RT Journal Article
SR Electronic
T1 Evaluation of spherical phantom inserts with thin wall thickness for quantitative small animal SPECT
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1424
OP 1424
VO 50
IS supplement 2
A1 Jianhua Yu
A1 Greta  Mok
A1 John Jaszczak
A1 Martin Pomper
A1 Benjamin Tsui
YR 2009
UL http://jnm.snmjournals.org/content/50/supplement_2/1424.abstract
AB 1424 Objectives Our goal is to evaluate the effect of wall thickness (WT) of phantom inserts used in quantitative small animal (SA) SPECT. Methods Spherical phantom inserts of different sizes and WT (Data Spectrum Corp.) were filled with Tc-99m solution, placed inside a rat-size cylindrical phantom, and imaged using a commercial SPECT/CT system. Three inserts with WT of 0.5, 1 and 2mm and inner diameter (ID) of 3.9mm were scanned with source-to-background ratios (SBR) of 2 and 4. The former scan with SBR of 4 was repeated using different pinhole diameters of 0.5, 1 and 2mm corresponding to system resolution of 1.0, 1.6 and 2.9mm, respectively. For 1mm pinhole and SBR of 4, two insert sets with WT of 0.5 and 1mm, each with different ID of 3.9, 4.9, 6.2 and 7.8mm, were imaged. The index for quantitative assessment was the ratio (RWT) of measured activity within a region-of-interest with size of the actual insert to the known activity. Results The dips in the activity profile through the center of the 1mm-WT insert were less significant than that of 2mm-WT, and were not observed in that of 0.5mm-WT. The R0.5mm was 12.6% (15.9%) and 6.5% (8.3%) higher than R1mm (or R2mm) for 1mm pinhole and SBR of 2 and 4. It was 7.5% (9.3%) and 4.3% (5.3%) higher for 0.5mm and 2mm pinhole and SBR of 4. For the inserts with ID of 3.9, 4.9, 6.2 and 7.8mm, R0.5mm were 12.0%, 5.8%, 2.3% and 2.0%, respectively, higher than R1mm. Conclusions Thick WT of a spherical insert has significantly negative impact on SA SPECT quantitation, especially for low SBR, high system resolution and small object size. Phantom inserts with WT smaller than the system resolution are recommended for quantitative SA SPECT. Research Support This work was funded in parts by NIH grant CA92781 and EB1558.