bluuebunny/crossref_metadata_2025 huggingface dataset:
Aspects of the morphology and ecology of two British tubificids (Oligochaeta)
Authors: Bird G. J. , Ladle M.
Published: December 2010

Two poorly known tubificids have recently been identified from rivers and streams in Britain. Examination of new specimens of Haber simsi (=Peloscolex simsi Brinkhurst, 1966) has shown that the original description is essentially correct. This tubificid shows superficial similarities to Tubifex ignotus and a comparison of the chactae is made. H. simsi has very low population densities in Bere Stream (maximum of three individuals in forty cores of 0.002 m2 area), and mature and breeding individuals have been found from June to November. A form of the genus Limnodrilus, superficially similar to Limnodrilus hoff‐meisteri, with a scalloped margin on the penis tube hood has been recorded from several sites in Britain. The mean ratio of length of penis tube/base width is 6.8±0.3 (x̄±s.d.) compared with 9.6±0.2 of L. hoffmeisteri. The chaetae of this type closely resemble those of Limnodrilus claparedeianus.
The ultrastructure of the sperm funnel and non‐glandular vas deferens of Tubifex tubifex (Annelida: Oligochaeta)
Authors: Fleming T. P.
Published: December 2010

The sperm funnel, which consists of a ciliated epithelium bounded by a flattened peritoneum, is characterized by a “halo” of vertically orientated spermatozoa. The spermatozoa nuclei terminate within the ciliary zone of the funnel but junctional attachments between sperm and cilia have not been observed. The epithelial cells synthesize an electron dense secretion at centrally placed Golgi cisternae. The secretion tends to accumulate within the distal cytoplasm and appears to be released at the cell apex. It is hypothesized that the secretion, which is exclusive to this region of the male duct, may function as an attractant to newly differentiated spermatozoa. The active exchange of material between the funnel epithelium and the surrounding coelomic fluid is further indicated by the accumulation of mitochondria within the distal cytoplasm and the presence of microvilli and pinocytotic profiles, in addition to cilia, along the apical plasma membrane.

The non‐glandular vas deferens, consisting of thin and thick walled regions, is highly coiled and is constructed of ring‐shaped epithelial cells invested in longitudinal muscle and peritoneum. The thin walled duct contains spirally placed cilia which possess multiple rootlets orientated at an acute angle to the lumen surface. Aggregates of 5 nm micro‐filaments encircle the cell and are inserted onto infoldings of the basal (outer) plasma membrane enclosing lateral extensions of the basal lamina. Microfilaments of comparable size and orientation also occur in the distal (luminal) epithelial cytoplasm of the thick walled duct and are inserted onto neighbouring regions of the lateral plasma membrane. The vas deferens microfilaments are interpreted as contractile units assisting in the passage of spermatozoa along the duct at the time of copulation.

In the thick walled duct, cell apices protrude into the lumen resulting in a crenellated profile in longitudinal section. Lateral plasma membranes contain extensive radial folds or “pleats”. The lumen surface is unciliated but is characterized by laminate cytoplasmic projections which are loosely organized into groups displaying uniform orientation. The ultrastructural features of the thick walled vas deferens indicate a role in fluid transportation which is discussed with reference to sperm transmission.
Scavenging of mammal carcases by birds in West Scotland
Authors: Hewson Raymond
Published: December 2010

In a series of preference tests with wild birds, Buzzards, Great black‐backed gulls and Hooded crows preferred rabbit to sheep or lamb. Ravens preferred rabbit to lamb but not to sheep. It was likely that breaking of carcases by foxes and badgers assisted scavenging birds. Territoriality and inter‐specific competition limited scavenging. Buzzards were dominant at carcases, then Great black‐backs, then (probably) Ravens, with Hooded crows subordinate to all three. Buzzards fed singly but Great black‐backs and Crows profited by feeding as pairs. Birds ate large quantities of carrion, often on successive days, and Hooded crows hoarded carrion.
Allometry of the leg muscles of mammals
Authors: Alexander R. McN. , Jayes A. S. , Maloiy G. M. O. , Wathuta E. M.
Published: December 2010

Measurements have been made of the leg muscles of mammals ranging from shrews Sorex to an elephant Loxodonta. Allometric equations based on body mass have been calculated for muscle masses, fibre lengths and moment arms and the thickness of a tendon, in several groups of mammals. Departures from geometric similarity in mammals in general (excluding bipedal hoppers) are noted and discussed. Differences between primates; fissipedes, bovids and bipedal hoppers are also demonstrated.
Effect of respiratory acidosis on body movements in the chronically instrumented fetal lamb
Authors: Bessho Takefumi , Taira Shozo , Koyama Koji
Published: December 2010

Background. In respirator) acidosis, it is reported that the fetal breathing movements as well as the fetal heart rate variability increase. As the increase of these two kinds of fetal activities is occasionally observed in normal conditions, it is difficult to distinguish respiratory acidosis and normal conditions by mere observation of these activities. As the third diagnostic variable, if a different feta! body movement response to respiratory acidosis is observed, it would be helpful for better diagnosis in combination with other activities. We investigated the effect of respiratory acidosis on body movements in the chronically instrumented fetal lamb. Methods. A total of four experiments were performed on four ewes. Respiratory acidosis was induced in the fetus by maternal administration of a high carbon dioxide gas mixture for 1 hour. Fetal body movements were observed by real‐time ultrasonography. The frequency of body movements was expressed as the number of each movement in a 30‐minute period. Results. The mean pCO2 increased from 42.9 ± 4.9 mmHg to 62.9 ± 14.8 mmHg. and the mean pH decreased from 7.368 ± 0.04 to 7.209 ± 0.04 during the experiments. The frequency of fetal body movements significantly decreased. The percentage reduction of these movements of the same fetus during the experiments as compared to the control periods were as follows; the high‐frequency movements, 89.2 ± 9.7%; the rolling movements. 55.6 ± 13.5%; the simple movements. 78.3 ± 18.4%. Conclusions Normoxemic respiratory acidosis, which is reported to increase fetal breathing movements, caused a marked reduction in fetal body movements. These findings suggest that the ultrasonographic dissociation of fetal behaviors in respiratory acidosis would be potentially helpful in the diagnosis of impending fetal jeopardy.
Enhanced expression of cytokines may play a fundamental role in the mechanisms of immunologically mediated recurrent spontaneous abortion
Authors: Shaarawy Mohamed , Nagui Abdel‐Rehim
Published: December 2010

Objectives. To determine circulatory levels of 1L‐1 β, TNFα, IFN‐γ and Neopterin in immunologically mediated recurrent abortion. Design. Blood samples were withdrawn from both groups of first trimester recurrent abortion and controls for the determination of serum IL‐lβ, TNFα, IFN‐γ by the corresponding IRMA and serum neopterin by a double antibody RIA. Setting. Department of Obstetrics & Gynecology, Cairo University Hospitals. Patients. Thirty pregnant women in their first trimester who presented with inevitable abortion with history of at least 3 prior spontaneous consecutive abortions, in addition to twenty‐three pregnant women in their first trimester presented with their first miscarriage due to chromosomal anomalies (controls). Every attempt was made to eliminate the possible known contributing factors of recurrent abortion except for the presence of cervical mucus sperm antibodies which were present in 24 out of 30 cases. Interventions. None. Results. Serum ILiβ, TNFα and IFN‐γ levels of the abortion group were significantly elevated when compared to the corresponding levels of controls. The incidence of abnormal high values of these cytokines varied between 40 to 70%. There was no significant difference of serum neopterin between abortion and control groups. The increase of IFNγ, the most active principle inducing neopterin release, was below the concentration needed for neopterin stimulation. Conclusions. In view of the proven findings that cytokines do have detrimental effects on implantation, trophoblast proliferation, embryo development and fetal survival, our results suggest a potential mechanism of immunologic recurrent abortion which involves the secretion of IL‐iβ. TNFα, IFNγ and other cytokines by activated endometrial lymphocytes and macrophages in response to either trophoblast or sperm antigens and these cytokines could partially defuse or penetrate into the systemic circulation.
Nitric oxide metabolite in pregnant women before and after delivery
Authors: Okutomi Toshiyuki , Nomoto Keiko , Nakamura Kunie , Goto Fumio
Published: December 2010

Background. During pregnancy, systemic vascular resistance as well as vascular sensitivity to vasoconstrictive agents decreases in pregnant women. Methods and materials. The vascular resistance of the fetus is also maintained in the presence of low blood pressure. We believe that the main factors in this phenomenon are nitric oxide (NO), along with prostaglandin. NO is an unstable compound with a short half‐life; it is easily converted to nitrite (NO2) and nitrate (NO3). Since NO cannot be precisely quantified, we measured the NO2 concentration in maternal blood just before and after delivery and compared it with the values of non‐pregnant women. Results. NO2. concentrations in the 13 women who received cesarean deliveries under epidural anesthesia were not significantly changed by the anesthesia. Before anesthesia the NO2 concentration was 216 ± 115 pmol/mg protein, and after the induction of anesthesia, but before surgery, it was 218 ± 112 pmol/mg protein. The NO2 concentration then fell significantly after the surgery to 174 ± 75 pmol/mg protein (P < 0.05). In addition, after vaginal delivery, in 17 other patients we observed marked decreases in NO2 concentration, falling from 160 ± 82 to 125 ± 61 pmol/mg protein (p < 0.05). These values were significantly higher than those of nonpregnant women (3.4 ± 2.1 μM. 33 ± 22 pmol/mg protein) (p < 0.000I) Conclusion. These results suggest that NO contributes to the low vascular resistance observed in the mother and fetus during pregnancy.
Treatment‐related and treatment‐independent deliveries among infertile couples, a long‐term follow‐up
Authors: Sundström Inger , Ildgruben Anna , Högberg Ulf
Published: December 2010

Background. The aim of this hospital based long‐term follow‐up study was to further elucidate resolved and unresolved infertility in relation to risk factors and perinatal outcome considering treatment‐related and treatment independent pregnancies.

Methods. The study included all couples attending the out‐patient clinic of the Department of Gynecology in Umeå due to failure to initiate a pregnancy after at least 12 months during the period 1.1.1980 31.12. 1989. Data from the Swedish Medical Birth Registry consisting of all registered births during 1.1.1980 31.12. 1992 was linked to establish the number of children born.

Results. Six hundred and ninety‐one couples were analyzed, out of which 42% had a delivery outcome. Of these women. 53% conceived in relation to given treatment whereas 47% conceived treatment‐independently. Women with ovulatory disorder had a cumulative delivery rate of 82%. whereas those with unexplained infertility and tubo‐peritoneal pathology displayed delivery rates of 57% and 31% respectively. Duration of infertility >3 years was the major negative prognostic factor among patients with unexplained infertility. The frequency of premature deliveries, low birth weight and perinatal mortality was increased among patients with treatment related pregnancies.

Conclusion. For ovulatory disorders the prognosis for a resolved infertility is good. The results among patients with tubo‐peritoneal pathology emphasizes the need of in vitro fertilization in modern treatment of infertility. Unexplained infertility is accompanied with a high rate of spontaneous pregnancies but prolonged duration is a negative prognostic factor for these patients. Irrespective of diagnosis, the perinatal outcome is worse in patients with treatment‐related pregnancies.
A medical approach to management of spontaneous abortion using misoprostol
Authors: Chung Tony , Leung Peter , Cheung Lai Ping , Haines Christopher , Chang Allan M Z
Published: December 2010

Background. To compare a 48 hour non surgical policy in the management of spontaneous abortion with a policy of routine, universal uterine curettage.

Methods. A prospective, observational study on 354 women admitted to hospital with spontaneous abortion. Of these, 225 who had retained products of conception were treated with misoprostol for up to 48 hours after 101 were excluded because they had an empty uterus on transvaginal scan (TVS) and another 28 women because they were unsuitable for conservative management. Follow‐up was conducted over a 3 week period to assess morbidity. A reference group of 137 women, all of whom had an evacuation of retained products of cenception (ERPC) as a routine after they had a TVS documenting retained products of conception (POCs), was used for comparison.

Results. Evacuation of the uterus occurred within 24 hours in 107 women and in 148 at 48 hours after misoprostol treatment was started. There were three uterine curettages up to 14 days after discharge from hospital for persistent bleeding and two cases of pelvic infection. An ectopic pregnancy was diagnosed at follow‐up in one woman. In the reference group, there were nine women who had complications, four requiring another ERPC and five had infection, an overall complication rate of 6.6% in the reference group and 1.7 % in the protocol treatment group.

Conclusion A 48 hour regimen using transvaginal ultrasound and misoprostol for the management of spontaneous abortion was successful in avoiding surgery in 249 out of a possible 354 (70.6″ i) women with spontaneous abortion, with a low rate of subsequent morbidity.
The influence of thrombotic risk factors when oral contraceptives are prescribed a control‐only study
Authors: Lidegaard øjvind
Published: December 2010

Objectives. The aim of this study was to assess preferential prescribing of OC according to different thrombotic risk factors.

Material and methods. The control group in an ongoing Danish case‐control study on stroke and OCs collected in 1994 and 1995 underwent a control‐only analysis concerning the occurrence of thrombotic risk factors among users of different types of OC. Specific attention was given to differences between OCs with second and third generation progestagens. The association between specific risk factors and the pill types was assessed crude and after multivariate analysis with confounder control for age and other risk factors, in order to identify risk factors, which after these corrections still had a significant confounding influence on the prescribing of OC. Results. Users of OCs with third generation progestagens had a significantly higher proportion of familial thrombotic disposition (23.1%) than users of OCs with second generation progestagens (7.1%) (p = 0.01). After correction for age and other risk factors this difference was still highly significant (p = 0.002). Among users of third generation pills the proportion of short time users (< 1 year) (22.4%) was significantly higher than the per cent among users of OCs with second generation progestagens (5.5%) (p < 0.001). This difference was still significant after correction for age and other risk factors (p < 0.001).

Smoking, years of schooling, migraine, and body mass index did not differ significantly between the two pill groups.

Conclusion. In Denmark, women with familial thrombotic disposition are four times more likely being prescribed OCs with third versus second generation progestagens compared with women without such a disposition. At the same time users of OCs with third generation progestagens include significantly more short time users than users of OCs with second generation progestagens.

For thrombotic diseases where familial disposition or duration of use of OCs play a role for the pill‐associated risk, these differences may significantly influence the thrombotic risk measures in case‐control studies and non‐randomized cohort studies unless confounder control is conducted for this selection.
Anorectal manometry in women with urinary stress incontinence
Authors: Kjølhede Preben , Hallböök Olof , Rydén Gunnar , Sjödahl Rune
Published: December 2010

Objective. The aims of this prospective study were to determine the bowel function and the anal sphincter function in women with urinary stress incontinence by means of anorectal manometry and to look for manometric variables which could predict the development of surgery demanding genital prolapse after Burch colposuspension.

Subjects. During 1991–1992 twenty‐one women with urodynamicaiiy proven genuine stress urinary incontinence were consecutively operated upon with the Burch colposuspension. No concomitant prolapse repair surgery was performed. Forty‐four healthy subjects without anorectal disorders were used as controls.

Methods. All subjects were investigated with anorectal manometry using a microtransducer catheter. A standardized questionnaire concerning bowel function was answered at interview. The manometry and interview were performed preoperatively and one year after the Burch colposuspension.

Results. According to the preoperative questionnaire, fecal incontinence was found in 62%, constipation in 38% and straining at defecation in 71%. There were no significant differences in any of the manometric parameters between the preoperative and the one‐year postoperative assessment. The patients with prolapse operations after the colposuspension (n = 6) had a significanth lower anal squeeze pressure area (p = 0.029) preoperatively compared to the control subjects. The patients without prolapse surgery (n = 15) did not differ in manometric parameters from the control subjects.

Conclusion. Bowel dysfunction is common in women with stress urinary incontinence. The women with low anal squeeze pressure area preoperatively are at risk for the development of genital prolapse after Burch colposuspension.
Low‐risk human papillomavirus types 6 and 11 associated with carcinomas of the genital and upper aero‐digestive tract
Authors: Turazza Estela , Lapena Alicia , Sprovieri Osvaldo , Torres César Pires , Gurucharri Carlos , Maciel Alejandra , Lema Baltasar , Grinstein Saul , Kahn Tomas
Published: December 2010

Background. Human papillomavirus (HPVs) types 6 and 11, are frequently found in non‐malignant anogenital condylomas and laryngeal papillomas. However, in an ongoing epidemiological study in Argentina in which 163 anogenital and aero‐respiratory cancer biopsies were analyzed, several cases infected with low‐risk HPVs could be detected. Methods. Tumor samples were analyzed by Southern blot hybridization, using HPVs 6, 11, 16, 18, 30, 31, 33 and 35 as probes, and polymerase chain reaction (PCR) with type‐specific primers and probes.

Results. Four invasive carcinomas containing HPV 6 or 11 could be detected (2.4%) by Southern blot technique. HPV 6 DNA was found in a penile carcinoma, a groin carcinoma, and in a tonsillar carcinoma. One cervical carcinoma harbored HPV 11 DNA. Using HPVs 6, 11, 16, 18 and 33 anticontamination primers and probes in PCR, no additional high‐risk HPV types could be detected in these four cancers.

Conclusion. This report shows the presence of low‐risk HPVs (HPV 6 and 11) associated to malignant tumors in a frequency higher than usually observed. The data raise questions about which are the circumstances which may favor low‐risk HPV related oncogenesis.
The pharmacological advantage of prolonged dose rate gemcitabine is restricted to patients with variant alleles of cytidine deaminase c.79A>C
Authors: METHAROM Ekkaphon , GALETTIS Peter , MANNERS Susan , JELINEK Maria , LIAUW Winston , de SOUZA Paul L , HOSKINS Janelle M , LINKS Matthew
Published: December 2010

Aim:  Controversy exists over the optimal dosing for the nucleoside analogue gemcitabine. A pharmacological advantage is achieved by prolonging infusion times but evidence for a clinical benefit has been conflicting. We hypothesized that polymorphisms in genes involved in gemcitabine accumulation, particularly the cytidine deaminase CDA c.79A>C, may influence the optimal dosing regimen in individual patients.

Methods:  DNA was collected from 32 patients participating in a randomized crossover study comparing 30‐min with 100‐min infusions of gemcitabine. The relationships between seven polymorphisms among three genes (CDA, RRM1 and DCK) and (i) gemcitabine triphosphate accumulation; (ii) gemcitabine‐induced toxicity; and (iii) dose delivery were examined for each infusion time and week of administration.

Results:  There were trends for increased accumulation of gemcitabine‐triphosphate (GEM‐TP) with the variant alleles of CDA c.79A>C, and RRM1‐37C>A and ‐524T>C but none of these reached statistical significance in a univariate analysis. In a multivariable model there were significant effects of infusion duration and week of administration on GEM‐TP accumulation. There were significant interactions between CDA c.79A>C (P = 0.01) and RRM1‐37C>A (P = 0.019) genotypes, infusion time, and arm. More patients with one or two CDA c.79 variant alleles had doses delays (57 vs 13 %, P = 0.03) and a pharmacological advantage for prolonged infusion after week 1.

Conclusion:  It is important to consider both pharmacokinetics and pharmacogenetics in optimizing gemcitabine accumulation. This represents a classical interaction between genes and environment and provides support for the consideration of both CDA genotype and infusion duration in development of an individualized dosing strategy.
An effectiveness trial of cognitive behaviour therapy in a representative sample of outpatients with psychosis
Authors: Farhall John , Freeman Nerelie C. , Shawyer Frances , Trauer Tom
Published: December 2010

Objectives

The efficacy of cognitive behaviour therapies for psychosis (CBTp) has been sufficiently established for its inclusion in some national treatment guidelines. However, treatment efficacy does not guarantee effectiveness in routine practice, where clinician expertise and patient mix may be different. Thus, we evaluated the applicability, acceptability and effectiveness of CBTp when offered routinely in a public mental health service.

Design

A prospectively recruited representative sample (N = 94) of patients with psychotic disorders from a geographic catchment area in Melbourne, Australia, was randomized to CBTp or treatment as usual.

Method

The CBTp intervention included psychoeducation, positive symptom, and co‐morbid problem components. Therapists collaboratively negotiated goals with patients and utilized treatment components from a manual. Intention‐to‐treat analyses used data at baseline, 9 months and 18 months.

Results

Working alliance and client satisfaction measures indicated excellent acceptability. Both groups improved to a similar degree on the Positive And Negative Syndrome Scale, with no advantage for the CBTp group. The most frequent CBTp components implemented were co‐morbid disorders/personal issues and personalized psychoeducation; working with persisting symptoms was the main focus in relatively few sessions.

Conclusions

The lack of advantage for the CBTp group may be due to: the infrequent focus on positive symptoms (the most replicated outcome domain for CBTp); the unselected nature of the patients (rather than those with distressing symptoms or referred by clinicians); or, to insufficient therapist expertise.
Validation of a Chinese achievement goal orientation questionnaire
Authors: Lau Kit‐Ling. , Lee John C. K.
Published: December 2010

Background. The mixed findings of previous studies on the nature and effects of performance goals have led to a call for re‐examination of the dichotomous framework of achievement goal orientation theory. While the call for a revised achievement goal orientation theory has received considerable discussion in Western studies, it is not clear whether the revised theory can also be applied in other ethnic and cultural contexts.

Aims. Our aim was to validate the Chinese version of Elliot and Church's (1007) Goal Orientation Questionnaire and to initially test the revised goal orientation theory in the context of Chinese students in Hong Kong.

Sample. A total of 270 Chinese students (137 boys and 133 girls) from a primary and secondary school in Hong Kong participated in Study 1. Study 2 involved a total of 9,440 students (5,420 boys and 4,020 girls) from 10 primary and 18 secondary schools in Hong Kong.

Method. Participants in Study 1 completed a Chinese Goal Orientation Questionnaire (CGOQ) measuring three types of goal orientation. Exploratory factor analysis, item–total correlation, and reliability analyses were undertaken to assess the psychometric quality of the CGOQ. In Study 2, confirmatory factor analysis was used to provide further validation for the revised questionnaire. The relationships among different goal orientations and that with students' perceived classroom environment and self‐efficacy were also explored using structural equation modelling.

Results. Findings of exploratory factor analysis in Study 1 and confirmatory factor analysis in Study 2 supported the proposed factor structure of the CGOQ. All the subscales in the questionnaire also showed good internal consistency reliabilities. The construct validity of the CGOQ was supported by its significant relationship with criterion measures. While most of the relationships between the three types of goal orientation and the learning‐related variables measured in our study were consistent with the revised goal orientation theory, the positive relationships between performance‐avoidance goals, mastery goals, and perceived classroom environment were different from previous studies.

Conclusion. Our findings generally supported the trichotomous framework of the revised goal orientation theory with Chinese students in Hong Kong. Consistent with the revised goal orientation theory, our findings indicated that both mastery and performance‐approach goals had positive impacts on students' learning. However, the positive relationships between performance‐avoidance goals, mastery goals, and perceived classroom environment were contradictory to the conceptualization of performance‐avoidance goals in the revised theory. Cultural and social factors affecting Hong Kong students' goal orientations are discussed.
Divergent thinking: Strategies and executive involvement in generating novel uses for familiar objects
Authors: Gilhooly K. J. , Fioratou E. , Anthony S. H. , Wynn V.
Published: December 2010

Although the Alternative Uses divergent thinking task has been widely used in psychometric and experimental studies of creativity, the cognitive processes underlying this task have not been examined in detail before the two studies are reported here. In Experiment 1, a verbal protocol analysis study of the Alternative Uses task was carried out with a Think aloud group (N = 40) and a Silent control group (N = 64). The groups did not differ in fluency or novelty of idea production indicating no verbal overshadowing. Analysis of protocols from the Think aloud group suggested that initial responses were based on a strategy of Retrieval from long‐term memory of pre‐known uses. Later responses tended to be based on a small number of other strategies: property‐use generation, imagined Disassembly of the target object into components and scanning of Broad Use categories for possible uses of the target item. Novelty of uses was particularly associated with the Disassembly strategy. Experiment 2 (N = 103) addressed the role of executive processes in generating new and previously known uses by examining individual differences in category fluency, letter fluency and divergent task performance. After completing the task, participants were asked to indicate which of their responses were new for them. It was predicted and found in regression analyses that letter fluency (an executively loading task) was related to production of ‘new’ uses and category fluency was related to production of ‘old’ uses but not vice versa.
Modelling non‐ignorable missing‐data mechanisms with item response theory models
Authors: Holman Rebecca , Glas Cees A. W.
Published: December 2010

A model‐based procedure for assessing the extent to which missing data can be ignored and handling non‐ignorable missing data is presented. The procedure is based on item response theory modelling. As an example, the approach is worked out in detail in conjunction with item response data modelled using the partial credit and generalized partial credit models. Simulation studies are carried out to assess the extent to which the bias caused by ignoring the missing‐data mechanism can be reduced. Finally, the feasibility of the procedure is demonstrated using data from a study to calibrate a medical disability scale.
Fitting the factor analysis model in ℓ1 norm
Authors: Trendafilov Nickolay T.
Published: December 2010

The well‐known problem of fitting the exploratory factor analysis model is reconsidered where the usual least squares goodness‐of‐fit function is replaced by a more resistant discrepancy measure, based on a smooth approximation of the ℓ1 norm.

Fitting the factor analysis model to the sample correlation matrix is a complex matrix optimization problem which requires the structure preservation of the unknown parameters (e.g. positive definiteness). The projected gradient approach is a natural way of solving such data matching problems as especially designed to follow the geometry of the model parameters. Two reparameterizations of the factor analysis model are considered. The approach leads to globally convergent procedures for simultaneous estimation of the factor analysis matrix parameters. Numerical examples illustrate the algorithms and factor analysis solutions.
Real‐time dose computation: GPU‐accelerated source modeling and superposition/convolution
Authors: Jacques Robert , Wong John , Taylor Russell , McNutt Todd
Published: December 2010

Purpose:

To accelerate dose calculation to interactive rates using highly parallel graphics processing units (GPUs).

Methods:

The authors have extended their prior work in GPU‐accelerated superposition/convolution with a modern dual‐source model and have enhanced performance. The primary source algorithm supports both focused leaf ends and asymmetric rounded leaf ends. The extra‐focal algorithm uses a discretized, isotropic area source and models multileaf collimator leaf height effects. The spectral and attenuation effects of static beam modifiers were integrated into each source's spectral function. The authors introduce the concepts of arc superposition and delta superposition. Arc superposition utilizes separate angular sampling for the total energy released per unit mass (TERMA) and superposition computations to increase accuracy and performance. Delta superposition allows single beamlet changes to be computed efficiently. The authors extended their concept of multi‐resolution superposition to include kernel tilting. Multi‐resolution superposition approximates solid angle ray‐tracing, improving performance and scalability with a minor loss in accuracy. Superposition/convolution was implemented using the inverse cumulative‐cumulative kernel and exact radiological path ray‐tracing. The accuracy analyses were performed using multiple kernel ray samplings, both with and without kernel tilting and multi‐resolution superposition.

Results:

Source model performance was (data dependent) for a high resolution field using an NVIDIA (Santa Clara, CA) GeForce GTX 280. Computation of the physically correct multispectral TERMA attenuation was improved by a material centric approach, which increased performance by over 80%. Superposition performance was improved by to 0.058 and 0.94 s for and water phantoms; a speed‐up of 101–144× over the highly optimized Pinnacle3 (Philips, Madison, WI) implementation. times were 8.3 and 94 s, respectively, on an AMD (Sunnyvale, CA) Opteron 254 (two cores, 2.8 GHz).

Conclusions:

The authors have completed a comprehensive, GPU‐accelerated dose engine in order to provide a substantial performance gain over CPU based implementations. Real‐time dose computation is feasible with the accuracy levels of the superposition/convolution algorithm.
Micro‐CT dilatometry measures of molecular collagen hydration using bovine extensor tendon
Authors: Fullerton Gary D. , Amurao Maxwell , Rahal Andres , Cameron Ivan L.
Published: December 2010

Purpose:

This article introduces a new method to study macromolecular hydration using micro‐CT dilatometry. The complexity of hydration dependence on solvent temperature,, ionic charge, ionic activity, and ionic radii are barriers to comprehensive understanding of protein function. The crystalline character of collagen‐tendon suggests that tendon dilatometry may give direct access to measures of molecular tropocollagen solvation response.

Methods:

The molecular basis of thestoichiometric hydration model (SHM) provides tools to validate bovine tendon as a model to study protein‐solvent shape response by micro‐CT measures of tendon diameter, length, and mass during dehydration. The SHM relates macroscopic properties to molecular properties of water interacting with the surface of collagen molecules. There are marked changes at critical SHM hydration levels , 0.262, and 0.724 g water/g dry weight.

Results:

Micro‐CT analysis of the length, diameter, and volume combined with gravimetric measures of tendon mass as a function of hydration h(g water/g dry solid) shows asymmetric changes in length, diameter, and density as predicted by SHM. The collagen molecules perturb water properties of polar hydration waters per tripeptide unit or to confirm MDS prediction of elevated hydration density 20%–50% higher than bulk water.

Conclusions:

Results validate the use of tendon dilatometry amplification factors of as an effective model to investigate protein molecule shape change response to solvent molecules. The tendon model for the first time allows direct study of protein hydration and functional response under physiological conditions.
Automated segmentation of cerebral vasculature with aneurysms in 3DRA and TOF‐MRA using geodesic active regions: An evaluation study
Authors: Bogunović Hrvoje , Pozo José María , Villa‐Uriol María Cruz , Majoie Charles B. L. M. , van den Berg Rene , Gratama van Andel Hugo A. F. , Macho Juan M. , Blasco Jordi , San Román Luis , Frangi Alejandro F.
Published: December 2010

Purpose:

To evaluate the suitability of an improved version of an automatic segmentation method based on geodesic active regions (GAR) for segmenting cerebral vasculature with aneurysms from 3D x‐ray reconstruction angiography (3DRA) and time of flight magnetic resonance angiography (TOF‐MRA) images available in the clinical routine.

Methods:

Three aspects of the GAR method have been improved: execution time, robustness to variability in imaging protocols, and robustness to variability in image spatial resolutions. The improved GAR was retrospectively evaluated on images from patients containing intracranial aneurysms in the area of the Circle of Willis and imaged with two modalities: 3DRA and TOF‐MRA. Images were obtained from two clinical centers, each using different imaging equipment. Evaluation included qualitative and quantitative analyses of the segmentation results on 20 images from 10 patients. The gold standard was built from 660 cross‐sections (33 per image) of vessels and aneurysms, manually measured by interventional neuroradiologists. GAR has also been compared to an interactive segmentation method: isointensity surface extraction (ISE). In addition, since patients had been imaged with the two modalities, we performed an intermodality agreement analysis with respect to both the manual measurements and each of the two segmentation methods.

Results:

Both GAR and ISE differed from the gold standard within acceptable limits compared to the imaging resolution. GAR (ISE) had an average accuracy of 0.20 (0.24) mm for 3DRA and 0.27 (0.30) mm for TOF‐MRA, and had a repeatability of 0.05 (0.20) mm. Compared to ISE, GAR had a lower qualitative error in the vessel region and a lower quantitative error in the aneurysm region. The repeatability of GAR was superior to manual measurements and ISE. The intermodality agreement was similar between GAR and the manual measurements.

Conclusions:

The improved GAR method outperformed ISE qualitatively as well as quantitatively and is suitable for segmenting 3DRA and TOF‐MRA images from clinical routine.
Quantification of near‐field heating during volumetric MR‐HIFU ablation
Authors: Mougenot C. , Köhler M. O. , Enholm J. , Quesson B. , Moonen C.
Published: December 2010

Purpose:

High‐intensity focused ultrasound guided by magnetic resonance imaging has been extensively evaluated during the past decade as a clinical alternative for thermal ablation of tumor tissue. However, the maximal ablation volume is limited by the extensive treatment duration resulting from the small size of the focal point as compared to the average tumor size. Volumetric sonication has been shown to efficiently enlarge the ablated volume per sonication, but remains limited by the temperature increase induced in the skin and fat layers. In this study, multiplane MR thermometry is proposed for monitoring the near‐field temperature rise in order to prevent related unintended thermal damage.

Methods:

The method was evaluated by performing sonications in the thigh muscle of 11 pigs maintained under general anesthesia. Volumetric ablations were performed by steering the focal point along trajectories consisting of multiple outward‐moving concentric circles. Near‐field heating was characterized with MR temperature maps and thermal dose maps. The results from the MR measurements were compared to simulations.

Results:

In this study, the measured maximum temperature rise was found to correlate linearly with the surface energy density within the near field of the beam path with a slope of. This simple linear model appears to be almost independent of the trajectory pattern and the sonication depth. The safety limit to avoid lethal damage of the subcutaneous tissues of the porcine thigh was identified to be an absolute temperature of , corresponding to a surface energy density of at 1.2 MHz.

Conclusions:

A linear relationship can be established to estimate the temperature increase based on the chosen power prior to ablation, thereby providing ana priori safety check for possible excessive near‐field heating using a known surface energy density threshold. This method would also give the clinician the possibility to abort the sonication should excessive near‐field temperature rise be seen before fat layer damage or skin burns are inflicted.
An algorithm for efficient metal artifact reductions in permanent seed implants
Authors: Xu Chen , Verhaegen Frank , Laurendeau Denis , Enger Shirin A. , Beaulieu Luc
Published: December 2010

Purpose:

In permanent seed implants, 60 to more than 100 small metal capsules are inserted in the prostate, creating artifacts in x‐ray computed tomography (CT) imaging. The goal of this work is to develop an automatic method for metal artifact reduction (MAR) from small objects such as brachytherapy seeds for clinical applications.

Methods:

The approach for MAR is based on the interpolation of missing projections by directly using raw helical CT data (sinogram). First, an initial image is reconstructed from the raw CT data. Then, the metal objects segmented from the reconstructed image are reprojected back into the sinogram space to produce a metal‐only sinogram. The Steger method is used to determine precisely the position and edges of the seed traces in the raw CT data. By combining the use of Steger detection and reprojections, the missing projections are detected and replaced by interpolation of non‐missing neighboring projections.

Results:

In both phantom experiments and patient studies, the missing projections have been detected successfully and the artifacts caused by metallic objects have been substantially reduced. The performance of the algorithm has been quantified by comparing the uniformity between the uncorrected and the corrected phantom images. The results of the artifact reduction algorithm are indistinguishable from the true background value.

Conclusions:

An efficient algorithm for MAR in seed brachytherapy was developed. The test results obtained using raw helical CT data for both phantom and clinical cases have demonstrated that the proposed MAR method is capable of accurately detecting and correcting artifacts caused by a large number of very small metal objects (seeds) in sinogram space. This should enable a more accurate use of advanced brachytherapy dose calculations, such as Monte Carlo simulations.
Inverse planning for IMRT with nonuniform beam profiles using total‐variation regularization (TVR)
Authors: Kim Taeho , Zhu Lei , Suh Tae‐Suk , Geneser Sarah , Meng Bowen , Xing Lei
Published: December 2010

Purpose:

Radiation therapy with high dose rate and flattening filter‐free (FFF) beams has the potential advantage of greatly reduced treatment time and out‐of‐field dose. Current inverse planning algorithms are, however, not customized for beams with nonuniform incident profiles and the resultant IMRT plans are often inefficient in delivery. The authors propose a total‐variation regularization (TVR)‐based formalism by taking the inherent shapes of incident beam profiles into account.

Methods:

A novel TVR‐based inverse planning formalism is established for IMRT with nonuniform beam profiles. The authors introduce a TVR term into the objective function, which encourages piecewise constant fluence in the nonuniform FFF fluence domain. The proposed algorithm is applied to lung and prostate and head and neck cases and its performance is evaluated by comparing the resulting plans to those obtained using a conventional beamlet‐based optimization (BBO).

Results:

For the prostate case, the authors' algorithm produces acceptable dose distributions with only 21 segments, while the conventional BBO requires 114 segments. For the lung case and the head and neck case, the proposed method generates similar coverage of target volume and sparing of the organs‐at‐risk as compared to BBO, but with a markedly reduced segment number.

Conclusions:

TVR‐based optimization in nonflat beam domain provides an effective way to maximally leverage the technical capacity of radiation therapy with FFF fields. The technique can generate effective IMRT plans with improved dose delivery efficiency without significant deterioration of the dose distribution.
Reliability of EUCLIDIAN: An autonomous robotic system for image‐guided prostate brachytherapy
Authors: Podder Tarun K. , Buzurovic Ivan , Huang Ke , Showalter Timothy , Dicker Adam P. , Yu Yan
Published: December 2010

Purpose:

Recently, several robotic systems have been developed to perform accurate and consistent image‐guided brachytherapy. Before introducing a new device into clinical operations, it is important to assess the reliability and mean time before failure (MTBF) of the system. In this article, the authors present the preclinical evaluation and analysis of the reliability and MTBF of an autonomous robotic system, which is developed for prostate seed implantation.

Methods:

The authors have considered three steps that are important in reliability growth analysis. These steps are: Identification and isolation of failures, classification of failures, and trend analysis. For any one‐of‐a‐kind product, the reliability enhancement is accomplished through test‐fix‐test. The authors have used failure mode and effect analysis for collection and analysis of reliability data by identifying and categorizing the failure modes. Failures were classified according to severity. Failures that occurred during the operation of this robotic system were considered as nonhomogenous Poisson process. The failure occurrence trend was analyzed using Laplace test. For analyzing and predicting reliability growth, commonly used and widely accepted models, Duane's model and the Army Material Systems Analysis Activity, i.e., Crow's model, were applied. The MTBF was used as an important measure for assessing the system's reliability.

Results:

During preclinical testing, 3196 seeds (in 53 test cases) were deposited autonomously by the robot and 14 critical failures were encountered. The majority of the failures occurred during the first few cases. The distribution of failures followed Duane's postulation as well as Crow's postulation of reliability growth. The Laplace test index was −3.82, indicating a significant trend in failure data, and the failure intervals lengthened gradually. The continuous increase in the failure occurrence interval suggested a trend toward improved reliability. The MTBF was 592 seeds, which implied that several prostate seed implantation cases would be possible without encountering any critical failure. The shape parameter for the MTBF was 0.3859 , suggesting a positive reliability growth of this robotic system. At 95% confidence, the reliability for deposition of 65 seeds was more than 90%.

Conclusions:

Analyses of failure mode strongly indicated a gradual improvement of reliability of this autonomous robotic system. High MTBF implied that several prostate seed implant cases would be possible without encountering any critical failure.
Diagnostic efficacy of computer extracted image features in optical coherence tomography of the precancerous cervix
Authors: Kang Wei , Qi Xin , Tresser Nancy J. , Kareta Margarita , Belinson Jerome L. , Rollins Andrew M.
Published: December 2010

Purpose:

To determine the diagnostic efficacy of optical coherence tomography (OCT) to identify cervical intraepithelial neoplasia (CIN) grade 2 or higher by computer‐aided diagnosis (CADx).

Methods:

OCT has been investigated as a screening/diagnostic tool in the management of preinvasive and early invasive cancers of the uterine cervix. In this study, an automated algorithm was developed to extract OCT image features and identify CIN 2 or higher. First, the cervical epithelium was detected by a combined watershed and active contour method. Second, four features were calculated: The thickness of the epithelium and its standard deviation and the contrast between the epithelium and the stroma and its standard deviation. Finally, linear discriminant analysis was applied to classify images into two categories: Normal/inflammation/CIN 1 and CIN 2/CIN 3. The algorithm was applied to 152 images (74 patients) obtained from an international study.

Results:

The numbers of normal/inflammatory/CIN 1/CIN 2/CIN 3 images are 74, 29, 14, 24, and 11, respectively. Tenfold cross‐validation predicted the algorithm achieved a sensitivity of 51% (95% CI: 36%–67%) and a specificity of 92% (95% CI: 86%–96%) with an empirical two‐category prior probability estimated from the data set. Receiver operating characteristic analysis yielded an area under the curve of 0.86.

Conclusions:

The diagnostic efficacy of CADx in OCT imaging to differentiate high‐grade CIN from normal/low grade CIN is demonstrated. The high specificity of OCT with CADx suggests further investigation as an effective secondary screening tool when combined with a highly sensitive primary screening tool.
Nuclear Medicine Radiation Dosimetry, Advanced Theoretical Principles
Authors: Zanzonico Pat
Published: December 2010

Nuclear Medicine Radiation Dosimetry, Advanced Theoretical Principles. Brian J. McParland. Springer‐Verlag, London, 2010, $219.00. ISBN: 978‐1‐84882‐125‐5, 464 pp. (hardcover).