TY - JOUR T1 - Patient-Specific Radiation Dosimetry of <sup>99m</sup>Tc-HYNIC-Tyr<sup>3</sup>-Octreotide in Neuroendocrine Tumors JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1474 LP - 1481 DO - 10.2967/jnumed.111.088203 VL - 52 IS - 9 AU - Joshua Grimes AU - Anna Celler AU - Bozena Birkenfeld AU - Sergey Shcherbinin AU - Maria H. Listewnik AU - Hanna Piwowarska-Bilska AU - Renata Mikołajczak AU - Piotr Zorga Y1 - 2011/09/01 UR - http://jnm.snmjournals.org/content/52/9/1474.abstract N2 - 99mTc-hydrazinonicotinamide-Tyr3-octreotide (99mTc-HYNIC-TOC) is increasingly gaining acceptance as a new radiopharmaceutical for the diagnosis of pathologic lesions overexpressing somatostatin receptors. However, little information has been published about the radiation dosimetry of this agent. The aim of this study was to assess the biodistribution and radiation dosimetry of commercially available 99mTc-HYNIC-TOC. A dose calculation procedure designed to be feasible to implement in a busy clinical environment was used. Methods: Twenty-eight patients were imaged for suspected neuroendocrine tumors using a series of whole-body planar, dynamic planar, and SPECT/CT studies, after injection with 99mTc-HYNIC-TOC. Patient-specific dosimetry was performed using the OLINDA/EXM software with time-integrated activity coefficients estimated from a hybrid planar/SPECT technique. A phantom experiment was performed to establish adaptive thresholds for determination of source region volumes and activities. Results: Pathologic uptake, diagnosed as due to neuroendocrine tumors, was observed in 12 patients. Normal organs with significant uptake included the kidneys, liver, and spleen. The mean effective dose after 99mTc-HYNIC-TOC injection was 4.6 ± 1.1 mSv. Average normal-organ doses were 0.030 ± 0.012, 0.021 ± 0.007, and 0.012 ± 0.005 mGy/MBq for the spleen, kidneys, and liver, respectively. The interpatient kidney dose ranged from 0.011 to 0.039 mGy/MBq, whereas the range of tumor doses varied from 0.003 to 0.053 mGy/MBq. The ratio of tumor to kidney dose ranged from 0.13 to 2.9. The optimal thresholds for recovery of true activity in the phantom study were significantly lower than those used for volume determination. Conclusion: The patient-specific 3-dimensional dosimetry protocol used in this study is a clinically feasible technique that has been applied to demonstrate large dose variations in tumors and normal organs between patients imaged with 99mTc-HYNIC-TOC. ER -