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QUALITY ASSURANCE & ACR ACCREDITATION West Physics Consulting is a proud supporter of MTMI’s Diagnostic Imaging Programs. Thank you West Physics! WHY ACR ? Images property of Yu Liu PhD WHY ACR ? Images property of Yu Liu PhD IMAGE QUALITY • • • • • Diagnostic Accuracy Signal to Noise (SNR) Contrast to Noise (CNR) Spatial Resolution Absence of Artifacts SNR- Is the relationship between MR signal and background noise. • Signal- Is the processing of induced voltage (Faraday’s Law of Induction) in a receiver coil after excitation. • • • The voltage is dependent on the strength of the magnet (NMV) used for induction. Signal is not the only factor contributing to the quality of the image. Noise is refer as unavoidable background signals By evaluating SNR we can assess the overall quality of the MR Signal Images property of e-MRI.org CONTRAST to NOISE RATIO (CNR) CNR: Also refers as Contrast Resolution ,is the ability to distinguish between differences in intensity in an image. CNR is influence by the SNR and spatial resolution in the MR image. CONTRAST to NOISE (CNR) CNR : Is the ability to distinguished between two adjacent structures or tissue Matrix (In-Plane) 192 x 256 224 x 320 CONTRAST to NOISE (CNR) CNR : Is the ability to distinguished between two adjacent structures or tissue Slice Thickness 5mm 1.5mm IMAGE QUALITY SNR/Spatial Resolution & Absence of Artifacts Scanner Performance ACR (Q/A) The MRI Accreditation Program evaluates the qualifications of personnel, the quality control program, MR safety policies and image quality specific to MRI. • • Quaterly Preventive Maintenance Weekly Technologist Phantom – Phantom Scans • Annual Testing by a Physicist – Phantom Scans – Coil Testing • Re- Accreditation by the ACR – Every three years ACR MRI ACCREDITATION Getting Started: • Get the Team Together – Radiologist (Medical Director MRI) – Chief Technologist (Clinical Imaging) – MR Physicist (Scanner Testing) • Buy ACR Phantom (JM Specialty Part – San Diego,CA) • Weekly Technologist Phantom (3-6 months ACR recommends) • Scanner Testing by a Physicist (Annual/Initial) • Apply online for ACR Accreditation (Select Module desire) – – – – Survey Agreement (Site) Six Modules (Brain,Spine,Msk,Body,Vascular,Cardiac ) 45 days to complete your submission and return it to ACR Could go back 6 months to provide clinical images. ACR PHANTOM Level Phantom Correctly Images property of Chen Lin PhD ACR PHANTOM ACR WEEKLY PROTOCOL : • Sag Scout • Ax T1 SE • • • • • • • TR 500 TE 20 FOV 25 Matrix 256 x 256 Slices 11 Slice Thickness 5mm Gap 5mm ACR PHANTOM CENTER FREQUENCY: • • • • Set to the resonance frequency of water protons Depends on Main Magnetic Field (1.5T vs. 3T) Affects fat saturations Severity off resonance artifacts ACR recommended criteria < +/- 1.5ppm different between weekly test. Possible Causes of Failures : • Phantom not Isocenter • Magnet Drift ACR PHANTOM TRANSMITTER GAIN: • • • • RF power required to achived certain flip angles Depends on RF Coils,Phantom,and Pulse Sequence Should remain constant Severity off resonance artifacts . Possible Causes of Failures : • Defective RF Transmitter Coil • RF Amplifier ACR PHANTOM ACR Sequence Positioning: ACR PHANTOM Geometric Accuracy: Related to image distortion 190 mm 148 mm Images property of Chen Lin PhD ACR PHANTOM Geometric Accuracy: Related to image distortion . Possible Causes of Failures • Phantom not level appropriate • Gradient Non Linearity • Eddy Currents ACR recommended criteria +/- 2mm in all directions ACR PHANTOM SPATIAL RESOLUTION: • Ability to detect differences between small structures • Depends on Pixel/Voxel size (FOV/Matrix) ACR PHANTOM Spatial Resolution: ACR recommended criteria <= 1.0mm . Possible Causes of Failures • Poor SNR • Bad Receiver Coil • Eddy Currents • Gradient Calibration 1.1 mm 1.0mm 0.9mm ACR PHANTOM Low Contrast Detectability (LCD): • Ability to detect objects with subtle differences in signal intensity Possible Causes of Failures • Poor SNR • Inaccurate slice positioning • Artifacts ACR PHANTOM Additional Testing: • Image uniformity • Slice Thickness • Ghosting/Artifacts ACR PHANTOM Artifacts: Zipper/RF Leak ACR ACCREDITATION Clinical Modules: Images property of Chen Lin PhD ACR ACCREDITATION Clinical Images Evaluations : • • • • • • • Pulse Sequence Image Contrast Anatomical Coverage Imaging Planes Spatial Resolution (Pixel & Voxel size) Artifacts ID Exam ACR ACCREDITATION Tips & Suggestions • • • All clinical images must be done in patients (No Volunteer). Include all identification required (Patient & Parameters). DICOM images with a viewer. • • • • • Except Cardiac and Phantom DICOM only Record True Matrix,not Reconstructed Matrix (Pixel size). Check for Artifacts prior to submission . Present best cases,no motion on images. Submit all required sequences,include localizers. ACR ACCREDITATION Be Aware : • • • • • • • Spine Axial GRE T2*/TSE at 3T,CSF must be bright(no flow artifact) MRCP include entire Biliary Tree Anatomy (Best when using 3D rather 2D MRCP) Liver MRI ,use flouro technique to acquired true arterial phase. CE-MRA,no venous contamination (Neck Carotid) Cardiac MRI ,Viability exam myocardium fully saturated (Scar visible) Considered using Dixon for In/Out Phase at 3T Forms fill them out correctly(take your time) ACR ACCREDITATION Breast Accreditation: Facilities performing breast MRI must have the capacity to perform mammographic correlation, directed breast ultrasound, and MRI-guided intervention, or create a referral arrangement with a cooperating facility that could provide these services. • Radiologists – Requirement of Breast MRI read in the last 36 months • • Facilities must use the Breast Imaging Reporting and Data System (BIRADS®)7 final assessment codes and terminology for reporting and tracking outcomes. Technologists – Requirement of 50 MRI Breast examination prior 24 months. ACR ACCREDITATION Breast Accreditation: • • • Facility must submit 1 case with a known, enhancing, biopsyproven carcinoma clearly visible in the breast parenchyma. No Masectomy cases Pulse Sequences • • T2W/Bright Fluid T1W (Pre,Arterial,Delay) - Bilateral • Slice Thickness < 3mm(No Gap),In Plane Resolution/Pixel Size < 1.0 ACR ACCREDITATION Summary: • ACR Q/A Phantom needs to be done weekly • • Yearly Evaluation (PhD) • • Compares year to year scanner performance ACR Accreditation • • Check scanner image quality Done every three years ,includes clinical images and phantoms. Why ACR ? Is all about image quality!!!!!!