RT Journal Article
SR Electronic
T1 Change detection via signal subspace processing: Application to parathyroid gland detection
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 387P
OP 387P
VO 49
IS supplement 1
A1 Melvyn Carroll
YR 2008
UL http://jnm.snmjournals.org/content/49/supplement_1/387P.1.abstract
AB 1631 Objectives: The objective is to derive an optimal change detection algorithm which is robust with respect to local image misregistration. Methods: A test image, f2(x,y) potentially containing tumour signals is locally related to a reference, tumour free image, f1(u,v) by a set of filter coefficients h(x,y,u,v), i.e. f2(x,y)=h(x,y,u,v)f1(u,v). The locally spatially varying coefficients h(x,y,u,v) incorporates local misregistration and camera variation . Each point in the test image is a linear combination of the reference image and its spatially shifted versions around the current pixel. The coefficients of h(x,y,u,v) are spatially varying and derived through defining a linear signal subspace, in this case principal components(PC). For each pixel position in the test image a local window of 5x5 pixels are derived giving a 25x1 pixel test vector. In the reference image a homologous 5x5 window is defined along with shifted versions , +/- 2 pixels about the centre giving a vector set of 25x25 pixels. The first 7 eigenvalues of this matrix derive a set of PC’s capturing 99% of the data variance and form the coefficients of the filter h7(x,y,u,v). The 25x1 test vector is projected onto h7 and the error between the predicted and actual values of the test vector indicates the degree of change. Results: 12 patients with tertiary hyperparathyroidism were studied with I123/Tc99m MIBI dual isotope imaging prior to surgery. 44 out of 46 glands identified at surgery were detected using the subspace approach with a sensitivity of 97.8% and positive predictive value of 95.6%. Conclusions: Local subspace change detection is robust with respect to patient movement and sensitive down to 50mg detected gland size.