Small Lung Nodule Measurement...5/17/2018 4 Detection Slice Thickness & Recon Kernel Slice Thickness...
Transcript of Small Lung Nodule Measurement...5/17/2018 4 Detection Slice Thickness & Recon Kernel Slice Thickness...
5/17/2018
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QIBA CT Small Lung Nodule Profile
Profile Conformance Process and Feasibility Test Example
Ricardo S. Avila
May 16, 2018
Quantitative Imaging Biomarkers Alliance (QIBA) Annual Meeting
Small Lung Nodule Measurement
= 668 mm3 T2 = 661 mm3
DV = No
Change
Time 1 Time 2
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Lung Nodule Volumetric Error
Scan Specification1. Detector Rows2. mAs3. kVp4. Slice Thickness5. Recon Kernel6. Iterative Recon7. Dual Source8. Auto mA & kVp9. …
Detection &Measurement
Sem
i-A
uto
mat
ed
Soft
war
e
CT
Acq
uis
itio
n
AcquiredImagesAcquiredImagesAcquiredImages
Issues1. Large & Growing # Parameters2. Constantly Changing3. Operator Preferences/Errors4. Difficult to Fully Reproduce
Patient Characteristics1. Lesion Size2. Lesion Margin3. Patient Size4. Attachment5. Local Conditions6. High HU Objects7. Metal Implants8. Motion9. …
Challenges1. Internal Structures2. Large Complex Borders3. Changing Presentation4. Very Large Patients
Object Scanner SoftwareVolumetric
Performance
1 2 3
JMI 2016
Free CT Image Quality Report (2015-Present)
Accumetra.com
Tech Can Do
The Scan In
< 5 Minutes
Optimize
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Spatial Warping
0 mm100 mm200 mm
CT Lung Screening Protocol Guidelines
Detectors
>=
Thickness
<=
Spacing
<=Kernel
16 1.25 1.25Highest
Res.
64 1.25 1.25Highest
Res.
16 1.0 0.7No
Pref.
162.5,
1.0 pref.
No
Pref.
No
Pref.
162.5,
1.0 pref.
2.5,
1.0 pref.
Range,
Not Easy
CT Acquisition
2015 European Society of Radiology
2015 American College of Radiology
(10 Pillars Publication)
2016 RSNA/QIBA Small Nodule Profile (19% to 42%)
2016 AAPM Lung Cancer Screening Protocols
2016 I-ELCAP Guidelines
Our Specification: >= 16 detector rows, <=1.25 thickness , <=1.25 spacing
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Detection Slice Thickness & Recon Kernel
Slice
ThicknessSites
Soft
Recon
Medium
Recon
Edge En.
Recon
<= 0.625 4 (15%) 0 3 1
0.8, 1.0, 1.25 12 (46%) 6 2 4
>= 1.5 10 (38%) 6 3 1
3 used 2mm ST &
1mm spacing
QIBA CT Small Lung Nodule Profile
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Small Lung Nodule Profile Claims
Overview: The profile addresses accuracy/precision of CT volumetry for solid
lung nodules 6-10 mm in diameter.
Profile Claim 1: For a measured nodule volume of Y, and a CV as specified in
the table below, the true nodule volume is:
Y ± (1.96 Y CV), with 95% confidence.
Profile Claim 2: A measured change in nodule volume of X% indicates that a
true change in nodule volume has occurred if:
X > (2.77 x CV1 x 100), with 95% confidence.
To quantify the amount of change, if Y1 and Y2 are the volume measurements at
the two time points, and CV1 and CV2 are the corresponding values from the
table below, then the 95% confidence interval for the true change is:
(Y2-Y1) ± 1.96 ([Y1 CV1]2 + [Y2 CV2]2).
CV Table
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Profile Requirements & Steps
• CT Scanner
– >= 16 Slice
– Model has been verified to
be QIBA Compliant
– ACR CT accreditation
• CT Protocol
– <= 1.25mm slice thickness
– Slice spacing <= slice
thickness
– Pitch < 2.0
• Fundamental Image
Properties
– Edge Enhancement <= 5%
– 3D PSF Ellipsoid Volume
<= 1.5mm3
– PSF Z/X Aspect <= 2.0
– Linearity Bias < 35 HU
– Image Noise <= 50 HU SD
– Spatial Warping <= .3 mm
• Nodule Analysis
Software
– Software has been verified
to be QIBA Compliant
No Bias,
CV limits
Resolution: 3D PSF Sigma Ellipsoid Volume
3D Gaussian PSF along with
3D sampling rate represents the
resolution of the system
2D
Gaussian
1D
Gaussian
3D
Gaussian
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We are saying…
If you follow the profile
specifications and requirements
Your volumetric change error
should fall within this 95% CI
Conformance Without Tools Would Be
Extremely Challenging For Many
Clinical Sites
0.625 ST
CT Image Quality Compliance
Maintain Throughout The Full Scanner Field of View
1. Artifacts
2. 3D Distance
3. Linearity
4. Image Noise
5. 3D Resolution
6. 3D Edge Enhancement
7. 3D Spatial Warping
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Scanner Is GenerallyOperating OK
Rad
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Issu
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Scanner/Protocol/ScanIs OK
Scanner/ProtocolAchieves Specifications
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A QIBA Small Lung Nodule Phantom
Teflon (~950 HU)
Cylinder
Acrylic (~120 HU)
Cylinder
Delrin (~340 HU)
Concentric Cyl
Air (-1000 HU)
Room For
Other
Compartments
At Iso-Center
200 mm from
Iso-Center
Cost:
$200
CTLX1 Phantom
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RSNA/QIBA Conformance Certification Pilot Project
Using Cloud-Based Computing Services
http://quality.rsna.org
Optimize
Guidance
Webpages &
FAQs
Check Each
Time Scanner
or Protocol
Changes and
Once Per Year
~ 100 CTLX1 Phantoms Are
Being Globally Distributed
• Confirms Fundamental CT Image Properties
– 3D Resolution:
• 3D PSF Ellipsoid Volume <= 1.5 mm3
– 3D Resolution Aspect:
• PSF Z/X <= 2.0
– Linearity Bias:
• Air and Acrylic Bias < 35 HU
– Image Noise:
• Acrylic Noise <= 50 HU SD
– Recon Kernel Edge Enhancement:
• Air to Delrin Enhancement <= 5%
– 3D Spatial Warping:
• Delrin Cylinder RMSE <= 0.3 mm
• Lung Nodule Volume Change Performance
– Verifies That Image Quality Meets or Exceeds
The QIBA CT Lung Nodule Profile Volume
Change Measurement Claims
PCF
Funding
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International CT Image Quality Monitoring
60 CTLX1 Phantoms Sent Out As Of 5/17/2018
Data Received & Analyzed From:
• ~30 Sites
• ~50 Unique CT Scanners
• > 200 CT Scans
• 4 Manufacturers
• Siemens, GE, Philips, Toshiba
• > 20 Different Scanner Models
Automated CT Scanner/Protocol Image Quality Report
Image Quality
Measurements
Analysis
Status
Protocol
Settings
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Report With Issues
Quantitative Conformance Data
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QIBA SLN Conformance Certification
Pilot Project
Requested vs Observed Slice Thickness
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Research: Dose and Resolution Study
Software Conformance Certification Testing
Perform Volume Measurements on:
1. Clinical Zero Change Datasets
• Evaluate measurement precision in real nodules
2. CTLX1 Phantoms With Embedded Ellipsoids
• Evaluate measurement precision, bias, and linearity in
synthetic objects
• As a bonus we can look at volume measurement prediction
performance, but not needed for software conformance
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Clinical Zero Change Testing
• All datasets will be acquired with a conformant CT acquisition protocol
and a medium level of CT image quality characteristics (verified)
• 6.00 to 7.99 mm nodule– 15 solid nodule cases each with 5 repeat CT scans
– wCV in profile is 0.23
– Max allowable wCV by an actor is 0.19 to be 95% confident
• 8.00 to 9.99 mm– 15 solid nodule cases each with 5 repeat CT scans
– wCV in profile is 0.16
– Max allowable wCV by an actor is 0.14 to be 95% confident
• 10.00 to 11.99 mm (since our table goes up to 12 to support growth)– 15 solid nodule cases each with 5 repeat CT scans
– wCV in profile is 0.12
– Max allowable wCV by an actor is 0.10 to be 95% confident
Data
Collected,
About To Be
Measured
Example Zero Change Dataset (6.2mm)
1 2 3
4 5
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Bias Assessments
• Claim 1 in the Profile assumes no bias.
• Must verify that actor’s bias is <5%.
• With 3 replicate scans of the CTLX1S phantom,
we can estimate actor’s bias to within +1%.
• So even if an actor’s bias is 4%, we can verify,
with 95% confidence that their bias is <5%.
• Repeat this for each of the 5 ellipsoid sizes.
Measurement Linearity and Slope
• From the CTLX1S phantom data, actors will perform a
regression analysis.
𝑌 = 𝛽𝑜 + 𝛽1𝑋 + 𝛽2𝑋2
• They need to provide an estimate of the quadratic term, 𝛽2 .
This should be <0.5.
• They need to provide a 95% CI for the linear term, 𝛽1 .
• We have assumed that 𝛽1 equals one so the 95% CI for the
slope needs to be completely contained in the interval 0.95 to
1.05.
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CTLX1-S
CTLX1 w/Ellipsoid Modules Scan & Measure
16 Ellipsoids 7.0 x 6.0 x 6.0 mm
16 Ellipsoids 6.0 x 3.6 x 3.6 mm
• Will CT scan the enhanced CTLX1 phantom 3 times using a medium
level of CT IQ characteristics (resolution, sampling, noise, etc.)
• Ellipsoids will be volume measured and mean/stdev calculated
• Require 1 site for conformance of software name/version
• We should try to get this data from at least two sites using same
phantom
16 Ellipsoids 10.0 x 6.0 x 6.0 mm
16 Ellipsoids 9.0 x 5.4 x 5.4 mm
16 Ellipsoids 8.0 x 4.8 x 4.8 mm
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CTLX1-S
Scanner Conformance Certification
Design of Experiments
• Helps Prevent Issues In The Clinical Environment By Allowing
Vendors To Define Parameter Operating Envelopes
• Focuses On High Performance Risk Parameters Such As mA
and kVp
Slice Thickness
Tu
be
Cu
rre
nt
Slice Thickness
Tu
be
Cu
rre
nt
SingleOperating
Point
WiderOperatingEnvelope
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Scanner Conformance Certification
Design of Experiments
• CT Scanner DOE
Provide Recommended
CT Scanning Protocol
Test the Protocol Over
an Operating Envelope
Future Tools
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Next Steps
• Finish Up SLN Conformance Pilot Project Resources
– Pilot Project Conformance Certification Website
– Post Datasets & Spreadsheets
• Perform Final Technical Confirmation Testing
– Clinical Conformance : Launch Guidance Pages
– Software Conformance : CTLX1S Scan and Measure
– CT Scanner Conformance : DOE Testing
Thank You