| 1. |
- Kheddache, Susanne, 1949, et al.
(författare)
-
Storage phosphor and film-screen mammography: performance with different mammographic techniques
- 1999
-
Ingår i: European Radiology. - 0938-7994 .- 1432-1084. ; 9:4, s. 591-597
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare the image quality of storage phosphor plates with that in screen-film radiograms in mammography. Two anode/filter combinations were also compared ± Mo/ Mo and W/Rh. Storage phosphor plates, generation IIIN (Fuji, Tokyo, Japan) and a conventional screenfilm system (Kodak, Rochester, N.Y.) were evaluated using two mammographic units. One unit had a 0.6-mm focal spot, an anode/filter combination of Mo/Mo and no grid (A-Mo); the other had a 0.3-mm focal spot, a grid, and two possible combinations of anode/filter Mo/Mo (B-Mo) and W/Rh (B-W). Simulated tumours and microcalcifications were randomly positioned in an anthropomorphic breast phantom (RMI model 165, no. 210±009, Radiation Measurements Inc., Middleton, Wisconsin). The image quality was evaluated using a modified version of receiver operating characteristics analysis. Five observers evaluated 300 films and 300 hard copy images each. Radiation doses were also determined. The image Quality of the conventional screen-film images was significantly better than that for the storage phosphor plate mammograms. The B-Mo system rated best, for the detection of both tumours and microcalcifications, although it was not significantly different from the B-W system. Systems B-Mo and B-W rated significantly better than the A-Mo system for both image receptors studied. The mean absorbed dose was twice as high for the B-Mo system as for the A-Mo and B-W systems for both conventional and digital technique. The mammograms produced with the screen-film combination gave a significantly better detectability than the storage phosphor plates used in this study. Substantial dose reduction could be achieved using an anode/filter combination of W/Rh instead of Mo/Mo with no significant loss of information in the images.
|
|
| 2. |
- Sandborg, Michael, 1961-, et al.
(författare)
-
Demonstration of correlations between clinical and physical image quality measures in chest and lumbar spine screen-film radiography
- 2001
-
Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 74:882, s. 520-528
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to predict clinical image quality from physical measures is useful for optimization in diagnostic radiology. In this work, clinical and physical assessments of image quality are compared and correlations between the two are derived. Clinical assessment has been made by a group of expert radiologists who evaluated fulfilment of the European image criteria for chest and lumbar spine radiography using two scoring methods: image criteria score (ICS) and visual grading analysis score (VGAS). Physical image quality measures were calculated using a Monte Carlo simulation model of the complete imaging system. This model includes a voxelized male anatomy and was used to calculate contrast and signal-to-noise ratio of various important anatomical details and measures of dynamic range. Correlations between the physical image quality measures on the one hand and the ICS and VGAS on the other were sought. 16 chest and 4 lumbar spine imaging system configurations were compared in frontal projection. A statistically significant correlation with clinical image quality was found in chest posteroanterior radiography for the contrast of blood vessels in the retrocardiac area and a measure of useful dynamic range. In lumbar spine anteroposterior radiography, a similar significant correlation with clinical image quality was found between the contrast and signal-to-noise ratio of the trabecular structures in the L1-L5 vertebrae. The significant correlation shows that clinical image quality can, at least in some cases, be predicted from appropriate measures of physical image quality.
|
|
| 3. |
- Tingberg, Anders, et al.
(författare)
-
Inter-observer variation in masked and unmasked images for quality evaluation of clinical radiographs.
- 2005
-
Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 114:1-3, s. 62-8
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate the influence of masking on the inter-observer variation in image quality evaluation of clinical radiographs of chest and lumbar spine. BACKGROUND: Inter-observer variation is a big problem in image quality evaluation since this variation is often much bigger than the variation in image quality between, for example, two radiographic systems. In this study, we have evaluated the effect of masking on the inter-observer variation. The idea of the masking was to force every observer to view exactly the same part of the image and to avoid the effect of the overall 'first impression' of the image. A discussion with a group of European expert radiologists before the study indicated that masking might be a good way to reduce the inter-observer variation. METHODS: Five chest and five lumbar spine radiographs were collected together with detailed information regarding exposure conditions. The radiographs were digitised with a high-performance scanner and five different manipulations were performed, simulating five different exposure conditions. The contrast, noise and spatial resolution were manipulated by this method. The images were printed onto the film and the individual masks were produced for each film, showing only the parts of the images that were necessary for the image quality evaluation. The quality of the images was evaluated on ordinary viewing boxes by a large group of experienced radiologists. The images were examined with and without the masks with a set of image criteria (if fulfilled, 1 point; and not fulfilled, 0 point), and the mean score was calculated for each simulated exposure condition. RESULTS: The results of this study indicate that-contrary to what was supposed-the inter-observer variation increased when the images were masked. In some cases, especially for chest, this increase was statistically significant. CONCLUSIONS: Based on the results of this study, image masking in studies of fulfilment of image criteria cannot be recommended.
|
|
| 4. |
|
|
