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Monte Carlo-based inverse model for calculating tissue optical properties. Part II: Application to breast cancer diagnosis.
Palmer, GM, Zhu, C, Breslin, TM, Xu, F, Gilchrist, KW, Ramanujam, N
Applied optics. 2006;(5):1072-8
Abstract
The Monte Carlo-based inverse model of diffuse reflectance described in part I of this pair of companion papers was applied to the diffuse reflectance spectra of a set of 17 malignant and 24 normal-benign ex vivo human breast tissue samples. This model allows extraction of physically meaningful tissue parameters, which include the concentration of absorbers and the size and density of scatterers present in tissue. It was assumed that intrinsic absorption could be attributed to oxygenated and deoxygenated hemoglobin and beta-carotene, that scattering could be modeled by spheres of a uniform size distribution, and that the refractive indices of the spheres and the surrounding medium are known. The tissue diffuse reflectance spectra were evaluated over a wavelength range of 400-600 nm. The extracted parameters that showed the statistically most significant differences between malignant and nonmalignant breast tissues were hemoglobin saturation and the mean reduced scattering coefficient. Malignant tissues showed decreased hemoglobin saturation and an increased mean reduced scattering coefficient compared with nonmalignant tissues. A support vector machine classification algorithm was then used to classify a sample as malignant or nonmalignant based on these two extracted parameters and produced a cross-validated sensitivity and specificity of 82% and 92%, respectively.
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2.
Comparison of HR MAS MR spectroscopic profiles of breast cancer tissue with clinical parameters.
Sitter, B, Lundgren, S, Bathen, TF, Halgunset, J, Fjosne, HE, Gribbestad, IS
NMR in biomedicine. 2006;(1):30-40
Abstract
Breast cancer is the most frequent form of cancer in women and improved diagnostic methods are desirable. Malignant cells have altered metabolism and metabolic mapping might become a tool in cancer diagnostics. High-resolution magic angle spinning (HR MAS) MR spectroscopy of tissue biopsies provides detailed information on metabolic composition. The 600 MHz 1H HR MAS spectra were acquired of breast cancer tissue from 85 patients and adjacent non-involved tissue from 18 of these patients. Tissue specimens were investigated by microscopy after MR analysis. The resulting spectra were examined by three different approaches. Relative intensities of glycerophosphocholine (GPC), phosphocholine (PC) and choline were compared for cancerous and non-involved specimens. Eight metabolites, choline, creatine, beta-glucose, GPC, glycine, myo-inositol, PC and taurine, were quantified from the recorded spectra and compared with tumor histological type and size, patient's lymph node status and tissue composition of sample. The spectra were also compared with tumor histological type and size, lymph node status and tissue composition of samples using principal component analysis (PCA). Tumor samples could be distinguished from non-involved samples (82% sensitivity, 100% specificity) based on relative intensities of signals from GPC, PC and choline in 1H HR MAS spectra. Tissue concentrations of metabolites showed few differences between groups of samples, which can be caused by limitations in the quantification procedure. Choline and glycine concentrations were found to be significantly higher in tumors larger than 2 cm compared with smaller tumors. PCA of MAS spectra from patients with invasive ductal carcinomas indicated a possible prediction of spread to axillary lymph nodes. Metabolite estimates and PCA of MAS spectra were influenced by the percentage of tumor cells in the investigated specimens.
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A comparison of prediction equations for estimating glomerular filtration rate in adult patients with chronic kidney disease stages 4-5. Effect of nutritional status and age.
Fontseré, N, Bonal, J, Navarro, M, Riba, J, Fraile, M, Torres, F, Romero, R
Nephron. Clinical practice. 2006;(4):c160-8
Abstract
BACKGROUND The accuracy of prediction equations has not been validated in adult patients with chronic kidney disease (CKD) stages 4-5 in extreme situations of nutritional status and age. OBJECTIVE AND METHODS The significance of nutritional status, calculated with the creatinine production (CP) formula, and age (< or =64 years and >64 years) in the application of different prediction equations--modification of diet in renal disease (MDRD), simplified MDRD (sMDRD), Cockcroft-Gault (CG)--and the mean of urea and creatinine clearance (Cr-Ur) compared with the isotopic glomerular filtration rate (GFR) estimation calculated by 51Cr-EDTA was studied in 87 Caucasian adults with CKD stages 4-5 (GFR: 30-8 ml/min/1.73 m2). The Bland-Altman method and Lin's concordance coefficient (Rc) were used to study accuracy (bias) and precision. RESULTS The GFR calculated with 51Cr-EDTA in the study group was 22.2 +/- 6.9 ml/min/1.73 m2 (range: 8-30). CG and sMDRD were the best prediction equations with bias of -1.1 and -3.8 ml/min/1.73 m2 and Rc of 0.52-0.50. In this situation, the mean Cr-Ur proved the most inaccurate equation compared with the isotopic technique with bias of -5.4 ml/min/1.73 m2 and Rc of 0.32. In the analysis of patients with higher CP (> 0.90; n = 44), CG and sMDRD obtained the best bias of 1.2 and -2.7 ml/min/1.73 m2 and Rc of 0.54-0.53. In patients aged < or =64 (n = 44), these equations obtained a bias of 1.1 and -3.6 ml/min/1.73 m2 and Rc 0.50-0.49. Both in lower CP (< or =0.90; n = 43) and older age (>64 years; n = 43), all the equations underestimated the value obtained with isotopic GFR. In these situations, the results obtained with CG had a bias of -2.2 and -3.6 ml/min/1.73 m2 (Rc 0.29-0.56) and with sMDRD -4.0 and -4.1 ml/min/1.73 m2 (Rc 0.39-0.51). In these circumstances, Cr-Ur was the most inaccurate equation, obtaining a bias of -10.1 and -13.2 ml/min/1.73 m2 (Rc 0.14-0.16). CONCLUSIONS In the group with higher CP and age < or =64 years, results of the presented data yielded no evidence for superiority of the MDRD equation over CG formula in patients with advanced renal failure. On the basis of our results, we do not recommend the use of the Cr-Ur adjusted to 1.73 m(2) of body surface area, which was the most imprecise equation. Application of all the equations proved inaccurate in lower CP patients with or without advanced age, implying the premature start of substitution renal treatment. In these circumstances, ambulatory GFR determination by isotopic techniques would be indicated.
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4.
[Biochemical bone marrow markers and their significance in postmenopausal osteoporosis--a new method in the diagnosis of osteoporosis?].
Heiss, C, Keller, T, Wehr, U, Mohr, A, Lommel, D, Meyer, Ch, Rambeck, WA, Schnettler, R
Biomedizinische Technik. Biomedical engineering. 2004;(10):282-9
Abstract
This study analyzes the qualification of biochemical markers in the diagnosis of osteoporosis and evaluates the potential of a multiparametric classification of premenopausal and non-osteoporotic as well as osteoporotic postmenopausal women, which is based on biochemical marker profiles. For this evaluation data of 29 women in the age between 28-74 years were used. The classification of osteoporosis was done by the trabecular density of the lumbar spine using qCT-measurements. The biochemical markers of formation and resorption AP, bAP, OC, ucOC, PICP, PYD, DPD, NTX, BSP and vitamin K were analyzed on day 1 and 42 in all patients. For vitamin K we found significant distribution differences between non-osteoporotic and osteoporotic women (p<0.005). The crosslinks PYD and DPD showed weakly significant differences. All other parameters exhibited non-significant results. Vitamin K acted with a sensitivity of 64% and a specificity of 82%. The used multiparameter classification process improved sensitivity and specificity considerably. The parameter profiles of OC/PYD, vitamin K/PYD and vitamin K/bAP revealed the highest sensitivities with specificities of more than 82%.