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SU‐GG‐I‐163: A Scatter Correction Algorithm for Quantitative Yttrium‐90 SPECT Imaging
Author(s) -
Kappadath SC
Publication year - 2010
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 - 10.1118/1.3468199
Subject(s) - imaging phantom , nuclear medicine , collimated light , physics , spect imaging , projection (relational algebra) , iterative reconstruction , mathematics , optics , algorithm , medicine , computer science , artificial intelligence , laser
Purpose : To develop a scatter correction algorithm for quantitative 90 Y bremsstrahlung SPECT ( 90 Y QSPECT). Method and Materials : 90 Y SPECT/CT scans were acquired for 1mCi/10cc vial within a large acrylic phantom (STD) and anthropomorphic torso phantom with 13 μCi/cc in liver insert and two 16cc spheres with 1.66 mCi/sphere (sphere‐to‐liver ratio, S/L = 8). SPECT was acquired with two primary (PI: 65–95 & P2: 95–151 keV) and one scatter (S: 252–302 keV) window. Correlation analysis of projection profiles distal to 90 Y sources established that scatter in each P image could be modeled as a fraction of the S image to calculate scatter fractions (SFs). S projections scaled by the SF and smoothed with a 9.6 mm FWHM Gaussian filter were subtracted from the P projections, followed by 3D‐OSEM reconstruction of the scatter‐corrected P projections with CT‐based attenuation and system resolution compensations. Iterations (IT) and subsets (SUB) that yielded the correct S/L ratio was determined. SPECT reconstruction of the STD was used for 90 Y SPECT sensitivity calibration. Accuracy of 90 Y QSPECT was evaluated by comparing the calculated 90 Y activities in the RSD phantom to the true values. Results : The SFs for P1 and P2 were 1.06 and 1.23, respectively. The optimal IT and SUB for 90 Y SPECT were found to be 8 and 16. Based on 90 Y QSPECT images, the calculated activity (%error) in the RSD phantom liver insert was 14.2 (11%) & 13.1 (3%) μCi/cc for P1 & P2, while those for the two spheres (mCi) were 1.60 & 1.52 (6%) for P1, and 2.29 & 1.86 (25%) for P2. Conclusions : The measured accuracies for the liver insert (P1 & P2) and spheres (P1) are encouraging. The overestimation of sphere activity with P2 suggests improvements of the calibration and scatter correction algorithms are needed.