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Optimising phosphor screens in dose detectors or imaging sensor designs is a cumbersome and time- consuming work normally involving specialised measuring equipment and advanced modelling. It is known that crucial optical parameters of the same phosphor may vary within a wide range of values. The aim of this work was to experimentally assess a simple previously published model where the case specific optical parameters (scattering and absorption) are instead represented by a fixed, single parameter, the light extinction factor, ξ. The term extrinsic efficiency, N, of a phosphor is also introduced, differing from the common denotation “absolute efficiency”, after noting that unknown factors (such as temperature dependence) can have an influence during efficiency estimations and hence difficult to claim absoluteness. N is expressed as the ratio of light energy emitted per unit area at the phosphor surface to incident x-ray energy fluence. By focusing on ratios and relative changes in this study, readily available instruments in a Medical Physics Department (i.e. a photometer) could be used. The varying relative extrinsic efficiency for an extended range of particle sizes (7.5 and 25 µm) and layer thicknesses (220 to 830 µm) were calculated in the model from the input parameters: the mean particle size of the phosphor, the layer thickness, the light extinction factor and the calculated energy imparted to the layer. In-house manufactured screens (Gd2O2S:Tb) were used for better control of design parameters. The model provided good qualitative agreement to experiment with quantitative deviations in relative extrinsic efficiency within approximately 2%.

Conversion to a filmless technique of physical performance testing is becoming a topic of much interest to researchers. We assessed the use of a computed radiography (CR) system with postprocessing software as an alternative tool for performing the three physical performance tests of an x‐ray tube. Collimator and beam alignment, focal spot size, and milliampere second (mAs) linearity, were performed using a CR system. Results were then compared with those obtained from a conventional screen‐film (SF) system. The distances of collimator misalignment measured by the SF system were decreased while peak tube voltage (kVp) was increased (mAs was fixed), whereas those measured by CR were independent of exposure level. The degrees of beam collimator misalignment measured by the CR system were not different from those measured by the SF system. The differences in focal spot dimensions measured by SF and CR systems were less than 4% for large and small focal spot size in both width and length. The mAs linearity evaluated by the SF system agreed with those evaluated by the dose measurement at 50 kVp and 4 mAs, as well as 55 kVp and 3.2 mAs, while the mAs linearity test using the CR system agreed with those using the dose measurement method for all exposure levels. In summary, a CR system could be utilized to assess the three physical performance tests of a single x‐ray tube, but required more time than an SF system. Medical physicists with image processing skills were needed to perform the analyses.

To investigate optimal beam quality for chest flat panel detector (FPD) system by semi-quantitatively assessment using a realistic lung phantom. Chest FPD radiographs were obtained on a realistic lung phantom with simulated lung opacities using various X-ray tube voltage levels (90–140 kV) with/without copper filter. Entrance skin dose was set to maintain identical for all images (0.1 mGy). Three chest radiologists unaware of the exposure settings independently evaluated the image quality of each simulated opacity and normal structure using a 5-point scale (+ 2: clearly superior to the standard; + 1: slightly superior to the standard; 0: equal to the standard; − 1: slightly inferior to the standard; − 2: clearly inferior to the standard). The traditional FPD image obtained at a tube voltage of 120 kV was used as the standard. The scores of image quality were statistically compared using the Wilcoxon rank test with Bonferroni correction. FPD images using 90-kV shot with copper filter were superior to the traditional 120-kV shot without filter with respect to the visibility of vertebra, pulmonary vessels, and nodules overlapping diaphragm and heart (p

Objectives: To assess, objectively to determine the deterioration of the photostimulable phosphor plates (PSPs) after several acquisitions. Methods: Two new PSPs without preliminary use were exposed with an intraoral X-ray unit, and the EXPRESS® (Instrumentarium Imaging, Tuusula, Finland) unit was used for scanning of the PSPs. A 12-stepwedge aluminum scale were used superimposed with the PSPs during the X-rays exposures to perform the objective analyses. Objective analysis was carried out by mean gray values using the Image J software through a region of interest (ROI) of 0.1 × 0.1 mm, and the data were analyzed statistically using ANOVA. Results: For each, the Express® PSP a total of 1800 images were acquired during 60 days. The objective analysis showed loss of the mean gray values between the initial and final images. Besides, the percentage of mean gray values’ loss was between 0.7%, for the thickest step, and 8.4%, for the lowest thickness step. Conclusion: After many X-ray exposures of the Express® PSP a singular deterioration in the mean gray values could be observed.

Conventional mammography is a decisive tool in detecting breast cancer. Continuous efforts are undertaken in order to further improve the image quality as well as to reduce the applied doses. The purpose of our study was to compare diagnostic image quality of dose reduced computed mammography with a new needle-based detector system to full dose powder imaging plates.We retrospectively compared 360 randomly chosen mammographies performed on a GE Senographe DMR running the Agfa DX-M needle-based imaging plate system (NIP) with their preliminary examinations which were acquired at standard dose with the same GE mammography device and an Agfa CR85-X powdered storage phosphor imaging plate system (PIP). NIP-based mammographies were about 29.8 % dose-reduced. The preliminary examinations had to be performed not earlier than 2 years before the recent investigations. Exclusion criteria were changes in ACR level and appearance of the scored targets and not optimally positioned and exposed mammographies. The images were blinded and read separately twice by 2 mammography experts according to a 3-point score on diagnostic image quality and the visualization of parenchyma, cysts, fibroadenomas, physiologic lymph nodes, solitary microcalcifications and macrocalcifications.Dose reduced NIPs showed a significantly better visualization of parenchyma at ACR II/III and solitary microcalcifications at ACR I-III mammographies (p 0.001) whereas the difference in scoring macrocalcifications, cysts, fibroadenomas and physiologic lymph nodes was not significant. The reading showed an excellent intra- (r = 0.97/0.94) and interobserver agreement (r = 0.92).With computed mammography using the needle-based detector system a significant dose reduction is possible without loss of diagnostic image quality.

The use of digital radiographic systems has decreased the frequency of image retakes due to over/underexposure in general radiography. However, image retakes owing to patient positioning errors are likely to increase because of the convenience of a real-time image check on a console table. The purpose of the present study is to propose a novel radiographic examination procedure with an ultra-low-dose pre-test exposure that may be utilized to check patient positioning prior to taking an actual image, thereby reducing unnecessary patient exposure owing to image retakes. In this study, examination data from 714 knee joint radiographs, both submitted and retaken images, were included. Twelve radiological technologists (RTs) took all images. The actual total exposure dose for each patient was compared with simulated total doses utilized in the proposed procedure. The simulation assumed that each examination was completed following pre-test exposure. Therefore, this method did not involve retaking images although at least one pre-test exposure had been applied to all patients. Pre-test exposures at four dose levels corresponding to 25, 10, 5, and 2% of the actual exposure dose were evaluated to determine whether each dose level could be used to check patient positioning. The results indicated that when the pre-test exposure dose rate was 10% or lower, the total exposure dose reduction equaled or exceeded 8% for all patients. The use of the proposed procedure reduced the total exposure dose for all patients when compared to the exposure dose calculated from records.

Objectives: To assess the validity of using the calibration ruler for correcting magnification of linear measurements and to explore and compare the vertical and horizontal magnification of four digital cephalometric units. Methods: An acrylic box was imaged at seven sagittal positions using four digital cephalometric units: Orthopantomograph OC100, Orthopantomograph OC200, Sirona Orthophos CD, and Sirona Orthophos DS. The true linear lengths of the phantom, corrected, and uncorrected linear lengths on the images were measured and compared. The validity of measurements using the calibration ruler was assessed. The magnification values and distortion indices were calculated and compared among the four cephalometric units. Results: For linear measurements on the mid-sagittal plane and averaged linear measurements on bilateral symmetric sagittal planes, the bias 1.96 STD of the calibration ruler ranged from 1% to 2% for the four cephalometric testing units. For linear measurements on the single lateral sagittal plane, the bias 1.96 STD ranged from 3% to 6%. The vertical scanning charge-coupled device cephalometric unit produced the greatest distortion, ranging from 1.029 to 0.964. Conclusion: The metal millimeter calibration ruler is an accurate reference for linear measurement magnification correction. Because of unpredictability and machine specificity, the magnification and distortion of a cephalometric unit should be calibrated for the estimation of cephalometric measurement error.

DivIVA or Wag31, which is an essential pole organizing protein in mycobacteria, can self-assemble at the negatively curved side of the membrane at the growing pole to form a higher order structural scaffold for maintaining cellular morphology and localizing various target proteins for cell-wall biogenesis. The structural organization of polar scaffold formed by polymerization of coiled-coil rich Wag31, which is implicated in the anti-tubercular activities of amino-pyrimidine sulfonamides, remains to be determined. A single-site phosphorylation in Wag31 regulates peptidoglycan biosynthesis in mycobacteria. We report biophysical characterizations of filaments formed by mycobacterial Wag31 using circular dichroism, atomic force microscopy and small angle solution X-ray scattering. Atomic force microscopic images of the wild-type, a phospho-mimetic (T73E) and a phospho-ablative (T73A) form of Wag31 show mostly linear filament formation with occasional curving, kinking and apparent branching. Solution X-ray scattering data indicates that the phospho-mimetic forms of the Wag31 polymers are on average more compact than their phospho-ablative counterparts, which is likely due to the extent of bending/branching. Observed structural features in this first view of Wag31 filaments suggest a basis for higher order Wag31 scaffold formation at the pole.

Objective To evaluate how physical photostimulable phosphor (PSP) plate artifacts, such as those created by scratches, phosphor degradation, and surface peeling, affect the radiologic interpretation of periapical inflammatory disease. Study Design A novel technique was developed to digitally superimpose 25 real PSP artifact masks over 100 clinical complementary metal oxide semiconductor (CMOS) periapical images with known radiologic interpretations. These images were presented to 25 general dentists, who were asked to state their radiologic interpretations, their confidence in their interpretations, and their opinions on whether the plates should be discarded. Statistical analyses were conducted by using random intercept mixed models for repeated measures and χ2 tests of the pooled data. Results No statistically significant adverse effect on interpretation was seen, even at severe artifact levels. There was a statistically significant decrease in the clinicians’ confidence and an increase in discard proportions when interpreting images with severe PSP plate artifacts (P Conclusions Although diagnostic efficacy was unaffected, clinicians’ confidence decreased and proportionally more clinicians opted to discard sensors when interpreting images with severe artifacts. Future studies on the effects of artifacts on the efficacy of diagnosis of other dental diseases are recommended. Ultimately, these results can guide recommendations for PSP plate quality assurance.

Data from dental intraoral radiography quality controls was gathered from 1201 units (22% of the licensed X-ray units existing in Portugal), using film and digital image systems, between 2016 and 2018. The median incident air KERMA for standard superior molar tooth was evaluated in 0.9 mGy with the value of 1.3 mGy as the upper quartile. Comparisons with a 1990 published survey from dental exposures in Portugal were made. A 85% reduction for incident air KERMA per exposure was observed (6.0 mGy for the 1990 survey), which can be attributed to technical advances in the X-ray image receptors, as well as the implementation of legal requirements for technical acceptability of radiological units. It was also observed an increase of X-ray exams, which is related to an increase of dental practitioners, available radiological equipment and the level of dental healthcare.

Allosteric regulation of the Tet repressor (TetR) homodimer relies on tetracycline binding that abolishes the affinity for the DNA operator. Previously, interpretation of circular dichroism data called for unfolding of the α-helical DNA-binding domains in absence of binding to DNA or tetracycline. Our small angle X-ray scattering of TetR(D) in solution contradicts this unfolding as a physiological process. Instead, in the core domain crystal structures analyses show increased immobilisation of helix α9 and two C-terminal turns of helix α8 upon tetracycline binding. Tetracycline complexes of TetR(D) and four single-site alanine variants were characterised by isothermal titration calorimetry, fluorescence titration, X-ray crystal structures, and melting curves. Five crystal structures confirm that Thr103 is a key residue for the allosteric events of induction, with the T103A variant lacking induction by any tetracycline. The T103A variant shows anti-cooperative inducer binding, and a melting curve of the tetracycline complex different to TetR(D) and other variants. For the N82A variant inducer binding is clearly anti-cooperative but triggers the induced conformation.

Objective The aim of this study was to evaluate the effectiveness of a new sealing method for preventing cross-contamination of photostimulable phosphor (PSP) plates. Study Design Twelve new PSP plates were divided into 3 groups (PSP-a, PSP-b, and PSP- c) and placed in 3 different barriers (2 different brands of envelopes and a vacuum sealing method). All plates were exposed to X-rays with an aluminum step wedge, and the images were evaluated for the presence of any artifacts. After radiography, the PSP plates were removed from the barriers. The barriers and the PSP plates were disinfected and culture performed to assess any microorganism burden. Subsequently, the PSP plates were coated again with all barriers. The barriers were then contaminated and microbiologic specimens were collected. Subsequently, the barriers were wiped with alcohol. The PSP plates were removed, and microbiologic specimens were obtained. Results No artifacts were recorded on the radiographic images on the sensors in any group. Microorganisms were detected on the PSP plates placed in envelopes. No colonization of microorganisms was detected on the vacuum sealed PSP plates. Conclusions The new vacuum-sealing method may be useful in preventing cross-contamination of PSP plates during radiographic procedures.

This work assessed the appropriateness of the signal-to-noise ratio improvement factor (KSNR) as a metric for the optimisation of computed radiography (CR) of the chest. The results of a previous study in which four experienced image evaluators graded computer simulated chest images using a visual grading analysis scoring (VGAS) scheme to quantify the benefit of using an anti-scatter grid were used for the clinical image quality measurement (number of simulated patients = 80). The KSNR was used to calculate the improvement in physical image quality measured in a physical chest phantom. KSNR correlation with VGAS was assessed as a function of chest region (lung, spine and diaphragm/retrodiaphragm), and as a function of x-ray tube voltage in a given chest region. The correlation of the latter was determined by the Pearson correlation coefficient. VGAS and KSNR image quality metrics demonstrated no correlation in the lung region but did show correlation in the spine and diaphragm/retrodiaphragmatic regions. However, there was no correlation as a function of tube voltage in any region; a Pearson correlation coefficient (R) of -0.93 (p = 0.015) was found for lung, a coefficient (R) of -0.95 (p = 0.46) was found for spine, and a coefficient (R) of -0.85 (p = 0.015) was found for diaphragm. All demonstrate strong negative correlations indicating conflicting results, i.e. KSNR increases with tube voltage but VGAS decreases. Medical physicists should use the KSNR metric with caution when assessing any potential improvement in clinical chest image quality when introducing an anti-scatter grid for CR imaging, especially in the lung region. This metric may also be a limited descriptor of clinical chest image quality as a function of tube voltage when a grid is used routinely.

Many image-intensifier fluoroscopy systems have been replaced by flat-panel detectors in recent years. To compare the level of contrast, image resolution and radiation dose between an image-intensifier and a newer-generation flat-panel detector system in a pediatric radiology unit. We compared two systems — a conventional image intensifier and a newer-generation flat-panel system. We measured image quality and radiation dose using a technical phantom. Additionally, we retrospectively compared age-matched fluoroscopic pediatric voiding cystourethrography (n = 15) and upper gastrointestinal investigations (n = 25). In phantom studies image contrast was equal while image resolution was higher and mean radiation dose lower using the flat-panel system (P

Background Radiation exposure remains an unceasing concern in angiographic procedures. Modern angiography machines such as analog image intensifiers (AII) or the new flat panel detectors (FPD) aim at a further dose reduction. Purpose To present dose area products (DAP) in a broad spectrum of therapeutic angiographic procedures, comparing an AII to an FPD angiography system. Material and Methods A total of 999 peripheral therapeutic angiography procedures performed with an FPD ( n = 562) and an AII system ( n = 437) were evaluated. DAP, fluoroscopy time, and patients' body mass index (BMI) were recorded. Interventions were classified into five main groups: percutaneous transluminal angioplasty (PTA); PTA and stent placement; intra-arterial thrombolysis; embolization procedures; and specialized interventions. Results DAP values in therapeutic angiographic procedures were significantly higher when performed with the FPD compared to the AII system. The increase of the FPD versus AII system was 100.1% for PTA, 39.9% for PTA and stent placement, 187% for intra-arterial thrombolysis, 31.3% for embolization procedures, and 361% for specialized interventions. These differences persisted after standardizing DAP values to the geometric mean fluoroscopy duration of each procedure. Fluoroscopy times were shorter in all interventions performed at the FPD as compared to the AII system. DAPs increased with higher BMI, but the DAP increase of both systems with elevated BMI was variable, depending on the individual intervention. Conclusion In therapeutic angiographic procedures, the FPD system required higher DAPs despite shorter fluoroscopy times as compared to an AII system. Better ergonomics and speediness of the FPD system may be advantageous in the emergency setting.

In this project, we investigated the use of an electronic portal imaging device (EPID), together with the treatment planning system (TPS) and MLC log files, to determine the delivered doses to the patient and evaluate the agreement between the treatment plan and the delivered dose distribution. The QA analysis results are presented for 15 VMAT patients using the EPID measurements, the ScandiDos Delta4 dosimeter, and the beam fluence calculated from the multileaf collimator (MLC) log file. EPID fluence images were acquired in continuous acquisition mode for each of the patients and they were processed through an in‐house MATLAB program to create an opening density matrix (ODM), which was used as the input fluence for the dose calculation in the TPS (Pinnacle3). The EPID used in this study was the aSi1000 Varian on a Novalis TX linac equipped with high‐definition MLC. The actual MLC positions and gantry angles were retrieved from the MLC log files and the data were used to calculate the delivered dose distributions in Pinnacle. The resulting dose distributions were then compared against the corresponding planned dose distributions using the 3D gamma index with 3 mm/3% passing criteria. The ScandiDos Delta4 phantom was also used to measure a 2D dose distribution for all the 15 patients and a 2D gamma was calculated for each patient using the Delta4 software. The average 3D gamma using the EPID images was 96.1%±2.2%. The average 3D gamma using the log files was 98.7%±0.5%. The average 2D gamma from the Delta4 was 98.1%±2.1%. Our results indicate that the use of the EPID, combined with MLC log files and a TPS, is a viable method for QA of VMAT plans. PACS numbers: 87.55.Qr

Several algorithms exist to perform quality assurance for volumetric‐modulated arc therapy (VMAT) treatments based on electronic portal imaging devices (EPID). These algorithms are used to compare doses (convert into water, GLAaS) and fluences (in amorphous silicon (aSi), Varian portal dosimetry). The aim of this study is to compare the two methods using clinical data. In this study, Varian portal dosimetry (VPD) and Epiqa solutions were compared. We used a same set of patient images data treated with 6 MV and 20 MV photon energies and different locations. The response of the portal imaging device was also investigated with different field sizes, monitor units, dose rates, sag effect, and linac daily output. All images were acquired on an electronic portal imaging device (EPID) positioned at source detector distance (SDD) of 100 cm. A virtual water phantom was used for Epiqa to calculate the dose matrices at the maximum depth doses dmax. The 2D gamma evaluation index (GAI) was performed to quantitatively compare the results given by the two solutions. The response of the EPID gave a good agreement with Epiqa (deviation less than 1%) for MU greater than 20 for both 6 MV and 20 MV photon energies. For VPD, the upward sloping trend showed a good agreement for MU higher than 50. Dose rate evaluations for both methods gave a deviation of, respectively, 0.4 and 0.5 % for 6 MV and 20 MV. The gamma criteria of 3 mm for distance to agreement and 3 % for dose difference was, as mean ±1 SD, 99.81%±1.48% and 99.42%±0.97% for VPD and Epiqa, respectively, for 6 MV photon energy. The mean values of the gamma criteria for the collected data using 20 MV photon energy were, respectively, 98.33%±2.41% and 98.12%±1.99% for VPD and Epiqa. The output constancy deviation correction (a 10×10 cm2 reference field plan to obtain absorbed dose despite the linac monitor daily variations) showed a mean deviation of, respectively, 0.07%±0.57% and 0.16%±1.38% for 6 MV and 20 MV photon energies. For sag effect, a slight improvement was noticed for realignment of the integrated image and was 0.25%±0.69% for 6 MV and 0.40%±0.57% for 20 MV. The clinical data were used for pretreatment QA with the two systems, both VPD and Epiqa software, showed acceptable and similar results for low and high energies. Furthermore, Epiqa shows better linearity response for low MU. PACS number: 87.53.Bn, 87.55.km, 87.57.uq

In this study, we investigate the performance of the Gunma University Heavy Ion Medical Center's ion computed tomography (CT) system, which measures the residual range of a carbon-ion beam using a fluoroscopy screen, a charge-coupled-device camera, and a moving wedge absorber and collects CT reconstruction images from each projection angle. Each 2D image was obtained by changing the polymethyl methacrylate (PMMA) thickness, such that all images for one projection could be expressed as the depth distribution in PMMA. The residual range as a function of PMMA depth was related to the range in water through a calibration factor, which was determined by comparing the PMMA-equivalent thickness measured by the ion CT system to the water-equivalent thickness measured by a water column. Aluminium, graphite, PMMA, and five biological phantoms were placed in a sample holder, and the residual range for each was quantified simultaneously. A novel method of CT reconstruction to correct for the angular deflection of incident carbon ions in the heterogeneous region utilising the Bragg peak reduction (BPR) is also introduced in this paper, and its performance is compared with other methods present in the literature such as the decomposition and differential methods. Stopping power ratio values derived with the BPR method from carbon-ion CT images matched closely with the true water-equivalent length values obtained from the validation slab experiment.

Background: To determine the proportion of "true" interval cancers and tumor characteristics of interval breast cancers prior to, during and after the transition from screen-film mammography screening (SFM) to full-field digital mammography screening (FFDM).Methods: We included all women with interval cancers detected between January 2006 and January 2014. Breast imaging reports, biopsy results and breast surgery reports of all women recalled at screening mammography and of all women with interval breast cancers were collected. Two experienced screening radiologists reviewed the diagnostic mammograms, on which the interval cancers were diagnosed, as well as the prior screening mammograms and determined whether or not the interval cancer had been missed on the most recent screening mammogram. If not missed, the cancer was considered an occult ("true") interval cancer.Results: A total of 442 interval cancers had been diagnosed, of which 144 at SFM with a prior SFM (SFM-SFM), 159 at FFDM with a prior SFM (FFDM-SFM) and 139 at FFDM with a prior FFDM (FFDM-FFDM). The transition from SFM to FFDM screening resulted in the diagnosis of more occult ("true") interval cancers at FFDM-SFM than at SFM-SFM (65.4% (104/159) versus 49.3% (71/144), P Conclusions: An increase in the proportion of occult interval cancers is observed during the transition from SFM to FFDM screening mammography. However, this increase seems temporary and is no longer detectable after the second round of digital screening. Tumor characteristics and type of surgery are comparable for interval cancers detected prior to, during and after the transition from SFM to FFDM screening mammography, except of a lower proportion of invasive ductal cancers after the transition.

Recently, for medical imaging, digital radiography systems are widely used in clinical practices. However, a study in the past reported that a patient radiation exposure level by digital radiography is in fact not lower than that by analog radiography system. High level of attention needs to be paid for over-exposure when using the conventional analog radiography with a screen and a film, as it results in high density of the film. However, for digital radiography systems, since the automatic adjusting function of image density is equipped with them, no attention for radiation dose need to be paid. Thus technologists tend to be careless and results in higher chance for over-exposure. Current digital radiography systems are high-performance in the image properties and capable of patient dose reduction. Especially, the image quality of the flat panel detector system is recognized, higher than that of the computed radiography system by imaging plates, in both objective and subjective evaluations. Therefore, we technologists are responsible for optimizing the balance between the image quality of the digital radiogram and the radiation dose required for each case. Moreover, it is also required for us as medical technologists to make effective use of such evaluation result of medical images for patients.

Grid conversion factors were established for using grids with varying ratios for film-screen systems. Evidence from the physics community suggests that the relationship between grid conversion factors and exposure to the receptor does not apply with different types of digital imaging receptors.To evaluate the relationship among analog grid conversion factors when using various grid ratios with a photostimulable phosphor plate (PSP) receptor system.Three experiments were conducted using a range of grid ratios (6:1, 8:1, 12:1) to assess the effect of conversion factors on exposure indicators with a computed radiography PSP receptor.When using the analog grid conversion factors established for varying grid ratios with a PSP receptor and constant peak kilovoltage (kVp), the plate was overexposed with an exposure indicator outside the acceptable limits.The discussion of antiscatter grids in radiologic technologist literature should remain in the context of receptor type and digital imaging system being used so that technologists can make appropriate decisions about the use of grids while minimizing patient radiation dose. Calibrated grid conversions based on the digital systems in use and the radiologist's image quality preference could be created within radiology departments.

Navigation surgery on the skull base requires high navigation accuracy. The registration process is related to the main loss in accuracy. This study compared titanium screw registration with an inbuilt registration process of a 3-dimensional (3D) C-arm.Experimental phantom study.Operating room.Four skull models were fabricated with a 3D printer based on the patient's computed tomography (CT) data sets and fitted with an individually customized silicone skin. A 3D-isocentric C-arm fluoroscopic image intensifier system combined with a flat panel detector performed scans of petrous bones (PB) and paranasal sinuses (PS). The navigation accuracy of pair-point registration (PPR) with titanium screws was compared with C-arm-based registration.Overall navigation accuracy was 1.53 ± 0.51 mm after PPR and 1.26 ± 0.12 mm after C-arm registration (P = .0259). PPR showed the best accuracy results on PS (1.28 ± 0.69 mm), followed by right PB (1.43 ± 0.52 mm) and left PB (1.74 ± 0.69 mm). A significant difference was seen only between PS and left PB (P = .0206). In contrast, C-arm registration revealed significantly lower target registration errors (TREs) on PB (0.99 ± 0.23 mm right PB, P.0001; 1.2 ± 0.35 mm left PB, P = .0412) compared with PS. When comparing both registration modalities, C-arm registration was significantly superior on PB. With respect to specific anatomic locations, C-arm-based registration showed significantly lower TREs on the frontal and lateral skull base than PPR.C-arm-based navigation shows higher navigation accuracy on the skull base compared with PPR. As the 3D C-arm allows real-time imaging and real-time navigation, it will be a helpful tool for skull base surgeons.

A Monte Carlo model of a novel electronic portal imaging device (EPID) has been developed using Geant4 and its performance for imaging and dosimetry applications in radiotherapy has been characterised. The EPID geometry is based on a physical prototype under ongoing investigation and comprises an array of plastic scintillating fibres in place of the metal plate/phosphor screen in standard EPIDs. Geometrical and optical transport parameters were varied to investigate their impact on imaging and dosimetry performance. Detection efficiency was most sensitive to variations in fibre length, achieving a peak value of 36% at 50 mm using 400 keV x-rays for the lengths considered. Increases in efficiency for longer fibres were partially offset by reductions in sensitivity. Removing the extra-mural absorber surrounding individual fibres severely decreased the modulation transfer function (MTF), highlighting its importance in maximising spatial resolution. Field size response and relative dose profile simulations demonstrated a water-equivalent dose response and thus the prototype's suitability for dosimetry applications. Element-to-element mismatch between scintillating fibres and underlying photodiode pixels resulted in a reduced MTF for high spatial frequencies and quasi-periodic variations in dose profile response. This effect is eliminated when fibres are precisely matched to underlying pixels. Simulations strongly suggest that with further optimisation, this prototype EPID may be capable of simultaneous imaging and dosimetry in radiotherapy.

Structured Abstract Objectives To study size and shape of the sella turcica in individuals with Down syndrome (DS) and compare them to matched controls without the syndrome. Setting and sample population The Department of Pediatric Dentistry and Orthodontics. Lateral cephalograms of sixty DS individuals and sixty controls were obtained with an age range of 12–22 years. Materials and methods The length, depth, and diameter of the sella turcica were calculated. In addition, the shape of the sella turcica was described as either normal or with aberrations such as; oblique anterior wall, sella turcica bridging, extremely low sella turcica, irregularity in the posterior part of the dorsum sella, and pyramidal shape of the dorsum sella. Results An increase in the diameter and depth of sella turcica was found more frequently in DS group as compared to controls (P

Introduction The aim of the study was to compare the diagnostic ability to radiographically detect separated stainless steel (SS) versus nickel-titanium (NiTi) instruments located at the apical third of filled root canals with either AH 26 (Dentsply DeTrey GmbH, Konstanz, Germany) or Roth sealer (Roth International Ltd, Chicago, IL). Methods Sixty single-rooted extracted human teeth with 1 straight root canal were instrumented to a size 25 apical diameter. In 40 teeth, apical 2-mm segments of SS ( n = 20) or NiTi ( n = 20) files were intentionally fractured in the apical part of the root canal. The remaining 20 teeth without fractured files served as a control group. Subsequently, the root canals were filled using laterally condensed gutta-percha and either AH 26 sealer (AH) or Roth sealer (Roth). All teeth were radiographed using conventional Kodak film (Eastman Kodak Co, Rochester, NY) and a charge-coupled device digital sensor. The evaluation of the images for the presence of a fractured instrument was performed independently by 2 blinded observers. The data were statistically analyzed using McNemar and Fisher exact tests. Results The kappa values were 0.76 and 0.615 for the first and second observers, respectively, and 0.584 between the observers. There were no significant differences in the diagnostic ability between digital and conventional radiography or the different root canal sealers (AH vs Roth, P > .05). The sensitivity to detect fractured SS was significantly higher than NiTi ( P Conclusions It may be difficult to radiographically detect a retained separated instrument. It is easier to radiographically detect fractured SS than NiTi instruments retained at the apical third of the root canal.

The aim of this study was to compare the image quality of a compact mobile flat-panel computed tomography (FPCT) capable of extremity imaging and a multidetector computed tomography (MDCT) in examinations with the same radiation dose.Imaging with the FPCT was performed with default settings. Monte Carlo simulations were used to calculate equivalent dose settings for the 320-row MDCT. Simulations were based on and validated by dose measurements. Homogeneity, geometric distortion, artifacts, accuracy of Hounsfield values, contrast, and spatial resolution were evaluated in different imaging phantoms. Whitney-Mann U Test and Spearman ρ were used for statistical analysis.Homogeneity reached 2.5% for the FPCT and 0.5% for the MDCT. Hounsfield values were more accurate and contrast to noise ratios were higher for the MDCT than the FPCT (P ≤ 0.001). The MDCT depicted more rod inserts than the FPCT did. No significant geometric distortion was detected in either modality. The FPCT was more prone to artifacts around Krischner wires with a diameter of 2 mm (P = 0.05-0.001), whereas the MDCT showed a higher amount of artifacts around wires with a diameter of 0.8 mm (P ≤ 0.001). Spatial resolution was 1 lp/mm (xy), 1.7 lp/mm (z) for the FPCT and 1 lp/mm (xy), less than 1 lp/mm (z) for the MDCT.We compared a mobile FPCT and a 320-row MDCT by using the same radiation dose for scans. We found the spatial resolution to be higher in the FPCT. Hounsfield units were more accurate and homogeneity and contrast resolution were better in MDCT. The MDCT was also less prone to artifacts from thick Kirschner wires but showed comparably more artifacts around thin wires.

Dental radiographic imaging is slowly transferring to digital format. The decision to invest in this new technology should be based on a good understanding of the different types of digital imaging available within the dental field. This article outlines its use in general dental practice, highlighting the pros and cons of the various systems both for intra-oral and extra-oral radiography. Clinical Relevance: An understanding of the mechanisms of digital imaging and their associated potential problems are required by any clinician moving to film-less imaging.

The purpose of this study is to evaluate the accuracy and reproducibility of the IsoCal geometric calibration system for kilovoltage (kV) and megavoltage (MV) imagers on Varian C‐series linear accelerators (linacs). IsoCal calibration starts by imaging a phantom and collimator plate using MV images with different collimator angles, as well as MV and kV images at different gantry angles. The software then identifies objects on the collimator plate and in the phantom to determine the location of the treatment isocenter and its relation to the MV and kV imager centers. It calculates offsets between the positions of the imaging panels and the treatment isocenter as a function of gantry angle and writes a correction file that can be applied to MV and kV systems to correct for those offsets in the position of the panels. We performed IsoCal calibration three times on each of five Varian C‐series linacs, each time with an independent setup. We then compared the IsoCal calibrations with a simplified Winston‐Lutz (WL)‐based system and with a Varian cubic phantom (VC)‐based system. The maximum IsoCal corrections ranged from 0.7 mm to 1.5 mm for MV and 0.9 mm to 1.8 mm for kV imagers across the five linacs. The variations in the three calibrations for each linac were less than 0.2 mm. Without IsoCal correction, the WL results showed discrepancies between the treatment isocenter and the imager center of 0.9 mm to 1.6 mm (for the MV imager) and 0.5 mm to 1.1 mm (for the kV imager); with IsoCal corrections applied, the differences were reduced to 0.2 mm to 0.6 mm (MV) and 0.3 mm to 0.6 mm (kV) across the five linacs. The VC system was not as precise as the WL system, but showed similar results, with discrepancies of less than 1.0 mm when the IsoCal corrections were applied. We conclude that IsoCal is an accurate and consistent method for calibration and periodic quality assurance of MV and kV imaging systems. PACS numbers: 87.55.Qr, 87.56.Fc

Purpose: The purpose of this study was to gain insight into the distribution and application of digital intraoral radiographic techniques within general dental practices and to compare these with film-based systems in terms of patient dose reduction. Materials and Methods: 1100 questionnaires were handed out to general dental practitioners. Data was analyzed with respect to the type of system by using descriptive statistics and nonparametric tests, i. e. Kruskal-Wallis, Mann-Whitney and chi-square test (SPSS 20). Results: 64 % of the questioned dentists still use film-based radiology, 23 % utilize storage phosphor plate (SPP) systems and 13 % use a charge-coupled device (CCD). A strong correlation between the number of dentists working in a practice and the use of digital dental imaging was observed. Almost 3/4 of the film users work with E- or F-speed film. 45 % of them refuse to change to a digital system. The use of lead aprons was popular, while only a minority preferred thyroid shields and rectangular collimators. A fourfold reduction of exposure time from D-speed film to CCD systems was observed. Due to detector size and positioning errors, users of CCD systems take significantly more single-tooth radiographs in total. Considering the number of radiographs per patient, there is only a slight tendency towards more X-rays with CCD systems. Up to image generation, digital systems seem to be as or even more difficult to handle than film-based systems, while their handling was favored after radiographic exposure. Conclusion: Despite a slight increase of radiographs taken with CCD systems, there is a significant dosage reduction. Corresponding to the decrease in exposure time, the patient dose for SPP systems is reduced to one half compared to film. The main issues in CCD technology are positioning errors and the size of the X-ray detectors which are difficult to eliminate. The usage of radiation protection measures still needs to be improved. Key Points: • Responsible use of digital intraoral radiology results in a significant dose reduction in everyday practice. • The ALARA principle is only achieved by strict implementation of dose-reducing methods. • The efforts to use dose-reducing devices must be increased. Citation Format: • Anissi HD, Geibel MA. Intraoral Radiology in General Dental Practices – A Comparison of Digital and Film-Based X-Ray Systems with Regard to Radiation Protection and Dose Reduction. Fortschr Rontgenstr 2014; 186: 762 – 767

Quality assurance (QA) is essential in dental radiography. Digital radiography is becoming more common in dentistry, so it is important that appropriate QA tests are carried out on the digital equipment, including the viewing monitor. The aim of this article is to outline the tests that can be carried out in dental practice. Clinical Relevance: Quality assurance for digital equipment is important to ensure consistently high quality images are produced.

BACKGROUND AND PURPOSE: Flat detector CT has been increasingly used as a follow-up examination after endovascular intervention. Metal artifact reduction has been successfully demonstrated in coil mass cases, but only in a small series. We attempted to objectively and subjectively evaluate the feasibility of metal artifact reduction with various metallic objects and coil lengths. MATERIALS AND METHODS: We retrospectively reprocessed the flat detector CT data of 28 patients (15 men, 13 women; mean age, 55.6 years) after they underwent endovascular treatment (20 coiling ± stent placement, 6 liquid embolizers) or shunt drainage ( n = 2) between January 2009 and November 2011 by using a metal artifact reduction correction algorithm. We measured CT value ranges and noise by using region-of-interest methods, and 2 experienced neuroradiologists rated the degrees of improved imaging quality and artifact reduction by comparing uncorrected and corrected images. RESULTS: After we applied the metal artifact reduction algorithm, the CT value ranges and the noise were substantially reduced (1815.3 ± 793.7 versus 231.7 ± 95.9 and 319.9 ± 136.6 versus 45.9 ± 14.0; both P < .001) regardless of the types of metallic objects and various sizes of coil masses. The rater study achieved an overall improvement of imaging quality and artifact reduction (85.7% and 78.6% of cases by 2 raters, respectively), with the greatest improvement in the coiling group, moderate improvement in the liquid embolizers, and the smallest improvement in ventricular shunting (overall agreement, 0.857). CONCLUSIONS: The metal artifact reduction algorithm substantially reduced artifacts and improved the objective image quality in every studied case. It also allowed improved diagnostic confidence in most cases. ### Abbreviations CCF : carotid cavernous fistula FDCT : flat detector CT MAR : metal artifact reduction HU : Hounsfield unit

Objectives: The aim of this in vitro study was to compare the diagnostic accuracy of different radiographic imaging modalities in detecting occlusal caries lesions. Materials and Methods: Under standardized conditions, 125 extracted human permanent molar teeth with sound or occlusal caries lesions were radiographed using a conventional film system (F-speed), a direct digital imaging system (complementary metal oxide semiconductor sensor), an indirect digital imaging system (photostimulable phosphor plate) and a cone beam computed tomography system (CBCT). Two observers scored the resultant images for the presence or absence of caries. Then, the teeth were histologically prepared and a definite diagnosis was determined by stereomicroscopic assessment. The area under the receiver operating characteristic curve (Az), sensitivity, specificity and accuracy of each imaging modality were calculated, as well as the intra- and interexaminer reproducibility. Results: For both thresholds, interexaminer agreement were higher for CBCT. For intraexaminer agreement, observers had different scores for both thresholds, but the scores were generally higher for CBCT. Similar Az values were achieved with all imaging methods at a diagnostic D1 threshold. The Az values of the CBCT system were found to be statistically higher than those of the other imaging modalities at a diagnostic D3 threshold (p > 0.05); no significant differences were found among the other imaging modalities. All radiographic methods showed similar sensitivities, specificities and accuracy in detecting D1 threshold. The CBCT system showed higher sensitivity and accuracy in detecting dentine lesions. Conclusions: Within the limitations of this study, CBCT exhibited better performance in detecting deep occlusal caries lesions than the other radiographic systems.

SUMMARY: Radiologic assessment of cochlear implants can be limited because of metallic streak artifacts and the high attenuation of the temporal bones. We report on 14 patients with 18 cochlear implants (17 Med-El standard 31.5-mm arrays, 1 Med-El medium 24-mm array) who underwent flat panel CT with the use of high-resolution secondary reconstruction techniques. Flat panel CT depicted the insertion site, cochlear implant course, and all 216 individual electrode contacts. The calculated mean angular insertion depth for standard arrays was 591.9° (SD = 70.9; range, 280°). High-resolution secondary reconstructions of the initial flat panel CT dataset, by use of a manually generated field of view, Hounsfield unit kernel type, and sharp image characteristics, provided high-quality images with improved spatial resolution. Flat panel CT is a promising imaging tool for the postoperative evaluation of cochlear implant placement.

The radiation risk of patients undergoing invasive cardiology remains considerable and includes skin injuries and cancer. To date, submillisievert coronary angiography has not been considered feasible.In 2011, we compared results from 100 consecutive patients undergoing elective coronary angiography using the latest-generation flat-panel angiography system (FPS) with results from examinations by the same operator using 106 historic controls with a conventional image-intensifier system (IIS) that was new in 2002.The median patient exposure parameters were measured as follows: dose-area product (DAP) associated with radiographic cine acquisitions (DAP(R)) and fluoroscopy (DAP(F)) scenes, radiographic frames and runs, and cumulative exposure times for radiography and fluoroscopy. On the FPS as compared to the traditional IIS, radiographic detector entrance dose levels were reduced from 164 to 80 nGy/frame and pulse rates were lowered from 12.5/s to 7.5/s during radiography and from 25/s to 4/s during fluoroscopy. The cardiologist's performance patterns remained comparable over the years: fluoroscopy time was constant and radiography time even slightly increased. Overall patient DAP decreased from 7.0 to 2.4 Gy × cm(2); DAP(R), from 4.2 to 1.7 Gy × cm(2); and DAP(F), from 2.8 to 0.6 Gy × cm(2). Time-adjusted DAP(R)/s decreased from 436 to 130 mGy × cm(2) and DAP(F)/s, from 21.6 to 4.4 mGy × cm(2). Cumulative patient skin dose with the FPS amounted to 67 mGy, and the median (interquartile range) of effective dose was 0.5 (0.3 … 0.7) mSv.Consistent application of radiation-reducing techniques with the latest-generation flat-panel systems enables submillisievert coronary angiography in invasive cardiology.

This study investigated the feasibility of using intra-arterial injection-based cerebral blood volume (CBV) imaging with flat detector computed tomography (CT, IAFD-CBV). It is proven that this new method could provide comparable physiologic information as standard intravenous injection-based multi-slice computed tomography CBV imaging (IVCT-CBV). Twelve patients were examined using both IAFD-CBV and IVCT-CBV. An experienced neuroradiologist read both sets of generated CBV maps. If a physiologic perfusion disorder was detected in standard IVCT-CBV, the focus was to check whether IAFD-CBV indicated the same disorder or not. Otherwise, if no disorder was detected, relative CBV (rCBV) values at different basal ganglia regions were measured for both CBV maps and then compared. For three patients with lesions, IAFD-CBV and IVCT-CBV showed similar perfusion disorders in the corresponding regions. For nine patients without lesions, both CBV maps showed good symmetry of contrast agent (CA) distribution for left/right hemisphere, the total average of rCBV was found to be 0.94 –/+0.18 and 1.01 –/+0.14 (1.0 for perfect symmetry) in IAFD-CBV and IVCT-CBV, respectively. However, compared to IVCT-CBV, IAFD-CBV imaging required 70% less contrast agent (CA). In general, a good correlation between IAFD-CBV and IVCT-CBV was found for all 12 patients. Minor deviations of IAFD-CBV were only detected at regions supplied by the middle cerebral artery. IAFD-CBV imaging, which can be directly performed in a catheterization laboratory, was proven to be technically feasible for real-time CBV assessment of the whole brain with good accuracy, and minimized CA usage.

Objective To compare the detectability of simulated pulmonary nodules on chest radiographs between an irradiation side sampling indirect flat-panel detector (ISS-FPD) and computed radiography (CR). Materials and methods This study was an observer performance study. Simulated pulmonary nodules of 8 mm in diameter were superimposed on an anthropomorphic chest phantom. Chest radiographs were acquired under 2 exposure levels (4 and 3.2 mAs) with the ISS-FPD and the CR. Six thoracic radiologists evaluated all 40 images (10 patterns × 2 different exposure doses × 2 different systems) for the presence or absence of a lesion over each of 12 defined areas on a 3-megapixel monochrome liquid-crystal display. Receiver operating characteristic (ROC) curves were obtained for observation in predefined 480 areas. A jackknife method was used for statistical analysis. Differences with a P value of Results The analysis of the observer detection of simulated pulmonary nodules showed larger areas under the ROC curve (AUC) by the ISS-FPD than by the CR. There was a statistically significant difference between the two systems at 3.2 mAs ( P = 0.0330). Conclusion The ISS-FPD was superior to the CR for the detection of simulated pulmonary nodules at 3.2 mAs.

OBJECTIVES: To measure the reliability of tooth length measurements taken using dental pantomograms (DPT), long cone periapical radiographs (PR), and cone beam computed tomography (CBCT) and to compare their effective radiation dose. SUBJECTS AND METHODS: A model containing sixteen anterior teeth was used to simulate a patient undergoing fixed appliance treatment. PRs were taken at standardized vertical angulations to the occlusal plane (0, 5, 10, 15, and 20°) using conventional and digital techniques. DPT and CBCT images were also taken. Measurements of radiation dosages were used to estimate a risk benefit analysis for each of the techniques. RESULTS: DPT consistently overestimated tooth lengths by 2 mm or more [mean: 2·34 mm; 95% confidence interval (CI): 1·4-3·3 mm]. CBCT consistently underestimated tooth length (mean: -0·89 mm; 95% CI: -0·44 to -1·33 mm). PRs taken at 90° angulation closely resembled the actual tooth length (mean: -0·14 mm; 95% CI: -0·64 to 0·37 mm), but overestimation occurred with increasing PR film angulation. The radiation dosages ranged widely: DPT plus eight PRs that would be necessary to assess all teeth and root length of the upper and lower labial segments amounted to 23 μSv. Radiation dose from CBCT ranged from 17·8 to 60 μSv, depending on equipment and settings.

Objective This study examined the effect of basic fibroblast growth factor (FGF)-2 with an absorbable collagen sponge on angiogenesis and bone regeneration in rat calvarial critical-sized bone defects using microcomputed tomography. Methods Forty 7-week-old male Fischer rats were used. The symmetrical critical-sized calvarial bone defects (5 mm diameter) were created. An absorbable collagen sponge with or without FGF-2 (0.1% or 0.3%) was implanted into each bone defect. Results Blood vessel and bone volumes were significantly higher in the 0.3% FGF-2 group compared with the control and 0.1% FGF-2 groups on day 28. Significantly more osteoblast- and osteoclast-like cells were seen in the 0.3% FGF-2 group. Conclusions Thus, FGF-2 increased blood vessel and bone formation in rat calvarial critical-sized bone defects.

Purpose This retrospective study investigated 3-dimensional (3D) imaging with intraoperative Cone-Beam Computed Tomography (CBCT) in Mandibular Angle Fractures (MAF) treated by open reduction. The aim of this study was to demonstrate the image quality of intraoperative CBCT in this region and the benefit for the patients. Methods 83 patients with 86 MAF were included in this study. 8 patients were female and 75 male. Patient age ranged from 11 to 68 years (average age 26.8 years). All patients were examined with the mobile CBCT scanner ARCADIS Orbic 3D (Siemens Medical Solutions, Erlangen, Germany) directly after surgical treatment of the MAF. Results As a direct result of intraoperative CBCT four patients (5%) underwent intraoperative revision. The intraoperative acquisition of the data sets was uncomplicated and in all cases it was possible to effectively visualise and assess the MAF in 3D quality. Conclusion The results showed that intraoperative CBCT is a reliable imaging technique for real-time intraoperative assessment of treated MAF. Use of the mobile 3D CBCT scanner is easy to integrate into routine practice and offers the advantage that immediate revision surgery can be performed.

Iodinated and gadolinium contrast agents pose some risk for certain pediatric patients, including allergic-like reactions, contrast-induced nephropathy (CIN) and nephrogenic systemic fibrosis (NSF). Digital flat-panel detectors enhance image quality during angiography and might allow use of more dilute contrast material to decrease risk of complications that might be dose-dependent, such as CIN and NSF. To assess the maximum dilution factors for iodine- and gadolinium-based contrast agents suitable for vascular imaging with fluoroscopy and digital subtraction angiography (DSA) on digital flat-panel detectors in an animal model. We performed selective catheterization of the abdominal aorta, renal artery and common carotid artery on a rabbit. In each vessel we performed fluoroscopy and DSA during contrast material injection using iodinated and gadolinium contrast material at 100%, 80%, 50%, 33% and 20% dilutions. An image quality score (0 to 3) was assigned by each of eight evaluators. Intracorrelation coefficient, paired t-test, one-way repeated analysis of variance, Spearman correlation and receiver operating characteristic curve analysis were applied to the data. Overall the image quality scores correlated linearly with dilution levels. For iodinated contrast material, the optimum cut-off level for DSA when a score of at least 2 is acceptable is above 33%; it is above 50% when a score of 3 is necessary. For gadolinium contrast material, the optimum cut-off for DSA images is above 50% when a score of at least 2 is acceptable and above 80% when a score of 3 is necessary. Knowledge of the relationship between image quality and contrast material dilution might allow a decrease in overall contrast load while maintaining appropriate image quality when using digital flat-panel detectors.