scholarly journals Impact of B-Scan Averaging on Spectralis Optical Coherence Tomography Image Quality before and after Cataract Surgery

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Dominika Podkowinski ◽  
Ehsan Sharian Varnousfaderani ◽  
Christian Simader ◽  
Hrvoje Bogunovic ◽  
Ana-Maria Philip ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Image Quality ◽  
Cataract Surgery ◽  
Signal To Noise Ratio ◽  
Acquisition Time ◽  
Optical Coherence Tomography Image ◽  
Retinal Layer ◽  
Optical Coherence ◽  
Before And After ◽  
Image Averaging

Background and Objective. To determine optimal image averaging settings for Spectralis optical coherence tomography (OCT) in patients with and without cataract. Study Design/Material and Methods. In a prospective study, the eyes were imaged before and after cataract surgery using seven different image averaging settings. Image quality was quantitatively evaluated using signal-to-noise ratio, distinction between retinal layer image intensity distributions, and retinal layer segmentation performance. Measures were compared pre- and postoperatively across different degrees of averaging. Results. 13 eyes of 13 patients were included and 1092 layer boundaries analyzed. Preoperatively, increasing image averaging led to a logarithmic growth in all image quality measures up to 96 frames. Postoperatively, increasing averaging beyond 16 images resulted in a plateau without further benefits to image quality. Averaging 16 frames postoperatively provided comparable image quality to 96 frames preoperatively. Conclusion. In patients with clear media, averaging 16 images provided optimal signal quality. A further increase in averaging was only beneficial in the eyes with senile cataract. However, prolonged acquisition time and possible loss of details have to be taken into account.

scholarly journals A Comparative Evaluation of Macular Thickness after Phacoemulsification and Manual SICS in Diabetic Patients by Optical Coherence Tomography

2021 ◽  
Vol 8 (7) ◽  
pp. 468-472
Author(s):  
Saswati Biswas ◽  
Santosh Yadawrao Ingle ◽  
Samiran Das
Keyword(s):  
Optical Coherence Tomography ◽  
Cataract Surgery ◽  
Macular Edema ◽  
Macular Thickness ◽  
Diabetic Patients ◽  
Optical Coherence ◽  
Small Incision Cataract Surgery ◽  
High Rise ◽  
Small Incision ◽  
Before And After

Background: The main aim of the study is to compare the change in macular thickness after uncomplicated phacoemulsification versus uncomplicated manual SICS in known diabetic patients by optical coherence tomography Methods: This study was an observational study involving 50 patients with each group having 25 patients. Group 1 was operated with Phacoemulsification through limbal 2.8 mm incision with Foldable PCIOL implantation. & Manual small incision cataract surgery through 5.5 to 6.5 mm incision with sclerocorneal tunnel with PMMA PCIOL implantation. For all patients, macular OCT was performed during preoperative period & post-op 1st day,7th day, 1st month, 3rd month & 6th month. Statistical software SPSS, version 21.0 was used for statistical analysis. Results: In both PHACO & SICS group MCFT rose steadily during post-operative period and SICS group shows high rise during follow up.The MCFT shows a difference between PHACO & SICS group with the highest MCFT observed in 1st month follow up i.e., 231.6 micrometer (SD ±7.831) in PHACO group & 241.64 (SD ±7.35) micrometer in SICS group. The MCFT returned to near pre-op value by the 6th month. Conclusion: There is no effect of age and sex on macular thickness before and after in both PHACO and SICS groups. In SICS group significant macular thickness was observed as compared to PHACO group, so there should be more cautious to undertake SICS in those patients who are at risk of developing macular edema or who have a higher macular thickness as seen in diabetes patients. Keywords: Phacoemulsification (PHACO), small incision cataract surgery (SICS), Cystoid macular edema.

PET/CT BiographTM Sensation 16

2006 ◽  
Vol 45 (03) ◽  
pp. 126-133 ◽  
Author(s):  
Y. Bercier ◽  
M. Schwaiger ◽  
S. I. Ziegler ◽  
M.-J. Martínez
Keyword(s):  
Image Quality ◽  
Count Rate ◽  
Signal To Noise Ratio ◽  
Reconstruction Algorithm ◽  
Considerable Change ◽  
Acquisition Time ◽  
Average Increase ◽  
Scatter Fraction ◽  
Pet Ct ◽  
Before And After

SummaryAim: The new PET/CT Biograph Sensation 16 (BS16) tomographs have faster detector electronics which allow a reduced timing coincidence window and an increased lower energy threshold (from 350 to 400 keV). This paper evaluates the performance of the BS16 PET scanner before and after the Pico-3D electronics upgrade. Methods: Four NEMA NU 2–2001 protocols, (i) spatial resolution, (ii) scatter fraction, count losses and random measurement, (iii) sensitivity, and (iv) image quality, have been performed. Results: A considerable change in both PET count-rate performance and image quality is observed after electronics upgrade. The new scatter fraction obtained using Pico-3D electronics showed a 14% decrease compared to that obtained with the previous electronics. At the typical patient background activity (5.3 kBq/ml), the new scatter fraction was approximately 0.42. The noise equivalent count-rate (RNEC) performance was also improved. The value at which the RNEC curve peaked, increased from 3.7·104s-1 at 14 kBq/ml to 6.4·104s-1 at 21 kBq/ml (2R-NEC rate). Likewise, the peak true count-rate value increased from 1.9·105s-1 at 22 kBq/ml to 3.4·105s-1 at 33 kBq/ml. An average increase of 45% in contrast was observed for hot spheres when using AW-OSEM (4ix8s) as the reconstruction algorithm. For cold spheres, the average increase was 12%. Conclusion: The performance of the PET scanners in the BS16 tomographs is improved by the optimization of the signal processing. The narrower energy and timing coincidence windows lead to a considerable increase of signal- to-noise ratio. The existing combination of fast detectors and adapted electronics in the BS16 tomographs allow imaging protocols with reduced acquisition time, providing higher patient throughput.

scholarly journals Improved wavelet hierarchical threshold filter method for optical coherence tomography image de-noising

2018 ◽  
Vol 11 (03) ◽  
pp. 1850012 ◽  
Author(s):  
Jing Cao ◽  
Pinghe Wang ◽  
Bo Wu ◽  
Guohua Shi ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Signal To Noise Ratio ◽  
Visual Image ◽  
Objective Evaluation ◽  
Threshold Function ◽  
Filter Method ◽  
Optical Coherence Tomography Image ◽  
Optical Coherence ◽  
Threshold Functions ◽  
Threshold Filter

According to the speckle feature in Optical coherence tomography (OCT), images with speckle indicate not only noise but also signals, an improved wavelet hierarchical threshold filter (IWHTF) method is proposed. At first, a modified hierarchical threshold-selected algorithm is used to prevent signals from being removed by assessing suitable thresholds for different noise levels. Then, an improved wavelet threshold function based on two traditional threshold functions is proposed to trade-off between speckle removing and sharpness degradation. The de-noising results of an OCT finger skin image shows that the IWHTF method obtains better objective evaluation metrics and visual image quality improvement. When [Formula: see text], [Formula: see text] and [Formula: see text], the improved method can achieve 9.58[Formula: see text]dB improvement in signal-to-noise ratio, with sharpness degraded by 3.81%.

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