GE Logiq P5 User Manual
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Quality Assurance LOGIQ 5 Basic User Manual 18-25 Direction 2300002-100 Rev. 2 Typical Tests to Perform Quality assurance measurements provide results relating to system performance. Typically these are: • Axial Measurement Accuracy • Lateral Measurement Accuracy • Axial and Lateral Resolution • Penetration • Functional & Contrast Resolution • Gray Scale Photography. With these tests, a performance baseline can be set at installation with the phantom in your department. Future test results can be compared to the baseline in order to maintain a record of system performance trends. Frequency of tests Quality assurance tests are used to determine whether a scanner is providing the same level of performance from day to day. The frequency of testing varies with the amount of system usage and modes to be tested. It is recommended that the user perform quality assurance tests at least every three months or every 400 patient studies. Tests should also be performed when a question about system performance exists. A mobile system may require more frequent tests. Image quality should also be tested immediately after the following events: • Service calls • System upgrades/modifications • Dropped probe, power surge, etc.
User Maintenance 18-26 LOGIQ 5 Basic User Manual Direction 2300002-100 Rev. 2 Phantoms Quality Assurance Evaluations should be done with phantoms and test objects that are applicable to the parameters being evaluated or to the users clinical practice. Typical phantoms are composed of material that acoustically mimic human tissue. Pins, anechoic and echogenic targets are physically positioned to provide information for a variety of tests. Doppler phantoms are currently expensive and complicated to deal with on the user level. If a problem with any Doppler parameters or measurement is suspected, contact a local service representative for evaluation. The RMI 403GS phantom is still available. Due to the superior penetration and resolution capabilities of GE ultrasound systems, the RMI 405GSX is recommended. It is the most current one available to our field service personnel and will provide the targets and extended life necessary for consistent system testing.
Quality Assurance LOGIQ 5 Basic User Manual 18-27 Direction 2300002-100 Rev. 2 Phantoms (continued) Figure 18-9. Phantoms 1. Penetration 2. Axial Distance Measurement 3. Functional Resolution 4. Lateral Resolution 5. Lateral Distance Measurement 6. Axial Resolution 7. Contrast Resolution and Gray Scale Photography 8. Gray Scale Plane Targets
User Maintenance 18-28 LOGIQ 5 Basic User Manual Direction 2300002-100 Rev. 2 Baselines An absolute necessity for a quality assurance program is establishing baselines for each test or check. Baselines are established after the system has been verified to be working properly at installation or after a repair. If a probe or major assembly is replaced, new baselines should be generated. Baselines can be made by adjusting system parameters to prescribed levels or to the best possible image. The key factor to remember is reproducibility. The same conditions must be reproduced for each periodic check. All system parameters not displayed on the monitor should be recorded for the permanent record. Periodic Checks Periodic checks should be performed in accordance with your facility’s quality assurance requirements. For the data to be valid, periodic checks should mimic the baseline setup parameters. The resulting image, when scanning the phantom exactly as before, should be recorded and compared to the baseline. When a matching image is obtained, it can be assumed that the system performance has not degraded from the baseline. If a significant difference between the baseline and periodic check is noted, double check the system setup and repeat the test. If the difference between the baseline and periodic check persists, contact a local Service Representative. Failing to reproduce the control settings as in the baselines will introduce errors in the data and potentially invalidate the results.
Quality Assurance LOGIQ 5 Basic User Manual 18-29 Direction 2300002-100 Rev. 2 Results Lack of standardization among test instruments, the wide range of acceptance criteria, and incomplete knowledge regarding the significance of certain performance parameters prohibit the establishment of absolute performance criteria for these tests. Quality Assurance Evaluation results should be compared to previously-recorded results. Performance trends can then be detected. Unacceptable performance or diminishing trends should be identified for maintenance or repair before a malfunction or inappropriate diagnosis occurs. The user should determine the best method for recording and archiving the baseline and periodic checks. In most cases the choice is hard copy. It is important to maintain good consistent records for inspections that may arise, as well as to detect system performance trends.
User Maintenance 18-30 LOGIQ 5 Basic User Manual Direction 2300002-100 Rev. 2 System Setup The user should tailor the tests to their particular needs. It is certainly not necessary to make all checks with all probes. A representative example, with the probes used most often by the customer, should be adequate in judging system performance trends. Use a gray scale phantom as the scan object for the tests. Commercial phantoms are supplied with its own operator manual. Be familiar with proper phantom operating procedures prior to use for quality assurance evaluations. 1. Adjust image monitor. Brightness and contrast should be set to the normal viewing of a good gray scale image. 2. Check all recording devices for proper duplication of image monitor. Ensure that what is seen is what is recorded. Check the B/W or Color page printer, VCR, MIC, or Laser camera. 3. Annotate non-displayed image processing controls. 4. Set TGC slide pots to center (detent) position. 5. Place focal zone marker(s) in area of interest for an optimum image. Test Procedures The following are recommended Quality Assurance tests. A brief description of the test, the benefit it provides and steps to accomplish the test are supplied. The importance of recording scan parameters and consistent record keeping cannot be stressed enough. Reproducibility to monitor system trends is the key to quality assurance evaluations. Using the systems dual image display format is often very convenient and saves recording media.
Quality Assurance LOGIQ 5 Basic User Manual 18-31 Direction 2300002-100 Rev. 2 Axial distance measurements DescriptionAxial measurements are the distance measurements obtained along the sound beam. See Figure 18-9 for more information. BenefitThe accurate measurement of the size, depth and volume of a structure is a critical factor in determining a proper diagnosis. Most imaging systems use depth markers and/or electronic calipers for this purpose. MethodAxial distance should be measured in the near, mid and far fields as well as in zoom. If necessary, different depths or fields of view can be tested. ProcedureTo measure axial distance: 1. Scan a test phantom with precisely-spaced vertical pin targets. Adjust all scan controls, as necessary, for the best image of the pin targets to typical depths for the probe being used. 2. Press Freeze to stop image acquisition and perform a standard distance measurement between the pins at different points in the image. Record all images for archiving. 3. Scan the vertical pins in zoom or at different depth/scale factors. 4. Press Freeze to stop image acquisition; repeat the distance measurements between pins and record the images for archiving. 5. Document the measurements for reference and future comparison. Contact a Service Engineer if vertical measurements differ by more than 1.50% of the actual distance.
User Maintenance 18-32 LOGIQ 5 Basic User Manual Direction 2300002-100 Rev. 2 Lateral distance measurements DescriptionLateral measurements are distance measurements obtained perpendicular to the axis of the sound beam. See Figure 18-9 for more information. BenefitThe purpose is the same as vertical measurements. Precisely- spaced horizontal pin targets are scanned and results compared to the known distance in the phantom. MethodLateral distance should be measured in the near, mid and far fields as well as in zoom. If necessary, different depths of fields of view can be tested. ProcedureTo measure lateral distance: 1. Scan a test phantom with precisely-spaced horizontal pin targets. Adjust all scan controls, as necessary, for the best image of the pin targets from side to side. 2. Press Freeze to stop image acquisition and perform a standard distance measurement between the pins at different points in the image. Record all images for archiving. 3. Scan the horizontal pins in zoom or at different depth/scale factors. 4. Press Freeze to stop image acquisition; repeat the distance measurements between pins and record the images for archiving. 5. Document the measurements for reference and future comparison. Contact a Service Engineer if horizontal measurements differ by more than 3mm or 3% of that depth, whichever is greater.
Quality Assurance LOGIQ 5 Basic User Manual 18-33 Direction 2300002-100 Rev. 2 Axial resolution DescpritionAxial resolution is the minimum reflector separation between two closely-spaced objects to produce discrete reflections along the axis of the sound beam. It can also be monitored by checking the vertical size of known pin targets. See Figure 18-9 for more information. Axial resolution is affected by the transmitting section of the system and the probe. BenefitIn clinical imaging, poor axial resolution displays small structures lying close together as a single dot. This may lead to improper interpretation of the ultrasound image. ProcedureTo measure Axial resolution: 1. Scan a test phantom with precisely-spaced vertical pin targets. 2. Adjust all scan controls, as necessary, for the best image of the pin targets to typical depths for the probe being used. 3. Press Freeze to stop image acquisition. 4. Perform a standard distance measurement of the pin vertical thickness at different points in the image. Record all images for archiving. 5. Scan the vertical pins in zoom or at different depth/scale factors. 6. Press Freeze to stop image acquisition; repeat the vertical thickness measurements of the pins and record the images for archiving. 7. Document the measurements for reference and future comparison. Axial resolution should remain stable over time. Contact a Service Engineer if any changes are observed.
User Maintenance 18-34 LOGIQ 5 Basic User Manual Direction 2300002-100 Rev. 2 Lateral resolution DescriptionLateral resolution is the minimum reflector separation between two closely spaced objects to produce discrete reflections perpendicular to the axis of the sound beam. It can also be monitored by checking the horizontal size of known pin targets. See Figure 18-9 for more information. Lateral resolution is dependent upon the beam width produced by the probe. The narrower the beam, the better the lateral resolution. The beam width is affected by the frequency, degree of focusing, and distance of the object from the face of the probe. BenefitClinically, poor lateral resolution will display small structures lying close together as a single dot. This may lead to improper interpretation of the ultrasound image. ProcedureTo measure lateral resolution: 1. Scan a test phantom with precisely-spaced horizontal pin targets. 2. Adjust all scan controls, as necessary, for the best image of the pin targets from side to side. 3. Press Freeze to stop image acquisition and perform a standard distance measurement of the horizontal thickness of a pin at different points in the image. Record all images for archiving. 4. Scan the horizontal pins in zoom or at different depth/scale factors. 5. Press Freeze to stop image acquisition; repeat the horizontal thickness measurements of the pins and record the images for archiving. 6. Document the measurements for reference and future comparison. Pin width should remain relatively constant over time (1mm). Dramatic changes in pin width may indicate beamforming problems. Contact a Service Engineer if beam width changes consistently over 2 to 3 periodic tests.