Labelling of leukocytes with 99mTc-HMPAO for scintigraphy of inflammatory lesions and abscesses

A simplified and efficient procedure for ^99mTc-HMPAO-labelling of leukocytes is described. For this purpose, the pH and concentration of the ^99mTc-HMPAO preparation was modified. Leukocytes were isolated from a 20 mL mixture of patient blood, 5 mL ACD and 0.8 mL methylcellulose after 1 h sedimentation of erythrocytes and centrifugation (at 400 g) of the obtained plasma layer. Simultaneously, ^99mTc-HMPAO was prepared (one single-dose kit for two patients) by adding 2.2 mL ^99mTc-generator eluate and, after 10 min, 0.3 mL of phosphate buffer to lower the pH to 7. The isolated WBCs were then labelled by the addition of 1-1.2 mL of ^99mTc-HMPAO solution and incubated for 20 min. The unbound tracer was then discarded, the labelled WBC washed and finally resuspended in autologous cell-free plasma. Leukocytes labelled by this procedure were used for scintigraphic localization of inflammatory lesions and abscesses in the gastro-intestinal tract.The labelling efficiency was 60 ± 9%, with a separation yield of 55 ± 11%.     

Lipophilic 99mTc-nitride radiopharmaceuticals as potential myocardial imaging agents

Monocationic ^99mTc-nitrido complexes of a variety of diphosphine ligands have been prepared and the in vivo distribution of such cations has been examined in Sprague-Dawley rats. These complexes show initially high myocardial uptake with subsequent wash-out in this animal model. The lack of myocardial retention can be attributed to the facile in vivo reduction of these cations.     

99mTc-labeled MIBG derivatives: novel 99mTc complexes as myocardial imaging agents for sympathetic neurons

Radioactive-iodine-labeled meta-iodobenzylguanidine (MIBG) is currently being used as an in vivo imaging agent to evaluate neuroendocrine tumors as well as the myocardial sympathetic nervous system in patients with myocardial infarct and cardiomyopathy. It is generally accepted that MIBG is an analogue of norepinephrine and its uptake in the heart corresponds to the distribution of norepinephrine and the density of sympathetic neurons. A series of MIBG derivatives containing suitable chelating functional groups N2S2 for the formation of [TcvO]3+N2S2 complex was successfully synthesized, and the 99mTc-labeled complexes were prepared and tested in rats. One of the compounds, [99mTc]2, tested showed significant, albeit lower, heart uptakes post iv injection in rats (0.21% dose/g at 4 h) as compared to [125I]MIBG (1.7% dose/g at 4 h). The heart uptake of the 99mTc-labeled complex appears to be specific and can be reduced by co-injection with nonradioactive MIBG or by pretreatment with desipramine, a selective norepinephrine transporter inhibitor. Further evaluation of the in vitro uptake of [99mTc]2 in cultured neuroblastoma cells displayed consistently lower, but measurable uptake (approximately 10% of that for [125I]MIBG). These preliminary results suggested that the mechanisms of heart uptake of [99mTc]2 may be related to those for [125I]MIBG uptake. If suitable 99mTc-labeled MIBG derivatives can be further developed, the prevalent availability of 99mTc in nuclear medicine clinics will allow them to be readily available for widespread application.     

Radiotherapy and technetium-99m-labeled red blood cell scintigraphy for hemoptysis from chronic MRSA infection

Aim

To discuss the application of external beam radiotherapy (EBRT) and technetium-99m-labeled red blood cell scintigraphy (LRBCS) in life-threatening hemoptysis from a non-malignant condition.

Materials and methods

This case report presents a patient with persistent hemoptysis secondary to chronic Methicillin-resistant Staphylococcus aureus (MRSA) infection in whom conventional management failed to localize the site of pulmonary bleeding or to provide effective therapy.

Results

EBRT was successfully given for life-threatening hemoptysis with improvement in quality of life for nearly 1 year. LRBCS was used to localize the source of further bleeding and facilitate targeted therapy.

Conclusion

EBRT can be an effective and well-tolerated modality in treating life-threatening hemoptysis refractory to conventional methods. LRBCS is a non-invasive diagnostic tool that can be used to detect the source of pulmonary bleeding.     

The role of scintigraphy with the use of 99mTc-HYNIC-TOC in the diagnosis of medullary thyroid carcinoma

INTRODUCTION: Recently a new somatostatin analogue labelled with (99m)Tc ((99m)Tc-HYNIC-TOC) has been synthetized. Aim of this study was to evaluate the utility of (99m)Tc-HYNIC-TOC in the radionuclide imaging in patients with medullary thyroid carcinoma (MTC). MATERIAL AND METHODS: 30 patients with MTC aged 22-83 years in different stages of the disease were investigated. In 6 patients (group 1) scintigraphy was performed before surgery directly after diagnosis of MTC. Four patients (group 2) were qualified to the study in the phase of remission after surgical treatment that had been confirmed by low concentrations of calcitonin. Twenty patients (group 3) were investigated due to stagnation or recurrence confirmed by persistent hypercalcitoninemia. The scintigraphy using (99m)Tc-HYNIC-TOC (Tektrotyd, POLATOM) was performed 2 and 4 hours post injection of 20 mCi (740 MBq) of the tracer. Other imaging techniques were also employed and analysed in individual cases (US, CT, (99m)Tc(V)-DMSA, (131)I-MIBG, (99m)Tc-MDP, (111)In-octreotide and FDG-PET). RESULTS: Images obtained 2 and 4 hours p.i. were similar. In group 1, uptake of the tracer was found in the primary tumour of MTC in all patients. In group 2, a false positive result was found in 1 of 6 patients. In the remaining 5 of 6 cases no pathological foci were visualised. In group 3, uptake in the thyroid bed was found in 3 of 20 cases and in the lymph nodes in 14 of 20 patients. In 3 of 20 cases uptake in the bone metastases was found. Globally, sensitivity of the scintigraphy using (99m)Tc-HYNIC-TOC was 86.4%, specificity - 75.0%, and accuracy - 84.6%. CONCLUSION: The scintigraphy using (99m)Tc-HYNIC-TOC showed high utility in the diagnosis of MTC. Confirmation of the presence of somatostatin receptors with this method may be used for treatment planning: surgery or radionuclide therapy.     

Preparation and evaluation of 99mTc-t-butylisonitrile (99mTc-TBI) for myocardial imaging: a kit for hospital radiopharmacy

A previous method was modified to obtain [^99mTc(TBI)₆]⁺ by reacting Zn(TBI)₂Br₂ directly with ^99mTcO⁻₄ in the presence of Sn²⁺ ions. [Cu(TBI)₄]Cl was next used as a source of TBI. On reaction with ^99mTcO⁻₄ and Sn²⁺ ions for 3 min at 100 °C, [^99mTc(TBI)₆]⁺ product of radiochemical purity >90% and yield >70% was obtained. Data of biodistribution in rats (2–2.5% in heart) and biokinetics in rabbits were satisfactory. The kit formulation was found to be stable and also safe for administration.     

False-negative myocardial scintigraphy in balanced three-vessel disease,revealed by coronary pressure measurement

In nuclear perfusion imaging of the myocardium, a false-negative test result in patients with balanced three-vessel disease is a well-known pitfall. This paper describes a patient with typical chest pain and a negative myocardial perfusion scintigram. At coronary angiography, intermediate stenoses in the left anterior descending (LAD), left circumflex (LCX), and right coronary (RCA) arteries were present. Fractional flow reserve, measured by coronary pressure measurement, was 0.54, 0.56, and 0.66 respectively for the LAD, LCX, and RCA, unequivocally demonstrating the presence of balanced three-vessel disease. The patient underwent successful bypass surgery and remained event-free thereafter.     

Microdamage in bone: surface analysis and radiological detection

Microdamage accumulation leads to reduced bone strength and fracture. Intact, damaged and Rose Bengal stained cortical bone specimens were studied using SEM and EDXA imaging. SEM coupled with EDXA studies showed selective labelling of surface damage due to binding of dye at free lattice sites. A series of novel iodinated X-ray contrast agent were synthesised. These agents demonstrated excellent stability, water solubility and lack of atropisomerism. Preliminary imaging studies, using cone-beam mu-CT, demonstrated their ability to provide visible contrast in the solid state on bone surfaces.     

A novel method for labelling of leukocytes with technetium-99m and its comparative evaluation for abscess scintigraphy

A new method, based on the pretreatment of leukocytes with glucoheptonate prior to treating with reduced ^99mTc, has been developed for the preparation of ^99mTc labelled leukocytes. The leukocytes labelled with a ^99mTc concentration (5.59%/g tissue) similar to that of ¹¹¹In-leukocytes (6.27%/g tissue), in the experimental abscess were in rat thigh. Concentration of ^99mTc-leukocytes in blood at 24 h was only about 35% as compared to that of ¹¹¹In-leukocytes. Biodistribution in the rat organs was similar in both cases, except in the liver where ^99mTc-leukocytes exhibited about 4-fold greater concentration. Images of experimental abscess in rat by using ^99mTc-leukocytes were comparable to those obtained with ¹¹¹In-leukocytes.     

A Tc-99m-labeled long chain fatty acid derivative for myocardial imaging

C-11- and I-123-labeled long chain fatty acid derivatives have been reported as useful radiopharmaceuticals for the estimation of myocardial fatty acid metabolism. We have reported that Tc-99m-labeled N-[[[(2-mercaptoethyl)amino]carbonyl]methyl]-N-(2-mercaptoethyl)-6-aminohexanoic acid ([(99m)Tc]MAMA-HA), a medium chain fatty acid derivative, is metabolized by beta-oxidation in the liver and that the MAMA ligand is useful for attaching to the omega-position of fatty acid derivatives as a chelating group for Tc-99m. On the basis of these findings, we focused on developing a Tc-99m-labeled long chain fatty acid derivative that reflected fatty acid metabolism in the myocardium. In this study, we synthesized a dodecanoic acid derivative, MAMA-DA, and a hexadecanoic acid derivative, MAMA-HDA, and performed radiolabeling and biodistribution studies. [(99m)Tc]MAMA-DA and [(99m)Tc]MAMA-HDA were prepared using a ligand-exchange reaction. Biodistribution studies were carried out in normal mice and rats. Then, a high initial uptake of Tc-99m was observed, followed by a rapid clearance from the heart. The maximum heart/blood ratio was 3.6 at 2 min postinjection of [(99m)Tc]MAMA-HDA. These kinetics were similar to those with postinjection of p-[(125)I]iodophenylpentadecanoic acid. Metabolite analysis showed [(99m)Tc]MAMA-HDA was metabolized by beta-oxidation in the body. In conclusion, [(99m)Tc]MAMA-HDA is a promising compound as a long chain fatty acid analogue for estimating beta-oxidation of fatty acid in the heart.