title: A direct ROI quantification method for inherent PVE correction: accuracy assessment in striatal SPECT measurements.
abstract: OBJECTIVE
  The clinical potential of striatal imaging with dopamine transporter (DAT) SPECT tracers is hampered by the limited capability to recover activity concentration ratios due to partial volume effects (PVE). We evaluated the accuracy of a least squares method that allows retrieval of activity in regions of interest directly from projections (LS-ROI).
  
  
  METHODS
  An Alderson striatal phantom was filled with striatal to background ratios of 6:1, 9:1 and 28:1; the striatal and background ROIs were drawn on a coregistered X-ray CT of the phantom. The activity ratios of these ROIs were derived both with the LS-ROI method and with conventional SPECT EM reconstruction (EM-SPECT). Moreover, the two methods were compared in seven patients with motor symptoms who were examined with N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) (FP-CIT) SPECT, calculating the binding potential (BP).
  
  
  RESULTS
  In the phantom study, the activity ratios obtained with EM-SPECT were 3.5, 5.3 and 17.0, respectively, whereas the LS-ROI method resulted in ratios of 6.2, 9.0 and 27.3, respectively. With the LS-ROI method, the BP in the seven patients was approximately 60% higher than with EM-SPECT; a linear correlation between the LS-ROI and the EM estimates was found (r=0.98, p=0.03).
  
  
  CONCLUSIONS
  The LS-ROI PVE correction capability is mainly due to the fact that the ill-conditioning of the LS-ROI approach is lower than that of the EM-SPECT one. The LS-ROI seems to be feasible and accurate in the examination of the dopaminergic system. This approach can be fruitful in monitoring of disease progression and in clinical trials of dopaminergic drugs.
authors: Clinical Pathophysiology, University of Florence, Viale Morgagni, 85, Florence, 50134, Italy. e.vanzi@dfc.unifi.it
authors: Eleonora
authors: E
authors: Vanzi
authors: Maria Teresa
authors: MT
authors: De Cristofaro
authors: Silvia
authors: S
authors: Ramat
authors: Barbara
authors: B
authors: Sotgia
authors: Mario
authors: M
authors: Mascalchi
authors: Andreas Robert
authors: AR
authors: Formiconi
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D004298:Dopamine / Q000378:metabolism; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016018:Least-Squares Analysis; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015233:Models, Statistical; D019047:Phantoms, Imaging; D011849:Radioactive Tracers; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014326:Tropanes / Q000494:pharmacology*
chemical_list: D011849:Radioactive Tracers; D014326:Tropanes; C087552:2-carbomethoxy-8-(3-fluoropropyl)-3-(4-iodophenyl)tropane; D004298:Dopamine