99m Technetium-HMPAO-labeled platelet scan in practice: Preparation, quality control, and biodistribution studies

Abstract There is no biodistribution or imaging data on 99mtechnetium (Tc)-hexamethyl propylamine oxime (HMPAO)-labeled platelets in the literature. The current study aimed to present updated information about the clinical procedures for preparation and use of labeled platelets. Following two-step centrifugation at 1500 and 2500 rpm, the platelets were extracted from whole blood into platelet-rich plasma (PRP) above the buffy coat and then from PRP into a platelet pellet at the bottom of the tube. The 99mTc-HMPAO-labeled platelets were inspected for purity, viability, release of 99mTc from platelets, and sterility. Also, microscopic examination and thin layer chromatography (TLC) were performed. Biodistribution was assessed following necropsy in BALB/c mice and through imaging of New Zealand rabbits. The separation ratio was estimated at 98%, and radiochemical purity was measured to be 80%. The labeling efficiency was above 30% in more than half of the assays (range: 17-43%). The release of 99mTc from platelets was 9% per hour at 37ºC. After 24 hours, stability was estimated at 54% in the human serum. The target organs of mice included the spleen and liver. In rabbits, the imaging results indicated liver as the target organ. Thyroid uptake was negligible up to 90 minutes. Based on the findings, extraction of platelets and labeling them with 99mTc-HMPAO is a feasible and safe approach in routine practice.

A Study on the Labeling Efficiency and Cytotoxicity of Hepatocyte-targeting Galactosylated Chitosan Compounds / 대한핵의학회잡지

PURPOSE: In prior study, we synthesized 99mTc-galactosylated chitosan (GC) and performed in vivo biodistribution study, showed specific targeting to hepatocyte. The aim of this study is to evaluate the labeling efficiency and cytotoxicity of modified galactosylated chitosan compounds, galactosyl methylated chitosan (GMC) and HYNIC-galactosylated chitosan (GCH). MATERIALS AND METHODS: GC, GMC and GCH were synthesized and radiolabeled with 99mTc. Then, they were incubated for 6 hours at room temperature and human serum at 37 degrees C. Labeling efficiencies were determined at 15, 30 m, 1, 2, 3 and 6 h after radiolabeling. To evaluate cytotoxicity, MTT assay was performed in HeLa and HepG2 cells. RESULTS: In comparison with them of 99mTc-GC, labeling efficiencies of 99mTc-GMC were significantly improved (100, 97 and 89% in acetone and 96.3, 95.8 and 75.6% in saline at 15 m, 1 and 6 h, respectively). Moreover, 99mTc-GCH showed more improved labeling efficiencies (> 95% in acetone and human serum and > 90% in saline at 6 h). In MTT assay, cytotoxicity was very low and not different from that of controls. CONCLUSION: These results represent that these compounds are radiochemically compatible radiopharmaceuticals, can be used in hepatocyte specific imaging study and in vivo gene or drug delivery monitoring.

Effect of Carrier on Labeling and Biodistribution of Re-188-Hydroxyethylidene diphosphonate / 대한핵의학회잡지

PURPOSE: Re-188-Hydroxyethylidene diphosphonate (HEDP) is a new cost-effective agent for systemic radioisotope therapy of metastatic bone pain. We investigated the influence of carrier for labeling and biodistribution of Re-188-HEDP using HEDP kit with or without carrier (KReO4). MATERALS AND METHODS: The kits (HEDP 15 mg, gentisic acid 4 mg and SnCl2.2H2O 4.5 mg) with or without carrier (KReO4 0.1 mg) were labeled with Re-188 solution, made available from an in-house generator by boiling for 15 min. We compared the labeling efficiency and stability of carrier-added and carrier-free preparations of Re-188-HEDP. Biodistribution and imaging studies of each preparation were performed in ICR mice (1.85~3.7 MBq/0.1 ml) and SD rats (74.1~85.2 MBq/0.5 ml). RESULTS: The carrier-added preparation showed high labeling efficiency (95% at pH 5) and high stability in serum (88%, 3 hr). However, the carrier-free preparation showed low labeling efficiency (59% at pH 5) and low stability (43%, 3 hr). The carrier-added preparation showed high uptake in bone and low uptake in stomach and kidneys. However, the carrier-free preparation showed lower uptake in bone and higher uptake in both stomach and kidneys, which is supposed to be due to released perrhenate. The carrier-added preparation also showed better images with higher skeletal accumulation, lower uptake in other organs and lower soft tissue uptake than the carrier-free preparation. CONCLUSION: The results of these studies clearly demonstrate that addition of carrier perrhenate is required for high labeling efficiency, stability, bone uptake and good image quality of Re-188-HEDP.

Labeling and Biodistribution of Re-188-DTPA ( Diethylenetriaminepentaacetic acid ) / 대한핵의학회잡지

Re-188 is useful candidate for therapeutic radionuclide because it has a physical half life of 17 hours, contains beta ernissions suitable for therapy(maximum energy 2.12MeV) and emits a garnma ray that is suitable for quantitative diagnostic scanning(155keV). To use He-188 as a radionuclide compound of angioplasty balloon radiotherapy, we investigated the labelling method and biodistribution of Re-188- DTPA. We postulated that labeled Re-188-DTPA is preferable because it would be excreted via urinary system more easily than other compounds. To label Re-188 with DTI'A, 1ml of 222MBqI(6mCi) of Re-188 was added to DTPA solution(DTPA 20mg, SnC4 2HsO 10mg, pH 3.5) and boiled at 100C for 120min in water bath. pH was adjuted to 5 with 2.3Fo sodium acetate. I.abeling efficiency was measured using TLC-SG(acetone, saline). We evaluated biodistribution of Re-188-DTPA in sacrificed mice at 10 and 60 minutes after injection. We acquired images of kidneys, and drew tirne-activity r.urves in normal dogs and rats and calculated Trnax and Tl/2 in rats. The labelling efficiency was 95.7Yo on average. Labelling of Re-188-DTPA was stable(90% after 5hours) in vitro at room temperature. According to time-activity curves of dogs and rats, it took 15 to 20 minutes after injection for Re-188-DTPA to be washed out through kidneys. In conclusion, Re-188-DTPA was successfully labeled, Re-188-DTPA was stable in vitro and was excreted early via kidneys in animals. We could recornmend Re-188-DTPA as radionuclide of potential use in angioplasty balloon radiotherapy.