SU-E-T-491: A FLUKA Monte Carlo Computational Model of a Scanning Proton Beam Therapy Nozzle at IU Proton Therapy Center.

PURPOSE: Charged particle therapy, especially proton therapy is a growing treatment modality worldwide. Monte Carlo (MC) simulation of the interactions of proton beam with equipment, devices and patient is a highly efficient tool that can substitute measurements for complex and unrealistic experiments. The purpose of this study is to design a MC model of a treatment nozzle to characterize the proton scanning beam and commissioning the model for the Indiana University Health Proton Therapy Center (IUHPTC. METHODS: The general purpose Monte Carlo code FLUKA was used for simulation of the proton beam passage through the elements of the treatment nozzle design. The geometry of the nozzle was extracted from the design blueprints. The initial parameters for beam simulation were determined from calculations of beam optics design to derive a semi-empirical model to describe the initial parameters of the beam entering the nozzle. The lateral fluence and energy distribution of the beam entering the nozzle is defined as a function of the requested range. The uniform scanning model at the IUHPTC is implemented. The results of simulation with the beam and nozzle model are compared and verified with measurements. RESULTS: The lateral particle distribution and energy spectra of the proton beam entering the nozzle were compared with measurements in the interval of energies from 70 MeV to 204.8 MeV. The accuracy of the description of the proton beam by MC simulation is better than 2% compared with measurements, providing confidence for complex simulation in phantom and patient dosimetry with the MC simulated nozzle and the uniform scanning proton beam. CONCLUSIONS: The treatment nozzle and beam model was accurately implemented in the FLUKA Monte Carlo code and suitable for the research purpose to simulate the scanning beam at IUHPTC.

Arytenoid dislocation after cardiac surgery.

Occurring most usually as complications of upper aerodigestive tract instrumentation during endotracheal intubation or extubation, arytenoid cartilage dislocation and arytenoid subluxation are uncommon laryngeal injuries. Their precise cause, however, is usually difficult to determine. We encountered arytenoid dislocation following cardiac surgery requiring the use of transesophageal echocardiography (TEE). This case prompted us to review some of the mechanisms of injury to the cricoarytenoid joint. We conclude that even very subtle force may dislocate the arytenoid cartilage. We speculate that careless insertion of a TEE probe is mechanically capable of causing arytenoid dislocation and arytenoid subluxation. As ideal tools for intra-operative cardiovascular monitoring, TEE probes are increasingly being used routinely during cardiovascular surgery. So far, arytenoid cartilage dislocation and subluxation following TEE probe insertion have been reported rarely, but complications caused by TEE may increase in the near future. We wish to emphasize the pathophysiological risks of TEE monitoring and other procedures associated with anesthesia, and the need for a proper explanation to achieve informed consent before carrying out TEE monitoring during cardiac surgeries.

Practical issues in bispectral analysis of electroencephalographic signals.

IMPLICATIONS: The aim of this report was to confirm the methodology of bispectral analysis of electroencephalogram. In developing a software for real-time bispectral analysis, we encountered several practical problems in bispectrum calculation. We settled those and concluded that 3 min of monitoring are required to obtain reliable and reproducible bicoherence values.

Overexpression of heme oxygenase-1 protects allogeneic thyroid grafts from rejection in naive mice.

BACKGROUND: Endocrine allografts are an option for the treatment of endocrine failure. METHODS: One lobe of the thyroid was transplanted under the kidney capsule. RESULTS: C57BL/10 (H2(b)) thyroids were rejected in naive CBA (H2(k)) mice within 14 days after transplantation. When mice were treated with anti-CD4 monoclonal antibodies (mAb), all grafts survived for more than 60 days. The first grafts still survived after second C57BL/10 or Balb/c (H2(d)) thyroid grafts that were transplanted into the same recipients were rejected acutely, which suggests that the primary grafts were modified under anti-CD4 mAb treatment. To confirm this hypothesis, C57BL/10 thyroid grafts from anti-CD4 mAb-treated mice were retransplanted. All grafts survived in naive mice; this correlated with the overexpression of heme oxygenase-1 (HO-1) in the grafts. Next, an inhibitor of HO-1 (zinc protoporphyrin) or control compound (copper protoporphyrin) was injected intraperitoneally after transplantation of C57BL/10 thyroid grafts into the primary CBA recipients that had been treated with anti-CD4 mAb. The grafts in mice that had been treated with zinc protoporphyrin, but not copper protoporphyrin, were rejected when retransplanted to naive recipients. CONCLUSIONS: Overexpression of HO-1 correlated with the protection of fully allogeneic thyroid grafts from rejection when retransplanted into naive recipients.

[Anesthetic management of heart transplantation].

We anesthetized a 47-yr-old man with end-stage hypertrophic cardiomyopathy for heart transplantation. This is the first case of heart transplantation from a patient with brain death, since the organ transplantation law had become valid in Japan. Anesthesia was induced and maintained with fentanyl and diazepam. Aseptic technique was used in inserting and securing all catheters. The patient was assisted by left ventricular assist system, and hemodynamic suppression at anesthetic induction was trivial. Since complete AV block was present at the termination of cardiopulmonary bypass (CPB), VVI pacing and infusion of isoproterenol were started. In addition, nitroglycerin was given for pulmonary vasodilation. The cardiovascular support used for weaning from CPB included dobutamine, isoprote-renol, dopamine and milrinone. Following weaning from CPB sinus rhythm appeared spontaneously and function of the transplanted heart was satisfactory. When the patient was transported to ICU reduction in doses of catecholamines was possible, and dopamine and milrinone were infused. The patient was extubated 10 hours after admission to ICU.

Experimental parathyroid transplantation: human parathyroid grafts survived and functioned in mice treated with anti-CD4 monoclonal antibody.

Permanent hypoparathyroidism is one of the most difficult of all endocrine disorders to treat medically. To examine the possibility that xenotransplantation can be used to treat hypoparathyroidism, human parathyroid tissues were transplanted into mice. Human parathyroid tissue was taken from specimens excised from patients with hyperparathyroidism. Fresh human parathyroid tissue was implanted under kidney capsule of CBA (H2k) mice. Some mice were treated intraperitoneally with depleting anti-CD4 monoclonal antibody (mAb, YTA 3.1, 100 microg/dose, days -1. 0. 1, 2, 3, and 5). Mice were killed 30 days after transplantation. Survival of parathyroid grafts was examined microscopically and human parathyroid hormone in serum was measured by ELISA. All parathyroid grafts survived under kidney capsule and human parathyroid hormone was strongly detected in serum (621 +/- 576 pg/mL) when recipients were treated with short-course treatment of anti-CD4 mAb. Conversely, no parathyroid tissue was seen microscopically in any recipient mice without anti-CD4 mAb treatment. Human parathyroid hormone was undetectable by ELISA in naive mice and mice transplanted with human parathyroid tissue without short-course treatment of anti-CD4 mAb. Xenogeneic human parathyroid tissue survived and functioned in mice treated with short-course treatment of anti-CD4 mAb.

Aeration time following ethylene oxide sterilization for reusable rigid sterilization containers: concentration of gaseous ethylene oxide in containers.

Because ethylene oxide (EO) gas is toxic to humans, restrictions have been imposed on its use for sterilization, specifying allowable levels of residual EO remaining in sterilized apparatus and materials. However, the aeration time that optimizes the removal of the remaining EO when a rigid sterilizing container is used for a vessel had not been identified. Therefore, polyvinyl chloride, which easily adsorbs EO, was placed in rigid sterilizing containers, and aeration was carried out after 1, 8, 12, 17, and 24 hours. After standard EO sterilization, the EO concentrations remaining in the air in the rigid containers were measured. The results indicate that a period of 17 hours of aeration is appropriate when a rigid sterilizing container is used.

Infrared transmission of electronic information via LAN in the operating room.

Recent advances in technology have brought many kinds of monitoring devices into the operating room (OR). The information gathered by monitors can be channeled to the operating ward information system via a local area network (LAN). Connecting patients to monitors and monitors to the LAN, however, requires a large number of cables. This wiring is generally inconvenient and particularly troublesome if the layout of the OR is rearranged. From this point of view, wireless transmission seems ideally suited to clinical settings. Currently, two modes of wireless connectivity are available: radio-frequency (RF) waves or infrared (IR) waves. Some reports suggest that RF transmission is likely to cause electromagnetic interference (EMI) in medical devices such as cardiac pacemakers or infusion pumps. The risk of malfunctioning life-sustaining devices and the catastrophic consequences this would have on seriously ill patients rules out the use of RF. Here, we report an IR system using IR modems for LAN connectivity in the OR. In this study, we focused on the possible detrimental effects of EMI during wireless connectivity. In our trial, we found no evidence of EMI of IR modems with any of the medical devices we tested. Furthermore, IR modems showed similar performance to a wired system even in an electrically noisy environment. We conclude that IR wireless connectivity can be safely and effectively used in ORs.

The effects of propofol, isoflurane, and sevoflurane on oxygenation and shunt fraction during one-lung ventilation.

UNLABELLED: Propofol's effect on hypoxic pulmonary vasoconstriction during one-lung ventilation (OLV) has not been determined. Twenty patients who had long-term OLV for esophageal surgery were allocated randomly to one of two study groups; one in which isoflurane administration preceded propofol, and another in which sevoflurane administration preceded propofol. Arterial and mixed venous blood samples and hemodynamics were measured as follows: before OLV, during OLV, OLV at 4 cm of positive end-expiratory pressure (PEEP), OLV after conversion from volatile anesthetics to propofol, OLV at 4 cm of PEEP, and after OLV. After the application of 4 cm of PEEP during propofol anesthesia, PaO2 increased significantly in both groups. The shunt fraction (Qs/Qt) increased significantly after the initiation of OLV in both groups and decreased significantly after the conversion from volatile anesthetics to propofol in both groups. Propofol can be used safely during OLV because PaO2 increased after the application of 4 cm of PEEP during propofol anesthesia, and Qs/Qt decreased significantly after the conversion from inhaled anesthetics to propofol anesthesia. IMPLICATIONS: During one-lung ventilation, the arterial partial pressure of oxygen values with propofol were greater than those with isoflurane and sevoflurane, and shunt fraction values with propofol were lower than those with both volatile anesthetics. Propofol improved oxygenation and shunt fraction during one-lung ventilation compared with volatile anesthetics.

[Hemodynamic effects of amrinone combined with dopamine in patients undergoing living renal transplantation].

Systemic hypertension is a constant feature of chronic renal failure, mediated by renin and exacerbated by salt and fluid loading. Vascular atherosclerosis appears to accelerate in patients on long-term dialysis. Therefore, it is important to control hypertension and keep appropriate renal blood flow during living renal transplantation surgery. Amrinone, a phosphodiesterase inhibitor, produces vasodilation in arterial smooth muscle as well as venodilation in the capacitance bed. By increasing myocardial contractility it increases inotropic effect. Amrinone has potent inodilator effects because of its dual mechanism of action. The current study is aimed to compare hemodynamic effects between amrinone (3-5 mg.kg-1.min-1) (AMR group, n = 4) and nitroglycerin (0.3-1.0 mg.kg-1.min-1) (NTG group, n = 5), combined with dopamine (3-5 mg.kg-1.min-1) in nine patients undergoing living renal transplantation. Increase in cardiac index in AMR group was significantly larger than that in NTG group. Values of systemic and pulmonary vascular resistance in AMR group were significantly smaller than those in NTG group. No significant difference was found in renal function in the post-operative period.

Long-term culture of functional hepatocytes on chemically modified collagen gels.

For long-term maintenance of functional hepatocytes in primary culture, a new culture system with chemically modified type-I collagen gel was developed. Isolated hepatocytes spread as flat cells and rapidly lost their viability and functions when cultured on native collagen gel. In contrast, they survived for several weeks when cultured on collagen gels that had been modified by treatment with sodium-borohydride (NaBH(4)) or by digestion with pepsin, which resulted in destruction of crosslinking of collagen fibers and marked decrease in meachanical strength of the gels. These long-lived cells were round and aggregated and maintained high levels of various differentiated liver functions including albumin secretion and activities of tyrosine aminotransferase and P450. Moreover on collagen gels modified by treatment with NaBH(4) or pepsin, the cell showed less DNA synthesis in response to mitogenic stimulation than cells cultures on gel containing native collagen. Interestingly, crosslinking of these chemically modified gels with D-ribose resulted in changes in various phenotypes of hepatocytes cultures on them including shape, longevity, and functions expressed when the cells were cultured on native collagen gel, suggesting that the effect of modification of the collagen gel is reversible. Thus the structure of collagen gels, probably due to the degree of crosslinking, seems to affect the morphology, maintenance of differentiated functions, and growth of primary cultured hepatocytes.

Inhibitory effect of prostaglandin E1 on gastric secretion during general anesthesia in humans.

The present study was undertaken to clarify the effects of prostaglandin E1 (PGE1) on gastric secretion during general anesthesia. Thirty-three patients, 16 with (PGE1 group) and 17 without (control group) PGE1 administration, scheduled for selective surgery were studied during general anesthesia with nitrous oxide (67%) and enflurane (1%-2% inspired). PGE1 was administered at a rate of 50-200 ng·kg(-1)·min(-1) when hypotensive medication was required. In the PGE1 group, gastric juice was collected serially three times before and during administration and 60 min after discontinuation of PGE1. In the control group, it was collected three times corresponding to those in the PGE1 group. The pH of gastric juice increased significantly, and the acidity and pepsin activity decreased after the beginning of the administration of PGE1, and these changes were observed even 1h after discontinuation. There was significant differences in the pH, acidity, and pepsin activity between the two groups after administration of PGE1. The results indicate that PGE1 inhibits gastric secretion at doses that produce a sufficient hypotensive effect under general anesthesia.