Viscoelastic computational modeling of the human head-neck system: Eigenfrequencies and time-dependent analysis.

A subject-specific 3-dimensional viscoelastic finite element model of the human head-neck system is presented and investigated based on computed tomography and magnetic resonance biomedical images. Ad hoc imaging processing tools are developed for the reconstruction of the simulation domain geometry and the internal distribution of bone and soft tissues. Material viscoelastic properties are characterized point-wise through an image-based interpolating function used then for assigning the constitutive prescriptions of a heterogenous viscoelastic continuum model. The numerical study is conducted both for modal and time-dependent analyses, compared with similar studies and validated against experimental evidences. Spatiotemporal analyses are performed upon different exponential swept-sine wave-localized stimulations. The modeling approach proposes a generalized, patient-specific investigation of sound wave transmission and attenuation within the human head-neck system comprising skull and brain tissues. Model extensions and applications are finally discussed.

Computational comparison of aortic root stresses in presence of stentless and stented aortic valve bio-prostheses.

We provide a computational comparison of the performance of stentless and stented aortic prostheses, in terms of aortic root displacements and internal stresses. To this aim, we consider three real patients; for each of them, we draw the two prostheses configurations, which are characterized by different mechanical properties and we also consider the native configuration. For each of these scenarios, we solve the fluid-structure interaction problem arising between blood and aortic root, through Finite Elements. In particular, the Arbitrary Lagrangian-Eulerian formulation is used for the numerical solution of the fluid-dynamic equations and a hyperelastic material model is adopted to predict the mechanical response of the aortic wall and the two prostheses. The computational results are analyzed in terms of aortic flow, internal wall stresses and aortic wall/prosthesis displacements; a quantitative comparison of the mechanical behavior of the three scenarios is reported. The numerical results highlight a good agreement between stentless and native displacements and internal wall stresses, whereas higher/non-physiological stresses are found for the stented case.

Transarterial chemoembolization with degradable starch microspheres (DSM-TACE): an alternative option for advanced HCC patients? Preliminary results.

OBJECTIVE: To assess safety, feasibility and effectiveness of transarterial chemoembolization with degradable-starch-microspheres (DSM-TACE) in the treatment of patients with advanced hepatocellular carcinoma (HCC) dismissing or ineligible for multikinase-inhibitor chemotherapy administration (Sorafenib) due to unbearable side effects or clinical contraindications. PATIENTS AND METHODS: Six consecutive advanced HCC patients dismissing Sorafenib because of unbearable side effects or worsened clinical conditions were enrolled in our prospective single-center pilot study. DSM-TACE was performed via a lobar approach, based on extent and distribution of the disease (1 treatment session for every lobe involved, with a 2-week interval in case of bilobar disease). Tumor response based on mRECIST criteria was evaluated on MD-CT performed at 1 month after "complete treatment" and every 3 months thereafter. RESULTS: Eleven treatments were performed, and technical success was achieved in all patients. No intra/peri-procedural death/major complications occurred. No signs of liver failure or systemic toxicity were detected. At one month follow-up, 5 partial responses (83.3%) and 1 progression disease (16.6%) with an overall disease control (ODC) of 83.3% were observed. In two patients with ODC and residual viable tumor higher than 50%, a repeated DSM-TACE treatment was performed. During the mean follow-up of 11 months (range: 4-14 months), an ODC of 66.6% was obtained. Progression-free survival was 5.5 months with a cumulative 6-month and 1-year overall survival rates of 83.3% and 66.6%, respectively. CONCLUSIONS: DSM-TACE seems to be a promising option for advanced HCC patients ineligible for Sorafenib administration or dismissing it due to progressive disease or unbearable side effects.

Multi-detector CT angiographic imaging in the follow-up of patients after endovascular abdominal aortic aneurysm repair (EVAR).

BACKGROUND: Multidetector computed tomography (MDCT) angiography represents the standard of reference in the follow-up of patients after endovascular abdominal aortic aneurysm repair (EVAR), being effective in the detection of the full spectrum of possible complications on both axial and 3D images. METHODS: The purpose of this article is to review the normal CT angiography findings of the different types of stent-grafts and to describe the radiological findings of early and late complications after EVAR on axial and reconstructed images. A selection of cases of post-EVAR MDCT angiography is presented to learn the techniques most commonly used for endovascular treatment, the correct CT scanning technique to acquire the data, the full gamut of possible procedure-related complications and how these complications usually appear on CT images. CONCLUSION: MDCT angiography is an effective and specific technique in both the pre- and postoperative settings of EVAR procedures. A better understanding of the procedure, the devices, the normal postoperative imaging features and the possible procedure-related complications ensures optimal planning and follow-up of patients undergoing an EVAR procedure.

Aortic-neck dilation after endovascular abdominal aortic aneurysm repair (EVAR): can it be predicted?

PURPOSE: This study was performed to evaluate whether dynamic computed tomography (CT) can provide functional vessel information predicting outcomes of aortic neck in patients undergoing endovascular aneurysm repair (EVAR) of an abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: Twenty patients with and 20 without AAA were enrolled. Electrocardiographically (ECG)-gated data sets were acquired with a 64-slice CT scanner. Axial pulsatility measurements were taken at three levels: 2 cm above the highest renal artery; immediately below the lowest renal artery; 1 cm below the lowest renal artery. Three independent readers performed the measurements. Systolic and diastolic blood pressures were measured in the brachial artery to calculate arterial-wall distensibility expressed as pressure strain elastic modulus (Ep). Cross-sectional area change, wall distensibility and Ep value were statistically compared. RESULTS: No significant differences were found in terms of Ep values in the suprarenal and juxtarenal level. In the AAA group, a significantly higher value was obtained at the infrarenal level. A subgroup of patients with AAA (45%) had a significantly higher Ep value at the infrarenal level. CONCLUSIONS: Dynamic CT provided insight into the abdominal aorta pathophysiology. Identifying patients with higher infrarenal distensibility could change selection of graft size to improve proximal fixation.

A human umbilical cord stem cell rescue therapy in a murine model of toxic liver injury.

BACKGROUND: Several studies have demonstrated that bone marrow contains a subpopulation of stem cells capable of participating in the hepatic regenerative process, even if some reports indicate quite a low level of liver repopulation by human stem cells in the normal and transiently injured liver. AIMS: In order to overcome the low engraftment levels seen in previous models, we tried the direct intraperitoneal administration of human cord blood stem cells, using a model of hepatic damage induced by allyl alcohol in NOD/SCID mice. METHODS: We designed a protocol based on stem cell infusion following liver damage in the absence of irradiation. Flow cytometry, histology, immunohistochemistry and RT-PCR for human hepatic markers were performed to monitor human cell engraftment. RESULTS: Human stem cells were able to transdifferentiate into hepatocytes, to improve liver regeneration after damage and to reduce the mortality rate both in both protocols, even if with qualitative and quantitative differences in the transdifferentiation process. CONCLUSIONS: We demonstrated for the first time that the intraperitoneal administration of stem cells can guarantee a rapid liver engraftment. Moreover, the new protocol based on stem cell infusion following liver damage in the absence of irradiation may represent a step forward for the clinical application of stem cell transplantation.

Cell-based therapy for liver diseases.

Although liver transplantation has become standard therapy in the treatment of patients with liver failure, several problems should be considered in the management of these patients. Other approaches have been proposed, in particular cellular-based procedures. Isolated hepatocytes may be used instead of whole organ transplantation or integrated within the bioartificial devices, in order to replace the missing synthetic and metabolic liver functions. Moreover patient's own hepatocytes may be ex vivo genetically modified to provide the function of a mutant gene. However, new cell sources alternative to adult hepatocytes are actually under investigation, on the basis of recent advances in the field of liver repopulation. Xenogenic primary cells, human hepatoma cells, immortalized hepatocytes and stem cells have been testing in several experiments, even if up to now none of them represent a "gold-standard" for cell-based treatment of liver diseases. In the next future, it is possible that different clinical situations will require different therapeutic approaches, that will be finally defined from the concomitant advances in the development of artificial devices and liver cell biology.