QIBA CT Volumetrics - QIBA CT Volumetrics - Cross-Platform Study Cross-Platform Study
(Group 1C)(Group 1C)
March 29, 2009March 29, 2009
Interclinic Comparison of CT VolumetryInterclinic Comparison of CT Volumetry
Quantitative Imaging Biomarker AllianceQuantitative Imaging Biomarker Alliance
ChargeCharge1.1. To agree on the To agree on the scanner settings and other scanner settings and other
protocol elementsprotocol elements under which imagery is to under which imagery is to be collected.be collected.
2.2. To agree on requirements of To agree on requirements of phantomsphantoms to be to be imaged/measured.imaged/measured.
3.3. To agree on the To agree on the platforms and centersplatforms and centers to be to be selected for imagery collected.selected for imagery collected.
4.4. To identify the To identify the measurements and the measurements and the algorithmsalgorithms for use in image processing. for use in image processing.
5.5. To To specify the analysisspecify the analysis of the measurements. of the measurements.
GoalsGoals
1.1. Measure the volume of nodules on CT imagery Measure the volume of nodules on CT imagery collected from several CT scanners and sites collected from several CT scanners and sites (may include multiple settings on single (may include multiple settings on single scanners).scanners).
1.1. Measure image noise and other image quality Measure image noise and other image quality factors and determine their impact on the factors and determine their impact on the measurement of volume.measurement of volume.
2.2. Compare the Compare the accuracy and precisionaccuracy and precision of volume of volume measurements for these phantom datasets.measurements for these phantom datasets.
3.3. Determine the Determine the minimum detectable level of minimum detectable level of changechange that can be achieved when measuring that can be achieved when measuring nodules in nodules in phantom datasetsphantom datasets..
Goal 1Goal 1
1.1. Measure Measure nodule volumenodule volume on CT imagery on CT imagery collected from several collected from several CT scanners/sitesCT scanners/sites (including single scanners with varying (including single scanners with varying settings). Determine the systems to be used settings). Determine the systems to be used and the system settings to be varied.and the system settings to be varied.
(a)(a) kVp may be specified.kVp may be specified.
(b)(b) mAs may be specified.mAs may be specified.
(c)(c) collimation fixed (+)collimation fixed (+)
(d)(d) field of view (skin-to-skin = closest possible view)-field of view (skin-to-skin = closest possible view)-
(e)(e) reconstruction filters – follow-up Wendy & radiologistsreconstruction filters – follow-up Wendy & radiologists- Find “equivalent” filters.Find “equivalent” filters.
Site selection – poll the team for potential Site selection – poll the team for potential image collection sites.image collection sites.
Goal 2Goal 2
2.2. Measure “image noise” and determine its Measure “image noise” and determine its impact on the measurement of volume. impact on the measurement of volume. Facilitates inter-comparison of scanner Facilitates inter-comparison of scanner results.results.
(a)(a) Characterizing / specifying image Characterizing / specifying image qualityquality
(a)(a) Expert visual assessment of image Expert visual assessment of image quality. (Deni)quality. (Deni)
QIBA CT 1-C ProtocolQIBA CT 1-C Protocol- first branch- first branch
Using protocol for NLST (ACRIN 6678?) Using protocol for NLST (ACRIN 6678?) specify kVp, slice thickness, mAs, rotation specify kVp, slice thickness, mAs, rotation time, pitch, reconstruction kernel (affects time, pitch, reconstruction kernel (affects MTF). MTF). Use (water and ACR) phantoms Use (water and ACR) phantoms to to characterize the resolution and noise characterize the resolution and noise levels under this branch of the protocol.levels under this branch of the protocol.
Sample Protocol Chart for NLSTSample Protocol Chart for NLSTCagnon Cagnon et al.et al.
Parameter Siemens Vol Zoom/
Sensation 44-slice/0.5 sec
4 x 2.5
Siemens Vol Zoom/ Sensation 4
4-slice/0.5 sec4 x 1
SiemensSensation 16
16 x .75
SiemensSensation 64
64x.0.6(beam collimation 32x0.6)
kV 120 120 120 120
Gantry Rotation Time 0.5 sec 0.5 sec 0.5 sec 0.50 sec
mA (Regular patient-Large patient values) 75-150 80-160 75-150 50-100
mAs (Reg-Lg) 1 37.5-75 40-80 37.5-75 25-50
Scanner effective mAs2 (Reg-Lg) 25-50 20-40 25-50 25-50
Detector Collimation (mm) - T 2.5 mm 1 mm 0.75 mm 0.6 mm
Number of active channels - N 4 4 16 32
Detector Configuration - N x T 4 x 2.5 mm 4 x 1 mm 16 x .75 mm 32 x 0.6 mm
Collimation (on operator console) N/A N/A N/A 64x0.6mm
Table incrementation (mm/rotation) - I 15 mm 8 mm 18 mm 19.2 mm
Pitch ([mm/rotation] /beam collimation) - I/NT
1.5 2 1.5 1.0
Table Speed (mm/second) 30 mm/sec 16 mm/sec 36 mm/sec 38.4 mm/sec
Scan Time (40 cm thorax) 13 sec 25 sec 11 sec 11 sec
Nominal Reconstructed Slice Width 3 mm 2 mm 2 mm 2 mm
Reconstruction Interval 3 2.0 mm 1.8 mm 1.8 mm 1.8 mm
Reconstruction Algorithm3 B30 B30 B30 B30
# Images/Data set (40 cm thorax) 200 223 223 223
CTDI vol (Dose in mGy) 4 2.0 – 4.1 mGy 2.8 - 5.5 mGy 1.9 - 3.8 mGy 1.9 - 3.8 mGy
QIBA CT 1-C ProfilesQIBA CT 1-C Profiles- second branch- second branch
Specify PERFORMANCE metrics such as simple Specify PERFORMANCE metrics such as simple spatial resolution and noise metrics.spatial resolution and noise metrics.
kVp (affects contrast difference between materials)kVp (affects contrast difference between materials) Slice thickness, recon interval (affects z-axis resolution & Slice thickness, recon interval (affects z-axis resolution &
noise)noise) Rotation time and pitch (coverage, breath hold, etc.)Rotation time and pitch (coverage, breath hold, etc.) Recon kernel OR recon kernel performance - EXAMPLE: Recon kernel OR recon kernel performance - EXAMPLE:
– Choose kernel such that you can see 6 or 7 (but no more Choose kernel such that you can see 6 or 7 (but no more than 7) lp/cm on ACR phantom….orthan 7) lp/cm on ACR phantom….or
– 10% MTF should be between 6 and 7 lp/cm10% MTF should be between 6 and 7 lp/cm mA level performancemA level performance
– Choose effective mAs level so that std dev is between 20 Choose effective mAs level so that std dev is between 20 and 30 HU in a 20 cm water phantomand 30 HU in a 20 cm water phantom
Goal 3Goal 3
Compare the Compare the accuracy and precisionaccuracy and precision of of radiologists’ measurements of radiologists’ measurements of RECIST and Volume for these RECIST and Volume for these phantom datasets. (image mask?)phantom datasets. (image mask?)
a)a) RECISTRECIST vs. vs. volume.volume.b)b) Investigate Investigate variance & biasvariance & bias..c)c) Inter-system variation.Inter-system variation.d)d) Intra-system variation.Intra-system variation.
Goal 4Goal 4
4. DEFER: 4. DEFER: Determine the Determine the minimum minimum detectable level of changedetectable level of change that can be that can be achieved when measuring nodules in achieved when measuring nodules in phantom datasetsphantom datasets..
Required resourcesRequired resources
Use of Use of FDA phantom, water and ACR FDA phantom, water and ACR phantoms.phantoms.
Recruit clinical image Recruit clinical image collection collection sitessites through QIBA-CT group. through QIBA-CT group.
Use Use QIBA CT 1-A mark-upQIBA CT 1-A mark-up at Rad- at Rad-Pharm, generatingPharm, generating
RECISTRECIST Segmented volume.Segmented volume.
Future stepsFuture steps
Refine Questions and Experimental Design.Refine Questions and Experimental Design. Recruit participating clinics. Share and Recruit participating clinics. Share and
discuss plans with associated medical discuss plans with associated medical physicists.physicists.
Confirm availability and discuss reading with Confirm availability and discuss reading with Rad-Pharm.Rad-Pharm.
Confirm availability and schedule FDA Confirm availability and schedule FDA phantom.phantom.
