Imaging for Early Detection of Pancreatic Ductal Adenocarcinoma: Updates and Challenges in the Implementation of Screening and Surveillance Programs.

Pancreatic ductal adenocarcinoma (PDA) is one of the most aggressive cancers. It has a poor 5-year survival rate of 12%, partly because most cases are diagnosed at advanced stages, precluding curative surgical resection. Early-stage PDA has significantly better prognoses due to increased potential for curative interventions, making early detection of PDA critically important to improved patient outcomes. We examine current and evolving early detection concepts, screening strategies, diagnostic yields among high-risk individuals, controversies, and limitations of standard-of-care imaging.

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.

CT Esophagography for Evaluation of Esophageal Perforation.

Esophageal emergencies such as rupture or postoperative leak are uncommon but may be life threatening when they occur. Delay in their diagnosis and treatment may significantly increase morbidity and mortality. Causes of esophageal injury include iatrogenic (including esophagogastroduodenoscopy and stent placement), foreign body ingestion, blunt or penetrating trauma to the chest or abdomen, and forceful retching, also called Boerhaave syndrome. Although fluoroscopic esophagography remains the imaging study of choice according the American College of Radiology appropriateness criteria, CT esophagography has been shown to be at least equal to if not superior to fluoroscopic evaluation for esophageal injury. In addition, CT esophagography allows diagnosis of extraesophageal abnormalities, both as the cause of the patient's symptoms as well as incidental findings. CT esophagography also allows rapid diagnosis since the examination can be readily performed in most clinical settings and requires no direct radiologist supervision, requiring only properly trained technologists and a CT scanner. Multiple prior studies have shown the limited utility of fluoroscopic esophagography after a negative chest CT scan and the increase in accuracy after adding oral contrast agent to CT examinations, although there is considerable variability of CT esophagography protocols among institutions. Development of a CT esophagography program, utilizing a well-defined protocol with input from staff from the radiology, gastroenterology, emergency, and general surgery departments, can facilitate more rapid diagnosis and patient care, especially in overnight and emergency settings. The purpose of this article is to familiarize radiologists with CT esophagography techniques and imaging findings of emergent esophageal conditions. Online supplemental material is available for this article. ©RSNA, 2021.

Structured Reporting in Ultrasound.

Structured reporting of ultrasound examinations can add value throughout the imaging chain. Reports may be created in a more efficient manner, with increased accuracy and clarity. Communication with referring providers and patients may be improved. Patient care can be enhanced through improved adherence with guidelines and local best practices. Radiology departments may benefit from improved billing and quality reporting. Consistent discrete data can enable research and collaborations between institutions. This article will review the multifaceted impact of structuring ultrasound reports.

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.

White paper on pancreatic ductal adenocarcinoma from society of abdominal radiology's disease-focused panel for pancreatic ductal adenocarcinoma: Part I, AJCC staging system, NCCN guidelines, and borderline resectable disease.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive gastrointestinal malignancy with a poor 5-year survival rate. Accurate staging of PDAC is an important initial step in the development of a stage-specific treatment plan. Different staging systems/consensus statements convened by different societies and academic practices are currently used. The most recent version of the American Joint Committee on Cancer (AJCC) tumor/node/metastases (TNM) staging system for PDAC has shifted its focus from guiding management to assessing prognosis. In order to preoperatively define the resectability of PDAC and to guide management, additional classification systems have been developed. The National Comprehensive Cancer Network (NCCN) guidelines, one of the most commonly used systems, provide recommendations on the management and the determination of resectability for PDAC. The NCCN divides PDAC into three categories of resectability based on tumor-vessel relationship: 'resectable,' 'borderline resectable,' and 'unresectable'. Among these, the borderline disease category is of special interest given its evolution over time and the resulting variations in the definition and the associated recommendations for management between different societies. It is important to be familiar with the evolving criteria, and treatment and follow-up recommendations for PDAC. In this article, the most current AJCC staging (8th edition), NCCN guidelines (version 2.2019-April 9, 2019), and challenges and controversies in borderline resectable PDAC are reviewed.

Sonographic Appearances of Portal Vein Abnormalities.

Portal venous system evaluation is required in many clinical circumstances, as substantial morbidity and mortality can be associated with a spectrum of portal vein abnormalities. Portal venous system pathologies can be congenital or acquired, and the knowledge of their imaging appearances will allow for a confident diagnosis and appropriate treatment options. In addition, a firm understanding of anatomical variants is important for planning surgical procedures and percutaneous interventions of the liver. This article will review various imaging appearances of portal venous systems abnormalities.

Magnetic Resonance-Guided Focused Ultrasound: A Brief Review With Emphasis on the Treatment of Extra-abdominal Desmoid Tumors.

Magnetic resonance-guided focused ultrasound (MRgFUS) utilizes high-intensity focused ultrasound to noninvasively, thermally ablate lesions within the body while sparing the intervening tissues. Magnetic resonance imaging provides treatment planning and guidance, and real-time magnetic resonance thermometry provides continuous monitoring during therapy. Magnetic resonance-guided focused ultrasound is ideally suited for the treatment of extra-abdominal desmoid fibromatosis due to its noninvasiveness, lack of ionizing radiation, low morbidity, and good safety profile. Conventional treatments for these benign tumors, including surgery, radiation, and chemotherapy, can carry significant morbidity. Magnetic resonance-guided focused ultrasound provides a safe and effective alternative treatment in this often-young and otherwise healthy patient population. While there is considerable experience with MRgFUS for treatment of uterine fibroids, painful bone lesions, and essential tremor, there are few reports in the literature of its use for treatment of benign or malignant soft tissue tumors. This article reviews the principles and biologic effects of high-intensity focused ultrasound, provides an overview of the MRgFUS treatment system and use of magnetic resonance thermometry, discusses the use of MRgFUS for the treatment of extra-abdominal desmoid tumors, and provides several case examples.

CT automated exposure control using a generalized detectability index.

PURPOSE: Identifying an appropriate tube current setting can be challenging when using iterative reconstruction due to the varying relationship between spatial resolution, contrast, noise, and dose across different algorithms. This study developed and investigated the application of a generalized detectability index ( d gen ' ) to determine the noise parameter to input to existing automated exposure control (AEC) systems to provide consistent image quality (IQ) across different reconstruction approaches. METHODS: This study proposes a task-based automated exposure control (AEC) method using a generalized detectability index ( d gen ' ). The proposed method leverages existing AEC methods that are based on a prescribed noise level. The generalized d gen ' metric is calculated using lookup tables of task-based modulation transfer function (MTF) and noise power spectrum (NPS). To generate the lookup tables, the American College of Radiology CT accreditation phantom was scanned on a multidetector CT scanner (Revolution CT, GE Healthcare) at 120 kV and tube current varied manually from 20 to 240 mAs. Images were reconstructed using a reference reconstruction algorithm and four levels of an in-house iterative reconstruction algorithm with different regularization strengths (IR1-IR4). The task-based MTF and NPS were estimated from the measured images to create lookup tables of scaling factors that convert between d gen ' and noise standard deviation. The performance of the proposed d gen ' -AEC method in providing a desired IQ level over a range of iterative reconstruction algorithms was evaluated using the American College of Radiology (ACR) phantom with elliptical shell and using a human reader evaluation on anthropomorphic phantom images. RESULTS: The study of the ACR phantom with elliptical shell demonstrated reasonable agreement between the d gen ' predicted by the lookup table and d ' measured in the images, with a mean absolute error of 15% across all dose levels and maximum error of 45% at the lowest dose level with the elliptical shell. For the anthropomorphic phantom study, the mean reader scores for images resulting from the d gen ' -AEC method were 3.3 (reference image), 3.5 (IR1), 3.6 (IR2), 3.5 (IR3), and 2.2 (IR4). When using the d gen ' -AEC method, the observers' IQ scores for the reference reconstruction were statistical equivalent to the scores for IR1, IR2, and IR3 iterative reconstructions (P > 0.35). The d gen ' -AEC method achieved this equivalent IQ at lower dose for the IR scans compared to the reference scans. CONCLUSIONS: A novel AEC method, based on a generalized detectability index, was investigated. The proposed method can be used with some existing AEC systems to derive the tube current profile for iterative reconstruction algorithms. The results provide preliminary evidence that the proposed d gen ' -AEC can produce similar IQ across different iterative reconstruction approaches at different dose levels.

Automated quantification and evaluation of motion artifact on coronary CT angiography images.

PURPOSE: This study developed and validated a Motion Artifact Quantification algorithm to automatically quantify the severity of motion artifacts on coronary computed tomography angiography (CCTA) images. The algorithm was then used to develop a Motion IQ Decision method to automatically identify whether a CCTA dataset is of sufficient diagnostic image quality or requires further correction. METHOD: The developed Motion Artifact Quantification algorithm includes steps to identify the right coronary artery (RCA) regions of interest (ROIs), segment vessel and shading artifacts, and to calculate the motion artifact score (MAS) metric. The segmentation algorithms were verified against ground-truth manual segmentations. The segmentation algorithms were also verified by comparing and analyzing the MAS calculated from ground-truth segmentations and the algorithm-generated segmentations. The Motion IQ Decision algorithm first identifies slices with unsatisfactory image quality using a MAS threshold. The algorithm then uses an artifact-length threshold to determine whether the degraded vessel segment is large enough to cause the dataset to be nondiagnostic. An observer study on 30 clinical CCTA datasets was performed to obtain the ground-truth decisions of whether the datasets were of sufficient image quality. A five-fold cross-validation was used to identify the thresholds and to evaluate the Motion IQ Decision algorithm. RESULTS: The automated segmentation algorithms in the Motion Artifact Quantification algorithm resulted in Dice coefficients of 0.84 for the segmented vessel regions and 0.75 for the segmented shading artifact regions. The MAS calculated using the automated algorithm was within 10% of the values obtained using ground-truth segmentations. The MAS threshold and artifact-length thresholds were determined by the ROC analysis to be 0.6 and 6.25 mm by all folds. The Motion IQ Decision algorithm demonstrated 100% sensitivity, 66.7% ± 27.9% specificity, and a total accuracy of 86.7% ± 12.5% for identifying datasets in which the RCA required correction. The Motion IQ Decision algorithm demonstrated 91.3% sensitivity, 71.4% specificity, and a total accuracy of 86.7% for identifying CCTA datasets that need correction for any of the three main vessels. CONCLUSION: The Motion Artifact Quantification algorithm calculated accurate (<10% error) motion artifact scores using the automated segmentation methods. The developed algorithms demonstrated high sensitivity (91.3%) and specificity (71.4%) in identifying datasets of insufficient image quality. The developed algorithms for automatically quantifying motion artifact severity may be useful for comparing acquisition techniques, improving best-phase selection algorithms, and evaluating motion compensation techniques.

Characterizing indeterminate liver lesions in patients with localized pancreatic cancer at the time of diagnosis.

BACKGROUND: In patients with newly diagnosed pancreatic cancer, the classification of indeterminate liver lesions is an unanswered clinical dilemma as misclassification of these lesions can impact the assignment of clinical stage and subsequent treatment planning. Our objective was to design a standardized classification system to more accurately define the risk of malignancy in indeterminate liver lesions. METHODS: In this retrospective study, patients with localized, non-metastatic pancreatic cancer were identified and pre-treatment computed tomography (CT) scans were evaluated for the presence or absence of liver lesions. Liver lesions were defined as definitely benign (1) or indeterminate (2). Indeterminate lesions were further sub-classified as either indeterminate probably benign (2B) or indeterminate possibly malignant (2M). The index liver lesion was evaluated on follow-up imaging for stability or unequivocal disease progression. RESULTS: From 2008 to 2015, 304 patients with localized, non-metastatic pancreatic cancer were identified and 125 (41%) patients had liver lesions. Of the 125 patients, the liver lesions in 35 (28%) were classified as definitely benign and in 90 (72%) patients they were classified as indeterminate. The 90 patients with indeterminate lesions included 80 (89%) classified as indeterminate probably benign (2B) and 10 (11%) classified as indeterminate possibly malignant (2M). After a median follow-up of 56 weeks, no patient with a definitely benign lesion had metastatic disease progression of the index lesion. Of the 90 patients with indeterminate liver lesions, the index lesion progressed to unequivocal liver metastasis in 8 (9%) patients; 5 (6%) of the 80 lesions classified as indeterminate probably benign (2B), and 3 (30%) of the ten lesions classified as indeterminate possibly malignant (2M). The sensitivity of the classification system was 38% and the specificity was 91%. The positive predictive value was 30% and the negative predictive value was 94%. CONCLUSIONS: A significant proportion of patients with localized pancreatic cancer will have liver lesions identified at the time of diagnosis and most of these lesions will have indeterminate characteristics. A classification system which further stratifies indeterminate liver lesions by malignant potential can assist clinicians in determining optimal treatment plan and is associated with a high negative predictive value.

Evaluation of motion artifact metrics for coronary CT angiography.

PURPOSE: This study quantified the performance of coronary artery motion artifact metrics relative to human observer ratings. Motion artifact metrics have been used as part of motion correction and best-phase selection algorithms for Coronary Computed Tomography Angiography (CCTA). However, the lack of ground truth makes it difficult to validate how well the metrics quantify the level of motion artifact. This study investigated five motion artifact metrics, including two novel metrics, using a dynamic phantom, clinical CCTA images, and an observer study that provided ground-truth motion artifact scores from a series of pairwise comparisons. METHOD: Five motion artifact metrics were calculated for the coronary artery regions on both phantom and clinical CCTA images: positivity, entropy, normalized circularity, Fold Overlap Ratio (FOR), and Low-Intensity Region Score (LIRS). CT images were acquired of a dynamic cardiac phantom that simulated cardiac motion and contained six iodine-filled vessels of varying diameter and with regions of soft plaque and calcifications. Scans were repeated with different gantry start angles. Images were reconstructed at five phases of the motion cycle. Clinical images were acquired from 14 CCTA exams with patient heart rates ranging from 52 to 82 bpm. The vessel and shading artifacts were manually segmented by three readers and combined to create ground-truth artifact regions. Motion artifact levels were also assessed by readers using a pairwise comparison method to establish a ground-truth reader score. The Kendall's Tau coefficients were calculated to evaluate the statistical agreement in ranking between the motion artifacts metrics and reader scores. Linear regression between the reader scores and the metrics was also performed. RESULTS: On phantom images, the Kendall's Tau coefficients of the five motion artifact metrics were 0.50 (normalized circularity), 0.35 (entropy), 0.82 (positivity), 0.77 (FOR), 0.77(LIRS), where higher Kendall's Tau signifies higher agreement. The FOR, LIRS, and transformed positivity (the fourth root of the positivity) were further evaluated in the study of clinical images. The Kendall's Tau coefficients of the selected metrics were 0.59 (FOR), 0.53 (LIRS), and 0.21 (Transformed positivity). In the study of clinical data, a Motion Artifact Score, defined as the product of FOR and LIRS metrics, further improved agreement with reader scores, with a Kendall's Tau coefficient of 0.65. CONCLUSION: The metrics of FOR, LIRS, and the product of the two metrics provided the highest agreement in motion artifact ranking when compared to the readers, and the highest linear correlation to the reader scores. The validated motion artifact metrics may be useful for developing and evaluating methods to reduce motion in Coronary Computed Tomography Angiography (CCTA) images.

Pancreatic adenocarcinoma: cross-sectional imaging techniques.

Pancreatic adenocarcinoma is a common malignancy that has a poor prognosis. Imaging is vital in its detection, staging, and management. Although a variety of imaging techniques are available, MDCT is the preferred imaging modality for staging and assessing the resectability of pancreatic adenocarcinoma. MR also has an important adjunct role, and may be used in addition to CT or as a problem-solving tool. A dedicated pancreatic protocol should be acquired as a biphasic technique optimized for the detection of pancreatic adenocarcinoma and to allow accurate local and distant disease staging. Emerging techniques like dual-energy CT and texture analysis of CT and MR images have a great potential in improving lesion detection, characterization, and treatment monitoring.

Imaging for Oncologic Response Assessment in Lymphoma.

OBJECTIVE: The purpose of this article is to examine the role of different imaging biomarkers, focusing in particular on the use of updated CT and PET response criteria for the assessment of oncologic treatment effectiveness in patients with lymphoma but also discussing other potential functional imaging methods and their limitations. CONCLUSION: Lymph nodes are commonly involved by metastatic solid tumors as well as by lymphoma. Evolving changes in cancer therapy for lymphoma and metastases have led to improved clinical outcomes. Imaging is a recognized surrogate endpoint that uses established criteria based on changes in tumor bulk to monitor the effects of treatment. With the introduction of targeted therapies and novel antiangiogenic drugs, the oncologic expectations from imaging assessment are changing to move beyond simple morphologic methods. Molecular and functional imaging methods (e.g., PET, perfusion, DWI, and dual-energy CT) are therefore being investigated as imaging biomarkers of response and prognosis. The role of these advanced imaging biomarkers extends beyond measuring tumor burden and therefore might offer insight into early predictors of therapeutic response. Despite the potential benefits of these exciting imaging biomarkers, several challenges currently exist.

Exploration of Imaging Biomarkers for Predicting Survival of Patients With Advanced Non-Small Cell Lung Cancer Treated With Antiangiogenic Chemotherapy.

OBJECTIVE: The objective of this study was to compare imaging biomarkers, including (18)F-FDG PET, CT perfusion (CTP), and CT texture analysis (CTTA), in predicting the survival of patients with advanced non-small cell lung cancer (NSCLC) treated with antiangiogenic chemotherapy. SUBJECTS AND METHODS: A total of 35 patients (17 men and 18 women; median age, 64.0 years) with advanced NSCLC treated with antiangiogenic chemotherapy were evaluated. CTP and FDG PET were performed before the therapy, and blood flow, blood volume, mean transit time, and the maximum standardized uptake value (SUV max) of the tumor were measured. Texture parameters, including the mean value of pixels with positive values (MPP) and entropy (a measure of irregularity), were also measured on pretherapeutic unenhanced CT images, using CTTA software with a medium texture scale filtration. The best percent change in the tumor burden was also measured. These image-derived tumor parameters were then compared with progression-free survival (PFS) and overall survival (OS). RESULTS: In univariate Cox regression analysis, MPP and entropy were significantly correlated with PFS (p = 0.01 and p = 0.01, respectively), whereas SUV max, MPP, and entropy were significantly correlated with OS (p = 0.03, p = 0.04, and p = 0.0008, respectively). In Kaplan-Meier analysis, high MPP and low entropy were significantly associated with favorable PFS (p < 0.0001 and p = 0.03, respectively) and OS (p = 0.0009 and p = 0.005, respectively), and low SUV max was significantly associated with favorable OS (p = 0.01). CTP parameters and the best change in the tumor burden had no associations with survival. In multivariate analysis, only entropy was identified as an independent prognostic factor for OS (p = 0.02). CONCLUSION: CTTA is the optimal imaging biomarker for predicting the survival of patients with advanced NSCLC treated with antiangiogenic chemotherapy.

CT-guided implantation of intrahepatic fiducial markers for proton beam therapy of liver lesions: assessment of success rate and complications.

OBJECTIVE. The purpose of this study is to evaluate the safety and complications of CT-guided implantation of intrahepatic fiducial markers for proton beam therapy. MATERIALS AND METHODS. In this retrospective study, we reviewed 69 patients who underwent 149 percutaneous fiducial marker implantations for primary and metastatic hepatic tumors from April 2007 through July 2013. The implantations enabling satisfactory treatment planning and CT simulation were considered as technically successful. Major and minor procedure-related complications during and after fiducial marker implantation were documented. RESULTS. The success rate of fiducial marker implantation was 99.3% (148/149). In one patient, a fiducial marker migrated into the vascular system, which was realized during the procedure and required reimplantation. None of the patients was required to return for additional implantations. The major and minor complication rates were 0% and 2.9% (2/69), respectively. Both minor complications included small pneumothorax not requiring hospital admission. CONCLUSION. CT-guided placement of gold fiducial markers is associated with a high technical success rate with few complications, which is an essential step in the overall treatment planning and performance of proton beam therapy for the management of hepatic tumors.

New and evolving concepts in CT for abdominal vascular imaging.

Computed tomographic (CT) angiography has become the standard of care, supplanting invasive angiography for comprehensive initial evaluation of acute and chronic conditions affecting the vascular system in the abdomen and elsewhere. Over the past decade, the capabilities of CT have improved substantially; simultaneously, the expectations of the referring physician and vascular surgeons have also evolved. Increasingly, CT angiography is used as an imaging biomarker for treatment selection and assessment of effectiveness. However, the growing use of CT angiography has also introduced some challenges, as potential radiation-associated and contrast media-induced risks need to be addressed. These concerns can be partly confronted by modifying scanning parameters (applying a low tube voltage) with or without using software-based solutions. Most recently, multienergy technology has endowed CT with new capabilities offering improved CT angiographic image quality and novel plaque characterization while decreasing radiation and iodine dose. In this article, we discuss current and new approaches using both conventional and multienergy CT for studying vascular disease in the abdomen. We propose various approaches to overcoming commonly encountered image quality challenges in CT angiography. In addition, we describe supplemental strategies for improving patient safety that leverage the available technology.

Oncologic applications of dual-energy CT in the abdomen.

Dual-energy computed tomographic (DECT) technology offers enhanced capabilities that may benefit oncologic imaging in the abdomen. By using two different energies, dual-energy CT allows material decomposition on the basis of energy-dependent attenuation profiles of specific materials. Although image acquisition with dual-energy CT is similar to that with single-energy CT, comprehensive postprocessing is able to generate not only images that are similar to single-energy CT (SECT) images, but a variety of other images, such as virtual unenhanced (VUE), virtual monochromatic (VMC), and material-specific iodine images. An increase in the conspicuity of iodine on low-energy VMC images and material-specific iodine images may aid detection and characterization of tumors. Use of VMC images of a desired energy level (40-140 keV) improves lesion-to-background contrast and the quality of vascular imaging for preoperative planning. Material-specific iodine images enable differentiation of hypoattenuating tumors from hypo- or hyperattenuating cysts and facilitate detection of isoattenuating tumors, such as pancreatic masses and peritoneal disease, thereby defining tumor targets for imaging-guided therapy. Moreover, quantitative iodine mapping may serve as a surrogate biomarker for monitoring effects of the treatment. Dual-energy CT is an innovative imaging technique that enhances the capabilities of CT in evaluating oncology patients.