Gadolinium Deposition in the Rat Brain Measured with Quantitative MRI versus Elemental Mass Spectrometry.

Background T1-weighted MRI and quantitative longitudinal relaxation rate (R1) mapping have been used to evaluate gadolinium retention in the brain after gadolinium-based contrast agent (GBCA) administration. Whether MRI measures accurately reflect gadolinium regional distribution and concentration in the brain remains unclear. Purpose To compare gadolinium retention in rat forebrain measured with in vivo quantitative MRI R1 and ex vivo laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) mapping after gadobenate, gadopentetate, gadodiamide, or gadobutrol administration. Materials and Methods Adult female Sprague-Dawley rats were randomly assigned to one of five groups (eight per group) and administered gadobenate, gadopentetate, gadodiamide, gadobutrol (2.4 mmol/kg per week for 5 weeks), or saline (4.8 mL/kg per week for 5 weeks). MRI R1 mapping was performed at baseline and 1 week after the final injection to determine R1 and ΔR1. Postmortem brains from the same rats were analyzed with LA-ICP-MS elemental mapping to determine regional gadolinium concentrations. Student t tests were performed to compare results between GBCA and saline groups. Results Rats that were administered gadobenate showed gadolinium-related MRI ΔR1 in 39.5% of brain volume (ΔR1 = 0.087 second-1 ± 0.051); gadopentetate, 20.6% (ΔR1 = 0.069 second-1 ± 0.018); gadodiamide, 5.4% (ΔR1 = 0.055 second-1 ± 0.019); and gadobutrol, 2.2% (ΔR1 = 0.052 second-1 ± 0.041). Agent-specific gadolinium-related ΔR1 was detected in multiple forebrain regions (neocortex, hippocampus, dentate gyrus, thalamus, and caudate-putamen) in rats treated with gadobenate or gadopentetate, whereas rats treated with gadodiamide showed gadolinium-related ΔR1 in caudate-putamen. By contrast, LA-ICP-MS elemental mapping showed a similar regional distribution pattern of heterogeneous retained gadolinium in the forebrain of rats treated with gadobenate, gadopentetate, or gadodiamide, with the average gadolinium concentration of 0.45 µg · g-1 ± 0.07, 0.50 µg · g-1 ± 0.10, and 0.60 µg · g-1 ± 0.11, respectively. Low levels (0.01 µg · g-1 ± 0.00) of retained gadolinium were detected in the forebrain of gadobutrol-treated rats. Conclusion Differences in in vivo MRI longitudinal relaxation rate versus ex vivo elemental mass spectrometry measures of retained gadolinium in rat forebrains suggest that some forms of retained gadolinium may escape detection with MRI. © RSNA, 2022 Online supplemental material is available for this article.

Fat Fraction Measurements Using a Three-Material Decomposition Dual-Energy CT Technique Accounting for Bone Minerals: Evaluation in a Bone Marrow Phantom Using MRI as Reference.

Conventional two-material dual-energy CT (DECT) decomposition is insufficient to model bone marrow, which contains three materials: bone minerals, red marrow (water), and yellow marrow (fat). We explore an image-domain three-material decomposition DECT technique accounting for bone minerals in a bone-water-fat phantom. Three-material decomposition fat fraction (FF3MD) exhibited stronger correlation than two-material decomposition fat fraction (FF2MD) with MRI-based fat fraction (r = 0.95 vs r = 0.69). With increasing bone minerals, correlation of FF3MD remained stable (r = 0.81-1.02), whereas correlation of FF2MD decreased (r = 0.21-0.65).

Quantification of bone marrow edema using dual-energy CT at fracture sites in trauma.

PURPOSE: The purpose of our study was to analyze the change in water and fat density within the bone marrow using the GE Revolution dual-energy computed tomography (DECT) platform using two-material decomposition analyses at extremity, spine, and pelvic fracture sites compared to normal bone marrow at equivalent anatomic sites in adult patients who sustained blunt trauma. METHODS: This retrospective study included 26 consecutive adults who sustained blunt torso trauma and an acute fracture of the thoracolumbar vertebral body, pelvis, or upper and lower extremities with a total of 32 fractures evaluated. Two-material decomposition images were analyzed for quantitative analysis. Statistical analysis was performed using the paired t-test and Shapiro-Wilk test for normality. RESULTS: There were statistically significant differences in the water and fat densities in the bone marrow at the site of an extremity, vertebral body, or pelvic fracture when compared to the normal anatomic equivalent (p < 0.01). CONCLUSION: In this preliminary study, DECT basis material images, using water (calcium) and fat (calcium) decomposition illustrated significant differences in water and fat content between fracture sites and normal bone in a variety of anatomical sites.

Machine learning combining CT findings and clinical parameters improves prediction of length of stay and ICU admission in torso trauma.

OBJECTIVE: To develop machine learning (ML) models capable of predicting ICU admission and extended length of stay (LOS) after torso (chest, abdomen, or pelvis) trauma, by using clinical and/or imaging data. MATERIALS AND METHODS: This was a retrospective study of 840 adult patients admitted to a level 1 trauma center after injury to the torso over the course of 1 year. Clinical parameters included age, sex, vital signs, clinical scores, and laboratory values. Imaging data consisted of any injury present on CT. The two outcomes of interest were ICU admission and extended LOS, defined as more than the median LOS in the dataset. We developed and tested artificial neural network (ANN) and support vector machine (SVM) models, and predictive performance was evaluated by area under the receiver operating characteristic (ROC) curve (AUC). RESULTS: The AUCs of SVM and ANN models to predict ICU admission were up to 0.87 ± 0.03 and 0.78 ± 0.02, respectively. The AUCs of SVM and ANN models to predict extended LOS were up to 0.80 ± 0.04 and 0.81 ± 0.05, respectively. Predictions based on imaging alone or imaging with clinical parameters were consistently more accurate than those based solely on clinical parameters. CONCLUSIONS: The best performing models incorporated imaging findings and outperformed those with clinical findings alone. ML models have the potential to help predict outcomes in trauma by integrating clinical and imaging findings, although further research may be needed to optimize their performance. KEY POINTS: • Artificial neural network and support vector machine-based models were used to predict the intensive care unit admission and extended length of stay after trauma to the torso. • Our input data consisted of clinical parameters and CT imaging findings derived from radiology reports, and we found that combining the two significantly enhanced the prediction of both outcomes with either model. • The highest accuracy (83%) and highest area under the receiver operating characteristic curve (0.87) were obtained for artificial neural networks and support vector machines, respectively, by combining clinical and imaging features in the prediction of intensive care unit admission.

Liver trauma: hepatic vascular injury on computed tomography as a predictor of patient outcome.

OBJECTIVES: To evaluate hepatic vascular injury (HVI) on CT in blunt and penetrating trauma and assess its relationship to patient management and outcome. METHOD AND MATERIALS: This retrospective study was IRB approved and HIPAA compliant. Informed consent was waived. Included were patients ≥ 16 years old who sustained blunt or penetrating trauma with liver laceration seen on a CT performed at our institution within 24 h of presentation over the course of 10 years and 6 months (August 2007-February 2018). During this interval, 171 patients met inclusion criteria (123 males, 48 females; mean age 34; age range 17-80 years old). Presence of HVI was evaluated and liver injury was graded in a blinded fashion by two radiologists using the 1994 and 2018 American Association for the Surgery of Trauma (AAST) liver injury scales. Hospital length of stay and treatment (angioembolization or operative) were recorded from the electronic medical record. Multivariate linear regressions were used to determine our variables' impact on the length of stay, and logistic regressions were used for categorical outcomes. RESULTS: Of the included liver trauma patients, 25% had HVI. Patients with HVI had a 3.2-day longer length of hospital stay on average and had a 40.3-fold greater odds of getting angioembolization compared to those without. Patients with high-grade liver injury (AAST grades IV-V, 2018 criteria) had a 3.2-fold greater odds of failing non-operative management and a 14.3-fold greater odds of angioembolization compared to those without. CONCLUSION: HVI in liver trauma is common and is predictive of patient outcome and management. KEY POINTS: • Hepatic vascular injury occurs commonly (25%) with liver trauma. • Hepatic vascular injury is associated with increased length of hospital stay and angioembolization. • High-grade liver injury is associated with failure of non-operative management and with angioembolization.

Nonhomogeneous Gadolinium Retention in the Cerebral Cortex after Intravenous Administration of Gadolinium-based Contrast Agent in Rats and Humans.

Background Gadolinium retention after repeated gadolinium-based contrast agent (GBCA) exposure has been reported in subcortical gray matter. However, gadolinium retention in the cerebral cortex has not been systematically investigated. Purpose To determine whether and where gadolinium is retained in rat and human cerebral cortex. Materials and Methods The cerebral cortex in Sprague-Dawley rats treated with gadopentetate dimeglumine (three doses over 4 weeks; cumulative gadolinium dose, 7.2 mmol per kilogram of body weight; n = 6) or saline (n = 6) was examined with antemortem MRI. Two human donors with repeated GBCA exposure (three and 15 doses; 1 and 5 months after exposure), including gadopentetate dimeglumine, and two GBCA-naive donors were also evaluated. Elemental brain maps (gadolinium, phosphorus, zinc, copper, iron) for rat and human brains were constructed by using laser ablation inductively coupled plasma mass spectrometry. Results Gadopentetate dimeglumine-treated rats showed region-, subregion-, and layer-specific gadolinium retention in the neocortex (anterior cingulate cortex: mean gadolinium concentration, 0.28 µg ∙ g-1 ± 0.04 [standard error of the mean]) that was comparable (P > .05) to retention in the allocortex (mean gadolinium concentration, 0.33 µg ∙ g-1 ± 0.04 in piriform cortex, 0.24 µg ∙ g-1 ± 0.04 in dentate gyrus, 0.17 µg ∙ g-1 ± 0.04 in hippocampus) and subcortical structures (0.47 µg ∙ g-1 ± 0.10 in facial nucleus, 0.39 µg ∙ g-1 ± 0.10 in choroid plexus, 0.29 µg ∙ g-1 ± 0.05 in caudate-putamen, 0.26 µg ∙ g-1 ± 0.05 in reticular nucleus of the thalamus, 0.24 µg ∙ g-1 ± 0.04 in vestibular nucleus) and significantly greater than that in the cerebellum (0.17 µg ∙ g-1 ± 0.03, P = .01) and white matter tracts (anterior commissure: 0.05 µg ∙ g-1 ± 0.01, P = .002; corpus callosum: 0.05 µg ∙ g-1 ± 0.02, P = .001; cranial nerve: 0.02 µg ∙ g-1 ± 0.01, P = .004). Retained gadolinium colocalized with parenchymal iron. T1-weighted MRI signal intensification was not observed. Gadolinium retention was detected in the cerebral cortex, pia mater, and pia-ensheathed leptomeningeal vessels in two GBCA-exposed human brains but not in two GBCA-naive human brains. Conclusion Repeated gadopentetate dimeglumine exposure is associated with gadolinium retention in specific regions, subregions, and layers of cerebral cortex that are critical for higher cognition, affect, and behavior regulation, sensorimotor coordination, and executive function. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Kanal in this issue.

Polarization insensitive, metamaterial absorber-enhanced long-wave infrared detector.

Detecting low energy photons, such as photons in the long-wave infrared range, is a technically challenging proposition using naturally occurring materials. In order to address this challenge, we herein demonstrate a micro-bolometer featuring an integrated metamaterial absorber (MA), which takes advantage of the resonant absorption and frequency selective properties of the MA. Importantly, our micro-bolometer exhibits polarization insensitivity and high absorption due to a novel metal-insulator-metal (MIM) absorber design, operating at 8-12 µm wavelength. The metamaterial structures we report herein feature an interconnected design, optimized towards their application to micro-bolometer-based, long-wave infrared detection. The micro-bolometers were fabricated using a combination of conventional photolithography and electron beam lithography (EBL), the latter owing to the small feature sizes within the design. The absorption response was designed using the coupled mode theory (CMT) and the finite integration technique, with the fabricated devices characterized using Fourier-transform infrared spectroscopy (FTIR). The metamaterial-based micro-bolometer exhibits a responsivity of approximately 198 V/W over the 8-12 µm wavelength regime, detectivity of ∼ 0.6 × 109 Jones, thermal response time of ∼ 3.3 ms, and a noise equivalent temperature difference (NETD) of ∼33 mK under 1mA biasing current at room-temperature and atmosphere pressure. The ultimate detectivity and NETD are limited by Johnson noise and heat loss with thermal convection through air; however, further optimization could be achieved by reducing the thermal conductivity via vacuum packaging. Under vacuum conditions, the detectivity may be increased in excess of two-fold, to ∼ 1.5 × 109 Jones. Finally, an infrared image of a soldering iron was generated using a single-pixel imaging process, serving as proof-of-concept of this detection platform. The results presented in this work pave the road towards high-efficiency and frequency-selective detection in the long-wave infrared range through the integration of infrared MAs with micro-bolometers.

Accuracy of Dual-Energy CT Virtual Unenhanced and Material-Specific Images: A Phantom Study.

OBJECTIVE. The purpose of this study was to determine the quantification accuracy of virtual unenhanced images and establish the lower limit of iodine quantification as a function of dose. MATERIALS AND METHODS. A large elliptical and cylindric phantom mimicking the patient abdomen was scanned on two commercial dual-energy CT scanners, an IQon Spectral CT (Philips Healthcare) and a Revolution CT with Gemstone Spectral Imaging Xtream suite (GE Healthcare). The phantom contained simulated soft tissue, blood, and bone with known elemental composition. It also contained simulated iodine concentrations (0.2-15.0 mg/mL) and iodine-enhanced blood (0.5-5.0 mg/mL). The mean absolute error in CT value for virtual unenhanced images and mean absolute percent error in iodine, calcium, and fat-specific images were measured. RESULTS. For virtual unenhanced images, when excluding the simulated bone, the mean absolute error in CT value was 8.0 ± 5.0 (SD) HU and 9.0 ± 6.2 HU for the IQon and the Revolution CT, respectively (p = 0.61). The mean error in CT value of the simulated bone was -90.5 ± 111.6 HU and -98.5 ± 117.8 HU on the IQon and the Revolution CT, respectively (p = 0.08). For iodine-specific images, the mean absolute percent error was 13.7% and 8.3% for the IQon and the Revolution CT, respectively, above 0.5 mg/mL iodine concentration, and 150% and 100% at less than 0.5 mg/mL iodine concentration. The mean absolute percent error increased from 16.2% at 100% radiation dose to 18.9% and 24% at 75% and 50% dose, respectively, on the IQon; and from 8.8% at 100% dose to 11.1% and 17.8% at 75% and 50%, respectively, on the Revolution CT. CONCLUSION. Virtual unenhanced images are reasonably accurate for simulated soft tissues and contrast materials, except for simulated bone. The lower limit of iodine quantification is radiation-dose dependent. For typical dose levels, 0.5 mg/mL iodine concentration is the lower threshold for iodine detection accuracy.

Acute Radiologic Manifestations of America's Opioid Epidemic.

The United States is in the midst of an opioid use epidemic, which has severe medical, social, and economic consequences. Addictions to and abuse of prescription and illicit opioids are increasing, and emergency department radiologists are increasingly being faced with the task of examining patients who present with opioid-related complications. These complications may be the result of direct drug toxicity or nonsterile injection of the drugs. Neurologic, musculoskeletal, cardiopulmonary, genitourinary, and gastrointestinal complications may be evident at diagnostic imaging in emergent settings. Heroin-induced leukoencephalopathy, cerebral septic emboli, mycotic arterial aneurysms, soft-tissue infections, and infective endocarditis are some of the conditions that patients may be found to have after they present to the emergency department. In this article, the above topics, including clinical features, pathophysiology, imaging findings, and treatment options, are reviewed. Recognizing the limitations of diagnostic imaging modalities that are available to radiologists is equally important, as some conditions can be successfully diagnosed after the initial triage-for example, transesophageal echocardiography can be performed to diagnose infective endocarditis. The emergency department radiologist may be responsible for identifying acute conditions, which can be life threatening. Some of the more common emergent opioid-related conditions and complications are reviewed, with specific emphasis on cases in which emergency department radiologists encounter conditions for which additional expertise is required. Becoming familiar with the conditions directly related to the current opioid epidemic will enable the diagnosis of these entities in a timely and accurate manner. ©RSNA, 2018.

Diffusion-weighted imaging of the pericholecystic hepatic parenchyma for distinguishing acute and chronic cholecystitis.

PURPOSE: The purpose of this study is to measure the performance of restricted diffusion of the pericholecystic hepatic parenchyma for distinguishing between acute and chronic cholecystitis. METHODS: The institutional review board approved this HIPAA-compliant retrospective study. Two hundred sixty-six patients presenting with acute right upper quadrant pain between 10/3/2010 and 11/28/2012 undergoing MR within 48 h of equivocal utility of ultrasound (US) were included. Diffusion-weighted imaging (DWI) sequences (b = 0, 600 s/mm2, apparent diffusion coefficient (ADC) maps) were reviewed and graded in a blinded fashion by two abdominal fellowship-trained radiologists for the presence of restricted diffusion in the pericholecystic hepatic parenchyma and the gallbladder wall. Sensitivity, specificity, and inter-observer agreement for individual imaging signs were calculated using surgical pathology as the reference standard for acute cholecystitis. RESULTS: Of the 266 patients, 113 were treated conservatively and 153 underwent cholecystectomy. Restricted diffusion of the pericholecystic hepatic parenchyma showed low sensitivity (reviewer 1, 40%; reviewer 2, 30%) and moderately high specificity (reviewer 1, 84%; reviewer 2, 75%) for distinguishing acute and chronic cholecystitis. Restricted diffusion in the gallbladder wall showed low sensitivity (reviewer 1, 30%; reviewer 2, 7%) and high specificity (reviewer 1, 93%; reviewer 2, 97%) for distinguishing acute and chronic cholecystitis. CONCLUSION: Diffusion-weighted imaging of the pericholecystic hepatic parenchyma shows moderately high specificity for distinguishing between acute and chronic cholecystitis.

Effect of an Institutional Triaging Algorithm on the Use of Multidetector CT for Patients with Blunt Abdominopelvic Trauma over an 8-year Period.

Purpose To evaluate the effect of an institutional clinical triaging algorithm on the rate of multidetector computed tomography (CT) utilization in blunt abdominopelvic trauma (BAPT) over an 8-year period at an urban level 1 trauma center. Materials and Methods Adult patients (n = 13 096; mean age, 42 years; age range, 15-95 years) admitted with BAPT from January 1, 2006, to December 31, 2013, were included. Patients with BAPT were divided into two groups: those admitted before (referred to as the prealgorithm group, from January 1, 2006, to June 30, 2010) and after (referred to as the postalgorithm group, from July 1, 2010, to December 31, 2013) the implementation of an institutional clinical triaging algorithm. The following parameters were recorded from abdominopelvic CT study reports for the pre- and postalgorithm groups: number of abdominopelvic CT examinations at admission, number of abdominopelvic CT examinations with positive BAPT-related findings, injury severity score, length of hospital stay, and number of mortalities. The unpaired t test and χ2 analysis were used to determine significant differences. Results The percentage of patients admitted for BAPT who underwent an abdominopelvic CT study was 76.7% (5900 of 7688) in the prealgorithm group and 44.6% (2413 of 5408) in the postalgorithm group, a 32.1% decrease in use of CT (P < .001). The mean injury severity score increased from 10.1 ± 9.1 (standard deviation) to 13.3 ± 11.9 after implementation of the algorithm in patients admitted for BAPT who underwent abdominopelvic CT examination (P < .001). The percentage of abdominopelvic CT examinations with BAPT-related findings increased from 17.1% (1007 of 5900) to 19.8% (479 of 2413) (P = .003). There was a significant difference in average length of stay, from 4.8 days ± 7.0 to 4.2 days ± 6.2 (P < .001). Mortality decreased from 3.1% (242 of 7688) to 2.7% (148 of 5408) after implementation of the algorithm (P = .19). Conclusion The implementation of a clinical triaging algorithm resulted in decreased use of multidetector CT in patients who presented with BAPT to the emergency department. © RSNA, 2016.

Application of texture analysis on parametric T1 and T2 maps for detection of hepatic fibrosis.

PURPOSE: To assess the utility of texture analysis of T1 and T2 maps for the detection of hepatic fibrosis in a murine model of hepatic fibrosis. MATERIALS AND METHODS: Following Institutional Animal Care and Use Committee approval, a dietary model of hepatic fibrosis was used and 15 ex vivo murine livers were examined. Images were acquired using a 30 mm bore 11.7T magnetic resonance imaging (MRI) scanner with a rapid acquisition with relaxation enhancement sequence. Texture analysis was then employed, extracting texture features including histogram-based, gray-level co-occurrence matrix-based (GLCM), gray-level run-length-based features (GLRL), gray-level gradient matrix (GLGM), and Laws' features. Areas under the curve (AUCs) were then calculated to determine the ability of texture features to detect hepatic fibrosis. RESULTS: Texture analysis of T1 maps identified very good to excellent discriminators of hepatic fibrosis within the histogram and GLGM categories. Histogram feature interquartile range (IQR) achieved an AUC value of 0.90 (P < 0.0001) and GLGM feature variance gradient achieved an AUC of 0.91 (P < 0.0001). Texture analysis of T2 maps identified very good to excellent discriminators of hepatic fibrosis within the histogram, GLCM, GLRL, and GLGM categories. GLGM feature kurtosis was the best discriminator of hepatic fibrosis, achieving an AUC value of 0.90 (P < 0.0001). CONCLUSION: This study demonstrates the utility of texture analysis for the detection of hepatic fibrosis when applied to T1 and T2 maps in a murine model of hepatic fibrosis and validates the potential use of this technique for the noninvasive, quantitative assessment of hepatic fibrosis. LEVEL OF EVIDENCE: 1 J. Magn. Reson. Imaging 2017;45:250-259.

Stereotactic core needle breast biopsy marker migration: An analysis of factors contributing to immediate marker migration.

OBJECTIVES: To evaluate breast biopsy marker migration in stereotactic core needle biopsy procedures and identify contributing factors. METHODS: This retrospective study analyzed 268 stereotactic biopsy markers placed in 263 consecutive patients undergoing stereotactic biopsies using 9G vacuum-assisted devices from August 2010-July 2013. Mammograms were reviewed and factors contributing to marker migration were evaluated. Basic descriptive statistics were calculated and comparisons were performed based on radiographically-confirmed marker migration. RESULTS: Of the 268 placed stereotactic biopsy markers, 35 (13.1%) migrated ≥1 cm from their biopsy cavity. Range: 1-6 cm; mean (± SD): 2.35 ± 1.22 cm. Of the 35 migrated biopsy markers, 9 (25.7%) migrated ≥3.5 cm. Patient age, biopsy pathology, number of cores, and left versus right breast were not associated with migration status (P> 0.10). Global fatty breast density (P= 0.025) and biopsy in the inner region of breast (P = 0.031) were associated with marker migration. Superior biopsy approach (P= 0.025), locally heterogeneous breast density, and t-shaped biopsy markers (P= 0.035) were significant for no marker migration. CONCLUSIONS: Multiple factors were found to influence marker migration. An overall migration rate of 13% supports endeavors of research groups actively developing new biopsy marker designs for improved resistance to migration. KEY POINTS: • Breast biopsy marker migration is documented in 13% of 268 procedures. • Marker migration is affected by physical, biological, and pathological factors. • Breast density, marker shape, needle approach etc. affect migration. • Study demonstrates marker migration prevalence; marker design improvements are needed.

Principles of Quantitative MR Imaging with Illustrated Review of Applicable Modular Pulse Diagrams.

Continued improvements in diagnostic accuracy using magnetic resonance (MR) imaging will require development of methods for tissue analysis that complement traditional qualitative MR imaging studies. Quantitative MR imaging is based on measurement and interpretation of tissue-specific parameters independent of experimental design, compared with qualitative MR imaging, which relies on interpretation of tissue contrast that results from experimental pulse sequence parameters. Quantitative MR imaging represents a natural next step in the evolution of MR imaging practice, since quantitative MR imaging data can be acquired using currently available qualitative imaging pulse sequences without modifications to imaging equipment. The article presents a review of the basic physical concepts used in MR imaging and how quantitative MR imaging is distinct from qualitative MR imaging. Subsequently, the article reviews the hierarchical organization of major applicable pulse sequences used in this article, with the sequences organized into conventional, hybrid, and multispectral sequences capable of calculating the main tissue parameters of T1, T2, and proton density. While this new concept offers the potential for improved diagnostic accuracy and workflow, awareness of this extension to qualitative imaging is generally low. This article reviews the basic physical concepts in MR imaging, describes commonly measured tissue parameters in quantitative MR imaging, and presents the major available pulse sequences used for quantitative MR imaging, with a focus on the hierarchical organization of these sequences. ©RSNA, 2017.

Multidetector CT of Surgically Proven Blunt Bowel and Mesenteric Injury.

Blunt traumatic injury is one of the leading causes of morbidity and mortality in the United States. Unintentional injury represents the leading cause of death in the United States for all persons between the ages of 1 and 44 years. In the setting of blunt abdominal trauma, the reported rate of occurrence of bowel and mesenteric injuries ranges from 1% to 5%. Despite the relatively low rate of blunt bowel and mesenteric injury in patients with abdominal and pelvic trauma, delays in diagnosis are associated with increased rates of sepsis, a prolonged course in the intensive care unit, and increased mortality. During the past 2 decades, as multidetector computed tomography (CT) has emerged as an essential tool in emergency radiology, several direct and indirect imaging features have been identified that are associated with blunt bowel and mesenteric injury. The imaging findings in cases of blunt bowel and mesenteric injury can be subtle and may be seen in the setting of multiple complex injuries, such as multiple solid-organ injuries and spinal fractures. Familiarity with the various imaging features of blunt bowel and mesenteric injury, as well as an understanding of their clinical importance with regard to the care of the patient, is essential to making a timely diagnosis. Once radiologists are familiar with the spectrum of findings of blunt bowel and mesenteric injury, they will be able to make timely diagnoses that will lead to improved patient outcomes. ©RSNA, 2017.

Extremity CTA for penetrating trauma: 10-year experience using a 64-detector row CT scanner.

PURPOSE: The purpose of this study is to assess the performance of CT angiography (CTA) in the evaluation of penetrating vascular trauma to the extremities in a large cohort of patients at our level I trauma center. METHODS: A retrospective, IRB-approved review of consecutive CTAs for the evaluation of penetrating trauma to the extremities in 446 patients (M/F = 396:50, mean age = 27 years) from 1/1/2005 to 5/1/2015 was performed. Medical records were reviewed to correlate diagnostic imaging findings with clinical history and subsequent interventions. Image quality was quantified by measurement of CT attenuation coefficients in the major arteries of the extremities. The Fisher's exact test was used to analyze the relationships between the presence and type of vascular injury and subsequent clinical management. RESULTS: One hundred and thirty-one (29.4 %) of 446 patients with penetrating trauma demonstrated major vascular injury on CTA, 35 (26.7 %) of whom underwent subsequent surgical repair. None of the patients without vascular injury on CTA underwent subsequent vascular intervention. Fisher's exact test demonstrated a statistically significant difference in management and requirement for vascular repair in those patients with a vascular injury on CTA when compared to those without a vascular injury (p < 0.0001). The mean attenuation values achieved in upper and lower extremity CTAs in this population exceeded 250 HU. CONCLUSION: Extremity CTA is found to be an accurate tool for surgical triage in patients having sustained penetrating vascular trauma.

Utility of MDCT findings in predicting patient management outcomes in renal trauma.

PURPOSE: The purpose of this study is to assess the utility of computed tomography (CT) in predicting clinical outcomes in renal trauma. MATERIALS/METHODS: This retrospective study was IRB approved and HIPAA compliant; informed consent was waived. One-hundred-sixty-two, trauma-related renal injuries (157 adults) from January 01, 2006 to December 31, 2013 were included in this retrospective study. CT findings of vascular and collecting system (CS) injuries were recorded, and American Association for the Surgery of Trauma (AAST) renal injury grades were assigned. Fisher's exact test evaluated correlations between AAST grade and active hemorrhage, AAST grade and surgical/endovascular therapy, active hemorrhage and surgical/endovascular therapy, and size of perinephric hematomas and CS injuries. The unpaired t test correlated to the size of perinephric hematomas in CS injuries diagnosed on initial versus repeat imaging. RESULTS: AAST grades were as follows: 120 grades I-III and 42 grade IV/V. Active hemorrhage was diagnosed in 25 (15%) patients and CS injury in 22 (14%) patients. Seven (8%) patients received surgical/endovascular therapy. There were statistically significant correlations between AAST grade and active hemorrhage (p = 0.003), active hemorrhage and surgical/endovascular therapy (p < 0.0001), and large perinephric hematomas (>2 cm) and CS injuries (p < 0.0001). There was no significant correlation between AAST grade and surgical/endovascular therapy (p = 0.08). Of the CS injuries (50%), 11/22 had no evidence of CS injury on initial imaging, being detected on follow-up CT. These "masked cases" demonstrated significant differences in perinephric hematoma size when compared to CS injuries diagnosed on initial imaging (p = 0.01). CONCLUSION: Active hemorrhage in renal trauma is a significant predictor of surgical/endovascular therapy, in contradistinction to the AAST grade. In collecting system injuries, a large fraction was not detectable on initial CT, supporting the need for repeat imaging in cases with large perinephric hematomas.

Normal saline as a natural intravascular contrast agent for dynamic perfusion-weighted MRI of the brain: Proof of concept at 1.5T.

PURPOSE: Gadolinium-based contrast agents have associated risks. Normal saline (NS) is a nontoxic sodium chloride water solution that can significantly increase the magnetic resonance imaging (MRI) relaxation times of blood via transient hemodilution (THD). The purpose of this pilot study was to test in vivo in the head the potential of normal saline as a safer, exogenous perfusion contrast agent. MATERIALS AND METHODS: This Health Insurance Portability and Accountability Act (HIPAA)-compliant prospective study was approved by the local Institutional Review Board (IRB): 12 patients were scanned with T1 -weighted inversion recovery turbo spin echo pulse sequence at 1.5T. The dynamic inversion recovery pulse sequence was run before, during, and after the NS injection for up to 5 minutes: 100 ml of NS was power-injected via antecubital veins at 3-4 ml/s. Images were processed to map maximum enhancement area-under-the-curve, time-to-peak, and mean-transit-time. These maps were used to identify the areas showing significant NS injection-related signal and to generate enhancement time curves. Hardware and pulse sequence stability were studied via phantom experimentation. Main features of the time curves were tested against theoretical modeling of THD signal effects using inversion recovery pulse sequences. Pearson correlation coefficient (R) mapping was used to differentiate genuine THD effects from motion confounders and noise. RESULTS: The scans of 8 out of 12 patients showed NS injection-related effects that correlate in magnitude with tissue type (gray matter ∼15% and white matter ∼3%). Motion artifacts prevented ascertaining NS signal effects in the remaining four patients. Positive and negative time curves were observed in vivo and this dual THD signal polarity was also observed in the theoretical simulations. R-histograms that were approximately constant in the range 0.1 < |R| < 0.8 and leading to correlation fractions of Fcorr (|R| > 0.5) = 0.45 and 0.59 were found to represent scans with genuine THD signal effects. CONCLUSION: A measurable perfusion effect in brain tissue was demonstrated in vivo using NS as an injectable intravascular contrast agent. J. Magn. Reson. Imaging 2016;44:1580-1591.

CT of Major Vascular Injury in Blunt Abdominopelvic Trauma.

Blunt abdominopelvic trauma remains one of the leading causes of morbidity and mortality nationwide. Delays in diagnosis can be catastrophic, underscoring the crucial importance of prompt injury detection. Identification of vascular injuries in the setting of blunt abdominal trauma can pose a diagnostic challenge, as detection is reliant on appropriate multidetector computed tomography (CT) scanning protocols and familiarity with the various imaging presentations of vessel injury. The advent of multidetector CT and fine-tuning of department protocols has led to fast, accurate, and efficient diagnosis of the broad spectrum of major vascular injuries that can result from blunt abdominopelvic trauma. CT allows timely diagnosis, differentiation between various types of major vascular injury, identification of associated findings, and specific localization of the source of bleeding. Accurate and early diagnosis of major abdominopelvic vascular injuries is fundamental to initiation of appropriate treatment strategies and improvement of clinical outcomes in this patient population. (©)RSNA, 2016.

CT imaging signs of surgically proven bowel trauma.

The objective of this study was to determine the incidence and interobserver agreement of individual CT findings as well as the bowel injury prediction score (BIPS) in surgically proven bowel injury after blunt abdominal trauma. This HIPAA-compliant retrospective study was IRB approved and consent was waived. All patients 14 years or older who sustained surgically proven bowel injury after blunt abdominal trauma between 1/1/2004 and 6/30/2015 were included. Admission trauma MDCT scans were independently interpreted by two abdominal fellowship-trained radiologists who recorded the following CT findings: intraperitoneal fluid, mesenteric hematoma/fat stranding, bowel wall thickening/hematoma, active intravenous contrast extravasation, free intraperitoneal air, bowel wall discontinuity, and focal bowel hypoenhancement. Subsequently, the electronic medical records of the included patients, admission abdominal physical exam results, admission white blood cell count, and findings at exploratory laparotomy of the included patients were recorded. Thirty-three patients met the inclusion criteria. The incidence and interobserver agreement of the CT findings were as follows: intraperitoneal fluid 93.9 %, kappa = 0.784 (good); mesenteric hematoma/fat stranding 84.8 %, kappa = 0.718 (good); bowel wall thickening/hematoma 42.4 %, kappa = 0.491 (moderate); active IV contrast extravasation 36.3 %, kappa = 1.00 (perfect); free intraperitoneal air 21.2 %, kappa = 0.904 (very good), bowel wall discontinuity 6.1 %, kappa = 1.00 (perfect); and focal bowel hypoenhancement 6.1 %, kappa = 0.468 (moderate). An absence of the specified CT findings was encountered in 9.1 % with surgically proven bowel injuries (kappa = 1.00, perfect). In our study, 9/16 patients or 56.3 % had a bowel injury prediction score (BIPS) of 2 or more as defined by McNutt et al. (J Trauma Acute Care Surg 78(1):105-111, 2014). The presence of intraperitoneal fluid and mesenteric hematoma/fat stranding are the most common CT findings in bowel injuries proven at laparotomy. A small percentage of patients have no abnormal CT findings. This grading system did not prove to be useful in our study likely due to our inherently small patient population; however, the use of BIPS deserves further investigation as it may help in identifying blunt bowel and mesenteric injury patients with often subtle or nonspecific CT findings.