PT - JOURNAL ARTICLE AU - Arda Konik AU - Mark Madsen AU - John Sunderland TI - Evaluation of attenuation correction requirement in small animal PET and SPECT imaging DP - 2009 May 01 TA - Journal of Nuclear Medicine PG - 1465--1465 VI - 50 IP - supplement 2 4099 - http://jnm.snmjournals.org/content/50/supplement_2/1465.short 4100 - http://jnm.snmjournals.org/content/50/supplement_2/1465.full SO - J Nucl Med2009 May 01; 50 AB - 1465 Objectives Despite the growing interest in small animal emission tomography, little scientific information exist about the accuracy of attenuation methods on smaller size of objects, and what level of correction is required. The purpose of this work is to determine the role of attenuation correction as a function of object size through PET and SPECT simulations. Methods SPECT (at 140 keV) and PET simulations were performed using a mathematical emission and attenuation phantom that approximated a slice through the thorax. The emission object and the associated attenuation map were scaled to 5 different sizes approximating a human, dog, rabbit, rat and mouse. The simulated projections were reconstructed with three ways: 1) accurate correction using the actual attenuation map (AC), 2) attenuation correction using a constant attenuation map (CAC) inside the body contour, and 3) without attenuation correction (NC). Nine regions that sampled different areas of attenuation were evaluated. Results Table1 shows the error represented as a percent difference from the true value for both modalities. Compared to the uncorrected images, CAC images showed significant improvement in both modalities for all object sizes in non lung regions. In these regions, the mean errors in CAC images were 1.0% and 0.9% for mouse size, 2.4% and 2.1% for rat size, and 5.9% and 5.1% for rabbit size. Conclusions The results suggest that, in quantitative PET and SPECT studies requiring 5%-10% accuracy, uniform attenuation correction is sufficient up to rabbit size animals for the regions excluding the lungs. However, if accurate results are required throughout the body, it appears that transmission studies are required.