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Dose profile measurements during respiratory-gated lung stereotactic radiotherapy: A phantom study
- Introduction
- Materials and methods
- Results and discussions
- Conclusion
A detailed description of the BrainLAB Exactrac gating system can be found in Tenn et al. Five infrared (IR) markers were used as surrogates on the respiratory motion tracking phantom for gated radiation delivery. Radiation was delivered only during the expiratory phase within the port window. a) BrainLAB ET gating phantom and (b) respiratory and tumor motion as a sinusoidal function.
The dashed line shows the gate level and the solid line shows the upper and lower levels (20% gate window) of the gate window (area bracket). The accuracy of closed-gate radiation delivery was studied by evaluating the displacement of the fiducial marker projection on the film (shown as a "dip" in the dose profiles). The position of the lower dose projection of the fiducial marker was considered as the center of the target.
The center of the Perspex phantom was marked on the Gafchromic EBT2 films before irradiation to allow better accuracy in comparison. The respiratory-controlled dose profiles for different amplitudes of tumor motion were in good agreement with the delivery of static radiation. Figure 2(b) shows the dose profiles with different gate windows, and Figure 2(c) shows the dose profiles with different respiration times per cycle.
There were no significant differences in occluded radiation delivery at different breathing times per cycle. Figure 2(d) shows unsupervised radiation dose delivery while the tumor moves, simulating free-breathing SBRT without transition. Dose profiles during closed radiation delivery with different (a) breathing/target motion amplitude, (b) shutter windows, (c) breathing cycle time, and (d) independent radiation delivery with a moving target.
The 'dip' in the center of the dose profiles was caused by the shadowing effect of the fiducial marker. Measured displacements of reference marker during respiration-guided radiation delivery to the static radiation delivery. 10] Willoughby TR, Forbes A R, Buchholz D, Langen KM, Wagner TH, Zeidan OA, Kupelian P A and Meeks S L 2006 Evaluation of an infrared camera and x-ray system using implanted fiducials in patients with lung tumors for gated radiotherapy Int J Radiat Oncol Biol Phys 66 568-75.
Establishing daily quality control (QC) in screen-film
- Methodology
- Results
- Discussion
- Conclusion
Also, other measurable details in the phantom are evaluated separately against the limiting criteria provided in the user manual. The attenuator racks used in the AEC endurance test and the Leeds chest phantom exposure are 22 cm diameter semi-circular acrylic plates. The test forms available in the IAEA manual and the Leeds user manual were used for data recording.
To aid in the visualization of these test details, a 9x magnification lens available with the phantom kit is used. Tables 1 and 2 show the results of the mAs output, the film density measurements, and the evaluation of film frames over a six-day period for baseline values. Tables 3 and 4 present the observed range of measured and calculated data, as well as the results of the evaluation of the image quality parameters within the 40-day period.
The baseline output from the exposure of the 45 mm Leeds phantom was observed to be lower by 12.6 mAs compared to the baseline output from the exposure of the routine 45 mm acrylic plates (see Table 1). This may be due to the presence of test objects embedded in the test plate. The resolution limit of the screen-film combination was observed to consistently demonstrate the maximum number of lines per frame. millimeters (lp/mm) under a 9x magnifying lens.
Over the 40-day assessment, mAs output data was within ±10% of baseline mAs and mean background ODs within the ±0.2 tolerance specified in the IAEA protocol for AEC constancy. In addition, the sensitometry data met the minimum B+F, velocity index, and contrast index tolerances specified in the IAEA protocol. The results of the evaluation of the image quality parameters were consistent with the base scores.
Measurements from the use of the phantom were consistent with those of the measurements obtained from the separate tests on AEC constancy and light sensitometry. Results of the evaluation of the image quality parameters were observed to demonstrate consistency with the baseline scores. Monte Carlo simulation of the Tomotherapy treatment unit in the static mode using MC HAMMER, a Monte Carlo tool dedicated to Tomotherapy.
Helical tomotherapy optimized planning parameters for nasopharyngeal cancer
Material and methods
For each patient data set, three planning target volumes (PTV) were defined as PTV70, PTV59.4, and PTV54. For each patient data set, 18 treatment plans were created with different combinations of treatment planning parameters FW=1.0, 2.5, and 5.0 cm. The maximum and minimum penalty for PTV were changed for 250 iterations until the dose for PTV met ICRU83 recommendations.
All plans were evaluated using the 50% dose of both parotid gland volume (D50) and treatment times. The statistical result of both parotid glands D50 and treatment times were analyzed using SPSS statistics version 17.0. The student paired t-test was used to compare treatment times and the Wilcoxon test was performed to compare D50 of both parotid glands.
The mean D50 of both parotid glands for all patients is determined by combinations of different treatment planning parameters. Figure 1 shows the mean D50 of both parotid glands for all patients, the data set with the combination of different treatment planning parameters, a total of 108 treatment plans were generated. But the average D50 of both parotid glands is lowest when FW=1.0 cm was used to combine with other optimization parameters.
Figure 2 shows the mean D50 of all parotid glands of the patient with the different optimization parameters. FW demonstrates the main effect on D50 of parotid glands compared to PF and MF. Finally increasing the MF from 2.0 to 3.0 the mean treatment time increased significantly by about 3 minutes.
Mean treatment times per fraction for all patient datasets with different combinations of treatment planning parameters.
Discussions
Our study, the FW had a greater effect on D50 of both parotid glands than PF and MF was in agreement with Skorska M et al. The PF parameter was less effect on treatment time than FW and MF which is consistent with Woch et al. The last optimization parameter, when the MF is increased from 2.0 to 3.0, the average treatment time is increased by 22.28%.
They found that treatment plan with the MF value below 3.0, the treatment time was not shortened.
Conclusions
Automated calculation and analysis of impacts caused by anvil blocks of complex geometry in a mining machine IA Zhukov, AA Repin and EG Timofeev. Comparison of Central, Peripheral, and Size-Specific Weighted Dose in CT Choirul Anam et al. Fully automated calculation of size-specific dose estimates (SSDE) for chest and head CT scans.
A fully automated calculation of size-specific dose estimates (SSDE) in thoracic and head CT examinations
Method
The algorithm used a combination of basic segmentation techniques and specific information about the border of the patient body [13]. However, thresholding alone was unable to accurately contour the patient due to the presence of objects within the patient with HU values lower than -200. The second step was the determination of the diameters in the anterior-posterior (AP) and lateral (LAT) directions.
And the last step was to calculate the effective diameter from the root of the product of AP and LAT dimensions. The results of the automated design were used to crop the original images, and the area of the cropped image and the patient's average HU value were calculated. The relationship between Deff and DW in chest CT examinations is shown in Figure 1a.
On average, the DW value in the thoracic region is 4.5%. less than the value of Def. The relationship between Deff and DW in the head CT examinations is shown in Figure 1b. the value in the main region is on average 8.6% greater than the value of Def. one). This is most likely due to the exponential nature of the conversion factor (f), whose value decreases with increasing diameters (Deff and DW).
Deff and CTDIvol, (b) DW and SSDE; and DW and CTDIvol for thoracic examinations. a) Relationship between Deff and SSDE; and Deff and CTDIvol, (b) DW and SSDE; and DW. On the other hand, Fig. 1b shows that in head scans, the DW value. Because DW does not only take into account patient diameter, but also patient composition, DW.
In contrast, in a non-TCM technique, CTDIvol is constant with decreasing or increasing diameters (Deff and DW), because the tube current is constant and independent of patient diameter. For the pivotal studies, Figure 3a shows that while CTDIvol is constant with increasing Deff, SSDE decreases with increasing Deff. When examining the head, the radiation dose (SSDE) increases with a decrease in patient diameter, if TCM is not activated.
