title: Impact of a new respiratory amplitude-based gating technique in evaluation of upper abdominal PET lesions.
abstract: PET acquisition requires several minutes which can lead to respiratory motion blurring, to increase partial volume effect and SUV under-estimation. To avoid these artifacts, conventional 10-min phase-based respiratory gating (PBRG) can be performed but is time-consuming and difficult with a non-compliant patient. We evaluated an automatic amplitude-based gating method (AABG) which keeps 35% of the counts at the end of expiration to minimize respiratory motion. We estimated the impact of AABG on upper abdominal lesion detectability, quantification and patient management.
  
  
  METHODS
  We consecutively included 31 patients (82 hepatic and 25 perihepatic known lesions). Each patient underwent 3 acquisitions on a Siemens Biograph mCT (4 rings and time-of-flight): a standard free-breathing whole-body (SWB, 5-7 steps/2.5 min per step, 3.3±0.4 MBq/kg of 18F-FDG), a 10-min PBRG with six bins and a 5-min AABG method. All gated acquisitions were performed with an ANZAI respiratory gating system. SUVmax and target to background ratio (TBR, defined as the maximum SUV of the lesion divided by the mean SUV of a region of interest drawn in healthy liver) were compared.
  
  
  RESULTS
  All 94 lesions in SWB images were detected in the gated images. 10-min PBRG and 5-min AABG acquisitions respectively revealed 9 and 13 new lesions and relocated 7 and 8 lesions. Four lesions revealed by 5-min AABG were missed by 10-min PBRG in 3 non-compliant patients. Both gated methods failed to relocate 2 lesions seen on SWB acquisition. Compared to SWB, TBR increased significantly with 10-min PBRG and with 5-min AABG (respectively 41±59%, p=4.10-3 and 66±75%, p=6.10-5) whereas SUVmax did not (respectively 14±43%, p=0.29 with 10-min PBRG, and 24±46%, p=0.11 with 5-min AABG).
  
  
  CONCLUSIONS
  The AABG is a fast and a user-friendly respiratory gating method to increase detectability and quantification of upper abdominal lesions compared to the conventional PBRG procedure and the SWB acquisition.
authors: Department of Nuclear Medicine, Centre Hospitalier Princesse Grace, Monaco, Monaco. Electronic address: axel.vandergucht@gmail.com.
authors: Axel
authors: A
authors: Van Der Gucht
authors: Department of Medical Physics, Centre Hospitalier Princesse Grace, Monaco, Monaco.
authors: Benjamin
authors: B
authors: Serrano
authors: Department of Nuclear Medicine, Centre Hospitalier Princesse Grace, Monaco, Monaco.
authors: Florent
authors: F
authors: Hugonnet
authors: Department of Nuclear Medicine, Centre Hospitalier Princesse Grace, Monaco, Monaco.
authors: Benoît
authors: B
authors: Paulmier
authors: Department of Medical Physics, Centre Hospitalier Princesse Grace, Monaco, Monaco.
authors: Nicolas
authors: N
authors: Garnier
authors: Department of Nuclear Medicine, Centre Hospitalier Princesse Grace, Monaco, Monaco.
authors: Marc
authors: M
authors: Faraggi
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging*; D000008:Abdominal Neoplasms / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009038:Motion; D049268:Positron-Emission Tomography / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: PET; Respiratory gating; Respiratory motion; SUV; Upper abdominal lesions