The quarterly journal of nuclear medicine : official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR)
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Comparative Study
Diagnostic imaging in patients with paragangliomas. Computed tomography, magnetic resonance and MIBG scintigraphy comparison.
We compared iodine-131 metaiodobenzylguanidine (MIBG), computed tomography (CT) and magnetic resonance (MR) imaging studies in 40 patients with suspected or proven paragangliomas. ⋯ Our results suggest that CT and MR are particularly useful in the initial evaluation of patients with suspected paragangliomas. MIBG should be recommended during the post-surgical follow-up of such patients since recurrent, malignant or extra-adrenal disease frequently occur. Finally, while MR SIR and CT features are not able to distinguish malignant paragangliomas from benign tumors, MIBG uptake is higher in malignant lesions compared to benign tumors providing a diagnostic criterion to differentiate these lesions.
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The avidity of many metastatic pheochromocytomas and neuroblastomas for metaiodobenzylguanidine (MIBG) observed at diagnostic scintigraphy has led to attempts to treat these lesions with large doses of MIBG. We and others have achieved therapeutic responses with 131I-MIBG (usually partial) in about a third of malignant pheochromocytomas. ⋯ This has led to prolonged tumor stabilization and survival (> 19 to > 52 months) in 5 of 10 patients. MIBG radiopharmaceutical treatment of neuroendocrine tumor patients must still be considered an experimental but nevertheless promising treatment modality.
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Comparative Study
In vitro and in vivo studies with no-carrier added radioiodinated MIBG.
An important drawback of radioiodinated MIBG prepared by isotopic exchange (maximum specific activity: 100 Ci/mmol) is that a considerable amount of carrier is present in the "ready to use" radiopharmaceutical, thus affecting MIBG uptake in the target cells. To improve the therapeutic utility of MIBG an interesting method was developed for the no-carrier-added (n.c.a.) radioiodination of MIBG via a halodesilylation reaction using 3-trimethylsilybenzylguanidine (TMSBG) as precursor. In order to investigate its possible clinical usefulness, n.c.a. [125I]- and [131I]MIBG was prepared according this procedure. ⋯ MIBG uptake was also studied in the human neuroblastoma cell line SH-SY5Y which has a specific uptake system for MIBG. The kinetic parameters for MIBG in this line are: km = 0.27 +/- 0.03 microM, Vmax = 39.5 + 1.8 pmol/10(6) cell/10 min. Preliminary data from in vitro binding studies showed that significantly higher levels of specifically incorporated radioactivity can be achieved using n.c.a. [125I]MIBG instead of c.a. [125I]MIBG.
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In a group of 97 patients aged from 6 months to 12 years, all with suspected or proven neural crest tumours, metaiodobenzylguanidine (MIBG) scintigraphy was performed at the time of diagnosis and, in some instances, after induction chemotherapy. All the patients underwent a tumour biopsy with cytological and histological analysis, in addition to imaging examinations such as X-rays, ultrasound, computed tomography and magnetic resonance, within a short period before or after scintigraphy. In 82 of 97 cases MIBG was effective in detecting the primary tumour, hence the technique's sensitivity was 84%. ⋯ Out of 12 cases showing metastases at diagnosis, two cases with liver lesions became normal and in one case some, but not all, of the bone lesions were not detectable; 4 cases remained abnormal, while in 5 cases bone marrow involvement was not confirmed. Three cases were confirmed to be true negatives; in 4 other cases bone marrow involved not showing at diagnosis was revealed and confirmed by biopsy; 3 cases in which bone marrow involvement was not revealed by MIBG at diagnosis, had normal MIBG and biopsy results after IC; finally, 2 false negative bone marrow cases and 5 true negative cases at diagnosis remained unchanged, but were not checked by biopsy. Performing total body MIBG scintigraphy in childhood neuroblastoma at diagnosis is useful: 1) to predict the nature of the masses detected by other imaging techniques, when biopsy has not yet been performed; 2) for more accurate tumour staging, in addition to standard imaging investigations, MDP scintigraphy and bone marrow aspiration biopsy, thanks to its ability to detect metastatic lesions; 3) to anticipate the decrease in sensitivity of the technique in detecting both the primary mass and the metastases following induction chemotherapy.
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Comparative Study
A new 99mTc labelling method for leucocytes: in vitro and in vivo comparison with 99mTc-HMPAO.
A new method for the labelling of mixed leucocytes with 99mTc-tropolone was optimized and compared with a 99mTc-HMPAO leucocyte labelling procedure in vitro and in vivo. In the present study, leucocytes obtained from patients suffering from Crohn's disease, were isolated and labelled with 99mTc-HMPAO or labelled according the new 99mTc-tropolone procedure using 9.8 mM tropolone, 1 microM stannous chloride and 0.8 mM potassium borohydride (KBH4) at pH 5.5-6. Labelling efficiency with 99mTc-tropolone yielded 92 +/- 3%, which is higher compared to the 99mTc-HMPAO labelling procedure (64 +/- 13%) using 10(8) of leucocytes. ⋯ This was most likely due to a significant (P < 0.02) higher liver uptake at 4 hours after administration of the 99mTc-tropolone labelled leucocytes (19%) in comparison with 99mTc-HMPAO labelled cells (9%). Faster and significant (P < 0.02) higher accumulation of the 99mTc-tropolone labelled leucocytes was observed at the site of infection compared with 99mTc-HMPAO labelled leucocytes at all time-intervals after the administration of the 99mTc-labelled leucocytes. The new 99mTc-tropolone leucocyte labelling procedure, offers an attractive low-cost agent for research purposes.