bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sci‐Thur PM Therapy‐07: Improving IMRT plans delivery for head and neck cases using aperture‐based MLC segments
Authors: Lavoie C , Beaulieu F , Beaulieu L , Tremblay D , Gingras L , Nadeau S 
Published: July 2006

Purpose: To investigate the possibility of performing IMRT in head and neck treatment sites with less segments and monitor units (MU).Materials and methods: Six pharyngeal cases (n = 6) were analysed and four cases (n = 4), in the sinonasal region. For each one, an IMRT plan was first realized using a commercial software (Pinnacle3 — IMFAST segmentation algorithm —). Then, an‐in‐house inverse planning system, called Ballista, based on predetermined segments, was used to realize comparable plans. Its segments are generated with the subtraction of the projection of the OARs with the PTV (planning target volume).Results: For the pharyngeal Ballista plans, the average volume of the PTV that received at least 100% of the prescribed dose (V100) was 85.0±4.5% for the first prescription (PTV1) and the V100 for the second prescription (PTV2 — simultaneous integrated boost —) was 78.5±10.9%. With Pinnacle3, the V100 value was 86.6±4.8% and 81.5±12.4% respectively for PTV1 and PTV2 (see figure 2a and 2b). On average, Ballista plans have required 932±124 MUs and 52±10 segments compared to 1238±230 MU and 117±7 segments for Pinnacle3. For the sinonasal Ballista plans, the average V100 obtained was 80.0±3.1%. With Pinnacle3, the V100 gave 75.7±2.7%. Ballista plans have required an average of 406±54 MUs and 22±1 segments compared to 697±133 MUs and 99±14 segments for beamlet‐based IMRT.Conclusion: In step‐and‐shoot head and neck IMRT, an anatomy‐based MLC optimization system can achieve similar dosimetric plans comparable to traditional beamlet‐based IMRT with less number of segments and MU.
Sci‐Thur PM Therapy‐12: Use of patient‐specific planning target volumes in conformal radiotherapy of lung cancer: simple estimates of potential dosimetric benefit in tumor motion management
Authors: Burnett SSC , Hoisak JDP , Sixel KE , Cheung PCF 
Published: July 2006

Purpose: To estimate the volume of lung receiving at least 20 Gy (V20) for three tumor‐motion management strategies: population‐based uniform 15 mm margin, free‐breathing individualized margins, and reduced margins for gating with a 0.33 duty cycle.Methods: We have used a simple formula to combine set‐up error with target motion and to individualize planning target volumes (PTV) for four non‐small cell lung cancer patients. Previous measurements of set‐up error and fluoroscopy data synchronized to a spirometer were used as inputs for our calculations. Tumor motion was characterized in terms of the standard deviation of superior‐inferior (sup‐inf) displacements in each fluoroscopy image. Single‐phase treatment plans were generated such that at least 97% of the PTV was enclosed by the 60 Gy isodose, spinal cord dose was kept below 45 Gy, and V20 was minimized.Results: The table shows the PTV margins in the sup‐inf direction and the corresponding V20 values, as read from the dose‐volume histograms.Conclusion: Reductions in lung V20 and spinal cord dose are possible by use of patient‐specific margins. For more mobile tumors, gating may provide additional gains. Since tumor motion is predominantly in the superior‐inferior direction, uniform margins are not optimal.
Po‐Thur Eve General‐06: Experimental Validation of the Eclipse AAA Algorithm
Authors: Murray B , Newcomb C , Breitman K , Connors S , Dunscombe P , Field G , MacKenzie M , Rathee S , Robinson D , Warkentin H , Fallone B 
Published: July 2006

The Medical Physics departments of the Tom Baker Cancer Center (TBCC) and the Cross Cancer Institute (CCI) independently performed preliminary evaluation of the new Analytical Anisotropic Algorithm (AAA) implemented in Varian's Eclispe (v. 6.0) treatment planning system (TPS). The TPS was pre‐commissioned with “Golden Beam Data” from the vendor. We measured central and off‐axis profiles in several beam configurations including: open square, rectangular and asymmetric (half‐blocked) beams; wedged square and half‐blocked beams; square fields at three SSDs; open and wedged oblique beams; irregular field defined by MLC and cerrobend blocks. All measurements were performed on Varian 2100EX linear accelerators. Measurements were made to assess the dose in heterogeneous media at both the CCI (CIRS Thorax IMRT phantom) and at the TBCC (TLDs in a Rando phantom). Profiles were evaluated in the buildup, penumbra, inner and outer beam regions as per AAPM Task Group 53.Measured and calculated profiles agreement was very good in all regions except for the inner beam region at the CCI, attributed a difference in interpolation schemes at the two institutions and the large volume ion chamber used for measurements. The AAA penumbra was also found to be steeper than measured penumbra since AAA was pre‐commissioned using diode measurements. Total scatter factors for most measurements differed by less than 2% from the calculated ones except for the hard wedges where differences up to 4% were found. Anthropomorphic phantoms measurements differed from AAA by as much as 5.6%.Funding provided by Varian.
Po‐Thur Eve General‐25: Development of a Tissue Sample Analysis System Using Diffraction Enhanced Imaging and Small and Wide Angle Scattering
Authors: Bewer B , Chapman D , Cunningham I 
Published: July 2006

Current methods of x‐ray imaging, whether it is a dental x‐ray or an image of a broken bone, use absorption properties of the body for contrast in the image. This reliance on absorption to obtain an image creates problems when the soft tissues of the body are the subjects of interest. The difficulty in obtaining suitable contrast image is particularly challenging when the difference in absorption properties of two adjacent tissues are small.This challenge of obtaining a high contrast soft tissue image requires revisiting the processes of radiation interaction. The common x‐ray interactions within the diagnostic energy range are: 1) the photoelectric effect; 2) Compton scattering; and 3) Coherent scattering. For absorption x‐ray techniques the first process, the photoelectric effect, is responsible for the contrast in the image. The remaining processes of x‐ray interaction, scattering, degrade the absorption image and efforts are made to remove scattering from absorption images in the form of anti‐scatter grids and are somewhat effective. In recent years however techniques have emerged that are not degraded by scattering or even use scatter as a method of analysis and imaging.The first technique is diffraction enhanced imaging and uses x‐ray crystal diffraction as a method of removing scatter. The choice of the crystal diffraction plane will determine the level of scatter rejection. The second method is small and wide angle x‐ray scattering, (SAXS, WAXS). In this technique the unique scatter patterns from various tissues are used to form an image.
Po‐Thur Eve General‐31: Dosimetric Impact of Planning a Boost within a Boost in Permanent Seed Implants
Authors: Beaulieu L , Aubin S , Varfalvy N , Lessard E , Pouliot J , Vigneault E , Martin AG 
Published: July 2006

Purpose: To investigate the dosimetric impact on the target volume, boost volume (BV) and urethra of performing limited volume boosts in seed implants.Method and Materials: 35 localized prostate cancer patients with detailed biopsy results were treated with permanent seed implants Personalized plans in which BV corresponding to regions of positive biopsy were generated intra‐operatively based on a simulated annealing inverse planning algorithm. The dose objectives are 144 Gy to the prostate with a 3–4 mm margin, 2/3 (1/3) of the prostate covered by 150% (200%) of the prescription dose (PD), urethra V150 less than 10% and D5 should below 220 Gy. Finally, 100% of BV should receive 150% PD (or 216 Gy).Results: Comparing plans without and with BV show no significant change in the number of seeds, needles, prostate V100 and V200. Prostate V150 (D90) show significant differences increasing from 65% (187Gy) to 70% (191Gy). By forcing the coverage of the BV, the 150% isodose lines (which extend outside the prostate) shift inside of the prostate. Small increase in prostate V150 leads to significant increases of the BV V150 from 79% to 94%. BV do not translate to higher urethra doses. Thus multiple seed reconfigurations inside the prostate are achievable to cover BV.Conclusion: Specific areas within the prostate can be boost to receive 150% of the PD with no impact on the urethra. The plans lead essentially to a rearrangement of the seed positions. Potential radiobiological advantages could be obtained at no cost (procedure or time).
Po‐Thur Eve General‐33: Feasibility of a Multileaf Collimator and Method for Multi‐slice Tomotherapy
Authors: Cadman P , Mackie T , Reckwerdt P 
Published: July 2006

Purpose: Current methods for delivery of serial or helical tomotherapy are based on a collimator design which can, at most, irradiate two slices simultaneously as the source rotates around the patient. We investigate the feasibility of a novel multileaf collimator design and method for multi‐slice tomotherapy.Method and Materials: The MLC incorporates a compact pivoting leaf design. Intensity modulation is achieved through binary actuation of adjacent leaves. Multiple leaf banks are employed for multi‐slice tomotherapy delivery. Each fan beam will have a different divergence in the axial direction. Two multi‐slice delivery methods are evaluated where (a) pitch is determined by a given collimated slice which does not irradiate beyond the adjacent slice (regular pitch) or (b) pitch is determined by different collimated slices irradiating the same region in the patient (multi‐slice pitch). Junctioning effects were studied for a cylindrical phantom irradiated with open (unmodulated) fan beams.Results: A prototype MLC leaf has been tested which can switch between open and closed positions in a few tens of milliseconds. Regular pitch delivery produced the greatest inhomogeneity between regions irradiated by different collimated slices. The proposed multi‐slice pitch delivery method avoids regular pitch junctioning effects by irradiating all areas with all collimated slices.Conclusions: These results indicate that multi‐slice tomotherapy is feasible with the benefits of shorter treatment times and it may allow for the use of Co‐60 as a tomotherapy radiation source.Conflict of Interest: Research was supported in part through a licensing agreement with TomoTherapy Inc.
Po‐Thur Eve General‐38: The Virtual Radiotherapy Department
Authors: Murray B , Chwyl B , Campbell K , Connors S , Dundas G , Eberle S , Fawcett S , Field C , Richardson S , Sandahl D , Schouten M , Yakimovich C 
Published: July 2006

With the number of clinical cases increasing each year, there is pressure on all clinical staff to do more clinical service. At the same time there is a demand to train more students in all of the radiotherapy disciplines. Regulatory agencies are also demanding more continuing education and upgrading for existing staff. We have recently introduced a new clinical treatment planning system, which requires a significant amount of training for all staff members. To meet these increased demands for training all levels of learners we have developed a “Virtual Radiotherapy Department”. The Virtual Radiotherapy Department will provide on line teaching of basic physics and treatment planning for radiation therapy students, radiation oncology residents, and physics graduate students and residents. By using on‐line interactive tools it is possible to teach all the different students at different levels by making basic information available to all students, but linking to more advanced information for those that require it.On‐line videos have been created describing several clinical techniques using various equipment. These videos will be used to provide students instruction as well as for continuing education for existing staff or new staff. These tools will be used to provide training to all users as we introduce our new treatment planning system, showing them exactly how to complete various tasks. These videos are customized to our treatment processes; therefore, they show users exactly what is required in the most efficient manner.Funding Provided by Alberta Health and Wellness and Varian.
Sci‐Fri AM General‐06: The Moving Slanted‐Edge Method: A Novel Technique to Measure the Temporal Response of a Fluoroscopic System
Authors: Friedman SN , Cunningham IA 
Published: July 2006

Fluoroscopic procedures are generally acknowledged to lead to large patient doses. It is important to have a method of measuring detector performance. Applications of cascaded‐systems theory to measure detector performance of fluoroscopic systems have produced unexpectedly high results due to the reduction in measured noise caused by temporal averaging between frames as a result of system lag. Methods have been proposed to remove this affect of lag, which require the system temporal resolution through the system temporal modulation transfer function (MTF). No method currently exists to easily and accurately measure the system temporal MTF of a fluoroscopic system. We have developed a novel technique, the “moving slanted‐edge method”, to make measurements of system temporal MTF from the image data of a fluoroscopic system.We translate a tungsten sheet across the detector with constant velocity, vo, and calculate a spatiotemporal coordinate for each pixel based on distance and time from passage of the edge. The resulting data is used to calculate a vo‐dependent MTF. The system (spatial) MTF and vo‐dependent MTF are mapped onto the temporal axis using the edge velocity. The system temporal MTF is calculated by dividing the vo‐dependent MTF by the (spatial) MTF.This method was validated on a bench‐top fluoroscopic system consisting of a three‐year old Dunlee image intensifier coupled to a CCD camera. The system temporal MTF was calculated using the moving slanted‐edge method (vo=45 cm/s) and the optical decay curve of the image intensifier. Excellent agreement was found between the two methods.
Sci‐Sat AM (1) General‐04: Quantitative impact of 3D inter fractional patient setup errors on TCP/NTCP
Authors: Jans H , Syme A , Rathee S , Fallone B 
Published: July 2006

Patient setup errors in external beam radiation therapy are a cause for differences between planned dose distribution and the one delivered to the patient. A changed dose distribution results in a changed tissue response, expressed as tumor control probability (TCP) and normal tissue complication probability (NTCP). A method was developed to calculate the changes of TCP and NTCP resulting from measured patient setup errors.Patient position was measured with a 2D‐3D registration method using orthogonal EPID images of the patient in treatment position. Setup errors were expressed as 6 degrees of freedom (rigid body translations and rotations); non‐rigid transformations and internal organ motion was not considered. The measured setup errors were used to change beam angles and couch position in a copy of the original treatment plan, such that an equivalent beams‐eye‐view of the patient was achieved for each treatment beam. The dose distribution for this modified treatment plan was then calculated. This procedure was repeated in additional copies of the original treatment plan for each fraction in which patient position had been measured. Once the treatment was completed, dose distributions for all measured fractions were added and the dose‐volume‐histograms (DVHs) were calculated for each region of interest. The DVHs in turn served as a basis for the calculation of TCP and NTCP. This method was applied to two prostate patients, whose position was measured during six fractions of their treatment. The setup errors did not change the TCP, but NTCP of the rectum increased by 9.0% and 2.2% respectively.
Sci‐Sat AM (2) Therapy‐02: Calcifications and tissue composition in post‐implant prostate dosimetry: a clinical study with Monte Carlo
Authors: Carrier JF , D'Amours M , Martin A , Vigneault E , Beaulieu L 
Published: July 2006

We developed an automated Monte Carlo (MC) multipurpose program to study different tissue configurations for post‐implant prostate brachytherapy dosimetry. We used our program for a clinical study on 18 cases. The usage of the DICOM‐RT protocol allows for an efficient transfer of data (Hounsfield Units [HU], seed positions, and organ contours) from the SPOT Pro system (version 3, Nucletron B.V., The Netherlands) to the MC program. A complete model was developed: for each voxel, the density is set by the HU and the elemental composition is set according to the radiation oncologist's contours. Between 180 and 320 different materials (prostate tissue, muscle, rectum tissue, bladder tissue, calcification, adipose tissue, and various mixtures) are utilized for each patient. The comparison between the TG‐43 based dosimetry and the complete MC simulation leads to average differences of 12±3 Gy for the D90 CTV parameter.Three calcification scenarios were considered to finalize the MC model. When compared to the complete model, the first calcification scenario leads to an average decrease of 14 Gy on the D90 CTV parameter while the second calcification scenario leads to an average increase of 6 Gy. The impact on organs at risk was also evaluated. The inclusion of prostate calcifications in the MC model is important but it is not possible to establish which scenario is the most realistic with traditional CT data. Research on dual‐energy CT is underway to facilitate the management of calcifications.
ENSO Predictability of a Fully Coupled GCM Model Using Singular Vector Analysis
Authors: Tang Youmin , Kleeman Richard , Miller Sonya 
Published: July 2006

Abstract
Using a recently developed method of computing climatically relevant singular vectors (SVs), the error growth properties of ENSO in a fully coupled global climate model are investigated. In particular, the authors examine in detail how singular vectors are influenced by the phase of ENSO cycle—the physical variable under consideration as well as the error norm deployed. Previous work using SVs for studying ENSO predictability has been limited to intermediate or hybrid coupled models.
The results show that the singular vectors share many of the properties already seen in simpler models. Thus, for example, the singular vector spectrum is dominated by one fastest growing member, regardless of the phase of ENSO cycle and the variable of perturbation or the error norm; in addition the growth rates of the singular vectors are very sensitive to the phase of the ENSO cycle, the variable of perturbation, and the error norm. This particular CGCM also displays some differences from simpler models; thus subsurface temperature optimal patterns are strongly sensitive to the phase of ENSO cycle, and at times an east–west dipole in the eastern tropical Pacific basin is seen. This optimal pattern also appears for SST when the error norm is defined using Niño-4. Simpler models consistently display a single-sign equatorial signature in the subsurface corresponding perhaps to the Wyrtki buildup of heat content before a warm event. Some deficiencies in the CGCM and their possible influences on SV growth are also discussed.
An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models
Authors: Soden Brian J. , Held Isaac M. 
Published: July 2006

Abstract
The climate feedbacks in coupled ocean–atmosphere models are compared using a coordinated set of twenty-first-century climate change experiments. Water vapor is found to provide the largest positive feedback in all models and its strength is consistent with that expected from constant relative humidity changes in the water vapor mixing ratio. The feedbacks from clouds and surface albedo are also found to be positive in all models, while the only stabilizing (negative) feedback comes from the temperature response. Large intermodel differences in the lapse rate feedback are observed and shown to be associated with differing regional patterns of surface warming. Consistent with previous studies, it is found that the vertical changes in temperature and water vapor are tightly coupled in all models and, importantly, demonstrate that intermodel differences in the sum of lapse rate and water vapor feedbacks are small. In contrast, intermodel differences in cloud feedback are found to provide the largest source of uncertainty in current predictions of climate sensitivity.
Interdecadal Variations in AGCM Simulation Skills
Authors: Grimm Alice M. , Sahai A. K. , Ropelewski Chester F. 
Published: July 2006

Abstract
Global climate models forced by sea surface temperature are standard tools in seasonal climate prediction and in projection of future climate change caused by anthropogenic emissions of greenhouse gases. Assessing the ability of these models to reproduce observed atmospheric circulation given the lower boundary conditions, and thus its ability to predict climate, has been a recurrent concern. Several assessments have shown that the performance of models is seasonally dependent, but there has always been the assumption that, for a given season, the model skill is constant throughout the period being analyzed. Here, it is demonstrated that there are periods when these models perform well and periods when they do not capture observed climate variability. The variations of the model performance have temporal scales and spatial patterns consistent with decadal/interdecadal climate variability. These results suggest that there are unmodeled climate processes that affect seasonal climate prediction as well as scenarios of climate change, particularly regional climate change projections. The reliability of these scenarios may depend on the time slice of the model output being analyzed. Therefore, more comprehensive model assessment should include a verification of the long-term stability of their performance.
Impact of Balloon Drift Errors in Radiosonde Data on Climate Statistics
Authors: McGrath Ray , Semmler Tido , Sweeney Conor , Wang Shiyu 
Published: July 2006

Abstract
Radiosonde data are a valuable resource in the detection of climate change in the upper atmosphere. Long time series of stratospheric temperature data, carefully screened and corrected to remove errors, are available for this purpose. Normal reporting practice usually ascribes a fixed time and position (the station location) to all data reported in the ascent. In reality, the ascent may take around 90 min to complete and the spatial drift of the radiosonde may exceed 200 km. This note examines the magnitude of the errors associated with this practice using simulated radiosonde data generated from the ECMWF reanalysis archive. The results suggest that the temperature errors, while generally small in the troposphere, are locally significant in the stratosphere, particularly in the jet stream areas. However, the impact of the drift errors on global climate statistics is very small. Errors in the wind and humidity data are also examined.