16 research outputs found
Finite Element Analysis of Hepatic Radiofrequency Ablation Probes using Temperature-Dependent Electrical Conductivity
BACKGROUND: Few finite element models (FEM) have been developed to describe the electric field, specific absorption rate (SAR), and the temperature distribution surrounding hepatic radiofrequency ablation probes. To date, a coupled finite element model that accounts for the temperature-dependent electrical conductivity changes has not been developed for ablation type devices. While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed. METHODS: The results of four finite element models are compared: constant electrical conductivity without tissue perfusion, temperature-dependent conductivity without tissue perfusion, constant electrical conductivity with tissue perfusion, and temperature-dependent conductivity with tissue perfusion. RESULTS: The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures. These errors appear to be closely related to the temperature at which the ablation device operates and not to the amount of power applied by the device or the state of tissue perfusion. CONCLUSION: Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100°C
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Abstract T P274: Accreditation Status of Outpatient Cerebrovascular Testing Facilities Among Medicare Beneficiaries: The VALUE (Vascular Accreditation, Location & Utilization Evaluation) Study
OBJECTIVE:
Accreditation of cerebrovascular ultrasound laboratories by the Intersocietal Accreditation Commission (IAC) or equivalent bodies is supported by The Joint Commission certification of stroke centers. Limited information exists on the accreditation status and geographic distribution of these testing facilities in the US. The aims were to: (1) Identify the proportion of IAC accredited vascular testing facilities used by Medicare beneficiaries for outpatient cerebrovascular testing services; (2) Describe the geographical distribution of these facilities; and (3) Identify variation in the types and volumes of cerebrovascular testing procedures by accreditation status.
METHODS:
As a part of the VALUE (Vascular Accreditation, Location & Utilization Evaluation) Study, we examined the proportion of IAC accredited facilities that conducted cerebrovascular testing in a 5% CMS random Outpatient Limited Data Set (LDS) for the US in 2011 and investigated their geographical distribution using the Medicare Provider of Services (POS) file.
RESULTS:
Of the 7,864 total facilities billing Medicare for cerebrovascular testing procedures, only 22% (n=1,723) were IAC accredited. The percentage of facilities conducting cerebrovascular testing that were IAC accredited varied by region (Χ2[3]=400.4, p<0.0001), with 43%, 21%, 17% and 13% located in the Northeast, South, Midwest, and West, respectively. However, when examining the total number of cerebrovascular outpatient procedures conducted in 2011 (total n=38,646), 41% (15,729) were conducted in IAC accredited facilities. Moreover, when examining procedure type across all sites, 98% (38,011) of all cerebrovascular testing procedures conducted were carotid duplex, of which 41% (15,417) were conducted in IAC accredited facilities. In contrast, 1% (n=315) of all cerebrovascular procedures were transcranial (TCD), of which 56% (n=177) were conducted in IAC accredited facilities.
CONCLUSIONS:
The proportion of IAC accredited facilities conducting outpatient cerebrovascular testing is low and varies by region. The growing number of certified stroke centers should be accompanied by more accredited vascular testing facilities that could potentially improve quality of stroke care