Biomedical subjects

K Yuen

Publications and source records attributed to K Yuen.

58 records · Page 4Linked to original sources

PubMedDate not supplied

Laser-assisted tympanoplasty for preservation of the ossicular chain in cholesteatoma.

We report the use of potassium titanyl phosphate laser-assisted tympanoplasty in amputations of the malleus and incus in 2 patients with cholesteatoma medial to those ossicles that had not destroyed the ossicular chain continuity. In both cases, the laser successfully removed portions of the ossicles to allow removal of the cholesteatoma; importantly, the laser preserved certain ossicular ligaments, thus keeping the ossicular chain continuous. Postoperatively, both patients showed satisfactory hearing. Although the prevalence of cholesteatoma medial to the ossicles with maintained ossicular continuity is limited, the laser-assisted procedure described here is useful for maintaining hearing ability in these cases.

Adult↗

PubMedDate not supplied

A differential method for inhomogeneity correction on dose in a photon beam.

For a uniform slab of inhomogeneity in a supervoltage beam, correction factors can be calculated from the Batho equation. In this report, we present a method for calculating the effect of an annular inhomogeneity, concentric about the beam axis, upon the dose at a point on the axis and below the annulus. A derivation of the equation required in the calculation for supervoltage radiation is given. Results from measurements made in 60Co beams for polystyrene foam, cedar, and aluminum annuli, all having 3.0 x 2.0 cm2 in cross section but with different inside diameters, are compared with correction values calculated by the method. For situations where the annulus is just submerged in the phantom, measured and calculated values are in good agreement. For a general situation, two calculation types are proposed and the data show that in general the measured scatter perturbation lies between the calculated values of the two types. Application of our technique predicts a sign reversal in the scatter perturbation due to an inhomogeneity. This reversal has previously been observed and reported and is also demonstrated in our measurements.

Cobalt Radioisotopes↗

PubMedDate not supplied

Practical application of the differential Batho method for inhomogeneity correction on kerma in a photon beam.

The Batho equation gives a satisfactory method to correct the dose for points in the electronic equilibrium region for a uniform slab of inhomogeneity in a photon beam. In spite of the many investigations, we believe no simple and adequate method has been found for routine clinical dose calculations which require dose correction of a small-volume inhomogeneity in an arbitrary location. In the present report, we combine the values of the two calculation types of the differential Batho method, which we have developed previously, to give a new calculated value for the scatter perturbation due to an annulus of inhomogeneity. The coefficients in the combination, which we derived from a detailed analysis of the scatter perturbation, are simple geometrical ratios. The new calculated values are in good agreement with measured values. We believe this application of the differential Batho method can provide a practical and accurate method of correcting for inhomogeneities of any size and shape in clinical dose calculations.

Humans↗

PubMedDate not supplied

Laryngeal zoster with unilateral laryngeal paralysis.

The case of a 60-year-old man with a unilateral laryngeal mucosal lesion and complete left vocal cord paralysis is reported. The lesion localized to the left side of the larynx covered the laryngeal vestibule, arytenoid, false vocal cord and true vocal cord, but did not extend to the hypopharynx or oropharynx. Enzyme immunoassay for varicella-zoster virus (VZV) led to a diagnosis of VZV infection.

Antibodies, Viral↗