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At least 631 records · Page 35Linked to original sources
PubMed2001

Platelet concentration and its effect on bone formation in calvarial defects: an experimental study in rabbits.

STATEMENT OF PROBLEM: The use of the platelet concentration technique is widespread in dental implant surgery. However, its effect or mechanism is not clearly understood. PURPOSE: This study introduced an animal model for the platelet concentration technique and evaluated its effect on bone formation with natural cancellous bovine bone mineral. MATERIAL AND METHODS: Adult New Zealand white rabbits were used as the animal model. A density gradient medium was used to obtain a constant platelet count for the preparation of platelet concentrates. In the experimental group, natural cancellous bovine bone mineral with added platelet concentrates was grafted onto critically sized bony defects of the rabbit calvarium. Bone formation in the tissue sections was evaluated with soft x-ray imaging and computer tomography. RESULTS: The average platelet count of the rabbit platelet concentrates was 1487 x 10(3)/microL (287% concentrated). In all the tested parameters, greater bone densities were obtained in grafts that were combined with platelet concentrates. CONCLUSION: This study showed that the rabbit is a useful animal model for studying the platelet concentration technique. When combined with grafts of natural cancellous bovine bone mineral, the technique increased bone formation.

Anatomy, Cross-Sectional↗
PubMed1990

Thyroid carcinoma metastatic to the medial rectus muscle.

Isolated extraocular muscle metastasis is rare and is unreported for thyroid carcinoma. The authors describe a 72-year old man who presented with pain, redness, and proptosis of the right eye. Orbital computed tomography showed a large fusiform soft tissue mass along the medial aspect of the right orbit, involving the medial rectus. Orbital exploration disclosed a mass within the medial rectus muscle sheath involving the muscle belly. Histopathologic examination including electron microscopy, revealed metastatic thyroid carcinoma. Systemic treatment with radioactive iodine was recommended and refused by the patient. One year later, he died of complications from his metastatic disease.

Adenocarcinoma↗
PubMed1992

Progressive soft tissue uptake of Tc-99m MDP reflecting metastatic microcalcification.

A 49-year-old woman had longstanding renal impairment. Markedly increased uptake of Tc-99m MDP in the heart, lungs, and kidneys was an incidental finding on bone scintigraphy performed to exclude metastatic bone disease. These findings persisted on repeat bone imaging 1 year later. In addition, gastric and skeletal muscle uptake was subsequently seen. Soft tissue microcalcification was confirmed by computed tomography and renal biopsy. A consideration of the differential diagnosis is presented.

Bone Neoplasms↗
PubMed2002

Bilateral squamous cell carcinoma of the external auditory canals.

OBJECTIVES: To report a case of bilateral squamous cell carcinoma of the external auditory canals and to present a management algorithm for this difficult clinical scenario. STUDY DESIGN: Case report and literature review. METHODS: The study comprises a case report of a 69-year-old man who initially presented with complaints of bilateral otorrhea, left-sided otalgia, and a left-sided hearing loss. Following attempted treatment of a presumed case of otitis externa, biopsy of both external auditory canals revealed squamous cell carcinoma. A computed tomography scan demonstrated marked abnormal soft tissue in the left external auditory canal with no bony erosion and thickening of the soft tissue in the right external auditory canal. RESULTS: The left-sided lesion required a lateral temporal bone resection, a partial superficial and deep-lobe parotidectomy, and postoperative irradiation. The right-sided lesion was more limited and was managed with a lateral temporal bone resection and tympanoplasty for hearing preservation. CONCLUSIONS: Bilateral squamous cell carcinoma of the external auditory canals is an extremely uncommon but aggressive malignancy that may present with symptoms similar to a case of otitis externa, and this can result in delays in proper diagnosis. Early recognition is essential because management and prognosis are determined by the extent of the lesion.

Aged↗
PubMed2004

Isolated plexiform neurofibroma: treatment with three-dimensional conformal radiotherapy.

OBJECTIVES: To present a case of an unusual benign tumor of the tongue treated successfully with radiotherapy. STUDY DESIGN: Case report. METHODS: Retrospective chart review. RESULTS: A 60-year-old man presented with a painful submucosal lesion of the tongue base. Computed tomography showed an infiltrative soft-tissue mass involving the left base of the tongue. Operative biopsy revealed plexiform neurofibroma. Because of the patient's operative risk and the potential morbidity of surgical resection, he was treated with three-dimensional conformal radiotherapy (3DCRT). His treatment was accomplished using a five-field arrangement treating exclusively the mass lesion to a total tumor dose of 60 Gy. After treatment, the patient's tongue pain resolved, and he noted minimal transient xerostomia. Serial follow-up radiographic examinations showed the base of tongue mass to be slightly smaller 4 months after treatment. The most recent follow-up magnetic resonance image reveals a further decrease in size of the mass. The patient is now over 3 years out from treatment. CONCLUSIONS: Solitary plexiform neurofibroma of the tongue base is a rare tumor. These benign neoplasms are usually treated with either observation or surgical excision. This case demonstrates that, when significant symptoms necessitate active management, these lesions may be successfully treated with minimal morbidity using 3DCRT. The ability of this technique to deliver a conformal radiation dose to the tumor volume while sparing the surrounding normal tissues may expand the application of radiotherapy in the treatment of these benign lesions of the head and neck.

Biopsy↗
PubMed1999

Folding a protein by discretizing its backbone torsional dynamics.

The aim of this work is to provide a coarse codification of local conformational constraints associated with each folding motif of a peptide chain in order to obtain a rough solution to the protein folding problem. This is accomplished by implementing a discretized version of the soft-mode dynamics on a personal computer (PC). Our algorithm mimics a parallel process as it evaluates concurrent folding possibilities by pattern recognition. It may be implemented in a PC as a sequence of perturbation-translation-renormalization (p-t-r) cycles performed on a matrix of local topological constraints (LTM). This requires suitable representational tools and a periodic quenching of the dynamics required for renormalization. We introduce a description of the peptide chain based on a local discrete variable the values of which label the basins of attraction of the Ramachandran map for each residue. Thus, the local variable indicates the basin in which the torsional coordinates of each residue lie at a given time. In addition, a coding of local topological constraints associated with each secondary and tertiary structural motif is introduced. Our treatment enables us to adopt a computation time step of 81 ps, a value far larger than hydrodynamic drag time scales. Folding pathways are resolved as transitions between patterns of locally encoded structural signals that change within the 10 micros-100 ms time scale range. These coarse folding pathways are generated by the periodic search for structural patterns in the time-evolving LTM. Each pattern is recorded as a contact matrix, an operation subject to a renormalization feedback loop. The validity of our approach is tested vis-a-vis experimentally-probed folding pathways eventually generating tertiary interactions in proteins which recover their active structure under in vitro renaturation conditions. As an illustration, we focus on determining significant folding intermediates and late kinetic bottlenecks that occur within the first 10 ms of the bovine pancreatic trypsin inhibitor renaturation process. The probed cooperativity and nucleation effects, as well as diffusion-collision stabilization of secondary structure are shown to result from the persistence of relatively stable patterns through successive (p-t-r) cycles, thus acting as seeding patterns for further growth or hierarchical development.

Algorithms↗
PubMed2002

Approach to quantify the mechanical behavior of the intact embryonic chick heart.

The heart undergoes remarkable changes during embryonic development due to genetic programing and epigenetic influences such as mechanical loads. An important goal is to develop mathematical models that describe and predict the influence of mechanics on cardiac development, yet the data needed to develop such models remain scant. In particular, prior data from embryonic hearts have come from one-dimensional tests, which reveal well the general characteristic behaviors but are not sufficient for quantifying the complex material behavior exhibited by most soft tissues. We developed a computer-controlled system for quantifying in vitro the multiaxial, regionally dependent mechanical response of the intact embryonic chick heart to controlled distension pressures; such tests have not been accomplished heretofore but promise to contribute to our understanding for they better mimic the native loading conditions and geometry. Calibration of the device indicated that distending the hearts using low flow rates avoids significant viscous losses and thereby allows pressure to be measured directly over small ranges (0-2 mmHg) with good resolution (0.01 mm Hg). Likewise, an on-line video system allows two-dimensional strains to be measured regionally by tracking the motions of triplets of closely spaced (100 microm) microspheres to reasonable resolution (2.5 microm/pixel). Illustrative data from 18 hearts show the utility of the new system, confirm previous findings with regard to the strong viscoelastic response of the stage 18 embryonic chick heart, and provide guidance for the design of future experiments.

Animals↗
PubMed2001

A dose texture plot in a moving frame as a new planning tool for single-plane implants in HDR brachytherapy.

A dose-texture plot is a print of dose values on the points of interest in a super-plane. The super-plane is a moving frame across the treatment depth-surface(s) with a fixed distance from surgical bed. The moving frame has an axis tangent to the midline of two neighboring catheters and the other axis perpendicular to the midline. By setting the scales of the two axes in units of the dwell step-size and the local distance between the two catheters, we can easily locate the basal-dose points with pairs of integers. A dose-texture plot on the basal-dose points in the super-plane provides the dose and location information in one picture. Such a picture can concisely represent the dose distribution in the treatment depth and allows us to quickly and quantitatively evaluate the effect of the source-dwell times and positions. This treatment-planning-evaluation tool has been used for development of an iteration optimization algorithm. The results of the iteration optimization on clinical cases demonstrated significant improvements over the optimization algorithms used in a commercial planning system.

Algorithms↗
PubMed2004

Development of a laser photothermoacoustic frequency-swept system for subsurface imaging: theory and experiment.

In conventional biomedical photoacoustic imaging systems, a pulsed laser is used to generate time-of-flight acoustic information of the subsurface features. This paper reports the theoretical and experimental development of a new frequency-domain (FD) photo-thermo-acoustic (PTA) principle featuring frequency sweep (chirp) and heterodyne modulation and lock-in detection of a continuous-wave laser source at 1064 nm wavelength. PTA imaging is a promising new technique which is being developed to detect tumor masses in turbid biological tissue. Owing to the linear relationship between the depth of acoustic signal generation and the delay time of signal arrival to the transducer, information specific to a particular depth can be associated with a particular frequency in the chirp signal. Scanning laser modulation with a linear frequency sweep method preserves the depth-to-delay time linearity and recovers FD-PTA signals from a range of depths. Preliminary results performed on rubber samples and solid tissue phantoms indicate that the FD-PTA technique has the potential to be a reliable tool for biomedical depth-profilometric imaging.

Acoustics↗
PubMed1996

A higher order Bayesian neural network with spiking units.

We treat a Bayesian confidence propagation neural network, primarily in a classifier context. The one-layer version of the network implements a naive Bayesian classifier, which requires the input attributes to be independent. This limitation is overcome by a higher order network. The higher order Bayesian neural network is evaluated on a real world task of diagnosing a telephone exchange computer. By introducing stochastic spiking units, and soft interval coding, it is also possible to handle uncertain as well as continuous valued inputs.

Action Potentials↗
PubMed1986

Temporal bone region: high-resolution MR imaging using surface coils.

Specially designed surface coils for the region of the temporal bone enable high-resolution magnetic resonance (MR) imaging of the structures of the inner ear. Eight healthy volunteers and 21 patients (six with cholesteatomas, five with acoustic neuromas, five with glomus tumors, and five with mastoiditis) were examined using a 0.5-T MR imager. The demarcation of tumor extent with MR imaging was better than with computed tomography because of improved soft-tissue contrast and because the surrounding bony tissue did not generate any signal. High-resolution MR imaging is particularly useful for small acoustic neuromas because of its higher specificity compared with gas cisternography.

Brain Neoplasms↗
PubMed1990

Acute experimental osteomyelitis and abscesses: detection with MR imaging versus CT.

Acute experimental osteomyelitis and abscesses were induced in the proximal tibia and surrounding soft tissues, respectively, in 67 New Zealand white rabbits. Fifty-three rabbits were injected with a Staphylococcus aureus solution and 26, with sterile saline in tibial medullae and/or surrounding soft tissues. Contrast material-enhanced computed tomography (CT) and magnetic resonance (MR) imaging were performed 7 days after inoculation. Immediately after imaging, the animals were killed and necropsy was performed. MR imaging was more sensitive than CT in the detection of osteomyelitis (94% vs 66%, P less than .025) and abscesses (97% vs 52%, P less than .001). MR imaging was equally specific as CT in the exclusion of osteomyelitis (93% vs 97%, chi 2 = 0) but less specific than CT in the exclusion of abscesses (77% vs 100%, P less than .025). The overall accuracy of MR imaging was somewhat, although not significantly, greater than that of CT in the detection of both osteomyelitis (93% vs 80%) and abscesses (87% vs 75%).

Abscess↗
PubMedDate not supplied

Posttraumatic benign pleomorphic adenoma of the lacrimal gland.

A 55-year-old man presented with a painless and slowly developing mass in the right superior lateral eyelid region. He had sustained periorbital blunt injury about 4 years previously. The mass was observed several months later in the persisting traumatic tumefaction region. Computed tomography showed a cystic soft-tissue mass with central low density and peripheral enhancement over the upper anterior quadrant of the right orbit. Lateral orbitotomy was performed to remove the lesion. Histopathologic examination showed proliferation of epithelial and myoepithelial cells arranged in ductules and nests in the myxoid stroma. Benign pleomorphic adenoma of the lacrimal gland associated with traumatic tumefaction, as demonstrated in our patient, may be rare.

Adenoma↗
PubMed1989

[Olfactory neuroblastoma with intracranial extension. Report of two cases].

Two cases of olfactory neuroblastoma with intracranial extension are described. The radiological features, including those of magnetic resonance (MR) imaging, are emphasized. On plain X-rays, the nasal cavity, ethmoid, sphenoid, and/or frontal sinuses were opacified. Erosion of the bony confines of the sinuses and orbit was seen in Case 1, but no bony destruction was observed in Case 2 despite intracranial tumor invasion via the seemingly intact cribriform plate. Angiography showed tumor staining in the ethmoid sinus, and in Case 1 tumor vessels were also found in the base of the frontal lobe. Computed tomography (CT) disclosed a large, soft, enhanced tissue mass occupying the nasal cavity and paranasal sinuses and extending into the anterior cranial fossa. In Case 1, MR images (0.5 Tesla) with a short spin echo sequence (repetition time [TR], 600 msec; echo time [TE], 26 msec) and a long spin echo sequence (TR, 2100; TE, 30, 60, 90) were obtained. T1-weighted images delineated the tumor accurately in relation to the normal architecture. T2-weighted images revealed widespread brain edema, with the tumor recognizable as a mass of low signal intensity within the high-intensity region of brain edema. The CT and MR imaging findings are by no means specific to olfactory neuroblastoma. However, both modalities, particularly MR imaging, are of special value in demonstrating the precise extent of the tumor in three dimensions.

Humans↗
PubMed1991

Pediatric orbital eosinophilic granuloma with intra- and extracranial extension--case report.

A rare case of eosinophilic granuloma of the orbit in a 3-year-old boy presented as right upper eyelid swelling and proptosis. Computed tomographic scanning revealed a soft-tissue dense mass in the lateral wall of the right orbit. Magnetic resonance (MR) imaging demonstrated tumor extension into the orbit, anterior and middle cranial fossae, and extracranial region. The tumor was completely removed. Histological diagnosis was eosinophilic granuloma. No evidence of recurrence was found 14 months later. MR imaging is useful for diagnosis of the lesion, and particularly for surgical management.

Child, Preschool↗
PubMed2004

[A case of allergic fungal sinusitis caused by Bipolaris spicifera].

We describe a case of allergic fungal sinusitis (AFS) caused by Bipolaris spicifera, the first case reported in Japan. A 70-year-old man was admitted to our hospital because of diplopia following bilateral nasal obstruction and discharge. Radiological studies using computed tomographic scan showed a large soft tissue mass occupying the right frontal, bilateral ethmoid and sphenoid sinuses. He underwent drainage surgery and histopathological examination of the contents of the paranasal sinuses revealed scattered fungal hyphae within "allergic mucin". By cytological examination, these hyphae showed septation at irregular intervals, and were swollen to various sizes. Microbiological studies identified the fungus as Bipolaris spicifera. The presence of allergic mucin and scattered fungal hyphae were very important findings in making a diagnosis of AFS histopathologically, so squash cytology of the contents of the paranasal sinuses was quite useful to observe fungal elements and identify the strain in this case.

Aged↗