Lung Cancer Screening Eligibility and Use: A Population Health Perspective of One Community.

BACKGROUND Low-dose chest CT (LDCT) is the only effective screening test for lung cancer. Annual lung cancer screening (LCS) is recommended by the US Preventive Services Task Force (USPSTF) for individuals at high risk for primary lung neoplasm.METHODS We retrospectively identified patients receiving LCS from January 2016 through March 2018 whose residential addresses were within our health center's county. We estimated driving distance from the patient's address to our health center and obtained sociodemographic characteristics from the electronic health record (EHR). The census-tract-level LCS-eligible population size was estimated, and their population characteristics determined via US Census Bureau, Centers for Disease Control and Prevention (CDC), and Behavioral Risk Factor Surveillance System (BRFSS) data. The Cochran-Mantel-Haenszel test was used to determine differences amongst the LCS-eligible and LCS-enrolled populations. Multivariable regression was used to determine the effects of sociodemographic characteristics on LCS eligibility.RESULTS There was modest correlation between census-tract-level LCS-eligible population size and LCS enrollment (r = 0.68, P < .001). 5.9% (364/6185) of the estimated LCS-eligible population in our county received LCS, with census-tract LCS rates ranging from 1.5% to 12.5%. Nonwhite race status (Hispanic and African American) was associated with decreased likelihood of LCS enrollment compared to White race (OR = 95% CI, 0.765 [0.61, 0.95] and 0.031 [0.008, 0.124], respectively). Older age, Medicaid, and uninsured statuses were positively correlated with LCS eligibility (P ≤ .01).LIMITATIONS This analysis comprises a single county. Other LCS facilities within our health system in neighboring counties, as well as individuals receiving LCS outside of our health system, are not captured.CONCLUSIONS The uptake of LCS remains low, with disproportionately lower screening rates amongst Hispanic and African American populations. Medicaid and uninsured patients in our community are also more likely to be LCS-eligible. These populations may be targets for interventions aimed at increasing LCS awareness and uptake.

Long-term Evolution of Hepatocellular Adenomas at MRI Follow-up.

Background Hepatocellular adenomas (HCAs) are rare benign liver tumors. Guidelines recommend continued surveillance of patients diagnosed with HCAs, but these guidelines are mainly based on small studies or expert opinion. Purpose To analyze the long-term evolution of HCAs, including solitary and multiple lesions, and to identify predictive features of progression with MRI. Materials and Methods In a retrospective study, patients diagnosed with pathologically proven solitary or multiple HCAs between January 2004 and December 2015 were included; ß-catenin-mutated HCAs and HCAs with foci of malignancy were considered to be at risk for progression. MRI examinations were analyzed, and tumor evolution was evaluated by using Response Evaluation Criteria in Solid Tumors, version 1.1. Student t, Mann-Whitney, χ2, Fisher exact, and McNemar tests were used, as appropriate. Results In total, 118 patients (mean age, 40 years ± 10 [standard deviation]; 108 women) were evaluated, including 41 with a solitary HCA (mean age, 40 years ± 14; 36 women) and 77 with multiple HCAs (mean age, 40 years ± 10; 72 women). At a median follow-up of 5 years, 37 of 41 (90%) patients with a solitary HCA and 55 of 77 (71%) patients with multiple HCAs showed stable or regressive disease. After resection of solitary HCAs, new lesions appeared in only two of 29 (7%) patients, both of whom had HCAs at risk of progression. In patients with multiple HCAs, hepatocyte nuclear factor 1α-inactivated HCAs showed a higher rate of progression compared with inflammatory HCAs (11 of 26 [42%] vs seven of 37 [19%], P = .04) despite lower use (28 of 32 patients [88%] vs 45 of 45 patients [100%]; P = .03) and shorter duration (mean, 12.0 years ± 7.5 vs 19.2 years ± 9.2; P = .001) of oral contraceptive intake. Conclusion Long-term MRI follow-up showed that 78% of hepatocellular adenomas had long-term stability or regression. After resection of solitary hepatocellular adenomas, new lesions occurred only in hepatocellular adenomas at risk of progression. Patients with multiple hepatocellular adenomas were more likely to show progressive disease, with hepatic nuclear factor 1α-inactivated hepatocellular adenomas being the most common subtype showing progression. © RSNA, 2020 Online supplemental material is available for this article.

Sample size requirements for detecting treatment effect heterogeneity in cluster randomized trials.

Cluster randomized trials (CRTs) refer to experiments with randomization carried out at the cluster or the group level. While numerous statistical methods have been developed for the design and analysis of CRTs, most of the existing methods focused on testing the overall treatment effect across the population characteristics, with few discussions on the differential treatment effect among subpopulations. In addition, the sample size and power requirements for detecting differential treatment effect in CRTs remain unclear, but are helpful for studies planned with such an objective. In this article, we develop a new sample size formula for detecting treatment effect heterogeneity in two-level CRTs for continuous outcomes, continuous or binary covariates measured at cluster or individual level. We also investigate the roles of two intraclass correlation coefficients (ICCs): the adjusted ICC for the outcome of interest and the marginal ICC for the covariate of interest. We further derive a closed-form design effect formula to facilitate the application of the proposed method, and provide extensions to accommodate multiple covariates. Extensive simulations are carried out to validate the proposed formula in finite samples. We find that the empirical power agrees well with the prediction across a range of parameter constellations, when data are analyzed by a linear mixed effects model with a treatment-by-covariate interaction. Finally, we use data from the HF-ACTION study to illustrate the proposed sample size procedure for detecting heterogeneous treatment effects.

Negative Biopsy of Focal Hepatic Lesions: Decision Tree Model for Patient Management.

OBJECTIVE: The purpose of this study was to investigate patient- and procedure-related variables affecting the false-negative rate of ultrasound (US)-guided liver biopsy and to develop a standardized patient-tailored predictive model for the management of negative biopsy results. MATERIALS AND METHODS: We retrospectively included 389 patients (mean age ± SD, 62 ± 12 years old) who had undergone US-guided liver biopsy of 405 liver lesions between January 1, 2013, and June 30, 2015. We collected multiple patient- and procedure-related variables. By comparing pathology reports of biopsy and the reference standard (further histology or imaging follow-up), we were able to categorize the biopsy results as true-positive, true-negative, and false-negative. Diagnostic accuracy and diagnostic yield were measured. Univariate and multivariate analyses were performed to identify variables predicting false-negative results. A standardized patient-tailored predictive model of false-negative results based on a decision tree was fitted. RESULTS: Diagnostic accuracy and diagnostic yield were 93.8% (380/405) and 89.4% (362/405), respectively. The false-negative rate was 6.5% (25/387). Predictive variables of false-negative results at univariate analysis included body mass index, lesion size, sample acquisition techniques, and immediate specimen adequacy. The only independent predictors at multivariate analysis were patient age and Charlson comorbidity index. By combining lesion size and location with patient age and history of malignancy, we developed a decision tree model that predicts false-negative results with high confidence (up to 100%). CONCLUSION: False-negative results are not negligible at US-guided liver biopsy. The combination of selected lesion- and patient-specific variables may help predict when aggressive management is warranted in patients with likely false-negative results.

Multireader Determination of Clinically Significant Obstruction Using Hyperpolarized 129Xe-Ventilation MRI.

OBJECTIVE: The objective of our study was to identify the magnitude and distribution of ventilation defect scores (VDSs) derived from hyperpolarized (HP) 129Xe-MRI associated with clinically relevant airway obstruction. MATERIALS AND METHODS: From 2012 to 2015, 76 subjects underwent HP 129Xe-MRI (48 healthy volunteers [mean age ± SD, 54 ± 17 years]; 20 patients with asthma [mean age, 44 ± 20 years]; eight patients with chronic obstructive pulmonary disease [mean age, 67 ± 5 years]). All subjects underwent spirometry 1 day before MRI to establish the presence of airway obstruction (forced expiratory volume in 1 second-to-forced vital capacity ratio [FEV1/FVC] < 70%). Five blinded readers assessed the degree of ventilation impairment and assigned a VDS (range, 0-100%). Interreader agreement was assessed using the Fleiss kappa statistic. Using FEV1/FVC as the reference standard, the optimum VDS threshold for the detection of airway obstruction was estimated using ROC curve analysis with 10-fold cross-validation. RESULTS: Compared with the VDSs in healthy subjects, VDSs in patients with airway obstruction were significantly higher (p < 0.0001) and significantly correlated with disease severity (r = 0.66, p < 0.0001). Ventilation defects in subjects with airway obstruction did not show a location-specific pattern (p = 0.158); however, defects in healthy control subjects were more prevalent in the upper lungs (p = 0.014). ROC curve analysis yielded an optimal threshold of 12.4% ± 6.1% (mean ± SD) for clinically significant VDS. Interreader agreement for 129Xe-MRI was substantial (κ = 0.71). CONCLUSION: This multireader study of a diverse cohort of patients and control subjects suggests a 129Xe-ventilation MRI VDS of 12.4% or greater represents clinically significant obstruction.

Automated Early Identification of an Excessive Air-in-Oil X-ray Tube Artifact That Mimics Acute Cerebral Infarct.

PURPOSE: This study aimed to develop an automated, quantitative method to increase the likelihood of identifying and preventing such air-in-oil (AIO) artifact. METHODS: A 1-dimensional radial representation of the 2-dimensional noise power spectrum (NPS) was calculated from AIO artifact images and compared with artifact-free images. A quality control (QC) software program was modified to include measurements of NPS average frequency within the water section of daily phantom scans. Threshold values for each CT system were incorporated into daily QC. RESULTS: Noise power spectrum for AIO artifact images included a large low-frequency peak compared with artifact-free images; NPS average frequencies were 0.197 and 0.319 line pairs per millimeter for AIO artifact and artifact-free images, respectively. Automated QC successfully identified 3 AIO artifacts before detrimental clinical effect occurred. CONCLUSIONS: Serious clinical problems associated with AIO artifact can be detected and avoided by incorporating NPS average frequency measurements of daily phantom images into an automated QC program.

Liver imaging reporting and data system category 4 observations in MRI: Risk factors predicting upgrade to category 5.

PURPOSE: To identify demographic and imaging features in magnetic resonance imaging (MRI) that are associated with upgrade of Liver Imaging Reporting and Data System (LI-RADS) category 4 (LR-4) observations to category 5 (LR-5), and to assess their effects on risk of upgrade and time to upgrade. MATERIALS AND METHODS: Institutional Review Board approval was obtained for this retrospective, dual-institution Health Insurance Portability and Accountability Act (HIPAA)-compliant study. Radiologists reviewed 1.5T and 3T MRI examinations for 181 LR-4 observations in 139 patients, as well as follow-up computed tomography (CT) and MRI examinations and treatment. A stepwise multivariate Cox proportional hazards model analysis was performed to identify predictive risk factors for upgrade to LR-5, including patient demographics and LI-RADS imaging features. Overall cumulative risk of upgrade was calculated by using the Kaplan-Meier method. The cumulative risks were compared in the presence/absence of significant predictive risk factors using the log-rank test. RESULTS: The independent significant predictive risk factors in the 56 LR-4 observations that upgraded to LR-5 were mild-moderate T2 hyperintensity (P < 0.001; hazard ratio = 1.84), growth (P < 0.001; hazard ratio = 3.71), and hepatitis C infection (P = 0.02; hazard ratio = 1.69). The overall 6-month cumulative risk of upgrade was 32.7%. The 6-month cumulative risk rate was significantly higher in the presence of T2 hyperintensity (P = 0.03; 48.1% vs. 25.4%). CONCLUSION: For LR-4 observations, mild-moderate T2 hyperintensity, threshold growth, and hepatitis C infection are associated with significantly higher risk of upgrade to LR-5. Although mild-moderate T2 hyperintensity was the most useful risk factor for predicting upgrade, actual risk level was only mildly elevated, and the risk of upgrade associated with LR-4 observations is similar across subtypes. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 5 J. MAGN. RESON. IMAGING 2017;46:783-792.

Characterization of Small (< 4 cm) Focal Renal Lesions: Diagnostic Accuracy of Spectral Analysis Using Single-Phase Contrast-Enhanced Dual-Energy CT.

OBJECTIVE: The purpose of this study is to determine whether single-phase contrast-enhanced dual-energy quantitative spectral analysis improves the accuracy of diagnosis of small (< 4.0 cm) renal lesions, compared with conventional single-energy attenuation measurements. MATERIALS AND METHODS: In this retrospective study, 136 consecutive patients (95 men and 41 women; mean age, 54 years) with 144 renal lesions (111 benign and 33 malignant) underwent single-energy unenhanced and dual-energy contrast-enhanced CT of the abdomen. For each renal lesion, attenuation measurements were obtained, and an attenuation change of 15 HU or greater was considered evidence of enhancement. Dual-energy spectral attenuation curves were generated for each lesion. The slope of each curve was measured between 40 and 50 keV (λHU40-50), 40 and 70 keV (λHU40-70), and 40 and 140 keV (λHU40-140). Mean lesion attenuation values and spectral attenuation curve parameters were compared between benign and malignant renal lesions by use of the two-sample t test. Diagnostic accuracy was assessed and validated using cross-validation analysis. RESULTS: With the use of cross-validated optimal thresholds at 100% sensitivity, specificity for differentiating between benign and malignant renal lesions improved significantly when both λHU40-70 and λHU40-140 were used, compared with conventional enhancement measurements (93% [103/111; 95% CI, 86-97%] vs 81% [90/111; 95% CI, 73-88%]) (p = 0.02). The sensitivity of λHU40-70 and λHU40-140 was also higher than that of conventional enhancement measurements, although it was not statistically significant. CONCLUSION: Single-phase contrast-enhanced dual-energy quantitative spectral analysis significantly improves the specificity for characterization of small (< 4.0 cm) renal lesions, compared with conventional single-energy attenuation measurements.

Incidental Thyroid Nodules on CT or MRI: Discordance Between What We Report and What Receives Workup.

OBJECTIVE: The objective of this study was to determine the proportion of incidental thyroid nodules (ITNs) reported on CT or MRI that receive additional workup and the factors that influence workup. A secondary aim was to evaluate the effect of the American College of Radiology (ACR) white paper recommendations for reporting of ITNs. MATERIALS AND METHODS: We retrospectively reviewed patients with ITNs reported on CT or MRI studies over 12 months. We identified patients with ITNs that underwent workup and the factors associated with workup. The ACR white paper recommendations were retrospectively applied to estimate how their use would have changed the number of nodules reported in the impression section of radiology reports and the number of cancers diagnosed. The recommendations are based on suspicious imaging features, patient age, and nodule size. RESULTS: A total of 375 patients had ITNs reported. For 138 of these patients (37%), ITNs were reported by radiologists in the impression section of their reports; 26 patients (19%) received workup. Patients with ITNs reported in the impression section were 14 times more likely to undergo workup than were patients with ITNs reported only in the findings section of the radiology report. On multivariate analysis, the only factors associated with workup were younger patient age and larger nodule size (p ≤ 0.002). The ACR recommendations resulted in a 54% reduction in the number of ITNs reported in the impression section and one missed papillary cancer (TNM classification T1bN0M0). CONCLUSION: Only one in five patients with ITNs reported in the impression section of CT or MRI reports underwent additional workup, and this decision was influenced by younger patient age and larger nodule size. These factors are components of the ACR recommendations, which have the potential to reduce the number of reported ITNs and improve the standardization of radiology reporting.

Coil embolization of the splenic artery: impact on splenic volume.

PURPOSE: To determine the impact of coil embolization of the splenic artery on splenic volume based on computed tomography (CT) imaging. MATERIALS AND METHODS: Splenic artery embolization (SAE) was performed in 148 consecutive patients over an 8-year period in an institutional review board-approved retrospective study. Of these, 60 patients (36 men; mean age, 49 y) had undergone contrast-enhanced CT before and after SAE with a mean time interval of 355 days. Pre- and postembolization splenic volumes were calculated with volume-rendering software. Presence of Howell-Jolly bodies was ascertained on laboratory tests. A trauma control group consisted of 39 patients with splenic laceration and follow-up CT but no splenic intervention. RESULTS: SAE in trauma patients resulted in an insignificant decrease in mean spleen size from 224 cm(3) to 190 cm(3) (P = .222). However, postembolization splenic volume was significantly smaller than follow-up volume in the trauma control group (353 cm(3); P < .001). In nontrauma patients, the mean splenic volume decreased from 474 cm(3) to 399 cm(3) after SAE (P = .068). Multivariable analysis revealed that coil pack location was the only factor significantly affecting resultant splenic volume (P = .016). For trauma and nontrauma patients, distal embolization resulted in significant splenic volume loss (P = .034 and P = .013), whereas proximal embolization did not. No patients had persistent circulating Howell-Jolly bodies after SAE. No patients required repeat embolization or splenectomy. CONCLUSIONS: Coil embolization of the splenic artery resulted in a modest but significant decrease in splenic volume when performed distally; proximal embolization resulted in an insignificant volume change.

Computer-aided detection (CAD) of lung nodules in CT scans: radiologist performance and reading time with incremental CAD assistance.

OBJECTIVE: The diagnostic performance of radiologists using incremental CAD assistance for lung nodule detection on CT and their temporal variation in performance during CAD evaluation was assessed. METHODS: CAD was applied to 20 chest multidetector-row computed tomography (MDCT) scans containing 190 non-calcified > or =3-mm nodules. After free search, three radiologists independently evaluated a maximum of up to 50 CAD detections/patient. Multiple free-response ROC curves were generated for free search and successive CAD evaluation, by incrementally adding CAD detections one at a time to the radiologists' performance. RESULTS: The sensitivity for free search was 53% (range, 44%-59%) at 1.15 false positives (FP)/patient and increased with CAD to 69% (range, 59-82%) at 1.45 FP/patient. CAD evaluation initially resulted in a sharp rise in sensitivity of 14% with a minimal increase in FP over a time period of 100 s, followed by flattening of the sensitivity increase to only 2%. This transition resulted from a greater prevalence of true positive (TP) versus FP detections at early CAD evaluation and not by a temporal change in readers' performance. The time spent for TP (9.5 s +/- 4.5 s) and false negative (FN) (8.4 s +/- 6.7 s) detections was similar; FP decisions took two- to three-times longer (14.4 s +/- 8.7 s) than true negative (TN) decisions (4.7 s +/- 1.3 s). CONCLUSIONS: When CAD output is ordered by CAD score, an initial period of rapid performance improvement slows significantly over time because of non-uniformity in the distribution of TP CAD output and not to a changing reader performance over time.

Influence of background lung characteristics on nodule detection with computed tomography.

We sought to characterize local lung complexity in chest computed tomography (CT) and to characterize its impact on the detectability of pulmonary nodules. Forty volumetric chest CT scans were created by embedding between three and five simulated 5-mm lung nodules into one of three volumetric chest CT datasets. Thirteen radiologists evaluated 157 nodules, resulting in 2041 detection opportunities. Analyzing the substrate CT data prior to nodule insertion, 14 image features were measured within a region around each nodule location. A generalized linear mixed-effects statistical model was fit to the data to verify the contribution of each metric on detectability. The model was tuned for simplicity, interpretability, and generalizability using stepwise regression applied to the primary features and their interactions. We found that variables corresponding to each of five categories (local structural distractors, local intensity, global context, local vascularity, and contiguity with structural distractors) were significant ( p < 0.01 ) factors in a standardized model. Moreover, reader-specific models conveyed significant differences among readers with significant distraction (missed detections) influenced by local intensity- versus local-structural characteristics being mutually exclusive. Readers with significant local intensity distraction ( n = 10 ) detected substantially fewer lung nodules than those who were significantly distracted by local structure ( n = 2 ), 46.1% versus 65.3% mean nodules detected, respectively.

Geographic Access to CT for Lung Cancer Screening: A Census Tract-Level Analysis of Cigarette Smoking in the United States and Driving Distance to a CT Facility.

PURPOSE: Spatial access to health care resources is a requisite for utilization. Our purpose was to determine, at a census tract level, the geographic distribution of US smokers and their driving distance to an ACR-accredited CT facility. METHODS: The number of smokers per US census tract was determined from US Census Bureau data (American Community Survey, 2011-2015) and census tract smoking prevalence estimates. Driving distance, from the centroid of each census tract to the nearest CT facility, was determined using a geographic information system. Distance variations were assessed, and relationships with tract population density were examined with regression models. RESULTS: Most US smokers (81.8%) were within 15 miles of a CT facility; however, there was considerable inter- and intrastate variability. For census tracts containing ≥500 smokers, median distance to a CT was 4.3 miles. At the state level, median distance ranged from 1.4 (Washington DC) to 29.1 miles (Wyoming). Within each state, this variation was higher, with Washington, DC, exhibiting the lowest range (range, 4.3; 0.2-4.5 miles) and Maine exhibiting the highest range (range, 244.8; 0.2-245.0 miles). Distance to a CT facility was inversely associated with census tract population density. CONCLUSIONS: Geographic variability in CT facility access has implications for lung cancer screening (LCS) implementation. Individuals in densely populated areas have relatively greater spatial access to CT facilities than those in sparsely populated tracts. Further work is needed to identify access disparities to LCS to optimize LCS for all eligible populations.

Predicting intracranial progression following stereotactic radiosurgery for brain metastases: Implications for post SRS imaging.

PURPOSE: Follow-up imaging after stereotactic radiosurgery (SRS) is crucial to identify salvageable brain metastases (BM) recurrence. As optimal imaging intervals are poorly understood, we sought to build a predictive model for time to intracranial progression. METHODS: Consecutive patients treated with SRS for BM at three institutions from January 1, 2002 to June 30, 2017 were retrospectively reviewed. We developed a model using stepwise regression that identified four prognostic factors and built a predictive nomogram. RESULTS: We identified 755 patients with primarily non-small cell lung, breast, and melanoma BMs. Factors such as number of BMs, histology, history of prior whole-brain radiation, and time interval from initial cancer diagnosis to metastases were prognostic for intracranial progression. Per our nomogram, risk of intracranial progression by 3 months post-SRS in the high-risk group was 21% compared to 11% in the low-risk group; at 6 months, it was 43% versus 27%. CONCLUSION: We present a nomogram estimating time to BM progression following SRS to potentially personalize surveillance imaging.

Diagnostic performance of MDCT in identifying closed loop small bowel obstruction.

PURPOSE: To assess the diagnostic performance of MDCT in the diagnosis of closed loop small bowel obstruction. MATERIALS AND METHODS: One hundred fifty patients with CT reports including "small bowel obstruction (SBO)" between 1/30/2011 and 12/4/2012 were included (65 men, 85 women, mean age 63 years). CT examinations were independently and blindly reviewed by five radiologists to determine the presence of closed loop obstruction (CL-SBO) and to assess findings of bowel ischemia. Clinical records were reviewed to determine management and operative findings. Using operative findings as a gold standard, reader agreement for the diagnosis of and the CT findings associated with CLO was analyzed using Pearson's correlation (r). Positive predictive value (PPV) and negative predictive value for the diagnosis of CL-SBO and CT signs of bowel ischemia were analyzed. RESULTS: Eighty-eight of 150 patients underwent operative intervention for SBO and 24/88 were considered CL-SBO operatively. Average reader sensitivity and specificity for CL-SBO was 53 % (95 % CI 44-63 %) and 83 % (95 % CI 79-87 %). Reader agreement on CL-SBO was poor to moderate (K = 0.39-0.63). Reader agreement for CT signs of bowel ischemia resulting in a diagnosis of CL-SBO was weak (r = 0.19-0.32). CONCLUSION: The CT diagnosis of CL-SBO is complex and associated imaging findings have variable sensitivity for predicting a closed loop operative diagnosis. CT can be helpful in excluding a closed loop component in patients with SBO.

Natural history of liver imaging reporting and data system category 4 nodules in MRI.

PURPOSE: The purpose of this study was to characterize the MR imaging features and outcomes of liver imaging reporting and data system (LI-RADS) category 4 (LR4) nodules, with an emphasis on upgrade to category 5 (LR5) and development of contraindications to curative therapy. METHODS: Institutional review board approval was obtained for this retrospective, dual-institutional Health Insurance Portability and Accountability Act-compliant study. The requirement for informed consent was waived. Contrast-enhanced MRI studies performed on patients with cirrhosis were retrospectively assessed using LI-RADS 2014 by at least two readers. All nodules were individually evaluated to determine their major imaging features at diagnosis, and follow-up data were used to determine the associated imaging outcomes. RESULTS: One hundred eighty-one untreated LR4 nodules in 139 patients had adequate imaging and follow-up for inclusion in the study. Most (61% [111/181]) of these demonstrated arterial phase hyperenhancement, washout, and diameter less than 20 mm. During the follow-up period (median 163 days), 31% (56/181) of the nodules upgraded to LR5, 40% (73/181) remained stable, and 29% (52/181) downgraded. Of the nodules that upgraded, 61% (34/56) increased their size category and 54% (30/56) developed newly visualized capsules. No LR4 nodules developed venous invasion, satellites nodules, or new intrahepatic or extrahepatic metastatic disease. 75% (42/56) of the nodules that upgraded to LR5 did so within 6 months. CONCLUSIONS: Approximately one-third of LR4 nodules upgrade to LR5, and the short-term risk of developing venous invasion or metastasis is very low.

An analysis of the uncertainty and bias in DCE-MRI measurements using the spoiled gradient-recalled echo pulse sequence.

PURPOSE: The pharmacokinetic parameters derived from dynamic contrast-enhanced (DCE) MRI have been used in more than 100 phase I trials and investigator led studies. A comparison of the absolute values of these quantities requires an estimation of their respective probability distribution function (PDF). The statistical variation of the DCE-MRI measurement is analyzed by considering the fundamental sources of error in the MR signal intensity acquired with the spoiled gradient-echo (SPGR) pulse sequence. METHODS: The variance in the SPGR signal intensity arises from quadrature detection and excitation flip angle inconsistency. The noise power was measured in 11 phantoms of contrast agent concentration in the range [0-1] mM (in steps of 0.1 mM) and in onein vivo acquisition of a tumor-bearing mouse. The distribution of the flip angle was determined in a uniform 10 mM CuSO4 phantom using the spin echo double angle method. The PDF of a wide range of T1 values measured with the varying flip angle (VFA) technique was estimated through numerical simulations of the SPGR equation. The resultant uncertainty in contrast agent concentration was incorporated in the most common model of tracer exchange kinetics and the PDF of the derived pharmacokinetic parameters was studied numerically. RESULTS: The VFA method is an unbiased technique for measuringT1 only in the absence of bias in excitation flip angle. The time-dependent concentration of the contrast agent measured in vivo is within the theoretically predicted uncertainty. The uncertainty in measuring K(trans) with SPGR pulse sequences is of the same order, but always higher than, the uncertainty in measuring the pre-injection longitudinal relaxation time (T10). The lowest achievable bias/uncertainty in estimating this parameter is approximately 20%-70% higher than the bias/uncertainty in the measurement of the pre-injection T1 map. The fractional volume parameters derived from the extended Tofts model were found to be extremely sensitive to the variance in signal intensity. The SNR of the pre-injection T1 map indicates the limiting precision with which K(trans) can be calculated. CONCLUSIONS: Current small-animal imaging systems and pulse sequences robust to motion artifacts have the capacity for reproducible quantitative acquisitions with DCE-MRI. In these circumstances, it is feasible to achieve a level of precision limited only by physiologic variability.

Automated characterization of perceptual quality of clinical chest radiographs: validation and calibration to observer preference.

PURPOSE: The authors previously proposed an image-based technique [Y. Lin et al. Med. Phys. 39, 7019-7031 (2012)] to assess the perceptual quality of clinical chest radiographs. In this study, an observer study was designed and conducted to validate the output of the program against rankings by expert radiologists and to establish the ranges of the output values that reflect the acceptable image appearance so the program output can be used for image quality optimization and tracking. METHODS: Using an IRB-approved protocol, 2500 clinical chest radiographs (PA/AP) were collected from our clinical operation. The images were processed through our perceptual quality assessment program to measure their appearance in terms of ten metrics of perceptual image quality: lung gray level, lung detail, lung noise, rib-lung contrast, rib sharpness, mediastinum detail, mediastinum noise, mediastinum alignment, subdiaphragm-lung contrast, and subdiaphragm area. From the results, for each targeted appearance attribute/metric, 18 images were selected such that the images presented a relatively constant appearance with respect to all metrics except the targeted one. The images were then incorporated into a graphical user interface, which displayed them into three panels of six in a random order. Using a DICOM calibrated diagnostic display workstation and under low ambient lighting conditions, each of five participating attending chest radiologists was tasked to spatially order the images based only on the targeted appearance attribute regardless of the other qualities. Once ordered, the observer also indicated the range of image appearances that he/she considered clinically acceptable. The observer data were analyzed in terms of the correlations between the observer and algorithmic rankings and interobserver variability. An observer-averaged acceptable image appearance was also statistically derived for each quality attribute based on the collected individual acceptable ranges. RESULTS: The observer study indicated that, for each image quality attribute, the averaged observer ranking strongly correlated with the algorithmic ranking (linear correlation coefficient R > 0.92), with highest correlation (R = 1) for lung gray level and the lowest (R = 0.92) for mediastinum noise. There was a strong concordance between the observers in terms of their rankings (i.e., Kendall's tau agreement > 0.84). The observers also generally indicated similar tolerance and preference levels in terms of acceptable ranges, as 85% of the values were close to the overall tolerance or preference levels and the differences were smaller than 0.15. CONCLUSIONS: The observer study indicates that the previously proposed technique provides a robust reflection of the perceptual image quality in clinical images. The results established the range of algorithmic outputs for each metric that can be used to quantitatively assess and qualify the appearance quality of clinical chest radiographs.