Patient-specific finite element analysis of carotid artery stenting: a focus on vessel modeling

Finite element analysis is nowadays a well-assessed technique to investigate the impact of stenting on vessel wall and, given the rapid progression of both medical imaging techniques and computational methods, the challenge of using the simulation of carotid artery stenting as procedure planning tool to support the clinical practice can be approached. Within this context, the present study investigates the impact of carotid stent apposition on carotid artery anatomy by means of patient-specific finite element analysis. In particular, we focus on the influence of the vessel constitutive model on the prediction of carotid artery wall tensional state of lumen gain and of vessel straightening. For this purpose, we consider, for a given stent design and CA anatomy, two constitutive models for the CA wall, that is, a hyperelastic isotropic versus a fiber-reinforced hyperelastic anisotropic model. Despite both models producing similar patterns with respect to stress distribution, the anisotropic model predicts a higher vessel straightening and a more evident discontinuity of the lumen area near the stent ends as observed in the clinical practice. Although still affected by several simplifications, the present study can be considered as further step toward a realistic simulation of carotid artery stenting.

Metalloproteases and their inhibitors are altered in both torn and intact rotator cuff tendons

BACKGROUND

We evaluated the role of matrix metalloproteases (MMPs) and their inhibitors which are involved in extracellular matrix remodeling and degradation, in the pathogenesis of chronic rotator cuff tears.

MATERIALS AND METHODS

Tendon samples were harvested from 13 patients who underwent arthroscopic repair of a rotator cuff tear. Supraspinatus biopsy specimens were harvested en bloc from the arthroscopically intact middle portion of the tendon more than 1 cm from the torn edge, from the lateral edge of the tear, and from the superior one third of the macroscopically intact subscapularis tendon used as control. Histological analysis and an evaluation of the activity of specific metalloproteases and the tissue inhibitors of metalloprotease (TIMP-1, TIMP-2) was done blindly by multiplex sandwich ELISA (Search-Light technology) in each specimen

RESULTS

Histological evidence of tendinopathy was present in all patients with a tear of the rotator cuff, and not in the macroscopically intact subscapularis tendon. There was a significant increase in MMP 1, MMP 2, MMP 3 and in TIMP-1, TIMP-2 levels in all specimens examined, including the macroscopically intact portion of the supraspinatus tendon and in the control specimens

CONCLUSIONS

The tissue in the ruptured area of the supraspinatus tendon undergoes marked rearrangement at molecular levels. This involves the activity of MMP 1, 2 and 3, and supports the critical role of MMPs in the tendon physiology. Seemingly intact parts of the injured supraspinatus tendon can present tendinopathic features, with altered cellular metabolism.

Patient-specific aortic endografting simulation: from diagnosis to prediction

Traditional surgical repair of ascending aortic pseudoaneurysm is complex, technically challenging, and associated with significant mortality. Although new minimally invasive procedures are rapidly arising thanks to the innovations in catheter-based technologies, the endovascular repair of the ascending aorta is still limited because of the related anatomical challenges. In this context, the integration of the clinical considerations with dedicated bioengineering analysis, combining the vascular features and the prosthesis design, might be helpful to plan the procedure and predict its outcome. Moving from such considerations, in the present study we describe the use of a custom-made stent-graft to perform a fully endovascular repair of an asymptomatic ascending aortic pseudoaneurysm in a patient, who was a poor candidate for open surgery. We also discuss the possible contribution of a dedicated medical images analysis and patient-specific simulation as support to procedure planning. In particular, we have compared the simulation prediction based on pre-operative images with post-operative outcomes. The agreement between the computer-based analysis and reality encourages the use of the proposed approach for a careful planning of the treatment strategy and for an appropriate patient selection, aimed at achieving successful outcomes for endovascular treatment of ascending aortic pseudoaneurysms as well as other aortic diseases.

Fresh aromatic herbs containing methylchavicol did not exhibit the pro-oxidative effects of pure methylchavicol on a human hepatoma cell line, HepG2

Methylchavicol (CH(3)-CV), an important aromatic constituent of different plants like tarragon and basils, has been shown to be carcinogenic by a mechanism yet unclear, although it has been reported that carcinogenicity of CH(3)-CV in rodent might be linked to its metabolic conversion into a genotoxic electrophilic metabolite generated through a two steps bioactivation pathway catalyzed by cytochrome P450 enzymes and sulfotransferases. The induction of carcinogenesis by certain agents has been associated with the generation of oxidative stress. The aim of the present study was to determine whether pure methylchavicol applied on a human hepatoma cell line, HepG2, could promote oxidative stress and might alter the expression of procarcinogenic biomarkers such as the drug-metabolizing enzyme (CYP2E1), the inducible form of nitric oxide synthase (iNOS) and might induce the expression of Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and Mn-SOD that control the redox equilibrium of the cells. CH(3)-CV was shown to cause a significant induction of oxidative stress, as revealed by luminol-dependent chemiluminescence (LDCL) and to alter dramatically the expression of CYP2E1, iNOS and Mn-SOD, indicating that the toxic effect of CH(3)-CV could be mediated through a nitric oxide dependent mechanism. Under similar experimental conditions, the extracts from tarragon, chervil and basil did not induce such biological changes. These results provide evidence that the generation of an oxidative stress may be a significant event occurring during CH(3)-CV-induced toxicity. It also suggests that natural extracts containing different amounts of CH(3)-CV (tarragon, chervil and basil) did not elicit such toxicity and might contain compounds able to counteract this detrimental property.

Evaluation of carotid stent scaffolding through patient-specific finite element analysis

After carotid artery stenting, the plaque remains contained between the stent and the vessel wall, moving consequently physicians' concerns toward the stent capability of limiting the plaque protrusion, that is, toward vessel scaffolding, to avoid that some debris is dislodged after the procedure. Vessel scaffolding is usually measured as the cell area of the stent in free-expanded configuration, neglecting thus the actual stent configuration within the vascular anatomy. In the present study, we measure the cell area of four different stent designs deployed in a realistic carotid artery model through patient-specific finite element analysis. The results suggest that after deployment, the cell area change along the stent length and the related reduction with respect to the free-expanded configuration are functions of the vessel tapering. Hence, the conclusions withdrawn from the free-expanded configuration appear to be qualitatively acceptable for comparative purposes, but they should be carefully handled because they neglect the post-implant variability, which seems to be more pronounced in open-cell designs, especially at the bifurcation segment. Even though the investigation is limited to few stent designs and one vascular anatomy, our study confirms the capability of dedicated computer-based simulations to provide useful information about complex stent features as vessel scaffolding.

[Methodological aspects in the evaluation of turn-over and up/down sizing as indicators of work-related stress]

We discuss the methodological aspects related to the evaluation of turn-over and up-down sizing as indicators of work-related stress, in complex organizations like a university hospital. To estimate the active workers population we developed an algorithm which integrated several administrative databases. The indicators were standardized to take into account some potential confounders (age, sex, work seniority) when considering different hospital structures and job mansions. Main advantages of our method include flexibility in the choice of the analysis detail (hospital units, job mansions, a combination of both) and the possibility to describe over-time trends to measure the success of preventive strategies.

[Ischemic lesions in kidneys after extracorporeal shock wave lithotripsy demonstrated by Proton NMR spectroscopy of urine samples]

PURPOSE

The aim of this prospective study was to investigate the effect of extracorporeal shock wave lithotripsy (SWL) on kidneys of patients with pyelic stone disease. The effects of SWL were assessed by high-resolution proton nuclear magnetic resonance (HNMR) spectroscopy of urine samples.

METHODS

Twenty-three patients, aged 31-80years (mean: 55years), with pyelic stone disease were investigated before and after SWL. Multiparameter analysis was performed by HNMR spectroscopy of urine samples collected before and 5h after SWL (second miction post-SWL).

RESULTS

The most relevant resonances determined by HNMR spectroscopy were acetate, lactate, trimethylamine N-oxide and amino acids. Excretion of these markers increased significantly in comparison with pre-SWL urinary samples.

CONCLUSION

These results show that early ischemic damage occurs after SWL. Post-SWL. HNMR spectroscopy is an effective tool for noninvasive follow-up of renal damage.

[Herpes zoster in general medicine: experience of the Italian group Netaudit]

Herpes zoster is caused by the reactivation of the varicella-zoster virus (VZV) and usually appears many years after primary infection (varicella), induced by immunosuppression due to underlying diseases. Few epidemiological data in Italy are available concerning Herpes zoster, mainly because disease notification is not mandatory. An observational perspective trial was conducted for 12 months by 41 Italian general practitioners belonging to the Netaudit network to determine herpes zoster incidence and its correlation to patients' characteristics (age, gender, educational qualification, co-morbidities), the delay from correct diagnosis to the start of treatment and different drug prescription. In all, the study involved 193 patients with herpes zoster: this population included mostly female (60.6%) and elderly subjects (59.6%) with a mean age of 60.4 years. 46.1% of patients presented underlying diseases (diabetes 13%, solid tumours 5.7%). Correct diagnosis was achieved after a mean delay of 49 hours while therapy was started within 48 hours in most cases (75.1%). Aciclovir (51%) and valaciclovir (24%) were the most commonly used drugs. A significant correlation between educational level and prompt treatment suggests the major role of education in primary health prevention campaigns.

Home return 6 months after an intensive care unit admission for elderly patients

BACKGROUND

Home return after critical care is very important not only to patients and families. To move back home, patients have to fulfill two conditions: survive, and have a relatively good functional status. In addition, home return could be considered a low-cost outcome because of the reduced permanent healthcare costs.

METHODS

To determine the factors influencing the home-return probability of critically ill elderly patients 6 months after an intensive care unit (ICU) admission, we analyzed a cohort of patients aged 65 years or older admitted to an ICU. Demographic and social parameters, as well as admission diagnosis, underlying diseases, severity scores, ICU stay parameters, and complications were recorded. The final outcome was the place of stay (or death) 180 days after ICU admission.

RESULTS

Of 526 patients, 72% of the cohort and 93% of hospital survivors were able to return to their homes. Among the variables used in the multivariate logistic regression, advanced age, length of hospital stay before ICU admission, severity of acute illness, diagnosis category, and complications, as well as certain comorbidities, such as chronic heart failure or a neoplasia, were independently negatively associated with a home return.

CONCLUSION

Some interesting factors were identified in this single-center study. They could be considered for a multicenter study to build a universal prediction model for home return. Home return could be used for elderly patients as a surrogate for outcomes that are very important to the elderly but also to health politics.

Physical and clinical performance of the mCT time-of-flight PET/CT scanner

Time-of-flight (TOF) measurement capability promises to improve PET image quality. We characterized the physical and clinical PET performance of the first Biograph mCT TOF PET/CT scanner (Siemens Medical Solutions USA, Inc.) in comparison with its predecessor, the Biograph TruePoint TrueV. In particular, we defined the improvements with TOF. The physical performance was evaluated according to the National Electrical Manufacturers Association (NEMA) NU 2-2007 standard with additional measurements to specifically address the TOF capability. Patient data were analyzed to obtain the clinical performance of the scanner. As expected for the same size crystal detectors, a similar spatial resolution was measured on the mCT as on the TruePoint TrueV. The mCT demonstrated modestly higher sensitivity (increase by 19.7 ± 2.8%) and peak noise equivalent count rate (NECR) (increase by 15.5 ± 5.7%) with similar scatter fractions. The energy, time and spatial resolutions for a varying single count rate of up to 55 Mcps resulted in 11.5 ± 0.2% (FWHM), 527.5 ± 4.9 ps (FWHM) and 4.1 ± 0.0 mm (FWHM), respectively. With the addition of TOF, the mCT also produced substantially higher image contrast recovery and signal-to-noise ratios in a clinically-relevant phantom geometry. The benefits of TOF were clearly demonstrated in representative patient images.

Does age at observation time affect the clinical presentation of mild cognitive impairment?

BACKGROUND

To date, there are no published data investigating the role of age in the clinical and neuropsychological presentation of mild cognitive impairment (MCI). The aim of the study was to evaluate whether age at the time of evaluation modulates clinical, functional or cognitive profiles in MCI subjects.

METHODS

A total of 167 outpatients with a clinical diagnosis of MCI were consecutively enrolled and entered in the study. Clinical and demographic characteristics were carefully recorded. Each patient underwent a wide neuropsychological standardized assessment.

RESULTS

MCI subjects were divided into 3 groups according to their age at observation time: 58 MCI patients were classified as young (≤ 69 years), 89 as old (70-79 years) and 20 as very old (≥ 80 years). The 3 groups did not differ in demographic characteristics, general cognitive functions and memory impairment. Very old MCI subjects showed a significantly greater impairment than younger MCI patients in cognitive domains involving executive functions. In particular, very old MCI patients were more frequently classified as having multiple-domain amnestic MCI.

CONCLUSION

Present data highlight that the clinical presentation of MCI is affected by age: at presentation, very old MCI subjects show a worse performance than younger MCI subjects on multiple abilities, particularly on executive functions.