Clinical PET/CT imaging. PET/CT - Optimization of torso imaging. CT-based attenuation correction. PET/CT torso imaging

Transcription

1 / - Optimization of torso imaging Clinical / imaging Torso FDG, 1976 Torso FDG-/, 2007 Thomas Beyer thomas.beyer@cmi-experts.com CE 30, SNM Annual Meeting, Toronto, June 2009 Software Hardware Neck Thorax Abdomen Extremities -based attenuation correction / torso imaging I(x) I Tx (x) I 0 I Tx 0 : Emission scan (30 min) : Transmissions scan (15 min) µ/! [cm 2 /g] 0.3 Bone 2"10 6 GBq Standard 0.1-1GBq 0.2 Soft tissue Rod sources 0.1 Soft tisssue [kev] 500 image bone µ image 511 kev Delbeke et al., J Nucl Med 47, 2006

2 (FDG) / imaging protocol and are complementary imaging modalities 95% of all / examinations are torso scans /! replace TX- for -based attenuation correction 1. Patient preparation/positioning 2. Topogram (Scout scan) 3. Spiral scan ( contrast?) -based corrections 4. Multi-bed emission scan AC- reconstruction High-density materials Patient motion Patient setup / protocol optimization / risk benefit! Patient referral and choice of co-axial imaging range! / protocol parameters for re-/staging, therapy response (dose!)! Pitfalls in Torso / " Patient positioning " Muscle relaxation " Respiration " contrast " High-density implants Huang et al, Radiology (251) 2009

3 ! Judicious choice of / indications / protocol optimization -indication no check indication yes -indication no yes! Patient referral and choice of co-axial imaging range Recent available? yes! / scan parameters for re-/staging, therapy response (# exposure) no Loco-regional scan! Pitfalls in Torso / " Patient positioning " Muscle relaxation " Respiration /-indication Torso scan " contrast " High-density implants Whole-body scan /: Patient exposure /: Patient exposure 120 mas / 18 mgy [1]-[6] Brix et al J Nucl Med :608pp 4 German hospitals /w / installed in Clinically relevant TLD measurements on anthropomorphic torso phantom! Effective patient dose for whole-body 18 F-FDG /: ~25 msv Dose Image quality 24 mas / 1 mgy Hany et al. Radiology 225, 2002 Topo ce / A judicious medical justification is needed with every / referral, and scan parameters have to be chosen accordingly. Bockisch et al. Mol Imag Biol 6, 2004

4 / dose adaptation Spiral, volume : Overscanning Variable attenuation: in-plane and axial and are complementary imaging modalities 95% of all / examinations are torso scans /! replace TX- for -based attenuation correction Torso-/: effective patient dose # 30 msv! Adaptive Dose Shield! CareDose4D / protocol optimization Patient positioning! Patient referral and choice of co-axial imaging range! / protocol parameters for re-/staging, therapy response (dose!)! Pitfalls in Torso / " Patient positioning " Muscle relaxation " Respiration " contrast " High-density implants

5 Patient positioning Truncated field-of-view 1 min 25 min Truncated Masked Scan time Scatter and streak artifacts Recovered Recovered Truncation artifacts 46 y/o male, 105 kg Schaller et al, Radiology 225: 497P, 2002 Muscle relaxation: 2-phase protocol and are complementary imaging modalities 95% of all / examinations are torso scans /! replace TX- for -based attenuation correction Torso-/: effective patient dose # 30 msv Torso / with arms up Reduced truncation artifacts from efov post-processing Fast torso scan Torso Neck scan Head + Neck [min] Beyer et al, JNM 45, 2004

6 Respiration and are complementary imaging modalities 95% of all / examinations are torso scans /! replace TX- for -based attenuation correction Torso-/: effective patient dose # 30 msv Torso / with arms up Reduced truncation artifacts from efov post-processing Use of advanced patient positioning aids for disease-specific imaging Exasperation! -AV vs TX-AC: mislocalization in 2% patients Accounting for respiration mismatch! Review -AC and noac images! Acquire in mid-expiration retrospective 20 s 5 min Scan time! 30% change in SUV Osman et al, JNM 44, 2003! during quiet breathing (# multi-slice )! Average/cine! Gating (internal and external marker) pro-/retrospective 30%! / + low-dose in FIBH Major pitfalls! -AC based on FIBH! - Misregistration! Biased uptake values Erdi et al, JNM 45, 2004

7 Discovery ST Discovery ST! in mid-expiration single-/dual-slice No artifacts! / during quiet breathing multi-slice Mobility Methods measure and artifacts in torso / (1! N! 16) Results markedly reduced artifacts for 6! N low Mild artifacts high low /w LBH 30% % 60% R#6 Severe artifacts AC- R%6 limited breath hold LBH /w LBH 65%&15% Beyer et al., EJNM 2003 Beyer et al., EJNMMI 32, 2005! Gated and Cardiac / Option A. Breath-hold in NormExp. List-mode with respiratory gating (belt). Each of the 4 gates contains 25% counts. RV LV c/o J Czyborra, Paderborn Challenge: Mean Tracer Activity Advantage 4D Trigger Trigger time Option B. Respiratory motion tracking with retro gating. Prospective gating of using same trigger signal (reflector). co-registered RV LV RA LA RA LA LV Bin 1 Bin 8 Free breathing Norm Expiration Courtesy of J van den Hoff, FZ Rossendorf New Application Advantage 4D Signal from RPM system X-ray on First couch position Second couch position Third couch position location Time 30% SUV variation, Lesion shift!9mm, 21% variation in lesion size Erdi et al, JNM 45, 2004 mis-registered Gould et al, JNM 48, 2007 Schwaiger, Nekolla; JNM 2006

8 contrast agents and are complementary imaging modalities 95% of all / examinations are torso scans /! replace TX- for -based attenuation correction Torso-/: effective patient dose # 30 msv Torso / with arms up Reduced truncation artifacts from efov post-processing Use of advanced patient positioning aids for disease-specific imaging Limit respiration-induced mismatch through breath-hold, avg and FIBH Cardiac / mandates simultaneous respiratory and cardiac gating New-clear : Contrast enhancement FDG-/: lymphoma 63 y/o M /w B-cell lymphoma I Eur J Rad 67, 2008 METHDOS 66 patients for WB-/ LD-,, ce (single-phase) follow-up RESULTS! accuracy (nodal status) of /: 71% and ce/: 79%! altered therapy plan in 5% (3 pats) -based attenuation correction Contrast-enhanced / may result in an artifact [4/30 patients] Antoch et al, JNM 2002 water-air water-bone mix i.v. oral 0.04 contrast contrast AC IV contrast AC L ce/: Intestinal uptake in (I) and lymphoma in (L) Positive oral contrast

9 ! Low-dose for -AC and are complementary imaging modalities 95% of all / examinations are torso scans /! replace TX- for -based attenuation correction Torso-/: effective patient dose # 30 msv 1. Patient preparation/positioning 2. Topogram (Scout scan) 3. Spiral scan ( contrast?) -based corrections 4. Multi-bed emission scan AC- reconstruction low-dose ce Torso / with arms up Reduced truncation artifacts from efov post-processing Use of advanced patient positioning aids for disease-specific imaging Limit respiration-induced mismatch through breath-hold, avg and gating Cardiac / mandates simultaneous respiratory and cardiac gating contrast enhanced / useful IV: modified contrast administration; Oral: new, water-based oral contrast High-density implants High-density implants water-air water-bone mix i.v. oral metal 0.04 contrast contrast // AC noac Hip replacement AC Contrast-enhanced / may result in an artifact [4/30 patients] Antoch et al, JNM 2002 significant artifact was observed in 50% of studies with ICD leads DiFilippo et al, JNM 2005 AC Positive oral contrast IV contrast

10 High-density implants Implants Beam hardening Scatter Image distortion -bias (HU) Insufficient localization Biased AC- False uptake Metal-induced artifacts arise more from patient motion than from high values alone! limit patient potion (VacLock, masks, comfort) Head/Neck Goerres EJNM 2002, Kamel ER 2002, Goerres DR 2003 Hip Goerres EJNM 2002 Orthopedic braces Bujenovic MIB 2003 Cardiac pacemaker Halpern JNM 2004, DiFilipo JNM 2005 and are complementary imaging modalities 95% of all / examinations are torso scans /! replace TX- for -based attenuation correction Torso-/: effective patient dose # 30 msv Torso / with arms up Reduced truncation artifacts from efov post-processing Use of advanced patient positioning aids for disease-specific imaging Limit respiration-induced mismatch through breath-hold, avg and gating Cardiac / mandates simultaneous respiratory and cardiac gating contrast enhanced / useful IV: modified contrast administration; Oral: new, water-based oral contrast High-density implants: review noac/ac/ images carefully / acquisition guidelines New-Clear /: Protocol optimization retro Truncated FOV Positioning aids ext-fov Patient motion Positioning aids 2-phase protocol - Delbeke et al. J Nucl Med 47, 2006 Respiration Breath hold Gating Cardiac motion Gating AC* Metal implants - MAR IV contrast Modified injection - Oral contrast Water-based - Krause et al. Nuklearmedizin 46, 2007