title: Optimization of the accuracy of retention and washout measurements of 99mTc-Sestamibi from breast tumours using an anthropomorphic phantom.
abstract: Quantifying the retention or washout of (99m)Tc-Sestamibi (MIBI) in breast tumours in vivo may provide a basis for predicting the chemotherapy response. The aim of this study is to investigate the variations and limitations of the different methods used to quantify these parameters. A phantom was developed that allowed the modelling of MIBI pharmacokinetics in both the breast tumour and normal breast tissue. Washout and retention were calculated from tumour uptake values based on (1) background corrected counts or (2) total counts in the tumour region of interest (ROI), or (3) tumour to background ratios (TBR), or (4) normalized TBR (nTBR). Method 1 was the most accurate method of quantification whilst method 3 was the most inaccurate. The accuracy of method 1 was independent of the times at which images were acquired, but three sources of error are identified involving incorrect background selection, ROI reproducibility and inconsistent temporal separation of images. In conclusion, background subtracted tumour counts should be used in the calculation of MIBI retention or washout. Accurate results are dependent on selecting the appropriate background, drawing consistent ROIs and using reproducible time intervals between images.
authors.affiliation: Department of Medical Physics, Lincoln County Hospital, Lincoln, LN2 5QY, UK. chris.marshall@ulh.nhs.uk
authors.forename: Christopher
authors.initials: C
authors.lastname: Marshall
authors.forename: Peter A
authors.initials: PA
authors.lastname: Griffiths
mesh_terms: D000465:Algorithms; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D019047:Phantoms, Imaging; D011865:Radioisotope Dilution Technique; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics*
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi