Method development for genomic Legionella pneumophila DNA quantification by inductively coupled plasma mass spectrometry.

The development of a method for the quantification of Legionella pneumophila genomic deoxyribonucleic acid is considered. The method is based on the quantification by inductively coupled plasma mass spectrometry (ICP-MS) of the mass fraction of phosphorus, stoichiometrically presented in the DNA molecules. Through the DNA sequencing data, it was possible to convert the ICP-MS analysis results into DNA genome units. L. pneumophila DNA samples were analyzed using ICP-sector field MS and ICP-quadrupole MS with a collision/reaction cell. Spectrophotometric measurements of the absorbance at 260nm and real-time PCR techniques were used to independently confirm the ICP-MS results. The comparison of the methods showed that the ICP-MS method provides better accuracy with respect to currently applied analytical techniques such as UV spectrophotometry, fluorescent dye methods, and real-time PCR. Moreover, with the use of calibration standards whose values are traceable to the International System of Units and the possibility of evaluating the contribution to the overall uncertainty of each step of the measurement procedure, the method enables long-term comparability of the measurement results. These advantages make the ICP-MS method suitable for nucleic acid investigation, from nucleotides to genomic DNA, as well as for the certification of the reference materials containing nucleic acids.

7-tesla MR imaging of non-melanoma skin cancer samples: correlation with histopathology.

PURPOSE: The aims of this study were to compare in vitro magnetic resonance imaging (MRI) characteristics of keratinocytic skin cancer assessed by a 7-tesla (T) MRI with histopathology, and to describe MRI features of skin tumors. METHODS: This prospective study included 30 skin tumors treated by surgery. MR images of skin samples were acquired on a 7-T MR scanner using a fast spin-echo T(2)-weighted and an isotropic 3D gradient-echo T(1)-weighted sequence. Length, width, Breslow index and margins of the lesions were measured. The presence or absence of the following was noted: healthy margins, ulceration of the dermis, in situ lesions, superficial and deep dermis involvement, subcutaneous involvement, superficial and intratumoral keratin. MR results were compared to histopathology. RESULTS: Interclass correlation coefficient (ICC) was very good for the evaluation of the width (ICC = 0.86) and Breslow index (ICC = 0.87). The ICC was good for the evaluation of the margins (ICC = 0.70) but for length, ICC was lower (ICC = 0.67). Mean bias between MRI and histopathology was inferior to 1 mm for width, Breslow index and margin. CONCLUSION: In vitro 7-T MRI of keratinocytic skin cancer allows delineation of lesions with good correlation with histopathology. After in vivo confirmation it could have a diagnostic role regarding the delineation of surgical margins but its actual limitations prevent its practical adoption at this time.