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There is broad consensus that wildfire activity is likely to increase in western US forests and woodlands over the next century. Therefore, spatial predictions of the potential for large wildfires have immediate and growing relevance to near- and long-term research, planning, and management objectives. Fuels, climate, weather, and the landscape all exert controls on wildfire occurrence and spread, but the dynamics of these controls vary from daily to decadal timescales. Accurate spatial predictions of large wildfires should therefore strive to integrate across these variables and timescales. Here, we describe a high spatial resolution dataset (250 m pixel) of the probability of large wildfires ( > 405 ha) across forests and woodlands in the contiguous western US, from 2005 to the present. The dataset is automatically updated on a weekly basis using Google Earth Engine and a continuous integration pipeline. Each image in the dataset is the output of a random forest machine-learning algorithm, trained on random samples of historic small and large wildfires and represents the predicted conditional probability of an individual pixel burning in a large fire, given an ignition or fire spread to that pixel. This novel workflow is able to integrate the near-term dynamics of fuels and weather into weekly predictions while also integrating longer-term dynamics of fuels, the climate, and the landscape. As a continually updated product, the dataset can provide operational fire managers with contemporary, on-the-ground information to closely monitor the changing potential for large wildfire occurrence and spread. It can also serve as a foundational dataset for longer-term planning and research, such as the strategic targeting of fuels management, fire-smart development at the wildland–urban interface, and the analysis of trends in wildfire potential over time. Weekly large fire probability GeoTiff products from 2005 to 2017 are archived on the Figshare online digital repository with the DOI https://doi.org/10.6084/m9.figshare.5765967 (available at https://doi.org/10.6084/m9.figshare.5765967.v1). Weekly GeoTiff products and the entire dataset from 2005 onwards are also continually uploaded to a Google Cloud Storage bucket at https://console.cloud.google.com/storage/wffr-preds/V1 (last access: 14 September 2018) and are available free of charge with a Google account. Continually updated products and the long-term archive are also available to registered Google Earth Engine (GEE) users as public GEE assets and can be accessed with the image collection ID users/mgray/wffr-preds within GEE.

Over the past decade, housing supply restrictions across US cities have contributed to anemic housing construction and high prices in some of the most in-demand

Houston is known for its lack of Euclidean-style zoning, but the city still has various ordinances that control land use. In 1998, Houston reformed its subdivision rules to allow for parcels smaller than five thousand square feet citywide. In this paper, we discuss the unique land-use rules in place in Houston prior to reform and the circumstances that led to reform, including the “opt out” provisions, which mediated homeowner opposition to substantial increases in housing density. We then analyze the effects of reform. After relief from large lot requirements, post-reform development activity was heavily concentrated in middle-income, less dense, underbuilt neighborhoods.

Sweeping subdivision regulation reform in Houston, Texas, provides an instructive alternative to what can often seem like a no-win scenario for local planners. The circumstances surrounding the city’s 1998 reduction of minimum lot sizes for single-family homes hold important lessons for policymakers. This policy brief outlines what researchers know about minimum-lot-size regulation, sketches out Houston’s unique system of urban land use regulation, and draws lessons from Houston’s successful experience with subdivision liberalization.

This article provides a critical review of interdisciplinary literature on intercultural conflict management. The authors provide theoretical frameworks and evidence-based strategies to help group counselors more effectively identify and address potential sources of overt and covert intercultural conflict in groups. Using practical examples and integrated case studies, we examine the dynamics of intercultural conflict in groups, effective and ineffective group leader interventions, and implications for research and the practice of group work.

Minimum lot sizes regulate the density of housing in almost all American munici- palities. Our findings suggest that even moderate lot size minimums in rapidly growing Texas suburbs constrain density. Market outcomes are consistent with strong demand for single-family detached housing units built on lots of 5,000 to 7,000 square feet, a lot size rarely allowed by local zoning laws. The four suburban cities we examine depart frequently from their written zoning codes in order to offer such lots, approving noncompliant subdivisions and making extensive use of customized regulation for planned unit developments. Scholars agree that large- lot zoning as practiced in exclusionary coastal jurisdictions is a binding constraint on density. We go further: even modest minimum lot sizes in automobile-oriented suburbs are less dense than Americans want.

Purpose To describe a syndrome of hemorrhagic occlusive retinal vasculitis (HORV) that developed after seemingly uncomplicated cataract surgery. Design Retrospective case series. Subjects Eleven eyes of 6 patients from 6 different institutions. Methods Cases were identified after discussion among retina specialists. The findings on presentation, clinical course, and outcome of a series of 7 eyes of 4 patients were compared with a previous report of 4 eyes of 2 patients, and data from both series were combined for a comprehensive analysis. Main Outcome Measures Historical data, examination findings, imaging results, systemic evaluation findings, treatment regimens, and visual outcomes. Results Eleven eyes of 6 patients underwent otherwise uncomplicated cataract surgery, receiving viscoelastic and prophylactic intracameral vancomycin during the procedure. Despite good initial vision on postoperative day 1, between 1 to 14 days after surgery, all eyes demonstrated painless vision loss resulting from HORV. Extensive ocular and systemic evaluations were unrevealing in all patients. All patients were treated with aggressive systemic and topical corticosteroids. Additional treatments included systemic antiviral medication in 4 patients, intravitreal antibiotics in 4 eyes, and pars plana vitrectomy in 4 eyes. Skin testing for vancomycin sensitivity showed negative results in 3 patients and was not performed in the others. Neovascular glaucoma developed in 7 eyes, and all eyes received intravitreal anti–vascular endothelial growth factor (VEGF) injection, panretinal photocoagulation, or both for retinal ischemia. Final visual acuity was less than 20/100 in 8 of 11 eyes. Conclusions Postoperative HORV is an exceedingly rare and potentially devastating condition that can occur after otherwise uncomplicated cataract surgery. Although the precise cause remains unknown, this disease may represent a delayed immune reaction similar to vancomycin-induced leukocytoclastic vasculitis. Despite treatment with high-dose corticosteroids, antiviral medication, and early vitrectomy in many patients, visual outcomes typically were poor in this series. Early intervention with intravitreal anti-VEGF medication and panretinal photocoagulation may help to prevent additional vision loss resulting from neovascular glaucoma.

Purpose To report the outcomes of cataract surgery in eyes with previous herpes zoster ophthalmicus (HZO). Setting Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA. Design Retrospective case series. Methods Eyes with a history of HZO that had phacoemulsification and intraocular lens implantation were reviewed. The information analyzed included the ophthalmologic history, visual acuity, preoperative and postoperative adjunct treatments, and complications. Analysis of the mean corrected distance visual acuity (CDVA) at 1 month, 1 year, and the last follow-up was performed. Results Twenty-four eyes were evaluated. The mean CDVA improved from 20/112 (0.75 logMAR ± 0.63 [SD]) preoperatively to 20/53 (0.42 ± 0.56 logMAR) 1 month postoperatively ( P = .007) and 20/44 (0.34 ± 0.55 logMAR) at 1 year ( P = .052) but decreased to 20/71 (0.55 ± 0.72 logMAR) by last follow-up ( P = .605 versus preoperative CDVA). Eleven patients (45.8%) had recurrent keratouveitis after the first episode, 5 before cataract surgery and 6 after cataract surgery. Three had penetrating keratoplasty for worsening corneal opacification. Two patients had tractional retinal detachment from chronic uveitis and required vitrectomy and retinal repair. Conclusions Visual recovery after cataract surgery in HZO might be compromised by chronic factors such as ocular surface disease and keratouveitis. Despite long quiescent waiting periods before surgery and aggressive preoperative and postoperative maintenance therapy, visual improvement might be hindered by the inherent pathology associated with HZO. Nevertheless, with careful patient selection, reasonable visual improvement can be achieved. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

We use a near-field scanning optical microscope (NSOM) to perform local optical beam induced current measurements on strain-relaxed GeSi films on Si substrates. Topographic and near-field optical beam induced current (NOBIC) images are acquired simultaneously, enabling us to correlate topographic features and electrical activities of near surface defects. We demonstrate spatial resolution of approximately 100 nm in the NOBIC images. The resolution in NOBIC imaging of defects is examined using a two-dimensional carrier diffusion model with finite-size generation. We find that carrier diffusion length does not limit the resolution as previously thought. The ultrahigh resolution achieved in NSOM is due to reduction of the excitation volume and of the carrier lifetime near defects. Recent experiments using linearly polarized NSOM light reveal strain field variations associated with threading dislocations as well as with the cross-hatch patterns.

Reuse has long been a major goal of the knowledge engineering community. We present a case study of the reuse of constraint knowledge acquired for one problem solver, by two further problem solvers. For our analysis, we chose a well-known benchmark knowledge base (KB) system written in CLIPS, which was based on the propose and revise problem-solving method and which had a lift/elevator KB. The KB contained four components, including constraints and data tables, expressed in an ontology that reflects the propose and revise task structure. Sufficient trial data was extracted manually to demonstrate the approach on two alternative problem solvers: a spreadsheet (Excel) and a constraint logic solver (ECLiPSe). The next phase was to implement ExtrAKTor, which automated the process for the whole KB. Each KB that is processed results in a working system that is able to solve the corresponding configuration task (and not only for elevators). This is in contrast to earlier work, which produced abstract formulations of the problem-solving methods but which were unable to perform reuse of actual KBs. We subsequently used the ECLiPSe solver on some more demanding vertical transport configuration tasks. We found that we had to use a little-known propagation technique described by Le Provost and Wallace (1991). Further, our techniques did not use any heuristic “fix”’ information, yet we successfully dealt with a “thrashing” problem that had been a key issue in the original vertical transit work. Consequently, we believe we have developed a widely usable approach for solving this class of parametric design problem, by applying novel constraint-based problem solvers to data and formulae stored in existing KBs.

Lung cancer screening using low dose CT has been shown to reduce lung cancer related mortality and been approved for widespread use in the US. These scans keep radiation doses low while maximizing the detection of suspicious lung lesions. Tube current modulation (TCM) is one technique used to optimize dose, however limited work has been done to assess TCM’s effect on detection tasks. In this work the effect of TCM on detection is investigated throughout the lung utilizing several different model observers (MO). 131 lung nodules were simulated at 1mm intervals in each lung of the XCAT phantom. A Sensation 64 TCM profile was generated for the XCAT phantom and 2500 noise realizations were created using both TCM and a fixed TC. All nodules and noise realizations were reconstructed for a total of 262 (left and right lungs) nodule reconstructions and 10 000 XCAT lung reconstructions. Single-slice Hotelling (HO) and channelized Hotelling (CHO) observers, as well as a multislice CHO were used to assess area-under-the-curve (AUC) as a function of nodule location in both the fixed TC and TCM cases. As expected with fixed TC, nodule detectability was lowest through the shoulders and leveled off below mid-lung; with TCM, detectability was unexpectedly highest through the shoulders, dropping sharply near the mid-lung and then increasing into the abdomen. Trends were the same for all model observers. These results suggest that TCM could be further optimized for detection and that detectability maps present exciting new opportunities for TCM optimization on a patient-specific level.

Paediatric major trauma centres are being developed in the UK. As a paediatric unit within a large regional hospital that is co-located with a neurosciences centre, we conducted this study to establish what inpatient rehabilitation service is offered to patients with traumatic brain injury (TBI). It is known that early rehabilitation improves prognosis.A retrospective review of all patients under the age of 16 years admitted with an ICD-10 diagnosis of head injury was conducted. We collected data on the presentation, interventions, rehabilitation and follow up arrangements of this patient cohort.A total of 146 patients were identified, of whom50% had a traumatic lesion on brain computed tomography (CT) identified and 18% had a new diagnosis related to their TBI at discharge. 56% of patients with severe head injury were assessed by a neurodisability team member, but this dropped to 15% for the moderate cases and 5% for the mild cases.Many children who were admitted with TBI did not have access to early rehabilitation.

The purpose of this study was to examine the impact of an extracurricular geriatric program on medical students' knowledge of, and attitudes toward, the elderly and their interest in studying geriatric medicine. The participants were first-year medical students (n = 137) who joined the Senior Teacher Education Partnership (STEP) program that partnered medical students with community-dwelling elders. Although results show that the STEP program had minimal effect in changing first-year medical students' knowledge of the aged and aging, it did promote a more positive view of the elderly as being functionally independent and socially active. Statistical analyses also revealed that prior interest and participation in the STEP program are significant indicators of students' interest in pursuing geriatric medicine after completing their first year of medical school.

Objectives. The purpose of this study was to develop and evaluate a dynamic light scatteringbased method for monitoring the polymerization reaction of a light activated dental composite. Methods. Laser light back-scattered from thin disk-shaped composite samples was used to study the curing reaction kinetics. Samples were irradiated simultaneously on opposite surfaces with a 633 nm laser beam and a halogen curing lamp (320, 160, or 100 mW/cm 2 ). Dynamic laser speckle patterns were imaged onto a CCD camera at a rate of 32 frames/s for 2 min. The intensity decorrelation rate calculated from sequential speckle patterns was used to assess the rate of motion within the samples during the reaction. Results. Motion within the composite increased immediately upon the onset of light exposure for all trials. This was followed by a brief period characterized by a relatively constant high rate of motion. Finally the rate of motion decreased exponentially. The reaction acceleration, deceleration, and maximum rate were dependent upon the irradiance of the curing light source. Significance. This method monitors reaction rate and the change in reaction rate at high temporal resolution without contact. Reaction kinetics was shown to begin immediately after light exposure suggesting limited opportunity for viscous flow and stress relief.

A decision support tool which integrated a geographic information system (GIS) with decision tree models to predict pasture production and pasture responses to phosphate (P) and nitrogen (N) fertiliser was assessed on two farms with contrasting climate inNew Zealand. Scenarios of rainfall variability and different fertiliser application strategies were also analysed in this assessment. The results indicated that the models performed well in generating reliable predictions of pasture production and fertiliser responses. The integration of the decision tree models with the GIS provides an efficient tool to assess feed availability and to optimise fertiliser application strategies over landscapes at fine (paddock) scale with considerations of climate variability and environmental impact. The limitations of this decision support tool and possible improvements are also discussed.

The current research examined drinking and drug use among college students. Using a self-report survey of students from a midwestern university, the frequency of alcohol use, binge drinking, and drug use were explored. Particular attention was paid to drinking behaviors and drug use among Criminal Justice (CJ) students compared to students from other majors. Differences were found between CJ and non-CJ students especially in terms of drinking behavior; fewer differences were found between majors in terms of drug use. Issues of moral authority were examined as well as issues of employability. Implications for CJ students, faculty and advisors are discussed.

A large body of astronomical material remains from the Late Babylonian period (c. 750 BC to AD 75) covering observations, calculations and predictions of astronomical events. Astronomical texts from the period are generally divided into two categories: mathematical texts, which include theoretical schemes and calculated predictions; and non-mathematical texts, which include observations and empirical predictions derived from these observations. This paper attempts to catalogue some of the relationships between the various non-mathematical astronomical texts of the Late Babylonian period, particularly the use of Goal- Year Texts in compiling the predictive texts known as Almanacs and Normal Star Almanacs.

PURPOSE: Texture features have been investigated as a biomarker of response and malignancy. Because these features reflect local differences in density, they may be influenced by acquisition and reconstruction parameters. The purpose of this study was to investigate the effects of radiation dose level and reconstruction method on features derived from lung lesions. METHODS: With IRB approval, 33 lung tumor cases were identified from clinically indicated thoracic CT scans in which the raw projection (sinogram) data were available. Based on a previously-published technique, noise was added to the raw data to simulate reduced-dose versions of each case at 25%, 10% and 3% of the original dose. Original and simulated reduced dose projection data were reconstructed with conventional and two iterative-reconstruction settings, yielding 12 combinations of dose/recon conditions. One lesion from each case was contoured. At the reference condition (full dose, conventional recon), 17 lesions were randomly selected for repeat contouring (repeatability). For each lesion at each dose/recon condition, 151 texture measures were calculated. A paired differences approach was employed to compare feature variation from repeat contours at the reference condition to the variation observed in other dose/recon conditions (reproducibility). The ratio of standard deviation of the reproducibility to repeatability was used as the variation measure for each feature. RESULTS: The mean variation (standard deviation) across dose levels and kernel was significantly different with a ratio of 2.24 (±5.85) across texture features (p=0.01). The mean variation (standard deviation) across dose levels with conventional recon was also significantly different with 2.30 (7.11) (p=0.025). The mean variation across reconstruction settings of original dose has a trend in showing difference with 1.35 (2.60) among all features (p=0.09). CONCLUSION: Texture features varied considerably with variations in dose and reconstruction condition. Care should be taken to standardize these conditions when using texture as a quantitative feature. This effort supported in part by a grant from the National Cancer Institute's Quantitative Imaging Network (QIN): U01 CA181156; The UCLA Department of Radiology has a Master Research Agreement with Siemens Healthcare; Dr. McNitt-Gray has previously received research support from Siemens Healthcare.

PURPOSE: Quantitative Imaging and CAD tasks performed with CT (e.g. lung nodule detection, assessment of tumor size, etc.) may be sensitive to image acquisition and reconstruction parameters such as dose level, image thickness and reconstruction method (FBP, iterative, etc.). The purpose of this work was to develop a research pipeline for generating CT image series that represent a wide variety of acquisition and reconstruction conditions under which CAD and Quantitative Imaging performance would be evaluated. METHODS: With IRB approval, we have collected the raw CT data from hundreds of patients. These raw sinogram files serve as the input to the research pipeline. To simulate a wide range of dose levels, we developed software which adds noise to the sinogram. Multiple reduced-dose sinograms can be generated for a single patient, and those reduced-dose sinograms are then fed either to the scanner's reconstruction engine or to our in-house reconstruction engine; each has conventional filtered back projection (FBP) and iterative reconstruction methods. After generating image series across a range of dose levels and reconstruction methods, we can evaluate the performance of various quantitative imaging or CAD tools in tasks such as automated and semi-automated lesion segmentation, assessment of lesion size, and measurement of density or texture. RESULTS: We have successfully applied this pipeline across a range of clinical CT applications, including: (1) chest oncology, where the pipeline was used to quantify the effects of dose and reconstruction method on nodule volumetry, and (2) lung cancer screening, where the pipeline is being used to measure the robustness of an automated CAD algorithm with respect to dose. CONCLUSION: The acquisition/reconstruction pipeline shows promise for investigating and quantifying the effects of dose and reconstruction method on various clinical CT applications. NCI grant U01 CA181156 (Quantitative Imaging Network); Tobacco Related Disease Research Project grant 22RT-0131.

PURPOSE: To study the outcomes of cataract surgery in patients with graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). METHODS: Retrospective review of 72 eyes of 41 patients (age, 17-69 years at the time of surgery) with chronic GVHD after HSCT, who underwent cataract surgery between 2008 and 2012 at the Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan. Ophthalmic data collected included best-corrected visual acuity (BCVA), responses to Ocular Surface Disease Index (OSDI) questionnaire, dry eye severity, and postoperative complications. RESULTS: BCVA improved from 20/49 to 20/25 (P < 0.0001) after surgery. Eight patients (20%) had pretransplantation total body irradiation and 39 patients (95%) received systemic corticosteroids for the treatment of GVHD. Postoperative complications included cystoid macular edema (4 eyes), corneal ulceration with perforation (2 eyes: 1 infected and 1 sterile), and band keratopathy (1 eye). After surgery, subjective OSDI responses and dry eye disease (DED) did not change significantly from before cataract surgery, although OSDI showed a trend toward worsening. CONCLUSIONS: With careful monitoring and management of DED and concurrent ocular surface disease, cataract surgery generally has good visual outcomes in patients with GVHD. However, aggravation of the preexisting ocular surface disease is frequent, and despite meticulous postoperative maintenance therapy, vision-threatening complications may occur.

Aim To analyse observed and predicted distributional patterns of selected salticid genera in Australia and to examine these distributions in the light of the origins and attributes of the fauna. To detect and compare the locations of regional hotspots when measured using different scales. Location Australia. Methods A total of 4104 locality records for specimens of 51 genera were stored in BioLink. Maps of observed and predicted (using bioclim) distributions were prepared for each genus. The predicted distributions were combined to provide estimates of the number of genera likely to be found at each locality in the raster and for each of a set of landscape regions across Australia. The predictions were tested by comparing them with independent data sets. Results The Australian salticid fauna consists of radiations based on Oriental, Papuan and possibly Gondwanan forms, plus pantropical and peridomestic species. The predicted distributions of genera fall into a limited number of categories and these reflect the traditional biogeographical regions of Australia. Maximum regional diversity is predicted for central eastern Queensland, though diversity at single locations is highest further south in the New South Wales/Queensland border region. The locations of hotspots are therefore scale dependent. Patterns of distribution are not simply related to particular lifestyles. Fewer genera were predicted from inland Australia; however, recent work has shown that there are a large number of undescribed genera in the drier parts of Australia. The prediction maps allowed lists of genera potentially present in unstudied areas to be developed. Main conclusions (1) The current distribution of genera is predicted by their bioclimatic profiles rather than by their origins or ecology. Some Oriental genera, however, have not reached south-western Western Australia, though bioclimatic conditions there are predicted to be suitable for them; (2) the highest diversity of genera is predicted to be in south-eastern Queensland; (3) the results highlight the shortcomings of past fieldwork in Australia, which has concentrated on the areas with higher rainfall; (4) it seems likely that inland Australia will support a large, highly endemic, fauna adapted to the region, and ultimately perhaps 40 or more genera could be found in each region; (5) the results show the possibility of using the maps of predicted distribution of genera not only for biogeographical analyses but also for conservation management and survey purposes.

SummaryThe aim was to determine the relative contribution of the glenohumeral ligaments/joint capsule complex and the limited joint volume/adhesion-cohesion (LJV/AC) mechanisms to the static stability of the canine glenohumeral joint (GHJ). The GHJ of 32 complete cadaver specimens were manipulated to determine the presence of gross laxity (>2mm translation) at joint angles of 150°, 135° and 90°. Following the removal of the peri-articular muscles, laxity was measured by applying a 15N force to the scapula in a variety of directions whilst the humerus was fixed to a jig. This was repeated for the abovementioned angles in intact joints and after venting and flushing to eliminate the LJV/AC mechanisms. Results of clinical palpation and biomechanical studies were compared. Manipulation revealed a marked variation between joints although there was a tendency for progressive laxity as the joint was flexed. This finding was supported by the biomechanical study that also demonstrated no significant difference between intact and vented joints except in a cranio-caudal direction at 135° and 90°, and in a medial/lateral direction at 135°. Static stabilisers permitted a wide range of motion. Individual clinical palpations did not correlate well with biomechanical findings. Manipulation was difficult to perform and is unlikely to be a reliable method for determining subtle joint laxity. The static stabilisers do not appear to play a significant role in providing joint constraint during normal range of motion (except extension). Diagnoses of pathological laxity attributable to the static stabilisers should be made with caution and surgical treatments should take cognizance of the above-mentioned biomechanical features.

Purpose: A method to discriminate different types of renal cell carcinoma (RCC) was developed using attenuation values observed in multiphasic contrast-enhanced CT. This work evaluates the sensitivity of this RCC discrimination task at different CT radiation dose levels. Methods: We selected 5 cases of kidney lesion patients who had undergone four-phase CT scans covering the abdomen to the lilac crest. Through an IRB-approved study, the scans were conducted on 64-slice CT scanners (Definition AS/Definition Flash, Siemens Healthcare) using automatic tube-current modulation (TCM). The protocol included an initial baseline unenhanced scan, followed by three post-contrast injection phases. CTDIvol (32 cm phantom) measured between 9 to 35 mGy for any given phase. As a preliminary study, we limited the scope to the cortico-medullary phase—shown previously to be the most discriminative phase. A previously validated method was used to simulate a reduced dose acquisition via adding noise to raw CT sinogram data, emulating corresponding images at simulated doses of 50%, 25%, and 10%. To discriminate the lesion subtype, ROIs were placed in the most enhancing region of the lesion. The mean HU value of an ROI was extracted and used to discriminate to the worst-case RCC subtype, ranked in the order of clear cell, papillary, chromophobe and the benign oncocytoma. Results: Two patients exhibited a change of worst case RCC subtype between original and simulated scans, at 25% and 10% doses. In one case, the worst-case RCC subtype changed from oncocytoma to chromophobe at 10% and 25% doses, while the other case changed from oncocytoma to clear cell at 10% dose. Conclusion: Based on preliminary results from an initial cohort of 5 patients, worst-case RCC subtypes remained constant at all simulated dose levels except for 2 patients. Further study conducted on more patients will be needed to confirm our findings. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics; NIH Grant Support from: U01 CA181156

Purpose: Iterative reconstruction methods show promise for improving image quality and lowering the dose in helical CT. We aim to develop a novel model-based reconstruction method that offers potential for dose reduction with reasonable computation speed and storage requirements for vendor-independent reconstruction from clinical data on a normal desktop computer. Methods: In 2012, Xu proposed reconstructing on rotating slices to exploit helical symmetry and reduce the storage requirements for the CT system matrix. Inspired by this concept, we have developed a novel reconstruction method incorporating the stored-system-matrix approach together with iterative coordinate-descent (ICD) optimization. A penalized-least-squares objective function with a quadratic penalty term is solved analytically voxel-by-voxel, sequentially iterating along the axial direction first, followed by the transaxial direction. 8 in-plane (transaxial) neighbors are used for the ICD algorithm. The forward problem is modeled via a unique approach that combines the principle of Joseph's method with trilinear B-spline interpolation to enable accurate reconstruction with low storage requirements. Iterations are accelerated with multi-CPU OpenMP libraries. For preliminary evaluations, we reconstructed (1) a simulated 3D ellipse phantom and (2) an ACR accreditation phantom dataset exported from a clinical scanner (Definition AS, Siemens Healthcare). Image quality was evaluated in the resolution module. Results: Image quality was excellent for the ellipse phantom. For the ACR phantom, image quality was comparable to clinical reconstructions and reconstructions using open-source FreeCT_wFBP software. Also, we did not observe any deleterious impact associated with the utilization of rotating slices. The system matrix storage requirement was only 4.5GB, and reconstruction time was 50 seconds per iteration. Conclusion: Our reconstruction method shows potential for furthering research in low-dose helical CT, in particular as part of our ongoing development of an acquisition/reconstruction pipeline for generating images under a wide range of conditions. Our algorithm will be made available open-source as “FreeCT_ICD”. NIH U01 CA181156; Disclosures (McNitt-Gray): Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics

Purpose: To compare the effects of various tube current modulation (TCM) schemes – including attenuation-based, “organ-based” and combined schemes - on both the resulting tube current values as well as dose savings. Methods: An anthropomorphic adult thorax phantom was scanned using a Multidetector row CT scanner that offered both attenuation-based and “organ-based” TCM schemes that could be used separately or in combination (Definition AS64, Siemens Healthcare). A small ion chamber was attached to a medial location on the surface of the chest phantom to provide a reference value which served as proxy for organ dose. Scans were performed under each possible TCM configuration (fixed mA, attenuationbased only, organ-based only and combined organ and attenuation based) using the same nominal parameters (e.g. Quality Reference mAs). The actual TCM scheme was extracted from the raw projection data of each scan to illustrate the actual mA variations. The scanner CTDIvol and ion chamber readings were recorded for each scan and comparisons were made across TCM schemes. Results: Each of the TCM schemes showed substantially different mA patterns. All TCM schemes showed some reduction in CTDIvol compared to a fixed mA scan with the same nominal settings; however the values ranged from a decrease of 2% (organ based only) to 18% (attenuation based only). The dose reduction to the surface dose point varied from a decrease of 34% (organ based only) to an increase of 15% (attenuation based only) compared to the fixed mA scan. Examining the actual TCM schemes from the raw data files allows us to understand the effects of each scheme. Conclusion: Phantom scans allowed us to compare the effects of different TCM schemes on both CTDIvol values as well as point doses. Future work will focus on organ doses from each scheme using validated Monte Carlo techniques.

Purpose: Recent work has shown that current TCM profile designs boost detection of low-contrast lung lesions in the lung apices, but yield reduced detection performance in the mid and lower lung regions relative to fixed tube current cases. This observed imbalance suggests that the TCM scheme might be tailored in new ways to maximize nodule detection throughout the entire lung. In this work, we begin a preliminary investigation into custom TCM profiles in an attempt to achieve uniform lesion detection throughout the extent of the lung. Methods: Low-contrast (25HU), 6mm nodules representing ground glass opacities were simulated at 1mm intervals over the length the lungs in a voxelized model of the XCAT phantom, one nodule per lung, per simulated scan. Voxel values represented attenuation values at 80keV. CT projection data was created by simulating a finite focal spot and using Joseph's method for forward projection; scanner geometry was that of the Siemens Sensation 64 and the X-ray source was simulated as an 80keV monochromatic beam. Noise realizations were created using Poisson statistics, a realistic bowtie filter and varying tube current. 500 noise realizations were created for the custom TCM designs. All reconstruction was done with FreeCT_wFBP. An SKE/BKE task was used in conjunction with a 2D Hotelling Observer to calculate area-under-the-curve (AUC) as a proxy for “detectability.” AUC was plotted as a function of nodule Z-location to create a “detectability map.” The detectability map for the custom TCM curve was qualitatively assessed relative to previous results for the fixed TC and clinical TCM cases for uniformity. Results: Detection uniformity was improved throughout the mid and lower lungs, however detection remained disproportionately high in the upper lung region. Conclusion: Detection uniformity was improved with a custom TC profile. Future work will incorporate an analytic, task-specific approach to optimize the TC scheme for nodule detection. J. Hoffman: Part-time intern, Toshiba Medical Research Institute; M. McNitt-Gray: Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics; F. Noo: Institutional research agreement, Siemens Healthcare; Receives research funding from Siemens Healthcare

Purpose: The purpose of this study was to investigate the effects of reducing radiation dose levels on emphysema scores from lung cancer screening CT exams. Methods: 52 cases were selected from the National Lung Screening Trial (NLST) patients for which we had both the image series and the raw CT data. All scans were acquired with fixed effective mAs (25 for standard-sized patients, 40 for large patients) on a 64-slice scanner (Sensation 64, Siemens Healthcare) using 120kV, 64×0.6mm collimation and pitch 1.0. All images were reconstructed with 1mm slice thickness, B50 kernel. Based on a previously-published technique, we added noise to the raw data to simulate reduced-dose versions at 50% and 25% of the original dose (approximately 1.0- and 0.5-mGy CTDIvol). Lung segmentations were obtained via region growing from manual seed point at a threshold of 600HU followed by manual removal of trachea and major airways. Lung segmentations were only performed on original dose scans, and mapped to simulated reduced-dose scans. Emphysema scores based on relative area of lung with attenuation values lower than −950HU (RA950) were computed for all cases. Results: Average RA950 of all 50 cases were 31.6 (±5.5), 32.5 (±4.9) and 32.8 (±4.6) for 100%, 50% and 25% dose level respectively. The average absolute difference in RA950 between simulated and original dose scans were 1.0 (±0.7) and 1.4 (±1.1) for 50% and 25% dose level respectively. Conclusion: RA950 is relatively robust to dose level, with a difference of no more than 5 from the original dose scans. The average RA950 of this population was high for a two reasons: This was a high risk population of patients with substantial smoking history; The use of B50 kernel, which may be biased towards high emphysema scores. Further exploration with smoother kernels will be conducted in the future. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics; NIH grant support from U01 CA181156

This report provides an overview of the current state of autonomous system testing and evaluation methodologies and levels of autonomy for intelligent unmanned systems (UMSs). It is meant to be an extensive review of all past and ongoing efforts to define autonomy and set levels of autonomy for unmanned systems as related to military applications. Presented within are the current performance metrics for autonomous systems, the current standards that have been adopted for autonomous systems, and the leading frameworks for assessing levels of autonomy and autonomous mission performance.

The loss of teeth may result in patients experiencing problems of a functional, aesthetic and psychological nature. This section addresses the very important subject of occlusal considerations for partial and complete dentures. The occlusion is particularly important given the bearing that occlusal factors have, especially on edentulous patients.

Many theories and philosophies of occlusion have been developed. 1-12 The difficulty in scientifically validating the various approaches to providing an occlusion is that an 'occlusion' can only be judged against the reaction it may or may not produce in a tissue system (eg dental, alveolar, periodontal or articulatory). Because of this, the various theories and philosophies are essentially untested and so lack the scientific validity necessary to make them 'rules'. Often authors will present their own firmly held opinions as 'rules'. This does not mean that these approaches are to be ignored; they are, after all, the distillation of the clinical experience of many different operators over many years. But they are empirical. In developing these guidelines the authors have unashamedly drawn on this body of perceived wisdom, but we would also like to involve and challenge the reader by asking basic questions, and by applying a common sense approach to a subject that can be submerged under a sea of dictate and dogma.

Our high technology society continues to rely more and more upon sophisticated measurements, technical standards, and associated testing activities. This was true for the industrial society of the 20th century and remains true for the information society of the 21st century. Over the last half of the 20th century, information technology (IT) has been a powerful agent of change in almost every sector of the economy. The complexity and rapidly changing nature of IT have presented unique technical challenges to the National Institute of Standards and Technology (NIST) and to the scientific measurement community in developing a sound measurement and testing infrastructure for IT. This measurement and testing infrastructure for the important non-physical and non-chemical properties associated with complex IT systems is still in an early stage of development. This paper explains key terms and concepts of IT metrology, briefly reviews the history of the National Bureau of Standards/National Institute of Standards and Technology (NBS/NIST) in the field of IT, and reviews NIST's current capabilities and work in measurement and testing for IT. It concludes with a look at what is likely to occur in the field of IT over the next ten years and what metrology roles NIST is likely to play.

In this paper the authors describe the ongoing development of a specialized advisory service aimed at promoting innovation in local manufacturing SMEs. The first stage studies the levels of process and product innovation, and level of innovation need, through a telephone survey of 156 small and medium-sized manufacturing companies and a number of follow-up interviews. The following stage involves the development of audit tools designed to identify gaps in innovation capability, and a change methodology to help companies become more innovative. These tools will be piloted with a number of local SMEs and then disseminated more widely to companies and business support agencies. The paper focuses on issues related to innovation in small and medium-sized manufacturing companies and explores these in relation to the initial findings of the survey.

Using data from field observation of police patrol officers at work in two American cities, we explore similarities and differences between the tasks undertaken by generalist patrol officers and community policing specialists. As expected, community policing specialists are much more able to choose the work they do and the people they encounter. Specialists use their discretion to spend less “face time” with the public and more time “behind the scenes” than do patrol generalists, and to engage a higher-status and less problem-ridden clientele. Implications for adoption of community policing are discussed.

A goal of an imaging accreditation program is to ensure adequate image quality, verify appropriate staff qualifications, and to assure patient and personnel safety. Currently, more than 35,000 facilities in 10 modalities have been accredited by the American College of Radiology (ACR), making the ACR program one of the most prolific accreditation options in the U.S. In addition, ACR is one of the accepted accreditations required by some state laws, CMS/MIPPA insurance and others. Familiarity with the ACR accreditation process is therefore essential to clinical diagnostic medical physicists. Maintaining sufficient knowledge of the ACR program must include keeping up-to-date as the various modality requirements are refined to better serve the goals of the program and to accommodate newer technologies and practices. This session consists of presentations from authorities in four ACR accreditation modality programs, including magnetic resonance imaging, computed tomography, nuclear medicine, and mammography. Each speaker will discuss the general components of the modality program and address any recent changes to the requirements. Learning Objectives: 1. To understand the requirements of the ACR MR Accreditation program. The discussion will include accreditation of whole-body general purpose magnets, dedicated extremity systems well as breast MRI accreditation. Anticipated updates to the ACR MRI Quality Control Manual will also be reviewed. 2. To understand the requirements of the ACR CT accreditation program, including updates to the QC manual as well as updates through the FAQ process. 3. To understand the requirements of the ACR nuclear medicine accreditation program, and the role of the physicist in annual equipment surveys and the set up and supervision of the routine QC program. 4. To understand the current ACR MAP Accreditation requirement and present the concepts and structure of the forthcoming ACR Digital Mammography QC Manual and Program.

Purpose: The US Centers for Medicare & Medicaid Services (CMS) recently issued its final decision to approve the use of low dose CT for lung cancer screening and described some dose index requirements. The aim of this study is to evaluate CT dose indices from lung cancer screening taking into account patient size. Methods: CT dose index data (CTDIvol, DLP) and patient size (height and weight) to calculate body mass index (BMI) were collected for lung cancer screening exams from Jan 1st to Dec 31th, 2014. All exams used Tube Current Modulation with identical Image Quality Reference parameter (Quality Reference mAs). X-ray dose management software was used to mine the data. CTDIvol and DLP values were analyzed based on patient’s BMI classification. For a subset of patients, the average water equivalent diameter was estimated as well as Size Specific Dose Estimate (SSDE). All results were compared to the Medicare requirements (CTDIvol ≤ 3.0 mGy for a standard sized patient; appropriate reductions for smaller patients and increases for larger patients). Results: The dose indices over 351 patients were (mean ± SD): CTDIvol of 2.1 ± 0.7 mGy (min-max: 1.2 – 6.0 mGy); DLP of 75 ± 24 mGy*cm (min-max: 38 – 202 mGy*cm). The CTDIvol values by patient size (BMI) were 1.4 ± 0.2 mGy for underweight (BMI 3.0 mGy; for each of these cases, the BMI was at least 27.0. Conclusion: The scan protocol used resulted in CTDIvol values well within the Medicare requirements. Patients with larger BMI receive higher CTDIvol, but values > 3.0 mGy only occurred for overweight and obese patients.

Purpose: CT neuro perfusion scans are one of the highest dose exams. Methods to reduce dose include decreasing the number of projections acquired per gantry rotation, however conventional reconstruction of such scans leads to sampling artifacts. In this study we investigated a projection view-sharing reconstruction algorithm used in dynamic MRI – “K-space Weighted Image Contrast” (KWIC) – applied to simulated perfusion exams and evaluated dose savings and impacts on perfusion metrics. Methods: A FORBILD head phantom containing simulated time-varying objects was developed and a set of parallel-beam CT projection data was created. The simulated scans were 60 seconds long, 1152 projections per turn, with a rotation time of one second. No noise was simulated. 5mm, 10mm, and 50mm objects were modeled in the brain. A baseline, “full dose” simulation used all projections and reduced dose cases were simulated by downsampling the number of projections per turn from 1152 to 576 (50% dose), 288 (25% dose), and 144 (12.5% dose). KWIC was further evaluated at 72 projections per rotation (6.25%). One image per second was reconstructed using filtered backprojection (FBP) and KWIC. KWIC reconstructions utilized view cores of 36, 72, 144, and 288 views and 16, 8, 4, and 2 subaperturesmore » respectively. From the reconstructed images, time-to-peak (TTP), cerebral blood flow (CBF) and the FWHM of the perfusion curve were calculated and compared against reference values from the full-dose FBP data. Results: TTP, CBF, and the FWHM were unaffected by dose reduction (to 12.5%) and reconstruction method, however image quality was improved when using KWIC. Conclusion: This pilot study suggests that KWIC preserves image quality and perfusion metrics when under-sampling projections and that the unique contrast weighting of KWIC could provided substantial dose-savings for perfusion CT scans. Evaluation of KWIC in clinical CT data will be performed in the near future. R01 EB014922, NCI Grant U01 CA181156 (Quantitative Imaging Network), and Tobacco Related Disease Research Project grant 22RT-0131.« less

UNLABELLED: In the United States, Lung Cancer is responsible for more cancer deaths than the next four cancers combined. In addition, the 5 year survival rate for lung cancer patients has not improved over the past 40 to 50 years. To combat this deadly disease, in 2002 the National Cancer Institute launched a very large Randomized Control Trial called the National Lung Screening Trial (NLST). This trial would randomize subjects who had substantial risk of lung cancer (due to age and smoking history) into either a Chest X-ray arm or a low dose CT arm. In November 2010, the National Cancer Institute announced that the NLST had demonstrated 20% fewer lung cancer deaths among those who were screened with low-dose CT than with chest X-ray. In December 2013, the US Preventive Services Task Force recommended the use of Lung Cancer Screening using low dose CT and a little over a year later (Feb. 2015), CMS announced that Medicare would also cover Lung Cancer Screening using low dose CT. Thus private and public insurers are required to provide Lung Cancer Screening programs using CT to the appropriate population(s). The purpose of this Symposium is to inform medical physicists and prepare them to support the implementation of Lung Screening programs. This Symposium will focus on the clinical aspects of lung cancer screening, requirements of a screening registry for systematically capturing and tracking screening patients and results (such as required Medicare data elements) as well as the role of the medical physicist in screening programs, including the development of low dose CT screening protocols. LEARNING OBJECTIVES: 1.To understand the clinical basis and clinical components of a lung cancer screening program, including eligibility criteria and other requirements.2.To understand the data collection requirements, workflow, and informatics infrastructure needed to support the tracking and reporting components of a screening program.3.To understand the role of the medical physicist in implementing Lung Cancer Screening protocols for CT, including utilizing resources such as the AAPM Protocols and the ACR Designated Lung Screening Center program.UCLA Department of Radiology has an Institutional research agreement with Siemens Healthcare; Dr. McNitt-Gray has been a recipient of Research Support from Siemens Healthcare in the past. Dr. Aberle has been a Member of Advisory Boards for the LUNGevity Foundation (2011-present) and Siemens Medical Solutions. (2013).

The goal for Concentrating Solar Power (CSP) technologies is to produce electricity at 15 cents/kilowatt-hour (kWh) with six hours of thermal storage in 2015 (intermediate power) and close to 10 cents/kWh with 12-17 hours of thermal storage in 2020 (baseload power). Cost reductions of up to 50% to the solar concentrator are targeted through technology advances. The overall solar-to-electric efficiency of parabolic-trough solar power plants can be improved and the cost of solar electricity can be reduced by improving the properties of the selective coating on the receiver and increasing the solar-field operating temperature to >450 degrees C. New, more-efficient selective coatings will be needed that have both high solar absorptance and low thermal emittance at elevated temperatures. Conduction and convection losses from the hot absorber surface are usually negligible for parabolic trough receivers. The objective is to develop new, more-efficient selective coatings with both high solar absorptance (..alpha.. > 0.95) and low thermal emittance (..epsilon.. < 0.08 @ 450 degrees C) that are thermally stable above 450 degrees C, ideally in air, with improved durability and manufacturability, and reduced cost.

In May 1996, NIST management requested a white paper on metrology for information technology (IT). A task group was formed to develop this white paper with representatives from the Manufacturing Engineering Laboratory (MEL), the Information Technology Laboratory (ITL), and Technology Services (TS). The task group members had a wide spectrum of experiences and perspectives on testing and measuring physical and IT quantities. The task group believed that its collective experience and knowledge were probably sufficient to investigate the underlying question of the nature of IT metrology. During the course of its work, the task group did not find any previous work addressing the overall subject of metrology for IT. The task group found it to be both exciting and challenging to possibly be first in what should be a continuing area of study. After some spirited deliberations, the task group was able to reach consensus on its white paper. Also, as a result of its deliberations, the task group decided that this white paper should suggest possible answers rather than assert definitive conclusions. In this spirit, the white paper suggests: a scope and a conceptual basis for IT metrology; a taxonomy for IT methods of testing; status of IT testing and measurement; opportunities to advance IT metrology; overall roles for NIST; and recapitulates the importance of IT metrology to the U.S. The task group is very appreciative of having had the opportunity to produce this white paper. The task group hopes that this white paper will provide food for thought for our intended audience: NIST management and technical staff and our colleagues elsewhere who are involved in various aspects of testing and measuring IT.

The Canadian Nuclear Fuel Waste Management Program (CNFWMP) is evaluating the concept of disposal of nuclear fuel waste in an engineerted vault at a depth of 500 to 1000 m in the plutonic rock of the Canadian Shield. In common with engineered barrier system designs being developed in other countries, the waste would be contained within durable containers that, in turn, would be isolated from the host rock by clay-based materials. The objective of the CNFWMP is to develop a disposal concept that will protect human health and the natural environment far into the future. Assessments of the conceptual vault designs are based on system theory in which an attempt is made to correlate experiences with theoretical concepts of planned systems in such a way that the resulting coordination is sound and convincing. By necessity, since experiments with a total disposal system can never be performed, both the design and the performance assessment rely on experiments performed on physical models of vault elements over relatively short times and on information inferred from calculations (mathematical models) that simulate the probable behaviour of the system in the space-time domainof interest. For a simulation model to be successful, that is applied within a real world situation, the model must provide information regarding the behaviour of the system of interest that is clearly better, in some way, than the mental image or other abstract model that would be used instead. The results of a series of tests performed within the activity known as validation serve as tangible evidence regarding the success of a model in representing the system of interest. This paper focusses on the validation of the models that describe the hygro-thermo-mechanical behaviour of the engineered clay-barriers proposed for application in the Canadian disposal system concept. The strategy being used to address the key issues in modelling to minimize the model error and to maximize the usefulness of the simulation model, based on testing procedures, is reviewed. Finally, a concept of the validation of codes/models that describe the unsaturated behaviour of engineered clay barriers, is described.

Two dogs were found to have intraluminal gallbladder masses which caused partial or complete extrahepatic biliary obstruction. On histological examination, the gallbladder masses were confirmed to be mucoceles. Gallbladder mucoceles are rare in humans and previously have been described only after gallbladder rupture in two dogs. In the dogs of this report, the biliary obstruction was relieved by cholecystectomy. Each dog also had histological evidence of chronic liver disease with intrahepatic cholestasis. The clinical diagnosis of biliary obstruction was based on scintigraphic and sonographic findings which will be discussed and compared with other hepatobiliary diseases.

Purpose: The use of Quantitative Imaging (QI) methods in Clinical Trials requires both verification of adherence to a specified protocol and an assessment of scanner performance under that protocol, which are currently accomplished manually. This work introduces automated phantom identification and image QA measure extraction towards a fully-automated CT phantom QA system to perform these functions and facilitate the use of Quantitative Imaging methods in clinical trials. Methods: This study used a retrospective cohort of CT phantom scans from existing clinical trial protocols - totaling 84 phantoms, across 3 phantom types using various scanners and protocols. The QA system identifies the input phantom scan through an ensemble of threshold-based classifiers. Each classifier - corresponding to a phantom type - contains a template slice, which is compared to the input scan on a slice-by-slice basis, resulting in slice-wise similarity metric values for each slice compared. Pre-trained thresholds (established from a training set of phantom images matching the template type) are used to filter the similarity distribution, and the slice with the most optimal local mean similarity, with local neighboring slices meeting the threshold requirement, is chosen as the classifier's matched slice (if it existed). The classifier with the matched slice possessing the most optimal local mean similarity is then chosen as the ensemble's best matching slice. If the best matching slice exists, image QA algorithm and ROIs corresponding to the matching classifier extracted the image QA measures. Results: Automated phantom identification performed with 84.5% accuracy and 88.8% sensitivity on 84 phantoms. Automated image quality measurements (following standard protocol) on identified water phantoms (n=35) matched user QA decisions with 100% accuracy. Conclusion: We provide a fullyautomated CT phantom QA system consistent with manual QA performance. Further work will include parallel component to automatically verify image acquisition parameters and automated adherence to specifications. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics; NIH Grant support from: U01 CA181156.

Purpose: CT lung screening is already performed at low doses. In this study, we investigated the effects of further dose reduction on a lung-nodule CAD detection algorithm. Methods: The original raw CT data and images from 348 patients were obtained from our local database of National Lung Screening Trial (NLST) cases. 61 patients (17.5%) had at least one nodule reported on the NLST reader forms. All scans were acquired with fixed mAs (25 for standard-sized patients, 40 for large patients) on a 64-slice scanner (Sensation 64, Siemens Healthcare). All images were reconstructed with 1-mm slice thickness, B50 kernel. Based on a previously-published technique, we added noise to the raw data to simulate reduced-dose versions of each case at 50% and 25% of the original NLST dose (i.e. approximately 1.0 and 0.5 mGy CTDIvol). For each case at each dose level, a CAD detection algorithm was run and nodules greater than 4 mm in diameter were reported. These CAD results were compared to “truth”, defined as the approximate nodule centroids from the NLST forms. Sensitivities and false-positive rates (FPR) were calculated for each dose level, with a sub-analysis by nodule LungRADS category. Results: For larger category 4 nodules, median sensitivities were 100% at all three dose levels, and mean sensitivity decreased with dose. For the more challenging category 2 and 3 nodules, the dose dependence was less obvious. Overall, mean subject-level sensitivity varied from 38.5% at 100% dose to 40.4% at 50% dose, a difference of only 1.9%. However, median FPR quadrupled from 1 per case at 100% dose to 4 per case at 25% dose. Conclusions: Dose reduction affected nodule detectability differently depending on the LungRADS category, and FPR was very sensitive at sub-screening levels. Care should be taken to adapt CAD for the very challenging noise characteristics of screening. Funding support: NIH U01 CA181156; Disclosures (McNitt-Gray): Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics.

Purpose: The purpose of this work is to estimate effective and lung doses from a low-dose lung cancer screening CT protocol using Tube Current Modulation (TCM) across patient models of different sizes. Methods: Monte Carlo simulation methods were used to estimate effective and lung doses from a low-dose lung cancer screening protocol for a 64-slice CT (Sensation 64, Siemens Healthcare) that used TCM. Scanning parameters were from the AAPM protocols. Ten GSF voxelized patient models were used and had all radiosensitive organs identified to facilitate estimating both organ and effective doses. Predicted TCM schemes for each patient model were generated using a validated method wherein tissue attenuation characteristics and scanner limitations were used to determine the TCM output as a function of table position and source angle. The water equivalent diameter (WED) was determined by estimating the attenuation at the center of the scan volume for each patient model. Monte Carlo simulations were performed using the unique TCM scheme for each patient model. Lung doses were tallied and effective doses were estimated using ICRP 103 tissue weighting factors. Effective and lung dose values were normalized by scanspecific 32 cm CTDIvol values based upon the average tube current across the entire simulated scan. Absolute and normalized doses were reported as a function of WED for each patient. Results: For all ten patients modeled, the effective dose using TCM protocols was below 1.5 mSv. Smaller sized patient models experienced lower absolute doses compared to larger sized patients. Normalized effective and lung doses showed some dependence on patient size (R2 = 0.77 and 0.78, respectively). Conclusion: Effective doses for a low-dose lung screening protocol using TCM were below 1.5 mSv for all patient models used in this study. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics