Radiation Dose Measurements Research Articles

CONVENTIONAL ROOM EFFECTIVENESS TEST USING RAYSAFE IN RADIOLOGY UNIT SITI RAHMAH ISLAMIC HOSPITAL PADANG

Siti Rahmah Islamic Hospital is a health service center in the city fields with a large number of patients. The more the number of patients, the greater the number the examination was carried out in the radiology room at the Siti Islamic Hospital Rahmah if the walls of the Radiology room are not effective, the dose will be receive to the patient, the patient's family and radiation staff will increase. This research aims to determine the effectiveness and level of security in conventional spaces Radiology Unit of Siti Rahmah Islamic Hospital against radiation with use raysafe unfors. This research was conducted by sticking raysafe unfors from the inside and the outside on walls, doors and Pb glass in a conventional room in the Hospital Radiology Unit Islam Siti Rahmah with the type of quantitative research. The results of the measurement of the largest dose rate were found at the inner 3A point, which was 10.5198 mGy/h. While the results of the measurement of the smallest dose rate are at the outer 7B point, which is -0.0001 mGy/h. The dose before penetrating the material (D0) measured in a conventional room ranged from 10.5198 –1.3228 mGy/h. The dose value that varies at the measurement point is caused by the distance of the radiation source from the measurement point. Where in the conventional room (D0), the largest measured radiation dose is at point 3A 10.5198 mGy/h. This is because the measurement position is closest to the radiation source with a distance of 160 cm. Conventional space buildings are already effective against scattered radiation and safe as a radiation barrier with the effectiveness of values ranging from 99.9% to 100%. The results showed that the ability of walls, doors and Pb in a conventional room in the Radiology Unit of the Siti Rahmah Islamic Hospital absorb radiation.

Predictors of radiation dose for uterine artery embolisation are angiography system-dependent

This study sought to achieve radiation dose reductions for patients receiving uterine artery embolisation (UAE) by evaluating radiation dose measurements for the preceding generation (Allura) and upgraded (Azurion) angiography system. Previous UAE regression models in the literature could not be applied to this centre’s practice due to being based on different angiography systems and radiation dose predictor variables. The aims of this study were to establish whether radiation dose is reduced with the upgraded angiography system and to develop a regression model to determine predictors of radiation dose specific to the upgraded angiography system. A comparison between Group I (Allura, n = 95) and Group II (Azurion, n = 95) demonstrated a significant reduction in kerma-area product (KAP) and Ka, r (reference air kerma) by 63% (143.2 Gy cm2 vs 52.9 Gy cm2; P < 0.001, d = 0.8) and 67% (0.6 Gy vs 0.2 Gy; P < 0.001, d = 0.8), respectively. The multivariable linear regression (MLR) model identified the UAE radiation dose predictors for KAP on the upgraded angiography system as total fluoroscopy dose, Ka, r, and total uterus volume. The predictive accuracy of the MLR model was assessed using a Bland-Altman plot. The mean difference was 0.39 Gy cm2 and the limits of agreement were +28.49 and −27.71 Gy cm2, and thus illustrated no proportional bias. The resultant MLR model was considered system-dependent and validated the upgraded angiography system and its advance capabilities to significantly reduce radiation dose. Interventional radiologist and interventional radiographer familiarisation of the system’s features and the implementation of the newly established MLR model would further facilitate dose optimisation for all centres performing UAE procedures using the upgraded angiography system.

Evaluation of the radiological risk in cargo scanning by comparison with known biological consequences

This study proposes a quick, easy, and low-cost method that can be used to assess the radiological safety of an irradiation line used for cargo and container inspection facilities. The radiation-emitting equipment used was a Smiths Heimam particle accelerator model HCVP4029 operating at 4.5 MeV. The radiation dose measurements were performed using a personal radiation monitor Ultra Radac mod MRAD 111 (Geiger–Muller). The ambient equivalent dose H*(10) was estimated for two facilities: A (real) (1.12E-03 mSv per scan) and B (fictitious) (3.25E-03 mSv per scan). The dimensionless factor R, which represents a ratio between two specific scanning (Ss) quantities regarding the facilities A and B, is introduced as a reference for assessing the level of radiological safety. This study compares facilities A and B by using a simple alternative safety assessment based on the R factor. The dimensionless R-value appears to be able to facilitate both the personnel’s and the general public’s perception of risk levels, even with no fixed scale.

Evaluation of Peak Skin Doses and Lens Doses during Interventional Neuroradiology Using a Direct Measurement System.

In interventional neuroradiology (INR), the evaluation of the peak skin dose (PSD) and lens dose is important because the patient radiation dose increases in cases in which the procedure is more difficult and complex. This study evaluated the radiation doses during INR procedures using a direct measurement system. Radiation dose measurements during INR were performed in 332 patients with unruptured aneurysm (URAN), dural arteriovenous fistula (DAVF), and arteriovenous malformation (AVM). The PSD and bilateral lens doses were analyzed for each disease. The Pearson correlation test was used to determine whether the PSD and lens doses were linearly related to the reference air kerma (Ka,r). In all cases, the PSD and right and left lens doses were 2.36 ± 1.28 Gy, 114.2 ± 54.6 mGy, and 189.8 ± 160.3 mGy, respectively. The PSD and lens doses of the DAVF and AVM cases were significantly higher than those of the URAN case. The Pearson correlation test revealed statistically significant positive correlations between Ka,r and PSD, Ka,r and right lens dose, and Ka,r and left lens dose. The characteristics of radiation dose in INR were clarified. Owing to the concern of increased radiation doses exceeding the threshold values in DAVF and AVM cases, protection from radiation is required. Simple regression analysis revealed the possibility of precisely predicting PSD using Ka,r.

Calculated and Measured Radiation Dose in Water for the Low Energy Xoft Axxent Ebt X-Ray Source

Calculated and Measured Radiation Dose in Water for the Low Energy Xoft Axxent Ebt X-Ray Source

Dosimetry.

The dosimeters used to measure radiation dose produce a value which has to be calibrated to be in keeping with the values in an approved laboratory, which will be one of an international network of such laboratories at the center of which is the Bureau International des Poids et Mesures in France (BIPM). Dosimeters work by producing a quantitatively proportional change in status to the intensity of the radiation being measure. Amongst the techniques in use are thermoluminescent devices, radiographic film, radiochromic film, semiconductors, ionization chambers, silicon diodes and gel dosimeters. The Gamma Knife radiation has been difficult to measure directly because the beams have been to fine for accurate measurement by commonly available dosimeters. For more modern dosimeters this is less of a problem. During the treatment of a patient, a variety of indices are recorded to assist in the standardization and accuracy of treatment. Having determined the dose in the beams, it is necessary to calculate how much energy is lost during the passage of radiation from the source to the target. There has been a steady evolution of these calculations to make them more accurate.

Natural gamma radiation at the sea level around the Antarctic continent recorded south of the 62° parallel

This study presents the results of dosimetry radiation measurement performed in the Antarctic region at the surface of the sea which was conducted between January and March 2018. Over 2 200 records were collected using a portable Gamma Scout Online radiometer during a 72-day voyage circumnavigating the continent of Antarctica. The mean average of the measured radiation dose rate was 0.091 μSvh-1 and varied from 0.052 to 0.193 μSvh-1. These result are above global average dose rate of radiation at sea level (0.031 μSvh-1) and often higher than those recorded on the Antarctic continent. Yet generally our records fall within well recognized latitudinal trend of radiation being higher toward poles. This is results of troposphere begins at lower altitude in Antarctic in comparison to lower latitudes. The origin of this radiation is natural and results from the presence of higher cosmic rays and secondary radiation induced in the atmosphere. The presence of terrestrial radionuclides in the Antarctic environment has a local, secondary influence on the measured values of radiation. The theoretical calculated annual dose equivalent for humans present in Antarctica could often exceed the limit of 1 mSv as recorded for other Antarctic locations yet our results (0.772 mSv per year) do not confirm that.

Estimating the Concentrations of Natural Isotopes of 238 U and 232Th and Radiation Dose Rates for Wasit Province-Iraq by Gr-460 system

This paper includes the measurement of the concentrations of natural radioactive isotopes of 238U, 232Th, and radiation dose rates for selected areas of Wasit province.GR-460 system has been used for the radiological survey operations, it is a portable system, installed inside a minibus and inside the system, there is a Sodium Iodide Detector (NaI), that has the ability to measure the concentrations of natural radioactive isotopes in (ppm) unit and measure the radiation dose rates in µR/h unit. The measurement results showed the absence of any significant increase in the 238U and 232Th concentration where the concentration of isotopes 238U and 232Th, were 3.35 and 5.46 ppm respectively, it is authorized and acceptable. The values of radiation dose rates ranged between 45-65 ոSv/հ, and all these values are within the natural radiation background. Eleven radioactive sources type 226Ra have been detected beside destroyed industrial facility because of the war 2003 they had been used in the lightning arresters technology in the last regime. These sources treated and placed in armored containers and taken to the Iraqi main store (Iraqi Organization of Atomic Energy Site), the radiation dose measurements ranged between 72- 48 µR/h, which is higher than the natural radiation background.

Personalized 3D-printed anthropomorphic phantoms for dosimetry in charged particle fields

Anthropomorphic phantoms used for radiation dose measurements are designed to mimic human tissue in shape, size, and tissue composition. Reference phantoms are widely available and are sufficiently similar to many, but not all, human subjects. 3D printing has the potential to overcome some of these shortcomings by enabling rapid fabrication of personalized phantoms for individual human subjects based on radiographic imaging data. Objective. The objective of this study was to test the efficacy of personalized 3D printed phantoms for charged particle therapy. To accomplish this, we measured dose distributions from 6 to 20 MeV electron beams, incident on printed and molded slices of phantoms. Approach. Specifically, we determined the radiological properties of 3D printed phantoms, including beam penetration range. Additionally, we designed and printed a personalized head phantom to compare results obtained with a commercial, reference head phantom for quality assurance of therapeutic electron beam dose calculations. Main Results. For regions of soft tissue, gamma index analyses revealed a 3D printed slice was able to adequately model the same electron beam penetration ranges as the molded reference slice. The printed, personalized phantom provided superior dosimetric accuracy compared to the molded reference phantom for electron beam dose calculations at all electron beam energies. However, current limitations in the ability to print high-density structures, such as bone, limited pass rates of 60% or better at 16 and 20 MeV electron beam energies. Significance. This study showed that creating personalized phantoms using 3D printing techniques is a feasible way to substantially improve the accuracy of dose measurements of therapeutic electron beams, but further improvements in printing techniques are necessary in order to increase the printable density in phantoms.

Metrology for radiation protection: a new European network in the foundation phase

Abstract. More than 23 million workers worldwide are occupationally exposed to ionizing radiation and all people in the world are exposed to environmental radiation. The mean exposure, that is the mean annual dose of per person, is dominated by medical applications and exposure to natural sources. Due to recent developments in healthcare, e.g. the increasing application of ionising radiation in medical imaging with relative high doses like CT, and modern high dose applications (for example CT angiography), the exposure due to medical application has risen. Additionally, the changes in living conditions increase the exposure to natural radioactivity also: More living time is spent in buildings or in an urban environment, which causes higher exposure to Naturally Occurring Radioactive Materials (NORM) in building materials and higher exposure to radon. The level of radon activity concentration in buildings is far higher than in the environment (outdoor). This effect is often amplified by modern energy-efficient buildings which reduce the air exchange and thus increase the radon indoor activity concentration. In summary both medical application of ionizing radiation and natural sources are responsible for the increase of the mean annual exposure of the population. The accurate measurement of radiation dose is key to ensuring safety but there are two challenges to be faced: First, new standards and reference fields are needed due to the rapid developments in medical imaging, radiotherapy and industrial applications. Second, direct communication channels are needed to ensure that information on best practice in measurements reaches effectively and quickly the people concerned. It is therefore necessary to allow for an international exchange of information on identified problems and solutions. Consequently, a European Metrology Network (EMN) for radiation protection under the roof of EURAMET is in the foundation phase. This network EMN for Radiation Protection is being prepared by the project EMPIR 19NET03 supportBSS. The project aims to prepare this EMN by addressing this issue through the identification of stakeholder research needs and by implementing a long-term ongoing dialogue between stakeholders and the metrology community. The EMN will serve as a unique point of contact to address all metrological needs related to radiation protection and it will relate to all environmental processes where ionising radiation and radionuclides are involved. A Strategic Research Agenda and two roadmaps are in development, covering the metrology needs of both the Euratom Treaty and the EU Council Directive 2013/59/EURATOM pinning down the basic safety standards for protection against the dangers arising from exposure to ionizing radiation. Furthermore, long-term knowledge sharing, and capacity building will be supported and a proposal for a sustainable joint European metrology infrastructure is under way. This will significantly strengthen the radiation protection metrology and support radiation protection measures. The final goal of the network project is a harmonised, sustainable, coordinated and smartly specialised infrastructure to underpin the current and future needs expressed in the European regulations for radiation protection.

INNV-03. DEVELOPMENT OF A NOVEL DUAL-MODALITY BALLOON IMPLANT FOR SIMULTANEOUS HIGH-DOSE-RATE BRACHYTHERAPY AND MAGNETIC NANOPARTICLE HYPERTHERMIA OF BRAIN TUMOR RESECTION CAVITIES

Abstract PURPOSE To develop a novel thermobrachytherapy (TBT) balloon implant that delivers hyperthermia and radiation simultaneously, with three specific aims: 1) to fabricate a prototype TBT balloon device; 2) to verify compatibility of all heating and radiation delivery components and evaluate heat and radiation dosimetry in full size skull/brain phantom models; and 3) to characterize in vivo heating patterns in pig brain. METHODS Five 3cm diameter TBT balloons were fabricated. Each balloon has two layers: an inner layer to be filled with saline to expand the resection cavity, and an outer layer to be filled with magnetic nanoparticle (MNP) solution to absorb energy from an external magnetic field hence generate heat. The balloon shaft houses 4 ports to fill inner and outer layers, insert a high-dose-rate brachytherapy source into the balloon center, and a fiber optic sensor into the outer layer to monitor and control balloon temperature. A 3D-printed skull phantom was filled with brain tissue-equivalent gel for in-phantom measurements of heating around a TBT balloon. Optically stimulated luminescent dosimeters and Gafchromic film were used to measure radiation dose; while motorized temperature probes placed in catheters were inserted in surrounding gel for thermal mapping. For in vivo experiments, a 1cm balloon was specifically fabricated for pigs 40-50 kg. RESULTS The presence of MNP, magnetic field, and 43-55°C heating did not affect radiation dose significantly. Thermal mapping demonstrated spherically symmetric heating in both phantom and in vivo brain tissue, where a higher concentration of MNP and stronger magnetic field of 1.6-4.5 kA/m at 133 kHz was used to achieve temperatures of 55°C in the much smaller balloon. CONCLUSION Novel dual-modality balloons have been fabricated and tested successfully in the lab and in vivo, hence providing crucial information to validate thermal modeling for combined heat and radiation treatment of brain tumor resection cavities.

Measurement of Radiation Doses in Computed Tomography (CT) and Estimated Radiological Risk of Cancer

Measurement of Radiation Doses in Computed Tomography (CT) and Estimated Radiological Risk of Cancer

Radiochromic Fricke gels with eriochrome cyanine R for radiotherapy dosimetry

The chelator eriochrome cyanine R (ECR) in aqueous solutions forms metal complexes with Fe(III) ions with 1:1 (metal:ligand) stoichiometry. Because ECR absorbs light in the visible spectrum at different wavelengths for its free and complexed forms, this ligand may behave as a dose marker in a Fricke gel (FG) dosimeter. This is the first investigation of the influence of the organic ligand ECR in Fricke gels produced with a polyvinyl alcohol matrix cross-linked with glutaraldehyde (FGECR). The concentrations of sulfuric acid, ECR, and Fe(II) ions were varied in the FG synthesis in order to optimize the detector sensitivity to ionizing radiation. For comparison sake, FG synthesized with xylenol orange (FGXO) was also produced. The formation of the Fe(III)-ECR complex after irradiation has two absorption bands in the visible region. The absorbance intensities vary linearly with the absorbed dose in the range of 0.0–40.0 Gy. The FGECR and FGXO showed similar properties: sensitivity of (0.072 ± 0.001) Gy-1 and (0.079 ± 0.001) Gy-1; and diffusion of (0.192 ± 0.006) mm2 h-1 and (0.184 ± 0.022) mm2 h-1, respectively. FGECR has some advantages for application in radiotherapy, as it presented sensitivity for low doses, whose minimum detectable dose was 0.67 Gy, with maximum optical absorption at low energy wavelengths, ideal for measuring radiation dose by optical tomography, and it has a high saturation dose. Therefore, FGECR has the potential for dosimetric studies in radiotherapy, including flash radiotherapy, which deposits high doses in extremely short times.

Signal Amplification of Fiber Integrated X-Ray Detector and Energy Independence

We developed a high spatial resolution and sensitive detector particularly suitable for radiation dose measurements in radiotherapy at small fields and X-ray imaging applications. The detector is based on a silica optical fiber whose sensitive terminal is functionalized by grafting Ag-doped ZnS scintillating materials that emit blue luminescence under X-ray irradiation. Due to the small scintillating head of the detector, the acquisition signal is quite low, and it is measured by a sensitive photon counter plugged at the other terminal of the fiber. The weaker signal can be enhanced significantly by adding a metal coating over the scintillator. Therefore, this study presents the effect of metal thickness and density on the signal amplification at high irradiation energies of 6 MeV and 15 MeV using a Linear Accelerator (LINAC). In addition, the stem effect was characterized for regular to small field beam size and shows that the detector is almost free from stem contribution during high energy irradiation.

Radiation Reduction and Protection for Radiosensitive Organs (Lens, Thyroid, and Genital Organs) of Patients Receiving Percutaneous Coronary Intervention-Real-World Measurement of Radiation Dose in a Single Center.

Backgrounds: Reducing radiation exposure is the basic principle for performing percutaneous coronary intervention (PCI). Many studies have confirmed the effect of radiation protection for medical staff, but studies about the effectiveness of protection for patients and real measurement of radiation dose in patients’ specific organs are lacking. Aim: To measure the radiation doses absorbed by patients’ radiosensitive organs during PCI and the effectiveness of radiation protection. Methods: A total of 120 patients were included and allocated into three groups as the ratio of 1:1:2. A total of 30 patients received PCI at 15 frames rate per second (fps), 30 patients at 7.5 fps, and 60 patients wore radiation protective hat and glasses during PCI at 7.5 fps. The radiation doses were measured at right eyebrow (lens), neck (thyroid), back (skin), and inguinal area (genital organs) by using thermoluminescent dosimeters (TLDs). Results: Dose-area product (DAP) reduced by 58.8% (from 534,454 ± 344,660 to 220,352 ± 164,101 mGy·cm2, p < 0.001) after reducing the frame rate, without affecting successful rate of PCI. Radiation doses measured on skin, lens, genital organs, and thyroid decreased by 73.3%, 40.0%, 40.0%, and 35.3%, respectively (from 192.58 ± 349.45 to 51.10 ± 59.21; 5.29 ± 4.27 to 3.16 ± 2.73; 0.25 ± 0.15 to 0.15 ± 0.15; and 17.42 ± 12.11 to 11.27 ± 8.52 μSv, p < 0.05). By providing radiation protective equipment, radiation doses at lens and thyroid decreased further by 71.8% and 65.9% (from 3.16 ± 2.73 to 0.89 ± 0.79; 11.27 ± 8.52 to 3.84 ± 3.49 μSv, p < 0.05). Conclusions: By lowering the frame rate and providing protective equipment, radiation exposure in radiosensitive organs can be effectively reduced in patients.

Novel pregnant model phantoms for measurement of foetal radiation dose in x-ray examinations

This study presents a comparison of novel pregnant model phantoms with a handmade phantom in terms of shape and radiation measurement points to determine which model is more suitable for measuring the foetal radiation dose during x-ray examinations. Novel pregnant model phantoms were constructed using an anthropomorphic phantom in combination with two differently-sized custom-made abdomen phantoms simulating pregnancy, which were constructed from a polyurethane resin. The size and shape of the polyurethane resin were designed based on abdominal sizes and shapes collected from the computed tomography examinations at 18 pregnant patients of one hospital. The handmade pregnant model phantom was constructed using an anthropomorphic phantom and a beach ball containing water. Compared with the handmade phantom, there were additional dose measurement points on the novel pregnant model phantoms. Our model phantoms improved upon the handmade phantom in terms of shape and radiation measurement points. We produced pregnant model phantoms that simulated the shapes and sizes of actual patients for the first time.

Thermoluminescence dosimetry properties of Tm3+ doped fluoroelpasolite Cs2NaYF6 crystals synthesized under hydrothermal conditions

Detailed research of thermoluminescence (TL) properties of Tm3+ doped fluoroelpasolite Cs2NaYF6 crystals synthesized under hydrothermal conditions has been carried out in order to develop new dosimetric material. The basic dosimetric properties of Cs2NaY0.99Tm0.01F6 crystals (Zeff = 33) exposed to beta radiation, such as a TL glow curve shape, beta-dose response, reproducibility, dark fading, have been investigated by using ordinary TL technique at a typical heating rate of 2 °C/s. At this heating rate the Cs2NaY0.99Tm0.01F6 crystal exhibits three well-separated TL peaks: a rapidly decaying peak at 100 °C (Peak 1), a stable peak at 171 °C (Peak 2), and one more low-intensity peak at 240 °C (Peak 3). The deviation of reproducibility for 10 repeated readings of individual samples after exposure to 5 Gy of beta irradiation is <1%. The TL output as a function of beta irradiation dose exhibits linear dose-response up to 1 kGy. The anomalous fading of the TL signal has been observed for the Cs2NaY0.99Tm0.01F6 crystals. The short time fading characteristics have been studied for different periods of up to one week. Using the various heating rates (VHR), Chen's peak shape, and computerized glow curve deconvolution (CGCD) methods, the kinetic parameters have been calculated specifically for the Peak 2 of the TL glow curve. Spectra of X-ray excited radioluminescence (RL) have been studied in the range of 200–1000 nm. The results of this study show that the simple TL glow curve structure, relatively high sensitivity to ionizing radiation, the wide range of measurable doses from 0.2 Gy up to 1 kGy, and reusability make this novel Cs2NaY0.99Tm0.01F6 dosimetric material a promising candidate for its applications in radiation dosimetry in particular for measurement of high radiation doses.

Use of Terbium Doped Phosphate Glasses for High Dose Radiation Dosimetry—Thermoluminescence Characteristics, Dose Response and Optimization of Readout Method

The phosphate glass samples doped with Tb2O3 oxide (general formula: P2O5-Al2O3-Na2O-Tb2O3) were synthesized and studied for usage in high-dose radiation dosimetry (for example, in high-activity nuclear waste disposals). The influence of terbium concentration on thermoluminescent (TL) signals was analyzed. TL properties of glasses were investigated using various experimental techniques such as direct measurements of TL response vs. radiation dose, Tmax–Tstop and VHR (various heating rate) methods, and glow curve deconvolution analysis. The thermoluminescence dosimetry (TLD) technique was used as the main investigation tool to study detectors’ dose responses. It has been proved that increasing the concentration of terbium oxide in glass matrices significantly increases the thermoluminescence yield of examined material. For the highest dose range (up to 35 kGy), the dependence of the integrated thermoluminescent signals vs. dose can be considered as a saturation-type curve. Additional preheating of samples improves linearity of signal vs. dose dependencies and leads to a decrease of the signal loss over time. All obtained data suggest that investigated material can be used in high-dose radiation dosimetry. Additional advantages of the investigated dosimetric system are its potential ability to re-use the same dosimeters multiple times and the fact that reading dosimeters only requires usage of a basic TL reader without any modifications.

Radiation dose rate variations in different measurement scenarios after prostate 125I brachytherapy

This study aimed to directly compare different measurement scenarios using a supplemental radiation exposure measurement data set. Two sets of measurement scenarios comparing different body postures, such as standing and chair sitting positions, and different measurement directions, such as anterior and posterior directions, were assessed for radiation dose rate variations in this study at the Tokyo Medical Center, Japan. The estimated precaution time for holding children in the spoon position while sitting was also calculated. Different radiation dose rate measurement scenarios showed different variation tendencies. Radiation dose rate measurement showed higher mean values of measured radiation dose tendency in the standing position than in the sitting positions. The measurement from the anterior direction showed a slightly lower tendency than that from the posterior direction. Assuming a dose limit of 1 mSv, the precaution time calculated for children being held in the spoon position for a certain duration every day was 51.5 (range, 12.5-152.2) minutes. Our study presented a supplemental radiation exposure measurement data set and directly compared different measurement scenarios. Several trends in radiation exposure variations were found in the measurement scenarios at different body postures and different measurement directions. Our study data set could be a useful source of concrete information regarding radiation safety and contribute to the review and revision of public guidance in the future.

Technical Note: A 3D-printed phantom for radiochromic film evaluation of moving lung tumor SBRT without dose convolution.

A common dosimetric quality assurance (QA) method in stereotactic body radiation therapy (SBRT) of lung tumors is to use lung phantoms with radiochromic film. However, in most phantoms, the film moves with the tumor, leading to the blurring effect. This technical note presents the QA performance of a novel phantom in which the film is fixed; this phantom can be used for both patient-specific QA and end-to-end testing. Lung tumor motion was simulated with the CIRS Model 008A phantom. A lung-equivalent insert that consisted of a fixed radiochromic film around which a 2-cm tumor moved in the inferior/superior direction (i.e., mimicking respiration-induced tumor motion) was generated by 3D printing. Two common SBRT plans [dynamic conformal arc (DCA) and volumetric-modulated arc therapy (VMAT)] were calculated on the average intensity projection (AIP) image set in Varian Eclipse using the dose calculation algorithm Acuros XB. The plans were delivered by a Varian TrueBeam STx accelerator using 6-MV flattening filter-free energy. EBT3 films were used for treatment-dose verification. The measured and planned dose distributions were compared by using the local gamma index at 3% and 2 mm. Mean gamma pass rates of film and planned dose distributions were all ≥95%. DCA and VMAT plans did not differ in gamma pass rates. Planned and measured dose distributions agreed well, as did planned and measured gamma maps. With this new insert, measured and planned dose distributions were very similar, which supports the current view in the field that dose calculations on AIP image sets account sufficiently for tumor motion during treatment. The phantom also performed well despite challenging breathing parameters (large tumor amplitude and slow breathing rate) and the application of a complex treatment technique (VMAT). This phantom could facilitate clinical and end-to-end film-based dosimetric QA for lung SBRT. Twenty-seven TH- Radiation dose measurement devices. Eleven Phantoms for dosimetric measurement.