Applied Radiation Protection Physics

Nuclear medicine is an area where both patients and occupational radiation doses are among the highest in diagnostic imaging modalities today. Therefore, a good understanding and proper application of radiation protection principles are of great importance. Such understanding will allow optimization of practice that will be translated into cost savings for health care administrations worldwide. This chapter will tackle: radiation protection in the routine practice of both diagnostic and therapy applications in nuclear medicine including PET, diagnostic facility design, safety aspects of the common radionuclides used in clinics, the safety of the pregnant and breast feeding patients, radiation effect of exposure to ionizing radiation, and risk estimates. The chapter will discuss the operational radiation safety program requirements applied to Conventional Nuclear Medicine using Gamma Cameras, SPECT/CT, PET/CT, and Radioiodine therapy facilities. The chapter will serve as a quick reference and as a guide to access more detailed information resources available in the scientific literature

Recent Advances in Biodistribution, Preclinical and Clinical Applications of Radiolabelled Iodine

Adequate understanding of radiopharmaceutical distribution in the body of the patient has both spatial and temporal characteristics and they are the key factor to consider when planning successful radio pharmaceutical therapy, because they are an integral part of the radiation dosimetry calculations of any proposed personalized treatment. In this chapter we will focus on radioiodine therapy for thyroid cancer patients since it is a widely known practice in clinical oncology. Factors affecting the radioiodine organs’ distribution will be examined in sufficient details using the available published research in the scientific literature. The literature will be reviewed extensively and summarized in this chapter. Another aim is to provide the medical practitioners with a quick reference guide to this clinically important area of expertise; often mastered by medical physicists with background in radiation physics, mathematics and medical imaging analysis. This chapter will cover recent advances in the area of radioiodine biodistribution modeling with applications in preclinical and clinical studies

Polymer Gel Dosimetry in Radiation Therapy Using Computed Tomography.

There have been developments in radiation therapy treatment techniques, which lead to an increase in the complexity of these treatments. The aim is to deliver highly conformal three-dimensional (3D) dose distributions, such as stereotactic radiosurgery (SRS). Polymer gel dosimetry offers three-dimensional (3D) dosimetry techniques for dose verification of dose distributions. N-isopropyl-acrylamide (NIPAM) polymer gel was the latest to develop and can be prepared under a normal atmospheric environment and has lower toxicity compared with the highly toxic polymer gels used earlier. NIPAM polymer gel using X-ray computed tomography (CT) was experimentally investigated in terms of its X-ray CT dose response, sensitivity and dose resolution. The effect of radiation beam type, radiation beam energy and radiation beam dose rate on X-ray CT dose response have also been studied. The temporal stability of NIP AM polymer gel has been examined over several days post-irradiation. The change in the polymer gel dosimeter’s physical and electron densities as a function of absorbed dose was also investigated. In this study two new prototype phantoms were designed and constructed for imaging and irradiation of polymer gel dosimeters to provide simplicity and practicality for clinical dosimetry. The dosimetric and water equivalence properties of four NIP AM based polymer gel dosimeter formulations have been studied by examining their physical properties, interaction probability, radiation transport parameters and performing Monte Carlo modelling of depth doses. NIPAM polymer gel dosimeter irradiated at different doses using 6 MeV photon beam and 400 MU min-1 dose rate were found to have higher CT dose response (up to 37. 8% at 10 Gy dose point) than results reported in the literature for NIP AM gel using similar concentration. The CT dose sensitivity of NIP AM polymer gel was found to be 0. 405+-0. 014 H Gy-1, which is 26. 2% higher than the reported sensitivity of 0. 321+-0. 008 H Gy-1 with similar NIP AM gel concentration. The maximum change in physical density as a function of absorbed dose for polymer gel dosimeters was found to be up to ~1. 0% for an absorbed dose of 20 Gy. The variations observed in the CT dose response curves for NIP AM gel dosimeters irradiated at different radiation dose rates were small. Therefore, NIP AM polymer gel dosimeters were found to be insensitive to variation in radiation beam dose rate for a 6 MeV photon beam. NIP AM polymer gel dosimeters showed very good temporal stability at different post-irradiation imaging times up to 14 days. The variations of NIP AM polymer gel dosimeters CT dose response were within experimental uncertainty for all dose rates and imaging times studied. Due to its low concentration NIP AM polymer gel had lower dose resolution of -1. 54 Gy compared with -0. 052 Gy for the highest NIP AM concentration published in the literature. The MDD was found to be -2. 5 Gy. NIPAM3% polymer gel formulation (the lowest concentration) had the most dosimetric and water equivalence properties over the energy range investigated. NIPAM15% had the least water equivalent properties due to its higher monomer concentration. NIPAM3% was found to be more water equivalent than other X-ray CT polymer gel dosimeters. In summary, X-ray CT polymer gel dosimetry is a low contrast and low sensitivity (and hence low dose resolution) technique due the fact that only small density changes occur within the irradiated polymer gel dosimeter. This has been the limiting factor of X-ray CT polymer gel dosimetry from gaining widespread acceptance for clinical dosimetry. Observations have shown that careful handling should be applied when transporting polymer gel dosimeters because of their sensitivity to movement shocks, when they may lose their gelling matrix integrity. Hence, it is recommended to establish polymer gel dosimetry as an in-house dosimetry technique, where full polymer gel dosimetry procedures can be performed on-site within the clinical facilities to eliminate errors

Polymer Gel Dosimetry in Radiation Therapy Using Computed Tomography.

There have been developments in radiation therapy treatment techniques, which lead to an increase in the complexity of these treatments. The aim is to deliver highly conformal three-dimensional (3D) dose distributions, such as stereotactic radiosurgery (SRS). Polymer gel dosimetry offers three-dimensional (3D) dosimetry techniques for dose verification of dose distributions. N-isopropyl-acrylamide (NIPAM) polymer gel was the latest to develop and can be prepared under a normal atmospheric environment and has lower toxicity compared with the highly toxic polymer gels used earlier. NIPAM polymer gel using X-ray computed tomography (CT) was experimentally investigated in terms of its X-ray CT dose response, sensitivity and dose resolution. The effect of radiation beam type, radiation beam energy and radiation beam dose rate on X-ray CT dose response have also been studied. The temporal stability of NIP AM polymer gel has been examined over several days post-irradiation. The change in the polymer gel dosimeter’s physical and electron densities as a function of absorbed dose was also investigated. In this study two new prototype phantoms were designed and constructed for imaging and irradiation of polymer gel dosimeters to provide simplicity and practicality for clinical dosimetry. The dosimetric and water equivalence properties of four NIP AM based polymer gel dosimeter formulations have been studied by examining their physical properties, interaction probability, radiation transport parameters and performing Monte Carlo modelling of depth doses. NIPAM polymer gel dosimeter irradiated at different doses using 6 MeV photon beam and 400 MU min-1 dose rate were found to have higher CT dose response (up to 37. 8% at 10 Gy dose point) than results reported in the literature for NIP AM gel using similar concentration. The CT dose sensitivity of NIP AM polymer gel was found to be 0. 405+-0. 014 H Gy-1, which is 26. 2% higher than the reported sensitivity of 0. 321+-0. 008 H Gy-1 with similar NIP AM gel concentration. The maximum change in physical density as a function of absorbed dose for polymer gel dosimeters was found to be up to ~1. 0% for an absorbed dose of 20 Gy. The variations observed in the CT dose response curves for NIP AM gel dosimeters irradiated at different radiation dose rates were small. Therefore, NIP AM polymer gel dosimeters were found to be insensitive to variation in radiation beam dose rate for a 6 MeV photon beam. NIP AM polymer gel dosimeters showed very good temporal stability at different post-irradiation imaging times up to 14 days. The variations of NIP AM polymer gel dosimeters CT dose response were within experimental uncertainty for all dose rates and imaging times studied. Due to its low concentration NIP AM polymer gel had lower dose resolution of -1. 54 Gy compared with -0. 052 Gy for the highest NIP AM concentration published in the literature. The MDD was found to be -2. 5 Gy. NIPAM3% polymer gel formulation (the lowest concentration) had the most dosimetric and water equivalence properties over the energy range investigated. NIPAM15% had the least water equivalent properties due to its higher monomer concentration. NIPAM3% was found to be more water equivalent than other X-ray CT polymer gel dosimeters. In summary, X-ray CT polymer gel dosimetry is a low contrast and low sensitivity (and hence low dose resolution) technique due the fact that only small density changes occur within the irradiated polymer gel dosimeter. This has been the limiting factor of X-ray CT polymer gel dosimetry from gaining widespread acceptance for clinical dosimetry. Observations have shown that careful handling should be applied when transporting polymer gel dosimeters because of their sensitivity to movement shocks, when they may lose their gelling matrix integrity. Hence, it is recommended to establish polymer gel dosimetry as an in-house dosimetry technique, where full polymer gel dosimetry procedures can be performed on-site within the clinical facilities to eliminate errors

Radiation dose verification of an X-ray based blood irradiator using EBT3 radiochromic films calibrated using Gamma Knife machine

AimBlood irradiators (BI) initial acceptance testing and routine annual dosimetry checks require radiation dose measurements in order to comply with regulatory requirements.BackgroundTraditionally thermo-luminescence dosimeters (TLD) have been used to measure the dose. The EBT3 film is reported to be a better dosimeter for low energy X-rays than its predecessors EBT2 and EBT. To the best of our knowledge, the use of EBT3 films to perform dosimetry on X-ray based BI has not been reported yet.Materials and methodsWe performed routine radiation dosimetry checks using EBT3 films on a new X-ray based BI and compared the results with TLD dosimetry. Calibration films were irradiated with radiation beam from a Co-60 Gamma Knife (GK) radiosurgery machine and, alternatively, using an Ir-192 high dose rate (HDR) brachytherapy device. The films were calibrated to cover a wide dose range from 1 to 40Gy. Such a wide dose range has not been reported yet in BI film dosimetry.ResultsWe obtained a relative difference of about 6.6% between doses measured using TLD and those measured using EBT3 films. Both irradiation methods using GK or HDR were found to be adequate for the calibration of the EBT3 Gafchromic films.ConclusionsWe recommend the use of EBT3 films in routine X-ray based BI dosimetry checks. The presented method takes advantage of available radiotherapy equipment that can be efficiently used for EBT3 films calibration. The method is fast, reproducible and saves valuable medical physicist's time