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cd. autorów: L. Cao48,‡, G. Caria145,‡, G. Casarosa57,‡, C. Cecchi56,‡,D. Cˇ ervenkov10,‡,M.-C. Chang22,‡, P. Chang92,‡, R. Cheaib146,‡, V. Chekelian83,‡, Y. Chen154,‡, B. G. Cheon28,‡, K. Chilikin77,‡, K. Cho70,‡, J. Choi14,‡, S.-K. Choi27,‡, S. Choudhury35,‡, D. Cinabro170,‡, L. M. Cremaldi146,‡, D. Cuesta47,‡, S. Cunliffe16,‡, N. Dash33,‡, E. de la Cruz Burelo9,‡, E. de Lucia52,‡, G. De Nardo54,‡, †Editor. ‡Belle II Collaborator. §Theory or external contributing author. M. De Nuccio16,‡, G. De Pietro59,‡, A. De Yta Hernandez9,‡, B. Deschamps129,‡, M. Destefanis60,‡, S. Dey116,‡, F.Di Capua54,‡, S.Di Carlo75,‡, J. Dingfelder129,‡, Z. Doležal10,‡, I. Domínguez Jiménez125,‡, T.V. Dong30,26,‡, D. Dossett145,‡, S. Duell129,‡, S. Eidelman6,96,77,‡, D. Epifanov6,96,‡, J. E. Fast100,‡, T. Ferber16,‡, S. Fiore18,‡, A. Fodor85,‡, F. Forti57,‡, A. Frey24,‡, O. Frost16,‡, B. G. Fulsom100,‡, M. Gabriel83,‡, N. Gabyshev6,96,‡, E. Ganiev61,‡, X. Gao3,‡, B. Gao23,‡, R. Garg101,‡, A. Garmash6,96,‡, V. Gaur169,‡, A. Gaz90,‡, T. Geßler65,‡, U. Gebauer24,‡, M. Gelb48,‡, A. Gellrich16,‡, D. Getzkow65,‡, R. Giordano54,‡, A. Giri35,‡, A. Glazov16,‡, B. Gobbo61,‡, R. Godang157,‡, O. Gogota110,‡, P. Goldenzweig48,‡, B. Golob141,109,‡,W. Gradl63,‡, E. Graziani59,‡, M. Greco60,‡, D. Greenwald114,‡, S. Gribanov6,96,‡, Y. Guan17,‡, E. Guido60,‡, A. Guo41,‡, S. Halder111,‡, K. Hara30,26,‡, O. Hartbrich138,‡, T. Hauth48,‡, K. Hayasaka94,‡, H. Hayashii91,‡, C. Hearty130,‡, I. Heredia De La Cruz9,‡, M. Hernandez Villanueva9,‡, A. Hershenhorn130,‡, T. Higuchi66,‡,M. Hoek63,‡, S. Hollitt124,‡, N. T. HongVan44,‡, C.-L. Hsu160,‡, Y. Hu41,‡, K. Huang92,‡, T. Iijima89,90,‡, K. Inami90,‡, G. Inguglia40,‡,A. Ishikawa119,‡, R. Itoh30,26,‡, Y. Iwasaki30,‡, M. Iwasaki97,‡, P. Jackson124,‡, W. W. Jacobs37,‡, I. Jaegle137,‡, H. B. Jeon73,‡, X. Ji41,‡, S. Jia3,‡,Y. Jin162,‡, C. Joo66,‡,M. Künzel16,‡, I. Kadenko110,‡, J. Kahn78,‡, H. Kakuno121,‡, A. B. Kaliyar36,‡, J. Kandra10,‡, K. H. Kang73,‡, Y. Kato90,‡, T. Kawasaki68,‡, C. Ketter138,‡, M. Khasmidatul143,‡, H. Kichimi30,‡, J. B. Kim71,‡, K. T. Kim71,‡, H. J. Kim73,‡, D.Y. Kim108,‡, K. Kim172,‡, Y. Kim172,‡, T. D. Kimmel169,‡, H. Kindo30,26,‡, K. Kinoshita135,‡, T. Konno68,‡, A. Korobov6,96,‡, S. Korpar144,109,‡, D. Kotchetkov138,‡, R. Kowalewski165,‡, P. Križan141,109,‡, R. Kroeger146,‡, J.-F. Krohn145,‡, P. Krokovny6,96,‡, W. Kuehn65,‡, T. Kuhr78,‡, R. Kulasiri67,‡, M. Kumar81,‡, R. Kumar101,‡, T. Kumita121,‡, A. Kuzmin6,96,‡, Y.-J. Kwon172,‡, S. Lacaprara55,‡, Y.-T. Lai30,‡, K. Lalwani81,‡, J. S. Lange65,‡, S. C. Lee73,‡, J.Y. Lee106,‡, P. Leitl83,‡, D. Levit114,‡, S. Levonian16,‡, S. Li3,‡, L. K. Li41,‡, Y. Li41,‡,Y. B. Li103,‡, Q. Li103,‡, L. Li Gioi83,‡, J. Libby36,‡, Z. Liptak138,‡, D. Liventsev169,‡, S. Longo165,‡, A. Loos158,‡, G. Lopez Castro9,‡, M. Lubej109,‡, T. Lueck57,‡, F. Luetticke129,‡, T. Luo23,‡, F. Müller16,‡, Th. Müller48,‡, C. MacQueen145,‡, Y. Maeda90,‡, M. Maggiora60,‡, S. Maity33,‡, E. Manoni56,‡, S. Marcello60,‡, C. Marinas129,‡, M. Martinez Hernandez4,‡, A. Martini59,‡, D. Matvienko6,96,77,‡, J. A. McKenna130,‡, F. Meier160,‡, M. Merola54,‡, F. Metzner48,‡, C. Miller165,‡, K. Miyabayashi91,‡, H. Miyake30,26,‡, H. Miyata94,‡, R. Mizuk77,88,87,‡, G. B. Mohanty111,163,‡, H. K. Moon71,‡, T. Moon106,‡,A. Morda55,‡, T. Morii66,‡, M. Mrvar109,‡, G. Muroyama90,‡, R. Mussa60,‡, I. Nakamura30,26,‡, T. Nakano99,‡, M. Nakao30,26,‡, H. Nakayama30,26,‡, H. Nakazawa92,‡, T. Nanut109,‡, M. Naruki72,‡, K. J. Nath34,‡, M. Nayak116,‡, N. Nellikunnummel151,‡, D. Neverov90,‡, C. Niebuhr16,‡, J. Ninkovic84,‡, S. Nishida30,26,‡, K. Nishimura138,‡, M. Nouxman143,‡, G. Nowak93,‡, K. Ogawa94,‡, Y. Onishchuk110,‡, H. Ono94,‡, Y. Onuki162,‡, P. Pakhlov77,88,‡, G. Pakhlova87,‡, B. Pal5,‡, E. Paoloni57,‡, H. Park73,‡, C.-S. Park172,‡, B. Paschen129,‡, A. Passeri59,‡, S. Paul114,‡, T. K. Pedlar80,‡, M. Perelló46,‡, I. M. Peruzzi52,‡, R. Pestotnik109,‡, L. E. Piilonen169,‡, L. Podesta Lerma125,‡, V. Popov87,‡, K. Prasanth111,‡, E. Prencipe21,‡, M. Prim48,‡, M. V. Purohit158,‡, A. Rabusov114,‡, R. Rasheed47,‡, S. Reiter65,‡, M. Remnev6,96,‡, P. K. Resmi36,‡, I. Ripp-Baudot47,‡, M. Ritter78,‡, M. Ritzert139,‡, G. Rizzo57,‡, L. Rizzuto141,109,‡, S. H. Robertson85,‡, D. Rodriguez Perez125,‡, J. M. Roney165,‡, C. Rosenfeld158,‡, A. Rostomyan16,‡, N. Rout36,‡, S. Rummel78,‡, G. Russo54,‡, D. Sahoo111,‡, Y. Sakai30,26,‡, M. Salehi143,78,‡, D. A. Sanders146,‡, S. Sandilya135,‡, A. Sangal135,‡, L. Santelj47,‡, J. Sasaki162,‡, Y. Sato30,‡, V. Savinov151,‡, B. Scavino63,‡, M. Schram100,‡, H. Schreeck24,‡, J. Schueler138,‡,C. Schwanda40,‡,A. J. Schwartz135,‡,R.M. Seddon85,‡,Y. Seino94,‡, K. Senyo171,‡, O. Seon90,‡, I. S. Seong138,‡, M. E. Sevior145,‡, C. Sfienti63,‡, M. Shapkin38,‡, C. P. Shen3,‡,M. Shimomura91,‡, J.-G. Shiu92,‡, B. Shwartz6,96,‡,A. Sibidanov165,‡, F. Simon83,113,‡, J. B. Singh101,‡, R. Sinha42,‡, S. Skambraks83,‡, K. Smith145,‡, R. J. Sobie165,‡, A. Soffer116,‡, A. Sokolov38,‡, E. Solovieva77,87,‡, B. Spruck63,‡, S. Staniˇc149,‡, M. Stariˇc109,‡, N. Starinsky147,‡, U. Stolzenberg24,‡, Z. Stottler169,‡, R. Stroili55,‡, J. F. Strube100,‡, J. Stypula93,‡, M. Sumihama25,‡, K. Sumisawa30,26,‡, T. Sumiyoshi121,‡, D. Summers146,‡, W. Sutcliffe48,‡, S. Y. Suzuki30,26,‡, M. Tabata13,‡, M. Takahashi16,‡, M. Takizawa107,‡, U. Tamponi60,‡, J. Tan145,‡, S. Tanaka30,26,‡, K. Tanida2,‡, N. Taniguchi30,‡, Y. Tao137,‡, P. Taras147,‡, G. Tejeda Munoz4,‡, F. Tenchini16,‡, U. Tippawan12,‡, E. Torassa55,‡, K. Trabelsi30,26,‡, T. Tsuboyama30,26,‡, M. Uchida120,‡, S. Uehara30,26,‡, T. Uglov77,87,‡, Y. Unno28,‡, S. Uno30,26,‡, Y. Ushiroda30,26,162,‡, Y. Usov6,96,‡, S. E. Vahsen138,‡, R. van Tonder48,‡, G. Varner138,‡, K. E. Varvell160,‡, A. Vinokurova6,96,‡, L.Vitale61,‡,M.Vos46,‡,A.Vossen17,‡,E.Waheed145,‡,H.Wakeling85,‡,K.Wan162,‡, M.-Z.Wang92,‡, X. L. Wang23,‡, B. Wang135,‡, A. Warburton85,‡, J. Webb145,‡, S. Wehle16,‡, C. Wessel129,‡, J. Wiechczynski93,‡, P. Wieduwilt24,‡, E. Won71,‡, Q. Xu41,‡, X. Xu41,‡, B. D. Yabsley160,‡, S. Yamada30,‡, H. Yamamoto119,‡, W. Yan3,‡, W. Yan154,‡, S. B. Yang71,‡, H. Ye16,‡, I. Yeo70,‡, J. H. Yin41,‡, M. Yonenaga121,‡, T. Yoshinobu94,‡, W. Yuan55,‡, C. Z. Yuan41,‡, Y. Yusa94,‡, S. Zakharov77,87,‡, L. Zani57,‡, M. Zeyrek86,‡, J. Zhang41,‡,Y. Zhang23,‡,Y. Zhang154,‡, X. Zhou3,‡, V. Zhukova77,‡, V. Zhulanov6,96,‡, and A. Zupanc141,109,‡ †Editor. ‡Belle II Collaborator. §Theory or external contributing author., "The Belle II Theory Interface Platform (B2TiP) was created as a physics prospects working group of the Belle II collaboration in June 2014. It offered a platform where theorists and experimentalists could work together to elucidate the potential impacts of the Belle II program, which includes a wide scope of physics topics: B physics, charm, τ , quarkonium physics, electroweak precision measurements, and dark sector searches. It is composed of nine working groups (WGs), which 6/654 Downloaded from https://academic.oup.com/ptep/article-abstract/2019/12/123C01/5685006 by Uniwersytet Slaski Biblioteka Glowna user on 20 February 2020 PTEP 2019, 123C01 E. Kou et al. are coordinated by teams of theory and experiment conveners: WG1, Semileptonic and leptonic B Decays; WG2, Radiative and Electroweak Penguins; WG3, φ1 and φ2 (Time-Dependent CP Violation) Measurements; WG4, φ3 Measurement; WG5, Charmless Hadronic B Decay; WG6, Charm; WG7, Quarkonium(-like); WG8, τ and Low-Multiplicity Processes; WG9, New Physics. We organized workshops twice a year from 2014 until 2016, which moved from KEK in Japan to Europe and the Americas, gathering experts in the respective fields for discussions with Belle II members. One of the goals for B2TiP was to propose so-called “golden and silver channels”: we asked each working group to choose, among numerous possible measurements, those that would have the highest potential impact and to focus on them for the writeup. Theorists scrutinized the role of those measurements in terms of understanding the theory behind them, and estimated the theoretical uncertainties now achievable as well as prospects for the future. For flavor physics, having tight control of hadronic uncertainties is one of the most crucial aspects in the field, and this is considered an important criterion in determining the golden or silver channels. Experimentalists, on the other hand, investigated the expected improvements with data from Belle II. For the channels where the errors are dominated by statistical uncertainties, or where systematic errors are reducible, the errors can decrease rapidly as more data becomes available. The impact of the upgraded performance from Belle II is a crucial element in reducing the uncertainties: we therefore include the latest available studies of the detector efficiency using Monte Carlo simulated events.We list the golden and silver channel table in the introductory chapter, as a guide for the chapters that follow. This book is not a collection of reports based on talks given at the workshops. The working group conveners endeavored to construct a coherent document that can be used by Belle II collaborators, and others in the field of flavor physics, as a reference. Two books of a similar type have been produced in the past: The BaBar Book [1] and The Physics of the B Factories [2]. In order to avoid too much repetition with respect to those references, we refer to them wherever possible for introductory material. We would like to thank the section editors and contributing authors for the many stimulating discussions and their tremendous efforts in bringing the book together." (Preface)

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.

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.

Optical nonlinearities usually appear for large intensities, but discrete transitions allow for giant nonlinearities operating at the single-photon level. This has been demonstrated in the last decade for a single optical mode with cold atomic gases, or single two-level systems coupled to light via a tailored photonic environment. Here, we demonstrate a two-mode giant nonlinearity with a single semiconductor quantum dot (QD) embedded in a photonic wire antenna. We exploit two detuned optical transitions associated with the exciton-biexciton QD level scheme. Owing to the broadband waveguide antenna, the two transitions are efficiently interfaced with two free-space laser beams. The reflection of one laser beam is then controlled by the other beam, with a threshold power as low as 10 photons per exciton lifetime (1.6 nW). Such a two-color nonlinearity opens appealing perspectives for the ealization of ultralow-power logical gates and optical quantum gates, and could also be implemented in an integrated photonic circuit based on planar waveguides.

International audience; In the context of fast developing quantum technologies, locating single quantum objects embedded in solid or fluid environment while keeping their properties unchanged is a crucial requirement as well as a challenge. Such ``quantum microscopes'' have been demonstrated already for NV-centers embedded in diamond [1], and for single atoms within an ultracold gas [2]. In this work, we demonstrate a new method to determine non-destructively the position of randomly distributed semiconductor quantum dots (QDs) deeply embedded in a solid photonic waveguide. By setting the wire in an oscillating motion, we generate large stress gradients across the QDs plane. We then exploit the fact that the QDs emission frequency is highly sensitive to the local material stress [3-5] to infer their positions with an accuracy ranging from +/- 35 nm down to +/-1 nm for close-to-axis QDs.

The Stereotactic Alignment for Linear Accelerator (S. A. Linac) system is developed to conveniently improve the alignment accuracy of a conventional linac equipped with stereotactic cones. From the Winston‐Lutz test, the SAlinac system performs three‐dimensional (3D) reconstruction of the quality assurance (QA) ball coordinates with respect to the radiation isocenter, and combines this information with digital images of the laser target to determine the absolute position of the room lasers. A handheld device provides near‐real‐time repositioning advice to enable the user to align the QA ball and room lasers to within 0.25 mm of the centroid of the radiation isocenter. The results of 37 Winston‐Lutz tests over 68 days showed that the median 3D QA ball alignment error was 0.09 mm, and 97% of the time the 3D error was ≤0.25 mm. All 3D isocentric errors in the study were 0.3 mm or less. The median x and y laser alignment coordinate error was 0.09 mm, and 94% of the time the x and y laser error was ≤0.25 mm. A phantom test showed that the system can make submillimeter end‐to‐end accuracy achievable, making a conventional linac a “Submillimeter Knife”. PACS numbers: 87.53.Ly, 87.55.Qr

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

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 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: 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.

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

Purpose: We have previously developed an accurate dose‐reconstruction algorithm that is based on non‐iterative inverse solution of deposited dose using Monte Carlo‐generated responses for known multi‐leaf collimator(MLC) positions. The method was time‐consuming in generating the responses. The objective of this study is to develop a faster algorithm that does not require MLC positions by using pre‐calculated virtual beamlet‐specific dose responses for an open beam, and thus can be used at the end of radiation delivery on‐the‐spot. Methods: The success of the method is based on the hypothesis that the ratio of dose responses in phantom and electronic portal imaging device(EPID) of delivered beam intensities is approximated by the ratio of virtual beam intensities. The possibility is mathematically shown by convolving reconstructed intensities from EPID to both numerator and denominator of the latter ratio. The inversion algorithm for the reconstruction is unchanged. To test the hypothesis, we have calculated virtual beamlet dose responses in Rando phantom and EPID for intensity modulated beams determined for prostate treatment. We have measured in EPID under the phantom and performed dose reconstruction for the two cases. A 6MV photon beam from a Varian 2100EX accelerator and aS500 EPID (integrated acquisition) was used. Results: When compared with a forwardly calculated dose in an isocentric plane within the phantom for an IMRT beam, the reconstructed doses of the two showed similar pass rates of >94.7%, given 3% dose difference or 3mm distance‐to‐agreement. The calculation used 5 minutes per beam using four 2.8GHz Intel XEON CPUs. Automation and the use of a higher data processor can potentially reduce the calculation time to less than a minute. Conclusion: A fast method of dose reconstruction was developed and more results will be presented. This method is applicable to detect delivery error. In part supported by Varian Medical Systems.

In gated radiation therapy, reproducibility of patient's internal motion between imaging and delivery is essential. However, changes in period, amplitude, shape of motion, and baseline shift occur. In this study, we investigated the dosimetric impact of the changes on the coverage of clinical and internal target volumes for phase and amplitude gating. We used conventional and intensity‐modulated beams that are designed to cover internal target volumes. We assumed a duty cycle of 40‐to‐60% phases and equivalent amplitudes, a period of 4.5sec, and an amplitude of 4cm as conditions used in imaging. We introduced the above changes from these and used actual patient's breathing motion in the measurement and computational simulation on a diode array (double precision). When a baseline shift of ‐1cm was assumed, only a part (67%) of clinical target volume (CTV) received a prescribed does for phase gating; a similar profile shift in delivereddose was observed for the amplitude gating (when the amplitude window was stationary). As the amount of the shift increased, the impact increased. An amplitude change by a few centimeters caused a shift in delivereddose profile and underdose in CTV for phase gating. The underdose was not observed for amplitude gating. The change in breathing periods did not affect the delivereddose profile. The change in breathing pattern from sinusoidal into linear shapes showed underdose in 12% of CTV and profile change for phase gating and no profile change and underdose for amplitude gating. The simulations agreed with the measurements, and used for the amplitude gating study. Results based on actual breathing patterns and intensity‐modulated fields will also be presented. This study has demonstrated that unless the amplitude opening is not adapting to the movement and extent of CTV, gated therapy is susceptible to the irreproducibility. Partly supported by Varian Medical Systems, Inc.