Reduced leadset selection and performance evaluation in the inverse problem of electrocardiography for reconstructing the ventricularly paced electrograms.

OBJECTIVE: Noninvasive electrocardiographic imaging (ECGI) is used for obtaining high-resolution images of the electrical activity of the heart, and is a powerful method with the potential to detect certain arrhythmias. However, there is no 'best' lead configuration in the literature to measure the torso potentials. This paper evaluates ECGI reconstructions using various reduced leadset configurations, explores whether one can find a common reduced leadset configuration that can accurately reconstruct the electrograms for datasets with different pacing sites, and compares two activation time estimation methods. APPROACH: We used 23 ventricularly-paced datasets with pacing sites on different regions of the epicardium. Starting with a full 192­leadset, we found "optimized" reduced leadsets specific to each dataset; we considered 64­lead and 32­lead configurations. Based on the histogram of individual "optimized" lead selections, we found a common reduced leadset. We compared the ECGI reconstructions and activation times of the individually optimized lead configurations with the common lead configurations. RESULTS: Both 64­lead configurations had similar performances to the 192­leadset. 32­leadset configurations, on the other hand, yielded noisy reconstructions, which affected their performance. SIGNIFICANCE: There are no statistically significant differences in the performance of the inverse solutions when a 64­lead common reduced leadset is used to estimate the electrograms and their respective pacing sites compared to using the full leadset. 32­lead configurations, on the other hand, require a more careful study to improve their performance. The activation time method used significantly affects the pacing site estimation performance, especially with fewer electrodes.

Micro-CT analyses of historical bone samples presenting with osteomyelitis.

OBJECTIVE: Osteomyelitis is an inflammation of the bone marrow mainly caused by bacteria such as Staphylococcus aureus. It typically affects long bones, e.g. femora, tibiae and humeri. Recently micro-computed tomography (µCT) techniques offer the opportunity to investigate bone micro-architecture in great detail. Since there is no information on long bone microstructure in osteomyelitis, we studied historic bone samples with osteomyelitis by µCT. MATERIALS AND METHODS: We investigated 23 femora of 22 individuals suffering from osteomyelitis provided by the Collection of Anatomical Pathology, Museum of Natural History, Vienna (average age 44 ±19 years); 9 femora from body donors made available by the Department of Applied Anatomy, Medical University of Vienna (age range, 56-102 years) were studied as controls. Bone microstructure was assessed by µCT VISCOM X 8060 II with a minimal resolution of 18 µm. RESULTS: In the osteomyelitic femora, most prominent alterations were seen in the cortical compartment. In 71.4% of the individuals with osteomyelitis, cortical porosity occurred. 57.1% of the individuals showed cortical thinning. In 42.9% trabecularisation of cortical bone was observed. CONCLUSION: Osteomyelitis is associated with severe alterations of cortical bone structure otherwise typically observed at old age such as cortical porosity and cortical thinning.

A reconstruction of the Vienna skull of Hadropithecus stenognathus.

Franz Sikora found the first specimen and type of the recently extinct Hadropithecus stenognathus in Madagascar in 1899 and sent it to Ludwig Lorenz von Liburnau of the Austrian Imperial Academy of Sciences. Later, he sent several more specimens including a subadult skull that was described by Lorenz von Liburnau in 1902. In 2003, some of us excavated at the locality and found more specimens belonging to this species, including much of a subadult skeleton. Two frontal fragments were found, and these, together with most of the postcranial bones, belong to the skull. CT scans of the skull and other jaw fragments were made in Vienna and those of the frontal fragments at Penn State University. The two fragments have been reunited with the skull in silico, and broken parts from one side of the skull have been replaced virtually by mirror-imaged complete parts from the other side. The parts of the jaw of another individual of a slightly younger dental age have also been reconstructed virtually from CT scans with mirror imaging and by using the maxillary teeth and temporomandibular joints as a guide to finish the reconstruction. Apart from forming a virtual skull for biomechanical and systematic analysis, we were also able to make a virtual endocast. Missing anterior pieces were reconstructed by using part of an endocast of the related Archaeolemur majori. The volume is 115 ml. Hadropithecus and Archaeolemur seem to have had relatively large brains compared with the other large-bodied subfossil lemurs.

Regional dissociated heterochrony in multivariate analysis.

Heterochrony, the classic framework to study ontogeny and phylogeny, in essence relies on a univariate concept of shape. Though principal component plots of multivariate shape data seem to resemble classical bivariate allometric plots, the language of heterochrony cannot be translated directly into general multivariate methodology. We simulate idealized multivariate ontogenetic trajectories and demonstrate their behavior in principal component plots in shape space and in size-shape space. The concept of "dissociation", which is conventionally regarded as a change in the relationship between shape change and size change, appears to be algebraically the same as regional dissociation - the variation of apparent heterochrony by region. Only if the trajectories of two related species lie along exactly the same path in shape space can the classic terminology of heterochrony apply so that pure dissociation of size change against shape change can be detected. We demonstrate a geometric morphometric approach to these issues using adult and subadult crania of 48 Pan paniscus and 47 P. troglodytes. On each specimen we digitized 47 landmarks and 144 semilandmarks on ridge curves and the external neurocranial surface. The relation between these two species' growth trajectories is too complex for a simple summary in terms of global heterochrony.

Body weight and the shape of the natural distribution of weight, in very large samples of German, Austrian and Norwegian conscripts.

OBJECTIVE: To investigate the shape of the natural distribution of body weight in conscripts. DESIGN: Investigation of weight and weight distributions in German, Austrian and Norwegian conscripts. SUBJECTS: A total of 10 706 651 West German conscripts (30 birth cohorts born between 1938 and 1971, except for the cohorts born 1941-1944), 507 095 Austrian conscripts (10 birth cohorts born between 1966 and 1975), and 27 311 Norwegian conscripts (1997 conscription). RESULTS: In Germans, average body weight increased by 100 g/y up to birth cohort 1965, thereafter by 400 g/y, and by 200 g/y in Austrians. Body weight is not normally distributed, but skewed to the right. Also power transformation was inadequate to sufficiently describe the shape of this distribution. The right tail of weight distributions declines exponentially, beyond a cut-off of +0.5 standard deviations. There is a strong relation between average weight and the prevalence of obesity, except for those cohorts that suffered from severe starvation (1945-1948) during early and mid-childhood. These cohorts appeared to be more resistant against obesity. CONCLUSION: Obesity appears to be a characteristic feature of a population as a whole, and does not seem to be a separate problem of only the obese people. It may be questioned whether (in terms of public health) the optimal solution for treating obesity is treating the obese people, or whether one should consider measures to reduce average weight in a population instead, as this might reduce the number obese people and the severity of the illness.

Virtual anthropology (VA): a call for glasnost in paleoanthropology.

The adventurous scientist, with a hat protecting him from the fierce sun as he travels from one remote place to another, hunting for fossils of our ancestors, has been a part of the romantic imagination associated with anthropological research in the 20th Century. This picture of the paleoanthropologist still retains a grain of truth. Indeed, many new sites were discovered under troublesome conditions in the recent past and have added substantial information about our origins. But on another front, probably less sensational but no less important, are contributions stemming from the analysis of the already discovered fossils. With the latter, a rapid evolution in anthropologic research took place concurrently with advances in computer technology. After ambitious activities by a handful of researchers in some specialized laboratories, a methodologic inventory evolved to extract critical information about fossilized specimens, most of it preserved in the largely inaccessible interior as unrevealed anatomic structures. Many methodologies have become established but, for various reasons, access to both the actual and the digitized fossils is still limited. It is time for more transparency, for a glasnost in paleoanthropology. Herein are presented some answers to the question of how a high-tech approach to anthropology can be integrated into a predominantly conservative field of research, and what are the main challenges for development in the future.

Virtual anthropology: the digital evolution in anthropological sciences.

The discovery and explanation of differences among organisms is a major concern for evolutionary and systematic biologists. In physical anthropology, the discrimination of taxa and the qualitative and quantitative description of ontogenetic or evolutionary change require, of course, the analysis of morphological features. Since the 1960s, a remarkable amount of fossil material was excavated, some of it still awaiting a detailed first analysis, some of it requiring re-examination by more developed methods. While the fossil record grew continuously, a revolution in anthropological research took place with advances in computer technology in the 1980s: a handful of innovative researchers working in specialized anthropology laboratories or medical departments developed the methodological inventory needed to extract critical information from subjects in vivo and from fossilized remains. A considerable part of this information is preserved in the physically heretofore inaccessible interior of anatomical structures. Virtual Anthropology (VA) is a means of making them visible and measurable. Thus, VA also allows access to 'hidden' landmarks; in addition, the large number of semilandmarks accessible on the form enhances the power of Geometric Morphometrics analysis. Furthermore, the density information in volume data allows manipulations such as segmentation, impossible with the real, physical object. Moreover, metric body measurements generally, and cranial measurements specifically, are also an important source of information for the analysis of the ontogenetic development of the skeletal system, and--last but not least--for clinical use (e.g., operation planning, operation simulation, prosthetics). Thus, there developed a fruitful interdisciplinary cooperation between statistics, medicine, and physical anthropology.

Endocranial capacity of the bodo cranium determined from three-dimensional computed tomography.

The 600,000-year-old cranium from Bodo, Ethiopia, is the oldest and most complete early Middle Pleistocene hominid skull from Africa. "Virtual endocast" models created by three-dimensional computed tomography (CT) techniques indicate an endocranial capacity of about 1,250 cc for this cranium (with a reasonable range between approximately 1,200-1,325 cc, depending on how missing portions of the basicranial region are reconstructed). From these determinations, several important implications emerge concerning current interpretations of "tempo and mode" in early hominid brain evolution: 1) already by the early Middle Pleistocene, at least one African hominid species, Homo heidelbergensis, had reached an endocranial capacity within the normal range of modern humans; 2) in spite of its large endocranial capacity, estimates of Bodo's encephalization quotient fall below those found in a large sample of Homo sapiens (both fossil and recent) and Neandertals; and 3) the greatest burst of brain expansion in the Homo lineage may not have been in the last several hundred thousand years, but rather much earlier in the Lower to early Middle Pleistocene.

Early hominid brain evolution: a new look at old endocasts.

Early hominid brain morphology is reassessed from endocasts of Australopithecus africanus and three species of Paranthropus, and new endocast reconstructions and cranial capacities are reported for four key specimens from the Paranthropus clade. The brain morphology of Australopithecus africanus appears more human like than that of Paranthropus in terms of overall frontal and temporal lobe shape. These new data do not support the proposal that increased encephalization is a shared feature between Paranthropus and early Homo. Our findings are consistent with the hypothesis that Australopithecus africanus could have been ancestral to Homo, and have implications for assessing the tempo and mode of early hominid neurological and cognitive evolution.

Endocranial capacity in Sts 71 (Australopithecus africanus) by three-dimensional computed tomography.

In a recent report on early hominid endocranial capacity, it was predicted that future studies would show that: (1) "several key early hominid endocranial estimates may be inflated"; (2) "current views on the tempo and mode of early hominid brain evolution may need reevaluation"; and (3) endocranial capacity in one of these, Sts 71, was "probably closer to 370 cm(3), very near the mean value for female chimpanzees, and not the currently accepted 428 cm(3)" (Conroy et al., Science, 1998; 280: 1730-1731; Falk, Science 1998; 20:1714). Subsequent studies tend to support the first two predictions, but not the third (Culotta, Science, 1999; 284: 1109; Falk, Am. J. Phys. Anthropol. Suppl., 1999; 28: 126; Falk et al., J. Hum. Evol. [in press]). Here we detail the reasons for thinking the currently accepted endocranial value for Sts 71 is probably correct by providing the first quantitative details of endocranial reconstruction in Sts 71 using three-dimensional computed tomography. Relative brain expansion in the hominid lineage started some half-million years before the earliest appearance of the genus Homo, possibly coincident with enhanced tool-making skills and carnivory.

Virtual reality and anthropology.

Since the discovery of the Tyrolean Iceman in 1991 advanced imaging and post processing techniques were successfully applied in anthropology. Specific techniques include spiral computed tomography and 3-dimensional reconstructions including stereolithographic and fused deposition modeling of volume data sets. The Iceman's skull was the first to be reproduced using stereolithography, before this method was successfully applied in preoperative planning. With the advent of high-end graphics workstations and biomedical image processing software packages, 3-dimensional reconstructions were established as a routine tool for analyzing volume data sets. These techniques opened totally new insights in the field of physical anthropology. Computed tomography became the ideal research tool to access the internal structures of various precious fossils without damaging or even touching them. Many of the most precious specimens from the species Autralopithecus (1.8-3.5 Myears), Homo heidelbergensis (200-600 kyears) or Homo neanderthalensis (40-100 kyears) were scanned during the last 5 years. Often the fossils are filled with a stone matrix or other materials. During the postprocessing routines highly advanced algorithms were used to remove virtually these incrustations. Thus it was possible to visualize the morphological structures that lie beneath the matrix. Some specimen were partially destroyed, so the missing parts were reconstructed on computer screen in order to get estimations of the brain volume and endocranial morphology, both major fields of interest in physical anthropology. Moreover the computerized form of the data allows new descriptions of morphologic structures by the means of 'geometric morphometrics'. Some of the results may change aspects and interpretations in human evolution. The introduction of new imaging and post processing techniques created a new field of research: Virtual Anthropology.

Thickness distribution of the occipital bone--a new approach based on CT-data of modern humans and OH 9 (H. ergaster).

A new approach for the analysis of cranial bone thickness is introduced. The study focuses on the occipital bone of modern humans and of a 1.25 Myr-old H. Ergaster/erectus specimen from Olduvai Gorge (OH 9). A semiautomatic algorithm detects a multitude of thicknesses from CT-data of the investigated bones. We find that every bone is characterized by its own distribution pattern of cranial thickness, which is then analyzed statistically. The results demonstrate that the thickness distribution of the occipital bone of OH 9 is within the normal range of the H. sapiens sample (which itself shows a remarkably high variance). This contributes to a further analysis of phyletic differences of hominid morphology by including distribution patterns of thickness combined with aspects of functional anatomy.

The iceman under pressure (Part I): A description of skull deformations due to 5100 years of glacial action.

Due to its long deposition in the glacier, the 'Iceman' (an ice-mummy from the Hauslabjoch) has been deformed, notably its skull. We introduce various comparative methods that describe these deformations, assuming they can be ascribed--to a large extent--to glacial action. While pressure is a scalar, the deformations must be described via a 2-tensor strain field (which can be represented by a matrix function value at every point throughout the skull). In this paper, we present the assumed deformations in numerous graphical forms and, furthermore, the limitations in interpretation--including an estimate of statistical variability--that can be revealed by this analysis. These methods, although describing the results of glacial action and implying a 2-tensor strain field (which will be presented in a subsequent paper), do not permit a straightforward reconstruction of the original, underformed skull. These methods have wider applications to the general problem of deformation.

Re-evaluation of the endocranial volume of the Guattari 1 Neandertal specimen (Monte Circeo).

The endocranial capacity of Guattari 1 originally was estimated by Sergi as approximately 1.550 cm3. Using three different approaches, a physical endocast, a stereolithographic model, and a virtual endocast, we have estimated the endocranial capacity of Guattari 1 as approximately 1.350 cm3. This paper explains our revision of the estimated endocranial volume of Guattari 1, provides a cautionary case concerning other estimates of endocranial volume, and demonstrates and encourages the use of recent advances in imaging, modeling, and analysis of endocranial volume.

New methods and techniques in anthropology.

Since the discovery of the Tyrolean Iceman in 1991, advanced imaging and post-processing techniques have been successfully applied to anthropological research. Among the specific techniques are spiral computed tomography and 3-dimensional reconstructions, which include stereolithographic and fused deposition modeling of volume data sets. The Iceman's skull was the first to be produced using stereolithography; subsequently, it has been successfully applied in preoperative planning. With the advent of high-end performance graphics workstations and biomedical image processing software packages, 3-dimensional reconstructions have become established as routine tools for analyzing volume data sets. These techniques enabled dramatically new insights to be gained in the field of physical anthropology. Computed tomography became the ideal research tool to access the internal structures of various precious fossils without even touching--let alone damaging--them. Among the most precious are specimens from the genus Australopithecus (1.8 Myr-3.5 Myr), as well as representatives of Homo heidelbergensis (200 kyr-600 kyr) and Homo neanderthalensis (40 kyr-100 kyr); such fossils have been CT-scanned during the last five years. The fossils often are filled with a stone matrix or other encrustations. During the post-processing routines, highly advanced algorithms were used to remove these encrustations virtually (the concrete fossils remain untouched). Thus it has been possible to visualize the morphological structures that are hidden by the matrix layer. Some specimens have been partially destroyed, but it has been possible for the missing parts were reconstructed on the computer screen in order to get estimations of brain volume and endocranial morphology, both major fields of interest in physical anthropology. Moreover, the data in computerized form allows new descriptions of morphological structures using geometric morphometrics. Some of the results may change aspects and interpretations in human evolution and approaches to long-standing questions in this field. We subsume the introduction of these new imaging and post-processing techniques into a new field of research: Virtual Anthropology.

Comparing frontal cranial profiles in archaic and modern homo by morphometric analysis.

Archaic and modern human frontal bones are known to be quite distinct externally, by both conventional visual and metric evaluation. Internally this area of the skull has been considerably less well-studied. Here we present results from a comparison of interior, as well as exterior, frontal bone profiles from CT scans of five mid-Pleistocene and Neanderthal crania and 16 modern humans. Analysis was by a new morphometric method, Procrustes analysis of semi-landmarks, that permits the statistical comparison of curves between landmarks. As expected, we found substantial external differences between archaic and modern samples, differences that are mainly confined to the region around the brow ridge. However, in the inner median-sagittal profile, the shape remained remarkably stable over all 21 specimens. This implies that no significant alteration in this region has taken place over a period of a half-million years or more of evolution, even as considerable external change occurred within the hominid clade spanning several species. This confirms that the forms of the inner and outer aspects of the human frontal bone are determined by entirely independent factors, and further indicates unexpected stability in anterior brain morphology over the period during which modern human cognitive capacities emerged. Anat Rec (New Anat): 257:217-224, 1999.

Endocranial capacity in an early hominid cranium from Sterkfontein, South Africa.

Two- and three-dimensional computer imaging shows that endocranial capacity in an approximately 2.8- to 2.6-million-year-old early hominid cranium (Stw 505) from Sterkfontein, South Africa, tentatively assigned to Australopithecus africanus, is approximately 515 cubic centimeters. Although this is the largest endocranial capacity recorded for this species, it is still markedly less than anecdotal reports of endocranial capacity exceeding 600 cubic centimeters. No australopithecine has an endocranial capacity approaching, let alone exceeding, 600 cubic centimeters. Some currently accepted estimates of early hominid endocranial capacity may be inflated, suggesting that the tempo and mode of early hominid brain evolution may need reevaluation.

Virtual anthropology (VA): methodological aspects of linear and volume measurements--first results.

Virtual Anthropology (VA) is the three-dimensional analysis of anthropological objects within a computer environment. For the investigation of fossil hominid material the VA approach is a very powerful and essential technique to obtain quantitative and qualitative data. The permanent accessibility of the virtual objects and the possibility to study inner structures are striking advantages. The present study is an attempt to evaluate the usefulness and problems of VA and to provide data on accuracy and reproducibility. 10 Homo sapiens skulls were CT-scanned and were measured on the computer and with established methods (calipers and mustard seeds/water displacement). Different co-variables like sex, age, observer, and class and dimension of measurement were included. The results are very promising: The mean of absolute difference for linear measurements is 0.71 mm +/- 0.55 (0.58% +/- 0.49), and 31.59 ccm +/- 13.37 (2.26% +/- 0.86) for volume measurements. Reproducibility is 0.11 mm +/- 0.15 for located landmarks and 0.37 mm +/- 0.41 for relocating landmarks. Age and class of measurement are significant factors.

A comparative study of stereolithographically modelled skulls of Petralona and Broken Hill: implications for future studies of middle Pleistocene hominid evolution.

Computer generated three-dimensional stereolithographic models of middle Pleistocene skulls from Petralona and Broken Hill are described and compared. The anterior cranial fossae of these models are also compared with that of another middle Pleistocene skull, Arago 21. Stereolithographic modelling reproduces not only the outer surfaces of skulls, but also features within the substance of the bones, and details of the internal braincase. The skulls of Petralona and, to a somewhat lesser degree, Broken Hill are extremely pneumatized. Previously undescribed features associated with pneumatization are detailed, along with their possible functional significance, polarity, and potential for understanding hominid cranial variation. Petralona and Broken Hill also exhibit a dramatic suite of cerebral features that is probably related to extensive pneumatization of the skull, namely frontal lobes that are tilted and located behind rather than over the orbits, laterally flared temporal lobes, marked occipital projection, and basal location of the cerebellum. Comparison of the anterior cranial fossae of Petralona, Broken Hill, and Arago 21 suggests that external resemblance of skulls may not always correlate with endocranial similarity. We believe that stereolithographic reconstructions have the potential for helping to resolve difficult questions about the origins of Neanderthal and anatomically modern people.