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The incidence of atypical femoral fractures (AFFs) was 2.95% among 6644 hip and femoral fractures. Independent risk factors included the use of bisphosphonates (BPs), osteopenia or osteoporosis, rheumatoid arthritis, increased femoral curvatures, and thicker femoral cortices. Patients with AFFs and BP treatment were more likely to have problematic healing than those with typical femoral fractures (TFFs) and no BP treatment. To determine the incidence and risk factors of atypical femoral fractures (AFFs), we performed a multicenter case-control study. We also investigated the effects of bisphosphonates (BPs) on AFF healing. We retrospectively reviewed the medical records and radiographs of 6644 hip and femoral fractures of patients from eight tertiary referral hospitals. All the radiographs were reviewed to distinguish AFFs from TFFs. Univariate and multivariate logistic regression analyses were performed to identify risk factors, and interaction analyses were used to investigate the effects of BPs on fracture healing. The incidence of AFFs among 6644 hip and femoral fractures was 2.95% (90 subtrochanter and 106 femoral shaft fractures). All patients were females with a mean age of 72 years, and 75.5% were exposed to BPs for an average duration of 5.2 years (range, 1–17 years). The use of BPs was significantly associated with AFFs (p

The diplomatic effort of all three Northeast Asian nations to forge institutionalized cooperation through the Trilateral Summit and the Trilateral Cooperation Secretariat often goes unnoticed. This essay takes stock of China, Japan, Korea (CJK) relations, drawing attention to the opportunities and limits provided by institutionalized trilateral cooperation. It argues that the Trilateral Summit/Secretariat has some positive effect in addressing non-controversial issues and building low levels of trust. However, the overriding weight of bilateral tensions has significantly limited the impact of trilateral cooperation in promoting peace and stability in Northeast Asia.

Although North Korea remains one of the most isolated countries in the world, hundreds of foreign actors continue to work quietly inside the country. What is the size and scope of foreign engagement inside the Democratic People's Republic of Korea (DPRK)? What types of activities do nongovernmental organizations, businesses, and other private actors conduct? What has been the experience and impact of those working inside the DPRK? Relying on an original data set and interviews with sixteen organizational field representatives and staff members with experience working inside the DPRK, I uncover basic trends related to people-to-people engagement in areas such as humanitarian relief, development assistance, educational assistance, professional training, and business interaction. Although impressive growth has taken place in foreign engagement in the DPRK, its potential impact remains unclear due to ongoing internal and external constraints.

Purpose: A method is proposed to reconstruct a four-dimensional (4D) dose distribution using phase matching of measured cine images to precalculated images of electronic portal imaging device (EPID). Methods: (1) A phantom, designed to simulate a tumor in lung (a polystyrene block with a 3 cm diameter embedded in cork), was placed on a sinusoidally moving platform with an amplitude of 1 cm and a period of 4 s. Ten-phase 4D computed tomography (CT) images of the phantom were acquired. A planning target volume (PTV) was created by adding a margin of 1 cm around the internal target volume of the tumor. (2) Three beams were designed, which included a static beam, a theoretical dynamic beam, and a planning-optimized dynamic beam (PODB). While the theoretical beam was made by manually programming a simplistic sliding leaf motion, the planning-optimized beam was obtained from treatment planning. From the three beams, three-dimensional (3D) doses on the phantom were calculated; 4D dose was calculated by means of the ten phase images (integrated over phases afterward); serving as “reference” images, phase-specific EPID dose images under the lung phantom were also calculated for each of the ten phases. (3) Cine EPID images were acquired while the beams were irradiated to the moving phantom. (4) Each cine image was phase-matched to a phase-specific CT image at which common irradiation occurred by intercomparing the cine image with the reference images. (5) Each cine image was used to reconstruct dose in the phase-matched CT image, and the reconstructed doses were summed over all phases. (6) The summation was compared with forwardly calculated 4D and 3D dose distributions. Accounting for realistic situations, intratreatment breathing irregularity was simulated by assuming an amplitude of 0.5 cm for the phantom during a portion of breathing trace in which the phase matching could not be performed. Intertreatment breathing irregularity between the time of treatment and the time of planning CT was considered by utilizing the same reduced amplitude when the phantom was irradiated. To examine the phase matching in a humanoid environment, the matching was also performed in a digital phantom (4D XCAT phantom). Results: For the static, the theoretical, and the planning-optimized dynamic beams, the 4D reconstructed doses showed agreement with the forwardly calculated 4D doses within the gamma pass rates of 92.7%, 100%, and 98.1%, respectively, at the isocenter plane given by 3%/3 mm criteria. Excellent agreement in dose volume histogram of PTV and lung-PTV was also found between the two 4D doses, while substantial differences were found between the 3D and the 4D doses. The significant breathing irregularities modeled in this study were found not to be noticeably affecting the reconstructed dose. The phase matching was performed equally well in a digital phantom. Conclusions: The method of retrospective phase determination of a moving object under irradiation provided successful 4D dose reconstruction. This method will provide accurate quality assurance and facilitate adaptive therapy when distinguishable objects such as well-defined tumors, diaphragm, and organs with markers (pancreas and liver) are covered by treatment beam apertures.

Purpose: To develop and evaluate a fast Monte Carlo(MC)dose calculation model of electronic portal imaging device(EPID) based on its effective atomic number modeling in the XVMC code. Methods: A previously developed EPIDmodel, based on the XVMC code by density scaling of EPID structures, was modified by additionally considering effective atomic number (Zeff) of each structure and adopting a phase space file from the EGSnrc code. The model was tested under various homogeneous and heterogeneous phantoms and field sizes by comparing the calculations in the model with measurements in EPID. In order to better evaluate the model, the performance of the XVMC code was separately tested by comparing calculated dose to water with ion chamber (IC) array measurement in the plane of EPID. Results: In the EPID plane, calculated dose to water by the code showed agreement with IC measurements within 1.8%. The difference was averaged across the in-field regions of the acquired profiles for all field sizes and phantoms. The maximum point difference was 2.8%, affected by proximity of the maximum points to penumbra and MC noise. The EPIDmodel showed agreement with measured EPIDimages within 1.3%. The maximum point difference was 1.9%. The difference dropped from the higher value of the code by employing the calibration that is dependent on field sizes and thicknesses for the conversion of calculated images to measured images. Thanks to the Zeff correction, the EPIDmodel showed a linear trend of the calibration factors unlike those of the density-only-scaled model. The phase space file from the EGSnrc code sharpened penumbra profiles significantly, improving agreement of calculated profiles with measured profiles. Conclusions: Demonstrating high accuracy, the EPIDmodel with the associated calibration system may be used for in vivodosimetry of radiation therapy. Through this study, a MCmodel of EPID has been developed, and their performance has been rigorously investigated for transit dosimetry.

In the study of the evolution of animal colors, the conspicuousness of a pair of colors (e.g., stimulus vs. background) is often modeled by determining the distance between them in perceptual color space. For similar colors, receptor noise models have been demonstrated to be an effective way to estimate discrimination thresholds. However, the best way to quantify conspicuousness of color pairs that are distant in perceptual space is not widely agreed upon. In experiments where an animal is presented with different colors that it can easily discriminate, its response may be strongly influenced by the biological significance of a color, in addition to its conspicuousness, a phenomenon known as color categorization. This has made it difficult to test and confirm the validity of different models of perceptual distance. We tested the relative conspicuousness of different stimulus/background color combinations in the lizard Anolis sagrei using a visual attention reflex, which has been shown in earlier experiments to be less influenced by color categorization than other commonly used behavioral assays. We compared the results to predictions based on two different visual system-based models. The Euclidian distance between pairs of points plotted in a lizard chromaticity diagram effectively predicted the relative responses. A receptor noise model, in which color space distance was estimated in units of “just noticeable difference,” yielded a similarly accurate prediction of the results. We concluded that for studies of color signal evolution, either of these methods may be effectively employed to make behaviorally-relevant predictions of perceptual distance among colors that are widely separated in visual space.

The incidence of atypical femoral fractures (AFFs) was 2.95% among 6644 hip and femoral fractures. Independent risk factors included the use of bisphosphonates (BPs), osteopenia or osteoporosis, rheumatoid arthritis, increased femoral curvatures, and thicker femoral cortices. Patients with AFFs and BP treatment were more likely to have problematic healing than those with typical femoral fractures (TFFs) and no BP treatment.To determine the incidence and risk factors of atypical femoral fractures (AFFs), we performed a multicenter case-control study. We also investigated the effects of bisphosphonates (BPs) on AFF healing.We retrospectively reviewed the medical records and radiographs of 6644 hip and femoral fractures of patients from eight tertiary referral hospitals. All the radiographs were reviewed to distinguish AFFs from TFFs. Univariate and multivariate logistic regression analyses were performed to identify risk factors, and interaction analyses were used to investigate the effects of BPs on fracture healing.The incidence of AFFs among 6644 hip and femoral fractures was 2.95% (90 subtrochanter and 106 femoral shaft fractures). All patients were females with a mean age of 72 years, and 75.5% were exposed to BPs for an average duration of 5.2 years (range, 1-17 years). The use of BPs was significantly associated with AFFs (p 0.001, odds ratio = 25.65; 95% confidence interval = 10.74-61.28). Other independent risk factors for AFFs included osteopenia or osteoporosis, rheumatoid arthritis, increased anterior and lateral femoral curvatures, and thicker lateral femoral cortex at the shaft level. Interaction analyses showed that patients with AFFs using BPs had a significantly higher risk of problematic fracture healing than those with TFFs and no BP treatment.The incidence of AFFs among 6644 hip and femoral fractures was 2.95%. Osteopenia or osteoporosis, use of BPs, rheumatoid arthritis, increased anterior and lateral femoral curvatures, and thicker lateral femoral cortex were independent risk factors for the development of AFFs. Patients with AFFs and BP treatment were more likely to have problematic fracture healing than those with TFFs and no BP treatment.

International audience; Summary form only given. Optical logic down to the single photon level holds the promise of data processing with a better energy efficiency than electronic devices [1]. In addition, preservation of quantum coherence in such logical components would enable optical quantum logical gates [2-8]. Optical logic requires optical non-linearities to allow for photon-photon interactions. Non-linearities usually appear for large intensities, but discrete transitions in a well coupled single two-level system allow for giant non-linearities operating at the single photon level.This is achieved by engineering what has been coined a "one-dimensional atom" [2], wherein a light emitter is predominantly coupled to a single propagating spatial mode. This favored coupling with a traveling mode is obtained either in a resonant optical cavity [3,4] or with non-resonant field confinement such as in single mode waveguides [5,6] or through the interaction with a focused optical beam [7,8] . Here we take advantage of the large coupling efficiency and the broadband operation of a photonic wire containing a semiconductor quantum dot (QD) [9] to implement a transistor using two different optical QD transitions. Our system is made of a single InAs QD embedded in a GaAs tapered photonic wire (fig. 1a). This system, in which the QD is efficiently coupled to a single guided mode, has been exploited to realize ultrabright single-photon sources [9]. We exploit here its broad operation bandwidth (>100 nm around 950 nm) to efficiently address two different transitions of the QD with two different laser beams to implement a two-color giant non-linearity: a weak probe laser has its reflectivity controlled by a few photons of the control laser.

Purpose: To evaluate EPID for dosimetry applications of arc and static‐gantry IMRT with sliding window (SW) and/or step‐and‐shoot (SS) deliveries Methods:IMRT beams (SW & SS) were designed that generate beam hold‐offs and dose rate modulation due to MLC motion under 10 × 10 cm jaw. An arcIMRT beam was designed by adding gantry movement to the SW field. A 10 cm × 10 cm open beam was also used. Despite differences in delivered dose rates/pulse characteristics, the four beams should deliver the same total dose. For each beam, various MUs with 6 MV beam at 300MU/min were irradiated on EPID which operated in image acquisition of integration mode (IM), continuous scanning mode with synchronization (CMs) and without (CMn) to beam pulses. Acquired images were evaluated in repeatability, dose linearity, and reproducibility (reproduce open beam output in IM). Results: In IM, repeatability, dose linearity, and reproducibility were within 1% for all dose levels and beams. In CMs, they were within 1–2% if dose rate was maintained steady (1) for SW beam (needed a minimum 1.3 MU/cm MLC motion) and (2) arcIMRT beam (needed a minimum 1 MU/degree and 2.8 MU/cm MLC motion) and (3) if a minimum of 38‐40 MU per shoot was used for SS beam. Nonlinearity was observed for fewer MUs. This is due to the response of EPID to pulse‐length reduction for fixed‐gantry therapy and pulse dropping for arc therapy. The latter produces in‐planar non‐uniformity making EPID unsuitable for temporal dosimetry of arcIMRT. Sacrifice in temporal resolution then became necessary such as multi‐frames per image (eg. ∼1 sec/image). In CMn the results were similar to those of CMs. However, they showed artifacts, thus this mode was not preferred. Conclusions: We found conditions under which integrating and temporal EPIDdosimetry can be used for IMRT and arcIMRT dose deliveries.

Anolis lizards communicate with colorful dewlaps that often include detailed patterns. We measured the visual acuity of Anolis sagrei. Lizards viewed a checkerboard pattern of red and yellow–green squares that were too small to resolve, and thus appeared uniform in color. We quickly replaced the center portion of the display with a pattern of larger squares. If the new pattern could be resolved, the lizards perceived a change in color and reflexively shifted their gaze toward the target. The acuity threshold was 1.21 cycles deg −1 . We also calculated acuity based on published anatomical data for Anolis carolinensis . It was similar to that of A. sagrei for the visual periphery. Foveal acuity was 10 times greater. We approximated the effects of viewing conditions on the visibility of fine details of a conspecific9s dewlap. For peripheral vision, no detailed patterns were visible at ≥0.5 m. For foveal vision, color-pattern details were visible at 1.0 m.

Summary Background Anticoagulation with warfarin is influenced by dietary changes but the effect of fasting on warfarin therapy is unknown. Objectives To study changes in international normalized ratio (INR) and the percentage of time within therapeutic range (%TTR) before, during and after the Muslim fasting month (Ramadan) in stable warfarinised Muslim patients. Methods/Patients In this prospective study, weekly INR readings were taken at home visits from participating patients during three study periods: before, during and after Ramadan. Readings were blinded to patients and their primary physicians except for when pre-set study endpoints were reached. Results Among 32 participating patients, mean INR increased by 0.23 (P = 0.006) during Ramadan from the pre-Ramadan month and decreased by 0.28 (P

Iris recognition systems often degrade in performance when the subjects' cooperation is not expected in a less-constrained environment captured from a greater distance by visible wavelength imaging system. Algorithms in this field have reported inaccurate segmentations due to non-circular geometry of the iris and various noise factors introduced by non-cooperative subjects. In this paper, we propose a local region based active contour model to segment non-circular iris shape from visible wavelength images which are normally noisy and inhomogeneous. Accurate segmentation can be achieved through the proposed bi-local neighborhood approach which allows contour evolution using local region based terms while simultaneously avoiding occlusions without the need of separate image processing steps. B-spline formulation in this approach ensures simplicity and efficiency of this algorithm, thereby overcoming the limitations of active contour based methods in terms of computational power. The proposed algorithm has demonstrated good segmentation accuracy on NICE.I and NICE.II databases.

Background: Patients with systemic lupus erythematosus (SLE) may require prolonged periods of corticosteroid therapy which lead to excessive weight gain and increased cardiovascular risk. Objective: To assess the utility of a low glycaemic index diet in patients with corticosteroid dependent SLE in achieving weight loss and improving glycaemic control. Design: A total of 23 women were enrolled in a 6 week study. All had mild, stable SLE, were receiving corticosteroids and had a body mass index > 25 kg/m2. Subjects were randomly assigned to a low glycaemic index (Low GI) diet or a calorie restricted (Low Cal) diet. The primary end point was weight loss. Secondary end points included tolerability of diet, bio-markers of cardiovascular risk, disease activity, fatigue and sleep quality. Results: Weight loss in both treatment groups was significant (mean ± SD: Low GI diet 3.9 ± 0.9 kg; Low Cal diet 2.4 ± 2.2 kg, p

To determine the frequency of haemorrhagic pigment epithelial detachment (PED) among patients presenting with either polypoidal choroidal vasculopathy (PCV) or choroidal neovascularization (CNV) and calculate the degree to which the presence of a haemorrhagic PED can be used to predict the diagnosis of PCV. A retrospective review of 290 eyes of 253 patients presenting to the Singapore National Eye Centre with serosanguineous maculopathy. Patients underwent ophthalmologic examination including digital colour fundus photography and stereoscopic fluorescein angiography and indocyanine green angiography (ICGA). Classification into PCV or CNV was based on ICGA findings, and presence or absence of haemorrhagic PED was documented. In total, 138 eyes of 123 patients were diagnosed with PCV and 152 eyes of 130 patients with CNV. A haemorrhagic PED was a significantly more common (P

Global Science experimental Data hub Center (GSDC) at Korea Institute of Science and Technology Information (KISTI) located at Daejeon in South Korea is the unique datacenter in the country which helps with its computing resources fundamental research fields dealing with the large-scale of data. For historical reason, it has run Torque batch system while recently it starts running HTCondor for new systems. Having different kinds of batch systems implies inefficiency in terms of resource management and utilization. We conducted a research on resource management with HTCondor for several user scenarios corresponding to the user environments that currently GSDC supports. A recent research on the resource usage patterns at GSDC is considered in this research to build the possible user scenarios. Checkpointing and Super-Collector model of HTCondor give us more efficient and flexible way to manage resources and Grid Gate provided by HTCondor helps to interface with the Grid environment. In this paper, the overview on the essential features of HTCondor exploited in this work is described and the practical examples for HTCondor cluster configuration in our cases are presented.

We demonstrate a single-photon collection efficiency of $(44.3\pm2.1)\%$ from a quantum dot in a low-Q mode of a photonic-crystal cavity with a single-photon purity of $g^{(2)}(0)=(4\pm5)\%$ recorded above the saturation power. The high efficiency is directly confirmed by detecting up to $962\pm46$ kilocounts per second on a single-photon detector on another quantum dot coupled to the cavity mode. The high collection efficiency is found to be broadband, as is explained by detailed numerical simulations. Cavity-enhanced efficient excitation of quantum dots is obtained through phonon-mediated excitation and under these conditions, single-photon indistinguishability measurements reveal long coherence times reaching $0.77\pm0.19$ ns in a weak-excitation regime. Our work demonstrates that photonic crystals provide a very promising platform for highly integrated generation of coherent single photons including the efficient out-coupling of the photons from the photonic chip., Comment: 13 pages, 8 figures, submitted

The importance of membrane technologies for waste water treatment has increased in recent years. In contrast to conventional organic membranes, inorganic membranes have a high mechanical, chemical and thermal persistence. They may be regenerated and there is no ageing process of the membrane material. To ascertain the advantages and disadvantages of various types of membranes agricultural waste waters such as wash water of potatoes and carrots, pig and cattle slurry and waste water of milking plants were tested. The studies were carried out under constant conditions for pressure, temperature and COD-concentration in the feed. The main results are: • • Compared with organic membranes PS-50,000 (cut-off: 50,000 g/mole) and PES-40,000 (cut-off: 40,000 g/mole), the inorganic membrane SiC-0.05 (cut-off: 0.05μm) had the greatest permeate flux and the best COD-rejection for cattle slurry, waste water of milking plants, wash water of potatoes and pig slurry. • • Compared with the membrane SiC-0.2 (cut-off: 0.2μm) the membrane SiC-0.05 had a greater permeate flux and COD-rejection. • • The optimum transmembrane pressure amounts to 2 bar for the membrane SiC-0.05. A higher pressure does not lead to a proportional increase of the permeate flux. • • There is no significant difference in permeate flux and COD-rejection (ultrafiltration of wash water of potatoes and carrots) between inorganic membranes Al 2 O 3 -0.1 (cut-off: 0.1μm) and SiC-0.05, although the membrane cut-off for Al 2 O 3 -0.1 is much lower.

The property of straightness is one of fundamental geometric tolerances to be strictly controlled for guideways of machine tools and measuring machines. Straightness measurement for long guideways is usually difficult to perform, and it requires additional equipment or special treatment with limited applications. In this paper, a new approach is proposed using the profile matching technique for the long guideways, which can be applied to most straightness measurements. An edge of relatively short length is located along a divided section of a long guideway, and the local straightness measurement is performed. The edge is then moved to the next section with several overlap points. After the local straightness profile is measured for every section along the long guideway with overlap, the global straightness profile is constructed using the profile matching technique based on the least-squares method. The proposed technique is numerically tested for two cases of known global straightness profile: arc profile and irregular profile, with and without random error intervention, respectively. The developed technique has been practically applied to a vertical milling machine of the knee type, and demonstrated a good performance. Thus the accuracy and efficiency of the proposed method are demonstrated, and show great potential for a variety of applications for most straightness measurement cases, including straight edges, laser optics and angular measurement equipments.

Purpose: A method of four dimensional dose reconstruction (4D-DR) using a cine mode of an EPID to determine the delivered 4D dose distribution has been suggested. This method, however, has not been tested under irregular breathing. This study investigated their effects on 4D-DR. Methods: The 4D-DR attempts to find the patient’s breathing phase associated with each EPID image by comparing it to pre-generated-EPID-quality DRRs of every breathing phases. A lung phantom with a tumor object (3cm diameter cylinder) on a moving platform was used for this test under conditions of amplitude reduction by 1/2 during (1) the entire delivery and (2) the duration when MLC blocked the tumor (hindering the phase determination). The dose delivered to the phantom was inversely reconstructed in the associated phase image of the phantom from each EPID image based on our documented inverse method of the 4D-DR; the phase-specific dose was integrated, generating the 4D reconstructed dose. Forward 4D Monte Carlo calculations were used as the 4D dose of a ground truth. Results: The reconstructed dose showed 98.1% gamma pass rate for 3%/3mm under regular breathing (i.e. no amplitude reduction) when compared with the forward 4D dose. When the irregular condition (#1) was adopted for treatment, the pass rate became 94.2%. The irregularity under the MLC block (#2) showed the pass rate of 91.3%. The two conditions did not affect the reconstruction noticeably in DVH plots of the tumor and lung-tumor. Conclusion: As long as the extent of on-treatment motion is smaller than that of the planning CT, the 4D-DR can be done accurately. Otherwise, ontreatment 4D CT images are necessary.

Purpose: To reconstruct on-treatment 4D CT images from planning 4D CT images by adapting deformation vector field (DVF) of the planning CT to the on-treatment condition, while the adaptation is based on the scaling of two amplitudes that are motion characteristics at the times of treatment and planning CT acquisition, respectively. Methods: An anthropomorphic digital phantom (XCAT) was used to generate 4D image sets with 1-cm and 2-cm tumor motions simulating conditions of planning CT and treatment, respectively. DVFs were acquired from the planning CT image set. The DRR images were acquired simulating setup kV images from the two CT image sets. On the DRR images, tumor positions and their motion amplitudes were quantified. The DVFs were scaled linearly by the amplitude ratio between the treatment and the planning CT times, assuming the elasticity of lung. The scaled DVFs were used to resample the planning 4D CT images generating on-treatment 4D CT images. The on-treatment 4D CT images thus acquired were compared with the reference on-treatment images (2-cm motion). Results: The resampled images showed good agreement within 1 mm residual errors with the reference images. The normalized cross correlation was 0.995. Conclusion: A linear model of amplitude scaling was developed to reconstruct on-treatment 4D CT images from planning 4D CT images using the setup KV images acquired during treatment. The model was validated on a digital phantom. For the model to fully work, a further research needs to be followed, that aims at utilizing a phase-specific CT image set that is geometrically identical between pretreatment and treatment conditions.

Purpose: To reconstruct patient images at the time of radiation delivery using measured transit images of treatment beams through patient and calculated transit images through planning CT images. Methods: We hypothesize that the ratio of the measured transit images to the calculated images may provide changed amounts of the patient image between times of planning CT and treatment. To test, we have devised lung phantoms with a tumor object (3-cm diameter) placed at iso-center (simulating planning CT) and off-center by 1 cm (simulating treatment). CT images of the two phantoms were acquired; the image of the off-centered phantom, unavailable clinically, represents the reference on-treatment image in the image quality of planning CT. Cine-transit images through the two phantoms were also acquired in EPID from a non-modulated 6 MV beam when the gantry was rotated 360 degrees; the image through the centered phantom simulates calculated image. While the current study is a feasibility study, in reality our computational EPID model can be applicable in providing accurate transit image from MC simulation. Changed MV HU values were reconstructed from the ratio between two EPID projection data, converted to KV HU values, and added to the planning CT, thereby reconstructing the on-treatment image of the patient limited to the irradiated region of the phantom. Results: The reconstructed image was compared with the reference image. Except for local HU differences>200 as a maximum, excellent agreement was found. The average difference across the entire image was 16.2 HU. Conclusion: We have demonstrated the feasibility of a method of reconstructing on-treatment images of a patient using EPID image and planning CT images. Further studies will include resolving the local HU differences and investigation on the dosimetry impact of the reconstructed image.

We investigate the non-linear mechanical dynamics of a nano-optomechanical mirror formed by a suspended membrane pierced by a photonic crystal. By applying to the mirror a periodic electrostatic force induced by interdigitated electrodes integrated below the membrane, we evidence superharmonic resonances of our nano-electro-mechanical system; the constant phase shift of the oscillator across the resonance tongues is observed on the onset of principal harmonic and subharmonic excitation regimes.

In Asian countries, age-related macular degeneration (AMD), specifically wet AMD or choroidal neovascularisation (CNV), is an important cause of blindness and visual handicap. Vascular endothelial growth factors (VEGF) play an integral role in the development of CNV and thus provide an important therapeutic target. Current treatment paradigms for neovascular AMD recognise the place of photodynamic therapy (PDT) in the management of this condition. However, combination therapy targeting different pathways to produce a synergistic effect may result in improved visual outcomes and reduced duration of treatment. Anti-VEGF therapy has greatly improved treatment outcomes in patients with CNV, and a growing body of evidence supports the role of these agents as monotherapy or in combination with PDT. In particular, anti-VEGF may be a first-line treatment option in certain types of subfoveal myopic CNV as well as for classic and occult juxtafoveal and subfoveal CNV. The implementation of evidence-based medicine into current clinical practice is paramount to improving patient care. The authors, who are also members of the Singapore Medical Retina Advisory Board, outline the consensus points and recommended treatment algorithms based on currently available knowledge to provide a structured management approach to the treatment of Asian patients with CNV.

Purpose To report clinical presentations and optical coherence tomographic features of spontaneous peeling of idiopathic epiretinal membranes in two young myopic females Methods Retrospective review of cases including clinical presentations and optical coherence tomography (OCT) scans Results Spontaneous peeling of idiopathic epiretinal membranes occurred in two young myopic females. The peeling occurred with posterior vitreous detachments which were documented sequentially with OCT over a 3 to 6 months duration. Case 1, a 31-year-old lady, with myopia of -6.0 dioptres spherical equivalent(SE), presented with decreased left visual acuity for one week. Left best corrected visual acuity (BCVA) was 6/12. Fundus examination revealed ERM confirmed by OCT. One month later BCVA improved to 6/9 as the ERM spontaneously peeled off partially with presence of PVD. However OCT still demonstrated vitreofoveal traction. BCVA normalized to 6/6 with complete peeling of ERM, resolution of vitreofoveal traction at both months 2 and 6. Case 2, a 35-year-old lady, with myopia of -2.0 dioptres SE, experienced 2 week history of decreased left visual acuity to BCVA 6/9 from ERM. 3 months later, spontaneous peeling of ERM occurred simultaneously with PVD. BCVA improved to 6/6 which remained stable one year later. Conclusion Spontaneous peeling of idiopathic ERM can occur in young female myopes. Two cases developed early PVD with spontaneous ERM peeling. OCT confirms the simultaneous occurrence of PVD with peeling of membranes which has not been demonstrated before. Idiopathic ERM should be monitored closely in myopic eyes of young females as they may undergo spontaneous peeling with normalisation of visual acuity.

Purpose: To develop a daily monitoring system for proton beam output check and beam uniformity check. Methods: Designed for continuously irradiated photon and electron beams with a field size of 20 cm x 20 cm, the daily output checker (Sun Nuclear, Inc.) is not suitable for monitoring proton beams with inter-pulse beam-off and a field size smaller than 14–16 cm in diameter. To allow such proton beam monitoring, the following tests were performed. 1. Absolute dose and array calibrations which accept continuous irradiation only, were performed using photon beams. 2. Five ion chambers within the central area of 8 cm x 8 cm were utilized to check constancy of output at the center of beam modulation and at distal edge and to check beam symmetry and flatness. 3. To simplify our evaluation, the array calibration was manually modified, such that all five chambers report equal values in spite of their differences in build-up thicknesses. 4. The chamber at the lower-right corner is placed under a buildup thickness that can offer dose measurement at the distal edge. This buildup thickness was determined by proton beam range measurements, which established buildup thickness for beam output measurement at the central chamber and range measurement at the corner chamber. 5. The beam-off delay which allows receipt of pulsed irradiation was activated and optimal delay times were determined for each proton beam at 149.6, 185.6, and 249.5 MeV. Results: The above system was tested by miss-steering proton beams and altering phantom thickness by 1 mm at a time. The system reliably monitored the beam with: 3% tolerance for beam flatness, symmetry and output. The range difference of 0.5 mm could be detected at all energies by setting a tolerance of 20%. Conclusion: A quick daily proton beam monitoring system was feasible.

Purpose: To develop and to test a method to generate a new 4D CT images of the treatment day from the old 4D CT and the portal images of the day when the motion extent exceeded from that represented by plan CTs. Methods: A motion vector of a moving tumor in a patient may be extended to reconstruct the tumor position when the motion extent exceeded from that represented by plan CTs. To test this, 1. a phantom that consists of a polystyrene cylinder (tumor) embedded in cork (lung) was placed on a moving platform with 4 sec/cycle and amplitudes of 1 cm and 2 cm, and was 4D-scanned. 2. A 6MV photon beam was irradiated on the moving phantoms and cineEPID images were obtained. 3. A motion vector of the tumor was acquired from 4D CT images of the phantom with 1 cm amplitude. 4. From cine EPID images of the phantom with the 2 cm amplitude, various motion extents (0.3 cm, 0.5 cm, etc) were acquired and programmed into the motion vector, producing CT images at each position. 5. The reconstructed CT images were then compared with pre-acquired “reference” 4D CT images at each position (i.e. phase). Results: The CT image was reconstructed and compared with the reference image, showing a slight mismatch in the transition direction limited by voxel size (slice thickness) in CT image. Due to the rigid nature of the phantom studied, the modeling the displacement of the center of object was sufficient. When deformable tumors are to be modeled, more complex scheme is necessary, which utilize cine EPID and 4D CT images. Conclusion: The new idea of CT image reconstruction was demonstrated. Deformable tumor movements need to be considered in the future.

Purpose: To test a method to reconstruct a four-dimensional (4D) dose distribution using the correlation of pre-calculated 4D electronic portal imaging device (EPID) images and measured cine-EPID images. Methods: 1. A phantom designed to simulate a tumor in lung (a polystyrene block with 3.0 cm diameter embedded in cork) was placed on a sinusoidally moving platform with 2 cm amplitude and 4 sec/cycle. Ten-phase 4D CT images were acquired for treatment planning and dose reconstruction. A 6MV photon beam was irradiated on the phantom with static (field size=5×8.5 cm2) and dynamic fields (sliding windows, 10×10 cm2, X1 MLC closing in parallel with the tumor movement). 2. 4D and 3D doses were calculated forwardly on PTV (1 cm margin). 3. Dose images on EPID under the fields were calculated for 10 phases. 4. Cine EPID images were acquired during irradiation. 5. Their acquisition times were correlated to the phases of the phantom at which irradiation occurred by inter-comparing calculated “reference” EPID images with measured images (2D gamma comparison). For the dynamic beam, the tumor was hidden under MLCs during a portion of irradiation time; the correlation performed when the tumor was visible was extrapolated. 6. Dose for each phase was reconstructed on the 4D CT images and summed over all phases. The summation was compared with forwardly calculated 4D and 3D dose distributions. Monte Carlo methods were used for all calculations. Results: For the open and dynamic beams, the 4D reconstructed doses showed the pass rates of 92.7 % and 100 %, respectively, at the isocenter plane given 3% / 3 mm criteria. The better agreement of the dynamic beam was from its dose gradient which blurred the otherwise sharp difference between forward and reconstructed doses. This also contributed slightly better agreement in DVH of PTV. Conclusion: The feasibility of 4D reconstruction was demonstrated.

Purpose: Radiographic film dosimetry suffers from energy dependence in Proton dosimetry, and thus is not suitable for absolute dosimetry. In this study, we investigate film dosimetry for the constancy check of percentage depth dose (PDD) and beam profile measurements in proton beams. Methods: From PDD measured by film and ion chamber (IC), calibration factors as a function of depth (IC/film) was obtained. These factors imply variable slopes (with energy and depth) of linear characteristic curves that relate film response to dose. They were used to convert day‐to‐day film measurements into dose. Film dosimetry of a 186 MeV proton beam was performed to investigate this hypothesis. In addition, Monte Carlos simulation of a 250 MeV proton beam was performed calculating proton fluence spectrum along the off‐axis direction. By multiplying stopping powers of film emulsion and water, respectively, to the spectrum, doses to film and water were calculated. The ratio of film dose to water dose was evaluated across the off‐axis distance to understand film response. Results: The measured and calibrated PDD approached to that of IC, but near the end of spread‐out‐bragg‐peak (SBOP), a spurious peak is observed due to the mismatch of distal edge between calibration film and measurement film. The SBOP width was measurable within 1mm. The distal edge was reproducible within 1.5mm. Entrance dose was reproducible within 5.5%. The possible sources of such errors include developer uncertainty, film emulsion nonuniformity, and misalignment of film edge to the phantom surface. For off‐axis evaluation, the dose ratio varied within 3%, and thus film is shown to be accurate for dosimetry across off‐axis distance. Conclusions: Radiographic film can be suitable for beam profile measurements and may be suitable for PDD constancy check for proton beams. Routine use will confirm such error which will be presented in this study.

Purpose: It has been evaluated that XVMC and BEAMnrc codes are suitable for dose calculation in patient. However, required accuracy of the codes at extended distance under scattering media is challenging. Furthermore, there is a growing importance of dose validation of complicated radiation therapy by exit dosimetry and dose reconstruction. Therefore, the purpose for this study is to predict the exit EPIDimages under phantom using XVMC simulation and compare them with ion chamber measurements and BEAMnrc calculation. Methods: For this study XVMC and BEAMnrc/DOSXYZnrc beam simulation algorithms were used to model a 6 MV Varian linear accelerator. The dose profiles at 150 cm were calculated under solid water flat phantoms that were isocentrically placed. Water phantom thicknesses were variable from 10 to 20 cm. On exit plane of calculation, a 2 cm‐thick build up phantom and a 5‐cm thick backscattering phantom were placed. The results were compared to PTW ion chamber measurements for various field sizes.Results: The XVMC and BEAMnrc simulation results were agreeable with the ion chamber reference exit dose measurements. The XVMC and BEAMnrc beam profile were in agreement in terms of dose profile for various field sizes and penumbrae. The Monte Carlo results were within 3% dose difference within 80% of each field size.Conclusions: Calculations were done to predict the exit doseimages using XVMC simulation and BEAMnrc calculation for various field sizes and phantom depth. When these were compared to a reference ion chamber the calculations were in agreement. The study shows that XVMC and BEAMnrc are applicable to predict EPIDimages at EPID depth.

Purpose: To evaluate dose reconstruction of volumetric modulated arc therapy (VMAT) from EPID image prediction. Methods: A test VMAT plan with dynamic MLCs was developed on a water equivalent cubic phantom with dimension of 31.4×34×34 cm3. From the initial MLC opening of 5×5 cm2 at gantry 0°, they moved with a constant speed as the gantry rotates, until they reached X1 at −2.5 cm and X2 at = −2.237 cm at gantry 90°. The plan was delivered while cine EPID images were acquired. For the 84 gantry angle segments, doses to the phantom were calculated by XVMC and reconstructed from EPID based on fast density-scaled model and non-iterative dose reconstruction method we have previously developed. The reconstructed dose was compared with the forwardly calculated dose individually over 84 gantry angle segments and cumulatively in terms of gamma evaluation and dose volume histogram for PTV (3×3×3 cm3) positioned at the center of the phantom. Results: 3D-gamma pass rate was 97.0 % cumulatively with 3 %/3 mm criteria and maximum 100% individually. The DVHs of PTV were indistinguishable except in the region of high dose (>95% of prescribed dose) where the difference of a few percent in volume was found. Conclusion: Showing good agreement with the forwardly calculated dose, we have extended our model of dose reconstruction successfully to the verification of VMAT. Although more clinical demonstration is to be followed, our study presents a promising tool for time-resolved and cumulative VMAT validation.

†† ‡ § † The purpose of this study was to develop a system of clinical application of reconstructed dose that includes dose reconstruction, reconstructed dose registration between fractions of treatment, and dose-volume-histogram generation and to demonstrate the system on a deformable prosta te phantom. To achieve this purpose, a deformable prostate phantom was embedded into a 20 cm-deep and 40 cm-wide water phantom. The phantom was CT scanned and the anatomical models of prostate, seminal vesicles, and rectum were contoured. A coplanar 4-field intensity modulated radiation therapy (IMRT) plan was used for this study. Organ deformation was simulated by inserting a “transrectal” balloon containing 20 ml of water. A new CT scan was obtained and the deformed structures were contoured. Dose responses in phantoms and electronic portal imaging device (EPID) were calculated by using the XVMC Monte Carlo code. The IMRT plan was delivered to the two phantoms and integrated EPID images were respectively acquired. Dose reconstruction was performed on these images using the calculated responses. The deformed phantom was registered to the original phantom using an in-house developed software based on the Demons algorithm. The transfer matrix for each voxel was obtained and used to correlate the two sets of the reconstructed dose to generate a cumulative reconstructed dose on the original phantom. Forwardly calculated planning dose in the original pha ntom was compared to the cumulative reconstructed dose from EPID in the original phantom. The prescribed 200 cGy isodose lines showed little difference with respect to the “prostate” and “seminal vesicles”, but appreciable difference (3%) was observed at the dose level greater than 210 cGy. In the rectum, the reconstructed dose showed lower volume coverage by a few percent than the plan dose in the dose range of 150 to 200 cGy. Through this study, the system of clinical application of reconstructed dose was successfully developed and demonstrated. The organ deformation simulated in this study resulted in small but observable dose changes in the target and critical structure.

ing of dose delivery under motion. This study has quantitatively demonstrated and analytically interpreted the impact of residual motion including penumbral broadening for both targets, perturbed but secured dose coverage on the CTV, and significant doses delivered in the neighboring normal tissues. Dose volume histogram analyses also demonstrated and interpreted the trend of dose coverage: for ITV, it increased as GW or MA decreased or CTV size increased; for IM, it increased as GW or MA decreased; for the neighboring normal tissue, opposite trend to that of IM was observed. This study has provided a clear understanding on the impact of the residual motion and proved that if breathing is reproducible gRT is secure despite discontinuous delivery and target motion. The procedures and computational model can be used for commissioning, routine quality assurance, and patient-specific validation of gRT. More work needs to be done for patient-specific dose reconstruction on CT images.

The concept of combination therapy implies the concurrent use of two or more slow-acting antirheumatic drugs to treat rheumatoid arthritis. This review places such combination therapy into an historical context and evaluates studies carried out before 1990. There were no published studies before 1980 of combination therapy, and between 1980 and 1990 there were 11 published studies. Three were conventional randomised controlled trials, three were non-randomised studies of parallel group design, four were observational open studies, and one was a retrospective review. Altogether 486 patients were studied with the numbers of cases in each study varying between 12 and 101. The main combinations used were penicillamine + hydroxychloroquine or chloroquine, gold + hydroxychloroquine, and sulphasalzine + penicillamine. Six studies concluded that combination therapy helped patients, three suggested possible benefits, and two gave essentially negative findings. These two negative studies were randomised controlled trials. Most studies indicated an increase in adverse events with combination therapy. The average erythrocyte sedimentation rate on combination therapy fell by 21.4%. A majority of patients remained on the therapy for 6-12 months. The balance of evidence in 1990 suggested that combination therapy had a modest advantage. However, the trials were too small to detect its true value, and the combinations used were not ideal. In particular, combining gold or penicillamine with other drugs appeared to give too much toxicity. The future development of the field would depend on identifying more effective combinations of drugs and undertaking larger and better-designed trials.

A considerable class of nonlinear systems can be described or approximated by polynomial functions with sufficiently high order, therefore can be described in tensor notation compactly. For the plants with polynomial functions in the state and input, a globally stable feedback control, using finite-time tensor product of an augmented state vector, is designed in this paper. Combining the input with the ordinary state to form the augmented state vector, the plants are dealt with as uniformly like linear systems. The concept of a quotient set is used to discard redundant information in the design. A genetic algorithm is employed to complete the design. The relative proofs and simulation are presented.

Purpose: To predict accurate exit EPID images below lung or bone phantoms by appropriate Monte Carlo modeling. It has been evaluated that XVMC and EGSnrc Monte Carlo codes are suitable for dose calculation in tissue equivalent material at both patient and EPID levels. However, the EPID image prediction is challenging due to its complex structure and material composition of high atomic number. Methods: A 6MV beam and phantom were modeled using BEAMnrc and XVMC codes. The accuracy of exit dose was validated through comparison with 2‐D ion chamber dose under a 2 cm build‐up layer. After the validation, Varian aS1000 EPID has been modeled to calculate the EPID response. The material composition of EPID has been used for modeling in EGSnrc user code, DOSRZnrc, whereas homogeneous layer modeling by density scaling of the composition has been applied in XVMC. Dose images at 150 cm were calculated under combinations of plastic water, lung and bone flat phantoms for various field sizes. The results were compared to EPID measurement. Results: Ion chamber array measurements at EPID level agreed with the XVMC and BEAMnrc/DOSRZnrc calculations within ∼3%. EPID images calculated by DOSRZnrc were in good agreement (∼1%) with the measurement in all cases. The results from XVMC were within ∼2% difference in plateau region, but penumbra slopes were sluggish and dose response at off‐axis was slightly lower. Conclusion: EPID dose images were calculated through EPID composition modeling by XVMC and BEAMnrc/DOSRZnrc. Both Monte Carlo calculations agreed with the measurements in all settings, except penumbra slopes and off‐axis responses in XVMC calculations. The EPID model by XVMC can be used for faster and less accurate calculations, whereas the other for more accurate, time spending calculations.

Purpose: The purpose of this study is to demonstrate time‐resolved dosimetry for verifying arc intensity modulated radiation therapy (arcIMRT) delivery, utilizing the continuous image acquisition of an electronic portal imaging device (EPID). Methods: An arcIMRT field was made of sliding, multi‐leaf collimator (MLC) motion of X1 leaves traveling from −5 cm to +5 cm and back, while Y opening was kept at 10 cm. For this field, this travel was repeated three times during the gantry rotation of 180°. The images were continuously acquired while the EPID was irradiated with 240 MU at a constant dose rate of 300 MU/min. By summing 10 frames, and thus reducing the temporal resolution to 1 second, a longitudinal non‐uniformity in the images was reduced to less than 3%. Dose images in EPID were also calculated by the XVMC code for MLC positions at 1 mm interval using the EPID model developed in our previous study. The calculated images at 1 sec resolution were then correlated to and compared with the images, validating the time‐resolved dosimetry. Results: Over the period of 48 seconds, 481 EPID images were acquired. The MLCs traveled at 1.25 cm/sec. Thus, 10 images were assigned to 1.25 cm of MLC travel for the correlation and for dose evaluation. For all gantry angles, the agreement of the gamma tests was above 90%, given 3 mm distance to agreement and 3% dose difference, when MLCs moved forwardly to the X2 side. However, when they travel back, the pass rates were below 90% due to MLC lagging which was detected in time‐resolved EPID dose imaging. Conclusion: Time‐resolved, four‐dimensional dose validation of arcIMRT was demonstrated, showing the temporal information of dynamic radiation delivery. This can be used for the validation of 4D treatment delivery techniques.

135 This work was supported by the Industrial Strategic technology development program (10035527) funded by the Ministry of Knowledge Economy (MKE, Korea). Submitted September, 27, 2012, Accepted September, 2, 2013 Corresponding Author: Rena Lee, Department of Radiation Oncology, School of Medicine, Ewha Womans University, Mok 5-dong, Yangcheon-gu, Seoul 158-710, Korea Tel: 02)2650-2022, Fax: 02)2654-0363 E-mail: heraash@hanmail.net The Effect of Breathing Biofeedback on Breathing Reproducibility and Patient’s Dose in Respiration-gated Radiotherapy

Although the rate of fracture healing has been studied in adults, little such work has been done in children. The authors' objective was to develop staging criteria for assessing callus formation in fractures in children and to determine the relation between the age and sex of the patient and callus formation. They studied callus formation in healing fractures of the femoral diaphysis in 25 patients, 15 boys and 10 girls, ranging in age from birth to 14 years. The patients were selected on a random basis from children presenting with femoral fractures (and no other injuries) to a tertiary-care pediatric hospital in Winnipeg over the period 1988 to 1991. The following staging criteria were developed from other examples of femoral fracture: stage 1, earliest radiographically visible calcification of the callus; stage 2, callus completely bridging the fracture site; and stage 3, mature callus. For the patients in the study, the average times to reach stages 1, 2 and 3 were 11.7, 18.7 and 55.3 days respectively. The sex of the patient had no effect on callus formation. The final stage of healing appeared to take longer with increasing patient age, although this observation was not statistically significant.

Purpose: To investigate the response of electronic portal imaging device(EPID) in integration mode for intensity modulated beams including step‐ and‐shoot (SS) and sliding window (SW) deliveries. Methods: We evaluated EPID dose response measurements of open, SS, and SW irradiations. We designed three beams using 6MV x‐rays with 10×10 cm2 field size. For the SS irradiation, two MLC leaves with 0.5 cm opening outside 10 × 10 cm2 were discontinuously moved by 10 cm during each segmental irradiation among ten segments of the entire delivery. For the SW beam, the same MLC leaves were continuously moved by 10 cm ten times during the delivery. The employment of the same open beam area ensures the same dose irradiation by the three. Monitor units were varied. We additionally investigated the dose linearity of EPID response. We used EPID‐ADU1000 operated with IAS3 system for the integrated acquisition. Results: The SS delivery showed a deviation greater than 2% from the open beam, if a segment employed less than 10 MUs. If it employed greater than 10 MUs, then a deviation less than 1% was observed. The SW delivery showed a maximum deviation of 1.4% at the lowest MU. The open beam irradiation showed linearity within 0.8%, the SW irradiation 1.2%, and the SS irradiation 1.7%. Conclusions: The SS delivery is associated with a greater error than the SW delivery due to beam instability at the start of acquisition and reading loss during MLC movement. Using large monitor units greater than 10 MUs/segment can minimize the deviation for the SS delivery from open beam. The linearity of EPID response to dose was better with the SW delivery than the SS delivery. This study will help understand dosimetric response of EPID for the SS delivery. This study was in part supported by Varian Medical Systems, Inc.

Purpose: To evaluate the dosedelivery retrospectively after treatment using breathing sessions recorded during the treatment. Methods: Two lungcancer patients were given 22 and 25 respiratory sessions for imaging and treatment. A computational model was developed in past for calculating dosedelivered to a moving target, given a planned dose distribution. We have determined ITV from the breathing traces acquired during CT using 30‐to‐70 and 35‐to‐75% phase windows, respectively, for the two patients. We used the same window within the traces acquired during treatment for dose reconstruction (the windows were given as tagged traces). The ITV margins were determined using first the difference between the maximum and minimum amplitudes within the windows and second the 95%‐ confidence interval of the difference from the entire patterns from CT. We added the second option as we could not locate the portion of the breathing traces that corresponds to the CT slices of tumor, while these slices are used for moving‐target contouring. So, using the entire pattern tends to overestimate internal margins. The magnitude of CTV was assumed to be 3 cm; the planned dose was justly covering PTV boundaries. The delivereddose profiles calculated for treatment sessions were compared to the planned distribution.Results: Using the determined ITV from the CT session, the CTV and normal tissue coverage were calculated. The CTV coverage was 100% for all sessions except one for patient A. For the patient B, the sessions which deliver the prescription dose to 100% of the CTV volume was 25% of the entire sessions. Almost all (23/24) sessions delivered 95% of the prescription dose to 95% of the CTV volume, affected by less reproducible breathing patterns than the patient A. Conclusions: We reconstructed the dose coverage in CTV and normal tissue within ITV. This study could help determine PTV margins. In part supported by Varian medical systems, Inc and in part supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MEST) (No. 2009‐0085999) and by the Industrial Strategic technology development program : 10035527 funded by the Ministry of Knowledge Economy(MKE, Korea)

Purpose: To reconstruct dose delivered to a deformable phantom from images acquired by an electronic portal imaging device(EPID) using a full‐scope Monte Carlo based non‐iterative reconstruction method we have developed and to evaluate the delivered dose to the deformed organs using the resulting reconstructed dose. Methods: A deformable prostate phantom was embedded into a 20cm‐deep and 40cm‐wide water phantom. The phantom was CT scanned and the anatomical models of prostate, seminal vesicles, and rectum were contoured. A coplanar 4‐field IMRT plan was used for this study. The XVMC Monte Carlo code, XVMC, was used for verification of planned dose in phantom and calculation of dose response by EPID.Organ deformation was simulated by inserting a “transrectal” balloon containing 20ml of water and air. A new CT scan was obtained and the deformed structures were contoured. The IMRT plan was delivered to the two phantoms and integrated EPIDimages were respectively acquired. Dose reconstruction was performed using these images with calculated EPID responses. The deformed phantom was registered to the original phantom using an in‐house developed software based on the Demons algorithm. The transfer matrix for each voxel was obtained and used to correlate the two sets of the reconstructed dose to generate a cumulative reconstructed dose on the original phantom. Results: Forwardly calculated planning dose in the original phantom was compared to the cumulative reconstructed dose from EPID in the original phantom. The prescribed 200 cGy isodose lines showed little difference with respect to the “prostate” and “seminal vesicles”, but appreciable difference (3%) was observed at 210cGy dose level. Conclusions: The results validate our dose reconstruction method for EPID dosimetry. Organ deformation resulted small but observable dose changes in the target and critical structure. This study was in part supported by Varian Medical Systems, Inc.

Purpose: Gated radiation therapy (gRT) reduces the effect of organ motion during treatment. Once internal margin due to residual motion is determined by four‐dimensional computer tomography, it is used throughout entire treatments. However, patient's breathing is not completely reproducible during treatments, so dose distribution within internal target volume (ITV) can change from planned distribution. Therefore, we aim at evaluating effect of breathing changes on dosedelivery of gRT. Methods: Each of nineteen patients with lungcancer was given five respiratory sessions,* and each session included free‐breathing (FB), audio‐instruction (A), and audio‐visual biofeedback (AV). We assumed that the first session generates breathing traces for ITV determination, and others traces for delivery determination. A computational model was developed for calculating delivereddose under motion for phase and amplitude gating: dose at virtual detectors was expressed as a function of phases and positions. The doses in clinical target volume and normal tissue within ITV were evaluated using the volume receiving >90% of the prescription dose (V90). Results: As we used a maximum extent of residual motion from the first session, CTV coverage did not show visible change during treatments. However, increases of 21.6% (range: −49.00% ∼ 211.61%) and 2.51% (−45.65% ∼ 45.27%) in V90 of normal tissue in ITV were observed for phase and amplitude gating, respectively. Phase gating showed that V90 of FB was higher than that of AV (FB: 27.23% and AV: 16.28%), while amplitude gating did not show notable differences. The amplitude gating saved more normal tissue than phase gating overall and particularly for FB. Use of maximum residual motion in ITV over the entire trace may not be possible, and CTV coverage is questionable. Conclusion: This study quantified dosedelivery for gRT. *We thank R. George for providing data. In part supported by Nuclear R&D project from MEST, Korea