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Showing 3 results for Radiation Dosage
Estimation of absorbed dose of radiosensitive organs and effective sose in patients underwent abdominopelvic spiral CT scan using impact CT patient dosimetry
Ayoub Amirnia, Parinaz Mehnati , Nasrollah Jabbari ,
Volume 75, Issue 2 (5-2017)
Abstract

Background: Due to the presence of radiosensitive organs in the abdominopelvic region and increasing the number of requests for CT scan examinations, concerns about increasing radiation doses in patients has been greatly elevated. Therefore, the goal of this study was to determine the absorbed dose of radiosensitive organs and the effective dose in patients underwent abdominopelvic CT scan using ImPACT CT patient dosimetry Calculator (version 1.0.4, Imaging Performance Assessment on Computed Tomography, www.impactscan.org).

Methods: This prospective cross-sectional study was conducted in Imam Reza Hospital from November to February 2015 February 2015 in the Imam Reza Hospital, in Urmia, Iran. The demographic and dosimetric information of 100 patients who underwent abdominopelvic CT scan in a 6-slice CT scanner were obtained through the data collection forms. The demographic data of the patients included age, weight, gender, and BMI. The dosimetric parameters included pitch value, CT dose volume index (CTDIvol), dose-length product (DLP), tube voltage, tube current, exposure time, collimation size, scan length, and scan time. To determine the absorbed dose of radiosensitive organs and also the effective dose in patients, ImPACT CT patient dosimetry calculator was used.

Results: The results of this study demonstrated that the mean and standard deviation (SD) of patients' effective dose in abdominopelvic CT scan was 4.927±0.164 mSv. The bladder in both genders had the greatest mean organ dose, which was 64.71±17.15 mGy for men and 77.56±18.48 mGy for women (P<0.001).

Conclusion: The effective dose values of this examination are in the same range as previous studies, as well as International Commission on Radiological Protection (ICRP) recommendations. However, the radiation dose from CT scan has the largest contribution to the medical imaging. According to the ALARA principle, it is recommended that the scan parameters, especially mAs, should be chosen so that the patient dose is minimum, and the image quality is maximum. Furthermore, other imaging modalities are used as an alternative to the CT scan.

Estimation and assessment of the effective doses for radiosensitive organs in women undergoing chest CT scans with or without automatic exposure control system
Daryoush Khorramian , Soroush Sistani , Amin Banaei , Salar Bijari ,
Volume 75, Issue 7 (10-2017)
Abstract
Background: There are several techniques for reducing the delivered dose from CT (Computed tomography) scanning such as the automatic exposure control (AEC). This technique modulates the tube current regarding the patient size and weight. The aim of this study was to estimate the effect of the AEC on the radiosensitive organs effective doses in women undergoing chest CT scanning.
Methods: This study was a cross-sectional, analytical and quantitative study that was performed during 3 months in the imaging section of the Firoozgar educational and therapeutic hospital (belonging to Shahid Beheshti University of Medical Sciences) in the spring of 2017. CT scan exposure parameters were gathered and registered for 54 women undergoing chest CT scan. 25 of these scans were performed using AEC system and 29 of them were performed without using AEC. CT dose indexes in the center and peripheral regions of the standard phantom were calculated using the exposure parameters. Weighted CT dose index was also calculated and effective organ doses were obtained using CT-Expo software, version 2 (Medizinische Hochschule, Hannover, Germany) for two mentioned groups. In addition, noise was measured for these two groups as an image quality parameter.
Results: Calculated weighted CT dose indexes were 9.94 mGy and 12.46 mGy using AEC system and without using AEC, respectively. The calculated effective doses were equal to 5.4 mSv and 6.3 mSv using AEC and without using AEC, respectively. Maximum organ effective doses were 15, 14, 14 and 14 mSv for breast, esophagus, lung and thymus respectively in the non-using AEC system imaging technique.
Conclusion: Our measurements indicated a decrease about 15% in weighted CT dose index (from 12.46 to 9.94 mGy) using AEC system. Beside of this fact, the noise increased about 11.3% (from 4.2 to 4.74) using AEC system. So, it can be said that using of AEC was an effective way for dose reduction in women undergoing chest CT scanning, and the additional noise was in the acceptable range.

A convenient and fast method for assessing the image quality of hepatic triphasic CT scan
Seyed Hamed Jafari, Hajar Zahedi Mehr , Banafsheh Zeinali-Rafsanjani , Sara Haseli, Mahdi Saeedi-Moghadam ,
Volume 80, Issue 6 (9-2022)
Abstract
Background: The image quality is paramount in interpreting the hepatic dynamic CT scan. A poor quality image results in repeating the procedure, which is very time-consuming for the patient and staff, and besides, it is not cost-efficient. This study intended to determine the correlation between image quality and the Hounsfield unit (HU) of the liver and its vessels in the arterial and venous phase to define the acceptable range of HUs for hepatic CT images.
Methods: The image quality of 146 dynamic CT scans was assessed by qualitative and quantitative methods at Namazi Hospital of Shiraz University of Medical Sciences from September 2019 to August 2021. Two radiologists performed the qualitative evaluation. They categorized the image qualities into three groups; poor, acceptable, and high quality. For quantitative assessment of image quality, the Hounsfield unit of the aorta, hepatic vein, main portal vein, right anterior, right posterior, and left lateral lobe of the liver were evaluated in both arterial and venous phases.
Results: According to the results of the qualitative evaluation of image quality, 59.6%, 17.8%, and 22.6% of triphasic CT scans had good, acceptable, and poor quality, respectively. There was a significant relationship between image quality and Hounsfield units of all ROIs in the arterial phase (P<0.005). Also, a significant relationship was observed between the Hounsfield units of the portal vein right on the anterior and posterior segments of the liver (P<0.03) in the venous phase.
Conclusion: In a high quality triphasic CT scan, the Hounsfield unit of different parts in the arterial phase should be as follows: aorta 310±78, portal vein 150±40, hepatic vein 44±7, right posterior and anterior and left lateral segments of liver 77±11, 77±7 and 78±12. Hounsfield units of the portal vein, hepatic vein, and right posterior and anterior segments of the liver in the venous phase should be 155±27, 167±30, 111±19, and 112±16, respectively.

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