| 1. |
- Hansson, Mattias, et al.
(författare)
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Segmentation of B-mode cardiac ultrasound data by Bayesian Probability Maps
- 2014
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Ingår i: Medical Image Analysis. - : Elsevier. - 1361-8415 .- 1361-8423. ; 18:7, s. 1184-1199
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a model for describing the position distribution of the endocardium in the two-chamber apical long-axis view of the heart in clinical B-mode ultrasound cycles. We propose a novel Bayesian formulation, including priors for spatial and temporal smoothness, and preferred shapes and position. The shape model takes into account both endocardium, atrial region and apex. The likelihood is built using a statistical signal model, which attempts to closely model a censored signal. In addition, the use of a censored Gamma mixture model with unknown censoring point, to handle artefacts resulting from left-censoring of the in US clinical B-mode, is to our knowledge novel. The posterior density is sampled by the Gibbs method to estimate the expected latent variable representation of the endocardium, which we call the Bayesian Probability Map; the map describes the probability of pixels being classified as being within the endocardium. The regularization parameters of the model are estimated by cross-validation, and the results are compared against the two-chamber apical model of Chen et al.
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| 2. |
- Lindahl, Katarina, et al.
(författare)
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Genotype-phenotype correlations and pharmacogenetic studies in 140 Swedish families with osteogenesis imperfecta
- 2012
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Ingår i: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 50, s. S109-S109
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Objective: Osteogenesis imperfecta (OI) is a rare heterogeneous disease of connective tissue leading to varying degrees of bone fragility. The worst form (type II) is peri-natally lethal whereas the mildest form (type I) is compatible with a normal life span. Over 1000 mutations causing OI have been described in the genes encoding collagen type I. As COL1A1 and COL1A2 are large genes, there are still many codon positions where no mutations have been reported and only a fraction of theoretically possible glycine substitutions have been described. In this study the spectrum of mutations causing OI in Sweden will be investigated and genotype–phenotype correlations as well as pharmacogenetics will be studied. Method: All patients with OI cared for at the Uppsala Osteoporosis Unit (Uppsala University Hospital) or Astrid Lindgren's Paediatric Hospital (Karolinska Institutet, Stockholm) were offered to enter the study. Patients from 140 unrelated families with OI accepted participation; 77 type I, 34 type IV, 20 type III, 5 without previous diagnosis and 4 with unclear OI type. Extensive clinical data is currently being collected on enrolled patients. Exons and flanking intron sequences of COL1A1 and COL1A2 are being sequenced in these families. Results: So far 133/140 families have been completely analyzed and in 27 no mutation was found. A total of 120 mutations have been detected, of which 104 are of a typical OI-type. In COL1A1 73 mutations were found and in COL1A2 31 mutations were noted. In 7 families 2 mutations were present, but only one of these was a typical OI-causing mutation. To date 16 amino acid changing mutations that were not of a typical OI-causing type have been noted and the majority of these have an unclear significance. Calculations of delta BMD Z-score response to bisphosphonate treatment did not show a difference in treatment response between groups with different types of OI or between patients with OI type I due to a qualitative vs. a quantitative collagen type I defect. Conclusion: The spectrum of mutations causing OI described in this Swedish cohort is of the expected type, with the exception of the amino acid changing mutations. It is notable that in seven families two separate mutations were identified. Calculations do not support a mutation dependent response to bisphosphonate treatment.
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