Medical Photon Counting in Israel

Transcription

1 Clinical Use of Photon Counting Detectors in CT Medical Photon Counting in srael D spect NM Alcyone Ventri MB Module manufacturer CT Swift Reuven Levinson CT Engineering GE Healthcare Haifa, srael Jerry Arenson- Haifa CT Eng Mgr Shaike Maoz שייקה מעוז Baruch Rosner ברוך רוזנר Lev Greenberg Jenia Kuksin Zimam Romman Daniel Rubin Лев Гринберг Евгений Куксин زمام رمان Даниель Рубин Galit Naveh גלית נוה שלום הרוזנברג Shalom Rosenberg עופר בנימיני ב Ofer Benjaminov Dept. of Diagnostic maging Rabin Medical Center Tel Aviv, srael Technology Paths to Dual-Energy CT Acquisition Tubes + Detectors Tube Spectra 140 kvp 1 Tube + 1 Detector Tube Spectra 140 kvp 80 kvp Dual-Layer Detector Detector Absorption 80 kvp Energy Discriminating Detector Detector Energy Bins 1 L L H # X-rays # X-rays # X-rays # X-rays Low 140 Energy 140 Energy Energy High Energy SEMENS Dual-Source Fast Switching PHLPS Dual-Layer Photon Counting Goals of Spectral CT Simultaneous Collection of Energy nformation ntrinsic simplicity outdates detector slicing technology Boost in resolution and dose efficiency Scintillator smaller pixels with minimal loss in dead-space Light Eliminate electronic noise floor photons digital counting of individual x-ray photons Gateway to ultimate MD tissue characterization maximize energy separation simultaneous collection for precise temporal registration Photodiode Standard CT Detector (X-ray light charge) electron-hole pairs ncident X-ray Photon Charge ntegrating DAS bias Spectral CT Detector (X-ray charge) ncident X-ray Photon Charge Pulse Counting DAS Semiconductor electron-hole pairs

2 darkbias current Spectral CT: Pulse Counting Electronics direct conversion sensor common pixilated cathode anode X-ray photon current - + HV X-ray on Photon pulses riding on photo-current and bias current current compensation preamplifier test input photo-current time voltage shaper filter X-ray on time Photon pulses following base-line restoration discriminators threshold level DA voltage DA energy thresholds X-ray on pulse counters voltage time Narrow bi-polar pulses Digital output Digital output Clean Digital Signal Processing ncoming photon pulses stripped off flowing detector current Pulse heights proportional to kev Threshold discriminators trigger high or low digital counters Optimum maging Performance zero electronic noise floor Precise energy separation Simultaneous energy acquisition Fully adjustable energy bins Supports multiple (>) energy acquisition CT Detector Challenges Count rates >100 Mcpsmm time Demanding stability X-ray on requirements Digital pulses trigger counter Photon-Counting CT system: detector imaging parameters CT Pixel size 1x1 mm Multi-slice Geometry D (1000x3) Flux rate (cpsmm ) Countsview (1 msec) No. of bins Optimal Spectral CT Performance: Paths to High-Flux X-ray Photon Counting Today s high-power scanners deliver >100 Mcpsmm count rates at the detector Future systems expected to double this requirement N O = 5 Mcps N O = 3.5 Mcps Channel still hasn t reached saturation at 50 Mcps Non-paralyzable detector response and linearization calibration ameliorate pile-up issues Smaller pixels 1mm Sub-pixelization Linear ntegration Photon Counting 4x 0.5mm Faster photon-counting DAS 0nsec shaper Hybrid Countingntegrating Layered Photon-Counting High Flux Readout Low-Energy Bin High-Energy Bin N O is when OCR=CR Low-Energy Bin High-Energy Bin

3 Swift Spectral CT Main Components 100% simultaneous dual-energy acquisition High-resolution direct-conversion detector array Ultra-dose-efficient photon-counting detection GPU-based recon and display system Swift 3-slice Spectral CT system Aluminum bowtie Recon and Display console A very happy hour Swift: The World s First EDCT Scanner First Swift Phantom Scan (May 10, 006) Wood Aculon Teflon odine Air Pixilated detector array & ASCs Plug&Play all-digital DAS 15 cm FOV 15 cm FOV Water VCT-64 gantry GPU technology First Swift Patient Scanning (May 007) New images in dual energy CT Axial Curved AVA V. Endoscopy D MP VR & Bone LM VR With Hard Plaque Removal 3D MP Radial MP mages Conventional CT (HU) Dual Energy monoe (mono-energetic equivalent (HU)) VNC (material density image (mgcc)) odine (material density image (mgcc)) Scan parameters: Helical, 3x0.65 mm, 140 kvp, 14 ma (eff), 1-sec rotation, pitch=0.5

4 Theory (dual energy) Attenuation basis functions Basis processes: Photo-electric (wo K-edge) & Compton Scatter µ T (E 1 )= µ PE (E 1 )+ µ Comp (E 1 ) µ T (E )= µ PE (E )+ µ Comp (E ) Basis Materials: Al, Delrin µ Al (E)= x PE µ PE (E)+ x Comp µ Comp (E) µ Delrin (E)= y PE µ PE (E)+ y Comp µ Comp (E) Material Decomposition basis function => unknowns (amount of each component) => different energies 1 = exp(-l Al µ Al (E 1 )-L Del µ Del (E 1 ) = exp(- L Al µ Al (E )-L Del µ Del (E ) Proc, Recon and mages in dual Energy Raw data (E1) Raw data (E) Raw data (E1) Raw data (E) Non- linear processing Prep data (E1) Prep data (E) Beam hardening Prep data (E1, E) FBP FBP FBP FBP CT MG (E1) CT MG (E) Material density image A Material density image B mage Space Recon Linear combinations Material density images Projection Space Recon Linear combinations MonoE nversion ( 1, )= G(L Al, L Del ) (L Al, L Del )=G -1 ( 1, ) -Material Basis Decomposition Aluminum image Aculon image SourceDetector: influence on dose efficiency M-PPU Cal Factor Status (vs Conventional CT) Function form Phantom scan Detector DQE Same; except low flux performance required for low energy beam Empirical detector data Bin energy separation NEW: does not exist in single energy E L, E H Al prep Ac prep Al image Ac image BH-free B&W image Aculon (Acetal) ~50 HU odine [mgml] Calcium (CaCl ) [mgml] H O 14cm diam H O Air H O Phantom legend Ca 80 H O Ca 30 Ca 40 Ca 160 Ca 80 B&W monoenergy image σ σ Bin flux ratios NEW: does not exist in single energy f L, f H Conventional CT σ = ( 1 N) DQE Dual Energy Tkaczyk et al, SPE 009 (758-15) g A gb 1 N µ B( E ) ( ) H µ B EL = ( ( ) ( ) ( ) ( )) ( ) ( ) µ A EL µ B EH µ A EH µ B EL µ A EH µ A EL f -1 (L) f -1 (H) DQE Bin energy separation Bin flux ratios

5 Energy separationbin flux ratio Variance vs flux (photon-counting vs energy integrating) Energy ntegrating Photon Counting Pile-up Electronic noise Carotid Arteriography Mono-energetic mages Mono60 Mono75 Mono100

6 Virtual Non-contrast maging Virtual Non-contrast maging Now you see it. Now you don t Swift Clinical Studies: Abdominal maging Pre-contrast images Energy ntegrating Photon Counting Swift Clinical Studies: VNC Performance TUE-MC Excreted Contrast Medium Delay-MC Calcified Structure Vs. Excreted Contrast Medium Delay-VUE Calcified Structure Spectral CT Virtual Unenhanced processing removes iodine while preserving calcium. 15 min delay from contrast injection - images displayed with and wo iodine. No need for pre-contrast study.

7 Swift Clinical Studies: Full FOV Abdominal maging World s 1 st Spectral CT abdominal study Mono 8KeV + C Z-map* images MC-70 kev *Color-mapping according to tissue atomic number Mono 8KeV + C Mono 8KeV + C

8 Mono 8KeV + C VNC (+C) VNC True Unh Mono 8KeV + C VNC (+C) odine VNC Performance A: Can VNC (+C) replace conventional (-C)? VNC -C VNC +C VCT -C VNC +C Lesion Fat Muscle -4 - VNC -C VNC +C

9 Adrenal Lesion Conventional CT vs Dual Energy CT (µ vs material density) VCT (-C) MC (-C) VNC (-C) VNC (+C) MC (+C) Delayed MC Subject 1 (Rt. Adrenal Lesion) Subject (Lt. Upper Lesion) NA Subject (Lt. Lower Lesion) NA Subject (Rt Upper Lesion) NA Subject 3 (Rt. Adrenal Lesion) Subject 7 (Lt. Adrenal Lesion) Subject 8 (Rt. Adrenal Lesion) Subject 8 (Lt. Adrenal Lesion) Average conv CT-C VNC -C Liver Spleen Aorta Muscle Retro. Fat Gall Bladder Portal vein Complete specificity: k-edge CT (Gd contrast) No Specificity Single Dual (Photo-Electric) Partial Spec. Soft tissue Gd contrast calcium Soft tissue No Gd contrast calcium Partial Spec. Complete Spec. Gd Contrast only Soft tissue calcium No Gd contrast Dual (Compton) Triple (kedge) Overlayed Gd contrast w Single Energy image

10 Complete specificity PET CT Summary Results on clinical trials show equivalent image quality for single energy scanning and potential for low-dose scanning PC delivers a single-tube, single-detector configuration for high-quality dual energy CT imaging PC provides a path for future k-edge imaging Great are the lights God created Pleasant is their radiance in all the world טובים מא ורות שברא ה' נוה זי ום ב כל העול ם CT PET PETCT Thank you for your attention