Optical characterization of normal, benign, and malignant thyroid tissue: a pilot study.

Fine-needle aspiration cytology is the standard technique to diagnose thyroid pathologies. However, this method has a high percentage of inconclusive and false-negative results for benign and malignant lesions. Hence, it is important to search for a new method to assist medical evaluation during these surgical procedures. The use of time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help to develop a portable, minimally invasive, and non-destructive method to assist medical evaluation. In this study, we investigated 17 human thyroid samples by absorbance, fluorescence, excitation, and time-resolved fluorescence measurements. This initial investigation has demonstrated that thyroid fluorescence originates from many endogenous fluorophores and culminates in several bands. The fluorescence lifetimes of benign and malignant lesions were significantly different, as attested by analysis of variance using Tukey test with individual confidence level of 98.06%. Our results suggest that fluorescence lifetimes of benign and malignant lesions can potentially assist diagnosis. After further investigations, fluorescence methods could become a tool for the surgeon to identify differences between normal and pathological thyroid tissues.

Optical Characterization of Parathyroid Tissues.

The parathyroid glands are small and often similar to lymph nodes, fat, and thyroid tissue. These glands are difficult to identify during surgery and a biopsy of the parathyroid for identification can lead to damage of the gland. The use of static and time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help to develop a portable, minimally invasive, and nondestructive method to assist medical evaluation of parathyroid tissues. In this study, we investigated 10 human parathyroid samples by absorbance, fluorescence, excitation, and time-resolved fluorescence measurements. Moreover, we compared the results of time-resolved fluorescence measurements with 59 samples of thyroid tissues. The fluorescence lifetimes with emission at 340 nm were 1.09 ± 0.10 and 4.46 ± 0.06 ns for healthy tissue, 1.01 ± 0.25 and 4.39 ± 0.36 ns for benign lesions, and 0.67 ± 0.36 and 3.92 ± 0.72 ns for malignant lesions. The lifetimes for benign and malignant lesions were significantly different, as attested by the analysis of variance with confidence levels higher than 87%. For each class of samples (healthy, benign, and malignant) we perceived statistical differences between the thyroid and parathyroid tissue, independently. After further investigations, fluorescence methods could become a tool to identify normal and pathological parathyroid tissues and distinguish thyroid from parathyroid tissues.

Effect of cyclophosphamide on the binding of 99mTcO-4 and 99mTc-MDP to blood cells and plasma proteins.

Since the introduction of technetium-99m (99mTc) and its rapid acceptance as a tool in nuclear medicine, very little information is available about its biological action as 99mTc-radiopharmaceuticals. We have determined if cyclophosphamide, an alkylating agent, used in oncology as a chemotherapeutic drug, modifies the binding of 99mTcO-4 and 99mTc-MDP (99mTc-methylenediphosphonic acid) to blood cells and to plasma proteins. The radiopharmaceuticals were injected intravenously (iv) into SW-55 mice (male and female, weight 25 g) and samples of plasma and blood cells were separated. Cyclophosphamide (50 micrograms) was injected iv 1 h before the radiopharmaceuticals. Samples of plasma and blood cells were also precipitated with 5% trichloroacetic acid and soluble and insoluble fractions were isolated. The following results were obtained: 1) cyclophosphamide did not alter (0.25 to 8 h) percent radioactivity of 99mTcO-4 in plasma or blood cells but increased the binding of 99mTc-MDP to blood cells; 2) cyclophosphamide did not alter (0.25 to 8 h) the binding of 99mTcO-4 in insoluble fraction of plasma and decreased (1 to 4 h) percent radioactivity of 99mTc-MDP in the insoluble fraction of plasma; 3) cyclophosphamide increased (0.25 to 4 h) percent radioactivity of 99mTcO-4 in the insoluble fraction of blood cells but did not alter the binding of 99mTc-MDP. Cyclophosphamide and/or its metabolites modified the effective half-life of these radiopharmaceuticals (to 99mTcO-4 was increased 2.3 to 3.4 h and to 99mTc-MDP was decreased 3.3 to 2.1 h) and possibly increased the permeability of blood cells to 99mTcO-4.

Object reconstruction from photon-limited centroided data of randomly translating images.

Centroiding is investigated as a simple and computationally fast technique of object reconstruction, at low light level, from randomly translating images. A relationship between the spectrum of the average N-photon centroided frame and the object spectrum is presented as well as an algorithm for retrieving the phase in the case of one-dimensional objects. Computer-simulated data are used to test the relationship and the reconstruction algorithm.