Blended Images Research Articles

Single-portal-phase low-tube-voltage dual-energy CT for short-term follow-up of acute pancreatitis: evaluation of CT severity index, interobserver agreement and radiation dose.

To intra-individually compare single-portal-phase low-tube-voltage (100-kVp) computed tomography (CT) with 120-kVp images for short-term follow-up assessment of CT severity index (CTSI) of acute pancreatitis, interobserver agreement and radiation dose. We retrospectively analysed 66 patients with acute pancreatitis who underwent initial dual-contrast-phase CT (unenhanced, arterial, portal phase) at admission and short-term (mean interval 11.4 days) follow-up dual-contrast-phase dual-energy CT. The 100-kVp and linearly blended images representing 120-kVp acquisition follow-up CT images were independently evaluated by three radiologists using a modified CTSI assessing pancreatic inflammation, necrosis and extrapancreatic complications. Scores were compared with paired t test and interobserver agreement was evaluated using intraclass correlation coefficients (ICC). Mean CTSI scores on unenhanced, portal- and dual-contrast-phase images were 4.9, 6.1 and 6.2 (120 kVp) and 5.0, 6.0 and 6.1 (100 kVp), respectively. Contrast-enhanced series showed a higher CTSI compared to unenhanced images (P < 0.05) but no significant differences between single- and dual-contrast-phase series (P > 0.7). CTSI scores were comparable for 100-kVp and 120-kVp images (P > 0.05). Interobserver agreement was substantial for all evaluated series and subcategories (ICC 0.67-0.93). DLP of single-portal-phase 100-kVp images was reduced by 41 % compared to 120-kVp images (363.8 versus 615.9 mGy cm). Low-tube-voltage single-phase 100-kVp CT provides sufficient information for follow-up evaluation of acute pancreatitis and significantly reduces radiation exposure. • Single-portal-phase CT provides sufficient evaluation for follow-up of acute pancreatitis. • Follow-up CT does not benefit from unenhanced or arterial-phase acquisition. • CT severity index scores are equal for dual-contrast-phase 100-/120-kVp acquisition (P > 0.05). • 100-kVp single-portal-phase follow-up CT of acute pancreatitis significantly reduces radiation exposure.

Corticospinal tract-sparing intensity-modulated radiotherapy treatment planning

AimTo establish intensity-modulated radiotherapy (IMRT) planning procedures that spare the corticospinal tract by integrating diffusion tensor tractography into the treatment planning software. BackgroundOrgans at risk are generally contoured according to the outline of the organ as demonstrated by CT or MRI. But a part of the organ with specific function is difficult to protect, because such functional part of the organ cannot be delineated on CT or conventional sequence of MRI. MethodsDiagnostic and treatment planning images of glioblastoma patients who had been treated by conventional 3-dimensional conformal radiotherapy were used for re-planning of IMRT. Three-dimensional fiber maps of the corticospinal tracts were created from the diffusion tensors obtained from the patients before the surgery, and were blended with the anatomical MR images (i.e. gadolinium-enhanced T1-weighted images or T2-weighted images). DICOM-formatted blended images were transferred and fused to the planning CT images. Then, IMRT plans were attempted. ResultsThe corticospinal tracts could be contoured as organs at risk (OARs), because the blended images contained both anatomical information and fiber-tract maps. Other OARs were contoured in a way similar to that of ordinary IMRT planning. Gross tumor volumes, clinical target volumes, planning target volumes, and other OARs were contoured on the treatment planning software, and IMRT plans were made. ConclusionsIMRT plans with diminished doses to the corticospinal tract were attained. This technique enabled us to spare specific neuron fibers as OARs which were formerly “invisible” and to reduce the probability of late morbidities.

µ-Mosaicing and Thermo-Mosaicing using Image In-painting

Microscopy has enormous applications in both medical and non-medical fields. This has gained interest of many researchers in the field of digital image processing to develop algorithms and applications helping in improving their observation and analysis. Here, novel method called ‘μMosaicing’ (read as Micro-Mosaicing) is introduced to create mosaics of microscopic images from a video sequence to obtain large view, high resolution images of specimen. A thermal camera forms images by sensing the infrared radiations from an object. High resolution thermal images can be used to determine temperatures in detailed thermal analysis. However, the cost of thermal camera increases with their resolution. While, thermo-graphy plays an important role in the diagnosis of various diseases, high resolution large field of view images will be certainly helpful in diagnosis and treatment. So a new approach to create mosaics of thermal images from video sequence, called ‘Thermo-Mosaicing’, is proposed which can find wide applications in medical field. Both, μ-Mosaicing and Thermo-Mosaicing employ Key Frame Selection Algorithm, Image Matching using Normalized Cross Correlation (NCC), Image Stitching using 3-point Mask Blending Algorithm and Image In-painting.

Effects of dual-energy CT with non-linear blending on abdominal CT angiography.

ObjectiveTo determine whether non-linear blending technique for arterial-phase dual-energy abdominal CT angiography (CTA) could improve image quality compared to the linear blending technique and conventional 120 kVp imaging.Materials and MethodsThis study included 118 patients who had accepted dual-energy abdominal CTA in the arterial phase. They were assigned to Sn140/80 kVp protocol (protocol A, n = 40) if body mass index (BMI) < 25 or Sn140/100 kVp protocol (protocol B, n = 41) if BMI ≥ 25. Non-linear blending images and linear blending images with a weighting factor of 0.5 in each protocol were generated and compared with the conventional 120 kVp images (protocol C, n = 37). The abdominal vascular enhancements, image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and radiation dose were assessed. Statistical analysis was performed using one-way analysis of variance test, independent t test, Mann-Whitney U test, and Kruskal-Wallis test.ResultsMean vascular attenuation, CNR, SNR and subjective image quality score for the non-linear blending images in each protocol were all higher compared to the corresponding linear blending images and 120 kVp images (p values ranging from < 0.001 to 0.007) except for when compared to non-linear blending images for protocol B and 120 kVp images in CNR and SNR. No significant differences were found in image noise among the three kinds of images and the same kind of images in different protocols, but the lowest radiation dose was shown in protocol A.ConclusionNon-linear blending technique of dual-energy CT can improve the image quality of arterial-phase abdominal CTA, especially with the Sn140/80 kVp scanning.

Can sinogram-affirmed iterative reconstruction improve the detection of small hypervascular liver nodules with dual-energy CT?

To optimize a dual-energy computed tomographic protocol with sinogram-affirmed iterative reconstruction algorithms for improving small nodules detection. The raw data of a dual-energy computed tomographic arterial acquisition of a cirrhotic patient were reconstructed with a standard filtered back projection (B20f) and 3 iterative (I26, I30, I31) kernels with different strength (S3-S5). The 80-kilovolt (peak) (kVp) and the linear blended (DE_0.5) images (80-140 kVp) were analyzed. For each series, 8-subcentimeter low-contrast lesions were simulated within the liver. Four radiologists performed a detectability test and rated the image quality (5-point scales) in all images. The sensitivity increased from 31% (B20f) to 87.5% with sinogram-affirmed iterative reconstruction S5 kernels without a difference between 80-kVp and DE_0.5 series (W test, P = 0.062). The highest image quality rating was 3.8 (B20 DE_0.5), without difference from DE_0.5 I30-S5 and I26-S3. Iterative reconstructions increase the sensitivity for detecting abdominal lesions, even in the 80-kVp series. The kernel I30-S5 was considered the best.

Research on Defect Images Fusion Method Based on Regional Energy Similarity

Because the fusion rules which are based on coefficient of a single point and coefficient of region has one-sidedness and are easy to make blending images lack fidelity, a new fusion rule is put forward. When this fusion rule fuses the low frequency sub-band resolved by wavelet method, it adequately consider the local areas regional energy and the regional energys similarity of the image which is need to fuse, and it use threshold to choose appropriate fusion rule. Experimental result indicated that this way can preferably keep detail features of the image, and it has some engineering application value.

Linear exchanging operation and random phase encoding in gyrator transform domain for double image encryption

We present an optical method for double image encryption by using linear exchanging operation and double random phase encoding (DRPE) in the gyrator transform (GT) domain. In the linear exchanging operation, two primitive images are linearly recombined via a random orthogonal transform matrix. The resultant blended images are employed to constitute a complex-valued image, which is then encoded into a noise-like encrypted image by a DRPE structure in the GT domain. One can recover the primitive images exactly with all decryption keys correctly applied, including the transform orders, the random phase masks and random angle function used for linear exchanging operation. Computer simulations have been given to demonstrate that the proposed scheme eliminates the difference in key spaces between the phase-based image and the amplitude-based image encountered in the previous schemes. Moreover, our scheme has considerably high security level and certain robustness against data loss and noise disturbance.

A comparison of shot‐encoding schemes for wave‐equation migration

ABSTRACTIn the last decade the seismic imaging industry has begun collecting data volumes with a substantial amount of data redundancy through new acquisition geometries including: wide‐azimuth, rich‐azimuth and full‐azimuth geometries. The increased redundancy significantly improves image quality in areas with complex geology, but requires considerably greater computational power to construct an image because of the additional data and the need to use advanced imaging algorithms. One way to reduce the computational cost of processing such datasets is to blend shot‐records, using shot‐encoding, together prior to imaging which reduces the number of migrations necessary for imaging. The downside to doing so is that blending introduces strong, non‐physical, cross‐talk noise into the final image. By carefully choosing the shot‐encoding scheme, we can reduce the additional noise inserted into the image and maximally reduce the number of migrations necessary. We describe a theory of blended imaging that explains all shot‐encoding schemes, and use the theory to design a new class of encodings that use amplitude weights instead of phase‐shifts or time‐delays. We are able to use amplitude encoding to produce blended images of the same quality as previous encoding schemes at a similiar computational cost. Furthermore, we compare the results of amplitude encoding with the results from well‐known shot‐encoding schemes from previous work including: plane‐wave migration, random‐time delay, modulated‐shot migration, and decimated shot‐record migration. In our comparison, we find that plane‐wave migration is in many ways an optimal shot‐encoding scheme. However, we find that plane‐wave migration produces results that are comparable to decimated shot‐record migration when the total cost of imaging is taken into account, thereby calling into question the utility of shot‐encoding in general. Overall, this work questions the potential for shot‐encoding in standard (shot‐record) seismic imaging because blended imaging does not appear to sufficiently reduce the cost of imaging given the quality of the blended image compared to decimated shot‐record migration.

Rightful ownership through image adaptive DWT-SVD watermarking algorithm and perceptual tweaking

In this paper, a tailored blended image adaptive watermarking scheme has been presented, which is based on DWT and SVD. Through this paper an attempt has been made to solve the problem of false positive while maintaining the robustness and imperceptibility with the help of principal component and perceptual tuning of the image. Perceptual tuning is a non-blind technique and based on the objective quality of image. The embedding strength is made dependent on watermark features as well as of host in wavelet domain by using tuning parameter which is user specific. The idea of embedding the principal component of intermediate frequency sub-bands of watermark image into singular values of perceptually tuned intermediate frequency sub-bands of host image have been exploited. The proposed algorithm is providing the adaptive behavior towards the image content for perceptual transparency and at the same time avoiding the possibility of false watermark extraction well supported by a private key, which is necessary at the time of extraction. Thus the proposed watermarking algorithm is a kind of non-blind, image adaptive and suitable for rightful ownership. Various comparative results make the algorithm superior in terms of intentional and non-intentional attacks. Also the algorithm is strong against the print and scan attack.

Dual Energy CT With Nonlinear Image Blending Improves Visualization of Delayed Myocardial Contrast Enhancement in Acute Myocardial Infarction

The objective of this study was to evaluate the effect of, and optimal parameters for, nonlinear image blending compared with linear image blending in the late-phase dual energy computed tomography (DECT) for the visualization of delayed myocardial contrast enhancement in acute myocardial infarction (MI). Acute reperfused MI was induced in 7 pigs by temporary occlusion of the left anterior descending or the left circumflex artery. Two hours after the reperfusion, a contrast-enhanced, late-phase DECT (80 kV/140 kV) scanning was performed. The DECT data were postprocessed with linear and nonlinear image blending techniques. Contrast and percentage signal differences between healthy and infarcted myocardium as well as the blood pool of the left ventricle were computed for the linear and nonlinear techniques and the low- and high-kilovolt images. Data were compared using repeated-measures analysis of variance and post hoc t tests. The nonlinear blending showed the highest signal differences for all contrasts and analyses. Repeated-measures ANOVA results confirmed that the differences were statistically significant for the different postprocessing techniques (P value ranging from <0.001-0.003). Paired-samples post hoc t tests proved the significance of these results (P value ranging from <0.001-0.037). The ideal settings for the nonlinear image blending can thus be deduced from the computed tomographic values of the regions of interest in the linearly blended images with the weighting factor 0.3. Nonlinear image blending improves the visualization of acute MI in the late-phase DECT. It is superior to linearly blended images and source images obtained at 80 or 140 kV.

Clinical Value of Dual-energy CT in Detection of Pancreatic Adenocarcinoma: Investigation of the Best Pancreatic Tumor Contrast to Noise Ratio

Objective To quantitatively compare and determine the best pancreatic tumor contrast to noise ratio (CNR) in different dual-energy derived datasets. Methods In this retrospective, single center study, 16 patients (9 male, 7 female, average age 59.4±13.2 years) with pathologically diagnosed pancreatic cancer were enrolled. All patients received an abdominal scan using a dual source CT scanner 7 to 31 days before biopsy or surgery. After injection of iodine contrast agent, arterial and pancreatic parenchyma phase were scanned consequently, using a dual-energy scan mode (100 kVp/230 mAs and Sn 140 kVp/178 mAs) in the pancreatic parenchyma phase. A series of derived dual-energy datasets were evaluated including non-liner blending (non-linear blending width 0-500 HU; blending center -500 to 500 HU), mono-energetic (40-190 keV), 100 kVp and 140 kVp. On each datasets, mean CT values of the pancreatic parenchyma and tumor, as well as standard deviation CT values of subcutaneous fat and psoas muscle were measured. Regions of interest of cutaneous fat and major psoas muscle of 100 kVp and 140 kVp images were calculated. Best CNR of subcutaneous fat (CNRF) and CNR of the major psoas muscle (CNRM) of non-liner blending and mono-energetic datasets were calculated with the optimal mono-energetic keV setting and the optimal blending center/width setting for the best CNR. One Way ANOVA test was used for comparison of best CNR between different dual-energy derived datasets. Results The best CNRF (4.48±1.29) was obtained from the non-liner blending datasets at blending center -16.6±103.9 HU and blending width 12.3±10.6 HU. The best CNRF (3.28±0.97) was obtained from the mono-energetic datasets at 73.3±4.3 keV. CNRF in the 100 kVp and 140 kVp were 3.02±0.91 and 1.56±0.56 respectively. Using fat as the noise background, all of these images series showed significant differences (P<0.01) except best CNRF of mono-energetic image sets vs. CNRF of 100 kVp image (P=0.460). Similar results were found using muscle as the noise background (mono-energetic image vs. 100 kVp image: P=0.246; mono-energetic image vs. non-liner blending image: P=0.044; others: P<0.01). Conclusion Compared with mono-energetic datasets and low kVp datasets, non-linear blending image at automatically chosen blending width/window provides better tumor to the pancreas CNR, which might be beneficial for better detection of pancreatic tumors.

Dual-Source Dual-Energy CT Evaluation of Complex Cystic Renal Masses

The purpose of this study was to assess the value of dual-source dual-energy CT in the evaluation of complex cystic renal masses. Seventy patients underwent contrast-enhanced dual-energy CT that included true unenhanced images acquired in single-energy mode, corticomedullary phase images acquired in dual-energy mode, and nephrographic phase images acquired in single-energy mode. Virtual unenhanced, blended weighted-average, and color-coded iodine overlay images were reconstructed. The acceptance level and image quality of virtual and true unenhanced images were evaluated. Contrast enhancement on both true unenhanced or blended weighted-average images and color-coded iodine overlay images was evaluated with both calculation in regions of interest and use of confidence level scales. Radiation dose parameters were estimated. Virtual unenhanced images of 70 lesions (97.2%) and true unenhanced images of 72 lesions (100%) were judged acceptable (p = 0.5). The mean quality score of virtual unenhanced images was 2.0 ± 0.7 and of true unenhanced images was 1.5 ± 0.5 (p < 0.001). Mean contrast enhancement measured on true unenhanced and blended weighted-average images was 45.9 ± 15.9 HU (range, 21-78 HU) and on color-coded iodine overlay images was 47.3 ± 16.8 HU (range, 22-75 HU) with no significant differences. Enhancement was excluded on color-coded iodine overlay images with a significantly (p < 0.03) higher level of confidence than it was on true unenhanced and blended weighted-average images. The mean dose reduction with use of a combined dual- and single-energy dual-phase CT protocol was 29.1% ± 11.9% (p < 0.001). Dual-source dual-energy CT is a reliable imaging technique in the evaluation of complex cystic renal masses. True unenhanced images can be replaced by virtual unenhanced images with considerable radiation dose reduction. The color-coded iodine overlay technique is a useful tool for both excluding and identifying endocystic enhancement.

Dual-source, dual-energy multidetector CT for the evaluation of pancreatic tumours

To investigate the potential diagnostic value of dual-energy CT (DECT) with virtual non-enhanced (VNE) and iodine-only images, and to determine the optimal mixed ratio of blended images for evaluation of pancreatic diseases. Multiphasic DECT was performed in 44 patients with focal pancreatic disease. DECT was used during the pancreatic and hepatic venous phases, and a peak kilovoltage of 120 kVp was used for both non-contrast phases. For qualitative analysis of the CT images, two radiologists assessed three image sets (VNE, iodine-only and blended images) in order to determine the acceptability of VNE in replacing true non-enhanced (TNE) images, the added value of iodine-only images and the preferred blending ratio. For quantitative analyses, the CT numbers and image noise of the pancreatic parenchyma, lesions, aorta and psoas muscle were measured. The contrast-to-noise ratio of the lesion was calculated on the pancreatic phase images. The effective radiation dose for DECT and TNE images was calculated. Statistical comparisons were made using the Friedman test, the Wilcoxon test, the paired t-test and repeated measures of analysis of variation with Bonferroni correction for multiple comparisons. The level of acceptance of the VNE images in replacing TNE images was 90.9%. Regarding the iodine-only images, 50% of the cases were found to have an added value. The linear-blended images with a weighting factor of 0.5 were preferred. DECT was able to provide high-quality VNE images that could replace TNE images and iodine-only images showing an added value. Blended images with a weighting factor of 0.5 were preferred by the reviewers.

Mountains of Data

A famous mountaineer and Microsoft researchers are blending images, data, and computer models to document how changing climate is affecting the Himalaya.

Multi-Sensor Fusion of Infrared and Electro-Optic Signals for High Resolution Night Images

Electro-optic (EO) image sensors exhibit the properties of high resolution and low noise level at daytime, but they do not work in dark environments. Infrared (IR) image sensors exhibit poor resolution and cannot separate objects with similar temperature. Therefore, we propose a novel framework of IR image enhancement based on the information (e.g., edge) from EO images, which improves the resolution of IR images and helps us distinguish objects at night. Our framework superimposing/blending the edges of the EO image onto the corresponding transformed IR image improves their resolution. In this framework, we adopt the theoretical point spread function (PSF) proposed by Hardie et al. for the IR image, which has the modulation transfer function (MTF) of a uniform detector array and the incoherent optical transfer function (OTF) of diffraction-limited optics. In addition, we design an inverse filter for the proposed PSF and use it for the IR image transformation. The framework requires four main steps: (1) inverse filter-based IR image transformation; (2) EO image edge detection; (3) registration; and (4) blending/superimposing of the obtained image pair. Simulation results show both blended and superimposed IR images, and demonstrate that blended IR images have better quality over the superimposed images. Additionally, based on the same steps, simulation result shows a blended IR image of better quality when only the original IR image is available.

Double image encryption based on linear blend operation and random phase encoding in fractional Fourier domain

A novel method for double image encryption is proposed by using linear blend operation and double-random phase encoding (DRPE) in the fractional Fourier domain. In the linear blend operation, a random orthogonal matrix is defined to linearly recombined pixel values of two original images. The resultant blended images are employed to constitute a complex-valued image, which is encrypted into an encrypted image with stationary white distribution by the DRPE in the fractional Fourier domain. The primitive images can be exactly recovered by applying correct keys with fractional orders, random phase masks and random angle function that is used in linear blend operation. Numerical simulations demonstrate that the proposed scheme has considerably high security level and certain robustness against data loss and noise disturbance.

A method of separating blended images in space debris observation

Due to the relative movement between space debris and background stars, the blending of objects and stars is ineluctable through observation. It brings down position accuracy of objects and even makes the tracking break down in worse conditions. In view of the difference of geometry between stars and objects in space debris observation, a technique for separating blended objects based on mathematical morphology is presented. It's sufficiently flexible to be applied in image processing, and the blending images can be separated effectively with a high degree of centroid precision.

Dual Energy Computed Tomography to Evaluate Hepatocellular Carcinoma Treated with Transcatheter Arterial Chemo-Embolization: Comparison between the Linear Blending and Nonlinear Moidal Blending Methods

Purpose: To compare the linear blending image with the nonlinear moidal blending image using dual energy CT for the evaluation of the viable portion of hepatocellular carcinoma (HCC) after transcatheter arterial chemoembolization (TACE). Materials and Methods: One-hundred and twenty three HCC patients incompletely treated after TACE were enrolled in this study. The dual energy mode (80 kVp and Sn140 kVp) was only applied in the late arterial phase scanning. A paired t-test was used to compare the lesion-to-liver contrast-to-noise ratio (CNR) and the image noise between the two blending images. Lesion conspicuity, image sharpness, image noise and the overall image quality between the two blending images were compared using the Wilcoxon matched-pair signed-ranks test. Results: The lesion-to-liver CNR was significantly higher on the moidal blending image (5.6 ± 3.2) than on the linear blending image (2.7 ± 1.6) (p < 0.001). The image noise was significantly lower on the moidal blending image (10.9 ± 3.5) than on the linear blending image (17.5 ± 5.5) (p < 0.001). The lesion conspicuity and overall image quality were significantly better on the moidal blending image for both reviewers (p < 0.001). However, with respect to image sharpness, the linear blending image was significantly better for both reviewers (p < 0.01). Conclusion: The nonlinear moidal blending image of dual energy CT showed an increased lesion-to-liver CNR, decreased noise and improved overall image quality for the evaluation of the viable portion of HCC after TACE.

Heterogeneous Nanoscale Morphology in Cross-Sections of Bulk Heterojunction Polymer Solar Cells Visualized by Analytical Electron Microscopy

Using analytical transmission electron microscopy, we investigated spectral images of blends of poly (3- hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM). We applied low energy loss spectroscopic imaging and statistical data analysis to create chemical contrast on ultrathin sections of a pristine and an annealed photoactive layer. P3HT and PCBM domains as well as composite phases were identified at nanometer resolution across the section. This allowed for the visualization of the development of domain sizes and compositions from a pristine to an annealed, more efficient morphology in vertical and lateral directions. By using these data, we could deduce high-resolution cross-sectional concentration profiles and compared them with profiles generated by an established method, secondary ion mass spectrometry.

Feasibility of Low-Tube-Voltage Excretory Phase Images During CT Urography: Assessment Using a Dual-Energy CT Scanner

The purpose of this study is to assess the feasibility of low-tube-voltage images during excretory phase CT urography. In this retrospective study, we examined 70 consecutive CT urograms (35 men and 35 women; mean age, 58.5 years) performed on a dual-energy CT scanner and compared excretory phase images obtained at 80 kVp and 340 mAs with blended images (0.3 × 140 kVp and 80 mAs; and 0.7 × 80 kVp and 340 mAs). Quantitative measurements of urinary system opacification (Hounsfield units), image noise (Hounsfield units), and effective dose (millisieverts) were compared using Student paired t test. Image noise was correlated with patient thickness. Two independent blinded readers qualitatively assessed opacification, image quality (both compared using Wilcoxon test), overall acceptability (compared using McNemar test), and detectability of urinary and extraurinary findings. The 80-kVp images yielded significantly higher opacification of renal pelvis (p < 0.0001), ureter (p < 0.0001), bladder (p < 0.0001), and aorta (p < 0.0001); higher image noise (p < 0.0001); and lower radiation dose (5.2 vs 11.9 mSv). Image noise increased along with increasing patient thickness (r = 0.86 for 80-kVp images). Qualitative opacification scores were better only in the bladder on 80-kVp images (p = 0.002). Although 80-kVp image quality was lower (p < 0.0001), the overall acceptability was similar. Of 42 urinary findings, 40 were detected on 80-kVp images (< 2-mm calyceal calculus and tiny foci of collecting system gas were missed in one patient each, both large patients). Of 137 extraurinary findings, 130 were detected on 80-kVp images (no findings of high clinical significance were missed). Low tube voltage (80 kVp) during excretory phase CT urography is feasible, with improved urinary system opacification, acceptable image quality, and lower radiation dose.