REDUCING ABSORBED DOSE TO THYROID IN NECK CT EXAMINATIONS: THE EFFECTS OF SABA SHIELDING

2020 ◽  
Vol 191 (3) ◽  
pp. 349-360
Author(s):  
Valiallah Saba ◽  
Jalal Kargar Shuraki ◽  
Abdollah Valizadeh ◽  
Mohsen Zahedinia ◽  
Maziar Barkhordari
Keyword(s):  
Image Quality ◽  
American Association ◽  
Absorbed Dose ◽  
Skin Dose ◽  
Radiation Attenuation ◽  
Patient Study ◽  
Entrance Skin Dose ◽  
Radiosensitive Organs ◽  
Attenuation Values

Abstract Bi shielding has been used for the protection of radiosensitive organs during computed tomography (CT) for 20 years. In 2017, American Association of Physicists in Medicine recommended against Bi shielding due to its degrading effects on image quality. Saba shielding introduced recently protecting organs as Bi shielding without degrading image quality. In this study, the Saba shield was modified and primary radiation attenuation values of the shields and entrance skin dose (ESD) on the thyroid were measured with and without shielding. Furthermore, the quality of images obtained using Saba shielding was investigated quantitatively and qualitatively. Saba and Bi shielding reduced the ESD on the thyroid by about 50%. Saba shielding had about 5–7 HU less noise and about 51–65 HU less CT numbers shift in comparison with Bi shielding at a distance of 1 cm from the shields. Saba shielding had no degrading effects on image quality in the patient study.

scholarly journals Investigation of Exposure Factors for Various Breast Composition and Thicknesses in Digital Screening Mammography Related to Breast Dose

2018 ◽  
Vol 27 (3) ◽  
pp. 211-216 ◽  
Author(s):  
Khaled Alkhalifah ◽  
Ajit Brindhaban
Keyword(s):  
Image Quality ◽  
Nonparametric Tests ◽  
Screening Mammography ◽  
Amorphous Selenium ◽  
Skin Dose ◽  
Reference Systems ◽  
Mean Glandular Dose ◽  
Entrance Skin Dose ◽  
Mammography Image

Objective: To investigate the effect of exposure factors used in digital screening mammography on image quality of different breast compositions. Material and Methods: A digital mammography unit, with tungsten (W) as target, rhodium (Rh) and silver (Ag) as filters, and amorphous selenium detectors, was used to image Computerized Imaging Reference Systems (CIRS) Model 12A phantoms of thickness 4, 5, and 6 cm. Images of each phantom were obtained using target-filter combinations of W/Rh and W/Ag, at 28, 30, and 32 kVp. Images were evaluated by 5 senior technologists with experience in mammography. Image scores were assigned, for each type of feature present in the phantom. Statistical analysis was performed using nonparametric tests to compare sets of image scores at p = 0.05. Results: A small but statistically significant improvement was detected in the visibility of microcalcifications (8.8 ± 0.2; p = 0.031) for the W/Rh combination but this did not show any differences in the visibility of masses or fibers. The entrance skin dose (ESD) and mean glandular dose (MGD) were lower for the W/Ag (ESD = 1.30–3.70; MGD = 0.44–0.93 mGy) combination compared to W/Rh (ESD = 1.66–5.40; MGD = 0.52–1.12 mGy). The Mann-Whitney test revealed that 30-kV exposure with the W/Rh combination showed a significantly better visibility of specks in the 30/70 phantom compared to other exposures. Conclusion: The use of an Rh filter showed a better image quality for all phantoms. 28 and 30 kVp with the W/Rh combination provided a slightly better image quality, and the MGD is less than 1.2 mGy.

scholarly journals Image Quality and Radiation Dose for Fibrofatty Breast using Target/filter Combinations in Two Digital Mammography Systems

2020 ◽  
Vol 10 ◽  
pp. 56
Author(s):  
Khaled Alkhalifah ◽  
Akram Asbeutah ◽  
Ajit Brindhaban
Keyword(s):  
Image Quality ◽  
Radiation Dose ◽  
Digital Mammography ◽  
High Performance ◽  
Signal To Noise Ratio ◽  
Filter Material ◽  
Skin Dose ◽  
Tissue Equivalent ◽  
Entrance Skin Dose ◽  
Noise Ratio

Objectives: The aim of this study was to determine the optimum combinations of target and filter materials for various X-ray tube voltage settings, as well as their effects on image quality and radiation dose. This was done using different digital mammography (DM) imaging systems with a breast equivalent phantom. Material and Methods: Two DM units with a tungsten (W) target, silver (Ag), and rhodium (Rh) filters and dual molybdenum (Mo) and Rh targets/filters were used. A tissue-equivalent mammography phantom of 6 cm thickness equivalent to a fibrofatty breast was exposed 20 times to different target/filter material combinations (W/Rh, W/Ag, Rh/Rh, Mo/Rh, and Mo/Mo) and various kV settings (28–34 kV). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for each exposure. Results: The W/Ag combination resulted in the lowest entrance skin dose and mean glandular dose (MGD). The MGD for the W/Rh combination was 60% less than that of the W/Ag combination at 34 kV (P < 0.05). There was a direct relationship in the SNR with the Mo/Mo, Mo/Rh, and Rh/Rh combinations and an inverse relationship with the CNR in the 34 kV range. There were statistically significant differences between all five target/filter combinations, and the best SNR and CNR were observed for the W/Rh combination with a reduced radiation dose in the range of 28–30 kV (P < 0.05). Conclusion: For a breast thicknesses of 6 cm with a fibrofatty nature, the W/Rh combination delivers high performance in terms of image quality at a lower dose.

Determination of Entrance Surface Dose of Digital Radiography for Adults at Public Medical Imaging Centers, Erbil

2021 ◽  
Author(s):  
Ilham Khalid Ibrahim
Keyword(s):  
Absorbed Dose ◽  
Public Hospitals ◽  
Adult Patients ◽  
Skin Dose ◽  
Surface Dose ◽  
Entrance Surface Dose ◽  
Entrance Skin Dose ◽  
Total Filtration ◽  
Ionizing Radiations

Introduction: Diagnostic X-ray is one of the ionizing radiations, the level of radiation dose received by the patient during medical examination is essential to prevent cancer risks. The aim of this study is to calculate entrance surface dose (ESD) and effective dose (ED) were estimated during chest, and lumber spine for adult patients in three hospitals in Erbil, using NOMEX MULTIMETER and PCXMC software.    Material and Methods: The study was conducted in three public hospitals, in Erbil on (250) adult patients, whose ages between (18-70) years, based on the results study, ESD and ED were calculated for chest (PA, lateral), and lumbar spine (AP, lateral) examinations. NOMEX MULTIMETER (PTW, Freiburg), used in measurement of tube voltage, dose, dose rate, time product current, and total filtration automatically during examination. ED was calculated by using PCXMC software (version 2.5). Results: The results of this work are compared with published international literatures. The mean entrance skin dose for examinations of chest (PA, Lat), and lumber spine (AP, Lat) 1.02, 1.06, 2.61 and 3.92 mGy respectively. ED value was from 0.08, 0.19, 0.32, and 0.33 mSv, for chest (PA, Lat), and lumber spine (AP, Lat), respectively. Conclusion: The ESD, and ED were calculated in this work were found to be agreement with the published reference values for chest, and lumber spine set by international levels. ALARA principle should be considered by radiographer, to reduce absorbed dose of adults’ patient undergoing imaging radiography.

scholarly journals Fast Model for Evaluation of the Thyroid Dosimetry During Chest Tumor Radiotherapy

Dose-Response ◽  
2019 ◽  
Vol 17 (4) ◽  
pp. 155932581988915
Author(s):  
Yiling Wang ◽  
Min Zheng ◽  
Ling He ◽  
Jinhui Xu ◽  
Gang Yin ◽  
...  
Keyword(s):  
Absorbed Dose ◽  
Dose Assessment ◽  
Planning System ◽  
Treatment Planning System ◽  
Skin Dose ◽  
Thermoluminescent Dosimeter ◽  
Regressive Model ◽  
Significant Linear Correlation ◽  
Entrance Skin Dose ◽  
Radiotherapy Dose

Due to the reported high incidence of thyroid cancer induced by radiotherapy, dose assessment is significant to prevent thyroid late effects. Thyroid dosimetry can be evaluated either by entrance skin dose (ESD) measured with thermoluminescent dosimeter (TLD) arrays or by absorbed dose (AD) computed with treatment planning system. However, their correlation has hardly been reported in any publications. Moreover, the reported measurement procedures for thyroid ESD are usually inefficient. This study aims to provide a fast model for efficient acquisition of thyroid ESD and analyze the coherent relationship between ESD and AD. We conducted the study on the China radiation anthropomorphic phantom with intentionally delineated cancers, irradiated by a Varian 23EX linac. We have measured the ESD with TLD at 5 different points, while computed AD with the Oncentra Masterplan TPS. The ESD at the middle gorge of thyroid has exhibited significant linear correlation with those measured at other points. Furthermore, a regressive model has been proposed to predict thyroid AD from ESD. Consequently, it is recommended to only measure the ESD at the middle gorge of thyroid for an efficient dose assessment. The validity of the regressive model to predict thyroid AD from ESD has also been demonstrated.

scholarly journals Reduction of Ovarian Radiation Dose and Image Quality Disruptive Effects: New Constructed Shields for CT Scanning of Abdomen and Pelvis

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Mehran Bagheri ◽  
Mohammad Reza Azimi Aval
Keyword(s):  
Image Quality ◽  
Dose Reduction ◽  
Ct Scanning ◽  
Quality Parameters ◽  
New Combination ◽  
Skin Dose ◽  
Entrance Skin Dose ◽  
Reduction Strategies ◽  
The Right ◽  
User Friendly

Background: Cumulative dose of ovary as a radiosensitive organ during abdominal and pelvic CT scan imaging is still a controversial challenge that requires practical dose reduction strategies. Although bismuth shields can reduce the dose in the right proportions, their use is controversial due to the reduced image quality. Objectives: The aim of this study was to investigate the performance of a new combination of X-ray absorber structures that have less effect on image quality parameters. Methods: First, various shields with different weight percentages of Cu and Bi were made, then the percentage of dose reduction and image quality were evaluated via phantoms. Finally, Shield with the least effect on image quality was evaluated for clinical evaluation on 20 patients. Results: Shielding with thicknesses of 1T and 3T reduced the Entrance skin dose of ovarian by about 52% and 73%, respectively. Shields with 90% cu-10% Bi and 100% Bi structures had the least and most destructive effects on image quality, respectively, and also have the same image quality. The 10% Bi-90% Cu shield provided a 21% greater dose reduction than the bismuth shield. Also, this 1T thick shield did not create an artifact in the reconstructed images. Conclusions: Shields are flexible, inexpensive, and user-friendly for ovarian shielding in abdominal and pelvic CT scans. Unlike bismuth shields, shields do not have the detrimental effects of image quality degradation.

OPTIMAL COLLIMATION SIGNIFICANTLY IMPROVES LUMBAR SPINE RADIOGRAPHY

2020 ◽  
Vol 189 (4) ◽  
pp. 420-427
Author(s):  
Anamaria Pazanin ◽  
Damijan Skrk ◽  
Jessica C O'Driscoll ◽  
Mark F McEntee ◽  
Nejc Mekis
Keyword(s):  
Lumbar Spine ◽  
Image Quality ◽  
Absorbed Dose ◽  
Field Size ◽  
Organ Doses ◽  
Dose Area Product ◽  
Spine Radiography ◽  
Spine Imaging ◽  
Radiosensitive Organs ◽  
Area Product

Abstract Purpose To determine the influence of optimal collimation during lumbar spine radiography on radiation dose and image quality. Material and methods 110 lumbar spine patients were split into two groups—the first imaged with standard collimation and the second with optimal collimation. Body mass index, image field size, exposure conditions and dose area product were measured. Effective and absorbed organ doses were calculated. Image quality was assessed. Results Optimal collimation reduced the primary field by up to 40%. The effective dose was reduced by 48% for the AP projection, while no differences were found for the LAT projection due to incorrect positioning of the central beam with standard collimation. The absorbed dose to selected radiosensitive organs decreased by 41 and 10% in the AP and LAT projections, respectively. Image quality for the LAT projection improved by 24% and maintained for the AP projection. Conclusion Optimal collimation in lumbar spine imaging significantly influences patient exposure to radiation.

scholarly journals A Comparison of Image Quality and Radiation Exposure Between the Mini C-Arm and the Standard C-Arm

Hand ◽  
2018 ◽  
Vol 14 (6) ◽  
pp. 765-769
Author(s):  
Juliaan R. M. van Rappard ◽  
Willy A. Hummel ◽  
Tijmen de Jong ◽  
Chantal M. Mouës
Keyword(s):  
Image Quality ◽  
Radiation Exposure ◽  
Hand Surgery ◽  
Exposure Dose ◽  
Skin Dose ◽  
Flat Panel ◽  
Scatter Radiation ◽  
Entrance Dose ◽  
Entrance Skin Dose ◽  
Intraoperative Fluoroscopy

Background: The use of intraoperative fluoroscopy has become mandatory in osseous hand surgery. Due to its overall practicality, the mini C-arm has gained popularity among hand surgeons over the standard C-arm. This study compares image quality and radiation exposure for patient and staff between the mini C-arm and the standard C-arm, both with flat panel technology. Methods: An observer-based subjective image quality study was performed using a contrast detail (CD) phantom. Five independent observers were asked to determine the smallest circles discernable to them. The results were plotted in a graph, forming a CD curve. From each curve, an image quality figure (IQF) was derived. A lower IQF equates to a better image quality. The patients’ entrance skin dose was measured, and to obtain more information about the staff exposure dose, a perspex hand phantom was used. The scatter radiation was measured at various distances and angles relative to a central point on the detector. Results: The IQF was significantly lower for the mini C-arm resulting in a better image quality. The patients’ entrance dose was 10 times higher for the mini C-arm as compared with the standard C-arm, and the scatter radiation threefold. Conclusions: Due to its improved image quality and overall practicality, the mini C-arm is recommended for hand surgical procedures. To ensure that the surgeons’ radiation exposure is not exceeding the safety limits, monitoring radiation exposure using mini C-arms with flat panel technology during surgery should be done in a future clinical study.

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