Rando Phantom Research Articles

Efficiency of non-lead and lead thyroid shields in radiation protection of CT examinations

BackgroundThyroid dose reduction during brain CT scan procedures, using protective lead clothing such as lead thyroid collars were approved in the last decades. Recently, investigators have focused on applying and designing light and non-toxic shields that contain no lead. ObjectiveThis study aimed to compare the efficiency of non-lead and lead thyroid shields in radiation protection during brain CT scans based on Monte Carlo (MC) simulation and experimental measurements. MethodsThis study was performed in two steps. The first step was the MC simulation of a different combination of shielding materials to assess the efficiency of X-ray attenuation in these shields. The second step was the construction and testing of the shield, which was more efficient in MC calculation as a thyroid shield in brain CT scan. The absorbed dose of a Rando phantom thyroid was determined by both non-lead and lead shields as thyroid protectors. The thyroid radiation dose was measured with and without the usage of radiation shields. The percentage difference between the dose in the presence of the shield and without the shield was calculated. ResultThe percentage difference of the surface radiation doses on thyroid location with non-lead (combination of 45% Tungsten- 55% Tin) and lead shields in comparison to without application of the radiation shield were 35.88% and 20.73, respectively. The dose reduction at the depth of the thyroid was 39.79% and 21.49% applying non-lead and lead shields, respectively. ConclusionAccording to the results, the use of non-lead shield can reduce the absorbed dose of thyroid more efficiently than the lead shields.

Modified Technique for the Visualization of C6/C7 in Lateral Cervical Spine Radiography

Introduction: In the Swimmer’s view, the C6 and C7 can be visualized as superimposed on the shoulders. This study aimed to explore the technique to demonstrate C1 to C7 in the lateral spine and improve the diagnostic value in that region. Material and Methods: An experimental study was carried out using a RANDO phantom to obtain images of the lateral cervical spine. Twelve radiographs were taken using different kVps at different centering points. The image quality of the radiographs was evaluated by two radiographers using the modified image quality criteria score sheet adapted from the Commission of European Communities on image quality. A dose area product meter was utilized to estimate the entrance surface dose (ESD); however, CALDose_X5 Monte Carlo software was used to estimate the effective dose. Results: The findings indicated that a higher centering point at 2 inches above the pinna of the ear can clearly visualize the lower cervical spine (C6/C7) and cervicothoracic junction (C7/T1). The results of the Kruskal-Wallis test revealed significant differences (p 0.05) in the ESD between different utilized centering points. The effective dose of the modified technique was reported to be lower, compared to that for the Swimmer’s view. Conclusion: The modified lateral technique can be used to replace the Swimmer’s view to adequately demonstrate the lower cervical spine and cervicothoracic junction with a lower radiation dose while not harming the patient due to movement during positioning.

Combined Use of a Transmission Detector and an EPID-Based In Vivo Dose Monitoring System in External Beam Whole Breast Irradiation: A Study with an Anthropomorphic Female Phantom

We evaluate the combined usage of two systems, the Integral Quality Monitor (IQM) transmission detector and SoftDiso software, for in vivo dose monitoring by simultaneous detection of delivery and patient setup errors in whole breast irradiation. An Alderson RANDO phantom was adapted with silicon breast prostheses to mimic the female anatomy. Plans with simulated delivery errors were created from a reference left breast plan, and patient setup errors were simulated by moving the phantom. Deviations from reference values recorded by both monitoring systems were measured for all plans and phantom positions. A 2D global gamma analysis was performed in SoftDiso for all phantom displacements. Both IQM signals and SoftDiso R-values are sensitive to small MU variations. However, only IQM is sensitive to jaw position variations. Conversely, IQM is unable to detect patient positioning errors, and the R-value has good sensitivity to phantom displacements. A gamma comparison analysis allows one to determine alert thresholds to detect phantom shifts or relatively large rotations. The combined use of the IQM and SoftDiso allows for fast identification of both delivery and setup errors and substantially reduces the impact of error identification and correction on the treatment workflow.

Investigation of 3D-Conformal and Intensity-Modulated Therapy Techniques to Determine the Absorbed Fetal Dose in Patients With Nasopharyngeal Cancer During Pregnancy

The aim of this research was to investigate the fetal doses of pregnant patients undergoing conformal radiotherapy or intensity-modulated radiation therapy (IMRT) for nasopharyngeal cancers at various times during pregnancy. In this work, the head and neck cancer treatment of a pregnant patient was experimentally simulated. Two treatment plans were calculated using a female RANDO anthropomorphic phantom. This phantom was irradiated using the Clinac DHX linear accelerator, according to the Standard treatment plans of both three-dimensional conformal radiation therapy (3-DCRT) and IMRT techniques. During pregnancy, the height of the fundus at different weeks was determined and a sign was placed on the phantom. OSLD (optically stimulated luminescence dosimeter) and MOSFET (Metal oxide semiconductor field effect transistor) dosimeters were used to measure the dose of virtually designated uterus area at various times during pregnancy. The data carried out by TPS were compared with measured data. PBC calculation method in the treatment planning system (TPS) was unable to estimate the peripheral doses in uterus area. TPS showed a dose of 0 cGy at many points. On the contrary, OSLD measurement results revealed that the uterus (fetus) doses were ranging from 14.46–43.05 cGy (mean 27.9 ± 10.1 cGy) for 7-field IMRT treatment plan and 6,12–27,3 cGy (mean 14,7 ± 7,97 cGy) for 3-DCRT in Alderson anthropomorphic female RANDO phantom. MOSFET measurements showed that the uterus (fetus) doses were ranging from 15–50.1 cGy (mean 36.25 ± 11.7 cGy) for 7-field IMRT treatment plan and 10–36.3 cGy (mean 21.3 ± 9.54 cGy) for 3-DCRT treatment plan. All the observed fetal dose for the measurements and TPS data for two techniques are given in the Table below. In summary, comparing two techniques, it is clear that IMRT causes higher fetal radiation dose than 3-D CRT due to its higher MU value. Considering that fetal radiogenic effects are seen at 5-10 cGy (American Association of Physicists in Medicine Radiation Therapy Committee Task Group 36), 3-D CRT is a more reliable method. The TPS is unable to estimate peripheral doses accurately. Since the TPS underestimates the fetal dose, relying on the dose calculated by TPS does not seem possible under the current circumstances. The fetal dose from radiotherapy may vary depending on the gestational age at the time of treatment. The use of special shielding devices can considerably reduce the fetal dose from radiation therapy.Tabled 1Abstract 2597; TableIMRT3DMOSFETOSLDTPSMOSFETOSLDTPS12weeks15 cGy14.46cGy0.0cGy12weeks10cGy6.12cGy0.0cGy16 weeks32.2cGy22cGy0.0cGy16 weeks12.3cGy8.68cGy0.0cGy20-22 weeks32.55cGy23.1 cGy0.7cGy20-22 weeks15.6cGy10.5cGy0.0cGy24-26 weeks36.5 cGy25.69 cGy0.7cGy24-26 weeks21.5cGy12.25cGy0.0cGy28 weeks39.6 cGy27.09 cGy11cGy28 weeks23.4cGy14.03cGy0.0cGy36 weeks50.1 cGy43.05 cGy15cGy36 weeks36.3cGy27.3cGy9.7cGy40 weeks47.8 cGy40.01cGy11.6cGy40 weeks30cGy24.1cGy9.7cGy Open table in a new tab

Estimated radiation doses to ovarian and uterine organs in breast cancer irradiation using radio-photoluminescent glass dosimeters (RPLDs).

IntroductionThe well‐being of breast cancer patients is essential, especially fertility in patients of reproductive age. The objective of this study was to estimate the radiation doses to the ovaries and uterus for different treatment techniques of breast cancer irradiation using radio‐photoluminescent glass dosimeters (RPLDs).MethodsA Farmer‐type ionisation chamber (IBA FC‐65G) and RPLDs were used to measure in‐ and out‐of‐field radiation doses in a solid water phantom. The field sizes were set to 10 × 10 cm2 and 8 × 17 cm2 with the central axis at out‐of‐field measurement distances of 30 or 50 cm. The Rando phantom’s left breast was planned using four different techniques: two tangential standard fields with and without electronic tissue compensator (E‐comp) techniques, intensity‐modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). The radiation doses in the ipsilateral ovary, contralateral ovary and uterus were measured using RPLDs.ResultsThe percentage ratio of out of field to in field was affected by distance from the central axis to the point of measurement, in addition to the field sizes associated with collimator scatter. Advanced techniques such as IMRT and VMAT produced higher doses to the ovaries and uterus. The estimated results of the worst‐case scenario for the ipsilateral ovary, contralateral ovary and uterus were 0.84% (42 cGy), 0.62% (31 cGy) and 0.76% (38 cGy), respectively, for a 5000 cGy prescription dose.ConclusionThe lowest to highest out‐of‐field radiation doses to the ovarian and uterine organs from breast irradiation were the two tangential field techniques, VMAT and IMRT. These advanced techniques yielded higher radiation leakage, which potentially contributed to the out‐of‐field radiation dose.

Optimization of paranasal sinus CT procedure: Ultra-low dose CT as a roadmap for pre-functional endoscopic sinus surgery.

To assess image quality and radiation dose associated with ultra-low dose CT protocol for patients with benign paranasal sinus diseases undergoing functional endoscopic surgery (FESS). We scanned the head portion of Alderson RANDO phantom on a second generation, dual-source, multidetector-row CT scanner (Siemens Definition Flash) using standard-dose and five low-dose protocols. Two radiologists assessed the image quality for each protocol to determine best ultra-low-dose protocols for imaging patients with benign paranasal sinus diseases undergoing FESS. The ultra-low-dose CT protocols were then used for scanning. Thereafter, 40 adult patients (age range 18-54years, M:F 23:17) were scanned with the four low dose scanning protocols (10 patients per protocol). On both transverse and coronal reformatted CT images, two radiologists assessed visibility of key anatomic landmarks for FESS on a 2-point scale (1=clear and complete visualization; 2=suboptimal visualization). Data were analyzed with descriptive statistics and Cohen's kappa coefficient for interobserver agreement. In phantom study, the lowest dose scan protocol (CTDIvol 2.1mGy, 70kV, 75 mAs) was unacceptable due to poor image quality. For patient studies, both radiologists gave acceptable image quality scores for ultra-low-dose scan protocol with axial scan mode, automatic tube potential selection and tube current modulation (CTDIvol 2.2mGy; DLP 22.9mGy.cm) with up to 60% lower dose compared to prior standard-dose CT (CTDIvol 5.3mGy; DLP 73.5mGy.cm). Ultra-low-dose CT protocol provides sufficient image quality for scanning patients undergoing functional endoscopic surgery for benign paranasal sinus diseases.

Commissioning of total body irradiation using plastic bead bags.

The goal of total body irradiation (TBI) is to deliver a dose to the whole body with uniformity within ±10%. The purpose of this study was to establish the technique of TBI using plastic bead bags. A lifting TBI bed, Model ORP-TBI-MN, was used. The space between the patient’s body and the acrylic walls of the bed was filled with polyacetal bead bags. Patients were irradiated by a 10 MV photon beam with a source to mid-plane distance of 400 cm. The monitor unit (MU) was calculated by dose-per-MU, tissue-phantom-ratio and a spoiler factor measured in solid water using an ionization chamber. The phantom-scatter correction factor, off-center ratio and the effective density of the beads were also measured. Diode detectors were used for in vivo dosimetry (IVD). The effective density of the beads was 0.90 ± 0.09. The point doses calculated in an I’mRT phantom with and without heterogeneity material showed good agreement, with measurements within 3%. An end-to-end test was performed using a RANDO phantom. The mean ± SD (range) of the differences between the calculated and IVD-measured mid-plane doses was 1.1 ± 4.8% (−5.9 to 5.0%). The differences between the IVD-measured doses and the doses calculated with Acuros XB of the Eclipse treatment planning system (TPS) were within 5%. For two patients treated with this method, the differences between the calculated and IVD-measured doses were within ±6% when excluding the chest region. We have established the technique of TBI using plastic bead bags. The TPS may be useful to roughly estimate patient dose.

Does dose optimisation in digital panoramic radiography affect diagnostic performance?

To compare the overall diagnostic performance of digital panoramic radiographs obtained with low-dose protocols and to estimate the absorbed dose in the head and neck. Forty-eight panoramic radiographs were obtained from eight imaging phantoms using six exposure protocols of progressively lower tube voltages (kVp) and currents (mA), as follows: (1) 70 kVp and 12.5 mA, (2) 66 kVp and 10 mA, (3) 66 kVp and 8 mA, (4) 66 kVp and 5 mA, (5) 66 kVp and 4 mA and (6) 66 kVp and 3.2 mA. Five oral radiologists independently evaluated the images and reported all detectable radiographic findings. Intra-examiner reproducibility was assessed by re-evaluation of 25% of the images. The data were analysed using the McNemar and weighted Kappa tests. Absorbed doses of the six protocols were obtained from thermoluminescent dosimeters placed inside a Rando phantom and compared using one-way ANOVA with post hoc Tukey (α = 0.05). The overall diagnostic performance of panoramic radiographs obtained with low-dose protocols did not differ from that of panoramic radiographs obtained with the highest dose (p > 0.05). Moreover, substantial agreement was observed between all protocols. Protocol 1 resulted in the highest absorbed dose and protocols 4, 5 and 6 in the lowest absorbed doses, with the difference being significant (p ≤ 0.05). Although digital panoramic radiography is considered a relatively low-dose examination, the radiation dose can be further reduced without negatively affecting its overall diagnostic performance. Considering the risks associated with X-rays, digital panoramic radiographs can be obtained at even lower exposure levels.

A collision prediction framework for noncoplanar radiotherapy planning and delivery.

PurposeNoncoplanar radiotherapy can provide significant dosimetric benefits. However, clinical implementation of such techniques is not fully realized, partially due to the absence of a collision prediction tool integrated into the clinical workflow. In this work, the feasibility of developing a collision prediction system (CPS) suitable for integration into clinical practice has been investigated.MethodsThe CPS is based on a geometric model of the Linear Accelerator (Linac), and patient morphology acquired at the simulator using a combination of the planning CT scan and 3‐D vision camera (Microsoft, Kinect) data. Physical dimensions of Linac components were taken to construct a geometric model. The Linac components include the treatment couch, gantry, and imaging devices. The treatment couch coordinates were determined based on a correspondence among the CT couch top, Linac couch, and the treatment isocenter location. A collision is predicted based on dot products between vectors denoting points in Linac components and patient morphology. Collision test cases were simulated with the CPS and experimentally verified using ArcCheck and Rando phantoms to simulate a patient.ResultsFor 111 collision test cases, the sensitivity and specificity of the CPS model were calculated to be 0.95 and 1.00, respectively. The CPS predicted collision states that left conservative margins, as designed, relative to actual collision locations. The average difference between the predicted and measured collision states was 2.3 cm for lateral couch movements. The predicted couch rotational position for a collision between the gantry and a patient analog differed from actual values on average by 3.8°. The magnitude of these differences is sufficient to account for interfractional patient positioning variations during treatment.ConclusionThe feasibility of developing a CPS using geometric models and standard vector algebra has been investigated. This study outlines a framework for potential clinical implementation of a CPS for noncoplanar radiotherapy.

Comparison of Radiotherapy Techniques in Breast Cancer with Inclusion of Internal Mammary Nodes through Thermoluminescent Dosimetry in a RANDO Phantom

Introduction: In the various techniques of breast cancer radiotherapy, the presence of the internal mammary nodes (IMNs) in the target volume is important to select the most appropriate technique. This study aimed to compare three radiotherapy techniques with the inclusion of IMNs regarding the dose homogeneity index (DHI) of regional lymph nodes, chest wall, and the dose received by the heart and left lung.Material and Methods: Three techniques were planned on the CT images of the RANDO phantom including wide tangent (WT) contained two opposed tangential 6 MV photon beams, oblique parasternal photon (OPP) and oblique parasternal electron (OPE) that included two opposed tangential 6 MV photon beams with an anterior oblique 6 MV photon beam and an anterior oblique 15 MeV electron beam added to two tangential beams, respectively. The doses reached to the contoured organs were compared in three techniques by using data gathered from the thermoluminescent dosimetry and treatment planning system.Results: The OPE technique caused a lower absorbed dose for the left IMNs than the other two techniques. For the OPP technique, the dose received by the left lung was higher than the tolerance, and the lung dose in the OPE is slightly lower than the WT technique. The absorbed dose by the heart was lowest for the WT technique and the DHI for this technique was better than the other two techniques.Conclusion: The WT technique showed better results regarding the IMNs and chest wall dose homogeneity distribution and the organ at risk protection.

Verification of dose distribution on the gamma knife perfexion radiosurgery using gafchromic EBT3 film: RANDO phantom study

Leksell gamma knife (LGK) is an advanced modality of radiation therapy sourced Co-60 radioactive for treating patient with intracranial lesion. Small field techniques with highly integrated radiation delivering to patients in single session must be calculated accurately and verified carefully. This study illustrates a procedure to verify the accuracy of dose distribution associated with Leksell Gamma Plan (LGP) using RANDO phantom and gafchromic EBT3 film dosimetry. First, we assessed the profile dose on LGK standard phantom with collimators size 4, 8 and 16 mm and compared the results with the profile dose based on RANDO to obtained Full Width Half Maximum (FWHM) and beam-symmetry. Absorbed-dose distributions on RANDO with various combinations of lesion volume, collimator size, location and number of shots assessed by EBT3 film using LGK Perfexion. Scanned images of the measured films were processed following standard EBT3 film-handling procedures. Dose distribution calculation were performed using ImageJ software and MATLAB in-house software. The study shows different FHWM and beam symmetry of collimator size of 16 mm on standard phantom between LGP and measurement is 1.83 % and 1.58 % respectively whereas the discrepancy in RANDO phantom is 2.15 %, and 1.64 % respectively. Verification of max dose shows the smallest discrepancy on collimator size 16 single shot is 1.9 % on 7.61 cc superior lesion volume, where 12.12 Gy obtained by measurement and 12.36 Gy from LGP. In conclusion, collimator size 16 mm have a highest accuracy of FWHM and beam-symmetry value. However, on smaller lesion volume, collimator 16 mm with single shot give higher deviation dose value.

Assessment of skin dose in breast cancer radiotherapy: on-phantom measurement and Monte Carlo simulation.

The main purpose of the present study is assessment of skin dose in breast cancer radiotherapy. Accurate assessment of skin dose in radiotherapy can provide useful information for clinical considerations. A RANDO phantom was irradiated using a 6 MV Siemens Primus linac with medial and tangential radiotherapy fields for simulating breast cancer treatment. Dosimetry was also performed on various positions across the fields using an EBT3 radiochromic film. Similar conditions of measurement on the RANDO phantom including field size, irradiation angle, number of fields, etc. were subsequently simulated via the Monte Carlo N-Particle Transport code (MCNP). Ultimately, dose values for corresponding points from both methods were compared. Considering dosimetry using radiochromic films on the RANDO phantom, there were points having underdose and overdose based on the prescribed dose and skin tolerance levels. In this respect, 81.25% and 18.75% of the points had underdose and overdose, respectively. In some cases, several differences were observed between the measurement and the MCNP simulation results associated with skin dose. Based on the results of the points which had underdose, it was suggested that a bolus should be used for the given points. With regard to overdose points, it was advocated to consider skin tolerance dose in treatment planning. Differences between the measurement and the MCNP simulation results might be due to voxel size of tally cells in simulations, effect of beam's angle of incidence, validation time of linac's head, lack of electronic equilibrium in the build-up region, as well as MCNP tally type.

Influence of Various Setup Parameters on Scattered Fraction in Interventional Cardiology

It is important to examine the positions of the medical staff involved in interventional cardiology in order to minimize their accumulated scattered radiation doses. This study used the design of experiment (DOE) method with three parameters (C-arm gantry tilt, position and height), each at three levels (low, medium and high), on both the left and right sides of the patient, to analyse the interactions between the parameters that influence the scattered fraction in interventional cardiology. In this experiment, a RANDO phantom and an Unfors Xi survey detector were used to measure the rate of the scattered dose exposed to staff without protective shielding in a Cath lab. The parameters that significantly influenced the scattered fraction at a confidence level of 95% (P< 0.05) to the right of the patient were the gantry tilt and the height. To the left of the patient, all parameters significantly influenced the scattered fraction.

Site Specific Calibration Curve And Its Implication in The Treatment Planning of Head And Neck Cancer.

Purpose: In this study, we created site specific Hounsfield Unit (HU) and Relative electron density(RED) calibration curves for computed tomography(CT) and cone beam computed tomography (CBCT) for head and neck radiotherapy dose calculation and compared them with standard calibration curves.&#x0D; Methods:&#x0D; The calibration curves between HU and RED were generated using RANDO phantom for CT and CBCT and fed in the treatment planning system for dose calculation for head and neck patients.The treatment plans for 10 head and neck cancer patients were calculated using the standard calibration curves generated with CATPHAN and head and neck calibration curves generated with RANDO phantom for both CT and CBCT. Dose accuracy of head and neck calibration curves(H/N CC) were compared to the standard calibration curves (SCC) using dose volume metrics and 3D gamma analysis.&#x0D; Results: The results show that slightly better dosimetric agreement from the SCC can be obtained when using this H/N CC.&#x0D; Conclusions: A site specific calibration curves have been proposed and tested for the head-and-neck patients and the results explain the dosimetric benefits.

The optimization of radiation protection to interventional cardiologists

Scattered dose radiation to occupational in interventional cardiology cannot be neglected due to the long time for each procedure. The limit dose for occupational is 20 mSv per year or 0.01 mSv/h. The aim of this study is to calculate the effective dose of occupational and to analyse the optimization of radiation protection in the Cath lab. The simulation has been done using Rando phantom as a patient and Unfors Xi as scattered dose measuring instrument (in mGy/h). The data is collected in 6 different positions from altitudes 25 cm to 75 cm with a range of 15 cm without protective shielding. Field size of primary beam is varied to 20×20 cm and 25×25 cm, while gantry tilt is varied to caudal, cranial, and Left Anterior Oblique (LAO). The obtained data is multiplied by weighting factor base on its height. The result shows that the effective dose of occupational is in the range of 0.18-0.94 mSv/h, which is exceed the limit dose. To accommodate the limit dose for occupational, we propose the limitation of procedure time to 21-110 hours a year or the use of protective shielding as thick as 1-1.6 mm lead.

Comparison of dosimetric accuracy of acuros XB and analytical anisotropic algorithm against Monte Carlo technique

This study reports the comparison between two dose calculation algorithms, Acuros XB 13.5 (AXB) and Analytical Anisotropic Algorithm (AAA) against Monte Carlo (MC) simulations for 3D-Conformal Radiation Therapy (3D-CRT) using a female pelvic rando phantom. 3D-CRT treatment plans were generated on the CT images of rando phantom using AXB and AAA with Source to Axis Distance (SAD) technique. Doses obtained using two algorithms and MC results were compared using MATLAB based software CERR. In house MATLAB code was developed to calculate the gamma dose distribution comparison in terms of dose difference (DD) and distance to agreement distribution (DTA). The results showed that the Dmean in the PTV TOTAL (PTV) volume for AXB and AAA was equal to the mean dose calculated by MC simulations. The gamma passing rates for AXB were more accurate in comparison to AAA with reference to MC for PTV, Bladder and Femoral Heads region. After analysing the dose comparison specially for the PTV, femoral heads, also the analysis of dose volume histogram (DVH) and gamma dose distribution comparison for PTV, femoral heads and bladder, it can be concluded that AXB is more accurate in comparison to AAA. It can be said that AXB is well suited for dose calculation in clinical setup when compared to MC calculations.

A study on the reduction of radiation dose using carbon fiber-reinforced plastic during X-ray examination of children and infants

The purpose of this study was to investigate the suitability of an assistive device for radiological examination. A Carbon Fiber-Reinforced Plastic (CFRP) with relatively high transmission factor was used to reduce unnecessary radiation exposure for patients and examiners and maintain a stable examination posture and reduce falling of the infant. An average of 10 entrance surface doses (ESDs) were used for the ATOM Phantom T-spine (T6) and the Rando Phantom Thyroid (T), Inguinal Area (I), and Eye Ball (E) for patients and examiners during each infant chest X-ray examination. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also measured and analyzed via paired sample T-test and Pearson's correlation analysis using SPSS statistics version 21.0 (Chicago, IL, U.S.A.) to quantitatively evaluate changes in image quality before and after using the ancillary device. During infant chest X-ray examination, EST results were as follow: ESDT6 of infants, 233.70 ± 5.74 μGy; ESTs for the examination assistant: ESDT151.40 ± 4.01 μGy; ESDI, 143.20 ± 3.22 μGy; and ESDE, 146.20 ± 3.19 μGy. When the SNR and CNR values of chest X-ray images involving infants were compared using Pearson's correlation analysis, significant (p < 0.001) differences were found between values obtained before and after applying the ancillary device. The radiological examination assist device can stabilize the infant's posture during examination. Thus, it can reduce unnecessary exposure of patients and examination assistants to radiation, ultimately improving the safety of infant X-ray examinations.

Characteristics of Megavoltage Electron Beams Directed through Silicone for Bolus Electron Therapy

In high energy electron beam therapy, a bolus can be used for the conformal dose to target and achieve the appropriate treatment quality. To evaluate the use of a customized silicone bolus, we analyzed the dosimetric properties of the electron beam according to the silicone bolus thickness. Eight silicone slits were fabricated using an acrylic mold. The size of each slit was 150 × 150 × 5 m3 (width × length × height). Degassing was performed to eliminate bubbles in the slits during the silicone casting process. Depth dose measurements were performed for a 6 MeV and 9 MeV electron beams with 10 × 10 cm2, 6 × 6 cm2 and 5 cm diameter circular fields with various silicone thickness and with the conventional bolus. For the depth dose measurement, the film was placed between two 6 cm solid water phantoms, and the electron beam was delivered parallel to the film. The Rando phantom dose with customized bolus were evaluated with the 10 × 10 cm2 6 MeV electron beam. As the slab thickness increased, the depth dose in the solid water phantom decreased after reaching the maximum dose depth (dmax). Depending on the silicone thickness, the surface dose of the phantom was increased until reaching the electron beam dmax and was decreased after dmax. The coefficient to convert the thickness of the silicone to water were 1.06 in 6 MeV and 1.07 in 9 MeV, respectively. We measured the electron beam dose properties for making patient-specific silicone boluses with optimal thickness. The results of this study can be used to predict the silicone bolus thickness required in order to deliver the appropriate dose to the target.

Determination of the Radiation Dose Level in Different Slice Computerized Tomography

Today, many imaging tools have emerged in the medical field using ionizing radiation. Computed tomography (CT) is regarded the most creative and common modality among the other imaging devices. In CT imaging, radiation may scatter to the environment from the patient and the interaction medium. In this study, two CT scanners with different slice numbers were used to measure the scatter radiation dose to the environment. Alderson rando phantom was utilized in the acquired CT exams as human body simulation. Radiation dose levels at different distances were determined by placing thermoluminescence dosimeters in the surrounding environment (at different distances) during phantom’s head-neck and thorax CT imaging. As a result, it has been found that the radiation dose varies between 13.90±1.96 µSv and 96.79±11.12 µSv in head and neck CT imaging. While, in thorax CT scan, the radiation dose varies between 5.28±0.84 µSv and 20.63±1.76 µSv.

Fabrication of anthropomorphic phantoms for use in total body irradiations studies

AbstractPurpose:The aim of this study was to produce a low-cost anatomical model of adult male including lower limbs to evaluate the three-dimensional dose distribution for dosimetry measurements, especially in total body irradiation (TBI) and total skin electron therapy (TSET).Materials and methods:Computed tomography (CT) scan images of the atomic energy organisation RANDO phantom and lower limb CT scan images of 20 healthy persons were averaged. Selections of different body tissues substitute materials and phantom validation were performed according to previous studies worked on construction of radiation therapy phantoms.Results:The dosimetry aspect of the selected substitute materials from all considered methods showed that they were in good agreement with real human tissue, especially bone, with a percentage error of 0·5%. The results show that the electron densities obtained from the linear attenuation coefficient (reDLAC) for the tissue equivalent material used in the phantom is a better option for validation.Conclusions:This validated phantom has numerous advantages over the origin type of RANDO phantom. Therefore, using it in TBI and TSET dosimetry is recommendable.