Early detection and monitoring of cartilage alteration in the experimental meniscectomised guinea pig model of osteoarthritis by 99mTc-NTP 15-5 scintigraphy.

PURPOSE: This study in the meniscectomised guinea pig aimed to demonstrate that the radiotracer (99m)Tc-NTP 15-5 would have pathophysiological validity for in vivo osteoarthritis imaging. METHODS: The specificity of (99m)Tc-NTP 15-5 for cartilage was determined in healthy animals (n = 13), by tissue radioactivity counting, joint autoradiography and scintigraphy. (99m)Tc-NTP 15-5 scintigraphy was performed at 20, 50, 80, 115, 130, 150 and 180 days after medial meniscectomy (n = 10 MNX) or sham operation (n = 5), and scintigraphic ratios (operated/contralateral) were calculated for femoral (F) and tibial (T) areas. F and T ratios were compared with those of (99m)Tc-MDP bone scintigraphy. At the study end-point, autoradiographic analysis of joint (99m)Tc-NTP 15-5 distribution and macroscopic scoring of cartilage integrity were performed. RESULTS: The high and specific accumulation of (99m)Tc-NTP 15-5 in normal cartilage (about 5.5 +/- 1.7 % of injected dose/g of tissue), which permitted joint imaging with high contrast, was affected by osteoarthritis. In the MNX group, (99m)Tc-NTP 15-5 accumulation in cartilage within the operated joint, relative to the contralateral joint, was observed to change in the same animals as pathology progressed. Although F and T ratios were significantly higher in MNX (F = 1.7 +/- 0.2; T = 1.6 +/- 0.1) than in shams (F = 1.0 +/- 0.1; T = 1.0 +/- 0.1) at day 50, they were significantly lower in MNX (F = 0.6 +/- 0.1; T = 0.7 +/- 0.1) than in shams (F = 1.0 +/- 0.1; T = 0.9 +/- 0.1) at day 180. No change in (99m)Tc-MDP uptake was observed over 6 months. Macroscopic analysis confirmed features of osteoarthritis only in MNX knees. CONCLUSION: These results in MNX guinea pigs provide additional support for the use of (99m)Tc-NTP 15-5 for in vivo imaging of osteoarthritis.

123I-N-(2-diethylaminoethyl)-2-iodobenzamide: a potential imaging agent for cutaneous melanoma staging.

Melanoma is a neoplasia of dramatically increasing incidence that has a propensity to spread rapidly. Early detection is fundamental and patient management requires reliable, sensitive and reproducible staging methods, such as a single examination by planar scintigraphy or single-photon emission tomography (SPET) using a radiopharmaceutical with selectivity for melanoma tissue. Among iodobenzamides reported to possess an affinity for melanoma, a new compound, N-(2-diethylaminoethyl)-2-iodobenzamide (BZA(2)), was selected for a clinical trial in view of its pharmacokinetic experimental profile in melanoma-bearing mice. Planar whole-body scintigraphy using (123)I-BZA(2) was performed in 25 patients with histologically proven cutaneous melanoma. Performance was evaluated in two groups of patients with one or more documented secondary lesions ( n=13) or with no known secondary lesions ( n=12), and results were compared with those of conventional investigation techniques. No adverse clinical or biological events were recorded. Lesions were imaged by increased tracer uptake, and good quality images were obtained 4 h after administration. After a follow-up of more than 1 year, the overall results of (123)I-BZA(2) scintigraphy on a per patient basis showed a sensitivity of 100%, a specificity of 95%, a positive predictive value of 86% and a negative predictive value of 100%. The proven secondary lesions were imaged with a sensitivity of 100% and a specificity of 91%. In seven patients with suspected metastases, the absence of (123)I-BZA(2) uptake was confirmed as true negative, and in one patient without suspected metastases, (123)I-BZA(2) scintigraphy revealed a gastric lesion. Hence eight diagnoses would have been modified by (123)I-BZA(2) scintigraphy data. (123)I-BZA(2) allowed discrimination between benign and malignant lesions and, in the case of malignancies, between those of melanomatous origin and others. This compound, which is selective for melanoma tissue, appears promising for the staging and restaging of melanoma.