[en] An overview of the important developments of the TUF code is presented. The TUF code has been designed for steady state and transient thermal-hydraulics analyses for CANDU reactors. The primary objective of the development of the TUF code is to provide analytical tool for design, safety and licensing analyses. Developments pertinent to the following analysis areas are described : large LOCA analyses, simulation of the ECI Accumulator response, analysis of the large secondary side steam line breaks, reverse flow induced bundle movement, and water hammer analysis. Developments relevant to the large LOCA application are reported separately in the Conference. The rest are described in the paper. Emphases are placed on the models and the sensitivity studies of the physical parameters, rather that on the detailed system responses in the simulations. Finally, some aspects about the code validation are discussed. (author) 14 refs., 2 tabs., 10 figs

[en] Short communication

[en] The radioactive beta-adrenergic antagonist [³H] dihydroalprenolol (DHA) binds to particulate preparations of human myometrium in a manner compatible with binding to the beta-adrenergic receptor. The binding of DHA is rapid (attaining equilibrium in 12 minutes), readily reversible (half time = 16 minutes), high affinity (K/sub D/ = 0.50 nM), low capacity (Bmax = 70 fmoles/mg of protein), and stereoselective ([-]-propranolol is 100 times as potent as [+] -propranolol in inhibiting DHA binding). Adrenergic agonists competed for DHA binding sites in a manner compatible with beta-adrenergic interactions and mirrored β₂ pharmacologic potencies: isoproterenol > epinephrine >> norepinephrine. Studies in which zinterol, a β₂-adrenergic agonist, competed for DHA binding sites in human myometrial particulate indicated that at least 87% of the beta-adrenergic receptors present are β₂-adrenergic receptors. Binding of DHA to human myometrial beta-adrenergic receptors provides a tool which may be used in the examination of gonadal hormonal modification of adrenergic response in human uterus as well as in the analysis of beta-adrenergic agents as potentially useful tocolytic agents

No abstract available

[en] Purpose: The increasing application of VMAT demands a more efficient workflow and QA solution. This study aims to investigate the feasibility of performing VMAT QA measurements on one linac for plans treated on other beam-matched Elekta Agility linacs. Methods: A single model was used to create 24 clinically approved VMAT plans (12 head-and-neck and 12 prostate using 6MV and 10MV respectively) on Pinnacle v9.10 (Philips, Einhoven, Netherlands). All head-and-neck plans were delivered on three beam-matched machines while all prostate cases were delivered on two beam-matched 10MV Agility machines. All plans were delivered onto PTW Octavius 4D phantom with 1500 detector array (PTW, Freiburg, Germany). Reconstructed volume doses were then compared with the Pinnacle reference plans in Verisoft 6.1 under 3%/3mm gamma criteria at local dose. Plans were considered clinically acceptable if >90% of the voxels passing the gamma criteria. Results: All measurements were passed (3D gamma passing rate >90%) and the result shows that the mean difference of 3D gamma of 12 head-and-neck cases is 1.2% with standard deviation of 0.6%. While for prostate cases, the mean difference of 3D gamma is 0.9% with standard deviation of 0.7%. Maximum difference of 3D gamma of all measurements between beam-matched machines is less than 2.5%. The differences of passing rates between different machines were statistically insignificant (p>0.05). Conclusion. The result suggests that ther Conclusion: The result suggests that there exists a 3D gamma threshold, in our case 92.5%, above which the VMAT QA performed in any one of beam-matched machine will also pass in another one. Therefore, VMAT QA efficiency may be increased and phantom set up time can be saved by implementing such method. A constant performance across all beam matched machines must be maintained to make this QA approach feasible.

[en] This paper reports on recent progress in the simulation of RD-14M single-phase pump rundown tests using the TUF pump model. TUF is an advanced two-fluid system thermalhydraulic computer code used in the safety and operational analysis of Ontario Hydro's nuclear reactors. RD-14M is an experimental facility possessing many of the physical and geometrical characteristics of a CANDU reactor heat transport system. In this paper, a recent series of RD-14M pump rundown experiments is described. The model used in TUF for simulating the steady and transient behaviour of the primary pumps is also presented. The pump model in TUF requires the user to input constitutive relationships in the form of constants for the homologous head and torque curves as well as a number of constants (e.g., moment of inertia, the coefficient of static friction, and the coefficient of dynamic friction) that are required for modelling the pump transient behaviour. Using the same methodology as that for characterizing the primary heat transport pumps in Darlington reactors, the constants required for modelling the RD-14M pumps were determined based on experimental data from three RD-14M rundown test (C9511, C9514 and C9519). The resulting TUF model of an RD-14M pump was then used to simulate a fourth independent RD-14M pump rundown test (C9513). Reasonable agreement was obtained between the computed results and experimental data. (author)

[en] Purpose: Following the method of in-phantom measurements of reference air kerma rate (Ka) at 100cm and absorbed water dose rate (Dw1) at 1cm of high-dose-rate 192Ir brachytherapy source using 60Co absorbed-dose-to-water calibrated (ND,w,60Co) ionization chamber (IC), we experimentally determined the in-phantom correction factors (kglob) of the PTW30013 (PTW, Freiburg, Germany) IC by comparing the Monte Carlo (MC)-calculated kglob of the other PTW30016 IC. Methods: The Dw1 formalism of in-phantom measurement is: M*ND,w,60Co*(kglob)Dw1, where M is the collected charges, and (kglob)Dw1 the in-phantom Dw1 correction factor. Similarly, Ka is determined by M*ND,w,60Co*(kglob)ka, where (kglob)ka the in-phantom Ka correction factor. Two thimble ICs PTW30013 and another PTW30016 having a ND,w,60Co from the German primary standard laboratory (PTB) were simultaneously exposed to the microselectron 192Ir v2 source at 8cm in a PMMA phantom. A reference well chamber (PTW33004) with a PTB transfer Ka calibration Nka was used for comparing the in-phantom measurements to derive the experimental (kglob)ka factors. We determined the experimental (kglob)Dw1 of the PTW30013 by comparing the PTW30016 measurements with MC-calculated (kglob)Dw1. Results: Ka results of the PTW30016 based on ND,w,60Co and MC-calculated (kglob)ka differ from the well chamber results based on Nka by 1.6% and from the manufacturer by 1.0%. Experimental (kglob)ka factors for the PTW30016 and two other PTW30013 are 0.00683, 0.00681 and 0.00679, and vary <0.5% with 1mm source positioning uncertainty. Experimental (kglob)Dw1 of the PTW30013 ICs are 75.3 and 75.6, and differ by 1.6% from the conversion by dose rate constant from the AAPM report 229. Conclusion: The 1.7% difference between MC and experimental (kglob)ka for the PTW30016 IC is within the PTB 2.5% expanded uncertainty in Ka calibration standard. Using a single IC with ND,w,60Co to calibrate the brachytherapy source and dose output in external radiotherapy is feasible. MC validation of the PTW30013(kglob)Dw1 is warranted.

[en] Background: Commercial treatment planning system Pinnacle3 (Philips, Fitchburg, WI, USA) employs a convolution-superposition algorithm for volumetric-modulated arc radiotherapy (VMAT) optimization and dose calculation. Study of Monte Carlo (MC) dose recalculation of VMAT plans for advanced-stage nasopharyngeal cancers (NPC) is currently limited. Methods: Twenty-nine VMAT prescribed 70Gy, 60Gy, and 54Gy to the planning target volumes (PTVs) were included. These clinical plans achieved with a CS dose engine on Pinnacle3 v9.0 were recalculated by the Monaco TPS v5.0 (Elekta, Maryland Heights, MO, USA) with a XVMC-based MC dose engine. The MC virtual source model was built using the same measurement beam dataset as for the Pinnacle beam model. All MC recalculation were based on absorbed dose to medium in medium (Dm,m). Differences in dose constraint parameters per our institution protocol (Supplementary Table 1) were analyzed. Results: Only differences in maximum dose to left brachial plexus, left temporal lobe and PTV54Gy were found to be statistically insignificant (p> 0.05). Dosimetric differences of other tumor targets and normal organs are found in supplementary Table 1. Generally, doses outside the PTV in the normal organs are lower with MC than with CS. This is also true in the PTV54-70Gy doses but higher dose in the nasal cavity near the bone interfaces is consistently predicted by MC, possibly due to the increased backscattering of short-range scattered photons and the secondary electrons that is not properly modeled by the CS. The straight shoulders of the PTV dose volume histograms (DVH) initially resulted from the CS optimization are merely preserved after MC recalculation. Conclusion: Significant dosimetric differences in VMAT NPC plans were observed between CS and MC calculations. Adjustments of the planning dose constraints to incorporate the physics differences from conventional CS algorithm should be made when VMAT optimization is carried out directly with MC dose engine.

[en] Purpose: To assess the plan robustness and safety margin in SRS from 4DMGDR in E2E QA based on clinical objectives. Methods: OCTAVIUS SRS 1000 detector array and 4D phantom (PTW, Freiburg, Germany) were used to measure 5 coplanar SRS plans with 1 and 2 mm planning target volume (PTV). 3 targets were clinical, and 2 were virtual simulated to be 1mm from the brainstem (BS), and between chiasm (CS) and optic nerve (ON). Planning was done on Monaco v5.0 (Elekta, Maryland Heights, MO) to achieve 95–99% PTV and 100% gross tumor volume (GTV) prescription dose coverage. CBCT setup of the 4D phantom by 6D robotic couch was performed as for real patient. 4D-MGDR in patient CT and dosimetric analysis were performed in PTW Verisoft v6.1. The safety margin that achieved 100% GTV coverage was determined, and doses to 2% (D2%) of BS, ON and CS were assessed from E2E QA. Results: 100% GTV coverage was achieved with 1mm margin for 2 plans and 2mm margin for all plans. 98.3% and 99.4% GTV coverage were found in E2E QA for 1mm PTVs that either had sharp changing contour, or was nearby CS and ON or BS, and had either low planned minimum GTV dose (∼101% of the prescribed dose vs.∼106%) or compromised PTV coverage (95% vs. 99%). D2% to CS obtained with 4D-MGDR for one virtual target were 18.8Gy for 1mm PTV and 19.2Gy for 2mm PTV, exceeding the planned tolerance of 18Gy/3 fractions for prescription dose of 24Gy. Conclusion: 1mm margin is generally sufficient for dose planning and machine delivery errors. Irregular GTV with just enough dose coverage to spare critical organs may need 2mm margin at the costs of possible higher organ doses. 4D MGDR in an E2E QA approach can put the treatment plan evaluation in clinical perspectives

[en] Purpose: To cross-validate the MGDR of COMPASS (IBA dosimetry, GmbH, Germany) and OCTAVIUS 4D system (PTW, Freiburg, Germany). Methods: Volumetric-modulated arc plans (5 head-and-neck and 3 prostate) collapsed to 40° gantry on the OCTAVIUS 4D phantom in QA mode on Monaco v5.0 (Elekta, CMS, Maryland Heights, MO) were delivered on a Elekta Agility linac. This study was divided into two parts: (1) error-free measurements by gantry-mounted EvolutionXX 2D array were reconstructed in COMPASS (IBA dosimetry, GmbH, Germany), and by OCTAVIUS 1500 array in Versoft v6.1 (PTW, Freiburg, Germany) to obtain the 3D doses (COM4D and OCTA4D). COM4D and OCTA4D were compared to the raw measurement (OCTA3D) at the same detector plane for which OCTAVIUS 1500 was perpendicular to 0° gantry axis while the plans were delivered at gantry 40°; (2) beam steering errors of energy (Hump=-2%) and symmetry (2T=+2%) were introduced during the delivery of 5 plans to compare the MGDR doses COM4D-Hump (COM4D-2T), OCTA4D-Hump (OCTA4D-2T), with raw doses OCTA3D-Hump (OCTA3D-2T) and with OCTA3D to assess the error reconstruction and detection ability of MGDR tools. All comparisons used Υ-criteria of 2%(local dose)/2mm and 3%/3mm. Results: Averaged Υ passing rates were 85% and 96% for COM4D,and 94% and 99% for OCTA4D at 2%/2mm and 3%/3mm criteria respectively. For error reconstruction, COM4D-Hump (COM4D-2T) showed 81% (93%) at 2%/2mm and 94% (98%) at 3%/3mm, while OCTA4D-Hump (OCTA4D-2T) showed 96% (96%) at 2%/2mm and 99% (99%) at 3%/3mm. For error detection, OCTA3D doses were compared to COM4D-Hump (COM4D-2T) showing Υ passing rates of 93% (93%) at 2%/2mm and 98% (98%), and to OCTA4D-Hump (OCTA4D -2T) showing 94% (99%) at 2%/2mm and 81% (96%) at 3%/3mm, respectively. Conclusion: OCTAVIUS MGDR showed better agreement to raw measurements in both error- and error-free comparisons. COMPASS MGDR deviated from the raw measurements possibly owing to beam modeling uncertainty