Patient-specific dosimetry using quantitative SPECT imaging and three-dimensional discrete Fourier transform convolution

J Nucl Med. 1997 Feb;38(2):308-14.

Abstract

The objective of this study was to develop a three-dimensional discrete Fourier transform (3D-DFT) convolution method to perform the dosimetry for 131I-labeled antibodies in soft tissues.

Methods: Mathematical and physical phantoms were used to compare 3D-DFT with Monte Carlo transport (MCT) calculations based on the EGS4 code. The mathematical and physical phantoms consisted of a sphere and a cylinder, respectively, containing uniform and non-uniform activity distributions. Quantitative SPECT reconstruction was carried out using the circular harmonic transform (CHT) algorithm.

Results: The radial dose profile obtained from MCT calculations and the 3D-DFT convolution method for the mathematical phantom were in close agreement. The root mean square error (RMSE) for the two methods was < 0.1%, with a maximum difference < 21%. Results obtained for the physical phantom gave a RMSE < 0.1% and a maximum difference of < 13%; isodose contours were in good agreement. SPECT data for two patients who had undergone 131I radioimmunotherapy (RIT) were used to compare absorbed-dose rates and isodose rate contours with the two methods of calculation. This yielded a RMSE < 0.02% and a maximum difference of < 13%.

Conclusion: Our results showed that the 3D-DFT convolution method compared well with MCT calculations. The 3D-DFT approach is computationally much more efficient and, hence, the method of choice. This method is patient-specific and applicable to the dosimetry of soft-tissue tumors and normal organs. It can be implemented on personal computers.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Algorithms
  • Fourier Analysis
  • Humans
  • Iodine Radioisotopes
  • Models, Theoretical*
  • Monte Carlo Method
  • Phantoms, Imaging
  • Radioimmunodetection
  • Radioimmunotherapy*
  • Radiotherapy Planning, Computer-Assisted*
  • Tomography, Emission-Computed, Single-Photon*

Substances

  • Iodine Radioisotopes