18-Fluoride labeled sodium fluoride positron emission tomography with computer tomography: the impact of pretreatment staging in intermediate- and high-risk prostate cancer.

BACKGROUND: 18-Fluoride labeled sodium fluoride (Na-18-F) positron emission tomography with computer tomography (PET/CT) has a better sensitivity and specificity than whole body bone scan (WBBS) in detecting osseous metastatic prostate cancer. We performed a pilot study of 20 men to examine what level of impact Na-18-F PET/CT has on management plans when used for staging newly diagnosed prostate cancer. MATERIALS AND METHODS: Twenty men were prospectively enrolled into the study in South Australia. Men were eligible if they had newly diagnosed, untreated, and biopsy-confirmed intermediate- or high-risk prostate cancer (D'Amico classification). WBBS and Na-18-F PET/CT scans were performed within 1 week of each other. Following review of the WBBS, treatment type and intent was documented by the treating urologist. The Na-18-F PET/CT scan was then reviewed. The impact of the Na-18-F PET/CT was measured on whether treatment modality or intent was subsequently altered: high impact = treatment intent or modality was changed; medium impact = treatment modality was modified; low impact = no change in treatment. RESULTS: In 18 men (90%), the WBBS and Na-18-F PET/CT were negative for osseous metastases. In one man (5%), the WBBS demonstrated widespread osseous metastases which were similarly demonstrated on the Na-18-F PET/CT. One man (5%) had a normal WBBS; however, the Na-18-F PET/CT demonstrated widespread osseous metastases. Subsequently, in 19 men (95%), the results of the two scans were congruent and the addition of the Na-18-F PET/CT scan demonstrated a low impact on management. In one man (5%), the addition of the Na-18-F PET/CT had a high impact as treatment type and intent was altered. CONCLUSIONS: Our pilot study is the first of its kind in Australia, and our findings suggest that Na-18-F PET/CT is a safe and feasible modality for staging prostate cancer. However, its true impact on prostate cancer management warrants further investigation.

Hybrid 99mTc-magnetite tracer for dual modality sentinel lymph node mapping.

Accuracy of sentinel lymph node identification using radioactive tracers in non-superficial cancers can be limited by radiation shine through and low spatial resolution of detection systems such as intraoperative gamma probes. By utilising a dual radioactive/magnetic tracer, sensitive lymphoscintigraphy can be paired with high spatial resolution intraoperative magnetometer probes to improve the accuracy of sentinel node detection in cancers with complex multidirectional lymphatic drainage. Dextran-coated magnetite nanoparticles (33 nm mean hydrodynamic diameter) were labelled with 99mTc and applied as a lymphotropic tracer in small and large animal models. The dual tracer could be radiolabelled with 98 ± 2% efficiency after 10 min of incubation at room temperature. Biodistribution studies of the tracer were conducted in normal rats (subdermal and intravenous tail delivery, n = 3) and swine (subdermal hind limb delivery, n = 5). In rats the dual tracer migrated through four tiers of lymph node, 20 min after subdermal injection. Results from intravenous biodistribution test for radiocolloids demonstrated no aggregation in vivo, however indicated the presence of some lower-molecular weight radioactive impurities (99mTc-dextran). In swine, the dual tracer could be effectively used to map lymphatic drainage from hind hoof to popliteal and inguinal basins using intraoperative gamma and magnetometer probes. Of the eight primary nodes excised, eight were positively identified by gamma probe and seven by magnetometer probe. The high-purity dual tracer shows early promise for sentinel node identification in complex lymphatic environments by combining sensitive preoperative lymphoscintigraphy with a high-resolution intraoperative magnetometer probe.

Preparation of 68 Ga-Mg-Ca-phytate colloid and its evaluation as a liver imaging agent.

The objective of this study was to investigate the radiosynthesis of 68 Ga-Mg-Ca-phytate colloid and then characterise the formulation for radiochemical purity (RCP), radioactive particle size distribution, and biodistribution in normal rats. This radiocolloid was prepared by mixing an aqueous solution of phytic acid, 68 Ga3+ ions, a dispersant, Mg2+ and Ca2+ ions, and then heating the contents at 100°C for 5 minutes. After cooling the vial to 5°C, the solution was basified to pH 5 and stored in the cold. The resulting product contained 92±3% RCP 68 Ga-colloidal particles and a low level (8±3%) of soluble 68 Ga-Mg-Ca-phytate. Particle size experiments defined the radioactive particle population was 6±4% <20 nm, 90±6% 20 to 200 nm, and 4% were >200 nm in diameter. Intravenous injection of the 68 Ga-colloid dispersion to rats resulted in 93% uptake by the liver plus spleen, 1% lungs, 1% total blood, and 6% in the carcass after 20 minutes. This optimal formulation remained stable at 5°C for 1½ hours in vitro, and it resulted in the same biodistribution as the formulation prepared at t = 0 hours. The preclinical data so far indicate that 68 Ga-Mg-Ca-colloid has excellent potential as a liver imaging agent.

68 Ga-Ca-phytate particles: A potential lung perfusion agent of synthetic origin prepared in a cold kit format.

The objective of this study was to investigate the radiosynthesis of 68 Ga-Ca-phytate particles and then characterize the formulation for radiochemical purity, radioactive particle size distribution, and biodistribution in normal rats. This radiotracer was prepared using a commercial phytate cold kit after reconstitution with saline, 68 Ga-chloride generator eluent, calcium chloride, and air, then heating at 100°C for 30 minutes to achieve 99% radiochemical purity of 68 Ga-particles that were 21% 3-5 µm, 8% 5-15 µm, and 71% >15 µm in diameter. This optimal formulation was stable for 2 hours at room temperature. Intravenous administration of 68 Ga-particles in rats resulted in an uptake of 93% in the lungs, 4% in the liver plus spleen, and 3% in the carcass after 20 minutes. Two-thirds of the carcass activity was radioactive blood, likely to be 68 Ga-transferrin. The positron emission tomography image was superior than the 99m Tc-MAA image because it displayed high lung uptake against a low background. Low uptake by the liver, spleen did not interfere with the diagnostic quality, and faint activity in the submandibular (salivary) glands was due to 68 Ga-transferrin. The preclinical data so far indicate that 68 Ga-Ca-phytate particles have good potential as a lung perfusion imaging agent.

A study of radiogallium aqueous chemistry: in vitro and in vivo characterisation of (67) Ga-hydrolysed-stannous fluoride particles.

The objective of this study was to explore the aqueous chemistry of gallium using (67) Ga-chloride starting material, by radiolabelling hydrolysed(h)-stannous fluoride particles and then characterising the optimal formulation for radiochemical purity (RCP) and radioactive particle size distribution in vitro. The pilot reactions determined stannous fluoride was added to (67) Ga-acetate under nitrogen and then heated at 100 °C for 20 min to achieve ≥95% RCP and (67) Ga-particles were >3 µm in diameter. A high radioactive concentration of (67) Ga-h-SnF2 particles could be prepared similarly in ≥97% RCP with 74% as 3-5 µm and 26% >5 µm in diameter. The latter formulation had larger particles than (99m) Tc-h-SnF2 colloid (96% of 1-3 µm), and it resulted in a rat biodistribution of 41% in the lungs, 41% in the liver plus spleen and 18% in the carcass at 20 min after injection. The carcass activity was attributed to bone marrow and some (67) Ga-transferrin formed in blood. Isolated mixed human leucocytes were radiolabelled with (67) Ga-h-SnF2 particles in 100% efficiency, and the (67) Ga-cells did not release soluble (67) Ga(3+) at room temperature over 3 h. The (67) Ga-h-SnF2 particle formulation could find a use in labelling leucocyte cells for in vivo homing studies when delayed animal imaging is required.

An improved assay for (68)Ga-hydroxide in (68)Ga-DOTATATE formulations intended for neuroendocrine tumour imaging.

The objective of this study was to identify a more rapid assay for (68)Ga(OH)3 impurity in (68)Ga-DOTATATE formulations. Three methods were used to prepare (68)Ga(OH)3 reference material (pharmacopoeial, bench titration and automated radiosynthesis), and four quality control methods for its assessment (thin layer chromatography, membrane filtration, HPLC and solid phase extraction). The optimal method of preparing (68)Ga(OH)3 was by titrating (68)Ga(3+) with buffered sodium hydroxide solutions to pH 5.6 ± 0.2. The precipitate was quantitatively isolated by membrane filtration (0.02 µm)/hydrochloric acid (HCl; pH 5.6) solvent, and also it remained 100% at the origin on instant thin layer chromatography with silica gel paper/HCl (pH 5.6) solvent. For (68)Ga-DOTATATE samples, the thin layer chromatography technique was used with a single paper strip developed separately on two occasions, once in HCl (pH 5.6) and next in methanol solvent. This so-called double-developed (DD) method separated (68)Ga(OH)3 impurity located at the origin, from (68)Ga-DOTATATE plus (68)Ga(3+) at ~Rf 0.4, and it was superior to the other methods. It assayed for the impurity similarly to the pharmacopoeial method. The advantages of the DD method were that it required inexpensive test materials and it reproducibly determined % (68)Ga(OH)3 in (68)Ga-DOTATATE in 12 min, 13 min earlier than the pharmacopoeial method. This time efficiency resulted in a surplus of 12% (68)Ga-DOTATATE counts in the product vial, and this provided a contingency of radioactivity or time for the injection/imaging processes in the Nuclear Medicine Department.

Radiotracers used for the scintigraphic detection of infection and inflammation.

Over the last forty years, a small group of commercial radiopharmaceuticals have found their way into routine medical use, for the diagnostic imaging of patients with infection or inflammation. These molecular radiotracers usually participate in the immune response to an antigen, by tagging leukocytes or other molecules/cells that are endogenous to the process. Currently there is an advancing effort by researchers in the preclinical domain to design and develop new agents for this application. This review discusses radiopharmaceuticals used in the nuclear medicine clinic today, as well as those potential radiotracers that exploit an organism's defence mechanisms to an infectious or inflammatory event.

Lymphoscintigraphy is more effective using higher specific activity (99m)Tc-antimony trisulfide colloid in the rat.

Technetium-99m-antimony trisulfide colloid ((99m)Tc-ATC) was investigated with varying specific activity in the rat lymphatic system, as well as its binding to rat blood cells in vitro. Low, moderate and high doses of (99m)Tc-ATC were subdermally injected into tails of rats (n=3) and 30min later whole body lymphoscintigraphic images were acquired. (99m)Tc-ATC was incubated for 30min at 37°C with whole blood (n=4) as for control, at 4°C as for hypothermia, as opsonized at 37°C and lipopolysaccharide (LPS) at 37°C. Cell types were separated by gradient centrifugation to assay for cell bound-radioactivity. These experiments were repeated using mixed leukocytes that were erythrocytes-free. Images showed direct drainage of (99m)Tc-ATC from the tail to the popliteal nodes, sacral node and beyond, along the para-aortic chain, and to a left inguinal lymph node that drained into the axillia. The higher specific activity dose resulted in more visible lymph nodes after 30min. (99m)Tc-ATC was predominantly not cell-bound. In rat whole blood (99m)Tc-ATC-neutrophils were only present to the extent of 3% for the control, 3% for the hypothermia test, 4% for the opsonized and 7% for the LPS test. In the erythrocytes-free samples, (99m)Tc-ATC-leukocytes were present to the extent of 5% (control), 4% (hypothermia), 6% (opsonized) and 11% (LPS). In conclusion, a higher specific activity radiocolloid may identify the sentinel lymph node sooner during lymphoscintigraphy, and there may be an advantage in detecting more counts with the γ-probe. Retention of (99m)Tc-ATC in lymph nodes in vivo is likely because of binding on macrophage surfaces, rather than from internalization by phagocytosis within a time frame of 30min after injection.

Postchemotherapy and tumor-selective targeting with the La-specific DAB4 monoclonal antibody relates to apoptotic cell clearance.

UNLABELLED: Early identification of tumor responses to treatment is crucial for devising more effective and safer cancer treatments. No widely applicable, noninvasive method currently exists for specifically detecting tumor cell death after cytotoxic treatment and thus for predicting treatment outcomes. METHODS: We have further characterized the targeting of the murine monoclonal antibody DAB4 specifically to dead tumor cells in vitro, in vivo, and in clinical samples. We found that sustained DAB4 binding to treated cells was closely associated with markers of intrinsic apoptosis and DNA double-strand break formation. In a competition binding assay, DAB4 bound EL4 murine thymic lymphoma cells in preference to the normal counterpart of murine thymocytes. Defective in vivo clearance of apoptotic cells augmented in vivo accumulation of DAB4 in tumors particularly after chemotherapy but was unchanged in normal tissues. Tumor targeting of DAB4 was selective for syngeneic murine tumors and for human tumor xenografts of prostate cancer (PC-3) and pancreatic cancer (Panc-1) before and more so after chemotherapy. Furthermore, DAB4 was shown to bind to dead primary acute lymphoblastic leukemic blasts cultured with cytotoxic drugs and dead epithelial cancer cells isolated from peripheral blood of small cell lung carcinoma patients given chemotherapy. CONCLUSION: Collectively, these results further demonstrate the selectivity of DAB4 for chemotherapy-induced dead tumor cells. This postchemotherapy selectivity is related to a relative increase in the availability of DAB4-binding targets in tumor tissue rather than in normal tissues. The in vitro findings were translated in vivo to human xenograft models and to ex vivo analyses of clinical samples, providing further evidence of the potential of DAB4 as a marker of tumor cell death after DNA-damaging cytotoxic treatment that could be harnessed as a predictive marker of treatment responses.

Host immune response determines visceral hyperalgesia in a rat model of post-inflammatory irritable bowel syndrome.

BACKGROUND: Irritable bowel syndrome (IBS) is associated with visceral hyperalgesia and frequently occurs after a transient gastrointestinal infection. Only a proportion of patients with acute gastroenteritis develop post-infectious IBS suggesting differences in host response to inflammatory stimuli. We aimed to investigate this concept by characterizing visceral sensitivity in two rat strains, following a chemically induced colitis. METHODS: Colorectal instillation of trinitrobenzenesulfonic acid (TNBS) in aqueous ethanol was used to induce a transient colitis in Lewis and F344 rats. The colitis was characterized semiquantitatively by histology, as well as by quantitative methods using (99m)Tc-leukocytes (radioactive organ assay) and plasma IL-2 and IL-6 levels. Visceromotor response to colorectal distensions was assessed after 2 h and, 5, 14, and 28 days. RESULTS: The colitis peaked on day 5 and dissipated to no visible mucosal damage on day 14. Cytokines were significantly increased in TNBS-treated rats at 2 h and on day 5. On day 14 cytokines were still significantly enhanced in Lewis but not Fisher rats. Both strains had a highly inflamed to non-inflamed tissue ratio at 3 h after TNBS instillation with increased uptake in Lewis compared to F344 rats. No (99m)Tc-tin-colloid-leukocytes were detected in colon samples on day 28. Visceromotor response was significantly elevated in both strains during the acute colitis (day 5), whereas only Lewis rats developed a post-inflammatory (day 28) visceral hyperalgesia. CONCLUSION: Genetically determined host factors account for prolonged immune activation in response to a standardized inflammatory stimulus and are linked to susceptibility for a post-inflammatory visceral hyperalgesia.

APOMAB, a La-specific monoclonal antibody, detects the apoptotic tumor response to life-prolonging and DNA-damaging chemotherapy.

BACKGROUND: Antineoplastic therapy may impair the survival of malignant cells to produce cell death. Consequently, direct measurement of tumor cell death in vivo is a highly desirable component of therapy response monitoring. We have previously shown that APOMAB representing the DAB4 clone of a La/SSB-specific murine monoclonal autoantibody is a malignant cell-death ligand, which accumulates preferentially in tumors in an antigen-specific and dose-dependent manner after DNA-damaging chemotherapy. Here, we aim to image tumor uptake of APOMAB (DAB4) and to define its biological correlates. METHODOLOGY/PRINCIPAL FINDINGS: Brisk tumor cell apoptosis is induced in the syngeneic EL4 lymphoma model after treatment of tumor-bearing mice with DNA-damaging cyclophosphamide/etoposide chemotherapy. Tumor and normal organ accumulation of Indium 111 ((111)In)-labeled La-specific DAB4 mAb as whole IgG or IgG fragments was quantified by whole-body static imaging and organ assay in tumor-bearing mice. Immunohistochemical measurements of tumor caspase-3 activation and PARP-1 cleavage, which are indicators of early and late apoptosis, respectively, were correlated with tumor accumulation of DAB4. Increased tumor accumulation of DAB4 was associated directly with both the extent of chemotherapy-induced tumor cell death and DAB4 binding per dead tumor cell. Tumor DAB4 accumulation correlated with cumulative caspase-3 activation and PARP-1 cleavage as tumor biomarkers of apoptosis and was directly related to the extended median survival time of tumor-bearing mice. CONCLUSIONS/SIGNIFICANCE: Radiolabeled La-specific monoclonal antibody, DAB4, detected dead tumor cells after chemotherapy, rather than chemosensitive normal tissues of gut and bone marrow. DAB4 identified late apoptotic tumor cells in vivo. Hence, radiolabeled DAB4 may usefully image responses to human carcinoma therapy because DAB4 would capture the protracted cell death of carcinoma. We believe that the ability of radiolabeled DAB4 to rapidly assess the apoptotic tumor response and, consequently, to potentially predict extended survival justifies its future clinical development as a radioimmunoscintigraphic agent. This article is part I of a two-part series providing proof-of-concept for the the diagnostic and therapeutic use of a La-specific monoclonal antibody, the DAB4 clone of which is represented by the registered trademark, APOMAB.

Lymphatic mapping with 99mTc-Evans Blue dye in sheep.

OBJECTIVE: 99mTc-Evans Blue (EB) is an agent that contains both radioactive and color signals in a single dose. Earlier studies in animal models have suggested that this agent when compared with the dual-injection technique of radiocolloid/blue dye can successfully discriminate the sentinel lymph node. The aim of this study was to investigate the potential of 99mTc-EB as an agent to map the lymphatic system in an ovine model. METHODS: Doses of 99mTc-EB (23 MBq) containing EB dye (4 mg) were administered intradermally to the limbs of four anesthetized sheep, and they were then imaged over 20-30 min using a gamma camera. The study protocol was repeated using 99mTc-antimony trisulfide colloid (ATC) and Patent Blue V dye. The lymph nodes (popliteal, inguinal, and iliac for hind limbs or prescapular for fore limbs) were identified with a gamma probe during the operative exposure, then dissected and counted in a large volume counter. RESULTS: Simple and complex (dual) drainage patterns were visible on the scans, and the sentinel node was more radioactive than higher tier nodes in a chain, for both radiotracers. For 99mTc-EB, maximum radioactive uptake was achieved at 3-6 min for popliteal lymph nodes, 12-14 min for iliac nodes, and 13-14 min for prescapular nodes. 99mTc-ATC resulted in maximum radioactive uptake at 4-6 min for popliteal lymph nodes, 13 min for an inguinal node, 13-20 min for iliac nodes, and 18 min for a prescapular node. Following 99mTc-EB injection, 15/15 lymph nodes harvested were all radioactive and blue. For 99mTc-radiocolloid/Patent Blue V injection, 8/14 nodes were radioactive and blue, and 6/14 nodes were radioactive only. CONCLUSIONS: The soluble radiotracer 99mTc-EB appeared to be a useful lymphoscintigraphic agent in sheep, in which radioactive counts from superficial lymphatic channels and lymph nodes were sufficient for planar imaging. In comparison with 99mTc-antimony trisulfide colloid, both tracers discriminated the sentinel lymph node up to 50 min after administration; however, 99mTc-EB had the advantage of providing radioactive (gamma probe) and color signals simultaneously during the operative exposure.

Colonic transit studies with 99mTc-rhenium sulfide colloid in live rats. A preliminary study.

Abnormal colonic motility is associated with clinical relevant conditions such as irritable bowel syndrome or constipation. Accurate assessment of colonic transit in an animal model would be useful in studying these conditions and screen potential drug candidates. The aim of this study was to assess if scintigraphic analyses could reliably evaluate total and segmental colonic transit as a measure of colonic motility of a non-absorbable radiotracer in rats. Normal Lewis rats (250-300 g) were given oral technetium-99m-rhenium sulfide colloid (15-20 MBq; 0.5 mL; n=4) followed by a rinse with water for injection (1.0 mL). Rats were fed and hydrated ad libitum. After 30 min, each rat was contained inside an 'imaging' tube then placed on a g-camera collimator. Whole body 5 min static images were acquired every 30 min up to 9 h, and then finally at 25 hours. Region of interest analyses were applied to the caecum/proximal colon, sigmoidal loop and distal colon/rectum. The tracer entered into the colon at approximately 4 hours, and the rats remained static to permit 'live' imaging. At 4 hours the % whole body activity was: 51% caecum/proximal colon, 39% sigmoidal loop, 6% distal colon/rectum; at 8 hours, 30% caecum/proximal colon, 13% sigmoidal loop, 7% distal colon/rectum. In the whole colon there was < or =1% of total activity present at 25 hours, and the half clearance time was determined as 4.0 hours. These results suggest this is a reliable technique of measuring regional colonic transit as a measure of colonic motility in normal rats. This methodology might be well suited to screen potential motility effects of drug candidates.

How regenerating lymphatics function: lessons from lizard tails.

Rational treatment of lymphoedema may be improved in the future with a better understanding of the physiological processes involved in the regeneration of new lymphatic vessels (lymphangiogenesis). Many lizard species undergo tail autotomy as a predator escape response and subsequently regenerate nonlymphoedematous tails. Such species may offer novel models for examining lymphangiogenesis. In this lymphoscintigraphic evaluation, three radioactive tracers were employed, (99m)Tc-antimony trisulphide colloid (approximately 10 nm diameter), (99m)Tc-tin fluoride colloid (approximately 2,000 nm; (99m)Tc-TFC), and (99m)Tc-diethylenetriaminepentaacetic acid (soluble; (99m)Tc-DTPA), to examine lymphatic function in regenerating tails of the Australian marbled gecko, Christinus marmoratus. Rate of local clearance and velocity of migration were determined in geckos with original tails and at 6, 9, 12, and >24 weeks after autotomy. In original-tailed geckos, the smaller radiocolloid was cleared to a greater extent and had a faster lymph velocity than in geckos with regenerated tails. The same parameters measured for larger particles were greater in early regeneration than later. (99m)Tc-TFC did not migrate from the injection site in fully regenerated and original gecko tails, which indicates that larger particles are increasingly impeded as tail regeneration progresses. Soluble (99m)Tc-DTPA diffused from the injection site extremely rapidly via venous capillaries in all tails, confirming that the slower clearance of the colloids is solely via the lymphatics. Differences in clearance and lymph velocity between differently sized colloids throughout tail regeneration may be influenced by changes in surrounding tissue structure density and the lymphatic vessel porosity.

The tissue distribution of Evans blue dye in a sheep model of sentinel node biopsy.

BACKGROUND: Tc-Evans blue is a 'single dose' agent for lymphatic mapping combining radioactivity and blue dye for sentinel node identification. The mechanism and distribution of blue dye retention in the lymph node is not clearly understood. OBJECTIVE: To demonstrate the cellular distribution of Tc-Evans blue in sheep sentinel lymph nodes by measuring the radioactivity of different tissue components and correlating this with pathological examination. METHODS: Tc-Evans blue was used to identify sheep lymph nodes. Part of each node was sent for pathological examination including imprint cytology, and frozen and permanent section examination. Sections were examined without stains, with only red stains and conventional haematoxylin & eosin staining. The remaining nodal tissue was homogenized and components separated by enzymatic digestion and density gradient centrifugation. Fractions representing each tissue component were counted in a gamma counter and the distribution of Tc-Evans blue calculated. RESULTS: A dispersed population of blue staining cells was found. Their distribution, number and size indicated that they were histiocytes such as macrophages or antigen presenting cells. Radioactivity was distributed throughout the lymph node. Over 70% remained in the plasma, 19% in the leukocyte layer, and 10% was associated with erythrocytes and undigested tissue. CONCLUSION: The accumulation of radioactivity and blue colour in the lymph nodes indicates the mechanism of retention is a result of the binding interaction between Tc-Evans blue-protein and lymph node histiocytes including macrophages and antigen presenting cells.

Scintigraphic imaging of experimental colitis with technetium-99m-infliximab in the rat.

The radiolabeled monoclonal antibody (99m)Tc-infliximab was assessed as an inflammation imaging agent in a rat colitis model in comparison with (99m)Tc-tin colloid-labeled-leucocytes. (99m)Tc-infliximab and (99m)Tc-tin fluoride colloid-labeled-leucocytes were administered to (n>3) rats previously exposed to 2,4,6-trinitrobenzenesulfonic acid by rectal instillation. Whole body scintigraphic images were acquired and physiological organ assays were performed to obtain quantitative data. Histological examination of colon samples was performed to assess the site and severity of the colitis. In the inflamed colon, (99m)Tc-infliximab resulted in inflamed target (T) to control (C) colon tracer uptake ratios of 2.7 +/- 1.0 (n=5) and 2.6 +/- 0.3 (n=5) at 1 and 4 h post tracer injection respectively. (99m)Tc-leucocytes gave higher ratios of 19.5 +/- 9.9 (n=3) and 41.2 +/- 16.1 (n=5) respectively. (99m)Tc-leucocytes gave higher ratios of 19.5 +/- 9.9 and 41.2 +/- 16.1 at the corresponding time points. (99m)Tc-infliximab accumulated at sites of inflammation in this rat model but not due to a specific tumor necrosis factor-alpha binding mechanism. Although the tracer uptake was lower than radioactive leucocytes, this easily prepared (99m)Tc-monoclonal antibody may have some advantages in imaging inflammatory bowel disease in humans based on its biological activity.

99mTc-Evans blue dye for mapping contiguous lymph node sequences and discriminating the sentinel lymph node in an ovine model.

BACKGROUND: The aim of this study was to investigate the potential of (99m)Tc-Evans blue for discriminating the sentinel lymph node in multitiered lymph node sequences by using an ovine model. (99m)Tc-Evans blue is an agent that has both radioactive and color signals in a single dose. Previous studies in smaller animal models suggested that this agent could have advantages over the dual-injection technique of radiocolloid/blue dye. METHODS: Doses of (99m)Tc-Evans blue ( approximately 21 MBq) containing Evans blue dye (approximately 4 mg) were administered to the hind limbs or fore limbs of sheep to map the lymphatic drainage patterns, validate its ability to identify the sentinel lymph node, and examine the reproducibility of the technique. The study protocol was repeated with (99m)Tc-antimony trisulfide colloid and Patent Blue V dye. After the operative exposure, lymph nodes were identified with the gamma probe and then excised and analyzed for radioactivity (percentage of injected dose) and blue color. RESULTS: After the administration of (99m)Tc-Evans blue, all lymph nodes harvested (35 of 35) in either short chains or long basins were hot and blue. The sentinel lymph nodes concentrated more radioactivity than the second-tier nodes to the extent of 2:1 to 215:1. For radiocolloid/Patent Blue V, the ratios were lower, at 2:1 to 3:1. CONCLUSIONS: (99m)Tc-Evans blue was found to better discriminate the sentinel lymph node than (99m)Tc-antimony trisulfide colloid/Patent Blue V in variable multitier lymph node anatomy, and it is an agent that promises to have positive clinical applications.

An improved (99m)Tc-aprotinin kit formulation: quality control analysis of radiotracer stability and cold kit shelf life.

(99m)Tc-aprotinin scintigraphy has been demonstrated to be a useful noninvasive imaging technique for amyloid deposits located in extraabdominal regions of patients. The aim of this study was to develop an improved aprotinin cold kit formulation, to validate the kit for long-term stability, as well as to assess the radiotracer stability by novel quality control methods. The aprotinin cold kit formulation of Trasylol, pyrophosphate (PYP)-chelated stannous reductant and an alkaline buffer, was dispensed into nitrogen-filled vials and aliquots frozen at -20 degrees C. After 0, 1, 2, 3 and 6 months of storage, three samples were reconstituted with 750-850 MBq of (99m)Tc-pertechnetate, followed by quality control analyses by paper chromatography methods at 25, 85 and 265 min postreconstitution (pr). Cation-exchange cartridge quality control methods were also investigated. The cold kits proved to be stable to long-term storage for up to 6 months, and the radiotracer was stable for at least 4 h pr. (99m)Tc-aprotinin was formed at greater than 95% efficiency at all time points tested with (99m)TcO2 present as the major impurity (1-4%) and (99m)Tc-pertechnetate and (99m)Tc-PYP present in trace amounts. An alternative, rapid, safe and reliable method was found in Oasis MCX-BSA-treated cartridges using saline as the eluting solution to assay for (99m)Tc-aprotinin.

Radiolabelling and biodistribution of 111In-antimony trisulphide colloid.

The aim of this study was to prepare 111In-antimony trisulphide colloid (111In-ATC) and evaluate its chemical properties in comparison with 99mTc-ATC. After reconstitution of an antimony trisulphide cold Kit with 111In-chloride, 111In-ATC was formed with >95% radiochemical purity in the presence of neutralising phosphate buffer. The product was found to be stable for 4.7 days when stored at room temperature, 80% of radioactive particles were < 20 nm in diameter and the mouse biodistribution assay was identical to that of 99mTc-ATC. In conclusion, pharmaceutical-grade 111In-ATC was successfully prepared and assessed to have properties that are suitable for dual-isotope lymphoscintigraphy studies at the clinical level.

Characterization and quality control analysis of 99mTc-bicisate.

The aim of this study was to investigate the mini cartridge versus paper chromatography quality control methods for determining the radiochemical purity (RCP) of (99m)Tc-bicisate. The 4 methods that were compared with the manufacturer's method included Whatman 17 paper/ethyl acetate solvent, instant thin-layer chromatography (ITLC) silica gel paper/saline solvent, reverse-phase C18 mini cartridge/saline solvent, and strong anion exchange mini cartridge/water solvent. At 30 min after reconstitution, (99m)Tc-bicisate was formed at 97%-98% RCP as assayed by the paper and cartridge methods, and the strong anion exchange/water for injection (WFI) system slightly underestimated the percentage at 96%. A significantly lower RCP was obtained for the C18/saline method when a faster flow rate was used. The lipophilic complex moved with ethyl acetate on Whatman 17, was separated from origin impurities on ITLC silica gel/saline, and remained on the column with C18/saline. For strong anion exchange/WFI, components in the radioactive formulation are likely to have influenced the percentage of (99m)Tc-bicisate. The time disadvantage for ITLC silica gel/saline analysis made the method less than ideal. The C18 mini cartridge/saline method was found to be the simplest and fastest; a result was obtained in 2 min with use of a safe solvent of elution.