Premium
Improved activity estimation with MC‐JOSEM versus TEW‐JOSEM in In 111 SPECT
Author(s) -
Ouyang Jinsong,
Fakhri Georges El,
Moore Stephen C.
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2907561
Subject(s) - imaging phantom , mathematics , standard deviation , relative standard deviation , statistics , expected value , monte carlo method , nuclear medicine , medicine , detection limit
We have previously developed a fast Monte Carlo (MC)‐based joint ordered‐subset expectation maximization (JOSEM) iterative reconstruction algorithm, MC‐JOSEM. A phantom study was performed to compare quantitative imaging performance of MC‐JOSEM with that of a triple‐energy‐window approach (TEW) in which estimated scatter was also included additively within JOSEM, TEW‐JOSEM. We acquired high‐count projections of a 5.5cm 3sphere ofIn111at different locations in the water‐filled torso phantom; high‐count projections were then obtained withIn111only in the liver or only in the soft‐tissue background compartment, so that we could generate synthetic projections for spheres surrounded by various activity distributions. MC scatter estimates used by MC‐JOSEM were computed once after five iterations of TEW‐JOSEM. Images of different combinations of liver/background and sphere/background activity concentration ratios were reconstructed by both TEW‐JOSEM and MC‐JOSEM for 40 iterations. For activity estimation in the sphere, MC‐JOSEM always produced better relative bias and relative standard deviation than TEW‐JOSEM for each sphere location, iteration number, and activity combination. The average relative bias of activity estimates in the sphere for MC‐JOSEM after 40 iterations was − 6.9 % , versus − 15.8 % for TEW‐JOSEM, while the average relative standard deviation of the sphere activity estimates was 16.1% for MC‐JOSEM, versus 27.4% for TEW‐JOSEM. Additionally, the average relative bias of activity concentration estimates in the liver and the background for MC‐JOSEM after 40 iterations was − 3.9 % , versus − 12.2 % for TEW‐JOSEM, while the average relative standard deviation of these estimates was 2.5% for MC‐JOSEM, versus 3.4% for TEW‐JOSEM. MC‐JOSEM is a promising approach for quantitative activity estimation inIn111SPECT.