gammex rmi ct phantom, 438 - ctug.org.uk...gammex rmi ct phantom, 438 (acr ct accreditation phantom,...
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CT Users Oct 2007
S. Edyvean, Jim WestonImaging Performance Assessment of CT ScannersSt. Georges Hospital, London
www.impactscan.org
Some images courtesy of Cynthia McCulloughMayo Clinic, Rochester, USA
Gammex RMI CT Phantom, 438
(ACR CT Accreditation phantom, 464)
ImPACT ImPACT
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CT Users Oct 2007
Gammex RMI CT Phantom, 438
• David Aikman– Gammex RMI Ltd.,Nottingham
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CT Users Oct 2007
4 3 2 1
20 c
m
4 cm
Head Foot
Alignment
CT #
Image width
Low contrast
resolution
Uniformity & noise
Distance accuracy
SSP
High contrast
resolution
Gammex RMI CT Phantom
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Gammex RMI CT Phantom
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CT Users Oct 2007
Documentation
Manual, also ACR (American College of Radiology) website
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CT Users Oct 2007
https://www.gammex.com
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CT Users Oct 2007
ACR CT Accreditation Program
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ACR documentation
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Setting up
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Air ≈-1000 HU
Water ≈0 HU
Polyethylene ≈ -97 HU
“Bone” ≈+910 HU
Acrylic ≈+120 HU
Module 1: alignment, image thickness, CT number
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CT Users Oct 2007
High-resolution chest technique
Must see all four BBs(in Modules 1 & 4)
Longer wire must have same number of lines above and below (±1)
Wires are 0.5 mm apart in z-direction
WW = 1000WL = 0
Module 1: alignment, image thickness, CT number
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11 / 2 = 5.5 mm
10 / 2 = 5 mm
Adult abdomen technique
Scan width measured at several scan widths
WW = 400WL = 0
Module 1: alignment, image thickness, CT number
Wires are 0.5 mm apart in z-direction
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CT Users Oct 2007
Adult abdomen technique
CT number measured in 5 materials
CT number of water measured at several scan widths and kVps WW = 400
WL = 0
Air ≈-1000 HU
Water ≈0 HU
Polyethylene ≈ -97 HU
“Bone” ≈+910 HU
Acrylic ≈+120 HU
Module 1: alignment, image thickness, CT number
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CT Users Oct 2007
ACR documentation: module 1
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CT Users Oct 2007
• Low contrast = 6 HU ± 0.5 HU– (cf Catphan 10, 5, 3 HU single object of each size)
Module 2: Low contrast detectability
6 mm
5 mm4 mm
3 mm
2 mm
25 mm
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CT Users Oct 2007
• Catphan is closest to a ‘standard’ phantom
Phantoms for low contrast detectability (LCD)
• Catphan 50010 HU contrast
5 HU contrast
3 HU contrast
2-15 mm diameter
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CT Users Oct 2007
• Low contrast = 6 HU ± 0.5 HU– (cf Catphan 10, 5, 3 HU single object of each size)
Module 2: Low contrast detectability
6 mm
5 mm4 mm
3 mm
2 mm
25 mm
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CT Users Oct 2007
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CT Users Oct 2007
Adult abdomen and head techniques
Measure uniformity and noise
Assess for artifacts
Measure distance accuracy(optional)
WW = 100WL = 0
100 mm
Module 3: uniformity, noise, distance, mtf & ssp
0.3 mm tungsten carbide beads
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CT Users Oct 2007
Adult abdomen, adult head and high-resolution chest techniques
Record the firsthighest frequency bar pattern for which the bars and spaces merge
WW = 100WL ≅≅≅≅ 1100
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4
6
7
8
10
Bar patterns:lp/cm
Aluminium in solid water
Module 4: high contrast spatial resolution
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CT Users Oct 2007
Gammex RMI CT Phantom
• Nicely designed phantom• Excellent phantom stand• Good additional documentation from ACR• Slightly limited for axial MSCT? (40 mm modules)• Bar pattern doesn’t go to maximum resolution• LCD of 6HU different from manufacturers spec. (use 3HU
from Catphan)
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CT Users Oct 2007
https://www.gammex.com
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CT Users Oct 2007
Gammex RMI CT Phantom
• David Aikman– Gammex RMI Ltd.,Nottingham– 01159850808, daa@gammex.com
• Cost– List price £5589 (not including stand),– Discount for early sales ~10%
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CT Users Oct 2007
Incidental Findings
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CT Users Oct 2007
Incidental Findings
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CT Users Oct 2007
Incidental Findings
CT Users Oct 2007
S. Edyvean, Jim WestonImaging Performance Assessment of CT ScannersSt. Georges Hospital, London
www.impactscan.org
Some images courtesy of Cynthia McCulloughMayo Clinic, Rochester, USA
Gammex RMI CT Phantom, 438
(ACR CT Accreditation phantom, 464)
ImPACT ImPACT
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