Investigations of the MGy dose level radiation effects on the photometric budget of a radiation-hardened CMOS-based camera.

We studied the impact of ionizing radiation at high dose levels (megagray, MGy) on the photometric budget of a radiation-resistant complementary metal oxide semi-conductor (CMOS)-based camera. This is achieved by measuring the radiation-induced degradation of each subpart, namely its illumination system, its optical system, and its CMOS image sensor. The acquired experimental results allow performing a rather realistic simulation of the radiation effects at the system level. Thanks to appropriate mitigation techniques, limited image darkening and color change are obtained at MGy dose levels. The presented results confirm the feasibility of a CMOS-based camera able to resist to MGy dose level of ionizing radiations with an acceptable degradation of the image quality, opening the way to its implementation in the most challenging harsh environments.

Real time monitoring of water level and temperature in storage fuel pools through optical fibre sensors.

We present an innovative architecture of a Rayleigh-based optical fibre sensor for the monitoring of water level and temperature inside storage nuclear fuel pools. This sensor, able to withstand the harsh constraints encountered under accidental conditions such as those pointed-out during the Fukushima-Daiichi event (temperature up to 100 °C and radiation dose level up to ~20 kGy), exploits the Optical Frequency Domain Reflectometry technique to remotely monitor a radiation resistant silica-based optical fibre i.e. its sensing probe. We validate the efficiency and the robustness of water level measurements, which are extrapolated from the temperature profile along the fibre length, in a dedicated test bench allowing the simulation of the environmental operating and accidental conditions. The conceived prototype ensures an easy, practical and no invasive integration into existing nuclear facilities. The obtained results represent a significant breakthrough and comfort the ability of the developed system to overcome both operating and accidental constraints providing the distributed profiles of the water level (0-to-5 m) and temperature (20-to-100 °C) with a resolution that in accidental condition is better than 3 cm and of ~0.5 °C respectively. These new sensors will be able, as safeguards, to contribute and reinforce the safety in existing and future nuclear power plants.

Radiation effects on optical frequency domain reflectometry fiber-based sensor.

We investigate the radiation effects on germanosilicate optical fiber acting as the sensing element of optical frequency domain reflectometry devices. Thanks to a new setup permitting to control temperature during irradiation, we evaluate the changes induced by 10 keV x rays on their Rayleigh response up to 1 MGy in a temperature range from -40°C up to 75°C. Irradiation at fixed temperature points out that its measure is reliable during both irradiation and the recovery process. Mixed temperature and radiation measurements show that changing irradiation temperature leads to an error in distributed measurements that depends on the calibration procedure. These results demonstrate that Rayleigh-based optical fiber sensors are very promising for integration in harsh environments.

Vulnerability of OFDR-based distributed sensors to high γ-ray doses.

Vulnerability of Optical Frequency Domain Reflectometry (OFDR) based sensors to high γ-ray doses (up to 10 MGy) is evaluated with a specific issue of a radiation-hardened temperature and strain monitoring system for nuclear industry. For this, we characterize the main radiation effects that are expected to degrade the sensor performances in such applicative domain: the radiation-induced attenuation (RIA), the possible evolution with the dose of the Rayleigh scattering phenomenon as well as its dependence on temperature and strain. This preliminary investigation is done after the irradiation and for five different optical fiber types covering the range from radiation-hardened fibers to highly radiation sensitive ones. Our results show that at these high dose levels the scattering mechanism at the basis of the used technique for the monitoring is unaffected (changes below 5%), authorizing acceptable precision on the temperature or strain measurements. RIA has to be considered as it limits the sensing range. From our vulnerability study, the OFDR sensors appear as promising candidates for nuclear industry even at doses as high as 10 MGy.

Placement of pedicle screws in the thoracic spine. Part I: Morphometric analysis of the thoracic vertebrae.

We studied the morphology of the thoracic vertebrae in the spines of seventeen human cadavera in order to define parameters that could be used as guidelines for the placement of hooks and screws in the pedicles to obtain internal fixation. We also reviewed computerized tomographic scans of nineteen thoracic spines in living patients who had no evidence of any vertebral deformity. The transverse diameter of the pedicle, which helps to determine the size of the screw, ranged from a mean (and standard deviation) of 4.5 +/- 1.2 millimeters in the fourth thoracic vertebra to a mean of 7.8 +/- 2.0 millimeters in the twelfth thoracic vertebra. The pedicles were inclined anteromedially throughout the thoracic spine, and the angle ranged from 0.3 degree toward the midline in the twelfth thoracic vertebra to 13.9 degrees in the fourth thoracic vertebra. The morphometric data revealed wide variations in the dimensions of the pedicles, demonstrating the importance of accurate preoperative imaging with transaxial computerized tomographic scans to visualize the precise osseous margins and angles of insertion of the thoracic pedicles.

Placement of pedicle screws in the thoracic spine. Part II: An anatomical and radiographic assessment.

We used computerized tomographic scans and subsequent dissections to evaluate the position of ninety pedicle screws that had been inserted bilaterally into the fourth through twelfth thoracic vertebrae of five fresh-frozen cadavera. The screws had been inserted by five experienced spine surgeons without the use of radiographs or imaging studies. Of the ninety screws, thirty-seven were found to have penetrated the cortex of the pedicle. Twenty-one screws had penetrated the medial cortex and entered the spinal canal, and sixteen had penetrated the lateral cortex. The aorta and the esophagus were at greatest risk for injury after advancement of the screws beyond the anterior vertebral cortex. Computerized tomographic scans of the thoracic spine in nineteen living controls who did not have a spinal abnormality confirmed the proximity of the posterior mediastinal structures to the misplaced screws.

Posterior spinal arthrodesis for atlantoaxial instability in Down syndrome.

Nine children with Down syndrome who had atlantoaxial instability underwent posterior spinal fusion. At follow-up, all patients had stabilization or improvement of their neurologic symptoms. Evaluation of the spine using flexion and lateral radiographs, as well as selective cineradiography, showed no instability over the fused area or adjacent motion segments. Stable fibrous union with no clinical significance was noted in three of the nine patients. We recommend posterior spinal fusion in situ with external immobilization as the safest and most effective means of surgical stabilization in the patient with Down syndrome who has symptomatic atlantoaxial instability.

Cervical spine trauma.

STUDY DESIGN: The authors reviewed the results of a large number of studies of patients with acute cervical spine dislocations and subluxations. OBJECTIVES: The authors make recommendations regarding the evaluation and treatment of acute cervical spine dislocations based on a thorough review of the available literature. SUMMARY OF BACKGROUND DATA: Realization that a significant percentage of patients with acute cervical dislocations also have disc herniations has led to some controversy regarding the timing of MRI evaluation and attempted closed reduction. This article review studies of spine dislocations at one institution. METHODS: The review of the literature included 131 consecutive patients with acute cervical spine dislocations treated by the senior author followed both retrospectively and prospectively. These results were compared with those of many other authors. RESULTS: Emergent attempted closed reduction remains the treatment of choice for alert cooperative patients with acute cervical spine dislocations. Open or closed reduction under general anesthesia with an uncooperative or unconscious patient should be preceded by an MRI scan. In this situation, the presence of a herniated disc mandates decompression before reduction.

The effect of torque pressure on halo pin complication rates. A randomized prospective study.

At Thomas Jefferson University Hospital, 102 consecutive patients treated in a halo vest orthosis were randomized into one of two torque protocol groups based on their date of birth. The pins of patients who were born in even-numbered months were inserted with 8 inch-lbs of torque and those born in odd-numbered months were inserted with 6 inch-lbs. All patients were placed in an identical model halo using a standardized technique of application. The patients were followed prospectively, and all potential complications were evaluated by a member of the orthopedic attending staff, using protocols established at the onset of the study. Statistical analysis indicated no significant differences in halo pin loosening, infection, pain, or scarring between the torque protocols, but there was a trend toward a higher complication rate in the 8-inch-lbs group. There was no direct evidence of skull penetration in either group, and no patients developed a deep infection. Based on the results of this study, we conclude that insertion torque has no significant effect on halo pin complications within the ranges tested by this study. Our current protocol calls for routine insertion of halo pins with 6 inch-lbs of torque.

Metastatic cystosarcoma phyllodes associated with paraplegia: an uncommon complication of an uncommon tumor.

Cystosarcoma phyllodes is a rare form of breast cancer that rarely metastasizes. This case represents the first reported case of a pathological spine fracture and neurologic injury as a result of metastatic cystosarcoma phyllodes. Physicians should be aware of a recently identified histological subtype of cystosarcoma that exhibits an increased incidence of hematogenous metastasis.

Fractures of the shaft of the radius after treatment of Colles fractures with pins and plaster or external fixation.

Refracture of the radius through a pin site after the removal of pins and plaster or an external fixator for Colles fracture is rarely mentioned in the literature. We present the details of three such cases and review two others reported in the literature. Our aim is to alert orthopedists to the potential for this complication. Patients with superficial or deep pin tract infections appear to be at greater risk.

Intervertebral disc injury complicating cervical spine trauma.

The incidence of acute herniated nucleus pulposus was determined in 55 patients with cervical spine trauma. A standardized protocol and a 1.5-T magnetic resonance image scanner was used to document a 42% incidence of acute herniated nucleus pulposus in patients studied within 72 hours of injury. The incidence of herniated nucleus pulposus was correlated with the patients' presenting neurologic status and mechanism of injury. The incidence of herniated nucleus pulposus was highest in patients with bilateral facet dislocations (80%) and anterior cord syndromes (100%). There was no statistically significant correlation between the incidence of herniated nucleus pulposus and patients' age or sex.