Biomedical subjects

P Rustemeyer

Publications and source records attributed to P Rustemeyer.

5 recordsLinked to original sources

PubMed2006

Mechanical response of cervical vertebral endplates to axial loading.

OBJECTIVE: After anterior cervical discectomy the implantation of a spacer is common practice. The majority of these spacers are trapezoid titanium cages. During the development of a height-adjustable cervical implant we needed to establish the testing limits for this device. A known phenomenon is subsidence of the cage into the vertebral endplates, which leads to a decrease in height and/or angulation of the cervical spinal segment. In contrast to the thoracic and lumbar spines, there are only limited data concerning the load-bearing ability of cervical endplates. The aim of our investigation was to obtain these data. METHODS: Bone density of 16 cervical vertebrae was estimated by quantitative computed tomography. After embedding of the vertebrae into PMMA, each endplate was slowly compressed until failure using a metal indenter resembling the form of a newly developed cervical implant. A fixed protocol with increasing loading cycles was followed. Endpoint was breakage of the endplate as established by failure to resist the increasing loading forces produced by the testing machine. RESULTS: The mean bone density of the 16 cervical vertebrae was 204 with a standard deviation of 52 mg Ca-HA/mL (range 130-281). The endplates failed with a mean loading of 1084 N +/- 314 (range 340-1550 N). The maximum load correlates with the bone density (R2 = 0.7347). With the 97.79 mm2 load bearing surface of the cage we calculate a mean cervical endplate break strength of 10.47 MPa and a 95 % confidence interval of 12.66-9.51 MPa. An initial settling produced by resting of the anchoring teeth in the cervical endplates was observed in 8 vertebrae at a load of 113 N (range 50-250 N). CONCLUSIONS: In contrast to the thoracic and lumbar spines, cervical endplates show a lower resistance against axial forces. The data are important to understand postoperative cage subsidence and to establish testing limits for the development of new implant designs.

Biomechanical Phenomena↗

PubMed2004

Low-dose dental computed tomography: significant dose reduction without loss of image quality.

PURPOSE: To measure and reduce the patient dose during computed tomography (CT) for dental applications. MATERIAL AND METHODS: Lithium fluoride thermoluminescent dosimeters were implanted in a tissue-equivalent humanoid phantom (Alderson-Rando-Phantom) to determine doses to the thyroid gland, the active bone marrow, the salivary glands, and the eye lens. Dental CT was performed with spiral CT and a dental software package. The usual dental CT technique was compared with a new dose-reduced protocol, which delivered best image quality at lowest possible radiation dose, as tested in a preceding study. Image quality was analysed using a human anatomic head preparation. In addition, the radiation dose was compared with panoramic radiography and digital volume tomography (DVT). Eight radiologists evaluated all images in a blinded fashion. A Wilcoxon rank pair test was used for statistical evaluation. RESULTS: Radiation dose could be reduced by a factor of 9 (max.) with the new dose-reduced protocol (e.g. bone marrow dose from 23.6 mSv to 2.9 mSv; eye lens from 0.5 mSv to 0.3 mSv; thyroid gland from 2.5 mSv to 0.5 mSv; parotid glands from 2.3 mSv to 0.4 mSv). Dose reduction did not reduce image quality or diagnostic information. CONCLUSION: A considerable dose reduction without loss of diagnostic information is achievable in dental CT. As radiation exposure of the presented low-dose protocol is expected to be in the same range as DVT, low-dose dental CT might be superior to DVT, because CT can be used to evaluate soft tissues as well.

Phantoms, Imaging↗

PubMed1999

[Low-dosage dental CT].

PURPOSE: The intention of this study was to reduce patient dose during dental CT in the planning for osseointegrated implants. METHODS AND MATERIALS: Dental CTs were performed with a spiral CT (Somatom Plus 4, Siemens) and a dental software package. Use of the usual dental CT technique [1] (120 kVp; 165 mA, 1 s rotation time, 165 mAs; pitch factor 1) was compared with a new protocol (120 kVp; 50 mA; 0.7 s rotation time; 35 mAs; pitch factor 2) which delivered the best image quality at the lowest possible radiation dose, as tested in a preceding study. Image quality was analysed using a human anatomic head preparation. Four radiologists analysed the images independently. A Wilcoxon rank pair-test was used for statistic evaluation. The doses to the thyroid gland, the active bone marrow, the salivary glands, and the eye lens were determined in a tissue-equivalent phantom (Alderson-Rando Phantom) with lithium fluoride thermoluminescent dosimeters at the appropriate locations. RESULTS: By mAs reduction from 165 to 35 and using a pitch factor of 2, the radiation dose could be reduced by a factor of nine (max.) (e.g., the bone marrow dose could be reduced from 23.6 mSv to 2.9 mSv, eye lens from 0.5 mSv to 0.3 mSv, thyroid gland from 2.5 mSv to 0.5 mSv, parotid glands from 2.3 mSv to 0.4 mSv). The dose reduction did not lead to an actual loss of image quality or diagnostic information. CONCLUSION: A considerable dose reduction without loss of diagnostic information is achievable in dental CT. Dose-reducing examination protocols like the one presented may further expand the use of preoperative dental CT.

Humans↗

PubMed1997

Radiation-induced malignant mesenchymoma of the chest wall following treatment for breast cancer.

21 years after radiotherapy for breast cancer, a 63-year-old woman developed a malignant mesenchymoma of the chest wall. The total irradiation dose was 132 Gy. The first clinical symptom of this second malignancy was a slight irregular calcification around the implanted silicon protheses observed in a conventional chest X-ray. Radiation-induced sarcoma is a very rare complication of radiotherapy. In cases of chest wall calcification after radiation therapy further investigation should be carried out, because some patients with radiation-induced sarcoma could be saved, if an early diagnosis is reached.

Adult↗

PubMed1989

[Mild forms of alcoholic embryopathy following excessive use of alcohol].

Within 15 years 171 children with fetal alcohol syndrome were diagnosed. Eight children showed an unusual low susceptibility to the harmful effects of alcohol in utero with mild expression of fetal alcohol syndrome or so-called alcohol effects, inspite of excessive maternal drinking (more than 180 gs alcohol per day). Increased tolerance of alcohol might be explained by two mechanisms: 1. By metabolic adaptation, mainly by swift increase of alcohol metabolizing; 2. by biochemical and structural adaptation at cellular membranes after chronic alcohol ingestion. The grade of severity in fetal alcohol syndrome does not depend on the amounts of alcohol but mainly on the development of metabolic and morphological tolerance and adaptation.

Adolescent↗