Solid state microdosimetry

A review of solid state microdosimetry is presented with an emphasis on silicon-based devices. The historical foundations and basics of microdosimetry are briefly provided. Various methods of experimental regional microdosimetry are discussed to facilitate a comparison with the more recent development of silicon microdosimetry. In particular, the performance characteristics of a proportional gas counter and a silicon microdosimeter are compared. Recent improvements in silicon microdosimetry address the issues of requirement specification, non-spherical shape, tissue equivalence, sensitive volume definition (charge collection complexity) and low noise requirements which have previously impeded the implementation of silicon-based microdosimetry. A prototype based on silicon-on-insulator technology is described along with some example results from clinical high LET radiotherapy facilities. A brief summary of the applications of microdosimetry is included.     

Ab initio electronic structure calculation of a new gene system using the negative factor counting method

It has been reported that cumulative carnitine losses through dialysis membranes may worsen hyperlipidemia during long-term hemodialysis. However, carnitine supplementation has not shown a consistent beneficial response. We undertook the present study to determine if there is any hypolipidemic effect of L-carnitine on Greek dialysis patients in concert with the dialysate buffer composition (acetate or bicarbonate). A total of 28 patients (16 male, 12 female), mean age 43 years (range 21-61), with end-stage renal disease on maintenance hemodialysis for a mean period of 25 months (range 7-84) were studied. The dialysis schedule was 4 h, 3 times/week using cuprophane hollow-fiber dialyzers and acetate (n = 14) or bicarbonate (n = 14) dialysate. In all patients L-carnitine (5 mg/kg body weight) was infused intravenously 3 times/week at the end of each hemodialysis session. Blood samples for carnitine and lipid determinations were obtained before treatment, and 3 and 6 months following treatment. Even though L-carnitine did not modify most of the serum lipid levels, a significant decrease in serum triglycerides was evident in the whole group of patients (from 225 +/- 76 to 201 +/- 75 mg/dl, p = 0.03). Furthermore, L-carnitine could decrease serum triglycerides only in hypertriglyceridemic patients (from 260 +/- 64 to 226 +/- 82 mg/dl, p < 0.05). L-Carnitine resulted in a reduction of serum triglycerides in both patients on bicarbonate and on acetate dialysis, while there were no significant differences in the changes of lipid parameters after L-carnitine between the two groups of hemodialysis patients. We conclude that relatively low doses of L-carnitine supplementation could contribute to the management of some hypertriglyceridemic hemodialysis patients.     

A calculation of the relative biological effectiveness of 125I and 103Pd brachytherapy sources using the concept of proximity function

The clinical application of encapsulated radioactive sources in brachytherapy plays an important role in the treatment of malignancy. 125I and 103Pd sources have been widely used in the permanent implant of prostate cancer. An important consideration for the choice of brachytherapy sources is their relative biological effectiveness (RBE). Previous calculations of this quantity have used the dose-averaged lineal energy, yD, as a measure of biological effectiveness. In this approach, however, the selection of a relevant site size remains an open question. Here we avoid this problem by using the generalized theory of dual radiation action to calculate the initial slope, alpha, of the dose-effect curves using the proximity function, t(x), and the biological response function, gamma(x). At low doses and/or low dose rates (e.g., prostate implants) the parameter alpha determines the RBE. Proximity function, t(x), is the probability distribution function of distances between pairs of sublesions; and the biological function, gamma(x), is the probability that two sublesions at a distance x apart results in a lesion. Functions t(x) have been calculated for each source using the Monte Carlo transport codes PHOEL and PROTON5. The function gamma(x) has been taken from a published analysis. The RBE values thus obtained are: 1.5 for 125I and 1.6 for 103Pd. The question of whether an "effective" site size exists where yD approximates best the variation of alpha with radiation quality is also addressed.     

Microdosemeter instrument (MIDN) for assessing risk in space

Radiation in space generally produces higher dose rates than that on the Earth's surface, and contributions from primary galactic and solar events increase with altitude within the magnetosphere. Presently, no personnel monitor is available to astronauts for real-time monitoring of dose, radiation quality and regulatory risk. This group is developing a prototypic instrument for use in an unknown, time-varying radiation field. This microdosemeter-dosemeter nucleon instrument is for use in a spacesuit, spacecraft, remote rover and other applications. It provides absorbed dose, dose rate and dose equivalent in real time so that action can be taken to reduce exposure. Such a system has applications in health physics, anti-terrorism and radiation-hardening of electronics as well. The space system is described and results of ground-based studies are presented and compared with predictions of transport codes. An early prototype in 2007 was successfully launched, the only solid-state microdosemeter to have flown in space.     

Miniature semiconductor detectors for in vivo dosimetry

Silicon mini-semiconductor detectors are found in wide applications for in vivo personal dosimetry and dosimetry and microdosimetry of different radiation oncology modalities. These applications are based on integral and spectroscopy modes of metal oxide semiconductor field effect transistor and silicon p-n junction detectors. The advantages and limitations of each are discussed.     

Anxiety disorders and intimate relationships: A study of daily processes in couples.

Although adults with anxiety disorders often report interpersonal distress, the degree to which anxiety is linked to the quality of close relationships remains unclear. The authors examined the relational impact of anxiety by sampling the daily mood and relationship quality of 33 couples in which the wife was diagnosed with an anxiety disorder. Use of a daily process design improved on prior methodologies by capturing relational processes closer to their actual occurrence and in the setting of the diagnosed partner’s anxiety. Analyses revealed significant associations between wives’ daily anxiety and both partners’ perceptions of relationship quality. Associations were moderated by anxiety-specific support. Results also indicated significant concordance between wives’ daily anxiety and husbands’ distress. Concordance was stronger for husbands who reported frequent accommodation of wives’ anxiety symptoms. Findings are discussed in the context of existing evidence on the social costs of anxiety disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automated finite-element analysis for deformable registration of prostate images

Two major factors preventing the routine clinical use of finite-element analysis for image registration are: 1) the substantial labor required to construct a finite-element model for an individual patient's anatomy and 2) the difficulty of determining an appropriate set of finite-element boundary conditions. This paper addresses these issues by presenting algorithms that automatically generate a high quality hexahedral finite-element mesh and automatically calculate boundary conditions for an imaged patient. Medial shape models called m-reps are used to facilitate these tasks and reduce the effort required to apply finite-element analysis to image registration. Encouraging results are presented for the registration of CT image pairs which exhibit deformation caused by pressure from an endorectal imaging probe and deformation due to swelling.     

Therapy processes and outcomes of psychological interventions for women diagnosed with gynecological cancers: A test of the generic process model of psychotherapy.

Objective: Little attention has been paid to the role of nonspecific therapy processes in the efficacy of psychological interventions for individuals diagnosed with cancer. The goal of the current study was to examine the three constructs from the generic model of psychotherapy (GMP): therapeutic alliance, therapeutic realizations, and therapeutic openness/involvement in the treatment outcome of women with gynecological cancers attending either a 7-session supportive counseling intervention or a coping and communication skills intervention. Method: Two hundred and three women completed measures of alliance, realizations, and openness after Intervention Sessions 2, 3, and 6, as well as measures of depressive symptoms after these sessions and 6 months after the pre-intervention assessment (posttreatment). Results: Consistent with the GMP, in early sessions, therapeutic bond predicted openness in terms of positive affect experienced during sessions, and both aspects of openness (positive and negative affect), in turn, predicted more therapeutic realizations. Therapeutic realizations predicted perceptions of greater session progress, and greater therapeutic bond predicted more therapeutic realizations. When early session GMP variables were used to predict later GMP processes and outcomes and posttreatment outcomes, early therapeutic bond predicted later session therapeutic realizations directly and indirectly via emotional arousal, emotional arousal predicted session progress, session progress predicted lower postsession depressive symptoms, and depressive symptoms as rated after Session 6 predicted depressive symptoms 3 months posttreatment. However, a number of additional associations among GMP processes were found. Conclusions: Our results suggest that therapy processes played a role in predicting both short- and long-term treatment outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)