Image Quality In Partially Erased Denoptix® Storage Phosphor Plates

This study aimed at investigating the effect of the partial erasing of DenOptix® system storage phosphor plates on the image quality of digital radiographs. Standardized digital radiographs were acquired of a phantom mandible, using size 2 intraoral DenOptix® storage phosphor plates (n = 10). Subsequently, the active areas of the plates were placed in a viewing box with a constant light intensity of 1,700 lux for 130 seconds to achieve complete erasing (control plate), as well as for 0, 5, 10, 1S, 20, 25, 34, 66, and 98 seconds, to compose the experimental group of partially erased plates. The same exposure settings were repeated using the control and experimental plates, which were scanned at a resolution of 300 dpi. Five radiologists independently examined the pairs of digital radiographs obtained with the control and partially erased plates, in random order, and indicated the best image for oral diagnosis. Cochran-Mantel-Haenszel's chi-square test, at a significance level of 5%, was used to compare the percentages of superior quality images in each combination of control and partially erased plates, subjectively assessed. No significant differences were found between radiographic images acquired with control and partially erased plates, except for the combination of 0 second (30%) versus 130 seconds (70%), p = 0.0047. It can be concluded that, under adequate light intensity conditions, erasing intraoral DenOptix® storage phosphor plates may require time intervals of as little as 5 seconds.2217883Akdeniz, B.G., Gröndahl, H.G., Kose, T., Effect of delayed scanning of storage phosphor plates (2005) Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 99 (5), pp. 603-607Akdeniz, B.G., Gröndahl, H.G., Degradation of storage phosphor images due to scanning delay (2006) Dentomaxillofac Radiol, 35 (2), pp. 74-77Almeida, S.M., Oliveira, A.E.F., Ferreira, R.I., Bóscolo, F.N., Image quality in digital radiographic systems (2003) Braz Dent J, 14 (2), pp. 136-141Borg, E., Attaelmanan, A., Gröndahl, H.G., Subjective image quality of solid-state and photostimulable phosphor systems for digital intra-oral radiography (2000) Dentomaxillofac Radiol, 29 (2), pp. 70-75Ferreira, R.I., Haiter-Neto, F., Tabchoury, C.P.M., Paiva, G.A.N., Bóscolo, F.N., Assessment of enamel demineralization using conventional, digital, and digitized radiography (2006) Braz Oral Res, 20 (2), pp. 114-119Wenzel, A., Gröndahl, H.G., Direct digital radiography in the dental office (1995) Int Dent J, 45 (1), pp. 27-34Oliveira, A.E., Almeida, S.M., Paganini, G.A., Haiter Neto, F., Bóscolo, F.N., Comparative study of two digjtal radiographic storage phosphor systems (2000) Braz Dent J, 11 (2), pp. 111-116Borg, E., Attaelmanan, A., Gröndahl, H.G., Image plate systems differ in physical performance (2000) Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 89 (1), pp. 118-124Martins, M.G.B.Q., Haiter Neto, F., Whaites, E.J., Analysis of digital images acquired using different phosphor storage plates (PSPs) subjected to varying reading times and storage conditions (2003) Dentomaxillofac Radiol, 32 (3), pp. 186-190(1998) DenOptix digital imaging system - user manual and installation guide, , Gendex Dental X-Ray Division, Des Plaines: The Division;Menig, J.J., The DenOptix digital radiographic system (1999) J Clin Orthod, 33 (7), pp. 407-410Berkhout WE, Beuger DA, Sanderink GC, van der Stelt PF. The dynamic range of digital radiographic systems: dose reduction or risk of overexposure? Dentomaxillofac Radiol. 2004;33(1):1-SHildebolt, C.F., Couture, R.A., Whiting, B.R., Dental photostimulable phosphor radiography (2000) Dent Clin North Am, 44 (2), pp. 273-297Martins, M.G.B.Q., Whaites, E.J., Ambrosano, G.M.B., Haiter Neto, F., What happens if you delay scanning Digora phosphor storage plates (PSPs) for up to 4 hours? (2006) Dentomaxillofac Radiol, 35 (3), pp. 143-146Gröndahl, H.G., Wenzel, A., Borg, E., Tammisalo, E., An image plate system for digital intra-oral radiography (1996) Dent Update, 23 (8), pp. 334-33

Vertex Cover Kernelization Revisited: Upper and Lower Bounds for a Refined Parameter

An important result in the study of polynomial-time preprocessing shows that there is an algorithm which given an instance (G,k) of Vertex Cover outputs an equivalent instance (G',k') in polynomial time with the guarantee that G' has at most 2k' vertices (and thus O((k')^2) edges) with k' <= k. Using the terminology of parameterized complexity we say that k-Vertex Cover has a kernel with 2k vertices. There is complexity-theoretic evidence that both 2k vertices and Theta(k^2) edges are optimal for the kernel size. In this paper we consider the Vertex Cover problem with a different parameter, the size fvs(G) of a minimum feedback vertex set for G. This refined parameter is structurally smaller than the parameter k associated to the vertex covering number vc(G) since fvs(G) <= vc(G) and the difference can be arbitrarily large. We give a kernel for Vertex Cover with a number of vertices that is cubic in fvs(G): an instance (G,X,k) of Vertex Cover, where X is a feedback vertex set for G, can be transformed in polynomial time into an equivalent instance (G',X',k') such that |V(G')| <= 2k and |V(G')| <= O(|X'|^3). A similar result holds when the feedback vertex set X is not given along with the input. In sharp contrast we show that the Weighted Vertex Cover problem does not have a polynomial kernel when parameterized by the cardinality of a given vertex cover of the graph unless NP is in coNP/poly and the polynomial hierarchy collapses to the third level.Comment: Published in "Theory of Computing Systems" as an Open Access publicatio