bluuebunny/crossref_metadata_2025_split huggingface dataset:
Appearance of granulated cells in blood films stained by automated aqueous versus methanolic Romanowsky methods
Authors: Allison Robin W. , Velguth Karen E. 
Published: September 2009

Background: Romanowsky stains are used routinely by veterinary clinical pathology laboratories for cytologic and blood film evaluations. Automated stainers are available for both aqueous and methanolic Romanowsky stains. Mast cell granules and canine distemper virus inclusions are known to stain differently by these 2 methods, but we have noticed differences in the staining characteristics of other granulated cells.Objective: The aim of this study was to investigate and document the variable appearance of basophils and large granular lymphocytes in blood films stained using aqueous and methanolic Romanowsky methods.Methods: Cytologic preparations from 1 canine mast cell tumor and blood films from 8 dogs, 1 cat, 1 rabbit, and 1 ostrich were stained using an automated aqueous stain (Aerospray 7120, with and without a predip fixative) and an automated methanolic stain (Hematek). Staining quality and intensity of the cytoplasmic granules in mast cells, basophils, and large granular lymphocytes was evaluated subjectively.Results: Cytoplasmic granules of mast cells, basophils, and large granular lymphocytes stained poorly or not at all with the automated aqueous stain but stained prominently and were readily identified with the automated methanolic stain. Use of the predip fixative with the Aerospray method improved the visibility of basophil granules but not mast cell granules, and had a variable affect on the visibility of granules in large granular lymphocytes.Conclusion: Clinical pathologists should be aware of the staining methodology used on the slides they evaluate to avoid incorrect interpretation of granulated cell populations.
New algorithm to simulate organ movement and deformation for four‐dimensional dose calculation based on a three‐dimensional CT and fluoroscopy of the thorax
Authors: Miyabe Yuki , Narita Yuichiro , Mizowaki Takashi , Matsuo Yukinori , Takayama Kenji , Takahashi Kunio , Kaneko Shuji , Kawada Noriyuki , Maruhashi Akira , Hiraoka Masahiro 
Published: September 2009

Purpose:The aim of this study was to develop a 4D‐modeling algorithm, designated “,” to simulate organ movement and deformation for 4D dose calculation without the need for 4D‐CT or deformable image registration and to assess the validity of this algorithm.Methods:This algorithm virtually creates 4D‐CT images by deforming static 3D‐CT data according to a typical motion model and motion data at multiple observation points collected via fluoroscopy. A typical motion model intended for patients with lung tumors immobilized with a vacuum pillow inside a stereotactic body frame was constructed. The geometric accuracy of virtual 4D‐CT images created using this algorithm was evaluated in eight patients by comparing the simulated results with actual 4D‐CT images in terms of visual assessment, landmark analysis, and comparison of the radial distance from the tumor centroid to the body or lung surface.Results:The average accuracy for all patients, as determined via landmark analysis, was, very similar to results obtained through 4D‐CT and deformable image registrations. Error in the radial distance from the tumor centroid to the body or lung surface was generally within 1.0 or 2.0 mm, respectively, in virtual versus actual 4D‐CT images. Therefore, it is assumed that these geometric errors would have only negligible effects on dose calculation.Conclusions:4D modeling of the thorax utilizing the algorithm shows acceptable accuracy and is more suited for routine clinical use in terms of processing time than conventional 4D‐CT and deformable image registration. The algorithm may be useful for simulating dose distribution for advanced beam delivery techniques, such as real‐time tumor tracking irradiation and adaptive radiation therapy.
Modeling and interpretation of the bioelectrical impedance signal for the determination of the local arterial stiffness
Authors: Collette Mathieu , Leftheriotis Georges , Humeau Anne 
Published: September 2009

Purpose:Stiffness of the large arteries (e.g., aorta) plays an important role in the pathogenesis of cardiovascular diseases. To date, the reference method for the determination of regional arterial stiffness is the measurement of the carotid‐femoral pulse wave velocity (PWV) by tonometric techniques. However, this method suffers from several drawbacks and it remains limited in clinical routine.Methods:In the present study, the authors propose a new method based on the analysis of bioelectrical impedance (BI) signals for the determination of the local arterial stiffness. They show, from a theoretical model, a novel interpretation of the BI signals and they establish the relationship between the variations in the BI signal and the kinetic energy of the blood flow in large arteries. From this model, BI signals are simulated in the thigh and compared to experimental BI data. Finally, from the model, they propose a new index related to the properties of the large artery for the determination of the local arterial stiffness.Results:The results show a good correlation between the simulated and the experimental BI signals. The same variations for both of them with different characteristics for rigid and elastic arteries can be observed. The measurement of the index on 20 subjects at rest (mean age of ) for the determination of the local aortic stiffness presents a significant correlation with the PWV reference method (; with the Spearman correlation coefficient and ).Conclusions:All the results suggest that the theoretical model and the new index could give a reliable estimate of local arterial stiffness.
Modeling acute and chronic hypoxia using serial images of PET
Authors: Wang Kelin , Yorke Ellen , Nehmeh Sadek A. , Humm John L. , Ling C. Clifton 
Published: September 2009

Purpose:Two types of tumor hypoxia most likely exist in human cancers: Chronic hypoxia due to the paucity of blood capillaries and acute hypoxia due to temporary shutdown of microvasculatures or fluctuation in the red cell flux. In a recent hypoxia imaging study using PET, the authors observed variation in tracer uptake in two sequential images and hypothesized that variation in acute hypoxia may be the cause. In this study, they develop an iterative optimization method to delineate chronic and acute hypoxia based on the PET serial images.Methods:They assume that (1) chronic hypoxia is the same in the two scans and can be represented by a Gaussian distribution, while (2) acute hypoxia varies in the two scans and can be represented by Poisson distributions. For validation, they used Monte Carlo simulations to generate pairs of PET images with known proportion of chronic and acute hypoxia and then applied the optimization method to the simulated serial images, yielding excellent fit between the input and the fitted results. They then applied this method to the serial PET images of 14 patients with head and neck cancers.Results:The results show good fit of the chronic hypoxia to Gaussian distributions for 13 out of 14 patients (with). Similarly, acute hypoxia appears to be well described by the Poisson distribution with three exceptions. The model calculation yielded the amount of acute hypoxia, which differed among the patients, ranging from to 52%, with an average of .Conclusions:This is the first effort to separate acute and chronic hypoxia from serial PET images of cancer patients.
A method to measure PET scatter fractions for daily quality control
Authors: de Jong H. W. , Lubberink M. , Watabe H. , Iida H. , Lammertsma A. A. 
Published: September 2009

Purpose:Regular monitoring of PET scanner performance is mandatory to assure quality of acquired data. While extensive performance measurements include many scanner characteristics such as resolution, count rate, uniformity, sensitivity, and scatter fraction (SF), most daily QC protocols are limited to uniformity and sensitivity measurements. These measurements may be too insensitive to detect more subtle drifts in detector gains that could lead to reduced detection of primary and increased detection of scattered events. Current methods to measure SF, such as those prescribed by the NEMA protocols (SF‐NEMA), however, require specially designed phantoms and are too cumbersome to be performed on a daily basis.Methods:In this study, a simple and versatile method to determine SF is described. This method (SF‐DAILY) does not require additional measurements, making it suitable for daily QC. The method was validated for four different scanners by comparing results with those obtained with the NEMA 1994 protocol.Results:For all scanner types and acquisition modes, excellent agreement was found between SF‐NEMA and SF‐DAILY.Conclusions:The proposed method is a very practical and valuable addition to current daily QC protocols. In addition, the method can be used to accurately measure SF in phantoms with other dimensions than the NEMA phantom.
Ionization chamber gradient effects in nonstandard beam configurations
Authors: Bouchard Hugo , Seuntjens Jan , Carrier Jean‐Francois , Kawrakow Iwan 
Published: September 2009

Purpose:For the purpose of nonstandard beam reference dosimetry, the current concept of reporting absorbed dose at a point in water located at a representative position in the chamber volume is investigated in detail. As new nonstandard beam reference dosimetry protocols are under development, an evaluation of the role played by the definition of point of measurement could lead to conceptual improvements prior to establishing measurement procedures.Methods:The present study uses the current definition of reporting absorbed dose to calculate ionization chamber perturbation factors for two cylindrical chamber models (Exradin A12 and A14) using the Monte Carlo method. The EGSnrc based user‐code EGS̱chamber is used to calculate chamber dose responses of 14 IMRT beams chosen to cause considerable dose gradients over the chamber volume as previously used byBouchard and Seuntjens [“ Ionization chamber‐based reference dosimetry of intensity modulated radiation beams,” Med. Phys. 31(9), 2454–5465 (2004)].Results:The study shows conclusively the relative importance of each physical effect involved in the nonstandard beam correction factors of 14 IMRT beams. Of all correction factors involved in the dosimetry of the beams studied, the gradient perturbation correction factor has the highest magnitude, on average, 11% higher compared to reference conditions for the Exradin A12 chamber and about 5% higher for the Extradin A14 chamber. Other perturbation correction factors (i.e.,, , and ) are, on average, less than 0.8% different from reference conditions for the chambers and beams studied. The current approach of reporting measured absorbed dose at a point in water coinciding with the location of the centroid of the chamber is the main factor responsible for large correction factors in nonstandard beam deliveries (e.g., intensity modulated radiation therapy) reported in literature.Conclusions:To reduce or eliminate the magnitude of perturbation correction factors in nonstandard beam reference dosimetry, two possible ways to report absorbed dose are suggested: (1) Reporting average dose to the sensitive volume of the chamber filled with water, combined with removing the reference field implicit gradient effect when measuring output factors, and (2) reporting average dose to the chamber itself during output factor verifications. The first option could be adopted if clinical beam correction factors are negligible. The second option could simplify quality assurance procedures when correction factors are not negligible and have to be calculated using Monte Carlo simulations.
2D‐3D registration for prostate radiation therapy based on a statistical model of transmission images
Authors: Munbodh Reshma , Tagare Hemant D. , Chen Zhe , Jaffray David A. , Moseley Douglas J. , Knisely Jonathan P. S. , Duncan James S. 
Published: September 2009

Purpose:In external beam radiation therapy of pelvic sites, patient setup errors can be quantified by registering 2D projection radiographs acquired during treatment to a 3D planning computed tomograph (CT). We present a 2D‐3D registration framework based on a statistical model of the intensity values in the two imaging modalities.Methods:The model assumes that intensity values in projection radiographs are independently but not identically distributed due to the nonstationary nature of photon counting noise. Two probability distributions are considered for the intensity values: Poisson and Gaussian. Using maximum likelihood estimation, two similarity measures, maximum likelihood with a Poisson (MLP) and maximum likelihood with Gaussian (MLG), distribution are derived. Further, we investigate the merit of the model‐based registration approach for data obtained with current imaging equipment and doses by comparing the performance of the similarity measures derived to that of the Pearson correlation coefficient (ICC) on accurately collected data of an anthropomorphic phantom of the pelvis and on patient data.Results:Registration accuracy was similar for all three similarity measures and surpassed current clinical requirements of for pelvic sites. For pose determination experiments with a kilovoltage (kV) cone‐beam CT (CBCT) and kV projection radiographs of the phantom in the anterior‐posterior (AP) view, registration accuracies were (MLP), (MLG), and (ICC). For kV CBCT and megavoltage (MV) AP portal images of the same phantom, registration accuracies were (MLP), (MLG), and (ICC). Registration of a kV CT and MV AP portal images of a patient was successful in all instances.Conclusions:The results indicate that high registration accuracy is achievable with multiple methods including methods that are based on a statistical model of a 3D CT and 2D projection images.
Treatment head disassembly to improve the accuracy of large electron field simulation
Authors: Faddegon Bruce A. , Sawkey Daren , O’Shea Tuathan , McEwen Malcolm , Ross Carl 
Published: September 2009

Purpose:The purposes of this study are to improve the accuracy of source and geometry parameters used in the simulation of large electron fields from a clinical linear accelerator and to evaluate improvement in the accuracy of the calculated dose distributions.Methods:The monitor chamber and scattering foils of a clinical machine not in clinical service were removed for direct measurement of component geometry. Dose distributions were measured at various stages of reassembly, reducing the number of geometry variables in the simulation. The measured spot position and beam angle were found to vary with the beam energy. A magnetic field from the bending magnet was found between the exit window and the secondary collimators of sufficient strength to deflect electrons 1 cm off the beam axis at 100 cm from the exit window. The exit window was 0.05 cm thicker than manufacturer's specification, with over half of the increased thickness due to water pressure in the channel used to cool the window. Dose distributions were calculated with Monte Carlo simulation of the treatment head and water phantom using EGSnrc, a code benchmarked at radiotherapy energies for electron scatter and bremsstrahlung production, both critical to the simulation. The secondary scattering foil and monitor chamber offset from the collimator rotation axis were allowed to vary with the beam energy in the simulation to accommodate the deflection of the beam by the magnetic field, which was not simulated.Results:The energy varied linearly with bending magnet current to within 1.4% from 6.7 to 19.6 MeV, the bending magnet beginning to saturate at the highest beam energy. The range in secondary foil offset used to account for the magnetic field was 0.09 cm crossplane and 0.15 cm inplane, the range in monitor chamber offset was 0.14 cm crossplane and 0.07 cm inplane. A 1.5%/0.09 cm match or better was obtained to measured depth dose curves. Profiles measured at the depth of maximum dose matched the simulated profiles to 2.6% or better at doses of 80% or more of the dose on the central axis. The profiles along the direction of MLC motion agreed to within 0.16 cm at the edge of the field. There remained a mismatch for the lower beam energies at the edge of the profile that ran parallel to the direction of jaw motion of up to 1.4 cm for the 6 MeV beam, attributed to the MLC support block at the periphery of the field left out of the simulation and to beam deflection by the magnetic field. The possibility of using these results to perform accurate simulation without disassembly is discussed. Phase‐space files were made available for benchmarking beam models and other purposes.Conclusions:The match to measured large field dose distributions from clinical electron beams with Monte Carlo simulation was improved with more accurate source details and geometry details closer to manufacturer's specification than previously achieved.
An MLC calibration method using a detector array
Authors: Simon Thomas A. , Kahler Darren , Simon William E. , Fox Christopher , Li Jonathan , Palta Jatinder , Liu Chihray 
Published: September 2009

Purpose:The authors have developed a quantitative calibration method for a multileaf collimator (MLC) which measures individual leaf positions relative to the MLC backup jaw on an Elekta Synergy linear accelerator.Methods:The method utilizes a commercially available two‐axis detector array (Profiler 2; Sun Nuclear Corporation, Melbourne, FL). To calibrate the MLC bank, its backup jaw is positioned at the central axis and the opposing jaw is retracted to create a half‐beam configuration. The position of the backup jaws field edge is then measured with the array to obtain what is termed the radiation defined reference line. The positions of the individual leaf ends relative to this reference line are then inferred by the detector response in the leaf end penumbra. Iteratively adjusting and remeasuring the leaf end positions to within specifications completes the calibration. Using the backup jaw as a reference for the leaf end positions is based on three assumptions: (1) The leading edge of an MLC leaf bank is parallel to its backup jaw's leading edge, (2) the backup jaw position is reproducible, and (3) the measured radiation field edge created by each leaf end is representative of that leaf's position. Data from an electronic portal imaging device (EPID) were used in a similar analysis to check the results obtained with the array.Results:The relative leaf end positions measured with the array differed from those measured with the EPID by an average of 0.11 ±0.09 mm per leaf. The maximum leaf positional change measured with the Profiler 2 over a 3 month period was 0.51 mm. A leaf positional accuracy of ±0.4 mm is easily attainable through the iterative calibration process. The method requires an average of 40 min to measure both leaf banks.Conclusions:This work demonstrates that the Profiler 2 is an effective tool for efficient and quantitative MLC quality assurance and calibration.
Monte Carlo study on secondary neutrons in passive carbon‐ion radiotherapy: Identification of the main source and reduction in the secondary neutron dose
Authors: Yonai Shunsuke , Matsufuji Naruhiro , Kanai Tatsuaki 
Published: September 2009

Purpose:Recent successful results in passive carbon‐ion radiotherapy allow the patient to live for a longer time and allow younger patients to receive the radiotherapy. Undesired radiation exposure in normal tissues far from the target volume is considerably lower than that close to the treatment target, but it is considered to be non‐negligible in the estimation of the secondary cancer risk. Therefore, it is very important to reduce the undesired secondary neutron exposure in passive carbon‐ion radiotherapy without influencing the clinical beam. In this study, the source components in which the secondary neutrons are produced during passive carbon‐ion radiotherapy were identified and the method to reduce the secondary neutron dose effectively based on the identification of the main sources without influencing the clinical beam was investigated.Methods:A Monte Carlo study with the PHITS code was performed by assuming the beamline at the Heavy‐Ion Medical Accelerator in Chiba (HIMAC). At first, the authors investigated the main sources of secondary neutrons in passive carbon‐ion radiotherapy. Next, they investigated the reduction in the neutron dose with various modifications of the beamline device that is the most dominant in the neutron production. Finally, they investigated the use of an additional shield for the patient.Results:It was shown that the main source is the secondary neutrons produced in the four‐leaf collimator (FLC) used as a precollimator at HIAMC, of which contribution in the total neutron ambient dose equivalent is more than 70%. The investigations showed that the modification of the FLC can reduce the neutron dose at positions close to the beam axis by 70% and the FLC is very useful not only for the collimation of the primary beam but also the reduction in the secondary neutrons. Also, an additional shield for the patient is very effective to reduce the neutron dose at positions farther than 50 cm from the beam axis. Finally, they showed that the neutron dose can be reduced by approximately 70% at any position without influencing the primary beam used in treatment.Conclusions:This study was performed by assuming the HIMAC beamline; however, this study provides important information for reoptimizing the arrangement and the materials of beamline devices and designing a new facility for passive carbon‐ion radiotherapy and probably passive proton radiotherapy.
Automated segmentation of lungs with severe interstitial lung disease in CT
Authors: Wang Jiahui , Li Feng , Li Qiang 
Published: September 2009

Purpose:Accurate segmentation of lungs with severe interstitial lung disease (ILD) in thoracic computed tomography (CT) is an important and difficult task in the development of computer‐aided diagnosis (CAD) systems. Therefore, we developed in this study a texture analysis‐based method for accurate segmentation of lungs with severe ILD in multidetector CT scans.Methods:Our database consisted of 76 CT scans, including 31 normal cases and 45 abnormal cases with moderate or severe ILD. The lungs in three selected slices for each CT scan were first manually delineated by a medical physicist, and then confirmed or revised by an expert chest radiologist, and they were used as the reference standard for lung segmentation. To segment the lungs, we first employed a CT value thresholding technique to obtain an initial lung estimate, including normal and mild ILD lung parenchyma. We then used texture‐feature images derived from the co‐occurrence matrix to further identify abnormal lung regions with severe ILD. Finally, we combined the identified abnormal lung regions with the initial lungs to generate the final lung segmentation result. The overlap rate, volume agreement, mean absolute distance (MAD), and maximum absolute distance between the automatically segmented lungs and the reference lungs were employed to evaluate the performance of the segmentation method.Results:Our segmentation method achieved a mean overlap rate of 96.7%, a mean volume agreement of 98.5%, a mean MAD of, and a mean of for all the cases in our database; a mean overlap rate of 97.7%, a mean volume agreement of 99.0%, a mean MAD of , and a mean of for the 31 normal cases; and a mean overlap rate of 96.1%, a mean volume agreement of 98.1%, a mean MAD of , and a mean of for the 45 abnormal cases with ILD.Conclusions:Our lung segmentation method provided accurate segmentation results for abnormal CT scans with severe ILD and would be useful for developing CAD systems for quantification, detection, and diagnosis of ILD.