Mapping initial and general recombination in scanning proton pencil beams.

The ion recombination is examined in parallel-plate ionization chambers in scanning proton beams at the Danish Centre for Particle Therapy and the Skandion Clinic. The recombination correction factor k s is investigated for clinically relevant energies between 70 MeV and 244 MeV for dose rates below 400 Gy min-1 in air. The Boutillon formalism is used to separate the initial and general recombination. The general recombination is compared to predictions from the numerical recombination code IonTracks and the initial recombination to the Jaffé theory. k s is furthermore calculated with the two-voltage method (TVM) and extrapolation approaches, in particular the recently proposed three-voltage (3VL) method. The TVM is in agreement with the Boutillon method and IonTracks for dose rates above 100 Gy min-1. However, the TVM calculated k s is closer related to the Jaffé theory for initial recombination for lower dose rate, indicating a limited application in scanning light ion beams. The 3VL is in turn found to generally be in agreement with Boutillon's method. The recombination is mapped as a function of the dose rate and proton energy at the two centres using the Boutillon formalism: the initial recombination parameter was found to be A = (0.10 ± 0.01) V at DCPT and A = (0.22 ± 0.13) V at Skandion, which is in better agreement with the Jaffé theory for initial recombination than previously reported values. The general recombination parameter was estimated to [Formula: see text] and [Formula: see text]. Furthermore, the numerical algorithm IonTracks is demonstrated to correctly predict the initial recombination at low dose rates and the general recombination at high dose rates.

Dose distribution of secondary radiation in a water phantom for a proton pencil beam-EURADOS WG9 intercomparison exercise.

Systematic 3D mapping of out-of-field doses induced by a therapeutic proton pencil scanning beam in a 300 × 300 × 600 mm3 water phantom was performed using a set of thermoluminescence detectors (TLDs): MTS-7 (7LiF:Mg,Ti), MTS-6 (6LiF:Mg,Ti), MTS-N (natLiF:Mg,Ti) and TLD-700 (7LiF:Mg,Ti), radiophotoluminescent (RPL) detectors GD-352M and GD-302M, and polyallyldiglycol carbonate (PADC)-based (C12H18O7) track-etched detectors. Neutron and gamma-ray doses, as well as linear energy transfer distributions, were experimentally determined at 200 points within the phantom. In parallel, the Geant4 Monte Carlo code was applied to calculate neutron and gamma radiation spectra at the position of each detector. For the cubic proton target volume of 100 × 100 × 100 mm3 (spread out Bragg peak with a modulation of 100 mm) the scattered photon doses along the main axis of the phantom perpendicular to the primary beam were approximately 0.5 mGy Gy-1 at a distance of 100 mm and 0.02 mGy Gy-1 at 300 mm from the center of the target. For the neutrons, the corresponding values of dose equivalent were found to be ~0.7 and ~0.06 mSv Gy-1, respectively. The measured neutron doses were comparable with the out-of-field neutron doses from a similar experiment with 20 MV x-rays, whereas photon doses for the scanning proton beam were up to three orders of magnitude lower.

Measurement of stray radiation within a scanning proton therapy facility: EURADOS WG9 intercomparison exercise of active dosimetry systems.

PURPOSE: To characterize stray radiation around the target volume in scanning proton therapy and study the performance of active neutron monitors. METHODS: Working Group 9 of the European Radiation Dosimetry Group (EURADOS WG9-Radiation protection in medicine) carried out a large measurement campaign at the Trento Centro di Protonterapia (Trento, Italy) in order to determine the neutron spectra near the patient using two extended-range Bonner sphere spectrometry (BSS) systems. In addition, the work focused on acknowledging the performance of different commercial active dosimetry systems when measuring neutron ambient dose equivalents, H(∗)(10), at several positions inside (8 positions) and outside (3 positions) the treatment room. Detectors included three TEPCs--tissue equivalent proportional counters (Hawk type from Far West Technology, Inc.) and six rem-counters (WENDI-II, LB 6411, RadEye™ NL, a regular and an extended-range NM2B). Meanwhile, the photon component of stray radiation was deduced from the low-lineal energy transfer part of TEPC spectra or measured using a Thermo Scientific™ FH-40G survey meter. Experiments involved a water tank phantom (60 × 30 × 30 cm(3)) representing the patient that was uniformly irradiated using a 3 mm spot diameter proton pencil beam with 10 cm modulation width, 19.95 cm distal beam range, and 10 × 10 cm(2) field size. RESULTS: Neutron spectrometry around the target volume showed two main components at the thermal and fast energy ranges. The study also revealed the large dependence of the energy distribution of neutrons, and consequently of out-of-field doses, on the primary beam direction (directional emission of intranuclear cascade neutrons) and energy (spectral composition of secondary neutrons). In addition, neutron mapping within the facility was conducted and showed the highest H(∗)(10) value of ∼ 51 µSv Gy(-1); this was measured at 1.15 m along the beam axis. H(∗)(10) values significantly decreased with distance and angular position with respect to beam axis falling below 2 nSv Gy(-1) at the entrance of the maze, at the door outside the room and below detection limit in the gantry control room, and at an adjacent room (<0.1 nSv Gy(-1)). Finally, the agreement on H(∗)(10) values between all detectors showed a direct dependence on neutron spectra at the measurement position. While conventional rem-counters (LB 6411, RadEye™ NL, NM2-458) underestimated the H(∗)(10) by up to a factor of 4, Hawk TEPCs and the WENDI-II range-extended detector were found to have good performance (within 20%) even at the highest neutron fluence and energy range. Meanwhile, secondary photon dose equivalents were found to be up to five times lower than neutrons; remaining nonetheless of concern to the patient. CONCLUSIONS: Extended-range BSS, TEPCs, and the WENDI-II enable accurate measurements of stray neutrons while other rem-counters are not appropriate considering the high-energy range of neutrons involved in proton therapy.

[Natural killer cell count in hemodialysis patients]. / Liczba naturalnych komórek cytotoksycznych u hemodializowanych chorych.

UNLABELLED: The patients with chronic renal failure present an immunodeficiency state manifested by prolonged tolerance to allografts, increased incidence of infections and abnormally high incidence of neoplasia. The present study aimed to assess the effect of chronic uraemia and haemodialysis treatment on the natural killer cells (NK cells) count. Peripheral blood NK cells (CD3-, CD16+), total lymphocytes, leukocytes, monocytes and granulocytes of 24 hemodialyzed patients with chronic renal failure and 32 healthy subjects were studied using flow cytometry. In the investigated group of patients with chronic renal failure treated with haemodialysis the count of NK cells (CD3-, CD16+) in the peripheral blood was significantly decreased in comparison to healthy subjects (137 +/- 11 versus 229 +/- 13, p < 0.001) and a significant negative correlation (r = -0.391, p < 0.05) was observed between the duration of haemodialysis treatment and the count of NK cells (CD3-, CD16+). CONCLUSIONS: 1) Chronic uraemia and haemodialysis treatment exerts a negative effect on NK cells (CD3-, CD16+) count in the peripheral blood. 2) The count of NK cells (CD3-, CD16+) in the peripheral blood in patients with chronic renal failure treated with haemodialysis could be a prognostic marker of susceptibility to infections and malignancy.

[Activity of sodium-lithium cotransport in erythrocytes of patients with diabetes mellitus type I (IDDM) complicated by diabetic nephropathy in the renal failure stage]. / Aktywnosc kotransportu sodowo-litowego w erytrocytach u chorych na cukrzyce typu I (IDDM) powiklana nefropatia cukrzycowa w stadium niewydolnosci nerek.

Sodium-lithium countertransport (SLC) in erythrocytes represents one of the transmembrane sodium transport systems. SLC activity is elevated in arterial hypertension, diabetes mellitus type I (IDDM) complicated with nephropathy, hyperlipidemia, hyperuricemia and pregnancy. Increase of SLC is considered as a genetic marker of primary arterial hypertension. In present paper SLC was assessed in 12 patients with IDDM without nephropathy (group I), 12 patients with IDDM complicated with diabetic nephropathy on hemodialytic treatment (group II), 15 patients treated with haemodialysis due to non-diabetic nephropathy (group III) and 12 healthy subjects (group IV). All groups were matched in respect of age. Serum creatinine concentration and inulin clearance were similar in groups I and IV as well as in groups II and III. SLC was assessed according to method described by Canessa and coworkers (1980). SLC activity in group II (0.60 mmol/l litre of erythrocytes/h; 0.43-0.94; 0.28-1.22) (median, 25%-75%, min.-max.) was significantly higher than in other groups-group I (0.30; 0.20-0.38; 0.12-0.57), group III (0.24; 0.16-0.33; 0.11-0.38) and group IV (0.20; 0.15-0.25; 0.12-0.27). In 3 patients of group I the values were higher than in all examined of groups III and IV and approximated to mean values of group II. The results confirm a significant rise of SLC activity in patients with IDDM complicated with end-stage diabetic nephropathy. SLC activity in end-stage renal disease due to non-diabetic nephropathy does not differ from values in healthy subjects. It seems that elevated SLC activity in IDDM might be a genetic marker foretelling development of nephropathy.

[The effect of repeated use of cuprophane and polysulfone dialyzers during hemodialysis on the count of natural killer cells in blood]. / Wplyw wielokrotnego uzycia dializatorów kuprofanowych i polisulfonowych w czasie hemodializy na liczbe naturalnych komórek cytotoksycznych we krwi.

UNLABELLED: The aim of the study was to compare the effect of hemodialysis with the reused cuprophane and polysulfone dialyzers and bicarbonate dialysis on the count of natural killer cells in the peripheral blood in patients with chronic renal failure during the hour of haemodialysis. The study was performed in 16 patients with chronic renal failure just before haemodialysis (0') as well as 15 and 60 minutes after the beginning of haemodialysis with the first and the fourth use of membranes. The count of natural killer cells (CD3-, CD16+) in the peripheral blood was assessed using the flow cytometry. CONCLUSIONS: 1) The count of natural killer cells (CD3-, CD16+) decreased transiently in the peripheral blood in observed patients during haemodialysis. 2) The use of new cuprophane membrane decreased the count of natural killer cells in peripheral blood during haemodialysis significantly more than the haemodialysis with the use of polysulfone membranes and reused cuprophane membrane. 3) The count of the natural killer cells (CD3-, CD16+) in the peripheral blood in patients with chronic renal failure assessed 15 minutes after the start of haemodialysis could be a marker of dialysis membrane hemocompatibility.

[Effects of opiate receptor blockade with naloxone on prolactin (PRL) secretion in patients with diabetes type I (IDDM) with chronic renal failure treated with hemodialysis (HD)]. / Wplyw blokady receptorów opioidowych naloksonem na wydzielanie prolaktyny (PRL) u chorych na cukrzyce typu I (IDDM) z przewlekla niewydolnoscia nerek leczonych hemodializami (HD).

The aim of the study was to answer the questions: 1) does the prolactin secretion in the TRH test (0.4 mg i.v.) differ in haemodialyzed patients with diabetes nephropathy in the end stage renal failure in comparison to haemodialyzed chronic renal failure patients with non-diabetic nephropathy and healthy subjects; 2) does the opiate receptors blockade with naloxone (2 mg i.v.) modify the prolactin secretion during the TRH test in those patients. 39 subjects were studied. The patients were divided into three groups: group I: 12 haemodialyzed patients with IDDM and diabetic nephropathy in the end stage renal failure, group II: 15 haemodialyzed chronic renal patients with non-diabetic nephropathy and the control group: 12 healthy persons. The basic prolactin secretion and area over basic value (AOBV) of the prolactin were estimated. Prolactin concentration was measured by LIA. 1) The basic prolactin secretion was significantly higher in the patients with chronic renal failure. 2) The basic prolactin secretion in IDDM patients with diabetic nephropathy in the end stage renal failure treated with haemodialysis was significantly lower than in haemodialyzed patients with chronic renal failure of non-diabetic etiology. 3) TRH and TRH with naloxone caused significant increase of prolactin secretion in all investigated groups, but the increase is significantly lower in chronic renal failure patients than in healthy subjects. 4) Naloxone decreases significantly the prolactin secretion during TRH test only in haemodialyzed patients with chronic renal failure of non-diabetic etiology.