Browsing by Subject "Repeatability"
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Item Open Access Intrasession Repeatability of OCT Angiography Parameters in Neurodegenerative Disease.(Ophthalmology science, 2023-06) Akrobetu, Dennis Y; Robbins, Cason B; Ma, Justin P; Soundararajan, Srinath; Quist, Michael S; Stinnett, Sandra S; Moore, Kathryn PL; Johnson, Kim G; Liu, Andy J; Grewal, Dilraj S; Fekrat, SharonPurpose
To assess the intrasession repeatability of macular OCT angiography (OCTA) parameters in Alzheimer's disease (AD), mild cognitive impairment (MCI), Parkinson's disease (PD), and normal cognition (NC).Design
Cross sectional study.Subjects
Patients with a clinical diagnosis of AD, PD, MCI, or NC were imaged. Images with poor quality and of those with diabetes mellitus, glaucoma, or vitreoretinal disease were excluded from analysis.Methods intervention or testing
All participants were imaged using the Zeiss Cirrus HD-5000 with AngioPlex (Carl Zeiss Meditec, Software Version 11.0.0.29946) and repeat OCTA images were obtained for both eyes. Perfusion density (PFD), vessel density (VD), and Foveal avascular zone (FAZ) area were measured from 3 × 3 mm and 6 × 6 mm OCTA images centered on the fovea using an ETDRS grid overlay.Main outcome measures
Intraclass correlation coefficients were used to quantify repeatability of PFD, VD, and FAZ area measurements obtained from imaging.Results
3 × 3 mm scans of 22 AD, 40 MCI, 21 PD, and 26 NC participants and 6 × 6 mm scans of 29 AD, 44 MCI, 29 PD, and 30 NC participants were analyzed. Repeatability values ranged from 0.64 (0.49-0.82) for 6 × 6 mm PFD in AD participants to 0.87 (0.67-0.92) for 3 × 3 mm PFD in AD participants. No significant differences were observed in repeatability between NC participants and those with neurodegenerative disease.Conclusions
Overall, similar OCTA repeatability was observed between NC participants and those with neurodegeneration. Regardless of diagnostic group, macular OCTA metrics demonstrated moderate to good repeatability.Financial disclosures
The authors have no proprietary or commercial interest in any materials discussed in this article.Item Open Access PET Lesion Quantitation Noise Estimates from Sub-Scan Data(2016) Brotman, David WilliamThe use of Positron Emission Tomography (PET) has been suggested as a tool for quantitative biological measurement to determine outcomes of therapy, diagnosis, and novel drugs, through measures of tumor change from repeated PET scans. However, inherent variability (due to technical and biological effects) results in different measurements even where there is no change in the tumor. This study evaluates the random component of variability due to the limited number of counts acquired in the scans. We have proposed using PET raw list mode data as a way to determine the variability associated with the scanner, including the nonlinear processes like the max standard uptake value (SUVmax) and iterative reconstruction processes. PET simulation (digitally simulated oval phantom), PET list mode whole body (WB) and tapering phantom (TP) data in addition to clinical data (prostate cancer patients) were used to divide a larger acquisition into sequentially smaller half scan durations to compare their variabilities with the ideal Poisson variability in a PET system. Poisson statistics predicts that variability decreases as 1/sqrt(n) of the number of counts (or scan duration).
The WB phantom contained 21 spheres (six 3 cm, six 2 cm, nine 1 cm), the TP contained spheres (thirty-two 1 cm spheres and twenty-four 2 cm spheres) distributed over four levels. Simulated data was used as an ideal scenario with larger statistical power, and showed excellent agreement (<10%) with its Poisson calculation using 4 mm
of smoothing. Through the use of simulation and phantom data variability among measurements using SUVmax have been shown. This data has demonstrated that maximum ROI methodology on iteratively reconstructed images retains the Poisson nature of PET coincidence counts in spite of the potential nonlinearities of both the reconstruction method and the ROI methodology.
Item Open Access Repeatability of Peripapillary OCT Angiography in Neurodegenerative Disease.(Ophthalmology science, 2021-12) Ma, Justin P; Robbins, Cason B; Stinnett, Sandra S; Johnson, Kim G; Scott, Burton L; Grewal, Dilraj S; Fekrat, SharonPurpose
To assess the repeatability of peripapillary OCT angiography (OCTA) in those with Alzheimer disease (AD), mild cognitive impairment (MCI), Parkinson disease (PD), or normal cognition.Design
Cross-sectional.Participants
Patients with a clinical diagnosis of AD, MCI, PD, or normal cognition were imaged. Those with glaucoma, diabetes mellitus, vitreoretinal pathology, and poor-quality images were excluded.Methods
Each eligible eye of each participant underwent 2 OCTA 4.5 × 4.5-mm peripapillary scans in a single session using a Zeiss Cirrus HD-OCT 5000 with AngioPlex (Carl Zeiss Meditec). The Zeiss software (v11.0.0.29946) quantified measures of perfusion in the radial peripapillary capillary (RPC) plexus in 4 sectors (superior, nasal, inferior, temporal). The average of these sectors was calculated and reported.Main outcome measures
Radial peripapillary capillary plexus perfusion was quantified using 2 parameters: capillary perfusion density (CPD) and capillary flux index (CFI). Intraclass correlation coefficients (ICCs) were used to quantify repeatability. For subjects who had both eyes included, the average values of each scan pair were used to assess interocular symmetry of CPD and CFI.Results
Of 374 eyes, 46 were from participants who had AD, 85 were from participants who had MCI, 87 were from participants who had PD, and 156 were from participants who had normal cognition. Capillary perfusion density ICC in AD = 0.88 (95% confidence interval [CI], 0.79-0.93), MCI = 0.95 (0.92-0.96), PD = 0.91 (0.87-0.94), and controls = 0.90 (0.87-0.93). Capillary flux index ICC in AD = 0.82 (0.70-0.90), MCI = 0.87 (0.80-0.91), PD = 0.91 (0.87-0.94) and controls = 0.85 (0.79-0.89). There were no significant differences in interocular variation in average CPD and CFI in AD, MCI, or PD (all P > 0.05). Isolated interocular sectoral CPD differences were noted in AD (nasal, P = 0.049; temporal, P = 0.024), PD (nasal, P = 0.036), and controls (nasal, P = 0.016). Interocular differences in CFI in the superior sector in MCI (P = 0.028) and in average CFI for controls (P = 0.035) were observed.Conclusions
Peripapillary OCTA repeatability in AD, MCI, and PD is good-excellent and similar to those with normal cognition. Insignificant interocular asymmetry in peripapillary OCTA suggests neurodegeneration may proceed uniformly; future studies may reveal the appropriateness of single-eye imaging.