肝内胆管囊腺瘤的多层螺旋CT诊断

目的 探讨多层螺旋CT对肝胆管囊腺瘤的诊断价值. 资料与方法 3例肝内胆管囊腺瘤均经病理证实.使用16层螺旋CT扫描仪.2例行冠状面、矢状面最大信号强度投影(MIP),1例行容积再现(VR);增强扫描行动脉期、门静脉期及延迟期扫描. 结果 3例均为多房性囊性结构肿块,囊壁及多房分隔平扫呈稍低密度,囊内液性部分呈低密度,增强动脉期、门静脉期囊壁及多房分隔呈不同程度强化,2例延迟期强化,囊壁及多房分隔显示较平扫清楚;其中1例多房分隔较薄不规则,可见壁结节,增强后冠状及矢状面MIP像上清晰显示囊肿内下部分较完整的分隔及壁结节;1例囊壁及多房分隔光滑,局部增厚,增强后冠状及矢状面MIP图像清楚显示不同角度的多房分隔的形态,VR图像显示门脉左支血管腔明显受压、变细、移位;1例囊壁及多房分隔较厚不规则. 结论 肝内胆管囊腺瘤的多层螺旋CT具有一定的特征性表现,结合三维重组图像及动态增强扫描对诊断有重要价值.     

Numerical deconvolution to enhance sharpness and contrast of portal images for radiotherapy patient positioning verification

Purpose

The quality of megavoltage clinical portal images is impaired by physical and geometrical effects. This image blurring can be corrected by a fast numerical two-dimensional (2D) deconvolution algorithm implemented in the electronic portal image device. We present some clinical examples of deconvolved portal images and evaluate the clinical advantages achieved by the improved sharpness and contrast.

Materials and methods

The principle of numerical 2D image deconvolution and the enhancement of sharpness and contrast thereby achieved are shortly explained. The key concept is the convolution kernel?K(x,y), the mathematical equivalent of the smearing or blurring of a picture, and the computer-based elimination of this influence.

Results

Enhancements of sharpness and contrast were observed in all clinical portal images investigated. The images of fine bone structures were restored. The identification of organ boundaries and anatomical landmarks was improved, thereby permitting a more accurate comparison with the x-ray simulator radiographs. The visibility of prostate gold markers is also shown to be enhanced by deconvolution.

Conclusion

The blurring effects of clinical portal images were eliminated by a numerical deconvolution algorithm that leads to better image sharpness and contrast. The fast algorithm permits the image blurring correction to be performed in real time, so that patient positioning verification with increased accuracy can be achieved in clinical practice.     

门静脉高压患者多层螺旋CT在体测量研究

目的 通过多层螺旋CT门静脉血管成像,探讨门静脉高压患者门静脉系统管径、肝脾体积、肝实质强化与病因及肝功能之间的关系.资料与方法 采用16排多层螺旋CT对126例临床和实验室指标提示门静脉高压患者和47例非门静脉高压者进行门静脉CTA,并进行胃左静脉、门静脉、脾静脉、肠系膜上静脉内径测量,肝脏、脾体积测量及门静脉期肝实质和门静脉主干CT值的测量,并用SPSS 11.0统计软件包对获得数据进行分析.结果 门静脉高压患者与正常对照组相比,门静脉内径分别为(13.73±3.36) mm和(13.61±1.90) mm,脾静脉内径分别为(10.30±3.28) mm和(9.23±1.39) mm,肠系膜上静脉内径分别为(10.83±2.03) mm和(10.46±1.32) mm,胃左静脉宽度分别为(5.10±3.49) mm和(1.48±1.59) mm,肝脏体积分别为(1189.46±305.36) cm3和(1322.40±283.81) cm3,脾体积分别为(809.37±471.14) cm3和(255.53±110.35) cm3.两组间对比有统计学意义(P＜0.05).结论 多层螺旋CT门静脉血管成像在显示门静脉高压患者相关血管形态、肝脾体积及肝实质强化等多方面能提供有价值的信息,可为临床治疗方案的选择和疗效的观察评估提供影像学依据.     

Electronic portal imaging device (EPID) portal image filtering for simplifying registration on radiation therapy

A simple method for improving the quality of electronic portal imaging device (EPID) portal images was proposed for the reduction of the burden on the registration between digital reconstruction radiography (DRR) and EPID portal images in radiation therapy. Conventional image filtering techniques in the spatial-frequency domain are applied to the proposed method. While a band-pass filter (BPF) is employed to extract spatial-frequency components included in the bone edge, a high-pass filter (HPF) is employed to obtain the effect corresponding to the general dynamic range compression. The band-pass filtered image is weighted by a parameter for adjusting the bone edge enhancement, and is added to the high-pass filtered image. This method was applied to the portal images in the neck region. In the image obtained by the proposed filtering, the bone edge was clearly observed. In addition, soft tissue structures were identified in the same display settings (window level/width; WL/WW) as the bone edge observation; that is, the adjustment of the display settings was not required for the observation of each object. These results suggested that both bone edge enhancement and dynamic range compression would be achieved successfully. It was estimated that the images obtained by the proposed method were more appropriate for the registration than conventional portal images, in 47 times registrations of 50 times in total (the registrations by five radiological technologists in ten patients). The proposed method was concluded to be useful for improving the quality of portal images, enabling the efficient registration.     

肝转移瘤高场MRI诊断

目的:探讨高场MRI在肝转移瘤(HMs)中的检出、诊断与鉴别诊断价值。方法:收集经临床、影像证实的HMs 43例,所有病例均进行高场MRI平扫和动脉期、门脉期、延迟期扫描,其中23例尚做螺旋CT平扫、动脉期、门脉期扫描,分析记录HMs螺旋CT、高场MRI平扫及多期增强扫描特征。结果:共计174枚瘤灶在MRI平扫上呈长T2长T1信号,动脉期122枚瘤灶不强化,门脉期174枚瘤灶均呈环状强化,延迟期108枚瘤灶呈向心性充填;23例79枚瘤灶螺旋CT平扫均呈低密度,动脉期49枚瘤灶不强化,30枚呈环状强化,门脉期73枚呈环状强化,4枚呈向心性充填;43例HMs高场MRI均准确诊断,螺旋CT漏检2例,误诊7例。结论:高场MRI对HMs的检出、诊断与鉴别诊断具重要价值,可作为HMs的首选检查方法。     

Cone-Beam CT Hepatic Arteriography in Chemoembolization for Hepatocellular Carcinoma: Angiographic Image Quality and Its Determining Factors

PurposeTo analyze image quality and the factors that determine it for cone-beam computed tomography (CT) hepatic arteriography in chemoembolization for hepatocellular carcinoma (HCC).Materials and MethodsFrom September 2009–December 2010, 399 consecutive patients referred for chemoembolization of HCC were scheduled for cone-beam CT scan. There were 12 patients (3%) excluded because of difficulty with breath-hold. Of the 387 patients who underwent cone-beam CT hepatic arteriography, 100 patients were ultimately included in the study according to inclusion criteria. Maximum intensity projection images were scored for image quality of each segmental hepatic artery. Potential determining factors for image quality were diaphragmatic motion, portal vein enhancement, and hepatic artery-to-parenchyma enhancement ratio. The flow rate of contrast media, x-ray delay, and location of the catheter tip were also evaluated.ResultsIt was possible to trace at least subsegmental hepatic arteries in 625 of 700 segments (89.3%) on cone-beam CT hepatic arteriography. Diaphragmatic motion, prominent portal vein enhancement, and low hepatic artery-to-parenchyma enhancement ratio worsened image quality (P < .001, P = .022, and P = .017). Owing to cardiac motion artifacts, image quality of the left lateral segments (S2 and S3) was poorer compared with the remaining hepatic segments (S4–S8).ConclusionsIn most cases, the quality of cone-beam CT hepatic arteriography images was good enough to trace subsegmental hepatic arteries at a minimum. Respiratory and cardiac motion, portal vein enhancement, and hepatic artery-to-parenchyma enhancement ratio significantly affected the image quality of cone-beam CT hepatic arteriography.     

The effect of fatty infiltration on the liver tissue enhancement during portal phase computed tomography

RATIONALE AND OBJECTIVES: To correlate the presence of fatty liver and the enhancement value of liver tissue during portal phase computed tomography. MATERIALS AND METHODS: Liver tissue enhancements during portal phase computed tomography were measured in 16 fatty liver and 35 control patients. All patients intravenously received 100 mL of non-ionic contrast material (320 mg iodine/ mL) at a rate of 3 mL/second, and the image acquisition started at 70 seconds. Attenuation values were measured on the 80-second portal phase images and the corresponding unenhanced images, and the contrast enhancement value (HU) of the liver tissue was calculated. Adjusted enhancement values were also calculated with the following equation: adjusted enhancement value = enhancement value (HU)/[dose (grams of iodine)/body weight (kg)]. RESULTS: The contrast enhancement value was significantly reduced in the fatty liver patients compared with the normal controls (37.0 +/- 7.2 vs 49.8 +/- 12.0 HU; P < .0001). This difference was still significant in adjusted enhancement value (80.1 +/- 13.7 vs 93.6 +/- 23.0 HU kg g(-1); P = .01). CONCLUSION: The liver tissue with fatty infiltration was less enhanced than controls, probably because of decreased portal perfusion.     

Differentiation of focal nodular hyperplasia and hepatocellular adenoma by contrast-enhanced ultrasound

Non-invasive differentiation of focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) is difficult. The aim of this study was to assess the accuracy of contrast-enhanced phase inversion ultrasound to differentiate between histologically proven FNH and HCA, analysing the arterial and (early) portal venous phase. 32 patients with histological proven FNH (n=24) or HCA (n=8) have been included in this prospective study. Examination technique: Siemens Elegra, phase inversion harmonic imaging (PIHI) with low mechanical index (MI)<0.2-0.3 using SonoVue (BR 1). The contrast enhancing tumour characteristics were evaluated during the hepatic arterial (starting 8-22 s) and early portal venous phase (starting 12-30 s). The image analysis was performed by three examiners. In 23 of 24 patients with FNH the contrast pattern revealed pronounced arterial and (early) portal venous enhancement. Homogeneous enhancement was detected during the hepatic arterial phase in all eight patients with HCA. In contrast to patients with FNH, no enhancement was seen during the portal venous phase. In conclusion, contrast-enhanced phase inversion ultrasound demonstrated pronounced arterial and portal venous enhancement in patients with focal nodular hyperplasia. In contrast, after homogeneous enhancement during hepatic arterial phase, no enhancement during hepatic portal venous phase was detected in patients with hepatocellular adenoma. Therefore, this technique might improve the functional characterization of benign hypervascular focal liver lesions.     

基于深度学习的重建算法对腹部胰腺和门静脉CT图像质量的改善价值

目的探讨深度学习重建算法(DLIR)相对于滤波反投影算法(FBP)和多模型迭代重建算法(ASIR-V)对腹部胰腺和门静脉CT图像质量的改善价值。方法选取行常规腹部CT增强检查的患者36例,所得图像分别采用DLIRL、DLIR-M、DLIR-H、FBP及30%ASIR-V、70%ASIR-V算法重建图像,所得6种重建图像由2位放射科医师采用双盲法对图像噪声、对比度及细微结构进行主观评价。通过分别测量不同重建算法图像的CT值、SD值、SNR和CNR,并进行组间比较,来观察不同重建算法对图像质量的影响。结果 6组图像的SNR、CNR差异均有统计学意义(P<0.05),其中DLIR-H图像的SNR和CNR最高。主观评分之间差异均有统计学意义(P<0.05),两位医师的主观评分一致性良好,Kappa≥0.70,其中DLIR-M的主观评分最高。结论与FBP和ASIR-V重建算法比较,DLIR能够有效降低图像噪声、提高图像质量,因此DLIR算法可用于提升腹部胰腺和门静脉CT图像质量,有较好的临床应用前景。     

CT of portal venous occlusion.

Thrombosis of a portion of the portal venous system can be directly imaged by contrast-enhanced CT as a low-attenuation lesion within the involved portal venous segment with or without expansion of the vessel or enhancement at the margin of the thrombus. Collateral venous pathways are often evident, which provide supporting evidence of the occlusion. Alterations in portal venous blood flow lead to metabolic disturbances in the liver and to abnormalities in parenchymal enhancement during dynamic CT scanning, and these changes are manifested as abnormalities in hepatic parenchymal density. The detection of portal venous thrombosis or occlusion, collateral veins, or abnormal liver enhancement should initiate a search for the diseases that cause these abnormalities.     

Multislice helical CT of the pancreas and spleen

Multislice helical CT (MSCT) with its multidetector technology and faster rotation times, has led to new dimensions in spatial and temporal resolution in CT imaging. In contrast to single-slice CT, smaller slice collimations can be applied that lead to almost isotropic voxels and allow high quality multiplanar and 3-D image reconstructions. The high speed of multislice CT can be used to reduce the time needed to cover a given volume, to increase the spatial resolution along the z-axis by applying thinner slice collimations, and to cover longer anatomic volumes. The speed of MSCT allows organ imaging in clearly defined perfusion phases, e.g. the arterial, parenchymal, and portal venous perfusion phases. Contrast agents with higher iodine concentrations (400 mg iodine per ml compared with 300 mg iodine per ml) lead to higher contrast enhancement of the pancreas (arterial+portal venous phases), the kidneys (arterial+portal venous phases), the spleen (arterial phase), the wall of the small intestine (arterial+portal venous phases), the larger and smaller arteries (arterial phase), and the portal vein (portal venous phase). All of these advancements lead to improved visualization of small structures and of various pathologies, such as pancreatic tumors, liver metastases, vessel infiltration, and vascular diseases.     

Portal imaging

Portal imaging is the acquisition of images with a radiotherapy beam. Imaging theory suggests that the quality of portal images could be much higher if the efficiency of the imaging media in detecting radiation could be improved. Introduction of new media (films and electronic portal imaging devices) has confirmed this by markedly increasing the quality of portal images. Images from these devices can then be used to verify a patient's treatment. Geometric verification requires the portal image to be registered with a reference image. Dosimetric verification requires the portal imager to be calibrated for dose. This review gives a brief overview of the current areas of interest in portal imaging: imaging theory; imaging media, film and electronic portal imaging devices; image registration; and dosimetry using these devices.     

Digital image processing of radiation therapy portal films

Digital image processing has the potential to enhance and improve several functions of a modern radiation oncology department. These functions may include improving perception of information for low contrast films, electronic transfer of images to remote facilities and back, and reducing storage space requirements for archiving once treatment is finished. This paper gives an overview of the digitization process and of image processing fundamentals. The clinical evaluation of digitized portal films is also discussed. The authors conclude that digitizing low contrast radiation therapy portal films is feasible with present technology and will produce images acceptable for routine clinical use in most instances. The role of image enhancement is less well established and remains investigational.     

Hepatic enhancement in multiphasic contrast-enhanced MDCT: comparison of high- and low-iodine-concentration contrast medium in same patients with chronic liver disease

OBJECTIVE: The aim of this study was to evaluate the degree of hepatic enhancement and image quality in patients with cirrhosis or chronic hepatitis who underwent multiphasic contrast-enhanced dynamic imaging on MDCT at least twice using standard (300 mg I/mL) and higher (370 mg I/mL) iodine concentrations in contrast medium during follow-up periods. MATERIALS AND METHODS: This study included 20 patients with chronic liver diseases who underwent at least two multiphasic contrast-enhanced dynamic MDCT examinations using 100 mL of standard (300 mg I/mL = group A) and higher (370 mg I/mL = group B) iodine concentrations in contrast medium. After we obtained unenhanced CT scans, we performed multiphasic scanning at 30 sec (arterial phase), 60 sec (portal phase), and 180 sec (late phase) after the start of contrast medium injection. The CT values of hepatic parenchyma, abdominal aorta, and portal vein were measured. The mean enhancement value was defined as the difference in CT values between unenhanced and contrast-enhanced images. Visual image quality was also assessed on the basis of the degree of hepatic and vascular enhancement, rated on a 4-point scale. RESULTS: The mean hepatic parenchyma enhancement values in group B was significantly greater (p < 0.001) than those in group A during the portal phase (43.8 +/- 8.2 H vs 36.2 +/- 7.3 H) and the late phase (33.7 +/- 7.0 H vs 27.3 +/- 3.9 H), but the difference on the arterial phase images between the two groups (9.4 +/- 3.2 H vs 8.3 +/- 2.5 H) was not significant. The mean aorta-to-liver contrast during the arterial phase in group B was significantly higher (p < 0.001) than that in group A (236 +/- 40 H vs 193 +/- 32 H). For qualitative analysis, the mean visual scores for hepatic parenchyma and vasculature enhancement in group B were significantly higher than those in group A in arterial phase (p < 0.018), portal phase (p < 0.0001), and late phase (p < 0.0001). CONCLUSION: In the same patients with chronic liver diseases, a higher iodine concentration (370 mg I/mL) in the contrast medium improves contrast enhancement of liver parenchyma in the portal phase and late phase images, improves overall image quality, and helps improve diagnostic accuracy for liver diseases on multiphasic contrast-enhanced dynamic MDCT.     

胃癌螺旋CT诊断方法探讨

目的 探讨螺旋CT不同的扫描方法对胃癌分期的价值。资料与方法 进展期胃癌232例进行螺旋CT扫描，其中门静脉单期增强84例，三期增强96例，人工气腹法螺旋CT增强（SCTPP）52例。结果 门静脉期单期增强，三期增强和SCTPP对进展期胃癌TNM分期准确性分别为75.0%,82.3%和96.2%。结论 胃癌术前分期首选螺旋CT三期增强，若仍无法准确评估分期的体瘦患者可选用SCTPP，术后复查首选螺旋CT门静脉期单期增强。     

Hepatic and vascular enhancement at dual-phase helical CT: comparison of Iobitridol 300 and Iohexol 300 in a prospective randomized study

The purpose of this study was to determine hepatic and vascular enhancement, clinical tolerance, and iconographic quality of Iobitridol (300 mg/ml) at dual-phase helical CT and to compare it with Iohexol (300 mg/ml). One hundred forty-six patients were randomly divided into two groups. Each group received 120 ml of Iohexol (group A) or Iobitridol (group B). Mean enhancement of liver, aorta and portal vein was obtained at the arterial phase and at the portal-venous phase. Overall image quality was assessed by two independent blinded investigators. Adverse reactions were recorded. There were no significant differences in demographic characteristics and distribution of patient intrinsic parameters between the two groups, except for blood pressure but without statistical correlation between the difference in blood pressure and the impact on enhancement measurements. There was no significant difference in clinical tolerance and image quality. Mean liver as well as aortic and portal vein enhancement measurements did not show any significant difference. Iobitridol compares favorably with Iohexol. Both products have similar safety, tolerance, and efficacy. Both contrast media have equivalent blood pool concentration and interstitial compartment diffusion.     

Contrast improvement in a new radiotherapy imaging system

PURPOSE: The aim of this paper is to compare the EC-L Kodak system for radiation therapy beam localization with a conventional one that could be daily employed in a radiotherapy department. BACKGROUND: The main purpose of portal images is to verify the treatment volume in actual clinical conditions. Low contrast is the main constraint affecting portal film image. METHODS: Kodak proposes a new imaging system (film and cassette) characterized by contrast enhancement as imaging standard for radiotherapy. The evaluation of system contrast was carried out by using a step-wedge consisting in 4 60 x 60 mm plexiglas steps and an anthropomorphic phantom. Portal films were exposed to a 6 MV photon beam by a linear accelerator (Varian Clinac 1800) with a 250 x 340 mm field size at the 1000 mm source film distance. The 2 imaging system performances were evaluated analyzing the image optical density. RESULTS: The use of the Kodak system results in a real contrast improvement, so it is satisfactory to describe the field placement as to the region of interest. CONCLUSIONS: The most critical characteristic attaining this method regards low contrast, i. e. the small optical density difference existing between different anatomical regions on the film. Since radiographic techniques can significantly influence quality of portal films, the adequate choice of film and screen combination, as well as the exposure technique is particularly useful in a radiotherapy quality assurance program.     

Radiation dose reduction in hepatic multidetector computed tomography with a novel adaptive noise reduction filter

Purpose The aim of this study was to optimize a novel adaptive noise reduction filter based on patient body weight and to investigate its utility for improving the image quality of low-dose hepatic computed tomography (CT) scans. Materials and methods The tube current-time product was changed from 140 to 180 and from 60 to 100 mAs at standard-and low-dose CT, respectively, based on the body weights of 45 patients. Unenhanced and two-phase contrast-enhanced helical scans were obtained at the standard dose during the hepatic arterial and equilibrium phases. During the equilibrium phase, we obtained low-dose scans of the liver immediately after standard-dose scans. The low-dose CT images were postprocessed with the filter. Two radiologists visually evaluated artifacts in the liver parenchyma and its graininess, the sharpness of the liver contour, tumor conspicuity, homogeneity of the enhancement of the portal vein, and overall image quality. Results There was no statistically significant difference between standard and filtered low-dose images with respect to artifacts in the liver, the graininess of the liver parenchyma, tumor conspicuity, homogeneity of enhancement of the portal vein, or overall image quality. Conclusion The adaptive noise reduction filter effectively reduced image noise. We confirmed the effectiveness of the filter by examining clinical hepatic images obtained at low-dose CT.     

肝脏门静脉期CT增强的影响因素与对策

随着CT技术的发展,尤其是近几年双能CT的出现,不仅提高了影像质量,而且能够实现物质定量分析,极大拓展了临床应用范围,但同时也对优化应用提出了新的挑战。在上腹部检查中由于肝脏双重供血的特点造成了增强检查的特殊性,这突出体现在门静脉期影像质量难以达到预期而降低诊断可靠性上。因此,分析影响门静脉期增强的对比剂、病人和CT扫描等方面因素,总结在提高影像质量的同时降低对比剂剂量和辐射剂量的研究进展,并展望基于双能CT的个性化的上腹部增强检查计划设计方案。     

Gadolinium-enhanced phase-contrast magnetic resonance portography.

PURPOSE: The purpose of this study was to investigate the effect and usefulness of gadolinium-chelated contrast medium in phase-contrast magnetic resonance (MR) portography. METHODS: Twenty-six patients (21 men, 5 women; aged 34 to 79 years, mean 62 years) underwent respiratory-triggered 3-dimensional phase-contrast portography before and after administration of gadolinium in a 1.5T MR unit. Coronal maximum intensity projection (MIP) images of the portal vein were reconstructed and compared to conventional arterial portograms regarding visualization. Signal-to-noise ratio (SNR) and portal vein-to-liver contrast-to-noise ratios (CNR) of main, right, right anterior, right posterior, left portal veins, and umbilical portion were measured on both non-enhanced and gadolinium-enhanced images and compared. RESULTS: Portal veins and branches were more clearly visualized on the gadolinium-enhanced than on the non-enhanced images. Compared to arterial portography, gadolinium-enhanced portography showed similar performances in visualization, except in the right posterior branch and left portal vein. No severe image degradation from respiration was experienced. SNR was significantly higher on the gadolinium-enhanced than on non-enhanced images except in the right anterior branch. CNR was significantly higher on the gadolinium-enhanced than on the non-enhanced images at all measured locations. CONCLUSIONS: Administration of gadolinium improves the SNR and CNR of phase-contrast portography and visualization of the portal vein. The phase-contrast technique with gadolinium enhancement can be used to evaluate the portal vein as a supplemental technique.