the hepatic surface on CT, size of ablation zone, and timing of the first roll-off and popping sound were compared between the groups. RESULTS: With parallel access, one contrast leak in group 1 (1/10, 10%) and nine in group 2 (9/10, 90%) (p < 0.001) were identified on post-ablation CT. With perpendicular access, six contrast leaks were identified in each group (6/11, 54.5%). The first roll-off and popping sound were significantly delayed in group 1 irrespective of the access method (p = 0.002). No statistical difference in the size of the ablation zone of the liver specimen was observed between the two groups (p = 0.247). CONCLUSION: Low-power RF ablation with parallel access is proposed to be effective and safe from extrahepatic tumor spreading in RF ablation of a solid hepatic tumor in the subcapsular location. Perpendicular placement of an electrode to the capsule is associated with a risk of extrahepatic tumor spreading regardless of the power applied.

Microwave ablation of liver tumors: degree of tissue contraction as compared to RF ablation.

PURPOSE: To compare the amount of tissue contraction after microwave (MW) versus radiofrequency (RF) ablation of liver tumors. MATERIALS AND METHODS: Seventy-five hepatic tumors in 65 patients who underwent percutaneous MW or RF ablations were included in this retrospective study. All patients underwent MRI within 6 months before the ablation and 24 h after the procedure. Two blinded radiologists, by consensus, performed measurements on the corresponding series of pre and post-ablation MRI. Absolute and relative contraction of liver, tumor, and control were calculated and compared. RESULTS: Thirty-one patients underwent MW ablations, and 44 patients underwent RF ablations. The absolute and relative contraction of the ablation zone were significantly greater with MW than RF ablation (p = 0.003 to <0.001). Thirty-two lesions were visible on both pre- and post-ablation MRI. MW ablation had significantly more tumor contraction as compared to RF ablation (p = 0.003 to 0.009). The control measurements demonstrated no significant difference in normal tissue variation between MW and RF groups. CONCLUSIONS: MW ablation of hepatic tumors produced significantly more contraction of tumor and ablated hepatic tissue compared to RF ablation. Tissue contraction should be taken into account during pre-procedural planning and assessing treatment response by comparing pre- and post-ablation images.

US characteristics for the prediction of neoplasm in gallbladder polyps 10 mm or larger.

PURPOSE: To evaluate the characteristics of gallbladder polyps 10 mm or larger to predict a neoplasm in US examinations. MATERIALS AND METHODS: Fifty-three patients with gallbladder polyps ≥ 10 mm with follow-up images or pathologic diagnosis were included in the retrospective study. All images and reports were reviewed to determine the imaging characteristics of gallbladder polyps. Univariate and multivariate analyses were used to evaluate predictors for a neoplastic polyp. RESULTS: A neoplastic polyp was verified in 12 of 53 patients and the mean size was 13.9 mm. The univariate analysis revealed that adjacent gallbladder wall thickening, larger size (≥15 mm), older age (≥57 years), absence of hyperechoic foci in a polyp, CT visibility, sessile shape, a solitary polyp, and an irregular surface were significant predictors for a neoplastic polyp. In the multivariate analysis, larger size (≥15 mm) was a significant predictor for a neoplastic polyp. CONCLUSION: A polyp size ≥15 mm was the strongest predictor for a neoplastic polyp with US. The hyperechoic foci in a polyp and CT visibility would be useful indicators for the differentiation of a neoplastic polyp, in addition to the established predictors. KEY POINTS: • A polyp size ≥15 mm is the strongest predictor for a neoplastic polyp with US. • Hyperechoic foci in a polyp and CT visibility are new predictors. • The rate of malignancy is low in polyps even 10 mm or larger (15.1 %).

CT Characteristics of Pleural Plaques Related to Occupational or Environmental Asbestos Exposure from South Korean Asbestos Mines.

OBJECTIVE: This study evaluated the CT characteristics of pleural plaques in asbestos-exposed individuals and compared occupational versus environmental exposure groups. MATERIALS AND METHODS: This study enrolled 181 subjects with occupational exposure and 98 with environmental exposure from chrysotile asbestos mines, who had pleural plaques confirmed by a chest CT. The CT scans were analyzed for morphological characteristics, the number and distribution of pleural plaques and combined pulmonary fibrosis. Furthermore, the CT findings were compared between the occupational and environmental exposure groups. RESULTS: Concerning the 279 subjects, the pleural plaques were single in 2.2% and unilateral in 3.6%, and showed variable widths (range, 1-20 mm; mean, 5.4 ± 2.7 mm) and lengths (5-310 mm; 72.6 ± 54.8 mm). The chest wall was the most commonly involved (98.6%), with an upper predominance on the ventral side (upper, 77.8% vs. lower, 55.9%, p < 0.001) and a lower predominance on the dorsal side (upper, 74.9% vs. lower, 91.8%, p = 0.02). Diaphragmatic involvement (78.1%) showed a right-side predominance (right, 73.8% vs. left, 55.6%, p < 0.001), whereas mediastinal plaques (42.7%) were more frequent on the left (right, 17.6% vs. left, 39.4%, p < 0.001). The extent and maximum length of plaques, and presence and severity of combined asbestosis, were significantly higher in the occupational exposure group (p < 0.05). CONCLUSION: Pleural plaques in asbestos-exposed individuals are variable in number and size; and show a predominant distribution in the upper ventral and lower dorsal chest walls, right diaphragm, and left mediastinum. Asbestos mine workers have a higher extent of plaques and pulmonary fibrosis versus environmentally exposed individuals.

Hepatobiliary phase of gadoxetic acid-enhanced MR in patients suspected of having gallbladder dyskinesia: comparison with hepatobiliary scintigraphy.

OBJECTIVE: To compare hepatobiliary phase of gadoxetic acid-enhanced magnetic resonance (HMR) and hepatobiliary scintigraphy (HBS) for evaluation of cystic duct patency and gallbladder contractility in patients suspected of having gallbladder dyskinesia. MATERIALS AND METHODS: Eighteen patients underwent HMR and HBS. Cystic duct patency and gallbladder ejection fraction (GBEF) were compared to determine a significant difference between HMR and HBS. RESULTS: HMR and HBS had 15 concordant and 3 discordant results for cystic duct patency. GBEF in eight patients showed no significant difference between both modalities. CONCLUSION: HMR may be an alternative to HBS for the functional evaluation of cystic duct patency and GBEF.

Image quality assessment of ultra low-dose chest CT using sinogram-affirmed iterative reconstruction.

OBJECTIVES: To assess the image quality of ultra-low-dose computed tomography (ULDCT) using sinogram-affirmed iterative reconstruction (SAFIRE) compared to reduced dose CT (RDCT). METHODS: Eighty-one consecutive patients underwent non-enhanced ULDCT using 80 kVp and 30 mAs and contrast-enhanced RDCT using automated tube potential selection and tube current modulation. CT images were reconstructed with SAFIRE. Image noise and subjective image quality of normal structures and various pulmonary lesions were assessed. RESULTS: The mean effective doses were 0.29 ± 0.03 and 2.88 ± 1.11 mSv for ULDCT and RDCT, respectively. ULDCT had significantly higher noise (p < 0.001). Image quality of five normal structures was diagnostic in 91.1 % of ULDCT and 100 % of RDCT. With ULDCT, the frequencies of non-diagnostic image quality were 2.0 (1/50), 4.6 (13/280), 25.5 (14/55), and 40.0 (8/20)% for BMIs of < 20, 20-25, 25-30, and >30. In the assessment of pulmonary lesions, non-diagnostic image quality was observed for 11.2 % of all lesions, 60.9 % of decreased attenuation (significantly more frequent for upper lung lesions), and 23.5 % of ground-glass nodules. CONCLUSION: ULDCT generates diagnostic images in patients with a BMI ≤25, but is of limited use for lesions with decreased attenuation, ground-glass nodules, or those located in the upper lobe. KEY POINTS: • Iterative reconstruction enables ultra-low-dose CT (ULDCT) with very low radiation doses. • Image quality of ULDCT depends on the patient body mass index (BMI). • Selection of kVp and mAs depends on both BMI and lesion type. • Diagnosis of pulmonary emphysema or ground-glass nodules requires higher radiation doses.