HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Novak, J. Articles by Metzler, S. PubMed Articles by Novak, J. Articles by Metzler, S.

Experimental and Monte Carlo measurement of the sensitivity and resolution dependence on the incidence angle of a slit-slat collimator

¹ Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; ; ² Radiology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania

1816

Objectives: A slit-slat (SS) collimator combines a slit parallel to the axis of rotation (AOR) of a gamma camera with a set of septa perpendicular to the AOR and evenly spaced in the axial direction. Analytic considerations suggest a sensitivity dependence of sin^x, where is the incidence angle and x=3, and axial and transaxial resolutions that are independent of . On-axis experimental and Monte Carlo (MC) sensitivity and resolution results have recently been reported; we report here on our experimental and MC measurement of the generalized off-axis dependence. Methods: A prototype SS collimator was constructed from pre-existing materials. ⁵⁷Co point source data were collected at heights above the slit ranging from 37 to 77 mm, and covering an incident angle range from 55 to 125°. The slat spacing was controlled with nylon strips. MC runs were carried out using the Geant4 simulation package both under ideal conditions (i.e., no penetration or scatter) and to assess the limitations of the experimental setup. Results: MC data under ideal conditions yield x=3.00±0.02, experimental data yield x=3.5±0.2, and MC data simulating slit and slat penetration and scatter yield x=3.47±0.02. Both experimental and MC axial and transaxial resolutions are consistent with no dependence. Conclusions: MC data not modeling penetration and scatter confirm the x=3 dependence expected from analytic considerations. In addition, MC data show that the deviation between theory and experiment can be explained by penetration and scatter, which are not modeled by the theory. It is interesting to note that although the on-axis SS sensitivity is the geometric mean of pinhole and parallel-beam sensitivity, this behavior does not extend to the angular dependence. Also, the only integer value for x consistent with all data is 3.

Research Support (if any): This research was supported by the National Institute for Biomedical Imaging and Bioengineering of the National Institutes of Health under grants R01-EB-001910 and R33-EB-001543.

Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Novak, J. Articles by Metzler, S. PubMed Articles by Novak, J. Articles by Metzler, S.