Dependence of the thermoluminescent high-temperature ratio (HTR) of LiF:Mg,Ti detectors on proton energy and dose

The high-temperature ratio (HTR) is a parameter quantifying changes of the shape of the high-temperature part of the LiF:Mg,Ti glow-curve after exposure to densely ionizing radiation. It was introduced in order to estimate the effective LET of an unknown radiation field and to correct the decreased relative TL efficiency for high Linear Energy Transfer (LET) radiation. In the present work the dependence of HTR on proton energy (14.5 to 58 MeV) and dose (0.5 to 30 Gy) was investigated. All measured HTR values were at the level of 1.2 or higher, therefore significantly different from the respective value for gamma rays (HTR is equal to 1), but HTR was found to be insensitive to changes of proton energy above 20 MeV. As a result the relationship between HTR and relative TL efficiency is not unequivocal. The HTR was found to be dependent on absorbed dose even for the lowest studied doses.Comment: Manuscript has been presented at the 17th International Conference on Solid State Dosimetry, Recife, Brasil, September 22-27,201

Detection of proton tracks with LiF Fluorescent Nuclear Track Detectors

Fluorescent nuclear track detectors based on LiF crystals were successfully applied for detection of proton induced tracks. Irradiations were performed with protons with energy ranging from 1 MeV up to about 56 MeV and for all proton energies the fluorescent tracks were observed. The tracks are not continuous, but consist of a series of bright spots. The gaps between spots tend to narrow with decreasing proton energy (increasing ionization density). For the highest of the studied energies, the spots are scattered so sparsely, that it is not possible to link spots belonging to one track. The intensity (brightness) of the fluorescent tracks increases with the increasing LET and agrees well with the trend established earlier for various heavier ions.Comment: 12 pages, 12 figure

Superficial lymph nodes involved by lymphoma in modern gray-scale ultrasound imaging

Background: Clinical evaluation by palpation of superficial lymph nodes involved by lymphoproliferative process is not sufficient. Ultrasound is a useful method of the initial differential diagnosis of lymph nodes. The aim was to assess the spectrum of ultrasound features of superficial lymphomatous nodes and possible diagnostic pitfalls. Material/Methods: Fifty five lymph nodes in 55 patients were prospectively examined in ultrasound with application of blood flow imaging modes and modern imaging techniques. Only forty lymph nodes with histopathologically proven lymphoma were selected for this analysis (3 Hodgkin, 37 non-Hodgkin). Results: 27.5% of the examined lymph nodes were longitudinal; 42.5% had an oval or round shape; 30% were oval-lobulated or lobulated. 32.5% of the nodes did not show an echogenic hilum, 20% had a normal hilum, and 25% - evidently abnormal. 12.5% of the nodes were anechoic. The general ultrasound impression of a reactive lymph node was presented by 37.5% of the lymphomatous nodes; 45% were suspicious. Among 26 patients with non-Hodgkin lymphoma with multiple lymph nodes involved, in 15 (58%) lymph nodes were modeling on each other. Conclusions: Lymphomatous nodes reveal diverse ultrasound presentations: from appearances indistinguishable from benign reactive lymph nodes to features typical of metastases. Ultrasound internal structure of lymphomatous nodes may be anechoic, causing the possibility of confusion with a cyst, especially in case of a single lymphomatous node. Multiple lymphomatous nodes with non-Hodgkin lymphoma often model on each other assuming geometrical shapes

Morphology and function of cryopreserved whole ovine ovaries after heterotopic autotransplantation

<p>Abstract</p> <p>Background</p> <p>The objective of this study was to perform complex characterization of cryopreserved and then autotransplanted ovaries including determination of the ability to respond to in vivo follicle stimulating hormone (FSH)-treatment, fertilizability of retrieved oocytes, and morphology, vascularization, cellular proliferation and apoptosis in sheep.</p> <p>Methods</p> <p>Mature crossbred ewes were divided into two groups; an intact (control) group (n = 4), and autotransplanted group (n = 4) in which oophorectomy was performed laparoscopically and ovaries with intact vascular pedicles frozen, thawed and transplanted back into the same animal at a different site. Approximately five months after autotransplantation, estrus was synchronized, ewes were treated with FSH, and ovaries were collected. For all ovaries, number of visible follicles was determined, and collected cumulus oocyte complexes (COC) were matured and fertilized in vitro. Remaining ovarian tissues were fixed for evaluation of morphology, expression of factor VIII (marker of endothelial cells), vascular endothelial growth factor (VEGF; expressed by pericytes and smooth muscle cells), and smooth muscle cell actin (SMCA; marker of pericytes and smooth muscle cells), and cellular proliferation and apoptosis. Two fully functional ovaries were collected from each control ewe (total 8 ovaries).</p> <p>Results</p> <p>Out of eight autotransplanted ovaries, a total of two ovaries with developing follicles were found. Control ewes had 10.6 +/- 2.7 follicles/ovary, oocytes were in vitro fertilized and developed to the blastocyst stage. One autotransplanted ewe had 4 visible follicles from which 3 COC were collected, but none of them was fertilized. The morphology of autotransplanted and control ovaries was similar. In control and autotransplanted ovaries, primordial, primary, secondary, antral and preovulatory follicles were found along with fully functional vascularization which was manifested by expression of factor VIII, VEGF and SMCA. Proliferating cells were detected in follicles, and the rate of apoptosis was minimal in ovaries of control and autotransplanted ovaries.</p> <p>Conclusion</p> <p>These data demonstrate successful autotransplantation of a portion of frozen/thawed ovaries manifested by restoration of selected ovarian function including in vitro maturation of collected oocytes, presence of follicles from several stages of folliculogenesis and blood vessels expressing specific markers of vascularization, and proliferation and apoptosis of ovarian cells. Thus, heterotopic autotransplantation of a whole frozen/thawed ovary allows for development of preovulatory follicles, oocyte growth, and for restoration of vascularization and cellular function. However, additional improvements are required to enhance the efficiency of autotransplantation of frozen/thawed ovaries to produce more oocytes.</p

Some clinical applications of MTS-type TLD detectors

An important part of any QA programme for radiotherapy is verification, in vitro or in vivo, of calculated doses and dose distributions. We studied the clinical applicability of LiF:MG, Ti sintered TL detectors produced, as type MTS-N, by the Institute of Nuclear Physics in Kraków (INP). These are solid pellets of diam 4.5mm and 0.8mm thickness. The TL reader was a modified planchet-type 770A, also produced at the INP, with linear heating and computerised glow curve recording.For analysis of in vivo applications, we measured, in a water phantom, the dose at 14 points aroud the Standard gynaecological applicator of our SELECTRON LDR/MDR afterloading unit with Cs-137 pellets and compared the measured values with doses calculated at these points by the in-house developed SELKOM computer code used for planning gynaecological brachytherapy at the Centre of Oncology in Kraków (COK). Agreement to within 5% was stated.To demonstrate the applicability of MTS dosemeters in calibration dosimetry, we studied the accuracy, stability and reproducibility of a batch of 100 detectors over several readout cycles at doses ranging from 0.5 to 2.5 Gy. At 1 Gy, the relative standard deviation of Individual Calibration Factors (ICF) over six readout cycles did not exceed 2.5% indicating that the error of dose estimation using individual MTS detectors should not exceed 2%.In an intercomparison of Co-60 beams at the COK and at Louvain performed with MTS detectors agreement to within less than 0.5% was found with an accuracy better than 1%.This work is partly supported by KBN Polish State Committee for Scientific Research, Research Project No. 8T11E02908

The problems associated with the monitoring of complex workplace radiation fields at European high-energy accelerators and thermonuclear fusion facilities

The European Commission is funding within its Sixth Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organisational framework for this project is provided by the European Radiation Dosimetry Group EURADOS. One task within the CONRAD project, Work Package 6 (WP6), was to provide a report outlining research needs and research activities within Europe to develop new and improved methods and techniques for the characterisation of complex radiation fields at workplaces around high-energy accelerators, but also at the next generation of thermonuclear fusion facilities. The paper provides an overview of the report, which will be available as CERN Yellow Repor

24. Validation of conformal radiotherapy treatment planning systems using an antro-pomorphic phantom and thermoluminescence dosimetry

Within the requirements of a Quality Assurance programme in a radiotherapy department, the ability of a treatment planning system (TPS) to accurately calculate dose distributions under realistic conditions encountered in radiotherapy (RT) should be validated. This may be accomplished by thermoluminescence (TL) dosimetry in simulated treatment of antropomorphic phantoms. In our radiotherapy department, several planning systems are used concurrently in 3D conformal treatment of larger volumes (with irregular fields obtained via individual shielding or multileaf collimation) and of very small volumes (stereotactic technique), by external megavoltage photon beams. Realistic 3D treatment plans were prepared using CadPlan, Theraplan and BrainLab TPS for treating volumes in an Alderson phantom, which was prepared for topometry (CT-scanned) and irradiated in fully simulated conditions of patient RT. Suitably selected TL detectors (some custom-produced for these measurements), were placed inside and around the treated volumes in the phantom. For every photon beam applied (Co-60, 6 MV or 9 MV) the TL detectors, individually corrected, were calibrated in a standard solid phantom against ionisation chamber dosimetry. For irradiation of larger volumes, standard MTS-N (LiF:Mg,Ti) detectors were used. For stereotactic irradiation of small volumes in the head (6 MV) special miniature thermoluminescent LiF:Mg,Ti and LiF:Mg,Cu,P were developed. The technique of detector calibration, preparation of Alderson phantom for simulated RT, detector readout and interpretation of the measured versus calculated values of dose at measurement points inside the phantom, will be described