In vivo neutron dosimetry during high-energy Bremsstrahlung radiotherapy

Purpose: A new technique is presented for in vivo measurements of the dose equivalent from photoneutrons produced by high-energy radiotherapy accelerators.Methods and Materials: The dosimeters used for this purpose are vials of superheated halocarbon droplets suspended in a tissue-equivalent gel. Neutron interactions nucleate the formation of bubbles, which can be recorded through the volume of gel they displace from the detector vials into graduated pipettes. These detectors offer inherent photon discrimination, dose-equivalent response to neutrons, passive operation, and small sensitive size. An in vivo vaginal probe was fabricated containing one of these neutron detector vials and a photon-sensitive diode. Measurements were carried out in patients undergoing high-energy x-ray radiotherapy and were also repeated in-phantom, under similar irradiation geometries.Results and Conclusion: Neutron doses of 0.02 Sv were measured in correspondence to the cervix, 50 cm from the photon beam axis, following a complete treatment course of 46.5 Gy with an upper mantle field of 18-MV x-rays. This fraction of dose from neutrons is measured reliably within an intense photon background, making the technique a valid solution to challenging dosimetry problems such as the determination of fetal exposure in radiotherapy. These measurements can be easily carried out with tissue-equivalent phantoms, as our results indicate an excellent correlation between in vivo and in-phantom dosimetry.     

An unusual complication of Cloward's procedure presenting to the otolaryngologist

We present the case of a 51-year-old lady who developed a CSF leak following a Cloward's procedure (anterior cervical surgery with fusion), which settled with conservative management. Two months following the surgery she was assessed by an otolaryngologist for persistent dysphagia and a swelling in the anterior triangle of her neck. A computed tomography (CT) scan identified a fluid-filled mass displacing the trachea and communicating with the anterior cervical vertebrae, thus confirming the persistence of a CSF leak.     

The Technical Efficiency of Hospitals under a Single Payer System: The Case of Ontario Community Hospitals

Using DEA, we investigated the impact of ownership, size, and location on the relative technical efficiency of community hospitals in Ontario, which has a single payer system. Consistent with Hansmann's theory of non-profit organizations and contrary to US-based research, we find no significant differences in efficiency across ownership types (government, religious or secular non-profit). Nor do we find significant differences in efficiency by size or location. Our findings suggest that model formulation and differences in payer mix across types of hospitals in the US have a strong influence on the measurement of the hospital ownership–efficiency relationship.     

The association of anemia and hypoalbuminemia with accelerated decline in GFR among adolescents with chronic kidney disease

We sought to describe rates of kidney function decline and to identify modifiable risk factors for CKD progression in a multicenter prospective cohort study of adolescents with CKD aged 11 to 18 years seen semiannually for up to three years. Of the 23 subjects meeting inclusion criteria, the average estimated GFR was 51 ± 27 ml/min/1.73 m² (0.85 ± 0.45 ml/s/1.73 m²) at entry. The overall annualized decline in GFR was 5.6 ml/min/1.73 m² (0.093 ml/s/1.73 m²) per year (95% confidence interval [95% CI]: 1.9 to 9.3 [0.032 to 0.16]). The adjusted annualized decline in GFR was found to be accelerated in males, as well as among those over 15 years of age. The adjusted annualized decline in GFR was greater among those with either anemia (hematocrit below 36%), or hypoalbuminemia (albumin below 4 g/dl [40 g/L]). After adjustment, anemia was associated with an accelerated decline of 7.8 ml/min/1.73 m² (0.13 ml/s/1.73 m²) (95% CI: 3.3 to 12 [0.055 to 0.20]) and hypoalbuminemia was associated with an accelerated decline of 17 ml/min/1.73 m² (0.28 ml/s/1.73 m²) (95% CI: 11 to 22 [0.18 to 0.37]). Further study is needed to evaluate whether treatment of anemia or hypoalbuminemia, as outlined in current clinical care guidelines for CKD, may slow the progression of CKD in adolescents.     

Cocaine-mediated enhancement of Tat toxicity in rat hippocampal cell cultures: the role of oxidative stress and D1 dopamine receptor

It is becoming widely accepted that psychoactive drugs can significantly alter the progression of neuropathological changes in the HIV-infected brain. The use of cocaine can aggravate the neurotoxic effects of HIV-1 proteins such as HIV-1 transactivating protein Tat and virus' envelope protein gp120. HIV-1 Tat is believed to play an important role in pathogenesis of HIV dementia (HAD). Tat is neurotoxic and a constantly growing body of evidence suggests that the toxic effects of Tat are oxidative stress-dependent. The current study reports that recombinant Tat 1-72 triggered mitochondrial depolarization, increased intracellular production of reactive oxygen species (ROS) and protein oxidation, and caused neuronal degeneration in primary hippocampal rat cell cultures. A 10 microM dose of the antioxidant Trolox, the water-soluble analog of Vitamin E, ameliorated increased intracellular ROS production and prevented cell viability decline in Tat-treated cell cultures. This fact demonstrates that Tat-induced changes in neuronal oxidative status play an important role in the mechanism of Tat neurotoxicity. While non-toxic by itself, a physiologically relevant dose of cocaine (1.5 microM) significantly enhanced Tat-induced oxidative stress and neurotoxicity in rat hippocampal cell cultures. The antioxidant Trolox significantly improved the survival of neurons exposed to the combination of 50 nM Tat and 1.5 microM cocaine but did not provide complete protection. The specific D1 dopamine receptor antagonist SCH 23390 (10 microM) did not affect Tat toxicity, but did suppress cocaine-mediated potentiation of Tat toxicity. Our results demonstrate that cocaine-mediated potentiation of Tat neurotoxicity may be related to its ability to augment Tat-induced oxidative stress.     

Spinal cord imaging by transesophageal echocardiography: A new modality of monitoring

A 45-year-old patient with known history of Aortic arch aneurysm presented in the emergency ward with features of rupture of the aneurysm into the left lung with compressive signs in the pulmonary parenchyma. Diagnosis was confirmed by magnetic resonance imaging. The patient underwent repair of thoracic aortic aneurysm with left upper lobectomy under general anesthesia and cardio-pulmonary bypass support. Transesophageal echocardiography (TEE) was used for an intraoperative monitoring. While imaging the thoracic aorta with TEE was underway, we accidentally visualized an image that was confirmed to be the spinal cord. So, in this article we discuss how the spinal cord monitoring can be made possible with TEE.     

Mechanical occlusion of the inferior vena cava: an unusual complication after repair of pectus excavatum using the nuss procedure

We describe the case of a 13-year-old girl with a pectus excavatum in whom acute occlusion of the inferior vena cava developed after a nuss repair. In this hemodynamically unstable patient, we evaluated the possibility of a penetrating injury to the thoracic and abdominal structures before confirming the diagnosis of inferior vena cava obstruction with a venogram. Removal of the nuss bar relieved the unexpected problem.     

Abstracts from the 14th International Symposium on NeuroVirology October 25–28, 2016, Toronto,Ontario, Canada

Journal of NeuroVirology -