bluuebunny/crossref_metadata_2025_split huggingface dataset:
INTERMINGLING OF DALLI‐TYPE DALL'S PORPOISES INTO A WINTERING TRUEI‐TYPE POPULATION OFF JAPAN: IMPLICATIONS FROM COLOR PATTERNS
Authors: Amano Masao , Hayano Azusa 
Published: July 2006

AbstractThere are two major color morphs, truei and dalli types, of the Dall's porpoise and the latter includes two minor morphs. A small number of dalli types are found among truei types off the Pacific coast of Japan, where truei types normally winter. Based on differences in the patch size of dalli‐type porpoises taken by the harpoon fishery, we determined that those dalli types contain both minor morphs. Although the total number of both types in the sample was similar, the proportion of the two types varied seasonally. Sex ratio, body length, and maturity rate were different among the dalli and truei types. These facts strongly suggest that these dalli types were not members of the truei‐type population and were actually migrants from adjacent dalli‐type populations. The definition of the subspecies Phocoenoides dalli dalli and P. d. truei as polymorphic groups is not supported, although we consider that each of the three color morphs is worthy of full subspecific status.
Allochtonous input and trophic level heterogeneity: impact on an aquatic food web
Authors: Lövgren J. , Reinikainen M. , Persson L. 
Published: July 2006

The impact of food web complexity in open and closed food webs was explored experimentally under controlled laboratory conditions. We used an aquatic model community consisting of two forms of primary producers, phytoplankton (Scenedesmus obtusiuscusculus) and periphyton (Nitzschia perminuta) and two types of consumers, Daphnia pulex feeding on phytoplankton and Chydorous sphaericus feeding on both periphyton and phytoplankton. Three different food webs all having the phytoplankton and periphyton, but having either one of the consumers or both were set up. These food webs were studied in an open and closed treatment. In the open treatment, phytoplankton was continuously flowing through the aquaria whereas in the closed system all the phytoplankton was delivered at the start of the experiment. D. pulex had a positive effect on the density of C. sphaericus in both the open and closed treatments. In the open treatment C. sphaericus increased to very high numbers and was able to depress phytoplankton and thereby negatively affect D. pulex. Our study shows that the explicit handling of the population dynamics of both grazers allowed us to show how a compensatory increase in one primary producer due to increased grazing on another primary producer creates a negative feedback between consumers: C. sphaericus increased and negatively affected D. pulex.
SU‐EE‐A1‐03: A Novel Three‐Dimensional Radiochromic Film Phantom for Use with Stereotactic Radiosurgery Units
Authors: Griffin S , DeWerd L 
Published: July 2006

Purpose: To create a three‐dimensional (3D) film dosimeter capable of simultaneously measuring the entire relative dose distribution of the volume fields of an Elekta Gamma Knife (GK) unit.Methods and Materials: A spherical head phantom was constructed out of Virtual Water™ (VW™). This phantom was constructed with a bored hole allowing the insertion of a stack of film 2.5cm in thickness and 5cm in diameter. The hole is fitted with two unique fiducial rods that prevent both rotation and inversion of the film. Radiochromic film with a thickness of 105 microns is used, allowing approximately 240 layers of film to be inserted into the phantom. One layer of film is assumed to be water/tissue equivalent; however, the water/tissue equivalency of a thick stack of film has not been determined. Monte Carlo MCNP5 methods were used to determine the water/tissue equivalency of a thick stack of radiochromic film. Results: Using MCNP5 simulations, the water/tissue equivalency of a stack of film 2.5cm thick was determined. For a simplified model of the film phantom, the dose distribution in the active layer of the pieces of film was found to be within −1.7% of the dose distribution in similar layers of VW™, demonstrating that a stack of radiochromic film may be used as 3D dosimeter. Conclusion: Using a stack of film as a 3D dosimeter limits the resolution of the determination of the relative dose distribution only by the resolution of the scanner and by the thickness of the film layers. This allows resolutions of 50×50×105 microns3 to be achieved. Most 3D dosimeters require advanced imaging equipment to read out the data but a 3D film dosimeter allows any institution which has a flat bed scanner to obtain 3D dose distribution information.
SU‐EE‐A2‐04: A Method of Online MLC Aperture Adjustment for Treatment of Patients with Set Up Variations
Authors: Islam M , Heaton R , Cho Y , Norrlinger B 
Published: July 2006

Purpose: To investigate MLC aperture adjustments to compensate patient setup variations, replacing couch shift methods for precision treatment delivery. Method and Materials: Patient setup variations can be described by 3‐D translational shifts. A scheme of adjusting MLC apertures to compensate for translational displacements of the patient has been developed. Patient shift information, such as provided by commercial image matching software, establishes the aperture shift vector. The projection of this vector into and orthogonal to the BEV plane was used to determine the displacement vector and divergence for the aperture. Modified beam apertures were generated and MLC leaf positions were determined through a polynomial interpolation.Dosimetric plan comparisons were made within Pinnacle 7.6c. Static field and segmented IMRT patient plans were investigated for pelvic as well as head and neck sites. Arbitrary shift vectors ranging from 3 mm up to 30 mm have been investigated. Non‐integral MLC leaf width shifts parallel to the leaf bank face to characterize leaf width effects. Results: Conformal plans show dose variations from the original plan of up to 3% in the pelvis for shifts of up to 30 mm. Dose coverage of the PTV was maintained except in the superior‐inferior direction, where coverage in the last 3 mm of target fell as low as 92% of the prescribed dose. Results for prostate and oropharynx IMRT plans showed little increase in maximum critical structure doses, and small increases in mean doses. DVH's for IMRT plans confirmed minimal impact on critical structure doses. Conclusion: An alternative method of on‐line adaptive treatment delivery has been explored which eliminates the need to adjust the patient position. This can potentially increase treatment accuracy and efficiency through minimizing patient disturbances and reducing the time between imaging and treatment.
SU‐EE‐A4‐04: Phase and Amplitude Binning for 4D‐CT Imaging
Authors: Abdelnour F , Nehmeh S , Pan T , Humm J , Vernon P , Schoder H , Rosenzweig K , Mageras G , Yorke E , Larson S , Erdi Y 
Published: July 2006

We compare the consistency and accuracy of two image binning approaches used in 4D‐CT imaging. In 4D‐CT the images and respiratory motion are correlated via RPM Respiratory Gating system (Varian, Palo Alto, CA). In phase binning (PB), RPM assigns each breathing cycle 2π radians, within which the images are grouped. Alternately, the images are assigned bins according to the signal's amplitude (AB). To quantitate both approaches, we used NEMA NU2‐2001 IEC phantom oscillating at random frequencies and amplitudes, simulating patients breathing. 4D‐CT images were obtained using 4‐slice GE Lightspeed CT operating in cine mode. We define consistency error as ability to correctly bin over breathing cycles in the same FOV. Average consistency error in PB ranged from 18%±20% to 30%±35%, while in AB the error ranged from 11%±14% to 20%±24%. For 28mm sphere, PB images were hardly consistent, with error of 43%±47%, while AB images for the same sphere resulted in error of only 18%±22%. In PB, while not all breathing cycles covered all phases, nearly all bins contained sphere slices. AB was more accurate, revealing empty bins where no sphere slices existed. As a proof of principle, we present examples of two NSCLC patients' 4D‐CT lung images binned by both approaches. While AB can lead to gaps in the images, depending on patients' breathing pattern, PB exhibits no gaps but suffers visible artifacts due to misbinning, yielding images that covered a relatively large amplitude range. AB was more consistent, though often resulting in gaps corresponding to CT slices where no data existed due to patients' breathing. We conclude AB is more accurate than PB, which should be factored into treatment planning and diagnosis.Work supported by GE Healthcare Technologies and Varian Medical Systems.
SU‐FF‐I‐80: Monte Carlo Simulations of GSF Family Voxel Phantoms for Quantification of Renal Planar Scintigraphy
Authors: Brambilla C , Burkhardt G , Borges J , Marques da Silva A 
Published: July 2006

Purpose: To analyze quantitatively the influence of different renal uptakes of ‐DMSA on the absolute index of renal function (IRF), using Monte Carlo simulated images of voxel phantoms family. Method and Materials: Four anthropomorphic phantoms of GSF family (Baby, Helga, Donna and Children) were simulated with SimSET code. The phantoms have different dimensions in the region of interest (e.g. renal depth, distance between kidneys, renal volume, body volume). Planar acquisitions were modeled using a parallel LEHR collimator. The phantoms were positioned 10 cm from the collimator. A 20% energy window was used to acquire projection onto 128 × 128 matrices. The energy resolution was modeled with a 10% Gaussian function. For each phantom, five normal and abnormal uptakes were assigned, from 50%–50% (normal) to 10%–90% (severe). The IRF was calculated using the software DMSAQuant, based on the Raynaud method. The results were compared with true activity in each kidney, known by Monte Carlo simulations. Results: The results of the IRF have shown differences between the calculated indexes and the true index. The higher deviations (75%) are associated with lower relative uptakes (10%). For relative uptakes higher than 40%, the difference between the calculated indexes and the true index remains constant between 5% and 10%. Conclusion: Our results showed that Raynaud method do not provide accurate values of the absolute IRF when lower relative uptakes are present due to renal diseases. The results have shown that the values of the absolute index of the diseased kidney are influenced by the contralateral kidney. This could be justified because the method only corrects renal depth and age. We suggest that more studies will need to be done to clarify the factors influencing the renal quantification and to model a new correction factor.This work was supported by CNPq, Radiopharmacus and FAPERGS.
SU‐FF‐J‐11: A Novel Use of a Real‐Time Tumor Positioning System in Reducing Cone Beam CT Artifacts
Authors: Parikh P , Santanam L , Hubenschmidt J , Malinowski K , Lechleiter K , Chaudhari A , Dimmer S , Mayse M , Bradley J , Low D 
Published: July 2006

Purpose: The Calypso® Medical 4D Localization system is capable of tracking real‐time dynamic motion without ionizing radiation. A limitation of any fiducial based system is the inability to visualize surrounding tissues. Cone beam CT (CBCT) of moving objects results in image blurring due to long acquisition times. We investigated the use of the Calypso® 4D localization system to improve motion artifacts obtained from the Varian Trilogy CBCT. Materials and Methods:. A research Calypso® 4D tracking system was installed in a Varian Trilogy vault. A rectangular phantom with implanted transponders was attached to an internally‐developed 4D stage. A CBCT was obtained while moving the phantom under the Calypso® measurement array using a patient tumor derived trajectory. The projection images were obtained and shifted using the corresponding Calypso® transponder positioning information and then reconstructed into CBCT images. This process was repeated for a dog with transponders implanted in the lung as part of an IRB‐approved study. Results: The Calypso® based image shifts caused the radiographic projection of the transponders remained stable in sinogram space. CBCT images from the shifted sinogram exhibited reduced image motion artifacts. Without artifact reduction, the transponders were visualized as multiple streaks and the surface of the phantom was heavily deformed. With artifact reduction, the transponders were accurately localized, and the deformation was removed. The dog's breathing cycle made qualitative image motion artifact reduction review difficult. Quantitative analysis of the reconstructed CT numbers showed sharper gradients through the transponders, indicating that the shifting process had improved the image quality. Conclusions: Use of a wireless electromagnetic implanted transponder system for motion correction of CBCT is possible. This preliminary sinogram shifting technique was very effective for non‐deforming objects. Further work will increase the synergy between real‐time tracking systems and volumetric imaging.This work was supported by Calypso® Medical Technologies.
SU‐FF‐J‐47: Determination of Internal Target Volume Reconstruction Algorithm Beyond the Time Dimension Using Second Model of a 256‐Slice CT
Authors: Mori S , Endo M , Kanematsu N , Asakura H , Tomoyasu Y , Shuhei K , Susumu K , Masayuki B 
Published: July 2006

To observing trajectory of moving tumor under free breathing, we compared two image‐processing methods and two reconstruction algorithms based on the FDK and adapted to the 256‐slice CT. These algorithms were namely 4D image average (4DIA) and 4D image maximum intensity projection (4DIM), 4D projection data average (4DPA) and 4D projection data maximum intensity projection (4DPM). The concept of 4DIA and 4DIM was generated on CT image after backprojection process. 4DIA was averaged each pixel value on the volumetric CT data along the time axis, and 4DIM was selected maximum each pixel value along the time axis. With regard to the 4DPA and 4DPM, these essential concepts are to process projection data along the time axis, rather than reconstructed CT images as 4DIA and 4DIM.Evaluations of these algorithms were done in the image noise, CT‐number accuracy, and target moving distance with various reconstruction time conditions using lung cancer patients and compared these results with those with volumetric cine images. As the results, it is difficult to observe the edge of the tumor in 4DIA and 4DPA images due to decreasing CT number from the original tumor CT number. While 4DIM images emphasized pulmonary vessels as increasing the processing time ranges and it makes difficult to observe the accurate tumor edge. From these results, 4DPM provides the accurate tumor movement and accurate CT‐number independent of the reconstruction conditions.
SU‐FF‐J‐66: Feasibility Study of Mobile Target Tracking by Breathing Synchronized Delivery (BSD)
Authors: Tewatia D , Zhang T , Paliwal B 
Published: July 2006

Purpose: To investigate the feasibility of mobile target tracking by Breathing Synchronized Delivery (BSD).Method and Materials: Target breathing motion compensation by real‐time tracking of dynamic multi‐leaf collimator (dMLC) is under development. We have used an alternative approach to circumvent this problem. Breathing‐delivery phase correlation is set in Breathing Synchronized Delivery (BSD) planning. During treatment the feedback is provided to the patients to maintain the correlation. A retrospectively binned 4D‐CT was acquired. The full exhalation (50%) phase images were exported to treatment planning system for planning. Smooth tumor trajectory was obtained using deformable registration algorithm and Fourier filtering. With constant dose rate (300MU/min) and breathing period, a motion incorporated BSD plan was obtained by superimposing instantaneous target motion to the leaf position at corresponding phase. BSD plan was delivered using the dynamic dose mode with a Varian's dMLC. For dosimetric verification, a computer controlled mobile phantom was used to simulate the actual superior‐inferior target motion obtained from 4D image registration. Dose was measured at the isocenter of the phantom in the coronal plane using EDR‐2 film. Three films were exposed, first for static phantom and conventional plan, second for the moving phantom and conventional plan and third moving phantom with motion compensated BSD plan. Results: The dose distributions in superior‐inferior direction were very similar if BSD planning is used on mobile phantom. Underdose and overdose of the order of 20% were observed at the superior‐inferior direction if motion is not compensated. Conclusion: Phantom dosimetry results show that BSD planning and delivery method can effectively compensate target motion. For the patients who may maintain reproducible breathing pattern with video or audio instructions, BSD method is a simple alternative to real‐time tracking.
SU‐FF‐J‐72: Growth and Initial Area Under Curve Correlation Data From DCE‐MRI For Treatment Planning and Monitoring in Orthotopic Tumor Models
Authors: Shetty A , Stafford R , Esparza‐Coss E , Elliott A , Hazle J 
Published: July 2006

Purpose: Human bladder carcinoma cells are grown in murine bladders to study antitumor effects of new‐targeted therapies. Lack of data on their neovascularity in mice, makes it difficult to evaluate new therapies like anti‐angiogenesis or potential of combinatorial treatments like radiation and hyperthermia. The purpose of this study is to understand the changes in neovascularity with tumor growth in relevant organ environment, with dynamic contrast enhanced magnetic resonance.Method and Materials: Eleven athymic nude mice underwent orthotopic injection of 106 253‐J B‐V cells. MR imaging was performed on a 4.7 T small animal MR scanner (Bruker Biospin). Axial T1 weighted spin‐echo and T2 weighted fast spin‐echo acquisitions were performed for volumetric measurements. For dynamic studies, an axial 3D fast RF‐spoiled gradient‐echo acquisition (TR:40ms, TE:1.4ms,slice thickness:1mm) with gadolinium‐DTPA (Magnevist, Schering) was used. The time points for imaging were day 15, day 21 and day 30 after inoculation. Results: The MR volume measurements were made from the fused T1 and T2 images, which were shown to better delineate tumor margins in previous experiments. The initial area under the curve was plotted at 90 seconds, 120 seconds and 200 seconds. An inverse relationship was noted between larger tumor sizes and their IAUC90 (correlation=−0.866 (p<0.05). There is no correlation between the slow growing tumors and the IAUC90 (p=0.708). No significant difference was noted between IAUC 90,120,200 of the whole tumor and tumor rim (p<. 05). Conclusion: The inverse relationship between the IAUC and tumor growths maybe indicative of developing necrotic core. The IAUC and tumor growth data correlation could be a predictive tool for radiation response. It could also assist in planning time points for anti‐angiogenic therapy. In future, we plan to use a higher molecular weight gadolinium agent, and stain the tissue for mean vessel density.
SU‐FF‐J‐129: Using Cone Beam CT to Investigate the Local Geometrical Uncertainties During Head and Neck Radiation Therapy
Authors: Zeng G , Breen S , Jaffray D , Bayley A , White E , Keller H 
Published: July 2006

Purpose: To develop a model to quantify the local displacements, rotations and deformations in head and neck during the treatment course using Cone Beam CT (CBCT). Methods: Five patients underwent weekly CBCTs, immobilized in head and shoulder thermoplastic masks (MedTech®, Orange City, USA). CBCT images were registered to the planning CT by matching the clivus and occipital bone. Eight points located at visibly distinguishable bony landmarks in the head were identified on all images. The displacements of the CBCT points relative to the CT were computed. Head rotation was calculated from the angular change of a plane constituted by three rigid bony points. The spinal canal was contoured in all the image sets and the geometrical centroid line was used as the cord surrogate. The cord deformation relative to the CT was quantified by the variation of the centroid lines.Results: The means of the inter‐fraction displacements, varied between −0.3 and 0.3 cm (standard deviations range from 0.02 to 0.3 cm), for all bony landmark points of each patient. Centrally located points have smaller displacements (mean between −0.1 to 0.1 cm) than circumferential points. The inter‐fraction average head spin (rotation in axial plane) was 2 degrees, while the rotations in the saggital and coronal planes were 4 degrees on average. Cord deformation was minimal superiorly (mean ranged over −0.1 to 0.1 cm) and increased inferiorly to the range of −0.3 to 0.4 cm (standard deviation, 0.3 cm). The deformation was larger in the sagittal plane than in the coronal plane. Conclusion: Sequential CBCTs enable the analysis of the spatial displacements in the head and neck. This method can be used to develop localized treatment margins for this patient population and immobilization technique.
SU‐FF‐T‐360: Planning Strategies to Reduce Unnecessary Skin Dose in Head and Neck IMRT, Including Experimental Verification
Authors: Court L , Tishler R 
Published: July 2006

Purpose: To investigate IMRT planning techniques that reduce skin dose without adversely impacting important doses at depth and to experimentally confirm these findings.Method and Materials: A semi‐cylindrical phantom was constructed with catheters at 3, 6, 9 and 12mm depths, allowing micro‐MOSFET dosimeters to be inserted to measure dose at multiple points on the surface and in the build‐up region. Critical structures, a node‐like CTV, and 2mm surface structure (‘skin’) were contoured on a CT image of the phantom with and without an immobilization mask. A PTV was generated by expanding the CTV 5mm in all directions up to the body contour; three modifications were then implemented, pulling back the PTV 0, 3 or 5mm from the body contour. Seven‐field IMRT plans were created using Eclipse to maximize PTV coverage, with one of the following strategies: (1) aim for maximum 110% hotspot, 115% allowed, (2) maximum 105% hotspot, (3) maximum 105% hotspot and 50% of skin to get maximum 70% of prescribed dose, (4) 99% of PTV volume to receive 90–93% of prescribed dose, maximum 105% hotspot, and dose to skin structure minimized. All twelve PTV and planning strategy combinations were investigated, with and without immobilization mask. The plans were then delivered using a Varian 21Ex, and dose to skin and build‐up region was measured.Results: From highest to lowest skin dose, the planning strategies were (3), (4), (2), (1), with little dependence on the PTV expansion approach. Technique (3), however, showed a tendency to underdose tissues at depth. Conclusion: The best strategy to reduce unnecessary skin dose, while maintaining target dose, is to pull the PTV back 3–5mm from the skin surface, and plan such that PTV coverage is maximized, with 99% of PTV volume receiving 90–93% of prescribed dose, maximum 105% hotspot, and the skin structure dose minimized.