Entrance Surface Dose Measurements Research Articles

Imaging dose assessment for cyberknife intra-cranial treatments

The aim of this study was to retrospectively assess patient treatment log files to determine an optimal imaging frequency for Intracranial Stereotactic Cyberknife treatments and thus, reducing the imaging dose received by the patient to ALARA while maintaining acceptable delivery accuracy. Image guided radiotherapy (IGRT) and stereotactic radiotherapy (SRT) have become fundamental treatment modalities in radiotherapy for ensuring accurate dose distribution to the intended target. To assess intra-fractional motion, frequent tracking can be employed to accurately track target motion during treatment. If an ionising radiation modality is used, the additional imaging dose received by the patient should be optimised.Patient entrance surface dose (ESD) was measured utilising solid water phantoms to mimic patient scatter for exposures used clinically. Imaging dose was quantified by applying ESD measurements to retrospective data for a cohort of 100 fractions and analysing patient position at each acquired image pair. Patient movement was established by the difference between two consecutive images for the duration of the treatment fraction. Patient movement along with plan robustness was used to determine imaging frequency. ESD was measured to be 0.24 mGy per image pair. In comparison to an original average imaging frequency of 43 s over all patients, an imaging frequency of 64 and 15 s has been suggested for Meningiomas (MEN)/Acoustic Neuromas (AN) and Trigeminal Neuralgia (TGN) respectively. By optimising the imaging frequency, the imaging dose received by patients may increase by up to 150% (TGN) or decrease by up to 20% (MEN/AN) while adequately tracking patient movement.

Examination of Dose Reduction Using Image Noise Reduction Technology in Cardiovascular X-ray Systems.

The aim of this study is to establish radiation exposure dose reduction protocols during cardiac intervention by decreasing the entrance dose at flat panel detector (FPD) with image quality evaluations. For measuring entrance surface dose (ESD), we have used a Radical 9015 dosimeter (6 cc ion chamber) placed under 20 cm thick acrylic plates at the patient's entrance reference point. We performed an image quality assessment based on quantitative as well as visual evaluation of the images obtained via current and dose reduction protocols. The visual evaluation was performed by measuring the signal to noise ratio and contrast using a cine/digital angiography cardiac phantom. The quantitative evaluation was performed by cardiologists and radiological technologists using the five-point scale method. For the dose reduction protocol, we used an image noise reduction technique to prevent the deterioration of image quality. The ESDs for the fluoroscopy and digital cine in the dose reduction protocol were 18.0 mGy/min and 0.18 mGy/frame, respectively, which corresponded to 81% and 49% of the ESD in the current protocol. Our results reveal that the ESD for fluoroscopy was lower than the diagnostic reference level (20 mGy/min) for interventional radiology. We recommend a lower dose setting and the maintenance of image quality using noise reduction techniques. This will ensure use of a lower FPD entrance dose compared to the initial dose setting currently recommended by manufacturers.

Preliminary Values of Diagnostic Reference Level for Selected X-Ray Examinations in Indonesia

The diagnostic reference levels form an efficient, concise, and powerful standard for optimizing the radiation protection of a patient. With an aim to contribute toward the establishment of the Indonesian National Diagnostic Reference Levels (NDRLs), a nationwide survey of the entrance surface doses received by adult patients during the most typical X-ray examinations has been performed. A number of 44 hospitals in 21 cities located in Java, Bali, Sumatera, Kalimantan, and Sulawesi islands were selected randomly to participate in this survey. Eight most common adult X-ray examinations in 13 projections, as well as four children X-ray examinations in six projections, were included in the list of procedures under consideration. Hospitals of different sizes and levels using different X-ray machines were represented in the survey. Standard thermoluminescence dosemeters were applied to measure entrance surface dose (ESD). A total of 1493 patients, consisting of 1208 adults and 285 children, were included in this study. The data were analyzed statistically and the minimum, median, mean, maximum, first quartile, and third quartile values of ESDs were reported. The ESDs calculated (third quartile) for adults varied from 0.18 mGy (for extremities AP) to 5.84 mGy (for lumbar spine LAT), and for children they varied from 0.16 mGy (for chest AP/PA) to 1.46 mGy (for skull AP/PA). Considering the geographic spread and size of Indonesia, those third quartile values calculated can only be regarded as preliminary DRL values for Indonesia. Compared with data from other countries, the calculated ESDs in this study are in general lower than the ESDs in those countries. Received: 16 November 2015 ; Revised: 27 April 2016 ; Accepted: 9 May 2016

Fundamental Study of nanoDot OSL Dosimeters for Entrance Skin Dose Measurement in Diagnostic X-ray Examinations

Background: In order to manage the patient exposure dose in X-ray diagnosis, it is preferred to evaluate the entrance skin dose; although there are some evaluations about entrance skin dose, a small number of report has been published for direct measurement of patient. We think that a small-type optically stimulated luminescence (OSL) dosimeter, named nanoDot, can achieve a direct measurement. For evaluations, the corrections of angular and energy dependences play an important role. In this study, we aimed to evaluate the angular and the energy dependences of nanoDot. Materials and Methods: We used commercially available X-ray diagnostic equipment. For angular dependence measurement, a relative response of every 15 degrees of nanoDot was measured in 40-140 kV X-ray. And for energy dependence measurement, mono-energetic characteristic X-rays were generated using several materials by irradiating the diagnostic X-rays, and the nanoDot was irradiated by the characteristic X-rays. We evaluated the measured response in an energy range of 8.1-75.5 keV. In addition, we performed Monte-Carlo simulation to compare experimental results. Results and Discussion: The experimental results were in good agreement with those of Monte- Carlo simulation. The angular dependence of nanoDot was almost steady with the response of 0 degrees except for 90 and 270 degrees. Furthermore, we found that difference of the response of nanoDot, where the nanoDot was irradiated from the randomly set directions, was estimated to be at most 5%. On the other hand, the response of nanoDot varies with the energy of incident X-rays; slightly increased to 20 keV and gradually decreased to 80 keV. These results are valuable to perform the precise evaluation of entrance skin dose with nanoDot in X-ray diagnosis. Conclusion: The influence of angular dependence and energy dependence in X- ray diagnosis is not so large, and the nanoDot OSL dosimeter is considered to be suitable dosimeter for direct measurement of entrance surface dose of patient.

Calculation of conversion factor relating measured patient entrance skin dose and scanner registered computed tomography dose index during sinus examination

Introduction Radiochromic films (RF) have successfully been used in measuring radiation doses in computed tomography (CT). The films were reported to have the ability to picture radiation dose profile, to measure entrance surface dose (ESD), and the peak surface dose (PSD). Purpose The objective of this work was to study the feasibility of using RF as in vivo dosimeters to measure ESD from patients undergoing routine CT examination of the sinus and relate the measurements to the scanner calculated computed tomography dose index ( CTDI vol ) available at the scanner console. Materials and methods Gafchromic XR-QA2 film strips were calibrated against the reading from a 300 mm long pencil type ionization chamber calibrated in terms of CT dose length product (DLP). The in vivo measured ESD and PSD from 12 patients using films were used to calculate the conversion factors: C S = ESD / CTDI vol and C PK = PSD / CTDI vol . Results The calculated conversion coefficients C S and C pk were 0.88 and 1.18 respectively. The films were easily and effectively implemented as In-vivo dosimeter during CT imaging of the sinus allowing for a more accurate estimate of typical surface doses found in CT imaging. Conclusion The films had the advantage of not interfering with the patient setup and did not produce any image artifacts. The method can be used to study other CT examinations specially the ones with larger beam width and high pitch factor, to predict the peak skin dose, to examine the CT dose profile and the radiation dose distribution during annual QA. Disclosure we have nothing to disclose in relation with the presented work.

Entrance surface dose measurements using a small OSL dosimeter with a computed tomography scanner having 320 rows of detectors.

Entrance surface dose (ESD) measurements are important in X-ray computed tomography (CT) for examination, but in clinical settings it is difficult to measure ESDs because of a lack of suitable dosimeters. We focus on the capability of a small optically stimulated luminescence (OSL) dosimeter. The aim of this study is to propose a practical method for using an OSL dosimeter to measure the ESD when performing a CT examination. The small OSL dosimeter has an outer width of 10mm; it is assumed that a partial dose may be measured because the slice thickness and helical pitch can be set to various values. To verify our method, we used a CT scanner having 320 rows of detectors and checked the consistencies of the ESDs measured using OSL dosimeters by comparing them with those measured using Gafchromic™ films. The films were calibrated using an ionization chamber on the basis of half-value layer estimation. On the other hand, the OSL dosimeter was appropriately calibrated using a practical calibration curve previously proposed by our group. The ESDs measured using the OSL dosimeters were in good agreement with the reference ESDs from the Gafchromic™ films. Using these data, we also estimated the uncertainty of ESDs measured with small OSL dosimeters. We concluded that a small OSL dosimeter can be considered suitable for measuring the ESD with an uncertainty of 30% during CT examinations in which pitch factors below 1.000 are applied.

Patient dose audit of the most frequent radiographic examinations and the proposed local diagnostic reference levels in southwestern Nigeria: Imperative for dose optimisation

Diagnostic reference levels (DRLs) is a veritable tool for dose optimisation and patient protection in diagnostic radiology. However, it is essential to have information on the local situation especially in a large hospital with several units or a cluster of healthcare centres within a geographical region with several X-ray units. In the present study, entrance surface doses (ESDs) were measured in twelve (12) healthcare centres consisting of 15 radiological units using thermoluminescent dosimeters (TLDs). Seven radiological procedures such as; chest PA, abdomen AP, pelvis AP, lumbar spine AP, skull AP, knee AP, and hand AP frequently carried out in Nigeria were included in the study, and their local diagnostic reference levels (LDRLs) were determined. The values of the determined LDRLs were compared with established NDRLs in UK, US, Slovenia, Italy and Brazil. The LDRLs determined in the two groups (healthcare centres) studied ranged from 1.78 to 3.01, 2.71 to 2.84, 2.11 to 3.79, 3.93 to 8.79, 1.06 to 1.73 and 1.10 to 1.44 mGy for chest PA, pelvis AP, lumbar spine AP, skull AP, knee AP and hand AP respectively. Large variations were found among the X-ray units studied even within the same centre. Entrance surface doses obtained in pelvis AP and lumbar spine AP in both GROUP A and were found to be lower than the NRPB-HPA 2010 review for UK, while in all other five examinations, value of the measured entrance surface dose (ESD) are higher than the doses reported in the UK review. The relative higher doses found in the study are attributable to higher tube load (mAs) used and indicative of the need for dose optimisation in Nigerian radiological practice.

Evaluation based on Monte Carlo simulation of lifetime attributable risk of cancer after neck X-ray radiography.

At present, concern regarding radiation exposure is increasing with the prevalence of radiologic examination. As radiation damages the human body, we have evaluated medical radiation dose values and studied the importance of optimizing radiation exposure. We measured entrance surface dose (ESD) values using a RANDO(®) phantom (neck) in 94 randomly selected locations in the central region of Korea. Thyroid and organ doses were calculated using Monte Carlo simulations (PCXMC 2.0.1) based on measured values. In addition, the lifetime attributable risk (LAR) of cancer was calculated for the thyroid, using the method proposed in the biological effects of ionizing radiation VII report. The average measured ESD values obtained using the RANDO(®) phantom (neck) were antero-posterior 1.33 mGy and lateral 1.23 mGy, for a total of 2.56 mGy. Based on the ESD values measured using the phantom, the organ doses were obtained using a Monte Carlo simulation (PCXMC 2.0.1). The thyroid dose was 1.48 mSv on average. In evaluating the LAR of thyroid cancer incidence, a frequency of 0.02 per 100,000 from 2.94 per 100,000 males and a frequency of 0.10 per 100,000 from 16.23 per 100,000 females were found. The risk of cancer was found to be higher when the patient's age was lower, and was also higher in females than in males. It was concluded that beneficial exams in the medical field should not be prohibited because of a statistically small risk, although acknowledgement of the dangers of ionizing radiation is necessary.

Examination of the relevance of using radiochromic films in measuring entrance skin dose distribution in conventional digital mammography.

Based on manufacturer specifications, radiochromic films are sensitive enough to be used for dosimetry in digital mammography (DM). The aim of this work was to study the feasibility of measuring entrance surface dose (ESD) distribution using Gafchromic XR-QA2 films. The films were irradiated following a standard clinical two-view screening mammography protocol using a full-field digital mammography (FFDM) imaging system. The films were then digitised using a flatbed scanner. The calibration curve relating the readings from a calibrated ionisation chamber and the films' net optical density (NOD) could not be obtained. The examination of the calibration data revealed non-sensitivity of the films to resolve dose differences below 20 mGy at 28 kVp. Therefore, radiochromic films were found not to be suitable for measuring ESD profiles in DM. A 2D map of the NOD of the irradiated films obtained using in-house developed MATLAB computer program is presented.

Patient-specific organ dose estimation during transcatheter arterial embolization using Monte Carlo method and adaptive organ segmentation

Abstract The purpose of this study was to evaluate organ doses for individual patients undergoing interventional transcatheter arterial embolization (TAE) for hepatocellular carcinoma (HCC) using measurement-based Monte Carlo simulation and adaptive organ segmentation. Five patients were enrolled in this study after institutional ethical approval and informed consent. Gafchromic XR-RV3 films were used to measure entrance surface dose to reconstruct the nonuniform fluence distribution field as the input data in the Monte Carlo simulation. XR-RV3 films were used to measure entrance surface doses due to their lower energy dependence compared with that of XR-RV2 films. To calculate organ doses, each patient׳s three-dimensional dose distribution was incorporated into CT DICOM images with image segmentation using thresholding and k -means clustering. Organ doses for all patients were estimated. Our dose evaluation system not only evaluated entrance surface doses based on measurements, but also evaluated the 3D dose distribution within patients using simulations. When film measurements were unavailable, the peak skin dose (between 0.68 and 0.82 of a fraction of the cumulative dose) can be calculated from the cumulative dose obtained from TAE dose reports. Successful implementation of this dose evaluation system will aid radiologists and technologists in determining the actual dose distributions within patients undergoing TAE.

Patient entrance surface dose measurements using XR-QA2 Gafchromic films during micturating cystourethrography procedures

The aim of this study was to test the feasibility of using Gafchromic XR-QA2 films in the measurements of patient entrance surface dose (ESD) during the micturating cystourethrogram (MCUG) examination in paediatric patients. Radiochromic films were used to map the entrance dose and to identify the location of peak surface dose (PSD). Direct in vivo measurements of entrance dose were conducted by placing a radiochromic film between the patient and the examination table. The measured ESD values for the commonly performed MCUG fluoroscopic examinations at the authors' institution was in the range of 1.2-7.8 mGy and the PSD in the range of 1.2-8.5 mGy per MCUG procedure for patients with age ranging from 1 to 12 y old. Gafchromic films (XR-QA2) were found to be an efficient and practical dosimetry method that can be easily used to measure clinical patient entrance doses during fluoroscopically guided procedures and potentially in other diagnostic investigations.

Performance Evaluation of Fiber-Optic Dosimeter According to Current-Time Product of Digital Radiography System

A fiber-optic dosimeter was developed using a plastic scintillating fiber, a plastic optical fiber, and a photomultiplier tube for measuring entrance surface dose over the low-energy range which is interested in diagnostic radiology. To evaluate the fabricated fiber-optic dosimeter, the scintillating light signals were measured by changing the current-time product whose values were determined by tube current and irradiation time of a digital radiography system. In conclusion, the trend of scintillating light signals of the fiber-optic dosimeter was similar with that of the entrance surface doses of a commercially available semiconductor dosimeter according to the current-time product.

Measurements of entrance surface dose using a fiber-optic dosimeter in diagnostic radiology

In this study, a fiber-optic dosimeter (FOD) was developed to measure entrance surface dose (ESD) in diagnostic radiology. We measured the scintillating lights in order to obtain ESDs, which changed with the various exposure parameters of a digital radiography (DR) system, such as tube potential, current-time product, focus-surface distance (FSD), and field size, using the fabricated FOD system. From the experimental results, the output light signals of the FOD were similar to the ESDs of the conventional semiconductor dosimeter. In conclusion, we characterized the measured ESDs as functions of exposure parameters by using two different types of dosimeters and demonstrated that the proposed FOD using a plastic scintillating fiber and a plastic optical fiber (POF) makes it possible to measure ESDs in the energy range of diagnostic radiology. From the results of this study, it is anticipated that the FOD will be a useful dosimeter in low-energy photon applications including diagnostic radiology.

Towards proposition of a diagnostic reference level for mammographic examination in the greater Khorasan Province, Iran

Although, over the past few years, the application of mammography has risen up sharply in Iran, very little, if any, has been reported of the extent of patient's dose from this type of imaging. The purpose of this study was to establish local diagnostic reference level (DRL) arising from mammography in the great Khorasan province of Iran. It is generally assumed that the glandular tissue is the most vulnerable type of breast tissue. Therefore, the mean glandular dose (MGD) has been widely accepted as the most appropriate dosimetric quantity to predict the risk of radiation-induced cancer. Literary, DRL for mammography is defined as the 75th percentile of MGD distribution. In Khorasan province, 7 out of 40 centres were randomly selected. In this work, 100 patients were studied. Thermoluminescence dosimeters have been used to measure entrance surface doses (ESDs). Since, it is difficult to directly measure MGD, Monte Carlo model-based conversion factors were utilised to conclude MGD from ESD. The results have revealed that patients dose is varied widely. The measured ESDs ranged from 0.74 to 19.81 mGy for the craniocaudal (CC) view and 1.20 to 25.79 mGy for the mediolateral oblique (MLO) view. The average MGDs per image were 0.88 and 1.11 mGy for CC and MLO views, respectively. Based on the internationally adopted definition, DRL arising from mammography tests for Khorasan is 1.33 mGy. Implementation of a dose reduction programme is suggested because of the large variations observed in patient MGD values. In this study, the DRL value is significantly lower than the corresponding values suggested by other researchers elsewhere.

Development of a scintillating fiber-optic dosimeter for measuring the entrance surface dose in diagnostic radiology

Abstract As a direct method, a scintillating fiber-optic dosimeter (SFOD) was fabricated using an organic scintillator, a plastic optical fiber, and a photomultiplier tube (PMT) to measure entrance surface doses (ESDs) in diagnostic radiology. In this study, we measured the scintillating lights, which are altered by to the exposure parameters, such as the tube potential, current-time product, and focus-surface distance (FSD), with an SFOD placed on the top of an acrylic and aluminum chest phantom to provide a backscatter medium. The scintillating light signals of the SFOD were compared with the ESDs obtained using conventional dosimeters. The ESDs that were measured using the dose-area product (DAP) meter, as an indirect method, and a semiconductor dosimeter, as a direct method, were distinguished according to differences in the measurement position and the method used. In the case of the two direct methods with the SFOD and the semiconductor dosimeter, the output light signals of the SFOD were similar to the ESDs of the semiconductor dosimeter. It is expected that the SFOD will be a useful dosimeter for diagnostic radiology due to its many advantages, including its small size, lightweight, substantial flexibility, remote sensing, real-time monitoring, and immunity to electromagnetic interference (EMI).

Assessment of entrance surface dose and health risk from common radiology examinations in Iran

Medical X-ray exposures are the largest man-made source of population exposure to ionising radiation in many countries. Although information on medical exposure is already incorporated into national legislative documents, in Isfahan there is no data on the assessment of patient's entrance surface dose (ESD) and the health risk from conventional radiography in daily clinical practice. The aim of this study was to investigate ESDs and the consequent health risk for the patients undergoing routine X-ray procedures in hospitals under the control of Isfahan University of Medical Sciences, Iran, in year 2011. The values of ESDs were measured for common radiographical examinations with the highest absorbed dose to the patient in seven hospitals (Alzahra, Ashrafi-Khomeini-shahr, Feyz, Isabne-Maryam, Kashani, Nour-Aliasghar and Seyed-Al Shohada) and six stationary X-ray machines (General Electric, USA; Phillips, The Netherlands; Siemens, Germany; Shimadzu, Japan; Toshiba, Japan and Varian, USA). The results of the ESD measurements as well as the calculated effective dose values between different X-ray examinations showed values significantly greater than those recorded in some other countries especially for the high tube potential technique (such as the skull) by factors of 2.5-5.0. Based on the fatality risk of 5 % per sievert, it was estimated that, for chest and skull examinations approximately two (40.18 person-Sv×5 % per sievert) and one (2.53 person-Sv×5 % per sievert) cases of health risk, respectively, may in the future be attributable to diagnostic X rays done in year 2011 in Isfahan. Efforts should be taken to further lower patient doses while securing image quality. The need to provide relevant education and training to staff in the radiology sections is of utmost importance.

파노라마촬영 시 조직등가물질을 이용한 갑상선보호대의 갑상선피폭선량 감소효과

파노라마방사선촬영 시 방사선감수성이 높은 갑상선의 방사선 피폭을 최소화하면서 진단에 유용한 영상을 얻기 위하여 조직등가물질인 보루스(bolus)를 차폐체로 사용하여 피폭선량 감소효과를 측정하였다. 실험은 2011. 6. 1일부터 6. 30일까지 두경부팬톰을 이용하여 갑상선 위치의 표면입사선량과 심부흡수선량을 측정하였다. 그 결과 갑상선 부위 입사표면선량은 평균 43.84 <TEX>${\mu}Gy$</TEX>이었고, 10 mm 두께의 보루스로 만든 갑상선보호대에서는 평균 28.39 <TEX>${\mu}Gy$</TEX>로 15.45 <TEX>${\mu}Gy$</TEX>(35.24%)가 감소되었다. 20 mm 갑상선보호대를 착용했을 경우에는 평균 25.38 <TEX>${\mu}Gy$</TEX>로 미착용 시 평균 43.84 <TEX>${\mu}Gy$</TEX>보다 18.46 <TEX>${\mu}Gy$</TEX>(42.10%)가 감소되었다. 그리고 표면에서 20 mm 깊이에서는 10 mm 두께의 갑상선보호대는 선량 감소효과가 없었고, 20 mm 갑상선보호대를 착용했을 경우에는 0.06 mSv (20%)의 선량감소효과가 있었다. Exposure-dose reducing effect was measured by using bolus, a tissue-equivalent material as a shield to obtain useful diagnostic images while minimizing the radiation exposure of thyroid which is highly sensitive to radiation during panoramic radiography. The experiment was performed within the period of 1 June 2001 through 30 June 2011 by measuring entrance surface dose and deep dose at the thyroid-corresponding site of a head and neck phantom. As a result, the entrance surface dose in the thyroid for using no shield was 43.84 <TEX>${\mu}Gy$</TEX> on the average, and the thyroid shield of bolus 10 mm in thickness reduced the dose by 15.45 <TEX>${\mu}Gy$</TEX>(35.24%) to 28.39 <TEX>${\mu}Gy$</TEX> on the average. The use of a 20 mm thyroid shield resulted in the dose of 25.38 <TEX>${\mu}Gy$</TEX> on the average, a 18.46 <TEX>${\mu}Gy$</TEX>(42.10%) drop from 43.84 <TEX>${\mu}Gy$</TEX> for using no shield. On the site 20 mm below the surface, a thyroid shield 10 mm in thickness had no dose-reducing effect, while a 20 mm thyroid shield reduced the dose by 0.06 mSv(20%).

TLD measurements and Monte Carlo simulations for glandular dose and scatter fraction assessment in mammography: A comparative study

The main purpose of this study was to validate and compare Mean Glandular Dose (MGD) values obtained using Monte Carlo simulations with experimental values obtained from Entrance Surface Dose (ESD) and depth dose measurements performed in a Hospital mammography unit. ESD and depth dose were measured using ThermoLuminescent Dosimeters (TLDs), and a tissue equivalent mammography phantom recommended by the American College of Radiology (ACR). Measurements and Monte Carlo simulations were also compared with the MGD calculated using the Automatic Exposure Control (AEC) system of the mammographic unit. In the simulations the Doppler energy broadening effect was also taken into account. The simulated ESD are about 5%–10% higher than the measured ESD values. The deviation between the measured and simulated MGD values in the phantom is of about 15%. The MGD evaluated using the AEC system is smaller both with respect to the Monte Carlo simulation and experimental result by a factor of about 15% and 25% respectively. Moreover the BackScatter Factor (BSF) estimated by Monte Carlo simulations was used for the MGD calculation according to the Wu’s method. Finally the inclusion of the energy broadening effect on MGD calculation produces negligible variations on the simulated results. ► Depth dose measurements in breast phantom with TLD and an X-ray mammography system. ► Entrance surface dose measurements with TLD. ► Monte Carlo assessment of mean glandular dose and comparison with experimental data. ► Dose variation inside the breast from 12% to 230% of the mean glandular dose. ► Monte Carlo estimation of backscatter factor and dose scatter fraction.

Measurement of Patient Skin Dose in Vertebroplasty Using Radiochromic Dosimetry Film

We studied the radiation doses to which patients were exposed during 17 vertebroplasty operations. The radiation doses during vertebroplasty were measured to determine maximum skin dose (MSD), a measure of the likelihood of radiation-induced skin effects. Vertebroplasty is performed with use of fluoroscopic guidance for needle placement and to monitor bone cement injection. This procedure requires relatively long duration of fluoroscopic guidance, and so, it demands dose measurements for patients. From May 2006 to April 2008, 16 patients (7 men and 9 women; mean age 70.19 years, range 30-87 years) underwent a total of 17 vertebroplasty procedures. Total dose-area product (DAP), duration of fluoroscopy, and the parameters for anteroposterior (AP) and lateral (LAT) fluoroscopic and fluorography projections were recorded for each procedure. Gafchromic films were placed on the patients' skin to measure entrance surface dose and to evaluate the MSD. The MSD and DAP were higher in the LAT plane than in the AP plane. These results were expected because the fluoroscopy time was longer, and the number of fluorography runs was higher in the LAT plane than in the AP plane.The MSD values for the AP plane ranged between 0.184 Gy and 1.834 Gy, whereas those for the LAT plane ranged between 0.417 Gy and 2.362 Gy. The frequency distribution of values for both planes showed that most MSD values were in the range of 0 to 0.5 Gy and 0.5 to 1 Gy for the AP plane and 0.5 to 1 Gy and 1 to 1.5 Gy for the LAT plane. There was great variability in the MSD at each value for the parameters among individual instances. When evaluating the MSD to a patient, a distinction should be made between AP and LAT projections, because an overall mean MSD value underestimates the contribution of x-ray absorption on the LAT plane. The use of radiochromic films to estimate radiation damage to the skin has been shown to have the limitation of relying on DAP values only.

Mean glandular doses for women undergoing mammographic breast screening in Oyo state, Nigeria

In this work, thermoluminescent dosimeters have been used to measure entrance surface doses (ESDs) of patients undergoing mammographic screening at the University College Hospital, Ibadan, Oyo state. The mean glandular doses (MGDs) were also calculated using the measured ESDs. The results showed that the ESDs ranged from 0.26 mGy to 21.26 mGy for the mediolateral oblique (MLO) views and 0.08 mGy to 5.36 mGy for the craniocaudal (CC) views. The calculated MGD ranged from 0.07 mGy to 3.57 mGy for the MLO views and 0.02 mGy to 0.98 mGy for the CC views. The possible reasons for the large variations in the individual ESD values and MGD values for both views are discussed using patients' data, equipment specific data and the technical parameters used for the examinations. Comparison showed that the mean ESD values and MGD values reported in this work are below published values. The mean of the calculated MGD values is also found to be lower than the recommended guidance level of 3.0 mGy when using grid. 92.5% of the patients had MGD values that are less than 2.5 mGy, hence a national reference MGD value of 2.5 mGy is proposed for Nigeria. Implementation of a dose reduction program in mammographic screening is also suggested because of the observed large variations in patients MGD values.