STIR – 1 Digital Phantom Project

1. STIR – 1Digital Phantom Project Kohsuke Kudo, Soren Christensen, Makoto Sasaki, and Leif Ostergaard

2. Background • A variety of post-processing programs and algorithms for CT perfusion and dynamic susceptibility contrast (DSC) MR perfusion are available from CT or MR manufacturers, third-party workstation vendors, and academic groups. • However, the accuracy and reliability of these programs have not been subject to standardized quality control.

3. Purpose • To design a digital phantom data set both for CT perfusion and DSC MR perfusion based on widely accepted tracer kinetic theory in which a range of true values of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and tracer arrival delay are known. • To evaluate the accuracy of post-processing programs using this digital phantom.

4. Methods – AIF/VOF • Arterial input function (AIF) was generated using Gamma-variate function. • Venous output function (VOF) was generated by deconvoluting AIF and Exponential R(t).

5. Methods – AIF/VOF • Concentration time curves, C(t), were converted to signal time curves, S(t), for MR.

6. Methods – Tissue Curves • Tissue curves were generated by deconvoluting AIF and R(t). Three kinds of R(t) were used, Exponential, Linear, and Box.

7. Methods – Tissue Curves • Tissue curves were also converted to signal curves for MR.

8. Slice #1 AIF/VOF Slice #2, 3 R(t) = Exp. CBV = 2, 4 % Slice #4, 5 R(t) = Linear CBV = 2, 4 % Slice #6, 7 R(t) = Box CBV = 2, 4 % Methods – Data Structure • The phantom data set had 7 slices and 50 phases (total 350 images). Curves for AIF/VOF were embedded in slice #1. Tissue curves were embedded in slice #2 to #7, with different R(t) and CBV.

9. Methods – AIF/VOF Image -3 -2 -1 Delay (s) = 0 +1 +2 +3 AIFs VOF • AIF without delay and VOF were used.

10. Methods – Tissue Images -3 -2 -1 Delay (s) = 0 +1 +2 +3 MTT (s) = 24 12 86 4.8 4 3.4 CBF (mL/100g/min) =5 10 15 20 25 30 35 (CBV = 2%) 10 20 30 40 50 60 70 (CBV = 4%)

11. Method – True Values • R(t): Exponential, Linear, and Box • Delay: -3, -2, -1, +0, +1, +2, and +3 sec • CBV: 2 and 4% • CBF: 5, 10, 15, 20, 25, 30, and 35 mL/100g/min • 10, 20, 30, 40, 50, 60, and 70 mL/100g/min • MTT: 3.4, 4, 4.8, 6, 8, 12, and 24 sec

12. Methods – Evaluation • CT Perfusion • Commercial Software • GE (CTP3, CTP4) • Hitachi (IF) • Philips (SVD) • Siemens (LMS) • Toshiba (bMTF, SVD+) • Academic Software • PMA (sSVD, bSVD) • MR Perfusion • Commercial Software • GE (FM) • Hitachi (FM) • Philips (FM) • Siemens (SVD) • Academic Software • EPITHET (SVD) • Penguin (sSVD, oSVD) • Rapid (sSVD, cSVD) • PMA (sSVD, bSVD)

13. Methods - Evaluation • Delay Sensitivity • Visual Assessment • Correlation coefficient with delay • Accuracy • Correlation coefficient with true value Significant Correlation = Delay Sensitive Higher Correlation = Accurate

14. Results Delay PMA CBF sSVD MTT/CBF

15. Results Delay PMA CBF bSVD MTT/CBF

16. Results – CTP Maps CBF CBV MTT GE CTP3 GE CTP4 Hitachi IF Philips SVD Siemens LLMS Toshiba bMTF Toshiba SVD+ PMA sSVD PMA bSVD

17. Results – MRP Maps CBF CBV MTT GE FM Hitachi FM Philips FM Siemens SVD Penguin sSVD Penguin oSVD Rapid sSVD Rapid cSVD PMA sSVD PMA bSVD Tmax EPITHET SVD Penguin sSVD Penguin oSVD Rapid sSVD Rapid cSVD PMA sSVD PMA bSVD

18. Results – Delay Dependency

19. Results - Accuracy

20. Delay Sensitivity Accuracy Correlation Coefficient to Delay Correlation Coefficient to True Value CBF CBV MTT CBF CBV MTT GE CTP3 -0.177 0.104 0.321 GE CTP3 0.940 0.974 0.907 GE CTP4 0.188 0.439 0.337 GE CTP4 0.699 0.698 0.888 Hitachi 0.000 0.316 0.404 Hitachi 0.844 0.898 0.885 Philips -0.438 0.011 0.376 Philips 0.720 0.867 0.828 Siemens Siemens Toshiba bMTF -0.444 0.027 0.455 Toshiba bMTF 0.327 0.985 0.851 Toshiba SVD+ Toshiba SVD+ PMA sSVD -0.331 0.000 0.341 PMA sSVD 0.844 0.958 0.880 PMA bSVD -0.002 0.000 0.016 PMA bSVD 0.942 0.958 0.965 Results – CTP r < 0.9 Significant correlation = Delay sensitive

21. Results – MRP r < 0.9 Significant correlation = Delay sensitive

22. Summary • CT Perfusion • Commercial Software • GE(CTP3) : accurate but delay sensitive • GE(CTP4) : sensitive to negative delay • Hitachi(IF) : CBV/MTT are delay sensitive • Philips(SVD) : delay sensitive • Siemens(LMS) : could not be analyzed • Toshiba(bMTF) : delay sensitive • Toshiba(SVD+) : could not be analyzed • Academic Software • PMA(sSVD) : delay sensitive • PMA(bSVD) : delay insensitive and accurate

23. Summary • MR Perfusion • Commercial Software • GE(FM) : delay insensitive but not accurate • Hitachi(FM) : delay insensitive but not accurate • Philips(FM) : delay insensitive but not accurate • Siemens(SVD) : delay sensitive • Academic Software • EPITHET(SVD) : only Tmax • Penguin(sSVD) : delay sensitive • Penguin(oSVD) : delay insensitive • Rapid(sSVD) : delay sensitive • Rapid(cSVD) : delay insensitive and accurate • PMA(sSVD) : delay sensitive • PMA(bSVD) : delay insensitive and accurate

24. Newer Version of Phantom • All the curves are embedded in “real” brain image, because some programs require anatomical configuration. AIF VOF • Only “positive delays” are used, because negative delays are not realistic if we choose proper AIF. • Five CBV values are embedded to see linearity of CBV. • Noise was added stronger to resemble clinical data.

25. Preliminary Results for CT CBF CBV MTT GE CTP3 GE CTP4 Hitachi IF Philips SVD Siemens LLMS Toshiba bMTF Toshiba SVD+ PMA sSVD PMA bSVD

26. Conclusion • The digital phantom can be used for the evaluation of accuracy and reliability of perfusion software packages, and also used for the certification and standardized quality control.

27. Thank you.