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DOE OSTI2022

Pore-scale observations of natural hydrate-bearing sediments via pressure core sub-coring and micro-CT scanning

Abstract Both intra-pore hydrate morphology and inter-pore hydrate distribution influence the physical properties of hydrate-bearing sediments, yet there has been no pore-scale observations of hydrate habit under pressure in preserved pressure core samples so far. We present for the first time a pore-scale micro-CT study of natural hydrate-bearing cores that were acquired from Green Canyon Block 955 in UT-GOM2-1 Expedition and preserved within hydrate pressure–temperature stability conditions throughout sub-sampling and imaging processes. Measured hydrate saturation in the sub-samples, taken from units expected to have in-situ saturation of 80% or more, ranges from 3 ± 1% to 56 ± 11% as interpreted from micro-CT images. Pore-scale observations of gas hydrate in the sub-samples suggest that hydrate in silty sediments at the Gulf of Mexico is pore-invasive rather than particle displacive, and hydrate particles in these natural water-saturated samples are pore-filling with no evidence of grain-coating. Hydrate can form a connected 3D network and provide mechanical support for the sediments even without cementation. The technical breakthrough to directly visualize particle-level hydrate pore habits in natural sediments reported here sheds light on future investigations of pressure- and temperature-sensitive processes including hydrate-bearing sediments, dissolved gases, and other biochemical processes in the deep-sea environment.

58 GEOSCIENCES↗

DOE OSTI2015

Renal Sympathetic Denervation by CT-scan-Guided Periarterial Ethanol Injection in Sheep

BackgroundRenal nerves are a recent target in the treatment of hypertension. Renal sympathetic denervation (RSD) is currently performed using catheter-based radiofrequency ablation (RFA) and because this method has limitations, percutaneous magnetic resonance (MR)-guided periarterial ethanol injection is a suggested alternative. However, few studies have been conducted on the effectiveness of percutaneous ethanol injection for RSD.AimTo evaluate the feasibility, efficacy, and complications of computed tomography (CT)-guided periarterial ethanol injection.MethodsEthanol (10 ml, 99.6 %) was injected around the right renal artery in six sheep under CT guidance with the left kidney serving as a control. Before and after the intervention, the sheep underwent MR imaging studies and the serum creatinine level was measured. One month after the intervention, the sheep were euthanized and norepinephrine (NE) concentration in the renal parenchyma was measured to evaluate the efficacy of the procedure. The treated tissues were also examined histopathologically to evaluate vascular, parenchymal, and neural injury.ResultsThe right kidney parenchymal NE concentration decreased significantly compared with the left kidney after intervention (average reduction: 40 %, P = 0.0016). Histologic examination revealed apparent denervation with no other vascular or parenchymal injuries observed in the histological and imaging studies.ConclusionEffective and feasible RSD was achieved using CT-guided periarterial ethanol injection. This technique may be a potential alternative to catheter-based RFA in the treatment of hypertension.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2016

SU-G-JeP3-15: Is the Reproducibility with Respect to Bone of Tumor Position at Simulation for Breath Hold CT Scans Correlated to the Reproducibility for Multiple Breath Hold CBCTs at Treatment in SBRT Thoracic Patients?

Purpose: To evaluate correlation between the reproducibility of tumor position under feedback guided voluntary deep inspiration breath hold gating at simulation and at treatment. Methods: All patients treated with breath hold (BH) have 3-6 BH CTs taken at simulation (sim). In addition, if the relationship between the tumor and nearby bony anatomy on treatment BH CT(or CBCT) is found to be greater than 5 mm different at treatment than it was at sim, a repeat BH CT is taken before treatment. We retrospectively analyzed the sim CTs for 19 patients who received BH SBRT lung treatments and had repeat BH CT on treatment. We evaluated the reproducibility of the tumor position during the simulation CTs and compared this to the reproducibility of the tumor position on the repeat treatment CT with our in-house CT alignment software (CT-Assisted Targeting for Radiotherapy). Results: Comparing the tumor position for multiple simulation BH CTs, we calculated: maximum difference (max) = 0.69cm; average difference (x) = 0.28cm; standard deviation (σ) = 0.18cm. Comparing the repeat BH CBCTs on treatment days we calculated: max = 0.44cm; x = 0.16cm; σ = 0.22cm. We also found that for 95% of our BH cases, the absolute variation in tumor position within the same imaging day was within 5mm of the range at the time of simulation and treatment. We found that 75% of the BH cases had less residual tumor motion on treatment days than at simulation. Conclusion: This suggests that a GTV contour based upon the residual tumor motion in multiple BH datasets plus 2 mm margin should be sufficient to cover the full range of residual tumor motion on treatment days.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2025

CT Scans of Cores Metadata, Utqiagvik (Barrow), Alaska, 2015

Individual ice cores were collected from Barrow Environmental Observatory in Barrow, Alaska, throughout 2013 and 2014. Cores were drilled along different transects to sample polygonal features (i.e. the trough, center and rim of high, transitional and low center polygons). Most cores were drilled around 1 meter in depth and a few deep cores were drilled around 3 meters in depth. Three-dimensional images of the frozen cores were constructed using a medical X-ray computed tomography (CT) scanner. TIFF files can be uploaded to ImageJ (an open-source imaging software) to examine soil structure and soil densities within each core.The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a 15-year research effort (2012-2027) to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research.The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska.Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2014

SU-E-T-117: Dose to Organs Outside of CT Scan Range- Monte Carlo and Hybrid Phantom Approach

Purpose: Epidemiological study of second cancer risk for cancer survivors often requires the dose to normal tissues located outside the anatomy covered by radiological imaging, which is usually limited to tumor and organs at risk. We have investigated the feasibility of using whole body computational human phantoms for estimating out-of-field organ doses for patients treated by Intensity Modulated Radiation Therapy (IMRT). Methods: Identical 7-field IMRT prostate plans were performed using X-ray Voxel Monte Carlo (XVMC), a radiotherapy-specific Monte Carlo transport code, on the computed tomography (CT) images of the torso of an adult male patient (175 cm height, 66 kg weight) and an adult male hybrid computational phantom with the equivalent body size. Dose to the liver, right lung, and left lung were calculated and compared. Results: Considerable differences are seen between the doses calculated by XVMC for the patient CT and the hybrid phantom. One major contributing factor is the treatment method, deep inspiration breath hold (DIBH), used for this patient. This leads to significant differences in the organ position relative to the treatment isocenter. The transverse distances from the treatment isocenter to the inferior border of the liver, left lung, and right lung are 19.5cm, 29.5cm, and 30.0cm, respectively for the patient CT, compared with 24.3cm, 36.6cm, and 39.1cm, respectively, for the hybrid phantom. When corrected for the distance, the mean doses calculated using the hybrid phantom are within 28% of those calculated using the patient CT. Conclusion: This study showed that mean dose to the organs located in the missing CT coverage can be reconstructed by using whole body computational human phantoms within reasonable dosimetric uncertainty, however appropriate corrections may be necessary if the patient is treated with a technique that will significantly deform the size or location of the organs relative to the hybrid phantom.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2019

Prevalence and variability in reporting of clinically actionable incidental findings on attenuation-correction CT scans in a veteran population

Background: Myocardial perfusion imaging (MPI) often employs attenuation-correction computed tomography (CTAC) to reduce attenuation artifacts and improve specificity. While there is no specific guideline on how they should be reported, incidental noncardiac findings identified on these scans may be clinically significant. The prevalence of these findings in veterans is not currently known. In addition, variability in reporting these findings may depend on the interpreting physician’s specialty. Methods: To guide future decision-making, CTACs in veterans referred for MPI were prospectively evaluated in a quality-control project for a set of prespecified actionable incidental findings by cardiologists and a radiologist. Results: On the 771 scans performed over eight months, 285 incidental noncardiac findings were identified by the interpreting cardiologists and 378 were identified by the interpreting radiologist. Pulmonary nodules were the most common occurring in 20% of studies read by the radiologist. Interreader agreements between cardiologists and the radiologist were poor for pulmonary nodules ≥ 10 mm and hiatal hernias; fair for pulmonary nodules < 10 mm, extracardiac masses, and aortic aneurysms; and moderate for pleural plaques. Conclusion: Incidental noncardiac findings on CTACs are common in our veteran population. Overall interobserver agreement in identifying these findings between cardiologists and radiologists is fair. Specific guidelines are needed on how CTACs should be read and reported.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2017

CT scanning and flow measurements of shale fractures after multiple shearing events

A shearing apparatus was used in conjunction with a Hassler-style core holder to incrementally shear fractured shale cores while maintaining various confining pressures. Computed tomography scans were performed after each shearing event, and were used to obtain information on evolving fracture geometry. Fracture transmissivity was measured after each shearing event to understand the hydrodynamic response to the evolving fracture structure. The digital fracture volumes were used to perform laminar single phase flow simulations (local cubic law with a tapered plate correction model) to qualitatively examine small scale flow path variations within the altered fractures. Fractures were found to generally increase in aperture after several shear slip events, with corresponding transmissivity increases. Lower confining pressure resulted in a fracture more prone to episodic mechanical failure and sudden changes in transmissivity. Conversely, higher confining pressures resulted in a system where, after an initial setting of the fracture surfaces, changes to the fracture geometry and transmissivity occurred gradually. Flow paths within the fractures are largely controlled by the location and evolution of zero aperture locations. Lastly, a reduction in the number of primary flow pathways through the fracture, and an increase in their width, was observed during all shearing tests.

04 OIL SHALES AND TAR SANDS↗

DOE OSTI2013

Dose equations for tube current modulation in CT scanning and the interpretation of the associated CTDI{sub vol}

Purpose: The scanner-reported CTDI{sub vol} for automatic tube current modulation (TCM) has a different physical meaning from the traditional CTDI{sub vol} at constant mA, resulting in the dichotomy “CTDI{sub vol} of the first and second kinds” for which a physical interpretation is sought in hopes of establishing some commonality between the two.Methods: Rigorous equations are derived to describe the accumulated dose distributions for TCM. A comparison with formulae for scanner-reported CTDI{sub vol} clearly identifies the source of their differences. Graphical dose simulations are also provided for a variety of TCM tube current distributions (including constant mA), all having the same scanner-reported CTDI{sub vol}.Results: These convolution equations and simulations show that the local dose at z depends only weakly on the local tube current i(z) due to the strong influence of scatter from all other locations along z, and that the “local CTDI{sub vol}(z)” does not represent a local dose but rather only a relative i(z) ≡ mA(z). TCM is a shift-variant technique to which the CTDI-paradigm does not apply and its application to TCM leads to a CTDI{sub vol} of the second kind which lacks relevance.Conclusions: While the traditional CTDI{sub vol} at constant mA conveys useful information (the peak dose at the center of the scan length), CTDI{sub vol} of the second kind conveys no useful information about the associated TCM dose distribution it purportedly represents and its physical interpretation remains elusive. On the other hand, the total energy absorbed E (“integral dose”) as well as its surrogate DLP remain robust between variable i(z) TCM and constant current i{sub 0} techniques, both depending only on the total mAs = t{sub 0}=i{sub 0} t{sub 0} during the beam-on time t{sub 0}.

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2015

Noninvasive differential diagnosis of dental periapical lesions in cone-beam CT scans

Purpose: This paper proposes a novel application of computer-aided diagnosis (CAD) to an everyday clinical dental challenge: the noninvasive differential diagnosis of periapical lesions between periapical cysts and granulomas. A histological biopsy is the most reliable method currently available for this differential diagnosis; however, this invasive procedure prevents the lesions from healing noninvasively despite a report that they may heal without surgical treatment. A CAD using cone-beam computed tomography (CBCT) offers an alternative noninvasive diagnostic tool which helps to avoid potentially unnecessary surgery and to investigate the unknown healing process and rate for the lesions. Methods: The proposed semiautomatic solution combines graph-based random walks segmentation with machine learning-based boosted classifiers and offers a robust clinical tool with minimal user interaction. As part of this CAD framework, the authors provide two novel technical contributions: (1) probabilistic extension of the random walks segmentation with likelihood ratio test and (2) LDA-AdaBoost: a new integration of weighted linear discriminant analysis to AdaBoost. Results: A dataset of 28 CBCT scans is used to validate the approach and compare it with other popular segmentation and classification methods. The results show the effectiveness of the proposed method with 94.1% correct classification rate and an improvement of the performance by comparison with the Simon’s state-of-the-art method by 17.6%. The authors also compare classification performances with two independent ground-truth sets from the histopathology and CBCT diagnoses provided by endodontic experts. Conclusions: Experimental results of the authors show that the proposed CAD system behaves in clearer agreement with the CBCT ground-truth than with histopathology, supporting the Simon’s conjecture that CBCT diagnosis can be as accurate as histopathology for differentiating the periapical lesions.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2026