Congruence Test Research Articles

TU-C-BRB-06: A Multipurpose Quality Assurance Phantom for the Small Animal Radiation Research Platform (SARRP)

Purpose: The suitability and performance of a mouse‐size MOSFET (‘Mousefet’) phantom is investigated for routine quality assurance (QA) of the Small Animal Radiation Research Platform (SARRP). Methods: The Mousefet phantom was constructed by custom integration of 5 micro MOSFETS, arranged in a quincunx pattern, within a miniature tissue equivalent phantom. The phantom was designed to facilitate SARRP QA tasks which may warrant daily evaluation: output constancy, isocenter congruency test, and cone beam computed tomography(CBCT)image geometric accuracy. For output constancy the phantom was irradiated with an open field and all 5 micro‐MOSFET readings taken. For the isocenter congruency test, an appropriate size collimator was used to irradiate one of the MOSFETs,imaged and positioned at CBCT isocenter. The acquired CBCTimage was then used to verify image geometric accuracy and other image quality parameters. Sample data from 10 days in a period of over one month was compared to reference measurements and evaluated for daily variation. Results: Output constancy measurements showed maximum daily variation of less than 3% for all MOSFETS, in consonance with observations from concurrent ion chamber measurements. The design of the Mousefet phantom allows the output check data to be used for prompt verification of beam energy and cone profile constancy. For the isocenter congruency test, it is demonstrated that the Mousefet Phantom can detect 0.3 mm deviations of the CBCT isocenter from the radiation isocenter. Meanwhile, results for CBCTimage geometric accuracy were consistently found to be within 2% of the expected value. Other CBCTimage‐quality parameters could also be assessed in terms of image intensity constancy, noise and image uniformity. Conclusions: Overall, the results establish the Mousefet phantom as a simple and time‐efficient multipurpose tool that could be employed effectively for routine quality assurance of the SARRP.

A multipurpose quality assurance phantom for the small animal radiation research platform (SARRP)

In this work, the suitability and performance of a mouse-size MOSFET (Mousefet) phantom is investigated for routine quality assurance (QA) of the small animal radiation research platform (SARRP). This Mousefet phantom is a simple construction consisting of five micro-MOSFETS custom integrated in a quincunx pattern within a tissue-equivalent phantom, allowing repeat/multiple QA tasks to be quickly performed in one experimental set-up. The Mousefet phantom is particularly evaluated for facilitating SARRP QA tasks which may warrant daily evaluation, including output constancy, isocenter congruency test and cone beam computed tomography (CBCT) image geometric accuracy. Results for the output constancy measurements showed a maximum daily variation of less than 2.6% for all MOSFETS, in consonance with observations from concurrent ion chamber measurements. It is also shown that the design of the Mousefet phantom allows the output check data to be used for prompt verification of beam energy and cone profile constancy. For the isocenter congruency test, it is demonstrated that the Mousefet phantom can detect 0.3 mm deviations of the CBCT isocenter from the radiation isocenter. Meanwhile, results for CBCT image geometric accuracy were consistently found to be within 2% of the expected value. Other CBCT image quality parameters could also be assessed in terms of image intensity constancy, noise and image uniformity. Overall, the results establish the Mousefet phantom as a simple and time-efficient multipurpose tool that could be employed effectively for routine QA of the SARRP.

Motor Imagery Ability in Patients With Traumatic Brain Injury

Oostra KM, Vereecke A, Jones K, Vanderstraeten G, Vingerhoets G. Motor imagery ability in patients with traumatic brain injury. ObjectiveTo assess motor imagery (MI) ability in patients with moderate to severe traumatic brain injury (TBI). DesignProspective, cohort study. SettingUniversity hospital rehabilitation unit. ParticipantsPatients with traumatic brain injury (mean coma duration, 18d) undergoing rehabilitation (n=20) and healthy controls (n=17) matched for age and education level. InterventionsNot applicable. Main Outcome MeasuresThe vividness of MI was assessed using a revised version of the Movement Imagery Questionnaire—Revised second version (MIQ-RS); the temporal features were assessed using the time-dependent motor imagery (TDMI) screening test, the temporal congruence test, and a walking trajectory imagery test; and the accuracy of MI was assessed using a mental rotation test. ResultsThe MIQ-RS revealed a decrease of MI vividness in the TBI group. An increasing number of stepping movements was observed with increasing time periods in both groups during the TDMI screening test. The TBI group performed a significantly smaller number of imagery movements in the same movement time. The temporal congruence test revealed a significant correlation between imagery and actual stepping time in both groups. The walking trajectory test revealed an increase of the imagery and actual walking time with increasing path length in both groups, but the ratio of imaginary walking over actual walking time was significantly greater than 1 in the TBI group. Results of the hand mental rotation test indicated significant effects of rotation angles on imagery movement times in both groups, but rotation time was significantly slower in the TBI group. ConclusionsOur patients with TBI demonstrated a relatively preserved MI ability indicating that MI could be used to aid rehabilitation and subsequent functional recovery.

Category Stretching: Reorienting Research on Categories in Strategy, Entrepreneurship, and Organization Theory

abstractWe advocate for more tolerance in the manner we collectively address categories and categorization in our research. Drawing on the prototype view, organizational scholars have provided a ‘disciplining’ framework to explain how category membership shapes, impacts, and limits organizational success. By stretching the existing straightjacket of scholarship on categories, we point to other useful conceptualizations of categories – i.e. the causal‐model and the goal‐based approaches of categorization – and propose that depending on situational circumstances, and beyond a disciplining exercise, categories involve a cognitive test of congruence and a goal satisfying calculus. Unsettling the current consensus about categorical imperatives and market discipline, we suggest also that audiences may tolerate more often than previously thought organizations that blend, span, and stretch categories. We derive implications for research about multi‐category membership and mediation in markets, and suggest ways in which work on the theme of categories in the strategy, entrepreneurship, and managerial cognition literatures can be enriched.

Category Stretching: Reorienting Research on Categories in Strategy, Entrepreneurship, and Organization Theory

We advocate for more tolerance in the manner we collectively address categories and categorization in our research. Drawing on the prototype view, organizational scholars have provided a ‘disciplining’ framework to explain how category membership shapes, impacts and limits organizational success. By stretching the existing straightjacket of scholarship on categories, we point to other useful conceptualizations of categories – i.e. the causal model and the goal-based approaches of categorization – and propose that depending on situational circumstances, and beyond a disciplining exercise, categories involve a cognitive test of congruence and a goal satisfying calculus. Unsettling the current consensus about categorical imperatives and market discipline, we suggest also that markets may tolerate more often than thought organizations that blend, span, and stretch categories. We derive implications for research about multi-category membership and mediation in markets, and suggest ways in which work on the theme of categories in the strategy, entrepreneurship, and managerial cognition literatures can be enriched.

WE‐C‐BRA‐03: Acceptance Testing and Commissioning of a Commercial 3D Surface Matching Video System

Non‐invasive 3D surface matching systems have become commercially available forinitial patient positioning and real‐time monitoring during radiotherapy treatment. Some systems are capable of providing surface motion surrogates that can be used for respiratory gating. All systems must undergo commissioning and acceptance prior to clinical use. First, clinical implementation of these systems requires the establishment of routine quality control proceduresthat range from phantom studies to monitoring clinical setups.In particular, the congruence of the surface imaging isocentermust be compared to both the imaging and treatment radiation isocenters. Isocenter congruence accuracy limitations may need to be tailored to the treatment site. For example, tighter accuracy is expected of isocenter congruence for treatment monitoring ofstereotactic radiosurgery patients compared to monitoring of breast patients due to the smaller planning target volume margins. For clinical commissioning studies, the correlation of 3D surface matching compared to the routinely‐used image‐guided procedures should be well characterized. Furthermore, understanding the accuracy, robustness, and limitations of the algorithms used to register two 3D surfaces is key to understanding the expected clinical results. We will summarize our institutional experience with acceptance testing and commissioning the AlignRT (VisionRT Ltd., London, UK) 3D surface matching system and its clinical implementation for positioningpatients receiving whole breast radiotherapy.Learning Objectives:1. List some acceptance testing procedures for surface imaging systems2. Understand the commissioning process of surface imaging systems for whole breast radiotherapy3. Understand how surface imagingisocenter congruence testing must be incorporated into ongoing quality assurance of image‐guided RT (IGRT)

No evidence for an afrotherian-like delayed dental eruption in South American notoungulates

The fossil South American ungulates are of great interest relative to the new phylogenetic framework elaborated for living placental mammals. In particular, studies on these endemic taxa can allow for testing congruence between southern placental phylogeny and plate tectonics, beyond what has already been suggested in the Atlantogenata hypothesis based on extant afrotherians and xenarthrans. The presence of delayed dental eruption relative to skull growth is one feature characterizing the extant afrotherians and possibly the xenarthrans. Late dental eruption has been mentioned previously in South American notoungulates, thus suggesting possible resemblance with afrotherians and perhaps xenarthrans. We provide here a detailed study of the dental eruption pattern relative to the skull growth in the notoungulates. In contrast to previous statements, our results demonstrate that there is currently no evidence for an afrotherian-like delayed dental eruption in this group. For now, the inferred absence of a delayed dental eruption in notoungulates does not support atlantogenatan/afrotherian affinities for the Notoungulata, but other atlantogenatan/afrotherian characteristics remain to be explored in more detail in this group and other South American ungulates.

Exploring the memory advantage for moving scenes

Recognition memory is better for moving images than for static images (the dynamic superiority effect), and performance is best when the mode of presentation at test matches that at study (the study–test congruence effect). We investigated the basis for these effects. In Experiment 1, dividing attention during encoding reduced overall performance but had little effect on the dynamic superiority or study–test congruence effects. In addition, these effects were not limited to scenes depicting faces. In Experiment 2, movement improved both old–new recognition and scene orientation judgements. In Experiment 3, movement improved the recognition of studied scenes but also increased the spurious recognition of novel scenes depicting the same people as studied scenes, suggesting that movement increases the identification of individual objects or actors without necessarily improving the retrieval of associated information. We discuss the theoretical implications of these results and highlight directions for future investigation.

Evaluation of the taxonomic utility of six-enzyme pulsed-field gel electrophoresis in reconstructing Salmonella subspecies phylogeny

Pulsed-field gel electrophoresis (PFGE) remains an important tool in the molecular epidemiological evaluation of strains emerging from disease outbreak clusters. Recent studies of Escherichia coli O157:H7 and Salmonella Enteritidis have noted marked improvements in the discriminatory power of PFGE when combining band profiles from up to six restriction enzyme datasets into a single concatenated analysis. This approach has provided more accurate assignments of genetic relationships among closely related strains and allowed effective phylogenetic inference of host and geographical reservoirs. Although this approach enhances epidemiological congruence among closely related strains, it remains unclear to what extent six-enzyme PFGE pattern similarity reiterates evolutionary relatedness among more distantly related Salmonella strains ( i.e., serovar or subspecies levels). Here, taxonomic accuracy of six-enzyme PFGE is tested phylogenetically across two distinct Salmonella enterica populations–Salmonella reference collection B (SARB), representing the breadth of taxonomic diversity of S. enterica subspecies I only, and Salmonella reference collection C (SARC), comprising the seven disparate subspecies of S. enterica plus S. bongori. Cladistic analysis of SAR strains revealed substantial polyphyly between the two strain collections such that numerous SARB strains clustered more closely with diverged SARC subspecies rather than with other members of subspecies I. Also, in several cases, SARC sibling strains from the same subspecies were evolutionary obscured—broken into distant locales on the most parsimonious six-enzyme trees. Genetic diversity among SARB and SARC strains was comparable at 45% and 47%, respectively, while congruence testing revealed discordance among individual enzyme datasets. While six-enzyme PFGE is effective in ascertaining accurate genetic relationships for more closely related strains ( e.g., strains within the same serovar), reconstitution of evolutionarily meaningful strain groupings may be elusive for Salmonella at the serovar level and above. Thus, caution is warranted when applying PFGE with a limited number of enzymes as the primary phylogenetic marker in these instances.

Analysis of dam deformation measurements with the robust and non-robust methods

Rapid developments in engineering structures and the growing interest in studying the earth crust movements, the analysis of deformation measurements, measurement methods and precision has revealed new demands. The purpose of this study is to determine the deformations that take place on dam crest due to different water level, water load and dam’s body weight. AltA±nkaya Dam, which is a rock fill dam, was selected as application area and a deformation network consisting of 6 reference and 11 object points was constructed. In this study, deformation measurements were performed between 2000 and 2002. Measurements were made every June and September in that the water level was minimum and maximum, respectively. Hence, measurements were made in 4 periods. All measurements were performed using static GPS measurement method. In this study, Iterative weighted transformation (IWST), Least Absolute Sum (LAS), Congruency test analysis method and Fredericton was used for performing two dimensional deformation analyses. Key words: GPS, dam, deformation, analysis, congruency test, IWST, LAS, Fredericton.

Inference of molecular homology and sequence alignment by direct optimization

That homologies exist and can be recognized and discovered is of central importance to comparative and evolutionary biology. Traditionally, homology assessment for both molecular and morphological data has been treated as a two-step process involving the generation of a proposition of homology and then the evaluation of that hypothesis through the test of congruence in a phylogenetic analysis. An alternative phylogenetic method, direct optimization, combines these into a one-step process in which positional homology and cladograms are co-estimated simultaneously. Here we examine the use of the term “homology” as it is applied to molecular data, and critique the concept of molecular homology one must accept if cladograms are to be interpreted as phylogenetic estimates. The test of congruence alone cannot be used to determine homologous (historically identical) features, and character analysis and the proposition of primary homology hypotheses is the only procedure that can identify correspondences between features justified as retaining phylogenetic information. The practical ramifications for phylogenetic analysis, such as data exclusion and the interpretation of tree-like diagrams as phylogenies, are discussed.

Phylogeny of the bristle worm family Eunicidae (Eunicida, Annelida) and the phylogenetic utility of noncongruent 16S, COI and 18S in combined analyses

The bristleworm family Eunicidae is distributed worldwide and well-known for the large size of many of its species, its hard jaws and its economic importance in the bait industry. Monophyly of Eunicidae has been contradicted in previous molecular and morphological phylogenetic analyses focusing on Eunicida or on its type genus, Eunice. The current study focused on the phylogeny of the family per se combining mitochondrial and nuclear genes in different analyses. It recovered well-resolved phylogenetic hypotheses supporting the monophyly of Eunicidae and Palola, the only monophyletic genus among the genera for which we tested their monophyly ( Eunice, Marphysa, Palola, Lysidice and Nematonereis). Four other stable clades containing the type species of different genera, or species deemed very similar to them, were recovered within Eunicidae. These clades may represent monophyletic redefinitions of current genera, except for Eunice, and of previous synonymized genera. Evolution of the number of peristomial cirri and prostomial appendages in Eunicidae happened by independent step-by-step reduction in the opposite order of their ontogenetic development, suggestive of sequential heterochrony. All three genes were informative, however, at different levels within the combined trees. 16S and COI were important in recovering a monophyletic Eunicidae and relationships within the family, while 18S was important in the resolution of basal eunicidan relationships, monophyly of Onuphidae and basal relationships within this family. Moreover, results of congruence tests (SH and WRST using PABA) indicate that hidden support is picked up in the combined analyses, which is not revealed in the single gene analyses. Further supporting the idea that congruence is not a requirement for combining different partitions.

A New Method for Vertical Deformation Detection Using Survey Control Networks

Usually, the Survey control networks are used for deformation detection in a specific area using observations taken at different epochs. Where the coordinates obtained from two epochs, using least squares technique, are compared in order to assess if a deformation of a specified magnitude exists. Traditionally, the global congruency test is carried out so as to detect if the area of the network has undergone any movement (uplift or subsidence) due to natural or manmade causes. As a next step, localization methods are used to determine deformations at specific points in case there are changes in shape. In this research a new method is developed to establish deformations at specific points directly. The method is tested using a vertical control network simulated at various epochs of observation. The results obtained are compared with those obtained by another used method. Results obtained using this method indicate that vertical deformations greater than 0.03m using a precision of observation less than 10 can be detected at a minimum significant level of 0.05 (95% confidence level).

Comparative innervation of cephalic photophores of the loosejaw dragonfishes (Teleostei: Stomiiformes: Stomiidae): Evidence for parallel evolution of long‐wave bioluminescence

Four genera of the teleost family Stomiidae, the loosejaw dragonfishes, possess accessory cephalic photophores (AOs). Species of three genera, Aristostomias, Malacosteus, and Pachystomias, are capable of producing far-red, long-wave emissions (>650nm) from their AOs, a character unique among vertebrates. Aristostomias and Malacosteus posses a single far-red AO, while Pachystomias possesses anterior and posterior far-red AOs, each with smaller separate photophores positioned in their ventral margins. The purpose of this study was to establish the primary homology of the loosejaw AOs based on topological similarity of cranial nerve innervation, and subject these homology conjectures to tests of congruence under a phylogenetic hypothesis for the loosejaw dragonfishes. On the basis of whole-mount, triple-stained specimens, innervation of the loosejaw AOs is described. The AO of Aristostomias and the anterior AO of Pachystomias are innervated by the profundal ramus of the trigeminal (Tpr), while the far-red AO of Malacosteus and a small ventral AO of Pachystomias are innervated by the maxillary ramus of the trigeminal (Tmx). The largest far-red AO of Pachystomias, positioned directly below the orbit, and the short-wave AO of Photostomias are innervated by a branch of the mandibular ramus of the trigeminal nerve. Conjectures of primary homology drawn from these neuroanatomical similarities were subjected to tests of congruence on a phylogeny of the loosejaws inferred from a reanalysis of a previously published morphological dataset. Optimized for accelerated transformation, the AO innervated by the Tpr appears as a single transformation on the new topology, thereby establishing secondary homology. The AOs innervated by the Tmd found in Pachystomias and Photostomias appear as two transformations in a reconstruction on the new topology, a result that rejects secondary homology of this structure. The secondary homology of AOs innervated by the Tmx found in Malacosteus and Pachystomias is rejected on the same grounds. Two short-wave cephalic photophores present in all four genera, the suborbital (SO) and the postorbital (PO), positioned in the posteroventral margin of the orbit and directly posterior to the orbit, respectively, are innervated by separate divisions of the Tmd. The primary homologies of the loosejaw PO and SO across loosejaw taxa are proposed on the basis of similar innervation patterns. Because of dissimilar innervation of the loosejaw SO and SO of basal stomiiforms, primary homology of these photophores cannot be established. Because of similar function and position, the PO of all other stomiid taxa is likely homologous with the loosejaw PO. Nonhomology of loosejaw long-wave photophores is corroborated by previously published histological evidence. The totality of evidence suggests that the only known far-red bioluminescent system in vertebrates has evolved as many as three times in a closely related group of deep-sea fishes.

Short article: When are moving images remembered better? Study–test congruence and the dynamic superiority effect

It has previously been shown that moving images are remembered better than static ones. In two experiments, we investigated the basis for this dynamic superiority effect. Participants studied scenes presented as a single static image, a sequence of still images, or a moving video clip, and 3 days later completed a recognition test in which familiar and novel scenes were presented in all three formats. We found a marked congruency effect: For a given study format, accuracy was highest when test items were shown in the same format. Neither the dynamic superiority effect nor the study-test congruency effect was affected by encoding (Experiment 1) or retrieval (Experiment 2) manipulations, suggesting that these effects are relatively impervious to strategic control. The results demonstrate that the spatio-temporal properties of complex, realistic scenes are preserved in long-term memory.

Assessing Congruence Among Ultrametric Distance Matrices

Recently, a test of congruence among distance matrices (CADM) has been developed. The null hypothesis is the incongruence among all data matrices. It has been shown that CADM has a correct type I error rate and good power when applied to independently-generated distance matrices. In this study, we investigate the suitability of CADM to compare ultrametric distance matrices. We tested the type I error rate and power of CADM with randomly generated dendrograms and their associated ultrametric distance matrices. We show that the test has correct type I error rates and good power. To obtain the significance level of the statistic, a single (as in the Mantel test) or a double (as in the double permutation test, DPT) permutation procedure was used. The power of CADM remained identical when the two permutation methods were compared. This study clearly demonstrates that CADM can be used to determine whether different dendrograms convey congruent information.

Morphological and molecular variation in tiger beetles of the Cicindela hybrida complex: is an ‘integrative taxonomy’ possible?

Current taxon assignments at the species level are frequently discordant with DNA-based analyses. Recent studies on tiger beetles in the Cicindela hybrida complex identified discordance between mtDNA patterns and the entities currently defined by the taxonomic literature. To test the accuracy of morphologically delimited groups, five named taxa (species) from 24 representative sampling sites across Europe were scored for 41 external morphological characters. Three of the named taxa were 'diagnosable', that is, defined by between one and three characters unique to each group. Newly sequenced ITS1 and existing mitochondrial cox1 markers established 20 and 22 different haplotypes, respectively, but only cox1 produced (four) diagnosable units. Phylogenetic analysis and statistical parsimony networks showed poor congruence of character variation with the taxonomic entities (and each other). Variation in morphological characters was therefore tested directly for association with DNA-based nesting groups at various hierarchical levels using permutational contingency analysis. Significant statistical associations of 11 (of 13 variable) morphological characters were observed with nesting groups from ITS1 and mitochondrial DNA markers, predominantly at the 4-step level. The analysis demonstrates the need for formal tests of congruence with morphological variation at the level of individual characters, a step that is omitted from recent studies of 'integrative taxonomy'. In addition, statistical correlation of particular morphological characters with DNA-based nesting groups can identify the lowest hierarchical level at which various character sets show congruence, as a means to define evolutionarily separated entities supported by diverse data sources.

Phylogenetics and Evolution of the Macaronesian Clade of Crassulaceae Inferred from Nuclear and Chloroplast Sequence Data

Abstract The Macaronesian clade of Crassulaceae comprises four genera (Aichryson, Aeonium, Greenovia, and Monanthes) that are largely endemic to Macaronesia, a region encompassing the Azores, Madeira, and the Cape Verde, Canary, and Salvage Islands. The monophyly of this clade has been supported by recent family-level phylogenetic analyses; however, the relationships within the clade remain uncertain. To resolve relationships within the Macaronesian clade, we sequenced several chloroplast DNA regions (matK and the trnL-trnF and psbA-trnH spacer regions) and the nuclear rDNA ITS region. Parsimony analyses of separate ITS and cpDNA data sets recover three major clades, corresponding to Aichryson, the perennial species of Monanthes, and Aeonium (including Greenovia). Congruence tests revealed significant heterogeneity between the ITS and cpDNA data sets. Comparison of the topologies resulting from analyses of these separate data sets indicated five instances of incongruence between the ITS and cpDNA that may...

African Dacus (Diptera: Tephritidae: Molecular data and host plant associations do not corroborate morphology based classifications

The genus Dacus Fabricius includes economically important pest fruit flies distributed in the Afrotropical and Indo-Australian regions. Two recent revisions based on morphological characters proposed new and partially discordant classifications synonymizing/revalidating several subgeneric names and forming species groups. Regardless these efforts, the phylogenetic relationships among Dacus species remained largely unresolved mainly because of the difficulties in assigning homologous character states. Therefore we investigated the phylogeny of African Dacus by sequencing 71 representatives of 32 species at two mitochondrial (COI, 16S) and one nuclear ( period) gene fragments. Phylogenetic relationships were inferred through Bayesian and Maximum Parsimony methods and hypotheses about the monophyly of Dacus subgenera were tested by Shimodaira–Hasegawa tests. The congruence tests and the analyses of the single gene fragments revealed that the nuclear gene supports similar conclusions as the two mitochondrial genes. Levels of intra- and inter-specific differentiation of Dacus species were highly variable and, in some cases, largely overlapping. The analyses of the concatenated dataset resolved two major bootstrap-supported groups as well as a number of well-supported clades and subclades that often comprised representatives of different subgenera. Additionally, specimens of Dacus humeralis from Eastern and Western African localities formed separate clades, suggesting cryptic differentiation within this taxon. The comparisons between the molecular phylogeny and the morphological classification revealed a number of discrepancies and, in the vast majority of cases, the molecular data were not compatible with the monophyly of the currently recognised subgenera. Conversely, the molecular data showed that Apocynaceae feeders are a monophyletic sister group of species feeding on both Cucurbitaceae and Passifloraceae (these latter being also monophyletic). These results show a clear association between the molecular phylogeny of African Dacus and the evolution of host plant choice and provide a basis towards a more congruent taxonomy of this genus.

USE OF ELECTRONIC PORTAL IMAGE DEVICE IN SOME QA TESTS

Introduction: In the present study a method to investigate light and radiation field congruence utilizing an amorphoussilicon electronic portal imaging device (EPID) was developed. An alternative method for routine dynamic multi-leafcollimator (DMLC) quality assurance (QA) using EPID was also described.Materials and Methods: This study employed an amorphous silicon (aSi) EPID, the associated EPI software and adiamond-shaped template. The collimator jaws of the linac (Elekta iViewGT) were aligned such that the light field fell directly on the corners of the diamond. A radiation detection algorithm within the EPI software determined the extent of the radiation field. The light and radiation field congruence was evaluated by comparing the vertices of the diamond reference structure to the detected radiation field. In addition, the digital jaw settings were recorded and later compared to the light field detected on Kodak x-omat films and EPIs. In this study an alternative method for routine dynamic multi-leaf collimator (DMLC) quality assurance (QA) using (EPID) was described. This QA was done by producing apattern of five 0.5-cm bands 5-cm apart and performing a visual spot-check for dose peak location, dose peak values,interband distance and band gaps measured at Full Width at Half-Maximum (FWHM) of the test pattern for this QA experiment. An aSi EPID and films are used for the DMLC QA to test the practicality and efficacy of EPID vis film.Results: Light radiation field congruence tests with films and EPIs were comparable, yielding a difference of less than 1.2 mm, well within the allowed 2-mm tolerance. A disparity was observed in the magnitude of the detected light field.The X and Y dimensions of the light field measured with film differed by less than or equal to 1.6 mm from the digital collimator settings, whereas the values extracted from the EPIs differed by up to 1.8 mm. The FWHM of the multi-leaf collimator (MLC) obtained by the EPID is 6.34 mm, which is slightly higher than the 6.18 mm for the film. The lowest dose at the valley is significantly lower for the EPID than for the film. The dose peak value of the EPID is found to be97.9 with standard deviation of ±1.59 and the dose peak value of film is found to be 96.5 with standard deviation of±2.41, respectively. Film and EPID track the distance between peaks with a mean of 49.8 and 49.53 mm and standarddeviation of ±0.3 and ±1.02 mm, respectively. EPID is able to track the location of individual dose peaks for all the leafpairs consistently to a standard deviation of ±0.12 to ±0.47 mm, slightly better than that of ±1.00 to ±1.26 mm for thefilm.Conclusion: EPIs were found to be a quick and reliable alternative to film for qualitative and relative analyses. AlsoEPID is as good as the film in resolving the band pattern of the DMLC test field. Although the resolution of the EPIDis lower than that of the film, it is high enough to faithfully reproduce the band pattern without significant distortion.Since EPID images can be acquired, analyzed and stored much more conveniently than film, EPID is a good alternativeto film for routine DMLC QA.