Radiotherapy has been the modality for treating cancer patients worldwide for more than 100 years. Radiation dose to patients is delivered through different techniques using high-energy photon beams generated by the linear accelerators. Radiotherapy techniques are developing at a speed never seen before. For continuous improvement, safe and effective radiotherapy delivery requires implementing adapted quality assurance (QA) programs and integral quality management (QM) systems. A key step in any QA program is the DOSIMETRY audit. It provides an effective tool to improve the accuracy of patients’ treatments. In the global panorama, DOSIMETRY audit programs are conducted by various institutions. Still, the largest of them is the International Atomic Energy Agency (IAEA) in Vienna, Austria, the Imaging and Radiation Oncology Core (IROC-H) Houston QA Center in the USA, and EQUAL (European Quality Laboratory) Laboratory in the framework of the ESTRO (European Society for Therapeutic Radiology and Oncology) ESTRO – EQUAL Laboratory in Villejuif Cedex, France.

Gamma ray measurement in various research fields requires high efficient detectors. In photon DOSIMETRY, NaI(Tl) scintillation detector as one of the inorganic scintillation detector is noticeable, due to have the high amount of light output. In this study, the basics determination of photon DOSIMETRY for the NaI(Tl) scintillation detector utilizing the Monte Carlo code (MCNPX) and using different methods of dose calculation (tally F6, * F4, + F6 and * F8) is studied. Regularly, the output of a radiation detector (counting the number of pulses) cannot be used to determine the radiation dose value. Therefore, in this study the spectro-DOSIMETRY method based on software method is used to find out the value of the conversion coefficients to convert the detector spectrum to the value of air karma. In this method, the radiation DOSIMETRY response is obtained with use of the MCNPX code simulation. The response function of the NaI(Tl) 3"×3" scintillation detector for several specific gamma rays was determined and then the functions of energy dependent conversion coefficients for calculating the dose values were obtained. Finally, with comparison of the measured data and simulation calculations results it is shown that the proposed method has a high accuracy in photon DOSIMETRY.

Background: 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. Materials and Methods: 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. Results: 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. Conclusion: 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.    

Application of radioactive isotopes is the treatment of choice around the globe for many cancer sites. In this technique, the accuracy of the radiation delivery is highly dependent on the accuracy of radiation DOSIMETRY around individual brachytherapy sources. Moreover, in order to have compatible clinical results, an identical method of source DOSIMETRY must be employed across the world. This problem has been recently addressed by Task Group 43 (TG43) from the American Association of Medical Physics (AAPM) with a protocol for dosimetric characterizatio n of brachytherapy sources. This new protocol has been further updated using published data from international sources, by a new Task Group from the AAPM. This has resulted in an updated protocol known as TG43U1 that has been published in March 2004 issue of Medical Physics. The goal of this presentation is to review the original TG43 protocol and associated algorithms for brachytherapy source DOSIMETRY. In addition, the shortcomings of the original protocol that has been resolved in the updated recommendation will be highlighted. I am sure that this is not the end of the line and more work is needed to complete this task. I invite the scientists to join this task and complete the project, with the hope of much better clinical results for cancer patients.

Background: Cardiac catheterization plays an essential role in the evaluation of suspected heart failure patients. This work aimed to determine the mean effective dose of patients undergoing catheterization tests and to estimate the associated radiation risk of malignancy. Material and Methods: Measurements were performed during 65 coronary angiographies (CA), 70 coronary angioplasties (PTCA) 27, radio fluoroscopy (RF) ablations and 25 electro physiologies procedures in a dedicated laboratory. The procedures were undertaken with the Siemens and General Electric X-ray equipment. A dose area product (DAP) meter was also used. The DAP values and fluoroscopy times were recorded for each patient. Results: The mean DAP values and patient effective doses were 19. 53 Gy. cm2 and 1. 71 mSv for CA, 49. 74 Gy. cm2 and 4. 57 mSv for PTCA, 153. 34 Gy. cm2 and 16. 38 mSv for ablations and 14. 88 Gy. cm2 and 1. 65 mSv for electrophysiology, respectively. The patient radiation risk was estimated at 13, 1. 3, 1. 3, 3. 6 fatal cancer per 10000 procedures of ablations, electrophysiology, CA and PTCA cases, respectively. Conclusion: Results showed that the radiation risk due to RF cardiac ablation is higher than the other complication procedures so, efforts should be made to minimize patient radiation risk from RF ablation procedures. Also we found no clear correlation between cardiologist level of experience and reduced level of patient,s dose.