ABSTRACT
Fluorodeoxyglucose (FDG) positron emission tomography-magnetic resonance (PET/MR) is useful for the evaluation of cognitively-impaired patients. This study aims to assess two different attenuation correction (AC) methods (Dixon-MR and atlas-based) versus index-standard computed tomography (CT) AC for the visual interpretation of regional hypometabolism in patients with cognitive impairment. Two board-certified nuclear medicine physicians blindly scored brain region FDG hypometabolism as normal versus hypometabolic using two-dimensional (2D) and 3D FDG PET/MR images generated by MIM software. Regions were quantitatively assessed as normal versus mildly, moderately, or severely hypometabolic. Hypometabolism scores obtained using the different methods of AC were compared, and interreader, as well as intra-reader agreement, was assessed. Regional hypometabolism versus normal metabolism was correctly classified in 16 patients on atlas-based and Dixon-based AC map PET reconstructions (vs. CT reference AC) for 94% (90%-96% confidence interval [CI]) and 93% (89%-96% CI) of scored regions, respectively. The averaged sensitivity/specificity for detection of any regional hypometabolism was 95%/94% (P = 0.669) and 90%/91% (P = 0.937) for atlas-based and Dixon-based AC maps. Interreader agreement for detection of regional hypometabolism was high, with similar outcome assessments when using atlas- and Dixon-corrected PET data in 93% (Κ =0.82) and 93% (Κ =0.84) of regions, respectively. Intrareader agreement for detection of regional hypometabolism was high, with concordant outcome assessments when using atlas- and Dixon-corrected data in 93%/92% (Κ =0.79) and 92/93% (Κ =0.78). Despite the quantitative advantages of atlas-based AC in brain PET/MR, routine clinical Dixon AC yields comparable visual ratings of regional hypometabolism in the evaluation of cognitively impaired patients undergoing brain PET/MR and is similar in performance to CT-based AC. Therefore, Dixon AC is acceptable for the routine clinical evaluation of dementia syndromes.
ABSTRACT
Un problema que sucede a menudo en la práctica clínica es la ausencia dental por diversos factores. Esto conduce a un gran desafío para surehabilitación, ya que debido a la pérdida dentaria se genera un colapsodel reborde alveolar, lo que ocasiona alteración en la morfología óseay gingival, o en diversos casos, se realizaron extracciones sin una planeación restaurativa, por lo que su sustitución implica mayores procedimientos. Una alternativa a esta ausencia dental es el diseño de póntico ovoide, siempre y cuando cumpla los requisitos clínicos para un mejor resultado estético, funcional e higiénico. El objetivo de este artículo es mostrar el empleo del póntico ovoide en el sector posterior con distintos aspectos clínicos: por un lado, utilizando la técnica de conformación del lecho gingival a presión y por el otro, la técnica directa postextracción, mediante prótesis fija de tres unidades en metal/porcelana.
A problem that often occurs in clinical practice is the dental absence caused by various factors. This leads to a great challenge for rehabilitation since due to tooth loss, a collapse of the alveolar ridgeis generated, causing an alteration in bone and gingival morphology; also, in many cases, extractions were made without restorative planning, so their replacement involves major procedures. An alternative to this dental absence is ovate pontic design, provided it meets the clinical requirements for better esthetic, functional and hygienic result. The aim of this article is to show the use of the ovoid pontic in the posterior region with different clinical aspects: first, using the technique of forming the gingival bed under pressure and on the other, postextraction direct technique through a three-unit fi xed prosthesis in metal/porcelain.
Subject(s)
Female , Humans , Adult , Middle Aged , Denture, Partial , Dental Prosthesis Design , Denture, Partial, Fixed , Tooth Extraction , Metal Ceramic Alloys , Immediate Dental Implant Loading , Gingiva/anatomy & histology , Denture, Partial, Temporary , Dental AbutmentsABSTRACT
It has been proposed that the DNA repair protein O6-alkylguanine-DNA alkyltransferase increases the mutagenicity of 1,2-dibromoethane by reacting with it at its cysteine acceptor site to form a highly reactive half-mustard, which can then react with DNA (Liu, L., Pegg, A. E., Williams, K. M., and Guengerich, F. P. (2002) J. Biol. Chem. 277, 37920-37928). Incubation of Escherichia coli-expressed human alkyltransferase with 1,2-dibromoethane and single-stranded oligodeoxyribonucleotides led to the formation of covalent transferaseoligo complexes. The order of reaction determined was Gua>Thy>Cyt>Ade. Mass spectrometry analysis of the tryptic digest of the reaction product indicated that some of the adducts led to depurination with the release of the Gly136-Arg147 peptide cross-linked to a Gua at the N7 position, with the site of reaction being the active site Cys145 as established by chromatographic retention time and the fragmentation pattern determined by tandem mass spectrometry of a synthetic peptide adduct. The alkyltransferase-mediated mutations produced by 1,2-dibromoethane were predominantly Gua to Ade transitions but, in the spectrum of such rifampicin-resistant mutations in the RpoB gene, 20% were Gua to Thy transversions. The latter are likely to have arisen from the apurinic site generated from the Gua-N7 adduct. Support exists for an additional adduct/mutagenic pathway because evidence was obtained for DNA adducts other than at the Gua N7 atom and for mutations other than those attributable to depurination. Thus, chemical and biological evidence supports the existence of at least two alkyltransferase-dependent pathways for 1,2-dibromoethane-induced mutagenicity, one involving Gua N7-alkylation by alkyltransferase-S-CH2CH2Br and depurination, plus another as yet uncharacterized system(s).
