Mammography Accreditation Phantom Research Articles

Does residual ultrasound transmission gel affect the diagnostic ability of mammography?

This study aimed to assess whether residual ultrasound transmission gel (USTG) caused artifacts in mammography using a model 156 mammographic accreditation phantom and step phantom. Moreover, pig tissues with structures similar to those of the breast were imaged to assess whether USTG on the tissue appeared as a shadow on the mammogram, and how these shadows may be interpreted in clinical practice. The results showed that the visualization scores obtained for phantom mammograms decreased significantly for the fiber and mass samples after the application of USTG. Moreover, USTG on the tissues affected the visual evaluation of mammograms, leading to misinterpretation of mammographic findings.

Contrast-enhanced spectral mammography with a compact synchrotron source.

For early breast cancer detection, mammography is nowadays the commonly used standard imaging approach, offering a valuable clinical tool for visualization of suspicious findings like microcalcifications and tumors within the breast. However, due to the superposition of anatomical structures, the sensitivity of mammography screening is limited. Within the last couple of years, the implementation of contrast-enhanced spectral mammography (CESM) based on K-edge subtraction (KES) imaging helped to improve the identification and classification of uncertain findings. In this study, we introduce another approach for CESM based on a two-material decomposition, with which we expect fundamental improvements compared to the clinical procedure. We demonstrate the potential of our proposed method using the quasi-monochromatic radiation of a compact synchrotron source—the Munich Compact Light Source (MuCLS)—and a modified mammographic accreditation phantom. For direct comparison with the clinical CESM approach, we also performed a standard dual-energy KES at the MuCLS, which outperformed the clinical CESM images in terms of contrast-to-noise ratio (CNR) and spatial resolution. However, the dual-energy-based two-material decomposition approach achieved even higher CNR values. Our experimental results with quasi-monochromatic radiation show a significant improvement of the image quality at lower mean glandular dose (MGD) than the clinical CESM. At the same time, our study indicates the great potential for the material-decomposition instead of clinically used KES to improve the quantitative outcome of CESM.

Imaging of fiber-like structures in digital breast tomosynthesis.

Fiber-like features are an important aspect of breast imaging. Vessels and ducts are present in all breast images, and spiculations radiating from a mass can indicate malignancy. Accordingly, fiber objects are one of the three types of signals used in the American College of Radiology digital mammography (ACR-DM) accreditation phantom. Our work focuses on the image properties of fiber-like structures in digital breast tomosynthesis (DBT) and how image reconstruction can affect their appearance. The impact of DBT image reconstruction algorithm and regularization strength on the conspicuity of fiber-like signals of various orientations is investigated in simulation. A metric is developed to characterize this orientation dependence and allow for quantitative comparison of algorithms and associated parameters in the context of imaging fiber signals. The imaging properties of fibers, characterized in simulation, are then demonstrated in detail with physical DBT data of the ACR-DM phantom. The characterization of imaging of fiber signals is used to explain features of an actual clinical DBT case. For the algorithms investigated, at low regularization setting, the results show a striking variation in conspicuity as a function of orientation in the viewing plane. In particular, the conspicuity of fibers nearly aligned with the plane of the x-ray source trajectory is decreased relative to more obliquely oriented fibers. Increasing regularization strength mitigates this orientation dependence at the cost of increasing depth blur of these structures.

Mammographic compression in Asian women.

ObjectivesTo investigate: (1) the variability of mammographic compression parameters amongst Asian women; and (2) the effects of reducing compression force on image quality and mean glandular dose (MGD) in Asian women based on phantom study.MethodsWe retrospectively collected 15818 raw digital mammograms from 3772 Asian women aged 35–80 years who underwent screening or diagnostic mammography between Jan 2012 and Dec 2014 at our center. The mammograms were processed using a volumetric breast density (VBD) measurement software (Volpara) to assess compression force, compression pressure, compressed breast thickness (CBT), breast volume, VBD and MGD against breast contact area. The effects of reducing compression force on image quality and MGD were also evaluated based on measurement obtained from 105 Asian women, as well as using the RMI156 Mammographic Accreditation Phantom and polymethyl methacrylate (PMMA) slabs.ResultsCompression force, compression pressure, CBT, breast volume, VBD and MGD correlated significantly with breast contact area (p<0.0001). Compression parameters including compression force, compression pressure, CBT and breast contact area were widely variable between [relative standard deviation (RSD)≥21.0%] and within (p<0.0001) Asian women. The median compression force should be about 8.1 daN compared to the current 12.0 daN. Decreasing compression force from 12.0 daN to 9.0 daN increased CBT by 3.3±1.4 mm, MGD by 6.2–11.0%, and caused no significant effects on image quality (p>0.05).ConclusionsForce-standardized protocol led to widely variable compression parameters in Asian women. Based on phantom study, it is feasible to reduce compression force up to 32.5% with minimal effects on image quality and MGD.

Comparison between image quality in electronic zoom and geometric magnification in digital mammography.

Magnification mammography is performed to enhance the visibility of small structures at the expense of relatively high radiation dose as a complementary examination to standard mammography. The introduction of post-processing capabilities and the widespread use of digital mammography has promoted some controversy in the last decade on whether similar visibility can be achieved using electronic zoom. The aim of this study is to compare the visibility of small structures in images obtained by the two techniques stated above for different exposure conditions. Images of a Fluke Biomedical Model 18-220 Mammography Accreditation Phantom were obtained using standard techniques and geometric magnification, using a digital mammography unit, with different exposure factors. Three different target/filter combinations (Mo/Mo,Mo/Rh,Rh/Rh), variable kVp (26-32), and automatic exposure control were used. Images obtained using standard technique were electronically zoomed and compared to the corresponding magnification mammograms. Comparisons were based on the visibility of structures evaluated by five senior technologist with extensive experience in mammography. Statistical analysis was performed using non-parametric tests. Visibility of structures was not affected by the kV used for a given target/filter combination for both techniques (p > 0.065). Target/filter combination of Mo/Mo provided better visibility of micro-calcification and fibers (p < 0.026) in geometric magnification technique and Mo/Rh in the digital zoom technique. No significant differences were observed in the visibility of simulated breast masses. The overall image score was significantly higher (p < 0.001) for geometric magnification over the digital zoom for Mo/Mo & Rh/Rh combinations. Although sufficient image quality was maintained in electronically zoomed images, geometric magnification provided better overall visualization of structures in the phantom.

SU‐D‐206‐06: Task‐Specific Optimization of Scintillator Thickness for CMOS‐Detector Based Cone‐Beam Breast CT

Purpose:To optimize the cesium iodide (CsI:Tl) scintillator thickness in a complimentary metal‐oxide semiconductor (CMOS)‐based detector for use in dedicated cone‐beam breast CT.Methods:The imaging task considered was the detection of a microcalcification cluster comprising six 220µm diameter calcium carbonate spheres, arranged in the form of a regular pentagon with 2 mm spacing on its sides and a central calcification, similar to that in ACR‐recommended mammography accreditation phantom, at a mean glandular dose of 4.5 mGy. Generalized parallel‐cascades based linear systems analysis was used to determine Fourier‐domain image quality metrics in reconstructed object space, from which the detectability index inclusive of anatomical noise was determined for a non‐prewhitening numerical observer. For 300 projections over 2π, magnification‐associated focal‐spot blur, Monte Carlo derived x‐ray scatter, K‐fluorescent emission and reabsorption within CsI:Tl, CsI:Tl quantum efficiency and optical blur, fiberoptic plate transmission efficiency and blur, CMOS quantum efficiency, pixel aperture function and additive noise, and filtered back‐projection to isotropic 105µm voxel pitch with bilinear interpolation were modeled. Imaging geometry of a clinical prototype breast CT system, a 60 kV Cu/Al filtered x‐ray spectrum from 0.3 mm focal spot incident on a 14 cm diameter semi‐ellipsoidal breast were used to determine the detectability index for 300–600 µm thick (75µm increments) CsI:Tl. The CsI:Tl thickness that maximized the detectability index was considered optimal.Results:The limiting resolution (10% modulation transfer function, MTF) progressively decreased with increasing CsI:Tl thickness. The zero‐frequency detective quantum efficiency, DQE(0), in projection space increased with increasing CsI:Tl thickness. The maximum detectability index was achieved with 525µm thick CsI:Tl scintillator. Reduced MTF at mid‐to‐high frequencies for 600µm thick CsI:Tl lowered the detectability index than 525µm CsI:Tl.Conclusion:For the x‐ray spectrum and imaging conditions considered, a 525µm thick CsI:Tl scintillator integrated with the CMOS detector is optimal for detecting microcalcification cluster.Funding support: Supported in part by NIH R01 CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or the NCI. Disclosures: SV, GV and AK ‐ Research collaboration, Koning Corp., West Henrietta, NY.

WE‐DE‐207B‐06: Artifact Reduction in Digital Breast Tomosynthesis with the Denoised Ordered‐Subset Statistically Penalized Algebraic Reconstruction Technique (DOS‐SPART) Algorithm

Purpose:Digital breast tomosynthesis (DBT) is an emerging breast imaging modality. It uses x‐ray absorption projection images acquired over a narrow angular span to provide high spatial resolution pseudo‐three dimensional images for breast cancer screening and diagnosis. Unfortunately, the narrow range used to acquire data (typically &lt;30 degrees) results in significant out of plane artifacts for high contrast objects when conventional reconstruction techniques are used. In this work, the denoised ordered‐subset statistically penalized algebraic reconstruction technique (DOS‐SPART) algorithm was adapted to breast tomosynthesis imaging to reduce out‐of‐plane blurring artifacts.Methods:The DOS‐SPART algorithm was implemented for use with DBT datasets. The ACR mammography accreditation phantom was imaged for quantitative measurement and subjective image analysis. The artifact spread function (ASF) was measured for images generated by the commercial reconstruction method as well as DOS‐SPART with different total number of iterations (5, 10, 15, and 20). The FWHM of the ASF was used to quantify out‐of‐plane blurring. A cluster of calcifications in the ACR phantom was also inspected subjectively, and images above and below the feature were examined for artifacts.Results:The DOS‐SPART algorithm was able to efficiently reconstruct sharp image at the in‐focus plane, while significantly reducing out‐of‐plane blurring artifacts (total reconstruction time &lt;90 seconds for a 1996×2457×70 voxel volume with 5 iterations). The FWHM of the ASF was reduced by as much as 35% using the algorithm. Subjectively, the out‐of‐plane artifacts from the high contrast calcification are still clearly visible in the commercial reconstruction at 1 cm above or below the in‐focus plane, whereas no artifacts from the calcification are detectable in the out‐of‐plane images generated with DOS‐SPART.Conclusion:The application of DOS‐SPART to DBT can help limit out‐of‐plane artifacts in DBT imaging, potentially improving localization of microcalcifications and image contrast for adjacent structures.Funding support: This work was support in part by NIH R01 EB020521. Disclosures: J Garrett: None. Y. Li: None. K. Li: None. GH Chen: Research funded, GE Healthcare and Siemens AX

SU‐D‐209‐07: Measure the Average Glandular Dose of a 2D+3D Breast Imaging Protocol Using GE SenoClaire Breast Tomosynthesis System

Purpose:To measure the average glandular dose (AGD) of a 2D+3D breast imaging protocol using GE SenoClaire breast tomosynthesis system.Methods:This study used a GE SenoClaire breast tomosynthesis unit, a Gammex ACR mammography accreditation phantom, 5 cm thick PMMA phantom, an Unfors RaySafe X2 mammography detector. The breast imaging protocol includes a regular 2D CC view and a 3D MLO view at 45 degree, using AUTO mode. Both ACR phantom and PMMA phantom were scanned under AUTO mode with 10 daN compression to obtain the techniques of 2D CC view, 3D MLO view, and 3D CC view. The techniques of ACR phantom were used for the following manual scan with only RaySafe X2 detector being positioned under the same compression paddle at the same height as the ACR phantom. The detector is at 3 cm from the chest wall edge and laterally centered in the X‐ray field. Measurements were repeated with detector at 6 cm and 9 cm from the chest wall edge. The above procedure were repeated using the manual techniques of PMMA phantom. The measured entrance skin air Kerma was then converted to the AGD using twoMethods:one was listed in GE QC manual; the other was based on AAPM Report 223.Results:The AGD from 2D+3D imaging for both breasts using AUTO mode is approximately 4.25 mGy for ACR phantom and approximately 6 mGy for 5 cm thick PMMA phantom. The difference between 3D MLO view and 3D CC view is less than 2%. The difference between two methods is also less than 3%.Conclusion:The AGD of a 2D +3D breast imaging using GE SenoClaire is comparable to two regular 2D images if both are scanned using AUTO mode.

Evaluation of the image quality in digital breast tomosynthesis (DBT) employed with a compressed-sensing (CS)-based reconstruction algorithm by using the mammographic accreditation phantom

In this work, we have developed a prototype digital breast tomosynthesis (DBT) system which mainly consists of an x-ray generator (28kVp, 7mAs), a CMOS-type flat-panel detector (70-μm pixel size, 230.5×339mm2 active area), and a rotational arm to move the x-ray generator in an arc. We employed a compressed-sensing (CS)-based reconstruction algorithm, rather than a common filtered-backprojection (FBP) one, for more accurate DBT reconstruction. Here the CS is a state-of-the-art mathematical theory for solving the inverse problems, which exploits the sparsity of the image with substantially high accuracy. We evaluated the reconstruction quality in terms of the detectability, the contrast-to-noise ratio (CNR), and the slice-sensitive profile (SSP) by using the mammographic accreditation phantom (Model 015, CIRS Inc.) and compared it to the FBP-based quality. The CS-based algorithm yielded much better image quality, preserving superior image homogeneity, edge sharpening, and cross-plane resolution, compared to the FBP-based one.

Correction of data truncation artifacts in differential phase contrast (DPC) tomosynthesis imaging

The use of grating based Talbot–Lau interferometry permits the acquisition of differential phase contrast (DPC) imaging with a conventional medical x-ray source and detector. However, due to the limited area of the gratings, limited area of the detector, or both, data truncation image artifacts are often observed in tomographic DPC acquisitions and reconstructions, such as tomosynthesis (limited-angle tomography). When data are truncated in the conventional x-ray absorption tomosynthesis imaging, a variety of methods have been developed to mitigate the truncation artifacts. However, the same strategies used to mitigate absorption truncation artifacts do not yield satisfactory reconstruction results in DPC tomosynthesis reconstruction. In this work, several new methods have been proposed to mitigate data truncation artifacts in a DPC tomosynthesis system. The proposed methods have been validated using experimental data of a mammography accreditation phantom, a bovine udder, as well as several human cadaver breast specimens using a bench-top DPC imaging system at our facility.

Toward Clinically Compatible Phase-Contrast Mammography.

Phase-contrast mammography using laboratory X-ray sources is a promising approach to overcome the relatively low sensitivity and specificity of clinical, absorption-based screening. Current research is mostly centered on identifying potential diagnostic benefits arising from phase-contrast and dark-field mammography and benchmarking the latter with conventional state-of-the-art imaging methods. So far, little effort has been made to adjust this novel imaging technique to clinical needs. In this article, we address the key points for a successful implementation to a clinical routine in the near future and present the very first dose-compatible and rapid scan-time phase-contrast mammograms of both a freshly dissected, cancer-bearing mastectomy specimen and a mammographic accreditation phantom.

Objective measurements of image quality in synchrotron radiation phase-contrast imaging versus digital mammography.

Phase-contrast mammography with synchrotron radiation is an innovative X-ray imaging practice that improves the identification of breast lesions. Previous studies have proven the superiority of the mammography images taken in the phase-contrast modality using synchrotron radiation beams as compared with images taken in conventional mammography by subjective analyses. However, to our knowledge, no previous study has compared different acquisition systems in order to quantify this improvement by means of objective robust indicators. In this research, we intend to quantify the superiority of phase-contrast imaging by means of objective metrics of image quality. Images from the American College of Radiology Mammographic Accreditation Phantom were obtained at hospitals, in two digital mammography equipment and at the Elettra synchrotron radiation facility (Trieste, Italy), using free space propagation phase-contrast modality. Regions of interest were selected to analyze image quality at the fibers (phase object) and masses (area object) simulated on the phantom by means of the signal-to-noise ratio, the figure of merit, the contrast and the edge visibility. The image contrast and edge visibility were significantly higher at the phase-contrast modality as compared with digital mammography equipment. The figure of merit using phase-contrast modality was higher for the fibers and comparable for the masses. The results showed an improvement of the contrast and edge visibility in phase-contrast images. These improvements may be important in the detection of small lesions and details.

TU-CD-207-08: Intrinsic Image Quality Comparison of Synthesized 2-D and FFDM Images

Purpose: With the combined interest of managing patient dose, maintaining or improving image quality, and maintaining or improving the diagnostic utility of mammographic data, this study aims to compare the intrinsic image quality of Hologic’s synthesized 2-D (C-View) and 2-D FFDM images in terms of resolution, contrast, and noise. Methods: This study utilized a novel 3-D printed anthropomorphic breast phantom in addition to the American College of Radiology (ACR) mammography accreditation phantom. Analysis of the 3-D anthropomorphic phantom included visual assessment of resolution and analysis of the normalized noise power spectrum. Analysis of the ACR phantom included both visual inspection and objective automated analysis using in-house software. The software incorporates image- and object-specific CNR visibility thresholds which account for image characteristics such as noise texture which affect object visualization. T- test statistical analysis was also performed on ACR phantom scores. Results: The spatial resolution of C-View images is markedly lower (at least 50% worse) than that of FFDM. And while this is generally associated with the benefit of reduced relative noise magnitude, the noise in C-View images tends to have a more mottled (predominantly low-frequency) texture. In general, for high contrast objects, C-View provides superior visualization over FFDM; however this benefit diminishes for low contrast objects and is applicable only to objects that are sufficiently larger than the spatial resolution threshold. Based on both observer and automated ACR phantom analysis, between 50–70% of C-View images failed to meet ACR minimum accreditation requirements – primarily due to insufficient (unbroken) fiber visibility. Conclusion: Compared to FFDM, C-View offers better depiction of objects of certain size and contrast, but provides poorer overall resolution and noise properties. Based on these findings, the utilization of C-View images in the clinical setting requires careful consideration, especially if considering the discontinuation of FFDM imaging.

SU-D-204-04: Average Glandular Dose (AGD) Measurement of GE Contrast-Enhanced Spectral Mammography (CESM) Using a ACR Mammography Accreditation Phantom

Purpose: To investigate a practical approach to measure the average glandular dose (AGD) for GE Contrast-Enhanced Spectral Mammography (CESM) using a ACR mammography accreditation phantom Methods: This study used a GE Senographe Essential unit with SenoBright CESM, a Gammex ACR mammography accreditation phantom, an Unfors RaySafe X2 mammography detector, and a Radcal 10×9−6M ion chamber. Five AUTO CESM exposures were done on the ACR phantom with 5 daN compression to select the target/filter combination, kVp, and mAs. These techniques were used for the following manual CESM exposures, and the regular mammography to simulate the low energy exposure of a CESM run. Both Unfors and Radcal detectors are positioned near the phantom as the regular AGD measurement of mammography. The unfors detector measured the high energy exposure of the CESM run directly. The Radcal detector was set to accumulated mode and measured the total output from a CESM run. For Radcal, the high energy exposure was determined by subtracting the output of the regular mammography which simulated the low energy run of CESM from the total output. We also measured the HVLs of the low and high energy exposure respectively. The measured entrance skin air Kerma was then converted to the AGD using two Methods: one was based on the tables provided by GE; the other was introduced by D R Dance and K C Young (2014). Results: The AGD from the AUTO CESM on a ACR mammography phantom is approximately 1.75 mGy, 13.5% higher than that of the regular CNT AUTO mode, and 94% higher than that of the regular STD AUTO mode of this GE unit. The high energy exposure contributes about 18% of the total AGD. The AGD results from two methods are agreed to each other within 2%. Conclusion: We provide a practical approach to measure the AGD of GE CESM.

Abstract 4299: Comparison of high-resolution 3D X-ray microCT and tomosynthesis imaging: A breast phantom study

Abstract We have demonstrated the feasibility of imaging a mammographic accreditation phantom using high-resolution 3D X-ray microCT as an alternative to tomosynthesis. While both X-ray microCT and tomosynthesis produce high-resolution 3D images, tomosynthesis requires compression of the specimen and yields asymmetrical voxels, resulting in high spatial resolution along two axes and more limited resolution along the third axis. MicroCT imaging, however, does not require compression and provides uniform, high resolution in all directions. The limited angular range of tomosynthesis is advantageous for pre-operative screening tasks, while the increased spatial and full angular range of microCT has been increasingly applied to the assessment of surgically excised breast tissue during breast conserving surgery. Rapid and accurate assessment of excised tissues is desirable to minimize risk of recurrence, which is highest in the first two years after surgery. We employed a 35-80 kV, 7.6-15W scan protocol in X-ray microCT to image the breast phantom. We also tested the ability to detect the phantom target features (2.00-0.16 mm) in long (25 minute) and short (5-6 minute) scans. The phantom was designed to simulate the X-ray attenuation of a slab of compressed human breast consisting of glandular and adipose tissue. Both X-ray microCT and tomosynthesis were able to capture the smallest features (0.16 mm) of the phantom. Both long- and short-duration microCT scans enabled detection of the smallest (0.16mm) features of the phantom. The results obtained here suggest that (1) microCT could be used, as an alternative to tomosynthesis, to identify and localize features on the order of 100-200 microns in ex vivo tumor specimens and (2) microCT could be used to detect features of this size on an intra-operative basis (in 5-6 minute scans). This study shows the feasibility of using microCT for intra-operative 3D examination of surgical specimens, an application which could aid clinical decision-making in assessment of excision margins. Additionally, if high-resolution 3D imaging techniques can distinguish between features of tumor and non-tumor areas of tissues, as is suggested by these results, then these imaging modalities could hold promise for identification of biomarkers and elucidation of the gross anatomy of breast tumor types, such as ductal carcinoma in situ. There is not yet an accepted phantom for testing the detection limits of 3D high-resolution X-ray imaging. The phantom used here is a validated tool for calibration of mammography instruments, but it seems that digital X-ray imaging technologies, such as microCT, can quite easily capture the features of this phantom. Therefore, while microCT performed as well as tomosynthesis in detection of features in this breast phantom study, there is a need for the development and validation of new phantoms to assess the ability of tomosynthesis and microCT to resolve features in the &amp;lt;100 micron range. Citation Format: Jolene M. Singh, Anthony H. Bui, James S. Michaelson. Comparison of high-resolution 3D X-ray microCT and tomosynthesis imaging: A breast phantom study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4299. doi:10.1158/1538-7445.AM2014-4299

Comparative performance of modern digital mammography systems in a large breast screening program

To compare physical measures pertaining to image quality among digital mammography systems utilized in a large breast screening program. To examine qualitatively differences in these measures and differences in clinical cancer detection rates between CR and DR among sites within that program. As part of the routine quality assurance program for screening, field measurements are made of several variables considered to correlate with the diagnostic quality of medical images including: modulation transfer function, noise equivalent quanta, d' (an index of lesion detectability) and air kerma to allow estimation of mean glandular dose. In addition, images of the mammography accreditation phantom are evaluated. It was found that overall there were marked differences between the performance measures of DR and CR mammography systems. In particular, the modulation transfer functions obtained with the DR systems were found to be higher, even for larger detector element sizes. Similarly, the noise equivalent quanta, d', and the phantom scores were higher, while the failure rates associated with low signal-to-noise ratio and high dose were lower with DR. These results were consistent with previous findings in the authors' program that the breast cancer detection rates at sites employing CR technology were, on average, 30.6% lower than those that used DR mammography. While the clinical study was not large enough to allow a statistically powered system-by-system assessment of cancer detection accuracy, the physical measures expressing spatial resolution, and signal-to-noise ratio are consistent with the published finding that sites employing CR systems had lower cancer detection rates than those using DR systems for screening mammography.

Quality of images acquired with and without grid in digital mammography

In this study, we assessed the quality of digital mammography images acquired with a grid and without a grid for different kVp values. A digital mammography system was used for acquisition of images of the CIRS Model 015 Mammography Accreditation Phantom. The images were obtained in the presence of the grid and then with the grid removed from the system. The energy of the X-rays was varied between 26 and 32 kVp. The images were evaluated by five senior radiologic technologists with extensive experience in mammography. Statistical analysis was carried out with the Mann-Whitney non-parametric test with the level of significance set at p=0.05. The comparison between images obtained with a grid and without a grid indicated that, for the visibility of fibers, the non-grid images at 28 kVp were significantly (p=0.032) better than the images acquired with a grid. At all other kVp values, the images were not statistically different regarding the visibility of fibers. For the visibility of specks and masses, the images did not show any significant differences at any of the kVp values of the study. Imaging with kVp higher than 30 requires a grid to improve the visibility of fibrous calcifications and specks. For the visibility of masses at 32 kVp, no statistically significant differences between the grid and non-grid images were found.

SU‐C‐116‐06: Evaluation of Image Quality in Digital Mammography and Digital Breast Tomosynthesis: Phantom Observer Study From American College of Radiology Imaging Network PA 4006

Purpose: Determine contributing factors for image quality in 2D and 3D from comparison of phantom scores and image acquisition parameters. Methods: Tomosynthesis 2D and 3D quality assurance images of the ACR Mammography Accreditation Phantom were obtained as part of the American College of Radiology Imaging Network PA‐4006 trial. Imaging was performed on Selenia Dimensions (Hologic, Bedford MA) systems at the Hospital of the University of Pennsylvania (n=176) and Einstein Medical Center, Philadelphia, PA (n=70). Four trained observers scored all available images according to manufacturer's instructions; image order was randomized by case number and modality for each observer. For tomosynthesis, observers selected the slice level maximizing conspicuity. Paired t‐test compared FFDM and DBT cumulative scores by site, multivariate regression related device parameters to image quality, and multi‐observer Kappa assessed interobserver agreement. Results: Fiber scores were higher for 3D than 2D at site B (p&lt;0.001) with no difference at site A. Speck and mass scores were greater for 2D than 3D at both sites (p&lt;0.001). At site A, regression analysis demonstrated positive correlation of exposure (mAs) with 2D mass, 3D fiber and 3D mass scores; no significant correlations were found for site B. Absolute level of interobserver agreement was highest for specks, followed by fibers and masses. There was substantially lower inter‐observer agreement for specks in 3D than 2D; the agreement between 2D and 3D for fibers and masses did not change significantly. Conclusion: Phantom scores differed significantly between 2D and 3D imaging; fibers were better visualized in 3D, while specks and masses were better visualized in 2D. Observers stated that scoring specks in 3D was more challenging; this is supported by the observation that inter‐observer agreement was significantly poorer in 3D than 2D only for specks. There are many factors that influence scoring. While phantom score was partially predicted by exposure, other factors were involved.

SU‐C‐116‐05: Using Maximum Intensity Projection in the Evaluation of Digital Breast Tomosynthesis: A Phantom Observer Study From the American College of Radiology Imaging Network PA 4006 Trial

Purpose: Characterize the effect of slice level and maximal intensity projection (MIP) slab thickness on image quality in digital breast tomosynthesis (DBT). Methods: Eight ACRIN 4006 PA DBT acquisitions of the ACR Mammography Accreditation Phantom were selected from the Hospital of the University of Pennsylvania (n=4) and Einstein Medical Center, Philadelphia, PA (n=4). An experienced medical physicist scored each phantom by first recording scores at single slice levels in increments of increasing depth to confirm the score for each level. Scoring was next repeated with a 40‐mm MIP by identical method. MIP thickness was then decreased in 10‐mm increments and scored again. If a difference in score occurred between 10‐mm MIP slab thickness differences, objects were rescored at the intermediate 5‐mm MIP slab thickness, and so forth. Results: Fiber, speck and mass scores are all sensitive to slice level (single slice) or central slice level (MIP). Specks are the most sensitive. Scores can change substantially if slice level is shifted by one slice when viewing single slices or MIP slabs which are less than 10 mm thick. Scores of fibers and masses decrease with increasing MIP slab thickness, while speck scores do not change substantially. Even when all objects are ostensibly in the MIP volume, their location in the volume affects the score. Scores are degraded when the objects are nearer the top or bottom slice of the MIP slab. Conclusion: In single slice review, slice level substantially affects phantom score, thus care in slice selection is necessary. Increasing MIP slab thickness does not appear to substantially degrade image quality of specks, supporting the clinical practice of using MIP in the review of calcifications. MIP review of phantoms may add value in visualizing artifacts outside the plane of review.

Which Phantom Is Better for Assessing the Image Quality in Full-Field Digital Mammography?: American College of Radiology Accreditation Phantom versus Digital Mammography Accreditation Phantom

ObjectiveTo compare between the American College of Radiology (ACR) accreditation phantom and digital mammography accreditation phantom in assessing the image quality in full-field digital mammography (FFDM).Materials and MethodsIn each week throughout the 42-week study, we obtained phantom images using both the ACR accreditation phantom and the digital mammography accreditation phantom, and a total of 42 pairs of images were included in this study. We assessed the signal-to-noise ratio (SNR) in each phantom image. A radiologist drew a square-shaped region of interest on the phantom and then the mean value of the SNR and the standard deviation were automatically provided on a monitor. SNR was calculated by an equation, measured mean value of SNR-constant coefficient of FFDM/standard deviation. Two breast radiologists scored visible objects (fibers, specks, and masses) with soft-copy images and calculated the visible rate (number of visible objects/total number of objects). We compared SNR and the visible rate of objects between the two phantoms and calculated the k-coefficient for interobserver agreement.ResultsThe SNR of the ACR accreditation phantom ranged from 42.0 to 52.9 (Mean, 47.3 ± 2.79) and that of Digital Phantom ranged from 24.8 to 54.0 (Mean, 44.1 ± 9.93) (p = 0.028). The visible rates of all three types of objects were much higher in the ACR accreditation phantom than those in the digital mammography accreditation phantom (p < 0.05). Interobserver agreement for visible rates of objects on phantom images was fair to moderate agreement (k-coefficients: 0.34-0.57).ConclusionThe ACR accreditation phantom is superior to the digital mammography accreditation phantom in terms of SNR and visibility of phantom objects. Thus, ACR accreditation phantom appears to be satisfactory for assessing the image quality in FFDM.