The effect of the nucleus random location on the cellular S-values - Based on Geant4-DNA.

INTRODUCTION: The nucleus is the most crucial target in cell micro-dosimetry. At cell division time, cells do not have concentric geometry synchronously. This issue will be more essential for the low-energy electron emitters. This study investigates the variety of mean absorbed dose (S-value) in the non-concentric cell-nucleus model and random nucleus location within the cell. METHODS: The S-values were calculated by Geant4-DNA for the cell and nucleus with different radius (with the RC/RN ratio = 1.2, 2, 3) and the cell geometry contains nuclei with varying positions inside the cell. Two important components, cytoplasm to the nucleus (N←Cy) and the cell surface to the nucleus (N←Cs) are considered in this work for mono energetic electrons (10-100 keV). To eliminate the effect of the nucleus position (during cell division) on the S-value, the nucleus location in each run was randomly selected inside the cell to represent the cell in a floating state. RESULTS: As the nucleus becomes closer to the cell membrane the differences are more noticeable especially for electrons with energy less than 20 keV as for RN/RC = 1.2, 2, and 3 about 18, 70, and 200%, respectively. CONCLUSION: Due to the variable position of the nucleus in cell division, using a random place defined in Geant4, the calculations are getting closer to the reality while there is not such possibility for analytical method used by MIRD.

Presentation of clinical guidelines via a rule-based expert charting system.

This paper discusses the theoretical basis and cumulative experience with EDECS, the Emergency Department Expert Charting System. This rule-based expert-system introduces clinical guidelines into the flow of patient care while creating the medical record and patient aftercare instructions.

EDECS: the Emergency Department Expert Charting System.

EDECS, the Emergency Department Expert Charting System, integrates clinical guidelines into the everyday practice of medicine. By generating the medical record and patient aftercare instructions, it facilitates patient care. For this reason, doctors are willing to use it. While using it, the doctors are continually presented with advice regarding documentation, testing, and treatment. Unlike guidelines that attempt to modify behavior through traditional educational methods, these computerized guidelines are seen by the physician every time she sees a patient. We have demonstrated this by directly integrating the guidelines into the process of patient care; we can increase compliance with the guidelines [1]. At present EDECS exists for the chief complaints of occupational exposure to body fluids, acute low back pain, recurrent seizure, fever in children, and males with penile discharge or dysuria. Upon examining the patient, the physician proceeds to the computer, which prompts him for essential information regarding the history and physical examination. Certain items are required for all patients with the chief complaint, others are required based on the answers to these items. Data is analyzed by the computer, which provides advice regarding testing and treatment. Once testing is completed, the system suggests a probable diagnosis and aids in patient disposition and discharge planning. Finally, EDECS prints the medical record as well as patient-specific aftercare instructions. EDECS is a user friendly system; most data is entered via mouse. It is written in the OS-based expert system shell AM(TM) and can be run on an IBM compatible PC or PC network. Rules are generally written in an "if...then" format, but more sophisticated rule structures, including Bayesian models, are used when needed. Each module contains separate subroutines for the history, physical, laboratory ordering, treatment, and disposition. These modules call each other in a dynamic fashion. The system is currently being evaluated for its effect on documentation, appropriateness of use of ancillary tests, appropriateness of use of treatments, physician satisfaction, patient satisfaction, and patient outcomes. Initial results of the system's effect on documentation and use of ancillary tests and treatments show much promise [1]. The Occupational Exposure to Body Fluids module has shown a statistically significant, and sometimes rather dramatic, increase in the level of documentation for nearly all items. Further, the advice given by EDECS has caused an increase in the appropriate use of testing and treatments. For example, unnecessary ancillary tests dropped from 1.5 per patient without the computer to 0.1 per patient with the computer's aid. EDECS facilitates quality management activities and research since it collects standardized information and stores it in an easily retrievable database format. It can also be used to educate medical students and residents about the proper care of patients with a given chief complaint. At this session, EDECS will be demonstrated, and issues regarding the development of guidelines, the encoding of guidelines in rules, and the organizational structure of the software will be presented and discussed.