The impact of spot size, spacing, pattern, duration and intensity of burns on the photocoagulation index in a geometric simulation of pan‐retinal laser photocoagulation

2018 ◽  
Vol 97 (4) ◽  
pp. e551-e558 ◽  
Author(s):  
Kentaro Nishida ◽  
Ken Miura ◽  
Hirokazu Sakaguchi ◽  
Motohiro Kamei ◽  
Taku Wakabayashi ◽  
...  
Keyword(s):  
Laser Photocoagulation ◽  
Spot Size ◽  
Spacing Pattern ◽  
Geometric Simulation ◽  
The Impact

A Study of Transient Thermal Spreading of VLSI Packaging With Multi Level Scaling

2007 ◽  
Author(s):  
Kazuaki Yazawa ◽  
Tenko Yamashita ◽  
Hideaki Kuroda
Keyword(s):  
Power Consumption ◽  
Hot Spot ◽  
Thermal Response ◽  
Spot Size ◽  
Thermal Interface ◽  
Vlsi Chip ◽  
Expected Performance ◽  
Chip Size ◽  
Transient Thermal ◽  
The Impact

Trend of VLSI chip power consumption sounds switch over from the Moore’s law to more moderate curve by the “multi core processing” paradigm. Many of the recent advanced VLSI chips adopt the multiple processing units since clock enhancement is no longer feasible to gain the expected performance based on realistic range of power consumption. Even though, heat flux may keep increasing by further fine semiconductor process and may keep localizing by further complex logics. In this study, thermal impact of hot spot size relative to chip size or the dimension of heat sink is investigated by analytic modeling as well as numerical analysis. The analytic transient thermal spreading model in a solid with transfer function has already proposed and was validated in our previous work. In this study, we have considered the impact of thermal interface between the heat source and conductive and spreading component to the sink. Thermal response in wide rage of scales is discussed from transistor level to a millimeter scale. Each level of such various sizes can be investigated individually and can be built up with some sort of cascade manner. Based on this model, thermal diffusion in silicon substrate, which has the thermal coupling with spreader and thermal interface, will be discussed for a further fine process generation of the chip. The result implies that passive thermal spreading can be achieving to the limit.

scholarly journals Dosimetric study of the interplay effect using three-dimensional motion phantom in proton pencil beam scanning treatment of moving thoracic tumours

2021 ◽  
pp. 1-10
Author(s):  
Hardev S. Grewal ◽  
Salahuddin Ahmad ◽  
Hosang Jin
Keyword(s):  
Treatment Planning ◽  
Three Dimensional ◽  
Spot Size ◽  
Passing Rate ◽  
Treatment Plans ◽  
Motion Phantom ◽  
Interplay Effect ◽  
The Impact ◽  
Motion Amplitude ◽  
Dose Difference

Abstract Aim: The dosimetric and clinical advantages offered by implementation of pencil beam scanning (PBS) proton therapy for moving thoracic tumours is hindered by interplay effect. The purpose of this study is to evaluate the impact of large proton beam spot size along with adaptive aperture (AA) and various motion mitigation techniques on the interplay effect for a range of motion amplitudes in a three-dimensional (3D) respiratory motion phantom. Materials and Methods: Point doses using ionisation chamber (IC) and planner dose distributions with radiochromic film were compared against the corresponding treatment planning system (TPS) information. A 3D respiratory motion phantom was scanned either for static or 4D computed tomographic (CT) technique for 6-, 10- and 14-mm motion amplitudes in SI direction. For free breathing (FB) treatment, a tumour was contoured on maximum intensity projection scan and an average scan was used for treatment planning. Each FB treatment was delivered with one, three and five volumetric repaintings (VRs). Three phases (CT40–60%) were extracted from the 4D-CT scans of each motion amplitude for the respiratory-gated treatment and were used for the treatment planning and delivery. All treatment plans were made using AA and robustly optimised with 5-mm set-up and 3·5% density uncertainty. A total of 26 treatment plans were delivered to IC and film using static, dynamic and respiratory-gated treatments combinations. A percent dose difference between IC and TPS for the point dose and gamma indices for film–TPS planner dose comparison was used. Results: The dose profile of film and TPS for the static phantom matched well, and percent dose difference between IC and TPS was 0·4%. The percent dose difference for all the gated treatments were below 3·0% except 14-mm motion amplitude-gated treatment. The gamma passing rate was more than 95% for film–TPS comparison for all gated treatment for the investigated gamma acceptance criteria. For FB treatments, the percent dose difference for 6-, 10- and 14-mm motion amplitude was 1·4%, −2·7% and −4·1%, respectively. As the number of VR increased, the percent difference between measured and calculated values decreased. The gamma passing rate met the required tolerance for different acceptance criteria except for the 14-mm motion amplitude FB treatment. Conclusion: The PBS technique for the FB thoracic treatments up to 10-mm motion amplitude can be implemented with an acceptable accuracy using large proton beam spot size, AA and robust optimisation. The impact of the interplay effect can be reduced with VR and respiratory-gated treatment and extend the treatable tumour motion amplitude.

Traumatic and Iatrogenic Choroidal Neovascularization

2017 ◽  
pp. 330-335
Keyword(s):  
Bone Marrow ◽  
Optical Coherence Tomography ◽  
Gene Transfer ◽  
Laser Photocoagulation ◽  
Optical Coherence Tomography Angiography ◽  
Spot Size ◽  
High Energy ◽  
Macular Surgery ◽  
Small Spot ◽  
Fibrovascular Proliferation

Iatrogenic CNVs have been reported primarily due to laser photocoagulation and, secondly, due to complications of macular surgery. It has been reported that chorio-ovitreal and subretinal fibrovascular proliferation following heavy focal photocoagulation are complications of high energy with small spot size application. Apart from the CNVs that occur as iatrogenic laser complications, CNVs formed by laser pointers can also be seen. During macular surgery, CNV may also develop due to RPE and BM trauma and deterioration of their integrity. While fundus exam, FFA, OCT, and Optical Coherence Tomography Angiography (OCTA) are valuable for diagnosis, in recent years, experimental animal laser-induced CNV studies, especially bone marrow-derived monocyte-macrophages playing an important role, and underlying related molecular mechanism studies have been intensified. One of the therapeutic examples of treatment is a gene transfer shown in experimental rat studies. Nevertheless, there is a need for further studies on diagnosis and treatment.

Laser photocoagulation spot-size errors stemming from the refractive state of the surgeon’s eye

Ophthalmology ◽  
2000 ◽  
Vol 107 (2) ◽  
pp. 329-333 ◽  
Author(s):  
Eytan Z Blumenthal ◽  
Christos N Serpetopoulos
Keyword(s):  
Laser Photocoagulation ◽  
Spot Size ◽  
Refractive State

Effects of Laser Beam Focusing Characteristics on Laser-Induced Breakdown Spectra

2020 ◽  
pp. 000370282096143
Author(s):  
David M. Surmick ◽  
Leon Taleh ◽  
Noureddine Melikechi
Keyword(s):  
Focal Spot ◽  
Ionic Species ◽  
Spot Size ◽  
Focal Spot Size ◽  
Breakdown Spectroscopy ◽  
Beam Focusing ◽  
Laser Focusing ◽  
Laser Induced Breakdown ◽  
The Impact ◽  
Sample Distance

The impact of altering laser focusing conditions on laser-induced breakdown spectroscopy experiments is investigated under ambient Earth laboratory and simulated Martian atmospheres. Experiments were performed in which the focal spot size was varied on a sample by altering the lens to sample distance with respect to targets of interest. Samples investigated include aluminum, copper, and steel. Specific neutral and ionic transitions of each sample were monitored. Atomic and ionic emissions show different intensity peak distributions along the varying lens to sample distance. Ionic species have peak emissions when laser plasma is initiated with a focused spot within the sample in ambient Earth laboratory air, while atomic emissions have peak intensities several millimeters deeper into a sample. In simulated Martian atmospheres, atomic emissions are observed to peak when the laser is focused within the sample, while ionic emissions have peak intensities when the laser is focused near the surface of a sample.

scholarly journals Sensitivity of gravito-inertial modes to differential rotation in intermediate-mass main-sequence stars

2018 ◽  
Vol 618 ◽  
pp. A24 ◽  
Author(s):  
T. Van Reeth ◽  
J. S. G. Mombarg ◽  
S. Mathis ◽  
A. Tkachenko ◽  
J. Fuller ◽  
...  
Keyword(s):  
Differential Rotation ◽  
Stellar Structure ◽  
Time Base ◽  
Stellar Rotation ◽  
Single Star ◽  
Spacing Pattern ◽  
Surface Rotation ◽  
Long Time ◽  
Core Rotation ◽  
The Impact

Context. While rotation has a major impact on stellar structure and evolution, its effects are not well understood. Thanks to high-quality and long-time base photometric observations obtained with recent space missions, we are now able to study stellar rotation more precisely.Aims. We aim to constrain radial differential rotation profiles inγDoradus (γDor) stars, and to develop new theoretical seismic diagnosis for such stars with rapid and potentially non-uniform rotation.Methods. We have derived a new asymptotic description which accounts for the impact of weak differential near-core rotation on gravity-mode period spacings. The theoretical predictions are illustrated from pulsation computations with the code GYRE and compared with observations ofγDor stars. When possible, we also derived the surface rotation rates in these stars by detecting and analysing signatures of rotational modulation, and computed the core-to-surface rotation ratios.Results. Stellar rotation must be strongly differential before its effects on period spacing patterns can be detected, unless multiple period spacing patterns can be compared. Six stars in our sample exhibit a single unexplained period spacing pattern of retrograde modes. We hypothesise that these are Yanai modes. Finally, we find signatures of rotational spot modulation in the photometric data of eight targets.Conclusions. If only one period spacing pattern is detected and analysed for a star, it is difficult to detect differential rotation. A rigidly rotating model will often provide the best solution. Differential rotation can only be detected when multiple period spacing patterns have been found for a single star or its surface rotation rate is known as well. This is the case for eight of the stars in our sample, revealing surface-to-core rotation ratios between 0.95 and 1.05.

Simulation of Panretinal Laser Photocoagulation Using Geometric Methods for Calculating the Photocoagulation Index

2016 ◽  
Vol 27 (2) ◽  
pp. 205-209 ◽  
Author(s):  
Kentaro Nishida ◽  
Hirokazu Sakaguchi ◽  
Motohiro Kamei ◽  
Nobuhiko Shiraki ◽  
Yoshihito Oura ◽  
...  
Keyword(s):  
Surface Area ◽  
Pulse Duration ◽  
Laser Photocoagulation ◽  
Curved Surface ◽  
Retinal Area ◽  
Spherical Dome ◽  
Geometric Methods ◽  
The Impact

Purpose To establish geometrically based methods for simulating panretinal laser photocoagulation (PRP) for the photocoagulation index. Methods A formula for calculating the curved surface area of a spherical dome was used for the simulation. If the radius of the dome is c and the height of the dome is h, then the curved surface area (S) of the dome is S = π (c2 + h2). We calculated the area of the whole retina using this formula and the anatomical dimensions of the standard eyeball. To simulate PRP with a 400-μm spot on the retina with 1-spot spacing, we drew 400-μm-diameter circles, separated by 400 μm, on a retinal map. We calculated the ratio of the total retinal photocoagulated area to the whole retina, termed the photocoagulation index, in order to investigate the impact of the extent of the photocoagulated area and the pulse duration on PRP. Results The whole retinal area was 1,092 mm2. The numbers of spots in the scattered and full-scattered PRP were 1,222 and 1,814, respectively. The photocoagulation index was 14.1% and 20.9% for scattered and full-scattered PRP, respectively. These values changed to 14.3% (5.6%) and 21.3% (8.3%), respectively, for PRP with a 100-ms pulse or a 20-ms pulse. Conclusions This method will be useful for investigating the impact of various PRP parameters (duration, spacing, intensity of burns, extent of photocoagulated area, etc.) on the photocoagulation index.

scholarly journals Influence of Retinal Microsecond Pulse Laser Treatment in Central Serous Chorioretinopathy: A Short-Term Optical Coherence Tomography Angiography Study

2021 ◽  
Vol 10 (11) ◽  
pp. 2418
Author(s):  
Michelle Prasuhn ◽  
Yoko Miura ◽  
Aysegül Tura ◽  
Felix Rommel ◽  
Vinodh Kakkassery ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Central Serous Chorioretinopathy ◽  
Vision Loss ◽  
Subretinal Fluid ◽  
Spot Size ◽  
Optical Coherence ◽  
Non Invasive ◽  
Central Vision Loss ◽  
The Impact ◽  
Fellow Eyes

Background: Central serous chorioretinopathy (CSC) is a common macular condition characterized by detachment of the neuroretina and is a frequent cause of central vision loss in adults. Among the various therapeutic strategies, subthreshold microsecond pulsed laser (SML) treatment has become a useful option. Despite the suggested involvement of choroidal circulatory disturbances in CSC, the effects of this treatment on macular microperfusion have not been fully evaluated yet. Herein, we report the impact of SML on retinal and choroidal microvascular flow using non-invasive optical coherence tomography (OCT) angiography (OCTA). Methods: In this study, CSC patients with persistent subretinal fluid (SRF) with or without secondary choroidal neovascularization (CNV) were included (referred to as the pachychoroid neovasculopathy (PNV) group and the CSC group, respectively). SML was conducted using a yellow (577 nm) laser with a duty cycle of 10%, spot size of 200 µm and duration of 200 ms. Best corrected visual acuity (BCVA) as well as OCT and OCTA images were evaluated at baseline and 4 weeks after SML. OCTA parameters of interest included full retinal perfusion (FRP), choriocapillaris perfusion (CCP), Sattler’s layer perfusion (SLP), and Haller’s layer perfusion (HLP), which were evaluated longitudinally and compared to unaffected fellow eyes. Results: 27 affected eyes and 17 fellow eyes from 27 patients were included. Before treatment, central retinal thickness (CRT) and subfoveal choroidal thickness (SFCT) of affected eyes were significantly larger than in fellow eyes. Four weeks after SML, CRT decreased significantly, whereas perfusion parameters did not change. In subgroup analyses, the CSC group showed a significant decrease in SFCT, whereas the PNV group did not despite the decrease in CRT. Conclusion: Our results suggest that the SML may affect the SFCT of the CSC, but not the PNV patients at least within four weeks following treatment. This effect seems to be independent of the change in choroidal perfusion measured with OCTA.

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