Scott F. Stekel

FOUR-YEAR EXPERIENCE WITH A CLINICAL ULTRASOUND QUALITY CONTROL PROGRAM

Ultrasound (US) quality control (QC) program data over a 4-year period from more than 45 scanners and more than 265 transducers were reviewed to optimize the program in terms of efficiency and effectiveness. Our program included evaluations of mechanical integrity, image uniformity, distance measurement accuracy and maximum depth of penetration (DOP). We computed failure rates and fraction of failures detected by each test. A total of 187 equipment problems were identified. Average annual scanner component and transducer failure rates were 10.5% and 13.9%, respectively. The mechanical integrity and uniformity evaluations detected 25.1% and 66.3% of all failures, respectively. Those evaluations plus defects detected by sonographers accounted for 98.4% of all detected failures. DOP and distance measurement accuracy were not effective at detecting equipment failures. For routine US QC, we recommend quarterly mechanical integrity and uniformity assessments of all transducers. A scanner with five transducers could be tested in an estimated 30 min or less.

Evaluation of a low-cost liquid ultrasound test object for detection of transducer artefacts

Routine quality control of ultrasound scanners and transducers is important for maintaining image quality. Our experience suggests that artefact and uniformity evaluation is the most effective single phantom test for detecting equipment problems. Current methods for assessing ultrasound images for artefacts have important limitations. To overcome these limitations, we have developed a novel, low-cost, liquid phantom with a flexible surface for assessing artefacts. A range of materials were evaluated and the optimal liquid phantom was found to be a water/cornstarch solution contained within a flexible latex balloon. When compared to a rigid tissue-mimicking phantom no deficiencies in overall image appearance or artefact detection for any transducer model was observed for the liquid phantom. With minimal training, reproducible clips were obtained by clinical sonographers with low inter- and intra-operator dependence, for a range of transducers models. The flexible scanning surface of the liquid phantom allows complete rapid coupling of all transducers. Due to its ease of use and low cost this liquid phantom appears superior to rigid phantoms for assessment of non-uniformity artefacts, and should allow clinical practices to perform routine artefact assessments of all ultrasound scanners and transducers.

Evaluations of UltraiQ software for objective ultrasound image quality assessment using images from a commercial scanner

Abstract We evaluated a commercially available software package that uses B‐mode images to semi‐automatically measure quantitative metrics of ultrasound image quality, such as contrast response, depth of penetration (DOP), and spatial resolution (lateral, axial, and elevational). Since measurement of elevational resolution is not a part of the software package, we achieved it by acquiring phantom images with transducers tilted at 45 degrees relative to the phantom. Each measurement was assessed in terms of measurement stability, sensitivity, repeatability, and semi‐automated measurement success rate. All assessments were performed on a GE Logiq E9 ultrasound system with linear (9L or 11L), curved (C1‐5), and sector (S1‐5) transducers, using a CIRS model 040GSE phantom. In stability tests, the measurements of contrast, DOP, and spatial resolution remained within a ±10% variation threshold in 90%, 100%, and 69% of cases, respectively. In sensitivity tests, contrast, DOP, and spatial resolution measurements followed the expected behavior in 100%, 100%, and 72% of cases, respectively. In repeatability testing, intra‐ and inter‐individual coefficients of variations were equal to or less than 3.2%, 1.3%, and 4.4% for contrast, DOP, and spatial resolution (lateral and axial), respectively. The coefficients of variation corresponding to the elevational resolution test were all within 9.5%. Overall, in our assessment, the evaluated package performed well for objective and quantitative assessment of the above‐mentioned image qualities under well‐controlled acquisition conditions. We are finding it to be useful for various clinical ultrasound applications including performance comparison between scanners from different vendors.

Clinical acceptance testing and scanner comparison of ultrasound shear wave elastography

Abstract Because of the rapidly growing use of ultrasound shear wave elastography (SWE) in clinical practices, there is a significant need for development of clinical physics performance assessment methods for this technology. This study aims to report two clinical medical physicists’ tasks: (a) acceptance testing (AT) of SWE function on ten commercial ultrasound systems for clinical liver application and (b) comparison of SWE measurements of targets across vendors for clinical musculoskeletal application. For AT, ten GE LOGIQ E9 XDclear 2.0 scanners with ten C1‐6‐D and ten 9L‐D transducers were studied using two commercial homogenous phantoms. Five measurements were acquired at two depths for each scanner/transducer pair by two operators. Additional tests were performed to access effects of different coupling media, phantom locations and operators. System deviations were less than 5% of group mean or three times standard deviation; therefore, all systems passed AT. A test protocol was provided based on results that no statistically significant difference was observed between using ultrasound gel and salt water for coupling, among different phantom locations, and that interoperator and intraoperator coefficient of variation was less than 3%. For SWE target measurements, two systems were compared — a Supersonic Aixplorer scanner with a SL10‐2 and a SL15‐4 transducer, and an abovementioned GE scanner with 9L‐D transducer. Two stepped cylinders with diameters of 4.05–10.40 mm were measured both longitudinally and transaxially. Target shear wave speed quantification was performed using an in‐house MATLAB program. Using the target shear wave speed deduced from phantom specs as a reference, SL15‐4 performed the best at the measured depth. However, it was challenging to reliably measure a 4.05 mm target for either system. The reported test methods and results could provide important information when dealing with SWE‐related tasks in the clinical environment.

Comprehensive Clinical Implementation of DICOM Structured Reporting Across a Radiology Ultrasound Practice: Lessons Learned

Clinical utilization of ultrasound imaging has always relied very heavily on measurements (distance, velocity, area, volume, etc). These were initially performed and labeled manually by the sonographer. Later, the use of predefined measurements and calculations on the scanner, configured in the measurement or calculation “package,” led to greater consistency and clarity. The introduction of examination protocols integrated on the scanner sped up the entire examination process in general, and predefined measurements could be integrated with specific protocol steps, leading to improved sonographer consistency and efficiency. Electronically transferring predefined measurements from the ultrasound scanner to the PACS (for quality checking, integration into clinical diagrams, etc) via DICOM structured reporting (SR) transactions, and then transferring measurements from the PACS to the transcription and reporting system, extends the efficiency gains to the radiologist and improves quality by reducing transcription errors. (Because of our specific practice data flow, in this article we assume SR transfer of measurements from ultrasound scanners to a PACS, but all comments apply equally well if measurements are transferred to other downstream receiving systems.)

SU-E-I-77: Review of Display Quality Control: Findings and Management

Purpose: Time spent and equipment purchased for diagnostic display testing costs money. It is important to understand the values of tests in order to balance cost and value. We describe our experience with both hands-on and remote quality control testing for diagnostic displays and provide a summary and implications of our findings. We find this information helpful in guiding our own QC program management and it may be of similar benefit to others. Methods: Our data is taken from 4 years of testing a fleet of about 650 color LCD, medical-grade diagnostic quality displays. The last 2.5 years of data include both hands-on and remote testing that was facilitated by front panel luminance sensors and remote fleet management tools. Quality control data is included for the following tests:-Luminance Uniformity-Artifact-Max/Min Luminance-DICOM GSDF conformance. Results: Within the first two years, the majority of displays failed. Fundamental equipment issues were uncovered by quality control testing and were subsequently addressed by the vendor. After the first two years, failures were found in approximately 1% of remote luminance tests done quarterly. Approximately 1–2% of remote tests resulted in communication errors during quarterly testing, most frequently because of USB cables coming unplugged. Primary failure modes are presented. Conclusion: Remote luminance testing (with recalibration only as needed) allowed us to assess the stability in the performance of our diagnostic display fleet. Initial, semiannual testing of new displays uncovered systematic problems with luminance stabilization and showed great value. Ongoing testing has resulted in finding more communication errors rather than luminance related failures, though communication errors have been greatly reduced through re-engineering. Remote testing does provide the ability to test and recalibrate without a site visit and can save time in the reading room where only qualitative testing is currently performed.

TU-A-9A-02: Analysis of Variations in Clinical Doppler Ultrasound Peak Velocity Measurements

PURPOSE Doppler ultrasound (US) peak velocity (Vmax) measurements show considerable variations due to intrinsic spectral broadening with different scanning techniques, machines and manufacturers. We developed a semi-automated Vmax estimation method and used this method to investigate the performance of a US system for clinical Doppler Vmax measurement. METHODS Semi-automated Vmax is defined as the velocity at which the computed mean spectral profile falls to within 1 background standard deviation of the background mean. GE LOGIQ E9 system with 9L and ML6-15 probes were studied with steady flow (5.3 - 12.5 ml/s) in a Gammex OPTIMIZER 1425A phantom. All Doppler spectra were acquired by 1 operator at the distal end of 5 mm angular tube using a modified clinical carotid artery protocol. Repeatability and variation of Vmax to scanning parameters and probes were analyzed and reported as percentage, i.e. (max-min)/mean. RESULTS Vmax estimation had good repeatability (3.1% over 6 days for 9L, and 3.6% for ML6-15). For 9L probe, varying gain, compression, scale, SV depth and length, and frequency had minimal impact on Vmax (all variations less than 4.0%). Beam steering had slightly higher influence (largest variations across flow rates were 4.9% for 9L and 6.9% for ML6-15). For both probes, Doppler angle had the greatest effect on Vmax. Percentage increase of Vmax was largely independent of actual flow rates. For Doppler angle varied from 30 to 60°, Vmax increased 24% for 9L, and 20% for ML6-15. Vmax measured by ML6-15 were lower than that by 9L at each Doppler angle with differences less than 5%. CONCLUSION The proposed Vmax estimation method is shown to be a useful tool to evaluate clinical Doppler US system performance. For the tested system and probes, Doppler angle had largest impact in measured Vmax.

MO‐D‐220‐09: Detection Methods of Ultrasound Transducer Artifacts: Dynamic Clips, Static Median, and Subtracted Median Images

Purpose: The detection of ultrasound artifacts due to transducer failure is important for maintaining image quality. The aim of this study is to evaluate 3 methods for detecting ultrasound artifacts, involving direct evaluation of dynamic B‐mode clips and 2 types of single frame statistical images. Methods: A range of artifacts of varying severity were artificially created for 28 transducers of varying models. The appearance of these artifacts was substantially similar to actual artifacts detected during ultrasoundscanner acceptance testing and routine quality assurance. A second set of 28 matching transducers contained no artifacts. A 10 second clip was recorded of a dynamic speckle pattern from a custom liquid phantom (“dynamic clip”). A single‐frame image was obtained by computing the median values at each pixel location over all frames of the clip (“median image”). This single frame median image was then subtracted from a baseline median image previously obtained with no induced artifact (“subtracted median”). All images were evaluated by 6 observers and the mean sensitivity and specificity for the three artifact detection methods estimated. Results: In all cases the dynamic clip had the lowest sensitivity (61%) of the three detection methods. The subtracted median images had the highest sensitivity of 97% and while maintaining a high specificity of 92%. Conclusions: For routine quality control, the use of subtracted median images allows detection of artifacts with very good sensitivity and specificity. For acceptance testing, where there are no previous baseline images available for subtraction, the use of median images is useful, although comparison with median images from different transducers of the same model and/or multiple observers should be made to decrease the incidence of false‐positive findings. If statistical images are not available, direct inspection of the dynamic B‐mode clips is useful for acceptance testing and quality control, but with lower sensitivity.

Features to Consider When Selecting New Ultrasound Imaging Systems

INTRODUCTION The selection of ultrasound imaging equipment is not a straightforward task. Many factors come into play, including image quality, workflow efficiency, ergonomics and system usability, and system serviceability. In this article, we focus on the selection of general imaging ultrasound scanners for use in radiology and describe our process for equipment selection. The involvement of radiologists, sonographers, medical physicists and technical services personnel, the inhouse equipment service group, and administrators in the equipment selection process is critical to achieving the best possible outcome. The first step in the process is assessment of the clinical practice in terms of commonly performed types of examinations, prevalence of portable imaging, mix of diagnostic work and procedures, resident or sonography student teaching, and the IT environment. This will help focus the practice’s needs for specific transducer models, imaging features, connectivity, and other capabilities. In the remainder of this article, we expand on the last two components of the selection process: evaluation of system features and in-house system evaluation.

SU‐GG‐I‐131: Assessment of Transducer Artifacts Using a Novel, Low Cost Ultrasound Phantom

Purpose:Ultrasound artifacts are often identified by scanning a uniform region of a rigid tissue‐mimicking phantom while moving the transducer across the scan surface, and identifying any deviations from the expected smooth echotexture. Due to the rigid nature of commercial phantoms it is difficult to simultaneously couple the entire face of curved array transducers. We have proposed a novel low cost liquid phantom with a flexible scan surface. The purpose of this work is to demonstrate the proof of concept of this unique phantom. Method and Materials: The phantom consisted of a water/cornstarch solution enclosed in a thin latex balloon (thickness 0.24 mm). When shaken, the cornstarch provides a dynamic speckle pattern. Initial experiments were conducted to establish the basic effectiveness of this innovative phantom to demonstrate artifacts, to assess reproducibility of image acquisition, and inter‐operator variability. The phantom was imaged using an Acuson Sequoia US scanner and 4 transducer models (9L4, 6C2, 4V1 and EC‐10C5), and dynamic clips of the changing speckle field were recorded. Two transducers with independently‐confirmed artifacts were also tested. Results: The flexible scanning surface allowed excellent acoustic coupling of the entire face of all transducer models with the phantom, including tightly curved arrays. Little manual transducer motion was required with the liquid phantom as a result of the dynamic speckle field. Artifacts due to inactive elements were detected, including a single crystal dropout. Using a defined scan protocol, reproducible clips exhibiting low inter‐ and intra‐ operator dependency were obtained by 5 operators with minimal training, for transducers with and without artifacts. Conclusion: Due to its ease of operation, low cost, and sensitivity, this phantom may be superior to current methods of detecting ultrasound artifacts, and has the potential to promote better acceptance and compliance of ultrasound quality control.