Simulations of slow positron production using a low-energy electron accelerator

Monte Carlo simulations of slow positron production via energetic electron interaction with a solid target have been performed. The aim of the simulations was to determine the expected slow positron beam intensity from a low-energy, high-current electron accelerator. By simulating (a) the fast positron production from a tantalum electron-positron converter and (b) the positron depth deposition profile in a tungsten moderator, the slow positron production probability per incident electron was estimated. Normalizing the calculated result to the measured slow positron yield at the present AIST linear accelerator, the expected slow positron yield as a function of energy was determined. For an electron beam energy of 5 MeV (10 MeV) and current 240 μA (30 μA), production of a slow positron beam of intensity 5 × 10(6) s(-1) is predicted. The simulation also calculates the average energy deposited in the converter per electron, allowing an estimate of the beam heating at a given electron energy and current. For low-energy, high-current operation the maximum obtainable positron beam intensity will be limited by this beam heating.

Intraoperative localization of early-stage upper gastrointestinal tumors using a magnetic marking clip-detecting system

BACKGROUND

Intraoperative tumor localization often is difficult during laparoscopic surgery for early-stage upper gastrointestinal tumors.

METHOD

This study enrolled 15 patients undergoing laparoscopic gastrectomy. A magnetic marking clip-detecting system was used to apply a marking clip to the tumor site during preoperative gastroscopy, and to detect a marking magnetic body.

RESULTS

In a basic ex vivo study, the mean permeance rate on the gastric wall serosal surface was 0.97 +/- 0.01. Magnetic flux densities required for exploration were 52.6 mT on the gastric wall serosal surface and 312.4 mT 10 mm away from the surface. In a clinical study, the mean distance between the detected tumor site and the clip along the longitudinal axis was 8.3 +/- 3.2 mm. The mean detection time was 5.7 +/- 2.3 min.

CONCLUSION

The magnetic marking clip-detecting system may be useful for tumor site detection during laparoscopic gastrectomy.

A vertical scanning Doppler probe identifies blood vessels during laparoscopic surgery

BACKGROUND

Using a conventional Doppler probe, it is difficult to identify blood vessels precisely in lymph node dissection during laparoscopic surgery.

METHODS

For 26 patients undergoing laparoscopic colectomy and 26 patients undergoing laparoscopic subtotal gastrectomy, we used conventional and vertical scanning Doppler probes to compare their ability to identify invisible blood vessels through differences in power output voltage.

RESULTS

The vertical scanning Doppler probe was 100% successful in identifying the target blood vessels regardless of the patient's body mass index (BMI), and also was superior to the conventional Doppler probe in detection sensitivity. The vertical scanning Doppler probe was useful for image training of recently qualified surgeons through real-time monitoring of the probe position and response on the monitor. Furthermore, findings showed that the vertical scanning Doppler probe was applicable to lymph node dissection as a forceps for laparoscopic usage.

CONCLUSION

The vertical scanning Doppler could identify the target blood vessels regardless of the patient's BMI. It was verified to be useful as a surgical assistive device apart from being a sensor and may serve in the education of recently qualified surgeons.

Antifogging effects of a socket-type device with the superhydrophilic, titanium dioxide-coated glass for the laparoscope

BACKGROUND

Lens fogging during laparoscopic surgery extensively deteriorates operative field visibility and may provoke serious complications.

METHODS

A simulation model study was conducted using a conventional laparoscope, a conventional laparoscope plus heating (100 degrees C, 10 s), a conventional laparoscope plus surfactant, and a conventional laparoscope plus both a titanium dioxide (TiO2)-coated glass (with > or = 15 h of preoperative ultraviolet irradiation) and a water supply. For each, the time from laparoscope insertion into the peritoneal cavity to fogging-induced interruption of surgery was measured.

RESULTS

The TiO2-coated glass had unique verified properties of exerting antifogging effects on the oil film after 15 or more hours of previous ultraviolet irradiation, and of inversely accelerating fogging after less than 15 h of previous ultraviolet irradiation. The clinical study showed later fogging with the TiO2-coated glass model, which successfully completed surgery without retraction of the laparoscope from the peritoneal cavity, as compared with the other models.

CONCLUSION

An antifogging device using superhydrophilic TiO2-coated glass was very effective in preventing fogging during laparoscopic surgery.

Depth Profile of Free Volume in a Mixture and Copolymers of Poly(N-vinyl-pyrrolidone) and Poly(ethylene glycol) Studied by Positron Annihilation Spectroscopy

Effect of hydrogen bonding on the depth profile of the free-volume in a mixture (weight ratio of 65:35) of poly(N-vinyl-pyrrolidone) (PVP) and poly(ethylene glycol) (PEG) and the copolymers of vinyl pyrrolidone with poly(ethylene glycol) diacrylate (PVP-PEGDA) and monomethacrylate (PVP-PEGMMA) was studied using positron annihilation spectroscopy. Doppler broadening energy spectra of annihilation radiation and positron annihilation lifetime were measured as a function of positron incident energy (0-30 keV). Significant variations of the free-volume depth profile in terms of the S parameter, ortho-positronium lifetime, intensity, and lifetime distribution are observed as a result of the hydrogen-bonding replacement of covalent bonds. The polymer mixture with hydrogen bonding through two sides of PEG short chains has a larger free volume and a wider distribution than the comb-structured PVP-PEGMMA and the network structured PVP-PEGDA. A longer ortho-positronium lifetime is observed near the surface than in the bulk. This is interpreted in terms of surface effect, free volume, and hydrogen bonding for drug delivery applications of polymeric materials.

Intraoperative localization of colorectal tumors in the early stages using a magnetic marking clip detector system (MMCDS)

BACKGROUND

In the laparoscopic surgical treatment of early stage colorectal carcinomas, intraoperative tumor site identification is often difficult. We developed a novel marking method using a magnetic marking clip and a modified magnetometer system.

METHODS

We applied magnetic marking clips at the tumor site during preoperative colonoscopy and identified the clip site with a magnetic marking clip detector system (MMCDS) of our design. Eleven patients who underwent laparoscopic colectomy were studied.

RESULTS

In a basic ex vivo study, magnetic bodies of more than 300 mT magnetic force were easily detected with a 100% detection ratio. In a clinical study, the marking site was detected in all 11 patients. The mean length between the detected site and clip along the longitudinal bowel axis was 14.1 mm (SD 5.6). The mean detection time was 2.4 min (SD 0.2).

CONCLUSION

MMCDS accurately identifies tumor sites. This method may be useful for tumor site identification during laparoscopic colectomy.

[A case of isolated sarcoidosis of the cerebral falx]

A 28 year-old man complaining of intermittent headaches for a month following an episode of general convulsions was admitted to the Department of Neurosurgery of our hospital. His brain CT scan showed a well-enhanced mass growing symmetrically along the anterior cerebral falx in a manner compatible with meningioma. Nothing abnormal was detected in chest radiography on admission. Histopathological examination of the mass after partial resection revealed multiple epithelioid cell granulomas with giant cells indicating sarcoidosis. After 4 weeks of treatment with oral prednisolone 30 mg/day, bronchoalveolar lavage was performed in our department. In the lavage fluid, both the total cell count and the percentage of lymphocytes were elevated. The lung specimens obtained by transbronchial biopsy also showed epithelioid cell granulomas. CNS sarcoidosis is reportedly usually observed in the vicinity of the hypothalamus with other organ involvement. In the present case, differential diagnosis of sarcoidosis from meningioma was difficult because the solitary lesion was growing along the anterior cerebral falx without radiographic evidence of bilateral hilar lymphadenopathy.

[Obstructive sleep apnea syndrome in a patient with superior vena cava syndrome caused by lung cancer]

A 48-year-old man was treated with chemotherapy and irradiation therapy for superior vena cava syndrome (SVCS) caused by adenocarcinoma of the lung, and his symptoms subsided temporarily. However, the same symptoms recurred, and severe snoring during sleep and daytime hypersomnolence developed. Obstructive sleep apnea syndrome (OSAS) was diagnosed by respiratory inductive plethysmography. After chemotherapy, the symptoms of edema of the face and arms, snoring, and daytime somnolence tendency were alleviated, and the patient's apnea hypopnea index decreased remarkably. In addition, lateral cephalograms disclosed improved patency of the upper respiratory tract and dilation of the soft palate. These findings suggested a relationship between SVCS and OSAS. OSAS may cause a deterioration of circulatory dynamics and the quality of life when it develops secondary to SVCS. Therefore, it is necessary to determine whether OSAS is present and accordingly provide suitable treatment in patients with SVCS.

Intraoperative localization of colorectal tumors in the early stages using a marking clip detector system

In laparoscopic colectomy the identification of the site of a tumor is often difficult. The topical injection of india ink or blue dye by preoperative colonoscopy is the most prevalent method to mark the tumor site; however, such a procedure also includes the intrinsic danger of possibly injecting dye into the peritoneal cavity. In addition, the injected marker may also spread so widely that the intended site may become obscure. A marking clip detector system was used to detect metallic marking clips in the luminal side that had been applied to the mucosa adjacent to the lesion during the course of preoperative colonoscopy. This method was able to identify the marked site in 40 percent of cases in which only one clip was applied to the mucosa. However, when the lesion sites were marked with two or three clips, then the detection rate increased to 100 percent. Based on our findings, this procedure was found to be a safe and reliable method for identifying lesions during laparoscopic-assisted colectomy.

A novel case of a sporadic desmoid tumour with mutation of the beta catenin gene

A 42 year old man without familial adenomatous polyposis had recurrent desmoid tumours in the left subclavicular site. Histological examination showed a typical desmoid tumour. Molecular analysis was performed in genomic DNA from this tumour, using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and direct sequencing methods. No mutation could be detected in the entire coding sequence of the APC gene, nor in H-ras, K-ras, N-ras, or p53 genes. On seeking a mutation of the beta catenin gene (CTNNB1), an activating mutation from ACC (Thr) to GCC (Ala) at codon 41 was found. Immunohistochemical staining showed that accumulated beta catenin protein was predominantly localised in the nuclei of desmoid cells. This is the first example of a sporadic desmoid tumour in which a mutation of the beta catenin gene was revealed.

Regulation of ventilation before and after sleep in patients with obstructive sleep apnoea

The objective was to examine whether abnormal breathing during sleep may affect regulation of ventilation after awakening in patients with obstructive sleep apnoea (OSAS). In 19 patients with OSA and 12 normal subjects we examined ventilatory responses to hypoxia (HVR) and to hypercapnia (HCVR) before and after sleep (BS and AS), and compared the changes in ventilatory responses with respiratory events during sleep. In the OSA group, the values of resting ventilation were significantly smaller in AS than those in BS and end-tidal partial pressure of CO2 in arterial blood (Pco2) (PETCO2) rose significantly from BS to AS. The slopes of the HVR or HCVR did not differ between BS and AS. However, both the response lines shifted downward and minute ventilation (VE)80 (VE at arterial oxygen saturation (Sao2) of 80%) in HVR and VE60 (VE at PETCO2 of 60 mmHg) in HCVR decreased significantly from BS to AS. The percentage changes of VE80 and VE60 were significantly correlated with mean Sao2, total sleep time below Sao2 of 90% and lowest Sao2 during sleep. However, in normal subjects we observed no circadian variation in their ventilatory responses. These data support the hypothesis that repeated episodes of nocturnal hypoxia and hypercapnia may modify the regulation of ventilation after awakening in patients with OSA.

[An autopsy case of Goodpasture's syndrome with P-ANCA and systemic vasculitis]

A 72-year-old woman was admitted because of anorexia and dyspnea. She was given a diagnosis of pulmonary hemorrhage and renal failure. Despite treatment with high-dose steroid and hemodialysis, the patient died of disseminated intravascular coagulation on the 9th hospital day. Autopsy revealed intra-alveolar hemorrhage, crescentic glomerulonephritis, and systemic vasculitis with fibrinoid necrosis. A direct immunofluorescence study demonstrated linear deposition of IgG along the glomerular basement membrane (GBM). Both anti-GBM antibody and anti-neutrophil cytoplasmic antibody with perinuclear pattern (P-ANCA) were detected in the patient's serum by enzyme immunoassay. Goodpasture's syndrome with P-ANCA was diagnosed. There has been some controversy as to whether vasculitis occurs in patients with Goodpasture's syndrome. This was a rare example of well-documented Goodpasture's syndrome with P-ANCA and systemic vasculitis, the exact etiologic relationships among which remain to be clarified.

Cardiovascular change in elderly male breath-hold divers (Ama) and their socio-economical background at Chikura in Japan

The Ama have existed for more than 2000 years in Japan and Korea. They have been diving for seaweed and molluscs. Their traditional way of fishing, with goggles or a mask, but without a wetsuit, is still practised as a result of laws against overfishing. We investigated cardiovascular diving responses, expressed as heart rate (HR) reduction, peripheral vasoconstriction indicated by skin blood flow (SkBF) and mean arterial blood pressure (MAP) during breath-hold face immersion in a group of eight elderly male Ama at Chikura, Japan. Their data were compared to those from three other groups: a) elderly non-divers; b) young divers and c) young non-divers. Our previous studies have shown that young divers show a more pronounced bradycardia than young non-divers. The present study of elderly Ama and elderly non-divers was performed to investigate if this difference persists in old age. We found that, in spite of many years of diving experience, HR reduction of the elderly professional divers observed during face immersion did not differ from that of elderly non-divers, but it was much less pronounced than in the two younger groups. We conclude that even if a well-developed diving response at young age has been reduced to the level of non-divers, the Ama are still able to continue their work of diving in old age. Ama that has been a traditionally female occupation, is mostly practised by men at Chikura today. No young have been recruited for this profession. Therefore, the present Ama are senior and the traditional breath-hold diving will probably cease to exist in the near future. The probable reasons for these changes are discussed.

[Extracorporeal membrane oxygenation for acute respiratory failure induced by Legionella pneumoniae. (Case report)]

We report a case of severe legionella pneumonia with acute respiratory failure, successfully managed with veno-venous extracorporeal membrane oxygenation (VV-ECMO). The patient presented with 4-day history of fever and cough. He was in critical condition, with exacerbated respiratory failure. Mechanical ventilation, volume replacement and antibiotic therapy were initiated. Despite increasing mechanical ventilatory support (FiO2 100%, TV 10 ml/kg, f 30/min, PEEP 5 cmH20), PaO2 fell below 40Torr and life sustaining measures were undertaken. VV-ECMO (flow 30 ml/kg/min) was commenced, and the patient responded well, with an elevation of PaO2. Erythromycin therapy was effective against the pneumonia. VV-ECMO was maintained for 92 hours, mechanical ventilation was successfully discontinued 11 days after and the patient was discharged 82 days after cessation of ventilator support. Serum antibody examination proved legionella infection. VV-ECMO may have a role in the management of patients with acute respiratory failure caused by bacterial pneumonia.

Contribution of peripheral chemoreceptor drive in exercise hyperpnea in humans

The peripheral chemoreceptors play a dominant role in the respiratory compensation of lactic acidosis during heavy exercise of humans. Our object was to determine the contribution of peripheral chemoreceptors to exercise hyperpnea during mild to moderate and heavy exercise above the anaerobic threshold. We used a hyperoxic suppression test in six normal male subjects. Inspired gas was abruptly changed without the subject's knowledge from air to pure oxygen for 5 to 6 breaths. The maximal ventilatory depression after O2 breathing was 5.5 +/- 1.7 L/min (BTPS) at mild exercise, and the depression increased with increasing exercise intensity up to 12.8 +/- 4.1 L/min (BTPS). The relative contribution of the peripheral chemoreceptors to ventilation in terms of percentage of the maximal ventilatory depression was maintained, being 20% throughout the entire work ranges studied. The contribution of the peripheral chemoreceptors to total ventilation is hardly altered by lactic acidosis caused by heavy exercise above the anaerobic threshold according to our data. These results suggested that the peripheral chemoreceptors may not be solely responsible for excessive hyperventilation, or residual activities of peripheral chemoreceptors still exist after O2 breathing especially during heavy exercise above the anaerobic threshold.

[Respiratory control in diffuse interstitial lung disease]

Whether the change of lung volume affect ventilatory responsiveness to chemical stimuli has not been studied in patients with interstitial lung disease (ILD). We measured the responses of minute ventilation (VE), tidal volume (VT), and occlusion pressure (P0.1) to hypercapnia (HCVR) and hypoxia (HVR) in these patients. Breathing efficiency (delta VE/delta P0.1) and effective compliance (delta VT/delta P0.1) were also measured under the same stimuli. 1) HCVR and HVR were measured in one female patient with hypersensitivity pneumonitis. VE responses during low VC phase (VC; 71% of predicted value) were similar to that during increased VC phase (VC; normal level) in both HCVR and HVR. However, VT responses of low VC phase were lower than those of increased phase, and P0.1 responses of low VC phase were higher than those of increased VC phase. Both breathing efficiency and effective compliance of low VC phase were lower than those of increased VC phase. 2) Thirty one patients with ILD were divided into two groups: low VC group; VC < 80% of predicted value, and normal VC group; VC > 80% of predicted value. HCVR and HVR were compared between two groups. Mean values of VE response to hypercapnia and hypoxia in low VC group were lower than those of in normal group, although they were not significantly different. VT response to hypercapnia and hypoxia were significantly lower of low VC group than those of normal VC group. Mean values of P0.1 responses to hypercapnia and hypoxia of low VC group were higher than those of normal VC group, although they were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Dependence of biphasic heart rate response to sustained hypoxia on magnitude of ventilation in man

We studied the dynamic profile of respiratory and circulatory activities during sustained isocapnic hypoxia in healthy males. In response to end-tidal PO2 depression to about 55 Torr, minute ventilation first increased briskly and then depressed. Such biphasic response to hypoxia was also observed in the heart rate. A significantly positive correlation was found between the magnitudes of ventilatory and heart rate responses. No significant increases were found in arterial noradrenaline and potassium, but adrenaline significantly increased gradually with time. Furthermore, when VT and f were intentionally maintained constant so as to prevent the biphasic ventilatory change, the biphasic heart rate response previously seen in spontaneous hypoxic breathing disappeared. We suggest that the heart rate is mainly determined by the pulmonary vagal inflation reflex. Putative neurochemicals to elicit hypoxic ventilatory depression, and arterial catecholamine and potassium concentrations may not be directly related to the specific profile of the biphasic heart rate response during moderate hypoxia.

Effect of verapamil on ventilatory and circulatory responses to hypoxia and hypercapnia in normal subjects

Recent investigations have shown that the calcium channel blocker verapamil attenuated the hypoxic ventilatory chemosensitivity of carotid body in animals. To determine whether this is also the case in humans, transient physiological chemodenervation by O2 breaths (withdrawal test) during sustained hypoxia (N = 7), and ventilatory and circulatory responses to progressive hypoxia and hypercapnia (N = 8) were examined after oral administration of verapamil. During sustained hypoxia after verpamil, there was a significant reduction of withdrawal response from 5th to 25th min value (p < 0.01), but not after placebo. On the other hand, no significant difference in ventilatory responses to progressive hypoxia and hypercapnia was observed after verapamil. Verapamil run reveals similar features with placebo run in circulatory parameters except blood pressure response, which tended to be suppressed by verapamil. We conclude that verapamil attenuates peripheral chemoreceptor activity with time during sustained mild hypoxia in normal adult humans and this may be explained by delayed depletion in intracellular Ca2+ for chemotransduction of the peripheral chemoreceptors.

Dynamic profile of cardiovascular activity in relation to augmented ventilation and humoral agents during hypercapnic hypoxia

A time course of cardiovascular activity in 8 healthy males in relation to augmented ventilatory activity and humoral factors was observed during step CO2 elevation with constant hypoxia. During the first step increase, by 3 Torr in end-tidal PCO2 (PETCO2), the heart rate (HR) initially tended to decrease, then slowly increased to slightly below that of the previous eucapnic level, whereas ventilation maintained a gradual rise throughout this period. On the other hand, during second step PETCO2 elevation, by a further 3 Torr, both HR and ventilation progressively increased. The plasma catecholamine (CA) concentration was also significantly elevated during this period, suggesting a concomitant enhancement in sympathetic activity. Blood pressure (Bp) was progressively augmented throughout the entire hypoxic challenge. We conclude that 1) the characteristic profile of HR change may be explained by the observation that initial HR depression by peripheral chemoreceptor stimulation is gradually overridden by delayed hyperventilation, CA elevation, and enhanced sympathetic activity; 2) Bp augmentation may be elicited by increased CA release and sympathetic activity; and 3) plasma K+ concentration does not change so as to affect cardiovascular and respiratory activity.

Contribution of chemical and non-chemical drives to breath-holding determined by visual analog scale (VAS)

Chemical and non-chemical contributions to breath-holding time (BHT) were directly determined by using a visual analog scale (VAS). These values were compared with those indirectly calculated from the method proposed by Godfrey and Campbell (1968). The magnitude of non-chemical factor at low PCO2 in our study was substantially less than the one obtained by the above investigators. We conclude that Godfrey and Campbell's model postulating linear augmentation of non-chemical sensation is inappropriate to explain dyspnea profile during breath-holding.