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M Stabin

Publications and source records attributed to M Stabin.

14 recordsLinked to original sources
PubMed1996

Effect of prior radiopharmaceutical administration on Schilling test performance: analysis and recommendations.

UNLABELLED: Previously administered diagnostic and therapeutic radiopharmaceuticals may interfere with performance of the Schilling test for prolonged periods of time. Additionally, presence of confounding radionuclides in the urine may not be suspected if baseline urine measurements have not been performed before the examination. METHODS: We assumed that a spurious contribution of counts corresponding to 1% of the administered Schilling dose would begin to contribute clinically significant interference. Based on the typical amounts of radiopharmaceuticals administered, spectra of commonly used radionuclides and best available pharmacokinetic models of biodistribution and excretion, we estimated the interval required for 24-hr urinary excretion of diagnostic and therapeutic radiopharmaceuticals to drop below this threshold of significant interference. RESULTS: For previously administered 99mTc-based radiopharmaceuticals and 123I-Nal, the interval required for urinary levels of activity to fall below thresholds of allowable interference are between 2-5 days. For 67Ga-citrate, several 111In compounds, 131I-MIBG and 201Tl-thallous chloride, periods of 12-44 days are estimated. Estimates for 131I-Nal vary greatly between 4 and 115 days, depending on the amount administered, and the degree of thyroid uptake. CONCLUSION: Patients should be interviewed before performing the Schilling test to ensure that interfering radiopharmaceuticals have not been recently administered. The estimates developed in this paper can serve as guidelines for the necessary waiting time between prior radiopharmaceutical administration and the Schilling examination.

Aged↗
PubMed1994

Whole-body biodistribution, radiation absorbed dose and brain SPECT imaging with iodine-123-beta-CIT in healthy human subjects.

UNLABELLED: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: Iodine-123-beta-CIT is a promising SPECT agent for imaging of the dopamine transporter in humans with favorable dosimetry and high brain uptake.

Adult↗
PubMed1993

Dosimetry of iodine-123 iodobenzamide in healthy volunteers.

The distribution of the dopamine D2-receptor specific ligand iodine-123 (S)-(-)-2-hydroxy-3-iodo-6-methoxy-N[(1-ethyl-2- pyrrolidinyl)methyl]-benzamide (123I-IBZM) was investigated in human adults from whole-body scans, blood samples and urine collected up to 48 h after injection. Results from the present study performed in six healthy volunteers were combined with those of five volunteers from a previous study. Using the brain, liver, lungs and spleen as source organs, the MIRD method was applied to calculate the absorbed radiation dose of the radioligand in various organs. The thyroid (despite blockage), gallbladder wall, large intestinal walls and spleen received the highest absorbed doses. The average effective dose equivalent of 123I-IBZM for adults was estimated to be 0.034 mSv/MBq. The absorbed dose to the thyroid may be a limiting factor for 123I-IBZM studies in children.

Adult↗
PubMed1993

Samarium-153-EDTMP biodistribution and dosimetry estimation.

Fifty-two patients were treated with single doses of 153Sm-EDTMP in a Phase I escalating dose protocol for palliation of bone pain from metastatic prostate carcinoma. Samarium-153 (T1/2 46.3 hr), maximum beta-particle energies 810 keV (20%), 710 keV (30%), 640 keV (50%), gamma photon 103 keV (28%), was complexed to the tetraphosphonate chelate, EDTMP. Five groups of patients were treated at doses of 1.0, 1.5, 2.0, 2.5, and 3.0 mCi/kg to evaluate toxicity from treatment. Patients were screened prior to treatment and followed after treatment with 99mTc-MDP bone scans. Biodistribution data on this group of patients were acquired and showed rapid uptake of 153Sm-EDTMP into bone with complete clearance of nonskeletal radiotoxicity by 6-8 hr. Also included are complete sets of dosimetry estimations on an additional seven patients who received 0.5 mCi/kg 153Sm-EDTMP Ca++ as part of a multiple dose therapy trial. Estimated radiation absorbed doses to bone surfaces averaged 25,000 mrad/mCi (6686 Gy/MBq), and urinary bladder doses averaged 3600 mrad/mCi (964 Gy/MBq).

Bone Neoplasms↗
PubMed1992

Radiation dosimetry for technetium-99m-MAG3, technetium-99m-DTPA, and iodine-131-OIH based on human biodistribution studies.

Radiation dose estimates were calculated for the renal agents 99mTc-DTPA, 99mTc-MAG3, and 131I-OIH from biodistribution data gathered in groups of healthy human volunteers. Biokinetics were evaluated by Anger camera imaging, blood sampling, and urine collection and counting. Collected data were fit to four- or five-compartmental models using the CONversational Simulation, Analysis, and Modeling (CONSAM) software. Radiation dose estimates were performed using standard MIRD techniques. Average residence times in urinary bladder, kidney, and remainder of the body were used to predict radiation dose equivalents and effective dose equivalents for the three agents. Doses for DTPA and MAG3 were very similar and much lower on a per unit injected activity than OIH. The effective dose equivalents were 3.3 mSv/370 MBq for 99Tc-DTPA, 3.7 mSv/370 MBq for 99mTc-MAG3, and 0.99 mSv/11.1 MBq for 131I-OIH for bladder voiding every 4.8 hr; effective dose equivalents were 2.0 mSv/370 MBq for 99mTc-DTPA, 1.5 mSv/370 MBq for 99mTc-MAG3, and 0.28 mSv/11.1 MBq for 131I-OIH for bladder voiding at 30 min and then every 4.0 hr. Patients should void at the conclusion of the study, as early voiding can reduce the gonadal radiation dose by a factor of 2 to 3.

Humans↗
PubMed1991

A list of nuclear medicine radionuclides and potential contaminants for operators of in-vivo counters.

Operators of in-vivo counters often encounter unusual photopeaks, some of which may be attributed to nuclear medicine radiopharmaceuticals recently received by the subject. This article lists the most common radiopharmaceuticals used in nuclear medicine, their common uses, their half-lives and principal decay energies, and the half-lives and decay energies of any contaminants or daughter products they may contain. The purpose is to help the in-vivo counter operator track down and eliminate causes of such unusual photopeaks.

Catalogs as Topic↗
PubMed1990

The radiation dosimetry of 99Tcm-exametazime.

The biodistribution of the regional cerebral perfusion imaging agent, 99Tcm-exametazime, has been studied with volunteer subjects at Aberdeen, Homburg, Manchester and Milan. Data from these studies have been pooled and analysed to formulate a kinetic biodistribution model, allowing estimation of time integrals of activity in various body organs. Estimates of radiation dose to humans injected with this material have been made by applying the MIRD formalism to these data. The highest doses occur to the lachrymal glands, gallbladder and kidneys (33, 27 and 18 mSv, respectively, per 500 MBq administered.) The lachrymal glands were visualized in only 6 of the 26 volunteer studies. The effective dose equivalent, for the worst case individual, is 8.3 mSv. In the majority of subjects where there was no uptake in the lachrymal gland, the effective dose equivalent reduces to 6.9 mSv.

Adult↗
PubMed1988

An improved tungsten-178/tantalum-178 generator system for high volume clinical applications.

Clinical utilization of the multiwire gamma camera (MWGC) requires low-energy radionuclides. The short-lived (9.3 min) tantalum-178 (178Ta) is ideally suited for the MWGC and can be produced from long-lived (21.7 day) tungsten-178 (178W) by a previously reported 178W/178Ta generator. This generator, however, is limited by sharp increase in breakthrough after elution of only 30-60 column-volumes. To optimize the 178W/178Ta generator for clinical use, varying eluant acid concentrations were evaluated. A reduced (from 0.1 to 0.03N) HCI concentration in the eluant, coupled with low operating temperatures (3 to 5 degrees C) allowed high (40 to 60%) 178Ta yield. Minimal 178W breakthrough (less than .01%) resulted, even after elution of more than 200 column-volumes. Each of six tested generators provided sterile, high activity (up to 100 mCi) 178Ta elutions for more than 30 days. Radiation dosimetry was estimated utilizing both human and animal biodistribution data. The whole body (critical organ) dose in adults and neonates were 1/20 (1/21) and 1/19 (1/50) respectively relative to that of technetium-99m (99mTc) as sodium pertechnetate. The optimized 178W/178Ta generator provides a commercially practical, safe source of low-energy radioisotope for the MWGC with substantial dosimetry advantages over 99mTc.

Animals↗
PubMed1988

Radiation absorbed dose estimates for oxygen-15 radiopharmaceuticals (H2(15)O, C15O, O15O) in newborn infants.

In preparation for measurement of regional cerebral oxygen metabolism by positron emission tomography, radiation absorbed dose estimates for 19 internal organs, blood, and total body were calculated for newborn infants following bolus intravenous administration of H2(15)O and brief inhalation of C15O and O15O. Cumulated activity for each radiopharmaceutical was calculated from a compartmental model based on the known biologic behavior of the compound. Values for mean absorbed dose/unit cumulated activity (S) for internal organs and total body were based on a newborn phantom. S was separately calculated for blood. Total radiopharmaceutical absorbed dose estimates necessary to measure cerebral oxygen metabolism in a 3.51-kg infant based on 0.7 mCi/kg H2(15)O and 1 mCi/kg C15O and O15O were determined to be 1.6 rad to the lung (maximum organ dose), 0.28 rad to the marrow, 0.46 rad to the gonads, and 0.22 rad to total body. These values are similar to those for current clinical nuclear medicine procedures employing 99mTc in newborn infants.

Administration, Inhalation↗