Radiation exposure from diagnostic nuclear medicine examinations in golestan province

Introduction: The aim of present study was to estimate effective dose from most common procedures performed in nuclear medicine departments of Golestan province. Methods: Data of nuclear medicine procedures performed in 2 nuclear medicine departments in Golestan province were collected during 4 years. Effective dose, collective effective dose and effective dose per examination were calculated using standard dosimetry tables. Results: Based on the data of this study, results of 10437 nuclear medicine procedures performed during 4 years have lead to 3.97 mSv as average effective dose per examination and 10.37 human-Sv as mean collective effective dose. It was also revealed that Tc-99m was the main source of effective dose (98.3%), bone scan was the most common procedure (25.9%) and cardiac scan (MIBI-rest) has the highest collective effective dose (33.5%) during 4 years. Conclusion: Beside the cardiac scan which was the most common nuclear medicine procedure and the main contributor of effective dose in patients, due to geographical condition of the northeast of Iran, bone scan was the highest performed nuclear medicine examination in the Golestan province

Image-based versus atlas-based patient-specific S-value assessment for Samarium-153 EDTMP cancer palliative care: A short study

Introduction: Use of SPECT/CT data is the most accurate method for patient-specific internal dosimetry when isotopes emit single gamma rays. The manual or semi-automatic segmentation of organs is a major obstacle that slows down and limits the patient-specific dosimetry. Using digital phantoms that mimic patient�s anatomy can bypass the segmentation step and facilitate the dosimetry process. In this study, the results of a patient-specific dosimetry based on CT data and XCAT phantom, a flexible phantom with predefined organs, are compared. Methods: The dosimetry results (S-value and SAF) were calculated for a patient with breast cancer who received Samarium-153 ethylenediamine-N,N,N�,N�-tetrakis(methylenephosphonic acid (153Sm-EDTMP). Biodistribution of activity was obtained from the SPECT scan. The anatomical data and attenuation map were extracted from CT as well as the XCAT phantom with different BMIs. GATE Monte-Carlo simulator was used to calculate the dose to different organs based on the activity distribution and segmented anatomy. Results: The whole body dosimetry results are the same for both calculations based on the CT and XCAT with different BMIs; however for target organs, the differences between SAFs and S-values are high. In the spine, the clinically important target organ for Samarium therapy, the dosimetry results obtained from phantoms with unmatched BMIs between XCAT phantom and CT are substantially different. Conclusion: We showed that atlas-based dosimetry using XCAT phantom even with matched BMI may lead to considerable errors as compared to calculations based on patient�s own CT. For accurate dosimetry results, calculations should be done using CT data. © 2018 Iranian Journal of Nuclear Medicine. All Rights Reserved

Evaluation of the impact of intraocular lens Tecnis Z9000 misalignment on the visual quality using the optical eye modeling

Purpose: The aim of this study was to investigate the effect of misalignment (tilt & decentration) of IOLs in cataract surgery using Liu-Brennan optical eye model in a simulation. Methods: A phantom with the real eye parameters -Liu-Brennan model- and Tecnis Z9000 IOL were used for simulation. Results: Results showed that with 0.4 mm decentration and more the modulation transfer function (MTF) and contrast were reduced continuously in the ±X Axes. IOL decentration in ±Y axes showed a symmetrical reduction of MTF and contrast and increasing the decentration. In the ±X and ±Y axes the 8° IOL tilt has no significant effect on the MTF and contrast of the eye. Conclusion: It can be said that the decentration of Tecnis Z9000 IOL in the ±X and ±Y axes will reduce the optical quality of the person, specially for decentration more than 0.4 mm this effect is very significant. Therefore using the compensation methods for improvement of the optical quality is essential. But up to 8° IOL tilt in vertical and horizontal axes have no significant effect on the visual quality of the patient. © 2013 by the Iranian Society of Ophthalmology

Evaluation of silicon and 10% bismuth shield with variable thickness compared with constant thickness on the dose reduction and image quality during chest CT examination

One of the best methods to reduce the breast radiation dose in chest CT scan exam is using the bismuth shield. Due to the fact that, in CT scan tests, the breast dose is higher in the central axis of body than other sides, so the bismuth shield with variable thickness (outer half 1 mm thick and inner half 2 mm thick) is designed in this study. The objective of this study is to investigate in effectiveness of silicon and 10% bismuth composite shied with variable thickness on reducing radiation dose and image quality parameters in chest CT scan test compare to 1 mm and 2 mm of fixed thickness shield. Physical chest phantom underwent chest CT scan without or with bismuth shields with thickness of 1 mm, 2 mm, and variable in 90, 120 and 140 kVp in inactive TCM mode. Dosimetry was performed by using TLD, and image quality was evaluated quantitatively (by drawing the ROI in the identical images like image j, calculation of noise, CT number, SNR and CNR) and qualitatively (by two expert radiologists). Designed bismuth shield with unsteady thickness in inner and outer side compare to 1 mm and 2 mm thickness shields is presented in 120 kVp, has a significant difference in the amount of breast dose reduction (19% reduction), as well as in 140 kVp, all these three bismuth shields resulted in a significant dose reduction almost in the same similarity. At 120 kVp, the bismuth shield with variable thickness lead to a significant change in CT numbers in the heart and lungs, but it does not have a remarkable effect on other image quality parameters. The bismuth shield with variable thickness can lead to a better effectiveness in reducing breast dose without any side effect on image quality at 120 kVp, which requires further studies in this field

Projected future risk of leukemia and brain tumors from unnecessary brain CT scans: a multi-center study in Iran

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

Radiation exposure of interventional cardiologists for different types of procedures in catheterization lab, is it more concern about extremities?

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