Difference In Contrast-to-noise Ratio Research Articles

Value of Sinogram-Affirmed Iterative Reconstruction for Evaluating Coronary Calcified Plaques

Background: Coronary computed tomography angiography (cCTA) technology as a kind of non-traumatic examination has been widely used in clinical practice. There are major issues that need to be considered. One is how to obtain high quality images and at the same time effectively reduce the radiation dose. The second is coronary artery calcified plaque artifacts that seriously affect the depiction of plaque morphology and luminal stenosis. In case of dose reduction, these artifacts are more outstanding. Objectives: This study determined the value of sinogram-affirmed iterative reconstruction (SAFIRE) technology to assess coronary-calcified plaques. This value was compared with filtered back-projection (FBP) reconstruction. Patients and Methods: Sixty-three cases with calcified plaques diagnosed via coronary CT examination were selected. The mean CT-number, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), number of calcium plaques, edges, lumen situation, and the subjective image quality ratings of the cases using FBP and SAFIRE1–SAFIRE5 (six groups) were analyzed and compared. Results: The subjective ratings of image quality using SAFIRE1–SAFIRE5 reconstructions were significantly higher than those using FBP, with SAFIRE3 achieving the highest rating. Compared with FBP reconstruction, the differences in noise, SNR, and CNR using SAFIRE1-SAFIRE5 were statistically significant (P 0.05). Conclusion: SAFIRE reconstruction provided better coronary image quality and displayed the number, morphology, and surrounding lumen of calcium plaques more accurately than traditional FBP reconstruction, with SAFIRE3 achieving the best results.

Coronary Computed Tomographic Angiography at Low Concentration of Contrast Agent and Low Tube Voltage in Patients with Obesity:: A Feasibility Study

Using lower tube voltage can reduce the exposure to radiation and the dose of contrast agent. However, lower tube voltage is often linked to more noise and poor image quality, which create a need for more effective technology to resolve this problem. To explore the feasibility of coronary computed tomographic angiography (CCTA) in patients with obesity at low tube voltage (100 kV) and low contrast agent concentration (270 mg/mL) using iterative reconstruction. A total of 48 patients with body mass index greater than 30 kg/m(2) were included and randomly divided into two groups. Group A received a traditional protocol (iopromide 370 mg/mL + 120 kV); group B received a protocol with low tube voltage (100 kV), low contrast agent concentration (270 mg/mL), and iterative reconstruction. The effective dose (ED), average attenuation values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), the figure of merit (FOM), image quality scores, and the total iodine intake were compared. No significant differences in average CT attenuations, SNR, CNR, and subjective scores were noticed between the two groups (P > 0.05), whereas the FOM of group B was significantly higher than that of group A. Effective radiation dose, total iodine, and iodine injection rate in group B were lower than those of group A (P <0.01). In patients with obesity, isotonic contrast agent with low iodine concentration and low-dose CCTA were feasible. Substantial reduction in radiation dose and the iodine intake could be achieved without compromising the image quality.

Heavily T₂-Weighted 3D-FLAIR Improves the Detection of Cochlear Lymph Fluid Signal Abnormalities in Patients with Sudden Sensorineural Hearing Loss.

Purpose:To compare the signal increase in cochlear lymph fluid on three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) in patients with sudden sensorineural hearing loss (SNHL) between regular contrast 3D-FLAIR (FL) and heavily T2-weighted 3D-FLAIR (HF).Methods:Twenty-five patients with unilateral sudden SNHL and eight healthy volunteers were included. Patients were divided into two groups: the mild group consisted of 9 patients, with an average hearing level of 60 dB or less; the severe group consisted of 16 patients, with an average hearing level of more than 60 dB. All patients and healthy volunteers underwent magnetic resonance (MR) cisternography for anatomical reference of the fluid space with FL and HF at 3 T. The region of interest (ROI) was manually drawn on the mid-modiolar section of the MR cisternography around the cochlea. The ROI for noise was drawn within the air space. ROIs were copied onto the FL and HF images. The contrast-to-noise ratio (CNR) between the affected and non-affected ear was measured in the patient group and the CNR between the right and left ear was also measured in the control group. Differences in the CNR on FL and HF images among the three groups were tested by one-way analysis of variance (ANOVA).Results:There was a statistically significant difference in mean CNR on HF among the three groups (P < 0.001). Furthermore, based on pairwise comparisons, there was a statistically significant difference between them in mean CNR on HF (P < 0.05). There was no statistically significant difference in mean CNR on FL among the three groups (P = 0.074).Conclusions:HF is more sensitive to signal alterations in cochleae with sudden SNHL than FL.

The best noise index combined with ASIR weighting selection in low-dose chest scanning

To discuss the best noise index combined with ASIR weighting selection in low-dose chest scanning based on BMI. 200 patients collected from May to December 2014 underwent non-contrast chest CT examinations, they were randomly assigned into standard dose group (Group A, NI15 combined with 30% ASIR) and low-dose groups (Group B, NI25 combined with 40% ASIR, Group C, NI30 combined with 50% ASIR, Group D, NI35 combined with 60% ASIR), 50 cases in each group; the patients were assigned into three groups based on BMI (kg/m2): BMI<18.5; 18.5≤BMI≤25; BMI>25. Signal-to-nosie ratio (SNR), contrast-to noise ratio (CNR), CT dose index volume (CTDIvol), dose-length product (DLP), effective dose (ED) and subjective scoring between the standard and low-dose groups were compared and analyzed statistically. Differences of SNR, CNR, CTDIvol, DLP and ED among groups were determined with ANOVA analysis and the consistency of diagnosis with Kappa test. SNR, CTDIvol, DLP and ED reduced with the increase of nosie index, the differences among the groups were statistically significant (P<0.05). Kappa value of the two reviewers were 0.888. Subjective scoring of four groups were all above 3 points in BMI<18.5 kg/m2 group; subjective scoring of ABC groups were all above 3 points in 18.5 kg/m2≤BMI≤25 kg/m2 group and subjective scoring of AB groups were all above 3 points in BMI>25 kg/m2 group. NI35 combined with 60% ASIR in BMI<18.5 kg/m2 group; NI30 combined with 50% ASIR in 18.5 kg/m2≤BMI≤25 kg/m2 group; NI25 combined with 40% ASIR in 18.5 kg/m2≤BMI≤25 kg/m2 group were the best parameters combination which both can significantly reduce the radiation dose and ensure the image quality.

Size-Specific Dose Estimates for Evaluation of Individual Patient Dose in CT Protocol for Renal Colic.

The purpose of this study is to retrospectively evaluate size-specific dose estimates of a renal-colic CT protocol and to assess the quality and diagnostic value of obtained images. The study population included 82 consecutive adult patients with acute renal colic undergoing CT with a reduced radiation dose (noise index, 59.1). The control group included 82 consecutive patients who underwent clinically indicated CT examination of the abdomen and pelvis with a routine-dose CT protocol (noise index, 22.0). The size-specific dose estimate was calculated with volume CT dose index and patient effective diameter. Subjective image quality analysis was based on visibility of the ureter. Ureters were tracked from the renal pelvis to the vesicoureteral junction. Objective image quality was based on the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). The size-specific dose estimates in the renal-colic group were 2.7 times lower than those in the control group. A linear relationship between patient size and size-specific dose estimate was noted. In the smallest patient, the conversion factor for the size-specific dose estimate calculation was 1.65. Overall image quality was better for the control patients, but there was no statistically significant difference in ureter visibility. The SNR was higher for the control group, whereas no difference in CNR was found. Small patients need the biggest correction for body size and require special attention in radiation dose estimation. We suggest the modification of scanning parameters on the basis of size-specific dose estimate to decrease patient dose in large patients.

Readout-segmented echo-planar imaging in diffusion-weighted MR imaging of acute infarction of the brainstem and posterior fossa: comparison of single-shot echo-planar diffusion-weighted sequences

ObjectiveThe purpose of this study was to evaluate the clinical usefulness of readout-segmented echo-planar imaging (rs-EPI) in the diagnosis of acute infarction of the brainstem and posterior fossa, by comparing its results with those of single-shot echo-planar imaging (ss-EPI) at 3-T magnetic resonance imaging. Materials and methodsTwenty-nine patients with acute infarctions of the brainstem and posterior fossa underwent both ss-EPI and rs-EPI. Two readers independently assessed two sets of diffusion-weighted (DW) images for the qualitative comparison of image quality. Signal-to-noise ratio (SNR), lesion contrast, and contrast-to-noise ratio (CNR) were calculated for the assessment of image parameters. ResultsThere were no significant differences in the conspicuity of acute infarction upon qualitative comparison; however, distinctions of anatomical structures, susceptibility artifact, the presence of uncertain high signal intensity in the brain parenchyma, and overall image quality were significantly better in rs-EPI DW images. There were no significant differences in SNR, lesion contrast, CNR, and apparent diffusion coefficient values of acute infarction and normal thalamus between rs-EPI and ss-EPI. Conclusionrs-EPI DWI is a clinically useful technique for evaluating lesions in the brainstem and posterior fossa by producing high-resolution DW images with reduced susceptibility artifact. However, there are no significant differences in the conspicuity of acute infarctions in the brainstem and posterior fossa between rs-EPI and ss-EPI.

SU‐E‐J‐14: A Comparison of a 2.5MV Imaging Beam to KV and 6MV Imaging Beams

Purpose:To compare image quality metrics and dose of TrueBeam V2.0's 2.5MV imaging beam and kV and 6MV images.Methods:To evaluate the MV image quality, the Standard Imaging QC‐3 and Varian Las Vegas (LV) phantoms were imaged using the ‘quality’ and ‘low dose’ modes and then processed using RIT113 V6.3. The LEEDS phantom was used to evaluate the kV image quality. The signal to noise ratio (SNR) was also evaluated in patient images using Matlab. In addition, dose per image was evaluated at a depth of 5cm using solid water for a 28.6 cm × 28.6 cm field size, which is representative of the largest jaw settings at an SID of 150cm.Results:The 2.5MV images had lower dose than the 6 MV images and a contrast to noise ratio (CNR) about 1.4 times higher, when evaluated using the QC‐3. When energy was held constant but dose varied, the different modes, ‘low dose’ and ‘quality’, showed less than an 8% difference in CNR. The ‘quality’ modes demonstrated better spatial resolution than the ‘low dose’; however, even with the ‘low dose’ all line pairs were distinct except for the 0.75lp/mm on the 2.5MV. The LV phantom was used to measure low contrast detectability and showed similar results to the QC‐3. Several patient images all confirmed that SNR were highest in kV images followed by 2.5MV and then 6MV. Qualitatively, for anatomical areas with large variability in thickness, like lateral head and necks, 2.5MV images show more anatomy, such as shoulder position, than kV images.Conclusions:The kV images clearly provide the best image metrics per unit dose. The 2.5MV beam showed excellent contrast at a lower dose than 6MV and may be superior to kV for difficult to image areas that include large changes in anatomical thickness.P Balter: Varian, Sun Nuclear, Philips, CPRIT

80-kVp CT angiography for endovascular aneurysm repair follow-up with halved contrast medium dose and preserved diagnostic quality.

Follow-up of endovascular aneurysm repair (EVAR) with life-long computed tomography angiography (CTA) surveillance exposes patients with impaired renal function to repeated risks of contrast medium-induced nephropathy (CIN). To retrospectively compare vascular attenuation, image noise, contrast-to-noise ratio (CNR), subjective image quality and effective radiation dose (mSv) for CTA with a 16-multirow detector CT (MDCT) equipment at 80 kVp after EVAR using a contrast medium (CM) dose that is half of that used at 120 kVp. Forty patients with estimated glomerular filtration rate (eGFR) <45 mL/min underwent 80-kVp CTA with 160 mg I/kg, and 40 patients with eGFR ≥45 mL/min 120-kVp CTA with 320 mg I/kg (maximum dose weight, 80 kg). Arterial phase analysis included vascular attenuation, image noise and CNR, and calculated effective dose. Subjective image quality was assessed on a 4-point scale by two blinded readers at three different levels as well as overall. Median values in the 80/120 kVp cohorts were: age, 74-75 years; body weight, 77/80 kg; BMI 24/27 kg/m(2); CM dose, 13/25 gram-iodine; gram-iodine/GFR ratio, 0.35/0.38; mean aortic attenuation, 313/326 HU; image noise, 26/32 HU; CNR 10-11; subjective image quality score, 3.0-3.5 (Reader 1) and 3.0-3.3 (Reader 2); number of non-diagnostic examinations, 0/1; and effective dose, 4.5/5.1 mSv. There was no statistically significant difference in aortic CNR and effective dose between the 80 and 120 kVp cohorts. 80 kVp 16-MDCT with halved CM dose tailored to body weight for CTA follow-up of EVAR may provide satisfactory diagnostic results compared to common standards and be beneficial for patients at risk of CIN, though the present CT equipment may limit the use of the method to patients below 90 kg or with a BMI below 35 kg/m(2).

Knowledge-based iterative reconstruction technique: effect of different reconstruction settings on noise reduction and image quality in hepatic contrast-enhanced CT at different radiation dose levels

Objective To evaluate the effects of different reconstruction settings of knowledge-based iterative reconstruction technique (IMR) on noise reduction and image quality in hepatic contrast-enhanced CT(CECT) at different radiation dose levels. Methods Patients who underwent hepatic CECT because of their diseases were enrolled in this prospective study. According to random number table, patients were randomly assigned to two groups (standard dose group, SD-group, n=29; low dose group, LD-group, n=25).All patients underwent both non-enhanced CT and triphasic CECT scan including hepatic arterial phase (HAP), portal-venous phase (PVP) and delayed phase. PVP images of SD-group were acquired with tube voltage of 120 kVp and tube current-time products of 250 mAs, and 80 kVp and 500 mAs for LD-group. PVP images were reconstructed with both filtered back projection (FBP) and IMR techniques. Settings applied in IMR reconstructions consisted of body routine (BR) and body soft tissue (BST) with three levels (L1 to L3), and image series included: L1BR, L2BR, L3BR, L1BST, L2BST and L3BST. Subjective assessment of image quality including low contrast detectability (LCD), image distortion (ID) and diagnostic confidence (DC) as well as objective image quality including image noise, signal to noise ratio (SNR) and contrast to noise ratio (CNR) were compared between groups. Effective radiation dose was recorded. Objective image quality and subjective image quality were compared by using Friedman H test and ANOVA, respectively. In addition, Student t test was used to compare effective radiation doses between groups. Results In SD-group, IMR settings of L2BST, L3BST scored highest in LCD with median score of 4; L3BST and L2BST scored lowest in ID with median score of 3, while FBP and L1BR scored highest with median score of 4; L1BR, L2BR and L1BST scored highest in DC with median score of 4, while L3BST scored lowest with median score of 3. In LD-group, the distribution of all reconstruction settings scores in LCD and ID were similar to those in SD-group; however, L1BST scored highest with median score of 4, and FBP scored lowest with median score of 2 in DC. There were statistical differences in LCD, ID and DC among all the reconstruction settings for both groups (P<0.05). In terms of FBP technique, the image noise, SNR and CNR were (9.8±2.0)HU, 13.3±3.3 and 6.0±1.9 in SD-group, and (16.2±4.1)HU, 12.9±3.3 and 6.6± 2.3 in LD-group, respectively. In SD-group, image noise exhibited a trend of decrease from L1BR to L3BST[from (4.5±0.9) HU to (3.2±0.2)HU], while SNR, CNR trended to increase (SNR: from 21.4±1.4 to 24.6±4.6; CNR: from 9.4±2.2 to 10.9±2.9, respectively). The image noise, SNR and CNR in LD-group showed the same trends as SD-group [image noise: from (5.8±0.2)HU to (3.9±0.6)HU; SNR: from 26.3±4.5 to 33.1±6.9; CNR: from 13.6±4.0 to 17.4±5.1, respectively]. In both groups, there were statistically differences in image noise, SNR and CNR among all IMR settings and FBP (F values were 15.50 to 131.39, P<0.01). The effective radiation dose of the LD-group was significantly lower than that of the SD-group [(4.19±0.22) versus (7.32±0.58) mSv, t=15.27, P<0.01). Conclusions IMR can reduce image noise and improve image quality in hepatic CECT at both standard and low dose levels. L1BR, L2BR and L1BST are the most optimized reconstruction settings for the standard dose protocol, while L1BST performs best for the low dose protocol. Key words: Liver; Tomography, X-ray computed; Radiation dosage

Pilot study on image quality and radiation dose of CT colonography with adaptive iterative dose reduction three-dimensional.

ObjectiveTo investigate image quality and radiation dose of CT colonography (CTC) with adaptive iterative dose reduction three-dimensional (AIDR3D).MethodsTen segments of porcine colon phantom were collected, and 30 pedunculate polyps with diameters ranging from 1 to 15 mm were simulated on each segment. Image data were acquired with tube voltage of 120 kVp, and current doses of 10 mAs, 20 mAs, 30 mAs, 40 mAs, 50 mAs, respectively. CTC images were reconstructed using filtered back projection (FBP) and AIDR3D. Two radiologists blindly evaluated image quality. Quantitative evaluation of image quality included image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Qualitative image quality was evaluated with a five-score scale. Radiation dose was calculated based on dose-length product. Ten volunteers were examined supine 50 mAs with FBP and prone 20 mAs with AIDR3D, and image qualities were assessed. Paired t test was performed for statistical analysis.ResultsFor 20 mAs with AIDR3D and 50 mAs with FBP, image noise, SNRs and CNRs were (16.4 ± 1.6) HU vs. (16.8 ± 2.6) HU, 1.9 ± 0.2 vs. 1.9 ± 0.4, and 62.3 ± 6.8 vs. 62.0 ± 6.2, respectively; qualitative image quality scores were 4.1 and 4.3, respectively; their differences were all not statistically significant. Compared with 50 mAs with FBP, radiation dose (1.62 mSv) of 20 mAs with AIDR3D was decreased by 60.0%. There was no statistically significant difference in image noise, SNRs, CNRs and qualitative image quality scores between prone 20 mAs with AIDR3D and supine 50 mAs with FBP in 10 volunteers, the former reduced radiation dose by 61.1%.ConclusionImage quality of CTC using 20 mAs with AIDR3D could be comparable to standard 50 mAs with FBP, radiation dose of the former reduced by about 60.0% and was only 1.62 mSv.

Low-Concentration Contrast Medium for 128-Slice Dual-Source CT Coronary Angiography at a Very Low Radiation Dose Using Prospectively ECG-Triggered High-Pitch Spiral Acquisition

To assess the impact of low-concentration contrast medium on vascular enhancement, image quality, and radiation dose of coronary computed tomography (CT) angiography (CCTA) by using prospectively electrocardiography (ECG)-triggered high-pitch spiral acquisition with low tube voltage in combination with iterative reconstruction. One hundred patients (body mass index≤25kg/m(2), heart rate≤65 beats per minute) were prospectively randomized to two groups, with 50 patients each, which were differed by contrast medium. All patients underwent prospectively ECG-triggered high-pitch spiral acquisition CCTA (2×128×0.6mm, 300mAs). Group A patients received iopromide 370 (370mgI/mL), were scanned using 100 kVp, and reconstructed with filtered back projection. Group B patients received Iodixanol 270 (270mg I/mL), were scanned using low tube voltage of 80 kVp, and reconstructed with iterative reconstruction techniques (IRT). CT attenuation was measured in coronary artery and other anatomic regions. Image quality score, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and radiation dose were calculated and compared. The iodixanol 270 group showed no significant difference in image quality score (1.61±0.69 vs 1.57±0.66; P>.05), CT attenuation (P>.05), noise (P>.05), SNR (47.89±14.03 vs 44.37±12.79; P>.05), and CNR (42.38±12.67 vs 38.13±11.38; P>.05) in comparison to the iopromide 370 group but at a significantly lower radiation dose (0.26±0.05 vs 0.57±0.10; P<.001), which reflects dose saving of 54.4%. Combining IRT with high-pitch spiral acquisition mode and low-tube-voltage technique, a low-concentration contrast medium of 270 mg I/mL can still maintain the contrast enhancement in coronary arteries without impairing image quality and significantly lower the radiation dose.

NI-08 * OPTIMIZATION OF MOLECULAR MR IMAGING OF GLIOMA

BACKGROUND: MRI has been widely recognized as a diagnostic tool for early cancer detection, treatment monitoring and image guided surgery. Of particular interest is imaging of high-grade gliomas due to their rapid growth and very poor prognosis with a median survival rate of only 9 months. Standard contrast enhanced MRI, not provide sufficiently high specificity for tumor diagnosis and thus require targeted contrast agents which can be applied to provide information on tumor status. Therefore we applied targeted contrast agents based on iron oxide, that shorten mostly T2 relaxation time. The aim of this study was to optimize contrast-to-noise ratio (CNR) using spin-echo (SE), gradient echo (GE) and GE with flow compensation (GEFC) pulse sequences in T2 contrast-enhanced molecular MRI of glioma. METHODS: A mouse model of glioma and 9.4T MRI were used. MR imaging was performed. The CNR was measured prior, 20 min, 2 hrs and 24 hrs post intravenous tail administration of the glioma targeted paramagnetic nanoparticles (NPs) using spin-echo (SE), gradeint-ech (GE), gradient-echo flow compensation (GEFC) pulse sequences. Susceptibility weighted images (SWI) based on GEFC were also obtained for comparison. RESULTS: The results showed significant differences in CNR among all pulse sequences prior injection. GEFC provided higher CNR post contrast agent injection when compared to GE and SE. Post injection CNR was the highest with SWI and significantly different from any other pulse sequence. The optimum CNR was found to be TE = 7 ms for GE and GEFC pulse sequences and TE = 60 ms for SE. CONCLUSION: The study showed, that molecular MR imaging using targeted contrast agents can enhance the detection of glioma cells at 9.4T if the optimal pulse sequence is used. Hence, the use of flow compensated pulse sequences, beside SWI, should to be considered in the molecular imaging studies.

Ultra low-dose of gadobenate dimeglumine for late gadolinium enhancement (LGE) imaging in acute myocardial infarction: A feasibility study

PurposeTo assess the feasibility of using an ultra-low dose (0.05mmol/kg of body weight [BW]) of high relaxivity contrast agent for late gadolinium enhancement (LGE) imaging in patients with acute myocardial infarction (AMI). Materials and methods17 consecutive patients (mean age, 60.1±10.3 years) with ST-segment elevation AMI underwent two randomized cardiac magnetic resonance studies (exam intervals between 24 and 48h) on a 1.5T unit during the first week after the event using gadobenate dimeglumine (Gd-BOPTA) at the dose of 0.1mmol/kg BW (standard dose or SD group) and 0.05mmol/kg BW (half dose or HD group). Image quality was qualitatively assessed. Quantitative analysis of LGE were performed by measuring signal intensity (SI), signal-to-noise ratio (SNR) in the infarcted myocardium (IM), non-infarcted myocardium (N-IM) and left ventricular cavity (LVC) in images acquired at 1, 3, 5, 10, 15 and 20min after administration of Gd-BOPTA using both contrast media protocol. Contrast-to-noise ratio (CNR) between IM and N-IM (CNR IM/N-IM) and between IM and LVC (CNR IM/LVC) were also quantified for each time point. Moreover the extent of infarcted myocardium was measured. Results102 LGE images were evaluated for each dose group. Quality score was significantly higher for SD at 1, 15 and 20min (0.002<p<0.046) and for HD at 5min (p=0.013). SNR has been higher in the SD group compared to the HD group even though not statistically significant at any time-point for both IM (SD vs. HD: 87.7±73 vs. 65±66; 0.15<p<0.38) and N-IM (SD vs. HD: 22±61 vs. 9.9±6.5; 0.09<p<0.43). LVC SNR was significantly higher with SD at 10min (p=0.03), 15min (p=0.001) and 20min (p=0.004). CNR between the IM and N-IM was significantly higher using SD compared to HD (1382.24±1049 vs. 695.4±500; 0.000<p<0.028) at 10, 15 and 20min. No significant differences in CNR IM/LVC were noted for HD acquired 5min after CM administration compared to SD acquired at 10 (p=0.34), 15 (p=0.96) and 20 (p=0.41) min, and between HD at 10min compared to SD acquired at 15min (p=0.78) and 20min (p=0.32). Good correlation between SD and HD (0.56<r2<0.85, p<0.024) was found at all time-points in the measuring of IA. ConclusionThe use of a 0.05mmol/kg dose of gadobenate dimeglumine is feasible for LGE imaging of acute MI and the best image quality is obtained at 5min after contrast administration. It could be beneficial in patient with renal failure and a solution to improve the identification of subendocardial infarction reducing examination time, costs and total gadolinium load. However, the standard dose of 0.1mmol/kg provides overall better image quality, with the best performance obtained at the delay of 10min or more after Gd-BOPTA administration, and it should be routinely preferred.

Reduced iodine load with CT coronary angiography using dual-energy imaging: A prospective randomized trial compared with standard coronary CT angiography

BackgroundThere is concern regarding the administration of iodinated contrast to patients with impaired renal function because of the increased risk of contrast-induced nephropathy. ObjectiveEvaluate image quality and feasibility of a protocol with a reduced volume of iodinated contrast and utilization of dual-energy coronary CT angiography (DECT) vs a standard iodinated contrast volume coronary CT angiography protocol (SCCTA). MethodsA total of 102 consecutive patients were randomized to SCCTA (n = 53) or DECT with rapid kVp switching (n = 49). Eighty milliliters and 35 mL of iodinated contrast were administered in the SCCTA and DECT cohorts, respectively. Two readers measured signal and noise in the coronary arteries; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. A 5-point signal/noise Likert scale was used to evaluate image quality; scores of <3 were nondiagnostic. Agreement was assessed through kappa analyses. ResultsDemographics and radiation dose were not significantly different; there was no difference in CNR between both cohorts (P = .95). A significant difference in SNR between the groups (P = .02) lost significance (P = .13) when adjusted for body mass index. The median Likert score was inferior for DECT for reader 1 (3.6 ± 0.6 vs 4.3 ± 0.6; P < .001) but not reader 2 (4.1 ± 0.6 vs 4.3 ± 0.5; P = .06). Agreement in diagnostic interpretability in the DECT and SCCTA groups was 91% (95% confidence interval, 86%–100%) and 96% (95% confidence interval, 90%–100%), respectively. ConclusionDECT resulted in inferior image quality scores but demonstrated comparable SNR, CNR, and rate of diagnostic interpretability without a radiation dose penalty while allowing for >50% reduction in contrast volume compared with SCCTA.

Improving Quantitative CT Perfusion Parameter Measurements Using Principal Component Analysis

To evaluate the improvements in measurements of blood flow (BF), blood volume (BV), and permeability-surface area product (PS) after principal component analysis (PCA) filtering of computed tomography (CT) perfusion images. To evaluate the improvement in CT perfusion image quality with poor contrast-to-noise ratio (CNR) in vivo. A digital phantom with CT perfusion images reflecting known values of BF, BV, and PS was created and was filtered using PCA. Intraclass correlation coefficients and Bland-Altman analysis were used to assess reliability of measurements and reduction in measurement errors, respectively. Rats with C6 gliomas were imaged using CT perfusion, and the raw CT perfusion images were filtered using PCA. Differences in CNR, BF, BV, and PS before and after PCA filtering were assessed using repeated measures analysis of variance. From simulation, mean errors decreased from 12.8 (95% confidence interval [CI] = -19.5 to 45.0) to 1.4 mL/min/100 g (CI = -27.6 to 30.4), 0.2 (CI = -1.1 to 1.4) to -0.1 mL/100 g (CI = -1.1 to 0.8), and 2.9 (CI = -2.4 to 8.1) to 0.2 mL/min/100 g (CI = -3.5 to 3.9) for BF, BV, and PS, respectively. Map noise in BF, BV, and PS were decreased from 51.0 (CI = -3.5 to 105.5) to 11.6 mL/min/100 g (CI = -7.9 to 31.2), 2.0 (CI = 0.7 to 3.3) to 0.5 mL/100 g (CI = 0.1 to 1.0), and 8.3 (CI = -0.8 to 17.5) to 1.4 mL/min/100 g (CI = -0.4 to 3.1), respectively. For experiments, CNR significantly improved with PCA filtering in normal brain (P < .05) and tumor (P < .05). Tumor and brain BFs were significantly different from each other after PCA filtering with four principal components (P < .05). PCA improved image CNR in vivo and reduced the measurement errors of BF, BV, and PS from simulation. A minimum of four principal components is recommended.

Optimal flip angle for high contrast balanced SSFP cardiac cine imaging

To determine the optimal flip angle (FA) for cardiac cine imaging that maximizes myocardial signal and blood-myocardium contrast. Bloch equation simulations of stationary myocardium and flowing blood with an imperfect slice profile were compared to in vivo measurements of blood and myocardium signal-to-noise ratio (SNR) and blood-myocardium contrast-to-noise ratio (CNR) in healthy subjects (N = 10) in the short-axis and four-chamber views and in patients (N = 7) in the three-chamber imaging plane. Left ventricular (LV) and right ventricular (RV) blood SNR and blood-myocardium CNR increases with increasing FA up to ≈105° in the short-axis view. A similar trend is seen in the RV four-chamber view, but a marked SNR difference between the LV and RV blood appears for FA>75°, especially during systole. Notable RV and LV SNR and CNR differences are also evident in the three-chamber view due to the predominant LV in-plane flow versus RV through-plane flow. Very high blood-myocardium CNR can be obtained with a FA of ≈105° in the short-axis plane and ≈75° in the three-chamber and four-chamber imaging planes. However, if through-plane flow is limited, as may occur for patients with low ejection fraction or low heart rates, then the FA may be limited to ≈ 75°.

Application of single shot free‐breathing fast imaging employing steady state sequence in cardiac magnetic resonance imaging

To investigate the imaging quality of single shot (SS) fast imaging employing steady state (FIESTA) sequence in contrast-enhanced cardiac magnetic resonance (MR) examination, in comparison with the segmented inversion recovery 2D fast gradient echo (IR FGRE) sequence. Fifty-two cases with suspected or known heart disease were enrolled in this study, including 24 patients who had enhanced myocardium in myocardial delayed enhancement (MDE). We analyzed the imaging quality of the sequences by measuring the myocardium and blood pool signal-to-noise ratios (SNR) and the contrast-to-noise ratios (CNR) of blood pool relative to normal myocardium and of enhanced myocardium relative to normal myocardium and compared the new sequences with traditional sequence. The scanning time of SS FIESTA was significantly shortened as compared to IR FGRE. The differences in the image quality scores, enhanced myocardium (EM) mass and percentages, SNR(bp), SNR(myo), CNR(myo/bp) and CNR(l/bg) were not statistically significant between SS FIESTA and IR FGRE (P > 0.05). However, the difference in CNR(em/myo) was statistically significant between SS FIESTA and IR FGRE (P < 0.0001), with CNR(em/myo) of IR FGRE higher than SS FIESTA. Single shot FIESTA speeded up the acquisition time, halving it to (27.6 ± 1.8 s) instead of 146 + 13.8 s (IR FGRE), it had higher SNR and CNR, and its image quality did not differ significantly from IR FGRE. The SS FIESTA is more suitable for patients with severely heart diseases or those unable to hold breath. 3D IR FGRE sequence had higher SNR(myo) than the others and it is suitable for displaying the subendocardial scar. However, it has more artefacts and poor imaging quality than IR FGRE.

Optimization of Kiloelectron Volt Settings in Cerebral and Cervical Dual-energy CT Angiography Determined with Virtual Monoenergetic Imaging

Dual-energy computed tomography (DECT) offers various fields of application, especially in angiography using virtual monoenergetic imaging. The aim of this study was to evaluate objective image quality indices of calculated low-kiloelectron volt monoenergetic DECT angiographic cervical and cerebral data sets compared to virtual 120-kV polyenergetic images. Forty-one patients (21 men, mean age 58 ± 14) who underwent DECT angiography of the cervical (n = 7) or cerebral vessels (n = 34) were retrospectively included in this study. Data acquired with the 80 and 140 kVp tube using dual-source CT technology were subsequently used to calculate low-kiloelectron volt monoenergetic image data sets ranging from 120 to 40 keV (at 10-keV intervals per patient). Vessel and soft tissue attenuation and image noise were measured in various regions of interest, and contrast-to-noise ratio (CNR) was subsequently calculated. Differences in image attenuation and CNR were compared between the different monoenergetic data sets and virtual 120-kV polyenergetic images. For cervical angiography, 60-keV monoenergetic data sets resulted in the greatest improvements in vessel attenuation and CNR compared to virtual 120-kV polyenergetic data sets (+40%, +16%; all P < .01). Also for cerebral vessel assessment, 60-keV monoenergetic data sets provided the greatest improvement in vessel attenuation and CNR (+40%, +9%; all P < .01) compared to virtual 120-kV polyenergetic data sets. 60-keV monoenergetic image data significantly improve vessel attenuation and CNR of cervical and cerebral DECT angiographic studies. Future studies have to evaluate whether the technique can lead to an increased diagnostic accuracy or should be used for dose reduction of iodinated contrast material.

Target definition for malignant gliomas: No difference in radiation treatment volumes between 1.5T and 3T magnetic resonance imaging

PurposeCurrently, most high-grade glioma patients undergo a 1.5T brain magnetic resonance (MR) for radiation treatment planning. We hypothesized that 3T MR imaging (MRI) scanning is superior to 1.5T due to higher signal-to-noise ratio (SNR), and thus will result in more accurate quantification of tumor volumes. The purpose of this prospective study was to determine differences in radiation planning volumes for high-grade gliomas when scanned on 3T MR versus 1.5T MR. Methods and materialsIn this prospective controlled trial, 23 patients with high-grade gliomas underwent brain MRI scanning in both 1.5T and 3T field strengths within a 24-hour period; no steroids or treatment changes were made in-between scans. After 3 investigators contoured the T2 fast low-angle inversion recovery (FLAIR) abnormality (gross tumor volumes or [GTV]) for all patients, clinical target volume (CTV) and planning treatment volumes (PTV) were defined. Calculations by an independent investigator included volumes, standard deviations, SNRs, and contrast-to-noise ratios (CNRs); statistical analysis was performed on raw data. ResultsPlanning treatment volume ratios (3T:1.5T) for each investigator were 0.95 ± 0.12 (range, 0.64-1.10), 0.98 ± 0.10 (range, 0.64-1.16), and 0.99 ± 0.06 (range, 0.86-1.13). By paired 2-tailed t test, these volumes were not statistically different (P = .051), although there is a trend to 3T producing smaller volumes than 1.5T. Dice similarity coefficients were 0.90 ± 0.05, 0.90 ± 0.06, and 0.91 ± 0.05 for the investigators. ConclusionsPlanning target volumes for high-grade gliomas were similar at 3T and 1.5T MR using our standard imaging protocols. However, in some patients, the 3T MR may reveal substantially smaller tumor volume due to inferior conspicuity of the lesion. These findings imply that while overall the radiation target volumes are comparable, there are differences in CNR and SNR that lead to differences in individual patients. The 1.5T may be better for gaining conspicuity of the tumor.

Assessment of Myocardial Infarction and Postinfarction Scar Remodeling With an Elastin-Specific Magnetic Resonance Agent

To prospectively evaluate an elastin-specific MR contrast agent (ESMA) for in vivo targeting of elastic fibers in myocardial infarction (MI) and postinfarction scar remodeling. MI was induced in C57BL/6J mice (n=40) by permanent ligation of the left anterior descending coronary artery. MRI was performed at 7 and 21 days after MI. The merits of gadolinium-based ESMA (Gd-ESMA) were compared with gadopentetic acid (Gd-DTPA) for infarct size determination, contrast-to-noise ratio (CNR), and enhancement kinetics. Specific binding in vivo was evaluated by blocking the molecular target using nonparamagnetic lanthanum-ESMA. In vivo imaging results were confirmed by postmortem triphenyltetrazolium chloride staining, elastica van Gieson staining, and Western blotting. Delayed enhancement MRI revealed prolonged enhancement of Gd-ESMA in the postischemic scar compared with Gd-DTPA. Infarct size measurements showed good agreement between Gd-ESMA and Gd-DTPA and were confirmed by ex vivo triphenyltetrazolium chloride staining. Preinjection of the blocking lanthanum-ESMA resulted in significantly lower CNR of Gd-ESMA at the infarct site (P=0.0019). Although no significant differences in CNR were observed between delayed enhancement imaging and Gd-DTPA between days 7 and 21 (1.8± versus 3.8; P=ns), Gd-ESMA showed markedly higher CNR on day 21 after MI (14.1 versus 4.9; P=0.0032), which correlated with increased synthesis of tropoelastin detected by Western blot analysis and histology. Higher CNR values for Gd-ESMA further correlated with improved ejection fraction of the mice on day 21 after MI. Gd-ESMA enables targeting of elastin within the infarct scar in a mouse model of MI. The imaging properties of Gd-ESMA allow quantification of intrascar elastin content in vivo and thereby provide potential for noninvasive characterization of postinfarction scar remodeling.