Modern fluoroscopes used for image guidance have become quite complex. Adding to this complexity are the many regulatory and accreditation requirements that must be fulfilled during acceptance testing of a new unit. Further, some of these acceptance tests have pass/fail criteria, whereas others do not, making acceptance testing a subjective and time-consuming task. The AAPM Task Group 272 Report spells out the details of tests that are required and gives visibility to some of the tests that while not yet required are recommended as good practice. The organization of the report begins with the most complicated fluoroscopes used in interventional radiology or cardiology and continues with general fluoroscopy and mobile C-arms. Finally, the appendices of the report provide useful information, an example report form and topics that needed their own section due to the level of detail.

To compare image quality, radiation and contrast doses required to obtain 3D‐Digital subtraction rotational angiography (3D‐DSRA) with 3D‐Digital rotational angiography (3D‐DRA) in infants (children ≤ 2 years of age) and adults with congenital heart diseases (ACHD).

Objectives The aim of this study was to evaluate the effectiveness of UltraBLOX™ radiation attenuating hand cream during lengthy cardiac catheterization procedures in children. Background The hands of interventional cardiologists receive high doses of radiation due to their proximity to the X‐ray beam. Radiation attenuating gloves have about a 26% attenuation rate, but reduce dexterity and tactile sensation. The UltraBLOX™ cream is a new FDA‐approved X‐ray attenuating cream that can be applied to the operator's hands for radio‐protection. Methods Two nanoDot™ dosimeters were secured side by side on the dorsum of the operator's ( n = 2) left hand close to the wrist. One dosimeter and the rest of the hand were covered with 0.2 mm layer of the cream. The other dosimeter was unshielded. Procedures were performed using 110 kVp fluoroscopy at 15 pulses/sec. The measurements were categorized into four groups dependent on the duration of the procedure. The patients in all four groups were well matched for age and size. Results Procedural and cumulative hand radiation doses were higher with longer procedural duration. The overall % attenuation by the cream was 39.7% (28.6–51.5) and was unaffected by the length of the procedure (median: 40.9% at 30 min and 41.4% at 180 min; P = 0.66) or the dose of radiation. The kappa statistic for interobserver agreement for good tactile sensitivity was 0.82. Conclusions UltraBLOX™ cream provides a new option for radio‐protection for the hands of interventional cardiologists without impairing tactile sensitivity. There was no decrease in attenuation up to 180 min. © 2016 Wiley Periodicals, Inc.

BACKGROUND:Three-dimensional rotational angiography (3DRA) offers more detailed anatomic information than 2D digital acquisition (2DDA). Concerns over potentially higher contrast and radiation doses have limited its routine use.OBJECTIVE:The primary objective of this study was to compare radiation doses required to obtain 3DRA using a customized low dose radiation protocol with 2DDA. The secondary objective was to compare total procedural radiation in pediatric cardiac catheterization procedures utilizing 3DRA to those that do not.STUDY DESIGN:Phantom studies were conducted to establish customized 3DRA protocols for radiation reduction. Comparison of 3DRA and non-3DRA procedures in age-, size- and diagnosis-matched controls was performed. Radiation doses were indexed to body surface area (BSA) to account for differing body habitus as validated from the phantom study.RESULTS:Study (n = 100) and control (n = 100) groups were matched for age (10.2 vs. 9.98 years; P = .239) and BSA (1.23 vs. 1.09 m2 ; P = .103). The dose area product (DAP) to acquire a 3DRA was similar to a 5 s, 15 frames/second 2DDA (278 vs. 241 cGy/cm2 ; P = .14). Despite the 3DRA group consisting of more complex interventions, no difference was found in the total procedural Air Kerma and DAP indexed to BSA (244 vs. 249 mGy/m2 ; P = .79 and 3348 vs. 3176 cGy/cm2 /m2 ; P = .48, respectively). The contrast volume to acquire a 3DRA compared to a 2DDA was greater (1.59 vs. 1.01 mL/kg; P < .001). However, no difference was found for the entire procedure (3.8 vs. 4 mL/kg, P = .494). This could have resulted from the need to obtain multiple 2DDAs to achieve the detail of a single 3DRA (11 vs. 7 per study; P < .001).CONCLUSIONS:When 3DRA, using the proposed protocols is employed, total procedural contrast and radiation doses are comparable with the sole use of biplane cine-angiograms. These protocols may allow for routine use of 3DRA for congenital cardiac catheterizations.

A high resolution x-ray imaging system designated the solid state x-ray image intensifier (SSXII) is being developed as a potential replacement of conventional lower-resolution x-ray detectors for neurovascular interventions. The SSXII consists of a CsI(Tl) phosphor to convert x-rays to light, a fiber optic taper to extend the field-of-view and to couple the phosphor to an Electron-Multiplying CCD (EMCCD) which has a built-in gain to boost the signal above the read-out noise floor. A parallel cascade linear-system model is explored and applied to quantitatively analyze the signal and noise transfer at each stage, and optimize the detector performance. The modulation transfer function (MTF), detective quantum efficiency (DQE) and frequency dependent instrumentation noise equivalent exposure (INEE) can be obtained from the theoretical model and experimental measurement. Agreement of these results validates the effectiveness of the model. Finally, compared with the traditional flat-panel detector (FPD), the SSXII exhibits better performance with higher spatial resolution, higher DQE and lower INEE.

A new Graphical User Interface (GUI) was developed using Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW) for a high-resolution, high-sensitivity Solid State X-ray Image Intensifier (SSXII), which is a new x-ray detector for radiographic and fluoroscopic imaging, consisting of an array of Electron-Multiplying CCDs (EMCCDs) each having a variable on-chip electron-multiplication gain of up to 2000x to reduce the effect of readout noise. To enlarge the field-of-view (FOV), each EMCCD sensor is coupled to an x-ray phosphor through a fiberoptic taper. Two EMCCD camera modules are used in our prototype to form a computer-controlled array; however, larger arrays are under development. The new GUI provides patient registration, EMCCD module control, image acquisition, and patient image review. Images from the array are stitched into a 2kx1k pixel image that can be acquired and saved at a rate of 17 Hz (faster with pixel binning). When reviewing the patient's data, the operator can select images from the patient's directory tree listed by the GUI and cycle through the images using a slider bar. Commonly used camera parameters including exposure time, trigger mode, and individual EMCCD gain can be easily adjusted using the GUI. The GUI is designed to accommodate expansion of the EMCCD array to even larger FOVs with more modules. The high-resolution, high-sensitivity EMCCD modular-array SSXII imager with the new user-friendly GUI should enable angiographers and interventionalists to visualize smaller vessels and endovascular devices, helping them to make more accurate diagnoses and to perform more precise image-guided interventions.

We evaluate a new method for measuring the presampled modulation transfer function (MTF) using the noise power spectrum (NPS) obtained from a few flat-field images acquired at one exposure level. The NPS is the sum of structure, quantum, and additive instrumentation noise, which are proportional to exposure squared, exposure, and a constant, respectively, with the spatial-frequency dependence of the quantum noise depending partly on the detector MTF. Cascaded linear-systems theory was used to derive an exact and generic relationship that was used to isolate noise terms and enable determination of the MTF directly from the noise response, thereby circumventing the need for precision test objects (slit, edge, etc.) as required by standard techniques. Isolation of the quantum NPS by fitting the total NPS versus exposure obtained using 30 flat-field images each at six or more different exposure levels with a linear regression provides highly accurate MTFs. A subset of these images from indirect digital detectors was used to investigate the accuracy of measuring the MTF from 30 or fewer flat-field images obtained at a single exposure level. Analyzing as few as two images acquired at a single exposure resulted in no observable systematic error. Increasing the number of images analyzed resulted in an increase in accuracy. Fifteen images provided comparable accuracy with the most rigorous slope approach, with less than 5% variability, suggesting additional image acquisitions may be unnecessary. Reducing the number of images acquired for the noise response method further simplifies and facilitates routine MTF measurements.

Purpose: The Control, Acquisition, Processing, and Image Display System (CAPIDS) for the Micro-Angiographic Fluoroscope (MAF) has been upgraded and is being evaluated for hospital clinical use. Method and Materials: The CAPIDS was developed and implemented using Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW) and provides a user-friendly interface that enables control of several clinical radiographic imaging modes of the MAF, including fluoroscopy, roadmapping, radiography, and digital-subtraction-angiography (DSA). The MAF is a high-resolution, high-sensitivity, real-time imager which consists of a 300 |im-thick CsI phosphor, a dual-stage micro-channel plate light image intensifier (LII) coupled to a fiber-optic taper (FOT), and a frame-transfer CCD camera, providing an image matrix of 1024×1024 35-μm square pixels with 12-bit depth. The region-of-interest (ROI) MAF can be inserted in front of a standard large field-of-view, standard-resolution flat-panel-detector (FPD) using a detector changer when higher resolution is needed during angiographic or interventional vascular imaging procedures. Several new features were added to CAPIDS including: saving DSA images as the mask for Roadmap mode, LII gain-drift correction, direct saving of patient images, and real-time window/level correction. Results: The upgraded CAPIDS has been used effectively for image guidance in over 10 rabbit aneurysm creation and treatment experiments, demonstrating the system's potential benefits for future clinical use. The CAPIDS controlled MAF increases the resolution of the x-ray image compared to a conventional FPD and thus should increase the accuracy of interventional procedures. Conclusion: The upgraded CAPIDS for the MAF was modified and used in pre-clinical interventional experiments. This upgrade enables the CAPIDS-MAF imaging system to perform in most common clinical x-ray imaging modes including: fluoroscopy, roadmapping, radiography, and DSA. The system is being evaluated for adaptation into a hospital-based clinical interventional suite. (Supported by: NIH Grants NIH Grant R01NS43924, R01-EB002873)

The low electronic noise, high resolution, and good temporal performance of electron-multiplying CCDs (EMCCDs) are ideally suited for applications traditionally served by x-ray image intensifiers. In order to improve an expandable clinical detector's field-of-view and have full control of the system performance, we have successfully built a solid-state x-ray detector. The photon transfer technique was used to quantify the EMCCD quantum performance in terms of sensitivity (or camera gain constant, K), read noise (RN), full-well capacity (FW), and dynamic range (DR). Measured results show the system maintains a K of 11.3 ± 0.9 e-/DN at unit gain, with a read noise of 71.5±6.0 e- rms at gain 1, which decreases proportionally with higher gains. The full well capacity was measured to be 31.3±2.7 ke-, providing a dynamic range of 52.8±0.7 dB using the chip manufacturer specified clocking scheme. Similar performance was measured with other commercial camera systems. The manufacturer data sheet indicates a dynamic range of 66 dB is plausible with improved read noise and full well capacity. Different clocking schemes are under investigation to assess their impact on improving performance towards idealized values. EMCCD driver clock voltage levels were adjusted individually to check the influence on quantum performance. The clocks work to transfer charge from the image area to readout amplifier through the storage area, horizontal and multiplication registers. Results indicate that the clock that contributes to lateral overflow drain bias is essential to the system performance in terms of dynamic range and full well capacity. The serial register clocks used for transporting charge stored in the pixels of the memory lines to the output amplifier had the largest effect on RN, while others had less of an impact. Initial adjustment of these clocks resulted in a variability of 16% in the performance of dynamic range- - , 38% in read noise and 56% in full well capacity. Quantifying the quantum performance provides valuable insight into overall performance and enables optimal adjustment of the clocking scheme. Further improvements are expected.

PURPOSE:The authors describe a new technique to determine the system presampled modulation transfer function (MTF) in digital radiography using only the detector noise response.METHODS:A cascaded-linear systems analysis was used to develop an exact relationship between the two-dimensional noise power spectrum (NPS) and the presampled MTF for a generalized detector system. This relationship was then utilized to determine the two-dimensional presampled MTF. For simplicity, aliasing of the correlated noise component of the NPS was assumed to be negligible. Accuracy of this method was investigated using simulated images from a simple detector model in which the "true" MTF was known exactly. Measurements were also performed on three detector technologies (an x-ray image intensifier, an indirect flat panel detector, and a solid state x-ray image intensifier), and the results were compared using the standard edge-response method. Flat-field and edge images were acquired and analyzed according to guidelines set forth by the International Electrotechnical Commission, using the RQA 5 spectrum.RESULTS:The presampled MTF determined using the noise-response method for the simulated detector system was in close agreement with the true MTF with an averaged percent difference of 0.3% and a maximum difference of 1.1% observed at the Nyquist frequency (fN). The edge-response method of the simulated detector system also showed very good agreement at lower spatial frequencies (less than 0.5 fN) with an averaged percent difference of 1.6% but showed significant discrepancies at higher spatial frequencies (greater than 0.5 fN) with an averaged percent difference of 17%. Discrepancies were in part a result of noise in the edge image and phasing errors. For all three detector systems, the MTFs obtained using the two methods were found to be in good agreement at spatial frequencies less than 0.5 fN with an averaged percent difference of 3.4%. Above 0.5 fN, differences increased to an average of 20%. Deviations of the experimental results largely followed the trend seen in the simulation results, suggesting that differences between the two methods could be explained as resulting from the inherent inaccuracies of the edge-response measurement technique used in this study. Aliasing of the correlated noise component was shown to have a minimal effect on the measured MTF for the three detectors studied. Systems with significant aliasing of the correlated noise component (e.g., a-Se based detectors) would likely require a more sophisticated fitting scheme to provide accurate results.CONCLUSIONS:Results indicate that the noise-response method, a simple technique, can be used to accurately measure the MTF of digital x-ray detectors, while alleviating the problems and inaccuracies associated with use of precision test objects, such as a slit or an edge.

Purpose: We report on new advancements with a solid state x-ray image intensifier (SSXII) to expand the field-of-view (FOV) and improve detector performance. Method and Materials: The SSXII is a new high-resolution, high-sensitivity radiographic and fluoroscopic imager based on electron-multiplying CCDs (EMCCDs), which views a CsI:Tl phosphor through a fiber optic taper (FOT). The SSXII has demonstrated the capabilities to significantly improve upon the inherent limitations of current state-of-the-art x-ray image intensifiers and dynamic flat panel detectors (FPD), with superior performance in terms of MTF, instrumentation noise, and DQE. To expand the FOV, a modular array has been constructed. The EMCCD camera electronics have been designed to enable a 2 × 2 abuttable array configuration. The 27 mm center-to-center distance enables use of 3.4:1 magnification ratio FOTs, thereby providing a FOV of 5.44 × 5.44 cm (an increase in area of 290% over the initial single module prototype). Larger arrays can be constructed. Performance of this next generation SSXII was extrapolated based on measured MTFs and transmission efficiencies of the individual components that comprise the detector. Results: Calculations indicate an averaged improvement in the MTF of a factor of 1.2 across the higher spatial-frequency range (5 to 10 cycles/mm). X-ray sensitivities are expected to increase by 40% due to a reduction in the FOT magnification ratio (from 4:1 to 3.4:1). The instrumentation noise equivalent exposure (INEE) was calculated to decrease from 0.2 to 0.03 μR, which is two orders of magnitude lower than present FPDs. The DQE was determined to improve by an averaged factor of 2.2 from 5 to 10 cycles/mm. Conclusions: With an expanded FOV, the SSXII is a promising candidate to replace existing state-of-the-art detectors, providing improved resolution, lower instrumentation noise, and better signal-to-noise ratio performance. (Support: NIH Grant RO1EB008425)

The new Solid State X-Ray Image Intensifier (SSXII) has the unique ability to operate in single photon counting (SPC) mode, with improved resolution, as well as in traditional energy integrating (EI) mode. The SSXII utilizes an electron-multiplying CCD (EMCCD), with an effective pixel size of 32μm, which enables variable signal amplification (up to a factor of 2000) prior to digital readout, providing very high-sensitivity capabilities. The presampled MTF was measured in both imaging modes using the standard angulated-slit method. A measured detector entrance exposure of 24μR per frame was used to provide approximately 0.8 interaction events per pixel in the 10μm-wide slit area. For demonstration purposes, a simple thresholding technique was used to localize events in SPC mode and a number of such frames were summed to provide an image with the same total exposure used for acquiring the EI image. The MTF for SPC mode, using a threshold level of 15% of the maximum 12-bit signal and 95% of the expected events, and for EI mode (in parentheses) was 0.67 (0.20), 0.37 (0.07), 0.20 (0.03), and 0.11 (0.01) at 2.5, 5, 7.5, and 10 cycles/mm, respectively. Increasing the threshold level resulted in a corresponding increase in the measured SPC MTF and a lower number of detected events, indicating a tradeoff between resolution and count efficiency is required. The SSXII in SPC mode was shown to provide substantial improvements in resolution relative to traditional EI mode, which should benefit applications that have demanding spatial resolution requirements, such as mammography.

The Solid-State X-ray Image Intensifier (SSXII) is a novel dynamic x-ray imager, based on an array of electron-multiplying CCDs (EMCCDs), that can significantly improve performance compared to conventional x-ray image intensifiers (XIIs) and flat panel detectors (FPDs). To expand the field-of-view (FOV) of the SSXII detectors while maintaining high resolution, a scalable component level modular design is presented. Each module can be fit together with minimum dead-space and optically coupled to one contiguous x-ray converter plate. The electronics of each of the modules consists of a detachable head-board, on which is mounted the EMCCD, and a driver board. The size of the head-boards is minimized to ensure that the modules fit together properly. The driver boards connect with the head-boards via flat cables and are designed to be plugged into the main mother-board that contains an FPGA chip that generates the driving clock signals for the EMCCDs and analog-to-digital converter (ADC). At the front-end, a high speed ADC on each of the driver boards samples and digitizes the EMCCD analog output signal and an extensible modular digital multiplexer back-end is used to acquire and combine image data from multiple modules. The combined digital data is then transmitted to a PC via a standard Camera Link interface. Eventually, this modular design will be extended to a 3×3 or larger array to accomplish full clinical FOVs and enable the SSXII to replace conventional lower-resolution XIIs or FPDs.