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STIR – 1 Digital Phantom Project
Kohsuke Kudo, Soren Christensen, Makoto Sasaki, and Leif Ostergaard
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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.
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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.
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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).
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Methods – AIF/VOF Concentration time curves, C(t), were converted to signal time curves, S(t), for MR.
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Methods – Tissue Curves
Tissue curves were generated by deconvoluting AIF and R(t). Three kinds of R(t) were used, Exponential, Linear, and Box.
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Methods – Tissue Curves
Tissue curves were also converted to signal curves for MR.
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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. Slice #1 AIF/VOF Slice #2, 3 R(t) = Exp. CBV = 2, 4 % Slice #4, 5 R(t) = Linear Slice #6, 7 R(t) = Box
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Methods – AIF/VOF Image
-3 -2 -1 Delay (s) = 0 +1 +2 +3 AIFs VOF AIF without delay and VOF were used.
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Methods – Tissue Images
-3 -2 -1 Delay (s) = 0 +1 +2 +3 MTT (s) = CBF (mL/100g/min) = (CBV = 2%) (CBV = 4%)
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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
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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)
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Methods - Evaluation Delay Sensitivity Visual Assessment
Correlation coefficient with delay Accuracy Correlation coefficient with true value Significant Correlation = Delay Sensitive Higher Correlation = Accurate
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Results PMA CBF sSVD Delay MTT/CBF
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Results PMA CBF bSVD Delay MTT/CBF
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Results – CTP Maps CBF CBV MTT GE CTP3 GE CTP4 Hitachi IF Philips SVD
Siemens LLMS Toshiba bMTF Toshiba SVD+ PMA sSVD PMA bSVD
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Results – MRP Maps CBF CBV MTT Tmax 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
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Results – Delay Dependency
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Results - Accuracy
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Significant correlation
Results – CTP Delay Sensitivity Accuracy CBF CBV MTT GE CTP3 -0.177 0.104 0.321 0.940 0.974 0.907 GE CTP4 0.188 0.439 0.337 0.699 0.698 0.888 Hitachi 0.000 0.316 0.404 0.844 0.898 0.885 Philips -0.438 0.011 0.376 0.720 0.867 0.828 Siemens Toshiba bMTF -0.444 0.027 0.455 0.327 0.985 0.851 Toshiba SVD+ PMA sSVD -0.331 0.341 0.958 0.880 PMA bSVD -0.002 0.016 0.942 0.965 Correlation Coefficient to Delay Correlation Coefficient to True Value Significant correlation = Delay sensitive r < 0.9
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Significant correlation
Results – MRP Significant correlation = Delay sensitive r < 0.9
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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
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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
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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.
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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
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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.
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Thank you.
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