Thyroid dose and dose reduction method from CT scan of head and neck

Introduction: Computed tomography (CT) consists of 11% of all imaging methods, but accounts for approximately 67% of radiation exposure due to diagnostic cases. More than one-third of all CT scans are done in the head and neck area. The thyroid gland is irradiated during CT head and neck. According to studies, this gland has the highest levels of radiation-induced cancer, and in children, due to longer life expectancy than adults, cancer has a greater chance of developing and developing. Therefore, awareness of the amount of thyroid dose and dose reduction methods are essential. Results: According to the results, when performing CT scans of the head and neck, thyroid gland radiation is very high, but the use of optimization techniques leads to a decrease in the amount of thyroid receiving dose. Dose optimization is divided into three stage s: 1-Before scanning 2- During the scan, which includes: patient position, scan parameters, and shields inside and outside the field; 3- After scanning, which includes: rehabilitation filter and quality control. For example,  the  use  of  protective  shields  during  head  and  neck  CT tests leads to a reduction in the thyroid dose of approximately 40% to 60%. Conclusion: According to the principle of ALARA, the aim of applying optimization techniques is to reduce the amount of thyroid receiving dose while mainta ining image quality. The most effective  of  these  techniques  in  head  and  neck  CT  scans  is  the  use  of protective shield that minimizes the thyroid dose