Performance Assessment / Quality Assurance in Cross Sectional Modalities

Performance Assessment / Quality Assurance in Cross Sectional Modalities

Module Learning Objectives

• Physical Principles: Explain the underlying physical principles of cross-sectional imaging modalities and how parameter selection impacts outcomes.
• Quality Assessment: Assess equipment operation through Quality Assurance (QA), Quality Control (QC), and radiation dosimetry tests.
• Hazard Evaluation: Examine potential hazards/errors (systemic/human) in imaging environments, identify causes, and propose solutions.

Session Learning Objectives

By the end of the session, participants will:

• Understand QA guidance documents and testing procedures for Ultrasound, CT, and MRI.
• Recognize the relevance of QA procedures in clinical practice.

Importance of Quality Assurance

• Quality Assurance (QA): Essential for ensuring system performance is suitable for clinical use and monitoring changes over time.
• Standardized Testing: The need for standardized methods and guidelines from professional bodies.

UK Guidance on QA for Imaging Modalities

• Ultrasound: Referencing IPEM Report 102 & BMUS QA guidelines.
• CT Imaging: Utilizing IPEM Reports 91 & 32 for testing protocols.
• MRI: Follow IPEM Report 112 for protocols and tests.
• Focus on user tests over physics tests.

General Principles of QA

• Clinical Use: Assess whether imaging systems are functioning properly for clinical applications.
• Performance Changes: Detect performance changes over time through systematic inspections.

QA Levels in Ultrasound

Three Levels of QA

1. Level 1: Infection control and damage checks to the scanner.
   • Daily cleaning protocols and damage inspection.
2. Level 2: Basic scanner and transducer testing.
   • Daily evaluations without test tools.
3. Level 3: In-depth performance evaluations using test tools.
   • Monthly assessments designed for fault detection.

Routine QA Tests for Ultrasound

Level 1 Tests Include:

• Clean transducer and cables after each use (multi-daily).
• Store transducers securely when inactive (multi-daily).
• Daily checks on monitor controls and cable inspections.

Level 2 Tests Include:

• Daily monitor settings checks, including image contrast and grey scale.
• Monthly air reverberation pattern checks and dropout tests if faults are suspected.

Ultrasound Image Quality Evaluations

• Identify image artifacts such as reverberation or dropout.
• Image Dropout: Characterize defects from the acoustic array and transducer damage.
• Cable Damage: Assess the impact of damaged cables on image quality.

Cross Sectional Imaging with CT

QA Testing Guidelines

• IPEM Report 91: Routine QA test lists and acceptable result tolerances.
• IPEM Report 32: Detailed testing methods and necessity.

Levels of Testing in CT

1. Level A: Simple, frequent tests performed by radiographers.
2. Level B: Analytical tests performed less frequently by medical physicists.

CT Image Quality Monitoring

• Noise Measurement: Monitor image noise post-calibration using QA phantoms. Remedial and suspension levels are clearly defined.
• CT Number Values: Perform regular measurements of CT numbers for consistency; significant changes may indicate issues with machinery.
• Scan Plane Alignment: Important for clinical procedures such as biopsies.

MRI Quality Assurance

QA Guidelines

• IPEM Report 112: Outlines QA tests and tolerances for MRI.

Key Factors Affecting MRI Performance

• Signal to Noise Ratio (SNR): Primary indicator of image quality; sensitive to system issues.
• Uniformity Testing: Assess how consistently the MRI system generates signals.

Summary of Quality Assurance in Imaging Modalities

• Consistent QA is critical across all cross-sectional imaging modalities.
• Testing frequency should match the perceived operational risk to patient safety and image quality.
• Maintain accurate records of QA tests and address any adverse findings promptly to ensure patient safety and operational integrity.