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Biomedical subjects

R Bays

Publications and source records attributed to R Bays.

10 recordsLinked to original sources
PubMed1999

Condylar position with rigid fixation versus wire osteosynthesis of a sagittal split advancement.

PURPOSE: In this randomized clinical study, two groups of patients who underwent a bilateral sagittal split osteotomy and either wire osteosynthesis or rigid fixation were compared. PATIENTS AND METHODS: Cephalometric radiographs obtained before surgery, immediately after surgery, and at 8 weeks, 6 months, and 1 and 2 years after surgery were available for 125 of these patients, 63 with wire fixation and 62 with rigid fixation. All were traced by an independent examiner, and vertical and horizontal changes in condylar position were recorded for each period. RESULTS: Condylar movement was slightly different with the two fixation techniques beyond 8 weeks postsurgery, but the ultimate position of the condyle was not different. The condyles in both groups moved posterior and superior. There initially was a correlation between the amount of advancement and the amount the condyle moved inferior in both groups, but this diminished with time. In addition, there was a weak but significant positive relationship between forward rotation of the proximal segment and superior condylar position immediately after surgery, which did not exist at later periods. CONCLUSIONS: Whether wire osteosynthesis or rigid fixation was used, the ultimate condylar position was posterior and superior after a bilateral sagittal split osteotomy to advance the mandible. No single factor could be identified to account for this change. It is suggested that change in mechanical load may have resulted in remodeling and adaptation of the condyles.

Adolescent↗
PubMed1997

Light dosimetry for photodynamic therapy in the esophagus.

BACKGROUND AND OBJECTIVE: Photodynamic therapy (PDT) is an efficient technique to treat superficial early cancers in the pharynx, esophagus, and tracheo-bronchial tree. However, the lack of selectivity of some of the clinically used photosensitizers can result in significant damage to the healthy tissue during the treatment. In the esophagus, this may lead to medical complications such as stenosis and fistula. Insufficient selectivity may be compensated to some extent by accurate light dosimetry. Here, we present an approach to safer and more efficient PDT by improved light dosimetry in the esophagus. STUDY DESIGN/MATERIALS AND METHODS: This includes the utilization of a suitable light distributor, the estimation of the radiant energy density in the tissue, and the knowledge of the esophagus morphology. The light distributor presently used in the clinic is described and several techniques to study light propagation in the esophageal wall have been investigated and are discussed. Thickness of different histological layers of the esophageal wall have been measured ex vivo and are presented. RESULTS: Under these conditions and based on a simple model of the light distribution in the tissue, some basic and clinically useful notions of light dosimetry can be drawn. These notions, associated with measured value of tissue optical properties at the wavelengths of interest with the presently used photosensitizers, are discussed regarding the particular morphology of the esophageal wall. In particular, the importance of the illumination wavelength from the safety point of view is shown. CONCLUSION: The proposed approach allows for improved safety and efficacy of PDT in the esophagus, particularly in the clinical tests of new photosensitizers.

Esophagus↗
PubMed1997

Three-dimensional optical phantom and its application in photodynamic therapy.

BACKGROUND AND OBJECTIVE: A technique to manufacture a stable, reproducible three-dimensional optical phantom is presented. This phantom reproduces the tissue's optical properties as well as the geometry and, to some extent, the mechanical properties of the organ concerned. Easy to make and to handle, this phantom is a useful tool for numerous medical applications involving light interaction with biological tissues. STUDY DESIGN/MATERIALS AND METHODS: The phantom is based on a transparent two-component silicone, which is molded into the desired shape and cured at room temperature. Specific optical properties are obtained by adding scatterers (Al2O3 particles or polystyrene microspheres) and absorbers (dyes or pigments). A method to measure the radiant energy fluence rate in the phantom is described. This method is based on a small isotropic optical detector. RESULTS: A three-dimensional phantom of the bronchial tree is presented. This phantom is used for testing new light distributors designed for photodynamic therapy of the bronchi. CONCLUSION: The proposed technique allows one to produce a stable three-dimensional phantom with accurately predictable optical properties.

Equipment Design↗
PubMed1995

Clinical pharmacokinetic studies of photofrin by fluorescence spectroscopy in the oral cavity, the esophagus, and the bronchi.

BACKGROUND: To optimize photodynamic therapy (PDT) and photodetection of cancer, two important variables that must be considered are the uptake of the dye and the dye contrast between normal and neoplastic tissue after injection. METHODS: To study these variables in a clinical context, an apparatus based on a noninvasive optical fiber that detects the dye by light-induced fluorescence (LIF) was constructed. RESULTS: Studies on the pharmacokinetics of the fluorescent fraction of Photofrin in patients with early squamous cell carcinoma in the oral cavity, esophagus or bronchi show a signal contrast ranging from 1.5 to 3.5 a short time after intravenous injection that rapidly decreases and tends to unity (one) about 12 hours later. The magnitude of this contrast appears to correlate with the staging of the cancer, the more invasive tumors showing the highest contrast. The more invasive tumors also show the highest uptake. The oral cavity pharmacokinetics are similar to those found in the esophagus and the bronchi. CONCLUSIONS: The oral cavity appears to be a good model, with easy access for optimizing photodetection and PDT in the esophagus and the bronchi. These pharmacokinetics can be used directly for optimizing photodetection. However, complementary information on the detailed localization of the drug by fluorescence microscopy and a correlation of these data with tumor necrosis efficacy are necessary to optimize PDT timing and therapeutic gain.

Adult↗
PubMed1993

Abdominal duplex ultrasound screening for occult aortic aneurysm during carotid arterial evaluation.

PURPOSE: The purpose of this study was to investigate the use of a modified abdominal ultrasound examination, which was performed at the time of routine diagnostic carotid artery duplex evaluation, to identify patients at risk for aortic aneurysms. METHODS: A prospective study was undertaken that consisted of a limited ultrasound examination of the abdominal aorta on patients referred to our facilities for duplex carotid evaluation. One hundred thirty-one patients were included in the study; 52% were men and 48% were women, who ranged in age between 40 to 93 years. These patients were not known or suspected to have an abdominal aortic aneurysm. RESULTS: Eleven infrarenal aortic aneurysms (8.4%) were detected, four in patients with positive carotid studies (11%) and seven in those with negative studies (7%); size ranged from 3.0 to 7.5 cm. Categoric data analysis did not produce significance, but a stepwise regression and discriminant analysis model revealed a significant relationship between abnormal velocities and occlusive changes in the carotid arteries and the presence of aortic aneurysms. CONCLUSIONS: Hemodynamically significant carotid artery disease, as diagnosed by duplex examination, appears to be a definite marker for an increased incidence of abdominal aortic aneurysm when compared with the general population. When selective abdominal aortic ultrasonography is done in conjunction with the carotid study, the requirements of additional equipment and technologist time are modest, and the potential benefit to the patient may be significant.

Adult↗
PubMed1990

Synovial chondromatosis with intracranial extension. A case report.

A case of unilateral synovial chondromatosis of the temporomandibular joint with intracranial extension is presented. Extracapsular extension of these lesions is rare, and few cases have previously been reported. The case presentation will also reflect the inadequacy of routine preoperative temporomandibular joint x-ray films to reflect the extent of the lesion. Despite the benign nature of the lesion, excision was done because of the clinical aggressive behavior.

Bone Diseases↗
PubMed1988

Osteoarthrosis of the temporomandibular joint following experimental disc perforation in Macaca fascicularis.

The aim of this experiment was to study the sequela of experimental temporomandibular joint (TMJ) disc perforation. Each TMJ of four Macaca fascicularis adult monkeys was surgically exposed, and a 4- to 6-mm perforation at the posterolateral portion of the avascular disc was produced by electrosurgery. Four monkeys were used as controls. The animals were killed 11 weeks (two experimental and two controls) or 12 weeks (two experimental and two controls) after disc perforation. The perforations were increased in size in five joints, and healed in one joint. In addition, two joints of one animal showed complete loss of the disc, denudation of articular surfaces, and bone-to-bone contact. In contrast to control joints, the experimental joints exhibited the following changes histopathologically: thick, highly cellular and fibrillated fibrous coverings of articular surfaces (five joints); marked hyperplasia of synovial membrane; migration of synovial cells on the surfaces of the disc and margins of perforation; multiple adhesions of disc to articular surfaces; increase in cellularity and vascularity of discs; and chondrocytic clustering in temporal fibrous covering; and osteophytes of condylar and temporal components and focal or complete denudation of articular surfaces (2 joints). Most of these changes were consistent with the diagnosis of osteoarthritis. From this study, one can conclude that disc perforation can lead to osteoarthritis.

Animals↗
PubMed1981

Neurological toxicity of vindesine used in combination chemotherapy of 51 human solid tumors.

The authors treated 51 patients with solid tumours with vindesine 4 mg/m2, generally every third week, in combination chemotherapy protocols scheduled according to diurnal variability of kinetics. No dose-related sensory disorders were observed: On the contrary, motor toxicity appeared cumulative: 1) Early depression of osteotendinous reflexes from the first course onward, with progressive deterioration. No more normal reflexes could be evoked after 55 mg; 2) Early appearance of neurogenic pattern in the electromyograph after 5-10 mg. Progressive alteration with no normal detection recordings after 45 mg; 3) Late slowing down of conduction speeds (normal in 50% of cases up to 55-60 mg). Improvement or even complete recovery of neuropathy was documented following reduction of the unit dose, increased time interval between doses, or discontinuation of the treatment. The drug had to be withheld in only three patients: in two cases a low dosage related to individual sensitivity was being used.

Adult↗