Higher Contrast-to-noise Ratio Values Research Articles

Compressed Sensitivity Encoding Artificial Intelligence Accelerates Brain Metastasis Imaging by Optimizing Image Quality and Reducing Scan Time.

Accelerating the image acquisition speed of MR imaging without compromising the image quality is challenging. This study aimed to evaluate the feasibility of contrast-enhanced (CE) 3D T1WI and CE 3D-FLAIR sequences reconstructed with compressed sensitivity encoding artificial intelligence (CS-AI) for detecting brain metastases (BM) and explore the optimal acceleration factor (AF) for clinical BM imaging. Fifty-one patients with cancer with suspected BM were included. Fifty participants underwent different customized CE 3D-T1WI or CE 3D-FLAIR sequence scans. Compressed SENSE encoding acceleration 6 (CS6), a commercially available standard sequence, was used as the reference standard. Quantitative and qualitative methods were used to evaluate image quality. The SNR and contrast-to-noise ratio (CNR) were calculated, and qualitative evaluations were independently conducted by 2 neuroradiologists. After exploring the optimal AF, sample images were obtained from 1 patient by using both optimized sequences. Quantitatively, the CNR of the CS-AI protocol for CE 3D-T1WI and CE 3D-FLAIR sequences was superior to that of the CS protocol under the same AF (P < .05). Compared with reference CS6, the CS-AI groups had higher CNR values (all P < .05), with the CS-AI10 scan having the highest value. The SNR of the CS-AI group was better than that of the reference for both CE 3D-T1WI and CE 3D-FLAIR sequences (all P < .05). Qualitatively, the CS-AI protocol produced higher image quality scores than did the CS protocol with the same AF (all P < .05). In contrast to the reference CS6, the CS-AI group showed good image quality scores until an AF of up to 10 (all P < .05). The CS-AI10 scan provided the optimal images, improving the delineation of normal gray-white matter boundaries and lesion areas (P < .05). Compared with the reference, CS-AI10 showed reductions in scan time of 39.25% and 39.93% for CE 3D-T1WI and CE 3D-FLAIR sequences, respectively. CE 3D-T1WI and CE 3D-FLAIR sequences reconstructed with CS-AI for the detection of BM may provide a more effective alternative reconstruction approach than CS. CS-AI10 is suitable for clinical applications, providing optimal image quality and a shortened scan time.

Salvaging low contrast abdominal CT studies using noise-optimised virtual monoenergetic image reconstruction.

Objectives:To assess the impact of noise-optimised virtual monoenergetic imaging (VMI+) on image quality and diagnostic evaluation in abdominal dual-energy CT scans with impaired portal-venous contrast.Methods:We screened 11,746 patients who underwent portal-venous abdominal dual-energy CT for cancer staging between 08/2014 and 11/2019 and identified those with poor portal-venous contrast.Standard linearly-blended image series and VMI+ image series at 40, 50, and 60 keV were reconstructed. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of abdominal organs and vascular structures were calculated. Image noise, image contrast and overall image quality were rated by three radiologists using 5-point Likert scale.Results:452 of 11,746 (4%) exams were poorly opacified. We excluded 190 cases due to incomplete datasets or multiple exams of the same patient with a final study group of 262. Highest CNR values in all abdominal organs (liver, 6.4 ± 3.0; kidney, 17.4 ± 7.5; spleen, 8.0 ± 3.5) and vascular structures (aorta, 16.0 ± 7.3; intrahepatic vein, 11.3 ± 4.7; portal vein, 15.5 ± 6.7) were measured at 40 keV VMI+ with significantly superior values compared to all other series. In subjective analysis, highest image contrast was seen at 40 keV VMI+ (4.8 ± 0.4), whereas overall image quality peaked at 50 keV VMI+ (4.2 ± 0.5) with significantly superior results compared to all other series (p < 0.001).Conclusions:Image reconstruction using VMI+ algorithm at 50 keV significantly improves image contrast and image quality of originally poorly opacified abdominal CT scans and reduces the number of non-diagnostic scans.Advances in knowledge:We validated the impact of VMI+ reconstructions in poorly attenuated DECT studies of the abdomen in a big data cohort.

Performance evaluation of fifth-generation ultra-high-resolution SPECT system with two stationary detectors and multi-pinhole imaging

BackgroundSmall-animal single-photon emission computed tomography (SPECT) systems with multi-pinhole collimation and large stationary detectors have advantages compared to systems with moving small detectors. These systems benefit from less labour-intensive maintenance and quality control as fewer prone parts are moving, higher accuracy for focused scans and maintaining high resolution with increased sensitivity due to focused pinholes on the field of view. This study aims to investigate the performance of a novel ultra-high-resolution scanner with two-detector configuration (U-SPECT5-E) and to compare its image quality to a conventional micro-SPECT system with three stationary detectors (U-SPECT+).MethodsThe new U-SPECT5-E with two stationary detectors was used for acquiring data with 99mTc-filled point source, hot-rod and uniformity phantoms to analyse sensitivity, spatial resolution, uniformity and contrast-to-noise ratio (CNR). Three dedicated multi-pinhole mouse collimators with 75 pinholes each and 0.25-, 0.60- and 1.00-mm pinholes for extra ultra-high resolution (XUHR-M), general-purpose (GP-M) and ultra-high sensitivity (UHS-M) imaging were examined. For CNR analysis, four different activity ranges representing low- and high-count settings were investigated for all three collimators. The experiments for the performance assessment were repeated with the same GP-M collimator in the three-detector U-SPECT+ for comparison.ResultsPeak sensitivity was 237 cps/MBq (XUHR-M), 847 cps/MBq (GP-M), 2054 cps/MBq (UHS-M) for U-SPECT5-E and 1710 cps/MBq (GP-M) for U-SPECT+. In the visually analysed sections of the reconstructed mini Derenzo phantoms, rods as small as 0.35 mm (XUHR-M), 0.50 mm (GP-M) for the two-detector as well as the three-detector SPECT and 0.75 mm (UHS-M) were resolved. Uniformity for maximum resolution recorded 40.7% (XUHR-M), 29.1% (GP-M, U-SPECT5-E), 16.3% (GP-M, U-SPECT+) and 23.0% (UHS-M), respectively. UHS-M reached highest CNR values for low-count images; for rods smaller than 0.45 mm, acceptable CNR was only achieved by XUHR-M. GP-M was superior for imaging rods sized from 0.60 to 1.50 mm for intermediate activity concentrations. U-SPECT5-E and U-SPECT+ both provided comparable CNR.ConclusionsWhile uniformity and sensitivity are negatively affected by the absence of a third detector, the investigated U-SPECT5-E system with two stationary detectors delivers excellent spatial resolution and CNR comparable to the performance of an established three-detector-setup.

Evaluation of reconstruction algorithms for a stationary digital breast tomosynthesis system using a carbon nanotube X-ray source array.

Breast cancer is the most frequently diagnosed cancer in women worldwide. Digital breast tomosynthesis (DBT), which is based on limited-angle tomography, was developed to solve tissue overlapping problems associated with traditional breast mammography. However, due to the problems associated with tube movement during the process of data acquisition, stationary DBT (s-DBT) was developed to allow the X-ray source array to stay stationary during the DBT scanning process. In this work, we evaluate four widely used and investigated DBT image reconstruction algorithms, including the commercial Feldkamp-Davis-Kress algorithm (FBP), the simultaneous iterative reconstruction technique (SIRT), the simultaneous algebraic reconstruction technique (SART) and the total variation regularized SART (SART-TV) for an s-DBT imaging system that we set up in our own laboratory for studies using a semi-elliptical digital phantom and a rubber breast phantom to determine the most superior algorithm for s-DBT image reconstruction among the four algorithms. Several quantitative indexes for image quality assessment, including the peak signal-noise ratio (PSNR), the root mean square error (RMSE) and the structural similarity (SSIM), are used to determine the best algorithm for the imaging system that we set up. Image resolutions are measured via the calculation of the contrast-to-noise ratio (CNR) and artefact spread function (ASF). The experimental results show that the SART-TV algorithm gives reconstructed images with the highest PSNR and SSIM values and the lowest RMSE values in terms of image accuracy and similarity, along with the highest CNR values calculated for the selected features and the best ASF curves in terms of image resolution in the horizontal and vertical directions. Thus, the SART-TV algorithm is proven to be the best algorithm for use in s-DBT image reconstruction for the specific imaging task in our study.

Contrast-enhanced spectral mammography with a compact synchrotron source.

For early breast cancer detection, mammography is nowadays the commonly used standard imaging approach, offering a valuable clinical tool for visualization of suspicious findings like microcalcifications and tumors within the breast. However, due to the superposition of anatomical structures, the sensitivity of mammography screening is limited. Within the last couple of years, the implementation of contrast-enhanced spectral mammography (CESM) based on K-edge subtraction (KES) imaging helped to improve the identification and classification of uncertain findings. In this study, we introduce another approach for CESM based on a two-material decomposition, with which we expect fundamental improvements compared to the clinical procedure. We demonstrate the potential of our proposed method using the quasi-monochromatic radiation of a compact synchrotron source—the Munich Compact Light Source (MuCLS)—and a modified mammographic accreditation phantom. For direct comparison with the clinical CESM approach, we also performed a standard dual-energy KES at the MuCLS, which outperformed the clinical CESM images in terms of contrast-to-noise ratio (CNR) and spatial resolution. However, the dual-energy-based two-material decomposition approach achieved even higher CNR values. Our experimental results with quasi-monochromatic radiation show a significant improvement of the image quality at lower mean glandular dose (MGD) than the clinical CESM. At the same time, our study indicates the great potential for the material-decomposition instead of clinically used KES to improve the quantitative outcome of CESM.

Effect of Different Breast Densities and Average Glandular Dose on Contrast to Noise Ratios in Full-Field Digital Mammography: Simulation and Phantom Study.

We aimed to investigate the effects of mammary gland density and average glandular dose (AGD) on contrast-to-noise ratio (CNR) of breast-equivalent phantoms with different mammary gland/fat tissue ratios. Full-field digital-mammography breast X-rays were performed on breast-equivalent phantoms with three different mammary gland/fat tissue ratios (Phantom A [30/70], Phantom B [50/50], and Phantom C [70/30]) and seven thicknesses ranging from 10 mm to 70 mm. The prediction formula for the CNR was calculated by multivariate analysis and the effects of the various parameters on CNR were evaluated using a multiple regression analysis model. Higher CNR values were obtained with lower mammary gland/fat tissue ratios and lower phantom thicknesses. Variation in CNR among the three breast models was low (coefficient of variation, 3.4–8.7%) at lower phantom thicknesses (10–30 mm) and high (coefficient of variation, 10.5–16.8%) at higher phantom thickness (50–70 mm). CNR showed a strong negative correlation (r = -0.8989) with AGD across all three mammary gland ratios. A predictive formula for CNR using AGD and mammary gland density was developed. CNR can be predicted with high precision using AGD and mammary gland density. The predicted CNR could be used to measure the diagnostic reliability of mammography in breast cancer.

Fluid-Attenuated Inversion Recovery Signal Intensity as a Predictor of Gadolinium Enhancement in Relapsing-Remitting Multiple Sclerosis.

Magnetic resonance imaging (MRI) is used to diagnose and monitor disease activity in relapsing-remitting multiple sclerosis (RRMS). The objective of this study was to explore the association of "ultrabright" axial fluid-attenuated inversion recovery (FLAIR) lesions with gadolinium enhancement in patients with RRMS using qualitative and quantitative approaches. MRIs from patients with RRMS from 2010 to 2015 were reviewed. Two radiologists independently identified ultrabright lesions on axial FLAIR sequences. The contrast-to-noise ratio (CNR) was measured for ultrabright and control lesions. Of 301 lesions included in the study, 77 (26%) were identified by both radiologists as ultrabright. Interrater agreement was moderate (κ = 0.77, P < .001). Lesions identified by both radiologists as ultrabright demonstrated an association with gadolinium enhancement (χ21 = 30.8, P < .001) but were not associated with MRI magnet strength (χ21 = 0.24, P = .65). Higher CNR values were associated with gadolinium enhancement for 1.5-T studies (OR, 1.05; 95% CI, 1.02-1.07; P = .001) and 3-T studies (OR, 1.02; 95% CI, 1.02-1.03; P < .001). Diagnostic accuracy of the quantitative model was good for 1.5-T studies (area under the curve, 0.79; 95% CI, 0.68-0.9; P < .001) and 3-T studies (area under the curve, 0.78; 95% CI, 0.73-0.84; P < .001). Positive predictive value of 100% was obtained for CNR values of 92 for 1.5-T and 184 for 3-T studies. Qualitatively and quantitatively identified ultrabright axial FLAIR lesions are significantly associated with gadolinium enhancement.

The Effects of Total Variation (TV) Technique for Noise Reduction in Radio-Magnetic X-ray Image: Quantitative Study

In order to reduce the amount of noise component in X-ray imaging system, various reduction techniques were frequently used in the field of diagnostic imaging. Although the previous techniques –such as median, Wiener filters and Anscombe noise reduction technique – were able to reduce the noise, the edge information was still damaged. In order to cope with this problem, total variation (TV) noise reduction technique has been developed and researched. The purpose of this study was to evaluate and compare the image quality using normalized noise power spectrum (NNPS) and contrast-to-noise ratio (CNR) through simulations and experiments with respect to the above-mentioned noise reduction techniques. As a result, not only lowest NNPS value but also highest CNR values were acquired using a TV noise reduction technique. In conclusion, the results demonstrated that TV noise reduction technique is proved as the most practical method to ensure accurate denoising in X-ray imaging system.

Optimal angular dose distribution to acquire 3D and extra 2D images for digital breast tomosynthesis (DBT)

The purpose of this study is to determine the optimal non-uniform angular dose distribution to improve the quality of the 3D reconstructed images and to acquire extra 2D projection images. In this analysis, 7 acquisition sets were generated by using four different values for the number of projections (11, 15, 21, and 29) and total angular range (±14°, ±17.5°, ±21°, and ±24.5° ). For all acquisition sets, the zero-degree projection was used as the 2D image that was close to that of standard conventional mammography (CM). Exposures used were 50, 100, 150, and 200 mR for the zero-degree projection, and the remaining dose was distributed over the remaining projection angles. To quantitatively evaluate image quality, we computed the CNR (contrast-to-noise ratio) and the ASF (artifact spread function) for the same radiation dose. The results indicate that, for microcalcifications, acquisition sets with approximately 4 times higher exposure on the zero-degree projection than the average exposure for the remaining projection angles yielded higher CNR values and were 3% higher than the uniform distribution. However, very high dose concentrations toward the zero-degree projection may reduce the quality of the reconstructed images due to increasing noise in the peripheral views. The zero-degree projection of the non-uniform dose distribution offers a 2D image similar to that of standard CM, but with a significantly lower radiation dose. Therefore, we need to evaluate the diagnostic potential of extra 2D projection image when diagnose breast cancer by using 3D images with non-uniform angular dose distributions.

Spectral CT imaging in patients with Budd-Chiari syndrome: investigation of image quality.

To assess the image quality of monochromatic imaging from spectral CT in patients with Budd-Chiari syndrome (BCS), fifty patients with BCS underwent spectral CT to generate conventional 140 kVp polychromatic images (group A) and monochromatic images, with energy levels from 40 to 80, 40 + 70, and 50 + 70 keV fusion images (group B) during the portal venous phase (PVP) and the hepatic venous phase (HVP). Two-sample t tests compared vessel-to-liver contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) for the portal vein (PV), hepatic vein (HV), inferior vena cava. Readers' subjective evaluations of the image quality were recorded. The highest SNR values in group B were distributed at 50 keV; the highest CNR values in group B were distributed at 40 keV. The higher CNR values and SNR values were obtained though PVP of PV (SNR 18.39 ± 6.13 vs. 10.56 ± 3.31, CNR 7.81 ± 3.40 vs. 3.58 ± 1.31) and HVP of HV (3.89 ± 2.08 vs. 1.27 ± 1.55) in the group B; the lower image noise for group B was at 70 keV and 50 + 70 keV (15.54 ± 8.39 vs. 18.40 ± 4.97, P = 0.0004 and 18.97 ± 7.61 vs. 18.40 ± 4.97, P = 0.0691); the results show that the 50 + 70 keV fusion image quality was better than that in group A. Monochromatic energy levels of 40-70, 40 + 70, and 50 + 70 keV fusion image can increase vascular contrast and that will be helpful for the diagnosis of BCS, we select the 50 + 70 keV fusion image to acquire the best BCS images.

Characterizing the modulation transfer function (MTF) of proton/carbon radiography using Monte Carlo simulations

To characterize the modulation transfer function (MTF) of proton/carbon radiography using Monte Carlo simulations. To assess the spatial resolution of proton/carbon radiographic imaging. A phantom was specifically modeled with inserts composed of two materials with three different densities of bone and lung. The basic geometry of the phantom consists of cube-shaped inserts placed in water. The thickness of the water, the thickness of the cubes, the depth of the cubes in the water, and the particle beam energy have all been varied and studied. There were two phantom thicknesses considered 20 and 28 cm. This represents an average patient thickness and a thicker sized patient. Radiographs were produced for proton beams at 230 and 330 MeV and for a carbon ion beam at 400 MeV per nucleon. The contrast-to-noise ratio (CNR) was evaluated at the interface of two materials on the radiographs, i.e., lung-water and bone-water. The variation in CNR at interface between lung-water and bone-water were study, where a sigmoidal fit was performed between the lower and the higher CNR values. The full width half-maximum (FWHM) value was then obtained from the sigmoidal fit. Ultimately, spatial resolution was defined by the 10% point of the modulation-transfer-function (MTF10%), in units of line-pairs per mm (lp/mm). For the 20 cm thick phantom, the FWHM values varied between 0.5 and 0.7 mm at the lung-water and bone-water interfaces, for the proton beam energies of 230 and 330 MeV and the 400 MeV/n carbon beam. For the 28 cm thick phantom, the FWHM values varied between 0.5 and 1.2 mm at the lung-water and bone-water interface for the same inserts and beam energies. For the 20 cm phantom the MTF10% for lung-water interface is 2.3, 2.4, and 2.8 lp/mm, respectively, for 230, 330, and 400 MeV/n beams. For the same 20 cm thick phantom but for the bone-water interface the MTF10% yielded 1.9, 2.3, and 2.7 lp/mm, respectively, for 230, 330, and 400 MeV/n beams. In the case of the thicker 28 cm phantom, the authors observed that at the lung-water interface the MTF10% is 1.6, 1.9, and 2.6 lp/mm, respectively, for 230, 330, and 400 MeV/n beams. While for the bone-water interface the MTF10% was 1.4, 1.9, and 2.9 lp/mm, respectively, for 230, 330, and 400 MeV/n beams. Carbon radiography (400 MeV/n) yielded best spatial resolution, with MTF10% = 2.7 and 2.8 lp/mm, respectively, at the lung-water and bone-water interfaces. The spatial resolution of the 330 MeV proton beam was better than the 230 MeV proton, because higher incident proton energy suffer smaller deflections within the patient and thus yields better proton radiographic images. The authors also observed that submillimeter resolution can be obtained with both proton and carbon beams.

SU‐E‐J‐25: A Quantitative Comparison of Contrast‐To‐Noise in Rib Suppressed Images

Purpose: To compare the contrast to noise ratio (CNR) of two different rib suppression methodologies ‐ dual‐energy (DE) image subtraction and blind signal separation (BSS)‐used for lung cancer patients receiving image‐guided radiotherapy. Methods: A database consisting of 28 planar radiographs obtained at 60 kVp and 120 kVp were used in this study. DE subtraction imaging was performed by taking a weighted logarithmic subtraction of the individual images. A weighting parameter of 2.1 was chosen to produce the optimal soft tissue (rib suppressed) images for each image pair. Similarly, BSS was used to extract the soft tissue and bony image components from a patient image. An open source program for performing BSS, called FastICA, was used in conjunction with the same 60 kVp and 120 kVp images. Regions of interest (ROIs) were contoured on the resultant images and the CNR from each technique was calculated and compared. Results: A paired t‐test was run on the CNR values, resulting in a p value &lt; 0.05, indicated there was a statistically significant difference in the CNRs generated by the two methods. For 24 of the 28 image sets that were evaluated, the CNR values were found to be higher for the DE subtraction images. Of these 24 images, 9 had CNR values &gt; 20% higher, and 4 had CNR values &gt; 40% higher. Conclusion: Based on this study, DE image subtraction creates images with higher CNR values than those generated with FastICA. This is likely due, at least in part, to the ability to customize the weighting factor of the DE subtraction images. However, there are numerous methods for performing BSS outside of FastICA, and further study is warranted to determine if alternative BSS methods could produce better rib suppressed images. This research was supported by Varian Medical Systems.

Spectral CT in patients with small HCC: investigation of image quality and diagnostic accuracy

To assess image quality and diagnostic accuracy of monochromatic imaging from spectral CT in patients with small HCC (≤3cm). Twenty-seven patients with 31 HCC underwent spectral CT to generate conventional 140-kVp polychromatic images (group A) and monochromatic images with energy levels from 40 to 140keV (group B) during the late arterial phase (LAP) and the portal venous phase (PVP). Two-sample t tests compared the tumour-to-liver contrast-to-noise ratio (CNR) and mean image noise. Lesion detection for LAP, reader confidence and readers' subjective evaluations of image quality were recorded. Highest CNRs in group B were distributed at 40, 50 and 70keV. Higher CNR values and lesion conspicuity scores (LCS) were obtained in group B than in group A (CNR 3.36 ± 2.07 vs. 1.47 ± 0.89 in LAP; 2.29 ± 2.26 vs. 1.58 ± 1.75 in PVP; LCS 2.82, 2.84, 2.63 and 2.53 at 40-70keV, respectively, vs. 1.95) (P < 0.001). Lowest image noise for group B was at 70keV, resulting in higher image quality than that in group A (4.70 vs. 4.07; P < 0.001). Monochromatic energy levels of 40-70keV can increase detectability in small HCC and this increase might not result in image quality degradation. • Spectral computed tomography may help the detection of small hepatocellular carcinoma. • Monochromatic energy levels of 40-70keV increase the sensitivity for detection. • Prospective study showed that monochromatic imaging provides greater diagnostic confidence. • Monochromatic energy level of 70keV improves the overall image quality.

Single‐ vs. Double‐dose in contrast‐enhanced magnetic resonance angiography of the carotid arteries

WE READ WITH great interest the article by Jourdan et al (1), published in the March 2007 issue of JMRI, in which the authors reported their results of dose comparison of single- vs. double-dose in contrast-enhanced magnetic resonance angiography (CE-MRA) of the carotid arteries. Their intraindividual crossover trial performed with 11 healthy volunteers confirms to a large extent our own conclusions after prospectively including 119 patients with suspected vascular occlusive disease in a similar study (2), stating that a single-dose of 0.1 mmol/kg body weight (BW) of an extracellular gadolinium agent may be the preferable dosage for the carotid arteries. Initially, we were surprised when reading that a double dose resulted in significantly (P < 0.05) higher signal intensity (SI), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) compared to a single dose, while our patient study could not reveal such a difference. To the contrary, dosing did not influence our contrast enhancement when comparing double-dose (mean CNR = 70.01 ± 20.7) and single-dose (CNR = 69.12 ± 19.8). The most probable explanation for this difference seems to be the different contrast administration scheme—in our case both dosages were administered at 3.0 mL/second followed by a saline flush of 30 mL at the same speed. In the study of Jourdan et al (1), the infusion time was generally fixed for the gadolinium bolus to 10 seconds—followed by a 20-mL saline flush at the same rate. Overall, one can calculate a mean injection speed of 1.5 mL/second for single-dose and 3.0 mL/second for double-dose considering the mean weight of 71 ± 16 kg. Apparently, a higher injection speed results in higher CNR values, even though these have little impact on the diagnostic quality, as stated in both studies. It would have been interesting to retrieve some more information about the total acquisition time and the k-space filling techniques used by the authors, as these are of growing importance when evaluating and improving MRA techniques (3). In fact, centric-elliptic reordering or radial k-space techniques using segmented k-space filling should allow further dose decrease while improving spatial resolution and suppressing venous overlay. Using initial central k-space encoding and fixed acquisition times of 19 seconds, we could not observe a decreased coverage in case of single-dose or higher frequencies of venous overlay within the double-dose group. This confirms the high robustness of the MR angiographic technique we had implemented with little differences in our qualitative results despite the presence of all kinds of vascular pathologies in both dose groups. Mean CNR levels were considerably lower in the study of Jourdan et al (1), but this is probably attributed to the higher spatial resolution they report, and in part to the unequal formulas they used to calculate SNR and CNR. Nevertheless, the SNR penalty due to higher spatial resolution must perhaps be corrected by higher dosing? Furthermore, our study results could show that CNR is inversely related to BW both for single- and double-dose groups. Apparently, patients with higher BW present lower CNR values. This did not seem to lead to a decay of diagnostic quality. It remains to be clarified if patients with higher BW are rather underdosed, or the opposite, if patients with lower BW could benefit from a dose reduction even beyond single-dose. Influence of dosing on the degree of overstaging of stenosis in CE-MRA compared to digital subtraction angiography. Optimal dosing when segmented k-space techniques are implemented. (4) Dose influence on resolution or in other words on outer k-space trajectories. Adaptation of dosing to BW or better to body-surface of the patients. Dosing at high field. (3) Dosing when using parallel acquisition techniques with high acceleration factors. To conclude, data of both studies together are suggestive that single-dose, when ideally timed for central k-space would likely be optimal, both from the diagnostic and economic point of view for CE-MRA of the carotids. Johannes M. Froehlich PhD*, Martin Unterweger MD*, Rahel A. Kubik-Huch MD*, * Institute of Radiology, Cantonal Hospital Baden, Baden, Switzerland.