bluuebunny/crossref_metadata_2025 huggingface dataset:
Information Reliability in Supply Chains: The Case of Multiple Retailers
Authors: Spiliotopoulou Eirini , Donohue Karen , Gürbüz Mustafa Çagri
Published: June 2015

Inventory decisions made at a centralized level often rely on demand forecast information passed from regional managers within a supply chain. Such managers often have unique insights into the demand patterns at their local sites that can help inform how much inventory to order for the system as a whole. Problems can arise with this setup, however, if these managers have incentives to misreport their forecasts and the central planner (CP), in turn, mistrusts this information. The goal of our research is to shed light on the existence, magnitude, and causes of such coordination problems using a combination of analytical models and behavioral experiments. The analytical analysis reveals that incentives are misaligned in this setting and no truth‐telling equilibrium exists in general, unless inventory competition or demand uncertainty is removed. With this theoretical grounding, we conduct a series of controlled laboratory experiments to test the magnitude of these problems and how they are impacted by inventory competition, strategic concerns regarding the other parties, and the demand environment. We find that inventory competition and market uncertainty harm the efficacy of forecast sharing and channel efficiency, while the possibility that untrustworthy reports are detected (identical local demand information) does not deter regional managers from misreporting their forecasts. Removing strategic concerns regarding the CP (automating the central ordering decision) does not improve profit but reduces order variability. Information sharing appears to be a dominant policy as it significantly improves profit in all treatments compared with no information sharing.
Association between intraoperative ventilator settings and plasma levels of soluble receptor for advanced glycation end‐products in patients without pre‐existing lung injury
Authors: Jabaudon Matthieu , Futier Emmanuel , Roszyk Laurence , Sapin Vincent , Pereira Bruno , Constantin Jean‐Michel
Published: June 2015

Background and objective

The soluble form of the receptor for advanced glycation end‐products (sRAGE) is elevated and correlated with severity in patients with acute respiratory distress syndrome (ARDS). The impact of ventilator settings on plasma levels of sRAGE, in patients with or without pre‐existing lung injury, remains under‐investigated to date. Our objective was to assess the effects of a lung‐protective ventilation strategy (combining low tidal volume, positive end‐expiratory pressure and recruitment maneuvers), as compared with a non‐protective approach (with high tidal volume and zero end‐expiratory pressure), on plasma levels of sRAGE in patients without lung injury undergoing major abdominal surgery.

Methods

Plasma samples were obtained from 95 patients enrolled in a large randomized controlled trial of lung‐protective ventilation for major abdominal surgery. Plasma levels of sRAGE were measured in duplicate with an enzyme‐linked immunoassay on day 1, immediately after surgery, and on postoperative days 1, 3 and 7.

Results

Early postoperative plasma levels of sRAGE were significantly lower in the lung‐protective ventilation group (n = 47) than in the non‐protective ventilation group (n = 48) (mean (standard deviation), 1782 (836) vs 2171 (1678) pg/mL, respectively, P = 0.03). Intraoperative changes in plasma sRAGE were associated with postoperative hypoxemia and ARDS.

Conclusions

A lung‐protective ventilation strategy decreased plasma sRAGE in patients without lung injury undergoing major abdominal surgery compared with the patients with non‐protective ventilation. This intraoperative decrease could reflect a lesser degree of epithelial injury.
A precise automatic system for the hair assessment in hair‐care diagnosis applications
Authors: Shih H.
Published: June 2015

Background/Purpose

One emerging subject in medical image processing is to quantitatively assess the health and the properties of cranial hairs, including density, diameter, length, level of oiliness, and others. This information helps hair specialists with making a more accurate diagnosis and the therapy required. We develop a practical hair counting algorithm. This analytic system calculates the number of hairs on a scalp using a digital microscope camera, providing accurate information for both the hair specialist and the patient. Our proposed hair counting algorithm is substantially more accurate than the Hough‐based one, and is robust to curls, oily scalp, noise‐corruption, and overlapping hairs, under various levels of illumination. Rather than manually counting the hairs on a person's scalp, the proposed system determines the density, diameter, length, and level of oiliness of the hairs.

Methods

We propose an automated system for counting the amount of hairs in the microscopy images. To reduce the effect of bright spots, we develop a robust morphological algorithm for color to smooth out the color and preserve the fidelity of the hair. Then, we utilize a modified Hough transform algorithm to detect the different hair lengths and to reduce any false detection due to noise. Our proposed system enables us to look at curved hairs as multiple pieces of straight lines. To avoid missing hairs when the thinning process is applied, we use edge information to discover any hidden or overlapping hairs. Finally, we employ a mutually associative regression method to label a group of line segments into a meaningful ‘hair’.

Results

We demonstrated a novel approach for accurately computing the number of hairs, and successfully solved the three main obstacles in automated hair counting, including (i) oily and moist hairs, (ii) wavy and curly hairs, and (iii) under‐estimation of the number of hairs occurs when hairs cross and occlude each other. The framework of this paper can be seen as the first step toward intelligent computer‐aided medical image processing for cosmetic treatment applications.

Conclusions

The goal of this study was to develop an automated hair counting system for clinical application using the microscope image from the hairs. The proposed method reduces the frequent errors and variances encountered when hairs are manually counted by human assessors. This clinical intelligent system can diagnose the health condition of a person's hair and can be applied in therapy recommendations by doctors for their patients.
Role modelling in medical education: the importance of teaching skills
Authors: Burgess Annette , Oates Kim , Goulston Kerry
Published: June 2015

Objectives

By observation of role models, and participation in activities, students develop their attitudes, values and professional competencies. Literature suggests that clinical skills and knowledge, personality, and teaching skills are three main areas that students consider central to the identification of positive role models. The aim of this study was to explore junior medical students' opinions of the ideal attributes of a good role model in clinical tutors.

Methods

The study was conducted with one cohort (n = 301) of students who had completed year 1 of the medical programme in 2013. All students were asked to complete a questionnaire regarding the ideal attributes of a good role model in a clinical tutor. The questionnaire consisted of seven closed items and one open‐ended question.

Results

The response rate to the questionnaire was 265/301 (88%). Although students found all three key areas important in a good role model, students emphasised the importance of excellence in teaching skills. Specifically, students see good role models as being able to provide a constructive learning environment, a good understanding of the curriculum and an ability to cater to the learning needs of all students.

Students see good role models as being able to provide a constructive learning environment

Conclusion

While acknowledging the importance of a patient‐centred approach, as well as clinical knowledge and skills, our findings reinforce the importance of the actual teaching abilities of role models within medical education.
High‐level expression and phosphorylation of phytochrome B modulates flowering time in Arabidopsis
Authors: Hajdu Anita , Ádám Éva , Sheerin David J. , Dobos Orsolya , Bernula Péter , Hiltbrunner Andreas , Kozma‐Bognár László , Nagy Ferenc
Published: June 2015

Optimal timing of flowering in higher plants is crucial for successful reproduction and is coordinated by external and internal factors, including light and the circadian clock. In Arabidopsis, light‐dependent stabilization of the rhythmically expressed CONSTANS (CO) is required for the activation of FLOWERING LOCUS T (FT), resulting in the initiation of flowering. Phytochrome A and cryptochrome photoreceptors stabilize CO in the evening by attenuating the activity of the CONSTITUTIVE PHOTOMORPHOGENIC 1–SUPPRESSOR OF PHYA‐105 1 (COP1–SPA1) ubiquitin ligase complex, which promotes turnover of CO. In contrast, phytochrome B (phyB) facilitates degradation of CO in the morning and delays flowering. Accordingly, flowering is accelerated in phyB mutants. Paradoxically, plants overexpressing phyB also show early flowering, which may arise from an early phase of rhythmic CO expression. Here we demonstrate that overexpression of phyB induces FT transcription at dusk and in the night without affecting the phase or level of CO transcription. This response depends on the light‐activated Pfr form of phyB that inhibits the function of the COP1–SPA1 complex by direct interactions. Our data suggest that attenuation of COP1 activity results in the accumulation of CO protein and subsequent induction of FT. We show that phosphorylation of Ser‐86 inhibits this function of phyB by accelerating dark reversion and thus depletion of Pfr forms in the night. Our results explain the early flowering phenotype of phyB overexpression and reveal additional features of the molecular machinery by which photoreceptors mediate photoperiodism.
Ex‐VivoEvaluation of a Modified Teno Fix®Device Repair Pattern Versus a 3‐Loop Pulley for Repair of Equine Flexor Tendons
Authors: McMaster Mattie A. , Munsterman Amelia S. , Weimar Wendi H. , Barrett Elizabeth J. , Hanson R.Reid
Published: June 2015

Objective

To compare the load to ultimate failure, load to a 2 mm gap, mode of failure, and gap at failure (mm) of the Teno Fix®(TF) to the 3‐loop pulley (3LP) for repair of equine tendon lacerations. The use of 4TF devices versus 5TF devices on load to ultimate failure and load to a 2 mm gap was also compared.

Study Design

Ex vivobiomechanical study; unbalanced incomplete block (horse) design.

Samples

Cadaveric equine forelimb superficial digital flexor tendon (n = 20 paired tendons).

Methods

Ten tendon pairs were selected randomly and repaired with a 3LP and 4TF pattern, and 10 tendon pairs repaired with a 3LP and 5TF pattern. Load to ultimate failure, load to a 2 mm gap, mode of failure, and gap at failure were obtained using materials testing.

Results

The 3LP had a significantly greater ultimate load to failure (P < .001, respectively) and a significantly higher load to a 2 mm gap than both TF repairs (P < .001, respectively). The most frequent mode of failure was suture pull‐out for the 3LP and anchor pull‐out for the TF. Gap at failure was significantly larger in the 3LP than both TF repairs (P < .001). The ultimate load to failure was significantly higher for the 5TF than the 4TF (P = .004) but there was no significant difference in load to a 2 mm gap, or gap at failure between both TF repairs (P = .11,P = .15, respectively).

Conclusions

Neither TF repair was stronger than the 3LP in load to ultimate failure and load to a 2 mm gap. Addition of a fifth TF device significantly increased the load to ultimate failure but did effect the load to a 2 mm gap over the 4TF.
Combined Influence of Synthetic Jet and Surface-Mounted Rib on Heat Transfer in a Square Channel
Authors: Qayoum Adnan , Panigrahi P. K.
Published: June 2015

This investigation reports the combined effect of synthetic jet and a surface-mounted rib on heat transfer in a square cross-section channel flow. The rib height to hydraulic diameter ratio is equal to 0.1625. The Reynolds number of the channel has been set equal to 5500. The synthetic jet actuator has been operated at different actuation voltages with different amplitude modulation frequencies. At actuation voltage of 55 V, the maximum overall heat transfer is enhanced by 132.6% compared with smooth duct flow.
Numerical Studies on Hydrogen Distribution in Enclosures in the Presence of Condensing Steam
Authors: Agrawal Nilesh , Das Sarit K.
Published: June 2015

Hydrogen release in confined spaces is an important safety issue, which is even more important in the context of severe accident in nuclear reactors. In severe accidents, hydrogen release is associated with release of steam and the condensation of steam on walls leads to increase in concentration of hydrogen in residual gas as well as condensation induced mixing. In the present paper, a model for falling film steam condensation in the presence of noncondensable gases is presented. The steam condensation model is incorporated into an in-house developed cfd code called hydrogen distribution simulator (HDS) and is used for hydrogen distribution studies. The validation of the CFD model with steam condensation against the experimental results from the CONAN facility is discussed. Subsequently, the model is applied to a typical release situation involving release of hydrogen and steam for some time and its distribution for a long time beyond it. The heat and mass transfer aspects of the problem are highlighted. It is seen that steam condensation has an important bearing on the distribution of hydrogen and the mixing behavior of gases in the enclosure.
A New Generation of Medium Temperature Collector for Solar Cooling1
Authors: Winston Roland , Jiang Lun
Published: June 2015

Prologue

In the early 1970s, I began a research effort at Argonne National Laboratory to develop the nonimaging nontracking solar concentrator I had recently invented which became known as the compound parabolic concentrator or CPC. I had lots of help; in particular from lab director, Robert G. Sachs 1, Gale Pewitt, William Schertz, and many others. The lab recruited some of the best scientists in the world, in the relevant fields to work with me: for optics, Walter Welford, and for solar energy, Frank Kreith. Our first project was solar domestic hot water (DHW) for the “Breadsprings elementary school” in a Navajo Indian reservation near Gallup, NM. The collector was a threefold concentration nonevacuated CPC. Because threefold concentration can only accept solar motions for half the year, it was oriented for winter. Like every other project I ever collaborated on with Frank Kreith, it was a big success. I thought it was fitting to submit a paper on a recent “CPC” for much higher temperature (200 °C), totally stationary, and driving a double-effect absorption chiller.
Elastodynamic Modeling and Analysis for an Exechon Parallel Kinematic Machine
Authors: Zhang Jun , Zhao Yan Q. , Jin Yan
Published: June 2015

As a newly invented parallel kinematic machine (PKM), Exechon has attracted intensive attention from both academic and industrial fields due to its conceptual high performance. Nevertheless, the dynamic behaviors of Exechon PKM have not been thoroughly investigated because of its structural and kinematic complexities. To identify the dynamic characteristics of Exechon PKM, an elastodynamic model is proposed with the substructure synthesis technique in this paper. The Exechon PKM is divided into a moving platform subsystem, a fixed base subsystem and three limb subsystems according to its structural features. Differential equations of motion for the limb subsystem are derived through finite element (FE) formulations by modeling the complex limb structure as a spatial beam with corresponding geometric cross sections. Meanwhile, revolute, universal, and spherical joints are simplified into virtual lumped springs associated with equivalent stiffnesses and mass at their geometric centers. Differential equations of motion for the moving platform are derived with Newton's second law after treating the platform as a rigid body due to its comparatively high rigidity. After introducing the deformation compatibility conditions between the platform and the limbs, governing differential equations of motion for Exechon PKM are derived. The solution to characteristic equations leads to natural frequencies and corresponding modal shapes of the PKM at any typical configuration. In order to predict the dynamic behaviors in a quick manner, an algorithm is proposed to numerically compute the distributions of natural frequencies throughout the workspace. Simulation results reveal that the lower natural frequencies are strongly position-dependent and distributed axial-symmetrically due to the structure symmetry of the limbs. At the last stage, a parametric analysis is carried out to identify the effects of structural, dimensional, and stiffness parameters on the system's dynamic characteristics with the purpose of providing useful information for optimal design and performance improvement of the Exechon PKM. The elastodynamic modeling methodology and dynamic analysis procedure can be well extended to other overconstrained PKMs with minor modifications.
A Design System for Six-Bar Linkages Integrated With a Solid Modeler
Authors: Sonawale Kaustubh H. , Michael McCarthy J.
Published: June 2015

This paper presents a design system for planar and spherical six-bar linkages, which is integrated with a solid modeler. The user specifies a backbone 3R chain in five task configurations in the sketch mode of the solid modeler and executes the design system. Two RR constraints are computed, which constrain the 3R chain to a single degree-of-freedom six-bar linkage. There are six ways that these constraints can be added to the 3R serial chain to yield as many as 63 different linkages in case of planar six-bar linkages and 165 in case of spherical six-bar linkages. The performance of each candidate is analyzed, and those that meet the required task are presented to the designer for selection. The design algorithm is run iteratively with random variations applied to the task configurations within user-specified tolerance zones, to increase the number of candidate designs. The output is a solid model of the six-bar linkage. Examples are presented, which demonstrate the effectiveness of this strategy for both planar and spherical linkages.
SU‐D‐210‐04: Using Radiotherapy Biomaterials to Brand and Track Deadly Cancer Cells
Authors: Altundal Y , Sajo E , Ngwa W
Published: June 2015

Purpose:

Metastasis accounts for over 90% of all cancer associated suffering and death and arguably presents the most formidable challenges in cancer management. The detection of metastatic or rare circulating tumor cells (CTCs) in blood or lymph nodes remains a formidable technological challenge. In this study, we investigated the time needed to label each cancer cell in‐situ (right at the source tumor) with sufficient number of GNPs that will allow enhanced non‐invasive detection via photoacoustic imaging in the lymph nodes. Such in‐situ labeling can be achieved via sustained release of the GNPs from Radiotherapy (RT) biomaterials (e.g. fiducials, spacers) coated/loaded with the GNP.

Methods:

The minimum concentration (1000 GNPs/cell for 50nm GNPs) to detect GNPs with photoacoustic imaging method was experimentally measured by Mallidi et al. and fixed at the tumor sub‐volume periphery. In this work, the GNPs were assumed to diffuse from a point source, placed in the middle of a 2–3cm tumor, with an initial concentration of 7–30 mg/g. The time required to label the cells with GNPs was calculated by solving the three dimensional diffusion‐reaction equation analytically. The diffusion coefficient of 10nm GNPs was experimentally determined previously. Stokes‐Einstein equation was used to calculate the diffusion coefficients for other sizes (2–50nm) of GNPs. The cellular uptake rate constants for several sizes of GNPs were experimentally measured by Jin et al.

Results:

The time required to label the cells was found 0.635–15.91 days for 2–50nm GNPs with an initial concentration of 7 mg/g GNPs in a 2 cm tumor; 1.379–34.633 days for 2–50nm GNPs with an initial concentration of 30 mg/g GNPs in a 3cm tumor.

Conclusion:

Our results highlight new potential for labeling CTCs with GNPs released from smart RT biomaterials (i.e. fiducials or spacers loaded with the GNP) towards enhanced non‐invasive imaging/detection via photoacoustic imaging.
SU‐E‐P‐37: Helical Tomotherapy to LINAC Plan Conversion Utilizing RayStation Fallback Planning
Authors: Zhang X , Penagaricano J , Liang X , Morrill S , Corry P , Griffin R , Paudel N , Ratanatharathorn V
Published: June 2015

Purpose:

RayStation Fallback (RSF) plan was developed to switch patient's treatment from Helical Tomotherapy (HT) to Varian TrueBeam. Helical Tomotherapy plans were compared with the corresponding RSF plans by looking at the following dosimetric parameters: PTV coverage (Dmean and D95), Paddick conformity index (CI), uniformity index (UI=(D98‐D2)/Drx) and organ‐at‐risk (OAR) doses.

Methods:

Five patients with five tumor sites including larynx, head and neck, esophagus, lung, and prostate previously treated with HT were re‐planned using RSF treatment planning station(TPS) to best match the HT treatment plans. IMRT technique with nine fields 6 MV X‐ray beams and a static multi‐leaf collimator (MLC) were used for RSF plans without any additional attempt to further optimize the RSF plans.

Results:

A physician evaluated and confirmed the clinical acceptability of the RSF plans. Both HT and RSF plans gave comparable PTV coverage with a maximum percentage difference for D95 of 0.7%. HT plans had a better CIs ranging from 2%–15% higher conformity compared to RSF plans. HT plans also had better UIs for all tumor sites except the esophagus. The UIs were 1.6% to 8.9% lower for HT plans compared to RSF plans. Both HT and RSF plans gave comparable and acceptable OAR doses. However, the integral dose was 1%–15% higher for HT plans compared to RSF plans.

Conclusion:

RSF plans were simple and fast to generate. In the study cases of 5 various tumor sites, RSF efficiently created clinically acceptable plans without further optimization. However, further optimization for any IMRT plan can be done if clinically warranted. The absolute differences in CI and UI were small between RSF and HT plans.
SU‐E‐P‐38: Comparison of Capri Applicator HDR Planning Methods to Meet the NCCN Uterine Neoplasm 2.2015 Guidelines
Authors: Klash S , Stanley T , Steinman J , Kim D , Yap J , Yi S
Published: June 2015

Purpose:

To establish a systematic planning approach for Capri intravaginal multichannel balloon applicators that meet updated Version 2.2015 NCCN guidelines for uterine neoplasms, which dictate delivery of 400 to 600 cGy in 2 to 3 fractions prescribed to the vaginal mucosa for HDR combined with EBRT as well as a regimen of 600 cGy × 5 (to the vaginal mucosa) for HDR brachytherapy alone.

Methods:

Studies have shown three different channel configurations of the Capri applicator are optimal for dosimetric conformity: central channel combined with the six inner ring channels (R12), all inner and outer ring channels (R23), or all thirteen channels (R123). To minimize the dose to the vaginal mucosa, a traditional 0.5cm expansion contour from the Capri surface was created. Optimization limits were set to push 600 cGy to 100% of the Capri volume, while simultaneously restricting dose to the expansion contour.

Results:

Plans were created using all three configurations (R12, R23, R123) and evaluated to determine which was best for delivering 600 cGy to the vaginal mucosa. Our criteria was: Capri V100 > 98%, Vaginal Mucosa Dmax < 125%, Bladder Dmax < 100%, Rectum Dmax < 100%. All configurations show Capri V100 values greater than 98.5%, with differences between plans varying by less than 1%. Vaginal mucosal Dmax values showed differences of roughly 5% of prescription. The R12 configuration proved the lowest vaginal mucosa Dmax, on average. The OAR Dmax values showed an average dose difference of roughly 2% of prescription, with the R23 configuration having the best results.

Conclusion:

The R12 channel configuration optimally fits our planning criteria and NCCN guidelines for 600 cGy prescribed to the vaginal mucosa. On average, it produced the highest Capri V100, the lowest vaginal mucosal Dmax, and a marginally higher OAR Dmax doses compared to the R23 and R123 plans.
SU‐E‐P‐39: Characterization of Dose Impact On Different Beam Fields Size Attenuation for Elekta IGRT Couch
Authors: Zhang R , Bai W , Xiaomei F , Chi Z , Runxiao L , Ren Q , Gao C
Published: June 2015

Purpose:

Quantification of the dosimetric impact of the Elekta IGRT treatment couch in different beam field sizes. Established the relationship of relative dose versus beam angle at different beam field sizes.

Methods:

Measurements of couch attenuation were performed at gantry angles from 180° to 120°, using a 0.125cc semiflex ionization chamber, isocentrically placed in the center of a homogeneous cylindric sliced RW3 phantom for 6 photon beams. Measurements were performed at six different field sizes (3×3, 5×5, 7×7,10×10, 12×12 and 15×15 cm2). The phantom were positioned at the center of the couche,100 MU were delivered at every gantry angle. The dose difference to the ion chamber was determined.

Results:

For oblique fields with 6 MV photons at the same gantry angle the attenuation coefficient value from the lagest to the smallest the order is field size 7 cm2,5 cm2,10 cm2,12 cm2,15 cm2 and 3 cm2. The biggest couch attenuation by up to 4.15% at the gantry angle of 140°for the field size of 7 cm2, while for the field size of 3 cm2 the couch attenuated value only 3.5%. The other field size couch attenuation values are between the couch attenuated value of field size of 7 cm2 and 3 cm2

Conclusion:

The recommended treatment couch attenuation measured beam field size is 10×10 or 12×12 cm2. When measured using the beam field size 3×3 cm2 the tested value will be lower, while measuerd using the beam field size 7×7 cm2 the tested value will be higer than the recommended beam field size. This should be noted when modeling the treatment couch in the treatment planning system.
SU‐E‐P‐40: Dosimetric Characteristics of Field Aperture Margin Design in Stereotactic Body Radiation Therapy (SBRT)
Authors: Zhu J
Published: June 2015

Purpose:

To characterize the dosimetric effects of field aperture margin design in Stereotactic Body Radiation Therapy (SBRT).

Methods:

Three artificial spherical PTVs, with diameter of 10mm, 20mm and 30mm, were created on CT images of a human body thoracic phantom. Seven non_coplanar isocentric fields were used for treatment planning. For each PTV, treatment plans with margins 0mm, 1mm, 2mm and 3mm were planned. Dosimetric comparison among plans was done considering the following parameters: prescribed isodose line for target coverage, maximum dose, mean dose as well as dose spillages of V80, V50, and V20.

Results:

Corresponding to aperture margins of 0mm, 1mm,2m and 3mm used in the treatment planning, the percentage of isodose line chosen for dose prescription increases from 65% to 93% for 10mm PTV, 70% to 92% for 20mm PTV, and 75% to 92% for 30mm PTV. The maximum dose decrease accordingly from 155.7% to 109.5% for 10mm PTV, 145% to 111.6% for 20mm PTV, 137% to 112.2% for 30mm PTV. The mean dose decrease from 138.% to 104.4% for 10mm PTV, 122.8% to 106.1% for 20mm PTV, 121.3% to 106% for 30mm PTV. Dose spillages (mm3) increase (V80−2.6 to 4.02, V50−4.55 to 9.3, V20–87.86 to 101.71) for 10 mm PTV, (V80−6.78 to 9.89, V50–13.46 to 20.4, V20‐119.16 to 219.1) for 20 mm PTV, (V80–22.01 to 28.59, V50–41.56 to 52.66, V20‐532.71 to 551.84) for 30 mm PTV.

Conclusion:

In SBRT treatment planning, tight field aperture margin requires prescribing dose to lower isodose line that leading to higher dose inhomogeneity and higher mean dose to PTV. Loose margin allows prescribing dose to higher isodose line, therefore improves the dose homogeneity. However, it increases dose spillages. Clinician could try different margins according to the PTV size and location of surrounding critical organs to optimize the dose delivered to the patient.
SU‐E‐P‐45: An Analytical Formula for Deriving Mechanical Iso‐Center of Rotational Gantry Treatment Unit Rotational Gantry Treatment Unit
Authors: Ding X , Bues M
Published: June 2015

Purpose:

To present an analytical formula for deriving mechanical isocenter (MIC) of a rotational gantry treatment unit. The input data to the formula is obtained by a custom‐made device. The formula has been implemented and used in an operational proton therapy facility since 2005.

Methods:

The custom made device consisted of 3 mutually perpendicular dial indicators and 5 clinometers, to obtain displacement data and gantry angle data simultaneously. During measurement, a steel sphere was affixed to the patient couch, and the device was attached to the snout rotating with the gantry. The displacement data and angle data were obtained simultaneously at angular increments of less than 1 degree. The analytical formula took the displacement and angle as input and derived the positions of dial indicator tips (DIT) position in room‐fixed coordinate system. The formula derivation presupposes trigonometry and 3‐dimentional coordinate transformations. Due to the symmetry properties of the defining equations, the DIT position can be solved for analytically without using mathematical approximations. We define the mean of all points in the DIT trajectory as the MIC. The formula was implemented in computer code, which has been employed during acceptance test, commissioning, as well as routine QA practice in an operational proton facility since 2005.

Results:

It took one minute for the custom‐made device to acquire the measurement data for a full gantry rotation. The DIT trajectory and MIS are instantaneously available after the measurement. The MIC Result agrees well with vendor's Result, which came from a different measurement setup, as well as different data analysis algorithm.

Conclusion:

An analytical formula for deriving mechanical isocenter was developed and validated. The formula is considered to be absolutely accurate mathematically. Be analyzing measured data of radial displacements as function of gantry angle, the formula calculates the MI position in room coordinate.
SU‐E‐P‐54: Evaluation of the Accuracy and Precision of IGPS‐O X‐Ray Image‐Guided Positioning System by Comparison with On‐Board Imager Cone‐Beam Computed Tomography
Authors: Zhang D , Wang W , Jiang B , Fu D
Published: June 2015

Purpose:

The purpose of this study is to assess the positioning accuracy and precision of IGPS‐O system which is a novel radiographic kilo‐voltage x‐ray image‐guided positioning system developed for clinical IGRT applications.

Methods:

IGPS‐O x‐ray image‐guided positioning system consists of two oblique sets of radiographic kilo‐voltage x‐ray projecting and imaging devices which were equiped on the ground and ceiling of treatment room. This system can determine the positioning error in the form of three translations and three rotations according to the registration of two X‐ray images acquired online and the planning CT image. An anthropomorphic head phantom and an anthropomorphic thorax phantom were used for this study. The phantom was set up on the treatment table with correct position and various “planned” setup errors. Both IGPS‐O x‐ray image‐guided positioning system and the commercial On‐board Imager Cone‐beam Computed Tomography (OBI CBCT) were used to obtain the setup errors of the phantom. Difference of the Result between the two image‐guided positioning systems were computed and analyzed.

Results:

The setup errors measured by IGPS‐O x‐ray image‐guided positioning system and the OBI CBCT system showed a general agreement, the means and standard errors of the discrepancies between the two systems in the left‐right, anterior‐posterior, superior‐inferior directions were −0.13±0.09mm, 0.03±0.25mm, 0.04±0.31mm, respectively. The maximum difference was only 0.51mm in all the directions and the angular discrepancy was 0.3±0.5° between the two systems.

Conclusion:

The spatial and angular discrepancies between IGPS‐O system and OBI CBCT for setup error correction was minimal. There is a general agreement between the two positioning system. IGPS‐O x‐ray image‐guided positioning system can achieve as good accuracy as CBCT and can be used in the clinical IGRT applications.
SU‐E‐I‐16: Scan Length Dependency of the Radial Dose Distribution in a Long Polyethylene Cylinder
Authors: Bakalyar D , Feng W , McKenney S
Published: June 2015

Purpose:

The area‐averaged dose in the central plane of a long cylinder following a CT scan depends upon the radial dose distribution and the length of the scan. The ICRU/TG200 phantom, a polyethylene cylinder 30 cm in diameter and 60 cm long, was the subject of this study. The purpose was to develop an analytic function that could determine the dose for a scan length L at any point in the central plane of this phantom.

Methods:

Monte Carlo calculations were performed on a simulated ICRU/TG200 phantom under conditions of cylindrically symmetric conditions of irradiation. Thus, the radial dose distribution function must be an even function that accounts for two competing effects: The direct beam makes its weakest contribution at the center while the scatter begins abruptly at the outer radius and grows as the center is approached. The scatter contribution also increases with scan length with the increase approaching its limiting value at the periphery faster than along the central axis. An analytic function was developed that fit the data and possessed these features.

Results:

Symmetry and continuity dictate a local extremum at the center which is a minimum for the ICRU/TG200 phantom. The relative depth of the minimum decreases as the scan length grows and an absolute maximum can occur between the center and outer edge of the cylinders. As the scan length grows, the relative dip in the center decreases so that for very long scan lengths, the dose profile is relatively flat.

Conclusion:

An analytic function characterizes the radial and scan length dependency of dose for long cylindrical phantoms. The function can be integrated with the results expressed in closed form. One use for this is to help determine average dose distribution over the central cylinder plane for any scan length.
SU‐E‐J‐138: On the Ion Beam Range and Dose Verification in Hadron Therapy Using Sound Waves
Authors: Fourkal E , Veltchev I , Gayou O , Nahirnyak V
Published: June 2015

Purpose:

Accurate range verification is of great importance to fully exploit the potential benefits of ion beam therapies. Current research efforts on this topic include the use of PET imaging of induced activity, detection of emerging prompt gamma rays or secondary particles. It has also been suggested recently to detect the ultrasound waves emitted through the ion energy absorption process. The energy absorbed in a medium is dissipated as heat, followed by thermal expansion that leads to generation of acoustic waves. By using an array of ultrasound transducers the precise spatial location of the Bragg peak can be obtained. The shape and intensity of the emitted ultrasound pulse depend on several variables including the absorbed energy and the pulse length. The main objective of this work is to understand how the ultrasound wave amplitude and shape depend on the initial ion energy and intensity. This would help guide future experiments in ionoacoustic imaging.

Methods:

The absorbed energy density for protons and carbon ions of different energy and field sizes were obtained using Fluka Monte Carlo code. Subsequently, the system of coupled equations for temperature and pressure is solved for different ion pulse intensities and lengths to obtain the pressure wave shape, amplitude and spectral distribution.

Results:

The proposed calculations show that the excited pressure wave amplitude is proportional to the absorbed energy density and for longer ion pulses inversely proportional to the ion pulse duration. It is also shown that the resulting ionoacoustic pressure distribution depends on both ion pulse duration and time between the pulses.

Conclusion:

The Bragg peak localization using ionoacoustic signal may eventually lead to the development of an alternative imaging method with sub‐millimeter resolution. It may also open a way for in‐vivo dose verification from the measured acoustic signal.
SU‐E‐J‐176: Characterization of Inter‐Fraction Breast Variability and the Implications On Delivered Dose
Authors: Sudhoff M , Lamba M , Kumar N , Ward A , Elson H
Published: June 2015

Purpose:

To systematically characterize inter‐fraction breast variability and determine implications on delivered dose.

Methods:

Weekly port films were used to characterize breast setup variability. Five evenly spaced representative positions across the contour of each breast were chosen on the electronic port film in reference to graticule, and window and level was set such that the skin surface of the breast was visible. Measurements from the skin surface to treatment field edge were taken on each port film at each position and compared to the planning DRR, quantifying the variability. The systematic measurement technique was repeated for all port films for 20 recently treated breast cancer patients. Measured setup variability for each patient was modeled as a normal distribution. The distribution was randomly sampled from the model and applied as isocentric shifts in the treatment planning computer, representing setup variability for each fraction. Dose was calculated for each shifted fraction and summed to obtain DVHs and BEDs that modeled the dose with daily setup variability. Patients were categorized in to relevant groupings that were chosen to investigate the rigorousness of immobilization types, treatment techniques, and inherent anatomical difficulties. Mean position differences and dosimetric differences were evaluated between planned and delivered doses.

Results:

The setup variability was found to follow a normal distribution with mean position differences between the DRR and port film between − 8.6–3.5 mm with sigma range of 5.3–9.8 mm. Setup position was not found to be significantly different than zero. The mean seroma or whole breast PTV dosimetric difference, calculated as BED, ranged from a −0.23 to +1.13Gy.

Conclusion:

A systematic technique to quantify and model setup variability was used to calculate the dose in 20 breast cancer patients including variable setup. No statistically significant PTV or OAR BED differences were found between immobilization, treatment or anatomical differences investigated.
SU‐E‐J‐183: Quantification of Motion During Hypo‐Fractionated Prostate Cancer Radiation Therapy
Authors: Ravindranath B , Zhang P , Xiong J , Mageras G , Hunt M
Published: June 2015

Purpose:

To quantify patient motion during hypo‐fractionated prostate cancer treatment as tracked by Calypso™ 4D localization system.

Methods:

50 prostate cancer patients with implanted Calypso beacons underwent hypofractionated IMRT treatment. Typical fraction size was 5 with doses of 5–8 Gy/fraction. 213 traces from the 50 patients were analyzed to quantify the probability of motion vs time starting from beam‐on. Couch corrections applied by therapists were undone to obtain the natural course of patient motion. The Calypso data was used to identify vector displacements greater than 2 mm from the starting position. The direction of this vector was classified into one of the 26 directions (combinations of L/R, A/P, S/I). The probability of motion >2mm was estimated by computing the fraction of traces that exceed the 2mm threshold at each time point. The violating motion points were also binned by direction in order to identify specific directions that were more prone to movement.

Results:

The overall probability of motion greater than 2 mm at 5 and 10 minutes from beam‐on were 27 % and 50% respectively. The primary directions in which motion occurred were Posterior‐Inferior (PI) and Inferior (I) with a probability of 8.5% and 4% at 5 minutes and 10% for both at 10 minutes. Motion was classified into the following bins: 0–2, 2–3, 3–4, 4–5, 5–6, 6–7, 7–8 and greater than 8 mm. It is observed that motion < 2mm decreases from the first 5 minutes to the next while the higher magnitude components increase with time.

Conclusion:

The probability of prostate motion increases with time. The trend seen in the PI and I directions can be attributed to physiological factors like bladder filling. This probability can be factored in for scheduling intrafraction imaging and used to compare dosimetric impact of VMAT vs. IMRT plans.

This work is supported in part by Varian Medical Systems
SU‐E‐J‐184: Volumetric Indices to Aid Definition of Respiratory Gates with Particular Reference to Lung Stereotactic Body Radiotherapy (SBRT)
Authors: Malhotra H , Gomez J
Published: June 2015

Purpose:

Conventional definition of respiratory gates relies on tumor motion determination in limited planes. We are proposing a new method to define the RPM gates in a consistent manner ensuring that the tumor motion is restricted to 4 mm in 3D for lung SBRT patients. The method relies on studying the ratio of volumes obtained by GTVnn intersection with GTV50+2mm margin and GTVnn where GTVnn is the GTV volume in phase nn (=0,10,30.) while GTV50+2mm is a pseudo structure created by adding an isotropic margin of 2mm to GTV50. If for any phase nn, above ratio equals 1, it ensures that the tumor motion is ≤ ±2 mm in 3D from GTV50.

Methods:

This method was tested for 50 patients (14‐Central, 36‐peripheral) to determine the RPM gates which were then compared with the gates used clinically. The minimum cut‐off value of the above coefficient for its inclusion of a phase in RPM gate was taken as 0.97 for central and 0.95 for peripheral tumors.

Results:

15 (30%) of the patients did not require any change in the RPM gates w.r.t. gates defined using conventional motion assessment methods. In 15(30%) cases, the RPM gates could have been smaller while in remaining 20 patients, gates could have been larger. 5(/14) patient's central tumors and 10 (/36) peripheral tumors did not need any gate change. 8(/50) patients could have RPM gate change of 30% while 10(/50) could have a gate change of up to 20%. 10, 20 & 30% RPM gate change could have happened for 11, 10 & 9 patients, respectively.

Conclusion:

Proposed volumetric indices based method allows a consistent, scientific and objective method to decide optimal RPM gates which is free from any inter or intra person variability and satisfies the tumor motion limits as defined by AAPM TG‐76 in totality.
SU‐E‐J‐192: Comparative Effect of Different Respiratory Motion Management Systems
Authors: Nakajima Y , Kadoya N , Kida S , Ito K , Kanai T , Kishi K , Sato K , Dobashi S , Takeda K , Jingu K
Published: June 2015

Purpose:

Irregular breathing can influence the outcome of four‐dimensional computed tomography imaging for causing artifacts. Audio‐visual biofeedback systems associated with patient‐specific guiding waveform are known to reduce respiratory irregularities. In Japan, abdomen and chest motion self‐control devices (Abches), representing simpler visual coaching techniques without guiding waveform are used instead; however, no studies have compared these two systems to date. Here, we evaluate the effectiveness of respiratory coaching to reduce respiratory irregularities by comparing two respiratory management systems.

Methods:

We collected data from eleven healthy volunteers. Bar and wave models were used as audio‐visual biofeedback systems. Abches consisted of a respiratory indicator indicating the end of each expiration and inspiration motion. Respiratory variations were quantified as root mean squared error (RMSE) of displacement and period of breathing cycles.

Results:

All coaching techniques improved respiratory variation, compared to free breathing. Displacement RMSEs were 1.43 ± 0.84, 1.22 ± 1.13, 1.21 ± 0.86, and 0.98 ± 0.47 mm for free breathing, Abches, bar model, and wave model, respectively. Free breathing and wave model differed significantly (p < 0.05). Period RMSEs were 0.48 ± 0.42, 0.33 ± 0.31, 0.23 ± 0.18, and 0.17 ± 0.05 s for free breathing, Abches, bar model, and wave model, respectively. Free breathing and all coaching techniques differed significantly (p < 0.05). For variation in both displacement and period, wave model was superior to free breathing, bar model, and Abches. The average reduction in displacement and period RMSE compared with wave model were 27% and 47%, respectively.

Conclusion:

The efficacy of audio‐visual biofeedback to reduce respiratory irregularity compared with Abches. Our results showed that audio‐visual biofeedback combined with a wave model can potentially provide clinical benefits in respiratory management, although all techniques could reduce respiratory irregularities.
SU‐E‐J‐194: Continuous Patient Surface Monitoring and Motion Analysis During Lung SBRT
Authors: Chung E , Rioux A , Benedict S , Yamamoto T
Published: June 2015

Purpose:

Continuous monitoring of the SBRT lung patient motion during delivery is critical for ensuring adequate target volume margins in stereotactic body radiotherapy (SBRT). This work assesses the deviation of the patient surface motion using a real‐time surface tracking system throughout treatment delivery.

Methods:

Our SBRT protocol employs abdominal compression to reduce the diaphragm movement to within 1 cm, and this is confirmed daily with fluoroscopy. Most patients are prescribed 3–5 fractions, and on treatment day a repeat motion analysis with fluoroscopy is performed, followed by a kV CBCT is aligned with the original planning CT image for 3D setup confirmation. During this entire process a patient surface data restricted to whole chest or the sternum at the middle of the breathing cycle was captured using AlignRT optical surface tracking system and defined as a reference surface. For 10 patients, the deviation of the patient position from the reference surface was recorded during the SBRT delivery in the anterior‐posterior (AP) direction at 3–6 measurements per second.

Results:

On average, the patient position deviated from the reference surface more than 4 mm, 3 mm and 2 mm in the AP direction for 0.95%, 3.7% and 11.1% of the total treatment time, respectively. Only one of the 10 patients showed that the maximum deviation of the patient surface during the SBRT delivery was greater than 1 cm. The average deviation of the patient surface from the reference surface during the SBRT delivery was not greater than 1.6 mm for any patient.

Conclusion:

This investigation indicates that AP motion can be significant even though the frequency is low. Continuous monitoring during SBRT has demonstrated value in monitoring patient motion ensuring that margins selected for SBRT are appropriate, and the use of non‐ionizing and high‐frequency imaging can provide useful indicators of motion during treatment.