SUMMARYThis paper addresses the problems of fingerprint identification and verification when a query fingerprint is taken under conditions that differ from those under which the fingerprint of the same person stored in a database was constructed. This occurs when using a different fingerprint scanner with a different pressure, resulting in a fingerprint impression that is smeared and distorted in accordance with a geometric transformation (e.g., affine or even non-linear). Minutiae points on a query fingerprint are matched and aligned to those on one of the fingerprints in the database, using a set of absolute invariants constructed from the shape and/or size of minutiae triangles depending on the assumed map. Once the best candidate match is declared and the corresponding minutiae points are flagged, the query fingerprint image is warped against the candidate fingerprint image in accordance with the estimated warping map. An identification/verification cost function using a combination of distance map and global directional filterbank (DFB) features is then utilized to verify and identify a query fingerprint against candidate fingerprint(s). Performance of the algorithm yields an area of 0.99967 (perfect classification is a value of 1) under the receiver operating characteristic (ROC) curve based on a database consisting of a total of 1680 fingerprint images captured from 240 fingers. The average probability of error was found to be 0.713%. Our algorithm also yields the smallest false non-match rate (FNMR) for a comparable false match rate (FMR) when compared to the well-known technique of DFB features and triangulation-based matching integrated with modeling non-linear deformation. This work represents an advance in resolving the fingerprint identification problem beyond the state-of-the-art approaches in both performance and robustness.

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Conversion to a filmless technique of physical performance testing is becoming a topic of much interest to researchers. We assessed the use of a computed radiography (CR) system with postprocessing software as an alternative tool for performing the three physical performance tests of an x‐ray tube. Collimator and beam alignment, focal spot size, and milliampere second (mAs) linearity, were performed using a CR system. Results were then compared with those obtained from a conventional screen‐film (SF) system. The distances of collimator misalignment measured by the SF system were decreased while peak tube voltage (kVp) was increased (mAs was fixed), whereas those measured by CR were independent of exposure level. The degrees of beam collimator misalignment measured by the CR system were not different from those measured by the SF system. The differences in focal spot dimensions measured by SF and CR systems were less than 4% for large and small focal spot size in both width and length. The mAs linearity evaluated by the SF system agreed with those evaluated by the dose measurement at 50 kVp and 4 mAs, as well as 55 kVp and 3.2 mAs, while the mAs linearity test using the CR system agreed with those using the dose measurement method for all exposure levels. In summary, a CR system could be utilized to assess the three physical performance tests of a single x‐ray tube, but required more time than an SF system. Medical physicists with image processing skills were needed to perform the analyses.

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Objective: To estimate entrance skin dose (ESD) of digital radiography (DR) examination using displayed dose area product (DAP)Material and Method: The functional relation between calculated ESD using x-ray tube output principle and displayed DAP were investigated. The displayed DAP was obtained from whole body phantom which underwent seven projections: skull anteroposterior (AP), skull lateral (Lat), chest posteroanterior (PA), abdomen AP, pelvis AP, lumbar spine AP and l umbar spine Lat. The estimating results were analyzed and compared with two other methods using one-way analysis of variance.Results: The high relation between the ESD calculated and the displayed DAP were founded with simple equation: ESD=0.0017.DAP+0.1546 (R2=0.88) The mean ESD estimated performed by DR examination with automatic exposure control (AEC) mode using our method, Mcparland method and Kisilewicz method were 1.07, 1.13 and 0.89 whereas without AEC mode were 3.25, 3.45 and 2.60 respectively. There was provided no statistically significant difference between our approach and two other methods (p-value>0.010).Conclusion: The displayed DAP can be used to estimate the ESD.