Effective dose to patient during neuroradiological procedures of c-arm CT
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Abstract:
We aimed to determine the effective dose given to patients during neuroradiological C-arm computed tomography (CT) procedures.Measurements were performed on 48 patients using a dose-area product (DAP) meter. A PC-based Monte Carlo program (PCXMC, STUK, Helsinki, Finland) was used to calculate the effective dose from the DAP values of each patient. Organ doses were also measured with thermoluminescent dosimeters (TLDs) using a human-shaped phantom.The difference between the organ doses measured using TLDs and PCXMC was not significant (P > 0.05). The mean DAP for 48 patients was 9.41±2.50 Gy·cm2; the mean effective dose for all procedures was 0.30±0.08 mSv. The coefficient for the correlation (R2) between the DAP and the effective dose was 0.97. The conversion factor between the effective dose and DAP was 0.030-0.035 mSv·Gy(-1)·cm(-2).DAP can be used as a dose indicator to calculate the organ dose and effective dose of patients based on Monte Carlo simulation. This method can provide important information on the absorbed dose and enhance the radiation protection of patients during C-arm CT procedures.Keywords:
Dose area product
Kerma
Dose area product
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Recently there has been a significant increase in the use of CT imaging resulting in a significant increase in radiation exposure to the population. Few studies have compared the degree of radiation exposure among the currently available MDCT units. Our objective is to make such a comparison.Using a Rando anthropomorphic phantom, we placed thermoluminescent dosimeters into the center, anterior, and lateral aspect of the lower chest of the phantom. Standard CT of the chest was performed with the current protocols used at our institution on 4-, 8-, and 16-MDCT GE Healthcare systems. Next, near-identical CT scans of the entire chest were performed on the same CT systems.The 4-detector array showed statistically significantly higher radiation dose compared with the 16-detector array with near-identical technique (p < 0.01). There is a trend toward decreasing radiation dose with the increasing number of detectors using both standard and near-identical technique. An inverse relationship exists between measured radiation dose and the number of detectors.We theorize that as the number of detectors increases, there is a decrease in the amount of nonutilized radiation exposure, thus resulting in a lower total radiation dose.
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Introduction: Interventional angiography procedures are increasingly used today. These techniques require a long time of standing near the patient and x-ray tube which lead to increase the radiation-dose of the staff and interventionists. This may also, in turn, lead to the occurrence of radiation deterministic effects. Since a large number of interventional radiology were performed in our center, it was necessary to monitor the radiation-dose of the interventionists and patients. This study intended to measure the patient dose and the radiation dose of the leg, hands and effective radiation-dose of the interventionist in order to determine whether they are under the dose limit or not.
Materials and Methods: To determine the radiation-dose of the interventionist’s leg an anthropomorphic phantom PBU-50 was used. Thermoluminescent-dosimeters (TLD-100) set on the leg of the phantom. The leg dose per each interventional procedures was calculated. In order to measure the dose of the hands and effective-dose the interventionists wear a ring containing three TLD chips and set two packs of TLD, one under the apron and one over the thyroid shield before the interventional procedures. The results of TLD readings were corrected for operational quantity HP (0.07) and HP (10) and using the Nilklason- algorithm, the effective-dose was calculated. To monitor the patient, dose the radiation dose, dose area product (dap) and radiation exposure time were recorded.
Results: The mean radiation-dose of leg per different procedures were 0.39mSv/Pro. The mean radiation-dose of hands per different procedures was between 19.79 to 34.90µSv/pro. The mean effective-dose provided by TLDs, and the annual dose of physicians resulted from these procedures were 30.38µSv, and 350.20µSv/y, respectively. The mean radiation-dose (mGy/min) and the mean dap (µGy.m2/min) of the patients per procedure were 57.27 and
546.89 respectively.
Conclusion: ICRP proposes that the annual dose limit of extremities should be < 500mSv to control the risk of temporary epilation and erythema. In this study, the radiation-dose of leg and hands were less than the dose limit. The annual dose to radiologists was less than the occupational dose limit. In most of the procedures, the patient dose was less than the erythema threshold dose. However, in one of the hepatic procedures (TIPS), the radiation- dose of the patient exceeds the threshold so that designing a plan to reduce the patient dose is necessary.
Although the interventional procedures are so time-consuming and deliver the most radiation-dose to the staff among the angiography procedures, if the protection devices were used properly the radiation-dose can be controlled under the dose limit value. In some limit procedures such as TIPS, the radiation-dose of the patients may exceed the threshold of deterministic effect of radiation so that some strategies should be considered to reduce their dose, such as limiting the time of the radiation exposure
Dose area product
Thermoluminescent Dosimetry
Lead apron
Dose profile
Interventional radiology
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Dose profile
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Abstract The radiation dose of X-ray radiation exposure that comes from a CT scan is not easy to determine, because a CT scan uses several beams of X-ray radiation for one scan. In addition, the X-ray exposure dose on the CT scan is not the sum of the X-ray radiation exposure doses from each beam. Therefore, the Size-SpecificDoseEstimate (SSDE) parameter is used, which means as the estimated radiation exposure dose received by the patient. The SSDE value is a function of the CTDI vol which is determined from the reference phantom or from the derived Dose Length Product (DLP) values. The CTDI vol value determined from the reference phantom has the same value for the weight interval of the patient, so that the patient gets the same dose of X-ray exposure even though the body size is different. The CTDI vol value determined by Dose Length Product (DLP) depends on the lateral length of the patient’s body. Because the lateral body length of each patient is different, the CTDI vol value will be different, so the SSDE value will vary more. The results showed different SSDE values for each patient according to body mass index.
Dose area product
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Background: Radiography examinations are the most widely used and indispensable tools in medical imaging. The dose received by the patient should be known to prevent the risk of radiation exposure. Patient dose in radiography examination can be best estimated in terms of entrance surface dose (ESD). ESD value can be obtained by using the recorded dose viewer installed on the device. However, not all devices have this feature. Other methods can be conducted using thermoluminescence dosimeter (TLD) although it practically requires a high cost. Purpose: The study aims to estimate the ESD as a dose profile for patients undergoing radiography examination using tube output. Method: The patient data and exposure factors were retrospectively recorded for 263 patients. The ESD was estimated from the measurements of the X-ray tube output and recorded exposure factors. Results: The ESD value varied from 0.002 to 0.41 mGy. In the thorax PA, thorax LAT, cervical LAT, cervical AP, skull AP, skull LAT, genu LAT and waters was found (0,23±0.05) mGy, (0,09±0,05) mGy, (0,07±0,04) mGy, (0,13±0,08) mGy, (0,03±0,01) mGy, (0,06±0,02) mGy, (0,04±0,00) mGy (0,04±0,02) mGy, respectively. These results were further used to determine the Local Diagnostic Reference Level (LDRL) value. Conclusion: The results revealed that LDRL fell below the national DRL value and international reference
Thorax (insect anatomy)
Computed radiography
Conventional radiography
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Patients with adolescent idiopathic scoliosis (AIS) frequently receive x-ray imaging at diagnosis and subsequent follow monitoring. The ionizing radiation exposure has accumulated through their development stage and the effect of radiation to this young vulnerable group of patients is uncertain. To achieve the ALARA (as low as reasonably achievable) concept of radiation dose in medical imaging, a slot-scanning x-ray technique by the EOS system has been adopted and the radiation dose using micro-dose protocol was compared with the standard digital radiography on patients with AIS.Ninety-nine participants with AIS underwent micro-dose EOS and 33 underwent standard digital radiography (DR) for imaging of the whole spine. Entrance-skin dose was measured using thermoluminescent dosimeters (TLD) at three regions (i.e. dorsal sites at the level of sternal notch, nipple line, symphysis pubis). Effective dose and organ dose were calculated by simulation using PCXMC 2.0. Data from two x-ray systems were compared using independent-samples t-test and significance level at 0.05. All TLD measurements were conducted on PA projection only. Image quality was also assessed by two raters using Cobb angle measurement and a set of imaging parameters for optimization purposes.Entrance-skin dose from micro-dose EOS system was 5.9-27.0 times lower at various regions compared with standard DR. The calculated effective dose was 2.6 ± 0.5 (μSv) and 67.5 ± 23.3 (μSv) from micro-dose and standard DR, respectively. The reduction in the micro-dose was approximately 26 times. Organ doses at thyroid, lung and gonad regions were significantly lower in micro-dose (p < 0.001). Data were further compared within the different gender groups. Females received significantly higher (p < 0.001) organ dose at ovaries compared to the testes in males. Patients with AIS received approximately 16-34 times lesser organ dose from micro-dose x-ray as compared with the standard DR. There was no significant difference in overall rating of imaging quality between EOS and DR. Micro-dose protocol provided enough quality to perform consistent measurement on Cobb angle.Entrance-skin dose, effective dose and organ dose were significantly reduced in micro-dose x-ray. The effective dose of a single micro-dose x-ray (2.6 μSv) was less than a day of background radiation. As AIS patients require periodic x-ray follow up for surveillance of curve progression, clinical use of micro-dose x-ray system is beneficial for these young patients to reduce the intake of ionizing radiation.
Digital radiography
Thermoluminescent Dosimetry
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To establish a correlation between radiation dose and diagnostic accuracy when employing a new digital method for angle determinations. The specific intention was to determine how far the radiation dose can be reduced without losing measuring accuracy and to compare this radiation dose with that employed with our conventional method.An image succession of an anthropomorphic phantom was generated with a computed radiography (CR) system, by reducing the exposure stepwise. The images were archived and transferred to a workstation for evaluation. The intraobserver variation of two angle determinations was used as an indicator of the evaluation accuracy. Patient radiation doses were measured with thermoluminescent dosimeters. The energy imparted, indicating the relative risk associated with exposure to ionising radiation, and the effective dose, which determines the absolute risk, were calculated.No significant correlation was found between patient dose and measuring accuracy within the evaluated exposure interval. At the lowest exposure of the CR system, the energy imparted to the patient was 30 microJ. Compared with our conventional analogue method this is a reduction by 98%. The effective dose was as low as 1.5 microSv. The CR technique creates possibilities to adapt exposure parameters, and thus the radiation dose to the patient, according to the purpose of the investigation.
Digital radiography
Automatic exposure control
Computed radiography
Dose profile
Dose area product
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This study evaluated the effective dose of Ga-67 for a patient undergoing Ga-67 citrate nuclear examination by applying thermoluminescent dosimeter (TLD) technique and an indigenous water phantom. The Ga-67 radionuclide remaining in the body inevitably generated a measurable internal dose even though gamma camera scanning took only minutes to complete the clinical examination. For effective simulation of the cumulated effective dose for a patient undergoing examination, 150 TLDs were placed inside the water phantom for 6 days to monitor the gamma ray dose from the distributed Ga-67 citrate solution. The inserted TLDs represented internal organs, and the effective dose was calculated according to data in the ICRP-60 report. The water phantom was designed to model the body of a healthy human weighing 70 kg, and the water that was mixed with Ga-67 citrate solution was slowly replaced with fresh feed water to yield the required biological half life of the phantom. After continuously feeding in fresh water throughout the 6 days of TLD exposure, the TLDs were analyzed to determine the effective doses from the various biological half lives of the phantom. The derived effective dose of 185 MBq Ga-67 citrate solution for male/female (M/F) was 10.7/12.2, 10.7/12.0, 8.7/9.9 and 6.0/6.8 mSv, of biological half lives of 6.0, 4.5, 3.0 and 1.5 days, respectively. Although these experimental results correlated well with earlier empirical studies, they were lower than most calculated values. The cumulated uncertainty in the effective dose was 12.5–19.4%, which was acceptable in terms of both TLD counting statistic and reproducibility.
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Dynamic experiments cannot be observed easy on patients for determination of dosimetry in human PET studies dosimeter studies.In this study, it is aimed to estimate dose amount absorbed by some critical organs (e.g.bladder, lung, thyroid and ovary) by using a developed phantom.The phantom was improved as an original anthropomorphic whole body phantom which has been arranged with dynamic system.Therefore, organ absorbed doses by applying of fluorine-18-fluorodeoxyglucose in PET studies and was observed by using the phantom, while TLD dosimeters were used for determination of internal absorbed doses.In medical physics, the accuracy of absorbed dose resulting from radiopharmaceutical application was determined by the medical internal radiation dose method that depends theoretically on the cumulated activity of the source organs and their mass.The MIRD calculation was also used for the study and comparatively evaluated with the experimental results which were collected by using improved phantom.
Internal dose
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