Differentiation of neoplastic from bland macroscopic portal vein thrombi using dual-energy spectral CT imaging: a pilot study

CT/MRI technical pitfalls for diagnosis and treatment response assessment using LI-RADS and how to optimize

Hepatocellular carcinoma (HCC), the most common primary liver cancer, is a significant global health burden. Accurate imaging is crucial for diagnosis and treatment response assessment, often eliminating the need for biopsy. The Liver Imaging Reporting and Data System (LI-RADS) standardizes the interpretation and reporting of liver imaging for diagnosis and treatment response assessment, categorizing observations using defined categories that are based on the probability of malignancy or post-treatment tumor viability. Optimized imaging protocols are essential for accurate visualization and characterization of liver findings by LI-RADS. Common technical pitfalls, such as suboptimal postcontrast phase timing, and MRI-specific challenges like subtraction misregistration artifacts, can significantly reduce image quality and diagnostic accuracy. The use of hepatobiliary contrast agents introduces additional challenges including arterial phase degradation and suboptimal uptake in advanced cirrhosis. This review provides radiologists with comprehensive insights into the technical aspects of liver imaging for LI-RADS. We discuss common pitfalls encountered in routine clinical practice and offer practical solutions to optimize imaging techniques. We also highlight technical advances in liver imaging, including multi-arterial MR acquisition and compressed sensing. By understanding and addressing these technical aspects, radiologists can improve accuracy and confidence in the diagnosis and treatment response assessment for hepatocellular carcinoma.

Spectral computed tomography in abdominal and pelvic pathologies. A practical guide

Spectral computed tomography has represented a major breakthrough in radiology thanks to its multiple applications and potential to provide more information than conventional CT techniques. It is very useful for diagnosing and describing findings as well as the management of patients, thus avoiding further imaging or invasive procedures. The aim of this article is to explain basic concepts of spectral CT and highlight key practical features in a range of abdominal and pelvic pathologies, along with a brief description of different post-processing maps and their clinical applications including incidental, oncological and urgent findings.

Role of contrast-enhanced ultrasound for differentiation of benign vs. malignant portal vein thrombosis in hepatocellular carcinoma - A systematic review a meta-analysis

INTRODUCTION/PURPOSE

Patients with cirrhosis and hepatocellular carcinoma (HCC) can develop both benign and malignant portal vein thrombosis (PVT). Characterising the nature of PVT is important for planning an optimal therapeutic strategy. In the absence of typical findings or contraindications to computed tomography (CT) or magnetic resonance imaging (MRI), contrast-enhanced ultrasound (CEUS) could help in this differentiation. The present meta-analysis aimed to evaluate the performance of CEUS for characterising PVT in patients with HCC.

METHODS

Electronic databases of PubMed, Embase and Scopus were searched from inception to 31 December 2022 for studies analysing the role of CEUS in the differentiation of benign and malignant PVT in HCC. Using the bivariate random effect model, pooled sensitivity and specificity were calculated, and the summary receiver operating characteristic (sROC) curve was plotted.

RESULTS

A total of 12 studies with data from 712 patients were included in the meta-analysis. The pooled sensitivity and specificity of CEUS for the diagnosis of tumour in vein were 97.0% (95% CI: 93.0-98.7) and 96.8% (95% CI: 92.1-98.7), respectively, without significant heterogeneity. A sROC curve was plotted, and the area under the receiver operating characteristic was 0.99 (95% CI: 0.98-1.00). Despite the presence of publication bias, sensitivity analysis did not show any change in sensitivity and specificity.

DISCUSSION

Our meta-analysis summarises the accuracy data from 12 studies, including >700 subjects. Contrast-enhanced ultrasound had excellent diagnostic accuracy with pooled sensitivity and specificity of 97.5% (95% CI: 93.5-99.1) and 98.2% (95% CI: 91.5-99.6), respectively, without any significant heterogeneity. Additionally, the pooled positive LR, negative LR and DOR were 54.6 (95% CI: 11.1-25.6), 0.02 (0.01-0.07) and 2186.8 (318.3-15022.2), respectively. A positive result increases the pretest probability of malignant PVT from 50% to 98%, whereas a negative result decreases it from 50% to 2%. Most of the studies included in our meta-analysis used identical techniques and 6-12-month follow-up scans to check for thrombus progression or regression. Our analysis showed no significant heterogeneity in the studies, and area under receiver operating characteristic curve (AUROC) with 95% CI was 1.00 (95% CI: 0.99-1.00). This critical meta-analysis thus propels CEUS to the forefront for differentiating benign from tumoural PVT and suggests routinely using CEUS in patients presenting with HCC and evidence of thrombus on greyscale ultrasound.

CONCLUSION

Contrast-enhanced ultrasound is an effective diagnostic modality differentiation of benign and malignant PVT in patients with HCC and can be an alternative modality to CT or MRI. Further studies are required to study the role of CEUS as initial diagnostic modality for the characterisation of PVT in HCC.

Dual-Energy, Spectral and Photon Counting Computed Tomography for Evaluation of the Gastrointestinal Tract

The use of dual-energy computed tomography (CT) allows for reconstruction of energy- and material-specific image series. The combination of low-energy monochromatic images, iodine maps, and virtual unenhanced images can improve lesion detection and disease characterization in the gastrointestinal tract in comparison with single-energy CT.

Breaking down tumor thrombus: Current strategies for medical management

Tumor thrombus, the intravascular extension of tumor into adjacent blood vessels, is frequently encountered in patients with renal cell carcinoma and hepatocellular carcinoma, and often involves the abdominal vasculature including the renal vein, portal vein, and the inferior vena cava. While a bland thrombus is composed of platelets and fibrin, in contrast, a tumor thrombus refers to an organized collection of tumor cells. Though oftentimes detected incidentally on imaging, tumor thrombus may have significant clinical implications and can be challenging to differentiate from bland thrombus. Additionally, the optimal management of tumor thrombus, including the use of anticoagulation, remains poorly described. This review summarizes common causes of tumor thrombus, as well as its impact on staging, prognosis, and treatment.

Quantitative dual-energy CT techniques in the abdomen

Advances in dual-energy CT (DECT) technology and spectral techniques are catalyzing the widespread implementation of this technology across multiple radiology subspecialties. The inclusion of energy- and material-specific datasets has ushered overall improvements in CT image contrast and noise as well as artifacts reduction, leading to considerable progress in radiologists' ability to detect and characterize pathologies in the abdomen. The scope of this article is to provide an overview of various quantitative clinical DECT applications in the abdomen and pelvis. Several of the reviewed applications have not reached mainstream clinical use and are considered investigational. Nonetheless awareness of such applications is critical to having a fully comprehensive knowledge base to DECT and fostering future clinical implementation.

Portal vein thrombosis in patients with chronic liver diseases: From conventional to quantitative imaging

Portal vein thrombosis is a pathological condition characterized by the lumen occlusion of the portal vein and its intrahepatic branches, commonly associated to chronic liver diseases. Portal vein thrombosis is often asymptomatic and discovered as an incidental finding in the follow-up of chronic hepatopathy. Imaging plays a pivotal role in the detection and characterization of portal vein thrombosis in patients with hepatocellular carcinoma. Ultrasound and Color-Doppler ultrasound are usually the first-line imaging modalities for its detection, but they have limits related to operator-experience, patient size, meteorism and the restrained field-of view. Unenhanced cross-sectional imaging doesn't provide specific signs of portal vein thrombosis except under certain specific circumstances. Conventional contrast-enhanced imaging can depict portal vein thrombosis as an endoluminal filling defect best detected in venous phase and can differentiate between non-neoplastic and neoplastic thrombus based on the contrast enhanced uptake, but not always rule-out the malignant nature. Functional and quantitative imaging techniques and software seem to be more accurate. The purpose of this work is to provide the reader with an accurate overview focused on the main imaging features of portal vein thrombosis.

Computed Tomography Techniques, Protocols, Advancements, and Future Directions in Liver Diseases

Computed tomography (CT) is often performed as the initial imaging study for the workup of patients with known or suspected liver disease. Our article reviews liver CT techniques and protocols in clinical practice along with updates on relevant CT advances, including wide-detector CT, radiation dose optimization, and multienergy scanning, that have already shown clinical impact. Particular emphasis is placed on optimizing the late arterial phase of enhancement, which is critical to evaluation of hepatocellular carcinoma. We also discuss emerging techniques that may soon influence clinical care.

Accuracy of spectral curves at different phantom sizes and iodine concentrations using dual-source dual-energy computed tomography

To validate the accuracy of spectral curves obtained by an image-data-based algorithm and clarify the error factors that reduce accuracy. Iodine rods of known composition and different concentrations were inserted into a cylinder or elliptic-cylinder phantom and scanned according to the dual-energy protocol. Spectral curves were obtained by (i) theoretical calculation, (ii) image-data-based 2-material decomposition, and (iii) using a dedicated workstation. Accuracy was verified by comparing the spectral curve obtained by theoretical calculations with those obtained by the image-data-based algorithms or the dedicated workstations. For a quantitative evaluation, the error and relative error (RE) were calculated. In the image-data-based calculation, the errors with respect to the theoretical CT number ranged from - 8.3 to 71.1 HU. For all 192 combinations, 80.7% of the errors were under ± 15 HU, and 97.9% of the REs were under 10%. In the dedicated workstation, the errors ranged from - 94.7 to 26.8 HU. For all combinations, 68.8% of the errors were under ± 15 HU, and 68.2% of the REs were under 10%. By appropriately setting the effective energy corresponding to the CT number of the basis materials, an accurate spectral curve can be obtained. The beam-hardening effect is canceled by the 2-material decomposition process even without beam-hardening correction. Accuracy is primarily reduced by scattered radiation rather than the beam-hardening effect.

Clinical Implementation of Dual-Energy CT for Gastrointestinal Imaging

Dual-energy CT (DECT) overcomes several limitations of conventional single-energy CT (SECT) for the evaluation of gastrointestinal diseases. This article provides an overview of practical aspects of the DECT technology and acquisition protocols, reviews existing clinical applications, discusses current challenges, and describes future directions, with a focus on gastrointestinal imaging. A head-to-head comparison of technical specifications among DECT scanner implementations is provided. Energy- and material-specific DECT image reconstructions enable retrospective (i.e., after examination acquisition) image quality adjustments that are not possible using SECT. Such adjustments may, for example, correct insufficient contrast bolus or metal artifacts, thereby potentially avoiding patient recalls. A combination of low-energy monochromatic images, iodine maps, and virtual unenhanced images can be included in protocols to improve lesion detection and disease characterization. Relevant literature is reviewed regarding use of DECT for evaluation of the liver, gallbladder, pancreas, and bowel. Challenges involving cost, workflow, body habitus, and variability in DECT measurements are considered. Artificial intelligence and machine-learning image reconstruction algorithms, PACS integration, photon-counting hardware, and novel contrast agents are expected to expand the multienergy capability of DECT and further augment its value.

Dual-energy CT in diffuse liver disease: is there a role?

Dual-energy CT (DECT) can be defined as the use of two different energy levels to identify and quantify material composition. Since its inception, DECT has benefited from remarkable improvements in hardware and clinical applications. DECT enables accurate identification and quantification of multiple materials, including fat, iron, and iodine. As a consequence, multiple studies have investigated the potential role of DECT in the assessment of diffuse liver diseases. While this role is evolving, this article aims to review the most relevant literature on use of DECT for assessment of diffuse liver diseases. Moreover, the basic concepts on DECT techniques, types of image reconstruction, and DECT-dedicated software will be described, focusing on the areas that are most relevant for the evaluation of diffuse liver diseases. Also, we will review the evidence of added value of DECT in detection and assessment of hepatocellular carcinoma which is a known risk in patients with diffuse liver disease.

Multimodality Imaging of Abdominopelvic Tumors with Venous Invasion

A broad range of abdominal and pelvic tumors can manifest with or develop intraluminal venous invasion. Imaging features at cross-sectional modalities and contrast-enhanced US that allow differentiation of tumor extension within veins from bland thrombus include the expansile nature of tumor thrombus and attenuation and enhancement similar to those of the primary tumor. Venous invasion is a distinctive feature of hepatocellular carcinoma and renal cell carcinoma with known prognostic and treatment implications; however, this finding remains an underrecognized characteristic of multiple other malignancies-including cholangiocarcinoma, adrenocortical carcinoma, pancreatic neuroendocrine tumor, and primary venous leiomyosarcoma-and can be a feature of benign tumors such as renal angiomyolipoma and uterine leiomyomatosis. Recognition of tumor venous invasion at imaging has clinical significance and management implications for a range of abdominal and pelvic tumors. For example, portal vein invasion is a strong negative prognostic indicator in patients with hepatocellular carcinoma. In patients with rectal cancer, diagnosis of extramural venous invasion helps predict local and distant recurrence and is associated with worse survival. The authors present venous invasion by vascular distribution and organ of primary tumor origin with review of typical imaging features. Common pitfalls and mimics of neoplastic thrombus, including artifacts and anatomic variants, are described to help differentiate these findings from tumor in vein. By accurately diagnosing tumor venous invasion, especially in tumors where its presence may not be a typical feature, radiologists can help referring clinicians develop the best treatment strategies for their patients. ^©RSNA, 2020.

Quantification of Fat Concentration and Vascular Response in Brown and White Adipose Tissue of Rats by Spectral CT Imaging

Objective

The purpose of the study was to non-invasively characterize and discriminate brown adipose tissue (BAT) from white adipose tissue (WAT) in rats using spectral computed tomography (CT) with histological validation.

Materials and Methods

A lipid-containing phantom (lipid fractions from 0% to 100%) was imaged with spectral CT. An in vivo, non-enhanced spectral CT scan was performed on 24 rats, and fat concentrations of BAT and WAT were measured. The rats were randomized to receive intraperitoneal treatment with norepinephrine (NE) (n = 12) or saline (n = 12). Non-enhanced and enhanced spectral CT scans were performed after treatment to measure the elevation of iodine in BAT and WAT. The BAT/aorta and WAT/aorta ratios were calculated and compared, after which isolated BAT and WAT samples were subjected to histological and uncoupling protein 1 (UCP1) analyses.

Results

The ex-vivo phantom study showed excellent linear fit between measured fat concentration and the known gravimetric reference standard (r² = 0.996). In vivo, BAT had significantly lower fat concentration than WAT (p < 0.001). Compared to the saline group, the iodine concentration of BAT increased significantly (p < 0.001) after injection of NE, while the iodine concentration of WAT only changed slightly. The BAT/aorta ratio also increased significantly after exposure to NE compared to the saline group (p < 0.001). Histological and UCP1 expression analyses supported the spectral CT imaging results.

Conclusion

The study consolidates spectral CT as a new approach for non-invasive imaging of BAT and WAT. Quantitative analyses of BAT and WAT by spectral CT revealed different characteristics and pharmacologic activations in the two types of adipose tissue.

Benefit of dual-layer spectral CT in emergency imaging of different organ systems

Computed tomography (CT) has been the first choice of imaging technique in the emergency department and has a crucial role in many acute conditions. Since its implementation, spectral CT has gained widespread application with the potential to improve diagnostic performance and impact patient care. In spectral CT, images are acquired at two different energy levels allowing this technique to differentiate tissues by exploiting their energy-dependent attenuation properties. Dual-layer spectral CT provides additional information with its material decomposition applications that include virtual non-contrast imaging, iodine density, and effective atomic number (Zeff) maps along with virtual monoenergetic images without the need for preselection of a protocol. This review aims to demonstrate its added value in the emergency department in different organ systems enabling better evaluation of inflammatory and ischaemic conditions, assessment of organ perfusion, tissue/lesion characterisation and mass detection, iodine quantification, and the use of lower volumes of contrast medium. With improved diagnostic performance, spectral CT could also aid in rapid decision-making to determine the treatment method in many acute conditions without increased radiation dose to the patient.

How to Best Detect Portal Vein Tumor Thrombosis in Patients with Hepatocellular Carcinoma Meeting the Milan Criteria: Gadoxetic Acid-Enhanced MRI versus Contrast-Enhanced CT

INTRODUCTION

The detection of portal vein tumor thrombosis (PVTT) in patients with hepatocellular carcinoma (HCC) meeting the Milan criteria is of critical importance as PVTT is known to be a contraindication to transplantation and an indicator of a dismal prognosis.

OBJECTIVE

To determine which modality may best detect PVTT, we compared the diagnostic performance of gadoxetic acid-enhanced MRI (GA-MRI) and contrast-enhanced CT (CECT) in HCC patients meeting the Milan criteria.

METHODS

We retrospectively enrolled 310 patients with HCCs meeting the Milan criteria who underwent both GA-MRI and CECT between June 2007 and May 2017. Among them, 44 patients were demonstrated to have PVTT while 266 patients had no PVTT. Two radiologists then assessed GA-MRI and CECT images for the presence of PVTT on a 5-point scale as well as vessel expansion, continuity with tumors, and enhancement on both modalities, as well as T2 hyperintensity and diffusion restriction on GA-MRI. The McNemar test was used to compare sensitivity and specificity of GA-MRI and CECT for the detection of PVTT, and Fisher's exact test was used to compare their imaging features.

RESULTS

GA-MRI showed higher sensitivity values than CECT in detecting PVTT (reviewer 1, 93.2% [41/44] vs. 77.3% [34/44]; reviewer 2, 88.6% [39/44] vs. 70.5% [31/44]) (both p = 0.039). Specificity of GA-MRI and CECT demonstrated no difference (reviewer 1, 95.5% [254/266] vs. 95.1% [253/266]; reviewer 2, 97.0% [258/266] vs. 97.4% [259/266]) (both p > 0.999). Continuity with tumors and enhancement were more frequently observed on GA-MRI than on CECT (p < 0.050, both reviewers).

CONCLUSION

GA-MRI detected PVTT more often than CECT in HCC patients meeting the Milan criteria and better depicted PVTT in continuity with tumors and those showing enhancement than CECT.

Imaging and implications of tumor thrombus in abdominal malignancies: reviewing the basics

Extension of tumor tissue within a vein is a recognized prognostic factor in abdominal malignancy because of its influence on tumor staging and selection of therapeutic management. With the advent of newer surgical techniques, and variable treatment strategies, imaging plays a crucial role in categorizing patients according to the tumor resectability and vascular reconstruction techniques during surgery. Understanding the clinical impact of tumor thrombus increases the awareness of the radiologist about the key findings in tumor staging and decision-making of surgical approach. Ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) can be used individually and in combination to accurately assess the tumor thrombus. In our pictorial review, we will discuss the imaging findings and clinical consequences of tumor thrombosis in abdominal malignancies, including hepatocellular carcinoma, pancreatic neuroendocrine tumor, renal cancer, and adrenal cortical carcinoma.

Characterization of Malignant Portal Vein Thrombosis with Contrast-Enhanced Ultrasonography

We prospectively evaluated the effectiveness of contrast-enhanced ultrasonography (CEUS) for differentiation of benign versus malignant portal vein thrombosis (PVT). We studied a total of 43 patients with chronic liver disease, hepatocellular carcinoma-suggestive nodules and confirmed PVT, in whom the nature of the PVT was confirmed by follow-up imaging (US, computed tomography and/or magnetic resonance imaging) performed up to 6 mo after CEUS. PVT was assessed by US, Doppler US and CEUS with respect to vessel wall disruption and/or invasion, color Doppler vascularization, pulsed Doppler vascularization pattern and CEUS enhancement and vascularization pattern, and thrombi were classified as benign or malignant based on these findings. Follow-up studies revealed malignant PVT in 22 of the 43 patients (51%) and benign PVT in 21 patients (49%). CEUS findings were consistent with follow-up studies in 41 of the 43 patients (95%), with κ = 0.903 (p < 0.0001), sensitivity = 91% and specificity = 100%, indicating that CEUS can be confidently used to differentiate benign from malignant portal vein thrombosis in the setting of chronic liver disease.

Value of CT spectral imaging in the differential diagnosis of thymoma and mediastinal lymphoma

Objective:

To investigate the imaging characteristics of thymoma and mediastinal lymphoma using spectral CT and evaluate whether the quantitative information can improve the differential diagnosis of these diseases.

Methods:

This retrospective study was approved by the institutional review board, and written informed consent was obtained from all patients. Overall, 39 patients with mediastinal tumors (24 thymomas and 15 mediastinal lymphomas) were examined with CT spectral imaging during the arterial phase (AP) and venous phase (VP). Iodine concentrations were derived from iodine-based material-decomposition CT images and normalized to the iodine concentration in the aorta. The difference in normalized iodine concentrations (NICs), HU curve slop(λ_HU), and the differences between AP and VP for CT values of lesions in 70 Kev were calculated. The two-sample t-test was performed to compare quantitative parameters, and non-quantitative parameters were compared with the Chi-square test (Fisher exact). Receiver operating characteristic (ROC) curves were generated to help establish threshold values for the parameters required for the significant differentiation of thymomas from mediastinal lymphomas. Two readers qualitatively assessed the lesion types according to the imaging features. The sensitivity and specificity of the qualitative and quantitative studies were compared.

Results:

NICs during the VP and λ_HU during the AP in patients with mediastinal lymphomas differed significantly from those in patients with thymomas. The mean NICs during the VP were 0.28 ± 0.08  mg ml⁻¹ (±standard deviation) vs 0.49 ± 0.15  mg ml⁻¹, respectively. The λ_HU during the AP was 0.69 ± 0.17 vs 1.26 ± 0.74, respectively. The NICs during the VP and λ_HU during the AP had high sensitivity and specificity in differentiating mediastinal lymphomas from thymomas. The tumor location, margin, necrosis, presence of swollen mediastinal lymph nodes, relationship with adjacent vessels, and enhancement pattern differed significantly between the groups (p < 0.05). The combination of NICs and λ_HU had higher sensitivity and specificity than did those of conventional qualitative CT image analysis during the combined phases.

Conclusion:

CT spectral imaging has promising potential for the diagnostic differentiation of mediastinal lymphomas and thymomas. The iodine content and λ_HU could be valuable parameters for differentiating thymomas and mediastinal lymphomas.

Advances in knowledge:

The iodine content and λ_HU, provided by spectral CT, could be used as new parameters to distinguish mediastinal lymphomas from thymomas.

Venous invasion by hepatic tumors: imaging appearance and implications for management

Venous invasion by hepatic tumors most commonly occurs with hepatocellular carcinoma and is associated with worse patient prognosis. Imaging plays an important role in the diagnosis of tumor thrombus in the liver. Moreover, differentiating between bland and tumor thrombus in the liver has important diagnostic, staging, therapeutic, and prognostic implications and may require a multimodal imaging approach including ultrasound, computed tomography, and/or magnetic resonance imaging. Treatment of hepatic malignancies with associated tumor thrombus is dependent on tumor type, disease extent within the liver, liver hemodynamics, and underlying liver function. Treatment of such tumors may involve surgical, locoregional and/or systemic therapies. The current review will focus on the imaging characteristics of venous invasion by hepatic tumors. The imaging findings most useful for differentiating hepatic venous tumor thrombus and bland thrombus will be highlighted and demonstrated with imaging examples. Imaging findings with implications for subsequent patient management will be described.

Imaging and minimally invasive endovascular therapy in the management of portal vein thrombosis

Thrombosis of the portal venous system, although rare in the general population, is commonly diagnosed in patients with specific underlying conditions including prothrombotic diseases, cirrhosis, hepatobiliary malignancy, and intraabdominal inflammation. Recent improvements in imaging have played a fundamental role in increased detection of portal vein thrombosis (PVT), frequently reported in asymptomatic patients as an incidental finding. Minimally invasive, endovascular therapy is a medically rational option to achieve recanalization of the portal vein as an adjunct to conservative medical management. This review focuses on the advances in imaging modalities to diagnose, stage and follow-up PVT, and gives a short overview of the available endovascular techniques in this field.

Impact of dual-energy CT post-processing to differentiate venous thrombosis from iodine flux artefacts

OBJECTIVES

To investigate the accuracy of dual-energy (DE) CT-based iodine maps (IM) and noise-optimised monoenergetic extrapolations (MEI+) at 40 keV for the detection and differentiation of venous thrombosis (VT) from iodine flux artefacts (IFA) in comparison to portal-venous phase CT (CT_PV).

METHODS

Ninety-nine patients were enrolled in this study. In all patients, VT or IFA was suspected on contrast-enhanced CT and confirmed by follow-up CT or colour-coded ultrasound. All examinations were performed on a third-generation dual-source CT system in DE mode during portal-venous phase. CT_PV, IM and 40-keV MEI+ were reconstructed and independently evaluated by two radiologists for the presence/absence of VT and/or IFA. Diagnostic confidence was rated on a three-point scale (3 = high confidence). Quantitative parameters were obtained by calculating contrast-to-noise ratios (CNRs), iodine content and thrombus volume. Diagnostic accuracy was assessed by calculating receiver operating characteristics (ROC) of CNR.

RESULTS

Diagnostic confidence was significantly higher for IM and MEI+ [both 3 (2-3)] compared to CT_PV [2 (1-3); p ≤ 0.03]. ROC analysis revealed significantly higher AUC values and increased sensitivity for IM and MEI+ (AUC = 88%/sensitivity = 79.1% and 86%/73.1%) than for CT_PV (75%/61.2%; p ≤ 0.01). Thrombus volume was significantly higher in MEI+ than in IM and CT_PV (p < 0.001). CNR of thrombosis was significantly higher in IM [11.5 (8.5-14.5), p < 0.001) and MEI+ [10.9 (8.8-15.5), p < 0.001] than in CT_PV [8.2 (5.8-11.4)]. Iodine quantification revealed significantly lower results in VT than in IFA [0.55 mg/ml (0.23-0.90) and 1.81 (1.60-2.12) mg/ml; p < 0.001].

CONCLUSIONS

IM and MEI+ 40 keV showed significantly higher diagnostic confidence and accuracy for the detection and differentiation of VT from IFA in comparison to CT_PV.

KEY POINTS

• Iodine maps and noise-optimised monoenergetic extrapolations at 40 keV increase diagnostic confidence and accuracy for the detection and differentiation of venous thrombosis from iodine flux artefacts. • Dual-energy post-processing can significantly increase contrast-to-noise ratio and the sensitivity for the diagnosis of venous thrombosis • Iodine load in venous thrombosis is significantly lower than in iodine flux artefacts.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 4: Abdominal and Pelvic Applications

This is the fourth of a series of 4 white papers that represent expert consensus documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This article, part 4, discusses DECT for abdominal and pelvic applications and, at the end of each, will offer our consensus opinions on the current clinical utility of the application and opportunities for further research.

Dual-energy CT with iodine quantification in distinguishing between bland and neoplastic portal vein thrombosis in patients with hepatocellular carcinoma

AIM

To investigate the diagnostic accuracy of dual-energy multidetector computed tomography (MDCT) with iodine quantification compared to conventional enhancement measurements in distinguishing bland from neoplastic portal vein thrombosis in patients with hepatocellular carcinoma.

MATERIAL AND METHODS

Thirty-four patients (26 men, eight women; mean age, 62 years) with hepatocellular carcinoma and portal vein thrombosis underwent contrast-enhanced dual-energy MDCT during the late hepatic arterial phase for the assessment of portal thrombosis (bland, n=21; neoplastic, n=13). Datasets were analysed separately by two different readers. Interobserver correlation and variability were calculated and compared with the Bland-Altman method. Diagnostic accuracy of conventional enhancement measurements and iodine quantification was calculated by setting either histopathology (n=7) or a reference standard based on MDCT imaging criteria and thrombus evolutionary characteristics compared to a previous MDCT examination (n=27). For iodine quantification threshold determination receiver operating characteristic (ROC) curves were drawn. p-Values <0.05 were considered significant.

RESULTS

For conventional enhancement measurements and iodine quantification interobserver correlation was 98% and 96%. Enhancement measurement resulted in a sensitivity of 92.3%, specificity of 85.7%, positive predictive value (PPV) of 80%, and negative predictive value (NPV) of 94.7%. An iodine concentration of 0.9 mg/ml optimised discrimination between neoplastic and bland thrombi (area under the ROC [AUC] 0.993) resulting in a sensitivity of 100%, specificity of 95.2%, PPV of 92.9%, and NPV of 100%. The overall diagnostic accuracy of iodine quantification (97%) was significantly better than conventional enhancement measurements (88.2%; p<0.001).

CONCLUSION

Compared to conventional enhancement measurements, iodine quantification improves the characterisation of portal vein thrombi during the late hepatic arterial phase in patients with hepatocellular carcinoma.

A primer on the use of dual-energy CT in the evaluation of commonly encountered neoplasms

Technical improvements in the acquisition and display of dual-energy computed tomography (DECT) have made this technique increasingly applicable to clinical practice, particularly in the setting of oncologic imaging. DECT allows for qualitative and quantitative analysis of tissue composition beyond the standard anatomical evaluation possible with single-energy computed tomography. For example, DECT can be used to interrogate iodine and calcium concentrations and to increase iodine signal, which makes many pathologic processes more conspicuous and provides improved understanding of internal structure within mass lesions. A working understanding of common postprocessing DECT displays will allow radiologists to maximize the additional diagnostic information available in DECT examinations. In this article, we describe common strategies for DECT interrogation by organ system, which may improve the conspicuity and understanding of suspected malignancies.

Cardiovascular involvement by osteosarcoma: an analysis of 20 patients

BACKGROUND

Although hematogenous spread of osteosarcoma is well known, the imaging findings of cardiovascular involvement by osteosarcoma are seldom reported and can be difficult to recognize. The enhanced resolution of modern CT and MRI scanners may lead to better detection of cardiovascular involvement.

OBJECTIVE

To describe the key imaging findings and clinical behavior of cardiovascular involvement by osteosarcoma.

MATERIALS AND METHODS

We retrospectively reviewed the imaging findings and clinical characteristics of 20 patients with cardiovascular involvement by osteosarcoma identified by two pediatric radiologists from a review of imaging studies at our institution from 2007 to 2013.

RESULTS

At initial diagnosis, the median age of the patients was 15.1 years (range 4.8-24.6 years), and 7 (35%) patients had detectable metastases. Median time to detection of cardiovascular metastases was 1.8 years (range 0-7.3 years). Sixteen patients died of disease; 4 have survived a median of 7.4 years since initial diagnosis. The sites of cardiovascular involvement were the systemic veins draining the primary and metastatic osteosarcoma, pulmonary arteries, pulmonary veins draining the pulmonary metastases, and heart. A dilated and mineralized terminal pulmonary arteriole is an early sign of metastatic osteosarcoma in the lung. Unfamiliarity with the imaging features resulted in under-recognition and misinterpretation of intravascular tumor thrombus as bland thrombus.

CONCLUSION

Knowledge of imaging findings in the era of modern imaging modalities has enhanced our ability to detect cardiovascular involvement and lung metastases early and avoid misinterpreting tumor thrombus in draining systemic veins or pulmonary arteries as bland thrombus.

Contrast-enhanced ultrasound in differentiating malignant from benign portal vein thrombosis in hepatocellular carcinoma

Portal vein thrombosis (PVT) may occur in liver cirrhosis patients. Malignant PVT is a common complication in cirrhotic patients with concomitant hepatocellular carcinoma (HCC) and, in some cases, it may be even the initial sign of an undetected HCC. Detection of malignant PVT in a patient with liver cirrhosis heavily affects the therapeutic strategy. Gray-scale ultrasound (US) is widely unreliable for differentiating benign and malignant thrombi. Although effective for this differential diagnosis, fine-needle biopsy remains an invasive technique. Sensitivity of color-doppler US in detection of malignant thrombi is highly dependent on the size of the thrombus. Contrast-enhanced computed tomography (CT) and contrast-enhanced magnetic resonance (MRI) can be useful to assess the nature of portal thrombus, while limited data are currently available about the role of positron emission tomography (PET) and PET-CT. In contrast with CT, MRI, PET, and PET-CT, contrast-enhanced ultrasound (CEUS) is a fast, effective, well tolerated and cheap technique, that can be performed even in the same session in which the thrombus has been detected. CEUS can be performed bedside and can be available also in transplanted patients. Moreover, CT and MRI only yield a snapshot analysis during contrast diffusion, while CEUS allows for a continuous real-time imaging of the microcirculation that lasts several minutes, so that the whole arterial phase and the late parenchymal phase of the contrast diffusion can be analyzed continuously by real-time US scanning. Continuous real-time monitoring of contrast diffusion entails an easy detection of thrombus maximum enhancement. Moreover, continuous quantitative analyses of enhancement (wash in - wash out studies) by CEUS during contrast diffusion is nowadays available in most CEUS machines, thus giving a more sophisticated and accurate evaluation of the contrast distribution and an increased confidence in diagnosis in difficult cases. In conclusion, CEUS is a very reliable technique with a high intrinsic sensitivity for portal vein patency assessment. More expensive and sophisticated techniques (i.e., CT, MRI, PET, and PET-CT) should only be indicated in undetermined cases at CEUS.

Dual-energy CT of the abdomen

Although conceived of in the 1970s, practical use of dual-energy CT in the clinical setting did not come to fruition until 2006, and since that time an ever expanding exploration of the technology has been underway. This article will discuss technical aspects of the two commercially available CT scanners, review the recent literature, and provide an organ-based description of abdominal dual-energy CT applications for the practicing radiologist.

Review article: portal vein obstruction--epidemiology, pathogenesis, natural history, prognosis and treatment

BACKGROUND

Portal vein obstruction may be due to portal vein thrombosis (PVT) or its sequale, the portal cavernoma. PVT is a common complication in liver cirrhosis, however, it may also occur as a primary vascular disorder, in absence of any liver disease.

AIM

To review the current knowledge on nomenclature, etiology, pathophysiology, clinical presentation, diagnostic workup and management of adult patients with obstruction in the portal vein, either as a primary vascular disease in adults, or as a complication of liver cirrhosis.

METHODS

A structured search in PubMed was performed using defined keywords (portal vein obstruction, extra-hepatic portal vein obstruction, PVT and portal cavernoma), including full text articles and abstracts in English language.

RESULTS

Several causes, operating both at local and systemic level, might play an important role in the pathogenesis of PVT. Frequently, more than one risk factor could be identified; however, occasionally no single factor is discernible. Diagnosis of portal vein obstruction depends on clinical presentation, imaging and laboratory investigations. Prompt treatment greatly affects the patient's outcome.

CONCLUSIONS

Portal vein obstruction occurring either due to thrombosis in the portal vein or due to the portal cavernoma, can contribute to significant morbidity and mortality in patients with or without cirrhosis. In recent years our understanding of etio-pathogenesis of portal vein obstruction has evolved tremendously, which has led to significant improvement in treatment outcomes. There are still areas where more studies are needed to better clarify the management issues of portal vein obstruction.

Oncological applications of dual-energy computed tomography imaging

Dual-energy computed tomography (DECT) imaging is a promising method used in oncology for accurate detection/diagnosis of malignant and benign lesions. Use of dual-energy spectral, weighted average, color-coded map, and virtual unenhanced images provides increased visual detection and easy lesion delineation. Lesion detectability, sensitivity, and conspicuity are significantly improved using DECT. Material characterization and decomposition are promising using DECT. Both anatomical and functional information related to oncology can be provided by DECT using single contrast-enhanced CT.

Spectral CT evaluation of interstitial brachytherapy in pancreatic carcinoma xenografts: preliminary animal experience

OBJECTIVES

We sought to evaluate the capability of spectral CT to detect the therapeutic response to (125)I interstitial brachytherapy in a pancreatic carcinoma xenograft nude mouse model.

METHODS

Twenty mice bearing SWl990 human pancreatic cancer cell xenografts were randomly separated into two groups: experimental (n = 10; 1.0 mCi) and control (n = 10; 0 mCi). After a two-week treatment, spectral CT was performed. Contrast-to-noise ratio (CNR) and iodine concentration (IC) in the lesions were measured and normalized to the muscle tissue, and nIC CD31 immunohistochemistry was used to measure microvessel density (MVD). The relationships between the nIC and MVD of the tumours were analysed.

RESULTS

The nIC of the experimental group was significantly lower than that of the control group during the multiphase examination. A significant difference in the MVD was observed between the two groups (P <0.001). The nIC values of the three-phase scans have a certain positive correlation with MVD (r = 0.57, p < 0.0001; r = 0.48, p = 0.002; r = 0.63, p = 0.0017 in the 10, 25, and 60 s phase, respectively).

CONCLUSIONS

Spectral CT can be a useful non-invasive imaging modality in evaluating the therapeutic effect of (125)I interstitial brachytherapy to a pancreatic carcinoma.

KEY POINTS

Spectral CT offers opportunities to assess therapeutic response in pancreatic cancer cases. Spectral CT findings correlated with vascular changes associated with (125)I seed implantation. Spectral CT with monochromatic imaging removed most (125)I seed artefacts.

Differentiation of bland from neoplastic thrombus of the portal vein in patients with hepatocellular carcinoma: application of susceptibility-weighted MR imaging

BACKGROUND

Neoplastic and bland portal vein thrombi (PVT) are both common in patients with hepatocellular carcinoma (HCC). The correct discrimination of them is essential for therapeutic strategies planning and survival predicting. The current study aims to investigate the value of susceptibility-weighted imaging (SWI) in differentiating bland from neoplastic PVT in HCC patients.

METHODS

20 HCC patients with bland PVT and 22 HCC patients with neoplastic PVT were imaged with non-contrast SWI at 3.0 Tesla MRI. The signal intensity (SI) of the PVT and HCC lesions in the same patients was compared on SW images. The phase values of the PVT were compared between neoplastic and bland thrombi cohorts. Receiver operator characteristics (ROC) analysis was conducted to evaluate the diagnostic ability of the phase values for neoplastic and bland thrombi discrimination.

RESULTS

20 of 22 neoplastic PVT were judged similar SI and 2 were judged lower SI than their HCC. For 20 bland PVT, 19 were judged lower SI and 1 was judged similar SI as their HCC (P<0.001). The average phase values (0.361 ± 0.224) of the bland PVT were significantly higher than those of the neoplastic PVT (-0.328 ± 0.127, P<0.001). The AUC for phase values in differentiating bland from neoplastic PVT was 0.989. The best cut-off value was -0.195, which gave a sensitivity of 95% and a specificity of 95.5%.

CONCLUSIONS

SW imaging appears to be a promising new method for distinguishing neoplastic from bland PVT. The high sensitivity and specificity suggest its high value in clinical practice.

Differential diagnosis of pancreatic serous oligocystic adenoma and mucinous cystic neoplasm with spectral CT imaging: initial results

AIM

To investigate the imaging characteristics of pancreatic serous oligocystic adenoma (SOA) and mucinous cystic neoplasms (MCNs) using spectral computed tomography (CT) and to evaluate whether quantitative information derived from spectral imaging can improve the differential diagnosis of these diseases.

MATERIALS AND METHODS

From February 2010 to June 2013, 44 patients (24 SOAs and 20 MCNs) who underwent spectral CT imaging were included in the study. Conventional characteristics and quantitative parameters were compared between the two disease groups. Logistic regression was used for multiparametric analysis. The receiver-operating characteristic curve was used to evaluate the diagnostic performance of single parameter and multiparametric analysis. Two radiologists diagnosed the diseases blinded and independently, without and with the information of the statistical analysis.

RESULTS

Tumour location, contour, size, and monochromatic CT values at 40 keV to 70 keV, iodine concentration, and effective atomic number (effective-Z) in the late arterial phase were the independent factors correlated with category. Multiparametric analysis with logistic regression showed that tumour size, location, and contour were the most effective variations, and obtained an area under the ROC curve (AUC) of 0.934. With the knowledge of statistical analysis, the accuracy of the first reader increased from 70.5% to 86.4%, and the accuracy of the second reader increased from 81.8% to 90.9%.

CONCLUSIONS

Although CT spectral imaging provided additional information and multiparametric analysis obtained better performance than single-parameter analysis in differentiating MCNs from SOAs, multiparametric analysis with the combination of quantitative parameters derived from CT spectral imaging did not improve the diagnostic performance. Tumour size, location, and contour played an important role in differentiating MCNs from SOAs.

Imaging in clinical decision-making for portal vein thrombosis

Thrombosis of the portal venous system is a frequent and potentially life-threatening condition that can take place in a number of different clinical settings including liver cirrhosis, hepatocellular carcinoma, other solid tumours, abdominal septic foci, acute pancreatitis, haematological malignancies and congenital or acquired prothrombotic disorders. Clinical decision-making in patients with thrombosis of the portal venous system is a particularly complex process owing to the heterogeneity of the population affected by this condition and the lack of high-quality evidence from randomized controlled trials for the use of anticoagulation therapy in these patients. This Review discusses the available data regarding how imaging can provide assistance to physicians involved in this decision-making process in different clinical settings. A flowchart illustrating how to use imaging in this setting, based on current evidence and on the experience of the Vascular Liver Diseases Group of the Hospital Clinic in Barcelona, is also presented.