ABSTRACT
The group velocity of light becomes superluminal in a medium with a tuned negative dispersion, using two gain peaks, for example. Inside a laser, however, the gain is constant, equaling the loss. We show here that the effective dispersion experienced by the lasing frequency is still sensitive to the spectral profile of the unsaturated gain. In particular, a dip in the gain profile leads to a superluminal group velocity for the lasing mode. The displacement sensitivity of the lasing frequency is enhanced by nearly five orders of magnitude, leading to a versatile sensor of hyper sensitivity.
Subject(s)
Lasers , Light , Optics and Photonics/instrumentation , Optics and Photonics/methods , Equipment Design , Gravitation , Luminescence , Models, Theoretical , RotationABSTRACT
Retrospective clinical experience with our first 46 patients monitored with a fiberoptic intracranial pressure device is described. In 43 of 46 patients, the transducer was introduced into brain parenchyma. A ventriculostomy system was used in 3 of 46 patients. The monitoring system was generally characterized by ease of placement and system maintenance and by technical simplicity. Several problems were encountered, including breakage of system components (12%), erroneous readings requiring transducer repositioning (8.6%), epidural hematoma (3.4%), and infection (1.7%). No infections or hematomas occurred in the 3 cases in which the ventriculostomy system was used. Overall, our experience with the Camino intracranial pressure fiberoptic monitoring system confirms previous reports of its favorable features.
Subject(s)
Brain Injuries/physiopathology , Cerebral Hemorrhage/physiopathology , Fiber Optic Technology , Intracranial Pressure/physiology , Monitoring, Physiologic/instrumentation , Brain Injuries/epidemiology , Cerebral Hemorrhage/epidemiology , Evaluation Studies as Topic , Humans , Retrospective StudiesABSTRACT
The traditional treatment for anaplastic astrocytoma (AAF) and glioblastoma multiforme (GBM) leads to local relapse. The recurring element is assumed to be previously radioresistant, reorganizing hypoxic cells that require up to three times the traditional photon irradiation dose for inactivation. We are proposing to coagulate the original lesion with high-dose precision brachytherapy, immediately followed by resection to save the patient from secondary effects of the necrotic region. The treatment then continues with adjuvant external beam radiation therapy to the local surrounding brain and concomitant chemotherapy. The approach inverts the traditional regimen. It has the virtue of being precise, avoiding secondary effects of the necrotic tumor, and satisfying accepted radiobiological principles.
Subject(s)
Astrocytoma/radiotherapy , Astrocytoma/surgery , Brain Neoplasms/radiotherapy , Brain Neoplasms/surgery , Glioblastoma/radiotherapy , Glioblastoma/surgery , Brachytherapy , Combined Modality Therapy , Humans , Iodine Radioisotopes/therapeutic use , Iridium Radioisotopes/therapeutic use , Radiotherapy Dosage , RecurrenceSubject(s)
Osteochondroma/complications , Spinal Cord Compression/etiology , Spinal Neoplasms/complications , Adult , Humans , Leg , Male , Muscle Spasticity/etiology , ThoraxABSTRACT
A 29-year-old man with spastic paraparesis of insidious onset was discovered to have thoracic cord compression by a combination of kyphosis and thoracic disc herniation. Radiologic evaluation showed evidence of Scheuermann's disease, of which thoracic kyphosis is one manifestation. Neurologic signs are uncommon in Scheuermann's disease and few cases have been successfully managed with resolution of neurologic deficit. This patient made a virtually complete recovery after thoracic cord decompressions by costrotransversectomy and transthoracic approaches.
Subject(s)
Scheuermann Disease/complications , Spinal Cord Compression/etiology , Adult , Humans , Intervertebral Disc Displacement/complications , Male , Radiography , Spinal Cord Compression/diagnostic imaging , Thoracic Vertebrae/diagnostic imagingABSTRACT
Twelve patients with neurologic complications of vertebral osteomyelitis are reported. Initial symptoms were due to diffuse intraspinal abscesses (epidural or subdural) in six patients and to kyphotic deformities in three. A localized anterior subligamentous abscess was found in one patient and a similar abscess with kyphosis in one. Kyphosis and diffuse epidural abscess were found in one patient. Operations were designed to relieve cord compression and maintain or improve spinal stability. Outcome was good in eight patients and poor in two; two patients died. Delayed neurologic deterioration after laminectomy occurred in two patients who presented with epidural abscess and minimal signs of osteomyelitis due to subsequent development of anterior abscess and spinal deformity. Therapy of this problem is discussed, with emphasis on choice of technique for neural decompression. Adequate decompression with attention to stability will yield a good result in the majority of cases.
