Radiochromic solutions for reference dosimetry

A chemical radiochromic dosimeter using hexa(hydroxyethyl)pararosaniline nitrile (HHEV-CN) dissolved in an aerated mixture of triethyl phosphate and dimethyl sulfoxide can be used over a wide absorbed dose range as a stable reference dosimeter, with useful characteristics, both for steady-state and pulsed radiation fields. Solutions of the leuco dye at 2-mM concentration, containing small amounts of acetic acid, p-nitrobenzoic acid and polyvinylbutyral, show high precision and a linear response for absorbed doses up to 4 kGy. When the leuco dye concentration is increased to 100 mM, the response is also linear, and absorbed doses as low as 0.5 Gy can be read with a precision of 1.3% (95% confidence limits). The radiation chemical yield is constant with changes in absorbed dose rate, but it increases with concentration of the leuco dye up to 10⁻¹ molarity. The radiation chemical yields for dye formation are: for 2-mM solution, G(dye) = 0.015 μmol J⁻¹; for 100-mM solution, G(dye) = 0.28 μmol J⁻¹. The uncertainties for these measured values are ±2.6% (95% confidence limits). The molar linear absorption coefficient at 605–608 nm wavelength is 1.0 × 10⁵ L mol⁻¹ cm⁻¹, the uncertainty (95% confidence limits) being ±2.2%. This dosimeter solution may be used in small sealed glass ampoules or plastic vials and is useful for measuring x- and γ-ray doses of interest in food irradiation and in clinical radiology. The combination of ingredients simulates water and biological tissue (muscle) in terms of radiation interaction cross sections, i.e. mass energy-absorption coefficients for photons (0.1–20 MeV) and mass collision stopping powers for electrons (0.1–50 MeV).     

Measurements of actinide gut-transfer factors in humans

Measurements have been made of the gastrointestinal absorption in humans of ²³⁹Np and ²⁴²Cm administered together in citrate media. Using five volunteers, consistent results of (2.0 ± 0.2) × 10⁻⁴ and (1.7 ± 0.3) × 10⁻⁴ were obtained for Np and Cm respectively; the quoted uncertainties are the standard errors of the means. A progress report is given of work to measure the f₁ value for Pu in humans. Early work suggests an f₁ value of 2 × 10⁻⁴.     

Effect of Silver ions in dichromate dosimetry

Dichromate solutions containing silver ions have been investigated for use in dosimetry. The marked effect of hydrogen on the ⁶⁰Co γ radiation-induced reduction of potassium dichromate solutions is completely inhibited by 1 × 10⁻³ M silver nitrate. A silver nitrate concentration of 1 × 10⁻⁴ M significantly improves the linearity and precision of response of dichromate to radiation, probably by inhibiting impurity effects as well as the hydrogen effect. G(−Cr₂O⁻²₇) values are given for a number of solutions containing different concentrations of silver and dichromate ions and sulphuric acid, for the measurement of doses up to 10 Mrad. The G(−Cr₂O²⁻₇) value decreases with increasing silver ion concentration and increases with increasing dichromate ion concentration. No difference was found between the response of solutions prepared using singly distilled water and those using triply distilled water. Simple empirical equations are given for the calculation of dose from the absorbance of solutions. The mean error for doses in the range 0.3–4.2 Mrad, estimated with solutions containing 1 × 10⁻⁴ M silver nitrate, was ± 1.5%; for doses of 1–9 Mrad from solutions containing 1 × 10⁻³ M silver nitrate, the mean error was ± 0.9%. Spectrophotometry at 350 nm on an undiluted solution of 4 × 10⁻⁴ M K₂Cr₂O₇/1 × 10⁻⁴ M AgNO₃/0.4 M H₂SO₄ allows measurements in the range 0.08 to 0.80 Mrad; the G(−Cr₂O²⁻₇) value for this solution was 0.37 ± 0.001.     

Pulse radiolysis of solutions of trans-stilbene in liquid methylamine at 298K

The transient spectrum observed in the range 330–800 nm had an absorption maximum corresponding to the stilbene anion at 490 nm. G_{(Stilbene⁻¹}) = 3.8 ± 0.3. The anion was found to decay by a first order process with a rate constant k₁ = (13.0 ± 2.4) × 10⁵ s⁻¹.     

In vivo carbon-edited detection with proton echo-planar spectroscopic imaging (ICED PEPSI): [3,4-13CH2]glutamate/glutamine tomography in rat brain

A method for in vivo carbon-edited detection with proton echo-planar spectroscopic imaging (ICED PEPSI) is described. This method is composed of an echo-planar based acquisition implemented with ¹³C-¹H J editing spectroscopy and is intended for high temporal and spatial resolution in vivo spectroscopic imaging of ¹³C turnover, from D-[1,6-¹³C]glucose to glutamate and glutamine, in the brain. At a static magnetic field strength of 7 T, both in vitro and in vivo chemical shift imaging data are presented with a spatial resolution of 8 μL (i.e., 1.25 × 1.25 × 5.00 mm³) and a maximum spectral bandwidth of 5.2 ppm in ¹H. Chemical shift imaging data acquired every 11 minutes allowed detection of regional [4-¹³CH₂]glutamate turnover in rat brain. The [4-¹³CH₂]glutamate turnover curves, which can be converted to tricarboxylic acid cycle fluxes, showed that the tricarboxylic acid cycle flux (V_TCA) in pure gray and white matter can range from 1.2 ± 0.2 to 0.5 ± 0.1 μmol/g/min, respectively, for morphine-anesthetized rats. The mean cortical V_TCA from 32 voxels of 1.0 ± 0.3 μmol/g/min (N = 3) is in excellent agreement with previous localized measurements that have demonstrated that V_TCA can range from 0.9–1.1 μmol/g/min under identical anesthetized conditions. Magn Reson Med 42:997–1003, 1999. © 1999 Wiley-Liss, Inc.     

Evaluation of a novel software application for magnetic resonance distortion correction in cranial stereotactic radiosurgery

This study aimed to validate a novel commercially available software for correcting spatial distortion in cranial magnetic resonance (MR) images. This software has been used to assess the dosimetric impact of MR distortion in stereotactic radiosurgery (SRS) treatments of vestibular schwannomas (VSs). Five MR datasets were intentionally distorted. Each distorted MR dataset was corrected using the Cranial Distortion software, obtaining a new corrected MR dataset (MRcorr). The accuracy of the correction was quantified by calculating the target registration error (TRE) for 6 anatomical landmarks identified in the co-registered MRcorr and planning computed tomography (pCT) images. Nine VS cases were included to investigate the impact of the MR distortion in SRS plans. Each SRS plan was calculated on the pCT (1 × 1 × 1 mm³ voxel) with the target and organs at risk (OARs) delineated using the planning MR dataset. This MR dataset was then corrected (MRcorr) using the Cranial Distortion software. Geometrical agreement between the original target and the corresponding corrected target was assessed using several metrics: MacDonald criteria, mean distance to agreement (MDA), and Dice similarity coefficient (DSC). Target coverage (D99%) and maximum doses (D2%) to ipsilateral cochlea and brainstem resulting on the MRcorr dataset were compared with the original values. TRE values (0.6 mm ± 0.3 mm) and differences found in Macdonald criteria (0.3 mm ± 0.4 mm and 0.3 mm ± 0.3 mm) and MDA (0.8 mm ± 0.2 mm) were mostly within the voxel size dimension of the pCT scan (1 × 1 × 1 mm³). High similarity (DSC > 0.7) between the original and corrected targets was found. Small dose differences for the original and corrected structures were found: 0.1 Gy ± 0.1 Gy for target D99%, 0.2 Gy ± 0.3 Gy for cochlea D2%, and 0.1 Gy ± 0.1 Gy for brainstem D2%. Our study shows that Distortion Correction software can be a helpful tool to detect and adequately correct brain MR distortions. However, a negligible dosimetric impact of MR distortion has been detected in our clinical practice.     

The degradation of triazo dye chlorantine fast green BLL in aqueous solutions by gamma radiation—III

The radiation degradation yield (G_{d values}) of Chlorantine Fast Green BLL (CFGBLL), G_d, i.e. the value of moles of dye molecules degraded per joule of energy absorbed (sometimes given in units of the number of molecules decomposed per 100 eV of radiation energy absorbed) was measured in aerated, oxygen- and nitrogen-saturated aqueous solutions. The G_d values were found to be 0.063, 0.0715 and 0.033 μmol/J or (0.61, 0.69 and 0.32/100 eV) respectively. The relatively low degradation yield indicates the absence of chain reactions and probably the poor efficiency and economics, in terms of the practical application of the radiation process. For applications in the radiation treatment of waste water, it is noted that in the presence of oxygen and at higher concentration of CFGBLL, the value of G_d increases markedly, so that it may be practical to monitor the extent of sterilization of water. In addition the radiation processing of CFGBLL waste water may also become economically feasible. The specific bimolecular rate constant of the reaction of CFGBLL with the ^.OH was determined by studying the effect of ethanol concentration on G_d using competition kinetics. This rate constant was found to be k = 2.32 × 10¹⁰ and 1.65 × 10¹⁰ L mol/s at 610 and 380 nm wavelengths, respectively. Suggestions are made for the possible use of CFGBLL aqueous solution as a chemical dosimeter in the range of absorbed dose from 0.1 to 5 kGy.     

Glow curve kinetics of sintered CaSO4-Dy TL dosimeters

Results of various experiments showed that TL centres responsible for the formation of the peak at around 300°C in glow curves of sintered CaSO₄-Dy dosimeters are formed during the sintering process and are probably located near grain boundaries in the sintered material. Kinetic parameters for this peak were evaluated by different methods. The glow peak at around 300°C has E_a = 1.61 ± 0.08 eV, s = 5 ± 2 × 10¹³s⁻¹ and its kinetic order b = 2.0 ± 0.2.     

Products of radiation removal of lead from aqueous solutions

The influence of typical ·OH radical scavengers as potassium formate and isopropanol on the radiation-induced removal of lead was individually studied. The lead can be completely removed from aqueous solutions containing 1×10^?2 mol/L of formate already at the dose of 2.5 kGy. With increasing concentration of formate (5×10^?5–1×10^?2 mol/L) increases the amount of Pb(formate)⁺ species in the solution before irradiation. The radiation product is metallic lead at low concentration of formate to PbCO₃ at higher concentration of scavenger. In the system with 10% isopropanol dominates the species Pb²⁺ and the product of radiation reduction is then metallic lead.     

Determination of 99mTc valent form in solids by measurement of internal conversion electrons

The core-level internal conversion electron spectroscopy (ICES) was used to study no-carrier-added compounds of ^99mTc in the form of solid deposits. The following chemical shifts of the electron binding energies were determined: ΔE_B(NH₄TcO₄NaTcO₄) = 0.0±0.3 eV, ΔE_B(NH₄TcO₄TcO₂·2H₂ O) = 3.±0.3 eV. Furthermore, two valent forms were distinguished in the decay-induced ^99mTc species created from the Na₂⁹⁹MoO₄ in the NaOH matrix. The smallest detectaable amount of ^99mTc in the minor valent form was ∼30μCi (6 × 10⁻¹²g). The observed shifts ΔE_B(NH₄TcO₄NaTcO_x) = ±0.0±3 eV and ΔE_B(Nh₄TcO₄-NaTcO_y) = 2.1±0.3 eV indicate the chemical form NaTc(VII)O₄ for the NaTcO_x and either Na₂Tc(Vi) or NaTc(V0O₃ for the NaTcO_y. Shift calculations based on the ground -state potential model prefer NaTcO₃.     

Binding of noradrenaline to bovine serum albumin

The binding of noradrenaline to bovine serum albumin (40 mg ml⁻¹) has been studied by gel filtration. Over the range of 5 × 10⁻⁹ M to 10⁻³ M of noradrenaline, the data obtained fit a model with three classes of noninteracting binding sites: a high affinity-low capacity site with a K_A of 1.18 × 10⁶ M⁻¹ and a capacity of 11.84 pmol per mg of protein; an intermediate site with a K_A of 7.42 × 10⁴ M⁻¹ and a capacity of 57.25 pmol mg⁻¹; and a low affinity-high capacity site with a K_A of 8.64 × 10² M⁻¹ and a capacity of 1265 pmol mg⁻¹. There are no significant differences in binding among the three bovine serum albumin preparations considered. Both (±) and (−) noradrenaline are bound equally well by albumin. The binding is a relatively slow process but has a very rapid initial rate, about 40-fold higher than the observed at the half-maximal binding. At pH 7.4 the binding capacity is about 1.7-times higher and the initial rate is about 10-fold higher than at pH 5, but the affinity is similar. There is no degradation of noradrenaline in the presence of serum albumin. The reversibility of binding is small by dialysis or acidic precipitation. At physiological concentrations of noradrenaline and serum albumin it is estimated that about 60% of noradrenaline would be bound. The possible physiological significance of binding is discussed.     

Determination of tritium by mass spectrometric measurement of 3He

A new technique for analysis of environmental tritium is described. The method consists of mass-spectrometer measurements of ³He allowed to accumulate for suitable times in degassed samples of water sealed in containers made of Corning type-1720 glass. Twelve samplesfrom the Pacific Ocean were measured by this method and also β-particle counting at the University of Miami. Agreement between the two methods in satisfactory, although our results seem to be systematically higher than the Miami results by ∼ 2%. Mass-spectrometric measurements were also made of the tritium concentration in the 1961 NBS tritiated water standard. These gave a concentration 1.6(±0.6)%higher than that calculated from the stated NBS activity per gram using a half-life of 12.26 years, which was also used to correct for decay to August 1975. If a half-life of 12.51 years is used, the above discrepancy is eliminated. As part of this work, the ³He/⁴He ratio in atmospheric helium has been redetermined, and found to be 1.384 × 10⁻⁶ (±0.4%), which is in good agreement with the value of 1.399 × 10⁻⁶ (±0.9%) measured by Mamyrin, Anufriyev, Kamenskiy and Tolstikhin.     

Acidic aqueous dichromate solutions as reference dosimeters in the 10–40 kGy range

The radiolytic reduction of dichromate ion in acidic aqueous solution has been investigated as a potential dosimetry system for the 10–40 kGy range of absorbed dose. Dilute sulphuric acid has been shown to be unsuitable as a solvent, and the use of 0.1 mol·dm⁻³ perchloric acid is recommended. A previously reported effect of silver ion in supressing reaction with hydrogen has been confirmed, and in addition, silver ions have been shown to be effective in eliminating dose rate effects. The temperature coefficient during irradiation has been determined as −0.2% per degree and post-irradiation storage effects are shown to be negligible. The precision of the system is about 0.5% at a dose of 25 kGy, and a suggested composition for a working dosimeter is given.     

Chemical dosimetry at less than 1000 rad: Aqueous trimesic acid solutions

Aqueous solutions of trimesic acid have been investigated for possible use as a chemical dosimeter. In aerated 10⁻² M sulphuric acid solution containing 10⁻³ M trimesic acid, a highly fluorescent product is formed with its maximum fluorescence at 450 nm when excited by 350 nm light. The product has fluorescence characteristics very similar to quinine in 0.05 M sulphuric acid. The fluorescence intensity is linear with dose in the range 1–1000 rad and a precision of ±2% was obtained from a number of runs. Solutions are stable for at least several days before and after irradiation. The yield is little affected by moderate changes in trimesic acid concentration, oxygen concentration, water purity, energy of radiation and irradiation temperature. The small dependence of the yield on dose rate and the effect of measurement temperature on the fluorescence signal have been quantified. The most significant factor affecting the fluorescence signal is the hydrogen ion concentration of the solution. In aerated neutral and alkaline (pH 10) solutions, hydroxytrimesic acid (HTMA) is formed with G(HTMA) equal to 2.07 ± 0.04 and 2.21 ± 0.04, for 10⁻³ M trimesate. In these solutions, G(HTMA) increases appreciably with increase in the trimesate concentration. The mauorescent product formed in irradiated acid solutions was not identified but it was not HTMA.     

A comprehensive mutation study in wide deep-rooted R1b Serbian pedigree: mutation rates and male relative differentiation capacity of 36 Y-STR markers

Haplotyping of Y-chromosomal short tandem repeats (Y-STRs) reflects the paternal lineage, although, the father-son pair profiles may differ due to the germline mutations. In order to discriminate between closely related males in criminal cases, as well as for the correct application of Y-STRs in the paternity/kinship analysis and determination of the most recent common ancestor in the familial searching or genealogy research, the assessment of mutation rates of routinely used Y-STRs is of a great importance. We genotyped 120 males belonging to one wide deep-rooted pedigree separated by 1–20 meiosis. The haplotypes of analyzed males distributed over 12 different families (according to their surnames), with 113 originating from one ancestor, and the remaining 7 from the second, closely related to the previous one, belong to the R1b haplogroup. The analysis was performed using Powerplex® Y23 kit, Yfiler^™ plus kit and 13 rapidly mutating (RM13) Y-STRs. In 20,855 allele transmissions, 175 mutations (61% repeat losses and 39% gains) and one gene conversion event were found at 25 out of 36 markers. The medians of locus-specific mutation rates estimated using the Bayesian approach ranged from 1.42 × 10⁻³ (95% credible interval (CI): 0.05 × 10⁻³ - 7.56 × 10⁻³) for loci with no observed mutations to 130.91 × 10⁻³ (95% CI: 102.91 × 10⁻³ - 162.78 × 10⁻³) for DYF399S1, with a median rate across all 36 markers of 10.06 × 10⁻³ (95% CI: 8.65 × 10⁻³ - 11.61 × 10⁻³). In 6349 male relative pairs, the 36 Y-STR set distinguished 98.4% relative pairs by at least one mutation, compared to 95.9%, 65.5% and 57.4% for RM13, Yfiler^™ plus, and Powerplex® Y23 set, respectively. The extra-pair paternity rate was estimated at 11.9 × 10⁻³ (95% CI: 4.4 × 10⁻³ – 25.8 × 10⁻³) fitting within the range reported for some European populations. A significant positive correlation was observed between fathers’ ages at the time of the Y chromosome transmission and mutability rates (R² = 0.9495, p = 0.0256), with more significant results when analyzing RM markers (R² = 0.9827, p = 0.0087).     

Production of [13N]NH3 with ultra-high specific activity

Aqueous solutions of [¹³N]NH₃ were synthesized according to well-known methods using the ¹⁶O(p, α)¹³N reaction under conditions rendering the smallest possible amount of nitrogen-contaminants. The specific activities and radiochemical yields were measured. Factors, affecting the specific activity of [¹³N]NH₃, were investigated using radio-ionchromatography. The achieved specific activities (GBq/μmol) and radiochemical yields (GBq) of [¹³N]NH₃ were 14±2.8 and 0.3±0.1 (TiCl₃ method)1, 590±200 and 5.4±1.1 (DeVarda's Alloy method), 5500±500 and 12.7±0.1 (ethanol method), and 6200±2700 and 2.8±0.3 (hydrogen method, 3 bar), respectively at 15 μA for 20 min irradiation (1; 5 μA, 5 min irradiation). More than 70% of the N-13 generated with the hydrogen method was of the chemical form [¹³N]N₂.     

Diffusion-Weighted MR Imaging of Primary and Secondary Lung Cancer: Predictive Value for Response to Transpulmonary Chemoembolization and Transarterial Chemoperfusion

PurposeTo examine predictive value of apparent diffusion coefficient (ADC) in diffusion-weighted imaging (DWI) for response of patients with primary and secondary lung neoplasms undergoing transpulmonary chemoembolization (TPCE) and transarterial chemoperfusion (TACP) treatment.Materials and MethodsThirty-one patients (mean age ± SD 64 ± 12.4 y) with 42 lung target lesions (13 primary and 29 secondary) underwent DWI and subsequent ADC analysis on a 1.5T MR imaging scanner before and 30.3 days ± 6.4 after first session of TPCE or TACP. After 3.1 treatment sessions ± 1.4 performed in 2- to 4-week intervals, morphologic response was analyzed by comparing tumor diameter and volume before and after treatment on unenhanced T1-weighted MR images. On a per-lesion basis, response was classified according to Response Evaluation Criteria In Solid Tumors.ResultsThreshold ADC increase of 20.7% indicated volume response with 88% sensitivity and 78% specificity (area under the curve [AUC] = 0.84). Differences between ADC changes in volume response groups were significant (P = .002). AUC for volume response predicted by ADC before treatment was 0.77. Median ADC before treatment and mean ADC change were 1.09 × 10⁻³ mm²/second and 0.36 × 10⁻³ mm²/second ± 0.23, 1.45 × 10⁻³ mm²/second and 0.14 × 10⁻³ mm²/second ± 0.16, and 1.30 × 10⁻³ mm²/second and 0.06 × 10⁻³ mm²/second ± 0.19 in partial response, stable disease, and progressive disease groups. In primary lung cancer lesions, strong negative correlation of ADC change with change in diameter (ρ = −.87, P < .001) and volume (ρ = −.66, P = .016) was found. In metastases, respective correlation coefficients were ρ = −.18 (P = .356) and ρ = −.35 (P = .061).ConclusionsADC quantification shows considerable diagnostic value for predicting response and monitoring TPCE and TACP treatment of patients with primary and secondary lung neoplasms.     

Diffusion tensor imaging of rectal carcinoma: Clinical evaluation and its correlation with histopathological findings

ObjectiveThis study sought to assess the feasibility of diffusion tensor imaging (DTI) to noninvasively evaluate histological grade and lymph node metastasis in patients with rectal carcinoma (RC).MethodsThirty-seven consecutive patients with histologically confirmed RC were examined by 1.5-T MRI. DTI was performed using a single-shot echo-planar imaging sequence with b values of 0 and 1000 s/mm² and motion-probing gradients in nine noncollinear directions. Fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD) maps were compared with histopathological findings.ResultsThe FA values (0.357 ± 0.047) of the RCs were significantly lower than those of the normal rectal wall, muscle, prostate, and uterus (P < 0.001 for all), while the AD, MD, and RD values (1.221 ± 0.131, 0.804 ± 0.075, and 0.667 ± 0.057 × 10⁻³ mm²/s, respectively) were also significantly lower than their respective normal values (P < 0.001 for all). The FA, AD, MD, and RD values for RC additionally showed significant inverse correlations with histological grades (r = −0.781, r = −0.750, r = −0.718, and r = −0.682, respectively; P < 0.001 for all). Further, the FA (0.430 vs. 0.611), AD (1.246 vs. 1.608 × 10⁻³ mm²/s), MD (0.776 vs. 1.036 × 10⁻³ mm²/s), and RD (0.651 vs. 0.824 × 10⁻³ mm²/s) (P < 0.001 for all) of the metastatic and nonmetastatic lymph nodes were significantly different.ConclusionsDTI may be clinically useful for the noninvasive evaluation of histological grade and lymph node metastasis in patients with RC.     

Regulation of bone blood flow in humans: The role of nitric oxide,prostaglandins, and adenosine

The mechanisms that regulate bone blood flow (BBF ) in humans are largely unknown. Animal studies suggest that nitric oxide (NO ) could be involved, and in this study, we investigated the effects of inhibition of nitric oxide synthase (NOS ) alone and in combination with inhibition of cyclooxygenase (COX ) enzyme, thus prostaglandin (PG ) synthesis on femoral bone marrow blood flow by positron emission tomography in healthy young men at rest and during one‐leg dynamic exercise. In an additional group of healthy men, the role of adenosine (ADO ) in the regulation of BBF during exercise was investigated by use of an adenosine receptor blocker (aminophylline). Inhibitors were directly infused into the femoral artery. Resting BBF was 1.1 ± 0.4 mL 100 g⁻¹min⁻¹ and increased to almost sixfold in response to exercise (6.3 ± 1.5 mL 100 g⁻¹ min⁻¹). Inhibition of NOS reduced BBF at rest to 0.7 ± 0.3 mL 100 g⁻¹ min⁻¹ (P  = .036), but did not affect BBF significantly during exercise (5.5 ± 1.4 mL 100 g⁻¹ min⁻¹, P  = .25). On the other hand, while combined NOS and COX inhibition did not cause any further reduction of blood flow at rest (0.6 ± 0.2 mL 100 g⁻¹min⁻¹), the combined blockade reduced BBF during exercise by ~21%, to 5.0 ± 1.8 mL 100 g⁻¹ min⁻¹ (P  = .014). Finally, the ADO inhibition during exercise reduced BBF from 5.5 ± 1.9 mL 100 g⁻¹ min⁻¹ to 4.6 ± 1.2 mL 100 g⁻¹ min⁻¹ (P  = .045). In conclusion, our results support the view that NO is involved in controlling bone marrow blood flow at rest, and NO , PG , and ADO play important roles in controlling human BBF during exercise.