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Irina Ionescu

Publications and source records attributed to Irina Ionescu.

8 recordsLinked to original sources
PubMed2006

Simulation of soft tissue failure using the material point method.

Understanding the factors that control the extent of tissue damage as a result of material failure in soft tissues may provide means to improve diagnosis and treatment of soft tissue injuries. The objective of this research was to develop and test a computational framework for the study of the failure of anisotropic soft tissues subjected to finite deformation. An anisotropic constitutive model incorporating strain-based failure criteria was implemented in an existing computational solid mechanics software based on the material point method (MPM), a quasi-meshless particle method for simulations in computational mechanics. The constitutive model and the strain-based failure formulations were tested using simulations of simple shear and tensile mechanical tests. The model was then applied to investigate a scenario of a penetrating injury: a low-speed projectile was released through a myocardial material slab. Sensitivity studies were performed to establish the necessary grid resolution and time-step size. Results of the simple shear and tensile test simulations demonstrated the correct implementation of the constitutive model and the influence of both fiber family and matrix failure on predictions of overall tissue failure. The slab penetration simulations produced physically realistic wound tracts, exhibiting diameter increase from entrance to exit. Simulations examining the effect of bullet initial velocity showed that the anisotropy influenced the shape and size of the exit wound more at lower velocities. Furthermore, the size and taper of the wound cavity was smaller for the higher bullet velocity. It was concluded that these effects were due to the amount of momentum transfer. The results demonstrate the feasibility of using MPM and the associated failure model for large-scale numerical simulations of soft tissue failure.

Animals↗
PubMed2006

Ballistic injury simulation using the material point method.

The Material Point Method is used in the computational simulation of ballistic projectile damage to the heart. A transversely isotropic hyperelastic material model is used to model the myocardium. Computed estimates of tissue damage are used to characterize damaged tissue. The method's potential to estimate the damaged tissue in the complete torso is considered.

Computer Simulation↗
PubMed2006

Unrelated cord blood transplants in adults with hematologic malignancies.

BACKGROUND AND OBJECTIVES: We analyzed outcomes and risk factors after unrelated cord blood transplantation (CBT) in adults with hematologic malignancies. DESIGN AND METHODS: One hundred and seventy-one patients were transplanted after 1997. Their median age was 29 years (15-55), and the median follow-up time was 18 months (1-71). Most patients had acute or chronic leukemia (n=142, 83%), 91 (53%) were transplanted in advanced phase and an autologous transplant had failed in 32 (19%). Most patients (87%) received an HLA-mismatched cord blood unit with 1-2 HLA disparities. At infusion, the median number of nucleated cells and CD34(+) cells was 2.1x10(7)/kg and 1x10(5)/kg, respectively RESULTS: The cumulative incidence of neutrophil recovery at day 60 was 72+/-3% with a median of 28 days (11-57). A higher neutrophil count and use of hematopoietic growth factors were independently associated with faster neutrophil recovery. The cumulative incidence of grade II-IV acute graft-versus-host disease was 32+/-4% and this complication was not associated with the number of HLA mismatches. The 2-year cumulative incidence of chronic graft-versus-host disease, transplant related-mortality and relapse were 36+/-10%, 51+/-4% and 22+/-4%, respectively. At 2-years, disease-free-survival for patients transplanted in early, intermediate and advanced phases of disease was 41+/-9%, 34+/-10% and 18+/-4%, respectively. In multivariate analyses, advanced disease status was an adverse factor for relapse and disease-free survival. INTERPRETATION AND CONCLUSIONS: Unrelated CBT is a clear alternative for adults with hematological malignancies lacking an HLA-matched related or unrelated donor. The choice of units containing a higher neutrophil count and a policy of earlier transplantation are likely to provide better results.

Adolescent↗
PubMed2005

Computational simulation of penetrating trauma in biological soft tissues using the material point method.

The objective of this research was to develop realistic computational models for soft tissues subjected to finite deformation and failure, and to test these models in the context of numerical simulations of penetrating trauma injuries. A transversely isotropic hyperelastic model with strain-based failure criteria was used to represent the behavior of anisotropic soft tissue. The constitutive model was implemented into an existing numerical code based on the Material Point Method (MPM). The penetration of a low-speed bullet through a myocardium material slab was simulated and several wounding scenarios were analyzed and compared. The material symmetry, the type of contact modeled between the bullet and the soft tissue and the bullet speed were shown to have a significant influence on the wound profile.

Computer Simulation↗
PubMed2004

Factors associated with outcomes of unrelated cord blood transplant: guidelines for donor choice.

OBJECTIVE: Optimizing cord blood donor selection based mainly on cell dose and human leukocyte antigen (HLA) disparities may further improve results of unrelated cord blood transplants (UCBT). MATERIALS AND RESULTS: We analyzed 550 UCBTs for hematologic malignancies reported to the Eurocord Registry. Main outcomes and prognostic factors were analyzed in univariable and multivariable analyses incorporating center and period effects and using death and relapse as competitive risks for nonfatal endpoints. Nucleated cell (NC) dose before freezing and number of HLA disparities had a significant influence on outcome. Cumulative incidence (CI) of neutrophil and platelet recovery was associated with the number of HLA mismatches, number of NC before freezing, and use of granulocyte colony-stimulating factor. Coexistence of HLA class I and II disparities and high CD34 cell dose in the graft were associated with graft-vs-host disease grades III-IV. CI of disease relapse was higher in matched transplants showing a graft-vs-leukemia effect increased in HLA-mismatched transplants. Overall 3-year survival was 34.4%. Prognostic factors for survival were recipient age, gender, and disease status. CONCLUSION: Our results provide indications for a better choice of cord blood units according to cord blood cell content and HLA.

Adolescent↗
PubMed2003

Unrelated cord blood transplantation for childhood acute myeloid leukemia: a Eurocord Group analysis.

Results of unrelated cord blood transplantation (UCBT) in childhood acute myeloid leukemia (AML) have not been previously reported. We analyzed 95 children receiving UCB transplants for AML (20 in first complete remission [CR1], 47 in CR2, and 28 in more advanced stage). Poor prognosis cytogenetic abnormalities were identified in 29 cases. Most patients received a 1 or 2 HLA antigens-mismatched UCB transplants. The median number of collected nucleated cells (NCs) was 5.2 x 107/kg. Cumulative incidence (CI) of neutrophil recovery was 78% +/- 4%, acute graft-versus-host disease (GVHD) was 35% +/- 5%, and 100-day transplantation-related mortality (TRM) was 20% +/- 4%. In multivariable analysis, a collected NC dose higher than 5.2 x 107/kg was associated with a lower 100-day TRM. The 2-year CI of relapse was 29% +/- 5% and was associated with disease status. The 2-year leukemia-free survival (LFS) was 42% +/- 5% (59% +/- 11% in CR1, 50% +/- 8% in CR2, and 21% +/- 9% for children not in CR). Children with poor prognosis cytogenetic features had similar LFS compared with other patients (44% +/- 11% vs 40% +/- 8%). In CR2, LFS was not influenced by the length of CR1 (53% +/- 11% in CR1 < 9.5 months compared with 50% +/- 12% in later relapses). We conclude that UCBT is a therapeutic option for children with very poor-prognosis AML and who lack an HLA-identical sibling.

Acute Disease↗
PubMed2002

Related umbilical cord blood transplantation in patients with thalassemia and sickle cell disease.

Allogeneic bone marrow transplantation (BMT) from HLA-identical siblings is an accepted treatment for both thalassemia and sickle cell disease (SCD). However, it is associated with decided risk of both transplant-related mortality (TRM) and chronic graft-versus-host disease (GVHD). We analyzed 44 patients (median age, 5 years; range, 1-20 years) given an allogeneic related cord blood transplant for either thalassemia (n = 33) or SCD (n = 11). Thirty children were given cyclosporin A (CsA) alone as GVHD prophylaxis, 10 received CsA and methotrexate (MTX), and 4 patients received other combinations of immunosuppressive drugs. The median number of nucleated cells infused was 4.0 x 10(7)/kg (range, 1.2-10 x 10(7)/kg). No patient died and 36 of 44 children remain free of disease, with a median follow-up of 24 months (range, 4-76 months). Only one patient with SCD did not have sustained donor engraftment as compared with 7 of the 33 patients with thalassemia. Three of these 8 patients had sustained donor engraftment after BMT from the same donor. Four patients experienced grade 2 acute GVHD; only 2 of the 36 patients at risk developed limited chronic GVHD. The 2-year probability of event-free survival is 79% and 90% for patients with thalassemia and SCD, respectively. Use of MTX for GVHD prophylaxis was associated with a greater risk of treatment failure. Related CBT for hemoglobinopathies offers a good probability of success and is associated with a low risk of GVHD. Optimization of transplantation strategies could further improve these results.

Acute Disease↗