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M H Selikson

Publications and source records attributed to M H Selikson.

6 recordsLinked to original sources
PubMed1997

A proposal for minimum detectable compartment in MIRD dosimetry modelling.

The accuracy of radiation dose estimates from radiopharmaceutical administrations has recently become more important for three main reasons: (i) clinical providers are demanding more information on diagnostic procedures; (ii) regulatory groups are scrutinizing dosimetry for research subjects; and (iii) accurate organ doses are crucial in therapeutic administrations. These dose estimates are a sensitive function of the residence times. Because most clinical data acquisition protocols are limited to the first 24 h after dose administration, the area under the remainder of the time-activity curve (TAC) must be estimated. Estimation methods range from assuming physical decay only (overly conservative) to extrapolating end point physiological kinetics (overly liberal). This study demonstrates how much the results from these two methods vary and develops an alternative method which more accurately estimates this remainder term. A method, called the minimum detectable compartment (MDC), is constructed so that an accurate dose estimate can be made with a realistic measure of the remainder term. The method for determining MDC uses standard hypothesis testing. Using an analogue of the traditional minimal detectable activity calculation, a model with and without constant compartments is fitted to the TAC. The size of the constant compartment is varied until the relative likelihood of the two models meets the desired measure of power and sensitivity. Computer simulations of a simple mono-exponential are used to demonstrate the MDC as a function of the model, the number of data points, the range of the data and the noise in the data. The MDC is a very sensitive function of the data range. It falls by more than 50% when the data range is increased from two to three half-lives. In addition, the MDC is moderately sensitive to the noise in the data and relatively insensitive to the number of data points. These findings suggest that the MDC method can also be uses a priori to indicate what type of data collection regimen is necessary to achieve a certain accuracy.

Humans↗
PubMed1993

Biodistribution and dosimetry of iodine-123-IBF: a potent radioligand for imaging the D2 dopamine receptor.

Iodine-123-labeled iodo-benzofuran (IBF) is a potent D2 dopamine receptor antagonist that has been developed as a potential SPECT imaging agent. This report documents its biodistribution and radiation dosimetry in seven healthy humans. Approximately 100 MBq of IBF were administered to each volunteer. Urine was collected to measure the fraction of the activity that was voided by the renal system. Conjugate images were serially acquired over 24 hr to determine the fraction of activity in the other organs. Standard image analysis techniques were used to measure the geometric mean count rates in the brain, GI tract, heart, liver, lungs and thyroid at each time point. Corrections for attenuation were made with 123I transmission scans. Multicompartmental modeling was used to stimulate and predict the biokinetic behavior of 123I-IBF in the rest of the body. The absorbed doses for 24 organs were then estimated with the MIRD formalism. Rapid biological washout minimized the absorbed dose to most tissues. The excretory organs were exposed to the most radiation. The lower large intestine received about 0.13 mGy/MBq (0.48 rad/mCi), and the urinary bladder received 0.11 mGy/MBq. This low radiation burden will allow more than 370 MBq (10 mCi) to be administered to healthy research subjects during each study of the D2 receptor. Since high quality images of the brain can be obtained with half this amount, the findings suggest that 123I-labeled IBF has a large margin of radiation safety in humans. Its stability in vivo and its high target-to-background contrast ratio in the human brain may make it a useful SPECT imaging agent.

Adult↗
PubMed1993

The dosimetry of iodine-123-labeled TISCH: a SPECT imaging agent for the D1 dopamine receptor.

TISCH is an iodinated D1 specific dopamine receptor antagonist that may be useful as a SPECT imaging agent. This report documents its pharmacological safety in animals and its radiation dosimetry in humans. The dose of radiation that 123I-TISCH delivered to seven healthy subjects was estimated with the absorbed fraction technique. Conjugate images of the body were serially acquired for up to 24 hr after the administration of a known amount of activity. The count rates in the organs that could be visualized were measured on each image. These count rates were corrected for attenuation with 123I transmission scans. The doses to the other organs that did not take up enough activity to be visualized on the images were estimated with established models. The dosimetry was calculated for each subject individually before the results were averaged. Rapid biological washout minimizes the radiation exposure to most organs. The dose to the large bowel is limiting in healthy volunteers. The proximal colon receives about 0.67 rad/mCi (180 microGy/MBq) or about 5 rads for every 7.5 mCi of TISCH injected. This low radiation burden should make it feasible to study the D1 dopamine receptor in patients who have neuropsychiatric disorders before and after treatment.

Adult↗