An optimal maximum likelihood (ML) method is described for an unbiased estimation of monoexponential T2 from magnitude spin-echo images. The algorithm is based on a Gaussian assumption of noise distribution. The validity of this assumption was checked by a statistical chi 2 test on spin-echo and fast low-angle shot surface coil images. Monte-Carlo simulations of magnitude data showed that the ML estimate standard deviation is lower than that produced by a weighted least-squares fitting on signal logarithm. Correction schemes are proposed to reduce bias deriving from magnitude reconstruction. The variance of the ML estimate converged rapidly toward the theoretical algebraic expression of the Cramér-Rao lower bound.

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.

ABSTRACT.Purpose: To assess the value of scintigraphy with [ Results: Ocular BZA-scintigraphy demonstrated a sensitivity of 86%, and a specificity of 83%. Whole-body scintigraphy was used in the follow-up of treated patients and could be repeated. We imaged orbital recurrence, known and occult metastases, specially in the liver. After 9 conservative treatments ocular BZAscintigraphy was negative in 9 eyes. Conclusion: The BZA-scintigraphy in combination with other diagnostic procedures appeared to be a suitable method in the diagnosis of ocular melanoma and a potentially useful imaging modality to screen for ocular malignant melanoma metastases.

It was concluded that the accumulation of 99mTc-labeled tetrofosmin by the mitochondria is related to their ability to transduce metabolic energy into electronegative membrane potential.