Introduction: Computer Tomography (CT) scans can deliver a relatively high radiation dose to the patient, therefore radiation protection for this modality is paramount. The present study determined the frequency of no abnormality detected (NAD) brain CT scans and probability of cancer induction in different age groups and genders. Methods: In this study, brain CT reports were used to identify any findings as abnormality detected (AD) and others as NAD. Then probability of future leukemia and brain cancer was estimated for different age and gender groups. Results: On average, in 65% of the cases the results were NAD (56% and 76% among males and females, respectively). Among children, 79% of the reports were NAD. The total number of projected brain cancers was 1.8 and 1.3 for males and females, respectively. The number of projected leukemia cases was 0.75 and 0.7 for males and females, respectively. For pediatric patients, brain CT scans can lead to leukemia cases about 4.5 times more often than adults. Conclusion: Brain CT scans can lead to additional cases of brain cancer and leukemia. A significant fraction of brain CTs were NAD (non-pathologic) and could practically be replaced by other radiation-free imaging modalities, especially in pediatric and young patients.

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Objectives: Brain computed tomography (CT) scans are approximately 30% of total computed tomography scan examinations in the world. It is because of the higher sensitivity of the CT for intracephalic organs. Moreover, the probability of abnormalities and cancers in these organs can be increased, therefore, the goal of this study is the measurement of absorbed dose in critical paired organs in brain CT scan, for patient's head surface and for different depths using anthropomorphic phantom and compared with each other. Methods: In this study, thermoluminescent dosimetries (TLD)-100 were used to measure the absorbed dose of organs in the phantom and 30 patients who underwent brain CT scans. Dosimetry was performed on 30 patients and then the average dose was calculated and compared to phantom data. Results: Phantom results showed that the average thyroid dose for three different depths were almost the same value and were about 0.6 mGy. Dose measurements for parathyroid increased from surface (2.22 mGy) to depth (3.02 mGy). Measurements of dose for the front surface of the cornea and eye lens were obtained respectively, 3.73 ± 0.70 mGy and 3.27 ± 0.26 mGy. The patient's dose measurements also agreed with the phantom surface doses. Conclusion: It is concluded that the better indication of organ dose is the average dose of each organ from surface to deep, but we can estimate the superficial organ doses from surface dosimetry of each patient and deep organ doses may be estimated accurately using humanoid phantom dosimetry. Also eye lenses receive maximum radiation dose compared to thyroid and parathyroid.

Introduction: Angiography and angioplasty expose cardiologists to a high level of X-ray comparing other radiographic methods, due to the high dose of radiation and the presence of the physician beside the patient bed during the procedure. Therefore, this study was designed to measure the absorbed dose in some important organs and extremities in cardiologists during different angiography and angioplasty procedures in catheterization lab. Methods: The entrance skin dose and extremity absorbed dose of the physicians in 100 angiography and angioplasty procedures were measured by TLD chips. The points on the physicians’ body, which were measured in this study, included: thyroid, right and left chest, right and left wrists, and left leg. The correlation of entrance skin dose in these six points to the exposure parameters is also evaluated. Results: The left leg has maximum dose and maximum correlation with total DAP for all three physicians in all procedure types. There was a weak correlation between left wrist absorbed dose and number of views among three physicians. Also, the maximum annual absorbed dose of the physicians in the left leg was lower than 150 mSv. Conclusion: According to the results of this study, it can be stated that periodic leg and hand dosimetry during operation is necessary for interventional cardiologists. Results also showed that, regardless of the type of procedure, the characteristics of device output, especially DAP, have a direct role in the absorbed dose of the organs and extremities, especially those outside the shield.

Introduction: Nowadays the use of cone beam computed tomography in dental imaging is increasing, although this method has a much lower dose than conventional CT scans, it delivers a higher dose than the panoramic and periapical patients therefore, , the aim of this study was to investigate the factors affecting the patients' dose in dental CBCTs and methods of optimizing and reducing the patients' dose. Various factors such as the use of thyroid collar, lead goggles, field size, device type, imaging parameters such as tube voltage and current, alternating or pulsed radiation; type, amount and shape of the filter, 360 degree or partial rotation of tube and scan time, can affect the absorbed dose of the patient in dental CT scans. Among these, the use of thyroid collar (42% reduction), lead goggles (6% reduction),the smallest possible field of view ( up to 90%), pulse irradiation, patient sitting position and 180o rotation angle instead of 360o (more than 50% reduction) cause significant reduction in the organ doses and effective dose of the patients. It should also be kept in mind that measures taken to reduce the patients' dose should not impair image quality and, depending on the patient's condition, the radiographer will select the dose reduction parameters without degrading the image quality.