Measurement of the Modulation Transfer Function for a Backscatter Radiography System Used in Nondestructive Examination

Traditional methods for measuring the modulation transfer function (MTF) of transmission x-ray systems cannot be directly applied to backscatter radiography units. This work presents two new methods for measuring the MTF of a backscatter radiography system based on imaging sharp edges and square-wave line pairs. Since the MTF of backscatter systems is dependent on the target material, test pieces were constructed of wood inlaid with lead line pairs. Signals from scanning the initial square-wave test pattern showed minimal contrast and high levels of noise, most likely attributable to insufficient attenuation provided by absorbing lead bars. Experimental results from the edge spread method show good agreement with theoretical data (mean difference within +/- 3%), indicating the potential use of this technique for measuring the MTF of a backscatter system. Inconclusive results from the line-pair method demonstrate the complexity of measuring the MTF for a backscatter system with this technique, most likely caused by insufficient attenuation, contributing scatter signal from material below the tool, and distortion from edge effects. We discuss a new design of an optimal line pair test tool for backscatter radiography, whose calculated MTF can then be compared to those from the edge spread method.

References
  1. Dunn W.L. and A.M. Yacout, “Corrosion Detection in Aircraft by X-Ray Backscatter methods”, Applied Radiation and Isotopes, Vol. 53, San Francisco: Elsevier (2000): p 625-632.
  2. Dugan E., A.M. Jacobs, and D. Shedlock, “Detection of Defects in Foam Thermal Insulation using Lateral Migration Backscatter X-ray Radiography”, SPIE Proceedings Volume 5541: Penetrating Radiation Systems and Applications VI, SPIE (October 2004).
  3. Callerame J., “X-Ray Backscatter Imaging: Photography Through Barriers”, Powder Diffraction, Vol. 21, Cambridge (2006): p 132-135.
  4. Samei E., M.J. Flynn, and D.A. Reimann, “ A Method for Measuring the Presampled MTF of Digital Radiographic Systems Using an Edge Test Device”, Medical Physics, No. 25, AIP (January 1998): p 102-113.
  5. Coltman J.W., “The Specification of Imaging Properties by Response to a Sine Wave Input”, Journal of the Optical Society of America, Vol. 44, No. 6. Washington D.C.: Optical Society of America, June 1954. p. 468- 469.
  6. Nill N., “Conversion Between the Sine and Square-Wave Spatial Frequency Response of an Imaging System, “ MITRE Technical Report, MITRE Corporation (2001).
  7. Yantao L. et al, “Depth Discrimination Methods Based on a Multirow Linear Array Detector for Push-broom Compton Scatter Imaging”, Applied Radiation and Isotopes, No. 82 San Francisco: Elsevier (2013): p 293-299.
  8. Buhr E. G., S. Gunther-Kohfahl, and U. Neitzel, “Accuracy of a Simple Method for Deriving the Presampled MTF of a Digital Radiographic System from an Edge Image”, Medical Physics, No. 30, AIP (2003): p 2323- 2331.
  9. International Electrotechnical Commission, “Medical Electrical Equipment-Characteristics of Digital X-ray Imaging Devices-Part 1: Determination of the Detector Quantum Efficient”, IEC 62220-1, Geneva: IEC (2003).
Metrics
Usage Shares
Total Views
56 Page Views
Total Shares
0 Tweets
56
0 PDF Downloads
0
0 Facebook Shares
Total Usage
56