Epson V700 Research Articles

Effect of mirror system and scanner bed of a flatbed scanner on lateral response artefact in radiochromic film dosimetry.

Radiochromic film, evaluated with flatbed scanners, is used for practical radiotherapy QA dosimetry. Film and scanner component effects contribute to the Lateral Response Artefact (LRA), which is further enhanced by light polarisation from both. This study investigates the scanner bed's contribution to LRA and also polarisation from the mirrors for widely used EPSON scanners, as part of broader investigations of this dosimetry method aiming to improve processes and uncertainties. Alternative scanner bed materials were compared on a modified EPSON V700 scanner. Polarisation effects were investigated for complete scanners (V700, V800, on- and off-axis, and V850 on-axis), for a removed V700 mirror system, and independently using retail-quality single mirror combinations simulating practical scanner arrangements, but with varying numbers (0-5) and angles. Some tests had no film present, whilst others included films (EBT3) irradiated to 6 MV doses of 0-11.3 Gy. For polarisation analysis, images were captured by a Canon 7D camera with 50 mm focal length lens. Different scanner bed materials showed only small effects, within a few percent, indicating that the normal glass bed is a good choice. Polarisation varied with scanner type (7-11%), increasing at 10cm lateral off-axis distance by around a further 6%, and also with film dose. The V700 mirror system showed around 2% difference to the complete scanner. Polarization increased with number of mirrors in the single mirror combinations, to 14% for 4 and 5 mirrors, but specific values depend on angles and mirror quality. Novel film measurement methods could reduce LRA effect corrections and associated uncertainties.

Effect of scanner lens on lateral response artefact in radiochromic film dosimetry

Radiochromic film is a good dosimeter choice for patient QA for complex treatment techniques because of its near tissue equivalency, high spatial resolution and established method of use. Commercial scanners are typically used for film dosimetry, with Epson scanners being the most common. Radiochromic film dosimetry is not straightforward having some well-defined problems which must be considered, one of the main ones being the Lateral Response Artefact (LRA) effect. Previous studies showed that the contributing factors to LRA are from the structure of the active ingredients of the film and the components and construction of the flatbed scanner. This study investigated the effect of the scanner lens on the LRA effect, as part of a wider investigation of scanner design effects and uncertainties. Gafchromic EBT3 films were irradiated with 40 × 40 cm2 field size 6 MV beams. Films were analysed using images captured by a Canon 7D camera utilising 18 mm, 50 mm and 100 mm focal length lenses compared to images scanned with a conventional Epson V700 scanner. The magnitude of the LRA was observed to be dependent on the focal length of the lens used to image the film. A substantial reduction in LRA was seen with the use of the 50 mm and 100 mm lenses, by factors of 3–5 for the 50 mm lens and 4–30 for the 100 mm lens compared to conventional desktop scanner techniques. This is expected to be from the longer focal length camera lens system being able to collect more light from distant areas compared to the scanner-based system. This provides an opportunity to design film dosimetry systems that minimise this artefact.

A comparison between EPSON V700 and EPSON V800 scanners for film dosimetry.

Radiochromic film is a good dosimeter choice for patient QA for complex treatment techniques (IMRT, VMAT, SABR, SBRT) because of its near tissue equivalency, very high spatial resolution and established method of use. Commercial scanners are usually used for film dosimetry, among which EPSON scanners are the most common. NCCI have used an EPSON V700 scanner, but recently acquired a new model EPSON V800 scanner. The purpose of this work was to evaluate any differences between these two scanners to consider whether they can be used interchangeably or not. Different aspects of film dosimetry, e.g. lateral response artefact (LRA) effect, orientation effect, scanner response etc., were compared. EBT3 films were irradiated with 40 × 40cm2 field size 6MV beams and scanned in both the scanners. The scanned images were read in ImageJ V1.49 software. The data obtained was then copied in MS Excel to compare the scanners. The V800 scanner causes more polarisation, which results in more LRA effect than for the V700 scanner. The responses of the scanners in all three colour channels are not the same for the same film and irradiation. The V800 scanner shows an increase of response of up to 1.6% compared to 3.7% increase in the V700 scanner after scanning a piece of irradiated film 20 times. The scanners cannot be used interchangeably. The correction factors for LRA effect and the calibration curves are different. Further characterisation, evaluation and commissioning is required before clinical use.

The Gafchromic EBT3® film as alpha detector

Film dosimetry is developed as a powerful tool for radiotherapy treatment verification and quality assurance. This project was done to study the response of Gafchromic EBT3® film for alpha particle detection. Gafchromic EBT3® film was exposed to alpha particle of energy 5.4 MeV from Am-241 source for different exposure time after one of the 125 μm polyester layer was removed. Then, the film was scanned with a flatbed scanner (Epson V700). From the results obtained, the maximum alpha particle absorbance was measured within the red light wavelength which was between 620 nm - 750 nm (alpha energy of 5.4 MeV). The absorbance also increased linearly with the exposure time. The exposure of film at different heights of pipe washer indicated that the film was energy dependent.

Accuracy of Surgical Prediction Following Mandibular Advancement

Objectives: The aim of this study is to evaluate the accuracy of newer computerized software (Onyx Ceph 3™) in comparison with the manual method for predicting hard tissue and soft tissue profiles following mandibular advancement. Materials and Methods: This is a retrospective cephalometric study of fifteen Class II skeletal subjects who had undergone mandibular advancement by bilateral sagittal split osteotomy. The cephalograms were converted into digital format using flatbed scanner (Epson V700 Perfection). The prediction for mandibular advancement was done using Onyx Ceph 3™ and compared with manual tracings made on acetate paper. A total of fourteen variables were compared, of which seven were hard tissue, and seven were soft tissue. Both angular and linear measurements were considered. Results: Onyx Ceph 3™ software overestimated mandibular advancement showing significant differences in OP-SN_M, Sella-Nasion-point B_D, N-Pog_D. The comparisons between the manual and digital error showed statistically significant differences in N-Pog ( P = 0.013), L i – L1 ( P = 0.043) Sn-Gn'-C ( P = 0.052), and G-Sn-Pog' ( P Conclusions: The prediction error was more in soft-tissue prediction performed digitally than manually. Onyx Ceph 3™ algorithms set for soft tissue have not matched the actual postsurgical treatment. Further, this software overestimated the mandibular advancement and has not accounted for the rotational movement associated with mandibular surgery.

Abstract WP212: Rapid Point-of-care Nr2 Peptide Test for Acute Stroke Detection

Background and Objectives: Time delay is a challenge in using biomarkers in guiding acute ischemic stroke (IS) therapy. Therapeutic decisions must be made quickly and standard blood draws with transport to a laboratory results in delay of results and possible degradation of biomarkers. We report the initial experience with rapid nanoparticle lateral flow (nLF) tests on fingerstick blood samples for the NR2 peptide (NP), a fragment of the NMDA receptor. This extends our prior research (PLoS ONE, 2012, 7, e42362). Methods: Capillary blood (20 microliter) withdrawn less than 15 hours after IS onset was developed within 5 min yielding test (T) and control ( C ) bands in a nLF assay (DRD/CIS Biotech, Inc, Atlanta, GA). An Epson V700 scanner and ImageJ software (Rasband, W.S., ImageJ, U. S. NIH, Bethesda, Maryland) were used to quantify the LF bands. Plasma measurements of NP using MP-ELISA were carried out as well. Patient Selection: Patients (n=13) with thrombotic and embolic stroke and controls (n=16) with non-vascular disease of the CNS and healthy volunteers were enrolled. Diagnosis of ischemic stroke was confirmed by clinical evaluation and neuroimaging (CT, MRI and transcranial doppler). Increased NR2 peptide was detected in plasma of 9/13 patients with IS, i.e., the rapid test showed 2 lines (control and test). In some patients both lines are visualized equally others the T-line is stained less intensively. In the control group there is only one band (16/16) Elevated NP correlated with new lesion areas on DWI/MRI with a slope of ~ 1ng per 5 ml stroke volume. Conclusions: NR2 peptide is elevated with IS and may be detected by rapid fingerstick tests. Plasma NR2 peptide levels correlate with stroke volume.

A study of four radiochromic films currently used for (2D) radiation dosimetry

We have measured the dose, D, and dose rate, D', dependences of the radiation-induced change in optical absorption of four radiochromic films currently used for (2D) dosimetry: GafChromic® types EBT3, MD-V3, HD-V2 and HD-810. We have irradiated the films using two 60Co γ-ray sources with dose rates of ~2 and ~30Gy/min and a 200kVp X-ray source with dose rates from ~0.2 to ~1.0Gy/min. The 48-bit RGB image files of the films, obtained using an Epson V700 flatbed scanner, were color-channel separated and the red, green and blue pixel levels, P(D), were determined using ImageJ software. The relationship P(D)/P(0)=[1+hD/m]/[1+D/m] is found to provide a good description of the dose dependence for all four films at all dose rates. The parameter h is the "plateau level" of P(D)/P(0) approached at high doses, i.e. P(∞)/P(0). The parameter m is the “median-dose” for which P(D)/P(0)(1+h)/2 which is the half point in the dynamic range of the particular film. The best-fit values of m over the dose rate range from ~0.2 to ~25Gy/min using the red pixels were 1.42±0.03, 11.1±0.4, 63.6±0.9 and 60.6±1.6Gy for EBT3, MD-V3, HD-V2 and HD-810 respectively. Using the green pixels the median dose is 1.8 times larger for the first 3 films and 2.5 times larger for HD-810. The blue pixels are considered unsuitable for dosimetry because of the large value of h (>0.4) and the resulting small dynamic range.

SU‐F‐T‐493: An Investigation Into the Feasibility of Using PipsPro Software with Film for Linac QA

Purpose:To determine the feasibility of using radiochromic and radiographic film with Pipspro software for quality assurance of linear accelerators with no on‐board imaging.Methods:The linear accelerator being used is a Varian Clinac 21EX. All IGRT is performed using the BrainLab ExacTrac system. Because of the lack of on board imaging, certain monthly and annual TG‐142 quality assurance tests are more difficult to perform and analyze to a high degree of accuracy. Pipspro was not designed to be used with hard film, and to our knowledge its use with film had not been investigated. The film used will be GafChromic EBT3 film and Kodak EDR2 film, scanned with an Epson V700 scanner. The following routine tests will be attempted: MLC picket fence, light vs. radiation field coincidence, starshots, and MLC transmission.Results:The only tests that gave accurate and reliable results were the couch, gantry, and collimator starshots. Typical MV and kV images are acquired with a much higher level of contrast between the irradiated and non‐irradiated areas when compared to film. Pipspro relies on this level of contrast to be able to automatically detect the fiducial points from its phantom devices, leaf edges for picket fence and transmission tests, and jaw edges for light vs. radiation field tests. Because of this, certain tests gave erroneous results and others were not able to be performed in the software at all, with either type of film. The number of monitor units delivered to the film, the experimental setup, and the scan settings was not able to rectify the problem.Conclusion:For linear accelerators with no on‐board imaging, it is not recommended to use hard film with PipsPro to perform TG‐142 quality assurance tests. Other software or methods should instead be investigated.

Practical IMRT QA dosimetry using Gafchromic film: a quick start guide.

This work outlines a method for using Gafchromic film for dosimetry purposes, by scanning it with currently available commercial scanners. The scanners used were: Epson V800, Epson V700, Epson V37 series, specifically a V370 and a Canon multi-function office printer/scanner. The Epson scanners have 16 bit RGB resolution, the Canon has 8 bit RGB (Red Green Blue) resolution, and the V800 and V700 allow scanning in transmission mode. The V700 uses an Epson White Cold Cathode Florescent Lamp; the recently released V800 uses an Epson light emitting diode (LED) light source, while the V37 series uses a reflective mode and the Epson LED light source. The Epson V37 series scanners are designed for non-professional use so the cost has been kept at a low "entry level" point, so they would be a suitable option for a department wanting to use Gafchromic film or with limited needs that did not justify a more sophisticated and expensive unit. Note that the V800 or V700 scanners are not expensive in context, costing approximately the same as a 25 sheet box of Gafchromic film. The Canon was included to demonstrate that a scanner with 8 bit RGB resolution can be used for dosimetry. These general multi-function units are available in most departments, and they would allow Gafchromic film to be evaluated as a dosimetry tool without a significant investment. Furthermore, they are generally capable of scanning large format film (425×350mm) in one part. Although this is not necessary for dosimetry, it is often useful for machine QA, where dividing the film into two parts to ensure accurate measurements is not practical. Moreover, this analytical method uses software that is freely or commonly available, particularly the image processing package ImageJ. Note ImageJ v1.48 was the version used. The results demonstrate that this method used with the scanners evaluated is a practical method of using Gafchromic film as a dosimeter for IMRT QA.

Development of a protocol for small beam bi-dimensional dose distribution measurements with radiochromic films

Gafchromic™ films have become popular due to their ease of use and their near water equivalence. This last property is crucial for stereotactic small beam dosimetry as demonstrated in recent papers. An accurate bi-dimensional dose measurement with Gafchromic™ films is very challenging mainly because of the non-uniformity response of flatbed scanners (used for films digitalization) and their own non-uniformity. The first proposal of this work is to develop bi-dimensional protocol for small beams and evaluate the associated uncertainty. The second proposal is to validate this protocol for the bi-dimensional measurements of treatment plans performed with the CyberKnife® system.First, the uniformity of an Epson V700 flatbed scanner and a batch of EBT3 Gafchromic™ films has been investigated. A “four films” dosimeter was designed to reduce the errors (statistic and systematic) due to their non-uniformity. Then, the “four films” dosimeter protocol in both a homogeneous (RW3 material) and heterogeneous (RW3, lung-like and bone-like materials) phantoms has been used to measure the bi-dimensional dose distributions of three simple CyberKnife® treatment plans. Two tumor locations (middle of the lung and near lung/bone interface) were considered for the heterogeneous phantom. These plans were achieved with the 10 mm fixed collimator and modeled with the PENELOPE Monte Carlo code in order to calculate accurate dose distributions. Finally, the “four films” bi-dimensional dose distributions were compared to the PENELOPE Monte Carlo simulations.Regarding the uncertainty associated to the bi-dimensional dose measurement protocol, the relative standard deviation σD on the dose was 1.2% in the range from 0.5 to 4.0 Gy. Regarding the protocol validation on CyberKnife® treatment plans, a very good agreement was found with all measurement points passing the {3% - 3 mm} Gamma Index criteria.

The implementation in-house dose verification for IMRT and VMAT on breast cancer and NPC cases

IMRT and VMAT have been widely implemented on breast cancer and NPC cases. Dose verification was conducted to ensure the comparison between dose delivered and prescribe dose in TPS to obtain optimal results and the dose delivered. The gafchromic films measurement was done for breast and NPC simulation on RANDO Phantom, irradiating film by 6 MV photon with 200 cGy and scanned with EPSON V700 using 72 dpi. Dose distribution was calculated using the MATLAB-based in-house algorithm. In order to evaluate the gamma index, gafchromic films and MatriXX 2D array were placed in the Multi Cube and irradiated with EPID in same position. Dose distribution differences for IMRT and VMAT with modalities to TPS on film was 5.34% and 6.68% for NPC PTV70; 12.81% and 6.15% for NPC PTV50; 11.14% and 10.80% for breast cancer. Gamma index differences on IMRT with modalities to MatriXX 2D array and EPID was -0.09% and 5.13% for NPC; 0.51% and 2.28% for breast cancer. On the other hand, gamma index difference on VMAT was -1.65% and 1.43% for NPC; 0.19% and 4.38% for breast cancer. This measurement method can be used to verify dose for breast cancer and NPC cases in IMRT and VMAT.

Comparison of vidar dosimetry advantage pro and epson perfection V700 scanner in densitometry of radiochomic EBT2 film in measurement of high dose gradient

Nowadays the radiochromic film is widely used to obtain dose distribution in two dimensions with high spatial resolution, less energy dependence and near tissue equivalent. It can be a commissioning tool to verify high dose gradient of dose distribution for IMRT and VMAT techniques. However, the film scanner could affect the accuracy of dose distribution if lack of precaution. In this study, the comparison between Epson perfection V700 and Vidar Dosimetry Pro Advantage (RED) is evaluated in terms of the capability to verify the 2D dose distribution for conventional and VMAT techniques. The Gafchromic® EBT2 films were read from two types of scanners (Epson perfection V700 and Vidar Dosimetry Pro Advantage) for volumetric modulated radiation therapy (VMAT) dosimetry. The software for analyzing the results of Epson perfection V700 and Vidar Dosimetry Pro Advantage are SNC Patient software and Omnipro’ IMRT software, respectively. Comparisons between measured and calculated dose distributions are reported as %passing rate and the gamma index for tolerance parameters of 3% and 3mm. The study found that the %passing rate obtained from Vidar scanner and Epson V700 scanner compared with Eclipse treatment planning system is more than 98% with the criteria of (3%/3mm).

SU‐E‐T‐519: Investigation of the CyberKnife MultiPlan Monte Carlo Dose Calculation Using EBT3 Film Absolute Dosimetry for Delivery in a Heterogeneous Thorax Phantom

PurposeTo characterize the Cyberknife (CK) robotic system's dosimetric accuracy of the delivery of MultiPlan's Monte Carlo dose calculations using EBT3 radiochromic film inserted in a thorax phantom.MethodsThe CIRS XSight Lung Tracking (XLT) Phantom (model 10823) was used in this study with custom cut EBT3 film inserted in the horizontal (coronal) plane inside the lung tissue equivalent phantom. CK MultiPlan v3.5.3 with Monte Carlo dose calculation algorithm (1.5 mm grid size, 2% statistical uncertainty) was used to calculate a clinical plan for a 25‐mm lung tumor lesion, as contoured by the physician, and then imported onto the XLT phantom CT. Using the same film batch, the net OD to dose calibration curve was obtained using CK with the 60 mm fixed cone by delivering 0– 800 cGy. The test films (n=3) were irradiated using 325 cGy to the prescription point. Films were scanned 48 hours after irradiation using an Epson v700 scanner (48 bits color scan, extracted red channel only, 96 dpi). Percent absolute dose and relative isodose distribution difference relative to the planned dose were quantified using an in‐house QA software program. Multiplan Monte Carlo dose calculation was validated using RCF dosimetry (EBT3) and gamma index criteria of 3%/3mm and 2%/2mm for absolute dose and relative isodose distribution measurement comparisons.ResultsEBT3 film measurements of the patient plans calculated with Monte Carlo in MultiPlan resulted in an absolute dose passing rate of 99.6±0.4% for the Gamma Index of 3%/3mm, 10% dose threshold, and 95.6±4.4% for 2%/2mm, 10% threshold criteria. The measured central axis absolute dose was within 1.2% (329.0±2.5 cGy) of the Monte Carlo planned dose (325.0±6.5 cGy) for that same point.ConclusionMultiPlan's Monte Carlo dose calculation was validated using the EBT3 film absolute dosimetry for delivery in a heterogeneous thorax phantom.

Solar ultraviolet radiation response of EBT2 Gafchromic, radiochromic film

Measurement of solar ultraviolet (UV) radiation is an important aspect of dosimetry for the improved knowledge of UV exposure and its associated health related issues. EBT2 Gafchromic film has been designed by its manufacturers as an improved tool for ionizing radiation dosimetry. The film is stated as exhibiting a significant reduction in UV response. However, results have shown that when exposed to UV from the ‘bottom side’ i.e. from the thick laminate side, the film exhibits a sensitivity to solar UV radiation which is both measurable and accurate for UV dosimetry. Films were irradiated in this position to known solar UV exposures and results are quantified showing a reproducibility of measurement to within ±7% (1 SD) when compared to calibrated UV meters. With an exposure of 20 J cm−2 broad spectrum solar UV, the films net OD change was found to be 0.248 OD ± 0.021 OD when analysing the results using the red channel region of an Epson V700 desktop scanner. This was compared to 0.0294 OD ± 0.0053 OD change with exposure to the same UV exposure from the top side. This means that solar UV dosimetry can be performed using EBT2 Gafchromic film utilizing the underside of the film for dosimetry. The main advantages of this film type for measurement of UV exposure is the visible colour change and thus easy analysis using a desktop scanner as well as its uniformity in response and its robust physical strength for use in outside exposure situations.

SU-E-T-24: A New Method Correcting the Parabola Effect of Flat-Bed Scanners Used in Radiochromic Film Dosimetry

Purpose: In flatbed scanners used to digitize radiochromic films, a system of mirrors provides a reduced optical image of the scanned film in the entrance plane of a small CCD array. In this optical system, artifacts of the optical density arise from anisotropic scattering and polarization of the scanner light. We quantified this perturbation effect and eliminated it by a software correction. Methods: In order to measure the nonuniformity of an Epson 10000XL scanner and an Epson V700 scanner, seven EBT3 films of 4x4 cm2, exposed to doses ranging from 0 to 3 Gy were scanned at different positions × on the axis parallel to the light source. An area of interest of 30×30 pixels at the center of each film was chosen for analysis. The corresponding red channel pixel values were averaged and converted to optical density OD. These optical density values were then fitted by a parabolic function OD(×), which fully characterizes the nonuniformity of the scanner. The correction algorithm transforms the OD value measured at position × into the corrected OD value, i.e. the value that would be measured at the apex position. The calibration films are scanned at the apex position and the calibration curve is related to the apex OD value. Results: To test the correction algorithm a 20× 20 cm2 6 MV photon field was measured by film and ionization chamber and the dose difference after correction was less than 2%. This Result can be achieved all over the scanner bed, so it is possible to correct wide dose distributions measured by radiochromic films. Conclusion: This new parabola correction algorithm reduces the scanner artifacts over the whole width of the scanner bed and presents an alternative approach or an extension to the three‐channel analysis [Micke et al Med Phys 38, 2012].

An efficient protocol for radiochromic film dosimetry combining calibration and measurement in a single scan

Radiochromic film provides dose measurement at high spatial resolution, but often is not preferred for routine evaluation of patient-specific intensity modulated radiation therapy (IMRT) plans owing to ease-of-use factors. The authors have established an efficient protocol that combines calibration and measurement in a single scan and enables measurement results to be obtained in less than 30 min. This avoids complications due to postexposure changes in radiochromic film that delay the completion of a measurement, often for up to 24 h, in commonly used methods. In addition, the protocol addresses the accuracy and integrity of the measurement by eliminating environmental and interscan variability issues. The authors collected dose-response data from six production lots of Gafchromic EBT3 film and three production lots of EBT2 film at doses up to 480 cGy. In this work, the authors used seven different scanners of two different models-Epson 10000XL and V700; postexposure times before scanning from 30 min to 9 days; ambient temperatures for scanning spanning 11 °C; and two film orientations. Scanning was in 48-bit RGB format at 72 dpi resolution. Dose evaluation was conducted using a triple-channel dosimetry method. To evaluate the measurement protocol, patient specific IMRT and volumetric modulated arc therapy (VMAT) plans were exposed onto EBT3 films on a Varian Trilogy Linac. Film scanning was done following the protocol under a number of different conditions and the dose maps were analyzed to demonstrate the equivalence of results. The results indicated that the dose-response data could be fit by a set of related rational functions leading to the description of a generic calibration curve. A simplified dosimetry protocol was established where dose-response data for a specific film lot, scanner, and scanning conditions could be derived from two films exposed to known doses. In most cases only one calibrated exposure was required since the dose for one of the films could be zero. Using the Gamma test criterion of 2%∕2 mm to evaluate the measurements, similar passing rates ranging between about 95% and 99% for the fields studied were obtained from application films digitized under a variety of conditions all of them different than the conditions under which the calibration films were scanned. The authors have developed a simplified and efficient protocol to measure doses delivered by an IMRT or VMAT plan using only the patient film, one calibration film, one unexposed film, and applying a single scan to acquire a digital image for calculation and analysis. The simplification and timesaving offer a potential practical solution for using radiochromic film for routine treatment plan quality assurance without sacrificing spatial resolution for convenience.

Comparison of Epson scanner quality for radiochromic film evaluation

Epson Desktop scanners have been quoted as devices which match the characteristics required for the evaluation of radiation dose exposure by radiochromic films. Specifically, models such as the 10000XL have been used successfully for image analysis and are recommended by ISP for dosimetry purposes. This note investigates and compares the scanner characteristics of three Epson desktop scanner models including the Epson 10000XL, V700, and V330. Both of the latter are substantially cheaper models capable of A4 scanning. As the price variation between the V330 and the 10000XL is 20‐fold (based on Australian recommended retail price), cost savings by using the cheaper scanners may be warranted based on results. By a direct comparison of scanner uniformity and reproducibility we can evaluate the accuracy of these scanners for radiochromic film dosimetry. Results have shown that all three scanners can produce adequate scanner uniformity and reproducibility, with the inexpensive V330 producing a standard deviation variation across its landscape direction of 0.7% and 1.2% in the portrait direction (reflection mode). This is compared to the V700 in reflection mode of 0.25% and 0.5% for landscape and portrait directions, respectively, and 0.5% and 0.8% for the 10000XL. In transmission mode, the V700 is comparable in reproducibility to the 10000XL for portrait and landscape mode, whilst the V330 is only capable of scanning in the landscape direction and produces a standard deviation in this direction of 1.0% compared to 0.6% (V700) and 0.25% (10000XL). Results have shown that the V700 and 10000XL are comparable scanners in quality and accuracy with the 10000XL obviously capable of imaging over an A3 area as opposed to an A4 area for the V700. The V330 scanner produced slightly lower accuracy and quality with uncertainties approximately twice as much as the other scanners. However, the results show that the V330 is still an adequate scanner and could be used for radiation dosimetry purposes. As such, if budgetary requirements are limited, the V700 scanner would be the recommended option at a price eight times cheaper than the 10000XL; however, the V330 produces adequate results at a price which is 2.5 times cheaper again. This may be a consideration for smaller institutions or individuals working with radiochromic film dosimetry.PACS number: 87.55.Qr; 87.56.Fc

Linearization of dose-response curve of the radiochromic film dosimetry system.

Despite numerous advantages of radiochromic film dosimeter (high spatial resolution, near tissue equivalence, low energy dependence) to measure a relative dose distribution with film, one needs to first measure an absolute dose (following previously established reference dosimetry protocol) and then convert measured absolute dose values into relative doses. In this work, we present result of our efforts to obtain a functional form that would linearize the inherently nonlinear dose-response curve of the radiochromic film dosimetry system. Functional form [ζ = (-1)[middle dot]netOD((2∕3))∕ln(netOD)] was derived from calibration curves of various previously established radiochromic film dosimetry systems. In order to test the invariance of the proposed functional form with respect to the film model used we tested it with three different GAFCHROMIC™ film models (EBT, EBT2, and EBT3) irradiated to various doses and scanned on a same scanner. For one of the film models (EBT2), we tested the invariance of the functional form to the scanner model used by scanning irradiated film pieces with three different flatbed scanner models (Epson V700, 1680, and 10000XL). To test our hypothesis that the proposed functional argument linearizes the response of the radiochromic film dosimetry system, verification tests have been performed in clinical applications: percent depth dose measurements, IMRT quality assurance (QA), and brachytherapy QA. Obtained R(2) values indicate that the choice of the functional form of the new argument appropriately linearizes the dose response of the radiochromic film dosimetry system we used. The linear behavior was insensitive to both film model and flatbed scanner model used. Measured PDD values using the green channel response of the GAFCHROMIC™ EBT3 film model are well within ±2% window of the local relative dose value when compared to the tabulated Cobalt-60 data. It was also found that criteria of 3%∕3 mm for an IMRT QA plan and 3%∕2 mm for a brachytherapy QA plan are passing 95% gamma function points. In this paper, we demonstrate the use of functional argument to linearize the inherently nonlinear response of a radiochromic film based reference dosimetry system. In this way, relative dosimetry can be conveniently performed using radiochromic film dosimetry system without the need of establishing calibration curve.

TH-E-BRB-02: Linearization of Dose Response Curve for the Radiochromic Film Dosimetry System

Purpose: In order to measure relative dose distribution with radiochromic film, one need to first measure an absolute dose (following previously established reference dosimetry protocol) and then convert measured absolute dose into relative dose. We present here result of our efforts to establish a functional form that converts the inherently non‐linear dose response curve of the radiochromic film dosimetry system into liner one. Methods: In order to test the invariance of the proposed functional form with respect to the film or scanner model used, we have tested it on film pieces from three different GAFCHROMICTM film models (EBT, EBT‐2, and EBT‐3) irradiated to various doses and scanned on a single scanner. for one of the film models we have also tested it by scanning with three different flatbed scanner models (Epson V700, 1680, and 10000XL). To test our hypothesis that the proposed functional argument linearizes the response of the radiochromic film dosimetry system, we performed a measurement of percent depth dose (PDD) curves in Cobalt‐60 beam. Results: Obtained R2 values indicate that the choice of the functional form of the new argument (ζ) appropriately linearizes the dose response of the radiochromic film dosimetry system we used. The linear behavior was insensitive to both film model and flatbed scanner model used. Measured PDD values using the green channel response of the GAFCHROMICTM EBT‐3 film model are well within ±2% window of the local relative dose value when compared to the tabulated Cobalt‐60 data. Conclusions: We demonstrate the use of a unique functional argument to linearize the inherently non‐linear response of a radiochromic film based reference dosimetry system. In this way, relative dosimetry can be conveniently performed using radiochromic film dosimetry system without the need of establishing an absolute calibration curve. One author is from GAFCHROMICTM films manufacturer

SU-E-T-165: Protocol for Simplified Radiochromic Film Dosimetry.

Radiochromic film provides dose measurement at high spatial resolution, but often is not selected for routine evaluation of patient-specific IMRT plans owing to ease-of-use factors. We have developed a simplified protocol that avoids complications encountered in commonly used methods. We evaluated the simplified protocol by collecting dose-response data from six production lots of EBT3 film at doses up to 480 cGy. In this work, we used eight different scanners of two different models - Epson 10000XL and V700; post-exposure times before scanning from 30 minutes to 9 days; ambient temperatures for scanning spanning 23°F and two film orientations. Scanning was in 48-bit rgb format at 72 dpi resolution. Dose evaluation was conducted using a triple-channel dosimetry method. To validate the simplified protocol, patient specific IMRT QA was performed using a Varian Trilogy Linac to expose EBT3 films. Scanning and film analysis was done following the protocol. The results indicated that the dose-response data could be fit by a set of related rational functions leading to the description of a universal calibration curve. A simplified protocol was established where dose-response data for a specific film lot, scanner, and scanning conditions could be derived from no more than two films exposed to known doses. In most cases only one calibrated exposure was required. Using the Gamma test criterion of 2%/2mm to evaluate the measurements, passing rates ranged between 95% and 99%. We have demonstrated a simplified protocol to measure doses delivered by an IMRT treatment plan using only the patient film, one calibration film, one unexposed film, and applying a single scan to acquire a digital image for calculation and analysis. The simplification and time-savings provide a practical solution for using radiochromic film for routine IMRT QA without sacrificing spatial resolution for convenience. David Lewis, Andre Micke and Xiang Yu are all employed by Ashland Specialty Ingredients the manufacturer of GAFCHROMIC EBT3 radiochromic film that is the subject of the work presented in the Abstract.