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© 2014 Ken L Schreibman, PhD/MD www.schreibman.info 1 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA.

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Presentation on theme: "© 2014 Ken L Schreibman, PhD/MD www.schreibman.info 1 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA."— Presentation transcript:

1 © 2014 Ken L Schreibman, PhD/MD 1 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Peering into the Black Hole… University of Wisconsin - Madison Ken Schreibman, PhD/MD, FACR Professor – UW MSK Section Professor – UW MSK Section Sylvester Youlo, MD Sylvester Youlo, MD PGY4 – UW Orthopedic Surgery PGY4 – UW Orthopedic Surgery James Brittin, MD James Brittin, MD PGY4 – UW Radiology Department PGY4 – UW Radiology Department Frank Ranallo, PhD, DABR Frank Ranallo, PhD, DABR Physicist- UW Radiology Department Physicist- UW Radiology Department Matthew Squire, MD, MS Matthew Squire, MD, MS Associate Professor, UW Orthopedic Surgery Associate Professor, UW Orthopedic Surgery

2 © 2014 Ken L Schreibman, PhD/MD 2 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Disclosures Bullet Pts. …or visit my website …or visit my website I will try to cover all 10 Bullet Points in less than 10 minutes Neither I nor my family have any financial disclosures We are members of the Disney Vacation Club UW Radiology Department has a partnership with GE No fancy PowerPoint animations in this talk For fancy PowerPoint see my ePoster…

3 © 2014 Ken L Schreibman, PhD/MD 3 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Peering into the Black Hole… This is the problem Poor CT visualization inside cupped femoral component Poor CT visualization inside cupped femoral component Cant see bone-metal interface Cant see bone-metal interface 140kVpAxial B,W 57yoM LateralRadiograph CT: Sagittal Can well see around tibial tray Can well see around tibial tray ?

4 © 2014 Ken L Schreibman, PhD/MD 4 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Pig Knee + Human Co-Cr Femoral Component To simulate the bone-metal interface within the cupped femoral component

5 © 2014 Ken L Schreibman, PhD/MD 5 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Implanted by Sylvester Youlo, Ortho Surg Resident Pounding component in place Drilling Target Lesions

6 © 2014 Ken L Schreibman, PhD/MD 6 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 We Created Target Erosions Target Target 7x7mm 5mm deep 6x6mm 3mm deep 14x9mm 7mm deep 3D CT without metal

7 © 2014 Ken L Schreibman, PhD/MD 7 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Stabilized on yardstick w/cable ties

8 © 2014 Ken L Schreibman, PhD/MD 8 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Placed in sealable Tupperware Filled with water to simulate attenuation of soft tissues surrounding the knee Sealed to eliminate air-fluid level CT Scout

9 © 2014 Ken L Schreibman, PhD/MD 9 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 GE 750 HD + GSI Scanned the phantom repeatedly varying one parameter at a time hok.comWIMR CSC UW Medical Campus

10 © 2014 Ken L Schreibman, PhD/MD 10 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 First tested the effect of changing kV using conventional Single Energy CT 4) 600 mA, Detail 0.625mm Source image 600 mA, Detail 0.625mm Source image 2) Single Energy Results: Comparing kV For all images: W=3000 L=1000 TargetTarget 140 kV 120 kV

11 © 2014 Ken L Schreibman, PhD/MD 11 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Single Energy Results: Comparing kV For all images: W=3000 L=1000 2) 140 kV Target 4) 120 kV Target 6) 100 kV Target Conclusion: With SECT, use 140 kV

12 © 2014 Ken L Schreibman, PhD/MD 12 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Then, holding kV=140, varied mA Single Energy Results: Comparing mA For all images: W=3000 L=1000 2) 140 kV 600 mA 8) 140 kV 300 mA 10) 140 kV 150 mA TargetTargetTarget Conclusion: Dont need to use max mA

13 © 2014 Ken L Schreibman, PhD/MD 13 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Disclaimer: On this slide I am going to try to explain physics that my physicist says I dont understand… On this slide I am going to try to explain physics that my physicist says I dont understand… Heres where things get confusing because there are two types of voltage. Heres where things get confusing because there are two types of voltage. The electricity applied into the CT tube is in volts, or kV The electricity applied into the CT tube is in volts, or kV The energy of emitted photons in electron-volts, or keV The energy of emitted photons in electron-volts, or keV put kV into CT tube get keV out… put kV into CT tube get keV out… …but what comes out is less than whats put in! …but what comes out is less than whats put in! Single Energy is actually a Spectrum of Energies Number of X-ray photons emitted from CT tube Energy of the X-ray photons (x10 3 electron-volts) ( keV ) 140kV 140kV 80kV 80kV Applying 140kV to the CT tube yields an X-ray spectrum… …nearly all with energies much less than 140keV. (We can ignore the pointy spikes not as relevant to this discussion) (We can ignore the pointy spikes not as relevant to this discussion) Applying 80kV to the CT tube yields lower energy spectrum. With physics + math, can use the CT attenuation data, measured from these two real energy spectra, to calculate what the attenuation would look like if we had single energy X-rays… 140keV 140keV

14 © 2014 Ken L Schreibman, PhD/MD 14 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Dual Energy is actually Single Energy Conventional Single Energy CT generates images from X-rays with a spectrum of energies. Collecting image data from 2 single energy spectra simultaneously is called Dual Energy. Dual Energy allows generation of images… …as if the X-rays were of a single energy! …as if the X-rays were of a single energy! Number of X-ray photons emitted from CT tube Energy of the X-ray photons (x10 3 electron-volts) ( keV ) 140kV 140kV 80kV 80kV 140keV 140keV

15 © 2014 Ken L Schreibman, PhD/MD 15 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 GE 750 HD with GSI GSI:Gemstone Spectral Imaging What GE calls their DECT What GE calls their DECT Its easy to turn on DECT Click On button Click On button With DECT, the presets control the kV and mA

16 © 2014 Ken L Schreibman, PhD/MD 16 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Since it takes several minutes to generate DE images, GSI first yields SE Quality Check (QC) images For technologists to check for coverage, etc. For technologists to check for coverage, etc. GE recommends discarding these images. GE recommends discarding these images. I found they looked as good as the best SE images we got with high kV and mA. I found they looked as good as the best SE images we got with high kV and mA. We archive them. We archive them. GSI generates both SE & DE images 600 mA 11) SE:140 kV GSI: QC Generated automatically Target 600 mA 2) SE:140 kV SECT Acquired earlier Target Conclusion: QC equivalent to SECT

17 © 2014 Ken L Schreibman, PhD/MD 17 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Results: SE & DE CT for Target Lesion 600 mA 2) SE:140 kV 600 mA 12) DE:140 keV Target Conclusion: DE at least as good as SE Target

18 © 2014 Ken L Schreibman, PhD/MD 18 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Results: SE & DE CT for Dose Chart of DLP (Dose Length Product) (mGy-cm) Values calculated by the CT scanner Values calculated by the CT scanner Conventional CT (kV)DECT (keV) CHANGING VOLTAGE CHANGING CURRENT (mA) % less than Conclusion: DECT lower dose than SE

19 © 2014 Ken L Schreibman, PhD/MD 19 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Results: SE & DE Metal Blooming (Phantom) 600 mA 2) SE:140 kV For all images: W=3000 L= mA 12) DE:140 keV Conclusion: DE Less Metal Blooming 13mm 10mm

20 © 2014 Ken L Schreibman, PhD/MD 20 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Results: SE & DE Metal Blooming (Patients) B,W 57yoM 630 mA, Detail 3mm Sagittal SE:140 kV A,C 69yoF 600 mA, Detail 3mm Sagittal DE:140 keV MetalBlooming DLP=2764DLP=1234 Cant see if osteolysis inside femoral component Much Less MetalBlooming CAN see osteolysis inside femoral component 55% less than 2764!

21 © 2014 Ken L Schreibman, PhD/MD 21 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Results: Metal Blooming +/- GE MARs Metal Artifact Reduction software Post-processing iterative technique Post-processing iterative technique It can be applied, or not, after scanning It can be applied, or not, after scanning Only available on GE scanners with GSI Only available on GE scanners with GSI MARs helps significantly in the reduction of artifacts from high density metal implants and allows the accurate visualization of the underlying bone and adjacent soft tissue November 2011 page mA 12) DE:140 keV 600 mA 13) DE:140 keV + MARs Black streak artifacts Black streak artifacts Eliminates Target?Target Conclusion: MARs may worsen bone-metal interface

22 © 2014 Ken L Schreibman, PhD/MD 22 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Limitations Ive only worked with GE 750 HD GSI Thats what we have at the UW Thats what we have at the UW Ive only worked with 2 TKA phantoms Got the same results Got the same results Both times failed to see largest target! Geometry of cupped femoral component? Geometry of cupped femoral component? We werent trying to minimize dose Just wanted to see what advantages DECT offered over SECT Just wanted to see what advantages DECT offered over SECT

23 © 2014 Ken L Schreibman, PhD/MD 23 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 What Were Presently Doing Because DECT seems to be no worse than SECT in seeing bone-metal interfaces Because DECT seems to be no worse than SECT in seeing bone-metal interfaces SECT & DECT found/missed same targets SECT & DECT found/missed same targets and because DECT metal blooming is less… and because DECT metal blooming is less… and because DECT dose is lower… and because DECT dose is lower… UW MSK Policy is now this: For patients getting bone/joint CT scans, whenever there is metal in scanning FOV, we recommend using DECT with 140keV. If DECT not available, use 140kV SECT. If DECT not available, use 140kV SECT.

24 © 2014 Ken L Schreibman, PhD/MD 24 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 What Were Planning on Doing Working with our physicists to optimize the DECT protocols so we can continue to get great images with minimum dose. Develop body part specific protocols Hopefully share all of this with all of you at SSR 2015! A,C 69yoF 600 mA, Detail 3mm Sagittal DE:140 keV

25 © 2014 Ken L Schreibman, PhD/MD 25 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 Anyone who wants to join me in a bike ride can meet me up front as soon as were done

26 © 2014 Ken L Schreibman, PhD/MD 26 of 24 TKA: Single vs Dual Energy CT 1.ProblemProblem 2.PhantomPhantom 3.ScannerScanner 4.kVkV 5.mAmA 6.DECTDECT 7.SE v DESE v DE 8.DoseDose 9.BloomingBlooming UW SSR Mon 3/17/14 12:10 How Does GSI Yield Lower Dose Than SECT? Answer from our UW Physicists: Good question. Good question. The 600 mA current is an average between what is being given at 80 kV and 140 kV. The current drops a bit at 80 kV compared to 140 kV (due to physics reasons), but the mA cannot be otherwise actively changed between the two kV's. The tube spends more time at 80 kV than at 140 kV so that it can get enough data at 80 kV with its greater patient attenuation. The CTDIvol or DLP at 80 kV is only about 25% compared to that at 140 kV, so the dose for dual energy at 600 mA will be much less than the dose at 600 mA using 140 kV single energy. Bonus Slide


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