Development of a generalized model for kidney depth estimation in the Chinese population: A multi-center study.

PURPOSE: To establish an accurate and reliable equation for kidney depth estimation in adult patients from different Chinese geographical regions. METHOD: This multicenter study enrolled Eastern Asian Chinese patients with abdominal PET/CT scans at 26 imaging centers from six macro-regions across China in 3 years. Age, gender, height, weight, primary disease and its extent on PET scans of the participants were collected as potential predictive factors. Kidney depth on CT, defined as the average of the vertical distances from the posterior skin to the farthest anterior and closest posterior surfaces of each kidney, was measured as the standard reference. The new kidney depth model was constructed using a multiple regression model, and its performance was compared to those of three established models by computing the absolute value of estimation errors in comparison with CT-measured kidney depth. RESULTS: A total of 2502 patients were enrolled and classified into training (n=1653) and testing (n = 849) subsets. In the training subset, two kidney depth models were constructed: Left (cm): 0.013×age+0.117×gender-0.044×height+0.087×weight+7.951, Right (cm): 0.005×age+0.013×gender-0.035×height+0.082×weight+7.266 (weight: kg, height: cm, gender = 0 if female, 1 if male). In the testing subset, one-way analysis of variance showed that the estimation errors of the new models did not significantly differ among the 6 regions. Bland-Altman analysis determined that new equations had lower estimated biases (left: 0.039 cm, right: 0.018 cm) compared with other existing models. CONCLUSION: The new equations were highly accurate for kidney depth estimation in adults from all over China, with lower estimation errors compared to other established models.

Imaging of VMAT2 binding sites in the brain by (18)F-AV-133: the effect of a pseudo-carrier.

OBJECTIVES: Recently, 9-[(18)F]fluoropropyl-(+)-dihydrotetrabenazine ((18)F-AV-133) was reported as a new vesicular monoamine transporter (VMAT2) imaging agent for diagnosis of Parkinson's disease (PD). To shorten the preparation of (18)F-AV-133 and to make it more widely available, we evaluated a simple, rapid purification with a solid-phase extraction method (SPE) using an Oasis HLB cartridge instead of high pressure liquid chromatography (HPLC). The SPE method produced doses containing a pseudo-carrier, 9-hydroxypropyl-(+)-dihydrotetrabenazine (AV-149). METHODS: To test the possible side effects of this pseudo-carrier, comparative dynamic PET scans of the brains of normal monkeys (2 each) and uni-laterally 6-OH-dopamine-lesioned PD monkeys (2 each) were performed using (18)F-AV-133 doses prepared by either SPE (containing pseudo-carrier) or HPLC (containing no pseudo-carrier). Autoradiographs of post mortem monkey brain sections were evaluated to confirm the relative (18)F-AV-133 uptake in the PD monkey brains and the effects of the pseudo-carrier on VMAT2 binding. RESULTS: The radiochemical purity of the (18)F-AV-133, whether prepared by SPE or by HPLC, was excellent (>99%). PET scans of normal and PD monkey brains showed an expected reduction of VMAT2 in the lesioned areas of the striatum. It was not affected by the presence of the pseudo-carrier, AV-149 (maximally 250 µg/dose). The reduced uptake in the striatum of the lesioned monkey brains was confirmed by autoradiography. Ex vivo inhibition studies of (18)F-AV-133 binding in rat brains, conducted with increasing amounts of AV-149, suggested that at the highest concentration (3.5mg/kg) the VMAT2 binding in the striatum was only moderately blocked (20% reduction). CONCLUSIONS: The pseudo-carrier, AV-149, did not affect the (18)F-AV-133/PET imaging of VMAT2 binding sites in normal or uni-laterally lesioned monkey brains. The new streamlined SPE purification method will enable (18)F-AV-133 to be widely available for routine clinical application in determining changes in monoamine neurons for patient with movement disorders or other psychiatric illnesses.