An experimental validation of a filtering approach for prompt gamma prediction in a research proton treatment planning system.

Prompt gamma (PG) radiation generated from nuclear reactions between protons and tissue nuclei can be employed for range verification in proton therapy. A typical clinical workflow for prompt gamma range verification compares the detected prompt gamma profile with a predicted one. Recently, a novel analytical prompt gamma prediction algorithm based on the so-called filtering formalism has been proposed and implemented in a research version of RayStation (RaySearch Laboratories AB), which is a widely adopted treatment planning system. In this work, the said algorithm is validated against experimental data and benchmarked with another well-established prompt gamma prediction algorithm implemented in a MATLAB-based software REGGUI. Furthermore, a new workflow based on several PG profile quality criteria and analytical methods is proposed for data selection. The workflow also calculates sensitivity and specificity information, which can help practitioners to decide on irradiation course interruption during treatment and monitor spot selection at the treatment planning stage. With the proposed workflow, the comparison can be performed on a limited number of selected high-quality irradiation spots without neighbouring-spot aggregation. The mean shifts between the experimental data and the simulated PG detection (PGD) profiles (ΔPGD) by the two algorithms are estimated to be 1.5~2.1 mm and -0.6~2.2 mm for the filtering and REGGUI prediction methods, respectively. The ΔPGD difference between two algorithms is observed to be consistent with the beam model difference within uncertainty. However, the filtering approach requires a much shorter computation time compared to the REGGUI approach.

The association between pre-diagnostic levels of psychological distress and adverse effects after radical prostatectomy.

Objectives: To prospectively analyse the associations between pre-diagnostic levels of anxiety and depression and patient-reported urinary and sexual adverse effects after radical prostatectomy in a population-based setting. Patients and Methods: In three Norwegian county hospitals, men referred with a suspicion of prostate cancer were asked to fill out a patient-reported outcome measurement (PROM) questionnaire prior to prostate biopsy. Those who later underwent radical prostatectomy were stratified into three distress groups according to their Hopkins Symptom Checklist 5-score. Additional PROM questionnaires, including the EPIC-26 to measure adverse effects, were collected at 6 and 12 months postoperatively. Multivariable mixed models were estimated and post hoc pairwise comparisons performed to explore differences in adverse effects between distress groups. Results: A total of 416 men were included at baseline and of those, 365 (88%) returned questionnaires at 6 months and 360 (87%) at 12 months. After adjusting for confounders, men with high distress at baseline had worse urinary incontinence domain score (58.9 vs. 66.8, p = 0.028), more urinary bother (64.7 vs. 73.6, p = 0.04) and a higher risk of using incontinence pads (70.6% vs. 54.2%, p = 0.034) at 6 months than those with low distress. There was no difference in the sexual domain scores between distress groups postoperatively, but the high-distress group expressed more sexual bother (24.9 vs. 37.5, p = 0.015) and the intermediate-distress group had a greater probability of using sexual medications or devices (63.8% vs. 50.0%, p = 0.015) than the low-distress group at 6 months. At 12 months scores generally improved slightly and differences between distress groups were less evident. Conclusion: Men with higher levels of anxiety and depression before prostate biopsy report more urinary and sexual adverse effects after radical prostatectomy. This should be considered both in treatment decision-making and during follow-up after radical prostatectomy.

Atomic structure and water arrangement on K-feldspar microcline (001).

The properties of clouds, such as their reflectivity or their likelihood to precipitate, depend on whether the cloud droplets are liquid or frozen. Thus, understanding the ice nucleation mechanisms is essential for the development of reliable climate models. Most ice nucleation in the atmosphere is heterogeneous, i.e., caused by ice nucleating particles such as mineral dusts or organic aerosols. In this regard, K-feldspar minerals have attracted great interest recently as they have been identified as one of the most important ice nucleating particles under mixed-phase cloud conditions. The mechanism by which feldspar minerals facilitate ice nucleation remains, however, elusive. Here, we present atomic force microscopy (AFM) experiments on microcline (001) performed in an ultrahigh vacuum and at the solid-water interface together with density functional theory (DFT) and molecular dynamics (MD) calculations. Our ultrahigh vacuum data reveal features consistent with a hydroxyl-terminated surface. This finding suggests that water in the residual gas readily reacts with the surface. Indeed, the corresponding DFT calculations confirm a dissociative water adsorption. Three-dimensional AFM measurements performed at the mineral-water interface unravel a layered hydration structure with two features per surface unit cell. A comparison with MD calculations suggests that the structure observed in AFM corresponds to the second hydration layer rather than the first water layer. In agreement with previous computation results, no ice-like structure is seen, questioning an explanation of the ice nucleation ability by lattice match. Our results provide an atomic-scale benchmark for the clean and water-covered microcline (001) plane, which is mandatory for understanding the ice nucleation mechanism on feldspar minerals.

Investigation of surface orientation dependent sputtering of Ag.

Sputtering of metal surfaces can be both a beneficial phenomenon, for instance in the coating industry, or an undesired side-effect, for instant materials subjected to irradiation. While the average sputtering yields are well known in common metals, recent studies have shown that the yields can depend on the crystallographic orientation of the surface much stronger than commonly appreciated. In this study, we investigate by computational means, molecular dynamics, the sputtering of single crystalline Ag surfaces under various incoming energies. The results at low and high energy are compared to experimental results for single crystalline Ag nanocubes of different orientations. We observe strong differences between the sputtering yields of different surface directions and ion energies. We analyze the results in terms of the atom cluster size of the sputtered materials, and show that the cluster size distribution is a key factor to understand the correspondence between simulations and experiments. At low energies mainly single atoms are sputtered, whereas at higher energies the sputtered material is mainly in atom clusters.

CBCT-Based Dose Monitoring and Adaptive Planning Triggers in Head and Neck PBS Proton Therapy.

PURPOSE: To investigate the feasibility of using cone-beam computed tomography (CBCT)-derived synthetic CTs to monitor the daily dose and trigger a plan review for adaptive proton therapy (APT) in head and neck cancer (HNC) patients. METHODS: For 84 HNC patients treated with proton pencil-beam scanning (PBS), same-day CBCT and verification CT (vfCT) pairs were retrospectively collected. The ground truth CT (gtCT) was created by deforming the vfCT to the same-day CBCT, and it was then used as a dosimetric baseline and for establishing plan review trigger recommendations. Two different synthetic CT algorithms were tested; the corrected CBCT (corrCBCT) was created using an iterative image correction method and the virtual CT (virtCT) was created by deforming the planning CT to the CBCT, followed by a low-density masking process. Clinical treatment plans were recalculated on the image sets for evaluation. RESULTS: Plan review trigger criteria for adaptive therapy were established after closely reviewing the cohort data. Compared to the vfCT, the corrCBCT and virtCT reliably produced dosimetric data more similar to the gtCT. The average discrepancy in D99 for high-risk clinical target volumes (CTV) was 1.1%, 0.7%, and 0.4% and for standard-risk CTVs was 1.8%, 0.5%, and 0.5% for the vfCT, corrCBCT, and virtCT, respectively. CONCLUSION: Streamlined APT has been achieved with the proposed plan review criteria and CBCT-based synthetic CT workflow.

Clinical evaluation of synthetic computed tomography methods in adaptive proton therapy of lung cancer patients.

Background and purpose: Efficient workflows for adaptive proton therapy are of high importance. This study evaluated the possibility to replace repeat-CTs (reCTs) with synthetic CTs (sCTs), created based on cone-beam CTs (CBCTs), for flagging the need of plan adaptations in intensity-modulated proton therapy (IMPT) treatment of lung cancer patients. Materials and methods: Forty-two IMPT patients were retrospectively included. For each patient, one CBCT and a same-day reCT were included. Two commercial sCT methods were applied; one based on CBCT number correction (Cor-sCT), and one based on deformable image registration (DIR-sCT). The clinical reCT workflow (deformable contour propagation and robust dose re-computation) was performed on the reCT as well as the two sCTs. The deformed target contours on the reCT/sCTs were checked by radiation oncologists and edited if needed. A dose-volume-histogram triggered plan adaptation method was compared between the reCT and the sCTs; patients needing a plan adaptation on the reCT but not on the sCT were denoted false negatives. As secondary evaluation, dose-volume-histogram comparison and gamma analysis (2%/2mm) were performed between the reCT and sCTs. Results: There were five false negatives, two for Cor-sCT and three for DIR-sCT. However, three of these were only minor, and one was caused by tumour position differences between the reCT and CBCT and not by sCT quality issues. An average gamma pass rate of 93% was obtained for both sCT methods. Conclusion: Both sCT methods were judged to be of clinical quality and valuable for reducing the amount of reCT acquisitions.

An optimized framework for cone-beam computed tomography-based online evaluation for proton therapy.

BACKGROUND: Clinical evidence has demonstrated that proton therapy can achieve comparable tumor control probabilities compared to conventional photon therapy but with the added benefit of sparing healthy tissues. However, proton therapy is sensitive to inter-fractional anatomy changes. Online pre-fraction evaluation can effectively verify proton dose before delivery to patients, but there is a lack of guidelines for implementing this workflow. PURPOSE: The purpose of this study is to develop a cone-beam CT-based (CBCT) online evaluation framework for proton therapy that enables knowledge transparency and evaluates the efficiency and accuracy of each essential component. METHODS: Twenty-three patients with various lesion sites were included to conduct a retrospective study of implementing the proposed CBCT evaluation framework for the clinic. The framework was implemented on the RayStation 11B Research platform. Two synthetic CT (sCT) methods, corrected CBCT (cCBCT), and virtual CT (vCT), were used, and the ground truth images were acquired from the same-day deformed quality assurance CT (dQACT) for the comparisons. The evaluation metrics for the framework include time efficiency, dose-difference distributions (gamma passing rates), and water equivalent thickness (WET) distributions. RESULTS: The mean online CBCT evaluation times were 1.6 ± 0.3 min and 1.9 ± 0.4 min using cCBCT and vCT, respectively. The dose calculation and deformable image registration dominated the evaluation efficiency, and accounted for 33% and 30% of the total evaluation time, respectively. The sCT generation took another 19% of the total time. Gamma passing rates were greater than 91% and 97% using 1%/1 mm and 2%/2 mm criteria, respectively. When the appropriate sCT was chosen, the target mean WET difference from the reference were less than 0.5 mm. The appropriate sCT method choice determined the uncertainty for the framework, with the cCBCT being superior for head-and-neck patient evaluation and vCT being better for lung patient evaluation. CONCLUSIONS: An online CBCT evaluation framework was proposed to identify the use of the optimal sCT algorithm regarding efficiency and dosimetry accuracy. The framework is extendable to adopt advanced imaging methods and has the potential to support online adaptive radiotherapy to enhance patient benefits. It could be implemented into clinical use in the future.

Fear of Recurrence in Prostate Cancer Patients: A Cross-sectional Study After Radical Prostatectomy or Active Surveillance.

BACKGROUND: Fear of recurrence (FoR) is a distressing consequence of cancer. Little is known about the prevalence of FoR in different treatment groups and factors associated with FoR among prostate cancer (PCa) survivors. OBJECTIVE: To investigate the prevalence of high FoR among PCa survivors after radical prostatectomy (RP) or under active surveillance (AS) and to explore clinical and psychological factors potentially associated with FoR. DESIGN SETTING AND PARTICIPANTS: This is a retrospective cross-sectional study of 606 patients with PCa, treated with either RP (n = 442) or AS (n = 164) at two Norwegian regional hospitals. The 440 patients (73%) who gave consent to participate were invited in 2017 to complete a questionnaire measuring FoR, self-rated health, adverse effects, and psychological factors at a mean of 4.1 yr (standard deviation 1.7) after their treatment decision. Clinical data were retrieved from medical records. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: FoR was measured using the Concerns About Recurrence Questionnaire, with high FoR defined as a sum score of =12 points (range 0-40). Using multivariable logistic regression analyses, factors associated with high FoR were identified. RESULTS AND LIMITATIONS: One-third of the participants had high FoR; scores were higher in the AS group and in the RP group with treatment failure. Younger age was significantly associated with high FoR in the AS group, while high prostate-specific antigen at diagnosis, biochemical recurrence, positive surgical margin, higher fatigue, and a type D personality were significantly associated with high FoR in the RP group. CONCLUSIONS: At 4 yr after a diagnosis of PCa, high FoR was common, especially among AS patients and among RP patients with treatment failure. PATIENT SUMMARY: In this study, we examined fear that their disease will return or progress among prostate cancer survivors. We found that such fear was common, especially among young patients under active surveillance and among radical prostatectomy patients with treatment failure or with certain psychological features.

Work status and work ability after radical prostatectomy or active surveillance for prostate cancer.

Objective: Being able to work is important for health-related quality of life (HRQoL), and little is known about work life after radical treatment for prostate cancer (PCa). The aim was to investigate work status (WS) and work ability (WA) after radical prostatectomy (RP) or active surveillance (AS) for PCa, and to identify factors associated with reduced WA.Materials and methods: This is a retrospective cross-sectional study of 606 men treated with RP (n = 442) or AS (n = 164) at two Norwegian general hospitals. In 2017, they were asked to complete questionnaires measuring adverse effects (AE), HRQoL, aspects of work life and psychological factors at a median of 4.1 (range 1.3-8.1) years after diagnosis. Clinical data were retrieved from medical records. WS was categorized into employed, unemployed or retired. WA was rated using the Work Ability Index. Regression analyses were performed to find factors associated with reduced WA.Results: WS was similar for the RP and AS groups at diagnosis and survey. There was a small reduction in WA from diagnosis to survey and the difference between the RP and AS groups was non-significant. Older age, poorer self-rated health, poorer incontinence score, more chronic fatigue, and increased anxiety and depressive symptoms were associated with reduced WA, while treatment method, urinary bother and use of pads were not.Conclusion: The impact of RP and AS on WS and WA was almost similar. Age and psychological variables were more strongly associated with reduced WA than cancer-related variables.

Psychometric properties of the expanded prostate cancer index composite - 26 instrument in a cohort of radical prostatectomy patients: theoretical and practical examinations.

BACKGROUND: Recently, the Expanded Prostate Cancer Index Composite 26-item version (EPIC-26) was recommended for the assessment of adverse effects after the treatment of prostate cancer without clear reasons. This decision encouraged us to review the questionnaire development from the UCLA Prostate Cancer Index (UCLA-PCI) to the EPIC-16 CP with a focus on psychometric properties. We also reviewed PubMed for papers concerning such properties of the EPIC-26 since 2012 (latest review in 2011). Finally, we examined the psychometric properties of the EPIC-26 in a sample of Norwegian males treated with robot-assisted laparoscopic prostatectomy (RALP). METHODS: This study used three methods: (1) Comparison of the content of the UCLA-PCI, EPIC-50, EPIC-26, and EPIC-16 CP; (2) Review of EPIC-26 and EPIC-16 CP papers in PubMed from 2012 to 2016, identifying papers reporting on the psychometric properties of these questionnaires; and (3) Psychometric examination of the EPIC-26 rating in 651 Norwegian men treated with RALP at a mean of 3.2 years post-surgery. RESULTS: The questionnaire development showed a significant increase in bother versus function items, and the EPIC-26 contains eight function and 18 bother items. Twelve papers concerning the EPIC-26 available on PubMed since 2012 support the psychometric properties of the EPIC-26. The Norwegian EPIC-26 findings supported the psychometric properties of the EPIC-26, but suggested six subdomains both by exploratory and confirmatory factor analyses. CONCLUSIONS: In general our examinations supported the adequate psychometric properties of the EPIC-26, although the factor structure, construct and predictive validity of the instrument should be examined further.

Early outcome of orchiopexy and analysis of predictive factors: a retrospective study from 2001 to 2010 in a Norwegian regional hospital.

OBJECTIVE: The primary aim of this study was to retrospectively analyse surgical treatment for undescended testes at the Department of Urology, Telemark Hospital, Norway, and to examine whether international standards were met regarding age at surgery and outcome. The secondary aim was to identify factors that predicted an unsuccessful outcome. MATERIAL AND METHODS: The department's medical records from 2001 to 2010 were searched, and selected variables were registered and analysed. RESULTS: Of 205 primary orchiopexies, 81% were considered immediately successful and 94% were successful after reoperation. Median age at the time of primary surgery was 3.7 years (range 0.1-17.5 years). Fourteen per cent were operated on before the age of 2 years and 40% before the age of 3 years. There was a tendency towards lower age at surgery in the later part of the study period. Younger patients had an increased risk of a primary unsuccessful result. Procedures performed by a surgeon with a low number of operations were less often successful. Preoperative testicular location and different surgical technique did not affect outcome significantly. CONCLUSIONS: The results may seem inferior to those reported by others but comparison is uncertain owing to differences in study design, patient selection criteria and follow-up time. Although age at surgery in this series was higher than recommended, and outcome of the very youngest needs to be improved, the authors argue that the quality of treatment was acceptable. Orchiopexies should be carried out by a limited number of dedicated surgeons in each department.