: A careful examination of the foundation upon which the concept of the Dose-Volume Histogram (DVH) is built, and the implications of this set of parameters on the clinical application and interpretation of the DVH concept has not been conducted since the introduction of DVHs as a tool for the quantitative evaluation of treatment plans. The purpose of the work presented herein is to illustrate problems with current methods of implementing and interpreting DVHs when applied to hollow anatomic structures such as the bladder and rectum.
: A typical treatment plan for external beam irradiation of a patient with prostate cancer was chosen to provide a data set from which DVH curves for both the bladder and rectum were calculated. The two organs share the property of being shells with contents that are of no clinical importance. DVHs for both organs were computed using a solid model and using a shell model. Typical treatment plans for prostate cancer were used to generate DVH curves for both models. The Normal Tissue Complication Probability (NTCP) for these organs is discussed in this context.
: For an eight-field conformal treatment plan of the prostate, a bladder DVH curve generated using the shell model is higher than the corresponding curve generated using the solid model. The shell model also has a higher NTCP. A six-field conformal treatment plan slo results in a higher DVH curve for the shell model. A treatment plan consisting of bilateral 120-degree arcs, results in a higher DVH curve for the shell model, as well as a higher NTCP.
: The DVH concept currently used in evaluation of treatment plans is problematic because current practices of defining exactly what constitutes “bladder” and “rectum.” Commonly used methods of tracing the bladder and rectum imply use of a solid structure model for DVHs. In reality, these organs are shells and the critical structure associated with NTCP is obviously and indisputably the shell, as opposed to its contents. Treatment planning algorithms for DVH computation should thus be modified to utilize the shell model for these organs. 相似文献
OBJECTIVE: Complementary and alternative medicine may influence cardiac surgical care by inducing coagulopathies and interacting with perioperative medications. We evaluated the significance of complementary and alternative medicine use in an acutely ill cardiac surgical population and assessed the willingness of patients to reveal these activities to their physicians and surgeons. METHODS: A total of 376 consecutive patients undergoing preoperative or postoperative cardiothoracic surgical evaluations at an urban academic medical center were approached to complete a survey regarding use and attitudes toward complementary and alternative medicine. All surveys were administered and collected between March and May 1998. RESULTS: Completion rate was 70% (n = 263). Respondents were predominantly male (72%), white (76%), and well educated (59%). The overall rate of complementary and alternative medicine use was 75%, but excluding prayer and vitamins, which are often not considered complementary and alternative medicine therapies, the rate was 44%. There was no correlation between the use of complementary and alternative medicine and the parameters of gender, age, race, or education level. Only 17% responded that they had discussed complementary and alternative medicine with their physicians, and 48% responded that they did not want to discuss the topic at all. CONCLUSIONS: Complementary and alternative medicine is used as frequently in patients undergoing cardiac surgery, as in the general population. Physicians and surgeons should be aware that patients have no inherent predisposition toward or against using complementary and alternative medicine, but that they are unlikely to volunteer their experience with it. The unwillingness of patients to discuss complementary and alternative medicine with physicians has serious implications for their safety, especially in acute care situations. 相似文献
