The criteria for measuring average density by x-ray attenuation: The role of spatial resolution
It is well known that the attenuation of X-rays as they pass through a material can be used to quantify the amount of matter in their path. This is the basis for the gamma ray densitometer which can measure the amount of material on a moving conveyor belt. It is also the rationale for using X-rays for medical imaging as the attenuation can discriminate between tissue of different density and composition, yielding images of great diagnostic utility. Spatial resolution is obviously important with regard to detecting small features. However, it is less obvious that it plays an important role in obtaining quantitative information from the X-ray transmission data since the spatial resolution of the instrument can affect the accuracy of those measurements. This problem is particularly severe in the case of computed tomography where the accuracy of the reconstruction is dependent on the accuracy of the initial projection data. It should be noted that spatial resolution is not a concern for the case where the material is uniform. Here uniform is defined by small variations related to either the scale size of the resolution element in the detector, or to the size of a collimated X-ray beam. However, if the material has non-homogeneous composition or changes in density on the scale size of the systems spatial resolution, then there can be effects that will compromise the transmission data before it is acquired and these errors can not be corrected by any subsequent data processing. A method is presented for computing the density measurement error which parameterizes the effect in terms of the actual modulation on the face of the detector and the attenuation in the material. For cases like stacks of lead plates the errors can exceed 80%.
- Research Organization:
- Knolls Atomic Power Lab., Niskayuna, NY (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC12-76SN00052
- OSTI ID:
- 754940
- Report Number(s):
- KAPL-P-000315; K99098; TRN: US0003547
- Resource Relation:
- Conference: Twenty-sixth Annual Review of Progress in Quantitative Nondestructive Evaluation, Montreal, Quebec (CA), 07/29/1999; Other Information: PBD: 29 Jul 1999
- Country of Publication:
- United States
- Language:
- English
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