title: 68Ga PET/CT ventilation-perfusion imaging for pulmonary embolism: a pilot study with comparison to conventional scintigraphy.
abstract: Ventilation-perfusion (V/Q) scintigraphy is established for regional assessment of lung function in a variety of diseases, including pulmonary embolism (PE). PET/CT may further improve the accuracy and utility of V/Q imaging because of its superior technical characteristics. This pilot study assessed the feasibility of performing V/Q PET/CT and compared diagnostic utility with conventional V/Q imaging in patients with clinical suspicion of PE.
  
  
  METHODS
  Ten patients undergoing conventional V/Q imaging were prospectively recruited. PET/CT V/Q imaging was performed after inhalation of (68)Ga-carbon nanoparticles ("Galligas") and administration of (68)Ga-macroaggregated albumin. Blinded to the results of the other study, SPECT/CT (n = 9) or SPECT (n = 1) images and PET/CT images were graded by a predefined scoring system for scan quality. The number of matched or unmatched defects and diagnosis were also measured and compared with a final diagnosis.
  
  
  RESULTS
  PET image quality was equivalent or superior to SPECT in all patients, with more homogeneous radiotracer distribution for both ventilation and perfusion studies (P < 0.01). Based on conventional V/Q imaging, the diagnosis was acute PE in 2 patients and no PE in 7 patients, and the imaging results were nondiagnostic in 1 patient. The PET/CT diagnosis was concordant in 8 patients, and these studies demonstrated a similar number and distribution of matched and unmatched defects. In 1 discordant case, a patient with a SPECT/CT study that was nondiagnostic because of severe airway disease showed no PE on PET/CT. In another, the diagnosis of PE established on SPECT/CT was not reported on PET/CT 2 d later, possibly because of interval clot lysis or migration.
  
  
  CONCLUSIONS
  This intraindividual comparative study demonstrated that V/Q PET/CT with (68)Ga-labeled radiotracers can be performed in clinical practice. Compared with conventional V/Q imaging, advantages include higher-resolution, fully tomographic images with potentially better regional quantitation of lung function. The short half-life of (68)Ga also enables more flexible acquisition protocols with the option of performing ventilation studies selectively on patients with abnormal perfusion. On the basis of our results, further studies are indicated to assess whether V/Q PET/CT can improve diagnostic algorithms for patients with suspected PE.
authors: Molecular Imaging, Centre for Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Australia. michael.hofman@petermac.org
authors: Michael S
authors: MS
authors: Hofman
authors: Jean-Mathieu
authors: JM
authors: Beauregard
authors: Thomas W
authors: TW
authors: Barber
authors: Oliver C
authors: OC
authors: Neels
authors: Peter
authors: P
authors: Eu
authors: Rodney J
authors: RJ
authors: Hicks
mesh_terms: D000328:Adult; D000368:Aged; D005710:Gallium Radioisotopes; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008875:Middle Aged; D010865:Pilot Projects; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D019275:Radiopharmaceuticals; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D014692:Ventilation-Perfusion Ratio; D055815:Young Adult
chemical_list: D005710:Gallium Radioisotopes; D019275:Radiopharmaceuticals