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All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

State-space self-tuner for on-line adaptive control

Dynamic systems, such as flight vehicles, satellites and space stations, operating in real environments, constantly face parameter and/or structural variations owing to nonlinear behavior of actuators, failure of sensors, changes in operating conditions, disturbances acting on the system, etc. In the past three decades, adaptive control has been shown to be effective in dealing with dynamic systems in the presence of parameter uncertainties, structural perturbations, random disturbances and environmental variations. Among the existing adaptive control methodologies, the state-space self-tuning control methods, initially proposed by us, are shown to be effective in designing advanced adaptive controllers for multivariable systems. In our approaches, we have embedded the standard Kalman state-estimation algorithm into an online parameter estimation algorithm. Thus, the advanced state-feedback controllers can be easily established for digital adaptive control of continuous-time stochastic multivariable systems. A state-space self-tuner for a general multivariable stochastic system has been developed and successfully applied to the space station for on-line adaptive control. Also, a technique for multistage design of an optimal momentum management controller for the space station has been developed and reported in. Moreover, we have successfully developed various digital redesign techniques which can convert a continuous-time controller to an equivalent digital controller. As a result, the expensive and unreliable continuous-time controller can be implemented using low-cost and high performance microprocessors. Recently, we have developed a new hybrid state-space self tuner using a new dual-rate sampling scheme for on-line adaptive control of continuous-time uncertain systems.

Shieh, L. S.↗
NASA NTRS1994

Determining the response of sea level to atmospheric pressure forcing using TOPEX/POSEIDON data

The static response of sea level to the forcing of atmospheric pressure, the so-called inverted barometer (IB) effect, is investigated using TOPEX/POSEIDON data. This response, characterized by the rise and fall of sea level to compensate for the change of atmospheric pressure at a rate of -1 cm/mbar, is not associated with any ocean currents and hence is normally treated as an error to be removed from sea level observation. Linear regression and spectral transfer function analyses are applied to sea level and pressure to examine the validity of the IB effect. In regions outside the tropics, the regression coefficient is found to be consistently close to the theoretical value except for the regions of western boundary currents, where the mesoscale variability interferes with the IB effect. The spectral transfer function shows near IB response at periods of 30 degrees is -0.84 +/- 0.29 cm/mbar (1 standard deviation). The deviation from = 1 cm /mbar is shown to be caused primarily by the effect of wind forcing on sea level, based on multivariate linear regression model involving both pressure and wind forcing. The regression coefficient for pressure resulting from the multivariate analysis is -0.96 +/- 0.32 cm/mbar. In the tropics the multivariate analysis fails because sea level in the tropics is primarily responding to remote wind forcing. However, after removing from the data the wind-forced sea level estimated by a dynamic model of the tropical Pacific, the pressure regression coefficient improves from -1.22 +/- 0.69 cm/mbar to -0.99 +/- 0.46 cm/mbar, clearly revealing an IB response. The result of the study suggests that with a proper removal of the effect of wind forcing the IB effect is valid in most of the open ocean at periods longer than 20 days and spatial scales larger than 500 km.

Fu, Lee-Lueng↗
NASA NTRS2002

Development of a Generic Creep-Fatigue Life Prediction Model

The objective of this research proposal is to further compile creep-fatigue data of steel alloys and superalloys used in military aircraft engines and/or rocket engines and to develop a statistical multivariate equation. The newly derived model will be a probabilistic fit to all the data compiled from various sources. Attempts will be made to procure the creep-fatigue data from NASA Glenn Research Center and other sources to further develop life prediction models for specific alloy groups. In a previous effort [1-3], a bank of creep-fatigue data has been compiled and tabulated under a range of known test parameters. These test parameters are called independent variables, namely; total strain range, strain rate, hold time, and temperature. The present research attempts to use these variables to develop a multivariate equation, which will be a probabilistic equation fitting a large database. The data predicted by the new model will be analyzed using the normal distribution fits, the closer the predicted lives are with the experimental lives (normal line 1 to 1 fit) the better the prediction. This will be evaluated in terms of a coefficient of correlation, R 2 as well. A multivariate equation developed earlier [3] has the following form, where S, R, T, and H have specific meaning discussed later.

Goswami, Tarun↗
NASA NTRS2022

Deriving Severe Hail Likelihood from Satellite Observations and Model Reanalysis Parameters using a Deep Neural Network

Geostationary satellite imagers, such as those of the Geostationary Operational Environmental Satellite (GOES) series, have been observing severe convection at 15–60-minute intervals for over 40 years. When properly assessed, such a data record can be valuable in efforts of estimating severe storm risk throughout the diurnal cycle based on automated detection of patterns consistently found atop severe storms. Furthermore, environmental conditions favorable for severe weather are well-known and are thought to be represented well by modern reanalysis products. Promoting resilience against such hazards on local and global scales is a chief goal the NASA Disasters program, which seeks to encourage use of satellite observations to mitigate risk. For instance, hail is the costliest severe weather hazard across the globe in terms of insured loss, but reporting inconsistencies for hail events globally make it difficult to develop models that can quantify the risk. Satellite observation and model reanalysis taken together have the potential to, with reasonable skill and specificity, characterize environmental conditions that are favorable for hazardous weather, and thereby enable creation of hazard climatologie. Such climatologies are particularly useful over regions without extensive radar networks or storm reporting. By mapping the multivariate combination of observed cloud features and reanalysis environmental parameters/indices to United States Next Generation Weather Radar (NEXRAD) radar-estimated Maximum Expected Size of Hail (MESH) by way of a deep neural network (DNN), estimates of likelihood for potentially severe hail can be produced. Such estimates are of greater complexity and efficiency than could be performed with previous multivariate or logistic regression analyses for observed points within convective systems. Statistical distributions of convective parameters from satellite and reanalysis are shown to highlight non-severe/severe class separation for well-known hailstorm predictors, e.g., overshooting cloud top characteristics, deep-layer wind shear, mid-level stability, helicity, and convective inhibition. These complex, multivariate predictor relationships are exploited within a DNN, which can efficiently produce a quantitative hail risk metric with better than 70% detection rate and under 30% false alarms. These hail classifications can then be aggregated across the satellite record to yield a hazard climatology for hail frequency and severity – knowledge of which is of particular interest to those who manage risk (e.g., insurers) and are seeking opportunities to identify hail-prone regions, particularly in developing nations. This NASA study uses satellite observations and model parameters in a DNN to perform climatological hailstorm analysis in support of catastrophe model development, with the hope of promoting risk resilience particularly in regions without adequate weather radar coverage.

Passive Remote Sensing↗
DOE OSTI2014

Heterogeneous recurrence monitoring and control of nonlinear stochastic processes

Recurrence is one of the most common phenomena in natural and engineering systems. Process monitoring of dynamic transitions in nonlinear and nonstationary systems is more concerned with aperiodic recurrences and recurrence variations. However, little has been done to investigate the heterogeneous recurrence variations and link with the objectives of process monitoring and anomaly detection. Notably, nonlinear recurrence methodologies are based on homogeneous recurrences, which treat all recurrence states in the same way as black dots, and non-recurrence is white in recurrence plots. Heterogeneous recurrences are more concerned about the variations of recurrence states in terms of state properties (e.g., values and relative locations) and the evolving dynamics (e.g., sequential state transitions). This paper presents a novel approach of heterogeneous recurrence analysis that utilizes a new fractal representation to delineate heterogeneous recurrence states in multiple scales, including the recurrences of both single states and multi-state sequences. Further, we developed a new set of heterogeneous recurrence quantifiers that are extracted from fractal representation in the transformed space. To that end, we integrated multivariate statistical control charts with heterogeneous recurrence analysis to simultaneously monitor two or more related quantifiers. Experimental results on nonlinear stochastic processes show that the proposed approach not only captures heterogeneous recurrence patterns in the fractal representation but also effectively monitors the changes in the dynamics of a complex system.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Hemobilia after CT-guided radiofrequency ablation of liver tumors: frequency, risk factors, and clinical significance

Purpose: The purpose of the study is to evaluate the frequency, risk factors, and clinical significance of hemobilia after percutaneous computed tomography (CT)-guided radiofrequency ablation (RFA) of liver tumors. Materials and methods: From January 2013 to September 2016, 195 patients received 267 sessions of CT-guided RFA for liver tumors at our institution. The CT images during and immediately after the RFA were retrospectively reviewed. The frequency of hemobilia development and clinical outcome of patients with hemobilia were studied. Risk factors were identified by comparison between the hemobilia and non-hemobilia groups using univariate and multivariate analysis. The clinical courses of patients with hemobilia were also reviewed. Results: The frequency of CT detected hemobilia after RFA was 8.2% (22/267). The majority of the clinical courses were self-limited. Univariate analysis showed that the tumor numbers (p = 0.015), the central type puncture track (p < 0.001), the length of the puncture track (p = 0.033), and the platelet count (p = 0.026) were significantly associated with the development of hemobilia. Multivariate analysis demonstrated that the central type puncture track (p < 0.024) and the platelet count (p = 0.023) were significant independent risk factors. Conclusion: Detection of hemobilia on CT images immediately after percutaneous RFA for liver tumors was not rare. Low platelet count and central type puncture track are independent risk factors. In most cases, hemobilia presented as a minor complication with favorable prognosis.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Pancreatic neuroendocrine tumors: MR imaging features preoperatively predict lymph node metastasis

Purposes: Predictive factors of lymph node metastasis (LNM) in pancreatic neuroendocrine tumors (pNETs) are not well established. We sought to identify the value of MR imaging features in preoperatively predicting the lymph node metastasis of pNETs. Materials and methods: In this study, we enrolled 108 consecutive patients with pNETs between January 2009 and June 2018. MR morphologic features and quantitative data were evaluated. Predictors of LNM were evaluated using univariate and multivariate logistic regression models. Results: A total of 108 patients with pNETs were finally enrolled, including 82 LNM-negative and 26 LNM-positive patients. Features significantly related to the LNM of pNETs at univariate analysis were tumor size > 2 cm (P = 0.003), Ki-67 > 5% (P = 0.002), non-enhancement pattern (P < 0.001), apparent diffusion coefficient value (P < 0.001), main pancreatic duct dilation (P < 0.001) and pancreatic atrophy (P = 0.032) and extrapancreatic tumor spread (P = 0.001), CNRs during arterial, portal and delay phase (P = 0.005, 0.047, and 0.045, respectively), and histological classification (P = 0.006). At multivariate analysis, non-enhancement pattern (P = 0.019; odds ratio, 6.652; 95% CI 1.369, 32.321) and main pancreatic duct dilation (P = 0.018; odds ratio, 6.745; 95% CI 1.379, 32.991) were independent risk factors for predicting the LNM of pNETs. Conclusion: The non-enhancement characteristic and main pancreatic duct dilation appear to be linked with LNM in pNETs. These radiological predictors can be easily obtained preoperatively, and may help to avoid missing pNETs with a high risk of LNM.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

A comparison of segmented abdominopelvic fluid volumes with conventional CT signs of abdominal compartment syndrome in a trauma population

Purpose: To compare the utility of abdominopelvic fluid volume measurements with established computed tomography signs for refractory post-traumatic abdominal compartment syndrome. Methods: This retrospective observational cohort study included 64 consecutive adult trauma patients with preoperative CT and diagnosis of refractory abdominal compartment syndrome requiring decompressive laparotomy at a level I trauma referral center between 2004 and 2014. We hypothesized that abdominal fluid volume measurements would be more predictive of the need for early laparotomy than previously described conventional CT signs of refractory ACS. Abdominopelvic fluid volumes were determined quantitatively using semi-automated segmentation software. The following conventional imaging parameters were recorded: abdominal anteroposterior:transverse ratio (round belly sign); infrahepatic vena cava diameter; distal abdominal aortic diameter; largest single small bowel wall diameter; hydronephrosis, inguinal herniation; and mesenteric and body wall edema. For outcome analysis, patients were stratified into two groups: those who underwent early (< 24 h) and late (≥ 24 h) decompressive laparotomy following CT. Correlation analysis, comparison of means, and multivariate logistic regression were performed. Results: Abdominal fluid volumes (p = 0.001) and anteroposterior:transverse ratio (p = 0.009) were increased and inferior vena cava diameter (p = 0.009) was decreased in the early decompressive laparotomy group. Multivariate analysis including conventional CT variables, fluid volumes, and laboratory values revealed abdominal fluid volumes (p = 0.012; Δ in log odds of 1.002/mL) as the only independent predictor of early decompressive laparotomy. Conclusions: Segmented abdominopelvic free fluid volumes had greater predictive utility for decision to perform early decompressive laparotomy than previously described ACS-related CT signs in trauma patients who developed refractory abdominal compartment syndrome.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

The Effect of Endovascular Revascularization of Common Iliac Artery Occlusions on Erectile Function

To determine the incidence of erectile dysfunction in patients with common iliac artery (CIA) occlusive disease and the effect of revascularization on erectile function using the sexual health inventory for males (SHIM) questionnaire. All patients (35 men; mean age 57 {+-} 5 years; range 42-67 years) were asked to recall their sexual function before and 1 month after iliac recanalization. Univariate and multivariate analyses were performed to determine variables effecting improvement of impotence. The incidence of impotence in patients with CIA occlusion was 74% (26 of 35) preoperatively. Overall 16 (46%) of 35 patients reported improved erectile function after iliac recanalization. The rate of improvement of impotence was 61.5% (16 of 26 impotent patients). Sixteen patients (46%), including seven with normal erectile function before the procedure, had no change. Three patients (8%) reported deterioration of their sexual function, two of whom (6%) had normal erectile function before the procedure. The median SHIM score increased from 14 (range 4-25) before the procedure to 20 (range 1-25) after the procedure (P = 0.005). The type of recanalization, the age of the patients, and the length of occlusion were related to erectile function improvement in univariate analysis. However, these factors were not independent factors for improvement of erectile dysfunction in multivariate analysis (P > 0.05). Endovascular recanalization of CIA occlusions clearly improves sexual function. More than half of the patients with erectile dysfunction who underwent endovascular recanalization of the CIA experienced improvement.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Pattern of Retained Contrast on Immediate Postprocedure Computed tomography (CT) After Particle Embolization of Liver Tumors Predicts Subsequent Treatment Response

PurposeTo determine if the pattern of retained contrast on immediate postprocedure computed tomography (CT) after particle embolization of hepatic tumors predicts modified Response Evaluation Criteria in Solid Tumors (mRECIST) response.Materials and MethodsThis study was approved by the Institutional Review Board with a waiver of authorization. One hundred four liver tumors were embolized with spherical embolic agents (Embospheres, Bead Block, LC Bead) and polyvinyl alcohol. Noncontrast CT was performed immediately after embolization to assess contrast retention in the targeted tumors, and treatment response was assessed by mRECIST criteria on follow-up CT (average time 9.0 {+-} 7.7 weeks after embolization). Tumor contrast retention (TCR) was determined based on change in Hounsfield units (HUs) of the index tumors between the preprocedure and immediate postprocedure scans; vascular contrast retention (VCR) was rated; and defects in contrast retention (DCR) were also documented. The morphology of residual enhancing tumor on follow-up CT was described as partial, circumferential, or total. Association between TCR variables and tumor response were assessed using multivariate logistic regression.ResultsOf 104 hepatic tumors, 51 (49 %) tumors had complete response (CR) by mRECIST criteria; 23 (22.1 %) had partial response (PR); 21 (20.2 %) had stable disease (SD); and 9 (8.7 %) had progressive disease (PD). By multivariate analysis, TCR, VCR, and tumor size are independent predictors of CR (p = 0.02, 0.05, and 0.005 respectively). In 75 tumors, DCR was found to be an independent predictor of failure to achieve complete response (p < 0.0001) by imaging criteria.ConclusionTCR, VCR, and DCR on immediate posttreatment CT are independent predictors of CR by mRECIST criteria.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Safety of Repeated Yttrium-90 Radioembolization

Purpose: Repeated radioembolization (RE) treatments carry theoretically higher risk of radiation-induced hepatic injury because of the liver's cumulative memory of previous exposure. We performed a retrospective safety analysis on patients who underwent repeated RE. Methods: From 2004 to 2011, a total of 247 patients were treated by RE. Eight patients (5 men, 3 women, age range 51-71 years) underwent repeated treatment of a targeted territory, all with resin microspheres (SIR-Spheres; Sirtex, Lane Cove, Australia). Adverse events were graded during a standardized follow-up. In addition, the correlation between the occurrence of RE-induced liver disease (REILD) and multiple variables was investigated in univariate and multivariate analyses in all 247 patients who received RE. Results: Two patients died shortly after the second treatment (at 84 and 107 days) with signs and symptoms of REILD. Both patients underwent whole liver treatment twice (cumulative doses 3.08 and 2.66 GBq). The other 6 patients demonstrated only minor toxicities after receiving cumulative doses ranging from 2.41 to 3.88 GBq. All patients experienced objective tumor responses. In the whole population, multifactorial analysis identified three risk factors associated with REILD: repeated RE (p = 0.036), baseline serum total bilirubin (p = 0.048), and baseline serum aspartate aminotransferase (p = 0.043). Repeated RE proved to be the only independent risk factor for REILD in multivariate analysis (odds ratio 9.6; p = 0.002). Additionally, the administered activity per target volume (in GBq/L) was found to be an independent risk factor for REILD, but only in whole liver treatments (p = 0.033). Conclusion: The risk of REILD appears to be elevated for repeated RE. Objective tumor responses were observed, but establishment of safety limits will require improvement in dosimetric measurement and prediction.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Root Cause Analysis of Gastroduodenal Ulceration After Yttrium-90 Radioembolization

Introduction: A root cause analysis was performed on the occurrence of gastroduodenal ulceration after hepatic radioembolization (RE). We aimed to identify the risk factors in the treated population and to determine the specific mechanism of nontarget RE in individual cases. Methods: The records of 247 consecutive patients treated with yttrium-90 RE for primary (n = 90) or metastatic (n = 157) liver cancer using either resin (n = 181) or glass (n = 66) microspheres were reviewed. All patients who developed a biopsy-proven microsphere-induced gastroduodenal ulcer were identified. Univariate and multivariate analyses were performed on baseline parameters and procedural data to determine possible risk factors in the total population. Individual cases were analyzed to ascertain the specific cause, including identification of the culprit vessel(s) leading to extrahepatic deposition of the microspheres. Results: Eight patients (3.2 %) developed a gastroduodenal ulcer. Stasis during injection was the strongest independent risk factor (p = 0.004), followed by distal origin of the gastroduodenal artery (p = 0.004), young age (p = 0.040), and proximal injection of the microspheres (p = 0.043). Prolonged administrations, pain during administration, whole liver treatment, and use of resin microspheres also showed interrelated trends in multivariate analysis. Retrospective review of intraprocedural and postprocedural imaging showed a probable or possible culprit vessel, each a tiny complex collateral vessel, in seven patients. Conclusion: Proximal administrations and those resulting in stasis of flow presented increased risk for gastroduodenal ulceration. Patients who had undergone bevacizumab therapy were at high risk for developing stasis.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Percutaneous Lung Thermal Ablation of Non-surgical Clinical N0 Non-small Cell Lung Cancer: Results of Eight Years’ Experience in 87 Patients from Two Centers

PurposeTo evaluate the survival outcomes of percutaneous thermal ablation (RFA + microwaves) for patients presenting N0 non-small-cell lung cancer (NSCLC) ineligible for surgery.Materials and MethodsEighty-seven patients from two comprehensive cancer centers were included. Eighty-two patients were treated with RFA electrodes and five with microwave antenna. Overall survival (OS) and disease-free survival (DFS) were estimated and predictive factors of local tumor progression, OS and DFS identified and compared by univariate and multivariate analysesResultsMedian follow-up was 30.5 months (interquartile range 16.7–51) and tumor size was 21 mm (range 10–54 mm). Treatment was incomplete for 14 patients with a local tumor progression of 11.5, 18.3, and 21.1 % at 1, 2, and 3 years, respectively. Two patients presented with neurological (grade III or IV) complications, and one died of respiratory and multivisceral failure as a result of the procedure at 29 days. In univariate analysis, increasing tumor size (P = 0.003) was the only predictive factor related to risk of local tumor progression. 5-year OS and DFS were 58.1 and 27.9 %, respectively. Sex (P = 0.044), pathology (P = 0.032), and tumor size >2 cm (P = 0.046) were prognostic factors for DFS. In multivariate analysis, pathology (P = 0.033) and tumor size >2 cm (P = 0.032) were independent prognostic factors for DFS.ConclusionsOversized and overlapping ablation of N0 NSCLC was well tolerated, effective, with few local tumor progressions, even over long-term follow-up. Increasing tumor size was the main prognostic factor linked to OS, DFS, and local tumor progression.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Early Stage Hepatocellular Carcinomas Not Feasible for Ultrasound-Guided Radiofrequency Ablation: Comparison of Transarterial Chemoembolization Alone and Combined Therapy with Transarterial Chemoembolization and Radiofrequency Ablation

PurposeTo report the results of combined therapy with transarterial chemoembolization (TACE) and radiofrequency ablation (RFA) for early stage hepatocellular carcinoma (HCC) considered infeasible for ultrasound (US)-guided RFA in comparison with those of TACE monotherapy.MethodsFrom January 2007 through December 2010, 91 patients with early or very early stage HCC infeasible for US-guided RFA received either TACE alone (TACE group; n = 54) or TACE immediately followed by RFA (TACE–RFA group; n = 37) as a first-line treatment. 1-month tumor response, time to progression (TTP), and overall survival (OS) rates were calculated. Univariate and multivariate analyses were performed to identify prognostic factors.ResultsTACE–RFA group showed a better 1-month tumor response than TACE group (P < .001). The mean TTP was 29.7 ± 3.4 months (95 % confidence intervals [CIs] 23.0–36.5) in TACE group and 34.9 ± 2.8 months (95 % CIs 29.4–40.4) in TACE–RFA group. TACE–RFA group had a significantly longer TTP (P = .014). Cumulative 1-, 2-, and 3-year OS rates in the TACE and TACE–RFA groups were 91, 79, and 71 % and 100, 97, and 93 %, respectively (P = .008). Initial treatment of TACE was found to be the only significant risk factor for tumor progression and OS in multivariate analysis.ConclusionTACE–RFA combination therapy appears superior to TACE monotherapy in terms of 1-month tumor response, TTP, and OS when performed for early stage HCC infeasible for US-guided RFA.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

MWA Versus RFA for Perivascular and Peribiliary CRLM: A Retrospective Patient- and Lesion-Based Analysis of Two Historical Cohorts

PurposeTo retrospectively analyse the safety and efficacy of radiofrequency ablation (RFA) versus microwave ablation (MWA) in the treatment of unresectable colorectal liver metastases (CRLM) in proximity to large vessels and/or major bile ducts.Method and MaterialsA database search was performed to include patients with unresectable histologically proven and/or {sup 18}F–FDG–PET avid CRLM who were treated with RFA or MWA between January 2001 and September 2014 in a single centre. All lesions that were considered to have a peribiliary and/or perivascular location were included. Univariate logistic regression analysis was performed to assess the distribution of patient, tumour and procedure characteristics. Multivariate logistic regression was used to correct for potential confounders.ResultsTwo hundred and forty-three patients with 774 unresectable CRLM were ablated. One hundred and twenty-two patients (78 males; 44 females) had at least one perivascular or peribiliary lesion (n = 199). Primary efficacy rate of RFA was superior to MWA after 3 and 12 months of follow-up (P = 0.010 and P = 0.022); however, after multivariate analysis this difference was non-significant at 12 months (P = 0.078) and vanished after repeat ablations (P = 0.39). More CTCAE grade III complications occurred after MWA versus RFA (18.8 vs. 7.9 %; P = 0.094); biliary complications were especially common after peribiliary MWA (P = 0.002).ConclusionFor perivascular CRLM, RFA and MWA are both safe treatment options that appear equally effective. For peribiliary CRLM, MWA has a higher complication rate than RFA, with similar efficacy. Based on these results, it is advised to use RFA for lesions in the proximity of major bile ducts.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Assessing Intra-arterial Complications of Planning and Treatment Angiograms for Y-90 Radioembolization

PurposeTo report hepatic arterial-related complications encountered during planning and treatment angiograms for radioembolization and understand any potential-associated risk factors.Materials and Methods518 mapping or treatment angiograms for 180 patients with primary or metastatic disease to the liver treated by Yttrium-90 radioembolization between 2/2010 and 12/2015 were retrospectively reviewed. Intra-procedural complications were recorded per SIR guidelines. Patient demographics, indication for treatment, prior exposure to chemotherapeutic agents, operator experience, and disease burden were reviewed. Technical variables including type of radioembolic (glass vs. resin microspheres), indication for angiography (mapping vs. treatment), variant anatomy, and attempts at coil embolization were also assessed.ResultsThirteen (13/518, 2.5%) arterial-related complications occurred in 13 patients. All but two complications resulted during transcatheter coil embolization to prevent non-target embolization. Complications included coil migration (n = 6), arterial dissection (n = 2), focal vessel perforation (n = 2), arterial thrombus (n = 2), and vasospasm prohibiting further arterial sub-selection (n = 1). Transarterial coiling was identified as a significant risk factor of complications on both univariate and multivariate regression analysis (odds ratio 7.8, P = 0.004). Usage of resin microspheres was also a significant risk factor (odds ratio 9.5, P = 0.042). No other technical parameters or pre-procedural variables were significant after adjusting for confounding on multivariate analysis (P > 0.05).ConclusionIntra-procedural hepatic arterial complications encountered during radioembolization were infrequent but occurred mainly during coil embolization to prevent non-target delivery to extra-hepatic arteries.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Survival Analysis of Advanced HCC Treated with Radioembolization: Comparing Impact of Clinical Performance Status Versus Vascular Invasion/Metastases

PurposeIn this study, we aim to compare the effects of prognostic indicators on survival analysis for Barcelona Clinic Liver Cancer (BCLC) C patients undergoing yttrium-90 radioembolization (Y-90).MethodsA prospectively acquired database (2003–2017) for BCLC C hepatocellular carcinoma (HCC) patients that underwent radioembolization with Y-90 was searched. The criteria for BCLC C status (Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 1 or 2, metastases, and/or portal vein thrombosis (PVT)) were recorded. Kaplan–Meier survival analyses were performed from the date of the first radioembolization with Y-90, censored to curative treatment, to determine median overall survival (OS). Cox regression hazards model was used for multivariate analyses. Significance was set at P < 0.05.Results547 BCLC C patients treated with radioembolization with Y-90 had a median OS of 10.7 months (range: 9.5–12.9). 43% (233 of 547) patients classified as BCLC C solely by their ECOG PS had a median OS of 19.4 months (14.7–23.7); 57% (314 of 547) patients with PVT/metastases had a median OS of 7.7 months (6.7–8.7). On multivariate analysis, ECOG PS was not found to be a statistically significant prognostic indicator of OS in BCLC C whereas metastases and PVT exhibited hazards ratios (95%CI) of 0.51 (0.38–0.69) and 0.49 (0.38–0.63), respectively (P < 0.0001).ConclusionPatients classified as BCLC C due to ECOG PS 1 demonstrated longer survival when compared to those presenting with PVT, metastases and/or ECOG PS 2. Hence, ECOG PS 1, as an isolated variable, may not be a true indicator of advanced disease.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Which Criteria Applied in Multi-Phasic CT Can Predict Early Tumor Response in Patients with Hepatocellular Carcinoma Treated Using Conventional TACE: RECIST, mRECIST, EASL or qEASL?

PurposeOur study aimed to evaluate quantitative tumor response assessment (quantitative EASL-[qEASL]) on computed tomography (CT) images in patients with hepatocellular carcinoma (HCC) treated using conventional transarterial chemoembolization (cTACE), compared to existing 1-dimensional and 2-dimensional methods (RECIST, mRECIST, EASL).Materials and MethodsIn this IRB-approved, single-institution retrospective cohort study, 52 consecutive patients with intermediate-stage HCC were consecutively included. All patients underwent contrast-enhanced CT scan at baseline and 4 weeks after cTACE.ResultsMedian follow-up period was 13.5 months (range 1.2–54.1). RECIST, mRECIST and EASL identified progression in 2 (4%), 1 (2%) and 1 (2%) patients, respectively, whereas qEASL identified 10 (19%) patients. qEASL was the only tumor response method able to predict survival among different tumor response groups (P < 0.05), whereas RECIST, mRECIST and EASL did not (P > 0.05). Both EASL and qEASL were able to identify responders and non-responders and were predictive of survival (P < 0.05). Multivariate analysis showed that progression was an independent predictor of overall survival with hazard ratio of 1.9 (P = 0.025). Patients who demonstrated progression with qEASL had significantly shorter survival than those with non-progression (7.6 vs. 20.4 months, P = 0.012). Similar multivariate analysis using RECIST, mRECIST and EASL could not be performed because too few patients were categorized as progressive disease.ConclusionqEASL could be applied on CT images to assess tumor response following cTACE and is a more sensitive biomarker to predict survival and identify tumor progression than RECIST, mRECIST and EASL at an early time point.Level of EvidenceLevel 2a, retrospective cohort study.

62 RADIOLOGY AND NUCLEAR MEDICINE↗