Natural Infection of Iris yellow spot virus in Twoscale Saltbush (Atriplex micrantha) Growing in Utah.

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) continues to be an economically important pathogen affecting onion bulb and seed production in several parts of the world and the United States (1). Several weeds were reported naturally infected with IYSV (1,2,4). Leaves of Atriplex micrantha Ledeb. (synonym A. heterosperma Bunge) were collected from naturally occurring plants in a weed trial conducted in commercial onions grown in Box Elder County, UT on 24 September 2008. Leaves displayed a range of symptoms including spotting, chlorosis, and necrosis. Symptomatic leaves were preferentially selected for subsequent diagnostic analyses. Samples were positive for IYSV when tested by double-antibody sandwich-ELISA using a commercially available kit (Agdia Inc., Elkhart, IN). For further confirmation, total nucleic acid extracts from the symptomatic parts of the leaves were prepared and tested for the presence of IYSV by reverse transcription-PCR with primers specific to the nucleocapsid (N) gene coded by the small (S)-RNA of IYSV. The forward and reverse primer pair, 5'-TCAGAAATCGAGAAACTT-3' and 5'-CACCAATGTCTTCAACAATCTT-3', respectively, amplifies a 751-nt fragment of the N gene (3). An amplicon of expected size was obtained, cloned, and sequenced. The nucleotide sequence analysis and comparison with known IYSV S-RNA sequences showed that the sequence of the amplicon from A. micrantha (GenBank Accession No. FJ493541) shared more than 84% nt sequence identity with the corresponding region of IYSV isolates available in GenBank, confirming the IYSV infection of the new host weed. The highest sequence identity (98%) was with an IYSV isolate from Jefferson County, OR (GenBank Accession No. DQ233479). To our knowledge, this is the first report of IYSV infection of A. micrantha under natural conditions. The role of A. micrantha and other weeds in IYSV epidemiology needs further investigation. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) C. Nischwitz et al. Plant Dis. 91:1518, 2007. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (4) R. Sampangi et al. Plant Dis. 91:1683, 2007.

Green Foxtail (Setaria viridis), A Naturally Infected Grass Host of Iris yellow spot virus in Utah.

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) is a serious virus pathogen in onion bulb and seed crops in the United States and several parts of the world (1). The virus is exclusively transmitted by onion thrips (Thrips tabaci). Besides onion and other susceptible crops such as garlic, leek, chives, and several ornamentals, weeds could be serving as potential reservoir sources of virus inoculum. There are reports of several weeds found naturally infected with IYSV (1,2,4). However, there is no report of IYSV infection of a grass species. Leaves of green foxtail (Setaria viridis (L.) Beauv.) were collected from two naturally occurring plants approximately 30 m apart in a weed trial conducted in commercial onions grown in Box Elder County, UT on 24 September 2008. Notes of IYSV symptoms on green foxtail were made only on the two grass plants sampled. Density of green foxtail in the weed trial was low and was not recorded. Leaves on both plants displayed a range of symptoms that included streaking, purpling, and chlorotic and necrotic lesions along leaf margins oriented along the axis of longitudinal venation. Samples were positive for IYSV by double-antibody sandwich-ELISA with a commercially available kit (Agdia Inc., Elkhart, IN). ELISA values of the grass samples were 2.64 and 2.23 for each plant sampled. Negative and positive control readings were 0.24 and 4.33, respectively. All absorbance readings were made at 405 nm. To provide a contrast of the grass data in context to the onion field where the weed trial was located, final visual assessments of onions in the field were made on 4 September 2009. Approximately 300 onion plants were assessed for incidence and severity of disease. Incidence of the disease among onions was 100% and the severity of iris yellow spot on leaves was 20 lesions per leaf. The average ELISA value over 30 individual onions arbitrarily sampled from the field on the same day was 3.50, and the ELISA values among the samples ranged from 1.37 to 4.38. The negative and positive controls were 0.19 and 4.40, respectively. To further verify the presence of IYSV in the grass specimen, reverse transcription-PCR was performed on total nucleic acid extracts obtained from the symptomatic parts of the leaves. Primers specific to the nucleocapsid (N) gene coded by the small (S)-RNA of IYSV were used (3). The forward and reverse primer pairs, 5'-TCAGAAATCGAGAAACTT-3' and 5'-CACCAATGTCTTCAACAATCTT-3', respectively, amplify a 751-nt fragment of the N gene (3). An amplicon of expected size was obtained, cloned, and sequenced. The nucleotide sequence analysis and comparison with known IYSV S-RNA sequences showed that the amplicon from foxtail (GenBank Accession No. FJ652594) samples had the highest nucleotide sequence identity (98%) with the corresponding region of an IYSV isolate from Jefferson County, OR (GenBank Accession No. DQ233479). To our knowledge, this is the first report of natural infection of a grass species by IYSV and the first report of a Tospovirus infecting a grass species. The data suggests grasses may serve as a new host reservoir for IYSV. The increasing number of weed hosts of IYSV warrants further study on the role of these weeds as hosts for onion thrips and in IYSV epidemiology. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) C. Nischwitz et al. Plant Dis. 91:1518, 2007. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (4) R. Sampangi et al. Plant Dis. 91:1683, 2007.

Gd-DTPA bolus tracking in the myocardium using T1 fast acquisition relaxation mapping (T1 FARM).

MRI methods currently used for bolus tracking in the myocardium, such as saturation recovery turbo-fast low-angle shot (FLASH) (srTFL), are limited by signal intensity (SI) saturation at high contrast agent (CA) concentrations. By using T1 fast acquisition relaxation mapping (T1 FARM), a Gd-DTPA bolus (0.075 vs. 0.025 mmol/kg) may be injected without causing saturation. This study tested the feasibility of in vivo T1 FARM bolus tracking under rest/stress conditions in seven beagles with multiple permanently occluded branches of the left anterior descending (LAD) coronary artery. Although it underestimated the myocardial perfusion reserve (MPR) measured ex vivo using radioactive microspheres (mean +/- SEM; 3.60 +/- 0.26), the MPR determined upon application of the modified Kety model (1.86 +/- 0.10) enabled distinction between normal and infarcted tissue. The partition coefficient (lambda) estimated at rest and stress using the modified Kety model underestimated ex vivo radioactive measurements in infarcted tissue (0.25 +/- 0.01 vs. 0.26 +/- 0.01 vs. 0.79 +/- 0.08 ml/g, P < 0.0001) yet was accurate in normal tissue (0.28 +/- 0.01 vs. 0.30 +/- 0.01 vs. 0.33 +/- 0.01 ml/g, P = NS). Thus, although unsuitable for myocardial viability assessment, T1 FARM bolus tracking shows potential for assessment of myocardial perfusion.

Magnetic field exposure and behavioral monitoring system.

To maximize the availability and usefulness of a small magnetic field exposure laboratory, we designed a magnetic field exposure system that has been used to test human subjects, caged or confined animals, and cell cultures. The magnetic field exposure system consists of three orthogonal pairs of coils 2 m square x 1 m separation, 1.751 m x 0.875 m separation, and 1.5 m x 0.75 m separation. Each coil consisted of ten turns of insulated 8 gauge stranded copper conductor. Each of the pairs were driven by a constant-current amplifier via digital to analog (D/A) converter. A 9 pole zero-gain active Bessel low-pass filter (1 kHz corner frequency) before the amplifier input attenuated the expected high frequencies generated by the D/A conversion. The magnetic field was monitored with a 3D fluxgate magnetometer (0-3 kHz, +/- 1 mT) through an analog to digital converter. Behavioral monitoring utilized two monochrome video cameras (viewing the coil center vertically and horizontally), both of which could be video recorded and real-time digitally Moving Picture Experts Group (MPEG) encoded to CD-ROM. Human postural sway (standing balance) was monitored with a 3D forceplate mounted on the floor, connected to an analog to digital converter. Lighting was provided by 12 offset overhead dimmable fluorescent track lights and monitored using a digitally connected spectroradiometer. The dc resistance, inductance of each coil pair connected in series were 1.5 m coil (0.27 Omega, 1.2 mH), 1.75 m coil (0.32 Omega, 1.4 mH), and 2 m coil (0.38 Omega, 1.6 mH). The frequency response of the 1.5 m coil set was 500 Hz at +/- 463 microT, 1 kHz at +/- 232 microT, 150 micros rise time from -200 microT(pk) to + 200 microT(pk) (square wave) and is limited by the maximum voltage ( +/- 146 V) of the amplifier (Bessel filter bypassed).

A comparison of rheumatoid arthritis and fibromyalgia patients and healthy controls exposed to a pulsed (200 microT) magnetic field: effects on normal standing balance.

Specific weak time varying pulsed magnetic fields (MF) have been shown to alter animal and human behaviors, including pain perception and postural sway. Here we demonstrate an objective assessment of exposure to pulsed MF's on Rheumatoid Arthritis (RA) and Fibromyalgia (FM) patients and healthy controls using standing balance. 15 RA and 15 FM patients were recruited from a university hospital outpatient Rheumatology Clinic and 15 healthy controls from university students and personnel. Each subject stood on the center of a 3-D forceplate to record postural sway within three square orthogonal coil pairs (2 m, 1.75 m, 1.5 m) which generated a spatially uniform MF centered at head level. Four 2-min exposure conditions (eyes open/eyes closed, sham/MF) were applied in a random order. With eyes open and during sham exposure, FM patients and controls appeared to have similar standing balance, with RA patients worse. With eyes closed, postural sway worsened for all three groups, but more for RA and FM patients than controls. The Romberg Quotient (eyes closed/eyes open) was highest among FM patients. Mixed design analysis of variance on the center of pressure (COP) movements showed a significant interaction of eyes open/closed and sham/MF conditions [F=8.78(1,42), P<0.006]. Romberg Quotients of COP movements improved significantly with MF exposure [F=9.5(1,42), P<0.005] and COP path length showed an interaction approaching significance with clinical diagnosis [F=3.2(1,28), P<0.09]. Therefore RA and FM patients, and healthy controls, have significantly different postural sway in response to a specific pulsed MF.

Human subjects exposed to a specific pulsed (200 microT) magnetic field: effects on normal standing balance.

Static and time-varying magnetic fields have been shown to alter animal and human behaviors, such as directional orientation, learning, pain perception (nociception or analgesia) and anxiety-related behaviors. Human volunteers (12 male, 12 female, 18-34 years old) stood on a force plate while within three square magnetic field coil pairs (2, 1.75 and 1.5 m) arranged orthogonal with the uniform magnetic field volume centered at head level. Analysis of the data shows a significant improvement of normal standing balance or center of pressure, with eyes open or eyes closed, by a specific pulsed 200 microT(pk) magnetic field (PEMF). There was no significance found in control condition testing, such as sham-sham exposure of subjects or sham/PEMF exposure of a 60 kg saline phantom. There were no significant effects of gender or age.

Simultaneous MRI measurement of blood flow, blood volume, and capillary permeability in mammary tumors using two different contrast agents.

A technique for the simultaneous measurement of three vascular parameters: blood flow (Frho), blood volume (v(b)), and the capillary permeability-surface area product (PSrho) in breast tumors using dynamic contrast-enhanced magnetic resonance imaging (MRI) is presented. Features of the technique include measurement of precontrast tumor T(1), rapid temporal sampling, measurement of the arterial input function, and use of a distributed parameter tracer kinetic model. Parameter measurements are compared that were determined using two contrast agents of different molecular weights, gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA; 0.6 kDa) and Gadomer-17 (17 kDa), in 18 spontaneous canine mammary tumors. Measurements of Frho and v(b) corresponded well with literature values, and the mean PSrho measured using Gd-DTPA was a factor of 15 higher than that measured using Gadomer-17. J. Magn. Reson. Imaging 2000;12:991-1003.

Rapid small-animal dual-energy X-ray absorptiometry using digital radiography.

Although dual-energy X-ray absorptiometry (DEXA) is an established technique for clinical assessment of areal bone mineral density (BMD), the spatial resolution, signal-to-noise ratio, scan time, and availability of clinical DEXA systems may be limiting factors for small-animal investigations using a large number of specimens. To avoid these limitations, we have implemented a clinical digital radiography system to perform rapid area DEXA analysis on in vitro rat bone specimens. A crossed step-wedge (comprised of epoxy-based materials that mimic the radiographic properties of tissue and bone) was used to calibrate the system. Digital radiographs of bone specimens (pelvis, spine, femur, and tibia from sham-ovariectomized [SHAM] and ovariectomized [OVX] rats) were obtained at 40 kilovolt peak (kVp) and 125 kVp, and the resulting areal BMD values were compared with those obtained with a clinical fan-beam DEXA system (Hologics QDR 4500). Our investigation indicates that the cross-wedge calibrated (CWC) DEXA technique provides high-precision measurements of bone mineral content (BMC; CV = 0.6%) and BMD (CV = 0.8%) within a short acquisition time (<30 s). Areal BMD measurements reported by the CWC-DEXA system are within 8.5% of those reported by a clinical fan-beam scanner, and BMC values are within 5% of the known value of test specimens. In an in vivo application, the CWC-DEXA system is capable of reporting significant differences between study groups (SHAM and OVX) that are not reported by a clinical fan-beam DEXA system, because of the reduced variance and improved object segmentation provided by the CWC-DEXA system.

Spectroscopic lineshape correction by QUECC: combined QUALITY deconvolution and eddy current correction.

Lineshape distortion due to residual eddy currents and magnetic field inhomogeneities are often present in short echo time (1)H spectroscopic data. Lineshape correction methods such as QUALITY deconvolution and eddy current correction (ECC), which use a separate reference spectrum for lineshape correction, have shortcomings when unsuppressed water is chosen as the reference. This paper outlines a method of integrating both techniques to overcome these limitations while still using unsuppressed water as the reference signal. This hybrid lineshape correction technique (QUECC) is demonstrated in vivo using stimulated echo acquisition mode (STEAM) localized 4.0 Tesla data. Metabolite quantification precision increased by an average of 7%-46% compared to QUALITY deconvolution (depending on filtering) and by an average of 6% compared to ECC.

Comparison of the quantification precision of human short echo time (1)H spectroscopy at 1.5 and 4.0 Tesla.

Precise quantification of human in vivo short echo time (1)H spectra remains problematic at clinical field strengths due to broad peak linewidths and low signal-to-noise ratio (SNR). In this study, multiple STEAM spectra (TE = 20 ms, volume = 8 cm(3)) were acquired in a single individual at 1.5 T and 4 T to compare quantification precision. Test-retest STEAM spectra (volume = 1.5 cm(3)) were also acquired from the anterior cingulate and thalamus of 10 individuals at 4.0 T. Metabolite levels were quantified using automated software that incorporated field strength-specific prior knowledge. With the distinct methods of data acquisition, processing, and fitting used in this study, peak height SNR increased approximately 80% while peak linewidth increased by approximately 50% in the 8 cm(3) volumes at 4.0 T compared to 1.5 T, resulting in an average increase in quantification precision of 39%. Metabolite levels from test-retest data (1.5 cm(3) voxels at 4.0 T) were quantified with similar inter- and intraindividual variability. Magn Reson Med 44:185-192, 2000. Published 2000 Wiley-Liss, Inc.

T(1) fast acquisition relaxation mapping (T(1)-FARM): optimized data acquisition.

A theoretical procedure for estimating the precision of the T(1) Fast Acquisition Relaxation Mapping sequence as a function of a number of acquisition parameters has been validated by both simulations and experimental results. These results have clarified the selection of sequence parameters to give optimal accuracy and precision in the R(1)* measurements. There is excellent agreement between theory, simulation, and experiment except for flip angles greater than 9 degrees, at which point slice profile imperfections significantly degrade the precision of the technique. The experimental results indicate that over a range of T(1)s that would be seen in a bolus tracking experiment (25-1200 ms), T(1) Fast Acquisition Relaxation Mapping can be used to obtain 64 x 128 R(1)* maps at a rate of 1 map/s, with a precision of 10% or better.

Factors affecting the quantification of short echo in-vivo 1H MR spectra: prior knowledge, peak elimination, and filtering.

Short echo 1H in-vivo brain MR spectra are difficult to quantify for several reasons: low signal to noise ratio, the severe overlap of spectral lines, the presence of macromolecule resonances beneath the resonances of interest, and the effect of resonances adjacent to the spectral region of interest (SRI). This paper outlines several different quantification strategies and the effect of each on the precision of in-vivo metabolite measurements. In-vivo spectra were quantified with no operator interaction using a template of prior knowledge determined by mathematically modeling separate in-vitro metabolite spectra. Metabolite level estimates and associated precision were compared before and after the inclusion of macromolecule resonances as part of the prior knowledge, and following two different methods of handling resonances adjacent to the SRI. The effects of rectangular and exponential filters were also investigated. All methods were tested using repeated in-vivo spectra from one individual acquired at 1.5 T using stimulated echo acquisition mode (STEAM, TE = 20 ms) localization. The results showed that the inclusion of macromolecules in the prior knowledge was necessary to obtain metabolite levels consistent with the literature, while the fitting of resonances adjacent to the SRI concurrent with modeled metabolites optimized the precision of metabolite estimates. Metabolite levels and precision were also affected by rectangular and exponential filtering, suggesting caution must be taken when such filters are used.

A short echo proton magnetic resonance spectroscopy study of the left mesial-temporal lobe in first-onset schizophrenic patients.

BACKGROUND: Past 1H magnetic resonance spectroscopy (MRS) studies of the temporal lobe in schizophrenic patients have shown decreased levels of N-acetylaspartate (NAA) suggesting reduced neuronal density in this region. However, the measured volumes have been large and included contributions from mostly white matter. METHODS: Short echo 1H MRS was used to measure levels of NAA and other metabolites (i.e., glutamate and glutamine) from a 6 cm3 volume in the left mesial-temporal lobe of 11 first-episode schizophrenic patients and 11 healthy control subjects of comparable age, gender, handedness, education, and parental education levels. Spectra were quantified without operator interaction using automated software developed in our laboratory. Metabolite levels were normalized to the internal water concentration of each volume studied. Images were also obtained to determine temporal lobe gray and white matter volumes. RESULTS: No significant differences were found between levels of NAA or other metabolites, or gray and white matter volumes, in first-episode schizophrenic patients and comparison subjects. CONCLUSIONS: Since the volume studied was small compared to previous studies and contained mostly gray matter, this result suggests consequential NAA decreases may be restricted to regions of white matter.

The addition of a raloxifene analog (LY117018) allows for reduced PTH(1-34) dosing during reversal of osteopenia in ovariectomized rats.

To test the hypothesis that an antiresorptive agent might reduce the dosing requirement for an anabolic drug during reversal of osteopenia due to estrogen deficiency, the following experiment was conducted in 6-month-old female rats. Ovariectomy or sham surgery was performed and the following six experimental groups were studied. Untreated (SHAM) or ovariectomized (OVX) animals served as control groups. Four weeks post-OVX, osteopenic rats (now 7 months old), were treated in one of four experimental protocols: human parathyroid hormone (hPTH(1-34)), 80 microg/kg/day, given by subcutaneous injection 5 days/week; a selective estrogen receptor modulator (SERM), raloxifene analog LY117018 (RA), 3 mg/kg/day, given by gavage 5 days/week; and two combinations of LY117018 at the same dose and frequency with hPTH(1-34) (same dose, 5 times/week) and a reduced dosing interval of hPTH(1-34) (same dose, 2 times/week). After 12 weeks of treatment, the four experimental groups were sacrificed at age 10 months. SHAM and OVX controls were also studied at 7 and 10 months of age. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry at four skeletal sites: two mixed cortical/trabecular sites (femur and tibia) and two predominantly trabecular sites (lumbar spine and pelvis). The differences in BMD were consistent at all four sites. RA alone maintained BMD at all skeletal sites, but the results were not significantly improved over OVX controls, at age 10 months. hPTH(1-34) injections given 5 days/week resulted in BMD increments significantly higher than in either OVX or SHAM controls (p < 0.001). While the RA did not enhance the anabolic effects of full doses of hPTH(1-34), the addition of RA treatment to twice-weekly hPTH(1-34) dosing resulted in BMD increments at all four skeletal sites that were similar to the more intensive anabolic regimen of hPTH(1-34) therapy given 5 times/week. Therefore, an antiresorptive agent such as SERMs may potentially reduce the pharmacologic doses of PTH needed to reverse estrogen deficiency-induced osteopenia.

Assessment of maintenance therapy with reduced doses of PTH(1-34) in combination with a raloxifene analogue (LY117018) following anabolic therapy in the ovariectomized rat.

This experiment was designed to evaluate the ability of a raloxifene analogue (RA), LY117018, with or without reduced dosing of human parathyroid hormone (hPTH)(1-34) to maintain gains in bone mass after a fully anabolic treatment regimen given to aging osteopenic rats. Six-month-old rats were ovariectomized (ovx) or sham-operated (sham). After 1 month, ovx rats were treated with an anabolic regimen consisting of subcutaneous hPTH(1-34) 80 microg/kg/day and oral raloxifene 3 mg/kg/day, each given 5 days/week for 3 months. Thereafter, the treated ovx rats went on to an 8 week maintenance phase of treatment with either RA alone at the same dose, hPTH(1-34) at a reduced dosing interval (twice a week), or a combination of the two. Bone mineral density (BMD) was measured ex vivo at four skeletal sites, lumbar spine (L2-4), proximal hemipelvis, whole femur, and tibia, by dual-energy X-ray densitometry. All four sites showed a similar pattern of response. After the 3 month anabolic phase, the sham group had significantly higher BMD values than ovx rats at all skeletal sites (p < or = 0.002). The ovx rats treated with PTH + RA during the anabolic phase of the protocol had significantly higher BMD than the sham group in the femur, tibia, and spine (p < or = 0.02) and higher but not significantly different values in the pelvis. Following the 2 month maintenance phase, comparisons were made with the PTH-RA group at the end of the anabolic phase. Decrements in BMD were seen in all three maintenance therapy groups, but they were not statistically significant in the RA plus reduced PTH dose group. However, reduced hPTH(1-34) dosing and RA alone resulted in significant reductions of bone mass measurements at several skeletal sites during the maintenance phase. We conclude that the raloxifene analogue LY117018 may be useful in maintaining bone mass in aging ovx rats following anabolic therapy with hPTH(1-34) and raloxifene analogue, but that this strategy only allows for dose reduction of hPTH(1-34) rather than its discontinuation.

Improved contrast agent bolus tracking using T1 FARM.

Current MRI bolus tracking techniques, such as saturation recovery Turbo-FLASH (srTFL), suffer from signal saturation at high contrast concentrations. In this study T1 Fast Acquisition Relaxation Mapping (T1 FARM) was compared to srTFL. In phantoms, T1 FARM maps were linear with [Gd-DTPA] up to 7.0 mmol/L while srTFL images saturated above 2.0 mmol/L. In the canine left ventricle, blood concentration curves determined from T1 FARM saturated with bolus injections exceeding 0.075 mmol/kg, while srTFL curves saturated above 0.025 mmol/kg of Gd-DTPA. Also, T1 FARM improved contrast-to-noise ratio in tissue concentration curves since higher contrast concentrations could be measured without saturating.

A 1H-decoupled 31P chemical shift imaging study of medicated schizophrenic patients and healthy controls.

BACKGROUND: Current 31P spectroscopy research in schizophrenia has examined phospholipid metabolism by measuring the sum of phosphomonoesters and the sum of phosphodiester-containing molecules. Proton decoupling was implemented to measure the individual phosphomonoester and phosphodiester components. This is the first study employing this technique to examine schizophrenic patients. METHODS: Multivoxel two-dimensional chemical shift in vivo phosphorous-31 magnetic resonance spectroscopy with proton decoupling was used to examine a 50-cm3 volume in prefrontal, motor, and parieto-occipital regions in the brain. Eleven chronic medicated schizophrenic patients were compared to 11 healthy controls of comparable gender, education, parental education, and handedness. RESULTS: A significant increase in the mobile phospholipid peak area and its full width at half maximum was observed in the medicated schizophrenic patients compared to the healthy controls in the prefrontal region. Inorganic orthophosphate and phosphocholine were lower in the schizophrenic group in the prefrontal region. CONCLUSIONS: The increased sum of phosphodiester [mobile phospholipid + glycerol-3-phosphoethanolamine (GPEth) + glycerol-3-phosphocholine (GPCh)] in schizophrenic patients, measured in earlier studies, arises from the phospholipid peak (MP) and not the more mobile phosphodiesters (GPEth, GPCh) as was originally suspected. A decrease in the phosphocholine component of the phosphomonoesters was also observed in the schizophrenic patients. These findings are consistent with an abnormality in membrane metabolism in the prefrontal region in schizophrenics.

Quantifying 1H decoupled in vivo 31P brain spectra.

Our objective was to develop a precise method for quantification of in vivo proton decoupled 31P spectra from the human brain. This objective required that an appropriate spectral model be created and that the quantification was performed using a non-subjective fitting technique. The precision of the quantification was assessed using Cramer-Rao standard deviations and compared using two different spectral models: one containing a pair of peaks representing 2,3-diphosphoglycerate, the other excluding this metabolite. The data was quantified using a Marquardt-Levenberg (ML) algorithm incorporating prior knowledge with a Hankel singular value decomposition (HSVD) performed initially to provide parameter estimates for the ML algorithm. Quantification was performed on two different in vivo 2-D CSI 31P data sets: the first examined 11 normal controls, the second examined a single individual six times. Spectra from a region in the parieto-occipital cortex were analyzed. The Cramer-Rao standard deviations were significantly lower for some metabolites with 2,3-diphosphoglycerate in the model: in the repeat study mobile phospholipids (p = 0.045) and phosphocholine (p = 0.034), and in the 11 controls mobile phospholipids (p = 0.003) and Pi (p = 0.002).

Fast acquisition of quantitative T2 maps.

A rapid new technique called T2 fast acquisition relaxation mapping (T2 FARM) was developed to allow T2 maps to be reconstructed directly from k-space data acquired in 3 sec. A single acquisition measured two sets of k-space data, the first with T1 and T2 weighting independent of phase encode position, and the second with T2 weighting varying with phase encode position. These data were processed using an iterative least squares algorithm to produce a quantitative T2 map from the k-space data. T2 values of phantoms and an egg were determined from T2 FARM maps and spectroscopic Carr-Purcell-Meiboom-Gill (CPMG) measurements, demonstrating the validity of the new technique.