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This study reports on the distribution and radiation dosimetry of iodine-123-labelled cis-11beta-methoxy-17alpha-iodovinyloestradiol (Z-[123I]MIVE), a promising radioligand for imaging of oestrogen receptors (ERs) in human breast cancer. Whole-body scans were performed up to 24 h after intravenous injection of 138-193 MBq Z-[123I]MIVE in five healthy female volunteers, four with and one without thyroid blockade. Blood samples were taken at various times up to 24 h after injection. Urine was collected up to 24 h after injection in order to calculate renal clearance and to aid in the interpretation of whole-body clearance, including faecal excretion. Time-activity curves were generated for the thyroid, heart, brain, breasts and liver, by fitting the organ-specific geometric mean counts, obtained from regions of interest, to a multicompartmental model. The MIRD formulation, using 11 source organs, was applied to calculate the absorbed radiation doses for various organs upon administration of Z-[123I]MIVE. The images showed rapid hepatobiliary excretion which resulted in good imaging conditions for the thoracic region. Imaging of the abdominal region was impeded due to extensive bowel activity. Diffuse uptake and retention of activity was seen in breast tissue, the breast-to-non-specific uptake ratio increasing over time. Z-[123I]MIVE was cleared by both the kidneys and the gastrointestinal tract. At 50 h p.i. the mean excretion in urine was predicted to be 58%+/-14% (SD) and that in faeces 31%+/-19%. If the thyroid was not blocked, it was the most critical organ (0.33 mGy/MBq). In general, the excretory organs received the highest absorbed doses, i.e. the lower and upper large intestinal walls (0.11 and 0.098 mGy/MBq, respectively), the urinary bladder wall (0.090 mGy/MBq), the gallbladder wall (0.087 mGy/MBq) and the small intestine (0.043 mGy/MBq). The average effective dose equivalent of Z-[123I]MIVE was estimated to be 0.033 mSv/MBq. The amount of Z-[123I]MIVE required for adequate breast cancer ER imaging results in an acceptable effective dose equivalent to the patient

This study reports on the biodistribution and radiation dosimetry of iodine-123-labelled N-omega-(flu- oropropyl)-2beta-carbomethoxy-3beta-(4-iodophenyl)tropane ([123I]FP-CIT), a promising radioligand for the imaging of dopamine transporters. In 12 healthy volunteers, conjugate whole-body scans were performed up to 48 h following intravenous injection of approximately 100 MBq [123I]FP-CIT. Attenuation correction was performed using a transmission whole-body scan obtained prior to injection of the radioligand, employing a 123I flood source. Blood samples were taken and urine was freely collected up to 48 h after injection of the radiotracer. For each subject, the percentage of injected activity measured in regions of interest over brain, striatum, lungs and liver were fitted to a multicompartmental model to give time-activity curves. The cumulative urine activity curve was used to model the urinary excretion rate and, indirectly, to predict faecal excretion. Using the MIRD method, nine source organs were considered in estimating absorbed radiation doses for organs of the body. The images showed rapid lung uptake and hepatobiliary excretion. Diffuse uptake and retention of activity was seen in the brain, especially in the striatum. At 48 h following the injection of [123I]FP-CIT, mean measured urine excretion was 60%+/-9% (SD), and mean predicted excretion in faeces was 14%+/-1%. In general, the striatum received the highest absorbed dose (average 0.23 mGy/MBq), followed by the urinary bladder wall (average 0.054 mGy/MBq) and lungs (average 0.043 mGy/MBq). The average effective dose equivalent of [123I]FP-CIT was estimated to be 0.024 mSv/MBq. The amount of [123I]FP-CIT required for adequate dopamine transporter imaging results in an acceptable effective dose equivalent to the patient

SPECT imaging with 123I-labeled methyl 3 beta-(4-iodophenyl)tropane-2 beta-carboxylate ([123I]beta-CIT) in nonhuman primates has shown brain striatal activity, which primarily reflects binding to the dopamine transporter. The biodistribution and calculated radiation-absorbed doses of [123I]beta-CIT administered to eight healthy subjects were measured with attention to the accurate determination of organ time-activity data.Whole-body transmission images were obtained with a scanning line source for attenuation correction of the emission images. Following administration of 92.5 +/- 22.2 MBq (2.5 +/- 0.6 mCi) of [123I]beta-CIT, subjects were imaged with a whole-body imager every 30 min for 3 hr, every 60 min for the next 3 hr and at 12, 24 and 48 hr postinjection. Regional body conjugate counts were converted to microcuries of activity, with a calibration factor determined in a separate experiment using a distributed source of 123I.The peak brain uptake represented 14% of the injected dose, with 2% of the activity approximately overlying the striatal region. Highest radiation-absorbed doses were to the lung (0.1 mGy/MBq, 0.38 rads/mCi), liver (0.087 mGy/MBq, 0.32 rads/mCi) and lower large intestine (0.053 mGy/MBq, 0.20 rads/mCi).Iodine-123-beta-CIT is a promising SPECT agent for imaging of the dopamine transporter in humans with favorable dosimetry and high brain uptake.