TY - JOUR T1 - Comparison of Y-90 dosimetry derived from post-therapy PET/CT and bremsstrahlung SPECT imaging JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1893 LP - 1893 VL - 57 IS - supplement 2 AU - Karin Knesaurek AU - Abbas Tuli AU - Edward Kim AU - Lale Kostakoglu Y1 - 2016/05/01 UR - http://jnm.snmjournals.org/content/57/supplement_2/1893.abstract N2 - 1893Objectives The aim of our study was to compare Y-90 dosimetry obtained from bremsstrahlung SPECT (bSPECT) and PET/CT post-therapy Y-90 imaging.Methods : In a continuing study, after selective internal radiation therapy (SIRT) with Y-90 microspheres, 25 patients were immediately imaged on a dual-head Infinia SPECT/CT gamma camera (GE Medical Systems, Milwaukee, WI), with MEGP collimator. For the Y-90 bSPECT studies, 60 views at 30 s per view were acquired and images were reconstructed using an ordered subset expectation maximization (OSEM) algorithm. Attenuation correction was performed using the CT scan, the reconstruc¬tion matrix size was 128 × 128 and the pixel size was 4.4 mm. The CT was performed with 10mm axial sampling, 140 kpV, 2.5 mA, 2.6 rpm and with 256 × 256 matrix size. After recovery which took 2-3 hours, patients were taken to a PET/CT suite (mCT, Siemens Medical) in the adjacent building. The low mA, non-diagnostic CT images were used for attenuation correction and localization of the Y-90 microspheres in the PET/CT studies. The acquisition time was 15 min. The reconstruction matrix size was 200x200x75 and voxel size 4.07x4.07x3.00 mm3. The data were reconstructed using the vendor’s reconstruction software and were transferred to a common platform where the bSPECT and PET/CT Y-90 images were used to calculate Y-90 dosimetry using MIM 6.5 software (MIM Software Inc.). Local deposition method with known activity of Y-90 was used to calculate dosimetry.Results The differences between mean doses to the liver obtained from bSPECT and PET/CT were large. In most cases bSPECT average dose was only 30% of the PET/CT average liver dose.Conclusions Quantitative bremsstrahlung imaging is very difficult due to scatter, septal penetration, the continuous nature of the bremsstrahlung energy spectrum, and inefficient bremsstrahl¬ung production. Post therapy PET/CT Y-90 images are far superior in quality and quantitatively then bSPECT Y-90 images. Uncorrected and unprocessed bSPECT Y-90 images cannot be used for Y-90 dosimetry. ER -