Wai -Hoi Wong 1 , Hongdi Li 2 , Yuxuan Zhang 1 , Rocio Ramirez 1 ,
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Transcript of Wai -Hoi Wong 1 , Hongdi Li 2 , Yuxuan Zhang 1 , Rocio Ramirez 1 ,
Wai-Hoi Wong 1, Hongdi Li 2, Yuxuan Zhang 1, Rocio Ramirez 1,
Hossain Baghaei1, Shaohui An2, Chao Wang2, Shitao Liu2, Yun Dong2
1 University of Texas MD Anderson Cancer Center, Houston, TX,
2 Shanghai United Imaging Healthcare Co, Shanghai, China.
A high-resolution time-of-flight clinical PET detection
system using the PMT-quadrant-sharing technology
• LYSO is expensive (1/5 the price of gold)
• The Objective is to get higher sensitivity per cc of LYSO
• More efficient use of LYSO by increasing the axial field of view while reducing the crystal depth
System Design
• GEANT4 MC simulation
• But large AFOV increases PMT and electronics cost
• Use PMT-quadrant-sharing reducing PMT usage by 75% for increasing AFOV cheaply
• 15mm deep LYSO, 28-cm AFOV
Detector Ring Design• To achieve ultrahigh resolution using large PMT to increase AFOV
2.35 x 2.35 mm pitch
38-mm PMT 16 x 16 LYSO block
Achieve decoding 256 crystals per PMT usage
• Adapt PMT-Quad-Sharing blocks to a gapless detector-ring geometry
Ring has 24 modules (3 x 7 blocks)
3 blocks in-plane and 7 blocks axial
The edge blocks are half-ground to fit the quadrant-sharing PMT
The “Slab-Sandwich-Slice” (SSS) Detector Production
These are 15 sets of inter-slab irregular reflecting masks for
a 16 x 16 array to decode 256 crystals / PMT
Each reflecting mask can be cut into any shape providing
many degrees of freedom to optimize crystal decoding
There are 4 sandwich types in this 16 x 16 block
The SSS production method is highly uniform and preciseas shown in the decoding map of these 72 detector blocks
NEMA Resolution Expectation (mm) Measured (mm)
Transaxial (1 cm) ≤2.8 mm 2.72
Axial (1 cm) ≤3.1mm 2.76
Trans Radial (10 cm) ≤3.3mm 3.36
Trans Tangential (10cm) ≤3.2mm 3.05
Axial (10cm) ≤3.6mm 2.96
NEMA image resolution measurement
Reconstruction algorithm: FBP2D (SSRB)
Pixel Size: 0.3 x 0.3 x 1.22
FWHM 0 cm 4 cm 8 cm 12 cm 16 cm 20 cm 24 cm 28 cm
Mid plane P (V) 1.47 1.55 1.64 1.78 1.76 1.89 1.97 2.46
Mid plane P (H) 1.55 1.44 1.60 1.61 1.56 1.81 1.77 1.79
¼ axis NP (V) 1.72 1.88 2.09 2.13 2.18 2.12 2.19 2.95
¼ axis NP (H) 2.00 2.03 2.19 2.28 2.58 3.13 3.90 4.46
V: Vertical H: Horizontal
PSF reconstructed image resolution (mm)
MIPTOF + PSF2 min/bed, 2 iterations
PSF3 min/bed, 3 iterations
TOF + PSF ReconSNR: TOF/PSF 2 min/bed 2 iterations = PSF 3 min/bed 3 iterations 2/3 scan time, faster recon, no loss of detectability
SNR = (Signal – Background) / SDBackground See Jakoby, et al, Phys. Med. Biol. 56
Conclusions
• With PMT-quadrant-sharing Detector design we have developed an ultrahigh resolution TOF PET/CT
• It has a resolution of 2.8 mm using FBP (1.5 mm using PSF)
• Large axial FOV 27.6 cm, ultrafine axial sampling of 1.22 mm
• This large system with ultrahigh resolution uses only 576 PMT (reducing PMT and electronics cost, while increasing reliability)
• It has 129,024 detectors with a TOF resolution of 473 ps