Development of Phantoms for Multimodal Magnetic Resonance Imaging and Magnetic Particle Imaging.

Phantoms are crucial for the development of imaging techniques based on magnetic nanoparticles (MNP). They serve as test objects to simulate application scenarios but are also used for quality assurance and interlaboratory comparisons. Magnetic particle imaging (MPI) is excellent for specifically detecting magnetic nanoparticles (MNP) without any background signals. To obtain information about the surrounding soft tissue, MPI is often used in combination with magnetic resonance imaging (MRI). For such application scenarios, this poses a challenge for phantom fabrication, as they need to accommodate MNP as well as provide MR visibility. Recently, layer-by-layer fabrication of parts using Additive Manufacturing (AM) has emerged as a powerful tool for creating complex and patient-specific phantoms, but these are characterized by poor MR visibility of the AM material. We present the systematic screening of AM materials as candidates for multimodal MRI/MPI imaging. Of all investigated materials, silicone (Dreve, Biotec) exhibited the best properties with sufficient MR-signal performance and the lowest absorption of MNP at the interface of AM materials. With the help of AM and the selection of appropriate materials, we have been able to produce suitable MRI/MPI phantoms.

Reproducibility of a protocol for standardized reading of chest X-rays of children household contact of patients with tuberculosis.

BACKGROUND: The interpretation of the chest radiograph may vary because it depends on the reader and due to the non-specificity of findings in tuberculosis (TB). We aim to assess the reproducibility of a standardized chest radiograph reading protocol in contacts of patients with pulmonary TB under the 5 years of age. METHODS: Descriptive, cross-sectional study with children under the age of five, household contacts of patients with confirmed pulmonary TB from Medellín, Bello and Itagüí (Colombia) between Jan-01-2015 and May-31-2016. Standardized reading protocol: two radiologists, blinded independent reading, use of template (Dr. Andronikou design) in case of disagreement a third reading was performed. Kappa coefficient for intra and inter observer agreement, and prevalence ratio were estimated of sociodemographic characteristics, TB exposure and interpretation of chest X-ray. RESULTS: From 278 children, standardized reading found 255 (91.7%) normal X-rays, 10 (3.6%) consistent with TB, and 13 (4.7%) other alterations. Global agreement was 91.3% (Kappa = 0.51). Inter-observer agreement between readers 1-2 was 90.0% (Kappa = 0.59) and 1-3 93.2% (Kappa = 0.59). Intra-observer agreement for reader 1 was 95.5% (Kappa = 0.86), 2 84.0% (Kappa = 0.51), and 3 94.7% (Kappa = 0.68). Greater inter-observer disagreement was between readers 1-2 for soft tissue density suggestive of adenopathy (4.6%), airspace opacification (1.17%) and pleural effusion (0.58%); between readers 1-3 for soft tissue density suggestive of adenopathy (4.2%), opacification of airspace (2.5%) and cavities (0.8%). CONCLUSIONS: Chest radiographs are an affordable tool that contributes to the diagnosis of TB, so having a standardized reading protocol showed good agreement and improves the reproducibility of radiograph interpretation.

Hereditary hypophosphatemic rickets and craniosynostosis.

BACKGROUND: Craniosynostosis is an underdiagnosed complication associated with hypophosphatemic rickets. The study aims to describe the clinical and auxological characteristic of children with hypophosphatemic rickets and craniosynostosis, describe the usual treatment, and compare the characteristics with those of children without craniosynostosis. METHODS AND PATIENTS: An observational and retrospective cohort study was conducted. Clinical notes and cranial images were reviewed. Out of 96 children, only the 50 patients who had skull images were included. RESULTS: Out of 50 patients, 26 (15 males) had craniosynostosis (52%). No differences were observed in birth size, age, height, body proportions, alkaline phosphatase, serum phosphate, or percent tubular reabsorption of phosphate at first appointment among children with or without craniosynostosis. Among patients with craniosynostosis, dolichocephaly was prevalent. The sagittal suture was affected in all patients with craniosynostosis, with 19 of 26 children (73%) affected with isolated scaphocephaly. Pan-sutural craniosynostosis was present in 7 children (27%). None of the children had microcephaly, 7 of them presented macrocephaly and, in the remaining subjects, head circumference was normal. Five patients had undergone at least 1 cranial remodeling surgery. One patient with craniosynostosis was diagnosed with a Chiari I malformation. Molecular characterization of PHEX gene was performed in 14 cases. CONCLUSIONS: Craniosynostosis is an underdiagnosed complication of hypophosphatemic rickets. Many patients with normal head size and growth may go undiagnosed, thus it is important to consider this association for early diagnosis and possible surgical treatment. A multidisciplinary approach is necessary for a correct long-term follow-up.

FGFR3-related hypochondroplasia: longitudinal growth in 57 children with the p.Asn540Lys mutation.

Background Children with hypochondroplasia (HCH), who have FGFR3 mutations c.1620C>A or c.1620C>G (p.Asn540Lys) appear to have a more severe phenotype than those with HCH without these mutations. We describe the change in height, leg length and body proportions in a retrospective cohort of children with HCH related-p.Asn540Lys mutation and we compared them with Argentine population. Methods Anthropometric measurements were initially taken and followed up by the same observer, with standardized techniques. Sitting height/height and head circumference/height ratio were calculated as a body disproportion indicator. In order to make a comparison with the Argentine population height average, centiles of height, leg length and body proportions were estimated by the LMS method. Results The sample consisted of 57 HCH children (29 males and 28 females) between the ages of 0-18 years. The median (interquartile range) number of measurements per child was 8 (4.3, 13) for height, 7 (4, 12) for sitting height and 7.5 (4, 12.8) for head circumference. Leg length increased from 17 cm at birth to approximately 54 cm in adolescents, 25 cm shorter than the leg length in non-HCH populations. Sitting height increased from 39 cm at birth to 81 cm in adolescents, 7 cm below mean in non-HCH adolescents. Mean (range) adult height were 143.6 cm (131-154.5) and 130.8 cm (124-138) for males and females, respectively. Conclusions The disharmonic growth between the less affected trunk and the severely affected limbs determine body disproportion in HCH.