title: Improving quantitative dosimetry in (177)Lu-DOTATATE SPECT by energy window-based scatter corrections.
abstract: OBJECTIVE
  Patient-specific dosimetry of lutetium-177 ((177)Lu)-DOTATATE treatment in neuroendocrine tumours is important, because uptake differs across patients. Single photon emission computer tomography (SPECT)-based dosimetry requires a conversion factor between the obtained counts and the activity, which depends on the collimator type, the utilized energy windows and the applied scatter correction techniques. In this study, energy window subtraction-based scatter correction methods are compared experimentally and quantitatively.
  
  
  METHODS
  (177)Lu SPECT images of a phantom with known activity concentration ratio between the uniform background and filled hollow spheres were acquired for three different collimators: low-energy high resolution (LEHR), low-energy general purpose (LEGP) and medium-energy general purpose (MEGP). Counts were collected in several energy windows, and scatter correction was performed by applying different methods such as effective scatter source estimation (ESSE), triple-energy and dual-energy window, double-photopeak window and downscatter correction. The intensity ratio between the spheres and the background was measured and corrected for the partial volume effect and used to compare the performance of the methods.
  
  
  RESULTS
  Low-energy collimators combined with 208 keV energy windows give rise to artefacts. For the 113 keV energy window, large differences were observed in the ratios for the spheres. For MEGP collimators with the ESSE correction technique, the measured ratio was close to the real ratio, and the differences between spheres were small.
  
  
  CONCLUSIONS
  For quantitative (177)Lu imaging MEGP collimators are advised. Both energy peaks can be utilized when the ESSE correction technique is applied. The difference between the calculated and the real ratio is less than 10% for both energy windows.
authors: aDepartment of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark bDepartment of Clinical Physics, Spaarne Hospital, Hoofddorp cDepartment of Medical Physics, Catharina Hospital, Eindhoven, The Netherlands.
authors: Robin
authors: R
authors: de Nijs
authors: Vera
authors: V
authors: Lagerburg
authors: Thomas L
authors: TL
authors: Klausen
authors: Søren
authors: S
authors: Holm
mesh_terms: D007091:Image Processing, Computer-Assisted / Q000379:methods*; D015282:Octreotide / Q000031:analogs & derivatives*; D009942:Organometallic Compounds; D019047:Phantoms, Imaging; D011874:Radiometry; D012542:Scattering, Radiation; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D009942:Organometallic Compounds; C447941:lutetium Lu 177 dotatate; D015282:Octreotide