Staffing the environmental services department. Experience a paradigm shift.
Explore the source record for details and available documents.
Housekeeping, Hospital↗
Biomedical subjects
J E Saunders
Publications and source records attributed to J E Saunders.
Cochlear implant-related osteoneogenesis in an animal model: fluorescent labeling.
Cochlear osteoneogenesis may result from a variety of pathologic conditions, including cochlear implantation. The etiology of cochlear osteoneogenesis following implantation, however, is not known. Cochlear implant-related osteoneogenesis has been demonstrated in laboratory animals, but the specific cause, extent, or time-course of this process has not been determined. In this preliminary study, fluorescent bone labels were used to assess osteoneogenesis in six chinchillas in three experimental categories: surgical trauma to the cochlea, chronic nonstimulated cochlear implantation, and intrascalar neomycin infusion. Computer image analysis was used to measure the area of labeled bone on representative mid-modiolar histologic sections. The amount of bone deposition was greatest in ears treated with intracochlear neomycin (mean = 2.3835 mm2, SD = 3.7308). Surgical trauma alone (mean = 0.9549 mm2, SD = 1.384) and chronic implantation without stimulation did not produce substantial bone growth when compared to contralateral control ears (mean = 0.0574 mm2, SD = 0.0731). Fluorochrome labeling was also used to differentiate types of bone deposition. The morphology and timing of new bone growth appeared to be related to the type of cochlear injury. These results confirm that intracochlear neomycin may contribute to osteoneogenesis in animal studies of cochlear implantation. This study supports the use of fluorescent bone labeling in the evaluation of cochlear osteoneogenesis.
Animals↗
A review of the physical properties and biological effects of the high amplitude acoustic field used in extracorporeal lithotripsy.
Extracorporeal shockwave lithotripsy (ESWL) has now been used for more than a decade in the treatment of urinary stone disease. During this period there has been a wide range of studies on the physical properties of the high-amplitude focussed fields used in ESWL and the biological effects of exposure to such fields, including their ability to fragment hard concretions. These studies form a distinct body of knowledge whose relevance to the broader literature on biological effects from lower amplitude exposures has yet to be fully evaluated. This review attempts to present the main results of biological-effects studies in ESWL along with what is known of the physical properties of lithotripsy fields with the aim of assisting this evaluation. In general, the reported biological effects of lithotripsy fields are compatible with those that have been observed at those lower amplitudes of focussed pulsed ultrasound in which transient cavitation is the dominant mechanism of interaction. The relatively large amplitudes and low frequencies in ESWL, however, make it a more potent generator of transient cavitation than most other forms of medical ultrasound. Biological-effects studies with lithotripsy fields may, therefore, be expected to extend our understanding of the nature of transient cavitation and, in particular, its effects in mammalian tissue.
Acoustics↗
Unusual cerebello-pontine angle tumours.
Fifty-nine unusual cerebello-pontine angle tumours have been studied. These lesions represent 19.3 per cent or 1 in 5 of a series of 305 cerebello-pontine angle tumours of which the rest, 246 (80.7 per cent), were acoustic neuromas. An analysis of the relative incidence, histology and presenting clinical features has been carried out. The various radiographical features and imaging techniques used to diagnose these fascinating tumours have been described and also the otoneurosurgical procedures necessary to excise them.
Adolescent↗
The spatial distribution of cavitation induced acoustic emission, sonoluminescence and cell lysis in the field of a shock wave lithotripter.
This study examines the spatial distribution of various properties attributed to the cavitation field generated by a shock wave lithotripter. These properties include acoustic emission and sonoluminescence, which result from violent bubble collapse, and the degree of cell lysis in vitro, which appears to be related to cavitation. The acoustic emission detected with a 1 MHz, 12 cm diameter focused hydrophone occurs in two distinct bursts. The immediate signal is emitted from a small region contained within the 4 MPa peak negative pressure contour. A second, delayed, burst is emitted from a region extending further along the beam axis. The delay between these two bursts has also been mapped, and the longest delay occurs at positions close to the regions of maximum peak negative pressure. Sonoluminescence from both single and multiple shocks occurs in a broader region than the acoustic emission but the measurement technique does not allow time resolution of the signal. Cell lysis occurs in a relatively small region that correlates closely with the immediate acoustic emission for a shock propagating in a gelatine solution.
Acoustics↗
The influence of fluid properties and pulse amplitude on bubble dynamics in the field of a shock wave lithotripter.
This study concerns the radial dynamics of a bubble driven by pulsed ultrasound of the type generated during extracorporeal shock wave lithotripsy. In particular, a numerical model has been used to examine the sensitivity of the bubble oscillations to changes in both the amplitude of the driving field and the physical conditions of the fluid surrounding the bubble: viscosity, surface tension, temperature and gas content. It is shown that, at high negative pressures (p- = 10 MPa) as in lithotripsy, the timing and amplitude of bubble collapses have a considerably reduced sensitivity to the initial bubble size and all fluid parameters, except gas content, compared with those expected in lower-amplitude fields (p- = 0.2 MPa). This study indicates that, in the lithotripsy fields, the differences in the viscosity, surface tension and temperature of body fluids and the initial bubble size will have little effect on bubble dynamics compared with those expected in water.
Humans↗
Optical performance of decentered bifocal contact lenses.
Contact lenses frequently do not center over the pupil. The potential changes in optical performance introduced by poor centration of bifocal contact lenses have only been described previously from theoretical considerations. The present study measured the modulation transfer function (MTF) of rigid concentric-design refractive and rigid diffractive bifocal contact lenses with varying apertures and amounts of decentration. Decentration was shown to have a greater effect on the MTF of the refractive than on the MTF of the diffractive bifocals. The MTF of the refractive bifocals was related to the proportion of the aperture covered by the central optic zone (COZ). Unexpectedly, the MTF of the distance focus of the diffractive bifocal contact lenses was reduced at moderately high spatial frequencies. The practitioner should be aware of the effects of decentration of bifocal contact lenses.
Contact Lenses↗
Acoustic emission and sonoluminescence due to cavitation at the beam focus of an electrohydraulic shock wave lithotripter.
The acoustic emission from cavitation in the field of an extracorporeal shock wave lithotripter has been studied using a lead zirconate titanate piezoceramic (PC4) hydrophone in the form of a 100-mm diameter focused bowl of 120-mm focal length. With this hydrophone directed at the beam focus of an electrohydraulic lithotripter radiating into water, it is possible to identify signals well above the noise level, at the 1-MHz resonance of the hydrophone, which originate at the beam focus. Light emission, attributed to sonoluminescence, is also shown to originate at the focal region of the lithotripter, and the signal obtained from a fast photomultiplier tube directed at the focus has similarities in structure and timing to the detected acoustic signals. The multiple shock emission resulting from a single discharge of an electrohydraulic source is shown to result in two separate bursts of cavitational activity separated by a period of 3-4 ms. The signal burst corresponding to the primary shock has a duration of about 600 microseconds with little noticeable structure. The signal burst associated with the secondary shock has a reproducible structure with two distinct peaks separated by about 200 microseconds depending on the shock amplitude. THe timing and structure of each burst is shown to be in reasonable agreement with the theoretical predictions made by Church (1989) based on the Gilmore model of bubble dynamics. In particular, it is shown that it is possible to obtain precise measurements of the time delay between the separate peaks within the signal burst detected following the secondary shock and this may, as predicted, provide a method of determining the size of bubbles remaining after the primary shock.
Acoustics↗
Triple fluorochrome labeling of cochlear bone growth.
A new technique is described which measures the extent and time course of intracochlear bone formation after cochlear implantation in an experimental animal model. A series of fluorescent histochemical markers is used to delineate the amount of intracochlear bone deposition during specified time periods.
Animals↗
A comparison of three commercially available PET imaging systems.
Three commercial positron emission tomography (PET) imagers were assessed using the same test protocol (Positron Corporation 'Posicam', Siemens Ecat 951/31 and the Scanditronix PC 4096-15WB). A cylindrical phantom and a 'Jaszczak' phantom both filled with 18F were employed to measure sensitivity, slice uniformity, transaxial and axial resolution and cold rod contrast. The spread of results were as follows: sensitivity varied from 2.08 to 3.73 kcps kBq-1 ml-1 (77-138 kcps microCi-1 ml-1); radial resolution on axis (at 17.5 cm) varied from 5.0 to 5.9 mm (6.7-8.1 mm); tangential resolution ranged from 5.4 to 5.8 mm (6.7-8.6 mm); axial resolution ranged from 4.6 to 11.5 mm (6.6-13.6 mm); contrast in the middle of a 30 mm diameter rod varied from 98 to 93% and for a 5 mm rod from 37 to 22%. The performance of all three systems approximated reasonably well to the manufacturers' published specifications. The most significant differences were found to be in sensitivity, axial resolution and deadtime correction and can be explained by the choice of crystal size and crystal/photomultiplier configuration.
Evaluation Studies as Topic↗
Reconstruction of the radical mastoid.
Open cavity techniques (radical mastoidectomy, canal wall down tympanomastoidectomy, modified radical mastoidectomy) are well established surgical procedures for the treatment of chronic otitis media. Despite their effectiveness in exteriorizing cholesteatoma, they are associated with a 20 to 60 percent incidence of persistent intermittent drainage. In an effort to eliminate this problem, we have employed a Palva flap and medial graft technique to reconstruct the mastoid cavity and middle ear space in those patients with chronically draining ears. Between 1987 and 1990, 28 patients underwent this procedure. Twenty-six of these (93%) had complete obliteration of the mastoid cavity and successful tympanic membrane reconstruction. Two of 28 (7%) had a persistent tympanic membrane perforation and intermittent drainage following their surgery. Based on these results, this procedure is effective in eliminating intermittent drainage associated with the open cavity techniques. The indications for this procedure, the specifics of the surgical technique, and the postoperative results are discussed.
Adult↗
Theoretical predictions of the acoustic pressure generated by a shock wave lithotripter.
A one-dimensional frequency domain model is used to predict the temporal peak acoustic pressures developed near the beam focus during extracorporeal shock wave lithotripsy (ESWL). The model includes consideration of finite amplitude effects, attenuation, diffraction and dispersion, and results are presented for the case of an electrohydraulic source with the beam geometry of the Dornier HM3 lithotripter. Propagation in castor oil, water and tissue is examined. The model predicts that nonlinear effects enhance the peak positive pressure (p+) at the beam focus in 6 cm of tissue in a Dornier type lithotripter by a factor of about 3 above that which would be expected for linear propagation. The negative peak pressure (p-), conversely, is predicted to be depressed by a factor of about 0.7 below the linear theory prediction. The model also indicates the occurrence of excess absorption due to shock formation. This is shown, for a Dornier HM3 type lithotripter, to cause a reduction in the peak positive pressure gain and a broadening of the focal depth as the output of the source is increased. A threshold aperture pressure is identified for a source with the same beam geometry as the Dornier HM3 below which shock formation does not occur. In this region the pressure gain increases and the focal depth narrows as the source output increases. These effects are characteristic of current commercial piezoelectric and electromagnetic lithotripsy fields.
Humans↗
Lipomas of the internal auditory canal.
Intracranial lipomas are rare tumors which may occur in the cerebellopontine angle (CPA) or internal auditory canal (IAC). Although seemingly innocuous in other parts of the body, lipomas within the CPA and IAC often involve the surrounding cranial nerves, making attempts at hearing conservation largely unsuccessful. In an attempt to differentiate the IAC lipoma from the more commonly found acoustic schwannoma, the preoperative imaging studies (magnetic resonance and computerized tomography) on five previously unreported cases of IAC lipomas were evaluated. Based on these studies, features were determined that may allow the surgeon to diagnose IAC lipomas preoperatively. These features will be discussed, as well as the surgical and pathological findings.
Adult↗
Magnetic resonance angiography: technique and skull-base applications.
Cerebral angiography has become essential in the evaluation and management of extensive skull-base lesions. However, with a 2.6 percent incidence of neurologic complications and a 0.3 percent incidence of permanent neurologic deficits associated with cerebral angiography, the procedure is not without risk. Recent advances in magnetic resonance angiography (MRA), allow one to visualize the skull-base vasculature without need of intravenous contrast injection or radiation exposure. Our initial experience in visualizing the normal vascular anatomy and pathology at the base of skull with this new imaging modality is presented. Two different MRA techniques were used: (1) thin-slice two-dimensional gradient echo pulse sequence acquisition with three-dimensional projection reconstruction, and (2) two-dimensional phase contrast angiography. The specifics of these techniques and their usefulness in the evaluation of lesions involving the skull base are discussed and demonstrated.
Adult↗
Dosimetric intercomparison in the British Institute of Radiology fractionation study of 3F/week versus 5F/week in radiotherapy of laryngo-pharynx cancer.
A dose intercomparison was carried out by the National Physical Laboratory between the seven radiotherapy centres which contributed the largest number of patients to the British Institute of Radiology fractionation study of three fractions per week versus five fractions per week in clinical cancer treatment. Six of the centres showed remarkable agreement within the acceptable limits of error of the measurements. In one centre there appeared to be a physical dose discrepancy of 2.8% which was materially less than could be detected clinically.
Humans↗
A survey of the acoustic output of commercial extracorporeal shock wave lithotripters.
A survey of the pressures and intensities generated by different commercial extracorporeal shock wave (ESWL) lithotripters is reported. The lithotripters included in the survey are the Dornier HM3, Wolf Piezolith 2200 and 2300, Siemens Lithostar, Technomed Sonolith 2000 and 3000, and EDAP LT-01. Measurements were made using a polyvinylidene difluoride (PVdF) membrane hydrophone in water. The zero crossing frequency of one complete cycle of the focused pulse from ESWL equipment is in the range 0.1 to 1 MHz. Spatial-peak temporal-peak positive and negative pressures up to 114 MPa and 10 MPa, respectively, have been measured and the rise times of the positive pressure half cycle at maximum output settings are 30 ns or less. The mean spatial-peak temporal-average intensity of the lithotripters is 5.0 x 10(2) W m-2 when operated at a pulse repetition frequency of 1 Hz. The spatial-peak pulse-average intensity ranges from 6.6 x 10(7) to 1.24 x 10(9) W m-2. The estimated acoustic energy in a single pulse (at the focus) at the maximum output setting of the lithotripters varies from 2.0 x 10(-3) J to about 9.0 x 10(-2) J. The beam area in the focal plane varies by a factor of 100 on different lithotripters and the temporal-peak pressure at the position of the skin at the entry point of the beam by a factor of 30. Measurement problems associated with hydrophone damage and the uncertainties in the hydrophone calibration at high pressures are discussed and an estimate of the total uncertainty in the absolute measurements of the spatial-peak temporal-peak positive pressure is given as +/- 36%.
Acoustics↗
An experimental shock wave generator for lithotripsy studies.
An electrohydraulic shock wave generator has been constructed to facilitate investigation of the acoustic field generated during extracorporeal shock wave lithotripsy (ESWL). Pressure waveforms at the generator aperture and the beam focus, measured using a PVDF needle hydrophone, are compared with those from a commercial lithotripter, the Dornier HM3.
Acoustics↗