Preparation of Tc-99m-macroaggregated albumin from recombinant human albumin for lung perfusion imaging.

Human serum albumin (HSA) extracted from pooled blood taken from human donors is used in the production of (99m)Tc-labelled macroaggregated albumin (MAA) for lung perfusion imaging. However, concerns for the safety of blood-derived products due to potential contamination by infective agents (e.g. new variant CJD), make alternative production methods necessary. Recombinant DNA technology is a promising method of albumin production avoiding problems associated with human-derived HSA. This paper presents results comparing MAA prepared from recombinant human albumin (rHA, Recombumin) (rMAA) with in-house produced HSA MAA (hMAA) and commercially available MAA (cMAA). (99m)Tc-MAA was prepared using previously published production methods by heating a mixture of albumin and stannous chloride in acetate buffer (pH 5.4) at 70 degrees C for 20 min. Parameters investigated include aggregate size, radiolabelling efficiency, radiochemical and aggregate stability at 4 degrees C and in vitro (in whole human blood) at 37 degrees C and biodistribution studies. Results showed that rMAA could be produced with similar morphology, labelling efficiency and stability to hMAA and cMAA. Our findings confirm that rHA shows significant potential as a direct replacement for HSA in commercially available MAA.

Biodistribution of (111)indium-labeled engineered human antibody CTMO1 in ovarian cancer patients: influence of protein dose.

Thirty-one patients suspected of having ovarian cancer received a single i.v. injection of radiolabeled (100 MBq (111)In) engineered human CTMO1 (hCTMO1) to investigate its potential as an internalizing drug carrier. hCTMO1 is a complementary-determining region-grafted human IgG4 monoclonal antibody recognizing an ovarian carcinoma-associated antigen, the MUC-1-gene product. The amount of radioactivity was determined in tumor tissue, various normal tissues, including liver biopsies, and blood samples obtained at laparotomy, 6 days after injection of either 0.1 or 1.0 mg hCTMO1/kg of body weight. Circulating antigen-15-3 was measurable in all patients before injection, and immune complex formation was already present at the end of infusion. In the 0.1 mg/kg group, most of the radioactivity was bound to immune complexes, whereas in the 1.0 mg/kg group, most was bound to IgG monomers. Increasing the hCTMO1 dose 10-fold did not influence the overall disappearance of (111)In from the blood, but the elimination half-life of (111)indium bound to immune complexes was increased 2-fold. Uptake in tumor tissue 6 days postinjection at the 0.1 mg/kg dose was 7.6 times higher (P = 0.0009) than in normal tissue and 2.5 times higher (P = 0.03) than in blood. At the 1.0 mg/kg dose, the uptake in tumor tissue was 14.0 times higher (P = 0.0003) than in normal tissue and 8.1 times higher (P = 0.0007) than in blood. Liver activity was substantial (23.7 +/- 10.5 and 18.3 +/- 6.7% of the injected dose/kg for the 0.1 and 1.0 mg/kg dose group, respectively). These results are superior to those found with other clinically tested anti-MUC-1 gene product antibodies. hCTMO1 seems to be a suitable carrier for cytotoxic agents in ovarian carcinoma patients; the better uptake results and tumor-to-blood ratios are obtained at the higher dose of 1.0 mg hCTMO1/kg body weight.

Targeting superficial bladder cancer by the intravesical administration of copper-67-labeled anti-MUC1 mucin monoclonal antibody C595.

PURPOSE: More effective intravesical agents are required to limit the recurrence and progression of superficial bladder cancer. This study assessed the ability of copper-67 ((67)Cu)-C595 murine antimucin monoclonal antibody to bind selectively to superficial bladder tumors when administered intravesically, with a view to its development for therapy. PATIENTS AND METHODS: Approximately 20 MBq of (67)Cu-C595 monoclonal antibody was administered intravesically to 16 patients with a clinical indication of superficial bladder cancer. After 1 hour, the bladder was drained and irrigated. Tissue uptake was assessed by imaging and by the assay of tumor and normal tissues obtained by endoscopic resection. RESULTS: Tumor was correctly identified in the images of 12 of 15 patients who were subsequently found to have tumors. Assay of biopsy samples at 2 hours showed a mean tumor uptake of 59.4% of the injected dose per kilogram (SD = 48.0), with a tumor-to-normal tissue ratio of 14.6:1 (SD = 20). After 24 hours (n = 5), this decreased to 4.3% of the injected dose per kilogram (SD = 2.9), with a tumor-to-normal tissue ratio of 1.8:1 (SD = 0.8). CONCLUSION: This study indicates a promising method for the treatment of superficial bladder cancer. Although the mean initial tumor uptake was high, effective therapy of bladder tumors will require an increased retention of the cytotoxic radionuclide in tumor tissue.

Oesophageal transit, disintegration and gastric emptying of a film-coated risedronate placebo tablet in gastro-oesophageal reflux disease and normal control subjects.

BACKGROUND: Risedronate sodium is a pyridinyl bisphosphonate, proven effective for the treatment and prevention of postmenopausal osteoporosis and glucocorticoid-induced osteoporosis and Paget's disease of the bone. AIM: To compare the oesophageal transit, disintegration and gastric emptying of the commercial film-coated risedronate tablet in subjects with gastro-oesophageal reflux disease (GERD) and normal control subjects. METHODS: A total of 30 subjects, 15 patients with GERD and 15 age- and sex-matched, normal control subjects, participated in a single-centre, open-label, comparative gamma scintigraphy study. The GERD subjects had active erosive oesophagitis within 4 weeks prior to dosing. RESULTS: The mean oesophageal transit (GERD, 4.4 s; controls, 3.1 s), mean disintegration (GERD, 21.8 min; controls, 19.2 min) and mean gastric emptying (GERD, 15.9 min; controls, 15.0 min) were similar in the two subject groups. The oesophageal transit is rapid and given the rapid disintegration and gastric emptying, oesophageal contact occurring via reflux of risedronate was unlikely since most, if not all, of the dosage form exited from the stomach within 30 min. CONCLUSIONS: The oval shape and film-coating on the commercial risedronate tablet promotes rapid oesophageal transit and minimizes oesophageal contact, even in the high-risk GERD population.

Ocular contact time of a carbomer gel (GelTears) in humans.

BACKGROUND/AIMS: Carbomers are widely used in products for the treatment of dry eye; however, the polymer gel thins on addition of probes (for example, fluorescein salt) confounding the comparison of products by objective clinical tests such as spectrophotofluorimetry or scintigraphy. A novel method of radiolabelling carbomer gels, with minimum change to their rheology, has permitted the non-invasive evaluation of precorneal residence of the gel in volunteers using gamma scintigraphy. The technique was used to evaluate the precorneal clearance of the liquid phase and of a suspended particulate in GelTears. METHODS: Low sodium technetium-99m labelled diethylenetriaminepentacetic acid (99mTc-DTPA) was used to label carbomer 940 gel, either adsorbed onto sterile charcoal to model an entrapped drug, or added directly to the gel to a final activity of 1 MBq per 25 microliters dose. The clearance of the labelled gels was then compared with 99mTc-DTPA labelled saline in 12 volunteers. RESULTS: The addition of the low sodium radiopharmaceutical produced insignificant rheological changes in the gel compared with conventional 99mTc-DTPA labelling. The residence times on the eye of the gel formulations were significantly greater than that of the saline control. At 8 minutes postdosing, the label levels retained (mean (SD)) on the ocular surface were: saline, 7% (7%); 99mTc-DTPA gel, 42% (27%); and 99mTc-carbon gel, 42% (20%) of administered dose. There was no difference observed in the precorneal distribution between 99mTc-DTPA solution and particulate markers. CONCLUSIONS: These data demonstrate that carbomer based gels significantly extend contact of solutes or suspended solids with the corneal surface. The method of labelling does not significantly change the initial viscosity and is superior to previous methods which have used sodium salts (for example, sodium fluorescein) and therefore underestimate contact time.

Night-time quiescence and morning activation in the human colon: effect on transit of dispersed and large single unit formulations.

OBJECTIVES: Controlling the delivery of drugs to different regions of the colon remains an elusive goal. The aim of this study was to define the diurnal variation in colonic transit and show how this influences the colonic distribution and residence time of different formulations given either in the morning or evening. METHODS: Colonic transit of small particulates and a large capsule was measured during nocturnal sleep and daytime wakefulness. Eighteen healthy volunteers participated in a randomised crossover study. 111In-labelled resin (150-300 microm) and a large 99mTc-labelled non-disintegrating capsule (22 x 8 mm) were swallowed at either 0800h or 1700h. MAIN OUTCOME MEASURES: The geometric centre of isotope (range 1-9) was calculated from serial scintiscans allowing comparison of overnight and daytime transit. RESULTS: Transit of resin was delayed in the overnight compared to daytime 8 h periods (change in geometric centres (GCs), mean +/- SEM, 0.59 +/- 0.14 vs 1.46 +/- 0.39 respectively, P < 0.02). Maximal resin movement occurred immediately after awakening, prior to breakfast, in 9/18 studies (P < 0.05). The capsule was more distal than the resin at the end of the study 15 h after dosing (P < 0.001). There was marked inter-individual variability in distribution of both resin and capsule at 15 h, the range of GCs being 2.8-9 and 2.2-9, respectively. CONCLUSION: Sleep delays colonic transit and large capsules travel faster than dispersed small particles. However, substantial inter-individual variability in transit makes targeting specific regions of the human colon unreliable with either dispersed or single unit formulations.

Human biodistribution of an ultrasound contrast agent (Quantison) by radiolabelling and gamma scintigraphy.

The biodistribution and kinetics of an air filled human serum albumin microcapsule formulation (Quantison) intended for use as an intravenous ultrasound contrast agent have been examined. 12 healthy subjects were administered with approximately 50 million microcapsules per kilogram body weight, radiolabelled with 50 MBq 123I. Imaging was performed over a period of 58 h using a large field-of-view gamma camera and the amount of labelled material present in the blood, urine and faeces measured. Imaging demonstrated that the liver was the organ with the highest uptake, with a mean uptake of 41.8% (SD 10.4%) of the administered dose 1 h following administration. The maximum uptake of the agent in the lungs was low, mean 4.0% (SD 3.4%). A small amount of uptake was visible in the bone marrow; however, this was not quantifiable. There was also evidence of minimal myocardial activity within 5 min of administration. No adverse events were observed and there were no changes in any of the individual post-study indices. The present study demonstrates the safety of Quantison. Gamma scintigraphy played a useful role in confirming the biodistribution of the agent with little lung uptake, high liver uptake and evidence of myocardial uptake.

Evaluation of the clearance characteristics of bioadhesive systems in humans.

This paper describes the characterisation, radiolabelling and clearance characteristics of three bioadhesive nasal delivery systems; starch microspheres, chitosan microspheres and chitosan solution. The time taken for 50% of these bioadhesive materials and a control to be cleared from the nasal cavity, after nasal administration to human volunteers, was evaluated using gamma scintigraphy. The data show that the control was cleared rapidly, with a half life of 21 min, whereas the bioadhesive delivery systems had much longer half lives. The clearance of the chitosan solution almost doubled to 41 min, whilst the half life of clearance for the starch microspheres more than tripled to 68 min and for the chitosan microspheres the half life of clearance quadrupled to 84 min. From the results reported in this study it is possible to determine that both chitosan systems and the starch microspheres have good bioadhesive characteristics. The results have supported the hypothesis that chitosan delivery systems can reduce the rate of clearance from the nasal cavity, thereby increasing the contact time of the delivery system with the nasal mucosa, providing the potential for increasing the bioavailability of drugs incorporated into these systems.

Dry powder dosing in liquid vehicles: ocular tolerance and scintigraphic evaluation of a perfluorocarbon suspension.

The ocular tolerance and precorneal disposition of 99mTc-labelled sterile carbon-perfluorodecalin (PFD) and carbon-aqueous suspensions were examined in a cohort of healthy volunteers. Formulations were prepared in PFD or saline using charcoal particles, radiolabelled with [99mTc]diethylenetriaminepentaacetic acid (DTPA) under GMP conditions. Colloidal silicon dioxide was used as a suspending agent. Ocular tolerance was examined following the instillation of each formulation to the eyes of 12 volunteers. The precorneal distribution of both formulations in man was monitored using gamma scintigraphy. Dynamic and static data acquisitions were taken over a period of 150 min after dosing. Carbon particulates suspended in PFD did not show any irritation to the eye. Administration of PFD formulation in man produced a significant increase in ocular retention over a saline formulation (mean residence time (MRT)=157+/-42 and 0.29+/-0.08 min, respectively, P=0.0001). Distribution of the carbon in man followed the same pattern as in a previous reported study in animals. The carbon deposited uniformly along the lid margin in the case of the PFD vehicle, whereas it agglomerated following dosing in the saline vehicle and was ejected from the eye. The novel non-aqueous vehicle system is able to significantly improve the ocular retention of charcoal particles in man and provides a unique distribution of the particles in the eye, which suggests a potential for the PFD system for the treatment of periocular diseases.

Esophageal transit of risedronate cellulose-coated tablet and gelatin capsule formulations.

Risedronate sodium is an orally active antiresorptive agent and a member of the pyridinyl class of bisphosphonates. It has been approved for the treatment of Paget's disease of the bone and is under development as a chronic therapy for the treatment and prevention of osteoporosis. A novel cellulose film-coated tablet formulation was developed to optimize esophageal transit of this bisphosphonate. The aim of the present study was to compare the esophageal transit of the film-coated tablet formulation of risedronate with its original gelatin capsule dose form. A total of 25 elderly, healthy volunteers (mean 66 years), who were dysphagia-free, participated in this randomized cross-over study. On separate occasions, volunteers swallowed radiolabeled placebo formulations with 50 ml water. Dynamic images with participants in a sitting position were recorded for 10 min using a gamma camera. Scintigraphic imaging showed a delay in esophageal transit (greater than 15 s) in 28% of patients in the capsule group but in none of the tablet group (P<0.05). The mean transit times of the capsules and tablets were 23.8 and 3.3 s, respectively. Esophageal transit of film-coated tablets was faster than gelatin capsules, suggesting that film-coated tablets would be the appropriate formulation for all pivotal trials with risedronate and for subsequent commercialization.

The use of scintigraphy to demonstrate the rapid esophageal transit of the oval film-coated placebo risedronate tablet compared to a round uncoated placebo tablet when administered with minimal volumes of water.

As our population ages, and the consumption of pharmaceutical products rises, the incidence of solid oral dosage forms lodging in the esophagus is likely to increase and may be formulation dependent. The aim of this study was to compare the esophageal transit of the commercial film-coated risedronate tablet and a round uncoated tablet resembling the alendronate 10 mg tablet which is reported to cause esophagitis if ingested with little to no water. Water volumes of 30 ml and 50 ml were selected as these volumes can detect formulations prone to esophageal adhesion and a habits and practice study showed that these volumes are within the range preferred by women (7-385 ml). A total of 28 healthy postmenopausal women completed the four-way crossover scintigraphy study. For both volumes of water, the film-coated placebo risedronate tablet had a statistically significant faster esophageal transit time than the uncoated placebo tablet (P=0.002 for 30 ml water and P<0.001 for 50 ml water). Among those taking the round, flat, uncoated tablet, five subjects had esophageal stasis (transit >20 s) and in three subjects the tablet remained in the esophagus at the end of the 10-min imaging period. No stasis was observed for the oval film-coated placebo risedronate tablet. This study demonstrates that tablet size, shape and coating are pharmaceutical parameters which can be controlled to minimize esophageal contact of a dosage form with esophageal tissue.

The stability of 99Tcm-DTPA in an aerosol delivery system.

99Tcm-DTPA is now widely used in aerosol nebulizers for routine ventilation lung scanning. The stability of a commercially available DTPA kit has been measured when used in an aerosol delivery system and compared with the stability when stored in the parent vial according to the manufacturer's instructions. No significant breakdown was measured up to 8 h after reconstitution in the parent vial and up to 3 h when used as an aerosol. Values of the half time of clearance of DTPA aerosols in a group of 23 patients are compared with values given in the literature.

A comparison of same day and separate day injection protocols for myocardial perfusion SPECT using 99Tcm-MIBI.

Three dose administration protocols for 99Tcm-MIBI were applied to groups of 15 patients with known or suspected ischaemic heart disease. Firstly, injections were given on consecutive days, with 300 MBq at rest and 500 MBq 24 h later at exercise. Secondly, both injections on the same day with 200 MBq at rest followed 1.5 h later by 1000 MBq during exercise. Finally, both injections on the same day with 200 MBq at rest followed 1.5 h later by 600 MBq during exercise. The diagnostic accuracy was significantly better when the administrations were on separate days than when given on the same day. There was no difference in diagnostic accuracy between the two same day protocols. The same day protocols gave a significantly higher false negative reporting rate than the separate day protocol.

The use of dual-isotope imaging to compare the gastrointestinal transit of food and pancreatic enzyme pellets in cystic fibrosis patients.

Cystic fibrosis patients require pancreatic enzyme supplements to aid food digestion. It is suspected that incorrect delivery of this enzyme may result in both significant malabsorption and the development of strictures in the proximal colon caused by the high-dose supplement reaching this region before the food. Investigations into the drug's delivery were performed using dual-isotope imaging; a method was developed to directly label the enteric-coated enzyme pellets with 111In, re-applying the enteric coating afterwards, and this was then ingested with a pancake meal labelled with 99Tcm-tin colloid. Consecutive image data, acquired over a period of > or = 4 h using a dual-headed gamma camera, were analysed to assess intestinal transit. In-vitro stability checks on these labelling techniques were encouraging, showing < 2% 99Tcm and < 7% 111In elution over 90 min in hydrochloric acid. In 5 of the 12 patients studied to date, the pellets were seen to pass through significantly faster than the food, with a mean difference in 50% gastric emptying time of greater than 93 min. The mean absolute difference in emptying time for all 12 patients was > 67 min. Thus, a technique has been developed to effectively radiolabel pancreatic enzyme pellets, and analysis of dual-isotope images using this preparation, together with radiolabelled solid food, has demonstrated significant differences in the transit of these two substances through the gastrointestinal tract of some cystic fibrosis patients.

Monoclonal antigranulocyte antibody imaging in inflammatory bowel disease: a preliminary report.

The 99Tcm-labelled antigranulocyte antibody BW250/183 has been used in the detection of intestinal inflammation in patients with active ulcerative colitis and Crohn's disease. Planar images were obtained up to 24 h after intravenous injection of the antibody. Eight out of nine patients with ulcerative colitis and six out of seven patients with Crohn's disease gave positive images. In 11 patients distribution of the inflammation was confirmed by barium studies, colonoscopy or surgery, whilst in two the antibody scan suggested more extensive disease than barium enema. None of the patients had any adverse reactions. Imaging with BW250/183 appears to give an accurate indication of the extent of inflammation in inflammatory bowel disease.

A comparison of planar and tomographic imaging of the myocardium using 99Tcm-t-butyl isonitrile.

Oblique reconstruction tomography for stress imaging of 99Tcm-t-butyl isonitrile was performed. Oblique reconstructions, transaxial reconstructions and conventional planar images were reported by three observers. These reports were compared in 12 patients with suspected heart disease, using ECG, cardiac enzymes and coronary angiography to derive diagnostic standards. Oblique reconstruction tomography gave better agreement between the observers and more accurate diagnoses than either transaxial reconstruction or planar imaging.

111In platelet deposition following peripheral arterial thrombolysis.

Streptokinase (Sk) and recombinant tissue plasminogen activator (rt-PA) have widely different effects on platelet aggregation. We have therefore undertaken a prospective evaluation of the deposition of indium-111 platelets following peripheral arterial thrombolysis. Seventeen patients were studied using autologous indium-111 labelled platelets. Patients were randomly allocated to receive 0.5 mg h-1 intra-arterial rt-PA (ten patients), or 5000 units h-1 Sk and 250 units h-1 heparin intra-arterially (seven patients). Initial uptake ratios (comparing affected limb to contra-lateral limb) at 24 h were usually low for both agents (medians: Sk 1.17; rt-PA 1.20) despite previous angioplasty or extensive thrombosis. There were minimally higher uptake ratios at 48 h and 72 h following Sk (1.64-1.45), than with intra-arterial rt-PA (0.93-1.43). Overall, two patients (one from each group) failed to achieve complete lysis or incurred early rethrombosis. Both were associated with a progressive increase in uptake ratio which was not present in those patients with successful initial lysis and continued patency at 30 days (1.18-0.94-1.19). We have been unable to demonstrate any significant difference in post-lysis platelet deposition between intra-arterial streptokinase and recombinant tissue plasminogen activator in this preliminary study. However, higher platelet deposition was associated with failure to achieve complete lysis and early rethrombosis. Concurrent therapy with antiplatelet agents may therefore be indicated in these patients.

Bedside nuclear medicine investigations in the intensive care unit.

The functional nature of nuclear medicine procedures makes them especially valuable in the management of patients undergoing intensive care. However, the severe nature of the patient's condition invariably prevents him or her from attending the nuclear medicine department for diagnostic investigations. We have piloted a bedside nuclear medicine service using a four-probe detector system linked to an IBM computer with curve processing software. Protocols for a range of radionuclide probe investigations, including renal, hepatobiliary, gastric outflow and lung vascular permeability, using 99Tcm and 111In radiopharmaceuticals have been established. The measurement of lung vascular permeability in patients with clinical symptoms of adult respiratory distress syndrome was considered to be a valuable procedure on the intensive care unit. Due to the poor availability of 113Inm, which had previously been used for the measurement of lung permeability, we used a technique based on in vivo labelling of serum transferrin with 111In-chloride together with 99Tcm-red blood cells for the calculation of the plasma protein accumulation index. Other procedures include the measurement of gastric outflow in patients previously on parenteral feeding, and the assessment of hepatobiliary and renal function. The equipment proved to be reliable and convenient for use at the bedside, although ultrasound imaging was essential for the correct positioning of the probe detectors over smaller organs such as the kidneys and the gallbladder. The high sensitivity of the probe detectors required only low administered amounts of activity, minimizing radiation protection measures for patients and staff. The administration of radiopharmaceuticals via indwelling lines and tubes presented particular problems and we recommend that parenteral injections should not be given through manifold giving set, or via Teflon cannulae.

A comparison between visual and quantitative analysis in a prospective evaluation of labelled 111In leucocyte imaging in vascular infection.

In a continuing evaluation of 111In-oxine labelled leucocyte imaging in vascular surgery, we have studied 16 patients with a clinical diagnosis of possible vascular graft infection. We have evaluated both visual and semi-quantitative analysis of the images obtained and have interpreted these in the light of the subsequent clinical outcome. Full length or multifocal uptake was seen in six patients, all of whom eventually required graft excision with two limbs surviving, and one death. These patients had a significantly higher uptake ratio (median = 3.26) than those with either localized (median = 1.12; p = 0.0027) or negative images (median = 0.72; p = 0.0003). Of four patients showing localized uptake only, one required amputation for continuing sepsis. Six patients had negative images, and had normal DSA and CT scans. Uptake ratios could not distinguish between those with localized images and those with negative images. Computer generated vertical profiles aided separation of patients with presumed localized and negative images. Semi-quantitative analysis has proved to be a reliable method which should allow a more direct comparison of the efficacy of various investigative techniques and of the results of therapy, independent of intra-observer subjective bias.

Leucocyte radiolabelling techniques: practical aspects.

Radiolabelled leucocytes migrate rapidly to sites of acute inflammation. The simplest technique for imaging intestinal inflammation involves radiolabelling patients' mixed while cells ex vivo with either 99mTc or 111In which are then reinjected. However, further purification of mixed white cells to granulocytes is needed for optimal results using 111In. Owing to the simpler labelling procedure, availability, image quality and dosimetry, 99mTc-HMPAO has gained favour for the investigation of acute inflammation including inflammatory bowel disease. Because of its longer half life. 111In is more suited to the imaging of chronic inflammation such as osteomyelitis. Attempts to radiolabel granulocytes in vivo using monoclonal anti-granulocyte antibodies have been largely unsuccessful to date, and this approach remains a challenge for the future.