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R Beck

Publications and source records attributed to R Beck.

209 records · Page 12Linked to original sources
PubMedDate not supplied

Electromagnetic phased arrays for regional hyperthermia: optimal frequency and antenna arrangement.

This paper investigates the effects of the three-dimensional arrangement of antennae and frequency on temperature distributions that can be achieved in regional hyperthermia using an electromagnetic phased array. It compares the results of power-based and temperature-based optimization. Thus, one is able to explain the discrepancies between previous studies favouring more antenna rings on the one hand and more antennae per ring on the other hand. The sensitivity of the results is analysed with respect to changes in amplitudes and phases, as well as patient position. This analysis can be used for different purposes. First, it provides additional criteria for selecting the optimal frequency. Secondly, it can be used for specifying the required phase and amplitude accuracy for a real phased array system. Furthermore, it may serve as a basis for technological developments in order to reduce both types of sensitivities described above.

Electromagnetic Fields↗
PubMedDate not supplied

Gd-DTPA enhanced MR imaging of the breast in patients with postoperative scarring and silicon implants.

Sixty patients with postoperative scarring with (30) or without (30) silicon implants have been examined by magnetic resonance (MR) with Gd-diethylenetriamine pentaacetic acid. The 60 patients consisted of 28 patients with obvious normal or abnormal findings and of 32 diagnostically difficult patients, who were referred to MR because of uncertain mammographic and/or clinical findings. Scarring older than 6 months postoperatively did not enhance noticeably, whereas scarring younger than 6 months postoperatively enhanced variably (nonsignificant, borderline, or significant). Since all carcinomas larger than the slice thickness enhance significantly (as also confirmed by other studies) contrast enhanced MR allowed an excellent discrimination between scarring older than 6 months and malignancy. Good visualization of the tissue around silicon implants proved to be another advantage of MR. When its use in the diagnostically difficult cases was analyzed, MR proved quite helpful in 23 of 32 cases by excluding or demonstrating malignancy.

Biopsy↗
PubMedDate not supplied

Contrast-enhanced MRI of the breast after limited surgery and radiation therapy.

OBJECTIVE: Posttherapeutic changes in the breast after tumorectomy (TE) and radiation therapy (RT) may mimic or obscure recurrent or new malignancies and thus interfere with conventional diagnostic studies. We investigated the enhancement of tissue during variable time intervals after therapy with contrast-enhanced MRI in 62 patients. MATERIALS AND METHODS: We report the results of 77 studies in 62 patients undergoing TE and RT. We include only those studies with at least 24 months of clinical and mammographic follow-up (n = 60) or histopathologic results (n = 17). RESULTS: Up to 9 months after therapy, differentiation between posttherapeutic changes and recurrence was frequently impossible because of the strong enhancement. Ten to 18 months after therapy, this posttherapeutic enhancement subsided slowly with some interindividual variations. After 18 months posttherapy, no significant enhancement was encountered in 30 of 32 cases. Diffuse or focal enhancement was present in all recurrent tumors and all recurrences were correctly diagnosed. Furthermore, 4 of 11 recurrences and 10 of 18 single recurrent foci were detected by MR alone, based on focal enhancement. CONCLUSION: Accordingly, contrast-enhanced MR is not recommended during the first 9 months after therapy. Nine to 18 months after therapy, it may be helpful in those two-thirds of cases where the scar does not enhance. If enhancement takes place (one-third of cases), it may represent either scar or tumor, and in such circumstances, enhanced MR is of no value. After 18 months, enhanced MRI has proven a valuable additional tool. By correctly detecting or excluding recurrent tumor, it can significantly improve diagnostic accuracy.

Breast↗
PubMedDate not supplied

Time-series designs in clinical nursing research: human issues.

Prospective time-series research methods require substantially greater commitment and effort from both subjects and investigators compared to designs that involve one-time data collection. Human issues such as retention, confidentiality, burnout, and clinician-researcher role conflict have not been adequately addressed in existing literature on time-series methodology. To maintain the scientific integrity of a time-series design and minimize unnecessary costs associated with subject and staff attrition, these issues should not be overlooked.

Adult↗
PubMedDate not supplied

Design and development of a new 193-nanometer excimer laser surgical system.

BACKGROUND: The 193-nanometer excimer laser is used for photoablative reprofiling of the cornea to correct refraction errors and to treat corneal pathologies. To use the unique properties of the excimer laser, some technical features should be provided by the excimer laser system. A new excimer laser system is presented. METHODS: The instrument has a fluence sensor for precise measurement of the actual fluence just before surgery, a new delivery system including an integrator system to homogenize the laser beam, a steelband with apertures and a zoom optic to get the desired form of central reprofiling, and an alignment system to reduce the possibility to decenter the optical zone. RESULTS: The fluence before surgery can be measured very precisely with the fluence sensor. The ablation zone size is at least 8 mm in diameter with a homogenous laser beam profile resulting in a smooth surface of the treated material. Different forms of ablations can be created using the steelband with different forms of apertures. The center of the ablation zone can be found using the alignment system. CONCLUSION: The new excimer laser system fulfills some important technical features for optimal use of the excimer laser in corneal surgery.

Cornea↗
PubMedDate not supplied

[Effects of decreasing sick leave benefits--results of a survey of Social Health Insurance members].

In Germany, a sick employee usually continues to get his wages from his employer for six weeks either in full or reduced. After that period, he only receives "sick benefit payments" (so-called Krankengeld) from the statutory bodies, which, up to 31 December 1996, amounted to 80% of his original gross wage earnings. This has been cut down to 70% of the gross wage earnings effective 1 January 1997. The purpose of this study was to assess the consequences of this general cutdown of sick benefits. A standardised questionnaire was posted to a total of 7,036 female recipients of sick benefit who were members of a South German statutory health insurance body and who resided in various parts of Germany (membership as on 17 December 1996). 2,416 completed questionnaires were returned by 19 February 1997 (= 34.9%). The average daily sick benefit payment dropped from DM 91.95 in December 1996 to DM 82.39 in January 1997, which is equivalent to a sick benefit payment reduction by 10.4 per cent. The average extra cost caused by the illness and not covered by sick benefit amounted to DM 152 per month; one-quarter of the questioned patients were even compelled to pay DM 200 per month extra from their own pocket. Sick benefit recipients must accept a very substantial real monthly income loss. The average income of an employee who is ill for more than 6 weeks is more than a quarter below that of a healthy employee. 78.5% of the questioned persons rated the financial burden and privations caused by the sick benefit cutdown as "extremely heavy" or "considerable". It became evident that the majority of the female patients receiving sick benefit were chronically ill (62.6%). The most frequently reported diseases were diseases of the spine (30.3%) and joints (16.3%), injuries and accidents (14%) and psychiatric illnesses (8.5%). The results of the survey show that the political motive underlying the attempted modification of illness behaviour by means of economic incentives to be healthy, is far removed from reality, for the cutdown of sickness benefit severely affects a group of gainfully employed persons who are in the midst of a deep existential crisis and sorely in need of extensive physical and mental support. From the sociomedical aspect the sick benefit cutdown is highly problematical as far as this group of persons is concerned, since recovery and cure are impeded by measures that lower the status and are experienced as punitive.

Adolescent↗