TY - JOUR T1 - Iodine-124 for quantitative PET imaging of macromolecule transport in CSF JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1195 LP - 1195 VL - 52 IS - supplement 1 AU - Vasily Belov AU - Alan Fischman AU - Ali Bonab AU - Mikhail Papisov Y1 - 2011/05/01 UR - http://jnm.snmjournals.org/content/52/supplement_1/1195.abstract N2 - 1195 Objectives Cerebrospinal fluid (CSF), which surrounds the brain and spinal cord, provides a promising drug delivery avenue to the CNS. The rates and character of drug molecule translocations in CSF need to be studied, preferably, in non-human primates that have similarly structured CNS. Such studies can be carried out non-invasively using PET. The potentially slow rates of the processes of interest require a label with a long physical half-life. Among the currently available positron emitters, 124I has the longest physical half-life (4.2 days). However, the impact of the spectral characteristics of the 124I emission on the data quality has to be assessed to assure the quantitative character of the studies. Methods Imaging was carried out using MicroPET P4 (Siemens/Concorde Microsystems). Spatial resolution (FWHM) was studied using a line source, Ø=0.19 mm, in aqueous surrounding. A cylindrical phantom was used to evaluate the count-rate performance and sensitivity of coincidence detection. Model proteins (enzyme replacement therapy candidates) were used in imaging studies in cynomolgus monkeys. The proteins labeled with 124I were administrated via intralumbar injection to the spinal CSF pool. Results The spatial resolution of PET images with 124I was satisfactory although lower than for the more conventional short-leaving positron emitters (2.45 mm for 124I vs. 1.69 mm for 18F vs. 1.69 mm for 64Cu). Linearity of the true coincidence count-rate was observed up to 1.2 mCi. The animal studies demonstrated excellent delineation and resolution of the tissues of interest, including lymph nodes and major nerves. The quality of numerical data was appropriate for the analysis of protein pharmacokinetics in all experimental timeframes, from minutes (dynamic studies) to several hours and days. Conclusions PET imaging with 124I is capable of providing the data suitable for quantitative analysis of drug transport in CSF in non-human primates. Research Support This work was supported by a grant from Shire HGT, Lexington, MA ER -