Quality Control In Digital Mammography Research Articles

A spiculated mass target model for clinical image quality control in digital mammography.

Quality assurance of breast imaging has a long history of using test objects to optimize and follow up imaging devices. In particular, the evaluation of new techniques benefits from suitable test objects. The applicability of a phantom consisting of spiculated masses to assess image quality and its dependence on dose in flat field digital mammography (FFDM) and digital breast tomosynthesis systems (DBT) is investigated. Two spiculated masses in five different sizes each were created from a database of clinical tumour models. The masses were produced using 3D printing and embedded into a cuboid phantom. Image quality is determined by the number of spicules identified by human observers. The results suggest that the effect of dose on spicule detection is limited especially in cases with smaller objects and probably hidden by the inter-reader variability. Here, an average relative inter-reader variation of the counted number of 31% was found (maximum 83%). The mean relative intra-reader variability was found to be 17%. In DBT, sufficiently good results were obtained only for the largest masses. It is possible to integrate spiculated masses into a cuboid phantom. It is easy to print and should allow a direct and prompt evaluation of the quality status of the device by counting visible spicules. Human readout presented the major uncertainty in this study, indicating that automated readout may improve the reproducibility and consistency of the results considerably. A cuboid phantom including clinical objects as spiculated lesion models for visual assessing the image quality in FFDM and DBT was developed and is introduced in this work. The evaluation of image quality works best with the two larger masses with 21 spicules.

Variations in signal-to-noise characteristics of tissue-equivalent attenuators for mammographic automatic exposure control system performance evaluation.

This work investigates the impact of tissue-equivalent attenuator choice on measured signal-to-noise ratio (SNR) for automatic exposure control (AEC) performance evaluation in digital mammography. It also investigates how the SNR changes for each material when used to evaluate AEC performance across different mammography systems. AEC performance was evaluated for four mammography systems using seven attenuator sets at two thicknesses (4 and 8 cm). All systems were evaluated in 2D imaging mode, and one system was evaluated in digital breast tomosynthesis (DBT) mode. The methodology followed the 2018 ACR digital mammography quality control (DMQC) manual. Each system-attenuator-thickness combination was evaluated using For Processing images in ImageJ with standard ROI size and location. The closest annual physicist testing results were used to explore the impact of varying measured AEC performance on image quality. The measured SNR varied by 44%-54% within each system across all attenuators at 4 cm thickness in 2D mode. The variation appeared to be largely due to changes in measured noise, with variations of 46%-67% within each system across all attenuators at 4 cm thickness in 2D mode. Two systems had failing SNR levels for two of the materials using the minimum SNR criterion specified in the ACR DMQC manual. Similar trends were seen in DBT mode and at 8 cm thickness. Within each material, there was 115%-131% variation at 4 cm and 82%-114% variation at 8 cm in the measured SNR across the four imaging systems. Variation in SNR did not correlate with system operating level based on visual image quality and average glandular dose (AGD). Choice of tissue-equivalent attenuator for AEC performance evaluation affects measured SNR values. Depending on the material, the difference may be enough to result in failure following the longitudinal and absolute thresholds specified in the ACR DMQC manual.

On the relevance of modulation transfer function measurements in digital mammography quality control.

Purpose: The relevance of presampling modulation transfer function (MTF) measurements in digital mammography (DM) quality control (QC) is examined. Two studies are presented: a case study on the impact of a reduction in MTF on the technical image quality score and analysis of the robustness of routine QC MTF measurements. Approach: In the first study, two needle computed radiography (CR) plates with identical sensitivities were used with differences in the 50% point of the MTF ( ) larger than the limiting value in the European guidelines ( change between successive measurements). Technical image quality was assessed via threshold gold thickness of the CDMAM phantom and threshold microcalcification diameter of the L1 structured phantom. For the second study, presampling MTF results from 595 half-yearly QC tests of 55 DM systems (16 types, six manufacturers) were analyzed for changes from the baseline value and changes in between successive tests. Results: A reduction of 20% in of the two CR plates was observed. There was a tendency to a lower score for task-based metrics, but none were significant. Averaging over 55 systems, the absolute relative change in between consecutive tests (with 95% confidence interval) was 3% (2.5% to 3.4%). Analysis of the maximum relative change from baseline revealed changes of up to for one a-Se based system and for a group of CsI-based systems. Conclusions: A limit of 10% is a relevant action level for investigation. If exceeded, then the impact on performance has to be verified with extra metrics.

277. A software toolset for quality control in digital mammography and DBT

Purpose The aim is to introduce a software toolset compliant with European protocols for quality control of physical and technical aspects of mammography screening (2DFFDM) and Digital Breast Tomosynthesis (DBT) Systems. Methods The toolset is developed as a suite of plugins of the well-known free software ImageJ. The mammographic systems under study are Hologic Selenia Value+ and Siemens Mammomat Inspiration PRIME and the ARTINIS EU DBT Test Set is used to perform QC sessions. IQWorks and OBJ_IQ softwares are used to investigate the consistence for NPS and MTF values while the plugins for analysis of the remaining parameters are directly derived from EUREF guidelines. Results The toolset allows full analysis of the parameters specified in european protocols, especially AEC steps and short term reproducibility, AEC long term reproducibility by SNR referred to 2D ROI and 3D voxel, SDNR, local dense area, image receptor response function, noise, image receptor homogeneity and stability based on 2D ROI and 3D voxel calculation, detector elements failure through text files analysis for visualization and comparison of bad pixel map, uncorrected defective detector elements, inter plate sensitivity variations, AGD from DICOM headers, MTF with edge and wire techniques, NPS from 2DFFDM images, NPS for full 3DDBT slices as well as by extraction. The toolset also evaluates distortions and tilt of the reconstructed 3DDBT planes. The sorting and renaming of a set of dicom images based on their acquisition time or slice position and the evaluation of homogeneity in every DBT focal plane (PV, variance, SNR variations) are also achievable. Conclusions The aim is to introduce a software toolset compliant with European protocols for quality control of physical and technical aspects of mammography screening (2DFFDM) and Digital Breast Tomosynthesis (DBT) Systems. The toolset is developed as a suite of plugins of the well-known free software ImageJ. The mammographic systems under study are Hologic Selenia Value+ and Siemens Mammomat Inspiration PRIME and the ARTINIS EU DBT Test Set is used to perform QC sessions. IQWorks and OBJ_IQ softwares are used to investigate the consistence for NPS and MTF values while the plugins for analysis of the remaining parameters are directly derived from EUREF guidelines. The toolset allows full analysis of the parameters specified in european protocols, especially AEC steps and short term reproducibility, AEC long term reproducibility by SNR referred to 2D ROI and 3D voxel, SDNR, local dense area, image receptor response function, noise, image receptor homogeneity and stability based on 2D ROI and 3D voxel calculation, detector elements failure through text files analysis for visualization and comparison of bad pixel map, uncorrected defective detector elements, inter plate sensitivity variations, AGD from DICOM headers, MTF with edge and wire techniques, NPS from 2DFFDM images, NPS for full 3DDBT slices as well as by extraction. The toolset also evaluates distortions and tilt of the reconstructed 3DDBT planes. The sorting and renaming of a set of dicom images based on their acquisition time or slice position and the evaluation of homogeneity in every DBT focal plane (PV, variance, SNR variations) are also achievable.

Implementation of the EFOMP protocol for quality control in digital mammography in a multi-hospital/vendor context

Introduction The European Federation of Organisations in Medical Physics (EFOMP) has recently released a protocol for quality control (QC) in digital mammography with the intent of harmonizing and simplifying the QC procedures across the European countries. Purpose The aim of this work was to report our experience regarding the implementation of the EFOMP protocol for QC in digital mammography in a multi-hospital/vendor context. Materials and methods QC tests suggested by the EFOMP protocol were merged with mandatory tests by national (Italian) regulations in order to build a local QC protocol. The protocol was applied to one DR and three CR mammography systems developed by different vendors. Time needed for routine QCs was measured. A fast weekly test was implemented to assess the long term reproducibility of relevant quantities (dose and SNR). Results By employing one physicist and one technologist, the time needed for routine QC was: 4.5 h ± 0.5 h (annual tests), 2.5 h ± 0.5 h (semiannual tests), 0.2 h ± 0.1 h (weekly tests). For weekly tests, coefficients of variation of dose and SNR were below 6.0% (four-months period evaluated). By applying the developed protocol, two major and five minor anomalies were identified and corrected. Conclusions The EFOMP protocol could be adapted to local (Italian) regulations with minor modifications. Flexibility and simplification of routine QCs were advantageous in a busy multi-hospital/vendor context. Disclosure None.

TH-B-301-01: FFDM Quality Control Testing in Canada - a Vendor-Neutral Approach

Lack of national and international standards for quality control for digital mammography dictates that users have to follow manufacturerˈs recommendations. This leads to significant additional work for facilities with digital mammography systems from multiple vendors. Therefore, a comprehensive and unified quality control test for medical physicists and mammography technologists was developed for the Screening Mammography Program of British Columbia (SMPBC), in collaboration with Ontario Breast Screening Program with the intent of using them as a national standard in Canada. The quality control tests developed for the ACRIN DMIST study were used as the starting point for the new tests; however, due to the recent implementation of AEC algorithms by some manufacturers, it has become difficult to use the uniform phantom suggested by DMIST work. To address this, a simple 19 cm diameter semicircle uniform phantom was designed. Furthermore, it was found that the technologist weekly image quality test should be performed on “FOR PRESENTATION” images so that changes in image processing algorithms (similar to changes in film processing conditions) can be identified. IHE Mammography Integration Profile compliance was also included as part of the Medical Physicists tests. The new unified quality control procedures have been adopted as the standard in the province of BC for more than two years. This unified approach has made it possible to streamline and manage the quality control of screening mammography facilities within the province. The technologist weekly image quality test done with “FOR PRESENTATION” images instead of “FOR PROCESSING” images (as suggested by ACRIN DMIST study findings) have uncovered changes in image processing algorithms that were implemented by manufacturers without the knowledge of the users. The new semicircle uniform phantom is found to be suitable for testing the AEC performance of every digital mammography unit used in the province of BC. Due to the success in the use of the new unified QC tests in the province of BC, we are in the process of promoting this as a national standard for digital mammography quality control in Canada. This presentation will provide an overview of the development and implementation of these vendor neutral unified quality control procedures and its advantages. Learning Objectives: 1. Understand the type of testing required for Digital mammography systems. 2. Understand the advantages of a unified QA procedure. 3. Understand some of the technical and logistical issues involved in implementing vendor neutral QA procedures. 4. Understand the importance of using IHE Mammography Integration Profile as part of the Medical Physicist testing.

北海道におけるデジタルマンモグラフィの現状と品質管理および画質・線量の調査

A questionnaire survey about mammography in Hokkaido was mailed to 121 facilities from August to September 2009. We surveyed the conditions of digital mammography with regard to quality control (QC) and average glandular dose at 79 facilities in Hokkaido in 2009, and the results of the survey were compared with those of 2004. We found that digital mammography techniques were widely used across Hokkaido and that computed radiography (CR) systems were quite widespread, with 70% of facilities having them. The average glandular dose ranged from 1.04 to 2.3 mGy (mean: 1.73 mGy) for digital equipment. The results revealed several problems. Although the use of 1-, 2-, and 3-megapixel (MP) liquid crystal displays (LCDs) was not uncommon, 5-MP LCDs were used in most cases when reading digital mammograms. Facilities that have mammography equipment are unlikely to have quality control instruments for mammography. Although daily QC is performed in most facilities, further quality control for digital mammography should be developed, including that for monitors. In a second study, we evaluated the 1 Shot Phantom M Plus (1 Shot Phantom), which enables objective evaluation by providing for one physical measurement rather than a subjective visual analysis. The results indicated that the 1 Shot Phantom was very useful for digital mammography systems in daily QC testing because it enabled objectivity.

SU‐GG‐I‐152: Rapid Evaluation of X‐Ray/Light Field Alignment for Digital Radiographic Systems

Purpose: This study investigated the development of a device to rapidly quantify x‐ray and light field alignment. The device is a useful alternative to traditional measurement techniques requiring film and is particularly useful for all‐digital facilities that no longer have film processors. The system that is investigated provides rapid and accurate evaluation of the difference between x‐ray and light fields. Method and Materials: A fiber‐optic coupled (FOC) dosimetry system was adapted to evaluate the misalignment between the light and x‐ray fields of mammography imaging systems. An FOC detector element providing a variable output as a function of exposed dosimeter length is used to measure the deviation of each side of the X‐ray/light field. Each detector element incorporates two FOC dosimeters which were constructed by coupling plastic scintillator fibers, 500 microns in diameter, one 2mm and the other 5cm in length, to sensitive photomultiplier tubes (PMTs). The detector element is positioned such that the 5 cm dosimeter intersects the edge of the light and X‐ray fields. The second dosimeter (2mm) is positioned entirely in the X‐ray field to provide a relative measure of beam intensity. Characterization involved varying the length of the 5 cm dosimeter exposed within the x‐ray field. Results: The system consistently demonstrated linearity with tube output and exposed length. Trials have shown a linear response of detected counts to length of scintillation material in the light field over the range of interest. The system's spatial resolution is evaluated and characterized for a variety of exposure parameters. Conclusion: Multiple PMTs allow all edges of the light field to be evaluated simultaneously, permitting x‐ray/light field alignment for a typical digital mammography system to be completed in approximately ten minutes. The time savings and improved accuracy over current alternatives makes the device an attractive tool for digital mammography quality control.

ディジタルマンモグラフィのための品質管理

ディジタルマンモグラフィのための品質管理

TU‐A‐330A‐01: Digital Mammography Quality Control and Accreditation

Since 2003, the number of full‐field digital mammography (FFDM) units in the United States has been increasing by about 4% per month. As of May 1, 2006, there were 1379 full‐field digital mammography units at 977 MQSA‐certified facilities in the United States. With the fall 2005 announcement that FFDM increased the effectiveness of detecting breast cancer in women with dense breasts (as well as premenopausal women and women under the age of 50), the rate of increase for digital units is expected to increase even further. FFDM systems are subject to the Food and Drug Administration's mammography regulations, as are analog systems). This presentation will discuss the steps medical physicists must take to ensure their facilities may expeditiously accredit their FFDM units. In addition, the presentation will cover preliminary QC recommendations made by the ACR's Subcommittee on Digital Mammography in preparation for their upcoming Digital Mammography FFDM Quality Control Manual.

Full-Field Digital Mammography Quality Control: Operational Considerations

Full-field digital mammography (FFDM) is gaining widespread clinical acceptance in the United States and has the potential to ultimately replace screen-film mammography (SFM). Since the introduction of the MQSA in 1992 by the US Congress, studies have demonstrated that, with increased attention to quality control, SFM has improved in quality across the United States. For FFDM to phase out and ultimately replace SFM, similar stringent quality control processes will be required of FFDM. The purpose of this article is to outline operational considerations during the implementation of FFDM quality control in a breast imaging facility.

Quality control for digital mammography in the ACRIN DMIST trial: Part I

The Digital Mammography Imaging Screening Trial, conducted by the American College of Radiology Imaging Network, is a clinical trial designed to compare the accuracy of full-field digital mammography (FFDM) versus screen-film mammography in a screening population. Five FFDM systems from four manufacturers (Fischer, Fuji, General Electric, and Lorad) were employed in the study at 35 clinical sites. A core physics team devised and implemented tests to evaluate these systems. A detailed description of physics and quality control tests is presented, including estimates of: mean glandular dose, modulation transfer function (MTF), 2D noise power spectra, and signal-to-noise ratio (SNR). The mean glandular doses for the standard breast ranged from 0.79 to 2.98 mGy, with 1.62 mGy being the average across all units and machine types. For the five systems evaluated, the MTF dropped to 50% at markedly different percentages (22% to 87%) of the Nyquist limit, indicating that factors other than detector element (del) size have an important effect on spatial resolution. Noise power spectra and SNR were measured; however, we found that it was difficult to standardize and compare these between units. For each machine type, the performance as measured by the tests was very consistent, and no predictive benefit was seen for many of the tests during the 2-year period of the trial. It was found that, after verification of proper operation during acceptance testing, if systems failed they generally did so suddenly rather than through gradual deterioration of performance. Because of the relatively short duration of this study further, investigation of the long-term failure characteristics of these systems is advisable.

Quality control for digital mammography: Part II recommendations from the ACRIN DMIST trial

The Digital Mammography Imaging Screening Trial (DMIST), conducted under the auspices of the American College of Radiology Imaging Network (ACRIN), is a clinical trial designed to compare the accuracy of digital versus screen-film mammography in a screening population [E. Pisano et al., ACRIN 6652-Digital vs. Screen-Film Mammography, ACRIN (2001)]. Part I of this work described the Quality Control program developed to ensure consistency and optimal operation of the digital equipment. For many of the tests, there were no failures during the 24 months imaging was performed in DMIST. When systems failed, they generally did so suddenly rather than through gradual deterioration of performance. In this part, the utility and effectiveness of those tests are considered. This suggests that after verification of proper operation, routine extensive testing would be of minimal value. A recommended set of tests is presented including additional and improved tests, which we believe meet the intent and spirit of the Mammography Quality Standards Act regulations to ensure that full-field digital mammography systems are functioning correctly, and consistently producing mammograms of excellent image quality.

Quality Control for Technologists in Digital Mammography

As of June 2006, there are 6 FDA-approved full-field digital mammography systems available for clinical use in the U.S. Each of these systems has a quality control program supplied by the manufacturer that sites must follow to satisfy FDA regulations. These tests are written to be similar to the quality control tests for screen-film mammography, but have differences due to the nature and physics of the digital detector, the soft-copy review workstation, and overall system design. These differences will be discussed in this paper as well as the requirements for performing quality control in digital mammography. Additionally, this document includes a section on tips and tricks that are not found in manufacturer’s quality control manuals.

Validation of MTF measurement for digital mammography quality control

The modulation transfer function (MTF) describes the spatial resolution properties of imaging systems. In this work, the accuracy of our implementation of the edge method for calculating the presampled MTF was examined. Synthetic edge images with known MTF were used as gold standards for determining the robustness of the edge method. These images simulated realistic data from clinical digital mammography systems, and contained intrinsic system factors that could affect the MTF accuracy, such as noise, scatter, and flat-field nonuniformities. Our algorithm is not influenced by detector dose variations for MTF accuracy up to 1/2 the sampling frequency. We investigated several methods for noise reduction, including truncating the supersampled line spread function (LSF), windowing the LSF, applying a local exponential fit to the LSF, and applying a monotonic constraint to the supersampled edge spread function. Only the monotonic constraint did not introduce a systematic error; the other methods could result in MTF underestimation. Overall, our edge method consistently computed MTFs which were in good agreement with the true MTF. The edge method was then applied to images from a commercial storage-phosphor based digital mammography system. The calculated MTF was affected by the size (sides of 2.5, 5, or 10 cm) and the composition (lead or tungsten) of the edge device. However, the effects on the MTF were observed only with regard to the low frequency drop (LFD). Scatter nonuniformity was dependent on edge size, and could lead to slight underestimation of LFD. Nevertheless, this negative effect could be minimized by using an edge of 5 cm or larger. An edge composed of lead is susceptible to L-fluorescence, which causes overestimation of the LFD. The results of this work are intended to underline the need for clear guidelines if the MTF is to be given a more crucial role in acceptance tests and routine assessment of digital mammography systems: the MTF algorithm and edge object test tool need to be publicly validated.

The current status of full-field digital mammography quality control

U.S. Food and Drug Administration (FDA) regulations require that medical physicists and technologists adhere to the procedures, testing frequencies, and performance criteria outlined in the quality control (QC) manuals provided by the manufacturers of full-field digital mammography (FFDM) systems. As a result of this requirement, QC for digital equipment has become both complicated and inconsistent. The objective of this study was to compare the current QC protocols for the tests to be performed by medical physicists for three commercially available FFDM systems (the Senographe 2000D, the SenoScan, and the Selenia). Although not yet approved by the FDA, the 5000 MA was also included because of its unique design and extensive use in a major ongoing clinical research trial involving the other three FFDM systems. It was found that currently, a high degree of discord exists between the FFDM QC protocols of the early commercial systems, with wide variation in opinion with respect to the minimum performance criteria and testing intervals and with respect to which tests are necessary and what quantities should be measured. Additionally, very few digital detector-specific tests are currently in place. Although technological differences between the early FFDM systems prohibit a strictly uniform set of QC procedures and performance guidelines, a much greater degree of consensus among manufacturers is desirable as FFDM continues to gain clinical presence during the next few years.

Implementing digital quality control in a breast center

Breast imaging centers in the United States are currently transitioning from traditional screen-film mammography to full-field digital mammography. Quality control for full-field digital mammography is more difficult, time consuming, and expensive than for traditional screen-film mammography. Full-field digital mammography quality control is more precise than screen-film mammography quality control at identifying noncompliant components. As per U.S. Food and Drug Administration requirements, each manufacturer of full-field digital mammography equipment designs and establishes its own quality control process.