In-phantom dosimetry using CaF2: Tm (TLD-300) ribbons

Parameters of calibrating CaF₂ : Tm for in-phantom dosimetry of therapeutically used fast neutron and ⁶⁰Co γ-ray beams have been studied. For ⁶⁰Co γ-ray beams the over-response, outside the main beam and at depths in phantom for large fields of irradiations is significant, and is higher for its 240°C glow peak than for its 150°C peak. The difference in the photon energy dependences of the two peaks of CaF₂ : Tm (Z_eff = 16.3), which is responsible for the above effect, is discussed. For therapeutically used cyclotron-produced fast neutron beams, the γ-ray absorbed dose component from photons of energy less than 200 keV is negligible.     

Digital recording of glow curves of the TLD-300 thermoluminescent dosimetry detector by adaptation of a sum of Gauss function to the measured values

Calciumfluoride doped with Thulium (TLD-300) can be used to measure simultaneously with one detector neutron and photon absorbed dose in mixed neutron-photon beams. The accuracy in dose measurements can be increased by use of a computer. Additionally the number of data needed to store a glow curve can be reduced from 240 to 24 by fitting a sum of Gauss functions to the measured glow curve.     

Clinical dosimetric properties of the TLD-300 thermoluminescent dosimetry detector and its use for measuring spatial dose distribution in patient radiation planning

Thermoluminescence dosimetry is often used to verify the calculation of dose distribution of treatment techniques and treatment planning by using a phantom. However, a quality assurance of therapy by comparison between treatment planning and actual dose values measured with TL-detectors on the patient, is only sporadically realized. The use of a single detector offers a solution for the measurement of both the neutron and gamma ray absorbed doses in mixed neutron-photon fields in fast neutron tumour therapy. The knowledge of both gamma ray and neutron absorbed doses is important because of the considerable difference in biological efficiency of these two types of radiation.     

Further studies on the annealing procedure for TLD-300

This paper concerns the same experiments as those carried out to find the effect of various annealing procedures on the TL response of TLD-300. Different heating and cooling rates have been tried, and the effect of different atmospheres during annealing time has been tested.     

High-resolution gel dosimetry using flat-panel detector cone-beam computed tomography: Preliminary study

This study compares the dose response of irradiated polymer gel with acrylic and styrofoam housing while applying multi-detector CT (MDCT) and cone-beam CT (CBCT). The dose response for MDCT and CBCT, while using an acrylic phantom is 1.34 and 0.67 ΔHU Gy^?1, respectively, and becomes 1.54 and 0.84 ΔHU Gy^?1 while using styrofoam, suggesting styrofoam is the better housing material. While the dose response of MDCT is better than that of CBCT, CBCT is yet a promising 3D dosimetry technique, given its potentially better spatial resolution and sensitive dose interpretation capability.     

Reusability and Fractional read-out in CaF2:Tm (TLD-300)

The first part of this paper is concerned with the reusability of CaF₂:Tm (TLD-300) ribbon without thermal treatment between read-out and irradiation. It has been checked up to a dose level of about 200 mGy and the results show that it is possible to reuse this material without annealing in the used dose range. In the second part of the paper a fractional method of TL readings is outlined. The peak separation is checked at different linear testing rates and with different reading times for each peak. The separation technique is then checked in a dose accumulation experiment.     

Study of the body's reactivity using pharmacological tests

Variations in the excretion of catecholamines (adrenalin, noradrenalin, dopamine and DOPA precursor) were studied in 34 test subjects who had undergone two drug tests at a two day interval: an insulin test at a dose of 0.15 Units/kg body weight and dopavein test at a dose of 800 microgram/day. In most cases these drugs caused an adequate response of the sympathoadrenal system which included its increased activity and reflected nonspecific reactions. It is concluded that a high (or an adequate) relative activity of the sympathoadrenal system during these tests is more favorable in terms of prediction of reactions of the body in harsh environments than a decreased activity of the sympatho-adrenal system, especially when it is combined with low background values of catecholamine excretion.     

Confirmation of needle cricothyroidotomy using an esophageal detector device in a porcine model

The difficult intubation is one of the most trying situations encountered in airway management. Transtracheal jet ventilation via needle cricothyroidotomy can provide temporary oxygenation in this critical situation in a minimally invasive fashion. The esophageal detector device (EDD) has been previously shown to be effective in determining the tracheal placement of endotracheal tubes. In this experiment, three commonly available EDDs are utilized to accurately identify 15 of 15 intratracheal placements of a 16-gauge i.v. catheter in five cadaveric domestic swine. The incorporation of EDDs in i.v. catheter placement for needle cricothyroidotomy is shown to be effective and merits further study. Likewise, further investigation is needed to identify a standardized apparatus for needle cricothyroidotomy in emergent situations.     

Annealing cycle effects on the TL sensitivity of CaF2 : Tm (TLD-300)

Several thermal procedures have been studied to obtain the highest sensitivity with the lowest standard deviation. A thermal annealing at 400°C for 2 h has been found to be the best. It seems, however, that different thermal procedures suggested by other workers could be attributed to the different heating and cooling rates in the annealing procedures themselves.     

金刚石探测器在Flash照射实时剂量测量中的应用

目的通过实验探究人工金刚石探测器用于Flash照射剂量测量的可行性。方法采用CIVIDEC? B1HV金刚石探头, 设计了基于预积分方法的大动态范围电流测量电路, 研制了一款实时输出脉冲电流的金刚石探测器样机, 分别在电子束和X射线超高剂量率照射下测试其剂量和剂量率响应, 并使用医用加速器对该金刚石探测器进行剂量标定。结果电子束0.08 ～ 0.50 Gy/pulse范围内探测器输出积分电荷与参考脉冲剂量呈现较好的线性相关(R2 = 0.99), 在电子束超高平均剂量率(400 Gy/s)和常规平均剂量率(0.3 Gy/s)照射模式下, 剂量线性响应较好(R2 = 0.99), 在X射线超高平均剂量率(75.5 Gy/s)和常规平均剂量率(0.5 Gy/s)照射模式下探测器输出积分电荷和参考剂量达到严格线性相关(R2 = 1), 获得电荷(电流)-剂量(率)实用转换系数0.751 7 μC/Gy和0.753 5 μA·Gy·s-1。结论该金刚石探测器在电子和X射线超高剂量率束流照射下均体现了较好的剂量线性响应, 能够为Flash预临床实验提供较快速、准确的剂量监测, 有潜力用于未来Fl...     

Investigations on TDCR measurements with the HIDEX 300 SL using a free parameter model

The Triple to Double Coincidence Ratio (TDCR) method requires a special counting system with three photodetectors. The systems currently used by National Metrology Institutes for activity standardizations are custom built, and up to now the HIDEX 300 SL counter is the only TDCR counter commercially available. At PTB, measurements with a special metrology version of this counter were carried out to investigate its applicability for activity standardizations. The activity results of measurements with the HIDEX counter are compared to those obtained with a PTB-TDCR counter, as such a comparison reduces the model dependence. In addition, a spectrometry method was applied to measure (109)Cd samples and a new TDCR-?erenkov method was tested with (32)P samples.     

Radiation dosimetry in tomography of the teeth and jaws using a multi-film cassette

The absorbed doses and energy imparted in lateral and antero-posterior tomography of the teeth and jaws were measured. A multi-film cassette with 5 films was exposed using a diameter of the circular collimator of 1.5 cm. With one exception, the absorbed doses were below 1 mGy. The parotid gland towards the roentgen tube received about 2 mGy in lateral tomography of the mandibular third molar. The energy imparted in lateral tomography was 0.6 mJ and in antero-posterior tomography about 2.5 mJ. Since the radiation doses in tomography of the teeth and jaws were low compared with estimated risk levels, they should not deter from using tomography.     

Additivity of fast neutron and gamma ray induced thermoluminescence and reusability of CaF2:TLD-300 ribbons

TL response of CaF2:Tm to fast neutrons and gamma rays is found to be additive. No significant change in the response is observed for a number of irradiation, anneal and readout cycles. Problems associated with mixed field dosimetry are discussed.     

Clinical dosimetry in xeromammography using the low dose system

The results obtained by utilizing low-dose plates in xeromammography are reported. Phantom experimental examinations and dosimetric measurements were made before using these plates. The new exposition data were then compared to those obtained with the old plates. Findings prove low-dose plates to be more sensitive--thus granting very good iconographic results with reduction of skin dose (about 30%) at FFD of 110 cm. The skin dose has been compared to that obtained with the most modern mammographs.