Several acoustic transmission and reflection technique measurements were carried out to determine mechanical properties (acoustic attenuation and velocity) versus frequency of polyvinylidene-fluoride (PVDF) and six other polymers. Acoustic measurements (0.5 to 12 MHz) included time-delay spectrometry (TDS; in which separate transmitting and receiving transducers utilize a swept frequency signal) and two pulse-echo methods (short tone burst echoes utilizing transducers with different center frequencies and Fourier analysis of echoes sent and received by damped transducers operating in the broadband pulse mode). Electrical impedance measurements of piezoelectric thin films of PVDF and P(VDF/TrFE) yielded comparable high frequency mechanical parameters. Of the seven acoustically examined polymers, PVDF had the greatest acoustic impedance, lowest acoustic velocity, and greatest mechanical loss (13.4 dB/cm per MHz). Polymethyl-methacrylate (PMMA; lucite) and polydimethyl-pentane (TPX) had the lowest loss. PMMA had the highest acoustic velocity, and TPX had the lowest acoustic impedance and a velocity almost identical to that of PVDF. These data are useful in the design of backing, matching, and lens materials to be used in association with PVDF transducers.

ABSTERMicrosurgical vascularized bone graft has been successfully used to treat large tibiat defects, The shape, size and length of the fibula make it a popular donor site for most tibia defects. The goal of this study is to numerically analyze the stress distribution in the transferred fibula and to evaluate the nature of the placement of the fibulur graft and its relations to failure. A finite element analysis was conducted lo investigate the stress distribution and to predict the stress fracture positions in transferred bones. The calculated results matched well with clinical observations. The simulation suggests that those grafts having a lower site transfer exhibit a higher level of stress distribution. The finite element model also suggests that the stress level of an obliquely placed graft is higher than thai of a vertically placed graft, especially at the distal tibia-fibula junction. A longer period of protection is therefore recommended for the treatment of a lower site transfer or an obliquely placed grafted bone to avoid bone stress fracture.Btomed Eng Appl Basis Comm, 2001 (October); 13: 218-225.

Objective. Patients with advanced renal insufficiency are at high risk of coronary artery disease (CAD) and complex lesions. Treating complex calcified lesion with rotational atherectomy (RA) in these patients might be associated with higher risks and poorer outcomes. This study was set to evaluate features and outcomes of RA in these patients. Method. Consecutive patients who received coronary RA from April 2010 to April 2018 were queried from the Cath Lab database. The procedural details, angiography, and clinical information were reviewed in detail. Results. A total of 411 patients were enrolled and divided into Group A (baseline serum creatinine <5 mg/dl, n = 338) and Group B (baseline serum creatinine ≥ 5 mg/dl through ESRD, n = 73). Most patients had high-risk features (65.7% of acute coronary syndrome (ACS), 14.1% of ischemic cardiomyopathy, and 5.1% of cardiogenic shock). Group B patients were significantly younger (66.8 ± 11.4 vs. 75.2 ± 10.7 years, p < 0.001 ) and had more RCA and LCX but less LAD treated with RA. No difference was found in lesion location, vessel tortuosity, bifurcation lesions, chronic total occlusion, total lesion length, or total lesion numbers between the two groups. Less patients in Group B obtained completion of RA (95.9% vs 99.1%, p = 0.037 ). There was no difference in the incidence of procedural complication or acute contrast-induced nephropathy. Group B patients had more deaths and MACE while in the hospital. The MACE and CV MACE were also higher in Group B patients at 180 days and one year, mostly due to TLR and TVR. Multivariate regression analysis showed that ACS, age, peripheral artery disease (PAD), advanced renal insufficiency, ischemic cardiomyopathy/shock, and high residual SYNTAX score were independent risk factors for in-hospital MACE, whereas ACS, advanced renal insufficiency, ischemic cardiomyopathy/shock, triple-vessel disease, and PAD independently predicted MACE at 6 months. Conclusions. Rotablation is feasible, safe, and could be carried out with very high success rate in very-high-risk patients with advanced renal dysfunction through ESRD without an increase in procedural complication.

BackgroundDespite advances being made in techniques and devices, certain chronic total occlusion (CTO) lesions remain uncrossable or undilatable. Rotational atherectomy (RA) is usually necessary for such lesions to achieve successful revascularization.MethodsInformation regarding consecutive patients who underwent coronary RA was retrieved from the catheterization laboratory database. Patients who underwent RA for CTO lesion refractory using other conventional devices were recruited, with propensity score-matched cases serving as controls.ResultsA total of 411 patients underwent coronary RA in the study period. Most patients had high-risk features (65.7% had acute coronary syndrome (ACS), 14.1% ischemic cardiomyopathy, and 5.1% cardiogenic shock), while only 20.2% of the patients had stable angina. Among them, 44 patients underwent RA for CTO lesions (CTO group), whereas the propensity score matched controls consist of 37 patients (non-CTO group). The baseline characteristics, high-risk features, coronary artery disease (CAD) vessel numbers, left ventricular function and biochemistry profiles of both groups were the same except for more patients with diabetes (67.6% vs. 45.5%, p = 0.046) in the non-CTO group and more 1.25 mm burr uses in the CTO group. There were no significant differences in acute procedural outcomes or incidence of acute contrast-induced nephropathy (CIN), and no patient demanded emergent CABG or died during the procedure. There was no significant difference in major adverse cardiovascular events (MACE), CV MACE or individual components between the two groups in the hospital, at 30, 90, and 180 days or at 1 year.ConclusionIn comparison with the propensity risk factor scores-matched controls, there was no difference in procedural complications, acute CIN or clinical outcomes during various stages of RA for CTO lesions. RA for CTO patients was highly efficient and showed safety and outcome profiles similar to those for non-CTO lesions.

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