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Physics Testing for ACRIN 6678 Protocol version 3.0 QIBA Group 1C

Get an overview of testing protocols and steps to determine scanner performance for spatial resolution and noise based on ACRIN 6678 protocols. Compare results for accuracy.

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Physics Testing for ACRIN 6678 Protocol version 3.0 QIBA Group 1C

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  1. Physics Testing for ACRIN 6678 Protocolversion 3.0QIBA Group 1C

  2. Goal Determine Scanner Performance for Spatial Resolution and Noise under protocol specified by ACRIN 6678. These will be compared with results from Performance Based Protocol Testing

  3. ACRIN 6678 Protocol(hyperlink)

  4. General Outline of Testing Protocol • Using protocol specified by ACRIN 6678 • Scan ACR phantom spatial resolution section • Record visible bar pattern size • Scan ACR phantom uniformity section • Place ROI in center of phantom and record std. deviation

  5. Testing Protocol (Details) • Record required data on accompanying spreadsheet, • On accompanying spreadsheet, record: • Scanner Manufacturer (e.g GE) • Model (e.g. VCT) • Site id (e.g Scanner 95) • Software version • Testing date (12-26-09) • All scanners use 120 kVp, record 120 in kVp field. • Record Scan Field of View or Patient Size (or equivalent) setting used. • Record Slice thickness between 0.75 to 1.25 mm (depending on scanner’s available reconstructed slice thickness) • Record nominal beam collimation (NxT such as 16 x 0.5mm, or 128x0.6mm, 320 x 0.5 mm) rotation time and pitch such that scan can cover a 35 cm thorax in 15 seconds or less • Values near pitch 1 are preferred. • Record reconstruction kernel. • Record mAs or effective mAs setting

  6. Specific Instructions for Testing Protocol 2. Using parameters specified in ACRIN 6678, Scan phantom once through section 4 of ACR CT accreditation phantom. • Reconstruct images, display with Level =1100, Window=100 • Record the name of recon filter • Record the size of the line pair object (e.g. 6 lp/cm etc.) observed for that filter • Provideimage (DICOM AND jpeg) Zoomed in B30 6 lp/cm 7 lp/cm ACR Spatial Resolution Section (Module 4)

  7. Specific Instructions for Testing Protocol 3 Using parameters specified in ACRIN 6678, Scan phantom once through section 3 of ACR CT accreditation phantom. • Reconstruct images, display with Level =100, Window=100 • From Reconstructed image, measure standard deviation by placing an ROI of approximately 400 mm2 at the center of the image • Record standard deviation on spreadsheet • Provideimage (DICOM AND jpeg)

  8. Example of Testing Protocol • Step 3 – Example on Siemens Sensation 64. • 100 eff. mAs • Tech. Params: • 120 kVp • 1mm • Pitch 1 • 0.5 sec • B30 100 eff. mAs; std dev = 17

  9. RESULTS Of Testing Protocol • For Siemens Sensation 64, using ACRIN 6678 parameters: • 120 kVp • Reconstructed Slice thickness 1.0 mm • Nominal beam collimation 64x0.6 (actually 32x0.6 with flying focal spot) • Rotation time 0.5 seconds • Pitch 1.0 • Recon kernel B30 • Effective mAs setting 100 • CTDIvol = 7.7 mGy • PERFORMANCE • Spatial Resolution = 6 lp/cm • Standard Deviation = 17 HU

  10. Next Scanner?

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