Psoas attenuation and cross-sectional area improve performance of traditional sarcopenia measurements in predicting one-year mortality among elderly patients undergoing emergency abdominal surgery: a pilot study of five computed tomography techniques.

BACKGROUND: Risk stratification is challenging in the growing population of geriatric patients requiring emergency surgery. Sarcopenia, which assesses muscle bulk, is a surrogate for frailty and predicts 1-year mortality, but does not incorporate potentially valuable additional information about muscle quality. OBJECTIVE: To describe five different CT methods of measuring sarcopenia and muscle quality and to determine which method has the greatest sensitivity for predicting 1-year mortality following emergency abdominal surgery in elderly patients. METHODS: This retrospective study includes 297 patients 70 years and older who underwent "urgent" or "emergent" laparotomy or laparoscopy for acute abdominal disease between 2006 and 2011 at a single quaternary academic medical center. All patients received a CT abdomen and pelvis with intravenous contrast within 1 month of surgery. Five different methods were applied to the psoas muscles on CT: method 1 (total psoas index TPI, which is total psoas area TPA normalized by height), method 2 ("pseudoarea" = anterior-posterior × transverse dimensions), method 3 (average HU), method 4 (TPA × HU), and method 5 ("pseudoarea" × HU). RESULTS: For all five CT measures, mortality was greatest for the lowest quartile by univariate and adjusted Cox proportional hazard analyses at all time points up to 1-year. The C-statistic was highest for Method 4, using a composite index of TPA and Hounsfield Units, indicating the greatest predictive ability to estimate mortality at all time points. CONCLUSION: Muscle quality and muscle size can be used in tandem to refine risk assessment of older patients undergoing emergency abdominal surgery. Routine calculation of the composite score of psoas cross-sectional area and HU in the emergency room setting may provide surgeons and patients valuable insight on the risk of 1-year mortality to guide preoperative decision-making and counseling. CLINICAL IMPACT: Muscle quality and size, both strong independent predictors of surgical outcomes in older patients undergoing emergency abdominal surgery, may be used in tandem to refine risk assessment. A composite score of psoas muscle cross-sectional area and Hounsfield units on CT may provide insight on 1-year mortality in this patient population.

Dual Energy-Derived Metrics for Differentiating Adrenal Adenomas From Nonadenomas on Single-Phase Contrast-Enhanced CT.

BACKGROUND. Adrenal masses are often indeterminate on single-phase postcontrast CT. Dual-energy CT (DECT) with three-material decomposition algorithms may aid characterization. OBJECTIVE. The purpose of this study was to compare the diagnostic performance of metrics derived from portal venous phase DECT, including virtual noncontrast (VNC) attenuation, fat fraction, iodine density, and relative enhancement ratio, for characterizing adrenal masses. METHODS. This retrospective study included 128 patients (82 women, 46 men; mean age, 64.6 ± 12.7 [SD] years) who between January 2016 and December 2019 underwent portal venous phase abdominopelvic DECT that showed a total of 139 adrenal lesions with an available reference standard based on all imaging, clinical, and pathologic records (87 adenomas, 52 nonadenomas [48 metastases, two adrenal cortical carcinomas, one ganglioneuroma, one hematoma]). Two radiologists placed ROIs to determine the following characteristics of the masses: VNC attenuation, fat fraction, iodine density normalized to portal vein, and for masses with VNC greater than 10 HU, relative enhancement ratio (ratio of portal venous phase attenuation to VNC attenuation). Readers' mean measurements were used for ROC analyses, and clinically optimal thresholds were derived as thresholds yielding the highest sensitivity at 100% specificity. RESULTS. Adenomas and nonadenomas were significantly different (all p < .001) in VNC attenuation (mean ± SD, 18.5 ± 12.9 vs 34.1 ± 8.9 HU), fat fraction (mean ± SD, 24.3% ± 8.2% vs 14.2% ± 5.6%), normalized iodine density (mean ± SD, 0.34 ± 0.15 vs 0.17 ± 0.17), and relative enhancement ratio (mean ± SD, 186% ± 96% vs 58% ± 59%). AUCs for all metrics ranged from 0.81 through 0.91. The metric with highest sensitivity for adenoma at the clinically optimal threshold (i.e., 100% specificity) was fat fraction (threshold, ≥ 23.8%; sensitivity, 59% [95% CI, 48-69%]) followed by VNC attenuation (≤ 15.2 HU; sensitivity, 39% [95% CI, 29-50%]), relative enhancement ratio (≥ 214%; sensitivity, 37% [95% CI, 25-50%]), and normalized iodine density (≥ 0.90; sensitivity, 1% (95% CI, 0-60%]). VNC attenuation at the traditional true noncontrast attenuation threshold of 10 HU or lower had sensitivity of 28% (95% CI, 19-38%) and 100% specificity. Presence of fat fraction 23.8% or greater or relative enhancement ratio 214% or greater yielded sensitivity of 68% (95% CI, 57-77%) with 100% specificity. CONCLUSION. For adrenal lesions evaluated with single-phase DECT, fat fraction had higher sensitivity than VNC attenuation at both the clinically optimal threshold and the traditional threshold of 10 HU or lower. CLINICAL IMPACT. By helping to definitively diagnose adenomas, DECT-derived metrics can help avoid downstream imaging for incidental adrenal lesions.

Clinical applications of dual-energy computed tomography in neuroradiology.

Dual-energy computed tomography (DECT) has developed into a robust set of techniques with increasingly validated clinical applications in neuroradiology. We review some of the most common applications in neuroimaging along with demonstrative case examples that showcase the use of this technology in intracranial hemorrhage, stroke imaging, trauma imaging, artifact reduction, and tumor characterization.

Prevalence of imaging findings of acute pancreatitis in emergency department patients with elevated serum lipase.

PURPOSE: To assess the association of imaging features of acute pancreatitis (AP) with the magnitude of lipase elevation in Emergency Department (ED) patients. METHODS: This Institutional Review Board-approved retrospective study included 509 consecutive patients presenting from 9/1/13-8/31/15 to a large academic ED with serum lipase levels ≥3× the upper limit of normal (ULN) (≥180 U/L). Patients were excluded if they did not have imaging (n = 131) or had a history of trauma, abdominal metastases, altered mental status, or transfer from an outside hospital (n = 190); the final study population was 188 patients. Imaging exams were retrospectively evaluated, and a consensus opinion of two subspecialty-trained abdominal radiologists was used to diagnose AP. Primary outcome was presence of imaging features of AP stratified by lipase level (≥3×-10× ULN and > 10× ULN). Secondary outcome was rate of discordant consensus evaluation compared to original radiologist's report. RESULTS: 25.0% of patients (47/188) had imaging features of AP. When lipase was >10× ULN (n = 94), patients were more likely to have imaging features of AP (34%) vs. those with mild elevation (16%) (p = 0.0042). There was moderately strong correlation between lipase level and presence of imaging features of AP (r = 0.48, p < 0.0001). Consensus review of CT and MRI images was discordant with the original report in 14.9% (28/188) of cases. CONCLUSION: Prevalence of imaging signs of AP in an ED population with lipase ≥3× ULN undergoing imaging is low. However, the probability of imaging features of AP increases as lipase value increases.

Radiation concerns in frequent flyer patients: should imaging history influence decisions about recurrent imaging?

Radiation risks from diagnostic imaging have captured the attention of patients and medical practitioners alike, yet it remains unclear how these considerations can best be incorporated into clinical decision-making. This manuscript presents a framework to consider these issues in a potentially at-risk population, the so called "frequent flyer" patients undergoing a large amount of recurrent imaging over time. Radiation risks from the low-dose exposures of diagnostic imaging are briefly reviewed, as applied to recurrent exposures. Some scenarios are then explored in which it may be helpful to incorporate knowledge of a patient's imaging history. There is no simple or uniformly applicable approach to these challenging and often nuanced clinical decisions. The complexity and variability of the underlying disease states and trajectories argues against alerting mechanisms based on a simple cumulative dose threshold. Awareness of imaging history may instead be beneficial in encouraging physicians and patients to take the long view, and to identify those populations of frequent flyers that might benefit from alternative imaging strategies.

Bone Marrow Edema at Dual-Energy CT: A Game Changer in the Emergency Department.

Dual-energy CT is increasingly being used in the emergency department to help diagnose acute conditions. Its applications include demonstrating bone marrow edema (BME) seen in the setting of occult fractures and other acute conditions. Dual-energy CT acquires data with two different x-ray energy spectra and is able to help differentiate materials on the basis of their differential energy-dependent x-ray absorption behaviors. Virtual noncalcium (VNCa) techniques can be used to suppress the high attenuation of trabecular bone, thus enabling visualization of subtle changes in the underlying attenuation of the bone marrow. Visualization of BME can be used to identify occult or mildly displaced fractures, pathologic fractures, metastases, and some less commonly visualized conditions such as ligamentous injuries or inflammatory arthritis. The authors' major focus is use of dual-energy CT as a diagnostic modality in the setting of trauma and to depict subtle or occult fractures. The authors also provide some scenarios in which dual-energy CT is used to help diagnose other acute conditions. The causes and pathophysiology of BME are reviewed. Dual-energy CT image acquisition and VNCa postprocessing techniques are also discussed, along with their applications in emergency settings. The authors present potential pitfalls and limitations of these techniques and their possible solutions.©RSNA, 2020.

Dual-energy CT for routine imaging of the abdomen and pelvis: radiation dose and image quality.

PURPOSE: To assess the radiation dose and image quality of routine dual energy CT (DECT) of the abdomen and pelvis performed in the emergency department setting, compared with single energy CT (SECT). MATERIALS AND METHODS: Seventy-five consecutive routine contrast-enhanced SECT scans of the abdomen and pelvis meeting inclusion criteria were compared with 75 routine contrast-enhanced DECT scans matched by size and patient weight (within 10 lbs), performed on the same dual-source DECT scanner. Cohorts were compared in terms of radiation dose metrics of CT dose index (CTDIvol) and dose length product (DLP), objective measurements of image quality (signal, noise, and signal-to-noise ratio of a variety of anatomical landmarks), and subjective measurements of image quality scored by two emergency radiologists. RESULTS: Demographics and patient size were not statistically different between DECT and SECT cohorts. Both average scans CTDIvol and DLP were significantly lower with DECT than with SECT. Average scan CTDIvol for SECT was 14.7 mGy (± 6.6) and for DECT was 10.9 mGy (± 3.8) (p < 0.0001). Average scan DLP for SECT was 681.5 mGy cm (± 339.3) and for DECT was 534.8 mGy cm (± 201.9) (p < 0.0001). For objective image quality metrics, for all structures measured, noise was significantly lower and SNR was significantly higher with DECT compared with SECT. For subjective image quality, for both readers, there was no significant difference between SECT and DECT in subjective image quality for soft tissues and vascular structures, or for subjective image noise. CONCLUSIONS: DECT was performed with decreased radiation dose when compared with SECT, demonstrated improved objective measurements of image quality, and equivalent subjective image quality.

Spectrum of diagnostic errors in cervical spine trauma imaging and their clinical significance.

PURPOSE: To describe and categorize diagnostic errors in cervical spine CT (CsCT) interpretation performed for trauma and to assess their clinical significance. METHODS: All CsCTs performed for trauma with diagnostic errors that came to our attention based on clinical or imaging follow-up or quality assurance peer review from 2004 to 2017 were included. The number of CsCTs performed at our institution during the same time interval was calculated. Errors were categorized as spinal/extraspinal, involving osseous/soft tissue structures, by anatomical site and level. Images were reviewed by a radiologist and two spine surgeons. For each error, the need for surgery, immobilization, CT angiogram of the neck, and MRI was assessed; if any of these were needed, the error was considered clinically significant. RESULTS: Of an approximate total 59,000 CsCTs, 56 reports containing diagnostic errors were included. Twelve were extraspinal, and 44 were spinal (26 fractures, 15 intervertebral disc protrusions, two subluxations, one lytic bone lesion). The most common sites of spinal fractures were vertebral body (n = 10) and transverse process (n = 8); the most common levels were C5 (n = 8) and C7 (n = 6). All (n = 26) fractures and two atlantooccipital subluxations were considered clinically significant, including three patients who would have required urgent surgical stabilization (two subluxations and one facet fracture). Two transverse processes fractures did not alter the need for surgical intervention/surgical approach, immobilization, or MRI. CONCLUSIONS: In our study, 66% of spinal diagnostic errors on CsCT were considered clinically significant, potentially altering clinical management. Transverse process and vertebral body fractures were commonly missed.

Impact Analysis of the Routine Use of Dual-Energy Computed Tomography for Characterization of Incidental Renal Lesions.

OBJECTIVE: The aim of this study was to quantify the prevalence of incidental, indeterminate renal lesions on routine contrast-enhanced abdominal computed tomography (CT) and the proportion of such lesions that could be exonerated by dual-energy CT (DECT) postprocessing as benign hyperdense cysts. METHODS: The reports for 2729 consecutive contrast-enhanced DECT scans in the emergency department setting were reviewed for the mention of any renal lesion. For scans with a reported lesion, images were reviewed to assess for the presence of an indeterminate lesion that could not be definitively characterized as benign. All indeterminate lesions were reviewed with DECT postprocessing by 2 radiologists to assess for enhancement and other imaging characteristics and characterized by readers as benign or not definitively benign. Agreement between readers was assessed statistically, and disagreement was resolved by consensus. RESULTS: Two thousand seven hundred twenty-nine scans were performed in 2406 unique patients; a renal lesion was reported in 805 unique patient scans (33.4%). Review of these 805 scans led to discovery of 137 indeterminate lesions in 125 scans (5.2% of patients). Of the 137 lesions, 70 (51.1%) were classified as benign hyperdense cysts by readers, with the remaining 67 lesions classified as not definitively benign (43 solid masses, 9 Bosniak IIF cysts, 8 Bosniak III cysts, 7 Bosniak IV cysts). CONCLUSIONS: Incidental indeterminate renal lesions are common on routine contrast-enhanced CT. More than half of these lesions could potentially be exonerated with DECT as benign Bosniak II cysts, which could avert the need for further workup in 2.8% of patients undergoing routine abdominal CT.

Radiation Dose Considerations in Emergent Neuroimaging.

Computed tomography is often the first-line diagnostic imaging modality in the evaluation of patients with neurologic emergencies. A patient-centered approach to radiation dose management in emergent neuroimaging thus revolves around the appropriate use of computed tomography, including clinical decision support for ordering providers, thoughtful protocol design, the use of available technological advances in computed tomography, and radiation exposure monitoring at a population level. A multifaceted approach can help to minimize radiation exposure to individual patients while preserving diagnostic quality imaging.

Dual energy CT for evaluation of polycystic kidneys: a multi reader study of interpretation time and diagnostic confidence.

PURPOSE: To compare dual-energy CT (DECT) iodine overlay images with renal mass protocol CT in the evaluation of polycystic kidneys with respect to reading time, diagnostic confidence, and detection of renal lesions that are not definitively benign. METHODS: Following IRB approval, portal venous phase dual-source DECT scans performed between September 2013 and February 2016 from 55 patients (mean age 67 ± 15 years, 31 male, 24 female) with polycystic kidneys (4 or more cysts) were included. For each patient, two image sets were created: (1) DECT post-processed iodine overlay images and (2) simulated renal mass protocol CT images (virtual noncontrast and mixed images). Two radiologists independently retrospectively reviewed both sets at separate time points, evaluating for the presence of lesions that were not definitively benign (enhancing lesions or Bosniak IIF cysts), as well as reading times and Likert scale diagnostic confidence ratings (scaled 1-5) for the presence of non-benign lesions. Reading times were compared with a t test, diagnostic confidence with a McNemar test, and lesion number detection with Cohen's kappa test. RESULTS: Iodine overlay images were read faster (mean 55 ± 26 s) than renal mass protocol (mean 105 ± 51 s) (p < 0.001). Readers assigned the highest diagnostic confidence rating in 64% using iodine overlay series, compared to 17% using renal mass protocol (p < 0.0001). The proportion of patients with recorded lesions was not significantly different between methods (p = 0.62). CONCLUSIONS: DECT improves lesion assessment in polycystic kidneys by decreasing reading times and increasing diagnostic confidence, without affecting lesion detection rates.

Multimodality Imaging, including Dual-Energy CT, in the Evaluation of Gallbladder Disease.

Imaging of the gallbladder has a key role in the examination of patients with abdominal pain-especially pain localized to the right upper quadrant. Pathologic conditions that affect the gallbladder include cholelithiasis and associated complications such as acute and chronic cholecystitis, choledocholithiasis, gallstone pancreatitis, and cancer. Modalities used to image the gallbladder include ultrasonography (US), computed tomography (CT), magnetic resonance (MR) imaging, and nuclear scintigraphy. US is the primary imaging modality used to evaluate entities suspected of being gallbladder disease, as it is both sensitive and specific for demonstrating gallstones, biliary duct dilatation, and inflammatory features. However, CT is often the first imaging examination performed in patients who present to the emergency department with acute abdominal pain. Because the CT appearance of gallstones is variable, depending on the composition of the stone, pattern of calcification, and presence of gas, gallstones and other gallbladder conditions can be difficult to detect at conventional multidetector CT, with which data are acquired by using a single x-ray energy spectrum. Dual-energy CT, with which one takes advantage of the material-dependent x-ray absorption behavior of concurrently acquired high- and low-kilovolt-peak data, can add value by increasing the conspicuity of noncalcified gallstones and improving the detection of acute cholecystitis and gallbladder malignancy. In addition, MR cholangiopancreatography can be helpful for assessing choledocholithiasis and complicated biliary duct disease. ©RSNA, 2018.

First-trimester emergencies: a radiologist's perspective.

The purpose of this article is to help the practitioner ensure early diagnosis and response to emergencies in the first trimester by reviewing anatomy of the developing embryo, highlighting the sonographic appearance of common first-trimester emergencies, and discussing key management pathways for treating emergent cases. First-trimester fetal development is a stepwise process that can be challenging to evaluate in the emergency department (ED) setting. This is due, in part, to the complex anatomy of early pregnancy, subtlety of the sonographic findings, and the fact that fewer than half of patients with ectopic pregnancy present with the classic clinical findings of a positive pregnancy test, vaginal bleeding, pelvic pain, and tender adnexa. Ultrasound (US) has been the primary approach to diagnostic imaging of first-trimester emergencies, with magnetic resonance imaging (MRI) and computed tomography (CT) playing a supportive role in a small minority of cases. Familiarity with the sonographic findings diagnostic of and suspicious for early pregnancy failure, ectopic pregnancy, retained products of conception, gestational trophoblastic disease, failed intrauterine devices, and complications associated with assisted reproductive technology (ART) is critical for any emergency radiologist. Evaluation of first-trimester emergencies is challenging, and knowledge of key imaging findings and familiarity with management pathways are needed to ensure early diagnosis and response.

Traumatic Hip Dislocation: What the Orthopedic Surgeon Wants to Know.

Hip dislocation is an important orthopedic emergency usually seen in young patients who have experienced high-energy trauma, often resulting in significant long-term morbidity. Rapid identification and reduction is critical, as prolonged dislocation increases the risk of developing avascular necrosis of the femoral head, and posttraumatic osteoarthritis is a common complication, even in the absence of associated fractures. Identification and timely management of hip dislocation are highly dependent on imaging, both at presentation and after attempted reduction. It is imperative for the radiologist to understand imaging features that guide management of hip dislocation to ensure timely identification, characterization, and communication of clinically relevant results. Although the importance of prompt identification of hip dislocation is universally recognized, the significance of imaging features that guide correct management and are thought to prevent complications is less emphasized in the radiology literature. In this article, the authors review the anatomy of the hip, common injury mechanisms for various types of dislocations, and imaging findings for associated injuries. They review the most commonly used classification systems and propose a simplified checklist approach to hip dislocation to aid rapid interpretation and communication of the most clinically relevant imaging features to the treating orthopedic surgeon. ©RSNA, 2017.

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.

Sarcopenia increases risk of long-term mortality in elderly patients undergoing emergency abdominal surgery.

BACKGROUND: Frailty is associated with poor surgical outcomes in elderly patients but is difficult to measure in the emergency setting. Sarcopenia, or the loss of lean muscle mass, is a surrogate for frailty and can be measured using cross-sectional imaging. We sought to determine the impact of sarcopenia on 1-year mortality after emergency abdominal surgery in elderly patients. METHODS: Sarcopenia was assessed in patients 70 years or older who underwent emergency abdominal surgery at a single hospital from 2006 to 2011. Average bilateral psoas muscle cross-sectional area at L3, normalized for height (Total Psoas Index [TPI]), was calculated using computed tomography. Sarcopenia was defined as TPI in the lowest sex-specific quartile. Primary outcome was mortality at 1 year. Secondary outcomes were in-hospital mortality and mortality at 30, 90, and 180 days. The association of sarcopenia with mortality was assessed using Cox proportional hazards regression and model performance judged using Harrell's C-statistic. RESULTS: Two hundred ninety-seven of 390 emergency abdominal surgery patients had preoperative imaging and height. The median age was 79 years, and 1-year mortality was 32%. Sarcopenic and nonsarcopenic patients were comparable in age, sex, race, comorbidities, American Society of Anesthesiologists classification, procedure urgency and type, operative severity, and need for discharge to a nursing facility. Sarcopenic patients had lower body mass index, greater need for intensive care, and longer hospital length of stay (p < 0.05). Sarcopenia was independently associated with increased in-hospital mortality (risk ratio, 2.6; 95% confidence interval [CI], 1.6-3.7) and mortality at 30 days (hazard ratio [HR], 3.7; 95% CI, 1.9-7.4), 90 days (HR, 3.3; 95% CI, 1.8-6.0), 180 days (HR, 2.5; 95% CI, 1.4-4.4), and 1 year (HR, 2.4; 95% CI, 1.4-3.9). CONCLUSION: Sarcopenia is associated with increased risk of mortality over 1 year in elderly patients undergoing emergency abdominal surgery. Sarcopenia defined by TPI is a simple and objective measure of frailty that identifies vulnerable patients for improved preoperative counseling, setting realistic goals of care, and consideration of less invasive approaches. LEVEL OF EVIDENCE: Prognostic study, level III.

Don't Forget the Abdominal Wall: Imaging Spectrum of Abdominal Wall Injuries after Nonpenetrating Trauma.

Abdominal wall injuries occur in nearly one of 10 patients coming to the emergency department after nonpenetrating trauma. Injuries range from minor, such as abdominal wall contusion, to severe, such as abdominal wall rupture with evisceration of abdominal contents. Examples of specific injuries that can be detected at cross-sectional imaging include abdominal muscle strain, tear, or hematoma, including rectus sheath hematoma (RSH); traumatic abdominal wall hernia (TAWH); and Morel-Lavallée lesion (MLL) (closed degloving injury). These injuries are often overlooked clinically because of (a) a lack of findings at physical examination or (b) distraction by more-severe associated injuries. However, these injuries are important to detect because they are highly associated with potentially grave visceral and vascular injuries, such as aortic injury, and because their detection can lead to the diagnosis of these more clinically important grave traumatic injuries. Failure to make a timely diagnosis can result in delayed complications, such as bowel hernia with potential for obstruction or strangulation, or misdiagnosis of an abdominal wall neoplasm. Groin injuries, such as athletic pubalgia, and inferior costochondral injuries should also be considered in patients with abdominal pain after nonpenetrating trauma, because these conditions may manifest with referred abdominal pain and are often included within the field of view at cross-sectional abdominal imaging. Radiologists must recognize and report acute abdominal wall injuries and their associated intra-abdominal pathologic conditions to allow appropriate and timely treatment. © RSNA, 2017.

Traumatic Finger Injuries: What the Orthopedic Surgeon Wants to Know.

Traumatic finger injuries account for a substantial number of emergency visits every year. Imaging plays an important role in diagnosis and in directing management of these injuries. Although many injuries can be managed conservatively, some require more invasive interventions to prevent complications and loss of function. Accurate diagnosis of finger injuries can often be difficult, given the complicated soft-tissue anatomy of the hand and the diverse spectrum of injuries that can occur. To best serve the patient and the treating physician, radiologists must have a working knowledge of finger anatomy, the wide array of injury patterns that can occur, the characteristic imaging findings of different finger injuries, and the most appropriate treatment options for each type of injury. This article details the intricate anatomy of the hand as it relates to common finger injuries, illustrates the imaging findings of a range of injuries, presents optimal imaging modalities and imaging parameters for the diagnosis of different injury types, and addresses which findings have important management implications for the patient and the orthopedic surgeon. With this fund of knowledge, radiologists will be able to recommend the most appropriate imaging studies, make accurate diagnoses, convey clinically relevant imaging findings to the referring physician, and suggest appropriate follow-up examinations. In this way, the radiologist will help improve patient care and outcomes. Online supplemental material is available for this article. (©)RSNA, 2016.

Use of Dual-Energy CT and Iodine Maps in Evaluation of Bowel Disease.

Dual-energy computed tomography (CT) relies on material-dependent x-ray absorption behavior from concurrently acquired high- and low-kilovolt peak data and has a range of imaging applications. This article focuses on use of dual-energy CT in assessment of bowel disease. After a summary of relevant dual-energy CT image acquisition and postprocessing principles, the authors describe dual-energy techniques of greatest utility in evaluation of benign and malignant pathologic conditions in the bowel, including neoplastic, vascular, infectious, and inflammatory disorders, as well as in assessment of abdominopelvic trauma. The dual-energy postprocessing techniques of iodine-selective imaging and virtual monochromatic imaging have the broadest applicability in bowel imaging. They may be used for improved visualization of subtle differences in bowel wall enhancement or for quantitative assessment of altered enhancement for evaluation of a neoplasm or bowel ischemia. Iodine images and virtual monochromatic low-kiloelectron volt images are particularly helpful for assessment of a neoplasm, ischemia, infection, or inflammation, while iodine maps paired with virtual nonenhanced images are most helpful to differentiate iodine from other dense materials, as in gastrointestinal bleeding or trauma. In most applications, radiation doses at dual-energy CT are comparable to those at traditional CT. However, dual-energy CT may allow reduction in radiation dose by using virtual nonenhanced images that obviate an additional nonenhanced CT acquisition. Limitations of dual-energy CT are discussed, including potential challenges in acquisition, postprocessing, and interpretation.