QIBA CT Volumetrics - QIBA CT Volumetrics - Cross-Platform Study Cross-Platform Study

(Group 1C)(Group 1C)

March 18, 2009March 18, 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 under which imagery is to be selected under which imagery is to be collected.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 (includes single scanners with varying settings).(includes single scanners with varying settings).

1.1. Measure image noise and determine its impact Measure image noise and determine its impact on the measurement of volume.on the 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 constant. kVp constant.

(b)(b) mAs constant. mAs constant.

(c)(c) collimation fixed (+)collimation fixed (+)

(d)(d) field of view ([rib-to-rib]skin-to-skin = closest possible field of view ([rib-to-rib]skin-to-skin = closest possible view)-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. Scanners follow Site selection – poll the team. Scanners follow sites.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 – What to do? QIBA – What to do? ExperimentsExperiments

Investigate parameter space to determine Investigate parameter space to determine which parameters make a difference in which parameters make a difference in the task (CT tumor volume and volume the task (CT tumor volume and volume measurement over time)measurement over time)

QIBA CT 1-A and 1-B already contribute to QIBA CT 1-A and 1-B already contribute to this investigation?this investigation?NOTE: Different biomarkers (e.g. lesion density or NOTE: Different biomarkers (e.g. lesion density or

mass) may be affected by different parameters.mass) may be affected by different parameters.

QIBA CT 1-C Profiles - 1QIBA CT 1-C Profiles - 1

As with NLST and ACRIN 6678, we could As with NLST and ACRIN 6678, we could specify kVp, slice thickness, mAs, rotation specify kVp, slice thickness, mAs, rotation time, pitch, reconstruction kernel (affects time, pitch, reconstruction kernel (affects MTF)MTF)(NOTE: These operating parameters serve as a (NOTE: These operating parameters serve as a

proxy for physical performance with respect to proxy for physical performance with respect to spatial resolution, noise and dose.)spatial resolution, noise and dose.)

QIBA CT 1-C Profiles - 2QIBA CT 1-C Profiles - 2ALTERNATIVE (not necessarily exclusive OR):ALTERNATIVE (not necessarily exclusive OR):

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 Recon kernel OR recon kernel performance

– e.g. Choose kernel such that you can see 6 or 7 (but no e.g. Choose kernel such that you can see 6 or 7 (but no more than 7) lp/cm on ACR phantom….ormore than 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/effective mAs level OR mA level performancemA/effective mAs level OR mA level performance

– e.g. Choose 40 effective mAs ORe.g. Choose 40 effective mAs OR– 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 20 cm water phantomand 30 HU in 20 cm water phantom

QIBA – What to do?QIBA – What to do?

Near Future:Near Future:– SpecifySpecify

MTFMTF NPSNPS Z-axis resolutionZ-axis resolution DoseDose Some SNR metric appropriate for measurement taskSome SNR metric appropriate for measurement task

Further:Further:– SpecifySpecify

3D MTF3D MTF 3D NPS3D NPS Organ doseOrgan dose Some SNR/Dose metric appropriate for measurement task/riskSome SNR/Dose metric appropriate for measurement task/risk

Example Protocol Chart for NLST Example Protocol Chart for NLST (from Cagnon et al)(from Cagnon 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

Goal 3Goal 3

Compare the Compare the accuracy and precisionaccuracy and precision of of measurements for these phantom measurements for these phantom datasets. Which measurements: image datasets. Which measurements: image mask? Volume? RECIST?mask? Volume? RECIST?

(a)(a) RECISTRECIST vs. vs. volumevolume(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..

Existing ResourcesExisting Resources

RadPharmRadPharm– What mark-up is recommended? What What mark-up is recommended? What

format? format? RECISTRECIST Segmentation mask. Formats?Segmentation mask. Formats?

Next StepsNext Steps

Continue to Refine Questions and Continue to Refine Questions and Experimental Design (similar to 1A and 1B) Experimental Design (similar to 1A and 1B)

Recruit participating clinics. Share and Recruit participating clinics. Share and discuss plan with associated medical discuss plan with associated medical physicists.physicists.