The costs and benefits of estimating T-1 of tissue alongside cerebral blood flow and arterial transit time in pseudo-continuous arterial spin labeling

Multi-post-labeling-delay pseudo-continuous arterial spin labeling (multi-PLD PCASL) allows for absolute quantification of the cerebral blood flow (CBF) as well as the arterial transit time (ATT). Estimating these perfusion parameters from multi-PLD PCASL data is a non-linear inverse problem, which is commonly tackled by fitting the single-compartment model (SCM) for PCASL, with CBF and ATT as free parameters. The longitudinal relaxation time of tissue T-1t is an important parameter in this model, as it governs the decay of the perfusion signal entirely upon entry in the imaging voxel. Conventionally, T-1t is fixed to a population average. This approach can cause CBF quantification errors, as T-1t can vary significantly inter- and intra-subject. This study compares the impact on CBF quantification, in terms of accuracy and precision, of either fixing T-1t, the conventional approach, or estimating it alongside CBF and ATT. It is shown that the conventional approach can cause a significant bias in CBF. Indeed, simulation experiments reveal that if T-1t is fixed to a value that is 10% off its true value, this may already result in a bias of 15% in CBF. On the other hand, as is shown by both simulation and real data experiments, estimating T-1t along with CBF and ATT results in a loss of CBF precision of the same order, even if the experiment design is optimized for the latter estimation problem. Simulation experiments suggest that an optimal balance between accuracy and precision of CBF estimation from multi-PLD PCASL data can be expected when using the two-parameter estimator with a fixed T-1t value between population averages of T-1t and the longitudinal relaxation time of blood T-1b

Stekende insecten Griendtsveen 2015-2018

De inventarisatie van steekmuglarven leverde in 2016 vier kleinere gebiedsdelen op met hoge aantallen steekmuglarven (de zogenaamde ‘hotspots’). In april-mei 2017 en 2018 zijn de larveninventarisaties herhaald. Hieruit bleek dat de larven van de moerassteekmug A. cinereus over het gehele gebied verspreid zijn met op twee van de vier ‘hotspots’ de hoogste aantallen. In de periode daarna vielen in beide jaren de meeste locaties droog. Het jaar 2017 was een droog jaar waarbij al vroeg in het voorjaar, mogelijk zelfs in de winter, veel potentiële tijdelijke wateren droog stonden. Na een natte winter werd 2018 een nog extremer droog jaar met veel droogval in het gebied. Het patroon van ontwikkeling van volwassen steekmuggen liet over 2017 een ‘klassiek’ beeld van een moerassteekmuggenpopulatie zien met hoge aantallen in het voorjaar die daarna snel uitdoven. Alleen in juni trad additioneel een kleine populatie van plantenboorsteekmuggen op. Dit beeld is een gevolg van het opdrogen van tijdelijke wateren in het voorjaar. De in totaal lagere aantallen in het gehele gebied en de beperking van deze aantallen tot de maand mei hebben ertoe geleid dat in het dorp Griendtsveen in 2017 geen overlast is ervaren. 2018 daarentegen was in de winter normaal nat wat, mogelijk in combinatie met de natheid van het gebied, leidde tot zeer hoge aantallen moerassteekmuggen. Dit waren de hoogste aantallen tot nu toe gemeten. De verdeling van de aantallen over de jaren 2015-2018 naar zone rondom en in het dorp laat zien dat er ieder jaar een afname van de aantallen optreedt richting de dorpskern. In de periode 2015-2018 is het aantallen verzamelde knutten jaarlijks toegenomen. De aantallen zijn in 2018 viermaal hoger t.o.v. 2015. Dit kan samenhangen met grotere oppervlakken nattere gebiedsdelen, nattere weilanden aan de zuidzijde, in het dorp en aan de westzijde. Ondanks de aanpak van de knutten hotspot, wat lokaal voor een aanzienlijke vermindering heeft gezorgd, zet de ontwikkeling van de knutten in andere gebiedsdelen (nog) door. De adviezen voor maatregelen om de ‘hotspots’ aan te pakken zijn in 2017 in gang gezet en ten dele in 2018 uitgevoerd. De resultaten zijn nog niet zichtbaar in de voorjaarsmetingen van 2018 omdat op dat moment de maatregelen nog moesten worden geïmplementeerd

Skills Labs - Deliverable 2.4.a: Casusidee Building with Nature: Blue Greens in Volkerak-Zoommeer

Blauw, T., Dekker, P., Stel, J., Klomp, R., Kortsmit, B., & Löhr, A. (2008). Skills Labs - Deliverable 2.4.a: Casusidee Building with Nature: Blue Greens in Volkerak-ZoommeerVolgens de Emergo-methode uitgewerkt casusidee van casus Building with Nature: Blue Greens in Volkerak-Zoommeer binnen het project Skills Labs.SURFFoundatio

Supporting measurements or more averages? How to quantify cerebral blood flow most reliably in 5 minutes by arterial spin labeling

Purpose To determine whether sacrificing part of the scan time of pseudo-continuous arterial spin labeling (PCASL) for measurement of the labeling efficiency and blood T1 is beneficial in terms of CBF quantification reliability. Methods In a simulation framework, 5-minute scan protocols with different scan time divisions between PCASL data acquisition and supporting measurements were evaluated in terms of CBF estimation variability across both noise and ground truth parameter realizations taken from the general population distribution. The entire simulation experiment was repeated for a single-post-labeling delay (PLD), multi-PLD, and free-lunch time-encoded (te-FL) PCASL acquisition strategy. Furthermore, a real data study was designed for preliminary validation. Results For the considered population statistics, measuring the labeling efficiency and the blood T1 proved beneficial in terms of CBF estimation variability for any distribution of the 5-minute scan time compared to only acquiring ASL data. Compared to single-PLD PCASL without support measurements as recommended in the consensus statement, a 26%, 33%, and 42% reduction in relative CBF estimation variability was found for optimal combinations of supporting measurements with single-PLD, free-lunch, and multi-PLD PCASL data acquisition, respectively. The benefit of taking the individual variation of blood T1 into account was also demonstrated in the real data experiment. Conclusions Spending time to measure the labeling efficiency and the blood T1 instead of acquiring more averages of the PCASL data proves to be advisable for robust CBF quantification in the general population

Characterisation and classification of oligometastatic disease : a European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus recommendation

Oligometastatic disease has been proposed as an intermediate state between localised and systemically metastasised disease. In the absence of randomised phase 3 trials, early clinical studies show improved survival when radical local therapy is added to standard systemic therapy for oligometastatic disease. However, since no biomarker for the identification of patients with true oligometastatic disease is clinically available, the diagnosis of oligometastatic disease is based solely on imaging findings. A small number of metastases on imaging could represent different clinical scenarios, which are associated with different prognoses and might require different treatment strategies. 20 international experts including 19 members of the European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer OligoCare project developed a comprehensive system for characterisation and classification of oligometastatic disease. We first did a systematic review of the literature to identify inclusion and exclusion criteria of prospective interventional oligometastatic disease clinical trials. Next, we used a Delphi consensus process to select a total of 17 oligometastatic disease characterisation factors that should be assessed in all patients treated with radical local therapy for oligometastatic disease, both within and outside of clinical trials. Using a second round of the Delphi method, we established a decision tree for oligometastatic disease classification together with a nomenclature. We agreed oligometastatic disease as the overall umbrella term. A history of polymetastatic disease before diagnosis of oligometastatic disease was used as the criterion to differentiate between induced oligometastatic disease (previous history of polymetastatic disease) and genuine oligometastatic disease (no history of polymetastatic disease). We further subclassified genuine oligometastatic disease into repeat oligometastatic disease (previous history of oligometastatic disease) and de-novo oligometastatic disease (first time diagnosis of oligometastatic disease). In de-novo oligometastatic disease, we differentiated between synchronous and metachronous oligometastatic disease. We did a final subclassification into oligorecurrence, oligoprogression, and oligopersistence, considering whether oligometastatic disease is diagnosed during a treatment-free interval or during active systemic therapy and whether or not an oligometastatic lesion is progressing on current imaging. This oligometastatic disease classification and nomenclature needs to be prospectively evaluated by the OligoCare study

High Biofilm Formation of Non-Smooth Candida parapsilosis Correlates with Increased Incorporation of GPI-Modified Wall Adhesins

Candida parapsilosis is among the most frequent causes of candidiasis. Clinical isolates of this species show large variations in colony morphotype, ranging from round and smooth to a variety of non-smooth irregular colony shapes. A non-smooth appearance is related to increased formation of pseudohyphae, higher capacity to form biofilms on abiotic surfaces, and invading agar. Here, we present a comprehensive study of the cell wall proteome of C. parapsilosis reference strain CDC317 and seven clinical isolates under planktonic and sessile conditions. This analysis resulted in the identification of 40 wall proteins, most of them homologs of known Candida albicans cell wall proteins, such as Gas, Crh, Bgl2, Cht2, Ecm33, Sap, Sod, Plb, Pir, Pga30, Pga59, and adhesin family members. Comparative analysis of exponentially growing and stationary phase planktonic cultures of CDC317 at 30 °C and 37 °C revealed only minor variations. However, comparison of smooth isolates to non-smooth isolates with high biofilm formation capacity showed an increase in abundance and diversity of putative wall adhesins from Als, Iff/Hyr, and Hwp families in the latter. This difference depended more strongly on strain phenotype than on the growth conditions, as it was observed in planktonic as well as biofilm cells. Thus, in the set of isolates analyzed, the high biofilm formation capacity of non-smooth C. parapsilosis isolates with elongated cellular phenotypes correlates with the increased surface expression of putative wall adhesins in accordance with their proposed cellular function.This work was funded by grants from the Spanish Ministry of Economy and Competitiveness (MINECO) (SAF2013-47570-P and SAF2017-86188-P) and the regional government of Castilla-La Mancha (JCCM) (SBPLY/19/180501/000114), all co-financed by the EU (FEDER), to P.W.J.d.G. and E.E., the Consejería de Educación, Universidades e Investigación (GIC15/78 IT-990-16) of Gobierno Vasco-Eusko Jaurlaritza to E.E., and the FP7-PEOPLE-2013-ITN—Marie-Curie Action: “Initial Training Networks”: Molecular Mechanisms of Human Fungal Pathogen Host Interaction, ImResFun, MC-ITN-606786, to O.B