bluuebunny/crossref_metadata_2025 huggingface dataset:
A detailed evaluation of acute respiratory decline in patients with fibrotic lung disease: Aetiology and outcomes
Authors: HUIE Tristan J. , OLSON Amy L. , COSGROVE Gregory P. , JANSSEN William J. , LARA Abigail R. , LYNCH David A. , GROSHONG Steve D. , MOSS Marc , SCHWARZ Marvin I. , BROWN Kevin K. , FRANKEL Stephen K.
Published: June 2010

Background and objective:  A comprehensive diagnostic evaluation is recommended for all patients with fibrotic lung disease and acute respiratory decompensation. However, the effect on clinical outcomes of this evaluation remains unknown.

Methods:  We evaluated 27 consecutive patients with fibrotic lung disease who were hospitalized for an acute respiratory decline between June 2006 and April 2009. An interstitial lung disease expert assisted with the acute care of each patient. A retrospective review of the patient charts was performed to obtain demographic and clinical data, and to assess outcomes.

Results:  Using a strict definition of acute exacerbation (AE) of fibrotic lung disease derived from the IPF Network Pulmonary Perspective statement, 10 of the 27 patients were classified as definite AE and nine as suspected AE. In eight patients, infectious agents were identified as potential explanations for the respiratory decline. No patients with congestive heart failure or pulmonary embolism were identified. Overall survival to discharge was 37.0%. One‐year survival was 14.8%. There were no differences in outcomes for patients with AE compared with those for whom potential infectious aetiologies were identified (log rank, P = 0.932). Patients with IPF showed a decreased rate of survival compared with patients with non‐IPF fibrotic disease (1‐year survival 0% vs 28.6%, log rank, P = 0.045).

Conclusions:  In patients with fibrotic lung disease and an acute respiratory decline, a detailed diagnostic evaluation revealed a potential infectious aetiology in up to one‐third of cases. However, there was no association between this finding and outcomes in these patients. One‐year survival was dismal in patients who suffered an acute respiratory decompensation.
The Residue of Colonial Anthropology in the History and Political Discourse of Northern Ghana: Critique and Revision
Authors: MacGaffey Wyatt
Published: June 2010

The received history of northern Ghana is based on anthropological assumptions imported by colonial officials at the end of the 19th century. This history is now unreflectively incorporated in the political discourse of the north, associated with ongoing conflicts that threaten at times to engulf all three northern regions in warfare. A critique of colonial anthropology, in combination with new research, suggests an alternative history of the North.
Language and Communication in the Spanish Conquest of America
Authors: Soler Daniel Wasserman
Published: June 2010

This article was originally presented as part of The 2009 Compass Interdisciplinary Virtual Conference. You can read the article along with two commentaries and discussion athttp://compassconference.wordpress.com/2009/10/19/conference‐paper‐language‐and‐communication‐in‐the‐spanish‐conquest‐of‐america/. One of the central questions arising from the encounter between Europeans and Amerindians concerns language and communication. An encounter between two peoples that had not known about the other’s existence – an encounter that scholars have long characterized as a clash of cultures – raises the question of how they managed to communicate with each other. Over 25 years ago, Tzvetan Todorov put forth one way of linking communication and conquest when he argued that Europeans conquered the Amerindians through their superior ability to understand ‘the Other’. More generally, he contended that Western Europeans had a general ‘superiority in human communication’, demonstrated by the fact that they used alphabetic writing (Todorov 251). For Todorov, Europeans displayed ‘remarkable qualities of flexibility and improvisation’, characteristics that allowed them to be more effective in imposing their ways of life on others (Todorov 247–8). They were so successful, Todorov argues, that in the centuries following the initial encounter between Europeans and Amerindians, Europeans were able to gradually assimilate the Other and eliminate alterity. While Todorov’s 1982 work initially received much acclaim, since then several scholars have challenged (directly and indirectly) his claims by subjecting the encounter between Europeans and Amerindians to further study. Scholars have questioned the extent to which these groups were able to communicate with one another, and in some cases, they have questioned what Spanish conquest, authority, and domination actually mean when Spaniards and Indians had such difficulty communicating their ideas to one another. By posing these questions, scholars of varied backgrounds in anthropology, history, religion, and art history have fundamentally reshaped the field of colonial Latin American studies. While they have shown that barriers impeded communication and understanding between Amerindians and Europeans, scholars have also demonstrated that both groups made important contributions to new cultural and religious syntheses. This article will explore a range of scholarly works over the past 25 years that responds to the question of how language and communication are interrelated with conquest.
Debates on Domesticity and the Position of Women in Late Colonial India
Authors: Banerjee Swapna M.
Published: June 2010

Tracing the genealogy of domesticity from India’s precolonial past, this essay problematizes the recent emphasis on the link between women and domesticity in late colonial India. Based on a review of the growing literature in the field, it considers the newly evolved notions of colonial domesticity as a moment of [re]consideration rather than a break with the past. The discursive formation of the new ideas of domesticity under colonial regime transcended the private‐public and often national boundaries, indicating an overlap where the most intimate details of the ‘private’, personal life were not only discussed and debated for public consumption but were also articulated in response to imperial and international concerns. This paper argues that domesticity as a new cultural logic became the motor of change for both the British and the colonized subjects and it particularly empowered women by giving them agency in the late colonial period. In conclusion, this paper signals the importance of children, childhood, fatherhood, and masculinity as critical components of domesticity, which are yet to be broached by South Asian historians.
CODE 75: operative protocols and a case report in preventive dental care in a department of neurorehabilitation for acquired cerebral lesions
Authors: Genovesi A , Marchisio O , Moggia F , Derchi G
Published: June 2010

To cite this article:
Int J Dent Hygiene 8, 2010; 169–177 DOI: 10.1111/j.1601‐5037.2010.00467.x Genovesi A, Marchisio O, Moggia F, Derchi G. CODE 75: Operative protocols and a case report in preventive dental care in a department of neurorehabilitation for acquired cerebral lesions.

Abstract:  CODE 75 is a neurorehabilitation department at the General Hospital of Versilia, which specializes in serious acquired cerebral lesions.

Objectives:  The therapy and the maintenance of oral hygiene in patients with cerebral lesions are critical to the overall success of the rehabilitation therapy. The purpose of our project was to improve patients’ quality of life, reducing the quantity of oral bacteria caused by the presence of layers of plaque on the tooth surfaces and in the oral mucosa.

Methods:  The dental department of Versilia Hospital conducted a 1 year follow‐up study to develop specific protocols designed to obtain and improve the maintenance of these patients’ oral hygiene. The oral prevention project was directed primarily at the department’s medical staff and carers, and focused on improving the information available to the medical team and their direct involvement. A case report is described to show an application of the protocol. Data were recorded before the start of the protocol (T0) and after 1 month (T1).

Results:  The analysis of the periodontal parameters shows a difference in values between T0 and T1. In T1 no bleeding on probing was recorded. After the causal therapy, the gingival hypertrophy and oedema disappeared as confirmed by the absence of BOP.

Discussions:  Results show that teamwork plays a fundamental role in this multi‐professional approach for the rehabilitation of patients with acquired cerebral lesions. The success of this protocol depends on the cooperation between personnel with specific skills in the department.
LjCYC Genes Constitute Floral Dorsoventral Asymmetry in Lotus japonicus
Authors: Wang Jiechen , Wang Yumei , Luo Da
Published: June 2010

Previous study shows that LjCYC2, a CYC‐like TCP (TB1, CYC and PCFs) gene in the model legume, Lotus japonicus, is involved in dorsal petal development, which together with the other two homologous genes, LjCYC1 and LjCYC3, belongs to an LjCYC gene cluster. In this report, we modified the transformation system in L. japonicus, and constructed different RNAi transgenes to target different LjCYC genes. The expression of three endogenous LjCYC genes was specifically suppressed by different specific RNAi transgenes, and a chimerical RNAi transgene that contains the specific sequences from LjCYC1 and LjCYC2 was found to downregulate the expression of both endogenous genes simultaneously. Effects of silencing three LjCYC genes were mainly restricted on either dorsal or lateral petals, demonstrating their dorsalizing and lateralizing activities during the development of zygomorphic flower. Furthermore, abolishing the expression of three LjCYC genes could give rise to complete loss of dorsoventral (DV) differentiation in the flower whose petals all resembled the ventral one in the wild type and displayed intact organ internal (IN) asymmetry. Our data demonstrate that during zygomorphic flower development, the DV asymmetry is constituted by the LjCYC genes, while the floral organ IN asymmetry is independently determined by other genetic factors.
Morph‐specific differences in metabolism related to flight in the wing‐dimorphicAphis gossypii
Authors: Shi Sheng‐Li , Liu Xiao‐Xia , Zhang Qing‐Wen , Zhao Zhang‐Wu
Published: June 2010

Abstract The cotton aphid,Aphis gossypiiGlover, is a wing‐dimorphic species, which causes globally important agricultural losses. In this present study, we compared the biochemical basis of wing polymorphism inA. gossypiiwith respect to trade‐off of energy resources, including glycogen, trehalose, lipids (total lipid, triglyceride and phospholipid), free fatty acids, and soluble protein between dispersal and reproduction morphs during the wing‐bud nymph and adulthood. Total lipid, triglyceride and free fatty acids were significantly higher in winged versus wingless morphs at 12 h of adulthood, the period during which alates are able to fly. By contrast, the wingless morph contained more glycogen than the winged morph from the 4th nymphal stage to adulthood. Trehalose content in the wingless morph was also higher than that in the winged morph during the 3rd and 4th nymphal stages, butvice versaat 12 h of adulthood. Finally, soluble protein content increased from nymphs to adults and was higher during adulthood in aptera versus alate. Whole‐body water content in 12‐h adults was significantly higher in apterae than that in alatae. These results indicate significant physiological differences between morphs related to specialization for flight.
Long‐Distance Coarticulation in Spoken and Signed Language: An Overview
Authors: Grosvald Michael
Published: June 2010

This study explores the phenomenon of coarticulation in spoken and signed language, focusing in particular on long‐distance effects, defined here as the articulatory influence of one phonetic element on another across at least one intervening segment. While a great deal of variability has been found among language users in the production and perception of such effects, the fact that long‐distance coarticulation occurs at all has important theoretical implications. Recent work on sign language, together with relevant spoken‐language results, offers new insights and raises interesting questions concerning the human language capacity in general.
Species Distribution Modeling
Authors: Miller Jennifer
Published: June 2010

The use of species distribution models (SDM) to map and monitor animal and plant distributions has become increasingly important in the context of awareness of environmental change and its ecological consequences. From their original inception as resource inventory and conservation mapping tools, SDM have evolved along with the increasing variety and availability of statistical methods, digital biological, and environmental data with which they are built in a geographic information system. Beyond predicting species distributions, these models have become an important and widely used decision‐making tool for a variety of biogeographical applications, such as studying the effects of climate change, identifying potential protected areas, determining locations potentially susceptible to invasion, and mapping vector‐borne disease spread and risk. This article outlines the steps involved in formulating an SDM and focuses on the conceptual and theoretical foundations on which it is based and identifies issues that have merited recent and will merit future research attention.
El impacto de la crisis sobre las administraciones de seguridad social: revisión de las conclusiones de la encuesta de la AISS
Authors: Orton Ian
Published: June 2010

Este artículo examina las conclusiones de una importante encuesta que la Asociación Internacional de la Seguridad Social (AISS) llevó a cabo en el año 2009, sobre el impacto de la crisis financiera y económica en las administraciones de seguridad social. Dichas conclusiones revelan que la mayoría de las administraciones se han visto negativamente afectadas por la disminución del rendimiento de las inversiones de los fondos de la seguridad social y por la reducción del ingreso procedente de las cotizaciones, y que se ven igualmente confrontadas al aumento de los gastos por concepto de prestaciones. A pesar de ello, las conclusiones indican que las administraciones han enfrentado estos desafíos de forma activa e innovadora. Sin embargo, otros desafíos se plantean. En este sentido, los más preocupantes incluyen la posibilidad de una lenta recuperación económica que supone una prolongada crisis del mercado de trabajo, así como los problemas que generan reservas financieras agotadas y una menor libertad fiscal.
Analysis Techniques for Congruence of the Patellofemoral Joint
Authors: Connolly K. D. , Ronsky J. L. , Westover L. M. , Küpper J. C. , Frayne R.
Published: June 2010

Quantifying joint congruence may help to understand the relationship between joint function and health. In previous studies, a congruence index (CI) has been used to define subject-specific joint congruence. However, the sensitivity of the CI algorithm to surface representation was unknown. The purpose of this study was to assess the effects of applying five modifications (M1–M5) to the CI algorithm to determine whether the magnitude and variability of the patellofemoral CI is dependent on the surface representation used. The five modifications focused on calculating the CI based on the principal curvature (M1) at the centroid of the contact region, (M2) using an root mean square value for the contact region, (M3) using a mean value for the contact region, (M4) using all digitized points of the patellar surface, and (M5) using all digitized points in contact. The CI found using the contact area (M1, M2, M3, and M5) provides a local measure for congruence, which was shown to increase (decreasing CI) with increasing joint angle. In ten healthy subjects measured with magnetic resonance (MR) images, the patellofemoral joint became significantly more congruent as the knee angle increased from 15 deg to 45 deg using method M5. The magnitude and variability of the patellofemoral CI was dependent on the surface representation used, suggesting that standardization of the surface representation is important to provide a consistent measure. Specifically, M5 provides a local measure of joint congruence, which can account for joint position and orientation. M5 balances the ability to detect differences in congruence between knee angles without introducing high variability.
An Improved Material-Mask Overlay Strategy for Topology Optimization of Structures and Compliant Mechanisms
Authors: Jain Chandini , Saxena Anupam
Published: June 2010

The honeycomb-based domain representation directly yields checkerboard and point flexure free optimal solutions to various topology design problems without requiring any supplementary suppression method. This is because the root cause behind the appearance of these pathologies, namely, the permitted single-point connectivity between contiguous subregions in rectangular-cell-based representation, is eliminated. The mesh-free material-mask overlay method further promises unadulterated “black and white” solutions in contrast to density interpolation schemes where the material is modeled between the “void” and “filled” states. Here, we propose improvements to the material-mask overlay method by judiciously increasing the number of material masks during a sequence of subsearches for the best solution. We used an alternative, mutation-based zero-order stochastic search, which, through a small population of solution vectors, can yield multiple solutions from a single search for nonconvex topology optimization formulations. Wachspress hexagonal cells are used as finite elements since they offer rich displacement interpolation functions. Singular solutions are penalized and filtered. With the improved material-mask overlay method, we showcase the synthesis using two classical small displacement problems each on optimal stiff structures and compliant mechanisms to illustrate the extraction of pathology-free, “black and white,” and multiple solutions.
Registration of myocardial PET and SPECT for viability assessment using mutual information
Authors: Marinelli Martina , Martinez‐Möller Axel , Jensen Brian , Positano Vincenzo , Weismüller Susanne , Navab Nassir , Landini Luigi , Schwaiger Markus , Nekolla Stephan G.
Published: June 2010

Purpose: The combination of sequentially acquired cardiac PET and SPECT data integrating metabolic and perfusion information allows the assessment of myocardial viability, a relevant clinical parameter for the management of patients who have suffered myocardial infarction and are now candidates for complex and cost intensive therapies such as bypass surgery. However, registration of cardiac functional datasets acquired on different imaging systems is limited by the difficulty to define anatomical landmarks and by the relatively poor inherent spatial resolution. In this article, the authors sought to evaluate whether it is possible to automatically register FDG‐PET and sestamibi‐SPECT cardiac data.

Methods: Automatic rigid registration was implemented with the ITK framework using Mattes mutual information as the similarity measure and a quaternion to represent the rotational component. The goodness of the alignment was evaluated by computing the mean target registration error (mTRE) at the myocardial wall. The registration parameters were optimized for robustness and speed using the data from 11 cardiac patients undergoing both PET and SPECT examinations (training datasets). The optimized algorithm was applied on the PET and SPECT data from 11 further patients (evaluation datasets). Quantitative (mTRE calculation) and visual (scoring method) comparisons were performed between automatic and manual registrations. Moreover, the automatic registration was also compared to the registration implicitly defined in the standard clinical analysis.

Results: The registration parameters were successfully optimized and resulted in a mean mTRE of 1.13 mm and 1.2 s average runtime on standard computer hardware for the training datasets. Automatic registration in the 11 validation datasets resulted in an average mTRE of 2.3 mm, with 7.5 mm mTRE in the worst case and an average runtime of 1.6 s. Automatic registration outperformed manual registrations both for the mTRE and for the visual assessment. Automatic registration also resulted in higher accuracy and better visual assessment as compared to the registration implicitly performed in the standard clinical analysis.

Conclusions: The results demonstrate the possibility to successfully perform mutual information based registration of PET and SPECT cardiac data, allowing an improved workflow for the sequentially acquired cardiac datasets, in general, and specifically for the assessment of myocardial viability.
Comparison of film dosimetry techniques used for quality assurance of intensity modulated radiation therapy
Authors: Ju Sang Gyu , Han Youngyih , Kum Oyeon , Cheong Kwang‐Ho , Shin Eun Hyuk , Shin Jung Suk , Kim Jin Sung , Ahn Yong Chan
Published: June 2010

Purpose

Accurate dosimetry is essential to ensure the quality of advanced radiation treatments, such as intensity modulated radiation therapy (IMRT). Therefore, a comparison study was conducted to assess the accuracy of various film dosimetry techniques that are widely used in clinics.

Methods

A simulated IMRT plan that produced an inverse pyramid dose distribution in a perpendicular plane of the beam axis was designed with 6 MV x rays to characterize the large contribution of scattered photons to low dose regions. Three film dosimetry techniques, EDR2, EDR2 with low‐energy photon absorption lead filters (EDR2 WF), and GafChromic®EBT, were compared to ionization chamber measurements as well as Monte Carlo (MC) simulations. The accuracy of these techniques was evaluated against the ionization chamber data. Two‐dimensional comparisons with MC simulation results were made by computing the gamma index with criteria ranging from 2% of dose difference or 2 mm of distance to agreement (2%/2 mm) to 4%/4 mm on the central vertical plane of a square solid water phantom. Depth doses and lateral profiles at depths of 5, 10, and 15 cm were examined to characterize the deviation of film measurements and MC predictions from ionization chamber measurements.

Results

In depth dose comparisons, the deviation between the EDR2 films was 9% in the low dose region and 5% in high dose region, on average. With lead filters, the average deviation was reduced to −1.3% and −0.3% in the low dose and high dose regions, respectively. EBT film results agreed within 1.5% difference on average with ionization chamber measurements in low and high dose regions. In two‐dimensional comparisons with MC simulation, EDR2 films passed gamma tests with a 2%/2 mm criterion only in the high dose region (, total of 63.06% of the tested region). In the low dose region, EDR2 films passed gamma tests with 3%/3 mm criterion (, total of 98.4% of the tested region). For EDR2 WF and GafChromic®EBT films, gamma tests with a 2% /2 mm criterion in the tested area was 97.3% and 96.8% of the tested region, respectively.

Conclusions

The EDR2 film WF and GafChromic®EBT film achieved an average accuracy level of 1.5% against an ionization chamber. These two techniques agreed with the MC prediction in 2%/2mm criteria evaluated by the gamma index, whereas EDR2 without filters achieved an accuracy level of 3%/3 mm with the decision criteria of agreement greater than 95% of the tested region. The overall results will provide a useful quantitative reference for IMRT verifications.
Automatic segmentation of intracranial arteries and veins in four‐dimensional cerebral CT perfusion scans
Authors: Mendrik Adriënne , Vonken Evert‐jan , van Ginneken Bram , Smit Ewoud , Waaijer Annet , Bertolini Giovanna , Viergever Max A. , Prokop Mathias
Published: June 2010

Purpose: CT angiography (CTA) scans are the current standard for vascular analysis of patients with cerebrovascular diseases, such as acute stroke and subarachnoid hemorrhage. An additional CT perfusion (CTP) scan is acquired of these patients to assess the perfusion of the cerebral tissue. The aim of this study is to extend the diagnostic yield of the CTP scans to also include vascular information.

Methods: CTP scans are acquired by injecting contrast material and repeatedly scanning the head over time. Therefore, time‐intensity profiles are available for each voxel in the scanned volume, resulting in a 4D dataset. These profiles can be utilized to differentiate not only between vessels and background but also between arteries and veins. In this article, a fully automatic method is proposed for the segmentation of the intracranial arteries and veins from 4D cerebral CTP scans. Furthermore, a vessel enhanced volume is presented, in which the vasculature is highlighted and background structures are suppressed. Combining this volume with the artery/vein segmentation results in an arteriogram and a venogram, which could serve as additional means for vascular analysis in patients with cerebrovascular diseases. The artery/vein segmentation is quantitatively evaluated by comparing the results to manual segmentations by two expert observers.

Results: Results (paired two‐tailed t‐test) show that the accuracies of the proposed artery/vein labeling are not significantly different from the accuracies of the expert observer manual labeling (ground truth). Moreover, sensitivity and specificity of the proposed artery/vein labeling, relative to both expert observer ground truths, were similar to the sensitivity and specificity of the expert observer labeling compared to each other.

Conclusions: The proposed method for artery/vein segmentation is shown to be very accurate for arteries and veins with normal perfusion. Combining the artery/vein segmentation with the vessel enhanced volume produces an arteriogram and a venogram, which have the potential to extend the diagnostic yield of CTP scans and replace the additional CTA scan, but could also be helpful to radiologists in addition to the CTA scan.
Assessing the intrinsic precision of 3D/3D rigid image registration results for patient setup in the absence of a ground truth
Authors: Wu Jian , Murphy Martin J.
Published: June 2010

Purpose

To assess the precision and robustness of patient setup corrections computed from 3D/3D rigid registration methods using image intensity, when no ground truth validation is possible.

Methods

Fifteen pairs of male pelvic CTs were rigidly registered using four different in‐house registration methods. Registration results were compared for different resolutions and image content by varying the image down‐sampling ratio and by thresholding out soft tissue to isolate bony landmarks. Intrinsic registration precision was investigated by comparing the different methods and by reversing the source and the target roles of the two images being registered.

Results

The translational reversibility errors for successful registrations ranged from 0.0 to 1.69 mm. Rotations were less than 1°. Mutual information failed in most registrations that used only bony landmarks. The magnitude of the reversibility error was strongly correlated with the success/failure of each algorithm to find the global minimum.

Conclusions

Rigid image registrations have an intrinsic uncertainty and robustness that depends on the imaging modality, the registration algorithm, the image resolution, and the image content. In the absence of an absolute ground truth, the variation in the shifts calculated by several different methods provides a useful estimate of that uncertainty. The difference observed by reversing the source and target images can be used as an indication of robust convergence.
Registration between ultrasound and fluoroscopy or CT in prostate brachytherapy
Authors: Fallavollita P. , Karim Aghaloo Z. , Burdette E. C. , Song D. Y. , Abolmaesumi P. , Fichtinger G.
Published: June 2010

Purpose

In prostate brachytherapy, transrectal ultrasound (TRUS) is used to visualize the anatomy, while implanted seeds can be visualized by fluoroscopy. Intraoperative dosimetry optimization is possible using a combination of TRUS and fluoroscopy, but requires localization of the fluoroscopy‐derived seed cloud, relative to the anatomy as seen on TRUS. The authors propose to develop a method of registration of TRUS images and the implants reconstructed from fluoroscopy.

Methods

A phantom was implanted with 48 seeds then imaged with TRUS and CT. Seeds were reconstructed from CT yielding a cloud of seeds. Fiducial‐based ground‐truth registration was established between the TRUS and CT. TRUS images are filtered, compounded, and registered to the reconstructed implants by using an intensity‐based metric. The authors evaluated a volume‐to‐volume and point‐to‐volume registration scheme. In total, seven TRUS filtering techniques and three image similarity metrics were analyzed. The method was also tested on human subject data captured from a brachytherapy procedure.

Results

For volume‐to‐volume registration, noise reduction filter and normalized correlation metrics yielded the best result: An average of seed localization error relative to ground truth. For point‐to‐volume registration, noise reduction combined with beam profile filter and mean squares metrics yielded the best result: An average of seed localization error relative to the ground truth. In human patient data, C‐arm fluoroscopy images showed 81 radioactive seeds implanted inside the prostate. A qualitative analysis showed clinically correct agreement between the seeds visible in TRUS and reconstructed from intraoperative fluoroscopy imaging. The measured registration error compared to the manually selected seed locations by the clinician was .

Conclusions

Fully automated registration between TRUS and the reconstructed seeds performed well in ground‐truth phantom experiments and qualitative observation showed adequate performance on early clinical patient data.
Radiation dose efficiency comparison between differential phase contrast CT and conventional absorption CT
Authors: Zambelli Joseph , Bevins Nicholas , Qi Zhihua , Chen Guang‐Hong
Published: June 2010

Purpose

The superior radiation dose efficiency of a newly implemented differential phase contrast CT imaging method compared to the conventional absorption CT method is demonstrated.

Methods

A differential phase contrast CT imaging method has recently been implemented using conventional x‐ray sources with a grating interferometer consisting of three gratings. This approach offers the possibility of simultaneous reconstruction of both attenuation contrast and phase contrast images from a single acquisition. This enables a direct comparison of radiation dose efficiency of both types of reconstructed images under identical conditions. Radiation dose efficiency was studied by measuring the change in contrast‐to‐noise ratio (CNR) with different exposure levels. A physical phantom of 28.5 mm diameter was constructed and used for measurement of CNR in both the absorption and phase contrast CT images, which were reconstructed from the same data set.

Results

For three of the four materials studied, at any given exposure level, the CNR of the differential phase contrast CT images was superior to that of the corresponding absorption contrast CT images. The most dramatic improvement was noted in the contrast between PMMA and water, where the CNR was improved by a factor of approximately 5.5 in the differential phase contrast CT images. Additionally, the CNR of phase contrast CT is empirically shown to have the same square root dependence on exposure, as is the case for absorption contrast CT.

Conclusions

The differential phase contrast CT method provided higher CNR than conventional absorption CT at equivalent dose levels for most of the materials studied, and so may enable achievement of the same object visibility as conventional absorption CT methods at a lower exposure level.
Electron paramagnetic resonance oxygen imaging of a rabbit tumor using localized spin probe delivery
Authors: Epel Boris , Haney Chad R. , Hleihel Danielle , Wardrip Craig , Barth Eugene D. , Halpern Howard J.
Published: June 2010

Purpose

Application ofin vivoelectron paramagnetic resonance (EPR) oxygen imaging (EPROI) to tumors larger than those of mice requires development of both instrumental and medical aspects of imaging.

Methods

250 MHz EPR oxygen imaging was performed using a loop‐gap resonator with a volume exceeding. The paramagnetic spin probe was injected directly into the femoral artery feeding the rabbit leg/tumor.

Results

The authors present continuous wave and electron spin echo EPR oxygen images of a large size (4 cm) VX‐2 tumor located on the leg of a New Zealand white rabbit.

Conclusions

This study demonstrates the feasibility of continuous wave and electron spin echo oxygen imaging modalities for investigation of volumes of tumor and normal tissue relevant to large animals. The injection of the spin probe directly into the artery feeding a rabbit leg will allow one to reduce, by over one order of magnitude, the amount of spin probe used as compared to whole animal IV injection.
Verification of MLC based real‐time tumor tracking using an electronic portal imaging device
Authors: Han‐Oh Sarah , Yi Byong Yong , Lerma Fritz , Berman Barry L. , Gui Minzhi , Yu Cedric
Published: June 2010

Purpose: The authors have developed a novel technique using an electronic portal imaging device (EPID) to verify the geometrical accuracy of delivery of dose‐rate‐regulated tracking (DRRT). This technique, called verification of real‐time tracking with EPID (VORTE), can potentially be used for both on‐line and off‐line quality assurance (QA) of MLC‐based dynamic tumor tracking.

Methods: The shape and position of target as a function of time, which is assumed to be known, is projected onto the EPID plane. This projected sequence of apertures as a function of time (target motion) is then used as the reference. The accuracy of dynamic MLC tracking can then be assessed by how well the delivered beam follows this projected target motion without the use of a physical moving phantom. The beam apertures controlled by DRRT (aperture motion) is detected by the EPID as a function of time. The aperture motion is compared to the target motion to evaluate tracking error introduced by DRRT. The accuracy of VORTE was measured using film measurements of ten static fields. The VORTE for dynamic tumor tracking was tested with several target motions, including (1) rigid‐body two‐dimensional (2‐D) cyclic motion in the superior‐inferior direction with various period and amplitude; (2) the above 2‐D cyclic motion plus cyclic deformation; and (3) 2‐D cyclic motion with both deformation and rotation. For each target motion, the controlled aperture motion resulting from DRRT was acquired at using EPID in the continuous‐acquisition mode. Leaf positions in all captured frames were measured from the EPID and compared to their expected positions. The passing rate of 2 mm criteria for all leaves from all frames was calculated for each of the four patterns of tumor motion. Additionally, the root‐mean‐square (RMS) deviations of the centroid of the apertures between the designed and delivered beams were calculated for all three cases.

Results: The accuracy of MLC‐leaf position determination by VORTE is 0.5 mm (1 standard deviation) by comparison to film measurements. With DRRT, the passing rates using the 2 mm criteria for all acquired frames are 100% for the 2‐D displacement, 99% for the 2‐D displacement with deformation, and 88% for the 2‐D displacement combined with both deformation and rotation. The RMS deviations are 0.6 mm for the 2‐D displacement, 1.0 mm for the 2‐D displacement with deformation, and 1.1 mm for the 2‐D displacement combined with both deformation and rotation.

Conclusions: The VORTE can measure the accuracy of MLC‐based tumor tracking without the necessity of employing a moving phantom. Moreover, it can be used for complex target motion (i.e., 2‐D displacement combined with deformation and rotation) that is difficult to create with physical moving phantoms. Therefore, the VORTE and the novel QA process illustrated by this study have a great potential for verifying real‐time tumor tracking.
Harmonic phase angle as a concentration‐independent measure of nanoparticle dynamics
Authors: Rauwerdink Adam M. , Weaver John B.
Published: June 2010

Purpose

The harmonic spectrum of magnetic nanoparticles contains valuable information about the quantity and environment of the particles. Harmonic amplitudes have been used to produce quantitative images and ratios of these amplitudes have been used to monitor changes in the particle environment. Harmonic phase angles have not yet been utilized in these pursuits. The authors explore harmonic phase angle as a concentration‐independent means of remotely monitoring the dynamic magnetization of nanoparticles.

Methods

A magnetic nanoparticle spectrometer was used to explore the impacts of viscosity and excitation frequency and amplitude on the phase angle of magnetization harmonics. A dynamic model, which accounts for particle relaxation times, was used to model some results.

Results

Harmonic phase angle can undergo large changes when a nanoparticle's Brownian motion is altered. Excitation parameters and particle characteristics have a profound effect on the extent of these changes.

Conclusions

Phase angle can allow for monitoring of various impacts on a nanoparticle's Brownian motion. When combined with other concentration‐independent metrics, such as ratios of harmonic amplitudes, valuable information about the particle's environment can be gathered.
Loss of radiobiological effect of imaging dose in image guided radiotherapy due to prolonged imaging‐to‐treatment times
Authors: Flynn Ryan T.
Published: June 2010

Purpose: Increased use of cone beam CT guidance in image guided radiotherapy has prompted the inclusion of the imaging dose in treatment plans, thus using imaging beams to treat tumors. Sublethal radiation damage repair during , the time between imaging and treatment, could reduce the effectiveness of the imaging dose, resulting in tumor underdosage. The theoretical magnitude of this effect was quantified using radiobiological modeling.

Methods: The therapeutic effective dose (TED), which, if delivered using only therapeutic beams, would result in the same tumor cell survival as for both the imaging and therapeutic beams, was derived using the generalized linear‐quadratic model. The correction factor by which therapeutic dose can be scaled to compensate for sublethal damage repair was also derived. TED and are dependent on , sublethal damage repair half‐time , imaging dose and dose rate , therapeutic dose and dose rate , and . TED and were calculated as a function of , and each parameter was varied independently while holding the remaining parameters at their reference values. The reference values were based on prostate cancer cells and were , , , , , , and . Estimates of the expected values of TED and , and , were calculated using and distributions from a few thousand prostate treatment fractions.

Results: For a typical value of 5.0 min and all other parameters set to their reference values, TED was 0.5% lower than the prescription dose . For and all other parameters at reference conditions, TED dropped by 5% relative to when was 20% and by 2% relative to when or . varied more with than when , varying by up to 1% over and by less than 0.1% over . Under the reference conditions, was lower than by 0.5%. For the extreme and all other parameters at their reference values, setting resulted in dropping below by 2.5% and setting resulted in dropping below by 4%. For tumors with a of 16 min or greater and of 11 Gy, dropped below by 0.2% or less.

Conclusions: For prostate tumors receiving a reasonable percentage of 5% of their total dose from imaging beams, the theoretical drop in relative to was 0.5%. This loss could be accounted for during treatment planning by scaling the therapeutic dose by the expected sublethal damage repair factor . For nonprostate tumors with values of 11 Gy, the theoretical drop in relative to the reference TED was low at 0.2%.
Quantitative imaging in breast tomosynthesis and CT: Comparison of detection and estimation task performance
Authors: Richard Samuel , Samei Ehsan
Published: June 2010

Purpose

This work investigates a framework for modeling volumetric breast imaging to compare detection and estimation task performance and optimize quantitative breast imaging.

Methods

Volumetric reconstructions of a breast phantom, which incorporated electronic, quantum, and anatomical noise with embedded spherical lesions, were simulated over a range of acquisition angles varying from 4° to 204° with a constant total acquisition dose of 1.5 mGy. A maximum likelihood estimator was derived in terms of the noise power spectrum, which yielded figures of merit for quantitative imaging performance in terms of accuracy and precision. These metrics were computed for estimation of lesion area, volume, and location. Estimation task performance was optimized as a function of acquisition angle and compared to the performance of a more conventional lesion detection task.

Results

Results revealed tradeoffs between electronic, quantum, and anatomical noise. The detection of a 4 mm sphere was optimal at an acquisition angle of 84°, where reconstructed images using a smaller acquisition angle exhibited increased anatomical noise and reconstructed images using a larger acquisition angle exhibited increased quantum and electronic noise. For all estimation tasks, accuracy was found to be fairly constant as a function acquisition angle indicating adequate system calibration, whereas a more significant dependence on acquisition angle was observed for precision performance. Precision for the 2D area estimation task was optimal at , while precision of the 3D volume estimation task was optimal at larger angles . Precision for the localization task showed orientation dependence where localization was significantly inferior in the depth direction. Overall, precision for localization was optimal at larger angles (i.e., ) compared to the size estimation tasks. Results suggested that for quantitative imaging tasks, the acquisition angle should be larger than currently used in conventional breast tomosynthesis for lesion detection.

Conclusions

Analysis of quantitative imaging performance using Fourier‐based metrics highlights the difference between estimation and detection task in volumetric breast imaging and provides a meaningful framework for optimizing the performance of breast imaging systems for quantitative imaging applications.
Enhancements to commissioning techniques and quality assurance of brachytherapy treatment planning systems that use model‐based dose calculation algorithmsa)
Authors: Rivard Mark J. , Beaulieu Luc , Mourtada Firas
Published: June 2010

The current standard for brachytherapy dose calculations is based on the AAPM TG‐43 formalism. Simplifications used in the TG‐43 formalism have been challenged by many publications over the past decade. With the continuous increase in computing power, approaches based on fundamental physics processes or physics models such as the linear‐Boltzmann transport equation are now applicable in a clinical setting. Thus, model‐based dose calculation algorithms (MBDCAs) have been introduced to address TG‐43 limitations for brachytherapy. The MBDCA approach results in a paradigm shift, which will require a concerted effort to integrate them properly into the radiation therapy community. MBDCA will improve treatment planning relative to the implementation of the traditional TG‐43 formalism by accounting for individualized, patient‐specific radiation scatter conditions, and the radiological effect of material heterogeneities differing from water. A snapshot of the current status of MBDCA and AAPM Task Group reports related to the subject of QA recommendations for brachytherapy treatment planning is presented. Some simplified Monte Carlo simulation results are also presented to delineate the effects MBDCA are called to account for and facilitate the discussion on suggestions for (i) new QA standards to augment current societal recommendations, (ii) consideration of dose specification such as dose to medium in medium, collisional kerma to medium in medium, or collisional kerma to water in medium, and (iii) infrastructure needed to uniformly introduce these new algorithms. Suggestions in this Vision 20/20 article may serve as a basis for developing future standards to be recommended by professional societies such as the AAPM, ESTRO, and ABS toward providing consistent clinical implementation throughout the brachytherapy community and rigorous quality management of MBDCA‐based treatment planning systems.
A time‐domain wavelet‐based approach for fluorescence diffuse optical tomography
Authors: Ducros Nicolas , Da Silva Anabela , Dinten Jean‐Marc , Seelamantula Chandra Sekhar , Unser Michael , Peyrin Françoise
Published: June 2010

Purpose

In the context of fluorescence diffuse optical tomography, determining the optimal way to exploit the time‐resolved information has been receiving much attention and differentfeatures of the time‐resolved signals have been introduced. In this article, the authors revisit and generalize the notion of feature, considering the projection of the measurements onto some basis functions. This leads the authors to propose a novel approach based on the wavelet transform of the measurements.

Methods

A comparative study between the reconstructions obtained from the proposed wavelet‐based approach and the reconstructions obtained from the reference temporal moments is provided. An inhomogeneous cubic medium is considered. Reconstructions are performed from synthetic measurements assuming Poisson noise statistics. In order to provide fairly comparable reconstructions, the reconstruction scheme is associated with a particular procedure for selecting the regularization parameter.

Results

In the noise‐free case, the reconstruction quality is shown to be mainly driven by the number of selected features. In the presence of noise, however, the reconstruction quality depends on the type of the features. In this case, the wavelet approach is shown to outperform the moment approach. While the optimal time‐resolved reconstruction quality, which is obtained considering the whole set of time samples, is recovered using only eight wavelet functions, it cannot be attained using moments. It is finally observed that the time‐resolved information is of limited utility, in terms of reconstruction, when the maximum number of detected photons is lower than .

Conclusions

The wavelet approach allows for better exploiting the time‐resolved information, especially when the number of detected photons is low. However, when the number of detected photons decreases below a certain threshold, the time‐resolved information itself is shown to be of limited utility.