bluuebunny/crossref_metadata_2025 huggingface dataset:
QUANTITATIVE CONTRAST ULTRASOUND ANALYSIS OF RENAL PERFUSION IN NORMAL DOGS
Authors: WALLER KENNETH R. , O'BRIEN ROBERT T. , ZAGZEBSKI JAMES A.
Published: June 2007

Eight normal dogs with no evidence of renal disease, weighing between 8 and 25 kg were imaged using contrast harmonic ultrasound after injection of a microbubble contrast medium. All dogs received three separate bolus injections of 0.05 ml of commercial contrast medium (Definity®). Time/mean pixel value (MPV) curves were generated for selected regions in the cortex and medulla of the left kidney in each dog. Upslope, downslope, baseline, peak intensity, and time to peak were calculated for each zone. For a bolus injection, within the renal cortex (averaging all subjects) the upslope was 7.4±1.5 MPV/s, downslope was −0.4±.2 MPV/s, baseline was 66.8±9.3 MPV, peak was 103.6±8.2 MPV, time to peak (from injection) was 12.8±5.3 s and from time of contrast medium reaching the kidney was 5.1±2.0 s. Within the renal medulla (averaging all subjects), upslope was 2.8±1.7 MPV/s, downslope was −0.3±.2 MPV/s, baseline was 39.3±6.0 MPV, peak was 65.2±14.3 MPV, time to peak from injection was 20.9±6.4 s and from time of contrast reaching the kidney was 11.6±4.1 s. These baseline data may prove useful in the evaluation of dogs with diffuse disease or vascular compromise.
Collaborative New Product Development Environments: Implications for Supply Chain Management
Authors: Tan Chong Leng , Tracey Michael
Published: June 2007

Input from managers at manufacturing firms was utilized to learn more about the state of new product development (NPD). This study confirms that many firms do not take an integrated approach to NPD despite the advantages of doing so. Senior managers can assist in attaining higher levels of customer satisfaction by shaping organizational settings conducive to collaborative NPD. Supply chain managers can promote integrated NPD by championing the inclusion of manufacturing, suppliers and customers.
A Conceptual Framework for Computing U.S. Non‐manufacturing PMI Indexes
Authors: Cho Danny I. , Ogwang Tomson
Published: June 2007

This research develops a conceptual framework for computing new weighted composite indexes for the U.S. non‐manufacturing sector using a two‐step sequential approach — a correlation analysis, followed by a principal components analysis. The results suggest that different weights (i.e., the highest weight to New orders and the lowest weight to Supply deliveries) be assigned if all diffusion indexes in the initial set of six are retained. It also turns out that a simpler index based on two (New orders and Supply deliveries) of the six diffusion indexes, with equal weights, can be computed with little information loss. The new indexes are shown to correlate highly with many key business/economic indicators.
Cerebellar leptomeningeal carcinomatosis in a dog
Authors: Mandara M. T. , Rossi F. , Lepri E. , Angeli G.
Published: June 2007

Diffuse cerebellar meningeal carcinomatosis secondary to haematogenous dissemination from an anaplastic solid mammary carcinoma was diagnosed in an old German shepherd dog suffering from seizures and rapidly progressing to stupor. A single computed tomography cerebellar scan identified an unusual homogeneous density area that was considered to be associated with a vascular disorder, in the absence of space‐occupying lesions. At necropsy, nodular masses were observed in the mammary gland, lungs, tracheobronchial lymph nodes and adrenals. Cerebellar leptomeninges were affected by diffuse blood effusion. Histology showed a solid mammary tumour, characterised by anaplastic cells with a cytoplasmic keratin‐positive and vimentin‐negative immunoreaction. The tumour had spread to the lungs, tracheobronchial lymph nodes and adrenals. Cerebellar leptomeninges were diffusely infiltrated by the cytokeratin‐positive neoplastic cells. Even though computed tomography scan gave no evidence of meningeal carcinomatosis, it was considered that a cerebellar vascular disorder might be present. This was subsequently confirmed by neuropathological investigation and seen to be associated with a cerebellar leptomeningeal carcinomatosis.
Syringomyelia in cavalier King Charles spaniels: the relationship between syrinx dimensions and pain
Authors: Rusbridge C. , Carruthers H. , Dubé M.‐P. , Holmes M. , Jeffery N. D.
Published: June 2007

Objectives: This study was designed to test the hypothesis that pain associated with syringomyelia in dogs is dependent upon size and involvement of the dorsal part of the spinal cord.

Methods: Masked observers determined syrinx dimensions and precise location within the spinal cord on magnetic resonance images of 55 cavalier King Charles spaniels with syringomyelia. After removal of masking, syrinx size and location were compared between the cohorts of dogs that exhibited pain with those that did not.

Results: Maximum syrinx width was the strongest predictor of pain, scratching behaviour and scoliosis in dogs with syringomyelia. Both pain and syrinx size were positively correlated with syrinxes located in the dorsal half of the spinal cord.

Clinical Significance: Large syrinxes associated with damage to the dorsal part of the spinal cord are associated with persistent pain suggesting that the pain behaviour expressed by this group of patients is likely to be “neuropathic pain,” resulting from disordered neural processing in the damaged dorsal horn. As such it is likely that conventional analgesic medication may be ineffective.
Photobleaching of Dissolved Organic Material from a Tidal Marsh‐Estuarine System of the Chesapeake Bay†
Authors: Tzortziou Maria , Osburn Christopher L. , Neale Patrick J.
Published: June 2007

Wetlands and tidal marshes in the Rhode River estuary of the Chesapeake Bay act as important sources of dissolved organic carbon and strongly absorbing dissolved organic matter (DOM) for adjacent estuarine waters. The effects of solar exposure on the photochemical degradation of colored DOM (CDOM) were examined for material derived from different sources (estuarine and freshwater parts of the Rhode River, sub‐watershed stream, marshes) in this estuarine ecosystem. Consistent with changes in fluorescence emission, absorption loss upon exposure to different portions of the solar spectrum (i.e. different long‐pass cut‐off filters) occurred across the entire spectrum but the wavelength of maximum photobleaching decreased as the cut‐off wavelength of the filter decreased. Our results illustrate that solar exposure can cause either an increase or a decrease in the CDOM absorption spectral slope, SCDOM, depending on the spectral quality of irradiation and, thus, on the parameters (e.g. atmospheric composition, concentration of UV‐absorbing water constituents) that affect the spectral characteristics of the light to which CDOM is exposed. We derived a simple spectral model for describing the effects of solar exposure on CDOM optical quality. The model accurately, and consistently, predicted the observed dependence of CDOM photobleaching on the spectral quality of solar exposure.
Accumulation of Photofrin in Lesions of Airway Stenosis Rabbit Models
Authors: Nakagishi Yoshinori , Morimoto Yuji , Fujita Masanori , Ozeki Yuichi , Maehara Tadaaki , Kikuchi Makoto
Published: June 2007

Airway stenosis in childhood is resistant to conventional treatments. Endoscope‐assisted photodynamic therapy (PDT) is a potent candidate for the therapeutic modality owing to the easy approach to the tracheal lesion and low degree of invasiveness. The aim of the present study was to examine whether a photosensitizer preferentially accumulates in the lesion of airway stenosis in order to explore the possible applicability of PDT. The tracheal mucosa of rabbits was scraped off, and the rabbits were intravenously administered with Photofrin. The tissue concentration of Photofrin was quantitatively measured by fluorometric analysis. Granulation formation was seen in the mucosa‐deprived lesion, causing airway stenosis. Photofrin concentration in the granulation tissue was four‐fold higher than that in the intact trachea and 10‐fold higher than that in the liver, spleen, skin and muscle. Photofrin preferentially accumulated in the lesion of airway stenosis. A preliminary experiment on PDT using transtracheal illumination showed an amelioration of airway stenosis, resulting in reduction in respiratory stridor.
Protective Effect of Sanguinarine on Ultraviolet B‐mediated Damages in SKH‐1 Hairless Mouse Skin: Implications for Prevention of Skin Cancer
Authors: Ahsan Haseeb , Reagan‐Shaw Shannon , Eggert David M. , Tan Thomas C. , Afaq Farrukh , Mukhtar Hasan , Ahmad Nihal
Published: June 2007

Excessive exposure of solar ultraviolet (UV) radiation, particularly its UVB component (280–320 nm), to human skin is the major cause of skin cancers. UV exposure also leads to the development of precancerous conditions such as actinic keratosis and elicits a variety of other adverse effects such as sunburn, inflammation, hyperplasia, immunosuppression and skin aging. Therefore, there is a need to intensify our efforts towards the development of novel mechanism‐based approaches/agents for the protection of UVB‐mediated damages. Chemoprevention is being investigated as a potential approach for the management of UV damages including skin cancer. We have earlier shown that sanguinarine, a benzophenanthridine alkaloid, inhibits UVB exposure‐mediated damages in HaCaT keratinocytes. In this study, to determine the relevance of our in vitro findings to in vivo situations, we assessed the effects of sanguinarine on UVB‐mediated damages in SKH‐1 hairless mice. Our data demonstrated that a topical application of sanguinarine (5 μmol 0.3 mL−1 ethanol per mouse), either as a pretreatment (30 min prior to UVB) or posttreatment (5 min after UVB), resulted in a significant decrease in UVB‐mediated increases in skin edema, skin hyperplasia and infiltration of leukocytes. Further, sanguinarine treatments (pre and post) also resulted in a significant decrease in UVB mediated (1) generation of H2O2 and (2) increases in the protein levels of markers of tumor promotion/proliferation viz. ornithine decarboxylase (ODC), proliferating cell nuclear antigen (PCNA) and Kiel antigen‐67. Based on this data, we suggest that sanguinarine could be developed as an agent for the management of conditions elicited by UV exposure including skin cancer. However, further detailed studies are needed to support this suggestion.
Regulatory processes interacting to maintain hepatic blood flow constancy: Vascular compliance, hepatic arterial buffer response, hepatorenal reflex, liver regeneration, escape from vasoconstriction
Authors: Lautt W. Wayne
Published: June 2007

Constancy of hepatic blood flow (HBF) is crucial for several homeostatic roles. The present conceptual review focuses on interrelated mechanisms that act to maintain a constant HBF per liver mass. The liver cannot directly control portal blood flow (PF); therefore, these mechanisms largely operate to compensate for PF changes. A reduction in PF leads to reduced intrahepatic distending pressure, resulting in the highly compliant hepatic vasculature passively expelling up to 50% of its blood volume, thus adding to venous return, cardiac output and HBF. Also activated immediately upon reduction of PF are the hepatic arterial buffer response and an HBF‐dependent hepatorenal reflex. Adenosine is secreted at a constant rate into the small fluid space of Mall which surrounds the terminal branches of the hepatic arterioles, portal venules and sensory nerves. The concentration of adenosine is regulated by washout into the portal venules. Reduced PFreduces the washout and the accumulated adenosine causes dilation of the hepatic artery, thus buffering the PF change. Adenosine also activates hepatic sensory nerves to cause reflex renal fluid retention, thus increasing circulating blood volume and maintaining cardiac output and PF. If these mechanisms are not able to maintain total HBF, the hemodynamic imbalance results in hepatocyte proliferation, or apoptosis, by a shear stress/nitric oxide‐dependent mechanism, to adjust total liver mass to match the blood supply. These mechanisms are specific to this unique vascular bed and provide an excellent example of multiple integrative regulation of a major homeostatic organ.
Hepatic iron accumulation may be associated with insulin resistance in patients with chronic hepatitis C
Authors: Sumida Yoshio , Kanemasa Kazuyuki , Fukumoto Kohei , Yoshida Naohisa , Sakai Kyoko
Published: June 2007

Background/Aim:  Insulin resistance and hepatic iron overload are frequently demonstrated in hepatitis C virus (HCV)‐related liver diseases. We investigated the relationship between insulin resistance and hepatic iron deposition in patients with chronic HCV infection.

Methods:  Insulin resistance was evaluated using the homeostasis model assessments for insulin resistance (HOMA‐IR) in 56 non‐diabetic non‐obese patients with biopsy proven chronic hepatitis C. The relationship between insulin resistance and serum ferritin levels or the grade of hepatic iron deposition was assessed.

Results:  The levels of plasma immunoreactive insulin (IRI) and HOMA‐IR were significantly correlated with serum ferritin levels and the grade of hepatic iron deposition (P = 0.003).Although IRI and HOMA‐IR increased in parallel with the development of hepatic fibrosis, insulin resistance (HOMA‐IR > 2) was observed in 11 (26.2%) of 42 patients even without severe fibrosis (F0–2). Among patients without severe fibrosis, IRI and HOMA‐IR were significantly higher in patients with iron deposits than in those without iron deposits.

Conclusion:  Hepatic iron overload may be associated with insulin resistance in patients with chronic hepatitis C, especially in patients with mild to moderate fibrosis.
Non‐alcoholic steatohepatitis in a child with cartilage‐hair hypoplasia syndrome
Authors: Randhawa Inderpal , Janner Donald , Zuppan Craig , Yanni George
Published: June 2007

We report an unusual pediatric case of cartilage‐hair hypoplasia (CHH) characterized by significantly impaired cellular immunity, recurrent sinopulmonary infections, severe non‐alcoholic steatohepatitis (NASH) and terminal liver failure. A 14‐year‐old boy was diagnosed clinically with CHH by age 1 year. His childhood was complicated by recurrent otitis media, bronchiectasis, and sinopulmonary infections due to bacteria and rare mold including Chaetomium. Immunological testing revealed absolute CD4 and CD8 count depletion. The diagnosis of CHH was confirmed by RNase mitochondrial RNA‐processing (RMRP) gene testing, which demonstrated not only the typical mutation at position c70 but an additional atypical mutation at position c213. By age 14, he had a 3‐year history of NASH. A diagnostic work‐up could not demonstrate any common etiologies for fatty liver including infectious,autoimmune, mitochondrial or metabolic etiologies. The terminal events of this child's life included hepatic failure and Chaetomium pneumonia. NASH involves the inability of hepatocytes to clear fat vesicles. CHH is largely a disorder of cellular proliferation. RMRP functions in mitochondrial DNA synthesis and in cleaving pre‐rRNA. This example of NASH with CHH raises the issue of whether the second, atypical mutation identified may be related to progressive liver disease, and whether the RMRP gene may have additional, currently unrecognized functions related to insulin resistance, liver metabolism or cellular immunity.
Calibration of a proton beam energy monitora)
Authors: Moyers M. F. , Coutrakon G. B. , Ghebremedhin A. , Shahnazi K. , Koss P. , Sanders E.
Published: July 2007

Delivery of therapeutic proton beams requires an absolute energy accuracy of to for patch fields and a relative energy accuracy of to for tailoring the depth dose distribution using the energy stacking technique. Achromatic switchyard tunes, which lead to better stability of the beam incident onto the patient, unfortunately limit the ability of switchyard magnet tesla meters to verify the correct beam energy within the tolerances listed above. A new monitor to measure the proton energy before each pulse is transported through the switchyard has been installed into a proton synchrotron. The purpose of this monitor is to correct and/or inhibit beam delivery when the measured beam energy is outside of the tolerances for treatment. The monitor calculates the beam energy using data from two frequency and eight beam position monitors that measure the revolution frequency of the proton bunches and the effective offset of the orbit from the nominal radius of the synchrotron. The new energy monitor has been calibrated by measuring the range of the beam through water and comparing with published range‐energy tables for various energies. A relationship between depth dose curves and range‐energy tables was first determined using Monte Carlo simulations of particle transport and energy deposition. To reduce the uncertainties associated with typical scanning water phantoms, a new technique was devised in which the beam energy was scanned while fixed thickness water tanks were sandwiched between two fixed parallel plate ionization chambers. Using a multitude of tank sizes, several energies were tested to determine the nominal accelerator orbit radius. After calibration, the energy reported by the control system matched the energy derived by range measurements to better than for all nine energies tested between 40 and with an average difference of . A study of different combinations of revolution frequency and radial offsets to test the envelope of algorithm accuracy demonstrated a relative accuracy of for small energy changes between 126 and . These new measurements may serve as a data set for benchmarking range‐energy relationships.
SU‐FF‐I‐30: Image Quality and Dose Trends in Tube‐Current Modulated Multi‐Detector CT Imaging
Authors: Fisher R , Hintenlang D , Arreola M
Published: July 2007

Purpose: This project quantifies image quality and dose trends in a multi‐detector CT system incorporating a tube‐current modulation system. Method and Materials: An elliptical phantom series constructed of a tissue‐equivalent pliable polyurethane elastomer material was used to test tube‐current modulation systems of a Siemens 16 slice CT scanner equipped with CareDose4D. A composite phantom comprised of elliptical segments of varying dimensions evaluated image quality and dose for both in‐plane and z‐axis tube‐current modulation. The standard deviation of CT number was recorded in reconstructed images in the slice plane as well as along the z‐axis of the scan in order to evaluate image quality at specific locations in the phantom. Image quality was compared for tube‐current modulated versus fixed tube‐current scans. CTDIw measurements were made with and without tube‐current modulation using a CTDI head phantom modified by the addition of elliptical phantom segments in order to independently evaluate the potential dose savings of tube‐current modulation. Results: CTDIw was invariant for scans with and without tube‐current modulation, an effect attributed to the inadequacy of CTDIw to adequately characterize dose for helical MDCT scanning modes. Image quality with tube‐current modulation was uniform along the entire scan length. Comparable scans with fixed tube‐current techniques showed variations in image quality of up to 40% along the z‐axis of the scan, and dose increases of up to 35%. In‐plane image quality measurements showed a trend towards larger variation in CT number towards the center of the phantom. The use of tube‐current modulation was demonstrated to reduce the effects of variable tissue thickness and geometry on image quality. Conclusion: Tube‐current modulation in CT provides more uniform image noise throughout the patient scan length while reducing dose as compared to fixed‐current techniques. Weighted CTDI is not an adequate measure of dose in comparing modulated to fixed‐current techniques.
SU‐FF‐I‐34: Radiation Dose in Cardiovascular Computed Tomography
Authors: Gingold E
Published: July 2007

Purpose: To assess the effective dose delivered to patients undergoing cardiovascular CT examinations at one institution. To highlight how adjustment of scan parameters to compensate for body habitus affects the CT dose index (CTDI), and how variations in CTDI and scan length combine to deliver a wide range of estimated effective dose. To evaluate the ability of manual scan parameter selection based on perceived patient size to maintain consistent image quality. Method and Materials: CT scan protocol parameters including kV, effective mAs, scan length, scan time, CTDIvol, dose length product (DLP), and effective dose were collected or calculated for cardiovascular CT examinations performed on a Philips Brilliance 64 scanner from Oct 2006 – March 2007. The effect of parameter selection on CTDIvol and effective dose was measured. Clinical factors were analyzed to determine the major contributors to CTDI and scan length, and thus to effective dose. Image contrast, noise and contrast‐to‐noise ratio were measured on clinical images to evaluate the ability of manual selection of kVp and mAs to compensate for body habitus and achieve consistent image quality. Results: The scan length in this patient population was 193.6 +/− 29 mm (range 125.6 – 279.2 mm). Effective dose measured 16.9 +/− 5.5 mSv (range 8.7 – 31.3 mSv). When the aorta and pulmonary arteries are also evaluated in “triple rule‐out” studies, scan length and thus effective dose tend to increase compared with simple coronary angiography. Image noise and contrast to noise ratio can be stabilized by adjusting kVp and mAs per slice based on patient size. Conclusions: Effective dose in CT depends linearly on both CTDIvol and scan length. Both of these factors can vary widely in cardiovascular CT, resulting in the potential for effective dose exceeding 30 mSv.
SU‐FF‐I‐43: Workload Weighed Transmission Curves of Brazilian Shielding Materials: Experimental Results
Authors: Costa P , Mello L
Published: July 2007

Purpose: Evaluation of attenuation properties of typical Brazilian shielding materials (Barite Concrete) used in diagnostic rooms from transmission measurements considering the local workload distribution. Method and Materials: Broad beam attenuation properties of three shielding materials were obtained following the method proposed by Archer et. al (Med. Phys. 21(9), 1994). These attenuation properties were measured by using a constant potential X‐ray machine operated in voltages from 60 to 150 kV. The primary and transmitted radiation from different material thicknesses were measured by using a Radcal 10×5–6 ion chamber. Moreover, workload spectra (Simpkin, Med. Phys. 23(4) 1996) of typical diagnostic rooms were obtained by observing 1060 patients. These data were combined following the method presented in NCRP 147. Results: The workload weighed transmission curves were obtained considering the different workload spectra and shielding material manufacturer. Results shows that for a same attenuation factor, for example 0.01, the thicknesses of material required for shielding a conventional radiation room to primary radiation ranges from 10 to 14.5 cm depending on the manufacturer. If the workload spectra are not considered, this range of thicknesses grows to 19 to 39 cm considering the 120 kV transmission curve. Conclusion: The new methods published in NCRP 147 for shielding calculation of diagnostic rooms incorporated a strong dependence on the quantities workload distribution and transmission through the shielding materials. Local evaluations are needed in order to adapt this method to the local workloads and used shielding materials. The correct consideration of the combined workload spectra and attenuation properties allows the optimized determination of the shielding material needed for protecting the environment.
SU‐FF‐I‐44: Workload Weighed Transmission Curves of Brazilian Shielding Materials: Computer Simulations
Authors: Costa P , Braga N , Mello L
Published: July 2007

Purpose: Evaluation of attenuation properties of typical Brazilian shielding materials (Barite Concrete) used in diagnostic rooms from computer simulations and considering the local workload distribution. Method and Materials: Computer simulations of X‐ray spectra by using the modified TBC Model (Costa, P. R. et. al, Health Physics 92(1), 2007) were generated in the range of 60 to 150 kV. Elemental compositions of four commercial barite concretes used for shielding diagnostic facilities were obtained from fluorescence spectroscopy. The NIST X‐COM software was used in order to obtaining the mass attenuation coefficient of each sample. Linear attenuation coefficients were obtained and used in order to simulate the transmission curve of each sample. Archer's equation (Med. Phys. 21(9), 1994) was used for obtaining a, b and g coefficients for each kV evaluated and for each shielding material. Moreover, workload spectra (Simpkin, Med. Phys. 23(4) 1996) of typical diagnostic rooms were obtained by observing 1060 patients. These data were combined following the method presented in NCRP 147. Results: The workload weighed transmission curves were obtained considering the different workload spectra and shielding material manufacturer. Results shows that for a same attenuation factor, for example 0.001, the thicknesses of material required for shielding a conventional radiation room to primary radiation ranges from 5 to 9.1 cm depending on the material manufacturer. If the workload spectra are not considered, this range of thicknesses grows to 13.5 to 20 cm. Conclusion: The new methods published in NCRP 147 for shielding calculation of diagnostic rooms incorporated a strong dependence on the quantities workload distribution and transmission through the shielding materials. The computer simulation method developed in the present work shows to be a practical tool for optimizing the composition of shielding materials. It can also be validated from experimental measurements of transmitted x‐ray spectra and transmission measurement.
SU‐FF‐I‐50: Whole Body and Distal Organ‐Specific Dosimetry Using Parallel SN Methods
Authors: Al‐Basheer A , Ghita M , Sjoden G , Bolch W , Lee C
Published: July 2007

Purpose: To create a new methodology for dose computations applicable to general medical physics applications, based upon a direct deterministic solution of the (3‐D) Boltzmann transport equation (BTE). Method and Materials: Using the multigroup discrete ordinates (SN) deterministic method in the PENTRAN‐MP (Parallel Environment Neutral‐particle TRANsport‐Medical Physics) code system, fluxes and corresponding doses were determined for a clinical test case using a UF Series B whole‐body voxelized pediatric patient phantom. With a 90 keV planar x‐ray source, we performed two sets of transport calculations based on the same phantom model, employing both the Monte Carlo (MC) and SN methods. SN calculations were performed using PENTRAN, and the MCNP5 code was used for MC calculations. Post processing in the PENTRAN‐MP code system includes seamless parallel data extraction using the PENDATA code, followed by application of the 3D‐DOSE code to compute dose in each phantom voxel, with dose‐volume histograms for critical organs of interest. Results: We demonstrate that the deterministic SN and MC solutions are, in the vicinity of the source region, completely in agreement; the largest statistical error of the MC simulation was <5%, typically averaging <2%. Moreover, the deterministic SN method also provided globally converged results in each voxel at sites distal to the source (in ∼3 hrs on 16 processors), where the MC results on the same computing platform had significant out of field error, and would require a significantly longer running time (estimated at >2000 hrs) to produce meaningful results with an acceptable stochastic error to enable comparison with the well‐converged SN results. Conclusions: A new methodology for 3D dose calculations has been developed based on a parallel discrete ordinates (SN) solution of the BTE. With the proper discretization applied, the SN method presents an accurate, fast solution yielding a complete 3‐D dose distribution without stochastic error.
SU‐FF‐I‐70: An Efficient Deformable Volume Rendering On Modern PC Graphics Hardware
Authors: Kim J , Li S , Zhao Y
Published: July 2007

Purpose: Direct volume rendering (DVR) is a common medical image visualization technique that provides better anatomy or object perception in three dimensional space than typical three orthogonal sectional images. In this study we present a fast and efficient deformable DVR method, implemented on modern consumer grade PC graphics hardware, which will be useful for intensity‐based deformable 3D/2D registrations as well as for deforming volume visualization during 3D/3D registrations. Method and Materials: The method consists of three steps: (1) a cubical grid is defined on the input volume; (2) the grid is deformed using global or local radial basis functions such as thin plate splines; and then (3) the volume is texture‐mapped to the deformed grid and projected to a predefined 2D pixel buffer. During projection, pixel intensities are scaled and accumulated using either attenuate or over blending operation. To minimize the intensity depth loss during the accumulation process, the pixel intensities are accumulated in a hidden pixel buffer, known as pbuffer in OpenGL. In our implementation we used 16 bit floating pbuffer instead of the standard 32 bit floating format because most graphics hardware did not support direct accumulation onto 32 bit floating buffers at the time of experiment. The accumulated intensity values are scaled to the valid display range [0,1]. Results: We were able to render a 256×256×256 anthropomorphic chest phantom CT image onto 512×512 render buffer with 20×20×20 grid at the speed of about 3 frames per second. The computer was equipped with a 1.8 GHz CPU, 512MB memory, 4× AGP, and an NVidia GeForce 6800 graphics adaptor. Conclusion: Deformable DVR on modern PC graphics hardware is efficient in terms of speed and quality. This method may be useful for deformable 3D/2D image registrations and visualization for 3D/3D image registrations.
SU‐FF‐J‐19: Prototype Fixture for IGRT Coordinate Registration and 4D CT Reconstruction
Authors: Jenkins T , Bonnerup C , Chen C , Allison R , Sibata C
Published: July 2007

Purpose: The potential use of in‐room CT technology for target localization requires accurate methods for mapping spatial and temporal data between the CT and linac coordinate spaces. This can be done by absolute calibration of the imaging device prior to scanning or by capturing known fiducial patterns within the image data. We have designed a hybrid technique for in‐room CTs that defines a unified coordinate system referenced to the treatment table. It is based on patterns encoded in the unused portion of CT images below the treatment table surface. These patterns have two primary functions: 1) to facilitate the registration of image coordinates for image‐guided radiation therapy; and 2) to encode an external respiratory signal for 4D CT reconstruction. Methods and Materials: A fixture was made from a 6 mm thick acrylic plate embedded with small aluminum rods. The rods formed a pattern used for spatial calibration. In addition, a long “V” shaped piece of extruded aluminum was mounted on the fixture between bearings and attached to a motor. The motor was computer controlled such that the “V” could point in any direction to encode a respiratory signal. The entire fixture was mounted beneath the “tennis racket” portion of a carbon fiber treatment table. Results: CT images clearly showed the spatial patterns and respiratory signal encoded by the fixture. Dynamic respiratory signals were imaged with minimal artifacts at angular velocities up to six rpm with 0.8s CT gantry rotation. Custom software was able to decode the image metadata and use it for IGRT coordinate registration and 4D CT reconstruction. Attenuation of 6 MV radiation by the fixture was measured to be < 3%. Conclusions: The prototype met all design goals and facilitated IGRT coordinate registration and 4D CT reconstruction. Conflict of Interest: Research sponsored by Siemens corporation.
SU‐FF‐J‐40: Image‐Guided Body Stereotactic Radiotherapy Using Cone‐Beam Computer Tomography for Treatment of Spinal Tumors
Authors: Wang C , Shiu A , Wang H , Chang E
Published: July 2007

Purpose: To report the technique and result of image‐guided stereotactic body radiotherapy (IG‐SBRT) for treatment of spinal tumors using a conebeam computer tomography (CT) for daily pretreatment imaging. Method and Materials: A spine phantom was first used to study the feasibility and accuracy of image‐guided stereotactic body radiotherapy using cone‐beam CT before one patient was treated with a prescription of 2700 cGy to the lesion at the level of L5 in three fractions. Planning CTs were taken using regular CT machines, and pretreatment daily CT scans were taken using the cone‐beam CT equipped on a Varian Trilogy Linac treatment machine. Pretreatment daily CT images were first registered with the planning CT images to find out the difference of the daily isocenter from its planning position, then shifts were made by moving the treatment couch to align the patient's daily isocenter to that of the treatment machine. A set of three reference points was used in each case to add accuracy to the localization and alignment of the daily isocenter. As final verification, the KV on‐board imaging (OBI) device was used to take orthogonal portal images to be registered with planning digitally reconstructed radiographs (DRR) before treatments were delivered. Results: Image registration found shifts of the spine phantom to be 16.4 mm laterally, 25.1 mm vertically, and 16.8 mm longitudinally. After shifting the couch accordingly, portal images showed perfect match in vertical and longitudinal directions, only 0.5 mm shift was detected in the lateral direction. For all the three treatments of the patient, daily shifts in any direction were found to be between 2–28 mm. Portal images demonstrated positioning accuracy within 1 mm. Conclusion: Phantom study and real patient treatment for IG‐SBRT of spinal tumor were successfully performed using cone‐beam CT. Satisfactory accuracy of patient positioning was achieved.
SU‐FF‐J‐41: Edge Enhancement Algorithm for Gold Seeds in Prostate Electronic Portal Images
Authors: Liu X , DeMarco J
Published: July 2007

Purpose: Implanted gold seed markers are currently used to localize the relative prostate position during radiation therapy. This is typically accomplished by manually matching each seed on an electronic portal image with the corresponding seed location on a reference DRR. This study evaluates an edge enhancement algorithm applied to an EPID image for accurately identifying gold seed marker position. Method and Materials: The algorithm is based on the gold seed size which determines the lower and upper bounds of a bandpass filter, and uses “Intensity Autoscale” and “Contrast Saturation” functions to produce a better visual contrast of the three gold seeds. A Siemens Oncor linear accelerator was used to image four prostate patients using standard AP and LLAT image projections. We tested the bandpass filters with two different bands to process the images. The first band is to set the larger structure down to 20 pixels and the smaller structure up to 3 pixels to pass. The second band is to set the larger structure down to 6 pixels and lower structure up to 3 pixels. After applying the bandpass filter, the “Intensity Autoscale” and “Contrast Saturation” functions are applied. The processed images were compared to the original EPID images that were filtered using histogram equalization and then edge enhancement. Results: This algorithm was successful for all images tested. The gold seed markers are clearly visualized on the processed images relative to the standard filtering functions provided with the EPID software. Conclusion: This new image enhancement method is fast and will easily integrate with an existing three‐point registration technique for localizing the prostate relative to a reference DRR. The method also has the potential to be used for computer automated detection of gold seeds in prostate electronic portal images.
SU‐FF‐J‐44: Accuracy of Automatic Couch Corrections with On‐Line Volumetric Imaging
Authors: Moseley D , Li W , Jaffray D
Published: July 2007

Purpose: To assess the accuracy of patient positioning using on‐line image‐guidance and automatic couch correction. Method and Materials: During device commissioning, automated movements of the robotic couch were assessed using a Rando phantom and a Polaris optical navigation system giving sub‐millimeter accuracy at approximately 18 Hz. Clinically, after assessment of a volumetric scan, a couch correction is applied if the displacement falls outside a pre‐defined action‐level of 3mm in any translational plane or greater than 5° of rotation. If the setup was outside of tolerance, the remote automatic couch was used to adjust patient position. Verification scans were acquired after the shift and the residual error analysis was evaluated retrospectively. The data from 34 patients over a one month period is included in this study, representing a total of 135 CBCT volumetric images. Results: The Rando phantom's residual error over 10 trials for a 10mm movement in the L/R, S/I, and A/P directions was 0.16±0.48mm, 0.32±0.30mm, and 0.11±0.12mm. The mean residual error for 34 patients in the L/R, S/I and A/P directions was 0.00±0.11cm, 0.01±0.10cm, and −0.03±0.08cm respectively. The rotational setup errors about the L/R, S/I and A/P axes were 0.67±1.33°, −0.47±1.30°, and −0.32±1.31°. The maximum measurement in the translational L/R, S/I and A/P directions was 0.28cm, 0.29cm, and 0.22cm, while the minimum values were −0.30cm, −0.29cm, and −0.27cm. The maximum rotational residual was 4.3°, 3.0°, and 3.1° about the L/R, S/I and A/P axes, while the minimum values were −2.2°, −3.9°, and −3.8°. Rotational errors are still apparent, as the remote couch does not correct for this. Conclusions: The remote automatic couch movement is reliable and accurate for adjusting the patient position. This gives the confidence that we can treat the intended target on a daily basis, quickly and efficiently.

Research sponsored by Elekta.
SU‐FF‐J‐45: A Comparison of Daily Megavoltage CT and Ultrasound Imaging Guided Radiation Therapy for Prostate Cancer
Authors: Peng C , Kainz K , Lawton C , Li X
Published: July 2007

Purpose: To compare the prostate localization capabilities of ultrasound imaging and megavoltage CT (MVCT) for on‐line daily image‐guided radiotherapy (IGRT) of the prostate cancer. Method and Materials: Daily shifts were analyzed to account for inter‐fractional variations collected from a total of 129 prostate cancer patients, 106 with ultrasound‐based imaging (BAT, B‐mode Acquisition and Targeting) and 23 with MVCT of a TomoTherapy (HiArt) unit. The shifts indicated by the two systems were compared statistically along the right/left (R/L), superior/inferior (S/I), and anterior/posterior (A/P) directions. The systematic and random variations among the daily alignments were calculated. Margins to account for these shifts were estimated. The daily shifts from the first 25 treatment fractions and from the remaining fractions were compared for both systems to examine whether a difference in the prostate motion pattern exists between the first 25 fractions and the rest. Results: The mean shifts and standard deviations along the R/L, S/I, and A/P directions were −0.11±3.80mm, 0.67±4.67mm, and 2.71±6.31mm for BAT localizations and −0.88±5.36mm, 0.41±3.38mm, and 0.91±3.33mm for MVCT localizations, respectively. It is clear that the systematic and random variations in daily shifts based on MVCT were generally smaller than those based on BAT, especially along the A/P direction. A t‐test showed this difference to be statistically significant. The PTV margins estimated to account for daily variations were 6.69 mm and 14.66 mm based on MVCT and BAT data, respectively. There was no statistically significant difference in the daily prostate movement pattern between the first 25 fractions and the remaining. Conclusion: The MVCT technique results in smaller variations in daily shifts than ultrasound imaging, indicating that MVCT is more reliable and precise for prostate localization. Ultrasound‐based localization may overestimate the daily prostate motion, particularly in the A/P direction.

This work is supported partially by MCW Cancer Center Fotsch Foundation.
SU‐FF‐J‐49: Reducting of Motion Artifacts in Cone Beam CT Using a Patient Specific Respiratory Motion Model
Authors: Zhang Q , Kriminski S , Ling C , Rosenzweig K , Mageras G
Published: July 2007

Purpose: Respiratory motion degrades the quality of cone beam computed tomography (CBCT) images in the thorax and abdomen and limits its localization accuracy. We describe a method of reducing motion‐induced artifacts in CBCT images in the thorax using a patient‐specific model to estimate 3‐dimensional respiration‐induced motion. Method and Materials: The patient‐specific model is derived from, and applied to, the same CBCT data, thus avoiding inconsistencies caused by changes in patient's breathing pattern when using different image sets. The CBCT scan uses a 1‐minute gantry rotation while recording patient respiration with an external monitor. The projection images are sorted into 4 to 6 phase bins according to the respiratory signal. Each phase bin is reconstructed to produce a series of 3D images. Nonrigid image registration calculates a series of deformation fields that maps each 3D image to a reference image at end expiration. A principle component analysis (PCA) reduces noise and redundancy in the deformation fields. The resultant deformation fields correct each 3D image by morphing it to the reference motion state. The corrected 3D images are combined to obtain a high‐resolution CBCT image. We evaluate the model by comparing CBCT images before and after motion correction, in patients receiving radiation treatment for lung cancer. Results: Motion‐corrected CBCT images show less respiration‐induced blurring and streaking artifacts compared to standard CBCT. Fine‐detailed features in lung tumor and airways become visible, and the liver boundary is more discernable. Conclusion: Preliminary results indicate that the proposed method is a potentially useful tool for improving CBCT image quality and localization accuracy in the thorax. Repeating the process at other phase bins can yield a high quality respiration‐correlated (4D) CBCT image set for evaluating respiration‐induced motion.
SU‐FF‐J‐51: Dosimetric Impact of Cone Beam Image Guided Setup for Paraspinal Patients
Authors: Ballangrud A , Guan Y , Hudka K , Della Biancia C , Yamada Y , Hunt M
Published: July 2007

Purpose: To quantify the impact of kV cone beam CT (CBCT)‐guided setup on delivered dose to target and critical organs in patients receiving paraspinal irradiation and to compare the relative benefits of CBCT versus orthogonal kV radiograph (2D)‐guided setup. Method and Materials: Initial, pre‐ and post‐treatment CBCTs from ten patients receiving single‐fraction radiotherapy were evaluated. Delivered dose based on CBCT‐guided treatment was calculated after transferring target and critical organ contours from pre‐treatment CBCT to planning CT. Similarly, delivered dose from a simulated 2D setup was calculated by registering orthogonal DRRs created from the initial CBCT with planning DRRs using bony anatomy, and then applying the resulting shifts to the initial CBCT contours before transfer to the planning CT. The magnitude of residual setup errors and intra‐fractional motion were evaluated by registering pre‐treatment CBCT to planning CT and post‐ to pre‐treatment CBCT, respectively. Results: Dosimetric impact was evaluated using PTV D95% and maximum dose to critical structures. Even with CBCT‐guided setup, small residual setup errors combined with steep dose gradients led to increases up to 27% in maximum cord dose. Likewise, increases in esophagus maximum dose up to 34% (CBCT) and 20% (2D) were observed. PTV D95% decreased to 85% (CBCT) and 87% (2D) of planned dose for one patient with a low planned PTV D95% (73%) and a steep dose gradient. Magnitudes of the 3D vector of residual setup errors following 2D and CBCT setup were 2.3±0.5 mm and 1.5±0.4 mm, respectively. The intra‐fractional error was 1.6±0.3 mm. Conclusion: Since paraspinal lesions occur near stable bony anatomy with no significant anatomical deformation, CBCT provides no additional benefit over 2D techniques for accurate positioning. CBCT does provide easier visualization of the anatomy to facilitate setup and CBCT requires about the same effort as 2D setup based on orthogonal kV‐images.
SU‐FF‐J‐60: Daily Localization for Prostate Bed Patients Based On Surgical Clips
Authors: Paskalev K , Horwitz E , Price R , Feigenberg S , Buyyounouski M , Chen Y , Konski A , Silverman J , Ma C , Pollack A
Published: July 2007

Purpose: Prostate cancer patients who undergo a radical prostatectomy and have high risk features are offered radiation therapy to the surgical bed. Modern planning and delivery techniques (like IMRT) that provide conformal dose coverage and steep dose fall‐offs require daily localization, especially when tight margins are utilized. The goal of this study is to investigate the use of surgical clips in and around the prostate bed as alignment landmarks. Materials and methods: During the simulation process the physicians contoured at least three different groups of clips as reference structures. The reference structures along with the isocenter were then electronically transferred to the alignment computer. CT‐on‐rails was then used for daily imaging and the clips were aligned with the reference structures. Each alignment was documented as a printout showing the pre‐treatment scan, the reference structures, and the anatomical structures in the three main planes. Every printout was evaluated by the treating physician. A total of 45 patients have been treated using this technique. Ten random patient charts (total of 306 alignments) were selected and the number of the satisfactory alignments was counted. Results: The physician approval rate was 100% for each of the ten patients coming from three different physicians. Furthermore, the physicians could not recall a misalignment that would violate the PTV margin used for planning (8 mm) over the total number of 45 patients (between 1300 and 1400 alignments). Conclusions: The presented results suggest that the technique described here results in a very high physician approval rate. The fact that planning and alignments are performed with the same imaging modality leads to a high level of confidence in both therapists and physicians.