Investigation of activation cross-sections of deuteron induced reactions on ruthenium up to 50 MeV.

The activation cross sections of deuteron induced reactions on natural ruthenium have been measured up to 50 MeV for production of radioisotopes of rhodium (105Rh, 102mRh,102gRh,101mRh,101gRh, 100gRh, 99mRh, 99gRh), ruthenium (105Ru,103Ru (cum), 102Ru (cum), 97Ru (cum), 95Ru (cum)) and of technetium (99mTc, 96gTc (m+), 95mTc (cum), 95gTc (cum), 94gTc,93gTc (m+)). The results are compared with the predictions of the most common theoretical nuclear reaction model codes (ALICE-D, EMPIRE-D and TALYS (TENDL)). From the measured cross section physical yields have been calculated for all measured radioisotopes. The medically important radioisotopes are discussed from the point of view of production routes by charged particle methods and other alternatives.

Target development for diversified irradiations at a medical cyclotron.

The irradiation facility at an old medical cyclotron (Ep=17 MeV; Ed=10 MeV) was upgraded by extending the beam line and incorporation of solid state targetry. Tests performed to check the quality of the available beam are outlined. Results on nuclear data measurements and improvement of radiochemical separations are described. Using solid targets, with the proton beam falling at a slanting angle of 20°, a few radionuclides, e.g. (75)Se, (120)I, (124)I, etc. were produced with medium currents (up to 20 µA) in no-carrier-added form in quantities sufficient for local use. The extended irradiation facility has considerably enhanced the utility of the medical cyclotron.

Limitation of the long-lived 121Te contaminant in production of 123I through the 124Xe(p,x) route.

The 13.2 h half-life radioisotope (123)I is widely used in clinical nuclear medicine diagnosis. At present it is mostly produced in nca form by proton irradiation of highly enriched (124)Xe in dedicated gas target set-ups and relying on the decay chain (123)Cs-(123)Xe-(123)I. Depending on the irradiation conditions contamination with long-lived (121)Te, a daughter product of the co-produced rather short lived (121)I, occurs and can limit the useful shelf life of the (123)I solution. Excitation function of the (124)Xe(p,α)(121)I, (124)Xe(p,2n)(123)Cs and (124)Xe(p,2p)(123)Xe reactions are measured up to 35 MeV using the stacked gas cell technique and high-resolution γ-ray spectrometry. The experimental data were compared with the earlier literature values, with new results of the ALICE-IPPE and EMPIRE-II codes and with the data taken from the TENDL-2009 database. Existing discrepancies in cross-section data are largely solved and new recommended values are proposed. From fits to the new excitation curves integral (123)I batch yields and (121)Te contaminations for realistic production conditions are derived. Optimization of irradiation and cooling times and energy degradation in the target can strongly influence the contamination level.

Training of attention and memory deficits in children with acquired brain injury.

UNLABELLED: This pilot study concerns cognitive rehabilitation of children with acquired brain injury (ABI). AIM: The aim is threefold; to determine (1) whether the Amsterdam Memory and Attention Training for Children (AMAT-C) programme for children with ABI can be integrated in the child's school, (2) whether supervision in the school-setting maintains the child's motivation throughout the training programme and (3) whether positive changes in memory, attention and executive functions are found with this implementation of the training method. METHODS: Seven children with memory and/or attention deficits after ABI were trained with AMAT-C. Measures used were programme evaluation questions, neuropsychological tests and a questionnaire concerning executive functions. RESULTS: Overall, children, parents and trainers were satisfied with the programme and the children were motivated throughout the programme. The children showed significant improvements in neuropsychological subtests, primarily in tests of learning and memory. No overall change in executive functions was noted. CONCLUSION: Provision of AMAT-C training and supervision at the child's school appears to ensure (1) satisfaction with the programme, (2) sustaining of motivation and (3) improvements in learning and memory.

Yield and purity of 82Sr produced via the natRb(p,xn) 82Sr process.

The recently reported cross-section data for the production of 82Sr via the natRb(p,xn) 82Sr process were evaluated. For the natRb(p,xn) 85Sr process, cross-sections were measured experimentally over the proton energy range of 25-45 MeV, a region where very few data existed. An evaluation of the recently published data on the formation of 85Sr was then also performed. From the recommended data curves, the integral yields of the desired radionuclide 82Sr and the impurity 85Sr were calculated. Yields were also determined experimentally over several energy ranges using thick natRbCl targets. The experimental and calculated yields were found to be in agreement within 15%. These integral tests add confidence to the evaluated cross-section data. For the production of 82Sr, an incident proton energy of 60 MeV or above is recommended; the 85Sr impurity then corresponds to <20%.

Assessment of the short-lived non-pure positron-emitting nuclide (120)I for PET imaging.

PURPOSE: The non-pure positron-emitting iodine isotope (120)I (T(1/2)=81 min) is a short-lived alternative to (124)I. (120)I has a positron abundance more than twice that of (124)I and a maximum positron energy of 4 MeV. This study was undertaken to evaluate and characterise the qualitative and quantitative PET imaging of (120)I. METHODS: (120)I was produced via the (120)Te(p,n) reaction on highly enriched (120)Te. The measurements were done with the Siemens scanner HR+ and the 2D PET scanner GE PC4096+. A cylinder containing three cold inserts and a phantom resembling a human brain slice were used to evaluate half-life, positron abundance and background correction. To analyse the image resolution, a -mm tube placed in water was filled with (120)I and (18)F. Comparisons with (18)F, (124)I and (123)I (measured with SPECT) were made using the Hoffman 3D brain phantom. RESULTS: The half-life of 81.1 min was reproduced by the PET measurements. The PET-based positron abundance ranged from 47.9% to 55.0%. The reconstructed image resolution found with the HR+ was 5.4 mm FWHM (12.3 mm FWTM), in contrast to 4.6 mm (8.6 mm) when using (18)F. Erroneous positive and negative numbers of radioactivity found in the cold inserts became nearly zero when the background of gamma-coincidences was corrected for. Images of the Hoffman phantom were inferior to those obtained when (18)F or (124)I was applied but superior to the (123)I-SPECT images. CONCLUSION: Our data show that (120)I of high radionuclidic purity can be regarded as a suitable nuclide for the PET imaging of radioiodine-labelled pharmaceuticals.

Some optimisation studies relevant to the production of high-purity 124I and 120gI at a small-sized cyclotron.

Optimisation experiments on the production of the positron emitting radionuclides 124I(T(1/2) = 4.18d) and (120g)I (T(1/2) = 1.35 h) were carried out. The TeO(2)-target technology and dry distillation method of radioiodine separation were used. The removal of radioiodine was studied as a function of time and the loss of TeO(2) from the target as a function of oven temperature and time of distillation. A distillation time of 15 min at 750 degrees C was found to be ideal. Using a very pure source and comparing the intensities of the annihilation and X-ray radiation, a value of 22.0 +/- 0.5% for the beta(+) branching in 124I was obtained. Production of 124I was done using 200 mg/cm(2) targets of 99.8% enriched 124TeO(2) on Pt-backing, 16 MeV proton beam intensities of 10 microA, and irradiation times of about 8 h. The average yield of 124I at EOB was 470 MBq(12.7 mCi). At the time of application (about 70 h after EOB) the radionuclidic impurity 123I (T(1/2) = 13.2 h) was <1%. The levels of other impurities were negligible (126I < 0.0001%;125I = 0.01%). Special care was taken to determine the 125I impurity. For the production of (120g)I only a thin 30 mg target (on 0.5 cm(2) area) of 99.9% enriched 120TeO(2) was available. Irradiations were done with 16 MeV protons for 80 min at beam currents of 7 microA. The 120gI yield achieved at EOB was 700 MBq(19 mCi), and the only impurity detected was the isomeric state 120 mI(T(1/2) = 53 min) at a level of 4.0%. The radiochemical purity of both 124I and 120gI was checked via HPLC and TLC. The radioiodine collected in 0.02 M NaOH solution existed >98% as iodide. The amount of inactive Te found in radioiodine was <1 microg. High purity 124I and 120gI can thus be advantageously produced on a medium scale using the low-energy (p,n) reaction at a small-sized cyclotron.

PET quantitation and imaging of the non-pure positron-emitting iodine isotope 124I.

A series of PET studies using phantoms is presented to characterize the imaging and quantitative performance of the positron-emitting iodine isotope 124I. Measurements were performed on the 2D-PET scanner GE 4096+ as well as on the Siemens PET scanner HRR+ operated in both 2D and 3D modes. No specific correction was applied for the gamma-rays emitted together with the positrons. As compared to 18F, in studies with 124I there is a small loss of image resolution and contrast, and an increase in background. The quantitative results varied between different scanners and various acquisition as well as reconstruction modes, with an average relative difference of -6 +/- 13% (mean+/-SD) in respect of the phantom radioactivity as measured with gamma-ray spectroscopy. We conclude that quantitation of a radiopharmaceutical labelled with 124I is feasible and may be improved by the development of specific corrections.

On-line visual control of aiming movements?

Two experiments are reported which addressed the flexibility of visuo-motor processing by manipulating the availability of visual information while executing a discrete aiming movement. The flexibility of visuo-motor processing was tested by unexpectedly changing the proportion of the movement trajectory that visual feedback was present. Visual feedback was manipulated for a short (0.30), medium (0.60) or long (0.90) proportion of the trajectory within a block of trials. Each of these three proportions of vision occlusion (Experiment 1) or visual disclusion (Experiment 2) during the initial trajectory was examined. Within a visual condition, one of the three visual feedback proportions occurred with a high probability (p = 0.72), whereas the remaining two proportions each occurred with a low probability (p = 0.14). The results clearly indicated that spatial accuracy was determined by the actual vision period, independent of its probability of occurrence. The data are consistent with a model of continuous on-line control of movement execution.

Attempted-suicide trends in Stockholm County, Sweden, 1975-1985.

A total of 22,961 admissions, representing 19,127 individuals, diagnosed as certain or undetermined attempted suicide were registered in the computer medical information system in Stockholm County for the study period 1975-1985. Two different statistical regression models were used to describe the trends of attempted suicide and undetermined attempted suicide. A simple linear ordinary least squares model generally performed better at describing the observed rates in sex- and age-specific rates of attempted suicide when the diagnosis of attempted suicide was certain. Significantly increasing attempted-suicide trends for men over 35 and women over 45 as well as for all ages pooled for both men and women were found. Undetermined attempted suicides were described better by a quadratic model than by the linear model. Women 35-44 and 65-85 years old and men 25-54 years old were found to have an increasing initial phase followed by a leveling out in the rates around 1980-1982, with weak evidence that the rate might even be slowly decreasing. Comparing earlier findings of decreasing rates in completed suicides for all ages, and findings in this study of increasing attempted-suicide trends during the same period, we believe that improved somatic and psychiatric treatment of attempted-suicide patients may partly account for the decreased rates of completed suicides.