bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining Registered Nurses' Readiness for Evidence‐Based Practice
Authors: Thiel Linda , Ghosh Yashowanto
Published: December 2008

Background: As health care systems worldwide move toward instituting evidence‐based practice (EBP), its implementation can be challenging. Conducting a baseline assessment to determine nurses' readiness for EBP presents opportunities to plan strategies before implementation. Although a growing body of research literature is focused on implementing EBP, little attention has been paid to assessing nurses' readiness for EBP.

 Objective: The purpose of this study was to assess registered nurses' readiness for EBP in a moderate‐sized acute care hospital in the Midwestern United States before implementation of a hospital‐wide nursing EBP initiative.

 Design and Methods: A descriptive cross‐sectional survey design was used; 121 registered nurses completed the survey. The participants (n= 121) completed the 64‐item Nurses' Readiness for Evidence‐Based Practice Survey that allowed measurement of information needs, knowledge and skills, culture, and attitudes. Data were analyzed using descriptive statistics and a post hoc analysis.

 Results: The majority (72.5%) of respondents indicated that when they needed information, they consulted colleagues and peers rather than using journals and books; 24% of nurses surveyed used the health database, Cumulative Index to Nursing & Allied Health Literature (CINAHL®). The respondents perceived their EBP knowledge level as moderate. Cultural EBP scores were moderate, with unit scores being higher than organizational scores. The nurses' attitudes toward EBP were positive. The post hoc analysis showed many significant correlations.

 Conclusions and Implications: Nurses have access to technological resources and perceive that they have the ability to engage in basic information gathering but not in higher level evidence gathering. The elements important to EBP such as a workplace culture and positive attitudes are present and can be built upon. A “site‐specific” baseline assessment provides direction in planning EBP initiatives. The Nurses' Readiness for EBP Survey is a streamlined tool with established reliability and validity.
Erectile Dysfunction and Mental Health in a General Population of Older Men
Authors: Korfage Ida J. , Pluijm Saskia , Roobol Monique , Dohle Gert R. , Schröder Fritz H. , Essink-Bot Marie-Louise
Published: December 2008

Introduction

Erectile dysfunction (ED) is more prevalent with increasing age. Previous studies showed that ED was negatively associated with mental health (MH) in specific patient groups.

Aim

To examine the association, and potential mediating factors, between ED and MH in healthy elderly men.

Main Outcome Measures

ED was defined as (almost) always having problems in achieving or maintaining an erection if desired, or not being sexually active because of erectile problems. MH was assessed with 36-item Short-Form Health Survey scale MH5 with five items on, e.g., being happy or depressed (range 0–100). Potential mediators between ED and MH were satisfaction with and importance attached to sex life.

Methods

The study population consisted of a consecutive sample of 3,810 participants from the European Randomized Study of Screening for Prostate Cancer, aged 57–78 years, who had screened negatively for prostate cancer. Associations between ED, potential mediating factors, and MH were tested by analysis of variance and analysis of covariance.

Results

Covariance analysis, adjusted for age, comorbidity, and use of erectile aids, showed that men with ED had significantly lower MH scores (80.8 ± 1.2) than men without ED (83.7 ± 1.2; P < 0.001). ED was also associated with the potential mediator “satisfaction with sex life” but not with “importance attached to sex life.” Men with ED were significantly more often dissatisfied with their sex lives (P < 0.001). Adjustment for satisfaction with sex life, but not for importance attached to sex life, reduced the strength of the association (β value) between ED and poor MH from 2.88 to −0.84.

Conclusions

ED was associated with poorer MH. Satisfaction with sex life, but not importance attached to sex life, may play a mediating role in this association. These results suggest that if men with ED can be helped to be satisfied with their sex lives despite ED, MH can be preserved.
Sexual Function and Tunica Albuginea Wound Healing Following Penile Fracture: An 18-year Follow-Up Study of 352 Patients from Kermanshah, Iran
Authors: Zargooshi Javaad
Published: December 2008

Introduction

We present a study on the experiences of penile fracture in an Iranian population.

Aim

To determine the long-term outcome of penile fracture.

Methods

Between April 1990 and May 2008, 373 patients presented with clinical features suggestive of penile fracture. Of these, 11 declined surgery. The remaining 362 were operated upon using a degloving incision. Ten patients had venous injury and 352 had penile fracture. At follow-up visits, in addition to answering our questionnaire, the patients completed the International Index of Erectile Function (IIEF), Erection Hardness Grading Scale (EHGS), and global self-assessment of potency (GSAP). To enhance documentation and to promote transparency, with the patients’ permission, their full name and hospital chart number was sent to the journal.

Main Outcome Measures

Clinical findings and IIEF and EHGS scores.

Results

Mean patients’ age was 29.6 years. Mean duration of follow-up was 93.6 months. Diagnosis was solely clinical. At presentation, 278 (78.9%) reported no pain. Cavernosography, ultrasonography, or magnetic resonance imaging was not used in any of the patients. Penile fracture was due to taqaandan in 269 patients (76.4%). Patients were treated with surgical exploration and repair within 24 hours of admission, regardless of delay in presentation. A nodule was found at follow-up in 330 patients (93.7%). The painless, mostly proximal nodule was palpated at the floor of the corpora cavernosa, in a deep midline position above the corpus spongiosum. The non-expansive nodule was not associated with erectile dysfunction (ED) or Peyronie’s disease. Postoperative complications included mild penile pain in cold weather (two patients), transient wound edema (one patient), mild chordee (four patients), and occasional instability of the erect penis (one patient).

Postoperatively, of the 217 patients who had partners, 214 (98.6%) were potent. Mean IIEF ED domain score was 29.8 ± 1.1. The EHGS score was 4 in 203 and 3 in 11. The GSAP score was 0 in 204, 1 in 8, and 2 in 2. ED in the remaining three could not be explained by penile fracture. Of 10 nonoperated patients, eight (80%) developed ED.

Conclusion

Pain is rare in penile fracture. Postoperatively, almost all patients develop a permanent, inconsequential, fibrotic nodule. Our time-tested approach provided excellent long-term sexual function.
Development of a Bispecific Monoclonal Antibody to Pesticide Carbofuran and Triazophos Using Hybrid Hybridomas
Authors: Jin R.Y. , Guo Y.R. , Wang C.M. , Wu J.X. , Zhu G.N.
Published: December 2008

ABSTRACT:  A mouse hybrid hybridoma (tetradoma) was derived from fusing hybridomas producing monoclonal antibody to N‐methylcarbamate pesticide carbofuran with hybridomas producing monoclonal antibody to organophosphorus pesticide Triazophos. The prepared tetradoma line (12C1 to 2H12) secreted hybrid immunoglobulin exhibiting parental and bispecific binding characteristics. The effect of relevant physicochemical factors on the immunoassay based on the 12C1 to 2H12 bispecific monoclonal antibody had been studied to optimize the ELISA performance. The developed immunoassay showed that the detection limit (I20) were 0.36 and 1.89 ng/mL for triazophos and carbofuran, respectively, without obvious cross‐reactivity to other related compounds. Water samples spiked with triazophos at 0.5, 1, and 5 ng/mL or carbofuran at 5, 10, and 20 ng/mL were directly analyzed by the developed ELISA format. The mean recovery of triazophos and carbofuran were 108.1% and 107.5%, with variation coefficient of 15.9% and 17.7%, respectively.
PCR Detection and Microbiological Isolation of Salmonella spp. from Fresh Beef and Cantaloupes
Authors: Gallegos‐Robles M.A. , Morales‐Loredo A. , Álvarez‐Ojeda G. , Osuna‐García J.A. , Martínez I.O. , Morales‐Ramos L.H. , Fratamico P.
Published: December 2008

ABSTRACT:  Species belonging to the genus Salmonella are an important cause of enteric fevers, gastroenteritis, and septicemia, and the pathogens are commonly transmitted through contaminated food. In this study, polymerase chain reaction (PCR) amplification of a 287‐bp region of the invA gene was compared to a microbiological technique to determine the presence of Salmonella in retail beef and in cantaloupe rinse samples. Both methods showed the same level of sensitivity, detecting 1 CFU/25 g of meat after enrichment for 24 h at 42 °C. The presence of Salmonella was determined in 50 commercial top sirloin beef samples that were not artificially inoculated. Three samples were positive by the microbiological method, and these samples and an additional sample were positive by the PCR. Both methods were also used to test surface rinses of cantaloupes collected from 4 farms in Nayarit, Mexico. Salmonella was detected by the microbiological method in 9 of 20 samples (45%), whereas the pathogen was detected by the PCR in 11 samples (55%). This study demonstrates the utility of the PCR targeting the invA gene to determine the presence of Salmonella spp. in beef and cantaloupe samples.
Mutagenicity and Safety Evaluation of Water Extract of Fermented Toona Sinensis Roemor Leaves
Authors: Liao J.‐W. , Yeh J.‐Y. , Lin Y.‐C. , Wei M.‐M. , Chung Y.‐C.
Published: December 2008

ABSTRACT:  The purpose of this study was to evaluate the mutagenicity and safety of water extract of fermented Toona sinensis Roemor leaves (WFTS). The WFTS was prepared by fermenting Toona sinensis Roemor leaves anaerobically for 14 d, and then extracting with boiling water. The mutagenic effects of WFTS were investigated using Ames test. No mutagenicity was found toward all tester strains (Salmonella typhimurium TA98, TA100, TA102, TA1535). In the acute oral toxicity study, a single limit dose of 2.5 or 5 g/kg body weight (bw) WFTS was given to male Sprague‐Dawley (SD) rats, then the rats were observed for 14 d. No acute lethal effect at a maximal dose of 5 g/kg bw WFTS was observed in rats. In the subacute study, the male rats were administered daily by gavage at a dose of 0.5 or 1 g/kg bw/d of WFTS for 28 d. The results indicated that no significant toxic effect was found in the parameters of body and organ weight, as well as hematological, biochemical, urinary, and pathological parameters between control and the WFTS‐treated rats. The level of no observed adverse effect level (NOAEL) of WFTS in male rats was 1 g/kg bw for subacute toxicity study.
Frequency and distribution of Epstein–Barr virus infection and its association with P53 expression in a series of primary nodal non‐Hodgkin lymphoma patients from South India
Authors: SASIKALA P. S. , NIRMALA K. , SUNDERSINGH S. , MAHJI U. , RAJKUMAR T.
Published: December 2008

This study investigated the prevalence of Epstein–Barr virus (EBV) infection and its association with P53 expression in a panel of 87 previously untreated nodal non‐Hodgkin lymphomas (NHLs) from India. Polymerase chain reaction specific for Epstein Barr nuclear antigen 1 (EBNA1) and EBNA‐3C was performed on the lymphnode tissue DNA, while P53 expression was analyzed by immunohistochemistry. EBV, predominantly type A strain, was detected in 27/87 (31%) nodal lymphoid malignancies, 11/46 diffuse large B‐cell lymphomas, 6/17 follicular lymphoma, 4/6 anaplastic large cell lymphomas (ALCL), 5/11 peripheral T‐cell lymphomas (PTCL) and 1/7 lymphoblastic lymphomas. EBV infection was more frequently observed in a specific subset of nodal NHL, suggesting a causative role of EBV infection in the pathogenesis of ALCL and PTCL. There was no significant association between EBV and P53 expression in our series of NHL patients.
Production targets
Authors: Caruana Guillermo , Einav Liran
Published: December 2008

We analyze a dynamic model of quantity competition, where firms continuously adjust their quantity targets, but incur convex adjustment costs when they do so. Quantity targets serve as a partial commitment device and, in equilibrium, follow a hump‐shaped pattern. The final equilibrium is more competitive than in the static analog. We then use data on monthly production targets of the Big Three U.S. auto manufacturers and show a similar empirical hump‐shaped dynamic pattern. Taken together, this suggests that strategic considerations may play a role in setting auto production schedules, and that static models may misestimate the industry's competitiveness.
Differential expression of the genes involved in amino acids and nitrogen metabolisms during liver regeneration of mice
Authors: Yuan Yunsheng , Wu Xiaoying , Ou Qiuxiang , Gao Jin , Tennant Bud C. , Han Wei , Yu Yan
Published: December 2008

Aim:  Liver regeneration is a highly coordinated response to hepatic injury or resection that is controlled by the body's overall requirement for liver function. The level of circulating amino acids in blood increases after acute liver injury and administration of amino acid mixtures induces hepatic DNA replication. These findings suggest a close connection between amino acid metabolism and hepatic proliferation. However, the underlying molecular mechanisms have not been completely elucidated. Here, we applied a cDNA micro‐array technique to analyze expression profiles of the genes associated with nitrogen and amino acid metabolism during liver regeneration in mice following treatment with CCl4.

Methods:  Seventy‐nine genes were identified for their significantly altered expression patterns at different stages of liver damage and regeneration.

Results:  We observed that the numbers of down‐regulated genes were remarkably higher than that of up‐regulated genes at 1.5 days following carbon tetrachloride administration when hepatic DNA replication was most active, indicating the existence of a counter balance between cell proliferation and liver metabolism functions.

Conclusions:  Our results suggest that suppression of amino acids metabolism after acute liver injury results in the accumulation of amino acids in plasma that serves as a driving force for liver regeneration.
Stress Induced Permanent Magnetic Signal Degradation of Perpendicular Magnetic Recording System
Authors: Lee Sung-Chang , Hong Soo-Youl , Kim Na-Young , Ferber Joerg , Che Xiadong , Strom Brian D.
Published: December 2008

Model scratches of the size found in hard disk drives are produced under controlled conditions at a series of applied loads on both longitudinal magnetic recording (LMR) media and perpendicular magnetic recording (PMR) media using a diamond tip. The scratches are created at low speed, eliminating thermal considerations from the interpretation of the media response. Nanoindentations are produced as well. The scratches and indentations are characterized by atomic force microscope (AFM), magnetic force microscope (MFM), and also by the same magnetic reader and writer used in an integrated hard disk drive (HDD). A comparison of the response of PMR and LMR media shows the PMR media to have larger scratches and greater magnetic signal degradation than LMR media for a given scratch load. The extent of magnetic damage, as measured by MFM, is greater than the extent of surface mechanical damage, as measured by AFM. Analysis of scratches using the HDD reveals that the magnetic damage is irreversible and permanent damage in magnetic layer, which is confirmed by cross section transmission electron microscope image. The experiments reveal the mechanism for magnetic scratch erasure in the absence of thermal effects. This understanding is expected to lead to improved designs for mechanical scratch robustness of next-generation PMR media.
Numerical Approach for Solving Reynolds Equation With JFO Boundary Conditions Incorporating ALE Techniques
Authors: Schweizer Bernhard
Published: December 2008

Calculating the fluid flow and pressure field in thin fluid films, lubrication theory can be applied, and Reynolds fluid film equation has to be solved. Therefore, boundary conditions have to be formulated. Well-established mass-conserving boundary conditions are the Jakobsson–Floberg–Olsson (JFO) boundary conditions. A number of numerical techniques, which have certain advantages and certain disadvantages, have been developed to solve the Reynolds equation in combination with JFO boundary conditions. In the current paper, a further method is outlined, which may be a useful alternative to well-known techniques. The main idea is to rewrite the boundary value problem consisting of the Reynolds equation and the JFO boundary conditions as an arbitrary Lagrangian–Eulerian (ALE) problem. In the following, an ALE formulation of the Reynolds equation with JFO boundary conditions is derived. Based on a finite element implementation of the governing boundary value problem, numerical examples are presented, and pressure fields are calculated for a plain hydrodynamic journal bearing with an axial oil groove.
Evaluation of DLC Coatings for High-Temperature Foil Bearing Applications
Authors: Jahanmir Said , Heshmat Hooshang , Heshmat Crystal
Published: December 2008

Diamondlike carbon (DLC) coatings, particularly in the hydrogenated form, provide extremely low coefficients of friction in concentrated contacts. The objective of this investigation was to evaluate the performance of DLC coatings for potential application in foil bearings. Since in some applications the bearings experience a wide range of temperatures, tribological tests were performed using a single foil thrust bearing in contact with a rotating flat disk up to 500°C. The coatings deposited on the disks consisted of a hydrogenated diamondlike carbon film (H-DLC), a nonhydrogenated DLC, and a thin dense chrome deposited by the Electrolyzing™ process. The top foil pads were coated with a tungsten disulfide based solid lubricant (Korolon™ 900). All three disk coatings provided excellent performance at room temperature. However, the H-DLC coating proved to be unacceptable at 300°C due to lack of hydrodynamic lift, albeit the very low coefficient of friction when the foil pad and the disk were in contact during stop-start cycles. This phenomenon is explained by considering the effect of atmospheric moisture on the tribological behavior of H-DLC and using the quasihydrodynamic theory of powder lubrication.
Lubrication and Surface Properties of Roach Cuticle
Authors: Cooper R. , Lee H. , González J. M. , Butler J. , Vinson S. B. , Liang H.
Published: December 2008

Using atomic force microscopic and tribometry techniques, we characterized the cuticle surface of the American cockroach (Periplaneta americana) and studied lubrication properties of the wax developed to protect the cuticle. Experimental results showed that the roach cuticle had the ability to self-clean and that there were dimples on its surface to naturally disperse wax. It was observed by changes in friction that a thicker layer of wax was formed at the ventral abdomen, where dimples were present, than at the dorsal abdomen, which had no major features. The wax was found to have similar lubrication properties as commercial automobile oil, but with the ability to form thin films and repel dust. The dust repelling qualities make it a potential candidate for the lubrication of microelectromechanical system and nanoelectromechanical system devices that require supercleaning surfaces that is cost effective.
Experimental Study of a Creeping Polymer Sphere in Contact With a Rigid Flat
Authors: Ovcharenko A. , Halperin G. , Etsion I
Published: December 2008

The creep of a polymer sphere contacting a rigid flat under a constant normal load is investigated experimentally. An optical technique is used to observe in situ the evolution of the contact area while the increase of contact interference is measured simultaneously. The experimental results obtained with polytetrafluoroethylene (PTFE) spheres of different diameters pressed against a sapphire flat under different normal loads are presented, and the effect of sphere diameter and normal load on the creep of the contact parameters is discussed. The present experimental study validates recently published theoretical results of a contact model for a creeping sphere and a rigid flat showing that a universal similarity solution exists for the dimensionless creep interference and dimensionless creep contact area as functions of the dimensionless time.
Traction in EHL Line Contacts Using Free-Volume Pressure-Viscosity Relationship With Thermal and Shear-Thinning Effects
Authors: Kumar Punit , Khonsari M. M.
Published: December 2008

This paper investigates the traction behavior in heavily loaded thermo-elastohydrodynamic lubrication (EHL) line contacts using the Doolittle free-volume equation, which closely represents the experimental viscosity-pressure-temperature relationship and has recently gained attention in the field of EHL, along with Tait’s equation of state for compressibility. The well-established Carreau viscosity model has been used to describe the simple shear-thinning encountered in EHL. The simulation results have been used to develop an approximate equation for traction coefficient as a function of operating conditions and material properties. This equation successfully captures the decreasing trend with increasing slide to roll ratio caused by the thermal effect. The traction-slip characteristics are expected to be influenced by the limiting shear stress and pressure dependence of lubricant thermal conductivity, which need to be incorporated in the future.
A simplified method of four‐dimensional dose accumulation using the mean patient density representation
Authors: Glide‐Hurst Carri K. , Hugo Geoffrey D. , Liang Jian , Yan Di
Published: December 2008

The purpose of this work was to demonstrate, both in phantom and patient, the feasibility of using an average 4DCT image set (AVG‐CT) for 4D cumulative dose estimation. A series of 4DCT numerical phantoms and corresponding AVG‐CTs were generated. For full 4D dose summation, static dose was calculated on each phase and cumulative dose was determined by combining each phase's static dose distribution with known tumor displacement. The AVG‐CT cumulative dose was calculated similarly, although the same AVG‐CT static dose distribution was used for all phases (i.e., tumor displacements). Four lung cancer cases were also evaluated for stereotactic body radiotherapy and conformal treatments; however, deformable image registration of the 4DCTs was used to generate the displacement vector fields (DVFs) describing patient‐specific motion. Dose discrepancy between full 4D summation and AVG‐CT approach was calculated and compared. For all phantoms, AVG‐CT approximation yielded slightly higher cumulative doses compared to full 4D summation, with dose discrepancy increasing with increased tumor excursion. In vivo, using the AVG‐CT coupled with deformable registration yielded clinically insignificant differences for all GTV parameters including the minimum, mean, maximum, dose to 99% of target, and dose to 1% of target. Furthermore, analysis of the spinal cord, esophagus, and heart revealed negligible differences in major dosimetric indices and dose coverage between the two dose calculation techniques. Simplifying 4D dose accumulation via the AVG‐CT, while fully accounting for tumor deformation due to respiratory motion, has been validated, thereby, introducing the potential to streamline the use of 4D dose calculations in clinical practice, particularly for adaptive planning purposes.
The future of heavy ion radiotherapy
Authors: Jäkel Oliver , Karger Christian P. , Debus Jürgen
Published: December 2008

Currently, there is an increasing interest in heavy ion radiotherapy (RT) and a number of new facilities are being installed in Europe and Japan. This development is accompanied by intensive technical, physical, and clinical research. The authors identify six research fields where progress is likely and propose a thesis on the expected achievements for each of the fields: (1) Synchrotrons with active energy variation and three‐dimensional beam scanning will be the standard in ion beam RT. (2) Common standards for precise measurement, prescription, and reporting of dose will be available. (3) Intensity‐modulated particle therapy will be state‐of‐the‐art. (4) Time‐adaptive treatments of moving targets will be feasible. (5) Therapeutic effectiveness of heavy ions will be known for the most important indications while cost effectiveness will remain to be shown. (6) The potential of high‐linear energy transfer radiation will be known. The rationale for each of these theses is described.
Determination of the prescription dose for biradionuclide permanent prostate brachytherapy
Authors: Nuttens V. E. , Lucas S.
Published: December 2008

A model based on the linear quadratic model that has been corrected for repopulation, sublethal cell damage repair, and RBE effect has been used to determine the prescription dose for prostate permanent brachytherapy using seeds loaded with a mixture of and or a mixture of and . The prescription dose was determined by comparing the tumor cell survival fractions between the considered biradionuclide seed implant and one monoradionuclide seed implant chosen from , , and . Prostate edema is included in the model. The influence of the value of the radiobiological parameters and RBE were also investigated. Two mixtures of radionuclides were considered: and , where the subscripts indicate the fractions of total initial internal activity in the biradionuclide seed. These fractions were selected in order to obtain a dose distribution that lies between that of and . As expected, the computed prescription dose values are dependent on the model parameters (edema half‐life and magnitude, radiobiogical parameters, and RBE). The radionuclide used as a benchmark also has a strong impact on the derived prescribed dose. The large uncertainties in the radiobiological parameters and RBE values produce big errors in the computed prescribed dose. Averaged over the range of all the parameters and depending on the radionuclide used as a benchmark (in subscript), the derived prescription dose for the first mixture (PdI) would be: and ; and and for the PdCs mixture. The uncertainties could be reduced if the radiobiological parameters and RBE value were known more accurately. However, as edema characteristics are patient dependent and can be obtained only after the treatment, an unpredictable error is unavoidable.
Texture classification‐based segmentation of lung affected by interstitial pneumonia in high‐resolution CT
Authors: Korfiatis Panayiotis , Kalogeropoulou Christina , Karahaliou Anna , Kazantzi Alexandra , Skiadopoulos Spyros , Costaridou Lena
Published: December 2008

Accurate and automated lung field (LF) segmentation in high‐resolution computed tomography (HRCT) is highly challenged by the presence of pathologies affecting lung borders, also affecting the performance of computer‐aided diagnosis (CAD) schemes. In this work, a two‐dimensional LF segmentation algorithm adapted to interstitial pneumonia (IP) patterns is presented. The algorithm employs ‐means clustering followed by a filling operation to obtain an initial LF order estimate. The final LF border is obtained by an iterative support vector machine neighborhood labeling of border pixels based on gray level and wavelet coefficient statistics features. A second feature set based on gray level averaging and gradient features was also investigated to evaluate its effect on segmentation performance of the proposed method. The proposed method is evaluated on a dataset of 22 HRCT cases spanning a range of IP patterns such as ground glass, reticular, and honeycombing. The accuracy of the method is assessed using area overlap and shape differentiation metrics (, , and ), by comparing automatically derived lung borders to manually traced ones, and further compared to a gray level thresholding‐based (GLT‐based) method. Accuracy of the methods evaluated is also compared to interobserver variability. The proposed method incorporating gray level and wavelet coefficient statistics demonstrated the highest segmentation accuracy, averaged over left and right LFs (, , , and ), which is statistically significant (two‐tailed student's test for paired data, ) with respect to all metrics considered as compared to the proposed method incorporating gray level averaging and gradient features (, , , and ) and the GLT‐based method (, , , and ). The performance of the three segmentation methods, although decreased as IP pattern severity level (mild, moderate, and severe) was increased, did not demonstrate statistically significant difference (two‐tailed student's test for unpaired data, for all metrics considered). Finally, the accuracy of the proposed method, based on gray level and wavelet coefficient statistics ranges within interobserver variability. The proposed segmentation method could be used as an initial stage of a CAD scheme for IP patterns.
Phantom evaluation of a commercially available three modality image guided radiation therapy system
Authors: Ploquin Nicolas , Rangel Alejandra , Dunscombe Peter
Published: December 2008

The authors describe a detailed evaluation of the capabilities of imaging and image registration systems available with Varian linear accelerators for image guided radiation therapy (IGRT). Specifically, they present modulation transfer function curves for megavoltage planar, kilovoltage (kV) planar, and cone beam computed tomography imaging systems and compare these with conventional computed tomography. While kV planar imaging displayed the highest spatial resolution, all IGRT imaging techniques were assessed as adequate for their intended purpose. They have also characterized the image registration software available for use in conjunction with these imaging systems through a comprehensive phantom study involving translations in three orthogonal directions. All combinations of imaging systems and image registration software were found to be accurate, although the planar kV imaging system with automatic registration was generally superior, with both accuracy and precision of the order of 1 mm, under the conditions tested. Based on their phantom study, the attainable accuracy for rigid body translations using any of the features available with Varian equipment will more likely be limited by the resolution of the couch readouts than by inherent limitations in the imaging systems and image registration software. Overall, the accuracy and precision of currently available IGRT technology exceed published experience with the accuracy and precision of contouring for planning.
A Comparison of daily megavoltage CT and ultrasound image guided radiation therapy for prostate cancer
Authors: Peng Cheng , Kainz Kristofer , Lawton Colleen , Li X. Allen
Published: December 2008

In order to quantify the differences between ultrasound‐imaging and megavoltage‐CT (MVCT) daily prostate localization in prostate‐cancer radiotherapy and their dosimetric impacts, daily shifts were analyzed for a total of 140 prostate cancer patients; 106 positioned using ultrasound‐based imaging [B‐mode Acquisition and Targeting (BAT)], and 34 using the MVCT from a TomoTherapy Hi‐Art 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 mean shifts and standard deviations along the R/L, S/I, and A/P directions were , , and for BAT localizations and , , and for MVCT localizations, respectively. 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 planning target volume margins in the A/P direction estimated to account for daily variations were 8.81 and based on MVCT and BAT data, respectively. There was no statistically significant difference in the daily prostate movement pattern between the first few fractions and the remaining fractions. Dosimetric comparison of MVCT and BAT prostate alignments was performed for seven fractions from a patient. The degradation from the plan caused by the MVCT alignment is trivial, while that by BAT is substantial. 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, negatively impacting prostate dose coverage and rectal sparing.
Low dose megavoltage cone beam computed tomography with an unflattened 4 MV beam from a carbon target
Authors: Faddegon Bruce A. , Wu Vincent , Pouliot Jean , Gangadharan Bijumon , Bani‐Hashemi Ali
Published: December 2008

Megavoltage cone beam computed tomography (MVCBCT) is routinely used for visualizing anatomical structures and implanted fiducials for patient positioning in radiotherapy. MVCBCT using a 6 MV treatment beam with high atomic number target and flattening filter in the beamline, as done conventionally, has lower image quality than can be achieved with a MV beam due to heavy filtration of the low‐energy bremsstrahlung. The unflattened beam of a low target has an abundance of diagnostic energy photons, detected with modern flat panel detectors with much higher efficiency given the same dose to the patient. This principle guided the development of a new megavoltage imaging beamline (IBL) for a commercial radiotherapy linear accelerator. A carbon target was placed in one of the electron primary scattering foil slots on the target‐foil slide. A PROM on a function controller board was programed to put the carbon target in place for MVCBCT. A low accelerating potential of 4.2 MV was used for the IBL to restrict leakage of primary electrons through the target such that dose from x rays dominated the signal in the monitor chamber and the patient surface dose. Results from phantom and cadaver images demonstrated that the IBL had much improved image quality over the treatment beam. For similar imaging dose, the IBL improved the contrast‐to‐noise ratio by as much as a factor of 3 in soft tissue over that of the treatment beam. The IBL increased the spatial resolution by about a factor of 2, allowing the visualization of finer anatomical details. Images of the cadaver contained useful information with doses as low as 1 cGy. The IBL may be installed on certain models of linear accelerators without mechanical modification and results in significant improvement in the image quality with the same dose, or images of the same quality with less than one‐third of the dose.
An EM approach to MAP solution of segmenting tissue mixture percentages with application to CT‐based virtual colonoscopy
Authors: Wang Su , Li Lihong , Cohen Harris , Mankes Seth , Chen John J. , Liang Zhengrong
Published: December 2008

Electronic colon cleansing (ECC) is an emerging technique developed to segment the colon lumen from a patient's abdominal computed tomography colonography (CTC) images. However, the residue stool and fluid tagged by contrast materials as well as mixed tissue distribution with partial volume (PV) effect impose several challenges for ECC, resulting in incomplete and overcomplete cleansings. To address the PV effect, this work investigated an improved maximum a posteriori expectation‐maximization (MAP‐EM) image segmentation algorithm which simultaneously estimates tissue mixture percentages within each image voxel and statistical model parameters for the tissue distribution. Given the segmented tissue mixture information beyond the image voxel level, not only the PV effect has been satisfactorily addressed as a particular case of tissue mixture problem, but incomplete and overcomplete ECC causes could also be maximally avoided. For clinical application to CTC that involves several issues transferring from theoretical analysis to practical validation, an innovative initialization procedure and refined estimation strategy were proposed to build an ECC pipeline based on the MAP‐EM segmentation. The pipeline was evaluated based on 52 patient CTC studies, downloaded from the website of the Virtual Colonoscopy Screening Resource Center, by two radiologists. A noticeable improvement over the authors’ previous ECC pipeline was documented. Several typical cases were also presented to show visually the improved performance of the presented ECC pipeline.
A new weighting function to achieve high temporal resolution in circular cone‐beam CT with shifted detectors
Authors: Maaß Clemens , Knaup Michael , Lapp Robert , Karolczak Marek , Kalender Willi A. , Kachelrieß Marc
Published: December 2008

The size of the field of measurement (FOM) in computed tomography is limited by the size of the x‐ray detector. In general, the detector is mounted symmetrically with respect to the rotation axis such that the transaxial FOM diameter approximately equals the lateral dimensions of the detector when being demagnified to the isocenter. To enlarge the FOM one may laterally shift the detector by up to 50% of its size. Well‐known weighting functions must then be applied to the raw data prior to convolution and backprojection. In this case, a full scan or a scan with more than 360° angular coverage is required to obtain complete data. However, there is a small region, the inner FOM, that is covered redundantly and where a partial scan reconstruction may be sufficient. A new weighting function is proposed that allows one to reconstruct partial scans in that inner FOM while it reconstructs full scan or overscan data for the outer FOM, which is the part that contains no redundancies. The presented shifted detector partial scan algorithm achieves a high temporal resolution in the inner FOM while maintaining truncation‐free images for the outer part. The partial scan window can be arbitrarily shifted in the angular direction, what corresponds to shifting the temporal window of the data shown in the inner FOM. This feature allows for the reconstruction of dynamic CT data with high temporal resolution. The approach presented here is evaluated using simulated and measured data for a dual source micro‐CT scanner with rotating gantry.
Accuracy of EGSnrc calculations at energies for the response of ion chambers configured with various wall materials and cavity dimensions
Authors: La Russa Daniel J. , Rogers D. W. O.
Published: December 2008

In this investigation, five experimental data sets are used to evaluate the ability of the EGSnrc Monte Carlo code to calculate the change in chamber response associated with changes in wall material and cavity dimension atenergies. Calculations of the ratios of response per unit mass of air as a function of cavity volume for walls ranging from polystyrene to lead are generally within 1%–3% of experiments. A few exceptions, which are discussed, include 20%–30% discrepancies with experiments involving lead‐walled chambers used by Attix et al. [J. Res. Natl. Bur. Stand. 60, 235–243 (1958)] and Cormack and Johns [Radiat. Res. 1, 133–157 (1954)], and 5% discrepancies for the graphite chamber of Attixet al.(relative to data for other wall materials). Simulations of the experiment by Whyte [Radiat. Res. 6, 371–379 (1957)], which varied cavity air pressure in a large cylindrical chamber, are generally within 0.5% (wall/electrode materials ranging from beryllium to copper). In all cases, the agreement between measurements and EGSnrc calculations is much better when the response as a function of cavity height or air pressure is considered for each wall material individually. High‐precision measurements [Burns et al., Phys. Med. Biol. 52, 7125–7135 (2007)] of the response per unit mass as a function of cavity height for a graphite chamber are also accurately reproduced, and validate previous tests of the transport mechanics of EGSnrc. Based on the general agreement found in this work between corresponding experimental results and EGSnrc calculations it can be concluded that EGSnrc can reliably be used to calculate changes in response with changes in various wall materials and cavity dimensions atenergies within a accuracy of a few percent or less.
Dose calculation with respiration‐averaged CT processed from cine CT without a respiratory surrogate
Authors: Riegel Adam C. , Ahmad Moiz , Sun Xiaojun , Pan Tinsu
Published: December 2008

Dose calculation for thoracic radiotherapy is commonly performed on a free‐breathing helical CT despite artifacts caused by respiratory motion. Four‐dimensional computed tomography (4D‐CT) is one method to incorporate motion information into the treatment planning process. Some centers now use the respiration‐averaged CT (RACT), the pixel‐by‐pixel average of the ten phases of 4D‐CT, for dose calculation. This method, while sparing the tedious task of 4D dose calculation, still requires 4D‐CT technology. The authors have recently developed a means to reconstruct RACT directly from unsorted cine CT data from which 4D‐CT is formed, bypassing the need for a respiratory surrogate. Using RACT from cine CT for dose calculation may be a means to incorporate motion information into dose calculation without performing 4D‐CT. The purpose of this study was to determine if RACT from cine CT can be substituted for RACT from 4D‐CT for the purposes of dose calculation, and if increasing the cine duration can decrease differences between the dose distributions. Cine CT data and corresponding 4D‐CT simulations for 23 patients with at least two breathing cycles per cine duration were retrieved. RACT was generated four ways: First from ten phases of 4D‐CT, second, from 1 breathing cycle of images, third, from 1.5 breathing cycles of images, and fourth, from 2 breathing cycles of images. The clinical treatment plan was transferred to each RACT and dose was recalculated. Dose planes were exported at orthogonal planes through the isocenter (coronal, sagittal, and transverse orientations). The resulting dose distributions were compared using the gamma index within the planning target volume (PTV). Failure criteria were set to . A follow‐up study with 50 additional lung cancer patients was performed to increase sample size. The same dose recalculation and analysis was performed. In the primary patient group, 22 of 23 patients had 100% of points within the PTV pass criteria. The average maximum and mean indices were very low (well below 1), indicating good agreement between dose distributions. Increasing the cine duration generally increased the dose agreement. In the follow‐up study, 49 of 50 patients had 100% of points within the PTV pass the criteria. The average maximum and mean indices were again well below 1, indicating good agreement. Dose calculation on RACT from cine CT is negligibly different from dose calculation on RACT from 4D‐CT. Differences can be decreased further by increasing the cine duration of the cine CT scan.
DOT guided fluorescence molecular tomography of arbitrarily shaped objects
Authors: Tan Yiyong , Jiang Huabei
Published: December 2008

The authors demonstrate an approach for truly quantitative three‐dimensional fluorescence molecular tomography (FMT) of arbitrarily shaped objects where the distribution of optical properties is obtained using diffuse optical tomography (DOT). The method is tested and evaluated using phantom geometries mimicking mouse anatomic structures. The experiments were conducted using the authors’ optical‐fiber‐free, multiangle transmission system. The results indicate that with the knowledge of optical property distribution, the accuracy of the recovered fluorophore absorption coefficient of indocyanine green is improved significantly over that without such a priori information using the authors’ finite element reconstruction approach. In particular, the absolute value of from their DOT guided FMT is quantitatively consistent with that obtained with spectroscopic methods.
Anniversary Paper: A sampling of novel technologies and the role of medical physicists in radiation oncology
Authors: Balter Stephen , Balter James M.
Published: December 2008

Physicists have and continue to play a major role in the creation and introduction of novel technology into medical care. This review covers some of the highlights of contributions of medical physicists to the field of radiation oncology during the history of the AAPM. While not comprehensive, the broad scope of developments and their impact hints at the importance of the medical physicist in advancing the field in the past, present, and future.
Multiphasic contrast injection for improved precision of parameter estimates in functional CT
Authors: Kim S. M. , Cho Y. B. , Haider M. A. , Milosevic M. , Yeung I. W. T.
Published: December 2008

Contrast injection protocol is known to affect the estimation of kinetic parameters in functional CT. A novel method is proposed to maximize the precision of parameter estimates by modulating the contrast injection scheme. The method models the intravenous contrast bolus to be dispersed by a “patient function” to give rise to the arterial input function, which, in turn, carries the contrast agent to tissue leading to contrast enhancement. The covariance matrix analysis was applied to calculate the uncertainty of parameter estimates as the coefficients of variation (CV) in the adiabatic tissue homogeneity (ATH), two‐compartment, and the modified Kety model in which tumor pathophysiology is modeled. An optimization scheme was used to determine the optimal injection protocol which would minimize the CV of a particular kinetic parameter. For clinical utility, a recommended injection protocol was suggested from a statistical analysis with the optimal injection protocols obtained from the first group of 12 patients with cervix cancer. The efficacy of the recommended injection protocol was tested with a second group of 12 patients. In addition, the robustness of the recommended injection protocol to longitudinal study has been investigated in the presence of variations in arterial input function and tumor pathophysiology. Based on the data of the second group of patients, and using the ATH model, the recommended biphasic injection of two boluses improves the precision in the estimation of blood flow and mean transit time (MTT), by 36.9% and 38.4%, respectively, compared to the standard uniphasic injection protocol in the CV. However, measurement of the permeability surface area product and extravascular extracellular space volume favors a single fast bolus of the same contrast amount. The two‐compartment model and the modified Kety model also benefited from the single fast bolus. The effect of variation in the arterial input function and tumor pathophysiology on the applicability of the recommended injection was also investigated. Based on computer simulation for a range of variations in the arterial input function and pathophysiology, the recommended biphasic injection was found to improve the precision in blood flow and MTT estimates by 31.4% and 36.5% on average, respectively, compared to the uniphasic injection.