DEVELOPMENT OF A BEAM-SPECIFIC PLANNING TARGET VOLUME AND A ROBUST PLAN ANALYSIS TOOL FOR PROTON THERAPY

Proton therapy is growing increasingly popular due to its superior dose characteristics compared to conventional photon therapy. Protons travel a finite range in the patient body and stop, thereby delivering no dose beyond their range. However, because the range of a proton beam is heavily dependent on the tissue density along its beam path, uncertainties in patient setup position and inherent range calculation can degrade thedose distribution significantly. Despite these challenges that are unique to proton therapy, current management of the uncertainties during treatment planning of proton therapy has been similar to that of conventional photon therapy. The goal of this dissertation research was to develop a treatment planning method and a planevaluation method that address proton-specific issues regarding setup and range uncertainties. Treatment plan designing method adapted to proton therapy: Currently, for proton therapy using a scanning beam delivery system, setup uncertainties are largely accounted for by geometrically expanding a clinical target volume (CTV) to a planning target volume (PTV). However, a PTV alone cannot adequately account for range uncertainties coupled to misaligned patient anatomy in the beam path since it does not account for the change in tissue density. In order to remedy this problem, we proposed a beam-specific PTV (bsPTV) that accounts for the change in tissue density along the beam path due to the uncertainties. Our proposed method was successfully implemented, and its superiority over the conventional PTV was shown through a controlled experiment.. Furthermore, we have shown that the bsPTV concept can be incorporated into beam angle optimization for better target coverage and normal tissue sparing for a selected lung cancer patient. Treatment plan evaluation method adapted to proton therapy: The dose-volume histogram of the clinical target volume (CTV) or any other volumes of interest at the time of planning does not represent the most probable dosimetric outcome of a given plan as it does not include the uncertainties mentioned earlier. Currently, the PTV is used as a surrogate of the CTV’s worst case scenario for target dose estimation. However, because proton dose distributions are subject to change under these uncertainties, the validity of the PTV analysis method is questionable. In order to remedy this problem, we proposed the use of statistical parameters to quantify uncertainties on both the dose-volume histogram and dose distribution directly. The robust plan analysis tool was successfully implemented to compute both the expectation value and its standard deviation of dosimetric parameters of a treatment plan under the uncertainties. For 15 lung cancer patients, the proposed method was used to quantify the dosimetric difference between the nominal situation and its expected value under the uncertainties.

AN EVALUATION OF THE CONSISTENCY OF IMRT PATIENT-SPECIFIC QA TECHNIQUES

To ensure the integrity of an intensity modulated radiation therapy (IMRT) treatment, each plan must be validated through a measurement-based quality assurance (QA) procedure, known as patient specific IMRT QA. Many methods of measurement and analysis have evolved for this QA. There is not a standard among clinical institutions, and many devices and action levels are used. Since the acceptance criteria determines if the dosimetric tools’ output passes the patient plan, it is important to see how these parameters influence the performance of the QA device. While analyzing the results of IMRT QA, it is important to understand the variability in the measurements. Due to the different form factors of the many QA methods, this reproducibility can be device dependent. These questions of patient-specific IMRT QA reproducibility and performance were investigated across five dosimeter systems: a helical diode array, radiographic film, ion chamber, diode array (AP field-by-field, AP composite, and rotational composite), and an in-house designed multiple ion chamber phantom. The reproducibility was gauged for each device by comparing the coefficients of variation (CV) across six patient plans. The performance of each device was determined by comparing each one’s ability to accurately label a plan as acceptable or unacceptable compared to a gold standard. All methods demonstrated a CV of less than 4%. Film proved to have the highest variability in QA measurement, likely due to the high level of user involvement in the readout and analysis. This is further shown by how the setup contributed more variation than the readout and analysis for all of the methods, except film. When evaluated for ability to correctly label acceptable and unacceptable plans, two distinct performance groups emerged with the helical diode array, AP composite diode array, film, and ion chamber in the better group; and the rotational composite and AP field-by-field diode array in the poorer group. Additionally, optimal threshold cutoffs were determined for each of the dosimetry systems. These findings, combined with practical considerations for factors such as labor and cost, can aid a clinic in its choice of an effective and safe patient-specific IMRT QA implementation.

Specificity of somatostatin receptor and G -protein interactions as characterized by somatostatin receptor subtype specific antibodies

The neuropeptide somatostatin is a widely distributed general inhibitor of endocrine, exocrine, gastrointestinal and neural functions. The biological actions of somatostatin are initiated by interaction with high affinity, plasma membrane somatostatin receptors (sst receptors). Five sst receptor subtypes have been cloned and sequence analysis shows they are all members of the G protein coupled receptor superfamily. The G proteins play a pivotal role in sst receptor signal transduction and the specificity of somatostatin receptor-G protein coupling defines the possible range of cellular responses. However, the data for endogenous sst receptor and G protein coupling is very limited, and even when it is available, the sst receptor subtypes involved in G protein coupling and signal transduction are unknown due to the expression of multiple sst receptor subtypes in target cell lines or tissues of somatostatin.^ In an effort to characterize each individual sst receptor subtypes, antisera against unique C-terminal regions of different sst receptor subtypes have been developed in our lab. In this report, antisera made against the sst1, sst2A and sst4 receptors are characterized. They are highly specific to their corresponding receptors and efficiently immunoprecipitate the sst receptors. Using these antibodies, the cell lines expressing these sst receptor subtypes were identified with both immunoprecipitation and Western blot methods. The development of sst receptor subtype specific antibodies make it possible to determine the specificity of the sst receptor subtype and G protein coupling in target cells or tissues expressing multiple sst receptors, two questions were addressed by this thesis: (1) whether different cellular environments affect receptor subtype and G protein coupling; (2) whether different sst receptors couple to different G proteins in similar cellular environments.^ Taken together our findings, both sst1 and sst2A receptors couple with G$\alpha\sb{\rm i1},$ G$\alpha\sb{\rm i2}$ and G$\alpha\sb{\rm i3}$ in CHO cells, G$\alpha\sb{\rm i2}$ and G$\alpha\sb{\rm i3}$ in GH$\sb4$C$\sb1$ cells. Further, sst2A receptors couple with G$\alpha\sb{\rm i1},$ G$\alpha\sb{\rm i2}$ and G$\alpha\sb{\rm i3}$ in AR4-2J cells while sst4 receptors couple with G$\alpha\sb{\rm i2}$ and G$\alpha\sb{\rm i3}$ in CHO cells. Therefore, the G protein coupling of the same sst receptors in different cell lines is basically similar in that they all couple with multiple $\alpha$-subunits of the G$\rm \sb{i}$ proteins, suggesting cellular environment has little effect on receptor and G protein coupling. Moreover, different sst receptors have similar G protein coupling specificities in the same cell line, suggesting components other than receptor and G$\alpha$ subunits in the signal transduction pathways may contribute to specific functions of each sst receptor subtype. This series of experiments represent a novel approach in dissecting signal transduction pathways and may have general application in the field. Furthermore, this is the first systematic study of sst receptor subtype and G protein $\alpha$-subunit interaction in both transfected cells and in normal cell lines. The information generated will be very useful in our understanding of sst receptor signal transduction pathways and in directing future sst receptor research. ^

Isotopic signature of specific biomarkers derived from anaerobic methanotrophic archaea (ANME groups) and sulphate-reducing bacteria (SRB) at different cold seep provinces

Anaerobic methane-oxidizing microbial communities in sediments at cold methane seeps are important factors in controlling methane emission to the ocean and atmosphere. Here, we investigated the distribution and carbon isotopic signature of specific biomarkers derived from anaerobic methanotrophic archaea (ANME groups) and sulphate-reducing bacteria (SRB) responsible for the anaerobic oxidation of methane (AOM) at different cold seep provinces of Hydrate Ridge, Cascadia margin. The special focus was on their relation to in situ cell abundances and methane turnover. In general, maxima in biomarker abundances and minima in carbon isotope signatures correlated with maxima in AOM and sulphate reduction as well as with consortium biomass. We found ANME-2a/DSS aggregates associated with high abundances of sn-2,3-di-O-isoprenoidal glycerol ethers (archaeol, sn-2-hydroxyarchaeol) and specific bacterial fatty acids (C16:1omega5c, cyC17:0omega5,6) as well as with high methane fluxes (Beggiatoa site). The low to medium flux site (Calyptogena field) was dominated by ANME-2c/DSS aggregates and contained less of both compound classes but more of AOM-related glycerol dialkyl glycerol tetraethers (GDGTs). ANME-1 archaea dominated deeper sediment horizons at the Calyptogena field where sn-1,2-di-O-alkyl glycerol ethers (DAGEs), archaeol, methyl-branched fatty acids (ai-C15:0, i-C16:0, ai-C17:0), and diagnostic GDGTs were prevailing. AOM-specific bacterial and archaeal biomarkers in these sediment strata generally revealed very similar d13C-values of around -100 per mill. In ANME-2-dominated sediment sections, archaeal biomarkers were even more 13C-depleted (down to -120 per mill), whereas bacterial biomarkers were found to be likewise 13C-depleted as in ANME-1-dominated sediment layers (d13C: -100 per mill). The zero flux site (Acharax field), containing only a few numbers of ANME-2/DSS aggregates, however, provided no specific biomarker pattern. Deeper sediment sections (below 20 cm sediment depth) from Beggiatoa covered areas which included solid layers of methane gas hydrates contained ANME-2/DSS typical biomarkers showing subsurface peaks combined with negative shifts in carbon isotopic compositions. The maxima were detected just above the hydrate layers, indicating that methane stored in the hydrates may be available for the microbial community. The observed variations in biomarker abundances and 13C-depletions are indicative of multiple environmental and physiological factors selecting for different AOM consortia (ANME-2a/DSS, ANME-2c/DSS, ANME-1) along horizontal and vertical gradients of cold seep settings.

A relationship between aerosol transport and compound-specific d13C land plant biomarker and pollen records

We examined near-surface, late Holocene deep-sea sediments at nine sites on a north-south transect from the Congo Fan (4°S) to the Cape Basin (30°S) along the Southwest African continental margin. Contents, distribution patterns and molecular stable carbon isotope signatures of long-chain n-alkanes (C27-C33) and n-alkanols (C22-C32) are indicators of land plant vegetation of different biosynthetic types, which can be correlated with concentrations and distributions of pollen taxa in the same sediments. Calculated clusters of wind trajectories and satellite Aerosol Index imagery afford information on the source areas for the lipids and pollen on land and their transport pathways to the ocean sites. This multidisciplinary approach on an almost continental scale provides clear evidence of latitudinal differences in lipid and pollen composition paralleling the major phytogeographic zonations on the adjacent continent. Dust and smoke aerosols are mainly derived from the western and central South African hinterland dominated by deserts, semi-deserts and savannah regions rich in C4 and CAM plants. The northern sites (Congo Fan area and northern Angola Basin), which get most of their terrestrial material from the Congo Basin and the Angolan highlands, may also receive some material from the Chad region. Very little aerosol from the African continent is transported to the most southerly sites in the Cape Basin. As can be expected from the present position of the phytogeographic zones, the carbon isotopic signatures of the n-alkanes and n-alkanols both become isotopically more enriched in 13C from north to south. The results of the study suggest that this combination of pollen data and compound-specific isotope geochemical proxies can be effectively applied in the reconstruction of past continental phytogeographic developments.

Compound specific stable isotopes, BIT, pollen and spores of Miocene to Pliocene sediments of ODP Hole 175-1085A

Pollen and stable carbon (d13C) and hydrogen (dD) isotope ratios of terrestrial plant wax from the South Atlantic sediment core, ODP Site 1085, is used to reconstruct Miocene to Pliocene changes of vegetation and rainfall regime of western southern Africa. Our results reveal changes in the relative amount of precipitation and indicate a shift of the main moisture source from the Atlantic to the Indian Ocean during the onset of a major aridification 8 Ma ago. We emphasise the importance of declining precipitation during the expansion of C4 and CAM (mainly succulent) vegetation in South Africa. We suggest that the C4 plant expansion resulted from an increased equator-pole temperature gradient caused by the initiation of strong Atlantic Meridional Overturning Circulation following the shoaling of the Central American Seaway during the Late Miocene.

Specific conductivity and hydrogen ions measured on two ice core (NEEM and NGRIP)

A stratigraphy-based chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core has been derived by transferring the annual layer counted Greenland Ice Core Chronology 2005 (GICC05) and its model extension (GICC05modelext) from the NGRIP core to the NEEM core using 787 match points of mainly volcanic origin identified in the electrical conductivity measurement (ECM) and dielectrical profiling (DEP) records. Tephra horizons found in both the NEEM and NGRIP ice cores are used to test the matching based on ECM and DEP and provide five additional horizons used for the timescale transfer. A thinning function reflecting the accumulated strain along the core has been determined using a Dansgaard-Johnsen flow model and an isotope-dependent accumulation rate parameterization. Flow parameters are determined from Monte Carlo analysis constrained by the observed depth-age horizons. In order to construct a chronology for the gas phase, the ice age-gas age difference (Delta age) has been reconstructed using a coupled firn densification-heat diffusion model. Temperature and accumulation inputs to the Delta age model, initially derived from the water isotope proxies, have been adjusted to optimize the fit to timing constraints from d15N of nitrogen and high-resolution methane data during the abrupt onset of Greenland interstadials. The ice and gas chronologies and the corresponding thinning function represent the first chronology for the NEEM core, named GICC05modelext-NEEM-1. Based on both the flow and firn modelling results, the accumulation history for the NEEM site has been reconstructed. Together, the timescale and accumulation reconstruction provide the necessary basis for further analysis of the records from NEEM.

Planktic foraminiferal sieve size specific d13C and d18O values and maximum test diameter from ODP sites 171-1051 and 120-748

Many genera of modern planktic foraminifera are adapted to nutrient-poor (oligotrophic) surface waters by hosting photosynthetic symbionts, but it is unknown how they will respond to future changes in ocean temperature and acidity. Here we show that ca. 40 Ma, some fossil photosymbiont-bearing planktic foraminifera were temporarily 'bleached' of their symbionts coincident with transient global warming during the Middle Eocene Climatic Optimum (MECO). At Ocean Drilling Program (ODP) Sites 748 and 1051 (Southern Ocean and mid-latitude North Atlantic, respectively), the typically positive relationship between the size of photosymbiont-bearing planktic foraminifer tests and their carbon isotope ratios (d13C) was temporarily reduced for ~100 k.y. during the peak of the MECO. At the same time, the typically photosymbiont-bearing planktic foraminifera Acarinina suffered transient reductions in test size and relative abundance, indicating ecological stress. The coincidence of minimum d18O values and reduction in test size-d13C gradients suggests a link between increased sea-surface temperatures and bleaching during the MECO, although changes in pH and nutrient availability may also have played a role. Our findings show that host-photosymbiont interactions are not constant through geological time, with implications for both the evolution of trophic strategies in marine plankton and the reliability of geochemical proxy records generated from symbiont-bearing planktic foraminifera.

Aboveground community and species-specific plant biomass from the Jena Experiment (Main Experiment, time series since 2002)

This data set comprises a time series of aboveground community plant biomass (Sown plant community, Weed plant community, Dead plant material, and Unidentified plant material; all measured in biomass as dry weight) and species-specific biomass from the sown species of the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. Aboveground community biomass was harvested twice a year just prior to mowing (during peak standing biomass twice a year, generally in May and August; in 2002 only once in September) on all experimental plots of the main experiment. This was done by clipping the vegetation at 3 cm above ground in up to four rectangles of 0.2 x 0.5 m per large plot. The location of these rectangles was assigned by random selection of new coordinates every year within the core area of the plots (i.e. the central 10 x 15 m). The positions of the rectangles within plots were identical for all plots. The harvested biomass was sorted into categories: individual species for the sown plant species, weed plant species (species not sown at the particular plot), detached dead plant material (i.e., dead plant material in the data file), and remaining plant material that could not be assigned to any category (i.e., unidentified plant material in the data file). All biomass was dried to constant weight (70°C, >= 48 h) and weighed. Sown plant community biomass was calculated as the sum of the biomass of the individual sown species. The data for individual samples and the mean over samples for the biomass measures on the community level are given. Overall, analyses of the community biomass data have identified species richness as well as functional group composition as important drivers of a positive biodiversity-productivity relationship.

Specific microbial biomarker signatures from Congo fan sediments of ODP site 175-1075, Congo soils, wetland and estuary sediments

Methane (CH4) is a strong greenhouse gas known to have perturbed global climate in the past, especially when released in large quantities over short time periods from continental or marine sources. It is therefore crucial to understand and, if possible, quantify the individual and combined response of these variable methane sources to natural climate variability. However, past changes in the stability of greenhouse gas reservoirs remain uncertain and poorly constrained by geological evidence. Here, we present a record from the Congo fan of a highly specific bacteriohopanepolyol (BHP) biomarker for aerobic methane oxidation (AMO), 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol), that identifies discrete periods of increased AMO as far back as 1.2 Ma. Fluctuations in the concentration of aminopentol, and other 35-aminoBHPs, follow a pattern that correlates with late Quaternary glacial-interglacial climate cycles, with highest concentrations during warm periods. We discuss possible sources of aminopentol, and the methane consumed by the precursor methanotrophs, within the context of the Congo River setting, including supply of methane oxidation markers from terrestrial watersheds and/or marine sources (gas hydrate and/or deep subsurface gas reservoir). Compound-specific carbon isotope values of -30 per mil to -40 per mil for BHPs in ODP 1075 and strong similarities between the BHP signature of the core and surface sediments from the Congo estuary and floodplain wetlands from the interior of the Congo River Basin, support a methanotrophic and likely terrigenous origin of the 35-aminoBHPs found in the fan sediments. This new evidence supports a causal connection between marine sediment BHP records of tropical deep sea fans and wetland settings in the feeding river catchments, and thus tropical continental hydrology. Further research is needed to better constrain the different sources and pathways of methane emission. However, this study identifies the large potential of aminoBHPs, in particular aminopentol, to trace and, once better calibrated and understood, quantify past methane sources and fluxes from terrestrial and potentially also marine sources.

Aboveground community and species-specific plant biomass from the Jena Experiment (Dominance Experiment, time series since 2002)

This data set comprises a time series of aboveground community plant biomass (Sown plant community, Weed plant community, Dead plant material, and Unidentified plant material; all measured in biomass as dry weight) and species-specific biomass from the sown species of the dominance experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the dominance experiment, 206 grassland plots of 3.5 x 3.5 m were established from a pool of 9 species that can be dominant in semi-natural grassland communities of the study region. In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 3, 4, 6, and 9 species). Plots were maintained by bi-annual weeding and mowing. Aboveground community biomass was harvested twice a year, generally in May and August (in 2002 only once in September) on all experimental plots of the dominance experiment. This was done by clipping the vegetation at 3 cm above ground in two rectangles of 0.2 x 0.5 m per experimental plot. The location of these rectangles was assigned by random selection of new coordinates every year within the central area of the plots (excluding an outer edge of 50cm). The positions of the rectangles within plots were identical for all plots. The harvested biomass was sorted into categories: individual species for the sown plant species, weed plant species (species not sown at the particular plot), detached dead plant material, and remaining plant material that could not be assigned to any category. Biomass was dried to constant weight (70°C, >= 48 h) and weighed. Sown plant community biomass was calculated as the sum of the biomass of the individual sown species. The mean of both samples per plot and the individual measurements are provided in the data file. Overall, analyses of the community biomass data have identified species richness and the presence of particular species as an important driver of a positive biodiversity-productivity relationship.

Species-specific consequences of ocean acidification for the calcareous tropical green algae Halimeda, 2011

Ocean acidification (OA), resulting from increasing dissolved carbon dioxide (CO2) in surface waters, is likely to affect many marine organisms, particularly those that calcify. Recent OA studies have demonstrated negative and/or differential effects of reduced pH on growth, development, calcification and physiology, but most of these have focused on taxa other than calcareous benthic macroalgae. Here we investigate the potential effects of OA on one of the most common coral reef macroalgal genera,Halimeda. Species of Halimeda produce a large proportion of the sand in the tropics and are a major contributor to framework development on reefs because of their rapid calcium carbonate production and high turnover rates. On Palmyra Atoll in the central Pacific, we conducted a manipulative bubbling experiment to investigate the potential effects of OA on growth, calcification and photophysiology of 2 species of Halimeda. Our results suggest that Halimeda is highly susceptible to reduced pH and aragonite saturation state but the magnitude of these effects is species specific. H. opuntiasuffered net dissolution and 15% reduction in photosynthetic capacity, while H. taenicola did not calcify but did not alter photophysiology in experimental treatments. The disparate responses of these species to elevated CO2 partial -pressure (pCO2) may be due to anatomical and physiological differences and could represent a shift in their relative dominance in the face of OA. The ability for a species to exert biological control over calcification and the species specific role of the carbonate skeleton may have important implications for the potential effects of OA on ecological function in the future.

Sex-specific foraging during parental care in a size-monomorphic seabird

Sex differences in foraging behaviour are typically studied in size-dimorphic taxa. Data on sex-specific behavior in monomorphic taxa are needed to test theories of reproductive investment. It has been suggested that in seabirds foraging niche separation may be related to decreased intersexual competition for food between cooperating pair-bonded individuals. Alternatively, sex differences in foraging niches may be driven by different nutritional requirements of females associated with the reproductive costs of egg production and oviposition. To assess these possibilities, we studied a size-monomorphic colonial seabird, the Australasian Gannet (Morus serrator) at the Cape Kidnappers gannetry, New Zealand. We recorded maximum dive depths, and distinct diet composition of incubating females as indicated by stable isotopic signatures. Results suggested greater female foraging effort during early times of incubation, indicated by significantly deeper maximum dives. Sex-specific foraging patterns across other breeding stages were more variable. Nitrogen stable isotopic values showed that incubating females occupied a different trophic position compared to males at the same breeding stage, and also from those of gannets of both sexes at later stages of parental care. Overall, the data are consistent with cost-of-oviposition compensation in females necessitating male-bias in parental care in biparental breeders. Further research is needed to unravel the implications for the evolution of sex differences in behavior in this and other monomorphic taxa.

Polypharmacy and specific comorbidities in university primary care settings.

AIMS Polypharmacy is associated with adverse events and multimorbidity, but data are limited on its association with specific comorbidities in primary care settings. We measured the prevalence of polypharmacy and inappropriate prescribing, and assessed the association of polypharmacy with specific comorbidities. METHODS We did a cross-sectional analysis of 1002 patients aged 50-80years followed in Swiss university primary care settings. We defined polypharmacy as ≥5 long-term prescribed drugs and multimorbidity as ≥2 comorbidities. We used logistic mixed-effects regression to assess the association of polypharmacy with the number of comorbidities, multimorbidity, specific sets of comorbidities, potentially inappropriate prescribing (PIP) and potential prescribing omission (PPO). We used multilevel mixed-effects Poisson regression to assess the association of the number of drugs with the same parameters. RESULTS Patients (mean age 63.5years, 67.5% ≥2 comorbidities, 37.0% ≥5 drugs) had a mean of 3.9 (range 0-17) drugs. Age, BMI, multimorbidity, hypertension, diabetes mellitus, chronic kidney disease, and cardiovascular diseases were independently associated with polypharmacy. The association was particularly strong for hypertension (OR 8.49, 95%CI 5.25-13.73), multimorbidity (OR 6.14, 95%CI 4.16-9.08), and oldest age (75-80years: OR 4.73, 95%CI 2.46-9.10 vs.50-54years). The prevalence of PPO was 32.2% and PIP was more frequent among participants with polypharmacy (9.3% vs. 3.2%, p<0.006). CONCLUSIONS Polypharmacy is common in university primary care settings, is strongly associated with hypertension, diabetes mellitus, chronic kidney disease and cardiovascular diseases, and increases potentially inappropriate prescribing. Multimorbid patients should be included in further trials for developing adapted guidelines and avoiding inappropriate prescribing.

Application of factor decomposition techniques to vertical specialisation measurements

The increasing importance of vertical specialisation (VS) trade has been a notable feature of rapid economic globalisation and regional integration. In an attempt to understand countries’ depth of participation in global production chains, many Input-Output based VS indicators have been developed. However, most of them focus on showing the overall magnitude of a country’s VS trade, rather than explaining the roles that specific sectors or products play in VS trade and what factors make the VS change over time. Changes in vertical specialisation indicators are, in fact, determined by mixed and complex factors such as import substitution ratios, types of exported goods and domestic production networks. In this paper, decomposition techniques are applied to VS measurement based on the OECD Input-Output database. The decomposition results not only help us understand the structure of VS at detailed sector and product levels, but also show us the contributions of trade dependency, industrial structures of foreign trade and domestic production system to a country’s vertical specialisation trade.