[en] The sensitivity and selectivity of polyvinyl alcohol (PVA) / carbon black composite films have been found to vary depending upon the hydroxylation percentage (''-OH'') of the polymer. These chemiresistors made from PVA films whose polymer backbone is 88% hydroxylated (PVA88) have a high sensitivity to water, while chemiresistors made from PVA75 have a higher sensitivity to methanol. The minor differences in polymer composition result in films with different Hildebrand volubility parameters. The relative responses of several different PVA-based chemiresistors to solvents with different volubility parameters are presented. In addition, polyvinyl acetate (PVAC) films with PVA88 are used in an array to distinguish the responses to methanol-water mixtures

[en] Background: To evaluate early urinary (GU) and gastrointestinal (GI) adverse events (AEs) after two or one fraction of high-dose rate brachytherapy (HDR-BT) in advanced prostate cancer. Patients and methods: 165 patients were treated with 2 × 13 Gy (n = 115), or a single dose of 19 Gy (n = 24) or 20 Gy (n = 26) HDR-BT. Early AEs were assessed using the RTOG scoring system and the International Prostate Symptom Score (IPSS). Results: Week-2 prevalence of severe IPSS symptoms was higher after 20 Gy than after 26 or 19 Gy but by 12 weeks all groups were at pre-treatment levels or less. Grade-3 GU toxicity was observed ⩽9% of patients. No Grade 4 GU and no Grade 3 or 4 GI complications were observed. However, there was a significant increase in catheter use in the first 12 weeks after implant after 19 and 20 Gy compared with 2 × 13 Gy. Conclusion: Single dose HDR-BT is feasible with acceptable levels of acute complications; tolerance may have been reached with the single 19 Gy schedule

[en] Background: To evaluate late urinary (GU) and gastrointestinal (GI) adverse events (AEs) and biochemical control of disease after high-dose rate brachytherapy (HDR-BT) in locally advanced prostate cancer. Patients and methods: 227 consecutive patients were treated with 3 × 10.5 Gy (n = 109) or 2 × 13 Gy (n = 118) HDR-BT alone. Biochemical failure was assessed using the Phoenix definition of PSA nadir + 2 μg/l and late AEs using the RTOG scoring system and the International Prostate Symptom Score (IPSS). Results: Kaplan–Meier estimates and prevalence of late events indicate that urinary, bowel and IPSS symptoms are higher after 31.5 Gy than after 26 Gy, however differences are significant only for Grade 1 and 2 urinary toxicity. Kaplan–Meier estimates of morbidity are consistently and considerably higher than time-point estimates of prevalence; which reflects the transient nature of most symptoms. At 3 years 93% and 97% of patients treated with 26 and 31.5 Gy, respectively, were free from biochemical relapse (p = 0.5) and 91% for the latter regimen at 5 years. In univariate and multivariate analysis risk-category was the only significant predictor of relapse (p < 0.03). Conclusion: These HDR-BT schedules achieved high levels of biochemical control of disease in patients with advanced prostate cancer with few severe complications seen throughout the first 3 years

[en] Objective: To determine whether late genitourinary toxicity, biochemical control of prostate cancer, and dosimetric parameters in patients with large prostate glands is different from those variables in men with smaller glands after treatment with high-dose-rate brachytherapy alone (HDR-BT). Methods: From November 2003 to July 2009, 164 patients with locally advanced prostate carcinoma were sequentially enrolled and treated with 34 or 36 Gy in 4 fractions and 31.5 Gy in 3 fractions of ¹⁹²Ir HDR-BT alone. The median follow-up time was 71 months. Gland size was not considered in the selection criteria for this study. Estimates of freedom from biochemical relapse (FFbR) and late morbidity, stratified by median clinical target volume (CTV), were obtained, and differences were compared. Results: The median CTV volume was 60 cc (range, 15-208 cc). Dose–volume parameters D90 and V100 (ie, minimum dose to 90% of the prostate volume and volume receiving 100% of the prescribed isodose) achieved in patients with glands ≥60 cc were not significantly different from those with glands <60 cc (P≥.2). Nonetheless, biochemical control in patients with larger CTV was significantly higher (91% vs 78% at 6 years; P=.004). In univariate and multivariate analysis, CTV was a significant predictor for risk of biochemical relapse. This was not at the expense of an increase in either moderate (P=.6) or severe (P=.3) late genitourinary toxicity. The use of hormonal therapy was 17% lower in the large gland group (P=.01). Conclusions: Prostate gland size does not affect dosimetric parameters in HDR-BT assessed by D90 and V100. In patients with larger glands, a significantly higher biochemical control of disease was observed, with no difference in late toxicity. This improvement cannot be attributed to differences in dosimetry. Gland size should not be considered in the selection of patients for HDR-BT

[en] Background: To correlate dose and volume dosimetric parameters (D₉₀ and V₁₀₀) with biochemical control in advanced prostate cancer treated with high-dose rate brachytherapy (HDR-BT). Methods: One hundred and eight patients received external beam radiotherapy (EBRT) to 35.75 Gy in 13 fractions followed by HDR-BT of 2 × 8.5 Gy. Kaplan–Meier freedom-from-biochemical relapse (FFbR; nadir + 2 μg/L) fits were grouped by the first (Q1), second (Q2) and third (Q3) D₉₀ and V₁₀₀ quartiles. Groups were compared with the log-rank test. Univariate and multivariate Hazard Ratios (HR) for D₉₀ and V₁₀₀ and other co-variates (PSA, androgen deprivation therapy (ADT) were obtained using Cox’s proportional hazard model. Results: FFbR was significantly higher in patients whose D₉₀ and V₁₀₀ were at or above the second and third quartile (log rank p ⩽ 0·04). In multivariate analysis D₉₀, V₁₀₀ were significant covariates for risk of relapse. Conclusions: Dichotomising the data using 6 levels of response (above and below Q1, Q2 and Q3) showed a progressive and continuous improvement in biochemical control of disease across the entire dose (and volume) range. The data show that a minimum D₉₀ of 108% of the prescribed dose should be the target to achieve

[en] Background and purpose: To evaluate dosimetric parameters related to urethral strictures following high dose-rate brachytherapy (HDRBT) alone for prostate cancer. Material and methods: Ten strictures were identified in 213 patients treated with HDRBT alone receiving 34 Gy in four fractions, 36 Gy in four fractions, 31.5 Gy in 3 fractions or 26 Gy in 2 fractions. A matched-pair analysis used 2 controls for each case matched for dose fractionation schedule, pre-treatment IPSS score, number of needles used and clinical target volume. The urethra was divided into membranous urethra and inferior, mid and superior thirds of the prostatic urethra. Results: Stricture rates were 3% in the 34 Gy group, 4% in the 36 Gy group, 6% in the 31.5 Gy group and 4% in the 26 Gy group. The median time to stricture formation was 26 months (range 8–40). The dosimetric parameters investigated were not statistically different between cases and controls. No correlation was seen between stricture rate and fractionation schedule. Conclusions: Urethral stricture is an infrequent complication of prostate HDRBT when used to deliver high doses as sole treatment, with an overall incidence in this cohort of 10/213 (4.7%). In a matched pair analysis no association with dose schedule or urethral dosimetry was identified, but the small number of events limits definitive conclusions

[en] Chemoradiotherapy (CRT) followed by total mesorectal excision is the standard when MRI staging demonstrates threatened surgical margins in locally advanced rectal cancer (LARC). Interest in non-surgical management of LARC as an alternative to a resection has been provoked by published excellent long-term outcomes of patients who achieve clinical complete responses (cCR) after CRT. The present retrospective study aimed to determine whether similar rates of local disease control are seen in a UK cancer centre in patients with T3-4 tumours, who obtained a cCR after preoperative CRT, but did not undergo surgery. Method. The outcome and treatment details of 266 patients who underwent CRT for clinically staged T3-4 rectal adenocarcinomas between 1993 and 2005 were reviewed. Results. Fifty-eight patients did not proceed to surgery, 10 of whom were identified as having a cCR. Six of these 10 patients subsequently developed intrapelvic recurrent disease with a median time to local progression of 20 months. Local relapse preceded the development of metastatic disease or occurred simultaneously. No patients underwent salvage resection. Conclusion. CRT alone in cT3/T4 rectal cancers has a high rate of local relapse even after cCR. Delaying or avoiding surgery might be appropriate for cT1 or cT2 tumours, or elderly and frail patients with co-morbidity, but these results do not support the current uncritical move to extrapolate this approach to all surgically fit patients with rectal cancer

[en] One of the foremost challenges in nanofabrication is the establishment of a processing science that integrates wafer-based materials, techniques, and devices with the extraordinary physicochemical properties accessible when materials are reduced to nanoscale dimensions. Such a merger would allow for exacting controls on nanostructure positioning, promote cooperative phenomenon between adjacent nanostructures and/or substrate materials, and allow for electrical contact to individual or groups of nanostructures. With neither self-assembly nor top-down lithographic processes being able to adequately meet this challenge, advancements have often relied on a hybrid strategy that utilizes lithographically-defined features to direct the assembly of nanostructures into organized patterns. While these so-called directed assembly techniques have proven viable, much of this effort has focused on the assembly of periodic arrays of spherical or near-spherical nanostructures comprised of a single element. Work directed toward the fabrication of more complex nanostructures, while still at a nascent stage, has nevertheless demonstrated the possibility of forming arrays of nanocubes, nanorods, nanoprisms, nanoshells, nanocages, nanoframes, core–shell structures, Janus structures, and various alloys on the substrate surface. In this topical review, we describe the progress made in the directed assembly of periodic arrays of these complex metal nanostructures on planar and textured substrates. The review is divided into three broad strategies reliant on: (i) the deterministic positioning of colloidal structures, (ii) the reorganization of deposited metal films at elevated temperatures, and (iii) liquid-phase chemistry practiced directly on the substrate surface. These strategies collectively utilize a broad range of techniques including capillary assembly, microcontact printing, chemical surface modulation, templated dewetting, nanoimprint lithography, and dip-pen nanolithography and employ a wide scope of chemical processes including redox reactions, alloying, dealloying, phase separation, galvanic replacement, preferential etching, template-mediated reactions, and facet-selective capping agents. Taken together, they highlight the diverse toolset available when fabricating organized surfaces of substrate-supported nanostructures. (topical review)

[en] Waste characterization is probably the most costly part of radioactive waste management. An important part of this characterization is the measurements of headspace gas in waste containers in order to demonstrate the compliance with Resource Conservation and Recovery Act (RCRA) or transportation requirements. The traditional chemical analysis methods, which include all steps of gas sampling, sample shipment and laboratory analysis, are expensive and time-consuming as well as increasing worker's exposure to hazardous environments. Therefore, an alternative technique that can provide quick, in-situ, and real-time detections of headspace gas compositions is highly desirable. This report summarizes the results obtained from a Laboratory Directed Research and Development (LDRD) project entitled 'Potential Application of Microsensor Technology in Radioactive Waste Management with Emphasis on Headspace Gas Detection'. The objective of this project is to bridge the technical gap between the current status of microsensor development and the intended applications of these sensors in nuclear waste management. The major results are summarized below: (sm_bullet) A literature review was conducted on the regulatory requirements for headspace gas sampling/analysis in waste characterization and monitoring. The most relevant gaseous species and the related physiochemical environments were identified. It was found that preconcentrators might be needed in order for chemiresistor sensors to meet desired detection (sm_bullet) A long-term stability test was conducted for a polymer-based chemresistor sensor array. Significant drifts were observed over the time duration of one month. Such drifts should be taken into account for long-term in-situ monitoring. (sm_bullet) Several techniques were explored to improve the performance of sensor polymers. It has been demonstrated that freeze deposition of black carbon (CB)-polymer composite can effectively eliminate the so-called 'coffee ring' effect and lead to a desirable uniform distribution of CB particles in sensing polymer films. The optimal ratio of CB/polymer has been determined. UV irradiation has been shown to improve sensor sensitivity. (sm_bullet) From a large set of commercially available polymers, five polymers were selected to form a sensor array that was able to provide optimal responses to six target-volatile organic compounds (VOCs). A series of tests on the response of sensor array to various VOC concentrations have been performed. Linear sensor responses have been observed over the tested concentration ranges, although the responses over a whole concentration range are generally nonlinear. (sm_bullet) Inverse models have been developed for identifying individual VOCs based on sensor array responses. A linear solvation energy model is particularly promising for identifying an unknown VOC in a single-component system. It has been demonstrated that a sensor array as such we developed is able to discriminate waste containers for their total VOC concentrations and therefore can be used as screening tool for reducing the existing headspace gas sampling rate. (sm_bullet) Various VOC preconcentrators have been fabricated using Carboxen 1000 as an absorbent. Extensive tests have been conducted in order to obtain optimal configurations and parameter ranges for preconcentrator performance. It has been shown that use of preconcentrators can reduce the detection limits of chemiresistors by two orders of magnitude. The life span of preconcentrators under various physiochemical conditions has also been evaluated. (sm_bullet) The performance of Pd film-based H2 sensors in the presence of VOCs has been evaluated. The interference of sensor readings by VOC has been observed, which can be attributed to the interference of VOC with the H2-O2 reaction on the Pd alloy surface. This interference can be eliminated by coating a layer of silicon dioxide on sensing film surface. Our work has demonstrated a wide range of applications of gas microsensors in radioactive waste management. Such applications can potentially lead to a significant cost saving and risk reduction for waste characterization

[en] Highlights: • Of 180 patients who received 19 Gy high-dose-rate brachytherapy (HDR-BT) for localised prostate cancer, with a median follow up of 36 months, 19 (10.6%) patients developed biochemical recurrence of which 13 had a local relapse, including 7 at the site of dominant intraprostatic nodule (DIL). • The 19 biochemical recurrences (failures) were matched to 19 control patients, who were matched to pre-treatment CTV size, Gleason score, T stage, risk category and presence of a DIL. For these patients, clinical and dosimetric parameters were analysed to see if there were any predictors for biochemical recurrence, local recurrence or recurrence within the DIL. • There were no statistically significant differences in all OARs, CTV, PTV and DIL dosimetric parameters between the failures and controls. • In univariate analysis, there were no statistically significant clinical or dosimetric parameters that predicted for biochemical progression free survival, local recurrence free survival or DIL recurrence free survival. • Whilst a large proportion of patients recur at the site of original disease, and these results may support rationale for further dose escalation, in our cohort actual dose delivered to DIL was around 26 Gy. Other studies employing dose escalation to whole gland or focal boost have failed to show improved clinical outcomes to justify this approach, hence HDR-BT should be undertaken using a minimum of two fractions. Long-term follow up of single dose high-dose rate brachytherapy (HDR BT) for localised prostate cancer has revealed higher than expected rates of biochemical and local failure. This study aimed (i) to investigate the pattern of relapse within the prostate with reference to the initial site of disease in those patients; and (ii) to examine if there were any relationships between the HDR BT dosimetric parameters to these areas of recurrence.