TY - GEN

T1 - Map estimation of oxygen tension in retinal vessels with phosphorescence lifetime imaging

AU - Yildirim, Isa

AU - Ansari, Rashid

PY - 2012

Y1 - 2012

N2 - In phosphorescence lifetime imaging methods oxygen tension in retinal vessels has traditionally been indirectly determined from the estimates of intermediate variables whose noise-contaminated linear combinations are observed as phosphorescence intensity images. The classical least squares (LS) and regularized least squares (RLS) methods were used to obtain estimates of the intermediate variables. The estimates of the intermediate variables are then used to compute oxygen tension. The estimates of intermediate variables, however, do not yield an optimum estimate of oxygen tension due to its nonlinear dependence on the ratio of intermediate variables. Moreover, prior knowledge about the variables is very limited so that the level of noise cannot be reliably estimated, thereby affecting the automated choice of the regularization parameter in the RLS method. In this study the problem of optimally estimating oxygen tension in retinal vessels using the maximum a posteriori (MAP) criterion is addressed. For this purpose the conditional distribution of oxygen tension is derived given the phosphorescence lifetime imaging observations and model. The performance of MAP is compared with that of LS and the RLS methods using simulated data and its improved performance in the presence of different levels of noise is demonstrated.

AB - In phosphorescence lifetime imaging methods oxygen tension in retinal vessels has traditionally been indirectly determined from the estimates of intermediate variables whose noise-contaminated linear combinations are observed as phosphorescence intensity images. The classical least squares (LS) and regularized least squares (RLS) methods were used to obtain estimates of the intermediate variables. The estimates of the intermediate variables are then used to compute oxygen tension. The estimates of intermediate variables, however, do not yield an optimum estimate of oxygen tension due to its nonlinear dependence on the ratio of intermediate variables. Moreover, prior knowledge about the variables is very limited so that the level of noise cannot be reliably estimated, thereby affecting the automated choice of the regularization parameter in the RLS method. In this study the problem of optimally estimating oxygen tension in retinal vessels using the maximum a posteriori (MAP) criterion is addressed. For this purpose the conditional distribution of oxygen tension is derived given the phosphorescence lifetime imaging observations and model. The performance of MAP is compared with that of LS and the RLS methods using simulated data and its improved performance in the presence of different levels of noise is demonstrated.

KW - least squares

KW - maximum a posteriori

KW - oxygen tension

KW - Phosphorescence lifetime imaging

KW - regularized least squares

UR - http://www.scopus.com/inward/record.url?scp=84864829070&partnerID=8YFLogxK

U2 - 10.1109/ISBI.2012.6235523

DO - 10.1109/ISBI.2012.6235523

M3 - Conference contribution

AN - SCOPUS:84864829070

SN - 9781457718588

T3 - Proceedings - International Symposium on Biomedical Imaging

SP - 218

EP - 221

BT - 2012 9th IEEE International Symposium on Biomedical Imaging

T2 - 2012 9th IEEE International Symposium on Biomedical Imaging: From Nano to Macro, ISBI 2012

Y2 - 2 May 2012 through 5 May 2012

ER -