Intake and excretion of 99Tc in a common sea alga, hijiki (Hizikia fusiforme), as ingested in the daily diet--a measurement in an adult male

Ingestion and excretion of environmental 99Tc was measured in an adult male who ingested 'hijiki' food in his diet that contained a sub-bequerel activity per kg, and which was prepared from a marine alga, Hizikia fusiforme, or hijiki in Japanese, traditionally eaten in the Japanese diet. Harvested hijiki was boiled, dried and cooked. This was eaten at each meal five times over 2 d. All faeces and 24-h urine samples were collected during the 3 d before and subsequent 11 d starting from the day when the intake began. The ingestion intake was measured by analysing the dried hijiki material. 99Tc was determined by using liquid-liquid extraction and low-background beta ray spectrometry. The excreta were also analysed for minerals by atomic absorption spectrometry. The apparent absorption rate in the gastrointestinal tract for 99Tc under these conditions was calculated to be approximately 0.5. The present result from a single subject indicates the need for further studies.

Anti-CEA monoclonal antibody: technetium-99m labeling and the validation process of a scintigraphic animal model with a non-cellular antigenic implant

Animal models are currently used to verify the biodistribution of different radiopharmaceuticals before its clinical application in Nuclear Medicine; however, there may be some limitations. The utilization of labelled anti-tumor monoclonal antibodies (MoAb) in experimental models often requires implant of human antigens (usually a cellular implant), which cannot be achieved in immunocompetent animals. Our purpose was to label an anti-CEA MoAb with technetium-99m (99Tc) and to validate a simplified animal model using a noncellular antigenic implant. MoAb was directly labelled with 99mTc, after reduction with 2-mercaptoethanol. Labeling efficiency was checked by ascending chromatography and immunoreactive fraction was measured in plastic wells sensitized with the antigen. Radiopharmaceutical biodistribution was evaluated by dissection and scintigraphy in 5 mice groups; following the subcutaneous administration of Al(OH)3, CEA adsorbed Al(OH)2 and a control group evaluation. Labeling efficiency was 94+/-3%, which showed to be stable for 24 hr, with immunoreactive fraction above 50%. Invasive biodistribution evaluation showed prolonged blood retention, hepatic and renal uptake. A significant increase in uptake was observed in scintigraphic studies of animals with CEA-adsorbed Al(OH)3 implants compared with the other groups (p<0.05). The non-cellular antigenic implant model simplifies the pre-clinical evaluation of labelled MoAb.

Comparison of beclomethasone dipropionate delivery by easyhaler dry powder inhaler and pMDI plus large volume spacer

Dry powder inhalers (DPIs) provide a means of delivering inhaled asthma drugs without the use of propellants. Easyhaler is a multidose DPI, delivering 200 doses of beclomethasone dipropionate (BDP), 200 microg/dose. A gamma scintigraphic study has been carried out in 10 healthy volunteers to compare the deposition of BDP from Easyhaler with that from a pressurized metered dose inhaler (pMDI) coupled to a Volumatic spacer device delivering 250 microg BDP per dose. The spacer was used without any pretreatment to reduce static charge on the spacer walls. The study was conducted according to an open, randomized, crossover design. The volunteers inhaled the study drug using optimal inhalation technique for both devices. Lung deposition of 99mTc-labeled BDP averaged 18.9% (SD 9.5%) of the metered dose for Easyhaler, and 11.2% (SD 5.3%) for pMDI plus spacer (p < 0.05); when the data were expressed as mass of BDP deposited in the lungs, the difference in lung deposition just failed to reach statistical significance (Easyhaler 37.8 microg; pMDI plus spacer 28.0 microg). Oropharyngeal deposition was significantly reduced by use of the spacer. The results of this study show that Easyhaler delivers drug more efficiently to the lungs than pMDI plus Volumatic spacer when no measures are taken to eliminate static charge on the spacer walls.

Respiratory deposition patterns of salbutamol pMDI with CFC and HFA-134a formulations in a human airway replica

This paper describes a technique that uses a well-defined human airway replica and gamma counting as a standard method for evaluating and comparing the performance of medical inhalers and spacers. High-fidelity replicas reproduced as needed from master casts made from human cadavers include the oropharyngeal cavity, larynx, trachea, and five to nine generations of bronchi. Deposition in the small airways and alveoli region of the cast is simulated by material that passes through the upstream airways and is collected on foam filters. Deposition patterns in the respiratory tract replica were obtained by using radiolabel in the medical inhaler and by gamma scintigraphy. This technique was used to determine respiratory deposition patterns of salbutamol in a pressurized metered dose inhaler (pMDI) with chlorofluorocarbon (CFC, in-house formulation) and HFA-134 formulations (Proventil hydrofluoroalkane [HFA]). At an inspiration flow of 30 L/min, patterns in the salbutamol/CFC formula showed a high deposition in the oropharyngeal airway (78%) and a 16% deposition in the lung, similar to in vivo measurements reported in the literature. However, the salbutamol/HFA formula showed lower oral deposition (56%) but higher lung deposition (24%). The difference in the oral deposition patterns may be attributed to lower initial spray velocity, initial droplet evaporation rate, and possibly initial droplet sizes of Proventil HFA. The small orifice diameter (0.25 mm) of the Proventil HFA actuator produced a softer plume with a smaller impact force, resulting in lower oropharyngeal deposition. Cascade impactor measurements showed similar aerodynamic particle size distribution of the CFC and HFA formulations. We also showed that using spacers in the Proventil HFA resulted in a lower oropharyngeal deposition and higher lung deposition, indicating beneficial effects. Comparison of oropharyngeal deposition and those predicted by artificial throats used in the impactor measurements showed that, in general, the artificial throat predicted a lower deposition.

An advanced and detailed in vitro validation procedure for the radiolabeling of carrier-free terbutaline sulphate dry powder

The aerodynamic properties of 99mTc radiolabeled carrier-free terbutaline sulphate (TBS) have been thoroughly investigated following delivery by Turbuhaler (AstraZeneca Lund, Sweden). A full and detailed radiolabeling procedure is also reported. The in vitro radiolabel validation was performed to determine whether TBS radiolabeled in this way would be representative of the commercially available product Bricanyl Turbuhaler during clinical trials. The results indicated that variations in aerodynamic properties had been introduced and that the radiolabel would slightly underestimate the fine particle fraction of Bricanyl, but would nonetheless act as a suitable marker in vivo. Assumptions regarding the aerodynamic properties of doses likely to be received by clinical trial subjects were also examined. This has been achieved by extending the validation procedures beyond those usually reported to include dose number, time, and homogeneity dependent studies. It was found that doses extracted for testing purposes and simulated patient doses extracted shortly afterward had similar properties. Doses extracted 2 h after initial testing also had similar properties to the test doses. These results suggested that data from the test doses could be used for quality control purposes, would be representative of the doses to be received by clinical trial subjects, and that a short delay between initial testing and trial subject inhalation would be acceptable.

Guidelines for brain radionuclide imaging. Perfusion single photon computed tomography (SPECT) using Tc-99m radiopharmaceuticals and brain metabolism positron emission tomography (PET) using F-18 fluorodeoxyglucose. The Belgian Society for Nuclear Medicine

The purpose of these guidelines is to assist nuclear medicine practitioners in recommending, performing, interpreting, and reporting the results of brain perfusion SPECT studies using Tc-99m radiopharmaceuticals and brain metabolism PET studies using F-18 fluorodeoxyglucose (FDG). These guidelines have been adapted and extended from those produced by the Society of Nuclear Medicine (Juni et al., 1998) and the European Association of Nuclear Medicine by a Belgian group of experts in the field trained in neurology and/or nuclear medicine. Some indications are not universally approved (e.g. brain death), but largely supported by the literature. They have been included in these guidelines in order to provide recommendations and a standardised protocol.

99mTc-labeled neuropeptide Y analogues as potential tumor imaging agents

The possible use of neuropeptide Y (NPY) as a novel radiopeptide has been investigated. NPY is a 36-amino acid peptide of the pancreatic polypeptide family, which is expressed in the peripheral and central nervous system, and is one of the most abundant neuropeptides in the brain. Its receptors are produced in a number of neuroblastoma and the thereof derived cell lines. As structure-activity relationships of NPY are well-known, we could assume where a radionuclide might be introduced without affecting receptor affinity. We applied the novel [99mTc(OH2)3(CO)3]+ aqua complex and PADA (2-picolylamine-N,N-diacetic acid) as bifunctional chelating agent. The peptides were synthesized by solid-phase peptide synthesis, and PADA was coupled to the side chain of Lys4 of the resin-bound peptide. Upon postlabeling of [K4(PADA)]-NPY, 99mTc(CO)3 did not only bind to the desired PADA, but presumably as well to the His in position 26. Since the replacement of His26 by Ala only slightly decreased binding affinity, [K4(PADA),A26]-NPY was specifically postlabeled, and the 185Re surrogate maintained high binding affinity. Furthermore, the prelabeling approach has been applied for the centrally truncated analogue [Ahx5-24]-NPY, which is highly selective for the Y2 receptor. The resulting Ac-[Ahx5-24,K4(99mTc(CO)3-PADA)]-NPY was produced with a yield of only 16%. Therefore, postlabeling was applied for the short analogue as well, again substituting His26 by Ala. Competitive binding assays using (185)Re as a surrogate for 99mTc showed high binding affinity of Ac-[Ahx5-24,K4(185Re(CO)3-PADA),A26]-NPY. Internalization studies with the corresponding 99mTc-labeled analogue revealed receptor-mediated internalization. Furthermore, biodistribution studies were performed in mice, and stability was tested in human plasma. Our centrally truncated analogue revealed a 6-fold increased stability compared to the natural peptide NPY. We conclude that Ac-[Ahx5-24,K4(99mTc(CO)3-PADA),A26]-NPY has promising characteristics for future applications in nuclear medicine.

Cationic liposomes enhance cellular/nuclear localization of 99mTc-antisense oligonucleotides in target tumor cells

Efforts are underway to apply strategies developed in connection with antisense chemotherapy to antisense imaging in nuclear medicine. One such strategy is the use of cationic liposome to enhance the cellular uptake of antisense oligonucleotides.

METHODS

Using a 99mTc-labeled 18-mer uniformly phosphorothioate DNA antisense to the mRNA of the RI alpha subunit of PKA, the effects of a cationic liposome as carrier on cell uptake and efflux kinetics in tissue culture was evaluated in a RI alpha mRNA positive ACHN cell line. The sense DNA was used as control.

RESULTS

Cell uptake was increased 4-5 fold using the liposome carrier compared to the same dosage of naked DNA. Whether naked or liposome-bound, the antisense DNA showed slower efflux from cells compared to the control, resulting in statistically higher accumulation of the antisense compared to the control DNA and suggesting an antisense effect. The internalization and increased cellular accumulation for both antisense and control DNAs with liposomes were demonstrated by microautoradiography and by subcellular fractionation. Finally, using 99mTc-labeled 15-mer antisense DNA against the c-myc oncogene mRNA in MDA-MB-231 cells, significantly more radiolabel was found in total mRNA for the antisense compared to the sense control DNA, both with and without liposome carrier. In conclusion, in tissue culture, the use of a cationic liposome carrier greatly increased cellular uptake and target mRNA binding of 99mTc-labeled antisense DNA.

Localization of the sentinel node in breast cancer: identical results with same-day and day-before isotope injection

BACKGROUND

Although the technique of sentinel lymph node (SLN) biopsy in breast cancer is not fully standardized, an increasing number of centers map the SLN by using radioisotope supplemented by blue dye, and most have injected isotope on the day of surgery. Here we directly compare the results of same-day and day-before isotope injection in a large series of breast cancer patients having SLN biopsy with our mature technique.

METHODS

Starting with our 961st SLN procedure for breast cancer, 1320 consecutive patients had SLN biopsy after the injection of unfiltered 99mTc-labeled sulfur colloid given as a single-site, low-volume (0.05 ml) intradermal injection: 933 on the day of surgery (1-day protocol) and 387 on the day before (2-day protocol). All had intraparenchymal injection of blue dye.

RESULTS

The two groups were comparable in age, tumor location, histopathologic characteristics, and number of SLNs identified. LSG taken at 2 hours in the 2-day protocol was positive more often than LSG performed at 30 minutes in the 1-day protocol, and nonaxillary sites of lymphatic drainage were seen in <1% of each group. Absolute isotope counts and the ratio of SLN to axillary background counts were similar. Isotope localization of the SLN succeeded in a comparable fraction of patients, as did SLN identification overall.

CONCLUSIONS

The results of SLN mapping with same-day and day-before injection of radioisotope are virtually identical. The logistical advantages of day-before injection do not compromise the success of the procedure.

[Sentinel lymph nodes in breast cancer. Multidisciplinary approach; critical analysis of the learning curve; results obtained with a radiopharmaceutical not previously utilized]

Detection of the sentinel node is slowly becoming a new and promising procedure to stage patients suffering from breast cancer. Various articles have attempted to analyze objectively the predictive value of the histopathological examination to reveal the presence of metastatic cells in the axillary node without having to carry out an axillary dissection. In this paper, 60 patients with breast cancer (T up to 3 cm, clinically negative axilla) have been studied. A colloid bound to 99m Technetium was injected. Intra-surgical radioguided detection of the sentinel lymph node was performed and this was excised and its pathology was analyzed. After a complete axillary dissection was performed. With this technique it was possible to predict the condition ot the axilla in 96.5% of the cases and the sensitivity of the method was 92%. A training program on this technique has been developed and its application is suggested. The results of the use of a radiopharmaceutical which has not been previously documented in the published literature is discussed.

Adsorption of radiopharmaceuticals to syringes leads to lower administered activity than intended

In this study we examined the delivered activity of radiopharmaceuticals injected into patients and the various factors which lead to incomplete delivery. Four commonly used 99Tcm radiopharmaceuticals were included, namely pertechnetate, methylene diphosphonate (MDP), macro-aggregated albumin (MAA) and tetrofosmin. There was no appreciable residual activity after injection of pertechnetate and MDP other than that due to the dead space in syringes (0.06 ml, 4% of measured activity). However, there was considerable residual activity following an MAA injection. This was particularly dependent on the radiopharmaceutical residence time in the syringe prior to injection. If MAA was pre-dispensed there was up to 80% of activity remaining in the syringe following injection. We have shown that this activity is not bound and can be decreased by agitating the syringe prior to the injection. For tetrofosmin, the activity remaining in the syringe was shown to be mostly due to adsorption of the tetrofosmin onto the plastic syringe (up to 30% of the activity); in particular, onto the rubber plunger. The amount of binding probably depends on the formulation of the rubber plunger and the plastic barrel, which varies between manufacturers. Of the three commonly used syringe brands (Becton-Dickinson, Sherwood, and Braun syringes) the Braun syringes were shown to have the least binding (6%) and would be most suitable for tetrofosmin injection. We recommend the use of Braun syringes for tetrofosmin. We also recommend that pre-dispensed MAA injections should be gently agitated before injection into the patient. No special precautions are necessary for pertechnetate or MDP injections.

A comparison of radiopharmaceutical agents used for the diagnosis of pulmonary embolism

Radioactive gas or technetium-99m aerosols are used to perform pulmonary ventilation scintigraphy. The aim of this study was to compare three radiopharmaceuticals, Kryptoscan, Technegas and Venticis II, in terms of their costs and user preferences rather than on the basis of diagnostic efficacy. For each radiopharmaceutical agent, an analysis questionnaire was sent to nuclear medicine departments setting out the criteria (and subcriteria) to be assessed: diagnosis quality: imaging quality, distribution homogeneity, examination procedures and capacity to examine particular patients (e.g. smokers); safety: for patient, paramedical and medical staff and the environment; use: availability in cases of emergency, ergonomics of the apparatus, simplicity and time of preparation. A score, ranging from 0 to 5, and a weighting (importance of one criterion with regard to the others) were assigned to each criterion. The direct cost of a ventilation (drugs, generator systems, disposable materials) was calculated for each radiopharmaceutical agent according to the number of patients examined per day (1-6) and the number of examination days per week (2-5). Fourteen questionnaires concerning at least two of the products were returned out of the 30 mailed. A 'preference score' was calculated using Pharma Decision software. The mean score of Kryptoscan was significantly higher than that of Venticis II (444 vs. 286, P < 0.001) and higher than the mean score of Technegas (444 vs. 344, P < 0.01). For Venticis II and Technegas, the changes in patient direct costs were minor and depended on the number of patients per day and the number of examination days per week. Respectively, they were: $US 117.66 (5 patients.day-1; 5 days.week-1) to $US 147.74 (2 patients.day-1; 2 days.week-1) and $US 56.60 (6 patients.day-1; 5 days.week-1) to $US 132.08 (2 patients.day-1; 2 days.week-1). The direct cost of ventilation using Kryptoscan varied only according to the number of patients examined per day: $US 104.66 (6 patients.day-1) to $US 266.47 (2 patients.day-1). This study shows that Kryptoscan appears to be preferable for ventilation scintigraphy whenever at least four patients are examined daily.

Tc-99m-PEG-Liposomes for the evaluation of colitis in Crohn's disease

In the present study, the potential role of 99mTc-PEG-liposome to determine the extent and severity of active disease of Crohn's colitis was investigated. Patients suspected of having an exacerbation of Crohn's disease underwent a 99mTc-PEG-liposome scan (740 MBq, imaging at 4 and 24 h p.i.). A barium enema or endoscopy was performed as the standard verification procedure. Disease activity indices (Clinical Disease Activity Index and Van Hees Activity Index) were calculated. In seven patients positive images of colon segments affected by Crohn's colitis were obtained using 99mTc-PEG-liposomes. Only a moderate relation between 99mTc-liposome scan grading and verification procedures was found (Spearman rank r = 0.22). In accordance with previous studies, no significant correlation was found between the clinical disease activity indices and the verification procedures. This study was prematurely terminated because of unacceptable side-effects in 3 out of 9 patients, which occured almost immediately after starting the infusion. The complaints consisted of dyspnea and facial erythema. The symptoms were self-limiting when the infusion was stopped. In conclusion, the extent of Crohn's colitis can be established non-invasively with 99mTc-PEG-liposome scintigraphy. However, in view of the encountered side-effects, the PEG-liposomal preparation may have to be modified.

[Alteration in the biodistribution of 99mTc-albumin microspheres after its administration through a canalized umbilical vein]

We present the case of a newborn female patient with a suspected right hypoplastic lung who was referred to our Service to perform a perfusion lung scintigraphy. The tracer (99mTc-albumin microspheres) was injected with a central catheter through the umbilical vein. The lung scan showed abnormal extrapulmonary activity that was attributed to an erroneous canalization (catheter in Arantius duct). A new study, with injection through the peripheral vein, showed the lung perfusion, with a global decrease of activity in the right lung. This case demonstrates a cause of abnormal extrapulmonary perfusion tracer uptake, verifying that using the correct access route is mandatory.

Pharmacoscintigraphic evaluation of lung deposition of inhaled zanamivir in healthy volunteers

OBJECTIVE

The objective of this study was to determine the sites of zanamivir deposition in the respiratory tract and the pharmacokinetics of zanamivir after oral inhalation from the Diskhaler device and from a prototype of a novel breath-activated device.

DESIGN

This was a 2-period block-randomised study in which participants inhaled zanamivir from a Diskhaler and/or the prototype device on separate days.

STUDY PARTICIPANTS

13 healthy volunteers (5 men and 8 women) aged 20 to 42 years (mean age 29 years) and weighing 54.0 to 94.0 kg (mean bodyweight 69.2 kg) entered the study.

INTERVENTIONS

Participants were given dry powder zanamivir 10 mg formulated with 99mTc from the Diskhaler or the prototype device on separate days. Scintigraphic images of the chest and oropharynx were recorded. Blood samples for determination of serum zanamivir and urine for excretion studies were taken up to 8 hours after drug administration. Safety was evaluated by monitoring lung function tests, adverse events and laboratory parameters.

RESULTS

Orally inhaled zanamivir was well tolerated, as demonstrated by lung function tests. A mean of 13.2% (n = 11) of the 10 mg dose from the Diskhaler was deposited in the bronchi and lungs. The deposition pattern varied between individuals, showing a preferentially central deposition pattern in some and a uniform distribution pattern in others. The major deposition site was the oropharynx (mean 77.6%), with a mean of 1.2% deposited on the trachea and a mean of 3.2% retained in the blister. Similar data were obtained with the prototype device. Inhalation of zanamivir gave a broad peak of systemic absorption with mean maximum serum concentrations of approximately 30 to 40 micrograms/L after 1.5 hours. The rate and extent of absorption were similar irrespective of inhalation device. Less than 5% of drug was excreted unchanged in urine within 8 hours of inhalation, confirming the low bioavailability of zanamivir after pulmonary delivery. A significant correlation existed between systemic exposure and peripheral lung deposition.

CONCLUSIONS

The local concentrations of zanamivir that result from oral inhalation via the Diskhaler are estimated to be > 10 mumol/L throughout the respiratory tract, well in excess of the concentrations observed to inhibit influenza virus neuraminidases by 50% (0.64 to 7.9 nmol/L). Similar deposition data were obtained with the Diskhaler and the prototype device, which was consequently not developed further. Pharmacoscintigraphy was confirmed as being a reliable technique for measuring zanamivir deposition in the respiratory tract.

RinoFlow nasal wash and sinus system as a mechanism to deliver medications to the paranasal sinuses: results of a radiolabeled pilot study

Direct delivery of medication to the sinuses with standard nebulizers is difficult to achieve. The nasal inhalation of aerosolized medications is dependent on the size of the particles and the pressure with which they are delivered; when the particles are too small or the pressure is too low, the drug cannot reach the sinuses. The ability of topical medications to treat sinus disorders can be improved if the medication could be delivered directly to the sinuses. We tested the ability of the RinoFlow nasal aerosol delivery device to deposit aerosol directly to the paranasal sinuses. Five normal, healthy subjects used the device to administer technetium Tc 99m nasally. Nuclear scanning was used to detect deposition in the frontal and maxillary sinuses. Three subjects underwent additional testing after administration of a nasal decongestant. Three of the five subjects showed some evidence of direct delivery to the sinuses, although deposition was not uniform or complete. Pretreatment with a decongestant had no apparent effect on subsequent technetium delivery. We conclude that the results of this study are promising and that further study is warranted.

Imaging of adenosine bolus transit following intravenous administration: insights into antiarrhythmic efficacy

OBJECTIVE

To study the effects of the site of intravenous injection of adenosine and to assess the site of action of adenosine in the heart by correlating cardiac effects with bolus transit.

METHODS

Ten patients undergoing routine technetium (Tc-99m) gated blood pool ventriculography consented to the coadministration of intravenous adenosine. The dose of adenosine required to produce heart block during sinus rhythm was determined following antecubital vein administration. This dose (6-18 mg) was mixed with Tc-99m and given first into the same antecubital vein (proximal injection) and then repeated into a hand vein (distal injection). The ECG was recorded and the transit of the bolus was imaged using a gamma camera.

RESULTS

Heart block occurred in all 10 patients (second degree in seven, first degree in three) at (mean (SEM)) 17.5 (1.0) seconds after the proximal injection of adenosine. Distal injection produced heart block in six patients (second degree in two, first degree in four) at 21.9 (4.4) seconds (p < 0.01). In eight of 10 patients the electrophysiological effects were less with distal injection. The onset of heart block was close to the time of peak bolus Tc-99m activity in the left ventricle. Peak bolus activity was delayed (by about three seconds) and the duration of bolus activity in the left ventricle was increased with distal injection compared with proximal injection, at 17.2 (4.2) v 9.2 (3.1) seconds, p < 0.01.

CONCLUSIONS

The lesser electrophysiological effects of adenosine following distal intravenous injections were associated with delay in transit time and dispersion of the bolus. The correlation of adenosine induced heart block with bolus activity in the left heart indicated dependence on coronary arterial delivery of adenosine to the atrioventricular node.

Measurement of lymphatic function with technetium-99m-labelled polyclonal immunoglobulin

A reliable method for measuring lymph flow in physiological units would be valuable, especially in conditions in which it is uncertain whether lymph flow is increased or decreased. The requirements of a radiopharmaceutical for such measurement include stable radionuclide labelling and rapid access to lymphatic vessels following tissue injection but no access to blood vessels. A soluble macromolecule is likely to come closest to meeting these requirements. Technetium-99m-labelled human polyclonal immunoglobulin (HIG) was therefore investigated firstly in comparison with 99mTc-labelled human serum albumin (HSA) in patients undergoing routine lymphoscintigraphy and secondly with respect to injection site in a group of volunteers with post-mastectomy oedema (PMO). Subcutaneous injection of 99mTc-HIG into the web space of a distal extremity gave images in which lymphatic vessels were more clearly defined compared with images obtained after injection of 99mTc-HSA. Lymph nodes were also more clearly defined, suggesting specific retention of HIG, possibly through Fc-mediated binding. Peripheral blood sampling showed a delayed arrival in blood of radioactivity after 99mTc-HIG compared with 99mTc-HSA, although ultimately, the blood recovery of 99mTc-HIG was significantly higher (P < 0.05) than that of 99mTc-HSA. Clearance rates of radioactivity from the injection site were not significantly different, however, between the two agents. In patients with PMO, web space injection of 99mTc-HIG gave excellent images of normal lymphatic vessels, of lymph nodes and of abnormal lymph drainage such as dermal backflow in swollen arms. In contrast, neither lymphatic vessels nor lymph nodes were visualised after injection into the skin of the dorsum of the distal forearm. Although there was no difference in clearance rates from the injection sites between normal and swollen arms with either agent in PMO, clearance was significantly faster following injection into the web space (0.11% per minute for normal and swollen arms combined) than into the forearm (0.053% per minute; P < 0.05). These results suggest that (a) 99mTc-HIG is a potentially useful agent for measuring lymph flow and lymph node function; but (b) injection into the dorsum of the forearm is not a useful method of administration for these measurements; and (c) clearance rates from the injection site do not support the notion that PMO is the result of decreased lymph flow. Further studies are warranted to evaluate 99mTc-HIG as an agent for assessment of lymphatic function, especially with respect to measurement of lymph flow and possibly also for the evaluation of lymph node Fc-mediated immunocompetence.

Evaluation of flow characteristics of soft-tissue vascular malformations using technetium-99m labelled red blood cells

The estimation of intralesional haemodynamics is crucial in determining appropriate treatment for soft-tissue vascular malformations. The aim of this study was to develop a method to evaluate the flow characteristics of soft-tissue vascular malformations using technetium-99m labelled red blood cells (99mTc-RBCs). Seventy-nine soft-tissue vascular malformations, including 20 arteriovenous malformations and 59 venous malformations, in 57 patients were examined. Following the intravenous injection of 99mTc-RBCs, dynamic imaging was performed for 30 min with the lesion in the field of view (99mTc-RBC flow study). A time-activity curve was generated for the lesion, and the lesion was categorized as a high-flow or low-flow lesion by visual inspection of the curve. In low-flow lesions, mean vascular transit time (MTT) was calculated by curve fitting based on a two-compartment model. Twenty-nine lesions in 19 patients were examined twice, and reproducibility was assessed. In 23 venous malformations in 16 patients, 99mTc-Sn colloid was percutaneously injected into the intravascular space of the lesion, and dynamic data of 5-min duration were acquired (direct puncture scintigraphy). MTT was estimated from the washout curve and compared with MTT estimated by 99mTc-RBC flow study. 99mTc-RBC flow study classified all 20 arteriovenous malformations as high-flow lesions and all 59 venous malformations as low-flow lesions. In the low-flow lesions, MTT estimated by 99mTc-RBC flow study ranged from 61.2 to 2174.9 s. In the reproducibility study, complete concordance in classification and high correlation in MTT were shown between the first and second examinations. MTT estimated by 99mTc-RBC flow study was significantly correlated with that estimated by direct puncture scintigraphy. In summary, 99mTc-RBC flow study provides a quantitative indicator of intralesional haemodynamics in low-flow lesions in addition to accurate distinction between high-flow and low-flow lesions. The results of this study suggest the feasibility of detailed evaluation of flow characteristics in soft-tissue vascular malformations using 99mTc-RBCs.

Washing plastic spacers in household detergent reduces electrostatic charge and greatly improves delivery

Ionic detergents reduce electrostatic charge on plastic spacers, thereby improving in vitro drug delivery. The aim of this study was to gain practical information on the use of detergents and to evaluate the relevance of this information on in vivo drug deposition. Measurement of electrostatic charge and salbutamol particle size distribution was carried out on detergent-coated and noncoated plastic spacers. The efficiency of four household detergents was compared, and the influence of dilution and the duration of the antistatic effect were studied. In addition, the level of radiolabelled salbutamol deposition in the lungs of eight healthy adults was compared after inhalation through a new versus a detergent-coated spacer. In vitro, all tested detergents reduced the electrostatic charge on the spacer surface. This resulted in a mean increase of 37.4% (range 33.5-41.2) in small particle (<6.8 microm) salbutamol output compared with water-rinsed/drip-dried spacers. Dilution had no influence on the results and the effect lasted for at least four weeks. In vivo, the mean lung deposition of radiolabelled salbutamol in healthy subjects was 45.6% (range 43.4-49.5) through a detergent-coated spacer compared to 11.5% (range 7.6-17.9) through a static spacer (p<0.001). In conclusion, household detergents offer a simple and practical solution to the problem of static on plastic spacers and significantly improve both in vitro and in vivo delivery of salbutamol.

Scintigraphic measurement of regional gastrointestinal transit in the dog

Scintigraphic techniques can measure sequentially gastric emptying, small bowel transit, and colonic transit in humans, and comparable methods for experimental studies in animals would be useful. We developed such a method in dogs and examined the effects of prokinetic drugs on regional transit. Two isotopes were given to fasting dogs. Polystyrene pellets labeled with 99mTc were mixed in a can of dog food and 111In- labeled pellets were given in a gelatin capsule coated with a pH-sensitive polymer, designed to dissolve in the distal bowel. Gamma camera images were obtained for up to 24 h. Prokinetic drugs were given by intravenous injection. Duplicate baseline studies showed good agreement in seven dogs. In a second group (n = 4), intra- and interanimal variabilities were established. Two novel prokinetic drugs (AU-116 and AU-130) accelerated small bowel and colonic transit. A simple noninvasive method for measuring whole gut transit in dogs was developed and validated. Two new prokinetics accelerated small bowel and colonic transit.

Rapid detection of acute appendicitis with Tc-99m-labeled intact polyvalent human immune globulin

BACKGROUND

Acute appendicitis remains problematic for emergency clinicians. A rapid and definitive test is needed for detecting acute appendicitis before surgical intervention. The purpose of this clinical trial was to determine the efficacy of Tc-99m-labeled intact polyvalent human immune globulin (Tc-99m IgG) in the evaluation of acute appendicitis.

STUDY DESIGN

Thirty-five patients with clinically suspected acute appendicitis were evaluated with Tc-99m IgG. After the intravenous injection of 25 mCi (92.5 MBq) of Tc-99m IgG, anterior flow, single photon emission computerized tomography (SPECT) and planar delayed images of the abdomen were obtained. Any abnormal focal uptake of Tc-99m IgG in the right lower quadrant was considered to be a positive scan.

RESULTS

Twenty-one patients with a positive Tc-99m IgG scan underwent laparotomy and were found to have acute appendicitis. Of the 14 patients who had negative scans, 7 underwent surgery. In this series, Tc-99m IgG study yielded 21 true-positive, 12 true-negative, and 2 false-negative results with a sensitivity, specificity, and accuracy of 91%, 100%, and 94%, respectively. The positive and negative predictive values were 100% and 86%, respectively. There were no false-positive results.

CONCLUSIONS

Tc-99m IgG scintigraphy can provide the clinicians a simple, rapid, and definitive test for the diagnosis of acute appendicitis.

Aerosol deposition in equine lungs following ultrasonic nebulisation versus jet aerosol delivery system

Therapeutic aerosols pay an increasing role in the treatment of equine respiratory disorders. This route of delivery permits concentration of significant amounts of drugs at the site of action without unwanted high systemic concentration and resultant side effects. The efficiency of such a topical therapy depends on the quantity of inhaled drugs deposited in the lungs and, for some drugs, on the proportion retained in specific parts of the lungs. The objective of this study was to define and to compare quantitative (dose deposited) and qualitative (regional distribution) deposition of an aerosol in the equine lungs, using either a ultrasonic nebuliser (UN) currently used in human medicine or a high pressure jet nebuliser (JN) especially developed for the equine species. This comparison was possible owing to gamma-scintigraphy, a noninvasive technique ideally suited to give information about both total and regional deposition of inhaled drugs in the respiratory tract. The quantitative study did not point out any difference between the 2 systems concerning the activity released from the nebuliser proportionally to the initial loaded dose (mean +/- s.d. 45.95 +/- 4.93% for the UN vs. 46.47 +/- 8.49% for the JN). By contrast, the percentage of the dose released reaching the lungs was significantly lower with the UN compared to the JN (5.09 +/- 0.66% vs. 7.35 +/- 1.96%). The qualitative analysis did not show any significant difference in size of aerosol deposition image between the 2 nebulisers. However peripheral deposition was significantly higher with JN compared to UN. In conclusion, both nebulisers may be used for aerosol therapy in the equine species. The ultrasonic and pneumatic nebulisation achieved drug deposition in the peripheral part of the lungs (i.e. small airways and lung parenchyma).