水平微肋管内基于分层流流型的沸腾传热理论模型

本文提出了基于气液分层流的水平螺旋微肋管内沸腾传热理论预测模型。在模型建立过程中,采用了与开发微肋管冷凝分层流模型类似的理论处理方法。在气液分界面以上区域,相邻微肋之间的沟槽内的半月形液面形状取决于重力和表面张力之间的静力平衡关系,其中半月形液面中的薄液膜区域的传热特性由先前提出的薄液膜蒸发模型预测;分层流液体中的传热特性由Mori等建立的基于实验数据的关联式确定。将模型理论预测值与已由的四种不同结构的微肋管、三种有机工质下得到的实验数据进行了比较,结果表明,只要不发生管内部分烧涸现象,在Fr0<2.5时,理论预测值和实验数据符合得相当好。

水平微肋管内基于气液环状流流型的沸腾传热理论模型

本文提出了基于气液环状流的水平螺旋微肋管内沸腾传热理论预测模型。在模型建立过程中,假设环状流液膜是由基底液膜和叠加扰动波液膜单元组成,将无量纲准则数Fr_0=G/[gd_eρ_v(ρ_l-ρ_v)]^(0.5)作为汽液两相流环状流理论模型的判据建立的模型理论预测值与已由的四种不同结构的微肋管、三种有机工质下得到的实验数据进行了比较,结果表明,在Fr_0>4.0时,提出的环状流预测值理论值或者和预测值符合得较好,或者大幅度改善了原有分层流模型的预测效果,充分说明了提出的环状流理论模型的合理性。

Imaging pitfalls of pancreatic serous cystic neoplasm and its potential mimickers

The aim of this article is to clarify diagnostic pitfalls of pancreatic serous cystic neoplasm(SCN) that may result in erroneous characterization. Usual and unusual imaging findings of SCN as well as potential SCN mimickers are presented. The diagnostic key of SCN is to look for a cluster of microcysts(honeycomb pattern), which may not be always found in the center. Fibrosis in SCN may be mistaken for a mural nodule of intraductal papillary mucinous neoplasm(IPMN). The absence of cyst wall enhancement may be helpful to distinguish SCN from mucinous cystic neoplasm. However, oligocystic SCN and branch duct type IPMN may morphologically overlap. In addition, solid serous adenoma, an extremely rare variant of SCN, is difficult to distinguish from neuroendocrine tumor.

Clinical outcomes of symptomatic arterioportal fistulas after transcatheter arterial embolization

AIM: To evaluate the complications and clinical outcomes of transcatheter arterial embolization (TAE) for symptoms related to severe arterioportal fistulas (APFs). METHODS: Six patients (3 males, 3 females; mean age, 63.8 years; age range, 60-71 years) with chronic liver disease and severe APFs due to percutaneous intrahepatic treatment (n=5) and portal vein (PV) tumor thrombosis of hepatocellular carcinoma (n=1) underwent TAE for symptoms related to severe APFs [refractory ascites (n=4), hemorrhoidal hemorrhage (n=1), and hepatic encephalopathy (n=1)]. Control of symptoms related to APFs and complications were evaluated during the follow-up period (range, 4-57 mo). RESULTS: In all patients, celiac angiography revealed immediate retrograde visualization of the main PV before TAE, indicating severe APF. Selective TAE for the hepatic arteries was performed using metallic coils (MC, n=4) and both MCs and n-butyl cyanoacrylate (n=2). Three patients underwent repeated TAEs for residual APFs and ascites. Four patients developed PV thrombosis after TAE. During the follow-up period after TAE, APF obliteration and symptomatic improvement were obtained in all patients. CONCLUSION: Although TAE for severe APFs may sometimes be complicated by PV thrombosis, TAE can be an effective treatment to improve clinical symptoms related to severe APFs.

Image quality and diagnostic performance of free-breathing diffusion-weighted imaging for hepatocellular carcinoma

To retrospectively evaluate the diagnostic performance of free-breathing diffusion-weighted imaging (FB-DWI) with modified imaging parameter settings for detecting hepatocellular carcinomas (HCCs). METHODSFifty-one patients at risk for HCC were scanned with both FB-DWI and respiratory-triggered DWI with the navigator echo respiratory-triggering technique (RT-DWI). Qualitatively, the sharpness of the liver contour, the image noise and the chemical shift artifacts on each DWI with b-values of 1000 s/mm2 were independently evaluated by three radiologists using 4-point scoring. We compared the image quality scores of each observer between the two DWI methods, using the Wilcoxon signed-rank test. Quantitatively, we compared the signal-to-noise ratios (SNRs) of the liver parenchyma and lesion-to-nonlesion contrast-to-noise ratios (CNRs) after measuring the signal intensity on each DWI with a b-factor of 1000 s/mm2. The average SNRs and CNRs between the two DWI methods were compared by the paired t-test. The detectability of HCC on each DWI was also analyzed by three radiologists. The detectability provided by the two DWI methods was compared using McNemar’s test. RESULTSFor all observers, the averaged image quality scores of FB-DWI were: Sharpness of the liver contour [observer (Obs)-1, 3.08 ± 0.81; Obs-2, 2.98 ± 0.73; Obs-3, 3.54 ± 0.75], those of the distortion (Obs-1, 2.94 ± 0.50; Obs-2, 2.71 ± 0.70; Obs-3, 3.27 ± 0.53), and the chemical shift artifacts (Obs-1, 3.38 ± 0.60; Obs-2, 3.15 ± 1.07; Obs-3, 3.21 ± 0.85). The averaged image quality scores of RT-DWI were: Sharpness of the liver contour (Obs-1, 2.33 ± 0.65; Obs-2, 2.37 ± 0.74; Obs-3, 2.75 ± 0.81), distortion (Obs-1, 2.81 ± 0.56; Obs-2, 2.25 ± 0.74; Obs-3, 2.96 ± 0.71), and the chemical shift artifacts (Obs-1, 2.92 ± 0.59; Obs-2, 2.21 ± 0.85; Obs-3, 2.77 ± 1.08). All image quality scores of FB-DWI were significantly higher than those of RT-DWI (P < 0.05). The average SNR of the normal liver parenchyma by FB-DWI (11.0 ± 4.8) was not significantly different from that shown by RT-DWI (11.0 ± 5.0); nor were the lesion-to-nonlesion CNRs significantly different (FB-DWI, 21.4 ± 17.7; RT-DWI, 20.1 ± 15.1). For all three observers, the detectability of FB-DWI (Obs-1, 43.6%; Obs-2, 53.6%; and Obs-3, 45.0%) was significantly higher than that of RT-DWI (Obs-1, 29.1%; Obs-2, 43.6%; and Obs-3, 34.5%) (P < 0.05). CONCLUSIONFB-DWI showed better image quality and higher detectability of HCC compared to RT-DWI, without significantly reducing the SNRs of the liver parenchyma and lesion-to-nonlesion CNRs.

Resolution of epidural hematoma related to osteoporotic fracture after percutaneous vertebroplasty

We are the first to report a case that showed spontaneous resolution of epidural hematoma which was related to a steroid-induced osteoporotic compression fracture.The patient had a painful fracture with an intravertebral cleft at L1 accompanying an epidural hematoma posteriorly.Immediate pain relief was achieved after percutaneous vertebroplasty.Complete resolution of hematoma was noted three months after procedure.We theorized that intravertebral stability after treatment might have played a role in this patient.

Fibrosis in nonalcoholic fatty liver disease: Noninvasive assessment using computed tomography volumetry

AIM To evaluate the diagnostic performance of computed tomography(CT) volumetry for discriminating the fibrosis stage in patients with nonalcoholic fatty liver disease(NAFLD).METHODS A total of 38 NAFLD patients were enrolled. On the basis of CT imaging, the volumes of total, left lateral segment(LLS), left medial segment, caudate lobe, and right lobe(RL) of the liver were calculated with a dedicated liver application. The relationship between the volume percentage of each area and fibrosis stage was analyzed using Spearman's rank correlation coefficient. A receiver operating characteristic(ROC) curve analysis was performed to determine the accuracy of CT volumetry for discriminating fibrosis stage.RESULTS The volume percentages of the caudate lobe and the LLS significantly increased with the fibrosis stage(r = 0.815, P < 0.001; and r = 0.465, P = 0.003, respectively). Contrarily, the volume percentage of the RL significantly decreased with fibrosis stage(r =-0.563, P < 0.001). The volume percentage of the caudate lobe had the best diagnostic accuracy for staging fibrosis, and the area under the ROC curve values for discriminating fibrosis stage were as follows: ≥ F1, 0.896; ≥ F2, 0.929; ≥ F3, 0.955; and ≥ F4, 0.923. The best cut-off for advanced fibrosis(F3-F4) was 4.789%, 85.7% sensitivity and 94.1% specificity.CONCLUSION The volume percentage of the caudate lobe calculated by CT volumetry is a useful diagnostic parameter for staging fibrosis in NAFLD patients.

CT-guided radiofrequency ablation of osteoid osteoma in the long bones of the lower extremity

AIM:To present our initial experience with computed tomography guided radiofrequency ablation(RFA) of osteoid osteoma(OO) in our institution.METHODS:RFA was performed on eight patients(5 males and 3 females) with clinically and radiologically diagnosed OO(femoral neck,n = 4;femoral diaphysis,n = 2;tibial diaphysis,n = 1;fibular diaphysis,n = 1).Ablation was performed using an electrode with a 10-mm exposed tip for a total of 4-6 min at a targeted temperature of 90 degrees Celsius.No cooling system was used.The intervention was accepted as technically successful if the tip of the electrode could be placed within the center of the nidus.We defined clinical success as a disappearance within 2 wk after treatment of symptoms that had manifested at presentation.RESULTS:All procedures were technically successful.No major or immediate complications were observed.Clinical success was achieved in six of eight patients in the first procedure.A second procedure was performed for two patients who had recurrent or continued pain,and one of these cases was successfully treated.The overall rate of success was 87.5%(7/8).No complication was observed.CONCLUSION:Our preliminary results indicate a favorable success rate and no complications and are compatible with the previous reports of RFA of OO.

Balloon test occlusion of internal carotid artery: Angiographic findings predictive of results

AIM: To reveal angiographic findings to predict the re-sult of balloon test occlusion(BTO).METHODS: The cerebral angiograms of 42 consecu-tive patients who underwent cerebral angiography in-cluding both the Matas and Allcock maneuvers and BTO were retrospectively analyzed. Visualization of the an-terior cerebral artery(ACA) and the middle cerebral ar-tery(MCA) by the cross flow on the tested side during the Matas or Allcock maneuver was graded on a 5-point scale. Circle of Willis(COW) anatomy with respect to the presence/absence of a collateral path to reach the tested internal carotid artery(ICA) was classified intofour categories. A univariate logistic analysis was used to analyze the associations between each angiographic finding and the BTO result. Sensitivity, specificity, accu-racy, positive predictive value, and negative predictive value for each finding were calculated. RESULTS: Five patients(12%) were BTO-positive and the remaining 37 patients(88%) were BTO-negative. Visualizations of the ACA and MCA as well as the COW anatomy were significantly associated with the BTO re-sult(P = 0.0051 for ACA, P = 0.0002 for MCA, and P < 0.0001 for COW anatomy). In particular, good MCA vi-sualization and the presence of an anterior connection(collateral path to the tested ICA from the contralateral ICA via the anterior communicating artery) in the COW were highly predictive for negative BTO(negative pre-dictive value = 100% for both).

Transcatheter arterial embolization for chest wall metastasis of hepatocellular carcinoma

Hemothorax due to rupture of metastatic hepatocellular carcinoma (HCC) is a very rare complication with high mortality because of uncontrollable hemorrhage. A 71-year-old man treated by transcatheter arterial embolization for HCC with massive bleeding from chest wall metastasis is reported. Enhanced computed tomography and selective intercostal angiogram showed a hypervascular mass in the right chest wall and extravasation of contrast agent. After successful transcatheter arterial embolization with gelatin sponge particles and metallic coils, the patient recovered from shock without major complication. To our knowledge, a successfully treated case of hemothorax due to rupture of metastatic HCC has not previously been described.

The Effect of Treatment Position on Rectal and Bladder Dose-Volume Histograms for Prostate Radiotherapy Planned with 3-Dimensional Conformal Radiotherapy, Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy

Purpose: To compare target coverage and organ at risk (OAR) sparing in the supine and prone positions with 3-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in low- and high-risk prostate radiotherapy cases. Materials and Methods: Using magnetic resonance images of five healthy volunteers, six treatment plans (supine 3DCRT, prone 3DCRT, supine IMRT, prone IMRT, supine VMAT and prone VMAT) were generated. Planning target volume 1 (PTV1) was defined as the prostate gland plus the seminal vesicles with adequate margins in a high-risk setting, while PTV2 was defined as prostate only with margins in a low-risk setting. The mean dose for both PTV1 and PTV2 was set at 78 Gy. Plans generated by each of the 3 techniques were compared between the supine and prone positions using dose-volume histograms (DVHs). Results: For PTV1, prone 3DCRT provided a significantly higher D98% than did supine 3DCRT, and its homogeneity index (HI) was significantly better. IMRT and VMAT values did not differ significantly between the prone and supine positions. For PTV2, no values differed significantly between the supine and prone positions under any treatment plan. With respect to OAR, the rectal D mean, D2%, V50, and V60 values of PTV1 were statistically higher in supine 3DCRT than in prone 3DCRT, while there were no significant differences in rectal values between the supine and prone positions with IMRT or VMAT. The rectal Dmean, V50, V60, V70, and V75 values of prone 3DCRT were significantly higher than those of supine IMRT or supine VMAT. There were no significant differences in any values for the rectum and bladder for PTV2. Conclusion: Although prone 3DCRT was found to be superior to supine 3DCRT in terms of rectal sparing in high-risk prostate cancer, IMRT and VMAT techniques could possibly cover this disadvantage.

Computer-aided differential diagnosis system for Alzheimer’s disease based on machine learning with functional and morphological image features in magnetic resonance imaging

Alzheimer’s disease (AD) is a dementing disorder and one of the major public health problems in countries with greater longevity. The cerebral cortical thickness and cerebral blood flow (CBF), which are considered as morphological and functional image features, respectively, could be decreased in specific cerebral regions of patients with dementia of Alzheimer type. Therefore, the aim of this study was to develop a computer-aided classification system for AD patients based on machine learning with the morphological and functional image features derived from a magnetic resonance (MR) imaging system. The cortical thicknesses in ten cerebral regions were derived as morphological features by using gradient vector trajectories in fuzzy membership images. Functional CBF maps were measured with an arterial spin labeling technique, and ten regional CBF values were obtained by registration between the CBF map and Talairach atlas using an affine transformation and a free form deformation. We applied two systems based on an arterial neural network (ANN) and a support vector machine (SVM), which were trained with 4 morphological and 6 functional image features, to 15 AD patients and 15 clinically normal (CN) subjects for classification of AD. The area under the receiver operating characteristic curve (AUC) values for the two systems based on the ANN and SVM with both image?features were 0.901 and 0.915, respectively. The AUC values for the ANN-and SVM-based systems with the morphological features were 0.710 and 0.660, respectively, and those with the functional features were 0.878 and 0.903, respectively. Our preliminary results suggest that the proposed method may have potential for assisting radiologists in the differential diagnosis of AD patients by using morphological and functional image features.

Malignant Triton Tumor in the Abdominal Wall: A Case Report

Malignant triton tumor (MTT) is a rare variant of malignant peripheral nerve sheath tumor (MPNST) with rhabdomyosarcomatous differentiation. We report the case of a 54-year-old male without a history of neurofibromatosis type 1 (NF1) who had a growing abdominal wall tumor diagnosed as MTT. Computed tomography (CT), magnetic resonance imaging (MRI) and 2-[F-18]-fluoro-2-deoxy-D-glucose positron emission tomography/CT (FDG-PET/CT) were performed. The MRI and FDG-PET/CT indicated that the lateral component of the tumor was composed of many proliferative cells, corresponding to the histopathological finding of a cellular proliferation of spindle-shaped cells. In light of this case and previous reports, it is apparent that FDG-PET/CT is a helpful tool for distinguishing MTT from benign peripheral nerve sheath tumor.

Automated measurement of three-dimensional cerebral cortical thickness in Alzheimer’s patients using localized gradient vector trajectory in fuzzy membership maps

Our purpose in this study was to develop an automated method for measuring three-dimensional (3D) cerebral cortical thicknesses in patients with Alzheimer’s disease (AD) using magnetic resonance (MR) images. Our proposed method consists of mainly three steps. First, a brain parenchymal region was segmented based on brain model matching. Second, a 3D fuzzy membership map for a cerebral cortical region was created by applying a fuzzy c-means (FCM) clustering algorithm to T1-weighted MR images. Third, cerebral cortical thickness was three- dimensionally measured on each cortical surface voxel by using a localized gradient vector trajectory in a fuzzy membership map. Spherical models with 3 mm artificial cortical regions, which were produced using three noise levels of 2%, 5%, and 10%, were employed to evaluate the proposed method. We also applied the proposed method to T1-weighted images obtained from 20 cases, i.e., 10 clinically diagnosed AD cases and 10 clinically normal (CN) subjects. The thicknesses of the 3 mm artificial cortical regions for spherical models with noise levels of 2%, 5%, and 10% were measured by the proposed method as 2.953 ± 0.342, 2.953 ± 0.342 and 2.952 ± 0.343 mm, respectively. Thus the mean thicknesses for the entire cerebral lobar region were 3.1 ± 0.4 mm for AD patients and 3.3 ± 0.4 mm for CN subjects, respectively (p < 0.05). The proposed method could be feasible for measuring the 3D cerebral cortical thickness on individual cortical surface voxels as an atrophy feature in AD.

Contrast-Enhanced CT Colonography Features of Rectal Carcinoid Tumors

Purpose: The purpose of this study was to retrospectively assess the detectability and enhancement pattern of rectal carcinoid tumors on contrast-enhanced computed tomography colonography (CE-CTC). Methods: The study sample consisted of 12 lesions in nine patients of rectal carcinoid tumors. To evaluate the detectability, two radiologists reviewed axial and 3D images including air enema (AE), virtual endoscopy (VE), and virtual colon dissection (VCD). To determine the contrast enhancement pattern of the tumors, the CT attenuation value of each lesion was measured in three phases. Results: Four of the 12 lesions (33%) were detected on axial images in patients in both the prone and supine positions, the sizes of which were 6 mm or larger. Seven lesions (58%), including the four lesions mentioned above, were detected on 3D images including AE and VE in patients in the prone position, the sizes of which were 5 mm or larger. The ranges of CT attenuation values of the lesions at 40 s, 70 s and 240 s were 112 - 147, 116 - 140 and 82 - 97 HU, respectively. Conclusion: Rectal carcinoid tumors are challenging to detect on CE-CTC. They demonstrated enhancement at the early phase and washout at the delayed phase on CE-CTC.

用于FDG-PET和弥散加权MRI图像融合的最佳单色组合

目的研究用于FDG-PET和弥散加权(DW)MRI图像融合的最佳单色组合,以利于显示两者各自的病灶。方法6种线性单色红、蓝、绿、青、品红和黄色分别用于显示FDG-PET和弥散加权成像(DWI)。使用光度计测量病灶颜色的亮度和色度,计算病灶颜色的视觉差异。通过比较PET、DWI和PET-DWI融合图像各自显示的病灶阳性部分的平均显著性得分来评价病灶的视觉显著性。采用单因素方差分析和Spearman秩相关进行统计分析。结果在12种可能的单色组合中,红/青、品红/绿和红/绿组合显示的病灶显著性得分最高。PET图像病灶和融合图像病灶阳性部分的总颜色差别与显著性得分相关(ρ=0.2933,P<0.005),而以上两者的亮度差异与病灶显示的显著性得分呈显著负相关。

Detecting hepatic nodules and identifying feeding arteries of hepatocellular carcinoma: efficacy of cone-beam computed tomography in transcatheter arterial chemoembolization

Aim:To evaluate the effectiveness of using cone-beam computed tomography(CBCT)in transcatheter arterial chemoembolization(TACE)to detect hapatocellular carcinoma(HCC)nodules and their feeding arteries.Methods:Twenty-four patients with HCCs who underwent TACE using CBCT in addition to conventional digital subtraction angiography(DSA)were enrolled.After both conventional DSA and CBCT through the hepatic artery were acquired,TACE were performed.The nodules were defined as an HCC when dense accumulation of iodized oil was found within the nodule on CT obtained 2 weeks after the TACE.The number of detected nodules and identified feeding arteries,and their correlations with anatomical locations were assessed.Results:A total of 39 HCC nodules(tumor diameter,7-40 mm;mean,17.4±7.9 mm)were detected.Thirty-one nodules were detected by DSA alone but 8 nodules were additionally detected by adding CBCT to DSA.There were 53 feeding arteries associated with the 39 HCC nodules.Among these arteries,21 were identified by DSA alone;however,47 were identified by combining CBCT with DSA.Additional feeding arteries,especially for the nodules located at the right and caudate lobes,were identified by CBCT.On the other hand,there was no difference in detection of nodules between the anatomical locations by CBCT.Conclusion:The use of CBCT in addition to DSA offers potential for increasing the number of detected nodules,and the number of their feeding arteries at the right and caudate lobes.CBCT might improve the quality of TACE procedure for HCC than DSA alone.