RT Journal Article
SR Electronic
T1 Investigation of liquid urethane expanding foam as a lung equivalent material for quantitative SPECT/CT phantom studies
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1881
OP 1881
VO 57
IS supplement 2
A1 Miyaoka, Robert
A1 Hunter, William
A1 McDougald, Wendy
A1 Lewellen, Tom
A1 Vesselle, Hubert
YR 2016
UL http://jnm.snmjournals.org/content/57/supplement_2/1881.abstract
AB 1881Objectives Styrofoam beads with added water have traditionally been used to simulate lung in SPECT phantoms. However, this may not be appropriate for SPECT/CT using CT-based attenuation and scatter correction as the CT number at 120 kVp is typically -640 HU as opposed to approximately -750 to -850 HU for healthy lung and -900 to -950 HU for diseased lung. Two part liquid urethane expanding foam (UEF) was evaluated as a material that can be mixed with radioactivity to model lung attenuation for quantitative SPECT/CT imaging studies.Methods UEF consists of two liquid parts which determine the density of the final foam product. 3-lb/ft3 and 16-lb/ft3 kits were purchased which will allow production of foam with HU’s that vary from approximate -750 HU to -950 HU. Initial tesing was done using various combinations of the liquid mixtures to evaluate how foam density correlated with CT HU units. An assortment of phantoms was placed in the CT system’s field-of-view and CT data were collected. Radioactive foam phantoms were made by mixing a known amount of Tc-99m with the expanding liquid mixture. Eight 500-1000 ml radioactive phantoms with densities similar to lung were produced. All eight phantoms were placed together in the system’s imaging field-of-view and SPECT/CT data were collected. Images were reconstructed using iterative image reconstruction with resolution recovery, attenuation and scatter correction applied.Results For the non-radioactive samples the measured HU varied from -715 to -960 HU and were well correlated with the density of the samples. For the Tc-99m radioactive phantoms the average error in the estimate of activity for the eight phantoms was 4.5% with a range of 10.78% to 0.15%. For the radioactive samples, the small volume of liquid associated with the addition of Tc-99m to the urethane mixture had an impact on the density of the urethane foam (i.e., led to more expansion and a significant reduction in expected density).Conclusions Two part liquid urethane expanding foam can be used to simulate various states of healthy and diseased lung tissue for SPECT/CT imaging studies. Initial evaluation of the quantitative accuracy of SPECT/CT lung imaging using resolution recover, attenuation correction and scatter correction during image reconstruction demonstrates that biases as low as ~5% can be achieved. It is critical to minimize the liquid volumes of Tc-99m added to the two part liquid mixture for best density control of the final foam product.