Dual-energy Subtraction Technique Research Articles

Analysis of dual-energy mammography subtraction technique for the dose and image quality evaluation using 3D-printed breast phantom.

This study aimed to quantitatively assess the radiation dose using XR-QA2 and the image quality of the dual-energy subtraction mammography technique on an in-house phantom. The analysis was carried out to investigate the effect of targets/filters on dose value and image quality using an in-house phantom made of PLA + as an object representing compressed breasts. All irradiation parameters were performed in the craniocaudal position with manual mode. Mean glandular dose (MGD) was recorded, followed by the calculation of the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and modulation transfer function (MTF) for image quality assessment parameters. The results showed that the image quality was accepted at dose levels within the IAEA and BAPETEN tolerance limit for 60mm equivalent compressed breast using dual-energy mammography. Furthermore, the target/filter (W/Rh) reduced the dose by 1.03mGy compared to the Mo/Mo and Mo/Rh with an enhancement in image quality. This indicated that the target/filter (W/Rh) combination was optimal due to the image quality improvement obtained with lower MGD.

Development of Artificial Intelligence-Based Dual-Energy Subtraction for Chest Radiography

Recently, some facilities have utilized the dual-energy subtraction (DES) technique for chest radiography to increase pulmonary lesion detectability. However, the availability of the technique is limited to certain facilities, in addition to other limitations, such as increased noise in high-energy images and motion artifacts with the one-shot and two-shot methods, respectively. The aim of this study was to develop artificial intelligence-based DES (AI–DES) technology for chest radiography to overcome these limitations. Using a trained pix2pix model on clinically acquired chest radiograph pairs, we successfully converted 130 kV images into virtual 60 kV images that closely resemble the real images. The averaged peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) between virtual and real 60 kV images were 33.8 dB and 0.984, respectively. We also achieved the production of soft-tissue- and bone-enhanced images using a weighted image subtraction process with the virtual 60 kV images. The soft-tissue-enhanced images exhibited sufficient bone suppression, particularly within lung fields. Although the bone-enhanced images contained artifacts on and around the lower thoracic and lumbar spines, superior sharpness and noise characteristics were presented. The main contribution of our development is its ability to provide selectively enhanced images for specific tissues using only high-energy images obtained via routine chest radiography. This suggests the potential to improve the detectability of pulmonary lesions while addressing challenges associated with the existing DES technique. However, further improvements are necessary to improve the image quality.

Value of bone suppression software in chest radiographs for improving image quality and reducing radiation dose.

To compare image quality and radiation dose between dual-energy subtraction (DES)-based bone suppression images (D-BSIs) and software-based bone suppression images (S-BSIs). Chest radiographs (CXRs) of forty adult patients were obtained with the two X-ray devices, one with DES and one with bone suppression software. Three image quality metrics (relative mean absolute error (RMAE), peak signal-to-noise ratio (PSNR), and structural similarity index (SSIM)) between original CXR and BSI for each of D-BSI and S-SBI groups were calculated for each bone and soft tissue areas. Two readers rated the visual image quality for original CXR and BSI for each of D-BSI and S-SBI groups. The dose area product (DAP) values were recorded. Paired t test was used to compare the image quality and DAP values between D-BSI and S-BSI groups. In bone areas, S-BSIs had better SSIM values than D-BSI (94.57 vs. 87.77) but worse RMAE and PSNR values (0.50 vs. 0.20; 20.93 vs. 34.37) (all p < 0.001). In soft tissue areas, S-BSIs had better SSIM values than D-BSI (97.56 vs. 91.42) but similar RMAE and PSNR values (0.29 vs. 0.27; 31.35 vs. 29.87) (all p < 0.001). Both readers gave S-BSIs significantly higher image quality scores than D-BSI (p < 0.001). The mean DAP in software-related images (0.98 dGy·cm2) was significantly lower than that in the DES-related images (1.48 dGy·cm2) (p < 0.001). Bone suppression software significantly improved the image quality of bone suppression images with a relatively lower radiation dose, compared with dual-energy subtraction technique. • Bone suppression software preserves structure similarity of soft tissues better than dual-energy subtraction technique in bone suppression images. • Bone suppression software achieves superior image quality for lung lesions than dual-energy subtraction technique in bone suppression images. • Bone suppression software can decrease the radiation dose over the hardware-based image processing technique.

Improved accuracy of markerless motion tracking on bone suppression images: preliminary study for image-guided radiation therapy (IGRT)**This paper was presented at RSNA 2013 and was carried out at Kanazawa University, JAPAN.

The bone suppression technique based on advanced image processing can suppress the conspicuity of bones on chest radiographs, creating soft tissue images obtained by the dual-energy subtraction technique. This study was performed to evaluate the usefulness of bone suppression image processing in image-guided radiation therapy. We demonstrated the improved accuracy of markerless motion tracking on bone suppression images. Chest fluoroscopic images of nine patients with lung nodules during respiration were obtained using a flat-panel detector system (120 kV, 0.1 mAs/pulse, 5 fps). Commercial bone suppression image processing software was applied to the fluoroscopic images to create corresponding bone suppression images. Regions of interest were manually located on lung nodules and automatic target tracking was conducted based on the template matching technique. To evaluate the accuracy of target tracking, the maximum tracking error in the resulting images was compared with that of conventional fluoroscopic images. The tracking errors were decreased by half in eight of nine cases. The average maximum tracking errors in bone suppression and conventional fluoroscopic images were 1.3 ± 1.0 and 3.3 ± 3.3 mm, respectively. The bone suppression technique was especially effective in the lower lung area where pulmonary vessels, bronchi, and ribs showed complex movements. The bone suppression technique improved tracking accuracy without special equipment and implantation of fiducial markers, and with only additional small dose to the patient. Bone suppression fluoroscopy is a potential measure for respiratory displacement of the target.

Scatter correction using a primary modulator for dual energy digital radiography: A Monte Carlo simulation study

In conventional digital radiography (DR) using a dual energy subtraction technique, a significant fraction of the detected photons are scattered within the body, making up the scatter component. Scattered radiation can significantly deteriorate image quality in diagnostic X-ray imaging systems. Various methods of scatter correction, including both measurement- and non-measurement-based methods, have been proposed in the past. Both methods can reduce scatter artifacts in images. However, non-measurement-based methods require a homogeneous object and have insufficient scatter component correction. Therefore, we employed a measurement-based method to correct for the scatter component of inhomogeneous objects from dual energy DR (DEDR) images. We performed a simulation study using a Monte Carlo simulation with a primary modulator, which is a measurement-based method for the DEDR system. The primary modulator, which has a checkerboard pattern, was used to modulate the primary radiation. Cylindrical phantoms of variable size were used to quantify the imaging performance. For scatter estimates, we used discrete Fourier transform filtering, e.g., a Gaussian low-high pass filter with a cut-off frequency. The primary modulation method was evaluated using a cylindrical phantom in the DEDR system. The scatter components were accurately removed using a primary modulator. When the results acquired with scatter correction and without scatter correction were compared, the average contrast-to-noise ratio (CNR) with the correction was 1.35 times higher than that obtained without the correction, and the average root mean square error (RMSE) with the correction was 38.00% better than that without the correction. In the subtraction study, the average CNR with the correction was 2.04 (aluminum subtraction) and 1.38 (polymethyl methacrylate (PMMA) subtraction) times higher than that obtained without the correction. The analysis demonstrated the accuracy of the scatter correction and the improvement of image quality that could be obtained by using a primary modulator and showed the feasibility of introducing the primary modulation technique into dual energy subtraction. Therefore, we suggest that the scatter correction method with a primary modulator will be useful for use with the DEDR system.

Search for novel contrast materials in dual-energy x-ray breast imaging using theoretical modeling of contrast-to-noise ratio

Contrast-enhanced (CE) dual-energy (DE) x-ray breast imaging uses a low- and high-energy x-ray spectral pair to eliminate soft-tissue signal variation and thereby increase the detectability of exogenous imaging agents. Currently, CEDE breast imaging is performed with iodinated contrast agents. These compounds are limited by several deficiencies, including rapid clearance and poor tumor targeting ability. The purpose of this work is to identify novel contrast materials whose contrast-to-noise ratio (CNR) is comparable or superior to that of iodine in the mammographic energy range. A monoenergetic DE subtraction framework was developed to calculate the DE signal intensity resulting from the logarithmic subtraction of the low- and high-energy signal intensities. A weighting factor is calculated to remove the dependence of the DE signal on the glandularity of the breast tissue. Using the DE signal intensity and weighting factor, the CNR for materials with atomic numbers (Z) ranging from 1 to 79 are computed for energy pairs between 10 and 50 keV.A group of materials with atomic numbers ranging from 42 to 63 were identified to exhibit the highest levels of CNR in the mammographic energy range. Several of these materials have been formulated as nanoparticles for various applications but none, apart from iodine, have been investigated as CEDE breast imaging agents. Within this group of materials, the necessary dose fraction to the LE image decreases as the atomic number increases. By reducing the dose to the LE image, the DE subtraction technique will not provide an anatomical image of sufficient quality to accompany the contrast information. Therefore, materials with Z from 42 to 52 provide nearly optimal values of CNR with energy pairs and dose fractions that provide good anatomical images. This work is intended to inspire further research into new materials for optimized CEDE breast functional imaging.

PET/MRI in Lung Cancer

Introduction Imaging plays an important role in the diagnosis and management of lung cancer, which is the leading cause of cancer-related death in the world. Radiography is often the initial modality of diagnosis, but detection depends on the size and density of nodules. The sensitivity of detection may be improved by using the dual-energy subtraction technique, which generates a soft tissue reconstruction that is free of overlapping chest wall and bony structures, or by using tomosynthesis. Computed tomography (CT) has become the established modality for the screening, diagnosis, and staging of lung cancers. Radiation and the use of potentially nephrotoxic contrast media are the risk factors associated with it. Magnetic resonance imaging (MRI) does not involve radiation, but its use in lung cancer is limited by intrinsic low proton spin density, magnetic field inhomogeneities, and motion artifacts from cardiac and respiratory motion. However, novel sequences show potential in the evaluation of lung cancer. Positron emission tomography (PET) with 18-fluorodeoxyglucose (FDG-PET) is useful in determining the metabolic activity of the lung tumor. False-negative results are seen in small tumors and in bronchoalevolar carcinoma, whereas falsepositive findings are seen in cases of infection or inflammation. The hybrid imaging modality of PET/CT is now the standard of care in the staging of lung cancers, combining the morphologic information of CT with the metabolic information of PET. PET/MRI is a novel hybrid imaging technology that involves the fusion of 2 powerful imaging modalities: PET and MRI. MRI provides tissue characterization capabilities

Improving the Image Quality in Computed Tomographic Pulmonary Angiography With Dual-Energy Subtraction

The objectives of this study were to assess quantitative and subjective image quality in computed tomographic pulmonary angiography using dual-energy subtraction methods compared with those of the monochromatic images using optimal contrast-to-noise ratios and those of the routine polychromatic images and to select the best dual-energy subtraction method. A total of 1 routine polychromatic image, 3 sets of dual-energy subtraction images (DESIs), and 2 sets of monochromatic images with different optimal contrast-to-noise ratios from 30 patients were obtained. The signal intensity and noise were measured; signal-to-noise ratio and contrast-to-noise ratio (CNR) were calculated. The global subjective image quality was subjectively assessed. The DESI 3 got the highest CNR and the DESI 1 got the second highest CNR. The DESI 1 got the highest global subjective image quality score. The 3 subtraction image sets got the highest score in visualization of the pulmonary artery branches. Computed tomographic pulmonary angiography with dual-energy subtraction technique is feasible. The DESI 1 afforded the best balance between the quantitative analysis and the subjective evaluation.

A nonparametric-based rib suppression method for chest radiographs

This paper presents an automated and comprehensive system for eliminating rib shadows in chest radiographs, which integrates lung field identification, rib segmentation, rib intensity estimation, and suppression. We designed a region of interest (ROI)-based method to estimate a suitable initial lung boundary for active shape model (ASM) deformation by determining the translation and scaling parameters from the lung ROI. By considering the anatomical structure of the rib cage, we developed a locale sampling scheme to achieve nonparametric rib modeling. This scheme integrates knowledge-based generalized Hough transform (GHT) for accurate rib segmentation. We subsequently estimated rib intensity using the real-coded genetic algorithm (RCGA). Experimental results indicate that the relative conspicuity of the nodules increased after rib suppression, compared to the original image. Additionally, the proposed system uses only one standard chest radiograph, and the dual-energy subtraction technique is not required. Thus, this system is suitable for radiologists and computer-aided diagnosis (CAD) schemes for detecting lung nodules in chest radiographs.

X-ray Digital Linear Tomosynthesis Imaging for Artificial Pulmonary Nodule Detection.

The purpose of this paper is to identify indications for volumetric X-ray digital linear tomosynthesis (DLT) with single- and dual-energy subtraction techniques for artificial pulmonary nodule detection and compare X-ray DLT, X-ray digital radiography, and computed tomography.

Detection of small pulmonary nodules on chest radiographs: efficacy of dual-energy subtraction technique using flat-panel detector chest radiography

To investigate the effect of a double-exposure dual-energy subtraction (DES) technique on the diagnostic performance of radiologists detecting small pulmonary nodules on flat-panel detector (FPD) chest radiographs. Using FPD radiography 41 sets of chest radiographs were obtained from 26 patients with pulmonary nodules measuring <or=20mm and from 15 normal participants. Each dataset included standard and corresponding DES images. There were six non-solid, 10 part-solid, and 10 solid nodules. The mean size of the 26 nodules was 15+/-4.8mm. Receiver operating characteristic (ROC) analysis was performed to compare the performance of the eight board-certified radiologists. For the eight radiologists, the mean value of the area under the ROC curve (AUC) without and with DES images was 0.62+/-0.05 and 0.68+/-0.05, respectively; the difference was statistically significant (p=0.02). For part-solid nodules, the difference of the mean AUC value was statistically significant (AUC=0.61+/-0.07 versus 0.69+/-0.05; p<0.01); for non-solid nodules it was not (AUC=0.62+/-0.1 versus 0.61+/-0.09; p=0.73), and for solid nodules it was not (AUC=0.75+/-0.1 versus 0.78+/-0.08; p=0.23). For nodules with overlapping bone shadows, the difference of the mean AUC value was statistically significant (p=0.03), for nodules without overlapping, it was not (p=0.26). Use of a double-exposure DES technique at FPD chest radiography significantly improved the diagnostic performance of radiologists to detect small pulmonary nodules.

Effects of dual-energy subtraction chest radiography on detection of small pulmonary nodules with varying attenuation: receiver operating characteristic analysis using a phantom study

The aim of this study was to investigate the detectability of simulated pulmonary nodules with different X-ray attenuation by flat-panel detector (FPD) chest radiography using a dual-exposure dual-energy subtraction (DES) technique. Using a FPD radiography system, we obtained 108 sets of chest radiographs of a chest phantom. They consisted of 54 sets each of chest radiographs with and without simulated nodules. Each data set contained a standard and a corresponding dual-energy subtracted chest radiograph (DES image). The diameters of the simulated nodules were 8, 10, and 12 mm, respectively; nodules of each size manifested attenuation of -450, -200, and 30 Hounsfield units (HU). We performed receiver operating characteristic (ROC) analysis to compare the observers' performance in detecting nodules. For the -450 HU nodules the mean areas under the ROC curve (AUC) without and with DES images were 0.66 and 0.77, respectively; the difference was significant (paired t-test, P < 0.01). For nodules with -200 and 30 HU, there was no significant difference in the AUC value (0.79 vs. 0.77, P = 0.13; 0.92 vs. 0.94, P = 0.17, respectively). The addition of DES images to standard chest radiographs improved the performance of radiologists charged with detecting simulated nodules with an attenuation of -450 HU.

Dual-Energy Subtraction Imaging for Diagnosing Vocal Cord Paralysis with Flat Panel Detector Radiography

ObjectiveTo investigate the clinical feasibility of dual energy subtraction (DES) imaging to improve the delineation of the vocal cord and diagnostic accuracy of vocal cord paralysis as compared with the anterior-posterior view of flat panel detector (FPD) neck radiography.Materials and MethodsFor 122 consecutive patients who underwent both a flexible laryngoscopy and conventional/DES FPD radiography, three blinded readers retrospectively graded the radiographs during phonation and inspiration on a scale of 1 (poor) to 5 (excellent) for the delineation of the vocal cord, and in consensus, reviewed the diagnostic accuracy of vocal cord paralysis employing the laryngoscopy as the reference. We compared vocal cord delineation scores and accuracy of vocal cord paralysis diagnosis by both conventional and DES techniques using κ statistics and assessing the area under the receiver operating characteristic curve (AUC).ResultsVocal cord delineation scores by DES (mean, 4.2 ± 0.4) were significantly higher than those by conventional imaging (mean, 3.3 ± 0.5) (p < 0.0001). Sensitivity for diagnosing vocal cord paralysis by the conventional technique was 25%, whereas the specificity was 94%. Sensitivity by DES was 75%, whereas the specificity was 96%. The diagnostic accuracy by DES was significantly superior (κ = 0.60, AUC = 0.909) to that by conventional technique (κ = 0.18, AUC = 0.852) (p = 0.038).ConclusionDual energy subtraction is a superior method compared to the conventional FPD radiography for delineating the vocal cord and accurately diagnosing vocal cord paralysis.

Sequential dual-energy subtraction technique with a dynamic flat-panel detector (FPD): primary study for image-guided radiation therapy (IGRT)

A sequential dual-energy subtraction technique for image-guided radiation therapy (IGRT) was developed. Here, we report on a computerized method for creating sequential soft-tissue images and the accuracy of tracking targets on the images obtained, in comparison to conventional fluoroscopic images. Two sets of sequential chest images during respiration of a normal subject were obtained with X-rays of different energy separately with a flat-panel detector (FPD). Sequential soft-tissue images were created from the two sets of sequential images consisting of real-time images and reference template images, respectively. The creation of sequential soft-tissue images consisted of three steps: one-to-one image correspondence of the two sequential images, image registration, and image subtraction in each frame. Motion tracking of lung vessels was then performed by the template-matching technique. For evaluation of the accuracy of motion tracking on the sequential soft-tissue images, the results were compared with those on the original sequential images. Sequential soft-tissue images provided more accurate tracking than the original images (P < 0.01). There was no significant error throughout all frames in the soft-tissue images, whereas the rib shadow introduced a tracking error in the original images. The maximum errors were 4.1 +/- 0.3 mm in the sequential soft-tissue images and 28.1 +/- 20.0 mm in the original images. In conclusion, sequential soft-tissue images were helpful for tracking of a target affected by respiratory motion. Dual-energy subtraction has the potential to improve the accuracy of IGRT without implanted markers.

Detectability of lung nodules using flat panel detector with dual energy subtraction by two shot method: Evaluation by ROC method

The aim of this study was to evaluate the effectiveness of dual-exposure dual energy subtraction technique in flat-panel chest radiography for lung nodules detection. Chest radiographs were acquired in 100 patients (57 men and 43 women; mean age, 60.2 years; range, 18–89 years) using a flat-panel digital chest system. These images were evaluated by seven radiologists. A continuous rating scale of 0–100 was used to represent each observer's confidence level regarding the presence or absence of lung nodules. Observer performance for detection of lung nodules with subtraction images was tested by using receiver operating characteristic (ROC) analysis of individual and averaged reader data. The average area under the ROC curve (Az value) significantly increased with subtraction images (Az = 0.79 in standard radiographs versus Az = 0.84 with subtraction images, p < 0.05). In conclusion, the two-exposure dual-energy subtraction chest radiography significantly would improve detection of lung nodules.

Dual Energy Subtraction Digital Radiography

Emerging applications in digital radiography offer exciting advances in the evaluation of lung disease. Dual energy subtraction techniques have been recognized as a promising technique in the detection and characterization of pulmonary nodules. This essay will demonstrate a significantly expanded diagnostic role in the assessment of cardiothoracic disease with dual energy subtraction and digital radiography.

Image-processing technique for suppressing ribs in chest radiographs by means of massive training artificial neural network (MTANN)

When lung nodules overlap with ribs or clavicles in chest radiographs, it can be difficult for radiologists as well as computer-aided diagnostic (CAD) schemes to detect these nodules. In this paper, we developed an image-processing technique for suppressing the contrast of ribs and clavicles in chest radiographs by means of a multiresolution massive training artificial neural network (MTANN). An MTANN is a highly nonlinear filter that can be trained by use of input chest radiographs and the corresponding "teaching" images. We employed "bone" images obtained by use of a dual-energy subtraction technique as the teaching images. For effective suppression of ribs having various spatial frequencies, we developed a multiresolution MTANN consisting of multiresolution decomposition/composition techniques and three MTANNs for three different-resolution images. After training with input chest radiographs and the corresponding dual-energy bone images, the multiresolution MTANN was able to provide "bone-image-like" images which were similar to the teaching bone images. By subtracting the bone-image-like images from the corresponding chest radiographs, we were able to produce "soft-tissue-image-like" images where ribs and clavicles were substantially suppressed. We used a validation test database consisting of 118 chest radiographs with pulmonary nodules and an independent test database consisting of 136 digitized screen-film chest radiographs with 136 solitary pulmonary nodules collected from 14 medical institutions in this study. When our technique was applied to nontraining chest radiographs, ribs and clavicles in the chest radiographs were suppressed substantially, while the visibility of nodules and lung vessels was maintained. Thus, our image-processing technique for rib suppression by means of a multiresolution MTANN would be potentially useful for radiologists as well as for CAD schemes in detection of lung nodules on chest radiographs.

TH-C-I-611-05: Quantification of Coronary Artery Calcium Using Real Time Dual Energy Subtraction Based On a Flat Panel Detector

Purpose: To evaluate the feasibility of a real time dual-energy subtraction technique with dynamic filtration based on a flat panel detector for quantifying coronary arterial calcium. Method and Materials: In this dual-energy subtraction technique, the beam energy and filtration were switched at 30 Hz between 60 kVp and 120 kVp + 0.8 mm additional silver filtration. The calcium contrast and contrast-to-noise ratio (CNR) were measured using a Lucide step phantom and a 3 mm thick bone equivalent material. The performance of the dynamic filtration technique was compared with a static filtration technique (4 mm Al + 0.2 mm Cu for both beams). Arterial vessel phantoms with calcium aerial densities in the range of 30–140 mg/cm2 and a total calcium mass of 8–92 mg were imaged over a Lucite step phantom. The low and high energy images were corrected for scatter before subtraction. The total calcium mass was measured using a densitometry technique. The entrance exposure was measured and effective dose was estimated. Results: The dynamic filtration technique produced 60% higher calcium CNR and required 25% higher x-ray tube loading as compared to the static filtration technique. A calcium aerial density of approximately 30 mg/cm2 was detectable. The known (K) and measured (M) calcium mass were related by M=0.97K+0.028 (R=1.0). The calcium measurement precision was 4 mg, determined from 10 repeated dual energy images. The entrance exposure and effective dose were 7 mR and 5.2 μSv for each dual energy image, respectively. Conclusion: Dual-energy subtraction can be a potentially useful technique for the quantification of coronary arterial calcium and provide a noninvasive technique for diagnosis of coronary artery disease.

TU-C-I-609-07: Optimization of a Real Time Dual-Energy Subtraction Technique Based On a Flat Panel Detector

Purpose: To determine the optimal x-ray spectra for dual-energy subtraction with a flat panel detector (FPD), and to quantify the effects of dynamic filtration and FPD gain settings on image quality, tube loading, patient exposure, and overall system performance. Method and Materials: A simulation study was performed using available empirically determined data of x-ray spectra. The lungs and mediastinum of the chest were modeled with 12.5 cm and 20 cm thick regions of Lucite, respectively. Coronary calcification was modeled with a 1 mm thickness of bone-equivalent plastic. The FPD was modeled as an ideal detector with a 600 micron thick layer of CsI. Scatter was not considered in this study. Low and high energy images were normalized to a desired energy deposit in the detector dependent on FPD gain. A figure-of-merit (FOM) was used t6o quantify the overall system performance. The effects of various silver filter thicknesses (0–1000 microns), high to low energy image signal ratios (1–8), and two dual-energy noise reduction algorithms were evaluated for their effect on image quality, patient entrance exposure, tube loading, and FOM improvement. Results: As the thickness of the high-energy filter increased, image contrast, contrast-to-noise ratio, FOM and tube loading increased. Patient exposure was reduced by approximately 10% for the range of filter thicknesses studied. The FOM was maximized with a FPD signal ratio of approximately 3 without application of dual-energy noise reduction. However, dual gain operation did not show any improvement after noise reduction. Conclusion: An optimal dynamic filter combined with dual-energy noise reduction can improve the system FOM by a factor of 5. There is no further improvement in the system FOM when dual detector gain is used in conjunction with dual-energy noise reduction.

In-vivo validation of videodensitometric coronary cross-sectional area measurement using dual-energy digital subtraction angiography

Previous studies indicate that conventional geometric edge detection techniques, used in quantitative coronary arteriography (QCA), have significant limitations in quantitating coronary cross-sectional area of small diameter (D) vessels (D < 1.00 mm) and lesions with complex cross-section. As a solution to this problem, we have previously reported on an in-vitro validation of a videodensitometric technique that quantitates the absolute cross-sectional area including small vessel diameter (D < 1.00 mm) and any complex shape of the vessel cross-section. For in-vivo validation, plastic tubing (5-8 mm long) with different shape complex cross-section with known cross-sectional area (A = 0.8-4.5 mm2) were percutaneously wedged in the coronary arteries of anesthetized pigs (40-50 kg). Contrast material injections (6-10 ml at 2-4 ml/sec) were made into the left main coronary artery during image acquisition using a motion immune dual-energy subtraction technique, where low and high X-ray energy and filtration were switched at 30 Hz. A comparison was made between the actual and measured cross-sectional area using the videodensitometry and edge detection techniques in tissue suppressed energy subtracted images. In eighteen comparisons the videodensitometry technique produced significantly improved results (slope = 0.87, intercept = 0.24 mm2, r = 0.94) when compared to the edge detection technique (slope = 0.42, intercept = 1.99 mm2, r = 0.39). Also, a cylindrical vessel phantom (D = 1.00-4.75 mm) was used to test the ability to calculate and correct for the effect of the out of plane angle of the arterial segment on the cross-sectional area estimation of the videodensitometry technique. After corrections were made for the out of plane angle using two different projections, there was a good correlation between the actual and the measured cross-sectional area using the videodensitometry technique (slope = 0.91, intercept = 0.11 mm2, r = 0.99). These data suggest that it is possible to quantitate absolute cross-sectional area without any assumption regarding the arterial shape using videodensitometry in conjunction with the motion immune dual-energy subtraction technique.