Access control systems for radiotherapy treatment rooms

The role of the time-delay or start-up switch as a safety feature in radiotherapy treatment rooms is discussed. A simple optical system which can be retrofitted to any treatment room is described.     

Supraspinal control of spinal centers for antagonist muscles in man

Summary Monosynaptic testing with the H-reflex was used to determine reflex excitability of motoneurons of the gastrocnemius muscle during single voluntary movements: extension or flexion of the ankle. For the last 60 msec of the latent period before the onset of voluntary extension of the foot, reflex excitability of motoneurons of the gastrocnemius (the agonist in extension) gradually increases. With voluntary flexion of the ankle reflex excitability of motoneurons to the gastrocnemius (the antagonist in flexion) is unchanged throughout the latent period until the onset of movement. Simultaneously (accuracy to 10 msec) with the beginning of the myogram of voltary foot flexion, reflex excitability of motoneurons of the gastrocnemius (antagonist) drops sharply. These results provide a basis for discussing an hypothesis concerning supraspinal control of spinal centers for antagonist muscles in man.     

Technologies involved in molecular blood group genotyping

Background Until the 1990s, blood screening, typing and diagnostics depended entirely on serological techniques. For over a century, agglutination has been the gold standard for red blood cell (RBC) antigen detection used in all blood services. However, haemagglutination has certain limitations, such as, the difficulty to phenotype recently and multi-transfused patients or direct antiglobulin test (DAT)-positive patients. The haemagglutination test provides only indirect indications of risk or severity of haemolytic disease of the new born. In part, to overcome these limitations, nucleic acid-based technologies have been used in immunohematology reference laboratories. Methods There are many molecular methods available for red cell genotyping: PCR, PCR-RFLP, PCR-SSP or PCR-ASP, real time PCR, DNA sequencing and pirosequencing and methods with microarrays-based systems. Other molecular techniques that are under development and may be available for red cell genotyping in the next decade include fluidic or open microarrays; matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS); and mini-sequencing. Conclusions Although serology may be superior for some blood group typing, genotyping assays offer a good alternative for problems encountered by serology. In many laboratories, blood group genotyping is already used at a low-throughput level for diagnostics in cases of problematic serology. Especially in case of weak expression of antigens, the presence of rare antigens or auto-antibodies or after multiple transfusions, genotyping is superior. The non-invasive determination of the foetal RHD analysis in maternal plasma by real-time PCR is well established and already offered as a clinical service in a number of countries. The recent availability of automated, high throughput, DNA-array platforms, allows to introduce into the hospital and donor centres this DNA-based typing methodology. The evolution of molecular methods combined with automation and high-quality standards will make large-scale screening a cost-effective reality.     

Molecular epidemiological study of hepatitis B virus in blood donors from five Chinese blood centers

Although the genetic variability of hepatitis B virus (HBV) in HBV-infected patients has been extensively studied, reports on genotypes, subtypes and mutations in the S region of HBV strains from Chinese blood donors are limited. In this study, 245 blood samples from HBsAg-positive blood donors were collected from five geographically diverse blood centers in China. The S region of HBV was amplified, and the HBV genotype and subtype were determined. The amino acid sequences of the S region were aligned, and mutations related to the failure of immunization and HBsAg detection were determined. Of the 245 samples, 228 (93?%) were genotyped successfully. We found that genotypes B, C, D and A accounted for 58.8?%, 21.9?%, 6.6?% and 3.95?% of the isolates, respectively. The distribution of HBV antigen subtypes was as follows: adw (67.6?%), adr (23.3?%) and ayw (8.7?%). Mutations were present in 39 (17.1?%) of 228 samples in the major hydrophilic region (MHR) of the S region. This study demonstrated that HBV genotype/subtype B/adw was the most frequent strain circulating in HBV-infected Chinese blood donors, followed by C/adr. The occurrence of MHR mutants in HBV-infected blood donors and the potential failure to detect some of them in collected units poses a threat to transfusion safety.     

Cellular control of heparin in blood

Many investigators have observed the uptake of exogenous heparin by cells of the reticuloendothelial system (R.E.S.). When heparin is administered by the intravenous, intramuscular, subcutaneous, intraperitoneal and intratracheal routes the anticoagulant response observed is of varying magnitude. This has led us to examine the literature for evidence of a distribution of heparin between the cellular and blood compartments. A re-evaluation of such evidence has provided a new perspective on the pharmacokinetics of heparin. This is presented here in the cellular pool concept which is based on the premise that there exists in the body a pool of cells which takes up a portion of the administered heparin, stores it and later releases it to the circulation. This concept provides a rational explanation for the different types of anticoagulant response obtained with different modes of administration.     

The design of X ray equipment for use in operating rooms

X rays have been employed frequently during orthopaedic surgery. Recent developments in epuipment designed for use in the operating room have increased demand for X ray apparatus as a valuable aid for other kinds of surgery. Alongside the growing demand for both preoperative fluoroscopic examinations and the production of radiographs while the patient is in the operating room, there is an increase in demand for more advanced X ray facilities. Higher X-ray power, larger field size of the image intensifier and better sterility are the main facilities asked for by the surgeon. The advantages and disadvantages of permanently installed X ray units are discussed; the advantages and disadvantages of higher electrical power and the application of large-screen image intensifiers are also examined. Some hints are given on planning X ray equipment for the operating room and on how to solve the problems associated with the processing and reading of films.     

Laminated primary ceiling barriers for medical accelerator rooms

In this work the performance of a number of laminated shields used as the primary ceiling barrier for high-energy accelerator rooms was investigated. The neutron and photon dose equivalent rates were measured outside each shield. Based on the measured photon level and the calculated x-ray leakage level the dose equivalent rate due to photons produced by neutron interactions with the shield materials was estimated. Shielding parameters for polyethylene were established for photons and neutrons. It was found that the barriers designed using the techniques given in an NCRP Report suffered from excessive radiation leakage.     

Multi-objective blood glucose control for type 1 diabetes

For people with type 1 diabetes, automatic controllers aim to maintain the blood glucose concentration within the desired range of 60–120 mg/dL by infusing the appropriate amount of insulin in the presence of meal and exercise disturbances. Blood glucose concentration outside the desired range can be harmful to an individual’s health but concentration below 60 mg/dL, a state known as hypoglycemia, is considered to be more harmful than the concentration above 120 mg/dL, a state known as hyperglycemia. In this paper, two techniques to address this issue within a multi-parametric model based control framework are presented. The first technique introduces asymmetry into the objective function to penalize the deviation towards hypoglycemia more than the deviation towards hyperglycemia. The second technique is based upon placing higher priority on satisfaction of constraints on hypoglycemia than on satisfaction of constraints on hyperglycemia. The performance of both the control techniques is analyzed and compared in the presence of disturbances.