Mapping phosphorylation rate of fluoro-deoxy-glucose in rat brain by F chemical shift imaging

¹⁹F magnetic resonance spectroscopy (MRS) studies of 2-fluoro-2-deoxy-d-glucose (FDG) and 2-fluoro-2-deoxy-d-glucose-6-phosphate (FDG-6P) can be used for directly assessing total glucose metabolism in vivo. To date, ¹⁹F MRS measurements of FDG phosphorylation in the brain have either been achieved ex vivo from extracted tissue or in vivo by unusually long acquisition times. Electrophysiological and functional magnetic resonance imaging (fMRI) measurements indicate that FDG doses up to 500 mg/kg can be tolerated with minimal side effects on cerebral physiology and evoked fMRI-BOLD responses to forepaw stimulation. In halothane-anesthetized rats, we report localized in vivo detection and separation of FDG and FDG-6P MRS signals with ¹⁹F 2D chemical shift imaging (CSI) at 11.7 T. A metabolic model based on reversible transport between plasma and brain tissue, which included a non-saturable plasma to tissue component, was used to calculate spatial distribution of FDG and FDG-6P concentrations in rat brain. In addition, spatial distribution of rate constants and metabolic fluxes of FDG to FDG-6P conversion were estimated. Mapping the rate of FDG to FDG-6P conversion by ¹⁹F CSI provides an MR methodology that could impact other in vivo applications such as characterization of tumor pathophysiology.     

Differentiation between intra-axial metastatic tumor progression and radiation injury following fractionated radiation therapy or stereotactic radiosurgery using MR spectroscopy, perfusion MR imaging or volume progression modeling

Objective

To determine the accuracy of magnetic resonance spectroscopy (MRS), perfusion MR imaging (MRP), or volume modeling in distinguishing tumor progression from radiation injury following radiotherapy for brain metastasis.

Methods

Twenty-six patients with 33 intra-axial metastatic lesions who underwent MRS (n=41) with or without MRP (n=32) after cranial irradiation were retrospectively studied. The final diagnosis was based on histopathology (n=4) or magnetic resonance imaging (MRI) follow-up with clinical correlation (n=29). Cho/Cr (choline/creatinine), Cho/NAA (choline/N-acetylaspartate), Cho/nCho (choline/contralateral normal brain choline) ratios were retrospectively calculated for the multi-voxel MRS. Relative cerebral blood volume (rCBV), relative peak height (rPH) and percentage of signal-intensity recovery (PSR) were also retrospectively derived for the MRPs. Tumor volumes were determined using manual segmentation method and analyzed using different volume progression modeling. Different ratios or models were tested and plotted on the receiver operating characteristic curve (ROC), with their performances quantified as area under the ROC curve (AUC). MRI follow-up time was calculated from the date of initial radiotherapy until the last MRI or the last MRI before surgical diagnosis.

Results

Median MRI follow-up was 16 months (range: 2-33). Thirty percent of lesions (n=10) were determined to be radiation injury; 70% (n=23) were determined to be tumor progression. For the MRS, Cho/nCho had the best performance (AUC of 0.612), and Cho/nCho >1.2 had 33% sensitivity and 100% specificity in predicting tumor progression. For the MRP, rCBV had the best performance (AUC of 0.802), and rCBV >2 had 56% sensitivity and 100% specificity. The best volume model was percent increase (AUC of 0.891); 65% tumor volume increase had 100% sensitivity and 80% specificity.

Conclusion

Cho/nCho of MRS, rCBV of MRP, and percent increase of MRI volume modeling provide the best discrimination of intra-axial metastatic tumor progression from radiation injury for their respective modalities. Cho/nCho and rCBV appear to have high specificities but low sensitivities. In contrast, percent volume increase of 65% can be a highly sensitive and moderately specific predictor for tumor progression after radiotherapy. Future incorporation of 65% volume increase as a pretest selection criterion may compensate for the low sensitivities of MRS and MRP.     

Effect of melanin on phosphorus T1s in human melanoma xenografts studied by 31P MRS

³¹P MRS resonance ratios of tumors depend on the T₁s of the phosphorus compounds. The objective of the ³¹P MRS study reported here was to investigate whether the phosphorus T₁s of melanomas are influenced by the presence of melanin. One amelanotic (COX-t) and one melanotic (ROX-t) human melanoma xenograft line were studied at two different tumor volumes: 200 and 1000 mm³. ³¹P MRS was performed in nonanaesthetized mice at 4.7 T. The T₁s were measured by using the superfast inversion recovery technique. Fraction of necrotic tissue in the tumors was determined by histological examination. The ROX-t tumors showed shorter T₁s than the COX-t tumors at a volume of 200 mm³, where the fraction of necrotic tissue in the tumors was insignificant. The difference was similar in magnitude for all resonances. The T₁s were not significantly different for COX-t and ROX-t at a volume of 1000 mm³, where the tumors of both lines had developed significant necrosis. The phosphorus T₁s of melanomas without necrosis can be shortened significantly by the presence of melanin. The magnitude of the T₁ shortening is similar for all major compounds. ³¹P MRS resonance ratios of melanomas are not altered significantly by correcting for effects of partial saturation.     

The 19F(p,d)18F reaction studied at Ep = 19.3 MeV

The ¹⁹F(p, d)¹⁸F reaction was used at E_p = 19.3 MeV to study the level properties of ¹⁸F up to 6 MeV excitation energy. Angular distributions were measured over the angular range θ_lab = 10°–70° with an overall resolution of 35 keV. The experimental data were analyzed by DWBA theory to obtain l_n and C²S_l values, which were compared with existent theoretical nuclear structure calculations.     

The reaction19F(n,α)16N atE n =13.9 MeV and 15.6 MeV

Differential cross sections of the reaction¹⁹F(n, α)¹⁶N have been measured atE _n = 13.9 MeVd and 15.6 MeV. The results can be interpreted in terms of compound nucleus theory. Statistical model calculations were undertaken to clear up the different reaction behaviour of the reactions¹⁹F(n, α)¹⁶N and¹⁹F(p, α)¹⁶O at bombarding energies near 14 MeV.     

The g-factor of the Jπ=12+ isomeric state in188Hg

Using the reaction¹⁷⁵Lu(¹⁹F, 6n) theg-factor of the¹⁸⁸Hg isomeric state (J ^π=12⁺,T _1/2=135 ns) has been measured with the TDPAD method. The experimental value g=?0.168(10) supports the interpretation of an almost pure (vi13/2)^?2 configuration for this isomer.     

In vivo C magnetic resonance spectroscopy of a human brain tumor after application of C-1-enriched glucose

Objectives

As a unique tool to assess metabolic fluxes noninvasively, ¹³C magnetic resonance spectroscopy (MRS) could help to characterize and understand malignancy in human tumors. However, its low sensitivity has hampered applications in patients. The aim of this study was to demonstrate that with sensitivity-optimized localized ¹³C MRS and intravenous infusion of [1-¹³C]glucose under euglycemia, it is possible to assess the dynamic conversion of glucose into its metabolic products in vivo in human glioma tissue.

Materials and Methods

Measurements were done at 3 T with a broadband single RF channel and a quadrature ¹³C surface coil inserted in a ¹H volume coil. A ¹H/¹³C polarization transfer sequence was applied, modified for localized acquisition, alternatively in two (50 ml) voxels, one encompassing the tumor and the other normal brain tissue.

Results

After about 20 min of [1-¹³C]glucose infusion, a [3-¹³C]lactate signal appeared among several resonances of metabolic products of glucose in MR spectra of the tumor voxel. The resonance of [3-¹³C]lactate was absent in MR spectra from contralateral tissue. In addition, the intensity of [1-¹³C]glucose signals in the tumor area was about 50% higher than that in normal tissue, likely reflecting more glucose in extracellular space due to a defective blood–brain barrier. The signal intensity for metabolites produced in or via the tricarboxylic acid (TCA) cycle was lower in the tumor than in the contralateral area, albeit that the ratios of isotopomer signals were comparable.

Conclusion

With an improved ¹³C MRS approach, the uptake of glucose and its conversion into metabolites such as lactate can be monitored noninvasively in vivo in human brain tumors. This opens the way to assessing metabolic activity in human tumor tissue.     

On the interpretation of evaporation residue mass distributions in heavy-ion induced fusion reactions

Evaporation residue mass distributions measured recently for several heavy-ion induced fusion reactions are analyzed. The reactions investigated are ¹⁹F on ¹²C (E_lab = 50, 63 and 76 MeV), ¹⁹F on ²⁷Al (E_{lab = 40}, 63, 76 and 92 MeV) and ¹⁶O on ²⁷Al (E_{lab = 30}, 40, 60 and 80 MeV). Starting from the assumption that a compound nucleus is formed which decays by multiple emission of neutrons, protons, α-particles and γ-rays with probabilities as predicted by the statistical theory the mass spectra of the stable or long-lived products are calculated. It is shown that they are in good agreement with the experimental data, if reasonable assumptions are made about the level densities and the shape of the yrast line. The possibility to use these methods for studying the properties of highly excited nuclei at high angular momentum is investigated.     

Cystic intracranial mass lesions: Possible role of in vivo MR spectroscopy in its differential diagnosis

Thirty-four patients showing cystic intracranial mass lesions on MR imaging were evaluated by in vivo proton MR spectroscopy (MRS) with the aim of detecting lesion-specific spectral patterns that may assist imaging in better tissue characterization. In vivo spectroscopy was performed using stimulated echo acquisition mode with echo times 20 m and 270 m in all, and spin echo with echo time 135 m in 11 patients. All primary neoplasms (intra-as well as extra-axial) showed choline (3.22 ppm) resonance along with lipid and/or lactate (1.3 ppm). It was not possible to grade cystic gliomas based on N-acetyl asparate-to-choline ratio. High-grade gliomas (n = 8) showed lipid/lactate and low-grade gliomas (n = 6) showed only lactate. Seven patients with brain abscess showed resonances only from acetate (1.92 ppm), lactate (1.3 ppm) and alanine (1.5 ppm). Two cases of metastatic adenocarcinoma showed only lipid/lactate. In 7 patients with epidermoid cyst, lactate along with an unassigned resonance at 1.8 ppm was observed and could be easily differentiated from arachnoid cyst (n = 2), which showed only minimal lactate. A case of cystic meningioma could be differentiated from cystic schowannoma by the presence of alanine in the former. It is concluded that MR imaging, when combined with in vivo MRS, may help to better characterize intracranial cystic mass lesions.     

First observation of yrast band in odd-odd162Lu

High spin states of the odd-odd¹⁶²Lu nucleus have been studied via¹⁴⁷Sm(¹⁹F,4nγ)¹⁶²Lu reaction at 95 MeV beam energy. Level scheme for yrast band based onπ[h_11/2 v[i_13/2] quasiparticle configuration was established up to I ^π = (23^?) for the first time. This band shows the signature inversion in energy before backbending generally appeared in this mass region. It is stressed that the signature splitting in¹⁶²Lu is larger than that in the¹⁶⁰Tm nucleus.     

Mass spectrometry study of the kinetics of CdTe molecular-beam epitaxy: Part I. Cd, Te2, and CdTe

Surface processes in CdTe molecular-beam epitaxy were studied using in situ mass spectrometry. Modulated molecular Cd and Te₂ beams were used for measuring kinetic parameters. The experiments were performed at crystal temperatures of 600–730 K. The results were processed within a model in which condensation and evaporation occur through adsorption and desorption stages. The desorption rate was 2–10 s^?1 for Te₂ and more than 30 s^?1 for Cd. The CdTe evaporation activation energy and desorption energies were determined as E _ev = 1.1 eV, E _d (Cd) = 1.0 eV, and E _d (Te) = 0.6 eV. The adsorbate coverage was estimated as n(Cd) < 0.01 and n(Te) = 0.1–1 Te.     

g factor measurements of high spin isomeric states in 187,189,191 Au

The g factors of three high spin isomers in ^187,189,191Au have been measured, using the time differential perturbed angular distributions. The reactions used and the results obtained for the g factors and the lifetimes are: ¹⁷²Yb(¹⁹F, 4nγ) ¹⁸⁷Au, g (31/2- or 35/2-) = 0.25 (3), T_1/2 = 102 (5) ns; ¹⁸¹Ta ( ¹²C, 4nγ) ¹⁸⁹Au, g (31/2+) = 0.42 (2), T_1/2 = 242 (10) ns; and ¹⁷⁶Yb(¹⁹F, 4nγ) ¹⁹¹Au, g (31/2+) = 0.42 (3) T^1/2 = 402 (20) ns. These results show that the structure of these isomers is consistent with a 1 proton, 2 neutrons structure. The experimental set-up was cheked by measuring the g factor of the Coulomb excited 197 keV, T_1/2 = 89.3 ns level of the ¹⁹F beam stopped in the lead backing.     

Investigation of two resonances in the18O(p,n)18F reaction

Excitation functions for the¹⁸O(p,n)¹⁸F reaction were measured at bombarding energiesE _p=4.6 to 6.6 MeV. In and near two resonances of the yield curves atE _p=5.622 and 6.061 MeV, angular distributions were measured with neutron time-of-flight techniques. The strong neutron decay to theT=1 state in¹⁸F and the similarity of the¹⁸O(p,n) and¹⁸O(n,n) yield curves give good evidence that the structures in the¹⁸O(p,n) yield curve arise from the formation ofT=3/2 states in¹⁹F. A two-level-analysis does not give satisfactory fits to the strongly asymmetric angular distributions.     

Quantitative diffusion-weighted imaging and dynamic contrast-enhanced MR imaging for assessment of tumor aggressiveness in prostate cancer at 3T

PurposeTo compare diffusion-weighted imaging (DWI) and dynamic contrast-enhanced MR imaging (DCE-MRI) for characterization of prostate cancer (PC).Methods104 PC patients who underwent prostate multiparametric MRI at 3T including DWI and DCE-MRI before MRI-guided biopsy or radical prostatectomy. Apparent diffusion coefficient (ADC) with histogram analysis (mean, 0–25th percentile, skewness, and kurtosis), intravoxel incoherent motion model including D and f; stretched exponential model including distributed diffusion coefficient (DDC) and a; and permeability parameters including K^trans, K_ep, and V_e were obtained from a region of interest placed on the dominant tumor of each patient.ResultsADC_mean, ADC_0–25, D, DDC, and V_e were significantly lower and K_ep was significantly higher in GS ≥ 3 + 4 tumors (n = 89) than in GS = 3 + 3 tumors (n = 15), and also in GS ≥ 4 + 3 tumors (n = 57) than in GS ≤ 3 + 4 tumors (n = 47) (P < 0.001 to P = 0.040). f was significantly lower in GS ≥ 4 + 3 tumors than in GS ≤ 3 + 4 tumors (P = 0.022), but there was no significant difference between GS = 3 + 3 tumors and GS ≥ 3 + 4 tumors, or between the remaining metrics in both comparisons. In metrics with area under the curve (AUC) >0.80, there was a significant difference in AUC between ADC_0–25 and D, and DDC for separating GS ≤ 3 + 4 tumors from GS ≥ 4 + 3 tumors (P = 0.040 and P = 0.022, respectively). There were no significant differences between metrics with AUC > 0.80 for separating GS = 3 + 3 tumors from GS ≥ 3 + 4 tumors. ADC_0–25 had the highest correlation with Gleason grade (ρ = −0.625, P < 0.001).ConclusionsDWI and DCE-MRI showed no apparent clinical superiority of non-Gaussian models or permeability MRI over the mono-exponential model for assessment of tumor aggressiveness in PC.     

Low-lying states of the 16F nucleus

Low-lying proton-emitting states of ¹⁶F have been investigated through the sequential particle decay reactions ¹⁴N(³He, n)¹⁶F(p)¹⁵O. Excitation energies were determined by measuring outgoing proton energies. Estimations of proton decay widths and spin limitations were made from proton spectra and angular correlation data which were obtained by detecting the protons in time coincidence with the associated neutrons at θ_n = 0°. To date, the ground-state spin of ¹⁶F has been considered to be J = 0; however, the present work suggests J = 1 to be preferable.     

Raman scattering by zigzag fluoropolymer molecules

The Raman spectra of ultrafine powders consisting of F(CF₂)_nF fluoropolymer zigzag molecules treated as a one-dimensional nanocrystal are investigated. These spectra are compared with the Raman spectra of C_nF_2n+1Br compounds (n=6–10 and 14) and fluoroplastics. It is found that the frequencies of optical vibrations of F(CF₂)_nF fluoropolymer molecules are shifted by more than 10 cm^?1 with respect to the relevant frequencies of C₆F₁₃Br molecules. The length of nanoparticles comprising an organofluoric ultrafine powder is estimated to be L=2–2.5 nm. This estimate is obtained from the measured frequency shifts in terms of the vibrational theory for a crystalline diatomic chain of finite length.     

The Lorentz-Lorenz function of five gaseous and liquid saturated hydrocarbons

The refractive indices of compressed gaseous and liquid ethane, propane,n-butane,n-pentane, and liquidn-hexane were measured on up to seven isotherms at temperatures between 290 K and 500 K. Densities ranged from 0.2 g/cm³ to 0.7 g/cm³ at pressures up to 170 bar. The refractive index valuesn were combined with simultaneously measured density values ?, to compute the Lorentz-Lorenz function LL =(n ²-1)M/(n ²+2) ?=A _n+B_n(?/M), whereM is the molar mass andA _n andB _n are the first and second refractive index virial coefficients. Additionally, the functions LL/z (z=pV/nRT is the compressibility factor) of ethane, propane, andn-butane were computed to determine the second refractive index virial coefficientsB _n(T). The relative uncertainty of the measured LL functions is 0.1% in most cases. At constant temperature (LL?A _n)/A_n is ≦5·10^?3 for ethane, propane, andn-butane and ≦0.02 forn-pentane andn-hexane. The greatest deviations of the LL functions from theA _n value were measured at the temperatures near the critical points. TheA _n-values show a temperature dependence which increases with increasing molar mass (maximum value: ΔA _n/ΔT=0.0044 cm³/mol · K). The slopes of the LL-function become lower and the LL maxima become smaller with increasing distance of the temperature from the critical point. TheB _n values increase linearly with reciprocal temperature.     

Fine-structure measurements of two-photon transitions in atomic cesium with a tunable dye laser

Two-photon transitions have been observed from the 6²S ground state of atomic cesium to selected higher lying n²D levels up to n = 19. The transitions were excited by a narrowband dye laser pumped by a nitrogen laser and detected by a space charge limited cesium vapor photodiode. The fine structure intervals of the n²D levels for n = 15, 17 and 19 were measured by direct comparison with the ground-state hyperfine interval, and the line strength ratios of the fine-structure components were measured and compared with the predictions of a simple theoretical model.     

Structure of Na2O·MO·SiO2·CaF2 (M=Mg,Ca) oxyfluoride glasses

(9−x)CaO·xMgO·15Na₂O·60SiO₂·16CaF₂(x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with ²⁹Si and ¹⁹F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q³→Q⁴+Q² (Qⁿ is a SiO₄ tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO₄, and removed other modifying ions for charge compensation. This reaction was confirmed by ²⁹Si MAS NMR. ¹⁹F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si–F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF⁺ species. Meanwhile, some part of Na⁺ ions complex F⁻ in the form of F–Na(6).     

Selectivity of the 16O(7Li, α) reaction and states with (sd)3 and (sd)2(fp)1 configurations in 19F

The ¹⁶O(⁷Li, α)¹⁹F reaction has been studied at 35 MeV up to 11 MeV excitation energy. Comparison with the ¹⁶O(⁶Li, ³He)¹⁹F and ¹⁶O(⁶Li, t)¹⁹Ne reactions shows very good agreement up to 5.5 MeV excitation energy and large differences at higher excitation energies which can be explained by different angular momentum matching conditions in the different reactions. The identification of mirror states in A = 19 and of states with (sd)³ and (sd)² (fp)¹ configurations in ¹⁹F are discussed.