311 research outputs found
Reduced basis isogeometric mortar approximations for eigenvalue problems in vibroacoustics
We simulate the vibration of a violin bridge in a multi-query context using
reduced basis techniques. The mathematical model is based on an eigenvalue
problem for the orthotropic linear elasticity equation. In addition to the nine
material parameters, a geometrical thickness parameter is considered. This
parameter enters as a 10th material parameter into the system by a mapping onto
a parameter independent reference domain. The detailed simulation is carried
out by isogeometric mortar methods. Weakly coupled patch-wise tensorial
structured isogeometric elements are of special interest for complex geometries
with piecewise smooth but curvilinear boundaries. To obtain locality in the
detailed system, we use the saddle point approach and do not apply static
condensation techniques. However within the reduced basis context, it is
natural to eliminate the Lagrange multiplier and formulate a reduced eigenvalue
problem for a symmetric positive definite matrix. The selection of the
snapshots is controlled by a multi-query greedy strategy taking into account an
error indicator allowing for multiple eigenvalues
Scintigraphic assessment of bone status at one year following hip resurfacing : comparison of two surgical approaches using SPECT-CT scan
Objectives: To study the vascularity and bone metabolism of the femoral head/neck following hip resurfacing arthroplasty, and to use these results to compare the posterior and the trochanteric-flip approaches.
Methods: In our previous work, we reported changes to intra-operative blood flow during hip resurfacing arthroplasty comparing two surgical approaches. In this study, we report the vascularity and the metabolic bone function in the proximal femur in these same patients at one year after the surgery. Vascularity and bone function was assessed using scintigraphic techniques. Of the 13 patients who agreed to take part, eight had their arthroplasty through a posterior approach and five through a trochanteric-flip approach.
Results: One year after surgery, we found no difference in the vascularity (vascular phase) and metabolic bone function (delayed phase) at the junction of the femoral head/neck between the two groups of patients. Higher radiopharmaceutical uptake was found in the region of the greater trochanter in the trochanteric-flip group, related to the healing osteotomy.
Conclusions: Our findings using scintigraphic techniques suggest that the greater intra-operative reduction in blood flow to the junction of the femoral head/neck, which is seen with the posterior approach compared with trochanteric flip, does not result in any difference in vascularity or metabolic bone function one year after surgery
MRI in multiple myeloma : a pictorial review of diagnostic and post-treatment findings
Magnetic resonance imaging (MRI) is increasingly being used in the diagnostic work-up of patients with multiple myeloma. Since 2014, MRI findings are included in the new diagnostic criteria proposed by the International Myeloma Working Group. Patients with smouldering myeloma presenting with more than one unequivocal focal lesion in the bone marrow on MRI are considered having symptomatic myeloma requiring treatment, regardless of the presence of lytic bone lesions. However, bone marrow evaluation with MRI offers more than only morphological information regarding the detection of focal lesions in patients with MM. The overall performance of MRI is enhanced by applying dynamic contrast-enhanced MRI and diffusion weighted imaging sequences, providing additional functional information on bone marrow vascularization and cellularity. This pictorial review provides an overview of the most important imaging findings in patients with monoclonal gammopathy of undetermined significance, smouldering myeloma and multiple myeloma, by performing a 'total' MRI investigation with implications for the diagnosis, staging and response assessment. Main message aEuro cent Conventional MRI diagnoses multiple myeloma by assessing the infiltration pattern. aEuro cent Dynamic contrast-enhanced MRI diagnoses multiple myeloma by assessing vascularization and perfusion. aEuro cent Diffusion weighted imaging evaluates bone marrow composition and cellularity in multiple myeloma. aEuro cent Combined morphological and functional MRI provides optimal bone marrow assessment for staging. aEuro cent Combined morphological and functional MRI is of considerable value in treatment follow-up
Early MRI response monitoring of patients with advanced hepatocellular carcinoma under treatment with the multikinase inhibitor sorafenib
<p>Abstract</p> <p>Background</p> <p>New therapeutic principles in clinical oncology require the adjustment of response criteria to govern therapy decisions. For advanced hepatocellular carcinoma (HCC) a new era has recently begun by the approval of the multikinase inhibitor sorafenib. As a unique feature, HCC usually develops in a diseased liver and current imaging technologies employing classical response criteria have not been prospectively evaluated for this new treatment.</p> <p>Methods</p> <p>MRI signal patterns were assessed in 21 advanced HCC patients receiving sorafenib. MRI was performed at baseline and in short-term intervals thereafter. Signal changes under therapy on T1WI, T2WI and post-gadolinium images including necrosis volume and its ratio to the entire tumor volume were compared to baseline imaging. To assess the association between the categorical variables, Fisher's exact tests were applied for a statistical analysis. Survey time ranged from 2–65 weeks, and a total of 39 target lesions were evaluated.</p> <p>Results</p> <p>Signal abnormalities during sorafenib therapy were disclosed by T1WI and T2WI in 15/21 patients. The predominant tumor signal change was hyperintensity on both T1WI and T2WI. Interestingly, most patients developed MRI signal changes within 4 weeks of therapy; in contrast, two non-responders did not show any signal alteration at follow-up. Under therapy, 16/21 patients presented with new or progressive necrosis, whereas 7 patients achieved temporarily >75% tumor necrosis under sorafenib. Significantly associated MRI variables were increase in T1WI signal and tumor necrosis (p = 0.017) as well as increase of tumor necrosis with an elevated ratio of necrotic to vital tumor areas (p = 0.002). Remarkably, some (3/13) of the patients developing necrotic tumor areas showed a relevant (>20%) increase in tumor volume, which should be considered in the assessment of imaging studies.</p> <p>Conclusion</p> <p>As sorafenib induces early intralesional necrosis with profound changes in T1WI/T2WI MRI signal intensities and measurable necrotic tumor areas in most HCC patients, early MRI-based evaluation could pave the way for its rationale and cost-effective application.</p
C-arm computed tomography and volume perfusion computed tomography (VPCT)-based assessment of blood volume changes in hepatocellular carcinoma in prediction of midterm tumor response to transarterial chemoembolization: a single center retrospective trial
Role of radiography, MRI and FDG-PET/CT in diagnosing, staging and therapeutical evaluation of patients with multiple myeloma
Multiple myeloma is a malignant B-cell neoplasm that involves the skeleton in approximately 80% of the patients. With an average age of 60 years and a 5-years survival of nearly 45% Brenner et al. (Blood 111:2516–2520, 35) the onset is to be classified as occurring still early in life while the disease can be very aggressive and debilitating. In the last decades, several new imaging techniques were introduced. The aim of this review is to compare the different techniques such as radiographic survey, multidetector computed tomography (MDCT), whole-body magnetic resonance imaging (WB-MRI), fluorodeoxyglucose positron emission tomography- (FDG-PET) with or without computed tomography (CT), and 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) scintigraphy. We conclude that both FDG-PET in combination with low-dose CT and whole-body MRI are more sensitive than skeleton X-ray in screening and diagnosing multiple myeloma. WB-MRI allows assessment of bone marrow involvement but cannot detect bone destruction, which might result in overstaging. Moreover, WB-MRI is less suitable in assessing response to therapy than FDG-PET. The combination of PET with low-dose CT can replace the golden standard, conventional skeletal survey. In the clinical practise, this will result in upstaging, due to the higher sensitivity
Ret is essential to mediate GDNF’s neuroprotective and neuroregenerative effect in a Parkinson disease mouse model
Glial cell line-derived neurotrophic factor (GDNF) is a potent survival and regeneration-promoting factor for dopaminergic neurons in cell and animal models of Parkinson disease (PD). GDNF is currently tested in clinical trials on PD patients with so far inconclusive results. The receptor tyrosine kinase Ret is the canonical GDNF receptor, but several alternative GDNF receptors have been proposed, raising the question of which signaling receptor mediates here the beneficial GDNF effects. To address this question we overexpressed GDNF in the striatum of mice deficient for Ret in dopaminergic neurons and subsequently challenged these mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Strikingly, in this established PD mouse model, the absence of Ret completely abolished GDNF’s neuroprotective and regenerative effect on the midbrain dopaminergic system. This establishes Ret signaling as absolutely required for GDNF’s effects to prevent and compensate dopaminergic system degeneration and suggests Ret activation as the primary target of GDNF therapy in PD
Capecitabine plus oxaliplatin as first-line treatment in patients with advanced biliary system adenocarcinoma: a prospective multicentre phase II trial
This prospective multicentre phase II study characterises the toxicity and activity of first-line capecitabine and oxaliplatin combination therapy (CAPOX) in advanced biliary system adenocarcinomas. Patients received oxaliplatin (130 mg m−2, day 1) plus capecitabine (1000 mg m−2 b.i.d., days 1–14) every 3 weeks. Patients were stratified prospectively into two groups based on location of the primary (gallbladder carcinoma (GBC) or extrahepatic cholangiocarcinoma (ECC) versus intrahepatic mass-forming type cholangiocarcinoma (ICC)). Sixty-five patients were evaluable. The response rate in 47 patients with GBC/ECC was 27% (4% complete responses), and in 23 patients (49%) stable disease (SD) was encountered. In 18 patients with ICC, we observed no objective responses, but 6 patients (33%) had SD. Median survival was 12.8 months (95% CI, 10.0–15.6) for patients with GBC or ECC (GBC: 8.2 months; 95% CI, 4.3–11.7; ECC: 16.8 months; 95% CI, 12.7–20.5), and 5.2 months (95% CI, 0.6–9.8) for ICC patients. In both cohorts, therapy was well tolerated. The most common grade 3–4 toxicity was peripheral sensory neuropathy (11 patients). Our data suggest that the CAPOX regimen is a well-tolerated and active treatment option for advanced ECC and GBC but might produce poorer results for ICC
A multidisciplinary consensus on the morphological and functional responses to immunotherapy treatment
The implementation of immunotherapy has radically changed the treatment of oncological patients. Currently, immunotherapy is indicated in the treatment of patients with head and neck tumors, melanoma, lung cancer, bladder tumors, colon cancer, cervical cancer, breast cancer, Merkel cell carcinoma, liver cancer, leukemia and lymphomas. However, its efficacy is restricted to a limited number of cases. The challenge is, therefore, to identify which subset of patients would benefit from immunotherapy. To this end, the establishment of immunotherapy response criteria and predictive and prognostic biomarkers is of paramount interest. In this report, a group of experts of the Spanish Society of Medical Oncology (SEOM), the Spanish Society of Medical Radiology (SERAM), and Spanish Society of Nuclear Medicine and Molecular Imaging (SEMNIM) provide an up-to-date review and a consensus guide on these issues
Minimising impairment: Protocol for a multicentre randomised controlled trial of upper limb orthoses for children with cerebral palsy.
BACKGROUND: Upper limb orthoses are frequently prescribed for children with cerebral palsy (CP) who have muscle overactivity predominantly due to spasticity, with little evidence of long-term effectiveness. Clinical consensus is that orthoses help to preserve range of movement: nevertheless, they can be complex to construct, expensive, uncomfortable and require commitment from parents and children to wear. This protocol paper describes a randomised controlled trial to evaluate whether long-term use of rigid wrist/hand orthoses (WHO) in children with CP, combined with usual multidisciplinary care, can prevent or reduce musculoskeletal impairments, including muscle stiffness/tone and loss of movement range, compared to usual multidisciplinary care alone. METHODS/DESIGN: This pragmatic, multicentre, assessor-blinded randomised controlled trial with economic analysis will recruit 194 children with CP, aged 5-15 years, who present with flexor muscle stiffness of the wrist and/or fingers/thumb (Modified Ashworth Scale score =1). Children, recruited from treatment centres in Victoria, New South Wales and Western Australia, will be randomised to groups (1:1 allocation) using concealed procedures. All children will receive care typically provided by their treating organisation. The treatment group will receive a custom-made serially adjustable rigid WHO, prescribed for 6 h nightly (or daily) to wear for 3 years. An application developed for mobile devices will monitor WHO wearing time and adverse events. The control group will not receive a WHO, and will cease wearing one if previously prescribed. Outcomes will be measured 6 monthly over a period of 3 years. The primary outcome is passive range of wrist extension, measured with fingers extended using a goniometer at 3 years. Secondary outcomes include muscle stiffness, spasticity, pain, grip strength and hand deformity. Activity, participation, quality of life, cost and cost-effectiveness will also be assessed. DISCUSSION: This study will provide evidence to inform clinicians, services, funding agencies and parents/carers of children with CP whether the provision of a rigid WHO to reduce upper limb impairment, in combination with usual multidisciplinary care, is worth the effort and costs. TRIAL REGISTRATION: ANZ Clinical Trials Registry: U1111-1164-0572
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