Adsorption of analyte molecules is ubiquitous in nanofluidic channels due to their large surface-to-volume ratios. It is also difficult to quantify due to the nanometric scale of these channels. We propose a simple method to probe dynamic adsorption at electrodes that are embedded in nanofluidic channels or which enclose nanoscopic volumes. The amperometric method relies on measuring the amplitude of the fluctuations of the redox cycling current that arise when the channel is diffusively coupled to a bulk reservoir. We demonstrate the versatility of this new method by quantifying adsorption for several redox couples, investigating the dependence of adsorption on the electrode potential and studying the effect of functionalizing the electrodes with self-assembled monolayers of organothiol molecules bearing polar end groups. These self-assembled monolayer coatings are shown to significantly reduce the adsorption of the molecules on to the electrodes. The detection method is not limited to electrodes in nanochannels and can be easily extended to redox cycling systems that enclose very small volumes, in particular scanning electrochemical microscopy with nanoelectrodes. It thus opens the way for imaging spatial heterogeneity with respect to adsorption, as well as rational design of interfaces for redox cycling based sensors.

We present a radiomics model to discriminate between patients at low risk and those at high risk of treatment failure at long-term follow-up based on eigentumors: principal components computed from volumes encompassing tumors in washin and washout images of pre-treatment dynamic contrast-enhanced (DCE-) MR images. Eigentumors were computed from the images of 563 patients from the MARGINS study. Subsequently, a least absolute shrinkage selection operator (LASSO) selected candidates from the components that contained 90% of the variance of the data. The model for prediction of survival after treatment (median follow-up time 86 months) was based on logistic regression. Receiver operating characteristic (ROC) analysis was applied and area-under-the-curve (AUC) values were computed as measures of training and cross-validated performances. The discriminating potential of the model was confirmed using Kaplan-Meier survival curves and log-rank tests. From the 322 principal components that explained 90% of the variance of the data, the LASSO selected 28 components. The ROC curves of the model yielded AUC values of 0.88, 0.77 and 0.73, for the training, leave-one-out cross-validated and bootstrapped performances, respectively. The bootstrapped Kaplan-Meier survival curves confirmed significant separation for all tumors (P < 0.0001). Survival analysis on immunohistochemical subgroups shows significant separation for the estrogen-receptor subtype tumors (P < 0.0001) and the triple-negative subtype tumors (P  =  0.0039), but not for tumors of the HER2 subtype (P  =  0.41). The results of this retrospective study show the potential of early-stage pre-treatment eigentumors for use in prediction of treatment failure of breast cancer.

BackgroundPrevious studies have shown discrepancies between index and synchronous breast cancer in histology and molecular phenotype. It is yet unknown whether this observation also applies to the MRI phenotype.PurposeTo investigate whether the appearance of breast cancer on MRI (i.e. phenotype) is different from that of additional breast cancer (i.e. synchronous cancer), and whether such a difference, if it exists, is associated with prognosis.Study TypeRetrospective.PopulationIn all, 464 consecutive patients with early‐stage ER+/HER2– breast cancer were included; 34/464 (7.3%) had 44 synchronous cancers in total (34 ipsilateral, 10 contralateral).Sequence1.5T, contrast‐enhanced T1‐weighted.AssessmentWe assessed imaging phenotype using 50 quantitative features from each cancer and applied principal component analysis (PCA) to identify independent properties. The degree of phenotype difference was assessed. An association between phenotype differences and prognosis in terms of the Nottingham Prognostic Index (NPI) and PREDICT score were analyzed.Statistical TestsPCA; Wilcoxon rank sum test; Benjamini–Hochberg to control the false discovery rate.ResultsPCA identified eight components in patients with ipsilateral synchronous cancer. Six out of eight were significantly different between index and synchronous cancer. These components represented features describing texture (three components, P < 0.001, P < 0.001, P = 0.004), size (P < 0.001), smoothness (P < 0.001), and kinetics (P = 0.004). Phenotype differences in terms of the six components were split in tertiles. Larger phenotype differences in size, kinetics, and texture were associated with significantly worse prognosis in terms of NPI (P = 0.019, P = 0.045, P = 0.014), but not for the PREDICT score (P = 0.109, P = 0.479, P = 0.109). PCA identified six components in patients with contralateral synchronous cancer. None were significantly different from the index cancer (P = 0.178, P = 0.178, P = 0.178, P = 0.326, P = 0.739, P = 0.423).Data ConclusionThe MRI phenotype of ER+/HER2– breast cancer was different from that of ipsilateral synchronous cancer and a large phenotype difference was associated with worse prognosis. No significant difference was found for synchronous contralateral cancer.Level of Evidence: 3Technical Efficacy: Stage 4J. Magn. Reson. Imaging 2020;51:1858–1867.

Purpose: Inhomogeneous excitation at ultrahigh field strengths (7T and above) compromises the reliability of quantified dynamic contrast-enhanced breast MRI. This can hamper the introduction of ultrahigh field MRI into the clinic. Compensation for this non-uniformity effect can consist of both hardware improvements and postacquisition corrections. This paper investigated the correctable radiofrequency transmit (B + 1 ) range post-acquisition in both simulations and patient data for 7T MRI. Methods: Simulations were conducted to determine the minimum B + 1 level at which corrections were still beneficial because of noise amplification. Two correction strategies leading to differences in noise amplification were tested. The effect of the corrections on a 7T patient data set (N = 38) with a wide range of B + 1 levels was investigated in terms of time-intensity curve types as well as washin, washout and peak enhancement values. Results: In simulations assuming a common amount of T 1 saturation, the lowest B + 1 level at which the SNR of the corrected images was at least that of the original precontrast image was 43% of the nominal angle. After correction, time-intensity curve types changed in 24% of included patients, and the distribution of curve types corresponded better to the distribution found in literature. Additionally, the overlap between the distributions of washin, washout, and peak enhancement values for grade 1 and grade 2 tumors was slightly reduced. Conclusion: Although the correctable range varies with the amount of T 1 saturation, post-acquisition correction for inhomogeneous excitation was feasible down to B + 1 levels of 43% of the nominal angle in vivo. K E Y W O R D S 7T, B + 1 mapping, breast, DCE-MRI, flip-angle correction, RF field inhomogeneity | 1001 van RIJSSEL Et aL.