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All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Contouring and Constraining Bowel on a Full-Bladder Computed Tomography Scan May Not Reflect Treatment Bowel Position and Dose Certainty in Gynecologic External Beam Radiation Therapy

Purpose: To evaluate, in a gynecologic cancer setting, changes in bowel position, dose-volume parameters, and biological indices that arise between full-bladder (FB) and empty-bladder (EB) treatment situations; and to evaluate, using cone beam computed tomography (CT), the validity of FB treatment presumption. Methods and Materials: Seventeen gynecologic cancer patients were retrospectively analyzed. Empty-bladder and FB CTs were obtained. Full-bladder CTs were used for planning and dose optimization. Patients were given FB instructions for treatment. For the study purpose, bowel was contoured on the EB CTs for all patients. Bowel position and volume changes between FB and EB states were determined. Full-bladder plans were applied on EB CTs for determining bowel dose-volume changes in EB state. Biological indices (generalized equivalent uniform dose and normal tissue complication probability) were calculated and compared between FB and EB. Weekly cone beam CT data were available in 6 patients to assess bladder volume at treatment. Results: Average (±SD) planned bladder volume was 299.7 ± 68.5 cm{sup 3}. Median bowel shift in the craniocaudal direction between FB and EB was 12.5 mm (range, 3-30 mm), and corresponding increase in exposed bowel volume was 151.3 cm{sup 3} (range, 74.3-251.4 cm{sup 3}). Absolute bowel volumes receiving 45 Gy were higher for EB compared with FB (mean 328.0 ± 174.8 vs 176.0 ± 87.5 cm{sup 3}; P=.0038). Bowel normal tissue complication probability increased 1.5× to 23.5× when FB planned treatments were applied in the EB state. For the study, the mean percentage value of relative bladder volume at treatment was 32%. Conclusions: Full-bladder planning does not necessarily translate into FB treatments, with a patient tendency toward EB. Given the uncertainty in daily control over bladder volume for treatment, we strongly recommend a “planning-at-risk volume bowel” (PRV{sub B}owel) concept to account for bowel motion between FB and EB that can be tailored for the individual patient.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

TU-A-BRD-01: Outcomes of Hypofractionated Treatments - Initial Results of the WGSBRT

Stereotactic Body Radiation Therapy (SBRT) has emerged in recent decades as a treatment paradigm that is becoming increasingly important in clinical practice. Clinical outcomes data are rapidly accumulating. Although published relations between outcomes and dose distributions are still sparse, the field has progressed to the point where evidence-based normal tissue dose-volume constraints, prescription strategies, and Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) models can be developed. The Working Group on SBRT (WGSBRT), under the Biological Effects Subcommittee of AAPM, is a group of physicists and physicians working in the area of SBRT. It is currently performing critical literature reviews to extract and synthesize usable data and to develop guidelines and models to aid with safe and effective treatment. The group is investigating clinically relevant findings from SBRT in six anatomical regions: Cranial, Head and Neck, Thoracic, Abdominal, Pelvic, and Spinal. In this session of AAPM 2014, interim results are presented on TCP for lung and liver, NTCP for thoracic organs, and radiobiological foundations:• Lung TCP: Detailed modeling of TCP data from 118 published studies on early stage lung SBRT investigates dose response and hypothesized mechanisms to explain the improved outcomes of SBRT. This is presented from the perspective of a physicist, a physician, and a radiobiologist.• Liver TCP: For primary and metastatic liver tumors, individual patient data were extracted from published reports to examine the effects of biologically effective dose on local control.• Thoracic NTCP: Clinically significant SBRT toxicity of lung, rib / chest wall and other structures are evaluated and compared among published clinical data, in terms of risk, risk factors, and safe practice.• Improving the clinical utility of published toxicity reports from SBRT and Hypofractionated treatments. What do we want, and how do we get it? Methods and problems of synthesizing data from published reports. Learning Objectives: Common SBRT fractionation schemes and current evidence for efficacy. Evidence for normal tissue tolerances in hypofractionated treatments. Clinically relevant radiobiological effects at large fraction sizes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Water Management Strategies for Improved Coalbed Methane Production in the Black Warrior Basin

The modern coalbed methane industry was born in the Black Warrior Basin of Alabama and has to date produced more than 2.6 trillion cubic feet of gas and 1.6 billion barrels of water. The coalbed gas industry in this area is dependent on instream disposal of co-produced water, which ranges from nearly potable sodium-bicarbonate water to hypersaline sodium-chloride water. This study employed diverse analytical methods to characterize water chemistry in light of the regional geologic framework and to evaluate the full range of water management options for the Black Warrior coalbed methane industry. Results reveal strong interrelationships among regional geology, water chemistry, and gas chemistry. Coalbed methane is produced from multiple coal seams in Pennsylvanian-age strata of the Pottsville Coal Interval, in which water chemistry is influenced by a structurally controlled meteoric recharge area along the southeastern margin of the basin. The most important constituents of concern in the produced water include chlorides, ammonia compounds, and organic substances. Regional mapping and statistical analysis indicate that the concentrations of most ionic compounds, metallic substances, and nonmetallic substances correlate with total dissolved solids and chlorides. Gas is effectively produced at pipeline quality, and the only significant impurity is N{sub 2}. Geochemical analysis indicates that the gas is of mixed thermogenic-biogenic origin. Stable isotopic analysis of produced gas and calcite vein fills indicates that widespread late-stage microbial methanogenesis occurred primarily along a CO{sub 2} reduction metabolic pathway. Organic compounds in the produced water appear to have helped sustain microbial communities. Ammonia and ammonium levels increase with total dissolved solids content and appear to have played a role in late-stage microbial methanogenesis and the generation of N{sub 2}. Gas production tends to decline exponentially, whereas water production tends to decline hyperbolically. Hyperbolic decline indicates that water volume is of greatest concern early in the life of a coalbed methane project. Regional mapping indicates that gas production is controlled primarily by the ability to depressurize permeable coal seams that are natively within the steep part of the adsorption isotherm. Water production is greatest within the freshwater intrusion and below thick Cretaceous cover strata and is least in areas of underpressure. Water management strategies include instream disposal, which can be applied effectively in most parts of the basin. Deep disposal may be applicable locally, particularly where high salinity limits the ability to dispose into streams. Artificial wetlands show promise for the management of saline water, especially where the reservoir yield is limited. Beneficial use options include municipal water supply, agricultural use, and industrial use. The water may be of use to an inland shrimp farming industry, which is active around the southwestern coalbed methane fields. The best opportunities for beneficial use are reuse of water by the coalbed methane industry for drilling and hydraulic fracturing. This research has further highlighted opportunities for additional research on treatment efficiency, the origin of nitrogen compounds, organic geochemistry, biogenic gas generation, flow modeling, and computer simulation. Results of this study are being disseminated through a vigorous technology transfer program that includes web resources, numerous presentations to stakeholders, and a variety of technical publications.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2021

Spectral Induced Polarization-Biogeochemical Relationships for Remediation Amendment Monitoring

Geophysical tools such as electrical resistivity (ER) can indirectly monitor subsurface changes in response to remedial injections. These methods exhibit relatively low spatial resolution compared to sediment core characterization but are advantageous due to the ability to collect measurements non-intrusively over time across large volumes of the subsurface. Moreover, along with confirmatory groundwater or core sampling, geophysical methods can be used during active biogeochemical remedies to monitor short-term contaminant transformations and mobility, as well as part of an overall strategy for long-term monitoring of subsurface contaminated sites. The use of alternating current spectral induced polarization (SIP) provides significantly more information than conventional geophysical methods like direct current ER. SIP allows for monitoring changes in both solution and surface conductivity by separation of real and imaginary conductivity, respectively, as well as surface capacitance. In principle, SIP can measure indicators of remedy progression such as precipitation reactions that sequester contaminants, potentially providing a better indication of amendment delivery and reactivity as compared to conventional ER methods. However, multiple processes and material properties have overlapping (interacting) electrical responses across a range of frequencies. Hence, the purpose of this scoping study was to evaluate if SIP can be used to monitor (a) amendment delivery and (b) precipitation and reactivity of amendments under consideration at Hanford. SIP measurements were collected in fully saturated columns packed with sand and Hanford formation sediments containing (a) amendments that were highly conductive with significant capacitance (zero valent iron – ZVI, sulfur modified iron – SMI) and (b) amendments that exhibited low electrical conductivity with a small capacitance (calcite, apatite, bismuth). The sand was a quartz material with homogenous particle size that exhibited a relatively low surface conductivity. It was used as a control for comparison with the sediments from the Hanford Site, which have a greater surface conductivity because of their complex mineralogy and heterogeneous particle size distribution and may have complex interactions with amendments. The amendment mass fraction was varied to represent the different stages and subsurface locations associated with the delivery of a remedy. The primary objective was to identify the solution and solid surface changes associated with the delivery amendments and their secondary reactions within the subsurface. The figure below summarizes results for the amendments tested through this project. The SIP phase shift or imaginary conductivity change for the high conductivity amendments was more than 10 times that of the low conductivity amendments, highlighting the relative ease of detection of ZVI and SMI independent of the background signal from sand or Hanford sediments. The ZVI phase shift and imaginary conductivity changes occur primarily at high frequency (> 100 Hz) whereas SMI changes were at low frequency (0.01 to 10 Hz). SIP signals of SMI also increased over time and the maximum shifted to lower frequencies. The low conductivity amendments (calcite, abiotic and biotic apatite, bismuth subnitrate) exhibited relatively small phase and imaginary conductivity changes when added to sediments. The changes were above minimum detection limits (0.5 mrad for phase shift, 0.03 µS/cm for imaginary conductivity) for the highest concentration except for the commercial bismuth material. The lowest amendment concentration that can be detected is likely sediment specific, as minerals in sediments (clays, magnetite, Fe-oxides) have some capacitance and, therefore, exhibit a variable phase shift.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Evaluation of Uterine Contractility by Magnetic Resonance Imaging in Women Undergoing Embolization of Uterine Fibroids

Purpose: To assess uterine contractility using ultrafast magnetic resonance imaging (cine MRI) before and after uterine fibroid embolization (UFE). Materials and Methods: This is a prospective study of uterine contractility in 26 patients (age 30–41 years) undergoing UFE for symptomatic uterine fibroids. Cine MRI was performed before and 6 months after UFE. Two radiologists evaluated uterine contractility and classified it as absent, ordered, or disordered. Patients were then grouped into three distinct patterns of progression: unchanged contractility (group A), modified contractility (B), and loss of contractility (C). These findings were then confronted with factors that might have interfered with uterine contractility pattern (uterine volume, location of dominant fibroid, fibroid/myometrium index, and fibroid necrosis pattern). Results: Of the 26 patients, 8 (30.7%) had no contractility before the procedure, while 18 (69.2%) exhibited some form of contractility (11 [61%] ordered, 7 [39%] disordered). All 8 patients who had no contractility at baseline exhibited contractility after UFE (5 ordered, 3 disordered). Of the 11 who had ordered contractility at baseline, 9 remained ordered and 2 lost contractility after UFE. Of the 7 with disordered contractility at baseline, 1 remained disordered, 5 progressed to ordered contractility, and 1 lost contractility. Overall, 10 patients (38%) had no change in contractility after UFE (group A), 13 (50%) had a positive change (group B), and 3 (11%) lost contractility (group C). The potential interference factors assessed had no statistically significant effect in any group. Conclusion: In women of reproductive age with symptomatic fibroids, uterine contractility improved significantly after UFE. Level of Evidence: Level 3—non-randomized controlled cohort/follow-up study.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Long-Term Results From the Contura Multilumen Balloon Breast Brachytherapy Catheter Phase 4 Registry Trial

Purpose: To describe the long-term outcomes from a completed, multi-institutional phase 4 registry trial using the Contura multilumen balloon (CMLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer. Methods and Materials: Three hundred forty-two evaluable patients were enrolled by 23 institutions between January 2008 and February 2011. All patients received 34 Gy in 10 fractions, delivered twice daily. Rigorous target coverage and normal tissue dose constraints were observed. Results: The median follow-up time was 36 months (range, 1-54 months). For the entire patient cohort of 342 patients, 10 patients experienced an ipsilateral breast tumor recurrence (IBTR). Eight of these IBTR were classified as true recurrences/marginal miss (TRMM), and 2 were elsewhere failures (EF). Local recurrence-free survival was 97.8% at 3 years. For the entire cohort, 88% of patients had good to excellent overall cosmesis. The overall incidence of infection was 8.5%. Symptomatic seroma was reported in only 4.4% of patients. A separate analysis was performed to determine whether improved outcomes would be observed for patients treated at high-volume centers with extensive brachytherapy experience. Three IBTR were observed in this cohort, only 1 of which was classified as a TRMM. Local recurrence-free survival at high-volume centers was 98.1% at 3 years. Overall cosmetic outcome and toxicity were superior in patients treated at high-volume centers. In these patients, 95% had good to excellent overall cosmesis. Infection was observed in only 2.9% of patients, and symptomatic seroma was reported in only 1.9%. Conclusion: Use of the CMLB for APBI delivery is associated with acceptable long-term local control and toxicity. Local recurrence-free survival was 97.8% at 3 years. Significant (grade 3) toxicity was uncommon, and no grade 4 toxicity was observed. Treatment at high-volume centers was associated with decreased late toxicity.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

SU-E-J-124: 18F-FDG PET Imaging to Improve RT Treatment Outcome for Locally Advanced Lung Cancer

Purpose: To investigate spatial correlation between high uptake regions of pre- and 10-days-post therapy{sup 1} {sup 8}F-FDG PET in recurrent lung cancer and to evaluate the feasibility of dose escalation boosting only regions with high FDG uptake identified on baseline PET. Methods: Nineteen patients with stages II– IV inoperable lung cancer were selected. Volumes of interest (VOI) on pre-therapy FDG-PET were defined using an isocontour at ≥50% of SUVmax. VOI of pre- and post-therapy PET images were correlated for the extent of overlap. A highly optimized IMRT plan to 60 Gy prescribed to PTV defined on the planning CT was designed using clinical dose constraints for the organs at risk. A boost of 18 Gy was prescribed to the VOI defined on baseline PET. A composite plan of the total 78 Gy was compared with the base 60 Gy plan. Increases in dose to the lungs, spinal cord and heart were evaluated. IMRT boost plan was compared with proton RT and SBRT boost plans. Results: Overlap fraction of baseline PET VOI with the VOI on 10 days-post therapy PET was 0.8 (95% CI: 0.7 – 0.9). Using baseline VOI as a boosting volume, dose could be escalated to 78 Gy for 15 patients without compromising the dose constraints. For 4 patients, the dose limiting factors were V20Gy and Dmean for the total lung, and Dmax for the spinal cord. An increase of the dose to OARs correlated significantly with the relative size of the boost volume. Conclusion: VOI defined on baseline 18F-FDG PET by the SUVmax-≥50% isocontour may be a biological target volume for escalated radiation dose. Dose escalation to this volume may provide improved tumor control without breaching predefined dose constraints for OARs. The best treatment outcome may be achieved with proton RT for large targets and with SBRT for small targets.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Hydraulic fracturing experiments at 1500 m depth in a deep mine: Highlights from the kISMET project

In support of the U.S. DOE SubTER Crosscut initiative, we established a field test facility in a deep mine and designed and carried out in situ hydraulic fracturing experiments relevant to enhanced geothermal systems (EGS) in crystalline rock to characterize the stress field, understand the effects of rock fabric on fracturing, and gain experience in monitoring using geophysical methods. The project also included pre- and post-fracturing simulation and analysis, and laboratory measurements and experiments. The kISMET (permeability (k) and Induced Seismicity Management for Energy Technologies) site was established in the West Access Drift of the Sanford Underground Research Facility (SURF) 4757 ft (1450 m) below ground (on the 4850 ft level (4850L)) in phyllite of the Precambrian Poorman Formation. We drilled and continuously cored five near-vertical boreholes in a line on 3 m (10 ft) spacing, deviating the two outermost boreholes slightly to create a five-spot pattern around the test borehole centered in the test volume 40 m below the drift invert (floor) at a total depth of ~1490 m (4890 ft). Laboratory measurements of core from the center test borehole showed P-wave velocity heterogeneity along each core indicating strong, fine-scale (~1 cm or smaller) changes in the mechanical properties of the rock. Field measurements of the stress field by hydraulic fracturing showed that the minimum horizontal stress at the kISMET site averages 21.7 MPa (3146 psi) trending approximately N-S (356 degrees azimuth) and plunging slightly NNW at 12°. The vertical and horizontal maximum stresses are similar in magnitude at 42-44 MPa (6090-6380 psi) for the depths of testing, which averaged approximately 1530 m (5030 ft). Hydraulic fractures were remarkably uniform suggesting core-scale and larger rock fabric did not play a role in controlling fracture orientation. Analytical solutions suggest that the fracture radius of the large fracture (stimulation test) was more than 6 m (20 ft), depending on the unknown amount of leak-off.

Oldenburg, C↗
DOE OSTI2020

Electrolyte-phobic Surface for the Next-Generation Nanostructured Battery Electrodes

Nanostructured electrodes are among the most important candidates rationally designed to enable high capacity battery chemistry. Nanostructures can solve issues such as the volume change and mechanical fragmentations. However, the high surface area they usually possess would decrease the Coulombic efficiencies, since the side chemical reactions scale with surface area. Moreover, electrodes comprised of nanomaterials have significant intakes of liquid electrolytes, which reduces the overall energy density and increases the cost of the battery. Here we present a new strategy of limiting effective surface area by introducing an “electrolyte-phobic surface”. In this study, a porous Si anode functions as a model material to demonstrate this concept. Silicon boasts high theoretical capacity, but experiences large volume change during its lithiation and delithiation processes. Porous Si can address this volume change problem with the buffer effect of its inner pores. However, porous silicon shows low initial Coulombic efficiencies and high irreversible lithium loss, owing to its intrinsic high surface area. In this report, a covalently linked perfluorinated surface coating layer on porous Si particles serves as an electrolyte-phobic protection layer, minimizing the accessible surface area for the electrolytes, decreasing the side reactions between the electrolyte and Si surface, and thus significantly enhancing the initial Coulombic efficiencies, up to ~88% compared to ~60% for the pristine porous silicon. Meanwhile, the electrolyte-phobic protection layer of Si particles keeps the silicon surface compatible with the conventional polyvinylidene fluoride (PVDF) binder, which helps to stabilize the Si electrode for long-term battery cycling.

Qian, Chenxi↗
DOE OSTI2014

SU-E-T-141: Effect of a Single Gold Nanoparticle with Different Sizes Inside a Small Water Phantom

Purpose: This study is to investigate the effects of the gold nanoparticles (GNP), a series of micrometre scale simulations have been constructed with Geant4 to track particles and simulate the effects of those particles as they pass through water phantom. Methods: The simulations were used to calculate the number of secondary electrons which are emitted from the particle tracks and the amount of energy which is deposited in the cell tissue. More electrons means that more water molecules can undergo hydrolysis and create potentially dangerous free radical molecules, therefore breaking up DNA and killing off cells or causing damaging mutations. Results: For the 20nm GNP, all three proton energies saw a small increase of electrons above the control, while the X-rays nearly tripled the number of electrons in the phantom. For the 50 nm GNP, the 3 and 2 MeV protons saw a small increase again, however the 1 MeV protons saw a decrease in electrons, the X-rays saw a large increase of nearly 4 times the number of electrons. For the 110nm GNP, all three proton energies saw a decrease in the total number of electrons in the phantom, while the X-rays saw an increase of 8 times as many electrons. Conclusion: From the range of GNP sizes used, it was found that the X-rays have a larger dose enhancement effect as the GNP size increases, the relation between electron emissions and GNP size was linear. This is because the majority of the dose from the X-rays is delivered to the cell tissue through the initial high energy secondary electrons, any dose lost from the Augerelectrons being trapped inside the GNP volume is small compared to the dose that escapes with the high energy electrons.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Characterization of high level nuclear waste glass samples following extended melter idling

The Savannah River Site Defense Waste Processing Facility (DWPF) melter was recently idled with glass remaining in the melt pool and riser for approximately three months. This situation presented a unique opportunity to collect and analyze glass samples since outages of this duration are uncommon. The objective of this study was to obtain insight into the potential for crystal formation in the glass resulting from an extended idling period. The results will be used to support development of a crystal-tolerant approach for operation of the high-level waste melter at the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Two glass pour stream samples were collected from DWPF when the melter was restarted after idling for three months. The samples did not contain crystallization that was detectible by X-ray diffraction. Electron microscopy identified occasional spinel and noble metal crystals of no practical significance. Occasional platinum particles were observed by microscopy as an artifact of the sample collection method. Reduction/oxidation measurements showed that the pour stream glasses were fully oxidized, which was expected after the extended idling period. Chemical analysis of the pour stream glasses revealed slight differences in the concentrations of some oxides relative to analyses of the melter feed composition prior to the idling period. While these differences may be within the analytical error of the laboratories, the trends indicate that there may have been some amount of volatility associated with some of the glass components, and that there may have been interaction of the glass with the refractory components of the melter. These changes in composition, although small, can be attributed to the idling of the melter for an extended period. The changes in glass composition resulted in a 70-100 °C increase in the predicted spinel liquidus temperature (TL) for the pour stream glass samples relative to the analysis of the melter feed prior to the outage. This indicates that the potential for spinel crystallization increased as a result of idling for an extended period. However, the predicted TL of the pour stream glasses remained 150-200 °C below the mean melt pool temperature of about 1125 °C during the idling period. Given the change in predicted TL over the three month outage, the results indicate that it is important to have a thorough understanding of spinel crystallization within the melter for WTP to operate with a volume percent crystallization constraint. This knowledge will enable process control routines to be developed that avoid bulk crystallization in the melter and allow for recovery from off-normal events. The current WTP crystal-tolerant glass program will develop an improved understanding of spinel crystallization in the WTP melter to allow for operation at maximum waste loading in glass composition systems limited by predictions of spinel crystallization.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Advanced readout methods for superheated emulsion detectors

Superheated emulsions develop visible vapor bubbles when exposed to ionizing radiation. They consist in droplets of a metastable liquid, emulsified in an inert matrix. The formation of a bubble cavity is accompanied by sound waves. Evaporated bubbles also exhibit a lower refractive index, compared to the inert gel matrix. These two physical phenomena have been exploited to count the number of evaporated bubbles and thus measure the interacting radiation flux. Systems based on piezoelectric transducers have been traditionally used to acquire the acoustic (pressure) signals generated by bubble evaporation. Such systems can operate at ambient noise levels exceeding 100 dB; however, they are affected by a significant dead time (>10 ms). An optical readout technique relying on the scattering of light by neutron-induced bubbles has been recently improved in order to minimize measurement dead time and ambient noise sensitivity. Beams of infra-red light from light-emitting diode (LED) sources cross the active area of the detector and are deflected by evaporated bubbles. The scattered light correlates with bubble density. Planar photodiodes are affixed along the detector length in optimized positions, allowing the detection of scattered light from the bubbles and minimizing the detection of direct light from the LEDs. A low-noise signal-conditioning stage has been designed and realized to amplify the current induced in the photodiodes by scattered light and to subtract the background signal due to intrinsic scattering within the detector matrix. The proposed amplification architecture maximizes the measurement signal-to-noise ratio, yielding a readout uncertainty of 6% (±1 SD), with 1000 evaporated bubbles in a detector active volume of 150 ml (6 cm detector diameter). In this work, we prove that the intensity of scattered light also relates to the bubble size, which can be controlled by applying an external pressure to the detector emulsion. This effect can be exploited during the readout procedure to minimize shadowing effects between bubbles, which become severe when the latter are several thousands. The detector we used in this work is based on superheated C-318 (octafluorocyclobutane), emulsified in 100 μm ± 10% (1 SD) diameter drops in an inert matrix of approximately 150 ml. The detector was operated at room temperature and ambient pressure.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

The influence of respiratory motion on CT image volume definition

Purpose: Radiotherapy treatments are based on geometric and density information acquired from patient CT scans. It is well established that breathing motion during scan acquisition induces motion artifacts in CT images, which can alter the size, shape, and density of a patient's anatomy. The aim of this work is to examine and evaluate the impact of breathing motion on multislice CT imaging with respiratory synchronization (4DCT) and without it (3DCT). Methods: A specific phantom with a movable insert was used. Static and dynamic phantom acquisitions were obtained with a multislice CT. Four sinusoidal breath patterns were simulated to move known geometric structures longitudinally. Respiratory synchronized acquisitions (4DCT) were performed to generate images during inhale, intermediate, and exhale phases using prospective and retrospective techniques. Static phantom data were acquired in helical and sequential mode to define a baseline for each type of respiratory 4DCT technique. Taking into account the fact that respiratory 4DCT is not always available, 3DCT helical image studies were also acquired for several CT rotation periods. To study breath and acquisition coupling when respiratory 4DCT was not performed, the beginning of the CT image acquisition was matched with inhale, intermediate, or exhale respiratory phases, for each breath pattern. Other coupling scenarios were evaluated by simulating different phantom and CT acquisition parameters. Motion induced variations in shape and density were quantified by automatic threshold volume generation and Dice similarity coefficient calculation. The structure mass center positions were also determined to make a comparison with their theoretical expected position. Results: 4DCT acquisitions provided volume and position accuracies within ±3% and ±2 mm for structure dimensions >2 cm, breath amplitude ≤15 mm, and breath period ≥3 s. The smallest object (1 cm diameter) exceeded 5% volume variation for the breath patterns of higher frequency and amplitude motion. Larger volume differences (>10%) and inconsistencies between the relative positions of objects were detected in image studies acquired without respiratory control. Increasing the 3DCT rotation period caused a higher distortion in structures without obtaining their envelope. Simulated data showed that the slice acquisition time should be at least twice the breath period to average object movement. Conclusions: Respiratory 4DCT images provide accurate volume and position of organs affected by breath motion detecting higher volume discrepancies as amplitude length or breath frequency are increased. For 3DCT acquisitions, a CT should be considered slow enough to include lesion envelope as long as the slice acquisition time exceeds twice the breathing period. If this requirement cannot be satisfied, a fast CT (along with breath-hold inhale and exhale CTs to estimate roughly the ITV) is recommended in order to minimize structure distortion. Even with an awareness of a patient's respiratory cycle, its coupling with 3DCT acquisition cannot be predicted since patient anatomy is not accurately known.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

SU-E-T-613: Dosimetric Consequences of Systematic MLC Leaf Positioning Errors

Purpose: The purpose of this study is to determine the dosimetric consequences of systematic MLC leaf positioning errors for clinical IMRT patient plans so as to establish detection tolerances for quality assurance programs. Materials and Methods: Dosimetric consequences were simulated by extracting mlc delivery instructions from the TPS, altering the file by the specified error, reloading the delivery instructions into the TPS, recomputing dose, and extracting dose-volume metrics for one head-andneck and one prostate patient. Machine error was simulated by offsetting MLC leaves in Pinnacle in a systematic way. Three different algorithms were followed for these systematic offsets, and are as follows: a systematic sequential one-leaf offset (one leaf offset in one segment per beam), a systematic uniform one-leaf offset (same one leaf offset per segment per beam) and a systematic offset of a given number of leaves picked uniformly at random from a given number of segments (5 out of 10 total). Dose to the PTV and normal tissue was simulated. Results: A systematic 5 mm offset of 1 leaf for all delivery segments of all beams resulted in a maximum PTV D98 deviation of 1%. Results showed very low dose error in all reasonably possible machine configurations, rare or otherwise, which could be simulated. Very low error in dose to PTV and OARs was shown in all possible cases of one leaf per beam per segment being offset (<1%), or that of only one leaf per beam being offset (<.2%). The errors resulting from a high number of adjacent leaves (maximum of 5 out of 60 total leaf-pairs) being simultaneously offset in many (5) of the control points (total 10–18 in all beams) per beam, in both the PTV and the OARs analyzed, were similarly low (<2–3%). Conclusions: The above results show that patient shifts and anatomical changes are the main source of errors in dose delivered, not machine delivery. These two sources of error are “visually complementary” and uncorrelated (albeit not additive in the final error) and one can easily incorporate error resulting from machine delivery in an error model based purely on tumor motion.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Variable Circular Collimator in Robotic Radiosurgery: A Time-Efficient Alternative to a Mini-Multileaf Collimator?

Purpose: Compared with many small circular beams used in CyberKnife treatments, beam's eye view-shaped fields are generally more time-efficient for dose delivery. However, beam's eye view-shaping devices, such as a mini-multileaf collimator (mMLC), are not presently available for CyberKnife, although a variable-aperture collimator (Iris, 12 field diameters; 5-60 mm) is available. We investigated whether the Iris can mimic noncoplanar mMLC treatments using a limited set of principal beam orientations (nodes) to produce time-efficient treatment plans. Methods and Materials: The data from 10 lung cancer patients and the beam-orientation optimization algorithm 'Cycle' were used to generate stereotactic treatment plans (3 x 20 Gy) for a CyberKnife virtually equipped with a mMLC. Typically, 10-16 favorable beam orientations were selected from 117 available robot node positions using beam's eye view-shaped fields with uniform fluence. Second, intensity-modulated Iris plans were generated by inverse optimization of nonisocentric circular candidate beams targeted from the same nodes selected in the mMLC plans. The plans were evaluated using the mean lung dose, lung volume receiving {>=}20 Gy, conformality index, number of nodes, beams, and monitor units, and estimated treatment time. Results: The mMLC plans contained an average of 12 nodes and 11,690 monitor units. For a comparable mean lung dose, the Iris plans contained 12 nodes, 64 beams, and 21,990 monitor units. The estimated fraction duration was 12.2 min (range, 10.8-13.5) for the mMLC plans and 18.4 min (range, 12.9-28.5) for the Iris plans. In contrast to the mMLC plans, the treatment time for the Iris plans increased with an increasing target volume. The Iris plans were, on average, 40% longer than the corresponding mMLC plans for small targets (<80 cm{sup 3}) and {<=}121% longer for larger targets. For a comparable conformality index, similar results were obtained. Conclusion: For stereotactic lung irradiation, time-efficient and high-quality plans were obtained for robotic-controlled noncoplanar treatments using a mMLC. Iris is a time-efficient alternative for small targets, with similar or better plan quality.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Outcomes of Proton Therapy for Patients With Functional Pituitary Adenomas

Purpose/Objective(s): This study evaluated the efficacy and toxicity of proton therapy for functional pituitary adenomas (FPAs). Methods and Materials: We analyzed 165 patients with FPAs who were treated at a single institution with proton therapy between 1992 and 2012 and had at least 6 months of follow-up. All but 3 patients underwent prior resection, and 14 received prior photon irradiation. Proton stereotactic radiosurgery was used for 92% of patients, with a median dose of 20 Gy(RBE). The remainder received fractionated stereotactic proton therapy. Time to biochemical complete response (CR, defined as ≥3 months of normal laboratory values with no medical treatment), local control, and adverse effects are reported. Results: With a median follow-up time of 4.3 years (range, 0.5-20.6 years) for 144 evaluable patients, the actuarial 3-year CR rate and the median time to CR were 54% and 32 months among 74 patients with Cushing disease (CD), 63% and 27 months among 8 patients with Nelson syndrome (NS), 26% and 62 months among 50 patients with acromegaly, and 22% and 60 months among 9 patients with prolactinomas, respectively. One of 3 patients with thyroid stimulating hormone—secreting tumors achieved CR. Actuarial time to CR was significantly shorter for corticotroph FPAs (CD/NS) compared with other subtypes (P=.001). At a median imaging follow-up time of 43 months, tumor control was 98% among 140 patients. The actuarial 3-year and 5-year rates of development of new hypopituitarism were 45% and 62%, and the median time to deficiency was 40 months. Larger radiosurgery target volume as a continuous variable was a significant predictor of hypopituitarism (adjusted hazard ratio 1.3, P=.004). Four patients had new-onset postradiosurgery seizures suspected to be related to generously defined target volumes. There were no radiation-induced tumors. Conclusions: Proton irradiation is an effective treatment for FPAs, and hypopituitarism remains the primary adverse effect.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

SPOUTED BED DESIGN CONSIDERATIONS FOR COATED NUCLEAR FUEL PARTICLES

High Temperature Gas Cooled Reactors (HTGRs) are fueled with tristructural isotropic (TRISO) coated nuclear fuel particles embedded in a carbon-graphite fuel body. TRISO coatings consist of four layers of pyrolytic carbon and silicon carbide that are deposited on uranium ceramic fuel kernels (350µm – 500µm diameters) in a concatenated series of batch depositions. Each layer has dedicated functions such that the finished fuel particle has its own integral containment to minimize and control the release of fission products into the fuel body and reactor core. The TRISO coatings are the primary containment structure in the HTGR reactor and must have very high uniformity and integrity. To ensure high quality TRISO coatings, the four layers are deposited by chemical vapor deposition (CVD) using high purity precursors and are applied in a concatenated succession of batch operations before the finished product is unloaded from the coating furnace. These depositions take place at temperatures ranging from 1230°C to 1550°C and use three different gas compositions, while the fuel particle diameters double, their density drops from 11.1 g/cm3 to 3.0 g/cm3, and the bed volume increases more than 8-fold. All this is accomplished without the aid of sight ports or internal instrumentation that could cause chemical contamination within the layers or mechanical damage to thin layers in the early stages of each layer deposition. The converging section of the furnace retort was specifically designed to prevent bed stagnation that would lead to unacceptably high defect fractions and facilitate bed circulation to avoid large variability in coating layer dimensions and properties. The gas injection nozzle was designed to protect precursor gases from becoming overheated prior to injection, to induce bed spouting and preclude bed stagnation in the bottom of the retort. Furthermore, the retort and injection nozzle designs minimize buildup of pyrocarbon and silicon carbide on the retort wall and manage nozzle orifice accretions. The equipment and operating methods have yielded very good reproducibility in the TRISO coated particles batches.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

SU-E-T-289: Dose-Volume-Effect Relationships for Lung Cancer Patients Treated with SBRT On a Prospective Protocol

Purpose: Stereotactic body radiotherapy (SBRT) is commonly used to treat early stage lung tumors. This study was designed to evaluate associations between dose, volume and clinical outcomes including analysis of both clinical toxicity scores and quality of life (QOL) data for non-small cell lung cancer patients treated with SBRT. Preliminary results are presented. Methods: Sixty-seven NSCLC patients, 46 primarily with early stage, and 21 with recurrent disease were treated with dose regimens consisting mainly of 12 Gy x 4 fractions, and 3 or 5 fractions at lower dose, for patients with recurrent disease (Table 1). Follow-up data is being collected at baseline, after treatment and at 3, 6, 12, 18 and 24 months post-treatment. Clinical follow-up data acquired to date was assessed using the Charlson Comorbidity Clinical and Toxicity Scoring forms. QOL data was evaluated using the EQ-5D, and FACT-TOI validated surveys. All outcomes surveys are collected within an “in-house” developed outcomes database. Results: The median follow-up was 3.5±0.8 months. Mean lung doses (MLD) were converted to BED-2 Gy using the linear-quadratic model with an alpha/beta=3.0. Average MLD was 3.7+3.1 Gy (range: 0.4–20.9 Gy). The percentages of patients with > grade 2 cough, dyspnea and fatigue were 13.3, 17.0, 6.3%, respectively. Preliminary analyses (at 3 months after SBRT) show a mild correlation between MLD > 2 Gy and > grade 2 cough (borderline significant) and dyspnea (significant, p<0.05). One patient was observed with a grade 3 cough. Given the short follow-up, tumor control is not yet assessable. Conclusion: The SBRT dose fractionation regimen of 12 Gy x 4 was well tolerated at early time points. Additional follow-up is required to assess the long-term clinical outcome efficacy and toxicity profiles of the dose regimen.

60 APPLIED LIFE SCIENCES↗