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Objective:To evaluate the dose calculation accuracy of cone-beam CT (CBCT) image by actual measurement method.Methods:CBCT images of 60 patients in the Second Affiliated Hospital of Soochow University from September, 2021 to May, 2022 were retrospectively analyzed. CBCT images of full-fan and half-fan scanning of the head, half-fan scanning of the chest and pelvis were obtained by the Varian OBI system. Hounsfield unit - electron density (HU-ED) curves corresponding to the scanning conditions were established with CIRS electron density phantom. The radiotherapy plans were designed on the CBCT images, and the dose calculation results of the detection point were compared with the ionization chamber measurement results to analyze the dose error. Then, three-dimensional dose verification system was adopted to detect the accuracy of the CBCT image radiotherapy plans implementation process in 60 patients, and the accuracy of dose calculation was verified according to the D 99%, D mean, D 1% of target volume, D mean and D 1% of organs at risk (OAR), and the γ pass rate. Results:In point dose detection in phantom, the dose calculation errors of CBCT images in the above four scanning patterns were -1.06%±0.87%、-1.67%±0.86%, 0.91%±0.73%, -1.54%±0.90%, respectively. In dosimetric verification based on patients' CBCT image treatment plan, the mean difference of D mean, D 99%, and D 1% of planning target volume (PTV) in all scanning modes were not higher than 2%, and the D mean and D 1% differences of other OAR were not higher than 3%, except for the lens of patients in the head. The average γ values of target volume and OAR were less than 0.5 under the criteria of 3%/2 mm. Conclusions:Under the condition of correctly establishing HU-ED curves, intensity-modulated radiation therapy (IMRT) / volumetric-modulated arc therapy (VMAT) planning based on CBCT images can be employed to estimate and monitor the actual dose to target volume and OAR in adaptive radiotherapy. Full-fan scanning patterns can further improve the accuracy of dose calculation for the head of patients.
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Deterministic method is a numerical calculation method based on photon-electron coupled transport with high computational accuracy and speed, which has been widely applied in photon radiotherapy dose calculation in recent years. However, this method has been introduced into radiotherapy for only a short period of time, which has been rarely studied in China, and systematic understanding of its characteristics is still lacking. In this article, the principles of deterministic method, current development state and clinical application were reviewed, aiming to provide reference for carrying out relevant research.
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Objective:To develop and validate the accuracy of an independent dose calculation toolkit for the horizontal beamline of Shanghai Advanced Proton Therapy (SAPT) facility based on an open-source dose calculation engine.Methods:Machine data, such as absolute integral depth doses (IDDs) and lateral profiles in air were measured and lateral profiles in water were derived by Monte-Carlo simulations. The dose computation models for SAPT horizontal beamline pencil beams in water were achieved by combining machine data and dose calculation engine. The verification of the dose reconstruction toolkit included absolute dose verification and relative dose verification. The absolute dose verification is performed to mainly compare the reconstructed value and the measured value at different depths along the center axis of the beam direction of a cube plan. The relative dose verification is conducted to mainly compare the lateral profile or two-dimensional dose distribution between the measured value and the reconstructed value. Meanwhile, the precision of double-gaussian and single-gaussian lateral beam models was compared.Results:The deviations of the absolute dose between the calculated and measured values were basically within 2%. The deviations of 20%-80% penumbra between the measured and the calculated values were within 1 mm, and deviations of the full width at half height were within 2 mm. For 3 cube plans and 2 clinical cases, the two-dimensional gamma pass rates (3 mm/3%) between the measured and calculated dose distributions at the corresponding depths were greater than 95%. The double-gaussian lateral beam model was more accurate in the high dose gradient region and deeper depth.Conclusion:The precision of independent dose calculation toolkit is acceptable for clinical requirements, which can be employed to investigate other dose-related issues.
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Objective:To analyze the dosimetric differences of volumetric modulated arc therapy (VMAT) plans for lung cancer caused by different dose calculation algorithms and radiation field settings and thus to provide a reference for designing clinical VMAT plans for lung cancer.Methods:This study randomly selected 20 patients with lung cancer and divided them into four groups of VMAT plans, namely, a group adopting two fields and two arcs based on the AAA algorithm (2F2A_AAA), a group employing two fields and two arcs based on the AXB algorithm (2F2A_AXB), a group using two fields and two arcs based on the MC algorithm (2F2A_MC), and a group adopting one field and two arcs based on the MC algorithm (1F2A_MC). Then, this study evaluated the target coverage, high-dose control, dose homogeneity index (HI), conformity index (CI), and organs at risk (OARs) of the plans using different algorithms and radiation field settings.Results:The planning target volume (PTV) results of two fields combined with two arcs (2F2A) of three groups using different algorithms are as follows. 2F2A_MC achieved better results in both D1% and V 95% (the relative volume of the target volume surrounded by 95% of the prescribed dose) of planning gross target volume (PGTV) than 2F2A_AAA (D1%: t=-2.44, P=0.03; V95%:z=-2.04, P=0.04) and 2F2A_AXB (D1%: t=2.34, P=0.03; z=-3.21, P < 0.01). 2F2A_AXB outperformed 2F2A_AAA ( z=-3.66, P < 0.01) and was comparable to 2F2A_MC in terms of the CI of PGTV. Regarding OARs, 2F2A_AXB and 2F2A_MC decreased the V5 Gy of the whole lung by 0.68% ( z=-2.69, P=0.01) and 3.05% ( z=-3.52, P < 0.01), respectively compared to 2F2A_AAA. 2F2A_AXB achieved a whole-lung Dmean of 1776.44 cGy, which was superior to that of 2F2A_MC ( t=2.67, P=0.02) and 2F2A_AAA ( t=8.62, P < 0.01). Compared to 2F2A_AAA and 2F2A_MC, 2F2A_AXB decreased the V20 Gy of Body_5 mm by 1.45% ( z=-3.88, P < 0.01) and 2.01% ( z=-3.66, P < 0.01), respectively. The results of the two groups with different field settings showed that 1F2A_MC was superior to 2F2A_MC in both the CI of PTV1 and the HI of PTV2 (CI: t=2.61, P=0.02; HI: z=-2.20, P=0.03). Moreover, 1F2A_MC increased the Dmean of the whole lung by 26.29 cGy compared to 2F2A_MC ( t=2.28, P=0.04). Conclusions:Regarding the design of VMAT plans for lung cancer, the MC algorithm is suitable for the target priority and the AXB algorithm is suitable for the OAR priority. When only the MC algorithm is available, it is recommended to choose 1F2A in the case of target priority and select 2F2A in the case of OAR priority.
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Objective To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy ( SBRT ) plans, and to investigate the sensitivity of the result to three factors:interpolation of measured data, size of dose calculation grid and assessment threshold. Methods The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation ( 1. 00 mm) and non-interpolation ( 7. 62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i.e., 1. 0 mm, 2. 5 mm and 4. 0 mm were compared respectively. The threshold of dose assessment was selected as 10％, 20％ and 30％, respectively. Three criteria of γ analysis were selected: 2％/2 mm, 3％/2 mm and 3％/3 mm. Results Under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, the average γ passing rates were (86. 3±7. 3)％ and (93. 7±5. 6)％, (94. 1±4. 4)％ and(97. 7±3. 9)％, (97. 7 ±2. 2)％ and (99. 1±1. 7)％, respectively, with and without linear interpolation. Relative to the 1. 0 mm reference grid, the grids of 2. 5 mm and 4. 0 mm significantly decreased γ passing rates by 3. 8％, 1. 9％, 0. 8％ ( t=8. 41, 9. 06, 5. 30, P<0. 05) and by 6. 5％, 6. 0％, 3. 5％ ( t=-13. 76, -13. 15, -9. 80, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Relative to the 10％ reference threshold, the shresholds of 20％ and 30％ significantly decreasedγpassing rates by 2. 4％, 1. 0％, 0. 6％(t=-8. 60, -5. 86, -4. 68, P<0. 05) and by 4. 0％, 1. 7％, 0. 9％ (t=-9. 45, -6. 66, -5. 06, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Conclusions Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients.
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Objective@#To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy (SBRT) plans, and to investigate the sensitivity of the result to three factors: interpolation of measured data, size of dose calculation grid and assessment threshold.@*Methods@#The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation (1.00 mm) and non-interpolation (7.62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i. e., 1.0 mm, 2.5 mm and 4.0 mm were compared respectively. The threshold of dose assessment was selected as 10%, 20% and 30%, respectively. Three criteria of γ analysis were selected: 2%/2 mm, 3%/2 mm and 3%/3 mm.@*Results@#Under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, the average γ passing rates were (86.3±7.3)% and (93.7±5.6)%, (94.1±4.4)% and(97.7±3.9)%, (97.7 ±2.2)% and (99.1±1.7)%, respectively, with and without linear interpolation. Relative to the 1.0 mm reference grid, the grids of 2.5 mm and 4.0 mm significantly decreased γ passing rates by 3.8%, 1.9%, 0.8% (t=8.41, 9.06, 5.30, P<0.05) and by 6.5%, 6.0%, 3.5% (t=-13.76, -13.15, -9.80, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively. Relative to the 10% reference threshold, the shresholds of 20% and 30% significantly decreased γ passing rates by 2.4%, 1.0%, 0.6%(t=-8.60, -5.86, -4.68, P<0.05) and by 4.0%, 1.7%, 0.9% (t=-9.45, -6.66, -5.06, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively.@*Conclusions@#Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients.
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KylinRay-IMRT is the advanced radiotherapy treatment planning module of accurate radiotherapy system (KylinRay) aiming to provide accurate and efficient plan design platform. In this paper the system design, main functions and key technologies of KylinRay-IMRT were introduced. KylinRay-IMRT supports three dimensional conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT) and many other types of treatment plan design with function modules including patient data management, image registration and fusion, image contouring, image three dimensional reconstruction and visualization, three dimensional conformal radiotherapy planning, intensity modulated radiotherapy planning, plan evaluation and comparison, and report print. KylinRay-IMRT has been tested by the national standard YY/T 0889-2013, the results showed that the performance of KylinRay-IMRT can fully meet the standard requirements.
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Humans , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Radiotherapy, Conformal , Radiotherapy, Intensity-Modulated , Tomography, X-Ray ComputedABSTRACT
Objective To evaluate the clinical feasibility of localization CT enhanced image replacing plain CT scan image for target delineation and dose calculation.Methods Forty cases of NPC were collected and divided into two groups with different concentrations of contrast agents.The contours of planning target volume (PTV) and organs at risk (OARs) of each case were delineated in the plain scan image,and the contours of PTV and OARs were copied to the enhanced image.Two plans based on the plain scan image and the enhanced image were designed in the planning system of Eclipse.The dose distribution and OARs and MU were compared between the groups.Results No statistical differences were found in the dosimetry of PTV,OARs and MU (P＞0.05).Conclusion The image intensifier has little effect on the dose calculation of Eclipse for NPC.In the radiotherapy for NPC,the localization CT enhanced image can be used to replace the plain CT scan image for target delineation and dose calculation.
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Objective To realize independent 3D dose calculation for intensity-modulated radiotherapy (IMRT) by building a two-source beam model of medical linear accelerator combined with a collapsed-cone convolution/superposition (CCCS) algorithm.Methods Two-source beam models of medical linear accelerators (Varian and Elekta) were built to calculate the 3D dose distributions using the CCCS algorithm.Scp,percent depth dose,and off-axis dose distribution were compared with the scanning data of ion chamber to confirm the calculation model.Twelve intensity-modulated treatment plans from each accelerator (a total of 24 plans) were selected for comparison.The calculation results of treatment planning system (TPS) were independently validated,and further compared with the measurement results of detector matrix.Results The dose deviations at the center of rectangle fields were lower than 1%,the deviation between doses at the same position in the field was not higher than 1%,and the positional deviation in the penumbra region was not higher than 1 mm.Gamma analysis based on 3%/3 mm standard was used to compare the results calculated by detectors and TPS.The pass rates were higher than 90%.Conclusions The independent 3D dose calculation for IMRT based on two-source beam model combined with CCCS algorithm has been successfully set up.The comparison between regular field and IMRT plan indicates that this method and calculation model can be used for independent 3D dose calculation of clinical plan.
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Objective To divide computed tomography (CT) values into different ranges and investigate the influence of CT value division on dose calculation, and to propose a method to combine magnetic resonance imaging (MRI) with assigned CT values.Methods Ten CT images each were collected from patients with head and neck, chest, and pelvic tumors.Random sampling was performed for the CT values of main tissues or organs at the three parts, and then the mean CT value of each tissue or organ was calculated to divide the CT values into different ranges.A virtual phantom was built in the Varian Eclipse treatment planning system, and for the prescribed dose of 100 cGy, the machine output was recorded at different CT values.The influence of different CT value ranges on dose calculation was analyzed.The treatment plans of intensity-modulated radiotherapy were selected from 5 cervical cancer patients, and new CT values were assigned to the planning target volume (PTV) and organs at risk to obtain new CT images.The plans were transferred to the new CT images and compared with the results on the original CT images in terms of dosimetric parameters.Results After dividing the CT values into different ranges and verifying the results in dose calculation, the CT values corresponding to different human tissues or organs were-100 to 100 HU.The influence of CT value variation on dose calculation was within 3%.In the same treatment plan, there were small differences in dosimetric parameters between new CT images and original CT images.Dmax, Dmean, D98%, D95%, D5%, and D2% of PTV were all below 3%, and Dmax and Dmean of the bladder, rectum, small intestine, femoral head, and bone marrow were below 2%.Conclusions The influence of CT value division on dose calculation in the treatment planning for pelvic tumors is acceptable, so it can be used in combination with MRI.
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Objective To assess the feasibility for the automated treatment planning verification system Mobius3D (M3D) to perform an independent 3D dose calculation in intensity-modulated radiotherapy (IMRT) for cervical cancer.Methods Twenty patients with cervical cancer were randomly selected.With treatment planning systems (Pinnacle,Version 9.2;Eclipse,Version 13.5),all IMRT plans were divided into 7 fields to meet the dosimetric goals.The optimized plans were exported to the M3D server.The percentage differences in the volume of region of interest (ROI) and the dose calculation of target volume and organ at risk (OAR) were evaluated for the two treatment planning systems,and theγ passing rate was used to assess the accuracy of M3D calculation.Results The difference in the volume of ROI for Pinnacle 9.2 to M3D was less than that for Eclipse 13.5 to M3D,with maximum differences of 0.22％±0.69％ and 3.5％±1.89％ for Pinnacle 9.2 and Eclipse 13.5,respectively.The differences in the dose calculation of target volume and OAR for the two treatment planning systems to M3D were within ± 1％.After recalculating by M3D,the dose difference between Pinnacle 9.2 and M3D was smaller than that between Eclipse 13.5 and M3D,but the mean differences were all within ±3％.The γ passing rates for target volume and OAR were more than 95％ on average.Conclusions The method of utilizing the automated treatment planning verification system to validate the accuracy of plans is convenient.It can be used as a secondary check tool to improve accuracy in IMRT dose calculation.
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Objective To quantitatively investigate the image quality and dose calculation accuracy of megavoltage computed tomography (CT) in helical tomotherapy.Methods The megavoltage CT was used to scan the Cheese phantom,and the geometric accuracy of images,noise,image uniformity,spatial resolution,density-CT value conversion,and dose calculation accuracy were analyzed and compared with conventional kilovoltage CT.Results The geometric accuracy of megavoltage CT images was within 2 mm in three directions.The megavoltage CT was inferior to kilovoltage CT in terms of image noise,uniformity,and spatial resolution.The dose-volume histogram (DVH) in dose reconstruction based on CT images was well consistent with DVH in the kilovohage CT plan.Conclusions The megavoltage CT can obtain images with accurate geometric dimensions and has a low imaging dose and accurate dose calculation,which meets clinical requirements.
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Objective To study CT numbers correction of kilo?voltage cone?beam CT (KV?CBCT) images for dose calculation. Method Aligning the CBCT images with plan CT images, then obtain the background scatter by subtracting CT images from CBCT images. The background scatter is then processed by low?pass filter. The final CBCT images are acquired by subtracting the background scatter from the raw CBCT. KV?CBCT images of Catphan600 phantom and four patients with pelvic tumors were obtained with the linac?integrated CBCT system. The CBCT images were modified to correct the CT numbers. Finally, compare HU numbers between corrected CBCT and planning CT by paired T test. Evaluate the image quality and accuracy of dose calculation of the modified CBCT images. Results The proposed method reduces the artifacts of CBCT images significantly. The differences of CT numbers were 232 HU, 89 HU, 29 HU and 66 HU for air, fat, muscle and femoral head between CT and CBCT respectively (P= 0?? 39,0?? 66,0?? 59,1).The differences of CT numbers between CT and CBCT was reduced to within 5 HU. And the error of dose calculation with corrected CBCT images was within 2%. Conclusions The CT numbers of corrected CBCT are similar with plan CT images and dose calculations based on the modified CBCT show good agreement with plan CT.
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Objective: A correction factor was proposed to improve the accuracy of dose calculation in conventional radiotherapy when filed matching technique was used. Methods:Use the linear accelerator with independent collimator to implement semi-field irradiation under different equivalent-length field. Measure the dose and compare it with the calculation dose. Obtain a correction factor which change follow the equivalent-length through data fitting. Results:There is relationship to indicate the correction factor increase if the field area enlarge;the calculation dose will be close to the measure dose, and the accuracy will improve by correcting;Conclusion:The clinical dose of semi-field irradiation can be calculated by an equivalent square field technique , and then multiplied by the correction factor. it is a simple method to improve the accuracy of dose calculation in conventional radiotherapy by using semi-filed correction factor when filed matching technique was used.
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The dose re-calculation process using Megavoltage cone-beam CT images is inevitable process to perform the Adaptive Radiation Therapy (ART). The purpose of this study is to improve dose re-calculation accuracy using MVCBCT images by applying intensity calibration method and three dimensional rigid body transform and filtering process. The three dimensional rigid body transform and Gaussian smoothing filtering process to MVCBCT Rando phantom images was applied to reduce image orientation error and the noise of the MVCBCT images. Then, to obtain the predefined modification level for intensity calibration, the cheese phantom images from kilo-voltage CT (kV CT), MVCBCT was acquired. From these cheese phantom images, the calibration table for MVCBCT images was defined from the relationship between Hounsfield Units (HUs) of kV CT and MVCBCT images at the same electron density plugs. The intensity of MVCBCT images from Rando phantom was calibrated using the predefined modification level as discussed above to have the intensity of the kV CT images to make the two images have the same intensity range as if they were obtained from the same modality. Finally, the dose calculation using kV CT, MVCBCT with/without intensity calibration was applied using radiation treatment planning system. As a result, the percentage difference of dose distributions between dose calculation based on kVCT and MVCBCT with intensity calibration was reduced comparing to the percentage difference of dose distribution between dose calculation based on kVCT and MVCBCT without intensity calibration. For head and neck, lung images, the percentage difference between kV CT and non-calibrated MVCBCT images was 1.08%, 2.44%, respectively. In summary, our method has quantitatively improved the accuracy of dose calculation and could be a useful solution to enhance the dose calculation accuracy using MVCBCT images.
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Calibration , Cheese , Cone-Beam Computed Tomography , Electrons , Head , Lung , Neck , Noise , OrientationABSTRACT
For the determination of absorbed dose to water from a linear accelerator photon beams, it needs a exposure calibration factor Nx or air kerma calibration factor Nk of air ionization chamber. We used the exposure calibration factor Nx to find the absorbed dose calibration factors of water in a reference source through the TG-21 and TRS-277 protocol. TG-21 used for determine the absorbed dose in accuracy, but it required complex calculations including the chamber dependent factors. The authors obtained the absorbed dose calibration factor NdwCo-60 for reduce the complex calculations with unknown Ndw only with Nx or Nk calibration factor in a TM31010 (S/N 1055, 1057) ionization chambers. The results showed the uncertainty of calculated Ndw of IC-15 which was known the Nx and Ndw is within -0.6% in TG-21, but 1.0% in TRS-277. and TM31010 was compared the Ndw of SSDL to that of PSDL as shown the 0.4%, -2.8% uncertainty, respectively. The authors experimented with good agreement the calculated Ndw is reliable for cross check the discrepancy of the calibration factor with unknown that of TM31010 and IC-15 chamber.
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Air Ionization , Calibration , Particle Accelerators , Uncertainty , WaterABSTRACT
In this study, we evaluated the effect of grid size on dose calculation accuracy using 2 head & neck and 2 prostate IMRT cases and based on this study's findings, we also evaluated the efficiency of a 2D diode array detector for IMRT quality assurance. Dose distributions of four IMRT plan data were calculated at four calculation grid sizes (1.25, 2.5, 5, and 10 mm) and the calculated dose distributions were compared with measured dose distributions using 2D diode array detector. Although there was no obvious difference in pass rate of gamma analysis with 3 mm/3% acceptance criteria for the others except 10 mm grid size, we found that the pass rates of 2.5, 5 and 10 mm grid size were decreased 5%, 20% and 31.53% respectively according to the application of the fine acceptance criteria, 3 mm/3%, 2 mm/2% and 1 mm/1%. The calculation time were about 11.5 min, 4.77 min, 2.95 min, and 11.5 min at 1.25, 2.5, 5, and 10 mm, respectively and as the grid size increased to double, the calculation time decreased about one-half. The grid size effect was observed more clearly in the high gradient area than the low gradient area. In conclusion, 2.5 mm grid size is considered acceptable for most IMRT plans but at least in the high gradient area, 1.25 mm grid size is required to accurately predict the dose distribution. These results are exactly same as the precious studies' results and theory. So we confirmed that 2D array diode detector was suitable for the IMRT QA.
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Head , Neck , ProstateABSTRACT
Objective Using Eclipse and Pinnacle3 V 7.4f treatment planning sytems (TPS) for dose calculation of the CT images of simulation phantom,patients and homogeneous organization phantom,to compare the differences between the two TPS for the calculation of non-uniform organizations.Methods For the CT images of simulation phantom,patients and homogeneous organization phantom,the calculating results between the two TPS were compared,including the common used clinical indexes of V20 and V30 of the lung,D95 of the planning target volume,the doses of the ISO and eight points of interest inside ISO slice.Resuits For simulation phantom and patients,although the calculating differences of the isocenter doses between the two TPS were small,the differences of other indicators were large.For example,when using secondary collimator irradiation,the maximal D95 difference of planning target volume reached 10.17%for patients and 4.64%for simulation phantom.When using muhileaf collimator irradiation,the maximal D95 difference reached 10.74%for patients and 5.66%for simulation phantom.Sometimes the dose differences of points 1-4 at the edge of planning target volume were more than 10%.In addition,the V30 differences of the lung were large too.But for the homogeneous organization phantom,the calculating differences were small.Conclusions The calculating differences between the two TPS are less for simulation phantom than for patients,and more for simulation phantom and patients than for homogeneous organization phantom.
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Selection of the appropriate radiation quality is an important aspect of optimisation for every clinical imaging task in radiology, since it affects both image quality and patient dose. Spreadsheet calculations of attenuation and absorption have been applied to basic imaging tasks to provide an assessment of imaging performance for a selection of phosphors used in radiology systems. Contrast, which is an important component of image quality affected by radiation quality, has been assessed in terms of the contrast to noise ratio (CNR) for a variety of X-ray beams. Both CNR and patient dose fall with tube potential, and selection of the best option is a compromise that will provide an adequate level of image quality with as low a radiation dose as practicable. It is important that systems are set up to match the response of the imaging phosphor, as there are significant differences between phosphors. For example, the sensitivity of barium fluorohalides used in computed radiography declines at higher tube potentials, whereas that of gadolinium oxysulphide used in rare earth screens increases. Addition of 0.2 mm copper filters, which can reduce patient entrance surface dose by 50%, may be advantageous for many applications in radiography and fluoroscopy. The disadvantage of adding copper is that tube output levels have to be increased. Application of simple calculations of the type employed here could prove useful for investigating and assessing the implications of potential changes in X-ray beam quality prior to implementation of new techniques.
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In total body irradiation (TBI) for leukemia, we have a two methode. One is a AP (anterior-posterior) method and the other is a Lateral methode. Our hospital used lateral methode. TBI must consider about body contour, because of homogeneous dose distribution. For compensation about irregular body contour, we use compensator. For TBI treatment, we must be considered, accurate manufacture of compensator and accurate calculation of dose. We developed the automatic program for TBI. This program accomplished for compensator design and dose calculation for irregular body. This program was developed for uses to use in a windows environment using the IDL language. In this program, it use energy data for each energy: TMR, output factor, inverse square law, spoiler, field size factor. This program reduces the error to happen due to the manual. As a development of program, we could decrease the time of treatment plan and care the patient accurately.