Electron spin resonance (ESR), electron nuclear double resonance (ENDOR) and general triple resonance of irradiated biocarbonates

Several irradiated biocarbonates were studied by magnetic resonance techniques. Seven paramagnetic species, attributed to CO₂⁻, SO₂⁻ and SO₃⁻ were identified. Comparison between radiation induced defects in bioaragonites and aragonite single-crystals shows that isotropic and orhorhombic CO₂⁻ centers with broad line spectra are not produced in the latter samples. Vibrational and rotational properties of isotropic CO₂⁻ centers were studied from low temperature Q-band spectra. Vibrational frequency is determined from the ¹³CO₂⁻ hyperfine spectrum and yielded v=1.54 × 10¹³ s⁻¹. The correlation time for isotropic CO₂⁻, τ_c=1.2 × 10⁻¹¹s (T=300 K), is typical of radicals rotating in liquids. ENDOR and General Triple spectroscopy show that orthorhombic CO₂⁻ centers are surrounded by water molecules located in the second nearest CO₃²⁻ sites at 5.14, 5.35 and 6.02 Å. Water molecules replacing carbonates or as liquid inclusion of growth solution in local crystal imperfections may be responsible for the variety of orthorhombic and isotropic CO₂⁻ species, respectively.     

ESR dosimetry of a deceased radiation worker

A case of overexposure of an industrial radiographer using ¹⁹²Ir sources and having a filmbadge dosimeter record of 104 mSv has been examined with ESR dosimetry of postmortem tooth and bone specimens. ESR measurements of the tooth enamel showed an intense signal of CO₂⁻ and gave the equivalent dose (ED) of 14 Gy by the additive dose method using γ-rays from a source of ⁶⁰Co. The doses for a finger bone and humerus were 14.7 and 7.0 Gy, respectively. It was concluded that he had been exposed to radiation repeatedly over 10 yr and that ESR dosimetry can give a life-long cumulative dose for personnel using radiation.     

An ESR study of defects in irradiated hydroxyapatite

Radiation-induced defects in synthetic hydroxyapatite (HAp) of six different origins have been investigated by electron spin resonance (ESR), X-ray diffraction (XRD), Raman scattering and IR measurements. The orthorhombic CO₂⁻ radicals were detected in almost of all the samples examined, but the isotropic CO₂⁻ was produced only in water-containing HAp with low crystallinity. The doublet signal due to H⁰ was clearly detected in HAp with extreme calcium deficiency as compared to the stoichiometry. The results of ESR and FTIR suggest that water molecules in low crystalline HAp are not on the surface but embedded in the HAp crystalline lattice.     

C hyperfine interactions of CO2 in irradiated tooth enamel as studied by EPR

The EPR spectrum of tooth enamel caused by ¹³C hyperfine interactions of the CO₂⁻ radical were studied on γ-irradiated powdered samples annealed for 40 min at different temperatures up to 250°C. The lineshape and hyperfine splitting of the spectra were found to depend on the annealing temperature. Experimental spectra were compared with calculated ones assuming that EPR spectra are formed by two CO₂⁻ species—axial (rotating) and orthorhombic (braked) radicals. We assumed that the axial CO₂⁻ radicals are centers located in perfect areas of the hydroxyapatite crystals of tooth enamel whereas the orthorhombic CO₂⁻ radicals are rotating centers which are braked by defects. The thermal treatment of enamel samples leads to defective annealing and transformation of the orthorhombic centers into axial ones. This results in an increasing axial CO₂⁻ radical contribution to the EPR spectrum with increase of annealing temperature.     

Preliminary study for future ESR dating of solid SO2

Paramagnetic properties of irradiated solid SO₂ have been studied for future ESR dating of icy materials on Io, the satellite of Jupiter. Radical species in solid SO₂ formed by irradiation with γ-rays were measured with ESR at various temperatures to obtain the isothermal decay data, which gave their lifetimes at the ambient temperature on Io by the extrapolation in the Arrhenius plot. ESR parameters and speculative models for observed signals are presented.     

Diffusion-weighted MRI with parallel imaging technique: apparent diffusion coefficient determination in normal kidneys and in nonmalignant renal diseases

The purpose of the study was to assess the capability and the reliability of apparent diffusion coefficient (ADC) measurements in the evaluation of different benign renal abnormalities. Twenty-five healthy volunteers and 31 patients, divided into seven different groups (A–G) according to pathology, underwent diffusion-weighted magnetic resonance imaging (DW MRI) of the kidneys using 1.5-T system. DW images were obtained in the axial plane with a spin-echo echo planar imaging single-shot sequence with three b values (0, 300, and 600 s/mm²). Before acquisition of DW sequences, we performed in each patient a morphological study of the kidneys. ADC was 2.40±0.20×10⁻³ mm² s⁻¹ in volunteers. A significant difference was found between Groups A (cysts=3.39±0.51×10⁻³ mm² s⁻¹) and B (acute/chronic renal failure=1.38±0.40×10⁻³ mm² s⁻¹) and between Groups A and C (chronic pyelonephritis=1.53±0.21×10⁻³ mm² s⁻¹) (P<.05). An important difference was also observed among Group D (hydronephrosis=4.82±0.35×10⁻³ mm² s⁻¹) and Groups A, B, and C (P<.05), whereas no differences were found between Groups B and C (P>.05). A considerable correlation between glomerular filtration rate and ADC was found (P=.04). In conclusion, significant differences were detected among different patient groups, and this suggests that ADC measurements can be useful in differentiating normal renal parenchyma from most commonly encountered nonmalignant renal lesions.     

Influence de l'exposition au froid sur le seuil anaérobie

During a maximal effort performance test of short duration at 0°C, we have observed that the blood lactate concentration at max V˙O₂ is lower than the value obtained during the same cycling exercise at 20°C. In light of these results it is of interest to determine if the anaerobic threshold measured using various lactic acid values occurs at the same relative power output whether it is assessed in a cold or in a neutral thermic environment. Eleven male hockey players (mean age = 23.9 years) were tested during maximal cycle ergometer pedalling in a climatic chamber at 0°C and 20°C. Measurements of gas variables were made at rest and at the last minute of each work steps. Blood samples were collected at rest and thereafter during the last 15 sec of each third minute from an antecubital vein through an indwelling catheter for subsequent analysis of lactate concentration. Determination of percentage max V˙O₂ corresponding to the anaerobic threshold was assessed at a blood lactate concentration of 4 mmol.l⁻¹. Under thermal equilibrium (20°C), the onset of anaerobiosis occurred at 80% of the maximal oxygen uptake.V˙O₂ and pulmonary ventilation (V˙E) values at the onset of the anaerobic threshold were 3.5 (SD = 0.02)l.min⁻¹ and 99 (SD = 6.0)l.min⁻¹, respectively. Under cold conditions, the onset of anaerobiosis occurred at approximatively the same relative power output (82% max V˙O₂). Although max V˙O₂ is significantly higher under cold conditions than it is under a neutral environment, the max V˙O₂ value at the threshold is not significantly different than the one measured under the neutral environment (3.6 ± 0.1 l.min⁻¹). Heart rate is identical in both conditions and V˙E is not significantly different. Below the threshold workload, blood lactate concentrations are identical under both cold and thermal equilibrium conditions. For workload above the threshold, the blood lactate concentration increase under cold stress seems less (P < 0.05) in comparison to the accomplished pedalling exercise under thermal equilibrium (7.9 ± 0.29 vs 6.0 ± 0.42 mmol.l⁻¹). We can conclude that the effect of cold exposure above the anaerobic threshold is to decrease significantly the blood lactate concentration. However, cold stress does not lower the anaerobic threshold nor V˙E at which this threshold appears.     

Responsiveness of human natural killer cells during acute,incremental exercise up to exhaustion

Abstract Eight healthy male subjects performed a cycle ergometer incremental exercise up to exhaustion to study possible relationships between excess CO₂ production (CO_2-exc) and natural killer (NK) cells, measured in terms of concentration (NK_abs) and as a percentage of lymphocytes in peripheral blood (NK%). A parabola-like regression equation with its vertex downwards best fit the relationship between CO_2-exc at W_max and the difference between NK cell measurements at the maximum workload (W_max) and at the workload corresponding to the anaerobic threshold (W_AT). For NK cell concentration, the best equation was NK_abs (cells/mm³)=248.8413–0.3105 CO_2-exc (ml min^-1)+0.0001 CO_2-exc ² (ml min^-1) (p=0.044). For NK cells expressed as a percentage, the best equation was NK(%)=108.7636–0.1414 CO_2-exc (ml min^-1)+0.00001 CO_2-exc ² (ml min^-1) (p=0.032). Thus, the higher was the CO_2-exc the lower was the increase in both NK cell measurements at W_max with respect to the value observed at W_AT. However, when CO_2-exc reached more elevated values, then the direction of this relationship was inverted. It may be concluded that when strenuous exercise is performed, an anti-inflammatory/performance-preserving event takes place, while recovery towards a pro-inflammatory/anti-infection state tends gradually to re-establish when a subjects anaerobic power becomes too high.     

Evaluation of Dosimetric Parameters for Various Ir Brachytherapy Sources Under Unbounded Phantom Geometry by Monte Carlo Simulation

As per TG-43 dose calculation formalism, it is essential to obtain various dosimetric parameters such as the air-kerma strength, dose rate constant, radial dose function, and anisotropy function, as they account for accurate determination of dose rate distribution around brachytherapy sources. Most of the available reported Monte Carlo simulations were performed in liquid water phantoms with a bounded region of 30-cm diameter. In this context, an attempt was made to report the dosimetric parameters for various commercially available pulsed-dose rate (PDR) and high-dose rate (HDR) sources under unbounded phantom conditions, as the data may be used as input to treatment planning systems (TPSs) for quality control assistance. The air-kerma strength per unit activity, S_k/A, was computed for various Iridium-192 (¹⁹²Ir) sources in dry air medium. The air-kerma strength and dose rate constant for old PDR is (9.77 ± 0.03) 10⁻⁸ U/Bq and 1.124 ± 0.001 cGyh⁻¹U⁻¹; for new PDR, the values are (9.96 ± 0.03) 10⁻⁸ U/Bq and 1.124 ± 0.001 cGyh⁻¹U⁻¹; for old MHDR, the values are (9.80 ± 0.01) 10⁻⁸ U/Bq and 1.115 ± 0.001 cGyh⁻¹U⁻¹; for new MHDR, (9.80 ± 0.01) 10⁻⁸ U/Bq and 1.112 ± 0.001cGyh⁻¹U⁻¹; for old VHDR, the values are (10.32 ± 0.01) 10⁻⁸ U/Bq and 1.035 ± 0.002 cGyh⁻¹U⁻¹; for new VHDR, the values are (10.34 ± 0.02) 10⁻⁸ U/Bq and 1.096 ± 0.001 cGyh⁻¹U⁻¹. The computed radial dose function values and anisotropy function values are also in good agreement with available data.     

Évolution des erreurs techniques et de quelques variables physiologiques pendant la course d'orientation

During orienteering, the accumulation of technical errors (TE) can be an important factor of handicap at the arrival. In the same conditions of championships, ten voluntary national runners (age: 29.2 ± 3 years, height: 176.8 ± 3.5 cm, body mass: 65.0 ±6.8) participed to the study. Firstly in laboratory the subjects performed a treadmill test in order to study their physical capacity (aerobic fitness and oxygen consumption). The initial speed (12 km·h⁻¹) increased by 1 km·h⁻¹ every 4 minutes. During the last minute of each step a blood sample (50 μl) was taken on a finger for lactate analyze (Kontron). Two days later the subjects participed in an orienteering race (OR) of four loops (Bi₁, B₂, B₃, B₄) stepping in a central point; the first and third loops (B₁, B3) were technical orienteering while the second and the fourth (B₂, B₄) were rough orienteering. During the race the heart rate (HR) was recorded by means of a Sport Tester PE 4 000. The nature, the number and the moment of TE were determined with the help of the map area of each subject and time keeping. During OR the subject's physical capacity (running speed, HR, lactates, carbohydrate) was evaluated when the runners arrived at the crossing point of the loops. The results give some evidence that the anaerobic threshold quickly is reached during technical orienteering (B₁) and stay at a level hihger than 4 mmoles.l⁻¹ during the whole field test, suggesting that the energy expenditure was very high. It is difficult to compare the physical capacity and the psychological behavior of the subjects during OR yet two distinctive critical pediods have been observed for TE in OR (B₃, B₄); nevertheless our study confirms that the number of TE (which is a picture of the mental performance) is linked to the decrease of the physical capacity. Indeed the increase of HR (HRmax-HRmin) during OR stabilized in the first three loops (B₁, B₂, B₃) at 25 beats, min⁻¹, then the increase of HR was about 31 beats.min⁻¹ in B4. This increase of HR (HRmax-HRmin), is due to the muscular fatigue, the subjects must have some rest and they run slowly because the carbohydrates decrease, excepted for the best runners. Thus the consequences of an insufficient warm-up in the first quarter of the race and/or supply of energetics substrates during the whole OR has been brought to attention.     

Rapid determination of Sr impurities in freshly “generator eluted” Y for radiopharmaceutical preparation

⁹⁰Y is one of the most useful radionuclides for radioimmunotherapeutic applications and has a half-life (t_1/2=64.14 h) suitable for most therapeutic applications, beta particles of high energy and decays to a stable daughter. It is significant that ⁹⁰Y is available conveniently and inexpensively from a radionuclide “generator” by decay of its parent, ⁹⁰Sr. Nevertheless, current and planned clinical applications with [⁹⁰Y] labelled compounds employ activity levels that cannot be readily obtained from an in-house generator, but from commercial sources. We have evaluated Eichrom's Sr-resin, either as an “in-house” generator or as a fast QC method for analysis of ⁹⁰Y solutions.In particular, for the development as a generator, we investigated the percentage of the radio-Sr in the first 8 M HNO₃ eluate: in this fraction the concentration of ⁹⁰Sr must be smaller than 10⁻⁵% (recommendations of the International Commission on Radiological Protection). For evaluation as a rapid QC method, we analyzed the concentration of ⁹⁰Y in all the fractions containing “only” radio-Sr: ⁹⁰Y should not be present in these eluates. After the collection of β⁻ and γ spectra and analysis of them, we concluded that commercial Sr-resin minicolumn cannot give us the results expected; we developed an in-house system loaded with 4 mL of Sr-resin which gave better results as a generator and a rapid QC method.     

Aptitude physique des porteurs du trait drépanocytaire

In order to obtain informations about the exercise capacity, the functional tolerance and the cardiorespiratory response to exercise of sickle cell trait subjects (HbAS) compared to those of normal subjects (HbAA), two groups of six male adults formed into pairs HbAS-HbAA have performed a triangular Exercise Test (corresponding to a gradually maximal exercise of average duration) and a Square-Wave Endurance Exercise Test (SWEET 45 corresponding to a severe exercise of long duration) after an interval of 24 h. The exercise capacity of HbAS was equal to that of normal subjects and their functional tolerance of performed exercises was good. The cardiorespiratory response of the two groups was identical for the gradually maximal exercise of average duration. But it was different for the severe exercise of long duration. During this type of exercise, the ventilation (V˙E l. min⁻¹) and heart rate (HR b. min⁻¹) of HbAS subjects were more important than those of normal subjects whereas their oxygen uptake (V˙O₂ ml. kg⁻¹. min⁻¹) was weaker. These results suggest that the physical fitness of HbAS is normal in regard to V˙O₂ max but it is limited in regard to endurance because of a decrease of their oxygen transport related to their hemoglobinopathy.     

A comparative thermoluminescence and electron spin resonance study of synthetic carbonated A-type hydroxyapatite

Intensity of the 150 °C thermoluminescence peak of beta-irradiated carbonated synthetic A-type hydroxyapatite is approximately 12 times higher than that of the noncarbonated material. Deconvolution of the glow curve showed that this peak is a result of a trap distribution. An attempt was made to relate this thermoluminescence peak enhanced by carbonation with the ESR signal of the CO₂⁻ radical in natural or synthetic hydroxyapatite.     

Enzymatic synthesis of no-carrier-added 6-[F]fluoro- -dopa with β-tyrosinase

An enzymatic synthesis of nca 6-[¹⁸F]fluoro- -dopa has been developed. The process consists of a chemical synthesis of 4-[¹⁸F]fluorocatechol and its enzymatic reaction with β-tyrosinase. The 4-[¹⁸F]fluorocatechol was prepared by nucleophilic aromatic substitution of the NO₂ group on 6-nitroveratoraldehyde with [K/222]⁺¹⁸F⁻, followed by decarbonylation with tris(triphenylphosphine) rhodium(I) chloride and hydrolysis with hydroiodic acid. By C18 Sep-Pak purification, 4-[¹⁸F]fluorocatechol was obtained in ethanol with a radiochemical yield of 9.2%. An enzymatic reaction of 4-[¹⁸F]fluorocatechol, ammonium and pyruvate catalyzed by β-tyrosinase in an ethanolic Tris–HCl buffer (pH 9.0) containing ascorbate gave within 5 min 6-[¹⁸F]fluoro- -dopa with an approximate radiochemical yield of 60% without any isomers. The deproteinized reaction mixture was applied to a preparative reverse phase column, and the radiochemically and enantiomerically pure 6-[¹⁸F]fluoro- -dopa was obtained with a radiochemical yield of 2.0% based on [¹⁸F]F⁻ (decay-corrected). The synthesis time was 150 min from the EOB and the specific activity was >200 GBq/μmol.     

Separation of 90Sr from radioactive waste matrices—Microwave versus fusion decomposition

Radioactive waste (slurry) from a detention pond deriving from two research reactors and several inactive and active drain outlets at the Paul Scherrer Institute are the basis for the current ⁹⁰Sr investigation. For decomposition, a microwave method was applied, where 1 g of dry-ashed slurry was partially dissolved (HNO₃ (65%)/H₂O₂ (30%); v:v=8:2). In this slurry we obtained an ⁹⁰Sr activity of 5.3±0.2 Bq/g in solution. In a second run, we applied a borate-fusion (Li metaborate/Li tetraborate (80:20 w/w%) dissolving 1 g of dry-ashed “Si-free” slurry at 1100 °C in a muffle furnace. We achieved an ⁹⁰Sr activity of (7.8±0.3) Bq/g, yet observing BaSO₄ precipitation during the chromatographical separation of Sr. An alkali fusion using Na₂CO₃ was done using the Bunsen burner and the muffle furnace for 20 min at 1000 °C, in combination. During formation of the hot glass, the surplus of Na₂CO₃, produced Na₂SO₄ and BaCO₃ in solid form. The hot glass was dissolved in deionised water, removing thus the SO₄²⁻ ions. Dissolving the residue directly in HNO₃, solves Ba as Ba(NO₃)₂ and thus we achieved over 80% of the ¹³³Ba activity in the solution, as measured by γ-spectrometry. ⁸⁵Sr tracer of 88.0%±3.3% was recovered, yielding on average in (7.4±0.3) Bq/g of ⁹⁰Sr activity. The increase of 2.1–2.5 Bq/g of ⁹⁰Sr activity achieved with the alkali fusion, and the Li metaborate/Li tetraborate 80:20 w/w% fusion, respectively, clearly shows that some Sr must have been present as SrSO₄ in the slurry.     

A Monte Carlo brachytherapy study for dose distribution prediction in an inhomogeneous medium

The purpose of this study was to present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions. This study was carried out using a Monte Carlo simulation of the dose distribution in homogeneous medium for 3 commonly used brachytherapy seeds. The 3 seeds investigated in this study are iridium-192 (¹⁹²Ir) iodine-125 (¹²⁵I), and palladium-103 (¹⁰³Pd). The computer code was validated by comparing the specific dose rate (Λ), the radial dose function g(r), and anisotropy function F(r,θ) for all 3 seeds with the AAPM TG-43 dosimetry formalism and current literature. The ¹⁹²Ir seed resulted in a dose rate of 1.115 ± 0.001 cGy-hr⁻¹-U⁻¹, the ¹²⁵I seed resulted in a dose rate of 0.965 ± 0.006 cGy/h⁻¹/U⁻¹, and the ¹⁰³Pd seed resulted in a dose rate of 0.671 ± 0.002 cGy/h⁻¹/U⁻¹. The results for all 3 seeds are in good agreement with the AAPM TG-43 and current literature. The validated computer code was then applied to a simple inhomogeneous model to determine the effect bone has on dose distribution from an interstitial implant. The inhomogeneous model showed a decrease in dose rate of 2% for the ¹⁹²Ir, an increase in dose rate of 84% for ¹²⁵I, and an increase in dose rate of 83% for the ¹⁰³Pd at the surface of the bone nearest to the source.     

In vitro and in vivo studies of three radiolabelled somatostatin analogues:123I-Octreotide (OCT),123I-Tyr-3-OCT and111In-TIRA-d-Phe-1-OCT

Scintigraphy with long-acting somatostatin (SST) analogues may be useful for the localization of tumours expressing receptors (R) for SST. In this study we have analysed the in vitro and in vivo binding properties of three SST analogues,¹²³I-octreotide (OCT),¹²³I-Tyr-3-OCT and¹¹¹In-DTPA-d-Phe-l-OCT. In vitro binding studies performed with a variety of primary tumours (n=48) as well as with several tumour cell lines (A431, HT29, PANC1, COLO320, HMC1, KU812) indicated significant in vitro binding of these three radiolabelled SST analogues to two subpopulations of SSTR, high (K _d 0.2–2.0 nM) and low (K _d 5–15 nM) affinity ones. The number of SSTR on tumour cells was at least a 1000-fold higher as compared with normal peripheral blood cells. Comparative scintigraphic studies using¹²³I-OCT and/or¹²³I-Tyr-3-OCT and/or¹¹¹In-DTPA-d-Phe-1-OCT were performed in 21 patients with histologically verified intestinal carcinoid tumours. Corresponding scintigraphic results were obtained in 18 of 21 patients investigated with two different SSTR ligands, either¹²³I-OCT/¹²³I-Tyr-3-OCT (four of five),¹²³I-OCT/¹¹¹In-DTPA-d-Phe-1-OCT (eight of nine), or¹²³I-Tyr-3-OCT/¹¹¹In-DTPA-d-Phe-1-OCT (six of seven). We conclude that various tumours express high amounts of SSTR which are recognized by three radiolabelled SST analogues:¹²³I-OCT,¹²³I-Tyr-3-OCT and¹¹¹In-DTPA-d-Phe-1-OCT. Differences between these SST analogues in their in vitro binding and/or in vivo scanning properties are observed in a minority of patients. Thus, the labelling of OCT with iodine may be an alternative approach for those nuclear medicine departments for which¹¹¹In-DTPA-d-Phe-1-OCT is not easily available, or is too expensive.