Phosphorus in Agriculture: A Review of Results from 175 Years of Research at Rothamsted, UK.

Insight into the role of phosphorus (P) in soil fertility and crop nutrition at Rothamsted, UK, and its involvement in associated environmental issues, has come from long-term field experiments initially started by J. B. Lawes in 1843 and continued by others, together with experiments on different soils. Results from the 1940s confirmed that residues of P applied in fertilizers and manures build up reserves of P in soil. There is a strong relationship between crop yield and plant-available P (Olsen P), and a critical level of Olsen P can be determined. For soils near the critical level, P-use efficiency is high when the P applied and offtake by the crop is nearly equal. Soil inorganic P is associated with various soil components and is held there with a range of bonding energies so that when no P is applied, the decline in Olsen P follows a smooth curve. We conceptualize inorganic soil P as being in four pools of vastly varying size, availability for uptake, and extractability by reagents used in routine soil analysis, and with reversible transfer of P between pools. For very disparate soils at Rothamsted and in the United States, there is a strong relationship between the change in Olsen P and P removal/input ratios, suggesting an underlying similarity in inorganic P behavior. Maintaining soil near the critical level should optimize yield and the use of the global P resource while minimizing the risk of transfer of large amounts of P to the aquatic environment.

Sepiapterin Improves Vascular Reactivity and Insulin-Stimulated Glucose in Wistar Rats.

In the vasculature, sedentary behavior leads to endothelial abnormalities, resulting in elevated cardiovascular disease risk. Endothelial nitric oxide synthase (eNOS) aberrations characterize endothelial dysfunction; eNOS also regulates mitochondrial function. We hypothesized that sepiapterin (a precursor to eNOS cofactor tetrahydrobiopterin (BH4)) supplementation would improve endothelium-dependent vascular relaxation in sedentary animals via modulation of NOS function and mitochondrial activity. Sedentary male Wistar rats were fed ad libitum for a total of 10 weeks. Sepiapterin was administered in diet during the final 5 weeks. Intraperitoneal insulin and glucose tolerance tests (IP-ITT/IP-GTT) were conducted at baseline and endpoint. Aorta was assessed for vasoreactivity and mitochondrial respiration. Insulin tolerance, determined by IP-ITT, significantly improved in rats treated with sepiapterin (p < 0.05, interaction of time and treatment). Acetylcholine- (ACh-) driven vasodilation was significantly greater in aorta from sepiapterin-treated rats as compared with control (76.4% versus 54.9% of phenylephrine contraction at 20 µM ACh, p < 0.05). Sepiapterin treatment resulted in significantly elevated state 3 (9.00 oxygen pmol/sec∗mg versus 8.17 oxygen pmol/sec∗mg, p < 0.05) and 4 (7.28 oxygen pmol/sec∗mg versus 5.86 oxygen pmol/sec∗mg, p < 0.05) aortic mitochondrial respiration with significantly lower respiratory control ratio (p < 0.05) during octanoylcarnitine-driven respiration. Vasodilation and insulin sensitivity were improved through targeting NOS via sepiapterin supplementation.

The importance of long-term experiments in agriculture: their management to ensure continued crop production and soil fertility; the Rothamsted experience.

Long-term field experiments that test a range of treatments and are intended to assess the sustainability of crop production, and thus food security, must be managed actively to identify any treatment that is failing to maintain or increase yields. Once identified, carefully considered changes can be made to the treatment or management, and if they are successful yields will change. If suitable changes cannot be made to an experiment to ensure its continued relevance to sustainable crop production, then it should be stopped. Long-term experiments have many other uses. They provide a field resource and samples for research on plant and soil processes and properties, especially those properties where change occurs slowly and affects soil fertility. Archived samples of all inputs and outputs are an invaluable source of material for future research, and data from current and archived samples can be used to develop models to describe soil and plant processes. Such changes and uses in the Rothamsted experiments are described, and demonstrate that with the appropriate crop, soil and management, acceptable yields can be maintained for many years, with either organic manure or inorganic fertilizers. Highlights: Long-term experiments demonstrate sustainability and increases in crop yield when managed to optimize soil fertility.Shifting individual response curves into coincidence increases understanding of the factors involved.Changes in inorganic and organic pollutants in archived crop and soil samples are related to inputs over time.Models describing soil processes are developed from current and archived soil data.

Changes in soil organic matter over 70 years in continuous arable and ley-arable rotations on a sandy loam soil in England.

The sequestration in soil of organic carbon (SOC) derived from atmospheric carbon dioxide (CO2) by replacing arable crops with leys, has been measured over 70 years on a sandy loam soil. The experiment was designed initially to test the effect of leys on the yields of arable crops. A 3-year grazed grass with clover (grass + clover) ley in a 5-year rotation with arable crops increased percentage organic carbon (%OC) in the top 25 cm of the soil from 0.98 to 1.23 in 28 years, but with little further increase during the next 40 years with all-grass leys given fertilizer nitrogen (N). In this second period, OC inputs were balanced by losses, suggesting that about 1.3% OC might be near the equilibrium content for this rotation. Including 3-year lucerne (Medicago sativa) leys had little effect on %OC over 28 years, but after changing to grass + clover leys, %OC increased to 1.24 during the next 40 years. Eight-year leys (all grass with N or grass + clover) in 10-year rotations with arable crops were started in the 1970s, and after three rotations %OC had increased to ca. 1.40 in 2000-2009. Over 70 years, %OC declined from 0.98 to 0.94 in an all-arable rotation with mainly cereals and to 0.82 with more root crops. Applications of 38 t ha-1 farmyard manure (FYM) every fifth year increased %OC by 0.13% by the mid-1960s when applications ceased. Soil treated with FYM still contained 0.10% more OC in 2000-2009. Changes in the amount of OC have been modelled with RothC-26.3 and estimated inputs of C for selected rotations. Little of the OC input during the 70 years has been retained; most was retained in the grazed ley rotation, but 9 t ha-1 only of a total input of 189 t ha-1. In other rotations more than 98% of the total OC input was lost. Despite large losses of C, annual increases in OC of 4‰ are possible on this soil type with the inclusion of grass or grass + clover leys or the application of FYM, but only for a limited period. Such increases in SOC might help to limit increases in atmospheric CO2. HIGHLIGHTS: Can leys sequester significant amounts of atmospheric CO 2 in SOM and contribute to the 4‰ initiative?Changes in the percentage and amount of OC were measured and modelled over 70 years and OC losses estimated.Three-year grass or grass + clover leys increased %OC, but only to an equilibrium level that was then maintained.Despite large losses, sequestering CO 2-C at 4‰ year-1 by growing grass or grass + clover leys is possible.

Testing the distinctness of shoot ionomes of angiosperm families using the Rothamsted Park Grass Continuous Hay Experiment.

• The ionome is the elemental composition of a tissue or organism. Phylogenetic variation in the ionomes of plant shoots has been widely reported based on controlled experiments, vegetation surveys and literature meta-analyses. However, environmental effects on phylogenetic variation in shoot ionomes have not been quantified. This study tests the hypothesis that phylogenetic variation in shoot ionomes is robust to environmental perturbation and that plant families can be distinguished by their shoot ionomes. • Herbage was sampled from six subplots of the Rothamsted Park Grass Experiment. Subplots had received contrasting fertilizer treatments since 1856. Herbage was separated into its constituent species (n = 21) and concentrations of eleven mineral elements were determined in dried shoot material. • Shoot concentrations of calcium (Ca), zinc (Zn), manganese (Mn), magnesium (Mg) and sodium (Na) showed significant variation associated with plant species, and responded similarly to fertilizer treatments in diverse plant species. Species × treatment interactions were indicated for phosphorus (P), potassium (K), nickel (Ni), copper (Cu) and iron (Fe). Plant families could be distinguished by their shoot ionomes. The most informative elements for discriminant analysis were Ca > Mg > Ni > S > Na > Zn > K > Cu > Fe > Mn > P. • Whilst shoot ionomes were sensitive to fertilizer treatment, phylogenetic variation in a subset of the shoot ionome (Ca, Zn, Mn, Mg) was robust to this environmental perturbation.

Reductions and changing patterns of ambient PCDD/Fs in the UK: evidence and implications.

Archived herbage samples taken between the mid-1800s and the present day from the Park Grass permanent grassland experiment in the UK were analysed for PCDD/Fs. The concentrations of SigmaP((4-8))CDD/Fs ranged between 15 (in 2003-2004) and 320 pg/g (in 1963) and the SigmaTEQ ranged between 0.11 (2003-2004) and 2.4 pg/g in (1903). The underlying trend from the mid-1970s to the present is of a decline by about factor of 10, indicating a general reduction in the air concentration/deposition fluxes. The homologue pattern in samples from the first half of the 20th century was characterised by the lower (mono- to tri-) PCDFs, indicating the dominance of domestic wood/coal burning on the SigmaP((1-8))CDD/Fs signature. The second half of the 20th century saw a substantial decline in domestic wood/coal burning for space heating in the UK, but also the 'rise and fall' in the production/use of chloroaromatic compounds - notably pentachlorophenol (PCP). The isomer/homologue patterns for the 1960-2004 samples have a much lower contribution from the lower PCDFs and large contributions from the hepta and octa-CDDs. The possibility that these are related to PCP inputs via different routes is discussed. The UK - in line with other countries - has had a policy to reduce the environmental sources and the emissions of PCDD/Fs, by the introduction of new combustion control technologies and emissions standards. However, these were not introduced to specifically address PCDD/F emissions until the 1990s. The declines in PCDD/F levels in these samples: (a) pre-date the introduction of emission control measures on incinerators and other combustion sources in the UK; (b) appear to have been largely unaffected by them.

Comparison of haloacetic acids in the environment of the Northern and Southern Hemispheres.

Haloacetic acids (HAAs) are a family of compounds whose environmental concentrations have been extensively studied, primarily in Europe. Depending on the compound, their sources are believed to be both natural and anthropogenic. To better understand possible sources and contribute to the knowledge of the global distribution of these compounds, especially between the Northern and Southern Hemispheres, samples of precipitation, soils, and conifer needles were collected from Canada, Malawi, Chile, and the U.K. Precipitation samples exhibited highest HAA concentrations in collections from Canada, and lowest in those from Malawi. Malawi samples contained measurable levels of monobromoacetic acid (MBA) (56 ng/ L) unlike those from most other locations (< 9 ng/L). Soil HAA concentration levels were highest in the U.K. (e.g., 7.3 ng/g average TCA) and lowest in Malawi (0.8 ng/g average TCA), with Chile having higher levels (4.8 ng/g average TCA) than Canada (3 ng/g average TCA). Malawi soils contained small amounts of MBA (2 ng/g), in common with the two most southern of the 11 Chilean sites. Analysis of soil cores (10-cm depth sliced at 1 cm) from sites in Malawi and Chile showed that trichloroacetic acid (TCA) generally declined with depth while mono- and dichloroacetic acid (MCA and DCA) showed no trend. MCA, DCA, and TCA concentrations in archived U.K. soil samples increased by factors of 2, 4, and 5-fold over 75 years while TFA showed no consistent trend. Monochloroacetic acid (MCA) was detected in pine needles collected from Malawi. U.K. needle samples had the highest concentrations of all chloroacetic acids (CAAs): MCA, 2-18 ng/g; dichloroacetic acid (DCA), 2-38 ng/g; and trichloroacetic acid (TCA), 28-190 ng/g. Conifer needles from Canada and Chile contained CAAs at levels ranging from < 2 to 16 ng/g wet wt. Trifluoroacetic acid concentrations generally declined with increasing elevation in the samples from the Rocky Mountains in western Canada. The results indicate that concentrations of HAAs are greatest in the industrialized Northern Hemisphere but there are significant amounts of these compounds in the less industrialized Southern Hemisphere.

Time trends of atmospheric PBDEs inferred from archived U.K. herbage.

Aerial portions of vegetation receive the bulk of their burden of persistent organic pollutants (POPs) from the atmosphere. Vegetation can therefore be a useful indicator of the changing atmospheric burden of POPs. Samples of archived pasture, collected from Rothamsted Experimental Station in the United Kingdom between 1930 and 2004, were analyzed for a range of polybrominated diphenyl ethers (PBDEs). PBDEs could not be routinely detected in the pre-1970 samples. Thereafter, the dominant congeners BDE 28, 47, 49, 99, 100, 153, 154, and 183 were frequently detected. The general trend was (a) a rise through the 1970s; (b) a minipeak in the mid-1980s, strongly influenced by one particularly high sample for 1984; (c) values remaining high through the late 1980s/1990s; (d) an indication of a more recent decline for all congeners (except BDE-28), consistent with recent restrictions on PBDE usage in Europe. These trends were compared to recent modeled estimates of U.K. PBDE emissions. The congener profiles of technical mixtures, U.K. air, soil, and pasture were compared and shown to be broadly similar. The implications for environmental release mechanisms are discussed.

Determinants of species richness in the Park Grass Experiment.

The Park Grass Experiment at Rothamsted in southeast England was started in 1856, making it the longest-running experiment in plant ecology anywhere in the world. Experimental inputs include a range of fertilizers (nitrogen, phosphorus, potassium, and organic manures) applied annually, with lime applied occasionally, and these have led to an increase in biomass and, where nitrogen was applied in the form of ammonium sulfate, to substantial decreases in soil pH. The number of species per plot varies from three to 44 per 200 m(2), affording a unique opportunity to study the determinants of plant species richness and to estimate the effect sizes attributable to different factors. The response of species richness to biomass depends on the amount and type of nitrogen applied; richness declined monotonically with increasing biomass on plots receiving no nitrogen or receiving nitrogen in the form of sodium nitrate, but there was no relationship between species richness and biomass on plots acidified by ammonium sulfate application. The response to lime also depended on the type of nitrogen applied; there was no relationship between lime treatment and species richness, except in plots receiving nitrogen in the form of ammonium sulfate, where species richness increased sharply with increasing soil pH. The addition of phosphorus reduced species richness, and application of potassium along with phosphorus reduced species richness further, but the biggest negative effects were when nitrogen and phosphorus were applied together. The analysis demonstrates how multiple factors contribute to the observed diversity patterns and how environmental regulation of species pools can operate at the same spatial and temporal scale as biomass effects.

Observations on historical, contemporary, and natural PCDD/Fs.

PCDD/Fs were determined in samples of archived surface soils collected from different locations around the world in the early 1880s, in contemporary surface soils from around the world, in archived subsurface soils collected at Rothamsted Experimental Station in the 1870/1880s, and in sections of peat core deposited between 5000 BP and the present. PCDD/Fs were detected in most of the samples. The potential sources and implications of the levels and mixtures of PCDD/Fs present in the samples are discussed. The homologue and isomer patterns observed in most of the contemporary European surface soils are commonly observed for European air samples and soil samples. The homologue pattern in the Rothamsted surface soils collected in the 1800s was similar, suggesting that similar sources of atmospheric emissions of PCDD/ Fs were operating in the UK in the 1800s as currently. Very different patterns, dominated by OCDD and with contributions of HpCDD and HxCDD, were found in some other samples. It is proposed that the PCDD/Fs present in the subsurface Rothamsted soils, archived (1880s) surface soils from Illinois and the Congo, clay beneath the peat bog (deposited approximately 5000 BP), and possibly surface soil samples from Thailand and Australia are of a natural origin. The most abundant TeCDD/F congeners measured in the peat samples here were also those observed by previous workers who studied a Canadian peat bog and are consistent with the microbially mediated oxidative coupling of chlorophenols. The study provides evidence for the widespread occurrence of PCDD/Fs in the environment prior to 1900 and for a complex array of sources (including natural) and environmental transformation processes.

Possibilities for reducing nitrate leaching from agricultural land.

Agricultural soil is a contributor of nitrate to natural waters. High nitrate levels in water leached from soils are related to high nitrate concentrations in drinking water, and excess levels change the ecological balance of rivers and lakes. In this paper, sound solutions to the major environmental issue of limiting nitrate leaching by modifying agricultural practices are discussed. The causes of nitrate leaching from agricultural land are briefly explained and existing measures for the reduction of nitrate losses are described, analyzed and evaluated. Reduction of nutrient leaching is not a question of organic or conventional farming, but rather of the introduction and use of appropriate countermeasures. We propose the following guiding principles to minimize leaching from agricultural soils. To some extent these principles require a new way of thinking: i) environmental indexing of fields and consideration of spatial variability within fields in relation to their contribution to leaching losses within a catchment; ii) reduction of nitrogen inputs to soil to levels slightly below those expected to give the optimum yield by applying less nitrogen fertilizer and by a further reduction in animal density; and iii) use of a range of counter-measures (catch crops, minimum tillage, control of biological processes, etc.) depending on how sensitive the farming system, soil and climate are to the risk of nitrate leaching.

Polychlorinated naphthalenes in U.K. soils: time trends, markers of source, and equilibrium status.

Polychlorinated naphthalenes (PCNs) have been analyzed in archived soil from the U.K. to investigate historical trends. Samples were obtained from the Broadbalk experiment plots (1944-1986) and Luddington experiment station (1968-1990). Luddington samples also include a set of soils that received a one-time sludge treatment in 1968, and duplicate samples of this archived sludge were also analyzed. Peak residues of sumPCN (sum of all PCN congeners quantified) were approximately 9000 pg g(-1) dry weight in 1956, declining to approximately 300 pg g(-1) in contemporary soils. The one-time sludge application resulted in elevated soil residues that were 1.5-6 times higher than the control plot over the time series. This increase is consistent with the known application rate and the amount of sumPCN in the applied sludge (approximately 250,000 pg g(-1) dry wt). Half-lives forthe Luddington control soil and the sludge-amended soil for the period 1972-1990 were 5.3 and 9.9 years, respectively. Investigation of time trends revealed differences between homologue groups with the higher molecular weight congeners peaking earlier in the time series (pre-1950) and the lower molecular weight congeners peaking later, ca. 1970. Time trends of individual congeners were investigated in terms of their relative mass percent contribution to the sum of their homologue group. Significant (p < 0.05) increasing trends were observed for several congeners associated with combustion sources (CN-29, -51, -52/60, -54, and -66/67) suggesting that combustion related sources are more important now than they were in the past. However, no decreasing trend was observed for congeners that were thought to be susceptible to degradation by photolysis suggesting that this may not be a key elimination pathway of PCNs in the environment. A simple calculation of the fugacity status of PCNs in air and soil showed that the tri-CNs are exhibiting net outgassing, while the penta-CNs are still being deposited to soil. Interestingly, the penta-CNs associated with combustion show the largest gradient for air-to-soil transfer, supporting the notion that combustion sources are important contributors to contemporary air burdens of these congeners.

Further evidence for the existence of PCDD/Fs in the environment prior to 1900.

PCDD/Fs and PCBs have been analyzed in a series of archived soil samples collected from various depths during the 1800s and early 1900s. PCBs were not found in soil samples collected before 1900, whereas PCDD/Fs were present in concentrations between 43 and 110 pg/g in surface soils, and between 9 and 150 pg/g in soils collected from below the surface. The PCDD/F homologue patterns of all surface soils were consistent with each other. The homologue pattern of deeper soils altered with depth to one that was dominated by highly chlorinated PCDDs. The highest sigma(4-8)PCDD/F concentration (150 pg/g) was found in the deepest soil analyzed (230-250 cm below the surface). The cork from one of the storage bottles contained considerable quantities of both PCBs and PCDD/Fs. However, contamination of the soils, either by diffusion through the cork or by cork particles, was discounted on the basis that no PCBs were evident in the soil, and that the PCDD/F homologue pattern in the cork was very different to that found in the soil. Similar arguments were used to discount contamination of the soil by dust. A sample of ashed vegetation from the archive, that had no cork stopper, contained high concentrations of PCBs (78 ng/g), concentrations of mono- to tri-CDFs that were higher than in any of the soils (190 pg/g), but very low concentrations of sigma(4-8)PCDD/F (12 pg/g). This pattern of analytes was considered to be representative of contamination from store room air and was completely different from the pattern observed in the soils. Taken together these observations indicate that contamination during storage, or subsequent handling, is unlikely to have occurred in archived soil samples that were stored with cork and wax seal intact. The results imply surface soil sigma(4-8)PCDD/F concentrations of around 60 pg/g at Rothamsted (southeast England) in the late 1800s, compared with approximately 300 pg/g reported for rural UK soils in the 1990s.

Organochlorine pesticide residues in archived UK soil.

Archived background soils ("Broadbalk', 1944-1986) and sludge-amended soils ("Luddington", 1968-1990), collected from long-term agricultural experiments in the UK, were analyzed for a range of organochlorine (OC) pesticides to establish trends over time. Concentrations typically ranged from 0.1 to 10 ng/g of soil (dry weight), with gamma-hexachlorocyclohexane (gamma-HCH), dieldrin, and p,p'-DDE consistently having the highest concentrations. The trends in the Broadbalk background soils are largely consistent with usage patterns, with peak concentrations occurring in the 1960s for DDTs and between the 1960s and the 1980s for the other OCs. In the Luddington control and sludge-amended soils, several of the OCs show a significant decline in concentrations from the late 1960s to 1990, with half-lives ranging from approximately 7 years (alpha-HCH) to approximately 25 years (dieldrin). The sludge-amended plot received 125 tonnes of sludge per ha in 1968, which was mixed in to a depth of 15 cm. It appears that the sludge treatment had little effect on concentrations in the soil, with no significant difference between control soil and sludge-amended soil for most compounds, except for HCB, p,p'-DDE, and dieldrin. Enantiomeric fractions (EFs) of some chiral pesticides (alpha-HCH, cis- and trans-chlordane, and o,p'-DDT) were determined in the Luddington soils. Results reveal that enantioselective degradation of OC pesticides is occurring in these soils for trans-chlordane (TC) and cis-chlordane (CC). However, the depletion over time is not statistically significant, and there is no statistically significant difference between EFs in the control soil and sludge-amended soil. This indicates that enantioselective microbial degradation was not consistent over time and that the addition of sludge to soil did not significantly alter the enantiomeric preference of the microbial community.

Cyclic variation of integrated backscatter: dependence of time delay on the echocardiographic view used and the myocardial segment analyzed.

To determine the influence of myocardial anisotropy in ultrasonic tissue characterization, we measured the time delay (and magnitude) of the cyclic variation of myocardial integrated backscatter from specific segments visualized in the 4 standard transthoracic echocardiographic views. The cyclic variation data in 10 myocardial regions were obtained from analyses of 2-dimensional integrated backscatter images from 23 healthy subjects. Resultant values (mean +/- SD) for the time delay were as follows: parasternal long-axis view: 1.08 +/- 0.17 (septum) and 1.00 +/- 0.14 (posterior wall); parasternal short-axis view: 1.03 +/- 0.16 (anterior septum), 1.03 +/- 0.14 (posterior wall), 2.22 +/- 0.71 (lateral wall), and 1.65 +/- 0.66 (posterior septum); apical 4-chamber view: 1.08 +/- 0.31 (septum) and 2.20 +/- 0.79 (lateral wall); and apical 2-chamber view: 1.68 +/- 0.62 (inferior wall) and 2.04 +/- 0.72 (anterior wall). Hence, results of this study indicate that myocardial ultrasonic characterization that uses the cyclic variation is influenced by the echocardiographic view and the specific segment of the left ventricle.

Dependence of "apparent" magnitude on the time delay of cyclic variation of myocardial backscatter.

The goal of this study was to determine if the "apparent" magnitude of the cyclic variation, defined as the difference between the values of integrated backscatter at end-diastole and end-systole, was dependent on the corresponding time delay. We measured the cyclic variation in four myocardial segments of the parasternal short-axis view in 23 healthy subjects. The "apparent" magnitude, actual magnitude, and time delay were compared for each segment. Measured time delays were: 2.22+/-0.71 (lateral wall); 1.65+/-0.66 (inferior septum); and approximately 1.0 for the anterior septum and posterior wall. Segments exhibiting large time delays (> 1.0) resulted in a reversal in sign of the "apparent" magnitude of cyclic variation in one instance, and underestimated the true magnitude in both cases. Thus, estimates of the "apparent" magnitude of the cyclic variation are dependent on the associated time delay, whereas a properly defined magnitude is not.

Effects of tissue anisotropy and contrast acoustic properties on myocardial scattering in contrast echocardiography.

In this study we explored the potential effects that tissue anisotropy, in conjunction with the acoustic properties of contrast, may have on quantitative measurements of myocardial perfusion with the use of ultrasonic contrast agents. We used a computer simulation of the parasternal short-axis view, based on previously measured values for the anisotropy of backscatter and attenuation of myocardium, to predict the backscattered energy from 18 specific regions within the heart before and after myocardial contrast perfusion. Results demonstrated a regional variation of contrast enhancement in the short-axis view and variations caused by incremental increases in contrast level for specific myocardial regions. Thus quantitative assessment of myocardial perfusion with contrast echocardiography is influenced by the anisotropic properties of the myocardium, and the resulting postcontrast image will depend on the interaction between tissue properties and contrast acoustic properties. The degree of myocardial enhancement caused by the presence of contrast may depend on the spatial position of the specific region investigated with respect to the transducer and the amount of contrast in the myocardium.

Effects of myocardial fiber orientation in echocardiography: quantitative measurements and computer simulation of the regional dependence of backscattered ultrasound in the parasternal short-axis view.

We measured the regional disparity in backscattered ultrasound by means of obtaining integrated backscatter images of 10 healthy subjects and placing a region of interest in 18 distinct positions. A computer model simulating the short-axis view was implemented on the basis of previously measured values for the anisotropic ultrasonic properties of myocardium. Measurements showed that the integrated backscatter value was greatest for the anterior septum and decreased by 15.9 +/- 3.5 dB for the lateral wall and 17.7 +/- 3.5 dB for the inferior septum. The value in the posterior wall was 8.1 +/- 3.8 dB below the value for the anterior septum. The regional variation of backscatter predicted with the simulation correlated well with the clinical measurements. These results suggested that analyses based on measurements of backscatter may require compensation for the inherent anisotropic properties of myocardium.

Effects of tissue anisotropy on the spectral characteristics of ultrasonic backscatter measured with a clinical imaging system.

In this paper, we report the effects of inherent tissue anisotropy on the spectral properties of backscattered ultrasound when measured with a commercially-available imaging system. We insonified five specimens of bovine tendon immersed in a water tank and rotated in 10 degrees increments while being imaged with a Hewlett-Packard Sonos 1500 system. The backscattered RF signals corresponding to each angle of insonification were digitized and the spectral characteristics of the backscattered ultrasound were determined. The mean anisotropy, defined as the average difference between values at perpendicular and parallel insonification, for band-limited estimates of backscattered power, centroid frequency, upper-band to lower-band power ratio, and upper-band to total-band power ratio were found to be 24.6 +/- 1.1 dB, 142 +/- 27 kHz, 32 +/- 13%, and 22 +/- 5%, respectively (mean +/- SE). The magnitude of each of these backscatter spectral parameters was larger at perpendicular insonification compared with the corresponding values at parallel insonification, consistent with previous measurements of the inherent anisotropy of ultrasonic attenuation and backscatter in tissue.