Early Brain Amyloid Accumulation at PET in Military Instructors Exposed to Subconcussive Blast Injuries.

Background Traumatic brain injury (TBI) is the leading cause of disability in young adults. Recurrent TBI is associated with a range of neurologic sequelae, but the contributing factors behind the development of such chronic encephalopathy are poorly understood. Purpose To quantify early amyloid ß deposition in the brain of otherwise healthy adult men exposed to repeated subconcussive blast injury using amyloid PET. Materials and Methods In this prospective study from January 2020 to December 2021, military instructors who were routinely exposed to repeated blast events were evaluated at two different points: baseline (before blast exposure from breacher or grenade) and approximately 5 months after baseline (after blast exposure). Age-matched healthy control participants not exposed to blasts and without a history of brain injury were evaluated at similar two points. Neurocognitive evaluation was performed with standard neuropsychologic testing in both groups. Analysis of PET data consisted of standardized uptake value measurements in six relevant brain regions and a whole-brain voxel-based statistical approach. Results Participants were men (nine control participants [median age, 33 years; IQR, 32-36 years] and nine blast-exposed participants [median age, 33 years; IQR, 30-34 years]; P = .82). In the blast-exposed participants, four brain regions showed significantly increased amyloid deposition after blast exposure: inferomedial frontal lobe (P = .004), precuneus (P = .02), anterior cingulum (P = .002), and superior parietal lobule (P = .003). No amyloid deposition was observed in the control participants. Discriminant analysis on the basis of regional changes of amyloid accumulation correctly classified the nine healthy control participants as healthy control participants (100%), and seven of the nine blast-exposed participants (78%) were correctly classified as blast exposed. Based on the voxel-based analysis, whole-brain parametric maps of early abnormal early amyloid uptake were obtained. Conclusion Early brain amyloid accumulation was identified and quantified at PET in otherwise healthy adult men exposed to repetitive subconcussive traumatic events. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Haller in this issue.

Thoracic Endemic Fungi in the United States: Importance of Patient Location.

The digitization of radiographic studies along with high-speed transmission of images has formed the basis of teleradiology, which has become an integral component in the workflow of a contemporary radiology practice. It is with this advent and growing utilization of teleradiology that the significance of the source location of images has gained importance. Specifically, the importance of where the patient resides and what endemic fungi occur in that location cannot be underestimated. In the United States, histoplasmosis, coccidioidomycosis, blastomycosis, and cryptococcosis are caused by endemic fungi occurring in the Ohio and Mississippi river valleys, the Southwest, the Upper Midwest, and the Pacific Northwest, respectively. All of these organisms enter the body through the respiratory system and have the potential to cause significant morbidity and mortality. Patients infected with these fungi are often asymptomatic but may present with acute flulike symptoms such as fever, cough, or dyspnea. Patients may also present with vague chronic symptoms including cough, fever, malaise, and weight loss. Thoracic manifestations at radiography and CT include consolidation, nodules, cavities, lymphadenopathy, and pleural disease. PET may show fluorine 18-fluorodeoxyglucose uptake with active acute or chronic infections, and it is difficult to distinguish infections from malignancy. Imaging findings may be nonspecific and can be confused with other disease processes, including malignancy. The patient demographics, clinical history, and location are clues that may lead to a proper diagnosis of endemic fungal disease. The radiologist should be cognizant of the patient location to provide a correct and timely radiologic diagnosis that helps guide the clinician to initiate appropriate therapy. ©RSNA, 2021.

Volumetric characteristics of idiopathic pulmonary fibrosis lungs: computational analyses of high-resolution computed tomography images of lung lobes.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease involving progressive degeneration of lung capacity. Current diagnosis of IPF heavily relies on visual evaluation of fibrotic features in high-resolution computed tomography (HRCT) images of the lungs. Although the characteristics of this disease have been studied at the molecular and cellular levels, little is known about the mechanical characteristics of IPF lungs inferred from HRCT images. To this end, we performed a pilot study to investigate the radiographic and volumetric characteristics of lungs in subjects with IPF. METHODS: We collected HRCT images of healthy (N = 13) and IPF (N = 9) lungs acquired at breath-holds after full inspiration (expanded state) and full expiration (contracted state). We performed statistical analyses on Hounsfield unit (HU) histograms, lobar volumes (V: lobe volume normalized by the lung volume), and lobar flows (Q: the difference in lobe volume divided by the difference in lung volume between the expanded and contracted states). RESULTS: Parameters characterizing the HU histograms (i.e., mean, median, skewness, and kurtosis) significantly differed between healthy and IPF subjects, for all lobes in both expanded and contracted states. The distribution of V across lobes differed significantly between the groups in both states. The distribution of Q also differed significantly between the groups: Q values of the lower lobes for the IPF group were 33% (right) and 22% (left) smaller than those for the healthy group, consistent with the observation that radiographic scores were highest in the lower lung section in IPF. Notably, the root-mean-squared difference (RMSD) of Q, a measure of distance from the mean value of the healthy group, clearly distinguished the IPF subjects (RMSD of Q > 1.59) from the healthy group (RMSD of Q < 0.67). CONCLUSION: This study shows that lung volume and flow distribution change heterogeneously across the lung lobes of IPF subjects, with reduced capacity in the lower lobes. These volumetric changes may improve our understanding of the pathophysiology in IPF lungs.

FDG PET/MRI Coregistration Helps Predict Response to Gamma Knife Radiosurgery in Patients With Brain Metastases.

OBJECTIVE: The purpose of this study was to determine whether relative standardized uptake value (SUV) measurements at FDG PET/MRI coregistration are predictive of local tumor control in patients with brain metastases treated with stereotactic radiosurgery (SRS). MATERIALS AND METHODS: A retrospective review was conducted of the images and clinical characteristics of a cohort of patients with brain metastases from non-CNS neoplasms treated with gamma knife radiosurgery (GKRS) who underwent posttherapy FDG PET because of MRI findings concerning for progression. The PET and contrast-enhanced MR images were fused. Relative SUV measurements were calculated from ROIs placed in the area of highest FDG uptake within the enhancing lesion and in the contralateral normal-appearing white matter. Relative SUV was defined as the ratio of maximum SUV in the tumor to maximum SUV in healthy white matter. Two independent readers evaluated response to GKRS using serial posttherapy MRI performed at least 3 months after GKRS completion. The relation between relative SUV and local tumor progression was evaluated with respect to treatment effect. RESULTS: Eighty-five patients (48 [56.5%] women, 37 [43.5%] men; mean age at diagnosis, 60.5 ± 11.3 years) met the inclusion criteria. Thirty-three (38.8%) lesions progressed after SRS. There was a significant association between relative SUV and local tumor control (p = 0.035). Relative SUV provided a diagnostic ROC AUC of 0.67 (95% CI, 0.55-0.79). CONCLUSION: Quantitative relative SUV at posttherapy FDG PET serves as a biomarker of response to SRS in patients with brain metastases in cases in which lesion growth is identified at follow-up MRI. This prognostic data may affect management, supporting the need for further therapeutic actions for selected patients.

Unenhanced MRI as an Alternative to 99mTc-Labeled Dimercaptosuccinic Acid Scintigraphy in the Detection of Pediatric Renal Scarring.

OBJECTIVE: The purpose of this study was to determine whether unenhanced MRI without sedation is a feasible substitute for dimercaptosuccinic acid (DMSA) scintigraphy in the detection of renal scars in pediatric patients. SUBJECTS AND METHODS: Patients scheduled for 99mTc-labeled DMSA scintigraphy for assessment of possible renal scars were recruited to undergo unenhanced MRI (free-breathing fat-suppressed T2-weighted single-shot turbo spin-echo and T1-weighted gradient-echo imaging, 13 minutes' total imaging time). Scintigraphic and MRI studies were evaluated by two independent blinded specialty-based radiologists. For each imaging examination, readers identified scars in upper, middle, and lower kidney zones and rated their diagnostic confidence and the quality of each study. The scintigraphic readers' consensus score opinion for the presence of scars was considered the reference standard. RESULTS: DMSA scintigraphy showed scarring in 19 of the 78 (24.4%) evaluated zones and MRI in 18 of the 78 (23.1%). The two MRI readers found mean sensitivities of 94.7% and 89.5%, identical specificities of 100%, and diagnostic accuracies of 98.7% and 97.4%. Interobserver agreement was 98.7% for MRI and 92.3% for DMSA scintigraphy. The MRI readers were significantly more confident in determining the absence rather than the presence of scars (p = 0.02). MRI readers were more likely to rate study quality as excellent (84.6%) than were the scintigraphic readers (57.7%) (p = 0.024). CONCLUSION: Unenhanced MRI has excellent sensitivity, specificity, diagnostic accuracy, and interobserver agreement for detecting renal scars in older children who do not need sedation. It may serve as a substitute modality, especially when DMSA is not available.

FDG PET/MR Imaging Coregistration Helps Predict Survival in Patients with Glioblastoma and Radiologic Progression after Standard of Care Treatment.

Purpose To determine the correlation between metabolic activity at fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and survival in patients with glioblastoma and suspected progression at posttherapy magnetic resonance (MR) imaging. Materials and Methods The authors retrospectively examined the relationship between metabolic activity at FDG PET in the residual lesion identified at brain MR imaging and survival time in 56 patients with glioblastoma who were treated with postoperative concurrent radiation and temozolomide therapy and who underwent FDG PET/computed tomography because of radiologic deterioration at follow-up MR imaging between 2006 and 2015. A normalized metric of metabolic activity in the residual lesion (standardized uptake value ratio [SUVr]) was calculated as the maximum standardized uptake value (SUVmax) in the tumor relative to that in healthy white matter. The primary end point of the study was survival time from PET. Patients were stratified according to SUVr. Comparisons of risk for death between subgroups were made with the log-hazard ratio of the Cox proportional hazard model. Results There was a significant association between overall survival and SUVr in the residual lesion (P = .006), and a survival benefit was observed in patients with SUVr of less than 1.7, who had a median survival time of 23.1 months (95% confidence interval [CI]: 12.7, 38.9), which was significantly longer than that in patients with an SUVr of 2.0 to less than 2.5 and those with an SUVr of at least 2.5, who had a median survival time of 10.1 (95% CI: 2.4, 15.9; P = .008) and 7.5 (95% CI: 3.9, 9.7; P < .001) months, respectively. Conclusion Patients with glioblastoma whose posttherapy MR images showed a residual lesion with high relative metabolic activity at FDG PET had a shorter survival time than did those with low activity at FDG PET. © RSNA, 2016.

Detection of parathyroid adenomas using a monophasic dual-energy computed tomography acquisition: diagnostic performance and potential radiation dose reduction.

INTRODUCTION: The aims of the study were to compare the diagnostic performance of a combination of virtual non-contrast (VNC) images and arterial images obtained from a single-phase dual-energy CT (DECT) acquisition and standard non-contrast and arterial images from a biphasic protocol and to study the potential radiation dose reduction of the former approach. METHODS: All DECT examinations performed for evaluation of parathyroid adenomas during a 13-month period were retrospectively reviewed. An initial single-energy unenhanced acquisition was followed by a dual-energy arterial phase acquisition. "Virtual non-contrast images" were generated from the dual-energy acquisition. Two independent and blinded radiologists evaluated three different sets of images during three reading sessions: single arterial phase, single-phase DECT (virtual non-contrast and arterial phase), and standard biphasic protocol (true non-contrast and arterial phase). The accuracy of interpretation in lateralizing an adenoma to the side of the neck and localizing it to a quadrant in the neck was evaluated. RESULTS: Sixty patients (mean age, 65.5 years; age range, 38-87 years) were included in the study. The lateralization and localization accuracy, sensitivity, and positive predicted value (PPV) and negative predicted value (NPV) of the different image datasets were comparable. The combination of VNC and arterial images was more specific than arterial images alone to lateralize a parathyroid lesion (OR = 1.93, p = 0.043). The use of the single-phase protocol resulted in a calculated radiation exposure reduction of 52.8 %. CONCLUSIONS: Virtual non-contrast and arterial images from a single DECT acquisition showed similar diagnostic accuracy than a biphasic protocol, providing a significant dose reduction.

Development of bilateral coronary artery aneurysms in a child with Noonan syndrome.

Noonan syndrome is a constellation of congenital malformations including heart defects, facial anomalies and short stature. The cardiovascular defects are variable and extensive, with the most common being pulmonary stenosis and hypertrophic cardiomyopathy. Coronary artery anomalies have only been reported in a few cases. We report a child with Noonan syndrome status post pulmonary stenosis and atrial septal defect repair, who developed bilateral coronary artery aneurysms. The aneurysms were diagnosed with both cardiac magnetic resonance imaging and coronary computed tomography angiography. There had been no evidence of them on a cardiac MR exam 5 years previously.

Glomuvenous malformation: magnetic resonance imaging findings.

We report a case of a glomuvenous malformation involving the dorsal aspect of the right hand and distal forearm in an 11-year-old boy. He had a history of multiple vascular anomalies since birth and presented with increasing right hand pain. MRI played an important role in characterizing and determining the extent of the lesion. In particular, dynamic time-resolved contrast-enhanced MR angiography precisely defined its vascularity. The diagnosis was made histopathologically after partial resection of the lesion. Glomuvenous malformation is a rare developmental hamartoma that originates from the glomus body. Clinically they usually resemble a venous malformation but they are a different entity. In the appropriate clinical setting this rare condition must be included in the differential diagnosis of a vascular malformation, especially when subtle arterial enhancement, early venous shunting and progressive filling of dilated venous spaces are depicted on MRA.

Imaging follow-up of endovascular repair of type B aortic dissection with dual-source, dual-energy CT and late delayed-phase scans.

PURPOSE: To evaluate the diagnostic performance of dual-energy (DE) computed tomography (CT) after thoracic endovascular aortic repair (TEVAR) of type B dissection, and to investigate the value of late delayed (LD) acquisition in endoleak detection and false lumen patency assessment. MATERIALS AND METHODS: Twenty-four patients with TEVAR for type B dissection underwent 53 tripe-phase CT examinations. Single-source unenhanced acquisition was followed by single-source arterial-phase and DE LD phase (300-s delay) imaging. Virtual noncontrast images were generated from DE acquisition. Two blinded radiologists retrospectively evaluated the cases in three reading sessions: session A (triphasic protocol), session B (virtual noncontrast and arterial phase), and session C (virtual noncontrast and arterial and LD phases). Endoleak detection accuracy during sessions B and C compared with session A (reference standard) was investigated. False lumen patency was assessed. Effective radiation dose was calculated. RESULTS: Session A revealed 37 endoleaks in 30 of 53 studies (56.6%). Session B revealed 31 of the 37 endoleaks, with one false-positive case, 83.8% sensitivity, 95.8% specificity, 79.3% negative predictive value, and 96.9% positive predictive value. Session C correctly depicted all 37 endoleaks, with one false-positive case, 100% sensitivity, 95.8% specificity, 100% negative predictive value, and 97.4% positive predictive value. Underestimation of false lumen patency was found in session B (P = .013). Virtual noncontrast imaging resulted in 17% radiation exposure reduction. CONCLUSIONS: Virtual noncontrast imaging can replace standard unenhanced images in follow-up after TEVAR of type B dissection, thus reducing radiation dose. Delayed-phase imaging is valuable in low-flow endoleaks detection and false lumen patency assessment.

Gradient of apparent diffusion coefficient values in peritumoral edema helps in differentiation of glioblastoma from solitary metastatic lesions.

OBJECTIVE: Glioblastoma and solitary metastatic lesions can be difficult to differentiate with conventional MRI. The use of diffusion-weighted MRI to better characterize peritumoral edema has been explored for this purpose, but the results have been conflicting. The purpose of this study was to test the hypothesis that the gradient of apparent diffusion coefficient (ADC) values in peritumoral edema--that is, the difference in ADC values from the region closest to the enhancing tumor and the one closest to the normal-appearing white matter--may be a marker for differentiating glioblastoma from a metastatic lesion. MATERIALS AND METHODS: Forty patients, 20 with glioblastoma and 20 with a solitary metastatic lesion, underwent diffusion-weighted brain MRI before surgical resection. The ADC values were retrospectively collected in the peritumoral edema in three positions: near, an intermediate distance from, and far from the core enhancing tumor (G1, G2, and G3). The ADC gradient in the peritumoral edema was calculated as the subtractions ADCG3 - ADCG1, ADCG3 - ADCG2, and ADCG2 - ADCG1. The ADC values in the enhancing tumor, peritumoral edema, ipsilateral normal-appearing white matter, contralateral healthy white matter, and CSF were also collected. RESULTS: A gradient of ADC values was found in the peritumoral edema of glioblastoma. The ADC values increased from the region close to the enhancing tumor (1.36 ± 0.24 × 10(-3) mm(2)/s) to the area near the normal-appearing white matter (1.57 ± 0.34 × 10(-3) mm(2)/s). In metastatic lesions, however, those values were nearly homogeneous (p = 0.04). CONCLUSION: The ADC gradient in peritumoral edema appears to be a promising tool for differentiating glioblastoma from a metastatic lesion.

Cardiopulmonary effects of apneustic anesthesia ventilation in anesthetized pigs: a new mode of ventilation for anesthetized veterinary species.

Objective: To compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in anesthetized pigs and to describe a new mode of ventilation for anesthetized veterinary species. Study design: Randomized, crossover design without washout. Animals: Twelve healthy, female white Landrace pigs. Methods: Following ketamine-midazolam premedication and anesthetic induction with propofol, the trachea was intubated, and each pig was positioned in dorsal recumbency. Anesthesia was maintained with propofol and sufentanil infusions. Pigs were instrumented and their lungs were sequentially ventilated with each mode, in random order, for 1 h according to predefined criteria [fraction of inspired oxygen (FiO2) = 0.21, 10 mL kg-1 tidal volume (VT), and arterial carbon dioxide tension (PaCO2) within 40-45 mmHg]. Cardiopulmonary data were collected at baseline, 30 and 60 min. In 8 pigs, thoracic computed tomography (CT) was performed following the 60 min time point for each mode of ventilation and images were analyzed to quantify lung aeration. The effects of ventilation mode, time, and order were analyzed using repeated measures ANOVA. Paired t-tests were used to compare lung aeration between modes. Significance was defined as p < 0.05. Results: Data from 12 pigs were analyzed. A significant effect of mode was found for heart rate, mean arterial pressure (MAP), pulmonary artery occlusion pressure, cardiac index (CI), stroke volume index, systemic vascular resistance, pulmonary vascular resistance, oxygen delivery index (DO2I), oxygen extraction ratio (O2ER), VT, arterial oxygen tension, arterial hemoglobin saturation, PaCO2, end-tidal carbon dioxide tension, alveolar dead space (VDalv/VTalv), venous admixture ( Q . s / Q . t ), mean airway pressure, and dynamic compliance index (CRSI). Order effects were also observed for some cardiovascular and respiratory variables. For the eight pigs that underwent thoracic CT, AAV resulted in significantly larger proportions of normally and hyperaerated lung while CMV resulted in larger proportions of hypoaerated and atelectatic lung. Conclusions: In dorsally recumbent anesthetized pigs, ventilated with FiO2 = 0.21, both modes of ventilation supported adequate oxygenation while AAV resulted in higher CRSI, and lower VDalv/VTalv and Q . s / Q . t , compared with CMV. AAV was also associated with lower MAP, CI, and DO2I and higher O2ER compared with CMV. Further investigation of AAV in anesthetized animals is warranted.

Endoleak detection after endovascular repair of thoracic aortic aneurysm using dual-source dual-energy CT: suitable scanning protocols and potential radiation dose reduction.

OBJECTIVE: The objective of our study was to evaluate the diagnostic performance of dual-source dual-energy CT (DECT) in the detection of endoleaks after thoracic endovascular aortic repair for thoracic aortic aneurysm and to investigate if a double-phase (arterial and dual-energy late delayed phase) or a single-phase (dual-energy late delayed phase) acquisition can replace the standard triphasic protocol. MATERIALS AND METHODS: All DECT examinations performed for evaluation after thoracic endovascular aortic repair during a 30-month period were retrospectively reviewed. An initial single-source unenhanced acquisition was followed by a single-source arterial phase acquisition and a dual-energy 300-second late delayed phase acquisition. "Virtual noncontrast images" were generated from the dual-energy acquisition. Two independent and blinded radiologists evaluated the cases during three reading sessions: session A (triphasic protocol: standard unenhanced, arterial phase, and late delayed phase), session B (virtual noncontrast and late delayed phase), and session C (virtual noncontrast, arterial phase, and late delayed phase). The diagnostic accuracies of sessions B and C were calculated using session A as the reference standard. Contrast-to-noise ratios and effective radiation doses were calculated. RESULTS: Forty-eight patients (mean age, 66 years; age range, 19-84 years) underwent 74 triple-phase CT examinations. The single-phase studies (session B) were characterized by 85.7% sensitivity, 100% specificity, 100% negative predictive value (NPV), and 94.6% positive predictive value (PPV). The dual-phase study (session C) revealed 100% sensitivity, 100% specificity, 100% NPV, and 100% PPV. The use of the dual-phase protocol and single-phase protocol resulted in a radiation exposure reduction of 19.5% and 64.1%, respectively. CONCLUSION: Virtual noncontrast and late delayed phase images reconstructed from a single DECT acquisition can replace the standard triphasic protocol in follow-up examinations after thoracic endovascular aortic repair, thereby providing a significant dose reduction.

Ten frequently asked questions about MRI evaluation of soft-tissue vascular anomalies.

OBJECTIVE: The objective of this article was to address 10 frequently asked questions that radiologists face when planning, performing, and interpreting an MRI study in a patient with a soft-tissue vascular anomaly. CONCLUSION: MRI permits a comprehensive assessment of vascular anomalies. It is important for radiologists to be familiar with the classification and correct nomenclature of vascular anomalies as well as the MRI protocol and distinct imaging findings of the different vascular malformations and tumors.

Hyperpolarized Xenon-129: A New Tool to Assess Pulmonary Physiology in Patients with Pulmonary Fibrosis.

PURPOSE: The existing tools to quantify lung function in interstitial lung diseases have significant limitations. Lung MRI imaging using inhaled hyperpolarized xenon-129 gas (129Xe) as a contrast agent is a new technology for measuring regional lung physiology. We sought to assess the utility of the 129Xe MRI in detecting impaired lung physiology in usual interstitial pneumonia (UIP). MATERIALS AND METHODS: After institutional review board approval and informed consent and in compliance with HIPAA regulations, we performed chest CT, pulmonary function tests (PFTs), and 129Xe MRI in 10 UIP subjects and 10 healthy controls. RESULTS: The 129Xe MRI detected highly heterogeneous abnormalities within individual UIP subjects as compared to controls. Subjects with UIP had markedly impaired ventilation (ventilation defect fraction: UIP: 30 ± 9%; healthy: 21 ± 9%; p = 0.026), a greater amount of 129Xe dissolved in the lung interstitium (tissue-to-gas ratio: UIP: 1.45 ± 0.35%; healthy: 1.10 ± 0.17%; p = 0.014), and impaired 129Xe diffusion into the blood (RBC-to-tissue ratio: UIP: 0.20 ± 0.06; healthy: 0.28 ± 0.05; p = 0.004). Most MRI variables had no correlation with the CT and PFT measurements. The elevated level of 129Xe dissolved in the lung interstitium, in particular, was detectable even in subjects with normal or mildly impaired PFTs, suggesting that this measurement may represent a new method for detecting early fibrosis. CONCLUSION: The hyperpolarized 129Xe MRI was highly sensitive to regional functional changes in subjects with UIP and may represent a new tool for understanding the pathophysiology, monitoring the progression, and assessing the effectiveness of treatment in UIP.

Imaging Approach to Disease of the Pleura.

Diseases of pleura are not only common but also have a significant impact on patients' outcomes. While early detection and treatment are imperative in reducing this burden, many pleural entities present similarly, thus posing a diagnostic dilemma for radiologists requiring critical further workup. While chest radiography, CT, and image-guided thoracentesis are primarily utilized as the initial imaging techniques for the workup of pleural diseases, MRI, and FDG-PET/CT are also frequently employed to investigate the root cause of pleural abnormalities. By elucidating the common imaging features of neoplastic, inflammatory, and infectious pleural pathologies, clinicians can quickly and easily differentiate the various pleural diseases, rapidly reach the correct diagnosis, and ultimately improve patient outcomes.