Reliability of Linear and Curvilinear Measurements on Cone-Beam Computed Tomography Images for the Evaluation of Implant Sites and Jaw Pathologies

ABSTRACT Objective: To evaluate the intra-examiner and inter-examiner reliability of linear and curvilinear measurements for the complete assessment of implant sites and jaw pathologies using Cone-Beam Computed Tomography (CBCT). Material and Methods: Fifty cone-beam computed tomographic images of patients were retrieved from the archives of Dentomaxillofacial Radiology. CBCT images taken for implant planning and evaluation of intrabony jaw pathologies (benign cyst/tumor) were included. Two expert oral and maxillofacial radiologists analyzed the images independently and made the measurements. The images for implant planning were analyzed for width, the height of the edentulous site, and the qualitative analysis of bone in the region. Jaw pathologies were assessed for linear dimensions and curvilinear measurements. Results: The inter-observer measurement error for implant site analysis ranged from 0.12 to 0.42 mm with almost perfect agreement (ICC: 0.94 to 1). The inter-observer measurement error for jaw pathology was 0.09 to 0.25 mm (ICC: 0.98-1). Curvilinear measurements showed perfect agreement between the observers. The intraobserver reliability for the various parameters used for the assessment of the implant site and jaw pathologies indicated almost perfect agreement. Conclusion: Reliability between the radiologists is high for various measurements on CBCT images taken for implant planning and jaw pathologies.

A new method for intraoperative assessment of leg length, sizing and placement of the components in total hip replacement.

BACKGROUND: Intraoperative radiograph of the pelvis is a well-established way to avoid misplacement/undersizing of the components and leg length discrepancy (LLD) in total hip replacement (THR). We describe a method for the obtainment and the evaluation of intraoperative radiographs with a sophisticated wireless radiographic system and a computerized digital tool originally used for preoperative templating. METHODS: In this retrospective case-control study, 60 patients with unilateral hip osteoarthritis who underwent THR with intraoperative radiographic check with the conventional method (n = 30, control group) or the new method (AGFA flat panel DR14eG™/Orthosize™, n = 30, case group) were evaluated and compared for operation time, intraoperative changes in size/placement of the components and final radiological outcome (LLD, acetabular inclination and femoral offset) based on postoperative radiographs of the pelvis. RESULTS: Mean operation time was lower in case group (85.3 min vs. 103.3 min, p value < 0.005), as well as mean absolute LLD (1.93 mm vs. 2.94 mm, p value = 0.242). There was a higher percentage of intraoperative changes in the offset of the prostheses' head (70% vs. 40%, p value = 0.018) and a significantly lower percentage of patients with LLD > 5 mm in the case group (0% vs. 27%, p value = 0.002). CONCLUSIONS: This new method for the obtainment and assessment of intraoperative radiographs proved to be fast and assuring for keeping LLD below 5 mm in all patients.

Soft Tissue Cephalometric Measurements Among Malaysian Malays and Chinese

Abstract Objective: To obtain the standardized values of individuals of Malaysian Malay and Chinese for further relevant research, such as treatment planning and aesthetical considerations. Material and Methods: In this retrospective study, 440 (305 were Malays and 135 were Chinese) standardized lateral cephalometric radiographs of orthodontic patients selected through simple random sampling are profiled using Holdaway's analysis. The independent t-test was used to assess the disparities in race and gender. The significant level was p<0.05. Results: Significant differences were found between the Malays and Chinese in their skeletal profile convexity, superior sulcus depth, inferior sulcus to the H line and nose prominence. Between Malay females and males, there are significant differences in superior sulcus depth, soft tissue subnasale to H line, basic upper lip thickness, upper lip thickness and nose prominence. Between Chinese males and females, there were differences in their skeletal profile convexity, upper lip to H line, basic upper lip thickness and upper lip thickness. Conclusion: The findings demonstrated the difference between standardized norms and the unique profiles of Malaysian Malays and Chinese. There are significant gender disparities in the soft tissue cephalometric measurements among Malaysian Malay and Chinese subjects.

XAP-Lab: A software tool for designing flexible X-ray acquisition protocols.

BACKGROUND AND OBJECTIVE: The availability of digital X-ray detectors, together with the development of new robotized hardware and reconstruction algorithms, opens the opportunity to provide 3D capabilities with conventional radiology systems. This would be based on the acquisition of a limited number of projections with non-standard geometrical configurations. The versatility of these techniques is enormous, enabling the introduction of tomography in situations where a CT system is hardly available, such as during surgery or in an ICU, or in which a reduction of radiation dose is key, as in pediatrics. Computer simulations are a valuable tool to explore these possibilities before their actual implementation on real systems. Existing software tools generally simulate only standard acquisition protocols, such as cone-beam with circular trajectory, thus not allowing the users to evaluate more sophisticated projection geometries. The goal of this work is to design a simulation tool that enables the design of acquisition protocols with flexible projection geometries. METHODS: We present XAP-Lab, a software tool for the design of X-ray acquisition protocols with flexible trajectories. For a given projection geometry, defined through a graphical user interface, it allows the user to simulate projections using GPU-accelerated kernels, the visualization of the scanned field of view and the estimation of the total radiation dose. The complete acquisition protocol can then be exported with the appropriate format for its use on real systems. We tested the software by optimizing a tomosynthesis protocol and validating the results with real acquisitions using a SEDECAL NOVA FA radiography system and phantoms for quantitative and qualitative evaluation. RESULTS: Quantitative evaluation using a phantom showed a mean error under 4 mm for each position, below the ±5 mm tolerance of the system specified by the manufacturer. Visual evaluation on a thorax acquisition also showed a good geometrical agreement between simulated and real projections. CONCLUSIONS: Results showed an excellent matching with simulations, supporting the usefulness of XAP-Lab for the design of new acquisition protocols with non-standard geometries.

Automatic Registration for Navigation at the Anterior and Lateral Skull Base.

OBJECTIVE: Navigation systems create a connection between imaging data and intraoperative situs, allowing the surgeon to consistently determine the location of instruments and patient anatomy during the surgical procedure. The best results regarding the target registration error (measurement uncertainty) are normally demonstrated using fiducials. This study aimed at investigating a new registration strategy for an electromagnetic navigation device. METHODS: For evaluation of an electromagnetic navigation system and comparison of registration with screw markers and automatic registration, we are calculating the target registration error in the region of the paranasal sinuses/anterior and lateral skull base with the use of an electromagnetic navigation system and intraoperative digital volume tomography (cone-beam computed tomography). We carried out 10 registrations on a head model (total n = 150 measurements) and 10 registrations on 4 temporal bone specimens (total n = 160 measurements). RESULTS: All in all, the automatic registration was easy to perform. For the models that were used, a significant difference between an automatic registration and the registration on fiducials was evident for just a limited number of screws. Furthermore, the observed differences varied in terms of the preferential registration procedure. CONCLUSION: The automatic registration strategy seems to be an alternative to the established methods in artificial and cadaver models of intraoperative scenarios. Using intraoperative imaging, there is an option to resort to this kind of registration as needed.

Significant dose reduction using synchrotron radiation computed tomography: first clinical case and application to high resolution CT exams.

Since the invention of Computed Tomography (CT), many technological advances emerged to improve the image sensitivity and resolution. However, no new source types were developed for clinical use. In this study, for the first time, coherent monochromatic X-rays from a synchrotron radiation source were used to acquire 3D CTs on patients. The aim of this work was to evaluate the clinical potential of the images acquired using Synchrotron Radiation CT (SRCT). SRCTs were acquired using monochromatic X-rays tuned at 80 keV (0.350 × 0.350 × 2 mm3 voxel size). A quantitative image quality comparison study was carried out on phantoms between a state of the art clinical CT and SRCT images. Dedicated iterative algorithms were developed to optimize the image quality and further reduce the delivered dose by a factor of 12 while keeping a better image quality than the one obtained with a clinical CT scanner. We finally show in this paper the very first SRCT results of one patient who received Synchrotron Radiotherapy in an ongoing clinical trial. This demonstrates the potential of the technique in terms of image quality improvement at a reduced radiation dose for inner ear visualization.

Image based simulation of the low dose computed tomography images suggests 13 mAs 120 kV suitability for non-syndromic craniosynostosis diagnosis without iterative reconstruction algorithms.

OBJECTIVES: The aim of this study was to simulate low dose paediatric head CT images with different noise levels corresponding to various tube current time product values and assess simulated image suitability in non-syndromic craniosynostosis diagnostics. METHOD: 29 paediatric patients who underwent head CT examinations for cranial deformity were enrolled in the study. The low dose CT images, corresponding to 120 kV and 120 mAs, 100 mAs, 80 mAs, 50 mAs and 13 mAs settings, were synthesised by adding noise to original data. Three researchers evaluated suitability for diagnostics of original and simulated images by using questionnaire assessing image suitability. RESULT: 174 separate cases (containing 1 axial and 1 3D image) were evaluated. Percentage of images evaluated as suitable for diagnosis were 98.9% on original images, 100% on 120 mAs, 100% on 100 mAs, 97.1% on 80 mAs, 96.6% on 50 mAs and 96% on 13 mAs. CONCLUSIONS: Images registered with 120 kV 13 mAs can be used to diagnose non-syndromic craniosynostosis with statistically same accuracy as with standard protocol and correspond to decrease of effective dose from 4.98 mSv to 0.33 mSv (median values).

An iterative reconstruction algorithm for digital breast tomosynthesis imaging using real data at three radiation doses.

BACKGROUND: Iterative image reconstruction in Digital Breast Tomosynthesis (DBT) is a developing modality that produces three-dimensional (3D) reconstructed images of a breast to detect suspicious lesions. Algebraic reconstruction technique (ART), one of the iterative image reconstruction methods, was applied to reconstruct 3D data of breast and is becoming as one alternative method for the conventional image reconstruction techniques such as filtered back projection (FBP) in DBT imaging. OBJECTIVE: A new majorization-minimization (MM) algorithm was presented for TV denoising of signals. In the field of DBT, however, the algorithm has not yet been applied. In this study, we proposed a new method of "ART+TV3D+MM," which applies (MM) algorithm to the images reconstructed by ART+TV3D for different imaging dose levels to investigate a possible reduction of radiation dose. METHODS: Projections of a real breast phantom (CD Pasmam 1054) were acquired with a Siemens MAMMOMAT DBT system. The proposed new method was repeated and tested with 3 different radiation dose levels. The quality of the images reconstructed using the proposed new method were compared with those generated by the commonly used FBP method using both qualitative and quantitative assessments. RESULTS: The new method showed superior results in terms of visual assessment, contrast to noise ratios (CNR), full width at half maximum (FWHM) values and 1D profiles compared with FBP of the Siemens MAMMOMAT. CNR values were evaluated for two different region of interests (ROIs). For instance, CNR values of ROI-2 of FBP and of new method were 1.670 and 1.978 at 100 mAs, respectively. Moreover, while CNR value of ROI-1 of FBP at 100 mAs was 0.955, CNR value of ROI-1 of using new method at 100 mAs was 48.163. FWHM values for FBP and the new method were 2.328 and 1.765 at 56 mAs, 2.032 and 1.661 at 100 mAs, and 2.111 and 1.736 at 199 mAs, respectively. CONCLUSIONS: The results support that using the new method of "ART+TV3D+MM" could help decrease the radiation dose level, which is one of the most critical limitations of DBT imaging.

Mammography cancer detection: comparison of single 8MP and pair of 5MP reporting monitors.

OBJECTIVE:: To compare breast cancer detection using a single 8MP display with using a standard pair of 5MP monitors. METHODS:: An observer study was carried out in which mammograms were read using full field views only, and again with the additional use of magnified quadrant views. Seven observers read 300 cases, one view per breast, using each display type. Cases comprised 100 normal cases and 200 cases with cancers of subtle or very subtle appearance: 100 with malignant calcification clusters and 100 with non-calcified lesions. JAFROC software was used to analyse the results. RESULTS:: When mammograms were viewed full field only, observers performed better (p = 0.050) in detecting malignant calcification clusters when using the pair of 5MP monitors compared with a single 8MP monitor. This result became non-significant when results were generalised to a population of readers. Performance in detecting calcification clusters was improved by using quadrant view in addition to full field view when using either the pair of 5MP monitors or the 8MP monitor. There was no significant difference in detection of all types of cancer between the pair of 5MP monitors and the 8MP monitor when quadrant zoom was used. CONCLUSION:: Providing quadrant view is used in addition to full field view, there is no significant difference in cancer detection between the 8MP monitor and the pair of 5MP monitors. ADVANCES IN KNOWLEDGE:: Effect of magnification on the detectability of subtle malignant calcification clusters in breast screening.

Characterization of the a-Si EPID in the unity MR-linac for dosimetric applications.

Electronic portal imaging devices (EPIDs) are frequently used in external beam radiation therapy for dose verification purposes. The aim of this study was to investigate the dose-response characteristics of the EPID in the Unity MR-linac (Elekta AB, Stockholm, Sweden) relevant for dosimetric applications under clinical conditions. EPID images and ionization chamber (IC) measurements were used to study the effects of the magnetic field, the scatter generated in the MR housing reaching the EPID, and inhomogeneous attenuation from the MR housing. Dose linearity and dose rate dependencies were also determined. The magnetic field strength at EPID level did not exceed 10 mT, and dose linearity and dose rate dependencies proved to be comparable to that on a conventional linac. Profiles of fields, delivered with and without the magnetic field, were indistinguishable. The EPID center had an offset of 5.6 cm in the longitudinal direction, compared to the beam central axis, meaning that large fields in this direction will partially fall outside the detector area and not be suitable for verification. Beam attenuation by the MRI scanner and the table is gantry angle dependent, presenting a minimum attenuation of 67% relative to the 90° measurement. Repeatability, observed over two months, was within 0.5% (1 SD). In order to use the EPID for dosimetric applications in the MR-linac, challenges related to the EPID position, scatter from the MR housing, and the inhomogeneous, gantry angle-dependent attenuation of the beam will need to be solved.

A back-projection algorithm in the presence of an extra attenuating medium: towards EPID dosimetry for the MR-Linac.

In external beam radiotherapy, electronic portal imaging devices (EPIDs) are frequently used for pre-treatment and for in vivo dose verification. Currently, various MR-guided radiotherapy systems are being developed and clinically implemented. Independent dosimetric verification is highly desirable. For this purpose we adapted our EPID-based dose verification system for use with the MR-Linac combination developed by Elekta in cooperation with UMC Utrecht and Philips. In this study we extended our back-projection method to cope with the presence of an extra attenuating medium between the patient and the EPID. Experiments were performed at a conventional linac, using an aluminum mock-up of the MRI scanner housing between the phantom and the EPID. For a 10 cm square field, the attenuation by the mock-up was 72%, while 16% of the remaining EPID signal resulted from scattered radiation. 58 IMRT fields were delivered to a 20 cm slab phantom with and without the mock-up. EPID reconstructed dose distributions were compared to planned dose distributions using the [Formula: see text]-evaluation method (global, 3%, 3 mm). In our adapted back-projection algorithm the averaged [Formula: see text] was [Formula: see text], while in the conventional it was [Formula: see text]. Dose profiles of several square fields reconstructed with our adapted algorithm showed excellent agreement when compared to TPS.

Photon detection efficiency of laboratory-based x-ray phase contrast imaging techniques for mammography: a Monte Carlo study.

An important challenge in real-world biomedical applications of x-ray phase contrast imaging (XPCI) techniques is the efficient use of the photon flux generated by an incoherent and polychromatic x-ray source. This efficiency can directly influence dose and exposure time and ideally should not affect the superior contrast and sensitivity of XPCI. In this paper, we present a quantitative evaluation of the photon detection efficiency of two laboratory-based XPCI methods, grating interferometry (GI) and coded-aperture (CA). We adopt a Monte Carlo approach to simulate existing prototypes of those systems, tailored for mammography applications. Our simulations were validated by means of a simple experiment performed on a CA XPCI system. Our results show that the fraction of detected photons in the standard energy range of mammography are about 1.4% and 10% for the GI and CA techniques, respectively. The simulations indicate that the design of the optical components plays an important role in the higher efficiency of CA compared to the GI method. It is shown that the use of lower absorbing materials as the substrates for GI gratings can improve its flux efficiency by up to four times. Along similar lines, we also show that an optimized and compact configuration of GI could lead to a 3.5 times higher fraction of detected counts compared to a standard and non-optimised GI implementation.

Optimization of Couch Modeling in the Change of Dose Calculation Methods and Their Versions.

In external radiotherapy, the X-ray beam passes through the treatment couch, leading to the dose reduction by the attenuation of the couch. As a method to compensate for the reduction, radiation treatment planning systems (RTPS) support virtual couch function, namely "couch modeling method". In the couch modeling method, the computed tomography (CT) numbers assigned to each structure should be optimized by comparing calculations to measurements for accurate dose calculation. Thus, re-optimization of CT numbers will be required when the dose calculation algorithm or their version changes. The purpose of this study is to evaluate the calculation accuracy of the couch modeling method in different calculation algorithms and their versions. The optimal CT numbers were determined by minimizing the difference between measured transmission factors and calculated ones. When CT numbers optimized by Anisotropic Analytical Algorithm (AAA) Ver. 8.6 were used, the maximum and the mean difference of transmission factor were 5.8% and 1.5%, respectively, for Acuros XB (AXB) Ver. 11.0. However, when CT numbers optimized by AXB Ver. 11.0 were used, they were 2.6% and 0.6%, respectively. The CT numbers for couch structures should be optimized when changing dose calculation algorithms and their versions. From the comparison of the measured transmission to calculation, it was found that the CT numbers had high accuracy.

Diagnostic utility of endobronchial ultrasound with a guide sheath under the computed tomography workstation (ziostation) for small peripheral pulmonary lesions.

BACKGROUND AND AIMS: The application of radial probe endobronchial ultrasound (R-EBUS) and virtual bronchoscopic navigation has improved the diagnostic outcome of bronchoscopy for peripheral pulmonary lesions (PPLs). Nonetheless, while existing navigation systems are very useful for selecting the bronchus containing the target lesion, the associated introductory costs are high. Therefore, we focused on virtual bronchoscopy (VB) using the workstation, ziostation that was already available in many countries as an adjunct modality. METHODS: Consecutive patients who underwent bronchoscopy with R-EBUS for PPLs (major diameter ≤30 mm) were enrolled. From late June 2013 to November 2013, 121 patients were examined with ziostation, and from September 2012 to early June 2013, 113 patients were examined without ziostation. We compared the diagnostic yield, EBUS detection rate and procedure time between two groups to evaluate the utility of the VB. RESULTS: The ziostation group had significantly higher diagnostic yield than the non-ziostation group (77.7% vs 64.6%, P = 0.030). Following the multivariate analysis, use of ziostation was a significant factor affecting the diagnostic yield. Meanwhile, EBUS detection rate was significantly higher in the ziostation group (94.2% vs 75.2%, P < 0.001). And, procedure time was significantly shorter in the ziostation group (mean ± standard deviation: 24.0 ± 7.4 min vs 26.9 ± 7.9 min, P = 0.005). CONCLUSION: VB offered by the workstation was a valuable tool that facilitated more accurate and rapid bronchoscopy procedure for diagnosis of PPLs.

NPWE model observer as a validated alternative for contrast detail analysis of digital detectors in general radiography.

To propose and validate a non-prewhitening with eye filter (NPWE) model observer as an alternative means of quantifying and specifying imaging performance for general radiography detectors, in a comparative study with contrast detail analysis and detective quantum efficiency (DQE). Five different x-ray detectors were assessed, covering a range of detector technologies including powder computed radiography (CR), needle CR, and three indirect conversion flat panel digital radiography detectors (DR). For each detector, threshold contrast detail (c-d) detectability was measured using the Leeds TO20 test object. A tube voltage of 70 kV and 1 mm Cu added filtration was used and five target detector air kerma (DAK) levels were set, ranging from 0.625 µGy to 10 µGy. Three c-d images were acquired at the same DAK levels and these were scored by two observers. Presampling modulation transfer function (MTF) was measured using an edge method while contrast was measured with a 2 mm Al square of dimension 10 × 10 mm. The normalized noise power spectrum (NNPS) was calculated at the target DAK values of the c-d images. The MTF, NNPS and contrast data were then used to calculate a detectability index (d') with the NPWE model and compared to the human observer c-d results. The standard quantitative means of evaluating detector performance i.e. DQE, was then calculated for each detector. A linear correlation was found between the logarithm of threshold contrast and the logarithm of d' for all detectors, as DAK was increased. Furthermore, the absolute value of d' tracked threshold contrast between the five detectors, enabling the use of detectability to quantify image quality rather than the intrinsically subjective threshold contrast scored by human observers from c-d test object images. At 2.5 µGy target DAK, d' followed the differences in DQE between the five detectors. The NPWE detectability index can be used an alternative parameter for the quantification and specification of the image quality of general radiography x-ray detectors.

Does the choice of mobile C-arms lead to a reduction of the intraoperative radiation dose?

INTRODUCTION: Mobile C-arm imaging is commonly used in operating rooms worldwide. Especially in orthopaedic surgery, intraoperative C-arms are used on a daily basis. Because of new minimally-invasive surgical procedures a development in intraoperative imaging is required. The purpose of this article is investigate if the choice of mobile C-arms with flat panel detector technology (Siemens Cios Alpha and Ziehm Vision RFD) influences image quality and dose using standard, commercially available test devices. MATERIALS AND METHODS: For a total of four clinical application settings, two zoom formats, and all dose levels provided, the transmission dose was measured and representative images were recorded for each test device. The data was scored by four observers to assess low contrast and spatial resolution performance. The results were converted to a relative image quality figure allowing for a direct image quality and dose comparison of the two systems. RESULTS: For one test device, the Cios Alpha system achieved equivalent (within the inter-observer standard error) or better low contrast resolution scores at significantly lower dose levels, while the results of the other test device suggested that both systems achieved similar image quality at the same dose. The Cios Alpha system achieved equivalent or better spatial resolution at significantly lower dose for all application settings except for Cardiac, where a comparable spatial resolution was achieved at the same dose. CONCLUSION: The correct choice of a mobile C-arm is very important, because it can lead to a reduction of the intraoperative radiation dose without negative effects on image quality. This can be a big advantage to reduce intraoperative radiation not only for the patient but also for the entire OR-team.

Ultralow dose dentomaxillofacial CT imaging and iterative reconstruction techniques: variability of Hounsfield units and contrast-to-noise ratio.

OBJECTIVE: The aim of this study was to evaluate whether application of ultralow dose protocols and iterative reconstruction technology (IRT) influence quantitative Hounsfield units (HUs) and contrast-to-noise ratio (CNR) in dentomaxillofacial CT imaging. METHODS: A phantom with inserts of five types of materials was scanned using protocols for (a) a clinical reference for navigated surgery (CT dose index volume 36.58 mGy), (b) low-dose sinus imaging (18.28 mGy) and (c) four ultralow dose imaging (4.14, 2.63, 0.99 and 0.53 mGy). All images were reconstructed using: (i) filtered back projection (FBP); (ii) IRT: adaptive statistical iterative reconstruction-50 (ASIR-50), ASIR-100 and model-based iterative reconstruction (MBIR); and (iii) standard (std) and bone kernel. Mean HU, CNR and average HU error after recalibration were determined. Each combination of protocols was compared using Friedman analysis of variance, followed by Dunn's multiple comparison test. RESULTS: Pearson's sample correlation coefficients were all >0.99. Ultralow dose protocols using FBP showed errors of up to 273 HU. Std kernels had less HU variability than bone kernels. MBIR reduced the error value for the lowest dose protocol to 138 HU and retained the highest relative CNR. ASIR could not demonstrate significant advantages over FBP. CONCLUSIONS: Considering a potential dose reduction as low as 1.5% of a std protocol, ultralow dose protocols and IRT should be further tested for clinical dentomaxillofacial CT imaging. ADVANCES IN KNOWLEDGE: HU as a surrogate for bone density may vary significantly in CT ultralow dose imaging. However, use of std kernels and MBIR technology reduce HU error values and may retain the highest CNR.

AlluraClarity Radiation Dose-Reduction Technology in the Hybrid Operating Room During Endovascular Aneurysm Repair.

PURPOSE: To evaluate the effect of radiation dose reduction with the Allura ClarityIQ image processing technology for fixed C-arms in comparison with a mobile C-arm and an Allura fixed C-arm without ClarityIQ technology during endovascular aneurysm repair (EVAR) procedures. METHODS: Radiation dose data from 85 patients (mean age 74.2±7.8 years; 68 men) undergoing EVAR with mobile and fixed C-arm fluoroscopy were retrospectively analyzed. The radiation dose parameters included the kerma area product (KAP), fluoroscopic time (FT), and number of digital subtraction angiography (DSA) frames (FrDSA). KAPtotal consisted of KAPfluoro (KAP for fluoroscopic imaging) and KAPDSA (KAP for DSA and single shots). Linear regression analysis was used to explore differences in the association of KAP with the FT, FrDSA, and body mass index (BMI) among the 3 C-arms. RESULTS: The mean KAPtotal values for mobile, Allura C-arm, and AlluraClarity C-arm for noncomplex EVARs were 56±39, 245±142, and 157±120 Gy·cm(2) (p<0.001); for complex EVARs, the values were 110±43, 874±653, and 598±319 Gy·cm(2) (p<0.001), respectively. On average, KAPfluoro tripled when the mobile C-arm was replaced by the fixed C-arm. There were no significant differences in the KAPfluoro adjusted for the FT between Allura and AlluraClarity (p=0.69). However, there was a major 61% reduction in KAPDSA from 1.36 Gy·cm(2) per DSA frame for Allura to 0.54 Gy·cm(2) per DSA frame with AlluraClarity (p=0.03). For the mobile C-arm, BMI was not associated with KAP (p=0.13). The associations of BMI with KAPfluoro and KAPDSA were significant for both fixed C-arms but were more robust for Allura compared to AlluraClarity (p=0.02 for KAPfluoro and p<0.001 for KAPDSA). CONCLUSION: Changing a mobile C-arm for a fixed C-arm in a hybrid operating suite increased the average intraoperative dose during EVAR. Upgrading the Allura fixed C-arm with ClarityIQ technology resulted in a 61% reduction in the radiation per DSA frame.

Radiation risk reduction in cardiac electrophysiology through use of a gridless imaging technique.

AIMS: It has been previously demonstrated that use of appropriate frame rates coupled with minimal use of high-dose digital acquisition can limit radiation risk to patients undergoing diagnostic and therapeutic electrophysiology (EP). Imaging without the anti-scatter grid has been proposed as a means of achieving further radiation reduction. We evaluate application of a gridless imaging technique to deliver further reductions in radiation risk to both patients and personnel. METHODS AND RESULTS: Radiation and clinical data for EP procedures performed for 16 months from March 2012 were monitored. The period was divided into three phases: Phase 1 (March 2012-June 2012) provided a performance baseline (radiation output modelling and procedural risk adjustment calibration), Phase 2 (July 2012-September 2012) confirmation of performance with the grid, and Phase 3 (September 2012-June 2013) gridless imaging period. Statistical process control (SPC) charts were used to monitor for changes in radiation use and clinical outcomes (procedural success). Imaging without the grid halved the levels of radiation delivered in undertaking EP procedures. Although there was a perceptible impact on image quality with the grid removed. Review of the SPC chart monitoring procedural outcomes did not identify any discernable adverse impact on success rates. Selected use of the gridless technique is recommended with re-introduction of the grid in larger patients or during aspects of the procedure where image quality is important (e.g. transeptal punctures). CONCLUSION: Use of a gridless imaging technique can contribute to a significant reduction in radiation risk to both patients and operators during cardiac EP procedures.

Light beam diaphragm collimation errors and their effects on radiation dose for pelvic radiography.

PURPOSE: To investigate the range of collimation errors in x-ray rooms and to calculate their possible effects on the radiation dose for anteroposterior pelvic examinations. METHODS: A collimator test tool was suspended at 3 heights (14, 21, and 28 cm) above the table Bucky in 9 x-ray rooms. Heights corresponded to the typical patient thickness (mean, ± 2 SD) of 67 patients undergoing anteroposterior pelvic radiography. The x-ray beam was visually collimated to the inner boundary of the test tool and exposed to radiation. Differences between the visualized field size and the resultant x-ray field size (corrected for magnification) indicated a collimation error. Next, using a pelvic phantom, minimum textbook collimation was set and then changed and verified to simulate a range of possible collimation errors. Phantom examinations used a standard anteroposterior technique with exposure termination using outer automatic exposure control chambers. Dose area product (DAP) was recorded. RESULTS: All but 1 of the 9 x-ray machines had a smaller irradiated area than was visually set. Errors ranged from a 16% reduction in irradiated field size to a slight overirradiation by 0.4%. Assuming that these errors could be larger in other institutions, additional errors with a range of -27% to 18% were simulated. Increases in field size by 1 cm (superiorly/inferiorly) increased the DAP by 5%. Laterally, a 1-cm increase caused a 4% rise in DAP. Increases of 1 cm in both planes raised DAP by 4%. DISCUSSION: Within a single clinical department, minimal collimation errors were demonstrated. Further evidence from multiple centers would be beneficial; however, such low incidences might reflect strict legislative requirements governing the use of ionizing radiation. Understanding the magnitude of any error is important, but it is also important to ascertain an error's influence on the effective radiation dose for any given examination. CONCLUSION: Overall, collimation errors were minimal and favored underirradiation. Small collimation errors can affect DAP and are more dose significant in the superior/inferior plane.