Quality Assurance Phantom Research Articles

A phantom for testing Cone Beam CTs.

Cone Beam Computed Tomography (CBCT) scanners are becoming more common for dental and maxillofacial/head scanning, but performing image quality tests on these systems is difficult. There are quality assurance (QA) phantoms commercially available but they can be expensive, bulky and not optimised for CBCT imaging limits. Smaller phantoms often lack features that are recommended for testing CBCT systems. A custom made phantom can provide more useful test objects in a more convenient size and at a lower cost. The proposed phantom is called the "Karu" Cone Beam CT Phantom and is constructed with a 3D printed poly lactic acid (PLA) shell, with 3D printed inserts for holding the test details in place. Tests included are geometric accuracy (in three dimensions), Hounsfield Unit (HU) accuracy, low contrast detectability, spatial resolution (using line pairs), and uniformity/artifacts/noise. The phantom was scanned on a number of scanners and was clearly able to differentiate scanners producing poorer quality images from better quality ones. The phantom could be produced for under NZ $2000.

PO-1314: Creation of a 3D-printed plastic mouse phantom for pre-clinical dosimetry and quality assurance

PO-1314: Creation of a 3D-printed plastic mouse phantom for pre-clinical dosimetry and quality assurance

OC-0464: Quantification and reduction of susceptibility artefacts for a quality assurance phantom in MRgRT

OC-0464: Quantification and reduction of susceptibility artefacts for a quality assurance phantom in MRgRT

A new virtue of phantom MRI data: explaining variance in human participant data

Background: Magnetic resonance imaging (MRI) is an important yet complex data acquisition technology for studying the brain. MRI signals can be affected by many factors and many sources of variance are often simply attributed to “noise”. Unexplained variance in MRI data hinders the statistical power of MRI studies and affects their reproducibility. We hypothesized that it would be possible to use phantom data as a proxy of scanner characteristics with a simplistic model of seasonal variation to explain some variance in human MRI data. Methods: We used MRI data from human participants collected in several studies, as well as phantom data collected weekly for scanner quality assurance (QA) purposes. From phantom data we identified the variables most likely to explain variance in acquired data and assessed their statistical significance by using them to model signal-to-noise ratio (SNR), a fundamental MRI QA metric. We then included phantom data SNR in the models of morphometric measures obtained from human anatomical MRI data from the same scanner. Results: Phantom SNR and seasonal variation, after multiple comparisons correction, were statistically significant predictors of the volume of gray brain matter. However, a sweep over 16 other brain matter areas and types revealed no statistically significant predictors among phantom SNR or seasonal variables after multiple comparison correction. Conclusions: Seasonal variation and phantom SNR may be important factors to account for in MRI studies. Our results show weak support that seasonal variations are primarily caused by biological human factors instead of scanner performance variation. The phantom QA metric and scanning parameters are useful for more than just QA. Using QA metrics, scanning parameters, and seasonal variation data can help account for some variance in MRI studies, thus making them more powerful and reproducible.

A new virtue of phantom MRI data: explaining variance in human participant data.

Background: Magnetic resonance imaging (MRI) is an important yet complex data acquisition technology for studying the brain. MRI signals can be affected by many factors and many sources of variance are often simply attributed to "noise". Unexplained variance in MRI data hinders the statistical power of MRI studies and affects their reproducibility. We hypothesized that it would be possible to use phantom data as a proxy of scanner characteristics with a simplistic model of seasonal variation to explain some variance in human MRI data. Methods: We used MRI data from human participants collected in several studies, as well as phantom data collected weekly for scanner quality assurance (QA) purposes. From phantom data we identified the variables most likely to explain variance in acquired data and assessed their statistical significance by using them to model signal-to-noise ratio (SNR), a fundamental MRI QA metric. We then included phantom data SNR in the models of morphometric measures obtained from human anatomical MRI data from the same scanner. Results: Phantom SNR and seasonal variation, after multiple comparisons correction, were statistically significant predictors of the volume of gray brain matter. However, a sweep over 16 other brain matter areas and types revealed no statistically significant predictors among phantom SNR or seasonal variables after multiple comparison correction. Conclusions: Seasonal variation and phantom SNR may be important factors to account for in MRI studies. Our results show weak support that seasonal variations are primarily caused by biological human factors instead of scanner performance variation. The phantom QA metric and scanning parameters are useful for more than just QA. Using QA metrics, scanning parameters, and seasonal variation data can help account for some variance in MRI studies, thus making them more powerful and reproducible.

LEGO-compatible modular mapping phantom for magnetic resonance imaging

Physical phantoms have been widely used for performance evaluation of magnetic resonance imaging (MRI). Although there are many kinds of physical phantoms, most MRI phantoms use fixed configurations with specific sizes that may fit one or a few different types of radio frequency (RF) coils. Therefore, it has limitations for various image quality assessments of scanning areas. In this article, we report a novel design for a truly customizable MRI phantom called the LEGO-compatible Modular Mapping (MOMA) phantom, which not only serves as a general quality assurance phantom for a wide range of RF coils, but also a flexible calibration phantom for quantitative imaging. The MOMA phantom has a modular architecture which includes individual assessment functionality of the modules and LEGO-type assembly compatibility. We demonstrated the feasibility of the MOMA phantom for quantitative evaluation of image quality using customized module assembly compatible with head, breast, spine, knee, and body coil features. This unique approach allows comprehensive image quality evaluation with wide versatility. In addition, we provide detailed MOMA phantom development and imaging characteristics of the modules.

Applicator visualization using ultrashort echo time MRI for high-dose-rate endorectal brachytherapy

PurposeThe individual channels in an endorectal applicator for high-dose-rate endorectal brachytherapy are not visible on standard MRI sequences. The aim of this study was to test whether an ultrashort echo time (UTE) MRI sequence could be used to visualize the individual channels to enable MR-only treatment planning for rectal cancer. Methods and MaterialsWe used a radial three-dimensional (3D) UTE pulse sequence and acquired images of phantoms and two patients with rectal cancer. We rigidly registered a UTE image and CT scan of an applicator phantom, based on the outline of the applicator. One observer compared channel positions on the UTE image and CT scan in five slices spaced 25 mm apart. To quantify geometric distortions, we scanned a commercial 3D geometric quality assurance phantom and calculated the difference between detected marker positions on the UTE image and corresponding marker positions on two 3D T1-weighted images with opposing readout directions. ResultsOn the UTE images, there is sufficient contrast to discern the individual channels. The difference in channel positions on the UTE image compared with the CT was on average −0.1 ± 0.1 mm (left-right) and 0.1 ± 0.3 mm (anteroposterior). After rigid registration to the 3D T1-weighted sequences, the residual 95th percentile of the geometric distortion inside a 550-mm-diameter sphere was 1.0 mm (left-right), 0.9 mm (anteroposterior), and 0.9 mm (craniocaudal). ConclusionsWith a UTE sequence, the endorectal applicator and individual channels can be adequately visualized in both phantom and patients. The geometrical fidelity is within an acceptable range.

A study of the interplay effect for VMAT SBRT using a four‐axes motion phantom

PurposeTo assess the accuracy of volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) when treating moving targets (such as lung or liver lesions), focusing on the impact of the interplay effect in the event of complex breathing motion and when a gating window is used.MethodsA dedicated programmable motion platform was implemented. This platform can carry large quality assurance (QA) phantoms and achieve complex three‐dimensional (3D) motion. Volumetric modulated arc therapy SBRT plans were delivered with TrueBeam linac to this moving setup and the measured dose was compared to the computed one. Several parameters were assessed such as breathing period, dose rate, dose prescription, shape of the breathing pattern, the use of a planning target volume (PTV) margin, and the use of a gating window.ResultsLoss of dose coverage (D95%) was acceptable in most situations. The doses received by 95% of the CTV, D95% ( CTVm) ranged from 94 to 101% (mean 98%) and the doses received by 2% of the CTV D2% ( CTVm) ranged from 94% to 110% of the prescribed dose. A visible interplay effect was observed when no margin was used or when the number of breathing cycles during the treatment delivery was lower than 20.ConclusionsIn our clinical context, treating lung and liver lesions using VMAT SBRT is reasonable. The interplay effect was moderated and acceptable in all simulated situations.

Three-dimensional printing in radiation oncology: A systematic review of the literature.

Purpose/objectivesThree‐dimensional (3D) printing is recognized as an effective clinical and educational tool in procedurally intensive specialties. However, it has a nascent role in radiation oncology. The goal of this investigation is to clarify the extent to which 3D printing applications are currently being used in radiation oncology through a systematic review of the literature.Materials/methodsA search protocol was defined according to preferred reporting items for systematic reviews and meta‐analyses (PRISMA) guidelines. Included articles were evaluated using parameters of interest including: year and country of publication, experimental design, sample size for clinical studies, radiation oncology topic, reported outcomes, and implementation barriers or safety concerns.ResultsOne hundred and three publications from 2012 to 2019 met inclusion criteria. The most commonly described 3D printing applications included quality assurance phantoms (26%), brachytherapy applicators (20%), bolus (17%), preclinical animal irradiation (10%), compensators (7%), and immobilization devices (5%). Most studies were preclinical feasibility studies (63%), with few clinical investigations such as case reports or series (13%) or cohort studies (11%). The most common applications evaluated within clinical settings included brachytherapy applicators (44%) and bolus (28%). Sample sizes for clinical investigations were small (median 10, range 1–42). A minority of articles described basic or translational research (11%) and workflow or cost evaluation studies (3%). The number of articles increased over time (P < 0.0001). While outcomes were heterogeneous, most studies reported successful implementation of accurate and cost‐effective 3D printing methods.ConclusionsThree‐dimensional printing is rapidly growing in radiation oncology and has been implemented effectively in a diverse array of applications. Although the number of 3D printing publications has steadily risen, the majority of current reports are preclinical in nature and the few clinical studies that do exist report on small sample sizes. Further dissemination of ongoing investigations describing the clinical application of developed 3D printing technologies in larger cohorts is warranted.

Dosimetric characteristics of a 2D silicon diode array for stereotactic radiotherapy end-to-end patient-specific QA

The measurement accuracy of stereotactic radiotherapy (SRT) patient-specific quality assurance (QA) is challenging as small-field dosimetry contains lateral charge disequilibrium, partial blocking of the beam source, and limitations based on the detector size. The aim of this study was to investigate the dosimetric characteristics of a two-dimensional high-resolution silicon diode array for SRT end-to-end patient-specific QA.The dosimetric characteristics of the diode array, delivered to an end-to-end QA phantom, were evaluated for 6 MV, with a flattening filter (FF) and flattening filter-free (FFF), and 10 MV FFF photon beams. Dose linearity, dose rate dependence, dose-per-pulse dependence, field size dependence, angular dependence, and beam directivity were investigated for all photon beams. A total of 27 clinical plans were selected to evaluate the SRT end-to-end patient-specific QA for treatment delivery using volumetric modulated arc therapy (VMAT).For all beam qualities, the differences of dose and dose rate linearity of the diode array were below 0.7% (10–1400 MU range) and 0.6% (100–2400 MU/min range), respectively. The diodes had a decrease in sensitivity of about 4% for the 21-fold decrease in dose-per-pulse. Output factors were in good agreement for field size down to 2 × 2 cm2 (<0.6% for both 6 MV FF and FFF beams, <1.6% for the 10 MV FFF beam), while the field size down to 0.6 × 0.6 cm2 had an under-response (<4% for all beam qualities). Angular dependence was within ±2% and ±4%, for coplanar and non-coplanar beams, respectively. However, this was not the case for the beam direction nearly parallel to the diode array plane. Beam directivity response on both sides of the array was in excellent agreement. For the end-to-end patient-specific QA, the average gamma passing rate (GPR) with a 2%/1 mm criterion was 96.8% and the minimum value was 93.0%. There was no significant difference in the GPRs between coplanar and non-coplanar VMAT plans.The diode array, with several corrections, demonstrated good dosimetric characteristics for SRT QA. The GPRs of end-to-end patient-specific QA for non-coplanar and multiple metastases were as high as that for coplanar and single-target, and a gamma criterion of 2%/1 mm would be suitable for SRT QA when using the array.

Development of a total hip replacement phantom for the assessment of CT-image quality.

The quality of computed tomography (CT) imaging is important when used to judge the success of joint replacement surgery. Metal artefacts are a known source of error, typically compensated by noise reduction software. To develop a transportable and stable system for the assessment of image quality of bone lesions around orthopedic implants. The design and manufacture of a bone-implant-phantom is described, which is based on a calf acetabulum with surrounding pelvic bone structures. Bone lesions of several sizes were created in the acetabulum before implanting the cup of an uncemented hip prosthesis, which was fixed with a stainless-steel bone screw. Plastic strips were placed on a cobalt-chromium stemmed femoral component, simulating typical bone lesions around loosening or infected prostheses, before embedding the stem in material similar to bone and shaped like a femur. The head of the femoral component was then placed in the acetabular cup and CT scans were produced. It was possible to construct a durable CT hip phantom for quality assurance work. The usability of different materials and the choices made for the phantom are discussed. It is possible to construct a durable joint implant phantom for quality assurance and scanner hardware and software assessment with limited resources. The phantom was successfully used in the assessment of the hardware and software performance of different CT scanners.

Dosimetric Study of an Indigenous and Heterogeneous Pelvic Phantom for Radiotherapy Quality Assurance

Introduction: In vitro dosimetric verification prior to patient treatment plays a key role in accurate and precision radiotherapy treatment delivery. Since the human body is a heterogeneous medium, the aim of this study was to design a heterogeneous pelvic phantom for radiotherapy quality assurance. Material and Methods: A pelvic phantom was designed using wax, pelvic bone, borax powder, and water mimicking different biological tissues. Hounsfield units and relative electron densities were measured. Various intensity-modulated radiotherapy (IMRT) plans were imported to the pelvic phantom for verification and implemented on the Delta 4 phantom. The quantitative evaluation was performed in terms of dose deviation, distance to agreement, and gamma index passing rate. Results: According to the results of the CT images of an actual patient, relative electron densities for bone, fat, air cavity, bladder, and rectum were 1.335, 0.955, 0.158, 1.039, and 1.054, respectively. Moreover, the CT images of a heterogeneous pelvic phantom showed the relative electron densities for bone, fat (wax), air cavity, bladder (water), and rectum (borax powder) as 1.632, 0.896, 0.159, 1.037, and 1.051, respectively.The mean percentage variation between planned and measured doses was found to be 2.13% within the tolerance limit (< ±3%) .In all test cases, the gamma index passing rate was greater than 90%. Conclusion: The findings showed the suitability of the materials used in the design of the heterogeneous phantom. Therefore, it can be concluded that the designed phantom can be used for regular radiotherapy quality assurance

Design of a Monte Carlo model based on dual-source computed tomography (DSCT) scanners for dose and image quality assessment using the Monte Carlo N-Particle (MCNP5) code

Abstract The purpose of this work was to develop and validate a Monte Carlo model for a Dual Source Computed Tomography (DSCT) scanner based on the Monte Carlo N-particle radiation transport computer code (MCNP5). The geometry of the Siemens Somatom Definition CT scanner was modeled, taking into consideration the x-ray spectrum, bowtie filter, collimator, and detector system. The accuracy of the simulation from the dosimetry point of view was tested by calculating the Computed Tomography Dose Index (CTDI) values. Furthermore, typical quality assurance phantoms were modeled in order to assess the imaging aspects of the simulation. Simulated projection data were processed, using the MATLAB software, in order to reconstruct slices, using a Filtered Back Projection algorithm. CTDI, image noise, CT-number linearity, spatial and low contrast resolution were calculated using the simulated test phantoms. The results were compared using several published values including IMPACT, NIST and actual measurements. Bowtie filter shapes are in agreement with those theoretically expected. Results show that low contrast and spatial resolution are comparable with expected ones, taking into consideration the relatively limited number of events used for the simulation. The differences between simulated and nominal CT-number values were small. The present attempt to simulate a DSCT scanner could provide a powerful tool for dose assessment and support the training of clinical scientists in the imaging performance characteristics of Computed Tomography scanners.

Development of a low-cost imaging performance evaluation phantom for a generic multi-detector CT scanner

For quality assurance, an evaluation phantom is an important tool used to assess the imaging performance of a multi-detector CT (MDCT) scanner. In doing so, this would help to prevent the production of low-quality images that may lead to misdiagnosis and repeats of x-ray exposure. However, imaging performance test phantoms available commercially are too costly for resource-limited CT facilities to procure. This study aims to design an imaging performance evaluation phantom, fabricate a low-cost prototype of the design, and assess the suitability of use of the fabricated phantom under existing performance testing protocols. The phantom was designed according to recommended specifications from IAEA and AAPM and the prototype of the design was manufactured using engineering plastics and industrial metals through computer numerical controlled (CNC) machining and stereolithography (SLA) 3D printing. The fabricated phantom prototype was then tested with United Imaging 80-slice MDCT scanner and its usability was compared to Gammex ACR 464 phantom following the ACR QC assessment methods. This research was able to produce a three-module solid plastic phantom with a performance at par with the commercial phantom. Furthermore, the overall manufacturing cost for the fabrication of the phantom was 87% cheaper than the cost of acquiring a commercial phantom. Thus, local development of a quality assurance phantom for CT is a cost-effective solution for resource-limited facilities.

Performance of a linear accelerator couch positioning quality control task using an electronic portal imaging device.

Short and semi-automated quality assurance (QA) programs are becoming one of the most popular and highly demanding tasks in radiotherapy. The current research investigates the accuracy of a four degrees of freedom (4DoF) medical linear accelerator couch positioning with a fast and accurate method based on images acquired using an electronic portal imaging device (EPID). An accurate EPID QA phantom and a proper in-house code were used. A Siemens medical linear accelerator equipped with an a-Si EPID was used to acquire portal images. For verifying the mechanical performance of the EPID positioning, EPID sensitivity, and accuracy of the code response from the image processing point of view were investigated. To characterize the results, three deviations in the phantom positioning were deliberately created. The translational and rotational displacements of the treatment couch were then evaluated. The loading effect on the treatment couch was then investigated. The results of prerequisite tests, including the mechanical performance of the EPID, and the sensitivity and accuracy of the recognition codes, were assessed. The results were found to be within the tolerance range reported at AAPM TG-142. The mean deviations of the tests between expected and measured displacements by 4DoF treatment couch were found to be 0.13° ± 0.11°, 0.12 ± 0.17mm, 0.17 ± 0.13mm, and 0.04 ± 0.09mm for rotational, longitudinal, lateral, and vertical shifts, respectively. The results showed that the proposed method is a reliable and fast approach to find the uncertainties occurring intreatment couch positioning.

MRIgRT head and neck anthropomorphic QA phantom: Design, development, reproducibility, and feasibility study.

The purpose of this paper was to design, manufacture, and evaluate a tissue equivalent, dual magnetic resonance/computed tomography (MR/CT) visible anthropomorphic head and neck (H&N) phantom. This phantom was specially designed as an end-to-end quality assurance (QA) tool for MR imaging guided radiotherapy (MRIgRT) systems participating in NCI-sponsored clinical trials. The MRIgRT H&N phantom was constructed using a water-fillable acrylic shell and a custom insert that mimics an organ at risk (OAR) and target structures. The insert consists of a primary and secondary planning target volume (PTV) manufactured of a synthetic Clear Ballistic gel, an acrylic OAR and surrounding tissue fabricated using melted Superflab. Radiochromic EBT3 film and thermoluminescent detectors (TLDs) were used to measure the dose distribution and absolute dose, respectively. The phantom was evaluated by conducting an end-to-end test that included: imaging on a GE Lightspeed CT simulator, planning on Monaco treatment planning software (TPS), verifying treatment setup with MR, and irradiating on Elekta's 1.5T Unity MR linac system. The phantom was irradiated three times using the same plan to determine reproducibility. Three institutions, equipped with either ViewRay MRIdian 60 Co or ViewRay MRIdian Linac, were used to conduct a feasibility study by performing independent end-to-end studies. Thermoluminescent detectors were evaluated in both reproducibility and feasibility studies by comparing ratios of measured TLD to reported TPS calculated values. Radiochromic film was used to compare measured planar dose distributions to expected TPS distributions. Film was evaluated by using an in-house gamma analysis software to measure the discrepancies between film and TPS. The MRIgRT H&N phantom on the Unity system resulted in reproducible TLD doses (SD<1.5%). The measured TLD to calculated dose ratios for the Unity system ranged from 0.94 to 0.98. The Viewray dose result comparisons had a larger range (0.95-1.03) but these depended on the TPS dose calculations from each site. Using a 7%/4mm gamma analysis, Viewray institutions had average axial and sagittal passing rates of 97.3% and 96.2% and the Unity system had average passing rates of 97.8% and 89.7%, respectively. All of the results were within the Imaging and Radiation Oncology Core in Houston (IROC-Houston) standard credentialing criteria of 7% on TLDs, and >85% of pixels passing gamma analysis using 7%/4mm on films. An MRIgRT H&N phantom that is tissue equivalent and visible on both CT and MR was developed. The results from initial reproducibility and feasibility testing of the MRIgRT H&N phantom using the tested MGIgRT systems suggests the phantom's potential utility as a credentialing tool for NCI-clinical trials.

Evaluation of a 3D-printed heterogeneous anthropomorphic head and neck phantom for patient-specific quality assurance in intensity modulated radiation therapy

We evaluated an anthropomorphic head and neck phantom with tissue heterogeneity, produced using a personal 3D printer, with quality assurance (QA), specific to patients undergoing intensity-modulated radiation therapy (IMRT). Using semi-automatic segmentation, 3D models of bone, soft tissue, and an air-filled cavity were created based on computed tomography (CT) images from patients with head and neck cancer treated with IMRT. For the 3D printer settings, polylactide was used for soft tissue with 100% infill. Bone was reproduced by pouring plaster into the cavity created by the 3D printer. The average CT values for soft tissue and bone were 13.0 ± 144.3 HU and 439.5 ± 137.0 HU, respectively, for the phantom and 12.1 ± 124.5 HU and 771.5 ± 405.3 HU, respectively, for the patient. The gamma passing rate (3%/3 mm) was 96.1% for a nine-field IMRT plan. Thus, this phantom may be used instead of a standard shape phantom for patient-specific QA in IMRT.

Sensitivity analysis of different quality assurance methods for magnetic resonance imaging in radiotherapy.

Background and purposeThere are currently no standard quality assurance (QA) methods for magnetic resonance imaging (MRI) in radiotherapy (RT). This work was aimed at evaluating the ability of two QA protocols to detect common events that affect quality of MR images under RT settings.Materials and methodsThe American College of Radiology (ACR) MRI QA phantom was repeatedly scanned using a flexible coil and action limits for key image quality parameters were derived. Using an exploratory survey, issues that reduce MR image quality were identified. The most commonly occurring events were introduced as provocations to produce MR images with degraded quality. From these images, detection sensitivities of the ACR MRI QA protocol and a commercial geometric accuracy phantom were determined.ResultsMachine-specific action limits for key image quality parameters set at were comparable with the ACR acceptable values. For the geometric accuracy phantom, provocations from uncorrected gradient nonlinearity effects and a piece of metal in the bore of the scanner resulted in worst distortions of 22.2 mm and 3.4 mm, respectively. The ACR phantom was sensitive to uncorrected signal variations, electric interference and a piece of metal in the bore of the scanner but could not adequately detect individual coil element failures.ConclusionsThe ACR MRI QA phantom combined with the large field-of-view commercial geometric accuracy phantom were generally sensitive in identifying some common MR image quality issues. The two protocols when combined may provide a tool to monitor the performance of MRI systems in the radiotherapy environment.

Design of a Reconfigurable Quality Assurance Phantom for Verifying the Spatial Accuracy of Radiosurgery Treatments for Multiple Brain Metastases

Abstract Radiation therapy frequently involves highly customized and complex treatments, employing sophisticated equipment, that require extensive patient-specific validation to verify the accuracy of the treatment plan as part of the clinical quality assurance (QA) process. This paper introduces a novel, reconfigurable QA phantom developed for the spatial validation of radiosurgery treatments of multiple brain metastases (MBM). This phantom works in conjunction with existing electronic portal imaging detector (EPID) technology to rapidly verify MBM treatment plans with submillimeter accuracy. The device provides a 12 × 12 × 12 cm3 active volume and multiple, independently configurable markers, in the form of 3 mm diameter radiopaque spheres, which serve as surrogates for brain lesions. The device is lightweight, portable, can be setup by a single operator, and is adaptable for use with external beam radiotherapy (EBRT) techniques and stereotactic linear accelerators (LINACs). This paper presents the device design and fabrication, along with initial testing and validation results both in the laboratory, using a coordinate measuring machine (CMM) and under simulated clinical conditions, using a radiosurgery treatment plan with 15 lesions. The device has been shown to place markers in space with a 0.45 mm root-mean-square error, which is satisfactory for initial clinical use. The device is undergoing further testing under simulated clinical conditions and improvements to reduce marker positional error.

EFFECTS OF IMAGE PROCESSING UPON RADIOGRAPHIC IMAGE QUALITY

<h3>Background</h3> There is evidence that capture and processing of the digital radiographic images may contain artifacts that could reduce the diagnostic value of dental radiographs. This phenomenon has been reported through various case reports. However, its effect on radiographic image quality has not been studied. <h3>Objective(s)</h3> The purpose of this study was to evaluate the effect of image processing on the quality of dental digital radiographs using the most common type of filter—sharpening. <h3>Study Design</h3> Three imaging modalities (2 complementary metal-oxide-semiconductor [CMOS], 1 photostimulable phosphor [PSP]) were used to image a DDQA imaging phantom (Digital Dental Quality Assurance phantom) and to create a flatfield radiograph. Contrast resolution, spatial resolution, dynamic range, and radiographic noise were assessed for image quality. Overshoot artifact was also assessed. Each image was sharpened and then highly sharpened. Images were compared using Friedman's 2-way nonparametric analysis of variance (ANOVA). <h3>Results</h3> Image sharpening significantly affected spatial resolution and noise. Conversely, dynamic range and contrast resolution were not significantly affected by image sharpening. Overshoot artifact increased with image sharpening. <h3>Discussion/Conclusions</h3> Image sharpening can create artifacts that could be misinterpreted. Although image sharpening significantly affects spatial resolution, no significant effect was seen on dynamic range or contrast resolution.