Stereotactic radiosurgery: comparing different technologies

Radiosurgery can be defined as 3-dimensional stereotactic irradiation of small intracranial targets by various radiation techniques. The goal is to deliver, with great accuracy, a large, single fraction dose to a small intracranial target, while minimizing the absorbed dose in the surrounding tissue. This article describes certain technical aspects of radiosurgery and compares the different methods of performing such treatment. The 2 most frequently used types of devices for radiosurgery are units with multiple cobalt sources (e.g., the Gamma Knife) and those based on a linear accelerator. In the former, highly collimated beams of radiation from the cobalt sources intersect at the target. In the latter, the source of a highly collimated beam of high-energy photons directed at the target turns through an arc or set of arcs. The accuracy of target localization, the steepness of fall-off of the radiation dose outside the target and the ability to irradiate an irregularly shaped target are all comparable for these 2 types of devices, despite claims to the contrary.     

Ultrasonic pachymeter: a little different role

Background

Ultrasonic pachymeter, though primarily used in refractive surgery and in glaucoma evaluation, can evaluate and compare the change in corneal thickness following extracapsular cataract extraction (ECCE), small incision cataract surgery (SICS) and phacoemulsification.

Method

Six hundred patients were included in study. Patients were divided into three groups. Group 1 (200 eyes), group 2 (200 eyes) and group 3 (200 eyes) underwent ECCE, SICS, and phacoemulsification, respectively. Corneal thickness was evaluated pre-operatively and postoperatively on day 1, day 2, day 7, day 15, and day 30 by ultrasonic pachymetry.

Results

Mean pre-operative corneal thickness in central, superior, inferior, nasal, and temporal quadrants is 525.35 ± 32.34 μm, 592.23 ± 35.39 μm, 595.66 ± 31.68 μm, 589.29 ± 38.07 μm, and 581.19 ± 42.31 μm, respectively. Postoperatively, a highly significant (P<0.01) increase in central corneal thickness was observed up to day 15 in ECCE, day 7 in SICS whereas it was up to day 2 in phacoemulsification. In superior quadrant, it is up to day 15 in ECCE and SICS whereas it is up to day 7 in phacoemulsification. In inferior quadrant, it was up to day 2 in all three techniques. In temporal quadrant, it is up to day 7 in ECCE and up to day 2 in SICS and phacoemulsification. In nasal quadrant, a highly significant (P<0.01) increase in corneal thickness was observed up to day 7 in ECCE and SICS whereas it was up to day 2 in phacoemulsification.

Conclusion

Normal central corneal thickness is 525.35 ± 32.44 μm. At midperiphery, inferior cornea has maximum corneal thickness followed by superior, temporal, and nasal cornea. Postoperatively, pre-operative value of corneal thickness and visual rehabilitation is achieved earliest in phacoemulsifiaction followed by SICS and ECCE.     

Single incision laparoscopic right hemicolectomy: different approaches

Background Single incision laparoscopic colectomy has been performed in recent years,and has been shown to be feasible and safe.This study was to assess the feasibility of single incision laparoscopic ...     

脊髓内注射不同量液体及不同药物对正常大鼠神经功能的影响

目的探寻正常大鼠脊髓实质内注射,液体量大小及药物对脊髓神经功能的影响及适用于脊髓损伤基因治疗的安全注射量。方法采用（4×3）析因实验设计将96只成年健康SD大鼠随机分为12组,每组大鼠依分组情况分别于T13椎体水平注射NS或病毒缓冲液或Ad—LacZ（1×10^9pfu／ml）2、4、6、10μl。另取6只成年健康SD大鼠作为手术对照组,只行椎板减压术,不进行微注射。术后不同时间采用BBB评分标准对每组大鼠进行后肢运动功能检查。术后1、2、4周处死大鼠,病理学分析确定有效组织保留率。Ad—LacZ各组切片行X—ga染色,观察重组腺病毒在脊髓中的表达。结果神经功能损伤及组织损伤程度随注射量增大而加重,不同注射液体量间比较差异有统计学意义（P=0．000）。不同注射药物间进行比较,Ad—LacZ组损伤程度重于NS组及病毒缓冲液组,差异有统计学意义（P=0．044）。NS组与病毒缓冲液组比较,差异无统计学意义（P=1．000）。Ad—LacZ不同液体量各组均可完成对脊髓灰质神经细胞和胶质细胞的转染,术后4周阳性细胞数减少。结论脊髓实质内微注射本身就可引起组织损伤及神经功能障碍。重组腺病毒可引起组织的免疫反应,加重脊髓损伤。对于正常大鼠脊髓,4μl的重组腺病毒为相对安全注射量;6μl为临界注射量,应谨慎把握。     

Tissue reaction to sealing materials: different view at biocompatibility

The biodegradability of root canal sealers in areas other than the root canal system is crucial to the overall success rate of endodontic treatment. The aim of the present study was to investigate, the cell and tissue reaction to GuttaFlow and AHPlus, both in vitro and in vivo. For the in vitro experiments the materials were incubated with Human Periodontal Ligament Fibroblasts and cell proliferation and cytotoxicity analyses were performed. Additional fluorescence-microscope stainings were carried out in order to visualize cell growth and morphology. For assessment of the tissue reaction to the materials a subcutaneous implantation model in Wistar rats was employed and the inflammatory response to the materials was visualized by means of general and specific histology after 6 weeks. Human gingival fibroblasts proliferation seemed to be dependent upon dental material and cultivation time. After an incubation period of 96 hrs AHPlus proved to be significantly (p<0.002) more cytotoxic than GuttaFlow, as only a small number of fibroblasts survived on AHPlus. In vivo, GuttaFlow was surrounded by a fibrous capsule and no degradation took place, while AHPlus induced a well-vascularized granulation tissue in which the material was phagocyted by macrophages. The results of this study demonstrate that a potential cytotoxic effect of a sealing material may beneficial in order to have antibacterial properties and induce self degradation when accidentally extruded over the apical foramen.     

Population distribution residing at different altitudes: implications for hypoxemia

BACKGROUND: Hypoxemia can adversely affect health. The present study is aimed at estimating the prevalence of altitude-related low partial pressure of oxygen in arterial blood in Mexican population by means of census and geographic data. METHODS: Population, altitude, and characteristics of communities were obtained from the Mexican Institute of Statistics, Geography, and Informatics (INEGI). The population of each municipality (municipio) was assumed to have the same age distribution as that reported for the entire country. Partial pressure of oxygen in arterial blood (PaO(2)) was estimated from altitude and from a hypothetical alveolar-arterial oxygen gradient that increases with age. RESULTS: In Mexico, 3.95% of the population lives at altitudes 2,500 m above sea level. Census data for the year 1990 recount 3.6 million people distributed among 6,150 communities. Exposure to intermediate altitudes is considerable: one half of the Mexican population resides above 1,550 m, 32% above 2,000 m, 25% above 2,230 m, and 5% above 2,440 m. It was estimated that between 0.9 and 3.4% of the healthy population (between 800,000 and 3 million persons) have a resting PaO(2) <55 torr, a criterion frequently used for prescribing chronic oxygen therapy in patients with lung diseases. CONCLUSIONS; Although the exact prevalence of hypoxemia in Mexico awaits empirical data, a large number of people live in places where altitude may expose them to low partial pressure of oxygen in inspired air. Ensuing hypoxemia may adversely affect their health. Hypoxia may be particularly harmful to elderly persons and to patients suffering from respiratory diseases.