Dose-area Product Measurements Research Articles

Gel Rolls Increase Percutaneous Nephrolithotomy Radiation Exposure.

Introduction: Despite increasing interest in reducing radiation doses during endoscopic stone surgery, there is conflicting evidence as to whether percutaneous nephrolithotomy (PCNL) positioning (prone or supine) impacts radiation. We observed clinically that a patient placed prone on gel rolls had higher than expected radiation with intraoperative CT imaging and that gel rolls were visible on the coaxial imaging. We hypothesized that gel rolls directly increase radiation doses. Methods: Anthropomorphic experiments to simulate PCNL positions were performed using a robotic multiplanar fluoroscopy system (Artis Zeego Care+Clear, Siemens) and a 5-second coaxial imaging protocol (5s BODY). A fluoroscopy phantom was placed in various positions, including prone on a gel roll; prone on blankets of equal thickness; prone and supine directly on the table; and modified supine (MS) positions using a thin gel roll or rolled blanket. Impacts of C-arm direction and use of a 1 L saline bag were also evaluated. Measured dose area product (DAP) was compared for the groups. Results: Measured DAP was found to increase by 146 μGy*m2 (287%) when prone on gel rolls compared with only 62.29 (23%) when placed on blankets of equal thickness, although the model likely both overstates the relative impact and understates the absolute impact that would be seen clinically. Measured DAP between experimental groups also varied considerably despite fluoroscopy time being held constant. Conclusions: Our experiments support our hypothesis that gel rolls directly increase radiation dose, which has not been previously reported, using an anthropomorphic model. Surgeons should consider radiolucent materials for positioning to limit radiation exposure to patients and the surgical team.

Development of Electrometer for Dose Area Product (DAP) Measurement to Monitor Patient Dose in Radiography Examinations

This study aimed to develop an electrometer for dose area product (DAP) measurement to monitor patient doses on X-ray radiography examinations. The electrometer was developed based on the Atmega8535 microcontroller as the processing unit. This electrometer was operated at 12 volts of direct current (DC) and controlled by buttons for navigation. The system (i.e. in-house electrometer and DAP meter) was carefully designed so that it can easily perform calibration and dose measurements. The system was evaluated at variations of tube voltage, tube current, and exposure time. The developed system results in high accuracy and precision as indicated by low percent error (PE) and relative standard deviation (RSD) compared to standard system. The highest PE and RSD are 1.69% and 1.42% for tube voltage variation, 3.85% and 3.58% for tube current variations, and 12.10% and 0.92% for exposure time variations. In conclusion, the developed system is feasible to be used as a patient dose measurement tool to meet the needs of radiation protection to achieve the principle of “as low as reasonably achievable (ALARA).

Real-time 3D reconstruction of guidewires and stents using two update X-ray projections in a rotating imaging setup.

Vascular diseases are often treated minimally invasively. The interventional material (stents, guidewires, etc.) used during such percutaneous interventions are visualized by some form of image guidance. Today, this image guidance is usually provided by 2D X-ray fluoroscopy, that is, a live 2D image. 3D X-ray fluoroscopy, that is, a live 3D image, could accelerate existing and enable new interventions. However, existing algorithms for the 3D reconstruction of interventional material require either too many X-ray projections and therefore dose, or are only capable of reconstructing single, curvilinearstructures. Using only two new X-ray projections per 3D reconstruction, we aim to reconstruct more complex arrangements of interventional material than was previously possible. This is achieved by improving a previously presented deep learning-based reconstruction pipeline, which assumes that the X-ray images are acquired by a continuously rotating biplane system, in two ways: (a) separation of the reconstruction of different object types, (b) motion compensation using spatial transformernetworks. Our pipeline achieves submillimeter accuracy on measured data of a stent and two guidewires inside an anthropomorphic phantom with respiratory motion. In an ablation study, we find that the aforementioned algorithmic changes improve our two figuresof merit by 75% (1.76mm → 0.44mm) and 59% (1.15mm → 0.47mm) respectively. A comparison of our measured dose area product (DAP) rate to DAP rates of 2D fluoroscopy indicates a roughly similar doseburden. This dose efficiency combined with the ability to reconstruct complex arrangements of interventional material makes the presented algorithm a promising candidate to enable 3Dfluoroscopy.

Intraoral and dental panoramic imaging: A diagnostic reference level study comparing radiation dose using two dosimeters in Saudi Arabia

The purpose of this study was to determine local diagnostic reference levels (DRLs) for patients undergoing intraoral and panoramic dental examinations at the intraoral radiology units of the public hospitals in Najran, Saudi Arabia. DRLs were determined based on measurements of dose area product (DAP) at intraoral and dental panoramic radiology units. This study has covered over 47% of the public hospitals in Najran with the intention to establish the local DRLs for all the possible intraoral and panoramic X-ray examinations for children and adults. For intraoral, the values for the estimated DAP ranged from 6 to 70 mGy.cm2 (average: 27.6, 29.8, 39.9 and 39.6 mGy.cm2 for incisive, both premolar and canine, molar upper and lower jaw, respectively). For panoramic, the mean value of DAP is 61.5 and 89.8 mGy.cm2 for paediatric and adult patients, respectively. DRLs were established at the 3rd quartile for incisive, both premolar and canine, molar upper and lower jaw protocols are 29.2, 37.1, 50.2 and 50.1 mGy.cm2, respectively. Furthermore, DRLs for panoramic radiography for paediatric and adult patients are 72.7 and 92.3 mGy.cm2, respectively. The proposed DRLs were comparable to those previously reported in other countries, such as UK and India.

Determination of a cone-beam CT low-dose protocol for root fracture diagnosis in non-endodontically treated anterior maxillary teeth.

The aim of this study was to determine a "low-dose protocol" which provides acceptable diagnostic accuracy for detection of root fractures in unrestored anterior maxillary teeth, using an ex vivo model. 48 maxillary anterior teeth, half with horizontal or oblique root fractures, were imaged using CBCT in an anthropomorphic model. Nine X-ray exposure combinations were used, including the manufacturer's standard ("reference") exposure and high-resolution settings ("HiRes"), by varying kV, exposure time, and rotation angle. Measurements of Dose Area Product (DAP) were recorded. Five dental radiologists assessed the scans for root fractures and judged image quality. Parameters of diagnostic accuracy were calculated, including area under the Receiver Operating Characteristic curve (Az). Objective measures of image quality were made at the same exposure combinations using an image quality phantom. Although there was a significant linear relationship between DAP and mean Az, only the lowest DAP exposure combination had a mean Az significantly different to the reference exposure. There was no significant effect on other diagnostic accuracy parameters when using HiRes compared with the reference exposure. There was a significant positive relationship between DAP and contrast resolution. HiRes did not significantly improve contrast resolution and made a small improvement to spatial resolution. Scope existed for radiation dose reduction compared with the manufacturer's guidance. There was no improvement in diagnostic accuracy using HiRes settings. A cautious recommendation for this CBCT machine is that it is possible to achieve a dose reduction of about 20% compared with the reference exposure parameters.

Estimation of the radiation dose for dental spectral cone-beam CT.

The purpose of this study was to estimate the radiation dose for a dental spectral cone-beam CT (SCBCT) unit at different scanning parameters. Radiation dose measurements were performed for a commercially available dental SCBCT. Scans were obtained at different exposure times and fields of view (FOV), both for non-spectral (25×18 cm, 14×18 cm, 14×12 cm, 9×9 cm, 6×6 cm) and spectral modes (14×18 cm, 14×12 cm, 9×9 cm, 6×6 cm) with the tube voltage alternating between 80 and 110 kV for spectral mode, and fixed at 110 kV for non-spectral mode. An ion chamber was used for air kerma and dose area product (DAP) measurements. The effective dose was estimated based on the mAs using previously published logarithmic curves for CBCT units with a similar X-ray spectrum. The adult effective dose, in non-spectral mode, was 44-269 µSv for small FOVs, 131-336 µSv for the medium FOV, and 163-476 µSv for the large FOV. In spectral mode, the estimated adult effective doses were 96-206 µSv for small, 299 µSv for medium and 372 µSv for large FOV protocols. Paediatric effective doses were estimated to be 75% higher than corresponding adult doses. SCBCT showed comparable doses with other CBCT devices, but DAP values were generally above currently published DRLs. Spectral imaging might allow for artefact reduction at comparable dose levels, which should be assessed in further image quality studies at both a technical and diagnostic levels.

Radiography student comparison performing lumbar and thoracic spine imaging

Introduction: General radiography is a common imaging technique and X-ray examinations of the thoracic and lumbar spine are among the most frequent procedures undertaken. The aim of this research was to investigate the success rate, dose-area product (DAP), and effective dose values of 1st and 2nd cycle radiographer students performing X-ray imaging of the thoracic and lumbar spine using a phantom. Methods: The students were divided into four groups according to the year of study (1st, 2nd, and 3rd years of 1st cycle degree, and all 2nd cycle degree students). They were asked to perform imaging of thoracic and lumbar spine on the phantom in both anteroposterior and lateral projections where IQ and DAP measurements were collated. The study was blind, so they did not know about the purpose of the study. Results: First, we have inspected the acceptability rate of the images performed. The highest success rate of performing an optimal image was discovered with the 2nd cycle degree students where the 1st year students had the most difficulties there. In the second part, DAP and effective dose values were compared, only for the acceptable images in which case the 1st and 2nd years, students of the 1st cycle degree were most successful. Conclusion: Based on that, we can conclude, that the 2nd cycle degree students had the lowest rejection rate regarding the optimal image quality, which was the price of using a larger primary X-ray field which leads to higher dose values.

Association between distance from the radiation source and radiation exposure: A phantom‐based study

The study evaluated the association between distance from radiation source and radiation exposure. Radiation exposure during medical procedures is associated with increased risk of cancer and other adverse effects. An American National Standards Institute phantom was used to study the relationship between measured entrance surface exposure (MESE) and distance from the X-ray source in postero-anterior, left anterior oblique, and right anterior oblique projections. Three distance settings for table height were evaluated with "low" defined as 52 cm, "mid" 66 cm, and "high" 80 cm from the focal point of the X-ray source. Air-kerma and dose-area product measurements were recorded. Operator exposure with each of these conditions was measured, in a short operator (150 cm) as well as in a tall operator (190 cm). Aggregate results for the three projections were as follows. MESE (μGy/frame) significantly decreased as table-height increases (median, interquartile range, p-value) (low table-height 192.5 [122.4-201.2], mid table-height 105.8 [82.7-115.8], and high table-height 71.7 [58.4-75], p < .0005). The operator exposure (μGy/frame), significantly increased as the table-height increased (low table-height 0.0943 [0.0598-0.1157], medium table-height 0.1128 [0.0919-0.1397], and high table-height 0.158 [0.1339-0.2165], p < .0005). A shorter operator received higher radiation exposure compared to a taller operator (short operator 0.1405 [0.1155-0.1758] and tall operator 0.0995 [0.0798-0.1212], p < .0005). Increasing table-height is associated with a significant decrease in MESE. Operator radiation exposure increases with increasing table-height and shorter operators receive greater radiation exposure compared to taller operators.

Results of the clinical evaluation of the low-dose protocols of the digital linear tomography of the chest

High levels of tuberculosis morbidity in the Russian Federation lead to the extensive use of X-ray diagnostics for the tuberculosis screening and assessment of the effectiveness of treatment. Digital radiography and computed tomography are traditionally used for the diagnostics of tuberculosis. These methods are associated with significant drawbacks: low specificity for radiography, high costs per examination, significant patient doses, and limited availability for computed tomography. As an additional method for the assessment of the effectiveness of the tuberculosis treatment it is possible to use linear tomography performed on the digital X-ray units. The aim of the current study was to evaluate the possibility of utilization of the digital linear tomography for the control of the effectiveness of tuberculosis treatment in a dedicated antitubercular medical facility. The study was divided in two stages. The first stage was aimed at the assessment of the diagnostic image quality of the digital linear tomograms obtained using the previously developed low-dose imaging protocols. Image quality assessment was performed using an anthropomorphic chest phantom and dedicated imitators of the lung lesions. Image quality was assessed by the experts (radiologists) based on the developed image quality criteria. Results of the first stage of the study indicate that all low-dose protocols allow obtaining images with at least acceptable image quality. Hence it was possible to propose low-dose protocols for clinical evaluations. The second stage of the study was performed as a prospective cohort survey aimed at the evaluation of the structure of X-ray examinations, patient doses and clinical image quality of the digital linear tomograms in antitubercular early treatment center. The cohort survey included two patient samples, uniform by age and gender composition, anthropometric characteristics and structure of diagnosis. One of the samples was imaged using standard (vendor) digital linear protocols, other – using the proposed low-dose protocols. Dose data collection (measurement of dose-area product and subsequent calculation of effective dose) and expert image quality assessment was performed for each patient. The results of the second stage of the study indicate that the use of the low-dose protocols allow reducing the patient effective doses per examination up to a factor of 6–8 (0.56 – 5.9 mSv for standard protocols; 0.2 – 1.15 mSv for low-dose protocols) due to the reduction in tube current-time product (126 mean mAs and 11 mean mAs, respectively). The dose reduction is accompanied by the reduction in the image quality of the linear tomograms (from “excellent” or “good” for standard protocols to “acceptable” for low-dose protocols). However, that dose not hinder the conclusion decision and identification of pathologies. Results of the study indicate that digital linear tomography can be used for the evaluation of the dynamics of the pathological process in the lungs with the previously defined localization of the pathology. The presented low-dose protocols were implemented into radiological practice of the antitubercular early treatment center. Currently, the proposed low-dose protocols are under evaluation for the large-scale study on the base of general practice hospitals

Radiation dose reduction using novel size 1 and size 0 rectangular collimators in pediatric dental imaging.

Commercial intraoral rectangular collimators are available for collimating to size 2 image receptor. The benefits of reducing the x-ray beam to match the area of the image detector in adult intraoral radiography are endorsed internationally. However, in pediatric dentistry the image receptor can be further decreased to size 1 and 0. For this study size 1 and 0 rectangular collimators were fabricated using 1.65-mm lead sheets (Rotometals). The custom-fabricated collimators were fixed to the plastic body of a Rinn (Dentsply) Universal Collimator attachment. Aperture sizes were extrapolated based on the active imaging area of size 1 and 0 digital image receptors. A dose area product (DAP) measuring device was used to determine the change in radiation absorbed dose as a function of the imaging field of view. DAP measurements were evaluated in the 31.7 cm2 conventional round collimation, Rinn 12.0 cm2 Universal rectangular collimator, and in the manufactured size 1 (8.25 cm2) and size 0 (5.72 cm2) rectangular collimators. The size 1 collimator had a 32% DAP reduction from the size 2, and a 53% reduction for the size 0. Size 1 and size 0 rectangular collimators can be independently manufactured and utilized in pediatric dentistry. This study suggests that a considerable radiation dose reduction is possible in pediatric intraoral imaging when using the size 1 and 0 matched collimation. Since the pediatric population is vulnerable to radiation exposure, any measurable reduction has a potential for long-term health benefits and is therefore clinically significant.

Technical Note: Comprehensive evaluation and implementation of two independent methods for beam monitor calibration for proton scanning beam.

To clinically implement and comprehensively evaluate two independent methods for beam monitor calibration of scanning proton beam. Seven proton energies that represent the lowest to highest energy proton beams were selected. Single energy layer circular fields of diameter 15cm with 2.5mm spot spacing and 10 times of repainting (FS15cm ) were designed for all energies. The effective measurement points of Bragg peak chamber (BPC), advanced Markus chamber (AMC) and farmer chamber (FC) were all aligned to 2cm depth in water using SSD setup. The BPC and AMC were cross-calibrated with farmer chamber (FC) using the field FS15cm . In order to evaluate BPC's lateral response uniformity, a collimated narrow proton beam (5.8mm diameter) was delivered to the active area and edge of the BPC. The dose area product (DAP) was measured using two methods by two BPCs, one AMC and one FC. For method 1, a single spot proton beam was delivered to the geometric center of the BPC. For method 2, the fields FS15cm were delivered to FC and AMC, respectively. Accumulated charges by these chambers were converted to DAPs, and the quantitative difference of DAPs between both methods was calculated. The causes of the uncertainties were discussed, and the advantages of the two methods were compared. The two BPCs showed different lateral response uniformity. BPC1 has a uniform response from the center up to a radius of 3.5cm. BPC2 has a uniform response only to 2cm and the response dropped 1% to 2% at 3.5cm from center. BPC2 also has significant over-response compared to BPC1. A 2.2% systematic error would be transferred to DAP if the over-response from BPC2 was not considered. The DAPs measured by method 1 with two BPCs and by method 2 with FC and AMC were consistent to 0.5%. The major uncertainty component of method 1 is from the cross-calibration of the BPC. The two independent methods for DAP were shown to give consistent results, given the sources of uncertainties were carefully addressed in the measurements. Direct measurement of DAP with BPC is very efficient, but it may be subject to more than 2% systematic error if the BPC lateral response is not carefully evaluated.

Simple preoperative radiation safety interventions significantly lower radiation doses during central venous line placement in children

PurposeThe purpose of this study was to reduce radiation exposure during pediatric central venous line (CVL) placement by implementing a radiation safety process including a radiation safety briefing and a job-instruction model with a preradiation time-out. MethodsWe reviewed records of all patients under 21 who underwent CVL placement in the operating room covering 22 months before the intervention through 10 months after 2013–2016. The intervention consisted of a radiation safety briefing by the surgeon to the intraoperative staff before each case and a radiation safety time-out. We measured and analyzed the dose area product (DAP), total radiation time pre- and postintervention, and the use of postprocedural chest radiograph. Results100 patients with valid DAP measurements were identified for analysis (59 preintervention, 41 postintervention). Following implementation of the radiation safety process, there was a 79% decrease in median DAP (61.4 vs 13.1 rad*cm2, P < 0.001) and a 73% decrease in the median radiation time (28 vs 7.6 s, P < 0.001). Additionally, there was a significant reduction in use of confirmatory CXR (95% vs 15%, P < 0.01). ConclusionA preoperative radiation safety briefing and a radiation safety time-out supported by a job-instruction model were effective in significantly lowering the absorbed doses of radiation in children undergoing CVL insertion. Type of studyCase–control study. Level of evidenceLevel III.

The seamless integration of three-dimensional rotational angiography images into electroanatomical mapping systems to guide catheter ablation of atrial fibrillation.

It is important to visually confirm radiofrequency ablation lesions during atrial fibrillation (AF) ablation for procedural efficiency, which requires the integration of a three-dimensional (3D) left atrial image reconstructed from computed tomography (CT) or a magnetic resonance imaging. However, an EP Navigator allows seamless integration of 3D anatomy obtained through 3D rotational angiography (3D-ATG) into an electroanatomical mapping system. We hypothesized that 3D-ATG can be used during AF ablation while significantly reducing the effective dose (ED) and without compromising image morphology compared to a 3D-CT image. Organ dose was measured at 37 points with a radiophotoluminescence glass dosimeter inserted in an anthropomorphic Rando Phantom. The ED was calculated by multiplying the organ dose by the tissue weighting factor. The dose-area product (DAP)-to-ED conversion factor was calculated by measuring the DAP during radiation exposure. The ED for the CT examination was estimated from the dose-length product with a conversion factor of 0.014. ED was calculated from DAP measurements in 114 patients undergoing AF ablation using 3D-ATG. The DAP-to-ED conversion factor for 3D-ATG was 2.4 × 10-4mSv/mGycm2 in our hospital. The mean DAP for all patients was 7777 ± 1488mGycm2 for the 3D-ATG of the left atrium. The corresponding ED for 3D-ATG was 1.9 ± 0.4mSv. The ED for CT examinations was 13.6 ± 4.2mSv (P < 0.001). 3D-ATG can be used during AF ablation while significantly reducing the ED and without compromising image morphology.

Monitoring neurointerventional radiation doses using dose-tracking software: implications for the establishment of local diagnostic reference levels.

There is potential for high radiation exposure during neurointerventional procedures. Increasing regulatory requirements mandate dose monitoring of patients and staff, and justification of high levels of radiation exposure. This paper demonstrates the potential to use radiation dose-tracking software to establish local diagnostic reference levels. Consecutive neurointerventional procedures, performed in a single institution within a one-year period, were retrospectively studied. Dose area product (DAP) data were collected using dose-tracking software and clinical data obtained from a prospectively generated patient treatment database. Two hundred and sixty-four procedures met the selection criteria. Median DAP was 100 Gy.cm2 for aneurysm coiling procedures, 259 Gy.cm2 for arteriovenous malformation (AVM) embolisation procedures, 87 Gy.cm2 for stroke thrombolysis/thrombectomy, and 74 Gy.cm2 for four-vessel angiography. One hundred and nine aneurysm coiling procedures were further studied. Six significant variables were assessed using stepwise regression analysis to determine effect on DAP. Aneurysm location (anterior vs posterior circulation) had the single biggest effect (p = 0.004). This paper confirms variable radiation exposures during neurointerventional procedures. The 75th percentile (used to define diagnostic reference levels) of DAP measurements represents a reasonable guidance metric for monitoring purposes. Results indicate that aneurysm location has the greatest impact on dose during coiling procedures and that anterior and posterior circulation coiling procedures should have separate diagnostic reference levels. • Dose-tracking software is useful for monitoring patient radiation dose during neurointerventional procedures • This paper provides a template for methodology applicable to any interventional suite • Local diagnostic reference levels were defined by using the 75th percentile of DAP as per International Commission on Radiological Protection recommendations • Aneurysm location is the biggest determinant of radiation dose during coiling procedures. • Anterior and posterior circulation coiling procedures should have separate diagnostic reference levels.

Effective-dose estimation in interventional radiological procedures.

Interventional radiology is based on minimally invasive procedures that allow diagnosis and percutaneous treatment of diseases in almost all organ systems. Such procedures have many benefits, but they also contribute significantly to collective radiation dose. In this regard, effective dose (E) is a convenient quantity to estimate patients' stochastic radiation risk. However, E cannot be accurately evaluated immediately. In the present study, we aimed to estimate the E value in 15 selected interventional procedures. The estimation was based on dose area product (DAP) measurements and used case-specific conversion coefficients. The E values ranged from 3.3 to 69.9mSv, depending on the kind of procedure. This wide range was mainly due to the broad variation in DAP values, which in turn depend on the details of how the procedures are performed. This suggests that to ensure valid comparative studies and universal reference levels, all interventional procedures should be well classified.

Patient radiation dose and fluoroscopy time during ERCP: a single-center, retrospective study of influencing factors

Objectives: Recently, both the number and the complexity with associated increased technical difficulty of therapeutic ERCP procedures have significantly increased resulting in longer procedural and fluoroscopy times. During ERCP, the patient is exposed to ionizing radiation and the consequent radiation dose depends on multiple factors. The aim of this study was to identify factors affecting fluoroscopy time and radiation dose in patients undergoing ERCP.Materials and methods: Data related to patient demographics, procedural characteristics and radiation exposure in ERCP procedures (n = 638) performed between August 2013 and August 2015 was retrospectively reviewed and analyzed. Statistically significant factors identified by univariate analyses were included in multivariate analysis with fluoroscopy time (FT) and dose area product (DAP) as dependent variables. Effective dose (ED) was estimated from DAP measurements using conversion coefficient.Results: The factors independently associated with increased DAP during ERCP were age, gender, radiographer, complexity level of ERCP, cannulation difficulty grade, bile duct injury and biliary stent placement. In multivariate analysis the endoscopist, the complexity level of ERCP, cannulation difficulty grade, pancreatic duct leakage, bile duct dilatation and brushing were identified as predictors for a longer FT. The mean DAP, FT, number of acquired images and ED for all ERCP procedures were 2.33 Gy·cm2, 1.84 min, 3 and 0.61 mSv, respectively.Conclusions: Multiple factors had an effect on DAP and FT in ERCP. The awareness of these factors may help to predict possible prolonged procedures causing a higher radiation dose to the patient and thus facilitate the use of appropriate precautions.

Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry

Large area ionization chambers (LAICs) can be used to measure output factors of narrow beams. Dose area product measurements are proposed as an alternative to central-axis point dose measurements. Using such detectors requires detailed information on the uniformity of the response along the sensitive area. Eight LAICs were investigated in this study: four of type PTW-34070 (LAICThick) and four of type PTW-34080 (LAICThin). Measurements were performed in an x-ray unit using peak voltages of 100–200 kVp and a collimated beam of 3.1 mm (FWHM). The LAICs were moved with a step size of 5 mm to measure the chamber response at lateral positions. To account for beam positions where only a fraction of the beam impinged within the sensitive area of the LAICs, a corrected response was calculated which was the basis to calculate the relative response. The impact of a heterogeneous LAIC response, based on the obtained response maps was henceforth investigated for proton pencil beams and small field photon beams. A pronounced heterogeneity of the responses was observed in the investigated LAICs. The response of LAICThick generally decreased with increasing radius, resulting in a response correction of up to 5%. This correction was more pronounced and more diverse (up to 10%) for LAICThin. Considering a proton pencil beam the systematic offset for reference dosimetry was 2.4–4.1% for LAICThick and −9.5 to 9.4% for LAICThin. For relative dosimetry (e.g. integral depth-dose curves) systematic response variation by 0.8–1.9% were found. For a decreasing photon field size the systematic offset for absolute dose measurements showed a 2.5–4.5% overestimation of the response for 6 × 6 mm2 field sizes for LAICThick. For LAICThin the response varied even over a range of 20%. This study highlights the need for chamber-dependent response maps when using LAICs for absolute and relative dosimetry with proton pencil beams or small photon beams.

Dose-Decreasing Effect of the First Reversed Laser Beam Collimator for C-Arm Type Angiographic Equipment.

This is a study on the dose-decreasing effect of the first reversed laser beam collimator (RLBC) for C-arm type angiographic equipment. A laser beam was located at the center of each plane at an oblique angle to the angiographic equipment detector. A field of view, which could be seen with the naked eye, was made by focusing the laser beam in the direction of the X-ray source. The height of the table was fixed at 75 cm and the iron balls were located within 2 mm of the top, bottom, left, and right edges of the output image. The time needed for location fixing, fluoroscopy, and measurement of dose area product (DAP) were compared by having 30 radiologists perform location fixing by looking at the fluoroscopic image while performing location fixing (no radiation) and while the RLBC was turned on. In the next test, the time needed for location fixing, fluoroscopy, and DAP were compared when varying the location of the iron balls from 2 to 10 mm from the edges of the output image. The results showed that the time needed for location fixing, the time needed for fluoroscopy, and DAP decreased, both in the first test and the second test. This study confirmed that the use of a RLBC for C-arm type angiographic equipment decreases both the time needed to perform the procedure and the radiation dose received. It is expected that continuous advancement of RLBC technology will contribute greatly to decreasing the dose of radiation needed and improving convenience during angiography.

Estimation of effective dose for children in interventional cardiology

This study is devoted to the estimation of effective dose for children undergoing interventional cardiology examinations. The conversion coefficients (CC) from directly measured dose area product (DAP) value to effective dose (ED) were calculated within the approved effective dose assessment methodology (Guidelines 2.6.1. 2944-11). The CC, Ed K , [mSv / (Gy • cm 2 )] for newborn infants and children of 1, 5, 10 and 15 years old (main(range)) were calculated as 2.5 (1.8-3.2); 1.1 (0.8-1.3); 0.6 (0.4-0.7); 0.4 (0.3-0.5); and 0,22 (0,18-0,30) respectively. A special Finnish computer program PCXMC 2.0 was used for calculating the dose CC. The series of calculations were made for different values of the physical and geometrical parameters based on their real-existing range of values. The value of CC from DAP to ED were calculated for all pediatric age groups. This work included 153 pediatric interventional studies carried out in two hospitals of the city of St. Petersburg for the period of one year from the summer of 2015. The dose CC dependency from the patient’s age and parameters of the examinations were under the study. The dependence from the beam quality (filtration and tube voltage) and age of the patient were found. The younger is the patient, stronger is the filtration and higher is the voltage, the higher is the CC value. The CC in the younger (newborn) and older (15 years) age groups are different by the factor of 10. It was shown that the changes of the geometric parameters (in the scope of their real existing range) have small effect on the value of the effective dose, not exceed 30-50% allowable for radiation protection purpose. The real values of effective doses of children undergoing cardiac interventions were estimated. In severe cases, the values of ED can reach several tens of mSv.

Abstract 12818: First Experience of Three-dimensional Rotational Angiography Image Integration With Electroanatomical Mapping System to Guide Catheter Ablation of Atrial Fibrillation

Introduction: Rotational angiography of the left atrium with three-dimensional (3D) reconstruction (3D-ATG) represents a modern method enabling to create computed tomography (CT) like 3D images on a standard X-ray machine. Recently, electroanatomical mapping system can import 3D images reconstructed by 3D-ATG. Hypothesis: We assessed the hypothesis that atrial fibrillation (AF) ablation using 3D-ATG would be feasible with a significant reduction in effective dose without compromising image quality compared with 3D CT image. Methods: 3D-ATG was performed by using the Philips Allura Xper FD 10 system operated at a low-frame pulsed fluoroscopy (7.5 frames per second). Effective radiation dose was calculated from dose area product (DAP) measurements in 103 patients (mean age of 65 years, 71% men) undergoing AF ablation guided by 3D-ATG. Organ dose was measured at 37 points with a radiophotoluminescence glass dosimeter inserted in the position of an anthropomorphic Rando Phantom. Effective dose was calculated by multiplying organ dose by tissue weighting factor. The DAP to effective dose conversion factor was calculated by measurement of DAP at the same time of radiation exposure. Effective dose at CT examination was estimated from dose length product and conversion factor of 0.014. Left atrial dimensions and vertical ostial pulmonary vein (PV) diameters for each imaging method were compared. Results: The DAP to effective dose conversion factor of 3D-ATG was 2.4x10 -4 mSv/mGy•cm 2 by using the Philips Allura Xper FD 10 system in our hospital. Mean DAP for all patients was 7777±1488mGy•cm 2 for rotational angiography of the left atrium. The corresponding effective radiation doses for 3D-ATG were 1.9±0.4mSv. The effective doses for CT examinations were 13.6±4.2mSv (p&lt;0.001). The correlations of left atrial dimension were r=0.73 for sagittal plane, 0.76 for coronal, and 0.80 for vertical (p&lt;0.005). The correlation coefficient between 3D-ATG and 3D-CT for the ostial PV diameters was r=0.72 for left superior PV, 0.88 for left inferior PV, 0.60 for right superior PV, and 0.65 for right inferior PV (p&lt;0.005). Conclusions: AF ablation using 3D-ATG is possible with a significant reduction in effective dose without compromising image quality.