Development of a method of evaluating PuO2 particle diameters using an alpha-particle imaging detector.

It is very important to evaluate the diameters (activity median aerodynamic diameter) of plutonium dioxide (PuO2) particles for internal exposure dose evaluation. In this study, a method of evaluating PuO2 particle diameters using an alpha-particle imaging detector was developed. PuO2 particles with different diameters were modeled by Monte Carlo simulation, and the change in the shape of the energy spectrum for each particle diameter was evaluated. Two different patterns were modeled, namely, the case of 239PuO2 and the case of PuO2 (including isotopic composition of Pu). Multiple regression analysis was performed to determine the PuO2 particle diameter from the obtained parameters. The simulated diameters and the diameters obtained with the regression model were in good agreement. The advantage of using the alpha-particle imaging detector is to measure the alpha energy spectrum for individual particle, and this allows accurate measurement of particle diameter distribution.

Microvascular Decompression in Patients Aged 30 Years or Younger.

OBJECTIVE: The aim of this study was to identify the etiology of hemifacial spasm (HFS) and trigeminal neuralgia (TN) in patients aged 30 years or younger and to examine the efficacy of microvascular decompression (MVD). PATIENTS AND METHODS: Between 1996 and 2012, 228 HFS and 190 TN patients underwent MVD at Atsuchi Neurosurgical Hospital. Of these, 7 patients were 30 years of age or younger at the time of treatment (HFS: n = 6, TN: n = 1). Assessments were based on their medical history and on magnetic resonance imaging, magnetic resonance angiography, surgical, and follow-up findings. RESULTS: The age of the 6 HFS patients ranged from 23 to 30 years (mean 27.8 ± 1.8 [standard deviation] years) at the time of surgery; the earliest symptom onset was in an 11-year-old boy. We noted vascular variations in 5 patients, a duplicate posterior inferior cerebellar artery in 2 patients, a short basilar artery in 1 patient, and an aberrant arterial course in 2 patients. At the latest follow-up, 1-69 months after MVD, 5 of the HFS patients were asymptomatic and the 6th had mild residual symptoms. A 23-year-old TN female underwent straightening of the trigeminal nerve by separation of a thickened arachnoid membrane from the nerve and dislocation of a small branch of the superior cerebellar artery from the distal end of the root exit zone. While she continued to experience occasional facial pain 48 months after the operation, she required no medication because surgery yielded significant pain amelioration. CONCLUSION: Although the pathogenesis of early-onset HFS and TN remains unclear, our findings suggest that vascular variations may be related to the etiology of vascular compression symptoms in patients with HFS or TN. MVD was useful for the treatment of neurovascular compression symptoms in young patients.

Use of the guidewire for repositioning displaced spinal catheter during lumboperitoneal shunt placement.

BACKGROUND: During lumboperitoneal shunt operation, we may inadvertently pull and displace the spinal catheter after the catheter placement into the spinal canal. The authors introduce an easy and efficient technique for repositioning a prolapsed catheter into correct place. METHODS: After the confirmation of cerebrospinal fluid outflow from the end of the catheter, a guidewire for angiogram was gently inserted into the catheter until its tip reached the end of the catheter. The guidewire-inserted catheter was able to be pushed back manually and adequately placed in the spinal canal under the fluoroscope guidance. RESULTS: Three patients underwent repositioning using this "rescue wire technique" without complications. CONCLUSION: This "rescue wire technique" is useful for repositioning of the displaced catheter into the spinal canal.

Exploitation of Simple Classification and Space Created by the Tumor for the Treatment of Foramen Magnum Meningiomas.

OBJECTIVE: The resection of foramen magnum meningiomas (FMMs) presents neurosurgical challenges. We propose a simple classification of the tumor location and the operating space created by the tumor to help treatment planning. METHODS: We retrospectively analyzed 16 FMMs and divided them into 3 groups based on the tumor location--clival, foraminal, and atlantal tumors. The distance between the condyle and the neuraxis at the level of the foramen magnum was measured and defined as the available operative space (AOS). We also reviewed intraoperative video recordings to assess the surgical exposure of the tumor by the space created by the FMM and compared it with the AOS. RESULTS: There were 4 clival, 8 foraminal, and 4 atlantal tumors. The AOS of the clival tumors was 10 mm ± 1.7, the AOS of the foraminal tumors was 18 mm ± 3.7, and the AOS of the atlantal tumors was 12 mm ± 2.1. All foraminal and atlantal tumors could be detached without a brain retractor. Because a major portion of the clival tumors was covered by the spinomedullary junction, a brain spatula was needed to obtain the required surgical space. The difference in AOS between clival and foraminal/atlantal tumors was statistically significant (P = 0.044). Although 4 patients experienced postoperative complications, the average postoperative Karnofsky performance scale score improved. The surgical complication rate was significantly lower in foraminal and atlantal FMMs than in clival FMMs (P = 0.027). CONCLUSIONS: The simple classification of the tumor location helped to assess surgical difficulties. Knowledge of the space created by the FMMs between the condyle and the neuraxis is useful for planning the approach strategy, especially for estimating the available working space without resection of the occipital condyle.

Use of blunt scalp hooks for abdominal procedure in lumboperitoneal shunt placement: technical note.

In obese patients, we often find difficulty in laparotomy for placing a lumboperitoneal shunt catheter. The authors introduced an easy technique to get a sufficiently wide and shallow operative field through small abdominal incision in obese people. Four blunt scalp hooks and rubber bands, commonly used in craniotomy, were prepared. The fat layer and the rectus abdominis muscle layer were retracted and pulled up using these hooks. Blunt scalp hooks were useful for safe and effective retraction of abdominal wall, which made a sufficient and shallow operative field.

Clinical presentation and treatment of aneurysms associated with basilar artery fenestration.

Aneurysms associated with a fenestrated basilar artery are rare, and treatment strategies have yet to be established. A direct surgical approach to the basilar artery is challenging because the surrounding anatomy is complex. We retrospectively compared the clinical features and treatment outcomes of eight patients (seven female, one male) with aneurysms associated with a fenestrated basilar artery after clipping or coil embolisation and reviewed the literature. Of the eight aneurysms, four were ruptured; seven aneurysms were located at the proximal part of the basilar artery and one aneurysm was located at the middle of the basilar artery. Six aneurysms were surgically treated. Four aneurysms were embolised with Guglielmi detachable coils, two aneurysms were clipped via the transcondylar or temporopolar approach, and two aneurysms were not treated. All six surgically treated patients had good outcomes. We found that both coil embolisation and direct clipping to treat aneurysms associated with a fenestrated basilar artery have advantages and disadvantages. To obtain favourable outcomes, the selected treatment modality must consider the patient's age and clinical condition, the aneurysm size and shape, the direction of the dome, the relationship with perforators, and the neurosurgeon's expertise.

Development of a microcalorimeter with transition edge sensor for detection of LX rays emitted by transuranium elements.

A transition edge sensor (TES) microcalorimeter has been developed for use as an energy dispersive X-ray spectrometer. The TES microcalorimeter is a thermal detector that enables one to determine the energy of an incident photon by measuring the resultant increase in temperature. In this work, a Ti/Au TES microcalorimeter was developed to measure LX rays emitted by transuranium elements. The phase transition temperature was set at ~200 mK by using a bilayer structure composed of a 110-nm-thick Au layer and a 40-nm-thick Ti layer. An Au of 5 µm thickness was deposited on the Ti/Au bilayer to achieve an absorption efficiency of 35-80 % for the energy range of LX rays (10-25 keV). The developed TES microcalorimeter was irradiated with LX rays emitted by an (241)Am source at an operating temperature of 140 mK. An energy resolution of ~80 eV (full width at the half maximum) was obtained for L(ß1)X ray of 17.75 keV.

Feasibility of in vivo measurement of 239 Pu distribution in lungs using an imaging plate.

An in vivo measurement system using an imaging plate (IP) system was developed, which displayed images reflecting (239)Pu distribution in the lung of a phantom. The detection limits of the IP system for 1-12h exposures were between 1670 and 245 Bq at a 1.6 cm chest wall thickness. The detection limit of the IP system for a 2.5h exposure was equal to that of a germanium detector for a 0.5h measurement. The IP system could be used as a new device for in vivo measurement of (239)Pu in the lung.

Clinical presentation and treatment of distal posterior inferior cerebellar artery aneurysms.

Aneurysms located at the distal portion of the posterior inferior cerebellar artery (PICA) are rare, and their clinical features are not fully understood. We report the clinical features and management of 30 distal PICA aneurysms in 28 patients treated during the past decade at Kagoshima University Hospital and affiliated hospitals. Our series includes 20 women and eight men. Of their 30 aneurysms, 24 were ruptured, and six were unruptured; there were 27 saccular and two fusiform aneurysms; one was dissecting. Their location was at the anterior-medullary (n = 4), lateral-medullary (n = 9), tonsillomedullary (n = 7), telovelotonsillar (n = 6), and cortical (n = 4) segment of the PICA. In 18 patients, angiographic features suggested hemodynamic stress including an absent contralateral PICA or ipsilateral anterior inferior cerebellar artery, termination of the vertebral artery (VA) at the PICA, and hyperplasia or occlusion of the contralateral VA. As three patients died before surgery, 27 aneurysms in 25 patients were surgically treated. Of these, 6 were unruptured aneurysms; 20 were clipped via midline or lateral suboccipital craniotomy, and 5 were embolized with Guglielmi coils; in one, the PICA flow was reconstructed by OA-PICA anastomosis, and in the other one, the PICA was resected. Of the 25 surgically treated patients, 22 (88%) had good outcomes. The predominant contributor to the development of distal PICA aneurysms is thought to be increased hemodynamic stress attributable to anomalies in the PICA and related posterior circulation. Both direct clipping and coil embolization yielded favorable outcomes in our series. However, considering the difficulties that may be encountered at direct clipping in the acute stage and the availability of advanced techniques and instrumentation, aneurysmal coiling is now the first option to address these aneurysms.

Development of 241Am lung monitoring system using an imaging plate.

A new 241Am lung monitoring system without shielding was devised by using an imaging plate system. The Lawrence Livermore National Laboratory's realistic torso phantom containing a 241Am lung was covered by imaging plates sealed in lightproof bags. The imaging plate system displayed 241Am lung images characteristic of the lung shape of the torso phantom. The imaging plate system's lower detection limits of 14 Bq for 60 min exposure and 6 Bq for 300 min were the same levels as those of the phoswich detectors and the germanium detectors placed in shielded rooms. The imaging plate system for 60 min exposure detected about 2% of the annual limit of 740 Bq for 241Am inhalation. A lung monitoring system using imaging plates is applicable for 241Am lung monitoring.