Measurement quality assurance plans for optical devices should be a mandatory part of grant funding submissions and should explicitly affect scoring during review. These should include calibration strategy, standards selection strategy, performance verification plan, performance validation plan and thorough preclinical performance validation. A multispectral digital colposcope (MDC) has been designed to collect image data from patients as part of an NIH sponsored clinical trial, based on a technology assessment model. Calibration strategy, standards selection and performance verification methods are presented that may be used as a template for smaller groups or more limited studies. With the MDC, red green and blue fluorescence images are captured under ultraviolet light excitation and red and green images are captured under blue light excitation. Red, green and blue reflectance images are captured under broadband white light illumination from a metal halide lamp in three modes - ordinary reflectance, and with polarized illumination in combination with parallel and cross-polarized filtered imaging. The highly automated system was designed to collect images of the cervix prior to and following the application of acetic acid. Three systems have been built and will be operated in clinics in Vancouver, Canada, Houston, Texas and other locations in the developed and developing world including Nigeria. The system is designed with a comprehensive set of calibration and performance verification standards, based on our experience with large scale multi-center spectroscopy clinical trials and measurements are made frequently prior to and following patient measurements. Automated performance verification procedures are being designed based on measurements made during pilot studies to facilitate larger clinical trials.

With the development of fluorescence spectroscopy, multicenter clinical trials are becoming more common both in the academic and commercial arenas. To ensure the quality of quantitative and device independent results, standardization of the tissue spectra is essential for the comparison of data from various groups. An added concern is the potential degradation of instrumentation during a trial which may affect the instrument's ability to accurately represent the tissue spectra. Our group has recently completed a Phase II clinical trial for the detection of cervical neoplasia using two different generations of spectroscopic devices at multiple sites. Both positive and negative optical standards were used to calibrate the tissue spectra as well as aid in the diagnosis of potential instrumentation problems during the trial. We have also conducted a cross validation study of fiber optic probes, spectroscopic devices, and optical standards for the latest generation of devices. The spectroscopic data of optical standards were analyzed for both the clinical trial and cross validation studies. Results demonstrated perceptible differences in optical standards data between the two generations of spectroscopy devices in the clinical trial, as well as the cross validation study with multiple devices of the same generation. Although the spectra were unexpectedly different, tissue spectra measured with the different systems can be empirically corrected by use of the various optical standards. Device performance during the clinical trial also was a concern; however, with the use of optical calibration standards, instrumentation problems were easily identified. To eliminate the problems associated with instrumentation, we have recently developed real-time quality assurance software to assess the optical calibration standards immediately after acquisition.

BACKGROUND:The diagnostic ability of algorithms developed for the Multispectral Digital Colposcope (MDC) is highly dependent on the quality of the image. The field of objective medical image quality analysis has great potential but has not been well exploited. Various researchers have reported different measures of image quality but with an existence of a reference image. The quality of an image can be attributed to several sources of errors, a few of which would be inclusion of presence of extraneous components, improper illumination, or an image out of focus. This can be due to motion artifact or the region of interest out of the focal plane.METHODS:With spectroscopic measurements, assessment of data quality has been used by our group in the past to avoid hardware errors at the time of acquisition. We are currently developing algorithms that will help identify hardware and acquisition errors to the clinician in under a few seconds.RESULTS:Minimizing these errors not only provides quality images for a diagnostic algorithm, but reduces the necessity for complex and time intensive post-processing software for enhancing the images.CONCLUSION:We propose a no reference image quality system specifically designed for MDC that can be modified to similar spectroscopic imaging applications.

We report on a study designed to assess variability among three different fluorescence spectroscopy devices, four fiber optic probes, and three sets of optical calibration standards to better understand the reproducibility of measurements and interdevice comparisons of fluorescence spectroscopic data intended for clinical diagnostic use. Multiple measurements are acquired from all sets of standards using each combination of spectrometer, fiber optic probe, and optical standard. Data are processed using standard calibration methods to remove instrument-dependant responses. Processed spectra are analyzed using an analysis of variance to assess the percent variance explained by each factor that was statistically significant. Analysis of processed data confirms statistically significant differences among the spectrometers and fiber optic probes. However, no differences are found when varying calibration standards or measurement date and time. The spectrometers and fiber optic probes are significant sources of variability, but appropriate data processing substantially reduces these effects. Studies of inter- and intradevice variability are important methodological issues for optical device trials and must be included in the quality assurance studies for the clinical trial design.

BACKGROUND:Devices using fluorescence spectroscopy to differentiate high grade squamous intraepithelial lesions from normal tissue in the cervix have shown some diagnostic efficacy. Measurements from these devices produce large amounts of complex, multi-factored data. The purpose of this study is to isolate the effects of the particular care providers and equipment operators who are involved in taking measurements. METHODS:Data from spectroscopic measurements of the Phase II study of 850 patients with abnormal Papancicolau smears were used. The data were subject to a Principal Components Analysis and to MANOVA to control for variables that are known to affect outcomes. RESULTS:The analysis showed significant provider effects from both devices and significant operator effects from one device. CONCLUSION:We will repeat a similar analysis on data from a screening trial, on the combined diagnostic and screening study, and on the reflectance data. In the future, we hope to be able to design devices that address provider and operator effects.

The cochlea is the mammalian organ of hearing. Its predominant vibratory element, the basilar membrane, is tonotopically tuned, based on the spatial variation of its mass and stiffness. The constituent collagen fibers of the basilar membrane affect its stiffness. Laser irradiation can induce collagen remodeling and deposition in various tissues. We tested whether similar effects could be induced within the basilar membrane. Trypan blue was perfused into the scala tympani of anesthetized mice to stain the basilar membrane. We then irradiated the cochleas with a 694-nm pulsed ruby laser at 15 or 180 Jcm(2). The mice were sacrificed 14 to 16 days later and collagen organization was studied. Polarization microscopy revealed that laser irradiation increased the birefringence within the basilar membrane in a dose-dependent manner. Electron microscopy demonstrated an increase in the density of collagen fibers and the deposition of new fibrils between collagen fibers after laser irradiation. As an assessment of hearing, auditory brainstem response (ABR) thresholds were found to increase moderately after 15 Jcm(2) and substantially after 180 Jcm(2). Our results demonstrate that collagen remodeling and new collagen deposition occurs within the basilar membrane after laser irradiation in a similar fashion to that found in other tissues.

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.

Introduction. A study was designed to assess variability between different fluorescence spectroscopy devices. Measurements were made with all combinations of three devices, four probes, and thee sets of standards trays. Additionally, we made three measurements on the same day over 2 days for the same combination of device, probe, and standards tray to assess reproducibility over a day and across days.Materials and methods. The devices consisted of light sources, fiberoptics, and cameras. We measured thirteen standards and present the data from the frosted cuvette, water, and rhodamine standards. A preliminary analysis was performed with the data that were wavelength calibrated and background subtracted; however, the system has not been corrected for systematic intensity variations caused by the devices. Two analyses were performed on the rhodamine, water, and frosted cuvette standards data. The first one is based on first clustering the measurements and then looking for association between the 5 factors (device, probe, standards tray, day, measurement number) using chi-squared tests on the cross-tabulation of cluster and factor level. This showed that only device and probe were significant. We then did an analysis of variance to assess the percent variance explained by each factor that was significant from the chi-squared analysis.Results. The data were remarkably similar across the different combinations of factors. The analysis based on the clusters showed that sometimes devices alone, probes alone, but most often combinations of device and probe caused significant differences in measurements. The analysis showed that time of day, location of device, and standards trays do not vary significantly; whereas the devices and probes account for differences in measurement. We expected this type of significance using unprocessed data since the processing corrects for differences in devices. However, this analysis on raw data is useful to explore what combination of device and probe measurements should be targeted for further investigation. This experiment affirms that online quality control is necessary to obtain the best excitation-emission matrices from optical spectroscopy devices.Conclusion. The fact that the device and probe are the primary sources of variability indicates that proper correction for the transfer function of the individual devices should make the measurements essentially equivalent. (C) 2005 Elsevier Inc. All rights reserved.