Film Scanner Research Articles

Low energy ion beam monitoring system by dosimetry film and particle induced X-ray

A simple monitoring system for a low energy (less than 5MeV) proton beam by dosimetry film was developed. A few μm thick Ni foil was installed in front of the film to produce X-rays which develop the film. To eliminate heat damage by the ion beam, a Ni foil was prepared on a 500μm thick graphite sheet which stops the ion beam and effectively dissipates the heat transversely. To verify the linearity of development, 1–2.5MeV proton beams were irradiated at various fluences, and the irradiated films were analyzed by a UV–VIS spectrometer and a commercial film scanner. The system showed a good linearity of absorbance in the fluence range from 4.6×1013H+/cm2 to 1×1015H+/cm2 for 2.5MeV protons. The irradiated film showed a two-dimensional profile of the ion beam very well with a spatial resolution of about 2.8mm.

Comparison of 4 MV photon surface dose among Varian, Siemens, and Elekta linear accelerators for tangential breast treatment: a phantom study

We have compared the differences in a 4-MV photon surface dose among Varian, Siemens, and Elekta linear accelerators (linacs) with wedges for tangential breast treatment. The wedge factor and the surface dose were measured using a solid water phantom and an ion chamber for each linear accelerator with various field sizes and wedge angles. A tangential treatment plan was applied to an elliptical hollow cylinder water phantom with a radiochromic film placed thereon. A dose was delivered to a simulated target in the phantom, and the resulting dose distribution was analyzed using a film scanner. Varian's wedges resulted in the highest wedge factors, ranging from 0.37 to 0.75 depending on the wedge angles. Varian's wedges led to the highest normalized skin doses, ranging between 0.40 and 0.73 depending on the wedge angles and field sizes. In the cylinder phantom test with two tangential beams, the Varian linac provided a nearly 20% higher maximum dose than the Siemens and Elekta linacs. The Varian linac resulted in the highest surface doses, and the Elekta linac led to the lowest for nearly all the measurement conditions we employed, including open beams.

Development of New Software as a Convenient Analysis Method for Dental Microradiography

To the end of developing a convenient research tool to calculate the mineralization status of teeth in detail, a new program was developed using Visual Basic for Applications combined with Microsoft Excel 2004. To demonstrate the usefulness of this program, it was used to analyze tooth enamel mineralization after acid exposure. Transverse microradiography images (TMR) of specimens were digitalized with a charge-coupled device camera with a microscope (CCD camera) and a digital film scanner (FS). Subsequently, the mineral content profile of each specimen after de- and remineralization studies were calculated using the Angmar's formula. The newly developed program was applied to calculating the mineral loss (DeltaZ), lesion depth (Ld), surface zone depth (SZd), and lesion body depth (LBd) of tooth specimens. In addition, the outer surface zone (OSZ), inner lesion body (ILB), and sandwich area (SA) between OSZ and ILB- which together constituted DeltaZ - were calculated by the newly developed program. Data obtained with the newly developed program were in good agreement for both CCD camera and FS, indicating that the program was reliable for tooth enamel mineralization research studies.

Comparison of the Epson Expression 1680 flatbed and the Vidar VXR‐16 Dosimetry PRO™ film scanners for use in IMRT dosimetry using Gafchromic and radiographic film

Intensity-modulated radiotherapy (IMRT) treatment plan verification is often done using Kodak EDR2 film and a Vidar Dosimetry PRO film digitizer. However, since many hospitals are moving towards a filmless environment, access to a film processor may not be available. Therefore, we have investigated a newly available Gafchromic EBT film for IMRT dosimetry. Planar IMRT dose distributions are delivered to both EBT and EDR2 film and scanned with the Vidar VXR-16 as well as an Epson Expression 1680 flatbed scanner. The measured dose distributions are then compared to those calculated with a Pinnacle treatment planning system. The IMRT treatments consisted of 7-9 6 MV beams for treatment of prostate, head and neck, and a few other sites. The films were analyzed using FilmQATM (3cognition LLC) software. Comparisons between measured and calculated dose distributions are reported as dose difference (DD) (pixels within +/-5%), distance to agreement (DTA) (3 mm), as well as gamma values (y) (dose= +/-3%, dist. =2 mm). Using EDR2 with the Vidar scanner is an established technique and agreement between calculated and measured dose distributions was better than 90% in all indices (DD, DTA, and gamma). However, agreement with calculations deteriorated reaching the lower 80% for EBT film scans with the Vidar scanner in logarithmic mode. The EBT Vidar scans obtained in linear mode showed an improved agreement to the upper 80% range, but artifacts were still observed across the scan. These artifacts were very distinct in all EBT scans and can be attributed to the way the film is transported through the scanner. In the Epson scanner both films are rigidly immobilized and the light source scans over the film. It was found that the Epson scanner performed equally well with both types of film giving agreement to better than 90% in all indices.

Comparison of Kodak EDR2 and Gafchromic EBT film for intensity-modulated radiation therapy dose distribution verification

The quantitative dose validation of intensity-modulated radiation therapy (IMRT) plans require 2-dimensional (2D) high-resolution dosimetry systems with uniform response over its sensitive region. The present work deals with clinical use of commercially available self-developing Radio Chromic Film, Gafchromic EBT film, for IMRT dose verification. Dose response curves were generated for the films using a VXR-16 film scanner. The results obtained with EBT films were compared with the results of Kodak extended dose range 2 (EDR2) films. The EBT film had a linear response between the dose range of 0 to 600 cGy. The dose-related characteristics of the EBT film, such as post irradiation color growth with time, film uniformity, and effect of scanning orientation, were studied. There was up to 8.6% increase in the color density between 2 to 40 hours after irradiation. There was a considerable variation, up to 8.5%, in the film uniformity over its sensitive region. The quantitative differences between calculated and measured dose distributions were analyzed using DTA and Gamma index with the tolerance of 3% dose difference and 3-mm distance agreement. The EDR2 films showed consistent results with the calculated dose distributions, whereas the results obtained using EBT were inconsistent. The variation in the film uniformity limits the use of EBT film for conventional large-field IMRT verification. For IMRT of smaller field sizes (4.5 × 4.5 cm), the results obtained with EBT were comparable with results of EDR2 films.

Sensitivity of linear CCD array based film scanners used for film dosimetry

Film dosimetry is commonly performed by using linear CCD array transmission optical densitometers. However, these devices suffer from a variation in response along the detector array. If not properly corrected for, this nonuniformity may lead to significant overestimations of the measured dose as one approaches regions close to the edges of the scanning region. In this note, we present measurements of the spatial response of an AGFA Arcus II document scanner used for radiochromic film dosimetry. Results and methods presented in this work can be generalized to other CCD based transmission scanners used for film dosimetry employing either radiochromic or radiographic films.

Temps-multiplex stéréophotographie : évaluation qualitative et semi-quantitative en 2D et 3D de l’atrophie optique glaucomateuse

Real color documentation of the optic nerve head (ONH) is one of the most important methods in identifying early progression of glaucomatous optic nerve damage. This study qualitatively and semiquantitatively compared the evaluation of ONH photographs, using a 3D time-multiplexing system and conventional 2D photography, visualized on a computer monitor. Twelve 15 degrees sequential stereophotographs from the Erlangen Glaucoma Registry were scanned by a SprintScan 35 Plus Film scanner (Polaroid, Waltham, MA, USA) and converted by computer software (3D-PIX, NuVision, McNaughton Inc., Beaverton, OR, USA) in jps format (3D). The same ONH images were shown in 2D and 3D to 22 subjects: 12 residents and ten ophthalmologists and evaluated using a standardized questionnaire. We observed a significantly better evaluation with stereoscopic pictures for both qualitative parameters (cup depth, visibility of the retinal nerve fibers, and the thinnest location of the neuroretinal rim) and quantitative parameters (c/d ratio and size of the disc, depending on the training level: in 3D better evaluation by the residents, in 2D by the ophthalmologists). With 2D pictures, we found better evaluation of the B zone and the stage of atrophy. Other than the method used for the entire evaluation, there was no significant difference between the groups. For the parameters weighed for clinical importance, the score of correct answers was significantly better with stereoscopic pictures. This study showed a significantly better evaluation of glaucomatous ONH atrophy with 3D images than with 2D pictures, independently of the evaluators' clinical training level. The computer-based evaluation of ONH atrophy using a time-multiplexing system (shutter glasses) may improve the diagnosis of glaucoma patients.

Effect of long-term treatment with raloxifene on mammary density in postmenopausal women

To evaluate in a group of postmenopausal women the effects of long-term raloxifene treatment on breast density using a digitized analysis of mammograms and on insulinlike growth factor-1 (IGF-1), insulinlike growth factor binding protein-3 (IGFBP-3), and sex hormone-binding globulin (SHBG) plasma levels. Seventy healthy postmenopausal women with normal body weight were enrolled in this study and were divided into two groups based on their bone status, evaluated by dual-energy x-ray at the lumbar spine (L2-4). Fifty women (chronological age 52.4 +/- 4.1 y, menopausal age 42.1 +/- 3.9 y), in whom the L2-4 T score was less than -2.5 SD, were treated with raloxifene HCl 60 mg/day orally for 2 years. The other 20 women (chronological age 53.6 +/- 3.5 y, age at menopause 43.1 +/- 3.6 y), in whom the L2-4 T score ranged between -1 and -2.5 SD, were enrolled as controls. All 70 women received calcium (1 g/d orally) and cholecalciferol (880 UI/d orally) supplementation. Moreover, all women followed a normocaloric and personalized diet. All women had mammography at baseline and after 2 years of therapy. The mammographic images on traditional support (radiography) were acquired by using a film scanner and were then elaborated by means of ad hoc software. Moreover, assessments of IGF-1, IGFBP-3, and SHBG plasma levels were obtained at baseline and after 24 months. After 24 months of therapy, there was a significant variation in the raloxifene-treated group with respect to baseline in the distribution of gray classes of radiographic images. In particular, an attenuation of graphic trace with a reduction of the areas with the lowest and most elevated gray classes was observed. In the control group, no significant variations of graphic traces were observed. Moreover, raloxifene treatment significantly reduced IGF-1 and increased IGFBP-3 and SHBG plasma levels at 24 months. During follow-up, IGF-1, IGFPB-3, and SHBG levels did not change significantly in the control group. Long-term treatment with raloxifene in a population of postmenopausal women is able to reduce breast density. Such an effect could perhaps explain the reduction in the incidence of mammary carcinoma observed in the Multiple Outcomes of Raloxifene Evaluation study probably due to the direct antiestrogenic activity of raloxifene on mammalian tissue and/or its indirect activity increasing SHBG levels or modifying the IGF-1/IGFBP-3 ratio.

Membrane Potential-regulated Transcription of the Resting K+ Conductance TASK-3 via the Calcineurin Pathway

The 2P domain K(+) channel TASK-3 is highly expressed in cerebellar granule neurons where it has been proposed to underlie the K(+) leak conductance, IKso. In a previous work we showed that expression of TASK-3 increases in cerebellar granule neurons as they mature in culture. Here we show that within the cerebellum, levels of TASK-3 mRNA increase as granule neurons migrate to their adult positions and receive excitatory mossy fiber input. To understand the mechanism of this increase in TASK-3 expression we used an in vitro model culturing the neurons in either depolarizing conditions mimicking neuronal activity (25K, 25 mm KCl) or in conditions which approach deafferentation (5K, 5 mm KCl). An important increase in TASK-3 mRNA is uniquely observed in 25K and is specific since other background K(+) channel levels remain unchanged or decrease. The rise in TASK-3 mRNA leads to an increase in TASK-3 protein and the IKso conductance resulting in hyperpolarization. Blocking L-type calcium channels or their downstream effector calcineurin, abrogates TASK-3 expression and IKso, leading to hyperexcitability. This is the first study demonstrating that depolarization-induced Ca(2+) entry can directly regulate cellular excitability by dynamically regulating the transcription of a resting K(+) conductance. The appearance of this conductance may play an important role in the transition of depolarized immature neurons to their mature hyperpolarized state during neuronal development.

Digitisation of electron microscope films: Six useful tests applied to three film scanners

A series of simple tests have been used to measure the performance of flat-bed film scanners suitable for digitisation of electron micrographs. Two of the film scanners evaluated are commercially available and one has been constructed in the laboratory paying special attention to the needs of the electron microscopist. The tests may be useful for others.

TH‐E‐224A‐03: Orientation, Position, and Temperature Dependence On Optical Density Measurements When Using Sensitive Radiochromic Film and Fluorescent CCD Scanner

Purpose: We report systematic artifacts that were found to occur when scanning a commercial radiochromic film (RCF) (GAFCHROMIC EBT) with a charge‐coupled device (CCD) film scanner. Potential systematic sources of optical density (OD) measurement error were found be related to film orientation with respect to the scanner bed, film position on the scanner bed, and film temperature from repeated scanning. Method and Materials: We investigated the use of two flatbed CCD scanners that have been previously reported for use with the RCF, as well as two point densitometers that measure diffuse OD. Change in OD with film orientation was studied with small uniformly irradiated RCFs that were rotated and repeatedly scanned. A RCF from an IMRT QA measurement was scanned in portrait and landscape orientations to assess the magnitude of possible clinical errors. Film uniformity was assessed by evaluating profiles in the scan direction for large RCFs with graded uniform ODs produced by exposure to sunlight. A thermocouple was placed on the bed of a CCD scanner RCF was repeatedly scanned while recording temperature. Results: Sinusoidal variations of 15% were observed for rotating film measurements made with one CCD scanner (Epson) and 80% for the other (Microtek). The point densitometers did not demonstrate any variation with rotation. Changes in temperature in the range of 18–34°C lead to OD changes as large as 7%. The edges of the CCD scan beds demonstrated non‐uniformities as large as 15%. Conclusion: Care must be taken to avoid these systematic errors when using RCF for clinical dosimetry. We recommend: maintaining the orientation of films; scanning in the central portion of the scanner bed; and limiting the number of consecutive scans.This work was supported by NCI grants R01‐CA‐100636 and N43‐CM‐52214, Department of Health and Human Services Contract No HHSN261200522014C, and by Sun Nuclear Corporation.

SU‐FF‐T‐311: LINAC Dosimetry: Benchmark Data Set Uncertainty

Purpose: Determine sources of error in the collection of a Benchmark Data set for LINAC dosimetry and provide methods of error correction that will ensure the highest possible accuracy of the dosimetric data. Method and Materials: Guided by the measurement requirements for the Benchmark Datasets, the sources of experimental error can be divided into 3 sources: 1) discretization and volume averaging errors; 2) Stochastic errors; and 3) Systematic or artifactual errors. Measurements will be made in a 3D water phantom scanning system and in a water‐equivalent solid phantom that will allow the insertion of heterogeneous components. Results: We present theoretical analyses of the expected errors associated with ion chamber, radiochromic film, and diode measurements and provide specific techniques that will enable high spatial resolution of dose gradients resulting from beam limiters and dose perturbations in and around heterogeneity interfaces, such as air/tissue, lung/tissue, bone/tissue. These techniques include de‐convolution of chamber response and a 3D correction matrix of a film scanner. Conclusion: Theoretical limits of spatial resolution in LINAC dosimetry are achievable and demonstrable using dosimetric tools available today. These tools and methods will be used to collect accurate Benchmark Dosimetry data for future research in Monte Carlo techniques for treatment planning as well as automated software tools that will enable systematic QA of modern treatment planning systems. Conflict of Interest: This project has been funded in part with Federal funds from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services, under Contract No, HHSN261200522014C, NCI grants R01‐CA‐100636, and by Sun Nuclear Corporation.

SU‐FF‐T‐145: Comparison of the Epson Expression 1680 Flatbed and the Vidar VXR‐16 Dosimetry PRO™ Film Scanners for Use in IMRT Dosimetry Using Gafchromic and Radiographic Film

Purpose: We have investigated the consistency of the newly available self‐developing Gafchromic® EBT film relative to EDR2 for IMRT dosimetry QA when using flatbed scanner as opposing to the well established Vidar VXR‐16. Method and Materials: IMRT plans consisting of seven to nine 6 MV beams were calculated using Pinnacle treatment planning system. The patient specific dose distributions were delivered to the phantom containing either EDR2 or EBT film. The films were scanned with both the Vidar and Epson scanners and analyzed using FilmQA™ (3cognition LLC) software. Comparisons between measured and calculated dose distributions are reported as dose difference (DD) (pixels within ±5%), distance‐to‐agreement (DTA) (3 mm), as well as gamma values (dose difference = ±3%, distance=2 mm). Results: Our preliminary analysis of 9 IMRT cases showed that: (i) Vidar and Epson EBT scans differ on average by 7.2% for DD, 6.3% for gamma, and 8.6% for DTA; (ii) same comparison using EDR2 gives 2.2% for DD, 3.1% for gamma, and 2.2% for DTA; (iii) the Epson EBT and EDR2 scans differ on average by 3.4% for DD, 5.0% for gamma, and 2.9% for DTA; (iv) the same comparison between EBT and EDR2 films using Vidar gives 10.3% for DD, 6.8% for gamma, and 5.1% for DTA. Conclusions: Tissue equivalence, high spatial resolution, energy independence, and self developing properties make the choice of EBT film for IMRT QA more desirable and cost effective than silver based radiographic film. Much better agreement with calculations can be obtained using EBT with a flatbed scanner. While both scanners give equivalent results with EDR2 films, a flatbed scanner in transmission mode is recommended to achieve optimal results with the EBT films.

TH‐E‐224A‐04: IMRT Film QA in a Heterogeneous Anthropomorphic Phantom

Purpose: To study the agreement of heterogeneous IMRT treatment planning dose calculations with radiochromic film (RCF) and radiographic film (RGF) measured in anthropomorphic heterogeneous phantoms. We intend to use heterogeneous‐phantom film dosimetry to improve IMRT quality assurance (QA). Method and Materials: A commercial heterogeneous anthropomorphic head‐and‐neck phantom, with equivalent tissue bone, soft tissue and air regions was employed for dosimetry verification (CIRS, inc.). High sensitivity EBT radiochromic film (ISP, Inc.) and EDR2 radiographic film (Kodak) were employed simultaneously for film dosimetry. The phantom had 12 axial sections, each 25mm thick, with alignment pins and a compression plate. We selected a plane containing bone, soft tissue and an air gap for IMRT verification. The RCF and RGF were cut to match the selected plane, inserted between the sections and light sealed. A 6MV IMRT head & neck treatment plan with 7 beams was delivered using a commercial linac (Varian Clinac 2100/CD). The RCF was scanned avoiding artifact described in a companion work using a CCD film scanner (Epson 1680 scanner). The dose distributions were compared with the treatment plan. Results: Both RCF and RGF disagree with the treatment plan dose near the air cavities by 15%. Away the air cavities 5% agreement was obtained with RCF. Pronounced artifacts were observed in the RGF that were not observed in the RCF. Conclusion: IMRT dosimetry and quality assurance can be improved by using anthropomorphic phantoms that incorporate realistic heterogeneities such as bone, soft tissue and air gaps, and corrections to dose calculations can be applied. We hypothesize that RGF suffers from Cerenkov in air cavities and in less opaque phantom materials, and this will be investigated in further studies.This work was supported in part by NCI grants R01‐CA‐100636 and N43‐CM‐52214.

The Scanning of Colour and B&W Film and Photographs for Image Processing, Analysis and Archiving - On a Tight Budget

Abstract Despite the advent of the new PC based digital camera era, there is still a vast archive of film. The obvious thing to do is to scan film optically using a high resolution film scanner and to convert the image into a digital file for digital distribution, PC archiving, and image processing. The likes of NASA can easily afford the best $20k plus PMT drum scanners and pro flatbed scanners for their spaceflight photo archives. See some professional scanners at http://www.imacon.dk, http://www.aztek.com, http://graphics.kodak.com (Creo) and http://www.flatbed-scanner-review.org. You can download selections from the NASA digitised archive at http://grin.hq.nasa.gov.

Designing Camera Origination Films for Scan-Only Applications in Television and Digital Intermediate

With the growing popularity of digital intermediate in the feature film market and the continuing development of improved telecine technologies for television, the notion of traditional camera origination film design optimized around direct optical or contact printing is radically challenged. For scan-only film image capture systems where the camera film will be scanned exclusively to video or data and never directly printed, a very different approach is taken to sensitometric curve design. Rather than focusing on tonal characteristics, which yield acceptable and preferred results for overall contrast, grayscale neutrality, and shadow and highlight detail in a traditional printing paradigm, the film curves must instead be drawn to optimize the quality of signal provided to the digitization step in the film scanner. Further, standard constructs of color reproduction are also open for modification as the film's spectral sensitivity and color-enhancing chemistries are changed to better mesh with digital color-processing capabilities.

Evaluation of gafchromic EBT film for intensity modulated radiation therapy dose distribution verification

This work was undertaken with the intention of investigating the possibility of clinical use of commercially available self-developing radiochromic film – Gafchromic EBT film – for IMRT dose verification. The dose response curves were generated for the films using VXR-16 film scanner. The results obtained with EBT films were compared with the results of Kodak EDR2 films. It was found that the EBT film has a linear response between the dose ranges of 0 and 600 cGy. The dose-related characteristics of the EBT film, like post-irradiation color growth with time, film uniformity and effect of scanning orientation, were studied. There is up to 8.6% increase in the color density between 2 and 40 h after irradiation. There was a considerable variation, up to 8.5%, in the film uniformity over its sensitive region. The quantitative difference between calculated and measured dose distributions was analyzed using Gamma index with the tolerance of 3% dose difference and 3 mm distance agreement. EDR2 films showed good and consistent results with the calculated dose distribution, whereas the results obtained using EBT were inconsistent. The variation in the film uniformity limits the use of EBT film for conventional large field IMRT verification. For IMRT of smaller field size (4.5 × 4.5 cm), the results obtained with EBT were comparable with results of EDR2 films.

SU-FF-T-215: Radiation Leakage From the Electron Applicators in the Varian 21 EX Linear Accelerator

Purpose: Radiation dose leakage from the applicator is a well-known phenomenon in the electron radiotherapy. This study was to measure such scattered dose and find out its dependences with the angle of obliquity, cutout and applicator size using our clinical 4 MeV electron beam. A piece of lead foil wrapped around the lower part of the applicator could eliminate the dose. The increase of output due to the application of lead can be solved by a simple output correction factor measurement. Method and Materials: Calibrated Kodak TL film was used to measure the surface dose and dose at 1 cm depth in a solid water phantom using our Varian 21 EX linear accelerator with 10 × 10 cm2 applicator and cutout. A film scanner was used to determine the dose. The film measurement was verified with ionization chamber and MOSFET detector. A lead foil of 1 mm thickness was used to wrap the applicator up when needed. Results: Peripheral scattered dose was found at about 12 cm away from the field central axis of a 10 × 10 cm2 cutout. The surface dose was determined to be about 1.5 cGy when 150 cGy was given at 1 cm depth in the phantom (SSD = 100 cm). It is found that the surface dose increased with the angle of obliquity, and with the square cutout size. By warping the lower part of the applicator up with lead foil, such dose was not detectable. Conclusion: Peripheral scattered dose outside the applicator of 4 MeV beam was measured and located. Such dose depends on the angle of obliquity, applicator and cutout size. We suggested using a lead foil to wrap the applicator up with an output correction factor to eliminate the dose during the clinical treatment as and when required.

TH-C-T-6E-05: Evaluation of GafChromic EBT Film for IMRT QA Using Two Different Scanners

Purpose: Absolute film dosimetry for IMRT QA using radiographic film is very time‐ and film‐consuming because of film processing uncertainties. Radiochromic film requires only one calibration curve per energy per production lot. Applicability of new GafChromic EBT film for absolute IMRTdosimetry using two different film scanners was evaluated. Method and Materials: GafChromic EBT (ISP, Wayne, NJ) and Kodak EDR2 films irradiated in polystyrene phantoms on a Varian 2100C/D linear accelerator were compared using the Vidar VXR‐16 DosimetryPro and Epson Expression 1680 scanners. Vidar scanning was done with RIT113 software and a yellow filter for the EBT. Epson scans were done with the scanner software in 48 bit color, followed by red channel extraction. EBT films were scanned 24 hours after exposure. MSKCC's Contour software was used for dosimetric analysis. Results: EBT provided better intensity linearity with dose than EDR2 and higher pixel values in the clinical dose range. The pixel values of the EBT film differed by 3–9% (Epson) and 11–19% (Vidar) when rotating the film 90 degrees on the scanner, which resulted in up to 30% dose errors when mixing directions of IMRT and calibration films. The Vidar produced lower pixel values but higher optical density than the Epson. Calibration curves based on small films cut from one sheet coincided with the curves created from a set of sheets. EBT film IMRT dose distributions agreed well with EDR2 (1.9% on CAX for the Vidar, 3.6% for the Epson). Conclusion: GafChromic EBT film provides a good alternative for absolute IMRTdosimetry. Both film scanners provide equivalent dosimetric results. Calibration films and IMRT films have to be scanned in the same direction. The calibration curve can be created using small films cut from one large film. Conflict of Interest: Partial material support provided by ISP Corporation.

SU‐FF‐T‐144: Feasibility of a Novel Gafchromic Film for Routine IMRT QA

Purpose: To assess the feasibility of using an improved Gafchromic film, EBT (International Specialty Products), for routine IMRT QA. Method and Materials: EBT films were evaluated for clinical use in IMRT QA by comparing their performance to the widely used Kodak EDR2 film. As a clinical test, one hybrid phantom plan, consisting of seven IMRT fields, was calculated on a commercial treatment planning system with prescription levels of one to five Gray. The plans were delivered to EBT and EDR2 films loaded in a Bluebox film phantom. The films were digitized on Vidar VXR‐12 film scanner and analyzed using the RIT film dosimetry system. The percentage of pixels (exceedence) with plan/film dose difference above 5% tolerance level was used as a metric for film comparison. The symmetry and flatness for the same dose range were also determined for both types of films. Results: For EBT films, flatness and symmetry in two orthogonal directions improved as dose increased. Correlation between the plan and EBT film improved with increased dose, as indicated by a decrease in the exceedence (%): 22.9(1Gy), 11.9(2Gy), 11.2(3Gy), 6.6(4Gy), 4.1(5Gy). EDR2 films exhibited a different trend: 12.7(1Gy), 7.7(2Gy), 12.6(3Gy), 13.4(4Gy), 26(5Gy). Delivery time increased from 6 minutes for 1Gy plan to 9.5 minutes for 4Gy plan using dose rate of 600MU/min. Conclusion: At higher doses, EBT films show results comparable to, or improved over, EDR2 films. They demonstrate improved flatness and symmetry and IMRT QA results with increased dose. The additional 3.5 minutes necessary to deliver 4Gy to EBT film in order to achieve better results than with the EDR2 film is more than compensated by the convenience of using Gafchromic film. Further improvement of the digitization procedure and increase of the signal‐to‐noise ratio of EBT film should allow even lower dose for routine IMRT QA.