The ��Mill-Wheel�� Murmur and Computed Tomography of Intracardiac Air Emboli

The ‘water-wheel’ or ‘mill-wheel’ murmur is classically associated with large intracardiac air emboli and described as a “characteristic splashing auscultatory sound due to the presence of gas in the cardiac chambers.” We used 64-slice computed tomography (slice thickness, 0.5 mm; revolution time, 400 msec) and 3D fly-through software imagery to capture previously unreported intracardiac air–blood interface dynamics associated with this murmur and ineffective right ventricular contraction in a porcine model.Abbreviation: CT, computed tomographyMost venous air (gas) emboli are iatrogenic.^3,6,8-12,14 The consequences of venous air emboli are dependent on the presence of a pathway and gradient for gas flow, the volume and location of entrapped air, the rate of air accumulation, the patient''s position and hemodynamic and ventilatory status, and the presence of right-to-left shunts.^3,6,8-12,14There have been dramatic operative accounts of the direct visualization of “bubbles and froth” within distended veins, right heart and pulmonary artery that resulted from massive air emboli and of blood and air being “churned by the beating heart,” producing audible sounds^3,7,8 similar to fluid splashing in a half-filled plastic bag¹ or by a watermill.^2,3 The entrapment of clinically significant volumes of air (or other gases) within the pulmonary artery and right ventricular outflow track causes a condition analogous to an airlock, precipitating cardiovascular collapse.^3,5,9,13 Although large and potentially life-threatening venous air emboli during CT procedures are rare,¹³ contrast radiographic procedures are defined as “medium risk” procedures for venous air emboli in humans.⁹ Clinically insignificant small to moderate air emboli are reported to occur in 12% to 23% of subjects undergoing contrast procedures and in 11% of subjects after intravenous access.^4,15     

Evaluating HIV-Infected Patients With Headache: Who Needs Computed Tomography?

OBJECTIVE: To empirically test a clinical prediction rule for evaluating HIV-infected patients complaining of headache and to identify those at low risk for intracranial mass lesion who do not need immediate computed tomography of the head. DESIGN: Two retrospective clinical cohorts of HIV-infected patients clinically evaluated for headache. METHODS: To describe the headache clinical outcomes, medical records were abstracted from all HIV-infected patients evaluated for headache with computed tomography of the head at two urban hospitals. Patients were categorized as low, intermediate, or high risk based on clinical criteria (focal neurological signs, altered mental status, history of seizure) and immune status (CD4 lymphocytes < or =200 microL). Records were abstracted from a second unselected cohort of HIV-infected outpatients with headache who were all treated and followed in primary care (N=101). RESULTS: Of 101 unselected HIV-infected outpatients followed in primary care after headache, 1% (95% confidence interval [CI], 0% to 6%) had a treatable intracranial lesion. Of 364 HIV-infected patients with headache sent for evaluation with computed tomography of the head, the rate of any abnormality was zero in the low-risk group (95% CI, 0% to 10%; n=35); 9% in the intermediate-risk group (95% CI, 2% to 16%; n=242); and 21% in the high-risk group (95% CI, 12% to 29%; n=87). CONCLUSION: Most HIV-infected patients with headache may be treated with analgesics and followed up clinically. Those without focal neurological signs, altered mental status, seizure, or decreased CD4 lymphocytes are unlikely to have intracranial mass lesions.     

Automated Computed Tomography–Ultrasound Cross-Modality 3-D Contouring Algorithm for Prostate

A novel fully automated algorithm is introduced for 3-D cross-modality image segmentation of the prostate, based on the simultaneous use of co-registered computed tomography (CT) and 3-D ultrasound (US) images. By use of a Gabor feature detector, the algorithm can outline in three dimensions and in cross-modality the prostate, and it can be trained and optimized on specific patient populations. We applied it to 16 prostate cancer patients and evaluated the conformity between the automatically segmented prostate contours and the contours manually outlined by an experienced physician, on the CT–US fusion, using the mean distance to conformity (MDC) index. When only the CT scans were used, the average MDC value was 4.5 ± 1.7 mm (maximum value = 9.0 mm). When the US scans also were considered, the mean ± standard deviation was reduced to 3.9 ± 0.7 mm (maximum value = 5.5 mm). The cross-modality approach acted on all the largest distance values, reducing them to acceptable discrepancies.     

Can Computed Tomography Angiography of the Brain Replace Lumbar Puncture in the Evaluation of Acute‐onset Headache After a Negative Noncontrast Cranial Computed Tomography Scan?

Objectives: The primary goal of evaluation for acute‐onset headache is to exclude aneurysmal subarachnoid hemorrhage (SAH). Noncontrast cranial computed tomography (CT), followed by lumbar puncture (LP) if the CT is negative, is the current standard of care. Computed tomography angiography (CTA) of the brain has become more available and more sensitive for the detection of cerebral aneurysms. This study addresses the role of CT/CTA versus CT/LP in the diagnostic workup of acute‐onset headache. Methods: This article reviews the recent literature for the prevalence of SAH in emergency department (ED) headache patients, the sensitivity of CT for diagnosing acute SAH, and the sensitivity and specificity of CTA for cerebral aneurysms. An equivalence study comparing CT/LP and CT/CTA would require 3,000 + subjects. As an alternative, the authors constructed a mathematical probability model to determine the posttest probability of excluding aneurysmal or arterial venous malformation (AVM) SAH with a CT/CTA strategy. Results: SAH prevalence in ED headache patients was conservatively estimated at 15%. Representative studies reported CT sensitivity for SAH to be 91% (95% confidence interval [CI] = 82% to 97%) and sensitivity of CTA for aneurysm to be 97.9% (95% CI = 88.9% to 99.9%). Based on these data, the posttest probability of excluding aneurysmal SAH after a negative CT/CTA was 99.43% (95% CI = 98.86% to 99.81%). Conclusions: CT followed by CTA can exclude SAH with a greater than 99% posttest probability. In ED patients complaining of acute‐onset headache without significant SAH risk factors, CT/CTA may offer a less invasive and more specific diagnostic paradigm. If one chooses to offer LP after CT/CTA, informed consent for LP should put the pretest risk of a missed aneurysmal SAH at less than 1%. ACADEMIC EMERGENCY MEDICINE 2010; 17:444–451 © 2010 by the Society for Academic Emergency Medicine     

When Should Abdominal Computed Tomography Be Considered in Patients with Lower Rib Fractures?

Background

Lower rib fractures are considered as a marker of intra-abdominal organ injury. Abdominal computed tomography (CT) is the “gold standard” examination for patients with lower rib fractures. However, the reported incidence of concomitant intra-abdominal injuries (IAI) is 20%–40%.

Computed Tomography Image Analysis Before and After Treatment of Anti-Neutrophil Cytoplasmic Antibody−Associated Pulmonary Interstitial Fibrosis in 8 Patients

PurposeThe purpose of this study was to observe the treatment response of anti-neutrophil cytoplasmic antibody (ANCA)−associated pulmonary interstitial fibrosis in 8 patients before and after glucocorticoid or immunosuppressive therapy.MethodsThe clinical features and computed tomography imaging findings of the 8 patients in our hospital from October 2011 to October 2013, were retrospectively analyzed.FindingsMean age of the 8 patients was 72.6 (range 60−80) years. Five patients exhibited cough, sputum, and chest tightness, including 2 patients with fever. One patient developed hemoptysis, 1 patient exhibited abnormal urinalysis and developed renal insufficiency, and 1 patient developed limb pain. Two patients exhibited high urine erythrocytes and 2 patients had renal dysfunction and urinary abnormalities. One of the latter patients, upon renal biopsy, had focal proliferative necrotizing glomerulonephritis (consistent with vasculitis damage) with stage II to III mild nephropathy. Seven cases were anti−myeloperoxidase-ANCA, and 1 case was anti−proteinase 3-ANCA. All 8 cases exhibited streaks and grid shadows in chest imaging; 2 cases exhibited limited ground-glass patches; 1 case displayed multiple large patches of exudative shadows, indicating diffuse alveolar hemorrhage; 2 cases exhibited obvious honeycomb manifestations; and 1 case exhibited significant traction bronchiectasis. The ground-glass opacities disappeared after corticosteroid or immunosuppressive therapy; however, for streaks and grid shadows, no significant changes in the images were observed after treatment from 2 weeks to 10 months.ImplicationsANCA-associated pulmonary interstitial fibrosis most often in elderly patients with many complications. In these patients ground-glass opacities in computed tomography images, corticosteroid or immunosuppressant therapy may be effective. Clinicians should consider the poor efficacy and side effects of these therapies in the fibrosis stage of the disease.     

Analysis of Dosimetric Impacts of Cone Beam Computed Tomography–Based Volumetric Modulated Arc Therapy Planning

ObjectiveTo quantify the Hounsfield unit (HU) variations between computed tomography (CT) and cone beam CT (CBCT) and study its impact on volumetric modulated arc therapy (VMAT) plans.MethodsHU number variations in CT and CBCT images were evaluated using the Catphan-504 phantom, and changes in seven different materials within the phantom (air, polymethylpentene, low-density polyethylene, polystyrene, acrylic, Delrin, and Teflon) were studied. The HU variations in half-fan and full-fan modes of CBCT were evaluated. The effect of variations in the shape of the body cross sections was assessed by reducing the body of the Catphan by 0.5 cm and 1.0 cm. CBCT-based VMAT plans in 27 patients (10 prostate, 10 brain, and 7 head and neck (HN)) were compared with corresponding CT-based plans. The dosimetric variations were assessed referring to different points on the dose volume histogram (D_5%, D_50%, and D_95% for PTVs and D_1%, D_max, and D_mean for organs at risk). The relative percentage of difference (ΔD (%)) between CT- and CBCT-based VMAT plans were examined on these points. To evaluate the dosimetric accuracy, dose distributions were compared using Omnipro-I'mRT software. The VMAT plans were evaluated based on 3 mm-3%, 2 mm-2%, and 1 mm-1% gamma criteria.ResultsThe HU difference in CT and CBCT was highest for air, Delrin, and Teflon, whereas the difference was less than 20 HU for the other materials. The dose volume histograms of both CT- and CBCT-based plans were in excellent agreement in both phantom and patients, except in HN cases where the difference was 7%. The average 3 mm-3% gamma pass points in brain, prostate, and HN patients were 97 ± 0.2%, 96 ± 0.06%, and 93.3 ± 1.1%, respectively. The gamma pass rates reduced to 88.8 ± 0.06%, 91 ± 0.04%, and 79 ± 6% in 2 mm-2%, and further declined to 76.6 ± 0.09%, 75.2 ± 0.5%, and 60 ± 6% using the stringent 1 mm-1% gamma criteria for brain, prostate, and HN cases, respectively.ConclusionBased on the results of this study, it is our belief that CBCT images can be used as a tool for evaluating the dosimetric variation in patient VMAT plans.     

Does 16-Detector Computed Tomography Improve Detection of Non-traumatic Subarachnoid Hemorrhage in the Emergency Department?

The diagnosis of subarachnoid hemorrhage remains difficult to establish, yet the sensitivity of increasingly available 16-detector computed tomography (CT) has not been evaluated. The objective of this study was to estimate the sensitivity of 16-detector CT for the diagnosis of non-traumatic subarachnoid hemorrhage in the Emergency Department (ED). A retrospective review was performed in an academic tertiary care hospital. Patients presenting to the ED from September 2003 through December 2004 with symptoms suggestive of subarachnoid hemorrhage and having a final diagnosis of non-traumatic subarachnoid hemorrhage were eligible for study. Diagnosis was established by positive 16-detector CT examination of the brain, or spinal fluid analysis. Patient demographics and results of CT, angiogram, and spinal fluid analysis were reviewed. Sensitivity of 16-detector CT was calculated by comparing CT results and cerebral angiogram results. Refined Wilson Simple Asymptotic 95% confidence intervals were calculated. Sixty-one consecutive patients met the study criteria and had a final diagnosis of non-traumatic subarachnoid hemorrhage. One of these patients did not have subarachnoid hemorrhage identified by 16-detector CT, but had a positive lumbar puncture and an aneurysm confirmed on cerebral angiography. Sensitivity of 16-detector CT for subarachnoid hemorrhage was 97% (95% confidence interval 84-100%). Sixteen-detector CT did not improve detection of non-traumatic subarachnoid hemorrhage when compared with studies using single-detector CT. If there is high clinical suspicion for non-traumatic subarachnoid hemorrhage and non-contrast 16-detector CT scan is negative, further evaluation is suggested.     

Management of Pneumothoraces Detected on Chest Computed Tomography: Can Anatomical Location Identify Patients Who Can Be Managed Expectantly?

Background

Pneumothorax (PTX) can be readily detected by computed tomography (CT) or ultrasound. However, management of PTX in hemodynamically stable patients remains controversial.

Study Objectives

We sought to investigate whether a distinct anatomical distribution of PTX along prespecified chest zones as detected by CT can be described in patients with or without subsequent chest tube thoracotomy (CTT), thus potentially allowing the extended focused assessment with sonography for trauma (EFAST) ultrasound examination to guide PTX management.

Methods

We performed a retrospective review of chest CT scans performed in the emergency department (ED) of a Level I trauma center. CT scans were analyzed for PTX distribution according to a chest zone model. Medical records of subjects with PTX were reviewed for subsequent CTT.

Results

Of 3636 chest CT scans performed, 183 PTX (156 patients) were detected without CTT at the time of CT scan (69% male, mean age 42 years). Of these, 66 subjects (40%) underwent CTT; 43 chest tubes (63%) were placed in the ED, 9 (13%) during hospitalization and 9 (13%) in the operating room. Median time to CTT was 140 min (interquartile range 52–199). Initial hemodynamic parameters, need for surgery, and need for mechanical ventilation were similar in both groups (p > 0.05 for all). Anatomical distribution and size of PTX were similar in the two groups.

Conclusion

Although the majority of patients with traumatic PTX could be managed conservatively, we did not identify a characteristic anatomical PTX pattern, which could identify subjects who may not require CTT.     

Clinical Value of Combined Positron Emission Tomography/Computed Tomography Imaging in the Interpretation of 2-Deoxy-2-[F-18]fluoro-<Emphasis Type="SmallCaps">d</Emphasis>-glucose–Positron Emission Tomography Studies in Cancer Patients

Background Positron emission tomography (PET)/computed tomography (CT) is a new imaging modality that provides exact coregistration of anatomic and metabolic data. We have investigated to what degree this new technique might affect the interpretation of PET images in a nonselected group of consecutive cancer patients, reflecting routine condition in a busy cancer center.Methods Whole-body 2-deoxy-2-[F-18]fluoro-d-glucose (FDG)–PET and PET/CT fusion image sets were compared in 100 consecutive, nonselected patients: 21 with head and neck cancer, 39 with chest malignancies, and 40 with malignancies of the abdomen and pelvis. All studies were performed for primary staging or evaluation of therapy and were interpreted by two nuclear medicine physicians also trained in radiology. Areas of abnormal FDG uptake were identified on PET and graded as likely benign, equivocal, or likely malignant. Positron emission tomography/computed tomography fusion images were then made available, and the initial findings were amended if necessary.Results One hundred sixty-six areas with abnormal FDG uptake were identified. Based on PET alone, 51 sites were considered equivocal for malignancy. With PET/CT, the number of equivocal lesions decreased to 24. This difference is more marked in the head and neck as well as the abdomen and pelvis. When the equivocal sites were included in the analysis and grouped with the malignant sites, positive predictive value (PPV) of PET/CT was 89% compared with 75% for PET (p = 0.04).Conclusion Combined PET/CT results in increased reader confidence and 53% fewer equivocal readings, as well as improved PPV compared with PET alone.*Contributed equally to this work.     

Computed tomographic screening for thoracic and lumbar fractures: is spine reformatting necessary?

Introduction

Patients who sustain traumatic vertebral fractures often have multiple other associated injuries. Because of the mechanisms of injury, many of these patients routinely undergo chest computed tomographic (CCT) and/or abdominal/pelvic computed tomographic (APCT) scans to diagnose intrathoracic or intra-abdominal injuries. These scans are routinely reformatted to provide more detailed imaging of the spine. Although the patient does not incur more radiation, the charges associated with this are significant. This study compared the sensitivity of these CT modalities in detecting thoracolumbar spine fractures.

Methods

A retrospective chart review identified blunt trauma victims, admitted through the emergency department, with a discharge diagnosis of thoracic or lumbar spine fracture that received (1) a chest and T-spine CT, (2) an abdominal/pelvic and lumbar spine CT, or both. Final radiologic readings of these patients' CT scans were obtained, and the sensitivities of the different imaging methods were compared. Discharge diagnosis of spine fracture was considered the gold standard.

Results

One hundred seventy-six APCT scans with reformatting and 175 CCT scans with reformatting were available for comparison. There were 9 of 176 false-negative APCT scans vs 3/176 false-negative lumbar spine CT scans. There were 14/175 false-negative CCT scans vs 2/175 false-negative thoracic spine CT scans. The differences in sensitivity were significant (P < .001) for both comparisons.

Conclusions

Reformatting of CCT and APCT scans gives improved sensitivity in the detection of thoracic and lumbar spine fractures in trauma patients. Future study looking at clinically significant fractures or those that change clinical management decisions may find that the reformatted images are not routinely needed as a screening tool.     

Diagnostic Imaging in Newborns,Children and Adolescents Infected with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): Is There a Realistic Alternative to Lung High-Resolution Computed Tomography (HRCT) and Chest X-Rays? A Systematic Review of the Literature

Chest computed tomography has been frequently used to evaluate patients with potential coronavirus disease 2019 (COVID-19) infection. However, this may be particularly risky for pediatric patients owing to high doses of ionizing radiation. We sought to evaluate COVID-19 imaging options in pediatric patients based on the published literature. We performed an exhaustive literature review focusing on COVID-19 imaging in pediatric patients. We used the search terms “COVID-19,” “SARS-CoV2,” “coronavirus,” “2019-nCoV,” “Wuhan virus,” “lung ultrasound (LUS),” “sonography,” “lung HRCT,” “children,” “childhood” and “newborn” to query the online databases PubMed, Medical Subject Headings (MeSH), Embase, LitCovid, the World Health Organization COVID-19 database and Medline Bireme. Articles meeting the inclusion criteria were included in the analysis and review. We identified only seven studies using lung ultrasound (LUS) to diagnose severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in newborns and children. The studies evaluated small numbers of patients, and only 6% had severe or critical illness associated with COVID-19. LUS showed the presence of B-lines in 50% of patients, sub-pleural consolidation in 43.18%, pleural irregularities in 34.09%, coalescent B-lines and white lung in 25%, pleural effusion in 6.82% and thickening of the pleural line in 4.55%. We found 117 studies describing the use of chest X-ray or chest computed tomography in pediatric patients with COVID-19. The proportion of those who were severely or critically ill was similar to that in the LUS study population. Our review indicates that use of LUS should be encouraged in pediatric patients, who are at highest risk of complications from medical ionizing radiation. Increased use of LUS may be of particularly high impact in under-resourced areas, where access to chest computed tomography may be limited.     

Body Mass Index and Age Effects on Brain 11β-Hydroxysteroid Dehydrogenase Type 1: a Positron Emission Tomography Study

Molecular Imaging and Biology - Cortisol, a glucocorticoid steroid stress hormone, is primarily responsible for stimulating gluconeogenesis in the liver and promoting adipocyte differentiation and...     

How Available is Positron Emission Tomography in the United States?

Purpose Positron emission tomography (PET) has become a major clinical diagnostic and prognostic tool for oncology and multiple other arenas. To some, however, the perception exists that PET is not available as a resource in their community. Our goal with this project was to determine how available clinical PET was in the United States.Procedures We used existing lists of PET centers, websites from PET scanner manufacturers, as well as a common Internet search engine to find clinical PET facilities. A mapping program was then used to determine area coverage with a 75-mile radius for each PET scanner found, and the United States Census website was utilized as a source of population data for covered and not covered areas.Results We found that 97% of the US population lives within 75 miles of a clinical PET facility.Conclusion Thus, it appears that the idea of clinical PET being unavailable to many is a misconception, which may be limiting its use by some physicians who are unaware of how common it has become.     

Computed tomography angiography in patients with suspected pulmonary embolism-too often considered?

Background

Pulmonary embolism (PE) is a major cause of morbidity and mortality associated with surgery and medical illnesses. In recent years, pulmonary computed tomography angiography (CTA) has become the diagnostic method of choice. However, it remains unclear when to perform CTA and how often a decision based on clinical judgment results in positive or negative findings.

Methods

In a retrospective study, 261 patients admitted for suspected PE were evaluated with pulmonary CTA. Decisions to order CTA were based on clinical judgment and optionally quantitative d-dimer assays. Clinical, radiologic, and laboratory data were revisited and compared in patients with and without proven PE.

Results

The patients' mean age was 63 ± 1 years; almost 30% of all participants had at least a moderately reduced renal function. Pulmonary CTA demonstrated PE in only 14.9%; both age and sex distribution was comparable in the PE and non-PE group. Proximal deep vein thrombosis or pathologic chest x-rays were significantly more likely in patients with PE (P < .001 and P < .05), whereas echocardiography results were comparable. d-dimer values were noticeably higher in the PE group (P < .001); however, C-reactive protein and troponin T levels were not helpful.

Conclusions

Pulmonary CTA confirmed PE in only a minority of patients and may be overused. Clinical judgment in conjunction with d-dimer evaluation was of limited help to predict positive results but surprisingly comparable with previous results using pretest probability scoring systems. Using present and previous data, a simplified enhanced algorithm is proposed to reduce use of CTA.     

A Computational Positron Emission Tomography Simulation Model for Imaging β-Amyloid in Mice

Purpose We aimed to develop a computational simulation model for -amyloid (A) positron emission tomography (PET) imaging.Procedures Model parameters were set to reproduce levels of A within the PDAPP mouse. Pharmacokinetic curves of virtual tracers were computed and a PET detector simulator was configured for a commercially available preclinical PET-imaging system.Results We modeled the effects of A therapy and tracer affinity on the ability to differentiate A levels by PET. Varying affinity had a significant effect on the ability to quantitate A. Further, PET tracers for A monomers were more sensitive to the therapeutic reduction in A levels than total brain amyloid. Following therapy, the decrease in total brain A corresponded to the slow rate of change in total amyloid load as expected.Conclusions We have developed a first proof-of-concept A-PET simulation model that will be a useful tool in the interpretation of preclinical A imaging data and tracer development.