Myocardial Cut-off Sign is a Sensitive and Specific Cardiac Computed Tomography and Magnetic Resonance Imaging Sign to Distinguish Left Ventricular Pseudoaneurysms From True Aneurysms.

PURPOSE: The purpose of this study was to describe the myocardial cut-off sign, assess its ability to distinguish left ventricular pseudoaneurysms (LV PSAs) from true aneurysms (LVAs), and compare its performance with other imaging findings and quantitative measurements used to differentiate LV PSAs from LVAs. MATERIALS AND METHODS: This retrospective single-center study identified patients with preoperative cardiac computed tomography (CT) or magnetic resonance imaging (MRI) and surgically confirmed LVAs or LV PSAs over a 10-year period. Seventeen LV PSAs (11 MRI, 6 CT) and 18 LVAs (10 MRI, 8 CT) were included. The myocardial cut-off sign was objectively a >50% decrease in aneurysm sac wall thickness measured at 1 cm from the aneurysmal neck (measurements at 2 cm were also assessed) and subjectively an abrupt "cut-off" of myocardium for the aneurysm sac for PSA compared with a gradual tapering of sac wall thickness for LVA. Two radiologists independently evaluated images for the subjective presence of this sign. RESULTS: The myocardial cut-off sign was 91% sensitive and 97% specific when measured 1 cm from the aneurysm neck. When measured at 2 cm from the neck, the sign was 100% sensitive and 69% specific. Subjective analysis of whether the myocardium appeared "cut-off" was 94% to 100% sensitive and 78% to 94% specific with excellent agreement for both PSA (κ=0.94) and LVA (κ=0.83). CONCLUSIONS: The myocardial cut-off sign on cardiac CT and MRI is a sensitive and specific finding of LV PSA. Specificity is improved with objective measurements compared with subjective assessment (97% vs. 78% to 94%). This sign may help radiologists distinguish between LV PSAs and LVAs.

Epidemiology of Hepatic Steatosis at a Tertiary Care Center: An MRI-based Analysis.

RATIONALE AND OBJECTIVES: Little is known about the frequency and risk factors of hepatic steatosis in the tertiary care setting. Such knowledge is essential to clinicians making decisions about testing for this condition. Thus, our aim was to describe the epidemiology of hepatic steatosis, as captured by magnetic resonance imaging (MRI), at a tertiary care center. MATERIALS AND METHODS: A near-consecutive cohort of 1006 adult patients underwent standard-of-care liver MRIs. Images were retrospectively processed to derive proton density fat fraction (PDFF) maps. Data from three spatially distinct regions of interest (ROIs) were aggregated to derive overall hepatic PDFF values. Demographic, anthropometric, clinical, and laboratory variables were included in a multivariate analysis to determine predictors of hepatic steatosis grades (based on established PDFF cutoffs). Hepatic steatosis grades derived from single vs aggregated ROIs were compared. RESULTS: Hepatic steatosis was observed in 25% of patients (19% grade 1; 3% grade 2; 3% grade 3). Controlling for all other variables, the odds of hepatic steatosis increased by 7%-9% (P <.001) for each whole point increase in body mass index (BMI), whereas elevated serum bilirubin was associated with lower odds of hepatic steatosis (P = .002). Race, diabetes mellitus, dyslipidemia, and metabolic syndrome were not independently predictive of hepatic steatosis when controlling for other variables (eg, BMI). Employing single ROIs (rather than three aggregated ROIs) resulted in incorrect steatosis grading in up to 8.0% of patients. CONCLUSION: Many adult patients undergoing liver MRI at a tertiary care center have hepatic steatosis, with larger BMIs as the only independent predictor of higher grades. This information can be used by clinicians at such centers to make evidence-based decisions about when to test for hepatic steatosis in their patients.

Thrombolysis is an Independent Risk Factor for Poor Outcome After Carotid Revascularization.

BACKGROUND: Thrombolysis is the standard of care for acute ischemic stroke patients presenting in the appropriate time window. Studies suggest that the risk of recurrent ischemia is lower if carotid revascularization is performed early after the index event. The safety of early carotid revascularization in this patient population is unclear. OBJECTIVE: To evaluate the safety of carotid revascularization in patients who received thrombolysis for acute ischemic stroke. METHODS: The Nationwide Inpatient Sample database was queried for patients admitted through the emergency room with a primary diagnosis of carotid stenosis and/or occlusion. Each patient was reviewed for administration of thrombolysis, carotid endarterectomy, (CEA) or carotid angioplasty and stenting (CAS). Primary endpoints were intracerebral hemorrhage (ICH), postprocedural stroke (PPS), poor outcome, and in-hospital mortality. Potential risk factors were examined using univariate and multivariate analyses. RESULTS: A total of 310 257 patients were analyzed. Patients who received tissue plasminogen activator (tPA) and underwent either CEA or CAS had a significantly higher risk of developing an ICH or PPS than patients who underwent either CEA or CAS without tPA administration. The increased risk of ICH or PPS in tPA-treated patients who underwent carotid revascularization diminished with time, and became similar to patients who underwent carotid revascularization without tPA administration by 7 d after thrombolysis. Patients who received tPA and underwent CEA or CAS also had higher odds of poor outcome and in-hospital mortality. CONCLUSION: Thrombolysis is a strong risk factor for ICH, PPS, poor outcome, and in-hospital mortality in patients with carotid stenosis/occlusion who undergo carotid revascularization. The increased risk of ICH or PPS due to tPA declines with time after thrombolysis. Delaying carotid revascularization in these patients may therefore be appropriate. This delay, however, will expose these patients to the risk of recurrent stroke. Future studies are needed to determine the relative risks of these 2 adverse events.

Histogram analysis for characterization of indeterminate adrenal nodules on noncontrast CT.

OBJECTIVE: To determine the effectiveness of the CT histogram method to characterize indeterminate adrenal nodules above 10 Hounsfield units (HU) on noncontrast CT. MATERIALS AND METHODS: Retrospective review of clinical CT data from January 2005 through 2008 identified 194 indeterminate adrenal nodules (>10 HU on noncontrast CT) in 175 patients. 20 nodules in 18 patients were excluded due to large standard deviation (SD > 30) of HU values. Of the remaining 174 nodules, 131 were classified as benign lipid-poor nodules based on size stability for ≥1 year (104), in- and opposed-phase MRI (17), adrenal washout CT (3), or biopsy (7). 43 were classified as malignant by size increase over a short time (30), avid FDG uptake on PET/CT (15), or biopsy (5). Histogram analysis was performed by drawing a circular region of interest on all adrenal nodules. Mean attenuation, total number of pixels, number of negative pixels, and percentage of negative pixels were recorded for each nodule. RESULTS: At the threshold value of >10% negative pixels, 59/131 benign nodules were correctly characterized, but 1/43 malignant nodules was falsely characterized as benign (sensitivity 45%, specificity 98%, positive predictive value 98%). With a slightly higher threshold value of >15% negative pixels, there were no false benign judgments. 36 nodules had more than 15% negative pixels, all of which were benign (sensitivity 27%, specificity 100%, positive predictive value 100%). In the subgroup of benign nodules measuring 11-20 HU, 80% and 54% were identified with threshold values of >10% and >15% negative pixels, respectively. CONCLUSION: The CT histogram method with a threshold value of >10% negative pixels can identify many benign adrenal nodules with attenuation values >10 HU on unenhanced CT with extremely high specificity. A threshold of >15% negative pixels can achieve 100% specificity. This method is highly robust provided very "noisy" CT examinations (SD > 30) are eliminated.

Intravenous tissue-type plasminogen activator therapy is an independent risk factor for symptomatic intracerebral hemorrhage after carotid endarterectomy.

BACKGROUND: Carotid endarterectomy (CEA) for symptomatic carotid artery stenosis and intravenous tissue-type plasminogen activator (IV-tPA) for acute ischemic stroke are proven therapies; however, the safety of CEA in stroke patients who recently received IV-tPA has not been established. OBJECTIVE: To evaluate the safety of CEA in stroke patients who recently received IV-tPA. METHODS: A retrospective review of patients who underwent CEA for symptomatic carotid artery stenosis was performed. The primary end point was postoperative symptomatic intracerebral hemorrhage (sICH). A univariate analysis of potential risk factors for sICH, including IV-tPA therapy, timing of CEA, degree of stenosis, and stroke severity, was performed. Factors with a value of P < .1 on univariate analysis were tested further. RESULTS: Among 142 patients, 3 suffered sICH after CEA: 2 of 11 patients treated with IV-tPA (18.2%) and 1 of 131 patients not treated with IV-tPA (0.8%). Both IV-tPA patients suffering sICH underwent CEA within 3 days of tPA administration. On univariate analysis, IV-tPA (P = .02), female sex (P = .09), shorter time between ischemic event and CEA (P = .06), and lower mean arterial pressure during the first 48 hours of admission (P = .08) were identified as risk factors for sICH. On multivariate analysis, IV-tPA was the only significant risk factor (P = .002 by stepwise logistic regression; P = .03 by nominal logistic regression). CONCLUSION: This study indicates that IV-tPA is an independent risk factor for sICH after CEA. This suggests that CEA should be pursued cautiously in patients who recently received IV-tPA. Early surgery may be associated with an increased risk for sICH. ABBREVIATIONS: CEA, carotid endarterectomyIV-tPA, intravenous recombinant tissue-type plasminogen activatorMAP, mean arterial pressureNASCET, North American Symptomatic Carotid Endarterectomy TrialNIHSS, National Institutes of Health Stroke ScaleNINDS, National Institute of Neurological Disorders and StrokesICH, symptomatic intracerebral hemorrhageTIA, transient ischemic attack.

Two-tiered approach to MRI for headache: a cost-effective way to use an expensive technology.

OBJECTIVE: The purpose of this study was to compare the diagnostic efficacy and cost implications of a proposed two-tiered approach to MRI in patients with headache. MATERIALS AND METHODS: We identified 245 consecutive patients with headache using MRI studies performed at a tertiary care facility between October 2009 and July 2011. Three radiologists prospectively used FLAIR sequences from these MR studies to diagnose underlying abnormality or to identify the need for a comprehensive MRI study. We compared the diagnostic efficacy and the cost implications of such a two-tiered approach with those of conventional MRI from the perspectives of the payer, the patient, and the imaging facility. RESULTS: The sensitivity and specificity for two-tiered (83.3% and 100%, respectively) and conventional (91% and 97.8%, respectively) MRI approaches were not significantly different. Assuming a 50% reduction in the payment for the initial limited MRI performed as a first step of the two-tiered approach, this approach would have resulted in 44.8% savings to the payer. A substantial reduction in the scanner utilization time from 4168 minutes to 1249 minutes for the two-tiered approach would have enabled increased throughput at the imaging facility. Although 27 (11%) patients would have been recalled for a comprehensive MRI study in the two-tiered approach, the average time spent in the scanner by each patient would have been less for the two-tiered approach (5.1 minutes vs 17.0 minutes). CONCLUSION: A two-tiered approach to MRI can serve as a viable cost-effective alternative to the conventional approach.

Renal measurements on CT angiograms: correlation with graft function at living donor renal transplantation.

PURPOSE: To determine which measurement of donor renal size on computed tomographic (CT) angiograms has the greatest correlation with renal function preoperatively in the donor and postoperatively in the transplant recipient. MATERIALS AND METHODS: Informed consent was waived for this retrospective HIPAA-compliant study approved by the institutional review board. Renal length, total volume, and cortical volume were measured on renal donor CT angiograms in 111 patients. Preoperative serum creatinine values for donors and postoperative creatinine values for recipients at hospital discharge and 6, 12, 24, and 36 months after transplant were collected, and estimated glomerular filtration rate (eGFR) was calculated. Correlation coefficients with 95% confidence intervals (CIs) were obtained for renal measures and donor eGFR and for renal measures adjusted to recipient body habitus and posttransplant creatinine level in the recipient. Thresholds were set for adjusted length and volumes, and the odds ratio (OR) for creatinine level less than 1.5 mg/dL at 36 months was calculated. RESULTS: Renal volumes and length were correlated with donor eGFR (r=0.58 [95% CI: 0.44, 0.69] for cortical volume, 0.56 [95% CI: 0.42, 0.68] for total volume, and 0.43 [95% CI: 0.27, 0.57] for renal length). All three measures, adjusted to recipient body habitus, were correlated with recipient renal function from discharge (r=-0.41 to -0.43) up to 36 months after transplantation (r=-0.33 to -0.41). By using a threshold of 1.5 for cortical volume to recipient weight, 2.25 for total volume to recipient weight, and 0.175 for renal length to recipient weight, the odds of creatinine level greater than 1.5 mg/dL were four times as great for smaller kidney-to-recipient weight ratios, a statistically significant pattern for cortical volume (OR, 4.07; 95% CI: 1.10, 15.09) but not total volume (OR, 4.24; 95% CI: 0.90, 20.01) or renal length (OR, 4.08; 95% CI: 0.48-34.29). CONCLUSION: Renal length and volumes correlated with recipient renal function up to 36 months after transplant. A low ratio of cortical volume to recipient weight was associated with diminished renal function at 36 months after transplant.

Borden-Shucart Type I dural arteriovenous fistulas: clinical course including risk of conversion to higher-grade fistulas.

OBJECT: The goal of this study was to determine the clinical course of Borden-Shucart Type I cranial dural arteriovenous fistulas (DAVFs) and to calculate the annual rate of conversion of these lesions to more aggressive fistulas that have cortical venous drainage (CVD). METHODS: A retrospective chart review was conducted of all patients harboring DAVFs who were seen at the authors' institution between 1997 and 2009. Twenty-three patients with Type I DAVFs who had available clinical follow-up were identified. Angiographic and clinical data from these patients were reviewed. Neurological outcome and status of presenting symptoms were assessed during long-term follow-up. RESULTS: Of the 23 patients, 13 underwent endovascular treatment for intolerable tinnitus or ophthalmological symptoms, and 10 did not undergo treatment. Three untreated patients died of unrelated causes. In those who were treated, complete DAVF obliteration was achieved in 4 patients, and palliative reduction in DAVF flow was achieved in 9 patients. Of the 19 patients without radiographic cure, no patient developed intracranial hemorrhage or nonhemorrhagic neurological deficits (NHNDs), and no patient died of DAVF-related causes over a mean follow-up of 5.6 years. One patient experienced a spontaneous, asymptomatic obliteration of a partially treated DAVF in late follow-up, and 2 patients experienced a symptomatic conversion of their DAVF to a higher-grade fistula with CVD in late follow-up. The annual rate of conversion to a higher-grade DAVF based on Kaplan-Meier cumulative event-free survival analysis was 1.0%. The annual rate of intracranial hemorrhage, NHND, and DAVF-related death was 0.0%. CONCLUSIONS: A small number of Type I DAVFs will convert to more aggressive DAVFs with CVD over time. This conversion to a higher-grade DAVF is typically heralded by a change in patient symptoms. Follow-up vascular imaging is important, particularly in the setting of recurrent or new symptoms.

Balanced steady-state free-precession MR imaging for measuring pulsatile motion of cerebellar tonsils during the cardiac cycle: a reliability study.

INTRODUCTION: Assessment of the motion of the cerebellar tonsils is of interest in diseases affecting the CSF flow at the foramen magnum. Cardiac-gated balanced steady-state free-precession technique, which has recently been shown to demonstrate the pulsatile motion of neural structures, appears well suited to allow direct measurement of craniocaudal translation of cerebellar tonsils during the cardiac cycle. Our aim was to assess the intra-observer and inter-observer variability in the assessment of tonsillar motion utilizing this technique. METHODS: We retrospectively identified 44 patients who had undergone MR imaging with cine TrueFISP sequence, as a part of CSF flow study. Two neuroradiologists independently assessed the images. The tonsillar pulsatility was subjectively characterized into none, minimal, and marked categories after review of the images on a cine loop. For patients with identifiable tonsillar motion, the maximal extent of translation of the inferior edge of the cerebellar tonsil was directly measured. Both readers repeated the measurements after a minimum interval of 2 weeks. Intra- and inter-observer variability was characterized by calculating the kappa statistics. RESULTS: The intra-observer agreement for subjective assessment of tonsillar pulsatility was near perfect while the inter-observer agreement was substantial. A good intra- and inter-observer correlation was also seen for the objective measurements of the tonsillar motion. A good correlation was found between the subjective categorization of the tonsillar pulsatility and the objective measurements. CONCLUSION: Steady-state balanced free-precession MR imaging technique allows for a reproducible subjective and objective assessment of tonsillar pulsatility.

Immediate complications and pain relief associated with 296 fluoroscopically guided thoracic foraminal nerve blocks.

OBJECTIVE: The goal of this work is to review the thoracic foraminal nerve blocks and foraminal epidurals performed at a single institution to determine the incidence and types of immediate complications and pain relief associated with thoracic foraminal nerve blocks. MATERIALS AND METHODS: This retrospective study entailed a comprehensive review of the radiographs and reports of 296 injections performed in 225 examinations on 153 patients (60 men and 93 women). The overall mean age was 51.93 years (mean age for men, 50.71 years [range, 22-85 years]; mean age for women, 53.09 years [range, 18-84 years]). The data were later analyzed with contingency tables and chi-square tests. RESULTS: The overall complication rate was 4.1% (12/296). Complication rates at the different needle tip positions measured on frontal and lateral fluoroscopic views did not approach statistical significance (p = 0.15). Complications were higher with cephalocaudal flow outside local flow (p = 0.02). No serious complications occurred except for one pneumothorax, which could have been avoided. Immediate partial or complete pain relief was obtained in 88.5% (262/296) of the injections and 88.4% (199/225) of the examinations. CONCLUSION: Fluoroscopically guided thoracic foraminal nerve blocks are safe procedures and provide immediate partial or complete pain relief in a high percentage of patients.

Equating quantitative emphysema measurements on different CT image reconstructions.

PURPOSE: To mathematically model the relationship between CT measurements of emphysema obtained from images reconstructed using different section thicknesses and kernels and to evaluate the accuracy of the models for converting measurements to those of a reference reconstruction. METHODS: CT raw data from the lung cancer screening examinations of 138 heavy smokers were reconstructed at 15 different combinations of section thickness and kernel. An emphysema index was quantified as the percentage of the lung with attenuation below -950 HU (EI950). Linear, quadratic, and power functions were used to model the relationship between EI950 values obtained with a reference 1 mm, medium smooth kernel reconstruction and values from each of the other 14 reconstructions. Preferred models were selected using the corrected Akaike information criterion (AICc), coefficients of determination (R2), and residuals (conversion errors), and cross-validated by a jackknife approach using the leave-one-out method. RESULTS: The preferred models were power functions, with model R2 values ranging from 0.949 to 0.998. The errors in converting EI950 measurements from other reconstructions to the 1 mm, medium smooth kernel reconstruction in leave-one-out testing were less than 3.0 index percentage points for all reconstructions, and less than 1.0 index percentage point for five reconstructions. Conversion errors were related in part to image noise, emphysema distribution, and attenuation histogram parameters. Conversion inaccuracy related to increased kernel sharpness tended to be reduced by increased section thickness. CONCLUSIONS: Image reconstruction-related differences in quantitative emphysema measurements were successfully modeled using power functions.

Quantitative CT assessment of emphysema and airways in relation to lung cancer risk.

PURPOSE: To determine whether quantitative computed tomographic (CT) measurements of emphysema and airway dimensions are associated with lung cancer risk in a screening population. MATERIALS AND METHODS: Institutional review board approval and informed consent for the use of deidentified images were obtained. In this retrospective study, CT scans were analyzed from 279 participants in the CT screening arm of the National Lung Screening Trial who were diagnosed with lung cancer and 279 participants who were not diagnosed with lung cancer after a median follow-up period of 6.6 years. Quantitative CT measurements of emphysema and right upper lobe apical segmental and subsegmental airway dimensions, and multiple patient history-related variables, were compared between the two groups. Significant variables were tested in multivariate models for association with lung cancer by using multiple logistic regression. RESULTS: The emphysema index of percentage upper lung volume less than -950 HU had the strongest association with lung cancer (mean, 10.7% [standard deviation, 13.5] in patients vs 7.2% [standard deviation, 10.4] in control subjects; P < .001), but the relationship was weak (R(2) = 0.015, P < .001, c = 0.57). No CT measures of emphysema had an association with lung cancer independent of the patient medical history variables. Airway dimensions were not associated with lung cancer. CONCLUSION: Quantitative CT measurements of emphysema but not airway dimensions were only weakly associated with lung cancer, demonstrating no potential practical value for clinical risk stratification.

Objective assessment of operator performance during ultrasound-guided procedures.

PURPOSE: Simulation permits objective assessment of operator performance in a controlled and safe environment. Image-guided procedures often require accurate needle placement, and we designed a system to monitor how ultrasound guidance is used to monitor needle advancement toward a target. The results were correlated with other estimates of operator skill. METHODS: The simulator consisted of a tissue phantom, ultrasound unit, and electromagnetic tracking system. Operators were asked to guide a needle toward a visible point target. Performance was video-recorded and synchronized with the electromagnetic tracking data. A series of algorithms based on motor control theory and human information processing were used to convert raw tracking data into different performance indices. Scoring algorithms converted the tracking data into efficiency, quality, task difficulty, and targeting scores that were aggregated to create performance indices. After initial feasibility testing, a standardized assessment was developed. Operators (N = 12) with a broad spectrum of skill and experience were enrolled and tested. Overall scores were based on performance during ten simulated procedures. Prior clinical experience was used to independently estimate operator skill. RESULTS: When summed, the performance indices correlated well with estimated skill. Operators with minimal or no prior experience scored markedly lower than experienced operators. The overall score tended to increase according to operator's clinical experience. Operator experience was linked to decreased variation in multiple aspects of performance. The aggregated results of multiple trials provided the best correlation between estimated skill and performance. A metric for the operator's ability to maintain the needle aimed at the target discriminated between operators with different levels of experience. CONCLUSIONS: This study used a highly focused task model, standardized assessment, and objective data analysis to assess performance during simulated ultrasound-guided needle placement. The performance indices were closely related to operator experience.

Emphysema quantification in inflation-fixed lungs using low-dose computed tomography and 3He magnetic resonance imaging.

OBJECTIVE: To evaluate the use of inflation-fixed lung tissue for emphysema quantification with computed tomography (CT) and He magnetic resonance (MR) diffusion imaging. METHODS: Fourteen subjects representing a range of chronic obstructive pulmonary disease severity who underwent complete or lobar lung resection were studied. Computed tomographic measurements of lung attenuation and MR measurements of the hyperpolarized 3He apparent diffusion coefficient (ADC) in resected specimens fixed in inflation with heated formalin vapor were compared with measurements obtained before fixation. RESULTS: The mean (SD) CT emphysema indices were 56% (17%) before and 58% (19%) after fixation (P = 0.77; R = 0.76). Index differences correlated with differences in lung volume (R = 0.47). The mean (SD) 3He ADCs were 0.40 (0.15) cm/s before and 0.39 (0.14) cm/s after fixation (P = 0.03, R = 0.98). The CT emphysema index and the 3He ADC were correlated before (R = 0.89) and after fixation (R = 0.79). CONCLUSIONS: Concordance of CT and 3He MR imaging measurements in unfixed and inflation-fixed lungs supports the use of inflation-fixed lungs for quantitative imaging studies in emphysema.

Comparison of perceptions and treatment practices between neurosurgeons and plastic surgeons for infants with deformational plagiocephaly.

OBJECT: Deformational plagiocephaly (DP) is the leading cause of head shape abnormalities in infants. Treatment options include conservative measures and cranial molding. Pediatric neurosurgeons and craniofacial plastic surgeons have yet to agree on an ideal therapy, and no definable standards exist for initiating treatment with helmets. Furthermore, there may be differences between specialties in their perceptions of DP severity and need for helmet therapy. METHODS: Requests to participate in a web-based questionnaire were sent to diplomates of the American Board of Pediatric Neurological Surgery and US and Canadian members of the Pediatric Joint Section of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons and the American Cleft Palate-Craniofacial Association. Questions focused on educational background; practice setting; volume of DP patients; preferences for evaluation, treatment, follow-up; and incentives or deterrents to treat with helmet therapy. Six examples of varying degrees of DP were presented to delineate treatment preferences. RESULTS: Requests were sent to 302 neurosurgeons and 470 plastic surgeons, and responses were received from 71 neurosurgeons (24%) and 64 plastic surgeons (14%). The following responses represented the greatest variations between specialties: 1) 8% of neurosurgeons and 26% of plastic surgeons strongly agreed with the statement that helmet therapy is more beneficial than conservative therapy (p < 0.01); and 2) 25% of neurosurgeons and 58% of plastic surgeons would treat moderate to severe DP with helmets (p < 0.01). CONCLUSIONS: Survey responses suggest that neurosurgeons are less likely to prescribe helmet therapy for DP than plastic surgeons. Parents of children with DP are faced with a costly treatment decision that may be influenced more strongly by referral and physician bias than medical evidence.

Accuracy of emphysema quantification performed with reduced numbers of CT sections.

OBJECTIVE: The purpose of this study was to assess the accuracy of emphysema measurements obtained from systematic samples of evenly spaced CT images compared with measurements obtained from the entire scan. MATERIALS AND METHODS: Evenly spaced transverse sections from the CT studies of 136 heavy smokers who underwent screening for lung cancer in the National Lung Screening Trial and of 112 subjects who underwent imaging before lung volume reduction surgery were sampled retrospectively. The samples were acquired both by selection of specific numbers of evenly spaced images and by selection of images at specific distance intervals. The percentage of lung pixels with attenuation below specific thresholds was used as an emphysema index. The image sample error was determined as the difference in emphysema index between the image samples and the entire scan. RESULTS: The largest absolute image sample errors in the National Lung Screening Trial cohort with image sample sizes of five, 10, and 20 were 2.2, 0.8, and 0.5 index percentage points, respectively, at 1-mm section thickness (-960 HU threshold), and 2.6, 1.1, and 0.5 index percentage points at 5-mm section thickness (-930 HU threshold). The largest errors in the lung volume reduction surgery cohort for image sample sizes of five and 10 were 5.6 and 2.3 index percentage points at 8- to 10-mm section thickness (-900 HU threshold). Image sample errors were equivalent for the two sampling methods. CONCLUSION: Systematic sampling resulted in very small errors in emphysema quantification and may be useful for decreasing radiation exposure in clinical research studies of emphysema.

Effects of CT section thickness and reconstruction kernel on emphysema quantification relationship to the magnitude of the CT emphysema index.

RATIONALE AND OBJECTIVES: Computed tomography (CT) section thickness and reconstruction kernel each influence CT measurements of emphysema. This study was performed to assess whether their effects are related to the magnitude of the measurement. MATERIALS AND METHODS: Low-radiation-dose multidetector CT was performed in 21 subjects representing a wide range of emphysema severity. Images were reconstructed using 20 different combinations of section thickness and reconstruction kernel. Emphysema index values were determined as the percentage of lung pixels having attenuation lower than multiple thresholds ranging from -960 HU to -890 HU. The index values obtained from the different thickness-kernel combinations were compared by repeated measures analysis of variance and Bland-Altman plots of mean versus difference in all subjects, and correlated with quantitative histology (mean linear intercept, Lm) in a subset of resected lung specimens. RESULTS: The effects of section thickness and reconstruction kernel on the emphysema index were significant (P < .001) and diminished as the index attenuation threshold was raised. The changes in index values from changing the thickness-kernel combination were largest for subjects with intermediate index values (10%-30%), and became progressively smaller for those with lower and higher index values. This pattern was consistent regardless of the thickness-kernel combinations compared and the HU threshold used. Correlations between the emphysema index values obtained with each thickness-kernel combination and Lm ranged from r = 0.55-0.68 (P = .007-.03). CONCLUSION: The effects of CT section thickness and kernel on emphysema index values varied systematically with the magnitude of the emphysema index. All reconstruction techniques provided significant correlations with quantitative histology.

Effects of diffusion time on short-range hyperpolarized (3)He diffusivity measurements in emphysema.

PURPOSE: To characterize the effect of diffusion time on short-range hyperpolarized (3)He magnetic resonance imaging (MRI) diffusion measurements across a wide range of emphysema severity. MATERIALS AND METHODS: (3)He diffusion MRI was performed on 19 lungs or lobes resected from 18 subjects with varying degrees of emphysema using three diffusion times (1.6 msec, 5 msec, and 10 msec) at constant b value. Emphysema severity was quantified as the mean apparent diffusion coefficient (ADC) and as the percentage of pixels with ADC higher than multiple thresholds from 0.30-0.55 cm(2)/sec (ADC index). Quantitative histology (mean linear intercept) was obtained in 10 of the lung specimens from 10 of the subjects. RESULTS: The mean ADCs with diffusion times of 1.6, 5.0, and 10.0 msec were 0.46, 0.40, and 0.37 cm(2)/sec, respectively (P < 0.0001, analysis of variance [ANOVA]). There was no relationship between the ADC magnitude and the effect of diffusion time on ADC values. The mean linear intercept correlated with ADC (r = 0.91-0.94, P < 0.001) and ADC index (r = 0.78-0.92, P < 0.01) at all diffusion times. CONCLUSION: Decreases in ADC with longer diffusion time were unrelated to emphysema severity. The strong correlations between the ADC at all diffusion times tested and quantitative histology demonstrate that ADC is a robust measure of emphysema.

Automated matching of pulmonary nodules: evaluation in serial screening chest CT.

OBJECTIVE: The purpose of our study was to evaluate the performance of a computer-aided program that performs automated matching of pulmonary nodules imaged in three serial screening chest MDCT studies. MATERIALS AND METHODS: Forty subjects with pulmonary nodules depicted in three annual (T0, T1, T2) low-dose MDCT screening studies for lung cancer were selected from the National Lung Screening Trial database at a single institution. All CT images were reevaluated by two radiologists in consensus. One hundred forty-three nodules were identified and characterized by type (solid parenchymal, juxtavascular, juxtapleural, and ground-glass opacity) and size (< or = 4 mm, 4-6 mm, 6-8 mm, and > 8 mm). Using an automated program, nodules at T0 were matched to nodules at T1, and the same nodules at T1 were matched to nodules at T2. Associations between nodule matching rate (i.e., number of nodules matched by the program divided by the number of nodules determined to match by radiologists) and nodule type or size were analyzed. RESULTS: The combined matching rate of the nodules was 92.7% (T0 vs T1, 91.6%; T1 vs T2, 93.7%). By nodule type, the matching rate was 94.6% (parenchymal), 98.4% (juxtavascular), 85.8% (juxtapleural), and 100% (ground-glass opacity), with the rate significantly lower for juxtapleural nodules (p < 0.01). Matching rates were not significantly influenced by nodule size (p = 0.67). CONCLUSION: The automated matching rate for pulmonary nodules in screening MDCT scans was high (92.7%) and was not affected by the nodule size but was slightly lower with nodules at juxtapleural locations.