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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A hidden Markov model for population-level cervical cancer screening data

The Cancer Registry of Norway has been administrating a national cervical cancer screening program since 1992 by coordinating triennial cytology exam screenings for the female population between 25 and 69 years of age. Up to 80% of cancers are prevented through mass screening, but this comes at the expense of considerable screening activity and leads to overtreatment of clinically asymptomatic precancers. Here, we present a continuous-time, time-inhomogeneous hidden Markov model which was developed to understand the screening process and cervical cancer carcinogenesis in detail. By leveraging 1.7 million individual's multivariate time-series of medical exams performed over a 25-year period, we simultaneously estimate all model parameters. We show that an age-dependent model reflects the Norwegian screening program by comparing empirical survival curves from observed registry data and data simulated from the proposed model. The model can be generalized to include more detailed individual-level covariates as well as new types of screening exams. By utilizing individual screening histories and covariate data, the proposed model shows potential for improving strategies for cancer screening programs by personalizing recommended screening intervals.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Reader agreement and accuracy of ultrasound features for hepatic steatosis

Purpose: The purpose of the study is to assess the reader agreement and accuracy of eight ultrasound imaging features for classifying hepatic steatosis in adults with known or suspected hepatic steatosis. Methods: This was an IRB-approved, HIPAA-compliant prospective study of adult patients with known or suspected hepatic steatosis. All patients signed written informed consent. Ultrasound images (Siemens S3000, 6C1HD, and 4C1 transducers) were acquired by experienced sonographers following a standard protocol. Eight readers independently graded eight features and their overall impression of hepatic steatosis on ordinal scales using an electronic case report form. Duplicated images from the 6C1HD transducer were read twice to assess intra-reader agreement. Intra-reader, inter-transducer, and inter-reader agreement were assessed using intraclass correlation coefficients (ICC). Features with the highest intra-reader agreement were selected as predictors for dichotomized histological steatosis using Classification and Regression Tree (CART) analysis, and the accuracy of the decision rule was compared to the accuracy of the radiologists’ overall impression. Results: 45 patients (18 males, 27 females; mean age 56 ± 12 years) scanned from September 2015 to July 2016 were included. Mean intra-reader ICCs ranged from 0.430 to 0.777, inter-transducer ICCs ranged from 0.228 to 0.640, and inter-reader ICCs ranged from 0.014 to 0.561. The CART decision rule selected only large hepatic vein blurring and achieved similar accuracy to the overall impression (74% to 75% and 68% to 72%, respectively). Conclusions: Large hepatic vein blurring, liver–kidney contrast, and overall impression provided the highest reader agreement. Large hepatic vein blurring may provide the highest classification accuracy for dichotomized grading of hepatic steatosis.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Evaluating the frequency and severity of ovarian venous congestion on adult computed tomography

Purpose: While pelvic congestion syndrome and chronic pelvic pain are relatively common in women, no large- or medium-sized studies have been conducted to our knowledge to evaluate the frequency and severity of ovarian vein dilatation (OVD) on computed tomography (CT). The purpose of our study was therefore to analyze a large number of consecutive abdominal and pelvic CT scans in adult women to determine OVD frequency and severity. Methods: An IRB-approved, single-institution retrospective analysis of 1042 consecutive abdominal and pelvic CT scans in women ages 25–65 was performed. Scans were evaluated for the presence and severity of OVD and association with “nutcracker anatomy.” A gradation scheme was developed based on quartile analysis. Results: 143 of the CT scans had OVD (13.7%). Of the positive scans, 96 were bilateral, 29 were left-side only, 18 were right-side only, and 18 had nutcracker-type compression of the left renal vein (14.4% of scans with left or bilateral OVD). In positive scans, the mean and median left OVD were 7.5 and 7 mm, respectively, and right-side were 7.2 and 7 mm, respectively. Based on quartile analysis, OVD grading was mild (< 6 mm), moderate (6–8 mm), or severe (> 8 mm), with moderate including the middle 50% of patients. Conclusions: OVD was found on 13.7% of 1042 consecutive female abdominal and pelvic CT scans, with “nutcracker anatomy” present in 14.4% of the scans with left OVD. Moderate dilatation was defined as an OVD of 6–8 mm at the iliac crests.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Renal solitary fibrous tumor/hemangiopericytoma: computed tomography findings and clinicopathologic features

Purpose: To retrospectively characterize the clinical, pathological, and computed tomography (CT) findings of renal solitary fibrous tumor/hemangiopericytoma (rSFT/HPC). Methods: Twelve patients with rSFT/HPCs were enrolled. The CT findings and clinicopathological features were retrospectively reviewed. Results: This study included six male and six female patients (median age: 47; age range: 20–82 years). Eight benign (grade I) and four malignant (grade III) rSFT/HPCs were identified. Of the 12 lesions, 10 were in the renal sinus near the renal pelvis, while two replaced the whole kidney. Five lesions were well-defined, five were partially ill-defined, and two were ill-defined. Mild (5/12) and intermediate (1/12) hydronephrosis was observed. On the unenhanced CT images, ten tumors showed slightly higher density when compared to the normal renal parenchyma, and two masses were isodense to hypodense. After intravenous contrast medium injection, three enhancement patterns were observed, including “prolonged enhancement” (PE) (6/12), “gradual enhancement” (4/12), and “early washout” (2/12). A central fibrous scar was found in five patients. Compared to the grade I lesions, the grade III rSFT/HPC lesions tended to be larger (maximal diameter > 10 cm) and more heterogeneous with a higher incidence of the PE pattern. Conclusions: We have shown that rSFT/HPCs usually arise from the renal sinus, and present as lobulated, slightly hyperdense, gradually enhancing soft tissue masses. CT findings, including large size, heterogeneity, and the PE pattern, may assist in the pre-operative identification of malignant grade III rSFT/HPCs.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Association of advanced hepatic fibrosis and sonographic visualization score: a dual-center study using ACR US LI-RADS

Purpose: To evaluate the association between imaging and clinical features and visualization scores, as specified by American College of Radiology (ACR) Ultrasound Liver Imaging Reporting and Data System (LI-RADS), on hepatocellular carcinoma (HCC) screening ultrasound examinations. Methods: In this dual-center retrospective study, HCC screening ultrasound reports containing ultrasound elastography measurements (January to September, 2017) were reviewed. Ultrasound point shear wave elastography and 2-dimensional shear wave elastography were used to assess liver stiffness; median shear wave velocity was translated to METAVIR fibrosis scoring, per previously published data. Reports were analyzed for subject age, sex, reason for HCC screening, spleen size, fibrosis scores, and assigned ultrasound visualization scores. Jonckheere–Terpstra trend and Kendall’s tau-b coefficient analyses were performed. Results: 714 subjects (mean age 55; 51% male, 49% female) were included. 308 (43%) subjects had clinically declared cirrhosis; 406 (57%) did not. Majority (535, 75%) of exams were adequate (Visualization Score A), 156 (22%) moderately limited (Visualization Score B), and 23 (3%) severely limited (Visualization Score C). Increasing spleen size and patient age were associated with worsening visualization scores (p < 0.001). Suboptimal visualization was also associated with clinically significant fibrosis (≥ F2) by elastography (Kendall’s tau-b = 0.181, p < 0.001) and clinically declared cirrhosis (Kendall’s tau-b = 0.433, p < 0.001). There was no association with patient sex. Conclusion: Using ACR Ultrasound LI-RADS visualization score assessment, majority (75%) of HCC screening exams were diagnostically adequate, and only 3% were severely limited. Sonoelastographic diagnosis of clinically significant fibrosis, as well as clinical cirrhosis, increased patient age, and spleen size, were associated with greater diagnostic limitations.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Imaging findings of hemorrhagic hepatic cysts with enhancing mural nodules

Purpose: This study aimed to evaluate the clinical and radiological findings of hemorrhagic hepatic cysts with enhancing mural nodules. Methods: The radiology databases of five facilities were retrospectively searched for reports indicating hemorrhagic hepatic cysts or hepatic cystic tumors. Cases of hemorrhagic hepatic cysts with enhancing mural nodules based on pathological or radiological findings were identified and reviewed. Results: We included 14 cases (11 female and 3 male) with a mean patient age of 72.6 years. Up until the enhancing mural nodules were detected, the cysts had decreased in size in all ten cases for which radiological imaging was available for a period of > 3 years previous to detection. Dynamic contrast-enhanced CT or MRI showed focal enhancement in the early phase and progressive centrifugal enhancement in the delayed phase in all 16 mural nodules ≥ 10 mm in diameter. Thirteen of 14 MRI assessable enhancing mural nodules ≥ 10 mm in diameter showed a hypointense rim with central hyperintensity on T2-weighted imaging. All cases showed calcification of the cyst wall. In the three referred cases, {sup 18}F-fluorodeoxyglucose (FDG) positron emission tomography/CT demonstrated no intense FDG uptake in the enhancing mural nodules. In the four resected cases, histopathology of the enhancing mural nodules revealed neovascularization within an organized hematoma, including extensive dilated vessels and hemangioma-like lesions. Conclusions: Features including a decrease in cyst size, a progressive centrifugal enhancing pattern on dynamic contrast-enhanced CT or MRI, a hypointense rim with central hyperintensity on T2-weighted MRI, and cyst wall calcification may indicate a hemorrhagic hepatic cyst.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Transnasal stent-assisted targeting technique for percutaneous jejunostomy placement in patients with hiatal hernias

Purpose: To report the transnasal stent-assisted targeting technique for percutaneous jejunostomy placement in patients with hiatal hernias. Materials and methods: Four patients, including three (75%) females and one (25%) male, with mean age of 77.5 years (range 73–78 years), and with a hiatal hernia and intrathoracic stomach precluding gastrostomy placement and loop snare placement into the mid-jejunum underwent the transnasal stent-assisted targeting technique for percutaneous jejunostomy placement. In all patients, a duodenal stent was inserted into the jejunum in a transnasal fashion. The stent was partially unsheathed in an anterior loop of jejunum and percutaneously targeted using an 18-gauge needle through which a guidewire was advanced, trapped within the stent, and removed through the nose. The tract was serially dilated and a jejunostomy was placed. Technical success, procedure time, fluoroscopy time, radiation exposure, complications, time to enteral feeding, and follow-up were recorded. Results: Technical success was 100% (4/4) with all four patients requiring only one needle pass before successful jejunal cannulation. Mean procedure time was 108 min. Mean fluoroscopy time was 44 min. Mean dose area product was 3969.3 μGym{sup 2}. No minor or major complications occurred. All four patients received enteral feeding one day after the procedure. Mean follow-up was 366 days. Conclusion: The transnasal stent-assisted targeting technique is a novel method for primary jejunostomy placement in patients with hiatal hernias.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Extended abdominopelvic MRI versus CT at the time of adnexal mass characterization for assessing radiologic peritoneal cancer index (PCI) prior to cytoreductive surgery

Purpose: To evaluate whether extending the MRI scan to include the abdomen at the time of adnexal mass characterization could replace additional CT for peritoneal cancer index (PCI) assessment. Methods: After institutional review board approval for this prospective study, 36 consecutive females with ovarian and FT malignancies were included. All patients signed an informed consent. Patients underwent preoperative CT (32 patients) and MRI (36 patients). Images were interpreted by 2 independent observers. Surgical data were available in 27 patients. Region-by-region analysis was performed for detection rates of peritoneal carcinomatosis (PC). Inter-observer agreement for each region was evaluated by kappa statistics. Radiologic PCI was calculated by CT and MRI independently and inter-observer agreement for CT and MRI as well as agreement between radiologic and surgical PCI were evaluated by weighted-kappa statistics. Results: On region-by-region analysis, the highest detection rates of PC were noted at the central abdomen and pelvis. Detection rates were higher by MRI than CT, mainly in bowel serosal surface, pelvis, and right upper abdomen regions. Inter-observer agreement of MRI was higher than CT in most regions. The median PCI by CT was 5 and 4 for the first and second observers (range 0–21 for both observers), respectively. The median PCI by MRI was 6 (range 0–23 for both observers). The inter-observer agreement of PCI was excellent by both CT and MRI (k = 0.876 and k = 0.912, respectively). The agreement between CT and surgical PCI was 0.660 and 0.590 for the first and second observers, respectively. The agreement between MRI and surgical PCI was 0.797 and 0.798 for the first and second observers, respectively. Conclusions: Extending MRI scan to include the abdomen at the time of adnexal mass characterization allows accurate estimation of PC, with better results than CT, obviating the need for dedicated CT scan of abdomen and pelvis for imaging of PC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

CT and MRI features of undifferentiated carcinomas with osteoclast-like giant cells of the pancreas: a case series

Purpose: The purpose of this case series was to describe computed tomography (CT) and magnetic resonance imaging (MRI) features of undifferentiated carcinoma with osteoclast-like giant cells of the pancreas. Methods: Institutional ethics review board approval was obtained, and informed consent was waived for this case series. We reviewed CT and MRI of patients with pathologically confirmed undifferentiated carcinoma with osteoclast-like giant cells of the pancreas found in the medical records of our hospital between 2006 and 2016. Results: Seven patients (3 males and 4 females; age, 59–82 years (mean, 71)) with confirmation by surgical resection (n = 3) or biopsy (n = 4) were identified. They underwent CT (n = 7) and MRI (n = 6). The tumors 26–83 mm in diameter (mean, 44 mm) were located in the head (n = 4) or body (n = 3) of the pancreas. They were demonstrated as lower attenuation areas relative to the adjacent pancreas on CT images obtained in both pancreatic and portal vein phases (n = 7) with a well-defined smooth margin (n = 5). They were demonstrated as hypointense areas relative to the pancreas on T2-weighted images (n = 4) and T2*-weighted images (n = 4) and diffusion-weighted images (n = 3). They contained hemosiderin deposits on histology (n = 7). Conclusions: Undifferentiated carcinoma with osteoclast-like giant cells of the pancreas might be present as low attenuation areas with a well-defined smooth margin on CT images obtained in pancreatic and portal vein phases, and hypointense areas on T2-, T2*-, and diffusion-weighted images caused by hemosiderin deposits.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Comparison of navigator-gated and breath-held image acquisition techniques for multi-echo quantitative dixon imaging of the liver in children and young adults

Purpose: Acquired over a breath hold, multi-echo Dixon (mDixon) magnetic resonance imaging (MRI) of the liver can be used to quantify proton density fat fraction (PDFF) and iron-related signal decay. However, young, obese, and co-morbid patients may have limited breath holding capacity and could benefit from a motion-robust mDixon acquisition. The purpose of this study was to compare hepatic PDFF and R2* values between navigator-gated and breath-held mDixon MRI acquisition techniques in children and young adults with suspected liver disease. Materials and methods: This retrospective study was institutional review board-approved with a waiver of informed consent. Patients who underwent liver MRI with breath-held and navigator-gated mDixon sequences between January 2017 and July 2018 were included. One reviewer, blinded to sequence, measured PDFF and R2* on four images from each sequence. Another blinded reviewer graded respiratory motion (5-point Likert scale). Pearson correlation (r), Lin’s concordance coefficients (r{sub c}), and Bland–Altman analyses were used to assess agreement between techniques. Frequency of clinically limiting motion (score ≥ 3) was compared with Fisher’s exact test. Results: Forty-two patients were included (15 female, 27 male; mean age: 15.7 ± 4.6 years). Mean PDFF and R2* were 16.6 ± 13.1% and 29.3 ± 4.7 s{sup −1} (breath-held) versus 17.0 ± 13.2% and 29.6 ± 5.2 s{sup −1} (navigator-gated). PDFF agreed almost perfectly between sequences (r{sub c} = 0.997, 95% CI 0.994–0.998; mean bias: 0.3%; 95% limits of agreement: − 2.4 to +1.7%), while R2* values correlated very strongly but with poor agreement (r = 0.837, r{sub c} = 0.832, 95% CI 0.716–0.910). Navigator-gated images exhibited significantly higher frequency of clinically limiting respiratory motion (88% vs. 48%, p = 0.0001). Conclusion: Despite greater respiratory motion artifact, a free-breathing navigator-gated mDixon sequence produces PDFF values with almost perfect agreement to a breath-held sequence.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Interobserver agreement of computed tomography reporting standards for chronic pancreatitis

Aim: To assess the interobserver agreement of computed tomography (CT) reporting standards for chronic pancreatitis (CP). Subjects and methods: Retrospective analysis of CT of 47 patients (33 males and 11 females, age range 36 to 56 years) with CP who presented with abdominal pain (n = 41), steatorrhea (n = 37), and glucose intolerance (n = 31). The patients underwent CT study using a 16-multidetector CT scanner with a pancreatic protocol including a nonenhanced scan followed by pancreatic phase at 35 s and portal venous phase at 65 s after intravenous injection of nonionic contrast medium. Image analysis was performed by two radiologists according to reporting standards for CP. Results: There was excellent interobserver agreement (84.8 %) between the two reviewers in CT reporting standards for CP (K = 0.80, 95 % CI 0.75–0.85, P = 0.001). There was good interobserver agreement for pancreatic duct (PD) caliber (K = 0.71, 95 % CI 0.56–0.87, P = 0.001), PD contour (K = 0.76, 95 % CI 0.61–0.91, P = 0.001), PD stricture (K = 0.070, 95 % CI 0.53–0.88, P = 0.001), and distribution of findings (K = 0.69, 95 % CI 0.51–0.86, P = 0.001). There was excellent interobserver agreement for intraductal calculi (K = 0.84, 95 % CI 0.68–0.98, P = 0.001), pancreatic calcifications (K = 0.86, 95 % CI 0.84–0.98, P = 0.001), and pancreatic diameter (K = 0.87, 95 % CI 0.75–0.99, P = 0.001). Conclusion: CT reporting standards for CP is a reliable method for diagnosis of patients with CP.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Diffusion-weighted imaging as a part of PET/MR for small lesion detection in patients with primary abdominal and pelvic cancer, with or without TOF reconstruction technique

Objectives: To investigate the value of diffusion-weighted imaging (DWI) in detection of small lesions (≤ 10 mm) in patients with primary abdominal and pelvic cancer in hybrid PET/MR with or without time-of-flight (TOF) technique. Materials and methods: Twenty patients (11 females and 9 males, mean age 67.23 ± 12.90 years) with histologically confirmed primary abdominal and pelvic cancer underwent hybrid PET/MR examination. A total of 64 small lesions were included in this study, which were divided into two groups (≤ 10 mm and 10–30 mm). Visual scores of small lesion detection ability were rated by five-point ordinal scale. The visual scores and detectability of small lesions on TOF PET image, noTOF PET image, and DWI sequences of hybrid PET/MR examination with or without TOF technique were analyzed. Logistic regression model was established for analysis in the value of DWI in hybrid PET/MR examination with or without TOF technique in detection of the small lesions between two groups. Results: The visual evaluation revealed the small lesion (≤ 10 mm) visual scores of DWI (mean ± SD: 4.23 ± 1.41), TOF PET image (mean ± SD: 4.14 ± 0.89), and noTOF PET image (mean ± SD: 2.68 ± 1.13);.and the visual scores of small lesions (10–30 mm) on DWI (mean ± SD: 4.98 ± 0.15), TOF PET image (mean ± SD: 4.57 ± 0.59), and noTOF PET image (mean ± SD: 3.98 ± 1.05). The visual scores of all small lesions on DWI were higher than that on TOF PET data and noTOF PET data in both two groups (**P < 0.01). The missed diagnosis rates of small FDG avid lesions (≤ 10 mm) of DWI and noTOF PET image were 9.1% and 9.1%, respectively. However, the TOF PET-based clinical diagnosis detected all small lesions (≤ 30 mm). DWI was of great importance in detection of small lesions (≤ 10 mm) in the absence of TOF technique in PET/MR examination (**P < 0.01). DWI’s effect on detection of small lesions(10-30 mm) has shown no difference between PET/MR examinations with TOF and without TOF techniques (P > 0.05). Conclusion: DWI has significant value in the detection of small lesions (≤ 10 mm) in hybrid PET/MR examination without TOF technique for patients with primary abdominal and pelvic cancer. However, it had less detection benefits in the small lesions (≤ 10 mm) in hybrid PET/MR examination with TOF PET image.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

110 Patients with adenosquamous carcinomas of the pancreas (PASC): imaging differentiation of small (≤ 3 cm) versus large (> 3 cm) tumors

Objective: This study examined radiological imaging features of small (≤ 3 cm) and large (> 3 cm) adenosquamous carcinomas of the pancreas (PASC) lesions to better understand the morphology of these lesions. Methods: Images from 110 patients with pathologically proven PASC (80 males and 30 females, mean age: 62.6 years) were retrospectively reviewed. Two radiologists analyzed images and reached a consensus regarding the following features: location, shape, margins, presence of solid and necrotic components, rim enhancement, density/intensity during the portal venous phase, invasion of surrounding organs, vascular invasion, venous tumor thrombus formation, and enlarged lymph nodes. Differences in the imaging features between the two groups were evaluated with the Chi-square test or Fisher’s exact test. Results: There were 41 small PASC lesions (mean age: 60.59 years) and 69 large PASC lesions (63.74 years). Statistical analysis demonstrated significant differences in the location, shape, adjacent organ and vessel invasion, and venous tumor thrombus formation (P < 0.05). Small PASC lesions were more frequently detected in the pancreatic head and had an ovoid shape. There was no significant difference in the presence of solid and necrotic components (P = 0.090), including approximately 3/4 of the lesions with necrosis and 1/4 purely solid lesions, enlarged lymph nodes (P = 0.068) and other features. Conclusion: Regardless of the tumor size, 75% of PASC lesions present with central necrosis while 25% are purely solid. Small PASC lesions can be associated with lymph node metastasis at a relatively early stage. Large PASC lesions are likely to invade adjacent tissues and be associated with venous tumor thrombus formation.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Evaluation of diffusion kurtosis and diffusivity from baseline staging MRI as predictive biomarkers for response to neoadjuvant chemoradiation in locally advanced rectal cancer

Purpose: To evaluate the role of diffusion kurtosis and diffusivity as potential imaging biomarkers to predict response to neoadjuvant chemoradiation therapy (CRT) from baseline staging magnetic resonance imaging (MRI) in locally advanced rectal cancer (LARC). Materials and methods: This retrospective study included 45 consecutive patients (31 male/14 female) who underwent baseline MRI with high b-value sequences (up to 1500 mm/s{sup 2}) for LARC followed by neoadjuvant chemoradiation and surgical resection. The mean age was 57.4 years (range 34.2–72.9). An abdominal radiologist using open source software manually segmented T2-weighted images. Segmentations were used to derive diffusion kurtosis and diffusivity from diffusion-weighted images as well as volumetric data. These data were analyzed with regard to tumor regression grade (TRG) using the four-tier American Joint Committee on Cancer (AJCC) classification, TRG 0–3. Proportional odds regression was used to analyze the four-level ordinal outcome. A sensitivity analysis was performed using univariable logistic regression for binary TRG groups, TRG 0/1 (> 90% response), or TRG 2/3 (< 90% response). p < 0.05 was considered significant throughout. Results: In the univariable proportional odds regression analysis, higher diffusivity summary (D{sub sum}) values were observed to be significantly associated with higher odds of being in one or more favorable TRG group (TRG 0 or 1). In other words, on average, patients with higher D{sub sum} values were more likely to be in a more favorable TRG group. These results are mostly consistent with the sensitivity analysis, in which higher values for most D{sub sum} values [all but region of interest (ROI)-max D median (p = 0.08)] were observed to be significantly associated with higher odds of being TRG 0 or 1. Tumor volume of interest (VOI) and ROI volume, ROI kurtosis mean and median, and VOI kurtosis mean and median were not significantly associated with TRG. Conclusion: Diffusivity derived from the baseline staging MRI, but not diffusion kurtosis or volumetric data, is associated with TRG and therefore shows promise as a potential imaging biomarker to predict the response to neoadjuvant chemotherapy in LARC. Clinical relevance statement: Diffusivity shows promise as a potential imaging biomarker to predict AJCC TRG following neoadjuvant CRT, which has implications for risk stratification. Patients with TRG 0/1 have 5-year disease-free survival (DFS) of 90–98%, as opposed to those who are TRG 2/3 with 5-year DFS of 68–73%.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Measurement of spleen fat on MRI-proton density fat fraction arises from reconstruction of noise

Purpose: This study compares splenic proton density fat fraction (PDFF) measured using confounder-corrected chemical shift-encoded (CSE)-MRI to magnetic resonance spectroscopy (MRS) in human patients at 3T. Methods: This was a prospectively designed ancillary study to various previously described single-center studies performed in adults and children with known or suspected nonalcoholic fatty liver disease. Patients underwent magnitude-based MRI (MRI-M), complex-based MRI (MRI-C), high signal-to-noise variants (Hi-SNR MRI-M and Hi-SNR MRI-C), and MRS at 3T for spleen PDFF estimation. PDFF from CSE-MRI methods were compared to MRS-PDFF using Wilcoxon signed-rank tests. Demographics were summarized descriptively. Spearman’s rank correlations were computed pairwise between CSE-MRI methods. Individual patient measurements were plotted for qualitative assessment. A significance level of 0.05 was used. Results: Forty-seven patients (20 female, 27 male) including 12 adults (median 55 years old) and 35 children (median 12 years old). Median PDFF estimated by MRS, MRI-M, Hi-SNR MRI-M, MRI-C, and Hi-SNR MRI-C was 1.0, 2.3, 1.9, 2.2, and 2.0%. The four CSE-MRI methods estimated statistically significant higher spleen PDFF values compared to MRS (p < 0.0001 for all). Pairwise associations in spleen PDFF values measured by different CSE-MRI methods were weak, with the highest Spearman’s rank correlations being 0.295 between MRI-M and Hi-SNR MRI-M; none were significant after correction for multiple comparisons. No qualitative relationship was observed between PDFF measurements among the various methods. Conclusion: Overestimation of PDFF by CSE-MRI compared to MRS and poor agreement between related CSE-MRI methods suggest that non-zero PDFF values in human spleen are artifactual.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Hybrid Repair of Complex Thoracic Aortic Arch Pathology: Long-Term Outcomes of Extra-anatomic Bypass Grafting of the Supra-aortic Trunk

Hybrid repair constitutes supra-aortic debranching before thoracic endovascular aortic repair (TEVAR). It offers improved short-term outcome compared with open surgery; however, longer-term studies are required to assess patient outcomes and patency of the extra-anatomic bypass grafts. A prospectively maintained database of 380 elective and urgent patients who had undergone TEVAR (1997-2011) was analyzed retrospectively. Fifty-one patients (34 males; 17 females) underwent hybrid repair. Median age was 71 (range, 18-90) years with mean follow-up of 15 (range, 0-61) months. Perioperative complications included death: 10 % (5/51), stroke: 12 % (6/51), paraplegia: 6 % (3/51), endoleak: 16 % (8/51), rupture: 4 % (2/51), upper-limb ischemia: 2 % (1/51), bypass graft occlusion: 4 % (2/51), and cardiopulmonary complications in 14 % (7/51). Three patients (6 %) required emergency intervention for retrograde dissection: (2 aortic root repairs; 2 innominate stents). Early reintervention was performed for type 1 endoleak in two patients (2 proximal cuff extensions). One patient underwent innominate stenting and revision of their bypass for symptomatic restenosis. At 48 months, survival was 73 %. Endoleak was detected in three (6 %) patients (type 1 = 2; type 2 = 1) requiring debranching with proximal stent graft (n = 2) and proximal extension cuff (n = 1). One patient had a fatal rupture of a mycotic aneurysm and two arch aneurysms expanded. No bypass graft occluded after the perioperative period. Hybrid operations to treat aortic arch disease can be performed with results comparable to open surgery. The longer-term outcomes demonstrate low rates of reintervention and high rates of graft patency.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Radiofrequency Ablation of Large Renal Angiomyolipoma: Median-Term Follow-Up

Purpose. To study the feasibility of percutaneous radiofrequency ablation (RFA) of large angiomyolipomas (AMLs) using saline-cooled electrodes. Materials and Methods. Institutional Review Board approval for the study was received. Four patients (all female, age range 33-67 years) with large AMLs (maximal axis 6.1-32.4 cm) not suitable for embolotherapy or surgery consented to a trial of RFA. Procedures were performed under computerized tomographic guidance using 14G saline-infused electrodes. Two ablations (diameter 4-7 cm) were undertaken in each patient. Variables studied were technical success, treatment safety, alteration of tumor consistency, tumor size, effect on renal function, and medium-term freedom from haemorrhage. Results. All four patients underwent successful RFA without any intraprocedural complications. There has been no haemorrhage, or new renal specific symptom, during a minimum 48-month period, and normal renal function has been normal. On follow-up radiological imaging, the tumors have become fattier with involution of the soft-tissue elements (soft tissue-to-total tumor ratio decreased mean [range] of 0.26 [0.14-0.48] to 0.17 [0.04-0.34] U; p = 0.04 [paired Student t test]). Further evidence of treatment effect was the development of a capsule around the ablation zone, but there was no change in overall tumor volume (mean [range] 1,120 [118-2,845] to 1150 [90-3,013] ml; p = 1 [paired Student t test]). Conclusion. RFA of large AMLs is technically feasible using saline-infused electrodes. The soft-tissue elements decreased in volume; the tumors become fattier; and there has been no renal haemorrhage during a 48-month period.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Temporary Arterial Balloon Occlusion as an Adjunct to Yttrium-90 Radioembolization

Purpose. This study was designed to describe the technique of arterial occlusion using a temporary occlusion balloon system as an alternative to coil occlusion during Yttrium-90 radioembolization of hepatic tumors. Methods. Review of charts, angiography, and follow-up imaging studies of consecutive patients undergoing oncological embolization procedures in which a HyperForm system (ev3 Neurovascular, Irvine, CA) was used. Intraprocedural target vessel occlusion and patency of the target vessel on follow-up were recorded. Clinical data and Bremsstrahlung scans were reviewed for evidence of nontarget embolization. Results. Four radioembolization procedures were performed in three patients (all female, age 48-54 (mean 52) years). Five arteries were temporarily occluded (three gastroduodenal arteries, one right gastric artery, and one cystic artery). All radioembolization procedures were successfully completed. Follow-up imaging (either digital subtraction angiography (DSA) or computed tomography angiography (CTA)) was available for all patients between 28-454 (mean 183) days following the procedure, demonstrating all five vessels to be patent. No clinical or imaging evidence for nontarget embolization was found. Conclusions. Temporary balloon occlusion of small and medium-sized arteries during radioembolization allows safe therapy with preserved postprocedural vessel patency on early and midterm follow-up.

62 RADIOLOGY AND NUCLEAR MEDICINE↗