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Biomedical subjects

F F Knapp

Publications and source records attributed to F F Knapp.

At least 19 recordsLinked to original sources
PubMed2003

Repeated bone-targeted therapy for hormone-refractory prostate carcinoma: tandomized phase II trial with the new, high-energy radiopharmaceutical rhenium-188 hydroxyethylidenediphosphonate.

PURPOSE: We investigated the effect of repeated bone-targeted therapy with rhenium-188 hydroxyethylidenediphosphonate (HEDP) in patients with progressive, hormone-resistant prostate carcinoma and bone pain. The aim of this study was to determine the pain palliation and the antitumor effect of rhenium-188 HEDP treatments. PATIENTS AND METHODS: Sixty-four patients were randomly assigned to one of two groups for radionuclide therapy with rhenium-188 HEDP; patients of group A received a single injection, patients of group B received two injections (interval, 8 weeks). After therapy, patients were followed-up by assessment of pain palliation and clinical outcome until death. RESULTS: In both groups, toxicity was low, with moderate thrombopenia and leukopenia (maximum common toxicity criteria grade of 2). The effectiveness of rhenium-188 HEDP for pain palliation was better in the repeated treatment group (group B), with a response rate and time of response of 92% and 5.66 months, respectively (P =.006 and P =.001). In group B, 11 (39%) of 28 patients had a prostate-specific antigen decrease of more than 50% for at least 8 weeks, compared with two (7%) of 30 patients in the single-injection group (group A). The median times to progression of group A and group B were 2.3 months (range, 0 to 12.2 months) and 7.0 months (range, 0 to 24.1 months), respectively (P =.0013), and the median overall survival times were 7.0 months (range, 1.3 to 36.7 months) and 12.7 months (range, 4.1 to 32.2 months), respectively (P =.043). CONCLUSION: Compared with single-injection therapy, repeated bone-targeted therapy with rhenium-188 HEDP administered to patients with advanced progressive hormone-refractory prostate carcinoma enhanced pain palliation and improved progression-free and overall survival. Larger studies are justified to further evaluate the use of rhenium-188 HEDP.

Aged↗
PubMed2003

Neutron flux characterization of a peripheral target position in the High Flux Isotope Reactor.

The High Flux Isotope Reactor at the Oak Ridge National Laboratory provides the highest steady-state thermal neutron flux in the western world for a wide range of experiments and for isotope production. The highest available fluxes are located in a flux trap region created inside the nested fuel elements. The experimentally determined thermal and the empirically obtained epithermal flux values along the vertical axis of the peripheral target position were fit to cosine curves, with the thermal flux ranging from 1.1 x 10(15)ns(-1)cm(-2) at outer positions to 1.5 x 10(15)ns(-1)cm(-2) at the center. The corresponding epithermal flux ranged from 3.5 x 10(13) to 7.5 x 10(13)ns(-1)cm(-2), respectively. The fast neutron flux (En > or = 0.32 MeV in two positions and En > or = 1.5 MeV in two other positions) was approximately 6 x 10(14)ns(-1)cm(-2), corresponding to a fast to thermal ratio of approximately 0.4.

Gamma Rays↗
PubMed2003

Nuclear imaging is more sensitive for the detection of viable myocardium than dobutamine echocardiography.

Intact perfusion, preserved metabolism of free fatty acids and glucose, and the presence of contractile reserve have been used as markers of viable myocardium. However, not all viable myocardium may exhibit all these characteristics. Accordingly, these features were evaluated in patients with chronic coronary artery disease and left ventricular dysfunction. Fourteen patients with chronic ischaemic heart disease and depressed left ventricular function (LVEF 34+/-10%) perfusion was evaluated by early resting 201Tl single photon emission computed tomography (SPECT), fatty acid utilization by 15-p-[123I]iodophenyl-3-(R,S)-methylpentadecanoic acid SPECT, glucose utilization by 2-[18F]fluoro-2-deoxy-D-glucose SPECT and contractile reserve (CR) by dobutamine echocardiography. The comparison of the different modalities was restricted to akinetic or dyskinetic myocardium as assessed by resting 2-dimensional echocardiography. For all techniques a 13-segment model was used. Sixty-four of 182 segments (35%) showed akinesia or dyskinesia. Intact perfusion was found in 33/64 (52%) segments. Fatty acid utilization was maintained in 38/64 (59%) segments and glucose utilization was maintained in 38/64 (59%) segments. CR was present in significantly fewer segments: 21 of 64 (33%) (P<0.01 vs glucose and fatty acid utilization). In the 21 segments with preserved CR, perfusion was intact in 16/21 (76%) segments, fatty acid utilization in 19/21 (90%) segments and glucose utilization was preserved in all (100%) segments. Conversely, in the 43 segments without CR, 17 segments (40%) showed intact perfusion, 19 segments (44%) preserved fatty acid utilization and 17 (40%) still showed preserved glucose utilization. Disagreement in segments between the viability markers was caused mainly by segments without CR but preserved perfusion, fatty acid or glucose utilization. The substantial number of segments with preserved glucose and fatty acid utilization but without contractile reserve, suggests an underestimation of myocardial viability by dobutamine echocardiography.

Coronary Artery Disease↗
PubMed2002

DGAT1 is not essential for intestinal triacylglycerol absorption or chylomicron synthesis.

Dietary triacylglycerols are a major source of energy for animals. The absorption of dietary triacylglycerols involves their hydrolysis to free fatty acids and monoacylglycerols in the intestinal lumen, the uptake of these products into enterocytes, the resynthesis of triacylgylcerols, and the incorporation of newly synthesized triacylglycerols into nascent chylomicrons for secretion. In enterocytes, the final step in triacylglycerol synthesis is believed to be catalyzed primarily through the actions of acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes. In this study, we analyzed intestinal triacylglycerol absorption and chylomicron synthesis and secretion in DGAT1-deficient (Dgat1(-/-)) mice. Surprisingly, DGAT1 was not essential for quantitative dietary triacylglycerol absorption, even in mice fed a high fat diet, or for the synthesis of chylomicrons. However, Dgat1(-/-) mice had reduced postabsorptive chylomicronemia (1 h after a high fat challenge) and accumulated neutral-lipid droplets in the cytoplasm of enterocytes when chronically fed a high fat diet. These results suggest a reduced rate of triacylglycerol absorption in Dgat1(-/-) mice. Analysis of intestine from Dgat1(-/-) mice revealed activity for two other enzymes, DGAT2 and diacylglycerol transacylase, that catalyze triacylglycerol synthesis and apparently help to compensate for the absence of DGAT1. Our findings indicate that multiple mechanisms for triacylglycerol synthesis in the intestine facilitate triacylglycerol absorption.

Acyltransferases↗
PubMed2002

The impact of overexpression and deficiency of fatty acid translocase (FAT)/CD36.

Fatty acid translocase (FAT)/CD36 has been associated with diverse normal and pathologic processes. These include scavenger receptor functions (uptake of apoptotic cells and modified lipid), lipid metabolism and fatty acid transport, adhesion, angiogenesis, modulation of inflammation, transforming growth factor-beta activation, atherosclerosis, diabetes and cardiomyopathy. Although CD36 was identified more than 25 years ago, it is only with the advent of recent genetic technology that in vivo evidence has emerged for its physiologic and pathologic relevance. As these in vivo studies are expanded, we will gain further insight into the mechanism(s) by which CD36 transmits a cellular signal, and this will allow the design of specific therapeutics that impact on a particular function of CD36.

Adipocytes↗
PubMed2001

Defective fatty acid uptake in the spontaneously hypertensive rat is a primary determinant of altered glucose metabolism, hyperinsulinemia, and myocardial hypertrophy.

Genetic linkage studies implicated deficiency of CD36, a membrane fatty acid (FA) transporter, in the hypertriglyceridemia and hyperinsulinemia of the spontaneously hypertensive rat (SHR). In this study we determined whether loss of CD36 function in FA uptake is a primary determinant of the SHR phenotype. In vivo, tissue distribution of iodinated, poorly oxidized beta-methyliodophenyl pentadecanoic acid (BMIPP) was examined 2 h after its intravenous injection. Fatty acid transport was also measured in vitro over 20 to 120 s in isolated adipocytes and cardiomyocytes obtained from SHR and from a congenic line (SHRchr4) that incorporates a piece of chromosome 4 containing wild-type CD36. SHR heart and adipose tissue exhibited defects in FA uptake and in conversion of diglycerides to triglycerides that are similar to those observed in the CD36 null mouse. However, a key difference in SHR tissues is that fatty acid oxidation is much more severely impaired than fatty acid esterification, which may underlie the 4-5-fold accumulation of free BMIPP measured in SHR muscle. Studies with isolated adipocytes and cardiomyocytes directly confirmed both the defect in FA transport and the fact that it is underestimated by BMIPP. Heart, oxidative muscle, and adipose tissue in the SHR exhibited a large increase in glucose uptake measured in vivo using [(18)F]fluorodeoxyglucose. Supplementation of the diet with short-chain fatty acids, which do not require CD36-facilitated transport, eliminated the increase in glucose uptake, the hyperinsulinemia, and the heart hypertrophy in the SHR. This indicated that lack of metabolic energy consequent to deficient FA uptake is the primary defect responsible for these abnormalities. Hypertension was not alleviated by the supplemented diet suggesting it is unrelated to fuel supply and any contribution of CD36 deficiency to this trait may be more complex to determine. It may be worth exploring whether short-chain FA supplementation can reverse some of the deleterious effects of CD36 deficiency in humans, which may include hypertrophic cardiomyopathy.

Adipose Tissue↗
PubMed2001

Automation of the synthesis of highly concentrated 188Re-MAG3 for intracoronary radiation therapy.

We have developed an efficient method and an automated synthetic system for the preparation of highly concentrated 188Re-MAG3. Routine production of 188Re-MAG3 for use in intracoronary radiation therapy was performed by compressed air driven semi-automated shielded system. 188Re-MAG3 was prepared with a commercial kit and reducing agents, purified and concentrated by C18 Sep-Pak cartridges to desired radioactivity and volume. Using this automated system, reproducible radiolabeling yields of 80-85% were obtained.

Angioplasty, Balloon, Coronary↗
PubMed2001

Synthesis of a new bisphosphonic acid ligand (SEDP) and preparation of a (188)Re-(Sn)SEDP bone seeking radiotracer.

The new bisphosphonate ligand SEDP (2-sulfonato-1,1-ethylidene bisphosphonic acid) has been synthesized and characterized, including the determination of the protonation constants, and used to form (188)Re-(Sn)SEDP from Na(188)ReO4. The title compound (188)Re-(Sn)SEDP shows slightly greater bone uptake and less kidney uptake than (188)Re-(Sn)HEDP in rat biodistribution studies.

Animals↗
PubMed2001

Histologic study of effects of radiation synovectomy with Rhenium-188 microsphere.

Rhenium-188 microsphere is a relatively new radiation synovectomy agent developed for the treatment of rheumatoid arthritis. It has been shown that the levels of unwanted extra-articular radiation are negligible with this agent. A histologic study was conducted to assess the effect of radiation synovectomy on synovium and articular cartilage after intra-articular injection of various doses of Re-188 microspheres into the knee joints of rabbits. Intra-articular injection of Re-188 microspheres into rabbit knee joints resulted in mild reactive inflammation and thrombotic occlusion of vessels which subsided rapidly. Sclerosis of subsynovium could be seen 12 weeks after injection. No evidence of damage to articular cartilage was noted. There was no significant difference in the articular pattern after injection of 0.3 or 0.6 mCi Re-188 microspheres. This study suggests that a treatment dose of Re-188 microspheres causes transient inflammation of synovium without any detectable damage to the articular cartilage of knee joint.

Animals↗
PubMed2001

Efficacy of Re-188-labelled sulphur colloid on prolongation of survival time in melanoma-bearing animals.

UNLABELLED: In this study, the effectiveness of a 188Re labeled sulfur colloid with two particle size ranges was used to evaluate the effectiveness of this agent on melanoma tumors in mice in terms of animal lifespan. METHODS: Two separate group of animals were used for investigating biodistribution and survival time. A total of 188 B16F10-melanoma-bearing BDF(1) mice were injected intraperitoneally with 3.7 MBq (0.1mCi)/2mL of radiolabeled sulfur colloid ten days after intraperitoneal inoculation of 5x10(5) B16F10 melanoma cells/2ml. For group 1, 30 mice were sacrificed at 1, 4, 24, 48 and 72 hours for biodistribution studies. In group 2, 158 mice were divided into 9 groups (n=16 approximately 18/groups)each receiving respectively tumor alone, tumor with normal saline, cold colloid or hot colloid with 16, 23, 31, 46, 62, or 124 MBq activity. Each of these colloid groups was further divided into two groups, one receiving smaller particle sizes (<3 microm:80.4 +/-7.2%, colloid 1) and the other receiving larger particle sizes (<3 microm:12.3+/-1.0%, colloid 2). The animals were checked daily until death and their survival recorded. RESULTS: Colloid 2 showed higher accumulation in almost all tissues, the highest accumulation organ was tumor ( approximately 40%), then spleen ( approximately 20%), stomach ( approximately 15%), diaphragm ( approximately 3%), and liver ( approximately 2%). There was a significant increase in survival time with increasing amount of the larger-particle-size colloid. Administered levels of 16-31 MBq/mouse were most efficacious and with higher amounts the survival times decreased significantly below that of the controls. There was a significant difference in the dose-response curves for the two preparations. Protection factors (1/Relative-risk) of nearly 5 were achieved using the larger colloid size, and nearly 30 using the smaller colloid size. An amount of 16-31 MBq of the colloid 2 was the optimal activity in these studies. On the one hand, the survival data agreed well with the biodistribution data, where higher accumulation was found in tumor with colloid 2. CONCLUSION: Rhenium-188 offers on-site availability, medium half-life, higher beta-particle energy of 2.12 MeV for therapy and emission of 155keV gamma photon suitable for imaging. The present study demonstrated that 188Re-sulfur colloid is an effective agent in controlling tumor cells in the abdominal cavity in animals.

Animals↗
PubMed2001

Stereoselective synthesis, in vitro, and initial in vivo evaluation of 1-methylpiperidin-4-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (IPIP): a novel radioiodinated molecular probe with high affinity for the muscarinic receptor.

1-Methylpiperidin-4-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (IPIP, Fig. 1) was investigated as a potential radioiodinated molecular probe targeted to the muscarinic receptor complex. The IPIP stereoisomers were synthesized via a chiral intermediate in >95% enantiomeric excess. The R-isomers demonstrated a M(1) to M(2) subtype selectivity of approximately 3 to 1 and the S-isomers demonstrated non-subtype selective binding in vitro. IPIP was radiolabeled with iodide-125 with an average radiochemical yield of 74.4% (+/-14.8, n = 5), specific activities >800 mCi/micromol, and radiochemical purities >97%. In vivo the Z-isomers demonstrated high uniform cerebral uptake suggesting non-subtype selective binding. In contrast, E-R-IPIP, after allowing a low uptake in M(2) rich areas to clear, demonstrated a retention of activity in M(1) and M(4) rich cerebral regions. In addition, the cerebral uptake of E-R-IPIP and Z-S-IPIP were inhibited by 70-90% via pretreatment with R-QNB, an established muscarinic antagonist. An ex vivo metabolism study demonstrated Z-S-IPIP was stable at the receptor site with an absence of radiolabeled metabolites.

Animals↗
PubMed2000

Effects of beta(-)-emitting (188)Re balloon in stented porcine coronary arteries: an angiographic, intravascular ultrasound, and histomorphometric study.

BACKGROUND: Restenosis within stents may be prevented by ionizing radiation from an intravascular source. METHODS AND RESULTS: A liquid beta(-) radiation ((188)Re) balloon was evaluated in a randomized and blinded porcine coronary model of stent restenosis. Group A pigs (n=17) received 0,16, 22, or 29 Gy at 0.5-mm depth, followed by stenting. Restenosis was quantified by angiography, ultrasound, and histomorphometry at 30 days. Group B (n=7) was stented first and then treated with 0 or 29 Gy with follow-up at 60 days. There was a measurable effect at 16 Gy, which improved with increasing doses. At 29 Gy, the histological stenotic area was reduced by 67% (22% versus 66% in controls, P<0.001). Radiation after stenting was equally effective; the stenotic area was reduced (21% versus 65%, P<0.001). At 16 Gy, the vessel just distal to the stent was significantly smaller than control vessels because of intimal thickening (P=0.003). Radiated vessels had distinctive histology consisting of neointimal fibrin and reduced smooth muscle cells and matrix (P<0.0001). CONCLUSIONS: (188)Re balloon brachytherapy in porcine coronary arteries results in dose-dependent and injury-independent inhibition of stent restenosis for up to 60 days. Restenosis at the borders of the irradiated zone is a potential limitation and may be related to underdosing. Brachytherapy with the (188)Re balloon appears to be safe and feasible for clinical studies.

Angioplasty, Balloon, Coronary↗
PubMed2000

Defective uptake and utilization of long chain fatty acids in muscle and adipose tissues of CD36 knockout mice.

The transmembrane protein CD36 has been identified in isolated cell studies as a putative transporter of long chain fatty acids. In humans, an association between CD36 deficiency and defective myocardial uptake of the fatty acid analog 15-(p-iodophenyl)-3-(R, S)-methyl pentadecanoic acid (BMIPP) has been reported. To determine whether this association represents a causal link and to assess the physiological role of CD36, we compared tissue uptake and metabolism of two iodinated fatty acid analogs BMIPP and 15-(p-iodophenyl) pentadecanoic acid (IPPA) in CD36 null and wild type mice. We also investigated the uptake and lipid incorporation of palmitate by adipocytes isolated from both groups. Compared with wild type, uptake of BMIPP and IPPA was reduced in heart (50-80%), skeletal muscle (40-75%), and adipose tissues (60-70%) of null mice. The reduction was associated with a 50-68% decrease in label incorporation into triglycerides and in 2-3-fold accumulation of label in diglycerides. Identical results were obtained from studies of [(3)H]palmitate uptake in isolated adipocytes. The block in diglyceride to triglyceride conversion could not be explained by changes in specific activities of the key enzymes long chain acyl-CoA synthetase and diacylglycerol acyltransferase, which were similar in tissues from wild type and null mice. It is concluded that CD36 facilitates a large fraction of fatty acid uptake by heart, skeletal muscle, and adipose tissues and that CD36 deficiency in humans is the cause of the reported defect in myocardial BMIPP uptake. In CD36-expressing tissues, uptake regulates fatty acid esterification at the level of diacylglycerol acyltransferase by determining fatty acyl-CoA supply. The membrane transport step may represent an important control site for fatty acid metabolism in vivo.

Adipose Tissue↗
PubMed2000

Rhenium-188-labeled anti-neural cell adhesion molecule antibodies with 2-iminothiolane modification for targeting small-cell lung cancer.

We have evaluated the potential of 188Re-labeled monoclonal antibodies (MAbs) modified with 2-iminothiolane (2IT) for targeting small-cell lung cancer (SCLC). Radiolabeled MAbs NK1NBL1 and C218 recognizing neural cell adhesion molecule were injected i.v. into athymic mice inoculated with human SCLC tumors, and the biodistribution was examined. NK1NBL1 localized in the tumors better than C218. 188Re-labeled MAbs cleared from the blood faster than 125I-labeled counterparts, resulting in higher tumor-to-blood ratios. In conclusion, the 188Re-labeled MAbs are attractive candidates for imaging and therapy of SCLC.

Animals↗
PubMed2000

Dose escalation study with rhenium-188 hydroxyethylidene diphosphonate in prostate cancer patients with osseous metastases.

The aim of this study was to determine the maximum tolerated dose of rhenium-188 hydroxyethylidene diphosphonate (HEDP) in prostate cancer patients with osseous metastases who are suffering from bone pain. Twenty-two patients received a single injection of escalating doses of carrier-added 188Re-HEDP [1.3 GBq (35 mCi), 2.6 GBq (70 mCi), 3.3 GBq (90 mCi) and 4.4 GBq (120 mCi)]. Blood counts and biochemical parameters were measured weekly over a period of 8 weeks. Haematological toxicity (WHO grading) of grade 3 or 4 was considered unacceptable. Clinical follow-up studies including methods of pain documentation (medication, pain diary) were performed for 6 months after treatment. In the 1.3-GBq group, no haematological toxicity was observed. First haematotoxic results were noted in those patients with a dose of 2.6 GBq 188Re-HEDP. In the 3.3-GBq group, one patient showed a reversible thrombopenia of grade 1, one a reversible thrombopenia of grade 2 and three a reversible leukopenia of grade 1. In the 4.4-GBq group, thrombopenia of grades 3 and 4 was observed in one and two patients (baseline thrombocyte count <200x10(9)/l), respectively, and leukopenia of grade 3 was documented in one patient. The overall nadir of thrombopenia was at week 4. The individual, maximum percentage decrease in thrombocytes in the 1.3-, 2.6-, 3.3- and 4.4-GBq groups was 17%, 40%, 60% and 86%, respectively. In two patients, a transient increase in serum creatinine was observed (max. 1.6 mg/dl). Pain palliation was reported by 64% of patients, with a mean duration of 7.5 weeks. The response rate seemed to increase with higher doses, reaching 75% in the 4.4-GBq group. It is concluded that in prostate cancer patients, the maximum tolerated dose of 188Re-HEDP is 3.3 GBq if the baseline thrombocyte count is below 200x10(9)/l. In patients with thrombocyte counts significantly above 200x10(9)/l, a dose of 4.4 GBq might be tolerable. Thrombo- and leukopenia are the most important side-effects. Pain palliation can be achieved in 60%-75% of patients receiving a dose of 2.6 GBq or more of 188Re-HEDP. Studies in a larger patient population are warranted to evaluate further the palliative effect of 188Re-HEDP.

Bone Neoplasms↗
PubMed2000

Evaluation of Z-(R,R)-IQNP for the potential imaging of m2 mAChR rich regions of the brain and heart.

Alterations in the function or density of the m2 muscarinic (mAChR) subtype have been postulated to play an important role in various dementias such as Alzheimer's disease. The ability to image and quantify the m2 mAChR subtype is of importance for a better understanding of the m2 subtype function in various dementias. Z-(R)-1-Azabicyclo[2.2.2]oct-3-y (R)-alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (Z-(R,R)-IQNP) has demonstrated significant uptake in cerebral regions that contain a high concentration of m2 mAChR subtype in addition to heart tissue. The present study was undertaken to determine if the uptake of Z-(R,R)-IQNP in these regions is a receptor mediated process and to identify the radiospecies responsible for binding at the receptor site. A blocking study demonstrated cerebral and cardiac levels of activity were significantly reduced by pretreatment (2-3 mg/kg) of (R)-3-quinuclidinyl benzilate, dexetimide and scopolamine, established muscarinic antagonists. A direct comparison of the cerebral and cardiac uptake of [I-125]-Z-(R,R)-IQNP and [I-131]-E-(R,R)-IQNP (high uptake in ml, m4 rich mAChR cerebral regions) demonstrated Z-(R,R)-IQNP localized to a higher degree in cerebral and cardiac regions containing a high concentration of the m2 mAChR subtype as directly compared to E-(R,R)-IQNP. In addition, a study utilizing [I-123]-Z-(R,R)-IQNP, [I-131]-iododexetimide and [I-125]-R-3-quinuclidinyl S-4-iodobenzilate, Z-(R,R)-IQNP demonstrated significantly higher uptake and longer residence time in those regions which contain a high concentration of the m2 receptor subtype. Folch extraction of global brain and heart tissue at various times post injection of [I-125]-Z-(R,R)-IQNP demonstrated that approximately 80% of the activity was extracted in the lipid soluble fraction and identified as the parent ligand by TLC and HPLC analysis. These results demonstrate Z-(R,R)-IQNP has significant uptake, long residence time and high stability in cerebral and cardiac tissues containing high levels of the m2 mAChR subtype. These combined results strongly suggest that Z-(R,R)-IQNP is an attractive ligand for the in vivo imaging and evaluation of m2 rich cerebral and cardiac regions by SPECT.

Animals↗
PubMed2000

Preparation and biodistribution of rhenium-188 labeled albumin microspheres B 20: a promising new agent for radiotherapy.

Intra-arterial infusion of labeled particles is an effective method for endoradiotherapy of tumors. In this study, we radiolabeled biodegradable HSA microspheres (mean diameter = 25 microm) with the short-lived beta-emitter 188Re available from the aluminia-based 188W/188Re generator system. After 1 h 35-40% of the relative large amount of Sn(II) chloride required for effective reduction of Re(VII) for efficient attachment to the particles is precipitated as an amorphous coat of tin hydroxid colloid on the particle surface. The final 188Re bound to the particles was found to be stable in vitro. The radiolabelling yield was > 90%. The biological half-life was > 250 h and demonstrated sufficient in vivo stability after i.v. injection in Wistar rats. Because of the attractive properties of 188Re and the uniform particle size and stability, in vivo, this new agent is an attractive candidate for endoradiotherapy of tumors after selective catheterization.

Albumins↗