MRzero - Automated discovery of MRI sequences using supervised learning.

PURPOSE: A supervised learning framework is proposed to automatically generate MR sequences and corresponding reconstruction based on the target contrast of interest. Combined with a flexible, task-driven cost function this allows for an efficient exploration of novel MR sequence strategies. METHODS: The scanning and reconstruction process is simulated end-to-end in terms of RF events, gradient moment events in x and y, and delay times, acting on the input model spin system given in terms of proton density, T1 and T2 , and ΔB0 . As a proof of concept, we use both conventional MR images and T1 maps as targets and optimize from scratch using the loss defined by data fidelity, SAR penalty, and scan time. RESULTS: In a first attempt, MRzero learns gradient and RF events from zero, and is able to generate a target image produced by a conventional gradient echo sequence. Using a neural network within the reconstruction module allows arbitrary targets to be learned successfully. Experiments could be translated to image acquisition at the real system (3T Siemens, PRISMA) and could be verified in the measurements of phantoms and a human brain in vivo. CONCLUSIONS: Automated MR sequence generation is possible based on differentiable Bloch equation simulations and a supervised learning approach.

Performance and responses to competition in two congeneric annual species: does seed heteromorphism matter?

Variations in seed characteristics observed in heteromorphic species may affect various stages of their life cycles, e.g. seed dormancy, germination characteristics or even adult plant performance. Highly specialised seed morphs - described as colonisers and maintainers - exhibit a trade-off between colonisation capacity and competitive traits. The performance of distinct seed morph progeny under competitive conditions, and especially in multi-species arrangements, had previously not been given much attention. In this study, we compared performance and response to competition among distinct seed morph progenies in two congeneric, co-occurring species: the invasive Bidens frondosa and the non-invasive Bidens tripartita. We hypothesised that maintainer seed morphs of both species would perform better under increased plant densities and within inter-morphic mixtures, while coloniser morphs would show stronger responses to increased densities and perform relatively poorly in inter-morphic mixtures. We conducted a growth trial and a greenhouse experiment, which revealed that seed morph progeny differed significantly in plant height when grown without competition, while under competitive conditions such differences became less apparent. The observed pattern was more strongly pronounced in B. frondosa, which showed a general predominance in stature and biomass over its non-invasive congener. Although seed morphs performed equally well under competitive conditions, increased plant height and more rapid germination can favour the maintainer seed morph on sites where vegetation is already present.

[Megacystis-microcolon intestinal hypoperistalsis syndrome (MMIHS) as a rare differential diagnosis of foetal megacystis on ultrasonography]. / Megacystis-Microcolon intestinales Hypoperistaltik-Syndrom (MMIHS) als seltene Differenzialdiagnose bei fetaler Megacystis im Ultraschall.

INTRODUCTION: Foetal megacystis (incidence 1:1 500) occurring in the first trimester may already be a sign of congenital malformation. Often, urethral valves are causally responsible in male foetuses far more frequently than urethral atresia. As a further differential diagnosis, the "prune-belly syndrome" needs to be distinguished. Far more difficult to classify prenatally is the rare MMIHS which, in contrast to the diagnosis of urethral valves, is associated with an unfavourable prognosis. CASE REPORT: This is a report on a 28-year-old IG/0P, whose foetus of 26+4 gestational weeks was found on ultrasonography for the first time to have a megacystis of 48 mm diameter and bilateral hydronephrosis. The female foetus was surrounded by a normal amount of amniotic fluid which, during the further course of the pregnancy, developed into polyhydramnios. The serial puncture of the urinary bladder showed a normal karyotype and no impairment of the renal concentrating capacity or of protein loss. By reason of an immense enlargement of the abdomen due to the 100 mm large urinary bladder, a Caesarean section was conducted at 36+0 gestational weeks. A catheter could be inserted into the urinary bladder postpartum easily. However, nourishment was not possible and after radiological examination, MMIHS was diagnosed. CONCLUSION: In the case of a foetal megacystis detected by ultrasonography, especially associated with polyhydramnios and female gender, the rare MMIHS, which is infaust, should be taken into consideration.

Difference in dose area product between analog image intensifier and digital flat panel detector in peripheral angiography and the effect of BMI.

PURPOSE: Comparison of dose area products (DAP) in diagnostic angiography procedures between an image intensifier (II) and a flat panel detector (FPD) angiography system and the evaluation of DAP/body mass index (BMI) dependency. MATERIALS AND METHODS: An image intensifier system or a flat panel detector system was used to perform 571 diagnostic angiographies (n = 328 and n = 243, respectively) of 5 different types: peripheral arterial, venous, single leg, abdominal and upper extremity. The results were retrospectively analyzed. The DAP, fluoroscopy time (t) and the number of series of the respective interventions as calculated by the respective machines was compared for all interventions and for the respective subtypes and machines. The BMI dependency was calculated separately for both machines for all interventions by subdividing the patients into 6 BMI classes defined by the WHO. RESULTS: The average DAP for all diagnostic interventions was 1958.9 cGy×cm2 (t = 384.6 s, n = 7.85 series) for the II and 2927.4 cGy×cm2 (t = 267.4 s, n = 7.02 series) for the FPD. Group-dependent differences ranged between + 21 and + 252 % when using the FPD system. After time standardization, the respective increases were found to be 120 % for the FPD system. The DAPs increased considerably in patients with higher BMIs (766.7 cGy × cm2 - 6892.6 cGy × cm2, II machine, 950.5 cGy × cm2 - 12 487.7 cGy × cm2, FPD machine) with a greater DAP gain seen for the FPD. The average duration of the interventions was higher using the II machine. CONCLUSION: The use of an FPD system led to higher DAP values compared to the II system in diagnostic angiographic procedures. In addition, increased BMI values led to higher DAPs, especially for the FPD machine. However, the average fluoroscopy times were shorter.

[Late preterms: the influence of foetal gender on neonatal outcome]. / Late preterms: Auswirkungen des fetalen Geschlechts auf das neonatologische Outcome.

BACKGROUND: The group of the so-called late preterms (infants born at 34 0/7-36 6/7 weeks gestational age) has been underestimated with respect to their neonatal outcome. Among infants born before the 29th week of pregnancy, a gender-specific difference in favour of females regarding morbidity became evident. The aim of this study is to investigate whether these findings are transferable to the group of late preterms. METHODS: The neonatal outcome of 528 consecutive singletons, born at 34 0/7-36 6/7 weeks gestational age and requiring intensive care, was examined. RESULTS: Neonatal complications have been particularly analysed with regard to gender-specific differences. Boys (n=292) were significantly more frequently affected by sepsis (3.8 vs. 0.9%; p=0,0314, x²-test). Girls had significantly longer stays in the neonatal intensive care unit (median 12 (Q1:8; Q3:17) vs. 11 (6;16) days; p=0.0149, t-test). In a multiple logistic regression model, male gender and premature rupture of membranes were borderline significant with respect to the occurrence of sepsis - boys had a 4.4-fold risk (OR=0.228 [95% CI: 0.050-1.041]; p=0.0564) and premature rupture of membranes had a 3.5-fold risk (OR=3.462 [0.938-12.779]; p=0.0623). Strong cause variables for the length of stay in the neonatal intensive care unit were birth weight, gestational age and premature rupture of membranes after adjustment. CONCLUSION: The influence of foetal gender on the neonatal outcome in the late preterm group (34 0/7-36 6/7 gestational age) has been relativised.

Factors influencing the absorbed dose in intraoral radiography.

OBJECTIVES: The aim of the present study was to find out whether it was more effective to achieve a dose reduction in intraoral radiography with an increase in the tube potential setting (and a decrease of milliampere seconds) by an additional attenuation of the X-ray beam behind the film plane or by the use of digital radiography. A second aim was to find out if there were differences between the integral doses determined by two different detectors and two different phantoms. METHODS: The X-ray attenuation in this in vitro study was carried out using additional lead foils from the dental film packet fixed behind the film plane and with a metal film holder. The dose measurements were performed with two semiconductor detectors (Quart, Diados). Patient simulation was achieved by the Alderson phantom or by the use of a filter (6Al+0.8Cu). The absorbed doses were calculated by integrating an exponential function between the entrance dose and the body exit dose. In addition, organ doses were measured and the effective dose was determined according to the Implementation of the 1990 Recommendations of the ICRP (ICRP-60). RESULTS: The increase in tube potential levels did not provide a substantial reduction of the absorbed dose (90 kVp instead of 60 kVp: reduction to 92.4%), only a reduction of the entrance dose (by 30% to 35% at 90 kVp compared with 60 kVp). The use of three lead foils behind the film plane instead of one resulted in a 14.0% reduction of the absorbed dose (60 kVp); the use of a metal film holder resulted in a 27.8% reduction (60 kVp). When tube potential settings were increased, the dose reduction decreased. The absorbed dose was reduced to 52% when a storage phosphor plate was used instead of a film (60 kVp). It was possible to determine the amount of dose reduction with both the calculated absorbed dose and the effective doses. The integral doses obtained from the Alderson phantom showed values 5% higher than those obtained by the filter (r(2)=96.7%). For the comparison of the integral doses, the measurements performed with Quart had values higher by a factor of 1.139 than those performed with Diados. CONCLUSIONS: Instead of increasing the tube voltage or using additional lead foils or metal film holders, a substantial dose reduction is provided by digital radiography or more sensitive films while a low tube potential level is maintained and the milliampere seconds setting is reduced.

NhaA of Escherichia coli, as a model of a pH-regulated Na+/H+antiporter.

Na(+)/H(+) antiporters are ubiquitous membrane proteins that are involved in homeostasis of H(+) and Na(+) throughout the biological kingdom. Corroborating their role in pH homeostasis, many of the Na(+)/H(+) antiporter proteins are regulated directly by pH. The pH regulation of NhaA, the Escherichia coli Na(+)/H(+) antiporter (EcNhaA), as of other, both eukaryotic and prokaryotic Na(+)/H(+) antiporters, involves a pH sensor and conformational changes in different parts of the protein that transduce the pH signal into a change in activity. Thus, residues that affect the pH response, the translocation or both activities cluster in separate domains along the antiporter molecules. Importantly, in the NhaA family, these domains are conserved. Helix-packing model of EcNhaA based on cross-linking data suggests, that in the three dimensional structure of NhaA, residues that affect the pH response may be in close proximity, forming a single pH sensitive domain. Therefore, it is suggested that, despite considerable differences in the primary structure of the antiporters from the bacterial NhaA to the mammalian NHEs, their three-dimensional architectures are conserved. Test of this possibility awaits the atomic resolution of the 3D structure of the antiporters.