Fixational eye movements show scaling behaviour of the positional mean-squared displacement with a characteristic transition from persistence to antipersistence for increasing time-lag. These statistical patterns were found to be mainly shaped by microsaccades (fast, small-amplitude movements). However, our re-analysis of fixational eye-movement data provides evidence that the slow component (physiological drift) of the eyes exhibits scaling behaviour of the mean-squared displacement that varies across human participants. These results suggest that drift is a correlated movement that interacts with microsaccades. Moreover, on the long time scale, the mean-squared displacement of the drift shows oscillations, which is also present in the displacement auto-correlation function. This finding lends support to the presence of time-delayed feedback in the control of drift movements. Based on an earlier non-linear delayed feedback model of fixational eye movements, we propose and discuss different versions of a new model that combines a self-avoiding walk with time delay. As a result, we identify a model that reproduces oscillatory correlation functions, the transition from persistence to antipersistence, and microsaccades.

Ultrasound, including colour Doppler, enables an exact morphological analysis of the late results after surgically corrected cryptorchidism. The spectrum of findings does not show any correlation with the time of surgery. Thus, the value of even early surgery has to be questioned. Pre-existent primary damage (dysplasia) seems more important for long-term outcome of the testis. Additionally, US was of high value in demonstrating additional unexpected anomalies, the majority of which needed sonographic follow-up or even surgery.

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Purpose The characteristic MRI features of multiple sclerosis (MS) lesions make it conceptually appealing to pursue parametric mapping techniques that support simultaneous generation of quantitative maps of 2 or more MR contrast mechanisms. We present a modular rapid acquisition with relaxation enhancement (RARE)‐EPI hybrid that facilitates simultaneous T2 and T2∗ mapping (2in1‐RARE‐EPI). Methods In 2in1‐RARE‐EPI the first echoes in the echo train are acquired with a RARE module, later echoes are acquired with an EPI module. To define the fraction of echoes covered by the RARE and EPI module, an error analysis of T2 and T2∗ was conducted with Monte Carlo simulations. Radial k‐space (under)sampling was implemented for acceleration (R = 2). The feasibility of 2in1‐RARE‐EPI for simultaneous T2 and T2∗ mapping was examined in a phantom study mimicking T2 and T2∗ relaxation times of the brain. For validation, 2in1‐RARE‐EPI was benchmarked versus multi spin‐echo (MSE) and multi gradient‐echo (MGRE) techniques. The clinical applicability of 2in1‐RARE‐EPI was demonstrated in healthy subjects and MS patients. Results There was a good agreement between T2/T2∗ values derived from 2in1‐RARE‐EPI and T2/T2∗ reference values obtained from MSE and MGRE in both phantoms and healthy subjects. In patients, MS lesions in T2 and T2∗ maps deduced from 2in1‐RARE‐EPI could be just as clearly delineated as in reference maps calculated from MSE/MGRE. Conclusion This work demonstrates the feasibility of radially (under)sampled 2in1‐RARE‐EPI for simultaneous T2 and T2∗ mapping in MS patients.