Absolute Reconstruction Research Articles

Validation of absolute 99mTc-sestamibi quantification using prone SPECT/CT for therapy monitoring in locally advanced breast cancer: a feasibility study

Background Tumor resistance to neoadjuvant chemotherapy (NAC) is the major cause of therapy failure in breast cancer (BC) patients. So far, 99mTc-sestamibi (MIBI) is the most widely used non-Positron Emission Tomography tracer in BC. MIBI uptake is known to be an independent prognostic factor in BC, whereas increased tumor uptake and retention of MIBI is associated with better response to chemotherapy. A rapid washout of MIBI appears to correlate with chemoresistance. Recent improvements in Single-Photon Emission Computed Tomography (SPECT) reconstructions enable us to quantify MIBI uptake and retention and to study metabolic parameters to define their role in therapy monitoring. The aim of this study is to assess the accuracy of a new absolute quantitative image reconstruction technique (QMetrix®, GE Healthcare) in locally advanced breast cancer (LABC) using prone SPECT/Computed Tomography (CT).

4D scanning system for measurement of human body in motion

In this paper we propose 4DBODY system which realizes full body 4D scanning of human in motion. It consists eight measurement heads based on single frame structured light method. All heads works synchronously with frequency 120 Hz with spectral separation to eliminate crosstalk. Single frame method is based on projection of sinusoidal fringe pattern with special marker allowing for absolute phase reconstruction. We develop custom made unwrapping procedure adjusted for human body analysis. We could achieve 0.5 mm spatial resolution and 0.3 mm of accuracy within a 1.5 x 1.5 x 2.0 m3 working volume. We integrated treadmill into system which allows to perform walking experiments. We present some results of measurements with initial validation of 4DBODY system.

Time-of-flight spectrometry of ultra-short, polyenergetic proton bunches.

A common approach for spectrum determination of polyenergetic proton bunches from laser-ion acceleration experiments is based on the time-of-flight (TOF) method. However, spectra obtained using this method are typically given in relative units or are estimated based on some prior assumptions on the energy distribution of the accelerated ions. In this work, we present a new approach using the TOF method that allows for an absolute energy spectrum reconstruction from a current signal acquired with a sub-nanosecond fast and 10 µm thin silicon detector. The reconstruction is based on solving a linear least-squares problem, taking into account the response function of the detection system. The general principle of signal generation and spectrum reconstruction by setting up an appropriate system response matrix is presented. Proof-of-principle experiments at a 12 MV Tandem accelerator using different nanosecond-short (quasi-)monoenergetic and polyenergetic proton bunches at energies up to 20 MeV were successfully performed. Within the experimental uncertainties of 2.4% and 12.1% for energy and particle number, respectively, reconstructed energy distributions were found in excellent agreement with the spectra calculated using Monte Carlo simulations and measured by a magnetic spectrometer. This TOF method can hence be used for absolute online spectrometry of laser-accelerated particle bunches.

Multiwavelength surface contouring from phase-coded noisy diffraction patterns: wavelength-division optical setup

We propose an algorithm for absolute phase retrieval from multiwavelength noisy phase coded diffraction patterns. A lensless optical system is considered with a set of successive single wavelength experiments (wavelength-division setup). The phase masks are applied for modulation of the multiwavelength object wavefronts. The algorithm uses the forward/backward propagation for coherent light beams and sparsely encoding wavefronts, which leads to the complex-domain block-matching three-dimensional filtering. The key-element of the algorithm is an original aggregation of the multiwavelength object wavefronts for high-dynamic-range absolute phase reconstruction. Simulation tests demonstrate that the developed approach leads to the effective solutions explicitly using the sparsity for noise suppression and high-accuracy object absolute phase reconstruction from noisy data.

Southwest Pacific Absolute Plate Kinematic Reconstruction Reveals Major Cenozoic Tonga-Kermadec Slab Dragging.

Tectonic plates subducting at trenches having strikes oblique to the absolute subducting plate motion undergo trench‐parallel slab motion through the mantle, recently defined as a form of “slab dragging.” We investigate here long‐term slab‐dragging components of the Tonga‐Kermadec subduction system driven by absolute Pacific plate motion. To this end we develop a kinematic restoration of Tonga‐Kermadec Trench motion placed in a mantle reference frame and compare it to tomographically imaged slabs in the mantle. Estimating Tonga‐Kermadec subduction initiation is challenging because another (New Caledonia) subduction zone existed during the Paleogene between the Australia and Pacific plates. We test partitioning of plate convergence across the Paleogene New Caledonia and Tonga‐Kermadec subduction zones against resulting mantle structure and show that most, if not all, Tonga‐Kermadec subduction occurred after ca. 30 Ma. Since then, Tonga‐Kermadec subduction has accommodated 1,700 to 3,500 km of subduction along the southern and northern ends of the trench, respectively. When placed in a mantle reference frame, the predominantly westward directed subduction evolved while the Tonga‐Kermadec Trench underwent ~1,200 km of northward absolute motion. We infer that the entire Tonga‐Kermadec slab was laterally transported through the mantle over 1,200 km. Such slab dragging by the Pacific plate may explain observed deep‐slab deformation and may also have significant effects on surface tectonics, both resulting from the resistance to slab dragging by the viscous mantle.

A new approach for simulating the paleo-evolution of the Northern Hemisphere ice sheets

Abstract. Offline forcing methods for ice-sheet models often make use of an index approach in which temperature anomalies relative to the present are calculated by combining a simulated glacial–interglacial climatic anomaly field, interpolated through an index derived from the Greenland ice-core temperature reconstruction, with present-day climatologies. An important drawback of this approach is that it clearly misrepresents climate variability at millennial timescales. The reason for this is that the spatial glacial–interglacial anomaly field used is associated with orbital climatic variations, while it is scaled following the characteristic time evolution of the index, which includes orbital and millennial-scale climate variability. The spatial patterns of orbital and millennial variability are clearly not the same, as indicated by a wealth of models and data. As a result, this method can be expected to lead to a misrepresentation of climate variability and thus of the past evolution of Northern Hemisphere (NH) ice sheets. Here we illustrate the problems derived from this approach and propose a new offline climate forcing method that attempts to better represent the characteristic pattern of millennial-scale climate variability by including an additional spatial anomaly field associated with this timescale. To this end, three different synthetic transient forcing climatologies are developed for the past 120 kyr following a perturbative approach and are applied to an ice-sheet model. The impact of the climatologies on the paleo-evolution of the NH ice sheets is evaluated. The first method follows the usual index approach in which temperature anomalies relative to the present are calculated by combining a simulated glacial–interglacial climatic anomaly field, interpolated through an index derived from ice-core data, with present-day climatologies. In the second approach the representation of millennial-scale climate variability is improved by incorporating a simulated stadial–interstadial anomaly field. The third is a refinement of the second one in which the amplitudes of both orbital and millennial-scale variations are tuned to provide perfect agreement with a recently published absolute temperature reconstruction over Greenland. The comparison of the three climate forcing methods highlights the tendency of the usual index approach to overestimate the temperature variability over North America and Eurasia at millennial timescales. This leads to a relatively high NH ice-volume variability on these timescales. Through enhanced ablation, this results in too low an ice volume throughout the last glacial period (LGP), below or at the lower end of the uncertainty range of estimations. Improving the representation of millennial-scale variability alone yields an important increase in ice volume in all NH ice sheets but especially in the Fennoscandian Ice Sheet (FIS). Optimizing the amplitude of the temperature anomalies to match the Greenland reconstruction results in a further increase in the simulated ice-sheet volume throughout the LGP. Our new method provides a more realistic representation of orbital and millennial-scale climate variability and improves the transient forcing of ice sheets during the LGP. Interestingly, our new approach underestimates ice-volume variations on millennial timescales as indicated by sea-level records. This suggests that either the origin of the latter is not the NH or that processes not represented in our study, notably variations in oceanic conditions, need to be invoked to explain millennial-scale ice-volume fluctuations. We finally provide here both our derived climate evolution of the LGP using the three methods as well as the resulting ice-sheet configurations. These could be of interest for future studies dealing with the atmospheric or/and oceanic consequences of transient ice-sheet evolution throughout the LGP and as a source of climate input to other ice-sheet models.

A Regularized Volumetric Fusion Framework for Large-Scale 3D Reconstruction

Modern computational resources combined with low-cost depth sensing systems have enabled mobile robots to reconstruct 3D models of surrounding environments in real-time. Unfortunately, low-cost depth sensors are prone to produce undesirable estimation noise in depth measurements which result in either depth outliers or introduce surface deformations in the reconstructed model. Conventional 3D fusion frameworks integrate multiple error-prone depth measurements over time to reduce noise effects, therefore additional constraints such as steady sensor movement and high frame-rates are required for high quality 3D models. In this paper we propose a generic 3D fusion framework with controlled regularization parameter which inherently reduces noise at the time of data fusion. This allows the proposed framework to generate high quality 3D models without enforcing additional constraints. Evaluation of the reconstructed 3D models shows that the proposed framework outperforms state of art techniques in terms of both absolute reconstruction error and processing time.

Combined Optical and Electronic Readout for Event Reconstruction in a GEM-Based TPC

Optically read out time projection chambers (TPCs) based on gaseous electron multipliers (GEMs) combine 3-D event reconstruction capabilities with high spatial resolution and charge amplification factors. The approach of reconstructing particle tracks from 2-D projections obtained with imaging sensors and depth information from photomultiplier tubes is limited to specific cases such as straight particle trajectories. A combination of optical and electronic readout realized by a semitransparent anode placed between a triple-GEM stack and a camera in an optically read out TPC has been realized and used to reconstruct more complex particle tracks. High spatial resolution 2-D projections combined with a low number of charge readout channels enable accurate 3-D event topology reconstruction. Straight alpha tracks as well as more complex cosmic events have been reconstructed with the presented readout concept. Relative depth information from electronically read out charge signals has been combined with drift time information between primary and secondary scintillation pulses to absolute alpha track reconstructions.

First direct constraints on Fierz interference in free-neutron β decay

Precision measurements of free-neutron β decay have been used to precisely constrain our understanding of the weak interaction. However, the neutron Fierz interference term bn, which is particularly sensitive to beyond-standard-model tensor currents at the TeV scale, has thus far eluded measurement. Here we report the first direct constraints on this term, finding bn=0.067±0.005stat−0.061+0.090sys, consistent with the standard model. The uncertainty is dominated by absolute energy reconstruction and the linearity of the β spectrometer energy response.Received 7 July 2017Corrected 6 November 2017DOI:https://doi.org/10.1103/PhysRevC.96.042501©2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeta decayElectroweak interactionElectroweak interactions in nuclear physicsExtensions of fermion sectorNeutron physicsParticle decaysParticle interactionsPhysical SystemsNeutronsParticles & FieldsNuclear PhysicsAccelerators & Beams

Superfast high-resolution absolute 3D recovery of a stabilized flapping flight process.

Scientific research of a stabilized flapping flight process (e.g. hovering) has been of great interest to a variety of fields including biology, aerodynamics, and bio-inspired robotics. Different from the current passive photogrammetry based methods, the digital fringe projection (DFP) technique has the capability of performing dense superfast (e.g. kHz) 3D topological reconstructions with the projection of defocused binary patterns, yet it is still a challenge to measure a flapping flight process with the presence of rapid flapping wings. This paper presents a novel absolute 3D reconstruction method for a stabilized flapping flight process. Essentially, the slow motion parts (e.g. body) and the fast-motion parts (e.g. wings) are segmented and separately reconstructed with phase shifting techniques and the Fourier transform, respectively. The topological relations between the wings and the body are utilized to ensure absolute 3D reconstruction. Experiments demonstrate the success of our computational framework by testing a flapping wing robot at different flapping speeds.

Absolute reconstruction of the closing of the Mongol‐Okhotsk Ocean in the Mesozoic elucidates the genesis of the slab geometry underneath Eurasia

AbstractUnderstanding the present‐day fast seismic velocity anomalies in the mantle requires an accurate kinematic reconstruction of past convergent tectonics. Using the paleomagnetism‐based absolute reconstruction method from Wu and Kravchinsky (2014), we present here the restoration of the closing of the Mongol‐Okhotsk Ocean (MOO) that existed between Siberia and North China‐Amuria (NCA) during the Mesozoic. Three stages, i.e., 250–200 Ma, 200–150 Ma, and 150–120 Ma, are identified from the time‐varying convergence rates of Siberia and NCA. The spherical distance between the suture margins was reduced by approximately 66.7% at an average convergence rate of 8.8 ± 0.6 cm/yr during the first stage at 250–200 Ma, when approximately 62.5–76.1% of the slabs associated with the MOO lithosphere were formed primarily through intraoceanic convergence. In the second stage at 200–150 Ma, the spherical distance was reduced by another 21.1% with a convergence rate of 3.6 ± 0.3 cm/yr. During this stage, approximately 14.2–30.9% of the MOO slabs were formed and continental‐oceanic convergence outpaced intraoceanic subduction. In the last stage at 150–120 Ma, the convergence rate dropped to approximately 0.4–0.6 cm/yr with the formation of approximately 4.6–9.8% slabs associated with the MOO lithosphere. The final closure of the remnant MOO basin could have been accomplished by 130–120 Ma, which explains the origin of the fast‐velocity anomalies inside the restored continents at 120 Ma near the suture margins.

GPU acceleration of absolute EIT image reconstruction using simulated annealing

Electrical impedance tomography (EIT) is a portable low-cost medical image technique with fast time response characteristics. EIT can be approached as an optimization problem whose objective is to minimize the difference between the simulated and measured distributions. A preconditioned conjugated gradient is employed to solve a linear system with a symmetric sparse positive definite matrix. In order to increase its efficiency, a matrix format, the colored padded jagged diagonals storage (pJDS) format, is proposed. Parallelization is applied to several steps of the algorithm and at each step performance is observed to be superior to fast serial implementation. However, API overhead degraded the performance of the forward problem. Kernel consolidation combined with the pJDS format obtained a significant performance improvement. The inverse problem is solved as an optimization problem using the simulated annealing with adaptive neighborhood. While several instances of the conjugated gradients run on the GPU, the remaining processes are executed in parallel in the CPU. The GPU saturates at a speedup of 5 times as compared to CPU processing.

Regularizing Biomechanical Maps for Partially Known Material Properties

We present the solution of the inverse problem for partially known elastic modulus values, e.g., the elastic modulus is known in some small region on the boundary of the domain from measurements. The inverse problem is posed as a constrained minimization problem and regularized with two different regularization types. In particular, the total variation diminishing (TVD) and the total contrast diminishing (TCD) regularizations are employed. We test both regularization strategies with theoretical diseased tissues, such as a stiff tumor surrounded by healthy background tissue and an atherosclerotic plaque having a soft inclusion surrounded by a stiff cap. In the present study, it is assumed that no traction data is available and the absolute elastic modulus distribution is calibrated from partially known elastic modulus values. We observe that this calibration fails with TVD regularization, while TCD regularization yields well-recovered absolute elastic modulus reconstructions in the presence of high noise levels in the displacement data. Finally, we investigate this problem analytically and provide an explanation for these observations. This work will advance efforts in parameter identification of heterogeneous materials as it provides a methodology to incorporate partially known parameters into the inverse problem formulation that will ultimately drive the inverse solution to an absolute and unique parameter distribution. This has great importance in classifying breast tumors based on their elastic modulus values and in planning surgical interventions of atherosclerotic plaques.

Absolute Reconstructions Using Rotational Electrical Impedance Tomography for Breast Cancer Imaging.

A rotational Electrical Impedance Tomography (rEIT) methodology is described and shown to produce spatially accurate absolute reconstructions with improved image contrast and an improved ability to distinguish closely spaced inclusions compared to traditional EIT on data recorded from cylindrical and breast-shaped tanks. Rotations of the tank without altering the interior conductivity distribution are used to produce the rEIT data. Quantitatively, rEIT was able to distinguish two inclusions that were 1.5 cm closer together than traditional EIT could achieve for inclusions placed 2 to 3 cm from the center for the cylindrical tank, and rEIT was able to distinguish two tumor-like inclusions where traditional EIT could not reliably do so. Mathematical analysis showed that rEIT improves the number of stable singular vectors by up to 4.2 and 4.7 times than that of traditional EIT for the cylindrical and breast-shaped tanks, respectively, which is an indication of improved resolution. Direct investigations into measurements revealed minimum rotation angles that should yield data uncorrupted by noise. Two inverse approaches (one that inverts then fuses the data (I/DF) and one that fuses the data then inverts (DF/I)) and two mesh modeling approaches were considered. It was found that DF/I produces far better results compared to I/DF and a rotated-mesh approach produces further improvements. The ability to obtain improved absolute reconstructions using rEIT on a practical clinical scenario (breast-shaped tank experiment) is an important step towards using rEIT to improve previous EIT results in medical applications.

Multiphase permittivity imaging using absolute value electrical capacitance tomography data and a level set algorithm.

Multiphase flow imaging is a very challenging and critical topic in industrial process tomography. In this article, simulation and experimental results of reconstructing the permittivity profile of multiphase material from data collected in electrical capacitance tomography (ECT) are presented. A multiphase narrowband level set algorithm is developed to reconstruct the interfaces between three- or four-phase permittivity values. The level set algorithm is capable of imaging multiphase permittivity by using one set of ECT measurement data, so-called absolute value ECT reconstruction, and this is tested with high-contrast and low-contrast multiphase data. Simulation and experimental results showed the superiority of this algorithm over classical pixel-based image reconstruction methods. The multiphase level set algorithm and absolute ECT reconstruction are presented for the first time, to the best of our knowledge, in this paper and critically evaluated. This article is part of the themed issue 'Supersensing through industrial process tomography'.

A Novel Regularization Technique for Microendoscopic Electrical Impedance Tomography.

A novel regularization technique is developed for end-fired microendoscopic electrical impedance tomography using the dual-mesh method. The new regularization technique coupled with appropriate forward modeling and inverse mesh design is shown to produce dramatically improved reconstructions over previous methods. 3D absolute and difference reconstructions from measured saline tank and ex vivo adipose and muscle tissue experiments are used to validate the approach. The ex vivo experiments are used as a surrogate for prostate tissue, which is the primary clinical application for the probe. Inclusion center of mass errors were less than 0.47 mm for tank experiments with inclusion depths and radial offsets ranging less than 3 mm and 1.5 mm, respectively. Absolute 3D reconstructions on the tissue show quantitatively good accuracy and the ability to spatially distinguish small tissue features (adipose strands of approximately 2.5 mm in width). The reconstruction algorithm developed provides strong evidence for the promise of surgical margin detection using microendoscopic EIT.

Postmastectomy Radiation Therapy and Breast Reconstruction--Marching Forward Together or Apart?

Postmastectomyradiationtherapy (PMRT)and immediate reconstruction eachplay important roles in the treatment of patientswithbreast cancer.GivingPMRT increases cure rates for subgroupswith substantial risks of local-regional recurrence.1 Many individuals wish to have immediatebreast reconstruction to reduce the psychological and social consequences of mastectomy. However, PMRT increases the risks of complications andpoor cosmetic results after breast reconstruction. Immediate reconstruction limits the technical approaches available for delivering PMRT, potentially resulting in increased heart and lung doses. Improvements in surgical and radiation techniquesover timehavedecreasedbutnot entirely eliminated these problems.2,3 The studybyFrasier and colleagues4 in this issueof JAMA Oncology showed that use of both PMRT and breast reconstruction increasedduring the recentpast in theUnitedStates, despite these deleterious interactions. The increase in PMRT rates was almost entirely confined to patients with tumors 5 cm or smaller with 1 to 3 involved axillary nodes at “intermediate” risk of local regional recurrence, for whom the 2009 guidelines of the National Comprehensive Cancer Network (NCCN) said PMRT should be “strongly considered.” (This increase seems to have begun in earnest in 2007 [see their Figure4].This likely reflects the impactofearlierguidelinesand editorials that encouragedPMRT tobeusedmoreoften in this group.)Asexpected, absolute ratesof reconstruction throughout the study period remained higher for patientswith lowor intermediate risks of local-regional recurrence than for individuals at high risk, for whom the guidelines unequivocally recommended PMRT. These findings are quite plausible and consistent with other studies, which they ably discuss. The authors also cogently point out the many limitations of using the Surveillance, Epidemiology, and End Results (SEER) database to determine patterns of care. One major problem is that SEER does not capture PMRT or reconstructive surgery performed more than 4 months after the initiation of therapy. Many patients now receive postoperative chemotherapy programs lasting 3 to 6 months before starting PMRT; and, particularly but not exclusively in community practices, consultation with a radiation oncologist is often not scheduled until near the end of or after chemotherapy, delaying the final decision well beyond this 4-month window. (One way to overcome this analytic problem is to use health insurance databases that capture care over longer periods.5) Themost critical questions regarding theuseofPMRTand breast reconstructionare, however, difficult to answer in such a study as the present one. First, did patients who would potentially benefit from PMRT not receive it because they underwent reconstruction? Second, didpatientswhowanted reconstructionnot receive itbecause theirphysiciansanticipated that they might need PMRT preoperatively? Treating physicians’ opinions are important to patients trying to decide whether they will undergo PMRT.6 That seems even more likely when guidelines do not explicitly mandate whether treatment be given. Such ambiguity (reflecting a lack of consensus in the profession) leaves room for potentially relevant but also extraneous medical and nonmedical factors to affect decision making. The authors found that tumor size (T1 vs T2) and grade (1 vs 2 or 3) affected the frequency of PMRT use in the intermediate-risk subgroup. However, other pathologic findings often used to select patients for PMRT are not included in the SEER database (eg, the presence of lymphovascular invasion and margin involvement). Patient socioeconomic status and comorbidities are not available in SEER. Hence, biases against using PMRT in patients who already underwent reconstruction could be hard to tease out even with matched-pair and propensity analysis. Still, it might be helpful to examine whether PMRT was used more or less often for the subgroups of patients who did or did not undergo reconstruction, both for the population as a whole and for the NCCNdefined subgroups. This might shed light on the disturbing fact that only two-thirds of patients aged 64 years or younger in the “recommend radiotherapy” group received it at the end of the study period. Was the increased use of reconstruction in this group partly to blame for the rate not being higher? For almost all patients, recommendations for PMRT are made after surgery, based on the pathologic findings. (The exception is patients with clinical stage III, or “locally advanced,” breast cancer.) The decision whether to perform reconstruction is made without this knowledge, as the authors note. Nonetheless, in practice the well-known though imperfect relationship between clinical and pathologic stages results inapreoperative“impression”ofwhetherPMRTwill likely be needed thatmay influence physician and patient behavior. For example, do physicians equally often recommend immediate reconstruction topatientswith4-cmpalpablemassesand severalpalpable ipsilateralaxillarynodesastopatientswithnonpalpable 1-cm cancers and nonpalpable nodes? These recommendations again are likely tohave an effect becausepatients’ concernsabout increasedrisksofcomplications fromPMRTare often decisive in their decisions whether to undergo immediate reconstruction.7Perhaps therewasamodest increase in the useof reconstruction inpatientswhohadPMRTbut a substantial increase in reconstruction in patients who did not have PMRT. Or perhaps the use of reconstruction increased by the Related article page 95 Research Original Investigation Trends in Postmastectomy Radiation Therapy and Breast Reconstruction

Absolute 3D reconstruction of thin films topography in microfluidic channels by interference reflection microscopy.

The travel of droplets, bubbles, vesicles, capsules, living cells or small organisms in microchannels is a hallmark in microfluidics applications. A full description of the dynamics of such objects requires a quantitative understanding of the complex hydrodynamic and interfacial interactions between objects and channel walls. In this paper, we present an interferometric method that allows absolute topographic reconstruction of the interspace between an object and channel walls for objects confined in microfluidic channels. Wide field microscopic imaging in reflection interference contrast mode (RICM) is directly performed at the bottom wall of microfluidic chips. Importantly, we show that the reflections at both the lower and upper surface of the microchannel have to be considered in the quantitative analysis of the optical signal. More precisely, the contribution of the reflection at the upper surface is weighted depending on the light coherence length and channel height. Using several wavelengths and illumination apertures, our method allows reconstructing the topography of thin films on channel walls in a range of 0-500 nm, with a precision as accurate as 2 nm for the thinnest films. A complete description of the protocol is exemplified for oil in water droplets travelling in channels of height 10-400 μm at a speed up to 5 mm s(-1).

Environmental and diagenetic records from trace elements in the Mediterranean coral Cladocora caespitosa

Trace element contents in coralline aragonite have long been used as proxies to record environmental growth conditions such as sea surface temperature (SST). In this study we explored whether trace element contents in modern and fossil corals (Cladocora caespitosa) from the Mediterranean could help constrain SST temperature and seasonality of climate in late Pleistocene interglacials. In modern Adriatic C. caespitosa, the individual corallite Sr/Ca signal captures seasonal variation with up to 68% of the variance related to SST. A similar but weaker relationship is shown by Mg/Ca. However, published equations to quantify absolute water temperature from Sr and Mg contents in modern C. caespitosa did not yield consistent or credible results, because each corallite exerts a strong, non-predictable ‘vital effect’. With no constant species-specific offset from equilibrium, temperature-trace element relationships become, at best, colony specific and unsuitable for absolute palaeotemperature reconstruction. Despite this, temperature-related cyclicity in Sr and Mg is preserved in corallites up to at least MIS 7 age, allowing identification of seasonality in SST. In addition, unusual trace element anomalies in modern C. caespitosa can inform on events such as sediment discharge into the coastal zone. Partial diagenetic alteration of fossil C. caespitosa skeletons from aragonite to calcite destroys original SST driven cyclic trace element signals and is an effective indicator of corallite preservation quality.

Stable 18O and 13C isotope records of Viviparus diluvianus (Kunth, 1865) shells from Holsteinian (MIS 11) lakes of eastern Poland as palaeoenvironmental and palaeoclimatic proxies

The oxygen and carbon stable isotope composition of Viviparus diluvianus shells was determined in the palaeolakes of the Holsteinian interglacial (MIS 11) in eastern Poland: the Ortel Królewski, Hrud, Ossówka, Roskosz and Szymanowo lakes. The occurrence of V. diluvianus covers the Taxus zone, the so‐called intra‐interglacial cooling period (Pinus‐Larix zone), the climatic optimum (Carpinus‐Abies zone) and the post‐optimal period with an undefined pollen zone. The isotope record of V. diluvianus shells allowed palaeoclimate and palaeoenvironmental reconstructions. δ18O and δ13C vary from −8.7‰ in the post‐optimal period to −4.8‰ in the optimal period, and from −10.6‰ at the beginning of the Taxus zone to −4.2‰ at the climatic optimum, respectively. A positive correlation of the isotope curves indicates closed‐water bodies, and only at Roskosz was some occasional overflow inferred. Higher oxygen isotopes correspond to an increase in temperature and/or enhanced evaporation, which is well marked in the Carpinus‐Abies zone, whereas samples enriched in 13C are correlated with periods demonstrating a lower water level and higher productivity in the lakes. Episodes of lake shallowing and dense aquatic vegetation occurred in the Pinus‐Larix zone and during the climatic optimum. The isotope ratios for the climatic optimum significantly exceed those of the other periods, thus pointing to warmer conditions. An estimation of relative changes of average summer temperatures using the δ18O/temperature gradient yielded variation of 1–2 °C within the lakes. Absolute temperature reconstructions indicate the effects of specific local conditions. Hence, V. diluvianus shells offer a reliable proxy in qualitative studies of interglacial lake records.