Utilization of cone beam CT for reconstruction of dose distribution delivered in image-guided radiotherapy of prostate carcinoma - bony landmark setup compared to fiducial markers setup.

The purpose of this study was to compare two different styles of prostate IGRT: bony landmark (BL) setup vs. fiducial markers (FM) setup. Twenty-nine prostate patients were treated with daily BL setup and 30 patients with daily FM setup. Delivered dose distribution was reconstructed on cone-beam CT (CBCT) acquired once a week immediately after the alignment. Target dose coverage was evaluated by the proportion of the CTV encompassed by the 95% isodose. Original plans employed 1 cm safety margin. Alternative plans assuming smaller 7 mm margin between CTV and PTV were evaluated in the same way. Rectal and bladder volumes were compared with initial ones. While the margin reduction in case of BL setup makes the prostate coverage significantly worse (p = 0.0003, McNemar's test), in case of FM setup with the reduced 7 mm margin, the prostate coverage is even better compared to BL setup with 10 mm margin (p = 0.049, Fisher's exact test). Moreover, partial volumes of organs at risk irradiated with a specific dose can be significantly lowered (p < 0.0001, unpaired t-test). Reducing of safety margin is not acceptable in case of BL setup, while the margin can be lowered from 10 mm to 7 mm in case of FM setup.

Utilization of cone-beam CT for offline evaluation of target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment.

AIM: To assess target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment and to assess possibility of safety margin reduction. BACKGROUND: Implementation of IGRT should influence safety margins. Utilization of cone-beam CT provides current 3D anatomic information directly in irradiation position. Such information enables reconstruction of the actual dose distribution. MATERIALS AND METHODS: Seventeen prostate patients were treated with daily bony anatomy image-guidance. Cone-beam CT (CBCT) scans were acquired once a week immediately after bony anatomy alignment. After the prostate, seminal vesicles, rectum and bladder were contoured, the delivered dose distribution was reconstructed. Target dose coverage was evaluated by the proportion of the CTV encompassed by the 95% isodose. Original plans employed a 1 cm safety margin. Alternative plans assuming a smaller 7 mm margin between CTV and PTV were evaluated in the same way. Rectal and bladder volumes were compared with the initial ones. Rectal and bladder volumes irradiated with doses higher than 75 Gy, 70 Gy, 60 Gy, 50 Gy and 40 Gy were analyzed. RESULTS: In 12% of reconstructed plans the prostate coverage was not sufficient. The prostate underdosage was observed in 5 patients. Coverage of seminal vesicles was not satisfactory in 3% of plans. Most of the target underdosage corresponded to excessive rectal or bladder filling. Evaluation of alternative plans assuming a smaller 7 mm margin revealed 22% and 11% of plans where prostate and seminal vesicles coverage, respectively, was compromised. These were distributed over 8 and 7 patients, respectively. CONCLUSION: Sufficient dose coverage of target volumes was not achieved for all patients. Reducing of safety margin is not acceptable. Initial rectal and bladder volumes cannot be considered representative for subsequent treatment.

Issues and ethical problems of stem cell therapy--where is Hippocrates?

Stem cells and their therapeutic use present many questions associated with ethical problems in medicine. There is great effort on the part of physicians to help millions of patients while there are ethical problems with the use of new methods and technologies and all of these are affected by economic and political influences. How will the current generation deal with these problems? Medicine, in this begard, is experiencing a stormy evolution of human culture in the relationships between disease, patient and doctor. Philosophy approaches the same juncture of human culture, but seemingly from the other side. Both disciplines are facing a great problem: How to unite the content of current human morality and the desire for health? Both philosophers and physicians perceive this deficit in human culture as it does not provide immediately usable normatives, which the living generation of healthy and ill is waiting for. It may be said that medicine, as many times before, has reached a stage where it cannot rely only on the proved axiologic values from the past, ethical normatives or cultivated moral sense of its subjects. Medicine has no other alternative than to take an active part in resolution of interdisciplinary problems originating from philosophic-biologic or philosophic-medical inquiries of axiologic, ethical, and moral issues. Our paper indicates some ways of the search in forming ethical principles of the stem-cell therapy from the view of biologists and physicians. New ways are recommended in theoretical-methodological interdisciplinary research, especially, in theoretical and experimental biology, and theoretical and clinical medicine, as well as philosophy. In this paper important ethical problems are pointed out in order to find answers to some key problems connected with cell therapy and the use of stem cells.