title: Quantitation in PET using isotopes emitting prompt single gammas: application to yttrium-86.
abstract: Several yttrium-90 labelled somatostatin analogues are now available for cancer radiotherapy. After injection, a large amount of the compound is excreted via the urinary tract, while a variable part is trapped in the tumour(s), allowing the curative effect. Unfortunately, the compound may also be trapped in critical tissues such as kidney or bone marrow. As a consequence, a method for assessment of individual biodistribution and pharmacokinetics is required to predict the maximum dose that can be safely injected into patients. However, (90)Y, a pure beta(-)particle emitter, cannot be used for quantitative imaging. Yttrium-86 is a positron emitter that allows imaging of tissue uptake using a PET camera. In addition to the positron, (86)Y also emits a multitude of prompt single gamma-rays, leading to significant overestimation of uptake when using classical reconstruction methods. We propose a patient-dependent correction method based on sinogram tail fitting using an (86)Y point spread function library. When applied to abdominal phantom acquisition data, the proposed correction method significantly improved the accuracy of the quantification: the initial overestimation of background activity by 117% was reduced to 9%, while the initial error in respect of kidney uptake by 84% was reduced to 5%. In patient studies, the mean discrepancy between PET total body activity and the activity expected from urinary collections was reduced from 92% to 7%, showing the benefit of the proposed correction method.
authors.affiliation: Centre of Nuclear Medicine, University of Louvain Medical School, Brussels, Belgium. walrand@mnuc.ucl.ac.be
authors.forename: Stéphan
authors.initials: S
authors.lastname: Walrand
authors.forename: François
authors.initials: F
authors.lastname: Jamar
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mathieu
authors.forename: Joëlle
authors.initials: J
authors.lastname: De Camps
authors.forename: Max
authors.initials: M
authors.lastname: Lonneux
authors.forename: Mérence
authors.initials: M
authors.lastname: Sibomana
authors.forename: Daniel
authors.initials: D
authors.lastname: Labar
authors.forename: Christian
authors.initials: C
authors.lastname: Michel
authors.forename: Stanislas
authors.initials: S
authors.lastname: Pauwels
mesh_terms: D000465:Algorithms; D005720:Gamma Rays; D006801:Humans; D008452:Maximum Allowable Concentration; D008954:Models, Biological; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy*; D009928:Organ Specificity; D011786:Quality Control; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics / Q000652:urine; D011879:Radiotherapy Dosage; D017481:Receptors, Somatostatin / Q000378:metabolism; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed / Q000379:methods* / Q000592:standards; D014915:Whole-Body Counting / Q000295:instrumentation / Q000379:methods*; D015021:Yttrium Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use* / Q000652:urine
chemical_list: D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D015021:Yttrium Radioisotopes