Microangiographic Fluoroscope Research Articles

Comparison of High Resolution X-Ray detectors with Conventional FPDs using Experimental MTFs and Apodized Aperture Pixel Design for Reduced Aliasing.

Apodized Aperture Pixel (AAP) design, proposed by Ismailova et. al, is an alternative to the conventional pixel design1. The advantages of AAP processing with a sinc filter in comparison with using other filters include non-degradation of MTF values and elimination of signal and noise aliasing, resulting in an increased performance at higher frequencies, approaching the Nyquist frequency3. If high resolution small field-of-view (FOV) detectors with small pixels used during critical stages of Endovascular Image Guided Interventions (EIGIs) could also be extended to cover a full field-of-view typical of flat panel detectors (FPDs) and made to have larger effective pixels, then methods must be used to preserve the MTF over the frequency range up to the Nyquist frequency of the FPD while minimizing aliasing. In this work, we convolve the experimentally measured MTFs of an Microangiographic Fluoroscope (MAF) detector, (the MAF-CCD with 35μm pixels) and a High Resolution Fluoroscope (HRF) detector (HRF-CMOS50 with 49.5μm pixels) with the AAP filter and show the superiority of the results compared to MTFs resulting from moving average pixel binning and to the MTF of a standard FPD. The effect of using AAP is also shown in the spatial domain, when used to image an infinitely small point object. For detectors in neurovascular interventions, where high resolution is the priority during critical parts of the intervention, but full FOV with larger pixels are needed during less critical parts, AAP design provides an alternative to simple pixel binning while effectively eliminating signal and noise aliasing yet allowing the small FOV high resolution imaging to be maintained during critical parts of the EIGI.

WE‐DE‐207A‐04: Advances in Radiological Neuro‐Endovascular Interventional Imaging

WE‐DE‐207A‐04: Advances in Radiological Neuro‐Endovascular Interventional Imaging

WE‐DE‐207A‐02: Advances in Cone Beam CT Anatomical and Functional Imaging in Angio‐Suite to Enable One‐Stop‐Shop Stroke Imaging Workflow

WE‐DE‐207A‐02: Advances in Cone Beam CT Anatomical and Functional Imaging in Angio‐Suite to Enable One‐Stop‐Shop Stroke Imaging Workflow

WE‐DE‐207A‐03: Recent Advances in Devices Used in Neuro‐‐Interventions

WE‐DE‐207A‐03: Recent Advances in Devices Used in Neuro‐‐Interventions

WE‐DE‐207A‐01: Parallels in the Evolution of X‐Ray Angiographic Systems and Devices Used for Minimally Invasive Endovascular Therapy

WE‐DE‐207A‐01: Parallels in the Evolution of X‐Ray Angiographic Systems and Devices Used for Minimally Invasive Endovascular Therapy

WE‐DE‐207A‐00: Advances in Image‐Guided Neurointerventions‐Clinical Pull and Technology Push

WE‐DE‐207A‐00: Advances in Image‐Guided Neurointerventions‐Clinical Pull and Technology Push

SU‐C‐209‐01: Validation of the Simulated Detectability Metric (G‐ROD) Using the Experimental Generalized Measured Relative Object Detectability Metric (GM‐ROD)

Purpose:The Generalized Relative Object Detectability (G‐ROD) family of ideal observer metrics are a well‐characterized set of task‐based metrics used for quantitatively comparing imaging systems that include the detector, focal spot geometry and scatter characteristics on the basis of system abilities in imaging a given simulated object. The G‐ROD metric takes the integral over spatial frequencies of the Fourier transform of a simulated object function weighted with the detector generalized DQE (GDQE), divided by the comparable integral for another detector. When a measured image of an actual object is used, the generalized measured‐ROD (GM‐ROD) metric can compare detector systems without explicitly determining detector MTF. In this work, the results of simulated and measured ROD calculations for the same object are compared for the first time.Methods:G‐ROD calculations were performed to compare a high resolution microangiographic fluoroscopic (MAF) detector to a flat panel detector (FPD) using 5mm segments of simulated copper wires of varying diameter (d=0.05–0.6mm) as the object function for three different focal spot sizes at two magnifications. A GM‐ROD experiment with similar parameters was performed to compare the same detector system using three actual 5mm copper wires (d=0.113mm,0.238mm,0.558mm) imaged under identical but simulated conditions used in G‐ROD calculations to determine the agreement between simulated and experimentally obtained results.Results:The G‐ROD and GM‐ROD calculations examined relative detector system imaging performance. The GM‐ROD results for all three different sized wires imaged with low magnification and a small focal spot size were 2.1, 1.38, and 1.1, respectively, and the G‐ROD results for the same calculation was 1.81, 1.3, and 1.07, corresponding to percent deviations of 13%, 5.8%, and 2.7%.Conclusion:These results indicate experimental validation of the simulated metric results.Partial support from NIH grant R01EB002873 and an equipment grant from Toshiba Medical Systems Corp.

Quantitative comparison using Generalized Relative Object Detectability (G-ROD) metrics of an amorphous selenium detector with high resolution Microangiographic Fluoroscopes (MAF) and standard flat panel detectors (FPD).

A novel amorphous selenium (a-Se) direct detector with CMOS readout has been designed, and relative detector performance investigated. The detector features include a 25μm pixel pitch, and 1000μm thick a-Se layer operating at 10V/μm bias field. A simulated detector DQE was determined, and used in comparative calculations of the Relative Object Detectability (ROD) family of prewhitening matched-filter (PWMF) observer and non-prewhitening matched filter (NPWMF) observer model metrics to gauge a-Se detector performance against existing high resolution micro-angiographic fluoroscopic (MAF) detectors and a standard flat panel detector (FPD). The PWMF-ROD or ROD metric compares two x-ray imaging detectors in their relative abilities in imaging a given object by taking the integral over spatial frequencies of the Fourier transform of the detector DQE weighted by an object function, divided by the comparable integral for a different detector. The generalized-ROD (G-ROD) metric incorporates clinically relevant parameters (focal-spot size, magnification, and scatter) to show the degradation in imaging performance for detectors that are part of an imaging chain. Preliminary ROD calculations using simulated spheres as the object predicted superior imaging performance by the a-Se detector as compared to existing detectors. New PWMF-G-ROD and NPWMF-G-ROD results still indicate better performance by the a-Se detector in an imaging chain over all sphere sizes for various focal spot sizes and magnifications, although a-Se performance advantages were degraded by focal spot blurring. Nevertheless, the a-Se technology has great potential to provide breakthrough abilities such as visualization of fine details including of neuro-vascular perforator vessels and of small vascular devices.

SU-E-I-53: Comparison of Kerma-Area-Product Between the Micro-Angiographic Fluoroscope (MAF) and a Flat Panel Detector (FPD) as Used in Neuro-Endovascular Procedures

Purpose: To determine the reduction of integral dose to the patient when using the micro-angiographic fluoroscope (MAF) compared to when using the standard flat-panel detector (FPD) for the techniques used during neurointerventional procedures. Methods: The MAF is a small field-of-view, high resolution x-ray detector which captures 1024 × 1024 pixels with an effective pixel size of 35μm and is capable of real-time imaging up to 30 frames per second. The MAF was used in neuro-interventions during those parts of the procedure when high resolution was needed and the FPD was used otherwise. The technique parameters were recorded when each detector was used and the kerma-area-product (KAP) per image frame was determined. KAP values were calculated for seven neuro interventions using premeasured calibration files of output as a function of kVp and beam filtration and included the attenuation of the patient table for the frontal projections to be more representative of integral patient dose. The air kerma at the patient entrance was multiplied by the beam area at that point to obtain the KAP values. The ranges of KAP values per frame were determined for the range of technique parameters used during the clinical procedures. To appreciate the benefit of the higher MAF resolution in the region of interventional activity, DA technique parameters were generally used with the MAF. Results: The lowest and highest values of KAP per frame for the MAF in DA mode were 4 and 50 times lower, respectively, compared to those of the FPD in pulsed fluoroscopy mode. Conclusion: The MAF was used in those parts of the clinical procedures when high resolution and image quality was essential. The integral patient dose as represented by the KAP value was substantially lower when using the MAF than when using the FPD due to the much smaller volume of tissue irradiated. This research was supported in part by Toshiba Medical Systems Corporation and NIH Grant R01EB002873.

WE‐G‐204‐05: Relative Object Detectability Evaluation of a New High Resolution A‐Se Direct Detection System Compared to Indirect Micro‐Angiographic Fluoroscopic (MAF) Detectors

Purpose:To evaluate the task specific imaging performance of a new 25µm pixel pitch, 1000µm thick amorphous selenium direct detection system with CMOS readout for typical angiographic exposure parameters using the relative object detectability (ROD) metric.Methods:The ROD metric uses a simulated object function weighted at each spatial frequency by the detectors’ detective quantum efficiency (DQE), which is an intrinsic performance metric. For this study, the simulated objects were aluminum spheres of varying diameter (0.05–0.6mm). The weighted object function is then integrated over the full range of detectable frequencies inherent to each detector, and a ratio is taken of the resulting value for two detectors. The DQE for the 25µm detector was obtained from a simulation of a proposed a‐Se detector using an exposure of 200µR for a 50keV x‐ray beam. This a‐Se detector was compared to two microangiographic fluoroscope (MAF) detectors [the MAF‐CCD with pixel size of 35µm and Nyquist frequency of 14.2 cycles/mm and the MAF‐CMOS with pixel size of 75µm and Nyquist frequency of 6.6 cycles/mm] and a standard flat‐panel detector (FPD with pixel size of 194µm and Nyquist frequency of 2.5cycles/mm).Results:ROD calculations indicated vastly superior performance by the a‐Se detector in imaging small aluminum spheres. For the 50µm diameter sphere, the ROD values for the a‐Se detector compared to the MAF‐CCD, the MAF‐CMOS, and the FPD were 7.3, 9.3 and 58, respectively. Detector performance in the low frequency regime was dictated by each detector's DQE(0) value.Conclusion:The a‐Se with CMOS readout is unique and appears to have distinctive advantages of incomparable high resolution, low noise, no readout lag, and expandable design. The a‐Se direct detection system will be a powerful imaging tool in angiography, with potential break‐through applications in diagnosis and treatment of neuro‐vascular disease.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

SU-D-204-05: Quantitative Comparison of a High Resolution Micro-Angiographic Fluoroscopic (MAF) Detector with a Standard Flat Panel Detector (FPD) Using the New Metric of Generalized Measured Relative Object Detectability (GM-ROD)

Purpose: In endovascular image-guided neuro-interventions, visualization of fine detail is paramount. For example, the ability of the interventionist to visualize the stent struts depends heavily on the x-ray imaging detector performance. Methods: A study to examine the relative performance of the high resolution MAF-CMOS (pixel size 75µm, Nyquist frequency 6.6 cycles/mm) and a standard Flat Panel Detector (pixel size 194µm, Nyquist frequency 2.5 cycles/mm) detectors in imaging a neuro stent was done using the Generalized Measured Relative Object Detectability (GM-ROD) metric. Low quantum noise images of a deployed stent were obtained by averaging 95 frames obtained by both detectors without changing other exposure or geometric parameters. The square of the Fourier transform of each image is taken and divided by the generalized normalized noise power spectrum to give an effective measured task-specific signal-to-noise ratio. This expression is then integrated from 0 to each of the detector’s Nyquist frequencies, and the GM-ROD value is determined by taking a ratio of the integrals for the MAF-CMOS to that of the FPD. The lower bound of integration can be varied to emphasize high frequencies in the detector comparisons. Results: The MAF-CMOS detector exhibits vastly superior performance over the FPD when integrating over allmore » frequencies, yielding a GM-ROD value of 63.1. The lower bound of integration was stepped up in increments of 0.5 cycles/mm for higher frequency comparisons. As the lower bound increased, the GM-ROD value was augmented, reflecting the superior performance of the MAF-CMOS in the high frequency regime. Conclusion: GM-ROD is a versatile metric that can provide quantitative detector and task dependent comparisons that can be used as a basis for detector selection. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.« less

New Family of Generalized Metrics for Comparative Imaging System Evaluation.

A family of imaging task-specific metrics designated Relative Object Detectability (ROD) metrics was developed to enable objective, quantitative comparisons of different x-ray systems. Previously, ROD was defined as the integral over spatial frequencies of the Fourier Transform of the object function, weighted by the detector DQE for one detector, divided by the comparable integral for another detector. When effects of scatter and focal spot unsharpness are included, the generalized metric, GDQE, is substituted for the DQE, resulting in the G-ROD metric. The G-ROD was calculated for two different detectors with two focal spot sizes using various-sized simulated objects to quantify the improved performance of new high-resolution CMOS detector systems. When a measured image is used as the object, a Generalized Measured Relative Object Detectability (GM-ROD) value can be generated. A neuro-vascular stent (Wingspan) was imaged with the high-resolution Micro-Angiographic Fluoroscope (MAF) and a standard flat panel detector (FPD) for comparison using the GM-ROD calculation. As the lower integration bound increased from 0 toward the detector Nyquist frequency, increasingly superior performance of the MAF was evidenced. Another new metric, the R-ROD, enables comparing detectors to a reference detector of given imaging ability. R-RODs for the MAF, a new CMOS detector and an FPD will be presented. The ROD family of metrics can provide quantitative more understandable comparisons for different systems where the detector, focal spot, scatter, object, techniques or dose are varied and can be used to optimize system selection for given imaging tasks.

Micro-Angiographic Fluoroscope: Comparison for Different Input Phosphors

Although flat panel detectors are preferred for image-guided interventional endo-vascular treatments of stroke, they still have limitations in spatial resolution and excess additive noise, which restricts their low-dose performance. The Micro-Angiographic Fluoroscope (MAF), a CCD-based region-of-interest indirect X-ray imager recently developed, can meet the needs for high-resolution, high-sensitivity, real-time image guidance. Although the prototype MAF has better resolution (MTF) and detective quantum efficiency (DQE) than a standard flat panel detector, its performance could be improved by a change in the phosphor. The spatial resolution of such X-ray-to-light converting phosphors is limited by stochastic blurring and k-fluorescent X-ray reabsorption. Thinner phosphors generally improve resolution at the cost of lowering quantum detection efficiency (QDE) and increasing Swank noise, while thicker phosphors provide better absorption at the expense of spatial resolution. Two other Hamamatsu CsI(Tl) phosphors, 300- μm-thick HR, and 500- μm-thick HR, both without front reflective surface, were compared with the current 300- μm HL phosphor with front reflective surface. The phosphors were evaluated by comparing the MTF, NNPS, and DQE of the MAF detector used with each phosphor. All detector configurations showed linearity and quantum noise limited operation for a large range of exposures appropriate for both fluoroscopy and angiography. While the 300- μm HR type prototype demonstrated better resolution than the 500- μm HR type, the latter demonstrated better overall DQE and improved resolution compared to the original 300- μm HL, suggesting it would be the better choice for the MAF design.

SU‐E‐CAMPUS‐I‐04: Automatic Skin‐Dose Mapping for An Angiographic System with a Region‐Of‐Interest, High‐Resolution Detector

Purpose:Our real‐time skin dose tracking system (DTS) has been upgraded to monitor dose for the micro‐angiographic fluoroscope (MAF), a high‐resolution, small field‐of‐view x‐ray detector.Methods:The MAF has been mounted on a changer on a clinical C‐Arm gantry so it can be used interchangeably with the standard flat‐panel detector (FPD) during neuro‐interventional procedures when high resolution is needed in a region‐of‐interest. To monitor patient skin dose when using the MAF, our DTS has been modified to automatically account for the change in scatter for the very small MAF FOV and to provide separated dose distributions for each detector. The DTS is able to provide a color‐coded mapping of the cumulative skin dose on a 3D graphic model of the patient. To determine the correct entrance skin exposure to be applied by the DTS, a correction factor was determined by measuring the exposure at the entrance surface of a skull phantom with an ionization chamber as a function of entrance beam size for various beam filters and kVps. Entrance exposure measurements included primary radiation, patient backscatter and table forward scatter. To allow separation of the dose from each detector, a parameter log is kept that allows a replay of the procedure exposure events and recalculation of the dose components. The graphic display can then be constructed showing the dose distribution from the MAF and FPD separately or together.Results:The DTS is able to provide separate displays of dose for the MAF and FPD with field‐size specific scatter corrections. These measured corrections change from about 49% down to 10% when changing from the FPD to the MAF.Conclusion:The upgraded DTS allows identification of the patient skin dose delivered when using each detector in order to achieve improved dose management as well as to facilitate peak skin‐dose reduction through dose spreading.Research supported in part by Toshiba Medical Systems Corporation and NIH Grants R43FD0158401, R44FD0158402 and R01EB002873

SU‐E‐I‐83: Parallel Programming Upgrades for the Control Acquisition, Processing and Image Display System (CAPIDS) of the Micro Angiographic Fluoroscope (MAF)

Purpose:CAPIDS is a unique software platform designed to control and acquire images from the high‐resolution MAF detector, process them and display them in a clinical environment. The images are then stored for optional playback at a later stage. CAPIDS also acquires and records the exposure parameters from the x‐ray unit. We present new parallel programming modifications using the host computer system's Graphics Processing Unit (GPU) and Central Processing unit (CPU) to improve the system performance for the various MAF imaging tasks.Methods:Multicore CPU's allow for concurrent tasks to be executed at the same time in parallel. During runtime, CAPIDS has three concurrent tasks: image acquisition and processing, image saving, and exposure parameter acquisition. Parallel programming constructs from LabVIEW allow each tasks to be executed on a separate core.GPU's allow for the same task to be performed on independent data sets in parallel. During runtime, all the image processing including flat‐field correction, digital image subtraction, image averaging, and temporal recursive filtering are performed on the GPU.Results:The new version of CAPIDS with all the parallel programming updates was successfully used for the first time to control the MAF, acquire the images, process the images and display the images during an actual clinical intervention. The images were acquired under fluoroscopy, digital subtraction angiography, and roadmap modes.Conclusion:Distributing concurrent tasks to different cores of a multicore CPU results in an efficient utilization of resources, efficient power management and increases operation speed. Use of GPU's for image processing further enhances the speed of operation.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

SU‐E‐I‐13: Comparison of CCD and CMOS Micro‐Angiographic Fluoroscope (MAF) Detector Systems Using Contrast Measurements for Specific Imaging Tasks Related to Neuro‐Endovascular Image‐Guided Interventional (EIGI) Procedures

Purpose:To compare the performance of two high‐resolution detector systems for use during neuro‐EIGI procedures.Methods:The task‐specific performance of custom high‐resolution CCD and CMOS micro‐angiographic fluoroscopes (MAF) was compared. To simulate the attenuation of x‐rays by a patient in neuro‐EIGIs, a modified ANSI head phantom was used. A bar phantom with 0.05‐mm thick lead was used to simulate the contrast and size of EIGI devices used in neuro EIGIs. The bar phantom, placed at an angle of 6.5 degrees relative to the pixel rows of both detectors, was imaged for 88kVp using the small 0.3mm focal spot in order to decrease the geometric unsharpness and preserve the high‐resolution capabilities of both detectors. The resultant images have a geometric object magnification of 1.25, similar to that of a clinical neuro‐EIGI, and a fixed field size was used to keep the scatter the same for both detectors. For images obtained using each detector, we calculated and compared the contrast of the averaged line profiles for the 5.0, 5.6 and 6.3 lp/mm bar pattern groups, which have lead‐line widths of 100, 89, and 79 microns, respectively.Results:For the MAF‐CCD, the measured contrasts were 0.020, 0.019 and 0.013 for the 5.0, 5.6 and 6.3 line pair groups, respectively, and for the MAF‐CMOS the contrasts were 0.025, 0.019 and 0.014 for the 5.0, 5.6 and 6.3 line pair groups, respectively.Conclusion:For the very small lines of the bar pattern, the MAF‐CMOS appears to provide almost the same contrast as compared to the MAF‐CCD, within the measurement error; however, noise and dynamic range characteristics remain to be studied before concluding that the MAF‐CMOS can replace the MAF‐CCD during task‐specific neuro‐EIGI procedures where high spatial resolution is required.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.

SU‐E‐I‐29: Generalized Relative Object Detectability (G‐ROD): A Metric for Comparing X‐Ray Imaging Detector Systems

Purpose:To determine the relative task‐specific performance of two x‐ray imaging detectors including the effect of other components of the imaging chain.Methods:The relative object detectability (ROD) was defined as the ratio of the integral of the detective‐quantum efficiency (DQE) of a detector weighted by the square of the Fourier Transform (or frequency spectrum) of the object to the same integral for a second detector. The generalized ROD (G‐ROD) is calculated by replacing DQE by the generalized DQE (GDQE) which includes geometric unsharpness and scatter to evaluate the total imaging chain. The G‐ROD was calculated for the micro‐angiographic fluoroscope (MAF) relative to a flat‐panel detector (FPD) for low (1.05) and high (1.2) magnifications with two focal‐spot sizes, small (0.3 mm) and medium (0.5 mm), and for the same value of scatter fraction. Solid spheres from 50 to 600 microns were simulated as the objects for this evaluation. The G‐ROD results were compared with those of the ROD which considers the detectors alone.Results:For 50‐micron spheres, the ROD is 7.93 and, for the small [medium] focus, the G‐ROD is 6.74 [5.22] at low magnification and 3.03 [1.66] at high magnification, indicating superior performance of the MAF particularly at low magnification. Both ROD and G‐ROD decrease monotonically with size and remain around one above 400‐microns. The G‐ROD decreases more dramatically with low compared to high magnification for both focal spots.Conclusion:In all cases, the MAF performs better than the FPD and the decreasing trend of the G‐ROD indicates that the performance of both detectors becomes similar as the object size increases and becomes nearly equal above 400‐micron diameter sphere size. Finally, increased magnification and focal‐spot size decrease the G‐ROD, indicting that they degrade the performance of the MAF more than that of the FPD for a small‐object viewing task.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

SU‐E‐I‐40: New Method for Measurement of Task‐Specific, High‐Resolution Detector System Performance

Purpose:Although generalized linear system analytic metrics such as GMTF and GDQE can evaluate performance of the whole imaging system including detector, scatter and focal‐spot, a simplified task‐specific measured metric may help to better compare detector systems.Methods:Low quantum‐noise images of a neuro‐vascular stent with a modified ANSI head phantom were obtained from the average of many exposures taken with the high‐resolution Micro‐Angiographic Fluoroscope (MAF) and with a Flat Panel Detector (FPD). The square of the Fourier Transform of each averaged image, equivalent to the measured product of the system GMTF and the object function in spatial‐frequency space, was then divided by the normalized noise power spectra (NNPS) for each respective system to obtain a task‐specific generalized signal‐to‐noise ratio. A generalized measured relative object detectability (GM‐ROD) was obtained by taking the ratio of the integral of the resulting expressions for each detector system to give an overall metric that enables a realistic systems comparison for the given detection task.Results:The GM‐ROD provides comparison of relative performance of detector systems from actual measurements of the object function as imaged by those detector systems. This metric includes noise correlations and spatial frequencies relevant to the specific object. Additionally, the integration bounds for the GM‐ROD can be selected to emphasis the higher frequency band of each detector if high‐resolution image details are to be evaluated. Examples of this new metric are discussed with a comparison of the MAF to the FPD for neuro‐vascular interventional imaging.Conclusion:The GM‐ROD is a new direct‐measured task‐specific metric that can provide clinically relevant comparison of the relative performance of imaging systems.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation

Workflow for the use of a high-resolution image detector in endovascular interventional procedures.

Endovascular image-guided intervention (EIGI) has become the primary interventional therapy for the most widespread vascular diseases. These procedures involve the insertion of a catheter into the femoral artery, which is then threaded under fluoroscopic guidance to the site of the pathology to be treated. Flat Panel Detectors (FPDs) are normally used for EIGIs; however, once the catheter is guided to the pathological site, high-resolution imaging capabilities can be used for accurately guiding a successful endovascular treatment. The Micro-Angiographic Fluoroscope (MAF) detector provides needed high-resolution, high-sensitivity, and real-time imaging capabilities. An experimental MAF enabled with a Control, Acquisition, Processing, Image Display and Storage (CAPIDS) system was installed and aligned on a detector changer attached to the C-arm of a clinical angiographic unit. The CAPIDS system was developed and implemented using LabVIEW software and provides a user-friendly interface that enables control of several clinical radiographic imaging modes of the MAF including: fluoroscopy, roadmap, radiography, and digital-subtraction-angiography (DSA). Using the automatic controls, the MAF detector can be moved to the deployed position, in front of a standard FPD, whenever higher resolution is needed during angiographic or interventional vascular imaging procedures. To minimize any possible negative impact to image guidance with the two detector systems, it is essential to have a well-designed workflow that enables smooth deployment of the MAF at critical stages of clinical procedures. For the ultimate success of this new imaging capability, a clear understanding of the workflow design is essential. This presentation provides a detailed description and demonstration of such a workflow design.

Relative object detectability (ROD): a new metric for comparing x-ray image detector performance for a specified object of interest.

Relative object detectability (ROD) quantifies the relative performance of two image detectors for a specified object of interest by taking the following ratio: the integral of detective quantum efficiency of a detector weighted by the frequency spectrum of the object divided by that for a second detector. Four different detectors, namely the micro-angiographic fluoroscope (MAF), the Dexela Model 1207 (Dex) and Hamamatsu Model C10901D-40 (Ham) CMOS x-ray detectors, and a flat-panel detector (FPD) were compared. The ROD was calculated for six pairs of detectors: (1) Dex/FPD, (2) MAF/FPD, (3) Ham/FPD, (4) Dex/Ham, (5) MAF/Ham and (6) MAF/Dex for wires of 5 mm fixed length, solid spheres ranging in diameter from 50 to 600 microns, and four simulated iodine-filled blood vessels of outer diameters 0.4 and 0.5 mm, each with wall thicknesses of 0.1 and 0.15 mm. Marked variation of ROD for the wires and spheres is demonstrated as a function of object size for the various detector pairs. The ROD of all other detectors relative to the FPD was much greater than one for small features and approached 1.0 as the diameter increased. The relative detectability of simulated small iodine-filled blood vessels for all detector pairs was seen to be independent of the vessel wall thickness for the same inner diameter. In this study, the ROD is shown to have the potential to be a useful figure of merit to evaluate the relative performance of two detectors for a given imaging task.