Y-PET versus 90 Y-Bremsstrahlung SPECT

Transcription

1 90 Y-PET versus 90 Y-Bremsstrahlung SPECT First 90 Y microspheres injected intra-arterially imaging 90 Y TOF PET/CT 198 Au rays scan 90 Y bremsstrahlung scan Lhommel et al Simon and Feitelberg 1967 S Walrand Cliniques universitaires saint-luc, Brussels

2 Milestones in 90 Y positron emission studies Ford KW Phys Rev 1955 Nickles et al. IEEE TNM Y micro-derenzo phantom imaged 2 or e + e - with a micro-pet P4 scanner Hypothetical level diagram of 89 Zr as deduced from the neighboring nucleus 89 Y. A first excited 0+ state is expected because of the large mutual interaction of the (g 9/2 ) 2 configuration. Selwyn et al. ARI 2006 e+: 3.2x10-5 2x10-4 e+ observed Johnson et al. Phys Rev 1955

3 The decay of 90Y has a minor branch to the 0+ excited state[1], followed by an internal e + e - creation which happens in 32 out of one million decays [2]. Consequently, 90Y PET scan was proposed in order to assess the biodistribution [3] of 90Y-labelled therapeutic agents. A 61-year-old woman was referred for. 30min 1. Ford. Phys Rev Selwyn et al. Appl Radiat Isot Nickles et al. IEEE Nucl Sci Symp Record 2004 The additional liver low dose CT performed for the 90 Y PET/CT evaluation could be seen as an unjustified additional irradiation of the patient. 90 Y: ± 5000 msv CT: 2 msv amazing epoch

4 Feasibility of 90 Y TOF-PET based dosimetry in liver metastasis therapy using SIR-spheres. true TOF-PET Dosimetry by kernel dose convolution Relative activity 0 1 liver True mgy/mbq TOF-PET mgy/mbq Err (%) Lhommel,..., Walrand EJNMMI 2010

5 90 Y TOF-PET based dosimetry in liver metastasis therapy using resin spheres. necrotic tumour FDG TOF-PET (day 1) FDG TOF-PET (day 57) 90Y TOF-PET (day 15) progressive responding Mean SUV = 5.96 Max. SUV =12.0 Mean SUV = 2.86 Max. SUV = 6.41 Mean dose: 85.3 Gy Max. dose:153.0 Gy Mean dose: 29.9 Gy Max. dose: 37.7 Gy 90Y: 45min acquisition for 2 bed positions, i.e. 27cm Lhommel,..., Walrand EJNMMI 2010

6 Tumour early response-dose relationship in 90 Y liver SIRT 20 survival fraction R 2 = 0.96 R= metabolic ratio at week 7 post therapy HEF x D (Gy) HEF 1 R=0 94 Walrand et al. EJNMMIres Hb level (g/dl)

7 Comparison of different crystals in 90 Y PET GSO LYSO BGO van Elmbt, Vandenberghe, Walrand et al. PMB 2011

8 Comparison of different crystals in 90 Y PET high count rate phantom hot spheres (1.7GBq 90 Y) Gemini TF LYSO TOF Gemini TF LYSO non-tof 36min 24min 12min Allegro GSO Exact HR+ BGO van Elmbt, Vandenberghe, Walrand et al. PMB 2011

9 recovery (%) QUEST multicentric study summary (Willowson et al. EJNMMI 2015) Philips Gemini TF GE Discovery Y Sfactor Siemens Biograph mct Stabin et al. [14-1] van Elmbt et al. [11] Willowson et al. [13] Sfactor TOF + RR TOF + PSF TOF PSF hot sphere diameter (mm) recovery < 90 Y Sfactor local energy deposition method

10 Comparison of different crystals in 90 Y-DOTATOC PET spine: 2.5MBq-12ml plastic vial in 5cm diameter cylinder filled with K 2 HPO 4 solution modeling bone attenuation low count rate kidney MIRD P19 phantom modeling a 1h PET acquisition after a typical first 90 Y-DOTATOC therapy cycle Spline 100MBq Kidney 35MBq CT Gemini TF LYSO Exact HR+ BGO 50% plexiglas 50% H 2 O H 2 O missing activity (radioactivity of LYSO) Relative deviation: -18% -3% 7ml tumours: 11,25 MBq Walrand et al. JNM 2011 dosimetry after each cycle to optimize the next one

11 Fabbri et al. Canc Bioth 2015 PET <> brems-spect in 90 Y-DOTATOC therapy

12 90 Y-based PET and SPECT imaging in locoregional brain treatment for high-grade gliomas Fabbri et al. EJNMMI 2012

13 90Y PET <> brems-spect post synovectomy Barber et al. JMI&RO 2013 PET can provide superior image quality compared with brems-spect and may enable reliable detection of extra-articular 90 Y activity

14 Open issues in liver 90 Y PET 90 Y-PET spurious extra-hepatic counts counts Y vial in air true coincidences radial profile increasing tail measured profile source profile scc profile e+ e- pair production in LSO (X>1MeV)? (van Elmbt-Walrand) 1 90 Y-TOF PET bin acquired on a PET Biograph (courtesy of Dr. Ahmadzadehfar) Gate-GEANT4 simulations did not show any significant e + e - creation in LSO (Strydhorst et al. Med Phys 2016)

15 photon per MeV per decay Internal bremsstrahlung: a forgotten but significant effect in 90 Y SPECT and PET imaging. (Walrand et al. EANM Vienna 2017) nucleus E field Aston 1927 β- 1.E+1 1.E+0 1.E-1 1.E-2 1.E-3 1.E-4 1.E-5 1.E-6 h2o brems G4 fit h2o brems int brems [33] Venkataramaiah et al.1980 int brems [28] Cengiz et al.2004 fit int brems effect discovery knowledge in nuclear medicine e+ emission int. bremss E E (M) Int. Bremss. not modeled in Geant4

16 arbitrary units Internal bremsstrahlung: a forgotten but significant effect in 90 Y SPECT and PET imaging. (Walrand et al. EANM Vienna 2017) A 1.E+0 1.E-1 1.E-2 GSO-PET 111 In spectra 111In acquisition spectra gauss 171keV 171keV gauss gauss 245keV 245keV gauss spectra fit fit 1.E+0 1.E-1 1.E-2 B LYSO-PET 18 F spectra 1.E+0 18F acquisition spectra G4 511-Lu176 pileup 1.E-1 gauss 511keV 511keV gauss spectra fit fit 1.E-2 C LSO-PET 18 F spectra 1.E-3 1.E-4 1.E-3 1.E-4 1.E-3 1.E-4 acquisition 2.80E keV gauss 511keV gauss fit 1.E kev 1.E kev 1.E kev Crystal scintillation exhibits long energy resolution tail

17 cps per bin Internal bremsstrahlung: a forgotten but significant effect in 90 Y SPECT and PET imaging. (Walrand et al. EANM Vienna 2017) A GSO-PET 32 P true cc rate radial profile B B acq G4 int+h2o+gauss G4 h2o+tail G4 int+h2o+gauss theory 32 P vial 1.E+0 1.E kev bin >>250keV bin e- [450,650] kev A BUT

18 On the origin and on the reduction of spurious extrahepatic counts observed in 90Y non-tof PET imaging post radioembolization (Walrand et al. EANM Vienna 2017) Gate-GEANT4 simulations with int+ext bremss. A B C Brems Lu176 LOR-TOF Brems Lu176 3D-RAMLA Brems Lu176 3D-RAMLA D Brems Lu176 LOR-TOF E Brems Lu176 LORDS-3D-RAMLA F Brems Lu176 3D-RAMLA Spurious extrahepatic counts originate from randoms not perfectly corrected in non-tof PET

19 198 Au rays scan 90 Y bremsstrahlung scan Simon and Feitelberg 1967

20 back-scattering Counts / kev / MBq.s 90 Y SPECT: contamination components Total counts Primary photons Scattered photons reduced using a medium energy or high energy collimator >150keV [50,150]keV Camera backscatter Collimator scatter & penetration Lead x-rays geometrical Energy (kev) Pb PET decay emits positron 3D sensitivity: [50,150]keV SPECT 1.5% decay emits bremsstrahlung X ray in [50,150] kev Collimator sensitivity But scattered X rays

21 90 Y SPECT: state of the art MC reconstruction Total 90 Y bremss. in h 2 o without scatter correction Germanium detector with MC scatter correction Rault et al. Med Phys 2010 Dewaraja et al. Med Phys 2017 Not commercial available and collimator-camera dependent The liver concentration of 0.34 MBq/mL used in the phantom was limited by radiation safety requirements of the regulatory authority at our institution. Some radioprotection officers are imposing ALA R A can be a threat to imaging development (dead time, background) and at the end, also a threat patient care

22 90 Y bremsstrahlung Monte Carlo modeling Gate 6.2 : Geant4 9.5-p01 + Geant4 9.6-p02 for atom de-excitations and fluorescence emissions 90 Y source in perpex Lead housing crystal Pyrex lightguide Mu-metal shielding PMTs dynodes GE400 AC Crystal: NaI or BGO BGO camera based on Exact HR+ BGO-PMTs blocks + flat pinhole collimator Walrand et al. Front Oncol 2014

23 MC simulation of camera contaminating x-rays in bremsstrahlung imaging primary camera back-scattering β- MC simulation of the signal to scatter ratio 100 Pb NaI Pyrex Signal to scatter ratio signal > scatter scatter > signal PMT elect. boards E (kev) Walrand et al. Front Oncol 2014

24 MC simulation of camera contaminating x-rays in bremsstrahlung imaging primary β- MC simulation of the signal to scatter ratio 100 Pb BGO Signal to scatter ratio signal > scatter scatter > signal PMT elect. boards E (kev) Walrand et al. Front Oncol 2014

25 MC simulation of camera contaminating x-rays in bremsstrahlung imaging primary β- MC simulation of the signal to scatter ratio 100 Pb BGO Signal to scatter ratio signal > scatter scatter > signal PMT elect. boards E (kev) Continuous energy tomography (CET) Walrand et al. Front Oncol 2014

26 90 Y bremss. NaI-pinhole SPECT SIRT phantom evaluation pinhole SPECT of longitudinally extended organ requires helical acquisition helical non-circular acquisition, bed & camera manually moved positions measured by 3 tape rulers 2 hours for the motions Walrand EJNMMI research 2011 medium energy thyroid pinhole: focal length too long and 1/2 of the crystal area used

27 Bremsstrahlung helical pinhole SPECT is superior to 90 Y-TOF-PET 90Y TOF-PET true helical PH SPECT not commercially available 90Y liver-sirt d a f b e c 36 min 3.6 min 1 min dosimetry in 3min helical PH SPECT in catheterization room optimization patient physicist Walrand EJNMMI research 2011

28 Perspective: dose optimization in catheterization room

29 Perspective: dose optimization in catheterization room 1/3 of maximal MAA based activity 3 min SPECT liver dosimetry if wrong delivery: catheter repositioning or allowed activity to reach maximal safe liver dose

30 SNR (20 min acquisition time) 90 Y+L[Y]SO true CT ps-TOF bremss. helical MEPH 2H SPECT ( S versus MEGP) 500ps-TOF & rand. est. 9 36mm ps-TOF & rand. sub. 1.5 bremss. MEGP 2H SPECT ( T S SR=12mm) activity/4 and 4x20min GSO mm BGO 1.0 L[Y]SO non-tof Y activity (GBq in a liver lobe) van Elmbt... PMB 2011 Walrand... EJNMMI res 2011 kidney PRRT MIRD p19 Walrand... JNM 2010

31 Conclusions in 90 Y imaging PET supersedes commercial bremss. SPECT in all therapies PET is usable for dosimetry purpose (using local energy deposition method) TOF PET is preferable in post radioembolization delivery check State of the art MC reconstruction bremss. SPECT approaches PET performance Standard pinhole bremss. SPECT supersedes TOF-PET and could be used in catheterization room for optimization BGO (or GSO) pinhole bremss. SPECT is the optimal modality