Comparative assessment of the accuracy of maximum likelihood and correlated signal enhancement algorithm positioning methods in gamma camera with large square photomultiplier tubes

Document Type : Original Article

Authors

1 Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, Iran

2 Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran

Abstract

Introduction: The gamma cameras, based on scintillation crystal followed by an array of photomultiplier tubes (PMTs), play a crucial role in nuclear medicine. The use of square PMTs provides the minimum dead zones in the camera. The camera with square PMTs also reduces the number of PMTs relative to the detection area. Introduction of a positioning algorithm to improve the spatial resolution in the detector with square PMT have been of interest in recent years.
Methods: In this study, the maximum-likelihood and correlated signal enhancement positioning methods were implemented in a camera with square PMTs. The developed camera consists of 3/8” thick monolithic NaI(Tl) crystal coupled to the array of 76mm sized PMTs. The comparison is based on measuring full width at half maximum (FWHM) and standard deviation of FWHM of point sources in a 15×15 grid of samples with 2-mm grid spacing, produced using MLE and CSE positioning methods.
Results:The intrinsic spatial resolution in (x, y) directions was (3.8, 3.8), (4.3, 4.5) mm for CSE and MLE methods respectively. Also, the standard deviations was almost the same in both methods (0.5 and 0.6 for CSE and MLE respectively). Although by applying MLE method, the resolution degrades by 16% but the produced image introduced acceptable quality.
Conclusion: The results show the MLE method presented acceptable performance in comparison to CSE method as reference in the detector with large square PMTs. Note that the MLE method does not require any linearity correction process because it can estimate the exact position of events.

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References

  1. Anger HO. Scintillation camera. Rev Sci Instrum. 1958;29:27-33.
  2. Peterson TE, Furenlid LR. SPECT detectors: the Anger camera and beyond. Phys Med Biol. 2011;56:R145.
  3. Pani R, Pellegrini R, Soluri A, De Vincentis G, Scafe R, Pergola A. Single photon emission imaging by position sensitive PMT. Nucl Instrum Methods Phys Res A. 1998;409:524-528.
  4. Flower MA. Webb's physics of medical imaging. 2nd ed. CRC Press; 2012.
  5. Barrett HH, Hunter WC, Miller BW, Moore SK, Chen Y, Furenlid LR. Maximum-likelihood methods for processing signals from gamma-ray detectors. IEEE Trans Nucl Sci. 2009;56:725-735.
  6. Gray RM Macovski A. Maximum a posteriori estimation of position in scintillation cameras. IEEE Trans Nucl Sci. 1976;23:849-852.
  7. Moore S, Hunter W, Furenlid L, Barrett H. Maximum-likelihood estimation of 3D event position in monolithic scintillation crystals: Experimental results. IEEE Nucl Sci Symp Conf Record, 2007.
  8. Galasso M, Fabbri A, Borrazzo C, Cencelli VO, Pani R. A theoretical model for fast evaluation of position linearity and spatial resolution in gamma cameras based on monolithic scintillators. IEEE Trans Nucl Sci. 2016;63:1386-1398.
  9. Jansen FP, Binnie DM. Signal processing in scintillation cameras for nuclear medicine. Patent 5,504,334, 1996.
  10. Zeraatkar N, Sajedi S, Fard BT, Kaviani S, Akbarzadeh A, Farahani MH, Sarkar S, Ay MR. Development and calibration of a new gamma camera detector using large square Photomultiplier Tubes. J Instrum. 2017;12:P09008.
  11. Barrett HH. Detectors for small-animal SPECT II, statistical limitations and estimation methods. In: Kupinski MA, Barrett HH. Small-animal SPECT imaging. Boston, MA: Springer; 2005.p. 49-86.
  12. Anger HO. Scintillation camera with multichannel collimators. J Nucl Med.1964;5:515-531.
  13. Barrett HH, Myers KJ. Foundations of image science. John Wiley & Sons; 2013.
  14. Chen JC, Barrett HH. Likelihood window, energy window, and Bayesian window for scatter rejection in gamma cameras. IEEE Nucl Sci Symp Med Imaging Conf. (NSS/MIC), 1993.
  15. Chen JC: Modular gamma cameras: Improvements in scatter rejection, and characterization and initial clinical application. PhD thesis. University of Arizona, Committee on Optical Science (Graduate); 1995.
  16. ChenJC. Scatter rejection in modular gamma cameras for use in dynamic 3D SPECT brain imaging system. Comput Med Imaging Graph. 1997 Sep-Oct;21(5):283-91.
  17. Fessler JA, Rogers WL, Clinthorne NH, Robust maximum-likelihood position estimation in scintillation cameras. IEEE Nucl Sci Symp Med Imaging Conf. (NSS/MIC),1991.
  18. Bruyndonckx P, Léonard S, Tavernier S, Lemaître C, Devroede D, Wu Y, Krieguer M. Neural network-based position estimators for PET detectors using monolithic LSO blocks. IEEE Trans Nucl Sci. 2004;51(5):2520-2525.
  19. Talat D Guvenis A. Artificial neural network based positioning algorithm for PEM imaging. 14th National Biomedical Engineering Meeting; 2009 May 20-22; Balcova, Izmir, Turkey.
  20. Conde P, Iborra A, González A, Hernández L, Bellido P, Moliner L, Rigla JP, Rodríguez-Álvarez MJ, Sánchez F. Determination of the interaction position of gamma photons in monolithic scintillators using neural network fitting. IEEE Trans Nucl Sci. 2016;63(1):30-36.

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