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DeepSpectra: An end-to-end deep learning approach for quantitative spectral analysis
摘要： Learning patterns from spectra is critical for the development of chemometric analysis of spectroscopic data. Conventional two-stage calibration approaches consist of data preprocessing and modeling analysis. Misuse of preprocessing may introduce artifacts or remove useful patterns and result in worse model performance. An end-to-end deep learning approach incorporated Inception module, named DeepSpectra, is presented to learn patterns from raw data to improve the model performance. DeepSpectra model is compared to three CNN models on the raw data, and 16 preprocessing approaches are included to evaluate the preprocessing impact by testing four open accessed visible and near infrared spectroscopic datasets (corn, tablets, wheat, and soil). DeepSpectra model outperforms the other three convolutional neural network models on four datasets and obtains better results on raw data than in preprocessed data for most scenarios. The model is compared with linear partial least square (PLS) and nonlinear artificial neural network (ANN) methods and support vector machine (SVR) on raw and preprocessed data. The results show that DeepSpectra approach provides improved results than conventional linear and nonlinear calibration approaches in most scenarios. The increased training samples can improve the model repeatability and accuracy.
关键词： model accuracy,Inception,convolutional neural network,chemometrics,repeatability
更新于2025-09-23 15:23:52
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Repeatability assessment of biometric measurements with different refractive states and age using a swept-source biometer
摘要： Background: We aim to assess if refractive error or age may influence the repeatability of measurements using a swept-source biometer. Methods: A total of 61 subjects were evaluated with IOLMaster 700 acquiring measurements of axial length (AL), central corneal thickness (CCT), white-to-white distance (WTW), anterior aqueous depth (AQD), lens thickness (LT), and keratometry (K) readings. Repeatability was evaluated classifying the sample according to the refractive state and age by the calculation of the within-subject standard deviation (Sw), coefficient of repeatability, and intraclass correlation coefficient. Results: Very similar Sw was acquired among groups for AL, CCT, and WTW. Differences found for AQD, LT, keratometry and astigmatism among refractive and age groups were not clinically significant. Refractive groups obtained a Sw for AQD between 0.016 and 0.026, while for LT was between 0.023 and 0.029 mm. Besides, Sw showed values from 0.014 to 0.029 mm for keratometry. Age groups obtained a Sw of 0.025 and 0.016 mm for AQD, and 0.029 and 0.018 mm for LT, respectively. Sw was 0.019 vs 0.018 mm for K1, 0.014 vs 0.031 mm for K2. Conclusions: IOLMaster 700 showed good repeatability for biometric and keratometric parameters in eyes classified according to their refractive error or age.
关键词： anterior segment,Repeatability,biometry,swept-source biometer,refractive error,age
更新于2025-09-23 15:23:52
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Repeatability and reproducibility of retinal nerve fibre layer thickness measurements with the iVue-100 optical coherence tomographer
摘要： Background: Accurate and repeatable measurements of the retinal nerve fibre layer (RNFL) thickness are important in the diagnosis and management of glaucoma and other disorders. Objective: To assess the repeatability and reproducibility of the iVue-100 optical coherence tomographer (OCT). Methods: The thickness of the RNFL was measured for 50 healthy participants using the iVue-100 OCT. Although both eyes per participant were measured, only right eyes were analysed here. Repeatability and reproducibility of the iVue-100 OCT were assessed using the intraclass correlation coefficient (ICC), coefficient of variation (CoV), paired t-tests and Bland-Altman analysis. Results: Good intra-observer repeatability was obtained as indicated by the ICC of observer 1 (range: 0.941 - 0.976) and observer 2 (range: 0.829 – 0.953) as well by the CoV of observer 1 (range: 0.098 – 0.137) and observer 2 (0.091 – 0.132). In terms of inter-observer reproducibility, significant differences (p< 0.05) in mean measurements between the observers were noted for the average RNFL readings and in the superior and inferior quadrants as assessed with paired t-tests. Even though significant inter-session differences were found for the average RNFL thickness and the superior quadrant (p = 0.003 and p = 0.013, respectively), excellent ICCs were obtained for inter-session reproducibility (range: 0.914 – 0.979). Conclusion: The iVue-100 OCT demonstrated good repeatability and reproducibility for RNFL thickness measurements.
关键词： Retinal nerve fibre layer thickness,optical coherence tomography,repeatability,iVue-100 OCT,reproducibility
更新于2025-09-23 15:22:29
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Repeatability of wavefront measurements in pseudophakic eyes; Reproduzierbarkeit von Wellenfrontmessungen bei pseudophaken Augen;
摘要： Higher- as well as lower-order aberrations influence uncorrected visual quality after successful cataract surgery. Different techniques are used for measuring ocular wavefront aberrations, such as Hartmann–Shack aberrometers, laser ray tracing aberrometers, and automatic retinoscopy. The aim of our study was to assess the repeatability of a Hartmann–Shack aberrometer measurement in a pseudophakic study population. Methods This prospective study included patients who underwent cataract surgery 1 month prior to recruitment. Three consecutive Hartmann–Shack measurements (WASCA, Carl Zeiss Meditec AG, Germany) were performed after pharmacological dilation of the pupil. Results In total, 156 eyes of 156 patients were included. Repeatability of measurements was good in pseudophakic eyes for all Zernike polynomials up to the fourth order. The median values of the SD of all three measurements ranged between 0.042 and 0.125 for the Tecnis intraocular lens (IOL) and 0.028 and 0.148 for the CT Asphina 409MP IOL. Intraclass correlation coefficients ranged between 0.793592 and 0.97955 for the Tecnis IOL and between 0.673894 and 0.989172 for the CT Asphina 409MP IOL. Conclusion Postoperative unsatisfactory image quality, sometimes reported by patients, despite good defocus and astigmatism values calls for examination of higher-order aberrations. Hartmann–Shack measurements with the WASCA offers good repeatability in pseudophakic patients and, therefore, fulfills this task.
关键词： Repeatability,Higher-order aberrations,Hartmann–Shack aberrometry
更新于2025-09-23 15:22:29
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Variability and repeatability of quantitative uptake metrics in [ <sup>18</sup> F]FDG PET/CT imaging of non-small cell lung cancer: impact of segmentation method, uptake interval, and reconstruction protocol
摘要： OBJECTIVES: There is increased interest in various new quantitative uptake metrics beyond standardized uptake value (SUV) in oncology PET/CT studies. The purpose of this study is to investigate the variability and test-retest repeatability (TRT) of metabolically active tumor volume (MATV) measurements and several other new quantitative metrics in non-small cell lung cancer (NSCLC) using [18F]FDG PET/CT with different segmentation methods, user interactions, uptake intervals, and reconstruction protocols. METHODS: Ten advanced NSCLC patients received two whole-body [18F]FDG PET/CT scans at both 60 and 90 min post-injection. PET data were reconstructed with four different protocols. Eight segmentation methods were applied to delineate lesions with and without a tumor mask. MATV, maximum and mean SUV (SUVmax, SUVmean), total lesion glycolysis (TLG), and intralesional heterogeneity features were derived. Variability and repeatability were evaluated using a generalized estimating equations statistical model with Bonferroni correction for multiple comparisons. The statistical model, including interaction between uptake interval and reconstruction protocol, was applied individually to the data obtained from each segmentation method. RESULTS: Without masking, none of the segmentation methods could delineate all lesions correctly. MATV was affected by both uptake interval and reconstruction settings for most segmentation methods. Similar observations were obtained for the uptake metrics SUVmax, SUVmean, TLG, homogeneity, entropy, and zone percentage. No effect of uptake interval was observed on TRT metrics, while the reconstruction protocol affected the TRT of SUVmax. Overall, segmentation methods showing poor quantitative performance in one condition showed better performance in other (combined) conditions. For some metrics, a clear statistical interaction was found between the segmentation method and both uptake interval and reconstruction protocol. CONCLUSIONS: All segmentation results need to be reviewed critically. MATV and other quantitative uptake metrics, as well as their TRT, depend on segmentation method, uptake interval, and reconstruction protocol. To obtain quantitative reliable metrics, with good TRT performance, the optimal segmentation method depends on local imaging procedure, the PET/CT system and/or reconstruction protocol. Rigid harmonization of imaging procedure and PET/CT performance will be helpful in mitigating this variability.
关键词： non-small cell lung cancer,segmentation method,positron emission tomography imaging,repeatability,Variability
更新于2025-09-23 15:21:01
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Repeatability of High Resolution Laser Doppler Images of the hands in patients with systemic sclerosis and secondary Raynaud's phenomenon
摘要： Objectives The objective of the study was to establish the repeatability of baseline diagnostic images of the dorsum of the hands acquired using a high resolution Laser Doppler imager in patients with Raynaud’s phenomenon secondary to Systemic Sclerosis (SSc). Methods The dorsal side of the hands of 22 patients (8 male 14 female) , age range 29-73, median 62, with SSc and secondary Raynaud’s phenomenon were imaged over two consecutive days at approximately the same time using a Moor Instruments High Resolution Laser Doppler imaging unit. The images were analysed by taking regions of interest at discrete locations in the images to calculate dimensionless values of flux(PU). Repeatability of the diagnostic investigation was assessed by using methods described by Bland and Altman and by also plotting the results from visit 1 against visit 2 and calculating the line of best fit. Results and Conclusions Based on the criteria that 95% of all measurement differences should be within a factor of 1.96 of the standard deviations of the mean values, then high resolution Laser Doppler Imaging technique is probably repeatable when acquiring and analysing baseline images of patients with Raynaud’s phenomenon secondary to SSc. However a larger study with more patients is required to prove this conclusively - as only data from 19 patients was analysed [3 patients were not included due to technical issues] - and was therefore susceptible to marked clinical variations in patients presenting on different days for the investigations.
关键词： Laser Doppler imaging,Repeatability,Scleroderma,Raynaud’s
更新于2025-09-23 15:19:57
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Improved repeatability of dynamic contrast-enhanced MRI using the complex MRI signal to derive arterial input functions: a test-retest study in prostate cancer patients
摘要： Purpose: The arterial input function (AIF) is a major source of uncertainty in tracer kinetic (TK) analysis of dynamic contrast‐enhanced (DCE)‐MRI data. The aim of this study was to investigate the repeatability of AIFs extracted from the complex signal and of the resulting TK parameters in prostate cancer patients. Methods: Twenty‐two patients with biopsy‐proven prostate cancer underwent a 3T MRI exam twice. DCE‐MRI data were acquired with a 3D spoiled gradient echo sequence. AIFs were extracted from the magnitude of the signal (AIFMAGN), phase (AIFPHASE), and complex signal (AIFCOMPLEX). The Tofts model was applied to extract Ktrans, kep and ve. Repeatability of AIF curve characteristics and TK parameters was assessed with the within‐subject coefficient of variation (wCV). Results: The wCV for peak height and full width at half maximum for AIFCOMPLEX (7% and 8%) indicated an improved repeatability compared to AIFMAGN (12% and 12%) and AIFPHASE (12% and 7%). This translated in lower wCV values for Ktrans (11%) with AIFCOMPLEX in comparison to AIFMAGN (24%) and AIFPHASE (15%). For kep, the wCV was 16% with AIFMAGN, 13% with AIFPHASE, and 13% with AIFCOMPLEX. Conclusion: Repeatability of AIFPHASE and AIFCOMPLEX is higher than for AIFMAGN, resulting in a better repeatability of TK parameters. Thus, use of either AIFPHASE or AIFCOMPLEX improves the robustness of quantitative analysis of DCE‐MRI in prostate cancer.
关键词： arterial input function,dynamic contrast‐enhanced MRI,repeatability,prostate cancer,tracer kinetic analysis,complex signal
更新于2025-09-19 17:15:36
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Test–Retest Repeatability of Microperimetry at the Border of Deep Scotomas
摘要： PURPOSE. The purpose of this study was to examine the test–retest repeatability of microperimetric sensitivity at the border of deep scotomas. METHODS. Thirty normal participants underwent two examinations, each on the Macular Integrity Assessment (MAIA) microperimeter and on the MP-1 microperimeter (four examinations in total). A customized stimulus pattern allowed microperimetric sensitivity to be measured at the border of the optic nerve head (ONH), which acted as a model for the border of a deep scotoma—and also at the macular and peripapillary region. RESULTS. There were no significant changes in average point-wise sensitivity (PWS) values between the two examinations for all three regions using the MAIA microperimeter (P ≥ 0.262). The PWS coefficient of repeatability (CoR) was ±12.99 dB at the border of the ONH, which was significantly larger than points in the macular and peripapillary regions (P > 0.001). A significant decrease in average PWS, using the MP-1 microperimeter at the macular and peripapillary region (P < 0.001), meant that the PWS CoR could not be determined in these regions. No significant changes in average PWS were observed at the border of the ONH (P = 0.223), and the PWS CoR was ±7.52 dB in this region. CONCLUSIONS. Microperimetric test–retest repeatability at the border of a deep scotoma was worse than at other areas of normal retina, and this highlights the limitation of applying a single estimate of test–retest repeatability to determine whether significant functional decline has occurred at the border of a deep scotoma.
关键词： repeatability,test–retest,microperimetry,scotoma
更新于2025-09-19 17:15:36
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Comparison of accuracies of an intraoral spectrophotometer and conventional visual method for shade matching using two shade guide systems
摘要： Background and Objectives: This in vitro study compared the shade matching abilities of an intraoral spectrophotometer and the conventional visual method using two shade guides. The results of previous investigations between color perceived by human observers and color assessed by instruments have been inconclusive. The objectives were to determine accuracies and interrater agreement of both methods and effectiveness of two shade guides with either method. Methods: In the visual method, 10 examiners with normal color vision matched target control shade tabs taken from the two shade guides (VITAPAN Classical? and VITAPAN 3D Master?) with other full sets of the respective shade guides. Each tab was matched 3 times to determine repeatability of visual examiners. The spectrophotometric shade matching was performed by two independent examiners using an intraoral spectrophotometer (VITA Easyshade?) with five repetitions for each tab. Results: Results revealed that visual method had greater accuracy than the spectrophotometer. The spectrophotometer; however, exhibited significantly better interrater agreement as compared to the visual method. While VITAPAN Classical shade guide was more accurate with the spectrophotometer, VITAPAN 3D Master shade guide proved better with visual method. Conclusion: This in vitro study clearly delineates the advantages and limitations of both methods. There were significant differences between the methods with the visual method producing more accurate results than the spectrophotometric method. The spectrophotometer showed far better interrater agreement scores irrespective of the shade guide used. Even though visual shade matching is subjective, it is not inferior and should not be underrated. Judicious combination of both techniques is imperative to attain a successful and esthetic outcome.
关键词： spectrophotometer,shade guide,Accuracy,dental shade matching,repeatability
更新于2025-09-19 17:15:36
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The influence of minimal misalignment on the repeatability of PET images examined by the repositioning of point sources
摘要： Objective: We aimed to evaluate the influence of the minimal misalignment of the hot spot on the repeatability of PET images using the repositioning of point sources. Methods: Point sources with an inner-diameter of 1 mm were made with 1μL of 18F solution. Seven point sources were placed on the x-axis in the field-of-view. For fixed position imaging, PET data were acquired for 10 min 5 times serially. For variable position imaging, PET data were acquired for 10 minutes each with the point sources placed at 0 mm, ±0.5 mm, and ±1.0 mm in the x-axis direction. The data were reconstructed using ordered-subsets expectation maximization (OSEM) and OSEM with point-spread function (OSEM+PSF) algorithms. The image matrix was 128×128, 200×200, 256×256, 400×400, and 512×512 pixels. The normalized maximum count (rMax), the variation of rMax (CVmax) and full width at half maximum (FWHM) were analyzed. Results: The hot spots on OSEM images far from the center became faint and broad, while those on the OSEM+PSF images became small and dense. Although the rMax was overestimated at the 5 cm position on OSEM image, those at other positions were overestimated on OSEM+PSF images with a matrix size of ≥256×256. The rMax showed a similar pattern in fixed and variable position images. The CVmax in fixed position OSEM images were <2%, irrespective of the matrix size. In contrast, the CVmax in variable position images were higher in comparison to fixed position images. The CVmax of the OSEM+PSF images were higher in comparison to OSEM images. The FWHM increased at positions far from the center on OSEM image, while that was stable at all positions on OSEM+PSF images. Conclusion: The repeatability of the small hot spot was affected by the minimal misalignment, especially on the OSEM+PSF images. Precise positioning is necessary if PET is to be used as a biomarker. Professions should recognize that the PSF correction deteriorates the repeatability of the small hot spot although it improves the spatial resolution of PET images.
关键词： repositioning,repeatability,point-spread function,PET/CT
更新于2025-09-19 17:15:36