[Evaluation of dose distribution accuracy in HDR brachytherapy of esophagus cancer based on MRI normoxic polymer gel dosimetry]

The purpose of this work was to study the ability of MRI normoxic polymer gel dosimetry for evaluating the dose distribution in HDR brachytherapy of esophageal cancer at Imam Reza brachytherapy center [Mashahd, Iran]. Initially, 2 liters of normoxic gel [MAGIc] was fabricated and then poured into 12 calibration test tubes and placed in a perspex walled phantom. The gel phantom was irradiated with a brachytherapy remote-afterloader unit using a cobalt-60 brachytherapy source and the test tubes wee irradiated with a range of known doses with a cobalt-60 teletherapy unit. Imaging was performed with a multi-spin-eco protocol and a T2 quantitative technique using a Siemens 1.5 T MRI machine. The MRI images were transferred to a computer and then image processing was performed in the MATLAB environment to extract R2 maps of the irradiated area. In this study and at the reference point, the dose deviation between the gel dosimetry and the calculated data was 4.5%. The distance to agreement [DTA] for dose profiles was 2.7 mm. Also, dose sensitivity of the MAGIC gel dosimeter was 0.693 S-1Gy-1 [R2=0.9376]. In this work, the data obtained from TPS calculations were found in very good agreement with the measured results provided by gel dosimetry. It was evaluated using a comparison of isodoses and dose at the reference point, and dose profile verification. It is also concluded that the gel dosimetry systems have proven to be a useful tool for dosimetry in clinical radiotherapy applications

[Evaluation of an ultrasonic insulin delivery system in hyperglycemic rabbits]

Sonophoresis has been assessed as a novel approach to crate skin permeability and drug delivery using low frequencies of ultrasound waves in the range of 20 kHz to 3 MHz. In this study, a system including seven 40 kHZ piezoelectric transducers and an insulin chamber designed by the Medical Physics Research Center has been evaluated on hyperglycemic rabbits. Thirty five rabbits became hyperglycemic through Alloxan monophydrate injection and were divided into five groups. The rabbits were treated in two main groups [with insulin and ultrasound radiation in two radiation periods], one main control group and two further control groups [one group with ultrasound radiation with longer radiation period in absence of insulin and presence of normal saline; and the other group without ultrasound radiation in presence of insulin]. By filling the system chamber with insulin and placing in on the skin of the abdomen and activating the piezoelectric transducers, blood samples were drawn from the animals before ultrasound irradiation and after it is specified intervals. The glucose level was measured using a glucometer and the serum insulin level was determined using a radioimmunoassay method. Maximum decrease in glucose level was recorded for a 20 minute irradiation in a 180 minute period, and the highest increase in insulin level was recorded for the 10 minute radiation group in a 60 minute period. Because rapid uptake and reaching a peak in a short time and its swift decrease make a good scheme for controlling glucose level after meals, the 10 minute radiation seems to be more suitable. Also, it is predicted that irradiation time in the interval between food consumption and use of the instrument is critical