novel phantom design for brachytherapy quality assurance

Background: One major challenge in brachytherapy is to verify the accuracy of dose distributions calculated by the treatment planning system. In this project, a new phantom design has been introduced for quality assurance of dose distributions in gynocological [GYN] brachytherapy implants using EBT GafChromic film. Materials and Methods: This phantom has been designed and fabricated from 90 slabs of 18×16×0.2 cm[3] Perspex to accommodate a tandem and ovoids assembly, which is normally used for GYN brachytherapy treatment. In addition, this phantom design is allowing the use EBT GafChromic films for dosimetric verification of GYN implants with Cs-137 Selectron LDR system. With this assembly, GafChromic films were exposed using a plan designed to deliver 2.5 Gy dose to point "A" in Manchester system for tandem and ovoids configurations and to deliver 1.5 Gy of dose to 0.5 cm distance from the lateral surface of ovoids for using ovoid-pair. The measured dose distributions with GafChromic films were compared with the TPS isodose lines both numerically and spatially. For a quantitative analysis of the results, the measured doses values at several points of interest were evaluated with the treatment planning data and values obtained following the TG-43 dose calculation formalism. Results: The results of these investigations have indicated that the new phantom design enables us to measure differences of greater than +/-6% for LDR brachytherapy GYN treatments. Conclusion: The new phantom design could be utilized for the QA procedure of the brachytherapy remote after loading systems to confirm the accuracy of dose distribution in GYN implants

Effect of recruitment of first time blood donors on donor return behavior in Isfahan

Investigations have shown that the safest blood is driven from voluntary regular blood donors. Because of the importance of blood safety, the main goal of blood transfusion organizations is to provide the safest blood. Hence, the recuritment of blood donors is of most importance. The aim of this survey is to determine the return rate of first time blood donors both with and without invitation cards mailed following the first blood attempt. In a prospective study a questionnaire was handed out to the first time blood donors of Isfahan Blood Transfusion Center. After donation those with negative screening test results [HBsAg, HCV-Ab, HIV-Ab and RPR] were randomly divided into two groups. For one of these groups 3 to 4 months later an invitation card was sent to make an appointment for their next donation session, while the other group [control] did not receive any reminders. At least one year after the first donation attempt, repeat donations of the two groups were recorded. 1500 questionnaires were distributed among first time blood donors out of whom 939 remained in the study [416 in the group for whom invitation card was sent and 523 in the control group]. Frequency of blood donation after one year follow up was different in the two groups. Overall 117 [28.1%] blood donors receiving the invitation cards and 114 [21.8%] donors in the control group did donate again. The difference came out to be significant by chi-square test [chi[2]=5.002, p=0.013]. 25.6% of men and 13.6% of women had repeat donations which indicates a significant difference as analyzed by chi-square test [chi[2]=5.804, p=0.008]. There was no significant difference in return rate of married and unmarried blood donors with or without an invitation card [chi[2]-0.067, p=0.21]. Pearson's correlation showed no relation between age of the donors and return rate for the subsequent donation [r=0.012, p=0.27]. Spearman's rank correlation shows no correlation between education level of the donors and return rate for subsequent donation [r=0.002, p= 0.96]. There is no correlation between distance of donor residence from donation center and return rate for subsequent donation by Pearson's correlation test [r=0.021, p=0.53]. Regular blood donation is one of the important steps in blood safety, hence retention of regular blood donors, and education and recruitment of sporadic and first time donors can increase the rate of regular donation leading to higher blood safety. This investigation showed that mail of cards three to four months after the first donation attempt to invite first time blood donors for subsequent blood donation is an easy and cost effective method to change them into regular blood donors

Brachytherapy polymer gel dosimetry with xCT

Polymer gels are an emerging new class of dosimeters which are being applied to the challenges of modern radiotherapy modalities. Research on gel dosimetry involves several scientific domains, one of which is the imaging techniques with which dose data is extracted from the dosimeters. In the current work, we present our preliminary results of investigating capability of X-ray CT for extracting brachytherapy dose distributions from a normoxic gel dosimeter. A normoxic radiosensitive polymer gel was fabricated under normal atmospheric conditions and poured into three phantoms. Using Cs137 brachytherapy sources, the phantoms were irradiated with different dose distributions with a LDR Selectron remote after-loader. To improve SNR, 25 images were obtained of each slice for image averaging and an averaged background image of an un-irradiated gel phantom was then subtracted for artifact removal. To further improve the accuracy, a self-consistent normalized method was used for calibration of the dosimeters based on an assumption of a linear dose response between zero and maximum dose regions in the gel. Although results reveal very similar CT-number gradients to that of brachytherapy dose distributions, but the method does not fulfill brachytherapy dosimetry requirements. This might be due to the high prescribed doses in this study which in turn results in a large change in the CT numbers. This change in the CT numbers of the images can not be considered to have a linear relationship with dose which was the basic assumption of our calibration method, so the results are just qualitatively comparable. In this study, the results of using X-ray CT for brachytherapy polymer gel dosimetry is promising but not still satisfying. Improving a proper calibration method for correlating CT numbers to dose will be significantly helpful for performing measurements with CT. The main limitation for CT is still a low signal to noise ratio especially in lower dose areas

[ Comparison of bloodless and classic methods of coronary artery bypass grafting in Chamran hospital, Isfahan]

The idea of bloodless medicine and surgery emerged when physicians had to treat patients who defied transfusion for religious reasons [e.g. Jehovah's Witnesses]; moreover, problems in ensuring safe blood supplies, the relevant costs involved, and the post-transfusion complications gave also rise to bloodless method. The aim of this study is to evaluate the reduction of allogenic blood transfusion, postoperative infection and costs in the bloodless group compared to the control. A retrospective comparative study was undertaken for patients undergoing coronary artery bypass grafting [CABG] at Isfahan's Chamran hospital. Two groups of patients undergoing the classic CABG and the Bloodless techniques were compared [100 patients in each group]. For bloodless surgery in addition to considering principles of bloodless medicine and surgery, autologous normovolemic hemodilution was done before operation [1-2 units] and patients were not transfused unless their hemoglobin was 9 gm/dl. Data were analysed by t-test and Chi-square test. Various factors were compared between these two techniques such as units of packed cells [PC] and fresh frozen plasma [FFP] transfused, length of hospital stay, costs and postoperative complications [infection, bleeding, etc.]. In bloodless and classic surgery groups, 76% and 38% did not require PC transfusion, respectively. In addition, we observed a significant difference between FFP transfusion in the bloodless [93%] and classic technique [73%]. No patient in the bloodless group received platelets whereas 2% of the patients in the classic group did. Overall length of hospital stay and ICU stay were less in the bloodless method; hence, the costs were less too. Postoperative infection was less in the bloodless method. These differences were significant. The application of bloodless method for patients undergoing CABG significantly reduces PC and FFP consumption [P=0.001]; therefore, the complications of blood transfusion such as post transfusion HIV, hepatitis, allergic and immunological reactions are decreased. Length of hospital stay and postoperative infections are also reduced which in turn reduce the costs [P=0.001, 0.001 and 0.037, respectively]