Hero 642 rotary instruments transported canals less, especially at the middle and coronal thirds of the root canals than stainless steel K-files. Hero 642 instruments had better centreing ability.

A new, fast, 2D MR imaging technique allowing passive catheter visualization adequate for use as a tool for guiding the movement of a catheter during endovascular procedures is described. This imaging technique samples low spatial frequencies more often than high spatial frequencies; it also uses both k-space view sharing and temporal interpolation. Unlike other techniques for passive visualization that exploit magnetic-susceptibility-induced artifacts, we have adopted a strategy that takes advantage of the T1-shortening effect of paramagnetic contrast agents, such as Gd-DTPA and a projection dephaser. This not only permits visualization of the entire catheter length but also minimizes the risk of intravascular heating. Using this method, a temporal frame rate of up to eight images per second and a tip localization accuracy of +/- 1mm (root mean square difference) can be achieved.

No abstract

Materials that simultaneously mimic soft tissue in vivo for magnetic resonance imaging ͑MRI͒, ultrasound ͑US͒, and computed tomography ͑CT͒ for use in a prostate phantom have been developed. Prostate and muscle mimicking materials contain water, agarose, lipid particles, protein, Cu ϩϩ , EDTA, glass beads, and thimerosal ͑preservative͒. Fat was mimicked with safflower oil suffusing a random mesh ͑network͒ of polyurethane. Phantom material properties were measured at 22°C. ͑22°C is a typical room temperature at which phantoms are used.͒ The values of material properties should match, as well as possible, the values for tissues at body temperature, 37°C. For MRI, the primary properties of interest are T1 and T2 relaxations times, for US they are the attenuation coefficient, propagation speed, and backscatter, and for CT, the x-ray attenuation. Considering the large number of parameters to be mimicked, rather good agreement was found with actual tissue values obtained from the literature. Using published values for prostate parenchyma, T1 and T2 at 37°C and 40 MHz are estimated to be about 1100 and 98 ms, respectively. The CT number for in vivo prostate is estimated to be 45 HU ͑Hounsfield units͒. The prostate mimicking material has a T1 of 937 ms and a T2 of 88 ms at 22°C and 40 MHz; the propagation speed and attenuation coefficient slope are 1540 m/s and 0.36 dB/cm/MHz, respectively, and the CT number of tissue mimicking prostate is 43 HU. Tissue mimicking ͑TM͒ muscle differs from TM prostate in the amount of dry weight agarose, Cu ϩϩ , EDTA, and the quality and quantity of glass beads. The 18 m glass beads used in TM muscle increase US backscatter and US attenuation; the presence of the beads also has some effect on T1 but no effect on T2. The composition of tissue-mimicking materials developed is such that different versions can be placed in direct contact with one another in a phantom with no long term change in US, MRI, or CT properties. Thus, anthropomorphic phantoms can be constructed.

Objective To assess cardiac function by means of the modified myocardial performance index (Mod-MPI)