| 1. |
|
|
| 2. |
|
|
| 3. |
- Thaung, Jörgen, 1965, et al.
(författare)
-
The 'light scattering factor'. Importance of stimulus geometry, contrast definition, and adaptation.
- 1995
-
Ingår i: Investigative ophthalmology & visual science. - 0146-0404 .- 1552-5783. ; 36:11, s. 2313-7
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE. Paulsson and Sjöstrand have suggested that the light scattering factor (LSF) can be estimated by using the equation: LSF = L/E (M2/M1-1). Here L is the space average luminance of the target, E is the illuminance of the glare source, and M2 and M1 are modulation contrast thresholds in the presence and absence of the glare source. To compensate for change of adaptation. Abrahamsson and Sjöstrand later modified the above equation by introducing a correction factor (CF): LSF = L/E ((CF) (M2/M1-1). The purpose of this study is to analyze the validity of the above equations. METHODS. The importance of stimulus geometry, contrast definition, background luminance, and glare illumination is studied through theoretical analysis and comparison with earlier studies. Stimulus geometry and contrast definition are studied through optical modeling. Adaptation is modeled according to the laws of Weber and DeVries-Rose. RESULTS. The choice of contrast definition may corrupt the result by a factor of 2. At background luminance levels above approximately 10 cd/m2, the Paulsson-Sjöstrand equation agrees well with theory. At lower background levels, the Abrahamsson-Sjöstrand equation is used with correction factors derived from adaptation measurements. Using this equation and earlier published data from glare testing performed at 2 cd/m2, the results are found to be in fair agreement with the light scattering theory. CONCLUSIONS. Glare testing using the Paulsson-Sjöstrand equation is found to be valid as long as the measurements are performed at high luminance levels (above 10 cd/m2), with targets of low spatiotemporal frequencies (e.g., 2 cpd and 1 Hz) and with the use of a properly chosen definition of contrast. At lower luminance levels, the Abrahamsson-Sjöstrand equation may be used with well-derived correction factors.
|
|
| 4. |
- Farrell, Edward J., et al.
(författare)
-
Quantitative 3D visualization in nuclear medicine
- 1995
-
Ingår i: Proceedings of the SPIE Medical Imaging 1995. - : SPIE - International Society for Optical Engineering. - 0819417793 ; , s. 54-64
-
Konferensbidrag (refereegranskat)abstract
- SPECT is a powerful clinical tool. However, the low spatial resolution and ill-defined boundaries associated with SPECT require special consideration in visualization. Quantitative geometric and magnitude information are areas of particular usefulness in evaluating disease states. In this paper, we describe a set of practical 3D visualization tools to display and analyze SPECT data, and present interactive methods to measure (1) the relative position, size and shape of regions of interest and (2) the magnitude and distribution of radioactive count information. Interactive pick tools allow users to extract values at selected points, distance between points, or value profiles along selected line segments. In the three-dimensional reconstruction, transparent and opaque isosurfaces are formed simultaneously at specified activity levels, and the volume enclosed by the opaque surface is displayed. The utility of these tools is demonstrated with two types of patient studies: those using tumor-avid agents to identify active tumor in the chest and abdomen, and those used for evaluating the volume of perfused myocardium.
|
|
| 5. |
- Noz, Marilyn E., et al.
(författare)
-
Multimodality Image Correlation and Fusion
- 1995
-
Ingår i: Clinical SPECT Imaging. - : Ravan Press. - 9780781701907 ; , s. 79-95
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 6. |
|
|
| 7. |
|
|
