RT Journal Article SR Electronic T1 Whole-Body Distribution and Brain Tumor Imaging with 11C-4DST: A Pilot Study JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1322 OP 1328 DO 10.2967/jnumed.111.088435 VO 52 IS 8 A1 Jun Toyohara A1 Tadashi Nariai A1 Muneyuki Sakata A1 Keiichi Oda A1 Kenji Ishii A1 Takuya Kawabe A1 Toshiaki Irie A1 Tsuneo Saga A1 Kazuo Kubota A1 Kiichi Ishiwata YR 2011 UL http://jnm.snmjournals.org/content/52/8/1322.abstract AB Recently, we developed [methyl-11C]4′-thiothymidine (11C-4DST) as an in vivo cell proliferation marker. The present study was performed to determine the safety, distribution, radiation dosimetry, and initial brain tumor imaging of 11C-4DST in humans. Methods: Multiorgan biodistribution and radiation dosimetry of 11C-4DST were assessed in 3 healthy humans, who underwent 2-h whole-body PET scanning. Radiation dosimetry was estimated from the residence times of source organs using the OLINDA program. Six brain tumor patients underwent dynamic 11C-4DST scans with arterial blood sampling. These patients were also evaluated with 11C-methionine PET on the same day (n = 4) as, or 3 wk before (n = 2), 11C-4DST PET studies. Metabolites in plasma and urine samples were analyzed by high-performance liquid chromatography. Breakdown of the blood–brain barrier in tumor tissue was confirmed by gadolinium-enhanced T1-weighted MRI. Results: There were no serious adverse events in any subjects at any time during the study period. 11C-4DST PET demonstrated selective uptake in the bone marrow, which has a high rate of proliferation. In addition, high-level uptake was also seen in the liver. The highest absorbed organ dose was in the urinary bladder wall (17.6 μGy/MBq). The estimated effective dose for 11C-4DST was 4.2 μSv/MBq. 11C-4DST showed little uptake in normal brain tissues, resulting in low background activity for imaging of brain tumors. In contrast, 11C-4DST PET demonstrated rapid uptake in aggressive tumor masses, whereas no signal of 11C-4DST was seen in clinically stable disease in which 11C-methionine uptake was high. The distribution pattern of 11C-methionine in tumor regions was not always identical to that of 11C-4DST. Analysis of plasma samples by high-performance liquid chromatography indicated that more than 60% of the radioactivity was present as unchanged 11C-4DST at 20 min. Conclusion: The initial findings of the present study in a small group of patients indicated that 11C-4DST PET is feasible for imaging of brain tumors. Dosimetry and pharmacologic safety were acceptable at the dose required for adequate PET images.