The effect of breast shielding outside the field of view on breast entrance surface dose in axial X-ray examinations: a phantom study.

PURPOSE: The purpose of this study was to evaluate the effect of outside-field-of-view (FOV) lead shielding on the entrance surface dose (ESD) of the breast on an anthropomorphic X-ray phantom for a variety of axial skeleton X-ray examinations. METHODS: Using an anthropomorphic phantom and radiation dosimeter, the ESD of the breast was measured with and without outside-FOV shielding in anterior-posterior (AP) abdomen, AP cervical spine, occipitomental 30° (OM30) facial bones, AP lumbar spine, and lateral lumbar spine radiography. The effect of several exposure parameters, including a low milliampere-seconds technique, grid use, automatic exposure control use, wraparound lead (WAL) use, trolley use, and X-ray table use, on the ESD of the breast with and without outside-FOV shielding was investigated. The mean ESD (µSv) and standard deviation for each radiographic protocol were calculated. A one-tailed Student's t-test was carried out to evaluate whether ESD to the breast was reduced with the use of outside-FOV shielding. RESULTS: A total of 920 breast ESD measurements were recorded across the different protocol parameters. The largest decrease in mean ESD of the breast with outside-FOV shielding was 0.002 µSv (P = 0.084), recorded in the AP abdomen on the table with a grid, OM30 on the table with a grid, OM30 standard protocol on the trolley, and OM30 on the trolley with WAL protocols. This decrease was found to be statistically non-significant. CONCLUSION: This study found no significant decrease in the ESD of the breast with the use of outside-FOV shielding for the AP abdomen, AP cervical spine, OM30 facial bones, AP lumbar spine, or lateral lumbar spine radiography across a range of protocols.

A GATE Monte Carlo framework for dosimetric evaluation in mammography in an Algerian hospital.

A framework has been developed for dosimetric evaluation in mammography, using the GATE Monte Carlo (MC) platform, to simulate a MAMMOMAT 3000 Nova mammograph (Siemens) available at the University Hospital Center "1st November 1954" of Oran (EHU Oran 1er Novembre, 1954), Algeria. Calculated quantities such half-value layer (HVL), Entrance Surface Dose (ESD) and Mean Glandular Dose (MGD) have been compared to experimental data in order to validate the modeling of mammography examinations. Results are consistent with previous studies and show a good agreement between measurements and Monte Carlo calculations. By varying the tube voltage from 25 to 35 kV, we have estimated an increasing of a factor of 2.4 in ESD, and a factor of 2.75 for the MGD in a breast phantom. Furthermore, the current intensity of 100 mAs used for a beam quality combination (Mo/Mo) Anode/filter was found suitable for the tube voltages of 25-29 keV since the MGD does not exceed the limits set by the different quality insurance protocols. This GATE dose calculation framework thus provides a very useful tool for the optimization of mammography examinations at Oran hospital by allowing a better estimation of the dose delivered to patients according to the parameters of the examination.

Evaluation of patient dose during a digital breast tomosynthesis.

INTRODUCTION: When the patient dose in mammography is assessed, it is important to evaluate both average glandular dose (AGD) and entrance surface dose (ESD). A dose survey on both AGD and ESD in mammography has never been studied in Sri Lanka. Therefore, the present study aimed to evaluate the patient dose received during a full-field digital breast tomosynthesis (DBT) examination by determining both AGD and ESD. METHODS: The study was performed on 140 patients who underwent DBT examination. The AGD, ESD, compression breast thickness (CBT), half-value layer (HVL), target/filter combination, kVp, and mAs values were obtained from the machine, and AGD for each projection was calculated using the equation proposed by the Dance 2011. RESULTS: The measured mean AGDs and ESDs of both the breasts were statistically significantly lower than the reference values given by European protocol (p < 0.05). There were no statistically significant differences in both AGDs and ESDs between the right and left breast, between right craniocauidal (RCC) and left craniocaudal (LCC), and between right mediolateral oblique (RMLO) and left mediolateral oblique (LMLO) examinations (p > 0.05). The measured median AGDs and ESDs received for MLO projections of both breasts were statistically significantly higher than that of CC projections (p < 0.05). CONCLUSION: The patients receive a low radiation dose during their DBT examination with both lowered AGD and ESD than the recommended values. IMPLICATIONS FOR PRACTICE: The results can be used as a baseline to optimize the radiation dose in mammography in Sri Lanka.

Evaluation of radiation dose for inferior vena cava filter placement during pregnancy: A comparison of dosimetry and dose calculation software.

Numerous medical conditions are associated with pregnancy in women, including pulmonary thromboembolism, which can be fatal. An effective treatment of this condition is the positioning of an inferior vena cava filter (IVC-F) under the guidance of X-ray imaging. However, this procedure involves the risk of high radiation exposure to pregnant women and fetuses. Moreover, there are no published reports comparing the values of fetal dose, received during IVC-F placement in pregnant women, determined using dose calculation software and actual measurements. To address this issue, we compared the fetal radiation dose and entrance surface dose (ESD) for pregnant women for gestation periods of 6 and 9 months based on software calculations and actual measurements. The ESD and fetal doses were estimated for a pregnant woman for gestation periods of 6 and 9 months during IVC-F placement. For actual measurements, one pregnant model phantom was constructed using an anthropomorphic phantom, and two custom-made different-sized abdomen phantoms were used to simulate pregnancy. The custom-made abdomen phantoms were constructed using polyurethane. For software calculations, the software utilized a set of anatomically realistic pregnant patient phantoms. The ESD estimated using the software was consistent with the measured ESD, but the fetal dose estimations were more complicated due to fetal positioning. During fetal dose evaluation using software calculations, the user must carefully consider how much of the fetal length is in the irradiation field to prevent underestimation or overestimation. Despite the errors, the software can assist the user in identifying the magnitude of the dose approaching critical limits.

Increasing Source-Object Distance: A Computed Radiographybased Strategy to Reducing Radiation Dose in Occipital-Frontal Skull X-Ray

@#Introduction: Exploring potential optimization strategies and developing evident practices is critical. Previous studies show that radiation dose can be reduced by increasing the source-image distance (SID). Although most studies use digital radiography, many hospitals in underdeveloped countries still use computed radiography (CR). Therefore, research will investigate the relationship between SID and Entrance surface dose (ESD) using the CR. Methods: This study involved the measurement of radiation dose and image quality of a radiological procedure performed at a reference SID; 100cm and the tested SIDs; 110cm, 120cm, and 130cm, using constant technical factors (70kVp, 25mAs, grid). A LiF; Mg Ti thermoluminescence dosimeter (TLD-100) chip was placed in the center of the radiation field of the OF10° skull radiography examination to measure ESD. Image quality was assessed using the European Commission guidelines and graded using relative visual assessment analysis (VGA). Results: Significant ESD reduction from 21% and 45% when SID was increased from 100cm to 130cm (p <0.001), where SID was negatively correlated with ESD (r= - 0.98). The VGA scores showed no statistical difference in the image quality of the OF10° skull radiography examination for the tested and reference images (p=0.21). VGA scores for 120cm images showed the highest image quality among the SIDs tested with a dose reduction of 37%. Conclusion: ESD was statically reduced when SID was increased from 100cm to 130cm, while image quality was diagnostically acceptable. The study suggests that 120cm is the optimal SID when both dose and image quality are considered.

Suggested Local Diagnostic Reference Levels for Possible Pediatric X-Ray Optimization in Addis Ababa, Ethiopia.

Background: Early childhood radiation exposure carries an enhanced radiation risk of about two to three times as high as in adults. The objective of this study was to determine local diagnostic reference levels for the most frequent pediatric x-ray examinations in Addis Ababa, Ethiopia. Methods: A cross-sectional study was conducted on 18 public and private hospitals/clinics in Addis Ababa. A total of 864 pediatric patients, undergoing eight types of routine x-ray examinations with 13 projections were evaluated from December 18/2017 to March 17 /2018. All pediatrics were categorized under four age groups. Anthropometric and radiographic parameters of each patient were recorded .The minimum, maximum, mean and third quartile values of entrance surface dose were analyzed using SPSS version 23. Finally, the suggested local diagnostic reference levels were compared with national and international reference dose values. Results: Of the 864 pediatric patients, chest (AP/PA), lower and upper extremity (AP/PA) accounted for 501(58%), 110 (13%) and 103 (12%) respectively, accounting to 714(83%) of the total pediatric x-ray examinations. The suggested local diagnostic reference levels of chest X-ray (AP/PA) examinations in mGy were: (0.09,0.13,0.17,0.17) for age group (0-<1,1-<5 ,5-<10, and 10-<15), respectively. Similarly, for same age group (0-<1,1-<5 ,5-<10, and 10-<15) the suggested local diagnostic reference levels of lower and upper extremities in mGy were: (0.06,0.08,0.09,0.09) and (0.04,0.05,0.05,0.06), respectively. Conclusion: The suggested local diagnostic reference levels were slightly higher than the national and international guidance levels, indicating the need for establishment of diagnostic reference levels in the country.

[A Study of Patient's Dose Control at Radiography by Using a Dose Area Product Meter].

PURPOSE: The International Commission on Radiological Protection recommends adaptation of the diagnostic reference levels (DRLs). Japan DRLs 2020 apply the entrance surface dose (ESD) in radiography. However, it is difficult to measure ESD in the clinical setting. A dose area product meter has been proposed for use as a dose index in interventional radiology. We investigated the basic characteristic of a dose area product meter and the relationship of ESD and dose area product meter values in radiography. METHOD: We measured calibration factors from phantom studies and estimated ESD from the dose area product meter. Subject thickness was measured from the chest clinical images for calculation of ESD. Estimated ESD from the dose area product meter was compared with that calculated from program software (Surface Dose Evaluation Code, Sdec). RESULT: Relative dose (dose area product meter/ionization chamber) decreased when tube voltage was lower (60 kV) or higher (130 kV). A positive correlation was found between the estimated and calculated ESD. CONCLUSION: Dose area product meter can be used for patient's dose control in radiography.

Dosimetry of pediatric chest X-Ray examinations in Togo.

OBJECTIVE: To assess the entrance surface dose (ESD) of pediatric chest X-ray examinations in order to establish a diagnostic reference levels (DRLs) in Togo. MATERIALS AND METHODS: The study was carried out in 13 radiology departments within the 6 health regions of the country. This is a descriptive cross-sectional study relating to the dosimetric assessment of the skin of children aged from 0 to 15 years during chest X-ray examinations. The assessment was made by the empirical formula calculation of the entrance surface dose (ESD = 0.15 × (U/100)2 × Q × (1/FSD)2) and with the Internet Dose Calculation Module (MICADO) software online. Statistical assessment was performed using IBM SPSS 21 software. RESULTS: Our sample numbered 390 with a sex ratio of 1.3 and predominantly male. Examinations performed with the analog radiography units were more irradiating (0.14 mGy) than ones performed with digital detectors (0.12 mGy). The mean dose calculated with MICADO was low (Avg. = 0.12 mGy) compared to that calculated with the theoretical method (Avg. = 0.16 mGy). No significant relationship was found between the professional experience of operators and the entrance surface dose (r  > -1 with p = 0.146 not significant). MICADO doses increased with age. The values of the diagnostic reference levels used for the antero-posterior or postero-anterior chest X-ray examinations for children aged 0-1 year; 1-5 years; 5-10 years and 10-15 years were respectively, 0.15 mGy; 0.14 mGy; 0.15 mGy and 0.17 mGy. CONCLUSION: The entrance surface dose varied greatly from one health facility to another for this same examination. In most of the different age groups of children, the diagnostic reference level was higher than that found in literature. Thus, effective measures must be put in place to optimize the doses delivered to children during chest X-ray examinations.

Exposure of patients to low doses of X-radiation during neuro-interventional imaging and procedures: Dose estimation and analysis of γ-H2AX foci and gene expression in blood lymphocytes.

Radiation has widespread applications in medicine. However, despite the benefits of medical radiation exposures, adverse long-term health effects are cause for concern. Protein and gene biomarkers are early indicators of cellular response after low-dose exposure. We examined DNA damage by quantifying γ-H2AX foci and expression of twelve candidate genes in the blood lymphocytes of patients exposed to low doses of X-radiation during neuro-interventional procedures. Entrance surface dose (ESD; 10.92-1062.55 mGy) was measured by thermoluminescence dosimetry (TLD). Absorbed dose was estimated using γ-H2AX focus frequency and gene expression, with in vitro dose-response curves generated for the same biomarkers. γ-H2AX foci in post-exposure samples were significantly higher than in pre-exposure samples. Among the genes analysed, FDXR, ATM, BCL2, MDM2, TNFSF9, and PCNA showed increased expression; CDKN1A, DDB2, SESN1, BAX, and TNFRSF10B showed unchanged or decreased expression. Absorbed dose, estimated based on γ-H2AX focus frequency and gene expression changes, did not show any correlation with measured ESD. Patients undergoing interventional procedures receive considerable radiation doses, resulting in DNA damage and altered gene expression. Medical procedures should be carried out using the lowest radiation doses possible without compromising treatment.

Determination of backscatter factors based on the quality index for diagnostic kilovoltage x-ray beams.

PURPOSE: This study aims to investigate the relationship between backscatter factors and Al-half-value-layers (Al-HVL) by making the quality index (QI) a parameter for diagnostic kilovoltage x-ray beams. METHODS: Backscatter factors, Bw, for x-ray fluence spectra were calculated from the weighted average of Bw for monoenergetic photons of between 8 and 140 keV with field sizes of 10 cm × 10 cm to 40 cm × 40 cm. The value of Bw for monoenergetic photons was calculated from the ratio of the water kerma at the surface of a water phantom and that at the same point free-in-air using the EGSnrc/cavity code. The weighted averaged backscatter factors were validated by comparing them with those of direct Monte Carlo calculations for the x-ray fluence spectra. The Bw for the x-ray fluence spectra were classified by a QI of 0.35, 0.4, 0.5, 0.6, and 0.7 specified by the ratio of the effective energy and maximum energy. The relationship between Bw and Al-HVL was evaluated for the given QI values. The x-ray fluence spectra were generated for tube voltages of 40-140 kVp with Al-HVLs of 0.5-13.2 mm using the SpekCalc program. RESULTS: The weighted averaged backscatter factors for x-ray fluence spectra agreed within 0.7% with those of the direct Monte Carlo calculations. The backscatter factors were represented by the fitting curves of R2 > 0.99 with Al-HVL for the given QI values. CONCLUSIONS: It is possible to obtain Bw more accurately by using QI specified by the measured Al-HVL.

Examination of a dose evaluation method for floor-mounted kV X-ray image-guided radiation therapy systems.

Floor-mounted kV X-ray image-guided radiation therapy systems (such as ExacTrac) are used to treat tumors in movable body regions such as the head and neck. ExacTrac requires exposure dose control based on image acquisition. However, placement of the aluminum plate perpendicular to the dosimeter is difficult due to the oblique X-ray beam path. This study provides an evaluation of the entrance surface, organ, and effective doses delivered to the head and neck during image-guided radiation therapy. A semiconductor detector (Unfors Xi) and radiophotoluminescent glass dosimeter (RPLD) were used as dosimeters with entrance surface dose calculation (Sdec) and exposure estimation (PCXMC) software. When the Unfors Xi was placed in front of the flat panel detector (FPD), an accurate entrance surface dose was obtained by considering the X-ray attenuation due to the influence of the distance from X-ray tube to FPD.The couch absorption was 32% and incident air kerma at the patient entrance point was 0.094 mGy for Unfors Xi. The entrance surface doses were 0.12 and 0.122 mGy for the Sdec and RPLD, respectively. The thyroid organ doses were 0.044 and 0.058 mGy for the RPLD and PCXMC, respectively. The effective doses of PCXMC for ExacTrac and cone-beam computed tomography were 0.0068 and 0.31 mSv, respectively. The exposure dose of ExacTrac was approximately 2% of that of cone-beam computed tomography. The results demonstrated that the proposed software-based method is effective for the assessment and management of ExacTrac exposure.

Assessment of Patient Absorbed Radiation Dose during Hysterosalpingography: A Pilot Study in Southwest Nigeria.

BACKGROUND: Hysterosalpingography (HSG) is an indispensable tool for diagnosing infertility in females. The procedure exposes female reproductive organs to ionizing radiation as the genitals are irradiated during the process. Investigating patient absorbed dose during the procedures is essential for effective radiological protection of the patient. OBJECTIVE: This study aims to investigate the radiation dose received by patient during HSG examination in the study environment in order to enhance optimization of procedures and the associated dose, thereby minimizing radiation risks. MATERIAL AND METHODS: The prospective pilot study, was conducted in four tertiary healthcare institutions in Southwest Nigeria. Thermoluminescence dosimeter (TLD 100) was used to determine the Entrance Surface Dose (ESD) of 80 patients presented for HSG investigation. The corresponding effective dose, ovary, uterus and urinary bladder doses were evaluated using PCXMC software. RESULTS: The mean entrance surface doses (ESD) obtained from the four centers were 18.58±6.31 mGy, 15.18±2.27 mGy, 17.44±3.43 mGy and 34.24±11.98 mGy for SW1, SW2, SW3 and SW4 centers, respectively. The corresponding mean of effective doses were 1.54±0.63 mSv, 1.24±0.28 mSv, 1.41±0.30 mSv and 2.53±0.94 mSv for SW1, SW2, SW3 and SW4 centers, respectively. The resulting mean doses to the ovary, urinary bladder and uterus were also presented. CONCLUSION: The results obtained in general are comparable with international standards. It was, however, recommended that study centers with high doses should conduct dose audit in order to enhance patient safety.

Application of Digital Tomosynthesis in the Diagnosis of Urolithiasis: Comparison with MDCT.

Objective: To investigate the diagnostic value of digital tomosynthesis in urolithiasis compared with multidetector computed tomography (MDCT). Subjects and Methods: This study received the approval of institutional review board and obtained the informed consents of all subjects. Fifty patients with acute renal colic and hematuria from February 2014 to February 2015 were enrolled. They underwent both MDCT and digital tomosynthesis. Images were interpreted by two experienced radiologists, and inter-reader agreement was assessed. The diagnostic performance of urinary stones with digital tomosynthesis and MDCT was compared. The entrance surface dose (ESD) in MDCT and digital tomosynthesis for patients was measured and compared. Results: No significant difference was found between digital tomosynthesis and MDCT in the diagnosis of urinary stones (X2 = 1.357, p > 0.05). The ESD in digital tomosynthesis was lower than that in both routine-dose and low-dose MDCT for patients (p < 0.05). Conclusions: Digital tomosynthesis has great diagnostic value in urolithiasis. Compared with MDCT, digital tomosynthesis can significantly decrease ESD for patients and financial loan with a similar detection rate.

[Radiation Exposure in Computed Tomography Localizer Radiograph].

This research measured the radiation exposure of the computed tomography(CT) localizer radiograph of the trunk of the body. The entrance surface dose for CT localizer radiograph was measured using radiophotoluminescent glass dosimeter(RPLD) on four points of measurement, including the center of the phantom, on the surface of a phantom placed in the center of a CT bed, assuming that the subject has a thickness of 20 cm. The entrance surface dose of the localizer radiograph under the chest CT protocol manufacturer's initial setting conditions of 120 kV 35 mA was 0.80 mGy at the center and 0.53 for the 4-location average for the upper X-ray tube (excluding the CT bed), and 0.74 mGy at the center and 0.48 mGy for the 4-location average for the lower X-ray tube (including the CT bed). Compared to the Japan DRLs 2015 chest X-ray (P→A), the entrance surface dose was 2.67 times at the center and 1.77 times for the 4-location average for the upper X-ray tube and 2.47 times at the center and 1.60 times for the 4-location average for the lower X-ray tube. The CT radiation dose also cannot be ignored for the localizer radiograph entrance surface dose.

Consideration of diagnostic reference levels for pediatric chest X-ray examinations.

The use of diagnostic reference levels (DRLs) is currently recommended, and dose evaluation is considered to be important for establishing a Japanese radiological protection system in radiological medicine. Children, in particular, are sensitive to radiation, and their exposure levels must be taken into account. The DRL for the entrance surface dose (ESD) used in pediatric chest X-ray examinations in Japan is 0.2 mGy. However, the bodies of infants and young children show major changes with rapidly developing organs. Thus, the possibility that organ development may also be affected by radiation exposure should be taken into account. Therefore, radiological technologists must be conservative in setting radiographic conditions for pediatric examinations. The objective of this study was to evaluate the doses used in pediatric chest X-ray examinations at our hospital and compare them with the current DRLs, considering the assumption that setting conditions individually for different ages and subject thicknesses and performing more detailed dose evaluations will help reduce radiation exposure. The study was carried out to estimate the ESDs in 163 pediatric patients who underwent frontal or lateral chest X-ray examinations at our hospital. All doses were lower than 0.2 mGy, the dose recommended in the Japanese DRLs 2015. The doses showed a strong correlation with age, but a weaker correlation with subject thickness. These results suggest that instead of considering a common DRL for all children, the DRL should be evaluated on the basis of age.

Optimizing image quality using automatic exposure control based on the signal-difference-to-noise ratio: a phantom study.

This study proposes to adjust the sensitivity of automatic exposure control (AEC) for achieving consistent image quality over a range of subject thicknesses in abdominal radiography simulations. The relation between image quality and subject thickness was investigated using a digital radiography system with 10-, 15-, 20-, and 25-cm-thick acrylic phantom. Simple pixel signal-to-noise ratio (SNR) was measured to check the default AEC accuracy for each thickness, and image quality was evaluated using the signal-difference-to-noise ratio (SDNR) with an additional acrylic plate and bone-equivalent material. Based on the figure of merit theory, dose ratios to obtain constant image quality regardless of the subject thickness were calculated from SDNR results. The AEC setup was manually modified using this dose ratio, and visibility was examined using a CDRAD 2.0 contrast-detail analysis phantom. Moreover, the entrance surface dose (ESD) was estimated as an index of exposure dose using exposure parameters. The default AEC setup provided a constant simple pixel SNR for each subject thickness with a high accuracy. SDNRs decreased with an increase in the subject thickness. The calculated dose ratios relative to the results for 20 cm thickness were 0.424, 0.647, and 1.43 for 10, 15 and 25 cm, respectively, and a > 25% decrease in ESD was observed for smaller patients. CDRAD analysis using the modified AEC setup showed almost identical visibility for each thickness. Adjusting the sensitivity of AEC according to subject thickness can contribute toward the optimization of the exposure condition.

DNA damage and gene expression changes in patients exposed to low-dose X-radiation during neuro-interventional radiology procedures.

Interventional radiology-based imaging is the preferred choice for diagnosis and therapy of many complex diseases, despite possible adverse effects of the radiation exposures. We have measured induced DNA damage and changes in gene expression in relation to entrance surface dose (ESD) in peripheral blood samples of patients (n = 51) who underwent neuro-interventional radiological procedures. The ESD values, measured by thermoluminescence dosimetry, were 4.9-273 mGy (forehead), 14-398 mGy (eyes), 8-433.3 mGy (shoulders), and 4.7-242.5 mGy (thyroid). The in-built recorded Dose Area Product (DAP) values were 74.61-558.55 and 13.17-2825.12 Gy*cm2 for diagnostic and therapeutic procedures, respectively. The mean fluorescence intensity (MFI) on the phosphorylation of γ-H2AX and p53ser-15 was higher in samples obtained post-exposure vs. pre-exposure. However, the increase was statistically significant only for p53ser-15 (P < 0.01). Consistent with γ-H2AX, CDKN1A, FDXR, BAX, DDB2, SESN1, BCL2, MDM2, TNFSF10B, and PCNA showed (non-significant) decreased expression while GADD45A, ATM, and TNFSF9 showed (non-significant) increased expression. Our results suggest that most of the patients had increased DNA damage and altered gene expression after receiving relatively low doses of ionising radiation. This implies that these procedures should be carried out at the lowest possible doses of radiation that do not compromise image quality.

Effective Dose Display System in Gastric Cancer X-ray Screening.

PURPOSE: The purpose of this study is to build a system for effective dose display immediately after the gastric cancer X-ray screening. MATERIALS AND METHODS: The regression equation of effective dose and dose area product (DAP) was introduced from the data of 500 persons including DAP and effective dose calculated using program for X-ray Monte Carlo. RESULTS: The effective dose was 5.39 mSv of median, 1.18 mSv of minimum, and 38.38 mSv of maximum. The regression equation was Y=0.354+0.0003772X (Y: effective dose, mSv, X: DAP, mGy cm2). Using the regression equation, the effective dose can be estimated from DAP and displayed just after the individual screening. CONCLUSIONS: "Effective dose display system" was constructed to display effective dose immediately after gastric cancer X-ray screening. This system is on the way to be reformed by improving the regression equation on larger data.

Dosimetry of Critical Organs in Maxillofacial Imaging with Cone-beam Computed Tomography.

BACKGROUND: While the benefits of cone-beam computed tomography (CBCT) are well known in maxillofacial imaging, the use of this modality is not risk-free. OBJECTIVE: The aim of this study was to evaluate the exposure doses received by patients during maxillofacial imaging with CBCT. METHODS: Entrance surface dose (ESD) was measured by using thermoluminescent dosimeters (TLDs) attached to the eyes lids, parotid glands and thyroid of 64 patients in two imaging centers (A and B). Phantom dosimetry was performed by a cylindrical poly-methyl methacrylate (PMMA) head-size phantom and an ionization chamber for different exposure parameters. NewTom VGi and Planmeca Promax 3D CBCT scanners were used at centers A and B, respectively. RESULTS: The mean ESD of the eyes, parotid glands and thyroid were 2.57, 2.33 and 0.28 mGy in center A, 0.35, 2.11 and 0.37 mGy in center B, respectively. ESD of the eyes revealed a significant difference in two centers; in center B, it was 86.4% lower than center A. In the phantom dosimetry, the measured doses of NewTom VGi were 2.63 and 2.08 mGy, respectively by changing field of view (FOV) size from 8×8 cm2 (height × diameter) to 6×6 cm2. For Planmeca Promax 3D, it ranged from 0.98 to 3.24 mGy depending on exposure parameters. CONCLUSION: There is a wide range of radiation doses dependent on the units, patients and selected scan parameters. Inappropriate selection of exposure settings, especially FOV size, can seriously increase patient dose.

Simultaneous measurement of patient dose and distribution of indoor scattered radiation during digital breast tomosynthesis.

INTRODUCTION: Breast cancer incidence increases from the age of 30 years. As this age range coincides with that in which women usually pursue pregnancy, undergoing medical examinations for conditions such as breast cancer is a concern, especially when pregnancy is uncertain during the first eight weeks. Moreover, in this age range, breast often exhibits a high density, thus compromising diagnosis. For such density, digital breast tomosynthesis (DBT) provides a more accurate diagnosis than 2D mammography given its higher sensitivity and specificity. However, radiation exposure increases during DBT, and it should be determined. METHODS: We determined the entrance surface dose, scattered radiation dose, and average glandular dose (AGD), which can be mutually compared following an international protocol. Using our proposed method, the distribution of scattered radiation can be easily and quickly obtained with a minor load to the equipment. Then, we can determine the indoor scattered radiation and surface dose on patients during DBT. RESULTS: We obtained a maximum AGD of 2.32 mGy. The scattered radiation was distributed over both sides with maximum of approximately 40 µGy, whereas the maximum dose around the eye was approximately 10 µGy. CONCLUSION: By measuring doses using the proposed method, a correct dose information can be provided for patients to mitigate their concerns about radiation exposure. Although the obtained doses were low, their proper management is still required. Overall, the results from this study can help to enhance dose management for patients and safety management regarding indoor radiation.