title: Calibration standards for multicenter clinical trials of fluorescence spectroscopy for in vivo diagnosis.
abstract: In the context of clinical trials, calibration protocols for optical instruments that ensure measurement accuracy and the ability to carry out meaningful comparisons of data acquired from multiple instruments are required. A series of calibration standards and procedures are presented to assess technical feasibility of optical devices for cervical precancer detection. Measurements of positive and negative standards, and tissue are made with two generations of research grade spectrometers. Calibration accuracy, ability of standards to correct and account for changes in experimental conditions, and device components are analyzed. The relative frequency of measured calibration standards is investigated retrospectively using statistical analysis of trends in instrument performance. Fluorescence measurements of standards and tissue made with completely different spectrometers show good agreement in intensity and lineshape. Frequency of wavelength calibration standards is increased to every 2 h to compensate for thermal drifts in grating mount. Variations in illumination energy detected between standards and patient measurements require probe redesign to allow for simultaneous acquisition of illumination power with every patient measurement. The use of frequent and well-characterized standards enables meaningful comparison of data from multiple devices and unambiguous interpretation of experiments among the biomedical optics community.
authors.affiliation: University of Texas, Department of Biomedical Engineering, Austin, Texas 78712, USA.
authors.forename: Nena M
authors.initials: NM
authors.lastname: Marín
authors.forename: Nicholas
authors.initials: N
authors.lastname: MacKinnon
authors.forename: Calum
authors.initials: C
authors.lastname: MacAulay
authors.forename: Sung K
authors.initials: SK
authors.lastname: Chang
authors.forename: E Neely
authors.initials: EN
authors.lastname: Atkinson
authors.forename: Dennis
authors.initials: D
authors.lastname: Cox
authors.forename: Dan
authors.initials: D
authors.lastname: Serachitopol
authors.forename: Brian
authors.initials: B
authors.lastname: Pikkula
authors.forename: Michele
authors.initials: M
authors.lastname: Follen
authors.forename: Rebecca
authors.initials: R
authors.lastname: Richards-Kortum
mesh_terms: D002138:Calibration / Q000592:standards; D003952:Diagnostic Imaging / Q000295:instrumentation / Q000592:standards*; D019544:Equipment Failure Analysis / Q000592:standards; D005456:Fluorescent Dyes / Q000032:analysis* / Q000592:standards*; D015337:Multicenter Studies as Topic / Q000295:instrumentation / Q000592:standards*; D011785:Quality Assurance, Health Care / Q000379:methods / Q000592:standards*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000592:standards*; D014481:United States
chemical_list: D005456:Fluorescent Dyes