Dual-source, dual-energy multidetector CT for the evaluation of pancreatic tumours

[Current CT developments in imaging of pancreatic diseases]

BACKGROUND

Diseases of the pancreas are often diagnosed late and can have fatal consequences for patients.

PURPOSE

Current computed tomography (CT) developments in imaging of pancreatic diseases.

MATERIALS AND METHODS

Evaluation of numerous studies, especially considering modern CT techniques such as dual-energy CT and photon-counting CT but also artificial intelligence (AI) algorithms for disease detection.

RESULTS

Spectral imaging using dual-energy CT and photon-counting CT offers numerous advantages in the detection of pancreatic disease and can thus improve diagnostic performance but also provide additional information on any therapeutic response. Likewise, advances in the development of AI algorithms are improving diagnostic performance.

CONCLUSION

In the future, we can expect increasingly improved detection of pancreatic diseases, thereby enabling patients to be treated more quickly, which will consequently result in improved outcomes.

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.

Characterizing incidental mass lesions in abdominal dual-energy CT compared to conventional contrast-enhanced CT

BACKGROUND

Incidental findings are common in abdominal computed tomography (CT) and often warrant further investigations with economic implications as well as implications for patients.

PURPOSE

To evaluate the potential of dual-energy CT (DECT) in the identification and/or characterization of abdominal incidental mass lesions compared to conventional contrast-enhanced CT.

MATERIAL AND METHODS

This retrospective study from a major tertiary hospital included 96 patients, who underwent contrast-enhanced abdominal DECT. Incidental lesions in adrenals, kidneys, liver, and pancreas were evaluated by two board-certified abdominal radiologists. Observer 1 only had access to standard CT reconstructions, while observer 2 had access to standard CT as well as DECT reconstructions. Disagreements were resolved by consensus review and used as a reference for observers using McNemar's test.

RESULTS

Observers 1 and 2 identified a total of 40 and 34 findings, respectively. Furthermore, observer 1 registered 13 lesions requiring follow-up, of which seven (two renal and five adrenal lesions) were resolved following consensus review using DECT (P = 0.008). The inter-observer agreement was near perfect (κ = 0.82).

CONCLUSION

DECT has the potential to improve the immediate characterization of incidental findings when compared to conventional CT for abdominal imaging.

Deep learning image reconstruction to improve accuracy of iodine quantification and image quality in dual-energy CT of the abdomen: a phantom and clinical study

OBJECTIVES

To investigate the effect of deep learning image reconstruction (DLIR) on the accuracy of iodine quantification and image quality of dual-energy CT (DECT) compared to that of other reconstruction algorithms in a phantom experiment and an abdominal clinical study.

METHODS

An elliptical phantom with five different iodine concentrations (1-12 mgI/mL) was imaged five times with fast-kilovoltage-switching DECT for three target volume CT dose indexes. All images were reconstructed using filtered back-projection, iterative reconstruction (two levels), and DLIR algorithms. Measured and nominal iodine concentrations were compared among the algorithms. Contrast-enhanced CT of the abdomen with the same scanner was acquired in clinical patients. In arterial and portal venous phase images, iodine concentration, image noise, and coefficients of variation for four locations were retrospectively compared among the algorithms. One-way repeated-measures analyses of variance were used to evaluate differences in the iodine concentrations, standard deviations, coefficients of variation, and percentages of error among the algorithms.

RESULTS

In the phantom study, the measured iodine concentrations were equivalent among the algorithms: within ± 8% of the nominal values, with root-mean-square deviations of 0.08-0.36 mgI/mL, regardless of radiation dose. In the clinical study (50 patients; 35 men; mean age, 68 ± 11 years), iodine concentrations were equivalent among the algorithms for each location (all p > .99). Image noise and coefficients of variation were lower with DLIR than with the other algorithms (all p < .01).

CONCLUSIONS

The DLIR algorithm reduced image noise and variability of iodine concentration values compared with other reconstruction algorithms in the fast-kilovoltage-switching dual-energy CT.

KEY POINTS

• In the phantom study, standard deviations and coefficients of variation in iodine quantification were lower on images with the deep learning image reconstruction algorithm than on those with other algorithms. • In the clinical study, iodine concentrations of measurement location in the upper abdomen were consistent across four reconstruction algorithms, while image noise and variability of iodine concentrations were lower on images with the deep learning image reconstruction algorithm.

Imaging Modalities for Early Detection of Pancreatic Cancer: Current State and Future Research Opportunities

Simple Summary

While survival rates for many cancers have improved dramatically over the last 20 years, patients with pancreatic cancer have persistently poor outcomes. The majority of patients with pancreatic cancer are not suitable for potentially curative surgery due to locally advanced or metastatic disease stage at diagnosis. Therefore, early detection would potentially improve survival of pancreatic cancer patients through earlier intervention. Here, we present clinical challenges in the early detection of pancreatic cancer, characterise high risk groups for pancreatic cancer and current screening programs in high-risk individuals. The aim of this scoping review is to investigate the role of both established and novel imaging modalities for early detection of pancreatic cancer. Furthermore, we investigate innovative imaging techniques for early detection of pancreatic cancer, but its widespread application requires further investigation and potentially a combination with other non-invasive biomarkers.

Abstract

Pancreatic cancer, one of the most lethal malignancies, is increasing in incidence. While survival rates for many cancers have improved dramatically over the last 20 years, people with pancreatic cancer have persistently poor outcomes. Potential cure for pancreatic cancer involves surgical resection and adjuvant therapy. However, approximately 85% of patients diagnosed with pancreatic cancer are not suitable for potentially curative therapy due to locally advanced or metastatic disease stage. Because of this stark survival contrast, any improvement in early detection would likely significantly improve survival of patients with pancreatic cancer through earlier intervention. This comprehensive scoping review describes the current evidence on groups at high risk for developing pancreatic cancer, including individuals with inherited predisposition, pancreatic cystic lesions, diabetes, and pancreatitis. We review the current roles of imaging modalities focusing on early detection of pancreatic cancer. Additionally, we propose the use of advanced imaging modalities to identify early, potentially curable pancreatic cancer in high-risk cohorts. We discuss innovative imaging techniques for early detection of pancreatic cancer, but its widespread application requires further investigation and potentially a combination with other non-invasive biomarkers.

Dual-Energy CT in the Pancreas

Dual-energy computed tomography (DECT) is an evolving imaging technology that is gaining popularity, particularly in different abdominopelvic applications. Essentially, DECT uses two energy spectra simultaneously to acquire CT attenuation data which is used to distinguish among structures with different tissue composition. The wide variety of reconstructed image data sets makes DECT especially attractive in pancreatic imaging. This article reviews the current literature on DECT as it applies to imaging the pancreas, focusing on pancreatitis, trauma, pancreatic ductal adenocarcinoma, and other solid and cystic neoplasms. The advantages of DECT over conventional CT are highlighted, including improved lesion detection, radiation dose reduction, and enhanced image contrast. Additionally, data exploring the ideal protocol for pancreatic imaging using DECT is reviewed. Finally, limitations of DECT in pancreatic imaging as well as recommendations for future research are provided.

Correlative investigation between routine clinical parameters of dual-energy computed tomography and the outcomes of extracorporeal shock wave lithotripsy in children with urolithiasis: a retrospective study

PURPOSE

To evaluate the associations of DECT parameters with extracorporeal shock wave lithotripsy (ESWL) outcomes in pediatric patients.

METHODS

A retrospective study of consecutive patients with calculi who underwent ESWL and DECT in our hospital was performed in 2011-2019. The primary outcome was DECT imaging's correlation with ESWL outcomes. The secondary outcome was to determine DECT parameters independently predicting ESWL outcomes, including stone-free (SF) and residual stone (RS) statuses.

RESULTS

The study included 207 patients. The mean CT attenuations at 140 kVp, 80 kVp, and 120 kVp and effective atomic number (Zeff) were significantly correlated with stone free (SF) and residual stone (RS) (P < 0.05). Areas under the curves (AUCs) of CT attenuations at 120 kVp, 80 kVp, 140 kVp, and dual-energy index (DEI) were 0.784 (95% CI 0.672-0.897), 0.780 (95% CI 0.677-0.884), 0.766 (95% CI 0.658-0.885), and 0.709 (95% CI 0.578-0.840) (all P < 0.05). With cutoffs of 882.5, 1330.5, 1042.5, and 0.103 for CT attenuations at 140 kVp, 80 kVp, 120 kVp, and DEI, respectively, sensitivities and specificities were 75.0% and 31.1%, 83.3% and 31.8%, 80.3% and 31.1%, and 58.3% and 44.7%, respectively.

CONCLUSION

Our results demonstrated that the parameters of DECT could be used to predict ESWL outcomes (especially the SF status) in children with urolithiasis. ESWL success can be accurately predicted by DECT, and it is hard to predict ESWL failure.

Intraductal papillary mucinous neoplasm (IPMN) of the pancreas: recommendations for Standardized Imaging and Reporting from the Society of Abdominal Radiology IPMN disease focused panel

There have been many publications detailing imaging features of malignant transformation of intraductal papillary mucinous neoplasms (IPMN), management and recommendations for imaging follow-up of diagnosed or presumed IPMN. However, there is no consensus on several practical aspects of imaging IPMN that could serve as a clinical guide for radiologists and enable future data mining for research. These aspects include how to measure IPMN, define reporting terminology, standardize reporting and unify guidelines for surveillance. The Society of Abdominal Radiology (SAR) created multiple Disease-Focused Panels (DFP) comprised multidisciplinary panel members who focus on a particular disease, with the goal to develop ways for radiologists to improve patient care, education, and research. DFP members met to identify the current controversies and limitations of imaging pancreatic IPMN. This paper aims to provide a practical review of the key imaging characteristics of IPMN for trainees and practicing radiologists, to guide uniformity of performance and interpretation of surveillance imaging studies, and to improve communication with clinicians by providing a lexicon and reporting template based on the experience of the SAR-DFP panel members.

Evaluation of equivocal small cystic pancreatic lesions with spectral-detector computed tomography

BACKGROUND

Evaluation of small cystic lesions of the pancreas remains a challenging task, as due to their size appearance can be rather hypodense than clearly fluid-filled.

PURPOSE

To evaluate whether additional information provided by novel dual-layer spectral-detector computed tomography (SDCT) imaging can improve assessment of these lesions.

MATERIAL AND METHODS

For this retrospective study, we reviewed reports of 1192 contrast-enhanced portal-venous phase SDCT scans of the abdomen conducted between May 2017 and January 2019. On basis of the radiological report 25 small (≤1.5 cm) cystic pancreatic lesions in 22 patients were identified, in which additional short-term follow-up imaging was recommended to confirm/clarify cystic nature. Conventional images (CI) and spectral images (SI) including virtual-monoenergetic images at 40 keV (VMI), iodine-density and iodine-overlay images were reconstructed. Two readers indicated lesion conspicuity and confidence for presence of cystic nature on three-point scales. First, solely CI were evaluated, while in a second reading after a four-week interval, the combination of CI and corresponding SI were reviewed. Quantitatively, ROI-based mean attenuation was measured in CI and VMI.

RESULTS

In the subjective reading, SI significantly improved lesion conspicuity (CI 2 [1-2], SI 3 [2-3], P < 0.001) and confidence regarding presence of cystic nature (CI 2 [1-2], SI 3 [3-3], P < 0.001). Inter-observer agreement depicted by intraclass correlation coefficient improved considerably from 0.51 with only CI to 0.85 when the combination with SI was used. Further, VMI displayed significantly higher signal-to-noise (CI 1.2 ± 0.8, VMI 3.2 ± 1.8, P < 0.001) and contrast-to-noise ratios (CI 2.6 ± 0.8, VMI 4.7 ± 1.9).

CONCLUSION

Compared to CI alone, combination with SI significantly improves visualization and confidence in evaluation of small equivocal cystic pancreatic lesions.

Technical Note: Using virtual noncontrast images from dual-energy CT to eliminate the need of precontrast CT for x-ray radiation treatment planning of abdominal tumors†

PURPOSE

Radiation therapy (RT) planning frequently utilizes contrast-enhanced CT. However, dose calculations should not be performed on a contrast-enhanced CT because the patient will not receive bolus during treatment. It is typical to acquire CT twice during RT simulation: once before injection of bolus and once after. The registration between these datasets introduces errors. In this work, we investigate the use of virtual noncontrast images (VNC) derived from dual-energy CT (DECT) to eliminate the precontrast CT and the registration error.

METHODS

CT datasets, including conventional 120 kVp pre- and postcontrast CTs and postcontrast DECT, acquired for ten pancreatic cancer patients were evaluated. The DECTs were acquired simultaneously using a dual source (DS) CT simulator. VNC and virtual mono-energetic images (VMI) were derived from DECTs. Gross tumor volumes (GTV), planning target volumes (PTV), and organs at risks (OAR) were delineated on the postcontrast CT and then populated to the precontrast CT and the VNC. An IMRT plan (50.4 Gy in 28 fractions) was then optimized on the precontrast CT. Dose distributions were recalculated on the VNC images. Contours from the pre- and postcontrast CTs and the dose distributions based on both were compared.

RESULTS

On average, the distance of centroids of the populated duodenum contours on precontrast CT differed by 6.0 ± 4.0 mm from those on postcontrast CTs. The dose distributions on the precontrast CT and VNC were almost identical. The PTV mean and maximum doses differed by 0.1% and 0.2% between the two plans, respectively.

CONCLUSION

The VNC derived from DECT can be used to replace the conventional precontrast CT scan for RT planning, eliminating the need for an additional precontrast CT scan and eliminating the registration errors. Thus, VNC can become an important asset to the future of RT.

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 gland tumors: a comprehensive narrative review and differential diagnosis

Dual energy CT (DECT)with image acquisition at two different photon X-ray levels allows the characterization of a specific tissue or material/elements, the extrapolation of virtual unenhanced and monoenergetic images, and the quantification of iodine uptake; such special capabilities make the DECT the perfect technique to support oncological imaging for tumor detection and characterization and treatment monitoring, while concurrently reducing the dose of radiation and iodine and improving the metal artifact reduction. Even though its potential in the field of oncology has not been fully explored yet, DECT is already widely used today thanks to the availability of different CT technologies, such as dual-source, single-source rapid-switching, single-source sequential, single-source twin-beam and dual-layer technologies. Moreover DECT technology represents the future of the imaging innovation and it is subject to ongoing development that increase according its clinical potentiality, in particular in the field of oncology. This review points out recent state-of-the-art in DECT applications in gland tumors, with special focus on its potential uses in the field of oncological imaging of endocrine and exocrine glands.

Improved detectability of hypoattenuating focal pancreatic lesions by dual-layer computed tomography using virtual monoenergetic images

Background

Multidetector CT is the mainstay for radiologic evaluation of pancreatic pathology. Still, imaging of focal pancreatic lesions using MDCT is faced by a number of challenges that are related to the limited contrast between the lesion and surrounding parenchyma, such as detecting early-stage pancreatic cancer and subtle features of cystic lesions that point to malignancy. Dual-layer CT is the first dual-energy CT machine based on separation of high- and low-energy photons at the detector level. If improved contrast between the lesions and normal pancreatic parenchyma could be achieved on CT images, we may expect enhanced CT detection of pancreatic lesions. The purpose of this study was to evaluate whether virtual monoenergetic reconstructions generated using contrast-enhanced dual-layer CT could improve detectability of hypoattenuating focal pancreatic lesions compared to conventional polyenergetic reconstructions.

Results

Fifty-four lesions were identified and verified by histopathology or follow-up CT, MRCP, and/or EUS along with clinical data. Across the virtual monoenergetic spectrum, 40 KeV images had the highest contrast-to-noise and signal-to-noise ratios (p < 0.001, p < 0.001) and were significantly higher than conventional images (p < 0.001). Subjective scores for lesion visibility at low kiloelectron volt monoenergetic (40 and 50 KeV) images greatly exceeded conventional images (p < 0.001).

Conclusion

Low kiloelectron volt monoenergetic reconstructions of contrast-enhanced dual-layer CT significantly improve detectability of hypoattenuating focal pancreatic lesions compared to conventional polyenergetic reconstructions.

Replacing true unenhanced imaging in renal carcinoma with virtual unenhanced images in dual-energy spectral CT: a feasibility study

AIM

To investigate the clinical value of virtual unenhanced (VNC) spectral computed tomography (CT) images to replace the conventional true unenhanced spectral CT images (TNC) in diagnosing renal carcinoma.

MATERIALS AND METHODS

Fifty-six cases of renal carcinoma confirmed by histopathology underwent conventional plain CT and contrast-enhanced spectral CT at arterial phase (AP) and venous phase (VP). VNC images were generated on an AW4.6 workstation. The CT attenuation, image noise, contrast-to-noise ratio (CNR), and signal-noise-ratio (SNR) of the renal lesions and normal kidneys, long and short axis diameters of the lesion were measured from the three image sets and analysed using one-way analysis of variance (ANOVA). Two radiologists evaluated image quality subjectively using a five-point score, and lesion signature using a three-point score. Image quality scores were compared statistically and tested for consistency.

RESULTS

The two reviewers had good agreement for subjective evaluation (Kappa>0.70) and there was no difference in the quality of the scores among the three image groups. The lesion signature scores were all above the acceptable level. The CNR and SNR values in VNC were significantly higher than in TNC (p<0.05). VNC images had lower renal noise than in TNC (p<0.05). There was no difference in the long and short axis diameters of the lesion among the three image groups. VNC had higher CT attenuation values for the lesion and kidney than TNC (p<0.05), but the differences were <5 HU.

CONCLUSION

VNC images in spectral CT may be used to replace the conventional plain CT to reduce imaging duration and radiation dose in diagnosing renal carcinoma.

Endoscopic ultrasound versus computed tomography in determining the resectability of pancreatic cancer: A diagnostic test accuracy meta-analysis

BACKGROUND/AIM

Endoscopic ultrasound (EUS) and contrast-enhanced computed tomography (CT) with pancreas protocol are used in assessing the resectability of neoplastic pancreatic lesions. Here, we performed a diagnostic test accuracy (DTA) meta-analysis, comparing the diagnostic accuracy of EUS and CT in evaluating the resectability of pancreatic cancer using surgical assessment as the reference standard.

PATIENTS AND METHODS

A comprehensive electronic search was conducted up to March 2020. Studies comparing EUS and CT in assessing the resectability of pancreatic cancer using surgical assessment as reference standard were included. QUADAS-2 tool was used to assess the quality of the included studies. After data extraction, an analysis was done using DerSimonian Laird method (random-effects model) to estimate the overall diagnostic odds ratio (DOR) and determine the best-fitting receiver operating characteristics (ROC) curve.

RESULTS

Two studies, with 77 subjects combined, were included in the analysis. Overall, the risk of bias was moderate. EUS and CT were comparable in determining the resectability of pancreatic cancer with AUC = 75% (95% confidence interval (CI) 66%- 84%) for EUS as compared to 78% (95% CI 69%- 87%) for CT (P > 0.05). Pooled sensitivity and specificity was 87% (95% CI 70%- 96%) and 63% (95% CI 48%- 77%), respectively for EUS and 87% (95% CI 70%- 96%) and 70% (95% CI 55%- 83%), respectively for CT. DOR was 11.51 (95% CI 3.55- 36.81) for EUS as compared to 15.91 (95% CI 4.83- 51.62) for CT (P > 0.05).

CONCLUSIONS

Both EUS and CT provide reasonable sensitivity and specificity to detect the resectability of pancreatic cancer.

Advanced imaging techniques for chronic pancreatitis

MRI and MRCP play an important role in the diagnosis of chronic pancreatitis (CP) by imaging pancreatic parenchyma and ducts. MRI/MRCP is more widely used than computed tomography (CT) for mild to moderate CP due to its increased sensitivity for pancreatic ductal and gland changes; however, it does not detect the calcifications seen in advanced CP. Quantitative MR imaging offers potential advantages over conventional qualitative imaging, including simplicity of analysis, quantitative and population-based comparisons, and more direct interpretation of detected changes. These techniques may provide quantitative metrics for determining the presence and severity of acinar cell loss and aid in the diagnosis of chronic pancreatitis. Given the fact that the parenchymal changes of CP precede the ductal involvement, there would be a significant benefit from developing MRI/MRCP-based, more robust diagnostic criteria combining ductal and parenchymal findings. Among cross-sectional imaging modalities, multi-detector CT (MDCT) has been a cornerstone for evaluating chronic pancreatitis (CP) since it is ubiquitous, assesses primary disease process, identifies complications like pseudocyst or vascular thrombosis with high sensitivity and specificity, guides therapeutic management decisions, and provides images with isotropic resolution within seconds. Conventional MDCT has certain limitations and is reserved to provide predominantly morphological (e.g., calcifications, organ size) rather than functional information. The emerging applications of radiomics and artificial intelligence are poised to extend the current capabilities of MDCT. In this review article, we will review advanced imaging techniques by MRI, MRCP, CT, and ultrasound.

White paper on pancreatic ductal adenocarcinoma from society of abdominal radiology's disease-focused panel for pancreatic ductal adenocarcinoma: Part II, update on imaging techniques and screening of pancreatic cancer in high-risk individuals

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive gastrointestinal malignancy with a poor 5-year survival rate. Its high mortality rate is attributed to its aggressive biology and frequently late presentation. While surgical resection remains the only potentially curative treatment, only 10-20% of patients will present with surgically resectable disease. Over the past several years, development of vascular bypass graft techniques and introduction of neoadjuvant treatment regimens have increased the number of patients who can undergo resection with a curative intent. While the role of conventional imaging in the detection, characterization, and staging of patients with PDAC is well established, its role in monitoring treatment response, particularly following neoadjuvant therapy remains challenging because of the complex anatomic and histological nature of PDAC. Novel morphologic and functional imaging techniques (such as DECT, DW-MRI, and PET/MRI) are being investigated to improve the diagnostic accuracy and the ability to measure response to therapy. There is also a growing interest to detect PDAC and its precursor lesions at an early stage in asymptomatic patients to increase the likelihood of achieving cure. This has led to the development of pancreatic cancer screening programs. This article will review recent updates in imaging techniques and the current status of screening and surveillance of individuals at a high risk of developing PDAC.

Extracellular volume fraction determined by equilibrium contrast-enhanced dual-energy CT as a prognostic factor in patients with stage IV pancreatic ductal adenocarcinoma

OBJECTIVES

To evaluate the feasibility of equilibrium contrast-enhanced dual-energy CT (DECT), as compared with single-energy CT (SECT) and to calculate extracellular volume (ECV) fraction to predict the survival outcomes of pancreatic ductal adenocarcinoma (PDAC) patients with distant metastases (stage IV) treated with chemotherapy.

METHODS

The study cohort included a total of 66 patients with stage IV PDAC who underwent DECT before systemic chemotherapy between July 2014 and March 2017. Unenhanced and 120-kVp equivalent images during the equilibrium phase were used to calculate tumor SECT-derived ECV fractions, and iodine density images were obtained from equilibrium-phase DECT for DECT-derived ECV fractions. Correlations between SECT- and DECT-derived ECV fractions were identified using the Pearson correlation coefficient and Bland-Altman analysis. The effects of clinical prognostic factors and tumor SECT- and DECT-derived ECV fractions on progression-free survival (PFS) and overall survival (OS) were assessed by univariate and multivariate analyses using Cox proportional hazards models.

RESULTS

The correlation between SECT- and DECT-derived ECV fractions was strong (r = 0.965; p < 0.001). The Bland-Altman plot between SECT- and DECT-derived ECV fractions showed a small bias (- 3.4%). Increasing tumor SECT- and DECT-derived ECV fractions were associated with a positive effect on PFS (SECT, p = 0.002; DECT, p = 0.007) and OS (DECT, p = 0.014; DECT, p = 0.015). Only tumor DECT-derived ECV fraction was an independent predictor of PFS (p = 0.018) and OS (p = 0.022) in patients with stage IV PDAC treated with chemotherapy on multivariate analysis.

CONCLUSIONS

The ECV fraction determined by equilibrium contrast-enhanced DECT can potentially predict the survival of patients with stage IV PDAC treated with chemotherapy.

KEY POINTS

• Extracellular volume fraction of stage IV pancreatic ductal adenocarcinoma determined by dual-energy CT was strongly correlated to that with single-energy CT (r = 0.965, p < 0.001). • Tumor extracellular volume fraction was an independent predictor of progression-free survival (p = 0.018) and overall survival (p = 0.022). • Extracellular volume fraction determined by dual-energy CT could be a useful imaging biomarker to predict the survival of patients with stage IV pancreatic ductal adenocarcinoma treated with chemotherapy.

Dual-Energy CT of the Pancreas

This article explores the technical background of dual-energy CT (DECT) imaging along with its basic principles, before turning to a review of the various DECT applications specific to pancreatic imaging. In light of the most recent literature, we will review the constellation of DECT applications available for pancreatic imaging in both oncologic and non-oncologic applications. We emphasize the increased lesion conspicuity and the improved tissue characterization available with DECT post-processing tools. Finally, future clinical applications and opportunities for research will be overviewed.

Early Detection of Pancreatic Cancer: Opportunities and Challenges

Most patients with pancreatic ductal adenocarcinoma (PDAC) present with symptomatic, surgically unresectable disease. Although the goal of early detection of PDAC is laudable and likely to result in significant improvement in overall survival, the relatively low prevalence of PDAC renders general population screening infeasible. The challenges of early detection include identification of at-risk individuals in the general population who would benefit from longitudinal surveillance programs and appropriate biomarker and imaging-based modalities used for PDAC surveillance in such cohorts. In recent years, various subgroups at higher-than-average risk for PDAC have been identified, including those with familial risk due to germline mutations, a history of pancreatitis, patients with mucinous pancreatic cysts, and elderly patients with new-onset diabetes. The last 2 categories are discussed at length in terms of the opportunities and challenges they present for PDAC early detection. We also discuss current and emerging imaging modalities that are critical to identifying early, potentially curable PDAC in high-risk cohorts on surveillance.

Response assessment in pancreatic ductal adenocarcinoma: role of imaging

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive gastrointestinal (GI) malignancy with poor 5-year survival rate. Advances in surgical techniques and introduction of novel combination chemotherapy and radiation therapy regimens have necessitated the need for biomarkers for assessment of treatment response. Conventional imaging methods such as RECIST have been used for response evaluation in clinical trials particularly in patients with metastatic PDAC. However, the role of these approaches for assessing response to loco-regional and systemic therapies is limited due to complex morphological and histological nature of PDAC. Determination of tumor resectability after neoadjuvant therapy remains a challenge. This review article provides an overview of the challenges and limitations of response assessment in PDAC and reviews the current evidence for the utility of novel morphological and functional imaging tools in this disease.

Dual energy CT applications in pancreatic pathologies

Dual energy CT (DECT) is a technology that is gaining widespread acceptance, particularly for its abdominopelvic applications. Pancreatic pathologies are an ideal application for the many advantages offered by dual energy post-processing. This article reviews the current literature on dual energy CT pancreatic imaging, specifically in the evaluation of pancreatic adenocarcinoma, other solid and cystic pancreatic neoplasms, and pancreatitis. The advantages in characterization and quantification of enhancement, detection of subtle lesions, and potential reduction of imaging phases and contrast usage are reviewed. We also discuss directions for future research, and the ideal use of dual energy CT in routine clinical practice.

Role of Multi Detector Computed Tomography (MDCT) in Preoperative Staging of Pancreatic Carcinoma

INTRODUCTION

Pancreatic carcinoma is one of the leading causes of cancer related death in advanced countries and has shown rising trends in developing countries like India. Increase in the incidence has been linked to risk factors like lifestyle modification associated with increased alcohol consumption and rapid urbanization. Most patients at the time of diagnosis present with an advanced condition. Surgical resection offers the only chance for cure in them and imaging plays a crucial role in the early diagnosis of the condition.

AIM

To compare the staging of pancreatic carcinoma by MDCT (Multi Detector Computed Tomography) with surgery in a preoperative setting in a tertiary referral centre in Kerala.

MATERIALS AND METHODS

A cross-sectional observational study was performed between November 2014 and October 2016, 25 patients (12 men, 13 women), with a mean age of 54.2 years, were evaluated. MDCT was performed using 16 slice, 64 slice and 256 slice multi detector CT machines. The gold standard for diagnosis was histopathology and operative data. All statistical analysis was done using IBM SPSS version 20.0. Validity parameters like sensitivity, specificity, accuracy and Positive Predictive Value (PPV) / Negative Predictive Value (NPV) were computed for MDCT with respect to surgery.

RESULTS

Of the 25 patients who were evaluated for surgery, 15 (60%) cases were classified as resectable tumours, 3 (12%) as borderline resectable and 7 (28%) as unresectable tumours. CT showed a sensitivity of 82.3% with a specificity of 87.5%. However, for assessing vascular invasion, CT showed sensitivity and specificity of 100% and 93.3% respectively. Three (12%) patients in the study who were classified as borderline resectable pancreatic tumours underwent surgery.

CONCLUSION

Contrast-enhanced multiphase pancreatic imaging using MDCT plays a pivotal role in diagnosing and assessing resectability and vascular invasion of pancreatic tumours. It is very useful for determining borderline resectable tumours pre-operatively, which aids for better treatment planning.

Abdominal Applications of a Novel Detector-Based Spectral CT

Detector-based spectral computed tomography (SDCT) is a recently introduced technology that uses a single x-ray tube and 2 layers of detectors to simultaneously collect low- and high-energy data. In this article, we provide an overview of this novel SDCT technology in abdominal imaging. Several applications of SDCT in abdominal imaging are discussed and illustrated, along with a brief description of current literature on the status of dual-energy computed tomography in these applications. This includes urinary calculus composition, characterization of masses (renal, adrenal, hepatic, and others), tumor perfusion, improving vascular contrast, improving lesion conspicuity, decreasing artifacts, and reducing radiation dose.

Current Status and Future Directions for Screening Patients at High Risk for Pancreatic Cancer

It is well known that pancreatic ductal adenocarcinoma has a high mortality rate. Despite progress in understanding the biology and genetic basis of this disease, life expectancy has changed minimally in the last 50 years. This article highlights the importance of screening patients at high risk for developing pancreatic cancer and reviews current methods as well as methods in development for pancreatic cancer early detection and surveillance.

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 of liver metastases in patients with uveal melanoma

Objective

To investigate the value of different kVp images of dual-energy CT (DECT) for the detection of liver metastases.

Methods

20 Patients with uveal melanoma were investigated with DECT of the liver. In each patient contrast-enhanced DECT imaging with arterial delay was performed. Number and size of metastases were documented on arterial phase 80-kVp images, virtual 120-kVp images and following angiographic images (DSA) as part of hepatic chemoperfusion. Attenuation of metastases and several anatomic regions, subjective (image noise, image quality) and objective (SNR, CNR) parameters were documented.

Results

The mean number of liver metastases detected was significant higher on 80-kVp images than on virtual 120-kVp/DSA images (5.6 ± 2.1 vs. 4.1 ± 1.8/4.3 ± 1.6); (p < 0.001). All lesions sizes were significant better detected with 80 kVp images than with virtual 120 kVp and DSA-Images (80 kVp vs. 120 kVp: <10 mm: 34 vs. 19, p < 0.05; 10–20 mm:, 33 vs. 25, p < 0.05; >20 mm: 56 vs. 42, p < 0.05/80 kVp vs. DSA: <10 mm: 34 vs. 18 p < 0.05; 10–20 mm: 33 vs. 24, p < 0.05; >20 mm: 56 vs. 41, p < 0.05). Number of detected small lesions <10 mm with 120 kVp compared to DSA-images were significant higher (19 vs. 13; p < 0.05), lesions 10–20 mm and >20 mm were measured statistically equally. Noise, SNR and CNR of 80 kVp images were higher compared to 120 kVp images. Image quality of 120 kVp images was higher compared to 80 kVp images.

Conclusion

Low-kVp images of DECT datasets are more sensitive in detecting liver metastases of patients with uveal melanoma than virtual 120 kVp- and DSA images.

Treatment response after radioembolisation in patients with hepatocellular carcinoma-An evaluation with dual energy computed-tomography

PURPOSE

The aim of this prospective study was to examine the diagnostic value of dual-energy CT (DECT) in the assessment of response of HCC after radioembolisation (RE).

MATERIAL AND METHODS

40 HCC patients with 82 measurable target lesions were included in this study. At baseline and follow-up examination target lesions were evaluated with (IU), AASLD and Choi measurement criteria. Disease control was defined as the sum of complete response (CR), partial response (PR), progression disease (PD) and stable disease (SD).

RESULTS

With Choi and IU more patients were considered than PR and less than PD and SD. According to AASLD more patients were measured as SD and PD than PR. 26/40 patients were classified as PR with IU. In contrast measurements with AASLD in only 8/26 patients were also classified as PR. 6/12 SD patients measured with IU were measured as PD with AASLD. 4/26 patients classified with IU as PR were described as SD with CHOI, 10/14 SD patients measured with CHOI were SD according to IU, the other 4 patients were PR with IU. 2/4 PD patients according to CHOI were SD with IU.

CONCLUSION

More patients by IU were classified as SD versus PD and PR versus SD. We attribute this to the more detailed consideration of the HU differences between the virtual native and contrast-enhanced series generated by DECT. Iodine uptake (IU) in HCC measured and visualized with DECT is a promising imaging method for the assessment of treatment response after radioembolisations.

KEY POINTS

-dual energy CT of hypervascular tumors such as HCC allows to quantify contrast enhancement without native imaging. -this can be used to evaluate the therapy response after Radioembolization.

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.

Dual-energy CT increases reader confidence in the detection and diagnosis of hypoattenuating pancreatic lesions

PURPOSE

To prospectively compare detection and reader confidence of pancreatic lesions using a standard multi-detector computed tomography (MDCT) imaging protocol to a dual-energy computed tomography (DECT) imaging protocol with additional virtual non-contrast series.

METHODS

60 subjects imaged for suspected or known pancreatic lesions were included. Subjects underwent pancreatic MDCT including non-contrast, pancreatic phase, and portal venous phase (PVP). The PVP was performed in dual energy mode. Virtual non-contrast and blended 120 kVp weighted images were created from the DECT data. Overall noise and absolute attenuation differences of pancreatic lesions and normal pancreatic tissue were measured. Images were read by two staff radiologists blinded to the underlying diagnosis. MDCT and DECT scans were reviewed separately to evaluate image quality and level of confidence in diagnosis of a pancreatic lesion.

RESULTS

Image quality was ranked excellent for 90 % and 95 % of the 120 kVp studies and 93 % and 95 % of the 100 kVp studies by readers 1 and 2, respectively. VNC was ranked sufficient quality or better by both readers. Average attenuation difference was 74 HU (120 kVp) and 71 HU (100 kVp). Average noise was 11.31 HU (120 kVp) and 15.89 HU (100 kVp). No lesions were missed by either approach. There was increased confidence in diagnostic interpretation in 14 % (± 9 % [95 % CI]) and 9 % (± 7 % [95 % CI]) of DECT scans compared to MDCT.

CONCLUSIONS

DECT compared to MDCT pancreatic imaging leads to increased reader confidence with identical diagnostic sensitivity for pathologically proven cases. This approach could be implemented as a single phase acquisition study with calculated VNC leading to a significant dose savings to the patient.

Imaging preoperatively for pancreatic adenocarcinoma

Pancreatic cancer is a highly lethal malignancy which is increasing in incidence and mortality. The fourth leading cause of cancer death in the U.S., pancreatic cancer is projected to become the second leading cause of cancer death by 2020. Patients with pancreatic cancer have an abysmal 5-year survival of 6%, and 90% of these patients eventually die from the disease. This is in large part due to the commonly advanced stage of disease at the time of diagnosis. Currently, the only potentially curative therapy for pancreatic carcinoma is complete surgical resection. Patients who undergo incomplete resection with residual disease have similar survival rates to those patients with metastatic disease and should be spared this relatively morbid surgery. Thus, the key to impacting prognosis is the detection of smaller and earlier stage lesions, and the key to optimal management is accurately determining which patients have potentially resectable surgery and which patients would not benefit from surgery. Cross-sectional imaging plays an essential role in both the diagnosis and appropriate staging of pancreatic carcinoma. The diagnosis and staging of pancreatic adenocarcinoma is performed with cross-sectional imaging. Multi-detector computed tomography (MDCT) is the most commonly used, best-validated imaging modality for the diagnosis and staging of pancreatic cancer. Modern contrast-enhanced magnetic resonance imaging (MRI) has been demonstrated to be equivalent to MDCT in detection and staging of pancreatic cancer. Endoscopic ultrasound (EUS) is very sensitive for detecting pancreatic masses; however, due to limitations in adequate overall abdominal staging, it is generally used in addition to or after MDCT. Transabdominal ultrasound and positron emission tomography/computed tomography (PET/CT) have limited roles in the diagnosis and staging of pancreatic cancer. Preoperative imaging is used to characterize patients as having resectable disease, borderline resectable disease, locally advanced disease (unresectable) and metastatic disease (unresectable). As the definitions of borderline resectable and unresectable may vary from institution to institution and within institutions, it is essential to accurately assess and describe the factors relevant to staging including: local extent of tumor, vascular involvement, lymph node involvement and distant metastatic disease. To facilitate this, standardized reporting templates for pancreatic ductal adenocarcinoma have been created and published. Structured reporting for pancreatic cancer has been reported to provide superior evaluation of pancreatic cancer, facilitate surgical planning, and increase surgeons' confidence about tumor resectability.

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.

Optimal Pancreatic Phase Delay with 64-Detector CT Scanner and Bolus-tracking Technique

RATIONALE AND OBJECTIVES

To assess the optimal pancreatic phase delay in terms of parenchymal enhancement and tumor-to-pancreas contrast with a bolus-tracking method.

MATERIALS AND METHODS

Patients referred for suspicion of pancreatic tumor and undergoing 64-detector computed tomography scanner were randomized to an individualized scan delay of 10, 20, or 30 seconds of nonionic contrast material (370 mg I/mL) after aortic enhancement above 150 Hounsfield units. The volume of contrast was adjusted to patient weight. Pancreatic and tumor enhancements were measured. Statistical analysis included analysis of variance and post hoc Tukey tests.

RESULTS

One hundred and fifty patients were randomized to individualized scan delays of 10, 20, or 30 seconds. Pancreatic parenchymal enhancement in all patients (n = 150) was significantly higher with a delay of 20 or 30 seconds than that with 10 seconds (P < .001 for both). Tumor-to-pancreas contrast for solid tumors (n = 59) was significantly higher with a delay of 30 seconds than that with 10 seconds (P = .015). Adenocarcinoma-to-pancreas contrast during pancreatic phase was significantly higher for a 20- or 30-second delay than for a 10-second delay (P = .027 and .011, respectively) for one reader.

CONCLUSIONS

With a flow rate of 4 mL/s and weight-adjusted contrast volume, an individualized scan delay of 30 seconds after aortic transit time revealed higher pancreatic enhancement and tumor-to-pancreas contrast than that with a delay of 10 seconds.

Imaging diagnosis of pancreatic cancer: A state-of-the-art review

Pancreatic cancer (PC) remains one of the deadliest cancers worldwide, and has a poor, five-year survival rate of 5%. Although complete surgical resection is the only curative therapy for pancreatic cancer, less than 20% of newly-diagnosed patients undergo surgical resection with a curative intent. Due to the lack of early symptoms and the tendency of pancreatic adenocarcinoma to invade adjacent structures or to metastasize at an early stage, many patients with pancreatic cancer already have advanced disease at the time of their diagnosis and, therefore, there is a high mortality rate. To improve the patient survival rate, early detection of PC is critical. The diagnosis of PC relies on computed tomography (CT) and/or magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography (MRCP), or biopsy or fine-needle aspiration using endoscopic ultrasound (EUS). Although multi-detector row computed tomography currently has a major role in the evaluation of PC, MRI with MRCP facilitates better detection of tumors at an early stage by allowing a comprehensive analysis of the morphological changes of the pancreas parenchyma and pancreatic duct. The diagnosis could be improved using positron emission tomography techniques in special conditions in which CT and EUS are not completely diagnostic. It is essential for clinicians to understand the advantages and disadvantages of the various pancreatic imaging modalities in order to be able to make optimal treatment and management decisions. Our study investigates the current role and innovative techniques of pancreatic imaging focused on the detection of pancreatic cancer.