Determination Of Volume Changes Research Articles

An observational study to determine volume changes in the functional liver remnant following portal vein embolization.

Background and AimPortal vein embolization (PVE) prior to hepatic resection reduces the risk of hepatic insufficiency in the postoperative period by redistributing blood from the embolized unhealthy liver to the healthy liver, termed the functional liver remnant (FLR). A retrospective analysis of liver volumes after embolization in a single institution was performed to identify change in volume of the FLR and determine factors affecting this change.MethodsBetween 2013 and 2015, 21 patients undergoing PVE followed by hepatic resection for varied indications (colorectal metastases, hepatocellular carcinoma, cholangiocarcinoma, etc.) were included in this study. n‐butyl cyanoacrylate glue diluted with Lipiodol (35–45% strength) along with 75–100 μm of polyvinyl alcohol particles were used for embolization. Liver volumetric determination was performed before and after PVE and volume changes in the FLR were analyzed. Biochemical factors and factors affecting FLR hypertrophy were also analyzed.ResultsMajority of the patients (n = 18) underwent right‐lobe embolization. All were performed using the ipsilateral approach. No major complications occurred with only one patient developing post‐procedural ascites requiring percutaneous draining. A significant increase in the mean volume of the FLR by 63.7% ± 91.6%, P = 0.001 was noted after PVE. The FLR/total liver volume (TLV) increased significantly by 17% ± 18%. No significant demographic factors affected FLR hypertrophy and no significant biochemical changes were noted. Thirteen patients were successfully operated on after embolization.ConclusionsPVE is effective in inducing significant hypertrophy of the future FLR, prior to hepatic resection in our institution.

Differentiation of Benign from Malignant Pulmonary Nodules by Using a Convolutional Neural Network to Determine Volume Change at Chest CT.

Background Deep learning may help to improve computer-aided detection of volume (CADv) measurement of pulmonary nodules at chest CT. Purpose To determine the efficacy of a deep learning method for improving CADv for measuring the solid and ground-glass opacity (GGO) volumes of a nodule, doubling time (DT), and the change in volume at chest CT. Materials and Methods From January 2014 to December 2016, patients with pulmonary nodules at CT were retrospectively reviewed. CADv without and with a convolutional neural network (CNN) automatically determined total nodule volume change per day and DT. Area under the curves (AUCs) on a per-nodule basis and diagnostic accuracy on a per-patient basis were compared among all indexes from CADv with and without CNN for differentiating benign from malignant nodules. Results The CNN training set was 294 nodules in 217 patients, the validation set was 41 nodules in 32 validation patients, and the test set was 290 nodules in 188 patients. A total of 170 patients had 290 nodules (mean size ± standard deviation, 11 mm ± 5; range, 4-29 mm) diagnosed as 132 malignant nodules and 158 benign nodules. There were 132 solid nodules (46%), 106 part-solid nodules (36%), and 52 ground-glass nodules (18%). The test set results showed that the diagnostic performance of the CNN with CADv for total nodule volume change per day was larger than DT of CADv with CNN (AUC, 0.94 [95% confidence interval {CI}: 0.90, 0.96] vs 0.67 [95% CI: 0.60, 0.74]; P < .001) and CADv without CNN (total nodule volume change per day: AUC, 0.69 [95% CI: 0.62, 0.75]; P < .001; DT: AUC, 0.58 [95% CI: 0.51, 0.65]; P < .001). The accuracy of total nodule volume change per day of CADv with CNN was significantly higher than that of CADv without CNN (P < .001) and DT of both methods (P < .001). Conclusion Convolutional neural network is useful for improving accuracy of computer-aided detection of volume measurement and nodule differentiation capability at CT for patients with pulmonary nodules. © RSNA, 2020 Online supplemental material is available for this article.

Investigation of a Novel Decision Support Metric for Head and Neck Adaptive Radiation Therapy Using a Real-Time In Vivo Portal Dosimetry System.

In adaptive radiation therapy of head and neck cancer, any significant anatomical changes observed are used to adapt the treatment plan to maintain target coverage without elevating the risk of xerostomia. However, the additional resources required for adaptive radiation therapy pose a challenge for broad-based implementation. It is hypothesized that a change in transit fluence is associated with volumetric change in the vicinity of the target and therefore can be used as a decision support metric for adaptive radiation therapy. This was evaluated by comparing the fluence with volumetric changes in 12 patients. Transit fluence was measured by an in vivo portal dosimetry system. Weekly cone beam computed tomography was used to determine volume change in the rectangular region of interest from condyloid process to C6. The integrated transit fluence through the region of interest on the day of the cone beam computed tomography scan was calculated with the first treatment as the baseline. The correlation between fluence change and volume change was determined. A logistic regression model was also used to associate the 5% region of interest volume reduction replanning trigger point and the fluence change. The model was assessed by a chi-square test. The area under the receiver–operating characteristic curve was also determined. A total of 46 pairs of measurements were obtained. The correlation between fluence and volumetric changes was found to be −0.776 (P value <.001). The negative correlation is attributed to the increase in the photon fluence transport resulting from the volume reduction. The chi-square of the logistic regression was found to be 17.4 (P value <.001). The area under the receiver–operating characteristic curve was found to be 0.88. Results indicate the change in transit fluence, which can be measured without consuming clinical resources or requiring additional time in the treatment room, can be used as a decision support metric for adaptive therapy.

Measurement of Volume Changes of High Performance Cement Based Composites

Performed research work is focused on the experimental determination of volume changes of high-performance concrete. Studied topic is an essential problem of all cement based composites because of its influence to mechanical and durability properties due to crack formation. Special high-performance cement based mortars are often used for quick rehabilitation and renovation of current concrete structures where minimal level of total volume changes is required. Interpretation of final results is highly dependent on the way of measuring, as it is documented in the present experimental program.

Enlarged lateral ventricles inversely correlate with reduced corpus callosum central volume in first episode schizophrenia: association with functional measures.

The lateral and third ventricles, as well as the corpus callosum (CC), are known to be affected in schizophrenia. Here we investigate whether abnormalities in the lateral ventricles (LVs), third ventricle, and corpus callosum are related to one another in first episode schizophrenia (FESZ), and whether such abnormalities show progression over time. Nineteen FESZ and 19 age- and handedness-matched controls were included in the study. MR images were acquired on a 3-Tesla MRI at baseline and ~1.2years later. FreeSurfer v.5.3 was employed for segmentation. Two-way or univariate ANCOVAs were used for statistical analysis, where the covariate was intracranial volume. Group and gender were included as between-subjects factors. Percent volume changes between baseline and follow-up were used to determine volume changes at follow-up. Bilateral LV and third ventricle volumes were significantly increased, while central CC volume was significantly decreased in patients compared to controls at baseline and at follow-up. In FESZ, the bilateral LV volume was also inversely correlated with volume of the central CC. This inverse correlation was not present in controls. In FESZ, an inverse correlation was found between percent volume increase from baseline to follow-up for bilateral LVs and lesser improvement in the Global Assessment of Functioning score. Significant correlations were observed for abnormalities of central CC, LVs and third ventricle volumes in FESZ, suggesting a common neurodevelopmental origin in schizophrenia. Enlargement of ventricles was associated with less improvement in global functioning over time.

DIGITAL ELEVATION MODEL FROM NON-METRIC CAMERA IN UAS COMPARED WITH LIDAR TECHNOLOGY

Abstract. Digital Elevation Model (DEM) data as a representation of surface topography is highly demanded for use in spatial analysis and modelling. Aimed to that issue many methods of acquisition data and process it are developed, from traditional surveying until modern technology like LIDAR. On the other hands, in a past four year the development of Unamend Aerial System (UAS) aimed to Geomatic bring us the possibility to acquire data about surface by non-metric digital camera on board in a short time with good quality for some analysis. Data collectors have attracted tremendous attention on UAS due to possibility of the determination of volume changes over time, monitoring of the breakwaters, hydrological modelling including flood simulation, drainage networks, among others whose support in DEM for proper analysis. The DEM quality is considered as a combination of DEM accuracy and DEM suitability so; this paper is aimed to analyse the quality of the DEM from non-metric digital camera on UAS compared with a DEM from LIDAR corresponding to same geographic space covering 4 km2 in Artemisa province, Cuba. This area is in a frame of urban planning whose need to know the topographic characteristics in order to analyse hydrology behaviour and decide the best place for make roads, building and so on. Base on LIDAR technology is still more accurate method, it offer us a pattern for test DEM from non-metric digital camera on UAS, whose are much more flexible and bring a solution for many applications whose needs DEM of detail.

Qualitative and quantitative analysis of MR imaging findings in patients with middle cerebral artery stroke implanted with mesenchymal stem cells.

Mesenchymal stem cells have potential as a regenerative therapy in ischemic stroke. We sought to determine MR imaging findings after mesenchymal stem cell implantation in chronic middle cerebral artery infarcts and to compare brain volume changes in patients with mesenchymal stem cells with those in age-matched healthy controls and controls with chronic stable MCA infarcts. We retrospectively identified 5 patients receiving surgical mesenchymal stem cell implantation to an MCA infarct from January 1, 2005, to July 1, 2013, with MR imaging immediately and 1 year postimplantation. Images at both time points were evaluated for any postimplantation complications. Structural image evaluation using normalization of atrophy software was used to determine volume changes between time points and compare them with those in healthy and age- and sex-matched controls with chronic, stable MCA infarcts by using Kruskal-Wallis and Mann-Whitney U tests. Susceptibility signal loss and enhancement at the implantation site were seen. No teratoma, tumor, or heterotopia was identified. Volumetric analysis showed a trend toward less overall volume loss after mesenchymal stem cell implantation (0.736; 95% CI, -4.15-5.62) compared with that in age- and sex-matched controls with chronic, stable MCA infarcts (-3.59; 95% CI, -12.3 to -5.21; P = .09), with a significantly greater growth-to-loss ratio in infarcted regions (1.30 and 0.78, respectively, P = .02). A trend toward correlation of growth-to-loss ratio with improvement in physical examination findings was seen (r = 0.856, P = .06). Postoperative changes consistent with stereotactic implantation were seen, but no teratoma, tumor, or heterotopia was identified. Initial findings suggest a trend toward less volume loss after mesenchymal stem cell implantation compared with that in age- and sex-matched controls with chronic, stable MCA infarcts, with a significantly greater growth-to-loss ratio in the infarcted tissue.

Simultaneous Monitoring of Curing Shrinkage and Degree of Cure of Thermosets by Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy

We present a novel methodology to simultaneously monitor of the degree of cure and curing shrinkage of thermosetting formulations. This methodology is based on the observation of changes in the infrared absorption of reactive functional groups and the groups used as a standard reference for normalization. While the optical path length is exact and controlled in transmission infrared spectroscopy, in attenuated total reflection Fourier transform infrared (ATR FT-IR), the exact determination of volume changes requires the measurement of the refractive indices of the studied system throughout the curing process or at least an indirect parallel measurement of this property. The methodology presented here allows one to achieve quantitative measurements of the degree of cure and shrinkage for thermosets using in situ ATR FT-IR spectroscopy.

Effects of Pressure on the Adsorption of Proteins at Aqueous-Solid Interfaces

The spontaneous adsorption of proteins at aqueous-solid interfaces plays an important role in nature, medicine, and biotechnology. A sound understanding of the molecular mechanisms and interactions upon protein adsorption is required for the development of new materials coatings and for the choice of solvent conditions. So far, protein adsorption studies have been carried out mainly as a function of protein solution concentration, pH-value, and surface chemistry. In addition, several temperature-dependent studies have shed some light on the thermodynamics underlying protein adsorption. In contrast, effects of pressure on this process are widely unknown. Applying pressure to molecular systems generally offers access to all kinds of volume changes occurring during assembly of molecules, phase transitions, and chemical reactions. In the case of protein adsorption, using pressure as a thermodynamic variable allows for the determination of volume changes of adsorption, volume changes of unfolding in the adsorbed state, and changes of protein-interface interactions that determine the degree of protein adsorption. We have designed new high pressure cells for total internal reflection fluorescence (TIRF) spectroscopy and neutron reflectometry (NR) for pressures up to 2500 bar in order to access these quantities. The results obtained so far indicate a pressure-induced increase of the degree of protein adsorption at both the water-silica and water-poly(styrene) interfaces. Moreover, a drastic decrease of the volume change of unfolding has been found when proteins are adsorbed at the water-silica interface. Apparently, pressure exerts a distinct influence on the process of protein adsorption and provides a new complemental view on the underlying mechanism.

Heterogeneous mass loss of glaciers in the Aksu-Tarim Catchment (Central Tien Shan) revealed by 1976 KH-9 Hexagon and 2009 SPOT-5 stereo imagery

The meltwater released by the glaciers in the Aksu-Tarim Catchment, south of Tomur Peak (Central Tien Shan), feeds the Tarim River which is the main artery for the oases at the northern margin of the Taklamakan desert. The correct modeling of the contribution of the glaciers meltwater to the total runoff of the Tarim River is hampered by the lack of mass balance data. Multi-temporal digital terrain models (DTMs) allow the determination of volume changes for large samples of glacier. Here, we present the mass changes for 12 glaciers using 1976 KH-9 Hexagon, 2000 SRTM3 and 2009 SPOT-5 datasets. The results show that most of the glaciers have been losing mass since 1976. The largest glaciers, Koxkar and West Qongterang, lost −0.27±0.15mw.e.a−1 and −0.43±0.15mw.e.a−1 between 1976 and 2009, despite thick debris cover. However, some smaller glaciers show mass gain at their tongues indicating glacier surges. Using SRTM3 data the volume gain of Qinbingtan Glacier No. 74 could be dated to the time period 1999–2009. The overall mass budget of −0.33±0.15mw.e.a−1 (for 1976–2009) of the investigated glaciers is within the variability range of the global average. However, in the recent years (1999–2009) a slightly decelerated mass loss of −0.23±0.19mw.e.a−1 could be observed.

Accuracy of systolic pressure variation in monitoring blood volume

Objective To evaluate the accuracy of systolic pressure variation (SPV) in monitoring blood volume in patients.Methods Twenty-two ASA Ⅱ or Ⅲ patients (17 male,5 female),aged 49-79 yr,with body height 153-173 cm,weighing 55-89 kg,scheduled for elective coronary artery bypass grafting under cardiopulmonary bypass,were studied.Stroke volume variation (SVV) was monitored based on the arterial pressure wave and SPV measured based on the invasive arterial pressure wave after changing the title.After the chest was closed,the volume load test was immediately carried out.6％ hydroxyethyl starch 130/0.4 50-80 ml/min was infused via the jugular vein until cardiac index (CI) increased by 10％.HR,mean arterial pressure (MAP),SPV,CI,SVV,stroke volume index (SVI),systemic vascular resistance index (SVRI),central venous pressure (CVP),and pulmonary capillary wedge pressure (PCWP) were recorded in supine position (T1),at 30° head-down tilt before skin incision (T1'),before (T2) and after opening the chest in supine position (T2'),before (T3) and after the volume load test in supine position after closing the chest (T3'),in supine position after skin closure (T4),and at 30° head-down tilt after skin closure (T4').The difference in SPV and SVV (△SPV and △SVV) was calculated.The receiver operator characteristic curve for △SVV and △ SPV in determining blood volume changes was plotted.Results MAP,CVP,PCWP,CI,and SVRI were significantly increased,while SVV and SPV were decreased at T1' compared with those at T1 (P ＜ 0.05).HR was significantly increased,while CVP was decreased at T2' compared with those at T2 (P ＜ 0.05).MAP,CVP,PCWP,and CI were significantly increased,while SVV and SPV were decreased at T3' compared with those at T3 (P ＜ 0.05).MAP,CVP,and PCWP were significantly increased,while SVV and SPV were decreased at T4' compared with those at T4 (P ＜ 0.05).The area under receive operator characteristic curve for △SVV and △SPV in determining blood volume changes was 0.603 and 0.616 respectively,and there was no significant difference (P ＞ 0.05).Conclusion SPV can accurately monitor the blood volume in patients. Key words: Blood pressure; Vascular capacitance; Monitoring,intraoperative

Role of Internal Cavities as Determinants of Pressure Unfolding of Proteins

Pressure unfolds many proteins. In contrast to acid, heat and chemical denaturation, which have been studied with many proteins and which are relatively well understood, the molecular determinants of pressure unfolding of proteins are not known. Volume is the conjugate variable of pressure; therefore, the pressure unfolding of proteins is governed by differences in volume between the native and the unfolded ensembles. What is less obvious is where the differences in volume originate. Among the possibilities that have been considered are volume changes related to conformational fluctuations, volume changes related to hydration, and volume changes related to the loss of cavities present in the folded state. We have examined the role of cavities as determinants of pressure unfolding systematically, using staphylococcal nuclease as a model system. Ten different variants of a highly stable form of nuclease were engineered with single site substitutions in the hydrophobic core, designed to create cavities in the interior of the protein. High resolution crystal structures of all proteins were obtained to examine the state of the cavities and as starting structures for calculations of internal void volume with MD and MC methods. Pressure unfolding monitored with Trp fluorescence was used to measure volume changes upon unfolding. Our ultimate goal was to determine if volume changes measured in the equilibrium thermodynamic experiments correlated with the size of the cavities observed in the proteins. The mapping of experimentally determined cavity persistence ratios, combined with simulation data, provides new insight into the subtle interplay between local dynamics, water penetration, and structural properties of cavities in determining volume changes upon unfolding. Overall, the data suggest that internal cavities are one of the main determinants of the pressure-induced unfolding of proteins.

Physikalische und mechanische Eigenschaften von Sperrholz aus mit 1.3-Dimethylol-4.5-Dihydroxyethyleneurea (DMDHEU) modifizierten Birken- und Buchenfurnieren

The dimensional stability and some mechanical properties were tested in plywood produced with veneers modified with 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU). The experimental design included Betula sp. and Fagus sylvatica impregnated with 0.8 M, 1.3 M, and 2.3 M DMDHEU. The plywood consisted of five veneers glued with a phenolic resin. Dimensional stability tests were conducted after 10 cycles of soaking/oven-drying to determine volume changes and anti swelling efficiency (ASE). The mechanical properties tested were hardness (Brinell), modulus of elasticity in bending (MOE), bending strength (BS) and work to maximum load in bending (WMLB). The modified samples for both species were considerably more dimensionally stable than the untreated samples. The samples of Betula sp. and F. sylvatica modified with DMDHEU presented a MOE and a BS unaffected by the treatment. The WMLB was consistently lower in the modified samples than in the unmodified samples. As determined by the Brinell method, the DMDHEU-modified plywood of the Betula sp. and F. sylvatica was harder than the unmodified plywood.

Three-dimensional analysis of changes of the malar–midfacial region after LeFort I osteotomy and maxillary advancement

It has been the objective of the present prospective study to assess visible volume changes of the facial soft tissue after LeFort I osteotomy with advancement and to determine the soft-tissue-to-hard-tissue ratios of advancement. Twenty adult patients (ten female, ten male, mean age 33.9 +/- 14.9 years) received a LeFort I osteotomy with advancement because of a maxillary protrusion. Lateral skull radiographs and optical three-dimensional (3D) scans of the facial surface were assessed preoperatively and 12 months after surgery. The lateral skull radiographs were used to carry out standard linear and angular cephalometric measurements. The pre- and postoperative optical 3D surface scans were registered. A well-defined area in the malar region was used to determine the visible volume changes for each side separately. The mean accommodation vector that transforms the preoperative into the postoperative surface was assessed for each facial half separately. The soft-tissue-to-hard-tissue ratios between the incision superius and the labrale superius, the maximal parasagittal advancement of soft tissue, and the accommodation vectors were calculated. A mean advancement of the incision superius of 5.3 +/- 2.1 mm was accompanied by a volume increase of 5.2 +/- 4.1 cm(3) in the right malar-midfacial region and 4.6 +/- 4.7 cm(3) on the left side, respectively, revealing a symmetrical volume change (p = 0.370). The soft-tissue-to-hard-tissue ratios were 80 +/- 94% for labrale superius and incision superius, 56 +/- 79% (right) and 51 +/- 56% (left) for accommodation vector and incision superius and 97 +/- 79% (right) and 98 +/- 89% (left) for maximal parasagittal advancement of soft tissue and incision superius. The determination of volume changes and accompanying accommodation vectors complete the cephalometric analysis during the follow-up of patients undergoing LeFort I osteotomy. The data show that maxillary advancement leads to a more pronounced shifting of the soft tissues in the malar-midfacial area than of the upper lip. The new parameters will help to assess normative soft tissue data based on 3D imaging with a view to an improved three-dimensional prediction of the operative outcome of orthognathic surgery away from the midline.

First Determination of Volume Changes and Enthalpies of the High-Pressure Decomposition Reaction of the Structure H Methane Hydrate to the Cubic Structure I Methane Hydrate and Fluid Methane

Pressure-temperature (P-T) conditions of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane were studied with a piston-cylinder apparatus at room temperature. For the first time, volume changes accompanying this reaction were determined. With the use of the Clausius-Clapeyron equation the enthalpies of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane have been calculated.

Beer Head with Numbers

The article discusses the application of mathematician John von Neumann's theories on two-dimensional surfaces to three-dimensional microscopic crystal grains. Von Neumann stated changes due to surface tension in any two dimensional region will depend on the region's number of sides. Materials scientist David J. Srolovitz has helped form an equation that uses mean width to determine volume change caused by tension in three dimensions. The equation may help physicists create stronger materials.

PH-Dependent Mass and Volume Changes of Polypyrrole/Poly(styrene sulfonate)

(in basic pH) (2)In this paper, we first describe pH-induced ion transportbehaviors of polypyrrole/poly(styrene sulfonate) (PPy/PSS)in various electrolytes using an Electrochemical QuartzCrystal Microbalance (EQCN), which have been expected toshow simply opposite mass responses to PPy doped withmobile anions. This was performed since mass flow is amajor factor to determine volume changes of PPy.

Changes in Membrane Conductance Play a Pathogenic Role in Osmotic Glial Cell Swelling in Detached Retinas

Detachment of the neural retina from the pigment epithelium may be associated with tissue edema; however, the mechanisms of fluid accumulation are not understood. Because retinal detachment is usually not accompanied by vascular leakage, we investigated whether the osmotic swelling characteristics of retinal glial (Müller) cells are changed after experimental detachment of the porcine retina. Osmotic stress, induced by application of a hypotonic bath solution to retinal slices, caused swelling of Müller cell bodies in 7-day-detached retinas, but no swelling was inducible in slices of control retinas. Müller cell somata in slices of retinal areas that surround local detachment in situ also showed osmotic swelling, albeit at a smaller amplitude. The amplitude of osmotic Müller cell swelling correlated with the decrease in the K+ conductance, suggesting a causal relationship between both gliotic alterations. Further factors implicated in Müller cell swelling were inflammatory mediators and oxidative stress. We propose that a dysregulation of the ion and water transport through Müller cells may impair the fluid absorption from the retinal tissue, resulting in chronic fluid accumulation after detachment. This knowledge may lead to a better understanding of the mechanisms involved in retinal degeneration after detachment.

Airborne laser scanning for riverbank erosion assessment

Worldwide, rivers and streams are negatively impacted by sedimentation. However, there are few broad scale techniques for quantifying the sources of sediment, i.e. upland vs. river bank erosion. This research was designed to evaluate the use of airborne LIDAR for characterizing sediment and phosphorus contributions from river bank erosion. The evaluation was done on the main stem of the Blue Earth River in southern Minnesota. Detailed topographic data were collected on an annual basis in April 2001 and 2002 over a 56 km length of the river with a helicopter mounted Topeye laser system. The raw database included X, Y, Z coordinates of laser returns sampled from the river valley with a density of 1–3.3 elevations per m 2. Uniform 1 m bare earth digital elevation models were constructed by stripping vegetation laser returns and interpolation. The two models were differenced to determine volume change over time, which was then converted to mass wasting by multiplying volume change with bulk density. Mass wasting rates were further converted to sediment load based on percentage of transportable material in the bank strata. The average difference between LIDAR measured elevations and RTK GPS surveyed elevations on 5 highway bridge surfaces was 2.5 and 8.8 cm for the 2001 and 2002 scans, respectively. The elevation errors were quasi-normally distributed with standard deviation of 6.7 and 6.1 cm for 2001 and 2002, respectively. No elevation or planimetric corrections were made to the laser data before calculating mass wasting rates because it was not possible to determine the source of error or if it was uniform within and between scans. The mass wasting estimate from the LIDAR surveys varied from 23% to 56% of the sediment mass transported past the downstream gauging station depending on the range of textural material that was entrained once in the river. These estimates are in the range of values reported in the literature. Total P contribution due to bank erosion from the river reach was estimated to be 201 t/yr.

High-Dimensional Deformation Fields for Longitudinal Intraindividual Volumetry of Cerebral Infarction

The aim of this study is the analysis of 3D morphological changes of human brains after cerebral infarction. The change of brain volume caused by the infarction is measured by high-dimensional transformations. These are determined by a multiresolution full multigrid (FMG) movement model [4], resulting in a precise correlation of homologous structures. Thus, volume changes are detected with subvoxel accuracy to determine volume changes between the infarct and remote brain regions without manual interaction. High-dimensional transformations are determined by application of the theory according to Navier-Lamee. Volumes are modelled as an elastic medium. For complex deformations the elastic model is extended to a movement model and the total spatial differences are divided into discrete steps. The gray-value forces driving the movement of each voxel in the source object are determined by minimizing the gray-value difference between source and reference volume. The movement of each voxel is controlled by the data itself and smoothed with respect to noise by the elasticity properties defined by the Lamee parameters for each step. The numerical effort is overcome by a combined multiresolution, full-multigrid method and the correlation of homologous structures improved by application of the Scale-Space theory. To avoid rotational transformations, coarse and fine alignment is achieved by the extended principle axes theory [2, 3] and by a cross-correlation based procedure using a matrix-norm [1]. The MRI data sets are acquired at different times, enabling the determination of morphological changes over time. The application of the FMG model enables the investigation of morphological brain changes over time. Furthermore, it is possible to detect ischemia-induced spatial distortions and plastic alterations, as the changes of the volume are exactly determined by the deformation fields. The results show, that even small infarcts result in morphological changes not only adjacent to the ischemic area but also in remote areas and in some cases the contralateral hemisphere. Supported by the Deutsche Forschungsgemeinschaft (SFB 194 A6, A13, B2).