Portrait Orientation Research Articles

Characteristic of EBT-XD and EBT3 radiochromic film dosimetry for photon and proton beams

Recently, a new type of radiochromic film, the EBT-XD film, has been introduced for high dose radiotherapy. The EBT-XD film contains the same structure as the EBT3 film but has a slightly different composition and a thinner active layer. This study benchmarks the EBT-XD against EBT3 film for 6 MV and 10 MV photon beams, as well as for 97.4 MeV and 148.2 MeV proton beams and 15–100 kV x-rays. Dosimetric and film reading characteristics, such as post irradiation darkening, film orientation effect, lateral response artifact (LRA), film sensitivity, energy and beam quality dependency were investigated. Furthermore, quenching effects in the Bragg peak were investigated for a single proton beam energy for both film types, in addition measurements were performed in a spread-out Bragg peak. EBT-XD films showed the same characteristic on film darkening as EBT3. The effects between portrait and landscape orientation were reduced by 3.1% (in pixel value) for EBT-XD compared to EBT3 at a dose of 2000 cGy. The LRA is reduced for EBT-XD films for all investigated dose ranges. The sensitivity of EBT-XD films is superior to EBT3 for doses higher than 500 cGy. In addition, EBT-XD showed a similar dosimetric response for photon and proton irradiation with low energy and beam quality dependency. A quenching effect of 10% was found for both film types. The slight decrease in the thickness of the active layer and different composition configuration of EBT-XD resulted in a reduced film orientation effect and LRA, as well as a sensitivity increase in high-dose regions for both photon and proton beams. Overall, the EBT-XD film improved regarding film reading characteristics and showed advantages in the high-dose region for photon and proton beams.

The origin of the flatbed scanner artifacts in radiochromic film dosimetry—key experiments and theoretical descriptions

The optical origin of the lateral response and orientation artifacts, which occur when using EBT3 and EBT-XD radiochromic films together with flatbed scanners, has been reinvestigated by experimental and theoretical means. The common feature of these artifacts is the well-known parabolic increase in the optical density OD(x) = −log10 I(x)/I0(x) versus offset x from the scanner midline (Poppinga et al Med. Phys. 41 021707). This holds for landscape and portrait orientations as well as for the three color channels. Dose-independent optical subjects, such as neutral density filters, linear polarizers, the EBT polyester foil and diffusive glass, also present the parabolic lateral artifact when scanned with a flatbed scanner. The curvature parameter c of the parabola function OD(x) = c0 + cx2 is found to be a linear function of the dose, the parameters of which are influenced by the film orientation and film type, EBT3 or EBT-XD. The ubiquitous parabolic shape of function OD(x) is attributed (a) to the optical path-length effect (van Battum et al Phys. Med. Biol. 61 625–49), due to the increasing obliquity of the optical scanner light associated with increasing offset x from the scanner midline, and (b) and (c) to the partial polarization and scattering of the light leaving the film, which affect the ratio , thus making OD(x) increase with x2. The orientation effect results from the changes of effects (b) and (c) associated with turning the film position, and thereby the orientation of the polymer structure of the sensitive film layer. In a comparison of experimental results obtained with selected optical subjects, the relative weights of the contributions of the optical path-length effect and the polarization and scattering of light leaving the films to the lateral response artifact have been estimated to be of the same order of magnitude. Mathematical models of these causes for the parabolic shape of function OD(x) are given as appendices.

Celebrity chefs put their left cheek forward: Cover image orientation in celebrity cookbooks

ABSTRACTPortrait pose orientations influence perception: the left cheek is more emotionally expressive; females’ right cheeks appear more attractive. Posing biases are established in paintings, photographs, and advertisements, however, book covers have not previously been examined. This paper assesses cover image orientation in a book genre that frequently features a cover portrait: the celebrity cookbook. If marketers intuitively choose to enhance chefs’ emotional expressivity, left cheek poses should predominate; if attractiveness is more important, right cheek poses will be more frequent for females, with a left or no cheek bias for males. Celebrity cookbook covers (N = 493) were sourced online; identity, portrait orientation, photo type, and sex were coded. For celebrity cookbooks, left cheek covers (39.6%) were more frequent than right cheek (31.6%) or midline covers (28.8%); sex did not predict pose orientation. An interaction between photo type and sex bordered on significance: photo type did not influence females’ pose orientation; for males, the left cheek bias present for head and torso images was absent for full body and head only photos. Overall, the left cheek bias for celebrity cookbook covers implies that marketers intuitively select images that make the chefs appear happier and/or more emotionally expressive, enhancing engagement with the audience.

Moiré-reduction method for slanted-lenticular-based quasi-three-dimensional displays

In this paper we present a method for determining the preferred slanted angle for a lenticular film that minimizes moiré patterns in quasi-three-dimensional (Q3D) displays. We evaluate the preferred slanted angles of the lenticular film for the stripe-type sub-pixel structure liquid crystal display (LCD) panel. Additionally, the sub-pixels mapping algorithm of the specific angle is proposed to assign the images to either the right or left eye channel. A Q3D display prototype is built. Compared with the conventional SLF, this newly implemented Q3D display can not only eliminate moiré patterns but also provide 3D images in both portrait and landscape orientations. It is demonstrated that the developed slanted lenticular film (SLF) provides satisfactory 3D images by employing a compact structure, minimum moiré patterns and stabilized 3D contrast.

SU-F-T-581: The Effect of Scanning Orientation On New EBT-XD Film Using Vidar and Epson Scanners

Purpose: To study the effect of film scanning orientation for new EBT-XD film using Vidar and Epson scanners, compared with EBT3 films. Methods: The EBT-XD (lot#01081501) and EBT3 films (lot#11031501) were cut into 4cm×7cm pieces and each film piece was uniformly exposed to a 6MV photon beam (15×15cm2) at 5 cm depth and 100cm SAD in polystyrene phantom, one at a time. The doses delivered were 0,2.5,5,10,20,30,40 and 50 Gy for EBT-XD films, and 0,0.5,1,2,4,8,12 and 16 Gy for EBT3 films, respectively. All films were scanned at least 16 hours after irradiation, one at a time, in portrait or landscape orientation, using a Vidar DosimetryPro Advantage Red and an Epson 10000XL scanner (red channel). Each film piece was positioned at the center of a frame (36cm×36cm) with a cutout slightly larger than the film size for scanning. The scanned data (71 dpi), were analyzed using ImageJ and the average in the ROI (3cm×3cm) of each film at the center was obtained. Results: Dose response curves (netOD vs. dose) were established and compared with EBT-XD and EBT3 film in portrait or landscape orientation using these two scanners. The portrait to landscape (P/L) ratio for each film/scanner combination was determined. The EBT-XD film is about three times less sensitive than EBT3 film. The netOD is higher for portrait than landscape orientation for all the film/scanner combinations. For EBT-XD and EBT3, the average P/L ratios are 1.02 and 1.03 using Vidar scanner, and 1.03 and 1.05 using Epson scanner (red channel), respectively. Conclusion: The effect of film scanning orientation for new EBT-XD film using Vidar Advantage Red and Epson 10000XL scanners has been studied, in comparison with EBT3 film. The portrait/landscape ratios are the lowest for EBT-XD film using Vidar Advantage Red scanner among the four film/scanner combinations.

Mobile Phone Use Behaviors and Postures on Public Transportation Systems.

Mobile phones are common in our daily life, but the users’ preferences for postures or screen operating styles have not been studied. This was a cross-sectional and observational study. We randomly sampled passengers who used mobile phones on the Mass Rapid Transit (MRT) system in metropolitan Taipei. A checklist was used to observe their body postures and screen operating styles while sitting or standing. As a result, 1,230 subjects from 400 trips were observed. Overall, of all the passengers who were sitting, 41% of them were using mobile phones. The majority of the tasks involved browsing (84%) with their phones in a portrait orientation (93%). Different-hand holding/operating was the most commonly used operating style while sitting (46%) and same-hand holding/operating was the most common while standing (46%). The distribution of screen operating styles was significantly different for those sitting than for those standing and for different genders and age groups. The most frequently observed postures while sitting were having one’s trunk against a backrest, feet on the floor and with or without an arm supported (58%). As for the users who were standing, the both- and different-hands groups had a high proportion of arms unsupported, feet on the floor and either their trunk supported or not. In contrast, the same-hand group tended to have their trunk unsupported, were holding a pole or handstrap and had both feet on floor. Further studies are warranted to characterize the ergonomic exposure of these commonly used postures and operating styles, and our results will help guide the selection of experimental conditions for laboratory settings.

Young vs old – landscape vs portrait: a comparative study of touch gesture performance

Purpose – The purpose of this paper is to gain deeper insights into performance differences of younger and older users when performing touch gestures, as well as the influence of tablet device orientation (portrait vs landscape). Design/methodology/approach – The authors performed a comparative study involving 20 younger (25-45 years) and 20 older participants (65-85 years). Each participant executed six gestures with each device orientation. Age was set as a between-subject factor. The dependent variables were task completion time and error rates (missed target rate and finger lift rate). To measure various performance characteristics, the authors implemented an application for the iPad that logged completion time and error rates of the participants when performing six gestural tasks – tap, drag, pinch, pinch-pan, rotate left and rotate right – for both device orientations. Findings – The results show a significant effect of age on completion time and error rates. Means reveal faster completion times and lower error rates for younger users than for older users. In addition, a significant effect of device orientation on error rates could be stated. Means show higher error rates for portrait orientation than for landscape orientation. Qualitative results reveal a clear preference for landscape orientation in both age groups and a lower acceptance of rotation gestures among older participants. Originality/value – In this study the authors were able to show the importance of device orientation as an influencing factor on touch interaction performance, indicating that age is not the exclusive influencing factor.

Biomechanical Loading on the Hand, Wrist, and Forearm When Holding a Tablet Computer

OCCUPATIONAL APPLICATIONS Based upon the endurance of their hand and forearm, the maximum duration for holding a computer tablet statically with one hand was less than 10 minutes for many users. In everyday situations, users would likely change posture before this time, but for users whose options are more limited, such as during enterprise use, high levels of fatigue could develop. Therefore, for people in situations where holding a tablet for extended periods of time is required, it would be prudent to change grips frequently, support the tablet on a surface, use aids (such as a stand or strap), hold it with both hands, switch to alternative tasks, and/or take breaks.TECHNICAL ABSTRACT Background: The use of tablet computers at home and in the workplace has rapidly increased in recent years. Tablet users may hold them for extended periods, increasing the risk of developing fatigue and potential musculoskeletal disorders. Purpose: The goals of this study were to estimate the biomechanical loading on the forearm and hand when holding a tablet computer and to assess the effects of orientation, mass, and the execution of touch gestures on this loading. Methods: Multiple parallel approaches were used to assess an unsupported single-handed grip: maximum load, maximum holding time, biomechanical models to estimate strength demands, ratings of perceived exertion, and grip pressure. Ten males and 10 females participated. Results: A majority (75%) of the participants adopted a modified lateral pinch grip. Using the maximum load method, females exerted a significantly higher percentage of their maximum voluntary contraction than males in landscape orientation (18.5% versus 13.5% maximum voluntary contraction) but not in portrait orientation. In portrait orientation, maximum holding time was 11.5 minutes for females and 15.9 minutes for males. Orientation, but not gesturing, had statistically significant main effects on loading. Conclusions: Holding a tablet one-handed for an extended period of time, as might be found in some enterprise settings, was found to be very fatiguing for the hand; it would thus be prudent for such users to use both hands, support aids, frequent posture changes, or breaks involving rest or alternative tasks.

Correcting lateral response artifacts from flatbed scanners for radiochromic film dosimetry.

A known factor affecting the accuracy of radiochromic film dosimetry is the lateral response artifact (LRA) induced by nonuniform response of a flatbed scanner in the direction perpendicular to the scan direction. This work reports a practical solution to eliminate such artifacts for all forms of dose QA. EBT3 films from a single production lot (02181401) cut into rectangular 4 × 5 cm(2) pieces, with the long dimension parallel to the long dimension of the original 20.3 × 25.4 cm(2) sheets, were exposed at a depth of 5 cm on a Varian Trilogy at the center of a 20 × 20 cm(2) open field at seven doses between 50 and 1600 cGy using 6 MV photons. These films together with an unexposed film from the same production lot were lined one next to the other on an Epson 10000 XL or 11000 XL scanner in portrait orientation with their long dimension parallel to the scan direction. Scanned images were then obtained with the line of films positioned at seven discrete lateral locations perpendicular to the scan direction. The process was repeated in landscape orientation and on three other Epson scanners. Data were also collected for three additional production lots of EBT3 film (11051302, 03031401, and 03171403). From measurements at the various lateral positions, the scanner response was determined as a function of the lateral position of the scanned film. For a given color channel X, the response at any lateral position L is related to the response at the center, C, of the scanner by Response(C, D, X) = A(L,X) + B(L,X) ⋅ Response(L, D, X), where D is dose and the coefficients A(L,X) and B(L,X) are determined from the film measurements at the center of the scanner and six other discrete lateral positions. The values at intermediate lateral positions were obtained by linear interpolation. The coefficients were determined for the red, green, and blue color channels, preserving the ability to apply triple-channel dosimetry once corrections were applied to compensate for the lateral position response artifact. To validate this method, corrections were applied to several films that were exposed to 15 × 15 cm(2) open fields and large IMRT and VMAT fields and scanned at the extreme edges of the scan window in addition to the central location. Calibration and response data were used to generate dose maps and perform gamma analysis using single- or triple-channel dosimetry with FilmQAPro 2014 software. The authors' study found that calibration curves at the different lateral positions could be correlated by a simple two-point rescaling using the response for unexposed film as well as the response of film exposed at high doses between 800 and 1600 cGy. The coefficients A(L,X) and BL,X for each color channel X were found to be independent of dose at each lateral location L. This made it possible to apply the relationship Response(C, D, X) = A(L,X) + B(L,X) ⋅ Response(L, D, X), to the raw film responses, permitting correction of the response values at any lateral position to an equivalent response, as if that part of the film was located at the center of the scanner. This correction method was validated for several films exposed to open as well as large IMRT and VMAT fields. The work reported elaborates on the process using the correction procedures to eliminate the lateral response artifact and demonstrates improvements in the accuracy of radiochromic film dosimetry for the radiation therapy quality assurance applications.

The artefacts of radiochromic film dosimetry with flatbed scanners and their causation by light scattering from radiation-induced polymers

Optical experiments and theoretical considerations have been undertaken in order to understand the causes of the ‘orientation effect’ and the ‘parabola effect’, the artefacts impairing the desired light absorption measurement on radiochromic EBT3 films with flatbed scanners. EBT3 films exposed to doses up to 20.9 Gy were scanned with an Epson Expression 10000XL flatbed scanner in landscape and portrait orientation. The horizontally and vertically polarized light components of the scanner were determined, and another Epson Expression 10000XL flatbed scanner was disassembled to examine its optical components. The optical properties of exposed and unexposed EBT3 films were studied with incident polarized and unpolarized white light, and the transmitted red light was investigated for its polarization and scattering properties including the distribution of the scattering angles. Neutral density filters were studied for comparison. Guidance was sought from the theory of light scattering from rod-like macromolecular structures. The drastic dose-dependent variation of the transmitted total light current as function of the orientation of front and rear polarizers, interpreted by light scattering theory, shows that the radiation-induced polymerization of the monomers of EBT3 films produces light scattering oscillators preferably polarized at right angles with the coating direction of the film. The directional distribution of the scattered light is partly anisotropic, with a preferred scattering plane at right angles with the coating direction, indicating light scattering from stacks of coherently vibrating oscillators piled up along the monomer crystals. The polyester carrier film also participates in these effects. The ‘orientation’ and ‘parabola’ artefacts due to flatbed scanning of radiochromic films can be explained by the interaction of the polarization-dependent and anisotropic light scattering from exposed and unexposed EBT3 films with the quantitative difference between the scanner's horizontally and vertically polarized light supply and with the limited directional acceptance of the scanner's light recording system.

SU-E-T-123: Dosimetric Comparison Between Portrait and Landscape Orientations in Radiochromic Film Dosimetry

Purpose: To compare the dosimetric properties of radiochromic films with different orientation. Methods: A sheet of EBT3 film was cut into eight pieces with the following sizes: 15×15 cm2 (one piece), 5x15 cm{sup 2} (two) and 4×5 cm{sup 2} (five). A set of two EBT3 sheets was used at each dose level. Two sets were used changing the delivered doses (1 and 2 Gy). The 5×15 cm{sup 2} pieces were rotated by 90 degrees in relation to each other, such that one had landscape orientation and the other had portrait orientation. All 5×15 cm2 pieces were irradiated with their long side aligned with the x-axis of the radiation field. The 15×15 cm{sup 2} pieces were irradiated rotated at 90 degrees to each other. Five pieces, (a total of ten from two sheets) were used to obtain a calibration curve. The irradiated films were scanned using an Epson ES-2200 scanner and were analyzed using ImageJ software. In this study, no correction was applied for the nonuniform scanner signal that is evident in the direction of the scanner lamp. Each film piece was scanned both in portrait and landscape orientations. Dosimetric comparisons of the beam profiles were made in terms of themore » film orientations (portrait and landscape) and scanner bed directions (perpendicular and parallel to the scanner movement). Results: In general, portrait orientation exhibited higher noise than landscape and was adversely affected to a great extent by the nonuniformity in the direction of the scanner lamp. A significant difference in the measured field widths between the perpendicular and parallel directions was found for both orientations. Conclusion: Without correction for the nonuniform scanner signal in the direction of the scanner lamp, a landscape orientation is preferable. A more detailed investigation is planned to evaluate quantitatively the effect of orientation on the dosimetric properties of a film.« less

SU-E-T-121: Dosimetric Characterization of Gafchromic Film EBT3 Using Vidar DosimetryPro Advantage RED and EPSON Expression 10000XL Scanners

Purpose: The purpose of this paper is to characterize EBT3 using two types of scanner, analyzing the factors of influence of each dosimetry system. Methods: The film used in this study was GAFCHROMIC EBT3, the films were exposed at a dose range between 0Gy a 9Gy in a solid water phantom, SSD=100cm, 5cm depth and perpendicularly to the 6MV photon beam generated by a Novalis TX linear accelerator equipped with an HDMLC. A Farmer type ion chamber TN30013 (PTW) was used to determine the dose delivered to the film. The films were digitized with a scanner EPSON expression 10000XL and the VIDAR DosimetryPro Adventage RED. Software RIT113v6.1 was used for construction of the calibration curve and analysis. The film characteristics investigated were: response at different dose levels, sensitivity to orientation and side and resolution through the results of the spatial response function by analyzing a step pattern. Additionally, 20 IMRT treatment fields were measured with both scanner and compared with calculated dose using gamma index analysis (3%-3mm). Results: The OD obtained for dose level 2Gy in the orientation portrait of the film on the scanner EPSON is (0,222±0,19) and for Vidar RED (0,252±0,10) and landscape is for EPSON (0,211±0,25) and for Vidar RED (0,250±0,11) . The orientation dependence with respect to film side is about 0,09% for EPSON and about 0.03% for VIDAR. The spatial response function increase in response to the Gaussian function FWHM EPSON scanner (0.18mm) compared with VIDAR scanner function (less than 0.06mm) was observed. We analyzed 20 total plan dose distributions the number of pixels with gamma>1 (3%-3mm) was 0.7%±1.2 [0.1%; 2.82%] for EBT3-VIDAR y 2%±2.9 [0.2%; 3.5%] for EBT3-EPSON. Conclusion: VIDAR scanner shows better sensitivity. EBT3 film shows a different response between portrait and landscape orientation. Step pattern is better reproduce by VIDAR scanner.

A new correction method serving to eliminate the parabola effect of flatbed scanners used in radiochromic film dosimetry

The purpose of this study is the correction of the lateral scanner artifact, i.e., the effect that, on a large homogeneously exposed EBT3 film, a flatbed scanner measures different optical densities at different positions along the x axis, the axis parallel to the elongated light source. At constant dose, the measured optical density profiles along this axis have a parabolic shape with significant dose dependent curvature. Therefore, the effect is shortly called the parabola effect. The objective of the algorithm developed in this study is to correct for the parabola effect. Any optical density measured at given position x is transformed into the equivalent optical density c at the apex of the parabola and then converted into the corresponding dose via the calibration of c versus dose. For the present study EBT3 films and an Epson 10000XL scanner including transparency unit were used for the analysis of the parabola effect. The films were irradiated with 6 MV photons from an Elekta Synergy accelerator in a RW3 slab phantom. In order to quantify the effect, ten film pieces with doses graded from 0 to 20.9 Gy were sequentially scanned at eight positions along the x axis and at six positions along the z axis (the movement direction of the light source) both for the portrait and landscape film orientations. In order to test the effectiveness of the new correction algorithm, the dose profiles of an open square field and an IMRT plan were measured by EBT3 films and compared with ionization chamber and ionization chamber array measurement. The parabola effect has been numerically studied over the whole measuring field of the Epson 10000XL scanner for doses up to 20.9 Gy and for both film orientations. The presented algorithm transforms any optical density at position x into the equivalent optical density that would be measured at the same dose at the apex of the parabola. This correction method has been validated up to doses of 5.2 Gy all over the scanner bed with 2D dose distributions of an open square photon field and an IMRT distribution. The algorithm presented in this study quantifies and corrects the parabola effect of EBT3 films scanned in commonly used commercial flatbed scanners at doses up to 5.2 Gy. It is easy to implement, and no additional work steps are necessary in daily routine film dosimetry.

LC GRIN lens mode with wide viewing angle for rotatable 2D/3D tablet

AbstractTo widen the vertical and horizontal angular ranges where the lens performs well, the off‐axis performance of a liquid crystal gradient index (LC GRIN) lens is analyzed by the combined simulation system of an LC director simulator and a ray‐tracing simulator. We found that the angular difference between an LC alignment direction and an electrode array direction of the LC GRIN lens is one of significant parameters, and detailed conditions of structure are established. The measurement result shows that the developed structure reduces the degradation ratio in a luminance profile from 61% to 3.2%. We have applied a user tracking system for the rotatable 3D display, equipped with a detection of a panel orientation and a face position. As a result, we have developed a rotatable 2D/3D tablet whose 3D viewing azimuth angle is over 30° in both landscape and portrait orientations.

Holding a tablet computer with one hand: effect of tablet design features on biomechanics and subjective usability among users with small hands

The purpose of this study was to evaluate tablet size (weight), orientation, grip shape, texture and stylus shape on productivity, biomechanics and subjective usability and fatigue when the tablet was held with just the left hand. A total of 15 male and 15 female subjects, ages 16–64 years, tested eight tablets and three styluses. Overall, the usability, fatigue and biomechanical evaluation of tablet design features supported the use of smaller to medium-sized tablets, with a ledge or handle shape on the back and surfaced with a rubberised texture. Larger, heavier tablets had significantly worse usability and biomechanics and their use with one hand should be limited. The stylus with a tapered grip (7.5–9.5 mm) or larger grip (7.6 mm) had better usability and biomechanics than one with a smaller grip (5 mm). There were no significant differences in productivity between design features. These design parameters may be important when designing tablets. Practitioner Summary: Different tablet and stylus design features were evaluated for usability and biomechanical properties. On the basis of short-term tasks, emulating functional tablets, usability was improved with the smaller and medium-sized tablets, portrait (vs. landscape) orientation, a back ledge grip and rubberised texture. There were no differences in productivity between design features.

Tablet Keyboard Configuration Affects Performance, Discomfort and Task Difficulty for Thumb Typing in a Two-Handed Grip

When holding a tablet computer with two hands, the touch keyboard configuration imposes postural constraints on the user because of the need to simultaneously hold the device and type with the thumbs. Designers have provided users with several possible keyboard configurations (device orientation, keyboard layout and location). However, potential differences in performance, usability and postures among these configurations have not been explored. We hypothesize that (1) the narrower standard keyboard layout in the portrait orientation leads to lower self-reported discomfort and less reach than the landscape orientation; (2) a split keyboard layout results in better overall outcomes compared to the standard layout; and (3) the conventional bottom keyboard location leads to the best outcomes overall compared to other locations. A repeated measures laboratory experiment of 12 tablet owners measured typing speed, discomfort, task difficulty, and thumb/wrist joint postures using an active marker system during typing tasks for different combinations of device orientation (portrait and landscape), keyboard layout (standard and split), and keyboard location (bottom, middle, top). The narrower standard keyboard with the device in the portrait orientation was associated with less discomfort (least squares mean (and S.E.) 2.9±0.6) than the landscape orientation (4.5±0.7). Additionally, the split keyboard decreased the amount of reaching required by the thumb in the landscape orientation as defined by a reduced range of motion and less MCP extension, which may have led to reduced discomfort (2.7±0.6) compared to the standard layout (4.5±0.7). However, typing speed was greater for the standard layout (127±5 char./min.) compared to the split layout (113±4 char./min.) regardless of device orientation and keyboard location. Usage guidelines and designers can incorporate these findings to optimize keyboard design parameters and form factors that promote user performance and usability for thumb interaction.

SU‐E‐I‐87: Experimental Study of Anisotropic Light Scattering and Polarization Effects of EBT3‐Films

Purpose: Further experiments are needed to understand the underlying optical properties of flat‐bed scanned EBT3‐films. Methods: EBT3‐films, arranged in landscape orientation and irradiated with different doses, were illuminated with a homogeneous spot of unpolarized white light. Polarizer foils could be added in front of and behind the EBT3‐film. The light scattered by the film was collected by a plano‐convex lens and focused onto a diffusing glass plate placed at focal length distance. Thereby, the scattering angle was transformed into an offset from the optical axis, forming a characteristic corona. This image was digitized with a DSLR‐camera and the red color channel used for analysis. The effect of incident light polarization was investigated by stepwise rotating the electrical vector of a polarizer in front of the film, with 0° parallel to the preferred direction of the polymer fibres. The polarization of the scattered light was investigated by a second polarizer behind the lens. Results: With an unpolarized light source, anisotropic scattering is preferently propagated orthogonal to the direction of the active polymers, for both landscape and portrait orientation, and the amount of scattered light increases with dose. Scattering by the EBT3‐film varies from almost zero to a maximum when the electrical vector of the light source varies from parallel to orthogonal with the direction of the active polymers. The electrical vector of the scattered light is rotated by 90° compared with the incident light. Conclusion: By experimental separation between scattered and unscattered transmitted light it was proved that incident light polarization only affects the scattered component. This effect hints upon a role of the magnetic component in the excitation of anisotropic scattering. The effect may be utilized to enhance or suppress scattering influences in EBT‐3 film dosimetry.

15.2: Distinguished Paper: LC GRIN Lens Mode with Wide Viewing Angle for Rotatable 2D/3D Tablet

AbstractTo widen the vertical and horizontal angular ranges where the lens performs well, the off‐axis performance of an LC GRIN lens is analyzed, and the detailed conditions of structure are established. We have developed a rotatable 2D/3D display whose 3D viewing azimuth angle is over 30 degrees in both landscape and portrait orientations.

Shape Writing on Tablets: Better Performance or Better Experience?

Shape writing is a technology for text input that involves „drawing‟ the desired word with your finger or a stylus in one continuous motion on the virtual keyboard. Swype, initially introduced to smart phones, is a shape writing application that is advertised as being faster than traditional methods of keying on a virtual keyboard. This technology is relatively new to the market, and to date there is little available research on the performance of Swype on smart phones, and none on the even newer tablet devices, such as a Samsung Galaxy Tab. The present study investigated the performance (words per minute/average errors per word) and preference associated with the use of Swype for text input compared to keying on the virtual keyboard. The effect of keyboard sizes within landscape and portrait orientations was also examined. In the current implementation, the keying method did not have the benefit of a prediction algorithm, therefore prediction was turned off for Swype condition as well. No significant difference was found in typing speed between the two input methods, however, an effect of keyboard viewing orientation on typing speed was found. For average errors per word, the only significant effect was an interaction between input method and keyboard viewing orientation. Additionally, Swype was rated significantly better than keying on four out of five preference measures. Findings show that despite Swype not operating at its fullest ability, it performs just as well as keying and provides a better experience for users.

SU-E-T-128: Dosimetric Characteristics of Gafchromic EBT3 Films for Megavoltage Photon and Proton Beams.

Gafchromic film for quantitative analysis was renewed from EBT2 to EBT3 film in November 2011. The purpose of this study is to investigate the relevant characteristics of EBT3 film for its application in dosimetric verification for IMRT/VMAT or proton therapy. We investigated the characteristics of EBT3 film with comparison of previous EBT2 film. The experiments in this study composed two categories. At first, the photo spectroscopy for the irradiated film was compared between EBT2 and EBT3. The film 1 day after the irradiation was analyzed by a photo spectrometer (SR520: JASCO Corporation, Japan). Secondly, we investigated several calibration curves which obtained by same batch. The films were calibrated by irradiation the films to 13 dose steps. The irradiated films were scanned by a flatbed scanner (ES-10000XL, Epson-Seiko Corporation, Japan). The difference on scan orientation was evaluated alternate portrait and landscape directions. The photon and proton beams were delivered from Clinac 21EX (Varian) and Mitsubishi machine, respectively. The peak absorption wavelength of EBT3 film and its response at all active range were basically same with that of EBT2 film. The peak wavelength of photo absorption in EBT3 was observed at 585 and 634 nm. The fog optical density was increased due to the hazy matte polyester for active layer. However, there is no change the tendency of the calibration curve responding to megavoltage photon and proton beams. The scan orientation dependency of EBT3 film was observed with similar to EBT2 film. The optical density of portrait orientation was 10% higher than that of landscape orientation. The dosimetric characteristics of EBT3 film were basically same with EBT2 film. With regard to the matte polyester, the creation of Newton's rings during scanning procedure was reduced. However, the suitable scan protocol should be used for accurate film dosimetry.