Publications by authors named "Christianen M"

Article Synopsis
  • - The study aimed to identify errors in transrectal ultrasound (TRUS)-based reconstructions for high-dose-rate brachytherapy in prostate cancer, using an electromagnetic tracking (EMT) system to enhance accuracy during treatment.
  • - Out of 265 evaluated needle reconstructions, 23% had minor errors or worse, with 9% classified as major or severe, primarily due to issues like incorrect needle placement and user errors.
  • - The findings indicate that one-quarter of the reconstructions had errors exceeding 2mm, highlighting the potential of EMT to help detect and prevent these mistakes, improving patient care without affecting the clinical process.
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Article Synopsis
  • Many tropical coastal ecosystems are affected by human activities related to tourism and land/sea use.
  • We created a method to engage stakeholders early in ecological research to map the Social-Ecological System (SES) in Lac Bay, Bonaire, especially addressing the new challenge of massive sargassum landings.
  • Our Group Model Building methodology helped us uncover key drivers and feedbacks, prioritize urgent research questions, and develop management strategies for the conservation of seagrass beds and mangrove forests in the area.
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Objective: Hypofractionation has become the new clinical standard for prostate cancer. We investigated the management of acute toxicity in patients treated with moderate hypofractionation (MHF) or Ultrahypofractionation (UHF).

Methods: In a prospective cohort setting, patients (N=316) received either MHF (20 fractions of 3/3.

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Background: Electromagnetic Tracking (EMT) technology has been integrated in a prototype high-dose-rate brachytherapy (HDR-BT) afterloading device. Its potential for dwell position (DP) monitoring has earlier been demonstrated in prostate phantoms. However, its performance for prostate BT in the clinical setting remains to be assessed.

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Prostate cancer patients with an enlarged prostate and/or excessive pubic arch interference (PAI) are generally considered non-eligible for high-dose-rate (HDR) brachytherapy (BT). Steerable needles have been developed to make these patients eligible again. This study aims to validate the dosimetric impact and performance of steerable needles within the conventional clinical setting.

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Tropical seascapes rely on the feedback relationships among mangrove forests, seagrass meadows, and coral reefs, as they mutually facilitate and enhance each other's functionality. Biogeochemical fluxes link tropical coastal habitats by exchanging material flows and energy through various natural processes that determine the conditions for life and ecosystem functioning. However, little is known about the seascape-scale implications of anthropogenic disruptions to these linkages.

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Article Synopsis
  • Sargassum strandings in the tropical Atlantic create toxic sulfide levels that harm mangrove ecosystems.
  • An experiment tested whether adding iron(III) (hydr)oxides could reduce sulfide toxicity and greenhouse gas emissions in mangroves affected by Sargassum.
  • While iron failed to prevent mangrove death from high sulfide levels, it did reduce methane and nitrous oxide emissions significantly, highlighting the complex ecological impacts of Sargassum on mangroves.
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Climate change is altering the functioning of foundational ecosystems. While the direct effects of warming are expected to influence individual species, the indirect effects of warming on species interactions remain poorly understood. In marine systems, as tropical herbivores undergo poleward range expansion, they may change food web structure and alter the functioning of key habitats.

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Mangrove restoration is underway along tropical coastlines to combat their rapid worldwide decline. However, restoration success is limited due to local drivers such as eutrophication, and global drivers such as climate change, yet their interactions remain unclear. We conducted a mesocosm experiment to assess the impact of increased nutrients and temperature on the photosynthetic efficiency and development of black mangrove seedlings.

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Structurally complex habitats, such as mangrove forests, allow for rich assemblages of species that benefit from the provided space, volume and substrate. Changes in habitat complexity can affect species abundance, diversity and resilience. In this study, we explored the effects of habitat complexity on food web networks in four developmental stages of mangrove forests with differing structural complexities: climax > degrading > colonizing > bare, by analyzing food web structure, stable isotopes and habitat complexity.

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The COVID-19 pandemic created the need to use digital health resources (DR), as they sometimes were the only option to receive healthcare or social interaction. The aim of this research is to provide insight into the experiences during the lockdown of older people using DR for health in general and the points of improvement they see. A qualitative study was carried out using semi-structured interviews with older persons by telephone.

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Large grazers (megaherbivores) have a profound impact on ecosystem functioning. However, how ecosystem multifunctionality is affected by changes in megaherbivore populations remains poorly understood. Understanding the total impact on ecosystem multifunctionality requires an integrative ecosystem approach, which is especially challenging to obtain in marine systems.

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Understanding how megaherbivores incorporate habitat features into their foraging behavior is key toward understanding how herbivores shape the surrounding landscape. While the role of habitat structure has been studied within the context of predator-prey dynamics and grazing behavior in terrestrial systems, there is a limited understanding of how structure influences megaherbivore grazing in marine ecosystems. To investigate the response of megaherbivores (green turtles) to habitat features, we experimentally introduced structure at two spatial scales in a shallow seagrass meadow in The Bahamas.

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In high-dose-rate brachytherapy (HDR-BT) for prostate cancer treatment, interstitial hyperthermia (IHT) is applied to sensitize the tumor to the radiation (RT) dose, aiming at a more efficient treatment. Simultaneous application of HDR-BT and IHT is anticipated to provide maximum radiosensitization of the tumor. With this rationale, the ThermoBrachyTherapy applicators have been designed and developed, enabling simultaneous irradiation and heating.

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The combination of interstitial hyperthermia treatment (IHT) with high dose rate brachytherapy (HDR-BT) can improve clinical outcomes since it highly enhances the efficiency of cell kill, especially when applied simultaneously. Therefore, we have developed the ThermoBrachy applicators. To effectively apply optimal targeted IHT, treatment planning is considered essential.

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A review of studies on seminal vesicle motion was performed to improve the understanding of these treatment uncertainties. This will aid planning target volume margin reduction, which is necessary for hypofractionation of high-risk prostate cancer. Embase, Medline, Web of science Core collection, Cochrane CENTRAL register of trials and Google scholar were searched for publications including 3D information on seminal vesicle motion.

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Pleistocene environmental changes are generally assumed to have dramatically affected species' demography via changes in habitat availability, but this is challenging to investigate due to our limited knowledge of how Pleistocene ecosystems changed through time. Here, we tracked changes in shallow marine habitat availability resulting from Pleistocene sea level fluctuations throughout the last glacial cycle (120-14 thousand years ago; kya) and assessed correlations with past changes in genetic diversity inferred from genome-wide SNPs, obtained via ddRAD sequencing, in Caribbean hawksbill turtles, which feed in coral reefs commonly found in shallow tropical waters. We found sea level regression resulted in an average 75% reduction in shallow marine habitat availability during the last glacial cycle.

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Objective: In High Dose Rate Brachytherapy for prostate cancer there is a need for a new way of increasing cancer cell kill in combination with a stable dose to the organs at risk. In this study, we propose a novel ThermoBrachy applicator that offers the unique ability to apply interstitial hyperthermia while simultaneously serving as an afterloading catheter for high dose rate brachytherapy for prostate cancer. This approach achieves a higher thermal enhancement ratio than in sequential application of radiation and hyperthermia and has the potential to decrease the overall treatment time.

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The occasional westward transport of warm water of the Agulhas Current, "Agulhas leakage", around southern Africa has been suggested to facilitate tropical marine connectivity between the Atlantic and Indian oceans, but the "Agulhas leakage" hypothesis does not explain the signatures of eastward gene flow observed in many tropical marine fauna. We investigated an alternative hypothesis: the establishment of a warm-water corridor during comparatively warm interglacial periods. The "warm-water corridor" hypothesis was investigated by studying the population genomic structure of Atlantic and Southwest Indian Ocean green turtles (N = 27) using 12,035 genome-wide single nucleotide polymorphisms (SNPs) obtained via ddRAD sequencing.

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Background And Purpose: To investigate the accuracy of dwell position detection with a combined electromagnetic tracking (EMT) brachytherapy (BT) system for treatment verification, by quantifying positional errors due to EM field interference in typical pelvic BT clinical settings.

Materials And Methods: Dedicated prostate and cervix BT phantoms were imaged with CT. For the cervix phantom, the Utrecht applicator + interstitial catheters were used.

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Restoration is becoming a vital tool to counteract coastal ecosystem degradation. Modifying transplant designs of habitat-forming organisms from dispersed to clumped can amplify coastal restoration yields as it generates self-facilitation from emergent traits, i.e.

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Article Synopsis
  • The study focused on the population composition and dynamics of Caribbean green turtles in juvenile feeding grounds, particularly in Lac Bay, Bonaire, highlighting the importance of understanding migratory megafauna for conservation efforts.
  • Genetic analyses revealed a significant shift in population composition between 2006-2007 and 2015-2016, with juvenile recruitment patterns changing notably from different Caribbean regions.
  • The findings suggest potential issues in reproductive output at certain rookeries and emphasize the need for conservation of juvenile habitats and genetic monitoring to better track megafauna population trends.
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Increasing incubation temperatures may threaten the viability of sea turtle populations. We explored opportunities for decreasing incubation temperatures at a Caribbean rookery with extreme female-biased hatchling production. To investigate the effect of artificial shading, temperatures were measured under simple materials (white sheet, white sand, palm leaves).

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