Biological X-ray irradiator characterization for use with small animals and cells

Bruno, Alexandre Colello; Mazaro, S J; Amaral, Leonardo L.; Rego, Eduardo Magalhães; Oliveira, Harley Francisco de; Pavoni, Juliana Fernandes

doi:10.1590/1414-431x20165848

Cited by 10 publications

(10 citation statements)

References 8 publications

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“…The calculated HVLs of the 320 kVp F1, 200 kVp, and 320 kVp F2 beams based on the X‐ray spectra in Figure 3 were found to be 0.6, 1.0, and 3.6‐mm Cu, respectively. The 200 kVp beam HVL agreed with measured data 20 . It must be noted that since we did not have access to the geometry of the mirror and ionization chamber, these components were not included in the Monte Carlo model of the PXi XRAD unit, which might account for the softer beam compared to what was measured experimentally (with HVL values of 0.8–1.12 mm Cu for F1 and 3.7–4.0 mm Cu for F2) 30 .…”

Section: Discussionsupporting

confidence: 76%

Dose calculations for preclinical radiobiology experiments conducted with single‐field cabinet irradiators

et al. 2022

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Purpose To provide percentage depth dose (PDD) data along the central axis for dosimetry calculations in small‐animal radiation biology experiments performed in cabinet irradiators. The PDDs are provided as a function of source‐to‐surface distance (SSD), field size, and animal size. Methods The X‐ray tube designs for four biological cabinet irradiators, the RS2000, RT250, MultiRad350, and XRAD320, were simulated using the BEAMnrc Monte Carlo code to generate 160, 200, 250, and 320 kVp photon beams, respectively. The 320 kVp beam was simulated with two filtrations: a soft F1 aluminium filter and a hard F2 thoraeus filter made of aluminium, tin, and copper. Beams were collimated into circular fields with diameters of 0.5–10 cm at SSDs of 10–60 cm. Monte Carlo dose calculations in 1–5‐cm diameter homogeneous (soft tissue) small‐animal phantoms as well as in heterogeneous phantoms with 3‐mm diameter cylindrical lung and bone inserts (rib and cortical bone) were performed using DOSXYZnrc. The calculated depth doses in three test‐cases were estimated by applying SSD, field size, and animal size correction factors to a reference case (40‐cm SSD, 1‐cm field, and 5‐cm animal size), and these results were compared with the specifically simulated (i.e., expected) doses to assess the accuracy of this method. Dosimetry for two test‐case scenarios of 160 and 250 kVp beams (representative of end‐user beam qualities) was also performed, whereby the simulated PDDs at two different depths were compared with the results based on the interpolation from reference data. Results The depth doses for three test‐cases calculated at 200, 320 kVp F1, and 320 kVp F2 with half value layers (HVLs) ranging from ∼0.6 to 3.6 mm Cu, agreed well with the expected doses, yielding dose differences of 1.2%, 0.1%, and 1.0%, respectively. The two end‐user test‐cases for 160 and 250 kVp beams with respective HVLs of ∼0.8 and 1.8 mm Cu yielded dose differences of 1.4% and 3.2% between the simulated and the interpolated PDDs. The dose increase at the bone‐tissue proximal interface ranged from 1.2 to 2.5 times the dose in soft tissue for rib and 1.3 to 3.7 times for cortical bone. The dose drop‐off at 1‐cm depth beyond the bone ranged from 1.3% to 6.0% for rib and 3.2% to 11.7% for cortical bone. No drastic dose perturbations occurred in the presence of lung, with lung‐tissue interface dose of >99% of soft tissue dose and <3% dose increase at 1‐cm depth beyond lung. Conclusions The developed dose estimation method can be used to translate the measured dose at a point to dose at any depth in small‐animal phantoms, making it feasible for preclinical calculation of dose distributions in animals irradiated with cabinet‐style irradiators. The dosimetric impact of bone must be accurately quantified as dramatic dose perturbations at and beyond the bone interfaces can occur due to the relative importance of the photoelectric effect at kilovoltage energies. These results will help improve dosimetric accuracy in preclinical experiments.

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Section: Discussionsupporting

confidence: 76%

Dose calculations for preclinical radiobiology experiments conducted with single‐field cabinet irradiators

et al. 2022

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“…Filament heating uses a filament driver circuit, as illustrated in Figure 4, to authorize the current command in a step or gradient method to heat the filament [6][7][8][9]. However, as indicated in Equations ( 4), ( 5) and ( 8)- (11), the filament properties based on the temperature and variations in temperature exhibit a non-linear relationship with the input current. Therefore, the current and voltage command values are tuned according to the desired dose rate based on the experience of the medical personnel in terms of the conventional method.…”

Section: Conventional Methodsmentioning

confidence: 99%

“…Hence, it is difficult to configure a closed-loop control considering the directly measured temperature value. To solve this problem, the temperature of the tungsten filament was derived as indicated in Equation (11), considering the change in resistivity based on the tungsten filament temperatures listed in Table 1 [20]. The temperature of the current filament is indirectly estimated in Equation ( 11) by substituting the electrical resistivity value calculated in the digital signal processor (DSP) [21].…”

Section: Proposed Methodsmentioning

confidence: 99%

“…To validate the effectiveness of the proposed approach in comparison with that of the existing filament heating method, a comparative analysis was performed experimentally based on the changes in the dose rate and filament temperature over time. To compare the dose rate emitted by the X-ray tube, we measured the tube current, which is proportional to the dose rate [11]. Additionally, the filament temperature was observed over an empirical period that is suitable for the experimental conditions to verify that the emitted dose rate can be maintained constant by regulating the filament temperature.…”

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confidence: 99%

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Filament X-ray Tube Current Control Method Using Indirect Filament Temperature Estimation

2021

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The recent increase in ailments has increased the demand for diagnosis and surgery based on X-rays. An X-ray system using a filament-type tube heats the filament for operation, and the electrons emitted by the thermal energy during this process produce X-rays. Conventionally, current control-based methods are used to regulate heating. However, these methods do not control the temperature of the filament, resulting in lower or higher output than the desired dose rate. Therefore, we propose a filament temperature control method that enables constant temperature control, which cannot be achieved using the existing heating method for X-ray systems with filament tubes. Additionally, we developed an indirect temperature estimation algorithm for the tungsten filament to incorporate the proposed method. To validate the tube current control through temperature control, we performed experiments to compare the existing current-controlled heating and temperature control methods in terms of the filament temperature. As the tube current is proportional to the dose rate, it was measured through a comparative analysis of the change in the output of dose rate over time. The obtained results validate that the proposed method can maintain both the filament temperature and tube current at the desired level.

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“…A dosimetry of this unity is frequently accomplished to check the delivered doses. At the time of the irradiations, the dose rate was 1.27 ± 0.06 Gy/min in air [ 34 ].…”

Section: Methodsmentioning

confidence: 99%

Electron spin resonance (ESR) dose measurement in bone of Hiroshima A-bomb victim

2018

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Explosion of the bombs in Hiroshima and Nagasaki corresponds to the only historical moment when atomic bombs were used against civilians. This event triggered countless investigations into the effects and dosimetry of ionizing radiation. However, none of the investigations has used the victims’ bones as dosimeter. Here, we assess samples of bones obtained from fatal victims of the explosion by Electron Spin Resonance (ESR). In 1973, one of the authors of the present study (SM) traveled to Japan and conducted a preliminary experiment on the victims’ bone samples. The idea was to use the paramagnetism induced in bone after irradiation to measure the radiation dose. Technological advances involved in the construction of spectrometers, better knowledge of the paramagnetic center, and improvement in signal processing techniques have allowed us to resume the investigation. We obtained a reconstructed dose of 9.46 ± 3.4 Gy from the jawbone, which was compatible with the dose distribution in different locations as measured in non-biological materials such as wall bricks and roof tiles.

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Biological X-ray irradiator characterization for use with small animals and cells

Cited by 10 publications

References 8 publications

Dose calculations for preclinical radiobiology experiments conducted with single‐field cabinet irradiators

Dose calculations for preclinical radiobiology experiments conducted with single‐field cabinet irradiators

Filament X-ray Tube Current Control Method Using Indirect Filament Temperature Estimation

Electron spin resonance (ESR) dose measurement in bone of Hiroshima A-bomb victim

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