PURPOSE: This study was to search the optimal slice thickness of computed tomography (CT) in an intensity modulated radiation therapy plan through changing the slice thickness and comparing the change of the calculated absorbed dose with measured absorbed dose. MATERIALS AND METHODS: An intensity modulated radiation therapy plan for a head and neck cancer patient was done, first of all. Then CT with various ranges of slice thickness (0.125~1.0 cm) for a head and neck anthropomorphic phantom was done and the images were reconstructed. The plan parameters obtained from the plan of the head and neck cancer patient was applied into the reconstructed images of the phantom and then absorbed doses were calculated. Films were inserted into the phantom, and irradiated with 6 MV X-ray with the same beam data obtained from the head and neck cancer patient. Films were then scanned and isodoses were measured with the use of film measurement software and were compared with the calculated isodeses. RESULTS: As the slice thickness of CT decreased, the volume of the phantom and the maximum absorbed dose increased. As the slice thickness of CT changed from 0.125 to 1.0 cm, the maximum absorbed dose changed ~5%. The difference between the measured and calculated volume of the phantom was small (3.7~3.8%) when the slice thickness of CT was 0.25 cm or less. The difference between the measured and calculated dose was small (0.35~1.40%) when the slice thickness of CT was 0.25 cm or less. CONCLUSION: Because the difference between the measured and calculated dose in a head and neck phantom was small and the difference between the measured and calculated volume was small when the slice thickness of CT was 0.25 cm or less, we suggest that the slice thickness of CT should be 0.25 cm or less for an optimal intensity modulated radiation therapy plan.
Head ; Head and Neck Neoplasms ; Humans ; Neck

BACKGROUND: Mechanisms of secondary injury (post-ischemic injury) in the central nervous system have cently reported in a vast of amount of experiments. Among many factors which give rise to post-ischemic neuronal damage, glial deterioration probably mediated by calcium paradox, could be another of the aggravating deleterious factars to the already ischemic neurophil. METHODS: Here we have designed experiment to investigate calcium paradox in astroglial cell line, humsn asttocytoma U1242MG. Intracellular calcium alterations in experimental cells were monitored by using calcium indicating dye fura-2 and epifluorescent photometry system. RESULTS: Intracellular free calcium changes during reperfusion phase after exposure to low calcium led to a prampt increase in intracellular calcium level after 10 and 30 minutes. The way of calcium entry during the reperfusion phase was mediated by the revase mode of Na+/Ca(2+) exchanger. Cells that had a reduction of reperfusate calcium to 10 uM increased cell viability. Also we observed an inverse relationship between major enzymatic activity in the astrocytoma cells (i.e., glutamine synthetase activity) and the duration of reperfusion in the the same protocols. CONCLUSIONS: A relatively small amount of intracellular calcium increase by the reverse mode of Na+/Ca(2+) exchanger during the reperfusion period is related to a limitation of enzyme activity and viability 24 hours later.
Anesthesia* ; Astrocytoma ; Brain ; Calcium ; Capnography* ; Cell Line ; Cell Survival ; Central Nervous System ; Fura-2 ; Glutamate-Ammonia Ligase ; Ions ; Neuroglia ; Neurons ; Photometry ; Reperfusion

No abstract available.
Fistula*

BACKGROUND: The effects of various concentration (20, 50, 100 micrometer) of meperidine were studied in isolated guinea pig and rat ventricular papillary muscles. METHODS: Isometric force of guinea pig ventricular papillary muscle was examined in normal and 26 mM K+ Tyrode's solution. Experiments using rat and guinea pig papillary muscle under normal and low Na+ (40 mM), respectively, were performed to evaluate the effect on Ca2+ release from the sarcoplasmic reticulum (SR). Normal and slow action potentials (APs) were evaluated by using conventional microelectrode technique. Rapid cooling contractures were performed. RESULTS: Meperidine caused dose-dependent depression of peak force from rested-state (RS) to 3 Hz stimulation rates in guinea pig papillary muscles. Conduction block was frequently noted at high stimulation rates (2 and 3 Hz) at 150 micrometer meperidine. ~40% depression of peak force was shown at RS contraction under low Na+ Tyrode's solution, although contractile depression was not shown at RS and low stimulation rates in rat papillary muscles. 100 micrometer naloxone did not reverse the contractile depression caused by 100 micrometer meperidine. Either depression of dV/dt-max from 0.1 to 3 Hz stimulation rates or rate-dependent depression among 1, 2 and 3 Hz could be observed at 150 micrometer meperidine. In 26 mM K+ Tyrode's solution, 50 and 100 micrometer meperidine caused dose-dependent depression of early and late force development. In slow APs, changes of dV/dt-max were not shown at 100 micrometer meperidine. ~40% depression of contracture induced by rapid cooling following 2 Hz stimulation rates was shown at 100 micrometer meperidine. CONCLUSION: The direct myocardial depressant effect of meperidine seems likely to be caused by local anesthetic properties of meperidine, not by the opioid action. Inhibition of SR Ca2+ release, and decreased intracellular Ca2+ secondary to Na+ channel blocking action of meperidine may at least in part be related to direct myocardial depression.
Action Potentials ; Anesthetics* ; Animals ; Contracture ; Depression* ; Guinea Pigs ; Meperidine* ; Microelectrodes ; Myocardium* ; Naloxone ; Papillary Muscles ; Rats ; Sarcoplasmic Reticulum

No abstract available.
Child* ; Humans ; Natural History* ; Ureter* ; Ureterocele*

Pneumatic retinopexy was introduced by Hilton in 1986, and this methed is a recently described procedure used for the treatment of primary rhegmatogenous retinal detachment. A gas bubble is injected into the vitreous cavity so that the bubble closes the retinal break, permitting resorption of subretinal fluid. A chorioretinal adhesion formed around the break by cryotherapy or laser photocoagulation secures the retina in place. Indication of pneumatic retinopexy in A Two-step Outpatient Operation Without Conjuntival Incision described by Hilton in 1986 is retinal detachments secondary to one break or group of breaks no larger than 1 o'clock hour located within the superior 8 o'clock hours of the fundus. The ocular conditions of the 26 cases included in this study were proliferative vitreoretinopathy C1, C2, aphakia, multiple breaks in multiple quadrants, extensive retinal detachment more than 3 quadrants in size, pseudophakia. The overall success rate for primary pneumatic retinopexy was 73.1%(19 eyes). The greatest number of failure were due to delayed absorption of subretinal fluid (5 eyes). With subsequent procedure, 7 eyes that failed with primary pneumatic retinopexy were reattached.
Absorption ; Aphakia ; Cryotherapy ; Humans ; Light Coagulation ; Outpatients ; Pseudophakia ; Retina ; Retinal Detachment ; Retinal Perforations ; Subretinal Fluid ; Vitreoretinopathy, Proliferative

No abstract available.
Silicones*

The authors report two cases of aneurysms of basilar bifurcation approached by modified frontolateral transsylvian route: each aneurysm was clipped successfully through the space between internal carotid artery and posterior communicating artery in case 1 and the space between internal carotid artery, posterior communicating artery and oculomotor nerve in case 2. Historical background and surgical approaches are discussed.
Aneurysm* ; Arteries ; Carotid Artery, Internal ; Oculomotor Nerve

A spinal cord injury without radiographic abnormality(SCIWORA) was defined by Pang and Wilberger in 1982 as the "objective signs of myelopathy as a result of trauma" in which no evidence of fracture, subluxation, or instability on plain radiographs, or computed tomography is demonstrable. Inherent elasticity of the vertebral column in infants and young children, among other age-related anatomical peculiarities, render the pediatric bony cervical and thoracic spine exceedingly vulnerable to deforming forces. We report here on a case of SCIWORA in a 3-year-old girl who presented with lower extremity paralysis, paresthesia, and voiding difficulty. The mechanism of neural damage in this case was purely longitudinal distraction. Such stress on the spine resulted from severe pulling up the lower extremity by her father, which was not thought to be damaging at that time.
Child ; Child, Preschool ; Elasticity ; Fathers ; Female ; Humans ; Infant ; Lower Extremity ; Paralysis ; Paresthesia ; Spinal Cord Diseases ; Spinal Cord Injuries* ; Spinal Cord* ; Spine