Ultrasound Quality Assurance PDF

Importance of Ultrasound Quality Assurance Ensures the system is correctly set up and operates according to specified standards. Helps maintain consistent performance of the ultrasound system over time. Identifies and addresses potential issues at their earliest stage before they affect diagnosti...

Importance of Ultrasound Quality Assurance Ensures the system is correctly set up and operates according to specified standards. Helps maintain consistent performance of the ultrasound system over time. Identifies and addresses potential issues at their earliest stage before they affect diagnostic accuracy When should Quality Assurance be performed? Routine preventive maintenance involves daily or weekly checks by sonographers to ensure the ultrasound equipment functions optimally. For example, inspecting the transducer for damage. Routine performance testing is carried out weekly or monthly by sonographers to maintain the operational standards of the ultrasound system. For example, evaluation of the system's image resolution and depth capabilities Acceptance testing is conducted when new ultrasound equipment is installed, verifying that it meets specified manufacturer and regulatory standards before clinical use Three levels of Quality Control testing Level 1: Frequent QC testing (operator’s QC). Daily image quality checks and basic functionality tests. Level 2: Annual QC testing (medical physicist’s QC). Provide a thorough evaluation of the ultrasound system’s compliance with industry standards. Level 3: Acceptance testing Daily and Weekly checklist General machine cleanliness (keyboard and knobs clean – transducer - monitor clean - air filter clean) Mechanical and Electrical (wheels fastened securely and rotate easily - wheels locks work well – cords attached securely) Workstation (contrast and brightness between scanner and the ambient lighting in the room to reduce eye strain) Transducer inspection (cables – cracks – matching layer delamination) Annually or semi annually check list Performance test (Dead zone test – vertical & horizontal measurement – sensitivity test – uniformity test - grayscale test – Axial & lateral resolution) Doppler QC tests (signal sensitivity – angle accuracy – color display –flow accuracy) Dead zone (ring down) To assess the "dead zone" of the ultrasound system, which is the area directly beneath the transducer where ultrasound waves are unable to image due to close proximity. Test Setup: - A group of nine fiber reflectors. - Reflectors are positioned within the phantom at varying depths, ranging from 2 mm to 10 mm from the top of the phantom Distance Accuracy Test for Ultrasound Systems Position a phantom with a vertical column and a horizontal row of reflectors spaced at known distances. Use the digital caliper tool on the ultrasound software to measure the distance between the reflectors directly on the screen. The standard distance between reflectors is set at 10 cm. - Vertical measurement should be within 1.5% of the actual distance or 2 mm, whichever is greater. - Horizontal measurement should be within 3% of the actual distance or 3 mm, whichever is greater System sensitivity/penetration To ensure consistent image quality and system performance, periodically check the following key settings: Set the ultrasound machine to its maximum transmit power for deep tissue penetration. Adjust the receiver gain and Time Gain Compensation (TGC) to levels that clearly visualize echotexture in deeper regions, ensuring visibility across all tissue types. Position the transmit focus at the deepest depth possible to evaluate the system’s display capabilities at varying depths Compare these results over time to detect any changes or degradation in performance, which may indicate the need for maintenance or recalibration. Evaluating Axial and Lateral Resolution in Ultrasound Systems Spatial resolution in ultrasound imaging determines the system's ability to distinguish between objects that are close together. It can be assessed effectively through the following methods: 1. Counting Pins: Determine the minimum spacing at which individual pins (reflectors) can be distinguished without overlap in both the lateral and axial directions. 2. Measuring Pin Size: Measure the dimensions of the pins in both lateral and axial directions using the system’s on- screen calipers. Compare these measurements against the known actual sizes to evaluate accuracy. Contrast Resolution test It is commonly referred to as Gray Scale or Gray Scale Resolution. It evaluates the system’s and probe's ability to differentiate between objects of similar and varying densities. Scanner settings: -Set frequency according to the probe model's typical specifications -Adjust depth based on the phantom model used. -Position Focus at or just above the gray scale targets -Adjust overall gain and TGC to ensure a mid-range gray level across the entire image The Air test in ultrasound QA The air test in ultrasound QA is primarily used to check the transducer's sensitivity and to identify any faulty crystal elements. The test involves operating the transducer in air with its face clean and dry, typically at the lowest frequency and highest gain settings (both overall gain and time gain compensation). The image produced should display a series of horizontal bands due to reverberations, which are caused by the impedance mismatch between the transducer and the air The air test in ultrasound QA To perform the air test: Set the ultrasound machine to its routine clinical preset, adjust the frequency to its lowest value, and maximize the overall gain and time gain compensation. Activate the transducer in the air, ensuring that the face is clean and dry. Observe the image for horizontal reverberation bands. These bands can be used to assess uniformity across the image and transducer sensitivity. Faulty crystal elements might be indicated by a vertical line where echos are reduced, suggesting a drop in the sensitivity at that point. *This test allows for a subjective evaluation of certain aspects of transducer performance without requiring phantoms or other specialized equipment. The Paper Clip Test The primary purpose of the paper clip test is to detect faults in the ultrasound transducer’s crystal elements. Over time, some of these elements may fail due to damage impacting the overall image quality. It is a straightforward and low-cost method that can be quickly conducted without specialized equipment, making it an ideal choice for routine checks. The Paper Clip Test To perform the Paper Clip Test on an ultrasound transducer efficiently, follow these steps: Apply a small amount of ultrasound gel to the transducer's surface to aid ultrasound wave transmission. Slide an open paper clip gently across the transducer while the ultrasound system is on and displaying an image. Watch for a consistent line of bright echoes. Any dim or broken segments indicate possible malfunctioning crystal elements.