Significant Difference In Signal-to-noise Ratio Research Articles

Design and Evaluation of a Weighted Periodic Sparse Array for Low-Complexity 1-D Phased Array Ultrasound Imaging Systems.

A sparse array offers a significant reduction in the complexity of ultrasonic imaging systems by decreasing the number of active elements and associated electrical circuits needed to form a focused beam. Consequently, for 1-D arrays, it has been adopted in the development of miniaturized systems such as portable, hand-held, or smartphone-based systems. Previously, we developed an analytic method that can design a pair of 1-D periodic sparse arrays (PSAs) satisfying three specific constraints, which are the array size, desired grating lobe level, and sparseness factor (SF). In this study, we further developed our method by incorporating aperture weighting functions, which take the form of tapered rectangular functions to introduce null points on the beam pattern. These null points effectively suppress grating lobes generated by a matching pair of arrays. The design process commences with determining transmit and receive PSA patterns, followed by deriving corresponding aperture weighting functions. First, aperture functions of a base and weighting arrays are convolved, which is then up-sampled to the targeted array size. Lastly, the up-sampled aperture is convolved to an aperture function of a sub-array, resulting in weighted PSAs (wPSAs). Pulsed wave simulation confirmed improved grating lobe suppression with wPSAs compared to PSAs. Phantom imaging experiments using a 1-D phased array validated the enhanced contrast due to suppressed grating lobes, but at the cost of small degradation in lateral resolution. The signal-to-noise ratio (SNR) also gradually declined with the greater SFs but no significant difference in SNR was observed between wPSAs and PSAs. Finally, in vivo echocardiography imaging highlighted the clinical potential of wPSAs, particularly with high SFs. Overall, these results suggest that wPSAs can effectively enhance contrast compared to PSAs under the given SF, or alternatively, wPSA with greater SFs can achieve comparable image quality to PSAs with lower SFs. In conclusion, the wPSA approach holds promise for further reducing the complexity of ultrasound imaging systems.

High-speed bioimpedance-based gating system for radiotherapy: Prototype and proof of principle.

To investigate a novel bioimpedance-based respiratory gating system (BRGS) designed for external beam radiotherapy and to evaluate its technical characteristics in comparison with existing similar systems. The BRGS was tested on three healthy volunteers in free breathing and breath-hold patterns under laboratory conditions. Its parameters, including the time delay (TD) between the actual impedance change and the gating signal, temperature drift, root mean square (RMS) noise, and signal-to-noise ratio (SNR), were measured and analyzed. The gate-on TD and the gate-off TD were found to be 9.0±2.0ms [mean±standard deviation (M±SD)] and 7.2±1.3ms, respectively. The temperature drift of the BRGS output signal was 0.02 Ω after 30 min of operation. RMS noise averaged 0.14±0.05 Ω (M±SD) for all subjects and varied from 0.08 to 0.20 Ω with repeated measurements. A significant difference in SNR (p<0.001) was observed between subjects, ranging from 4 to 15. The evaluated bioimpedance-based gating system showed a high performance in real-time respiratory monitoring and may potentially be used as an external surrogate guidance for respiratory-gated external beam radiotherapy. Direct comparison with commercially available systems, 4D correlation studies, and expansion of the patient sample are goals for future preclinical studies.

Acceleration of uterine 3D T2-weighted imaging by compressed SENSE-a multicentre study.

To find the optimal acceleration factor (AF) of the compressed SENSE (CS) technique for uterine isotropic high-resolution 3D T2-weighted imaging (3D-ISO-T2WI). A total of 91 female volunteers from the First Affiliated Hospital of Dalian Medical University, Chu Hsien-I Memorial Hospital and Tianjin Institute of Endocrinology, and The Fourth Hospital of Harbin were recruited. A total of 44 volunteers received uterus sagittal 3D-ISO-T2WI scans on 3.0T MRI device with different CS AFs (including SENSE3, CS3, CS4, CS5, CS6, and CS7), 51 received 3D-ISO-T2WI scans with different degrees of fat suppression (none, light, moderate, and severe), while 4 volunteers received both series of scans. Image quality was subjectively evaluated with a 3-point scoring system. Junction zone signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and myometrial SNR were also calculated. Intraclass correlation coefficients were used to analyse the consistency of the measurement results by 2 observers. Analysis of variance test or Friedman rank sum test was used to compare the differences in subjective scores, SNR, and CNR under different AFs/different degrees of fat suppression. Images by AFs of CS3, CS4, and CS5 had the highest SNR and CNR. Among them, CS5 had the shortest scan time. CS5 also had one of the highest subjective scores. There was no significant difference in SNR and CNR among images acquired with different degrees of fat suppression. Also, images with moderate fat suppression had the highest subjective scores. The CS5 combined with moderate fat suppression is recommended for routine female pelvic 3D-ISO-T2WI scan. The CS5 has the highest image quality and has the shortest scan time, which is the best AF. Moderate fat suppression has the highest subjective scores. The CS5 and moderate fat suppression are the best combination for a female pelvic 3D-ISO-T2WI scan.

Short repetition time diffusion-weighted imaging improves visualization of prostate cancer.

This study aimed to assess whether short repetition time (TR) diffusion-weighted imaging (DWI) could improve diffusion contrast in patients with prostate cancer (PCa) compared with long TR (conventional) reference standard DWI. Our Institutional Review Board approved this retrospective study and waived the need for informed consent. Twenty-five patients with suspected PCa underwent multiparametric magnetic resonance imaging (mp-MRI) using a 3.0-T system. DWI was performed with TR of 1850ms (short) and 6000ms (long) with b-values of 0, 1000, and 2000s/mm2. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), visual score, apparent diffusion coefficient (ADC), and diagnostic performance were compared between short and long TR DWI for both b-values. The statistical tests included paired t-test for SNR and CNR; Wilcoxon signed-rank test for VA; Pearson's correlation and Bland-Altman plot analysis for ADC; and McNemar test and receiver operating characteristic analysis and Delong test for diagnostic performance. Regarding b1000, CNR and visual score were significantly higher in short TR compared with long TR (P = .003 and P = .002, respectively), without significant difference in SNR (P = .21). Considering b2000, there was no significant difference in visual score between short and long TR (P = .07). However, SNR and CNR in long TR were higher (P = .01 and P = .04, respectively). ADC showed significant correlations, without apparent bias for ADC between short and long TR for both b-values. For diagnostic performance of DWI between short and long TR for both b-values, one out of five readers noted a significant difference, with the short TR for both b-values demonstrating superior performance. Our data showed that the short TR DWI1000 may provide better image quality than did the long TR DWI1000 and may improve visualization and diagnostic performance of PCa for readers.

Effect of Imaging Parameters for High-resolution Diffusion-weighted Imaging on Signal-to-noise Ratio and ADC in Prostate Examination

Readout-segmented echo-planar imaging (readout segmentation of long variable echo trains [RESOLVE]) can be set to higher resolution than single-shot echo planar imaging, but there is concern that the signal-to-noise ratio (SNR) is low. The purpose was to examine the effect of imaging parameters (repetition time: TR, number of excitations: NEX) for RESOLVE on SNR and apparent diffusion coefficient (ADC) value in 1.5 T MRI, assuming a prostate examination. We imaged eight healthy male volunteers at a b value of 800 s/mm2. SNR and ADC value were calculated by setting the ROI in the transition zone (TZ) and the peripheral zone (PZ) of the prostate. Then, 3 radiologists visually evaluated the graininess. In TZ, there was no significant difference in SNR with changing TR. In PZ, SNR increased with increasing TR. In PZ, median SNR was 8.1 [6.9-9.3] at TR=11000 ms and NEX=2. On the other hand, at TR=5000 ms and NEX=3,4, median SNRs were 8.5 [7.5-9.3] and 9.8 [8.8-11.2]. Moreover, NEX=5 with median SNR of 11.1 [10.7-11.7] was significant (p<0.008). Setting more NEX was more effective in increasing SNR. In addition, visual evaluation showed similar results. The ADC value in TZ was around 1404×10-6 mm2/s, and the ADC value in PZ was around 1469×10-6 mm2/s. There were no significant differences under each condition. In conclusion, NEX is more effective than TR for improving SNR both quantitatively and visually in PZ.

Free‐breathing three‐dimensional isotropic‐resolution MR sequence for simultaneous vessel wall imaging of bilateral renal arteries and abdominal aorta: Feasibility and reproducibility

Many diseases can simultaneously involve renal arteries and the adjacent abdominal aorta. This study proposed a free-breathing three-dimensional (3D) isotropic-resolution magnetic resonance sequence for simultaneous vessel wall imaging (VWI) of bilateral renal arteries and adjacent abdominal aorta. A respiratory-triggered isotropic-resolution sequence that combined the improved motion-sensitized driven-equilibrium (iMSDE) preparation with the spoiled gradient recalled (SPGR) readout (iMSDE-SPGR) was proposed for simultaneous VWI of renal arteries and abdominal aorta. The proposed iMSDE-SPGR sequence was optimized by positioning spatial saturation pulses (i.e., REST slabs) elaborately to further alleviate respiratory and gastrointestinal motion artifacts and selecting appropriate first-order gradient moment (m1 ) of the iMSDE preparation. Thirteen healthy subjects and 13 patients with renal artery stenosis underwent simultaneous VWI with the optimized iMSDE-SPGR sequence at 3.0 T. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and morphology of renal arterial wall and aortic wall were measured. Reproducibility of intra-observer, inter-observer, and scan-rescan (n=13 healthy subjects) in measuring SNR, CNR, and morphology was evaluated. For the reproducibility test, the agreement was determined using intraclass correlation coefficients (ICC), and the differences were compared using paired t-test or nonparametric Wilcoxon test when appropriate. Bland-Altman plots were used to calculate the bias between observers and between scans. The proposed iMSDE-SPGR sequence was feasible for simultaneous VWI both in the healthy subjects and the patients. The sequence showed good to excellent inter-observer (ICC: 0.615-0.999), excellent intra-observer (ICC: 0.801-0.998), and scan-rescan (ICC: 0.768-0.998) reproducibility in measuring morphology, SNR, and CNR. There were no significant differences in SNR, CNR, and morphology measurements between observers and between scans (all p>0.05). Bland-Altman plots showed small bias in assessing SNR, CNR, and morphology. The proposed free-breathing 3D isotropic-resolution iMSDE-SPGR technique is feasible and reproducible for simultaneous VWI of bilateral renal arteries and adjacent abdominal aorta.

Optimization of Computed Tomography Angiography Protocols for Follow-Up Type B Aortic Dissection Patients by Using 3D Printed Model

Thoracic endovascular aortic repair (TEVAR) is a life-saving therapy for type B aortic dissection (TBAD). However, surveillance computed tomography (CT) scans in post-TEVAR patients are associated with high radiation dose, thus resulting in potential risk of radiation-induced malignancy. In this study, we developed a patient-specific three-dimensional (3D) printed phantom with stent grafts in situ, then scanned the phantom with different CT protocols to determine the optimal scanning parameters for post-treatment patients. The CT scans were conducted with different kVp and pitch values (80, 100, 120 kVp and pitch of 1.2, 1.5, 2.0, 2.5), resulting in a total of 12 datasets. Signal-to-noise ratio (SNR) was measured to determine and compare the image quality between different datasets. Results showed no significant differences in SNR between different kVp when the pitch value was 1.2. At low pitch values, a decrease in kVp from 120 to 80 led to a significant effective dose reduction by more than 20%. SNR decreased by 30% when pitch was increased from 1.2 to 2.5 at 80 kVp, and 20% at 120 kVp. In contrast, there was only a 3.9% decrease in SNR when kVp was reduced from 120 to 80 at pitch 1.2, and 15.9% at pitch 2.5. High pitch with 100 kVp can effectively reduce the dose while maintaining image quality.

Detection of mural inflammation with low b-value diffusion-weighted imaging in patients with active Takayasu Arteritis.

To evaluate the performance of low b-value diffusion-weighted imaging (DWI) for detection of inflamed vessels in active Takayasu arteritis (TA). Forty patients with active TA involving the thoracic aorta and its super-aortic branches underwent low b-value (50 s/mm2) DWI, T2-weighted imaging (T2WI), and delayed enhancement T1-weighted imaging (DEI). Corresponding images on these 3 sequences at the same diseased level were evaluated qualitatively and quantitatively using Friedman and Kruskal-Wallis test, and the agreement between them in detection of inflamed vessels was assessed using Cochran's Q test. The overall image quality of DEI, DWI, and T2WI was scored 7.97 ± 1.15, 7.32 ± 1.73, and 6.51 ± 1.69 respectively. The score of DEI and DWI was higher than that of T2WI (p < 0.001). The quality of blood suppression was rated higher in DWI than T2WI and DEI (p < 0.001). Both the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the diseased vessel walls measured on DEI and DWI were significantly higher than those on T2WI (p < 0.001). However, there was no significant difference in SNR and CNR between DEI and DWI (p = 0.283 and 0.063). In detection of mural inflammation, significant advantage was observed when comparing the findings from DEI/DWI to those from T2WI (p < 0.001). But no significant difference was found between the findings of DWI and DEI (p > 0.99). Low b-value DWI may be used as a promising alternative to DEI for detecting inflamed vessels in active TA. • Currently, the most widely used imaging modality in detection of mural inflammation is contrast-enhanced MRI. • Low b-value DWI is shown comparable to contrast-enhanced MRI and superior to T2WI in identifying mural inflammation in patients with active Takayasu arteritis. • Low b-value DWI is a fast and unenhanced MRI technique which may potentially replace contrast-enhanced MRI in identifying disease activity of Takayasu arteritis.

Establishment of Submillisievert Abdominal CT Protocols With an In Vivo Swine Model and an Anthropomorphic Phantom

OBJECTIVE. The purpose of this study was to evaluate radiation dose, effective dose, and image quality of different low-dose abdominal CT protocols in a swine model and an anthropomorphic phantom using a third-generation dual-source CT scanner. MATERIALS AND METHODS. Four different abdominal low-dose protocols were established using a swine model and were regarded as diagnostic by two experienced radiologists on the basis of clarity and sharpness of anatomic structures. General image conditions such as noise and spatial resolution as well as diagnostic acceptability and artifacts were evaluated. Objective image quality was determined by measuring signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in different anatomic locations. To evaluate the effective dose, thermoluminescent dosimeter (TLD) measurements were repeated in a phantom. RESULTS. Diagnostic acceptability, spatial resolution, and noise were rated as optimal in all four protocols, which were therefore regarded as diagnostic. We found no statistically significant differences in SNR or CNR for the four low-dose protocols. Effective dose determined from the phantom measurements did not exceed 0.33 mSv for any protocol. Overall evaluation of the 86 TLD measurements for the four low-dose protocols revealed a statistically significant difference in radiation dose (p < 0.0001), showing that the dual-source protocol had the lowest radiation dose. CONCLUSION. Submillisievert abdominal CT is feasible with good image quality and doses even lower than conventional abdominal radiography. Our dual-source protocol achieved the lowest dose, which further shows that dual-source imaging is possible in the submillisievert range without additional dose.

Effect of Gradient Linearity and Static Magnetic Field Homogeneity on Diffusion Weighted Image: A Phantom Study

In this study, we assessed image quality and geometric accuracy as a function of the gradient physical linearity used for diffusion-weighted imaging (DWI) on both conventional-bore and wide-bore scanners. The signal to noise ratio (SNR) was calculated using b = 1000 DWI images for all acquisitions. To evaluate geometric accuracy, the diameter of a phantom on an image slice was measured in four directions. In comparison with the enhanced gradient mode, the default and maximum gradient modes showed higher SNRs with both bore sizes. There were significant differences in SNR among the various gradient modes of the two bore sizes. The geometric accuracy evaluations showed no statistically significant differences in the measured lengths among the various gradient modes and both bore sizes. The wide bore using default and maximum gradient mode showed higher SNR than the conventional bore, and comparable geometric accuracy.

Image quality of the CAIPIRINHA-Dixon-TWIST-VIBE technique for ultra-fast breast DCE-MRI: Comparison with the conventional GRE technique

PurposeThe aim of this study was to evaluate image quality of the CAIPIRINHA-Dixon-TWIST-Volume-Interpolated Breath-hold Examination (CDT-VIBE) technique for ultra-fast breast dynamic contrast enhanced (DCE) MRI with respect to conventional Gradient-Recalled Echo (GRE) technique. MethodsA total of 58 patients underwent a DCE-MRI based on CDT-VIBE sequence (temporal resolution: 11.9 s), immediately followed by 1 phase of a conventional T1 weighted GRE sequence (acquisition time: 68 s). The Signal-to-Noise Ratio (SNR) on phantom images, lesion/parenchyma signal ratio (LPSR), image quality, and morphological characterization were compared between the last phase of CDT-VIBE and conventional GRE images. The image quality was assessed by visual grading analysis (VGA). Reader agreement was assessed using Kappa analysis. ResultsThere was no significant difference in SNR (phantom) or LPSR (patient) between CDT-VIBE and conventional GRE images (P > 0.05). Significant parallel acquisition technique (PAT) noise and mild blurriness was observed on CDT-VIBE images. Visual grading analysis (VGA) confirmed significantly worse ratings for CDT-VIBE compared to the conventional GRE sequence in terms of PAT noise, lesion’s internal feature clarity, and therefore overall image quality (area under contrast curve [AUC] values: 0.578 ‒ 0.764, P < 0.05), but edge sharpness and lesion conspicuity were equivalent (P > 0.05). Kappa analysis revealed good agreement on image quality scores (к = 0.725 ‒ 0.908) and on morphologic terms (к = 0.745–1.000). ConclusionThe CDT-VIBE sequence provides excellent spatial resolution and adequate image quality in ultra-fast breast DCE-MRI. Further improvement in PAT noise and internal structure blurriness may be necessary.

Elimination of residual aliasing artifact that resembles brain lesion on multi-oblique diffusion-weighted echo-planar imaging with parallel imaging using virtual coil acquisition.

Single-shot diffusion-weighted echo-planar imaging (ssDW-EPI) acquired with parallel imaging and a multi-oblique scan plane may suffer from residual aliasing artifacts, resembling lesions on the calculated apparent diffusion coefficient (ADC) map. To combine ssDW-EPI and virtual coil acquisition and develop a self-reference reconstruction method to eliminate the residual aliasing artifact on multi-oblique ssDW-EPI sequence with parallel imaging and multiple signal averaging. Prospective. Three healthy subjects and 50 stroke patients. Conventional ssDW-EPI with parallel imaging, and proposed ssDW-EPI with virtual coil acquisition at 1.5T. The efficacy of the proposed method was evaluated in 50 stroke patients by comparing the ssDW-EPI with conventional parallel imaging reconstructions. The extent of residual aliasing artifacts were rated on a 5-point Likert scale by three independent raters. Only the data without residual aliasing artifacts on conventional ssDW-EPI were included for the assessment of signal-to-noise ratio (SNR), ghost-to-signal ratio (GSR), and ADC. The interobserver agreements for examining residual aliasing artifacts were measured by the intraclass correlation coefficient (ICC). A two-sample t-test was performed for comparing SNR, GSR, and ADC. There was a perfect agreement (ICC = 1.00) in the examination of residual aliasing artifacts on images obtained using the proposed method. The incidence rates of the residual aliasing artifact on the ADC maps obtained from the scanner console and proposed method were 60% (ie, 30 out of 50) and 0%, respectively. The proposed method offers significantly lower GSR than conventional parallel imaging reconstruction (P < 0.001). There was no significant difference in SNR (P = 0.20-0.51) and ADC values (P = 0.20-0.94) between conventional parallel imaging reconstructions and the proposed method. It appears that our method could effectively eliminate artifacts and significantly improve the GSR of b = 0 T2 WI and b > 0 DWI, as well as permit ADC measurement consistent with conventional techniques. Our method may be beneficial to clinical assessment of the brain that utilizes multi-oblique ssDW-EPI. 1 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:1442-1453.

The efficacy of tin-filtration for computed tomography in diagnosing urolithiasis

IntroductionThe purpose of this study was to evaluate the radiation dose and image quality of computed tomography urograms (CTU) using tin-filtration compared to conventional CTU (without tin-filtration) examinations in patients with suspected urolithiasis. MethodsGroup 1 consisted of 100 patients who were examined using the tin-filtered CTU protocols (Sn100kVp or Sn150kVp); Group 2 consisted of 100 patients who were examined using the same protocols but without tin-filtration (GE-NI41 or GE-NI43). The scanning protocol was based on the patients' body weight (<80 kg and ≥80 kg). The effective doses of all scans were compared between the two groups. Subjective image quality was evaluated by two blinded radiologists. The objective image quality was assessed for noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and figure-of-merit (FOM) using the CTU scans acquired from both the tin-filtered and non-tin-filtered protocols. ResultsTin-filtration resulted in the reduction of effective radiation dose ranging between 72% to 88% for the ≥80 kg and <80 kg patient groups respectively. For both groups, tin-filtration resulted in no significant differences in SNR and a significant increase in FOM. For the <80 kg group, tin-filtration resulted in significantly noisier images but with no significant difference in CNR. For the ≥80 kg group, tin-filtration resulted in significantly higher CNR. There was no significant difference in subjective image quality when assessed by the radiologists in terms of diagnostic confidence for urolithiasis. ConclusionTin-filtration significantly reduces patient dose while maintaining diagnostic image quality of CTUs for patients with suspected urolithiasis.

Optimization of computed tomography pulmonary angiography protocols using 3D printed model with simulation of pulmonary embolism.

Three-dimensional (3D) printing has been shown to accurately replicate anatomical structures and pathologies in complex cardiovascular disease. Application of 3D printed models to simulate pulmonary arteries and pulmonary embolism (PE) could assist development of computed tomography pulmonary angiography (CTPA) protocols with low radiation dose, however, this has not been studied in the literature. The aim of this study was to investigate optimal CTPA protocols for detection of PE based on a 3D printed pulmonary model. A patient-specific 3D printed pulmonary artery model was generated with thrombus placed in both main pulmonary arteries to represent PE. The model was scanned with 128-slice dual-source CT with slice thickness of 1 and 0.5 mm reconstruction interval. The tube voltage was selected to range from 70, 80, 100 to 120 kVp, and pitch value from 0.9 to 2.2 and 3.2. Quantitative assessment of image quality in terms of signal-to-noise ratio (SNR) was measured in the main pulmonary arteries and within the thrombus regions to determine the relationship between image quality and scanning protocols. Both two-dimensional (2D) and 3D virtual intravascular endoscopy (VIE) images were generated to demonstrate pulmonary artery and thrombus appearances. PE was successfully simulated in the 3D printed pulmonary artery model. There were no significant differences in SNR measured in the main pulmonary arteries with 100 and 120 kVp CTPA protocols (P>0.05), regardless of pitch value used. SNR was significantly lower in the high-pitch 3.2 protocols when compared to other protocols using 70 and 80 kVp (P<0.05). There were no significant differences in SNR measured within the thrombus among the 100 and 120 kVp protocols (P>0.05). For low dose 70 and 80 kVp protocols, SNR was significantly lower in the high-pitch of 3.2 protocols than that in other protocols with different pitch values (P<0.01). 2D images showed the pulmonary arteries and thrombus clearly, while 3D VIE demonstrated intraluminal appearances of pulmonary wall and thrombus in all protocols, except for the 70 kVp and pitch 3.2 protocol, with visualization of thrombus and pulmonary artery wall affected by artifact associated with high image noise. Radiation dose was reduced by up to 80% when lowering kVp from 120 to 100 and 80 kVp with use of 3.2 high-pitch protocol, without significantly affecting image quality. Low-dose CT pulmonary angiography can be achieved with use of low kVp (80 and 100) and high-pitch protocol with significant reduction in radiation dose while maintaining diagnostic images of PE. Use of high pitch, 3.2 in 70 kVp protocol should be avoided due to high image noise and poorer quality.

Patients safety as a priority of ultra low contrast and low radiation dose coronary computed tomography angiography one-beat acquisition

Coronary computed tomography angiography (CCTA) allows to accurately and precisely evaluate coronary arteries. Nevertheless, the main clinical concerns are radiation exposure and contrast media (CM) dose. Dose and contrast reduction is an essential factor for providing a cardiac CT for extended patient population. To minimize CM and radiation dose by optimizing injection protocols with maintaining the high image quality. We prospectively included 204 consecutive patients. CCTA was performed on a 256-slices CT one-beat acquisition with standard tube voltage 120 kV. Patients were divided into two groups according to the injection protocols. Group A was scanned by using a standard three-phase injection protocol by using smart shot dual injector. Patients of group B underwent a new three-phase injection protocol with 63% CM dose reduction. Radiation dose, image noise, signal-to-noise ratio (SNR) were calculated. Image quality was evaluated using 4-point Likert scale. The mean age was 61,5 ± 12,2, and 50,5% were males. The body mass index (BMI) was significantly lower in group B (28,1 ± 5,3 kg/m 2 vs. 24,4 ± 2,9 kg/m 2 respectively, P < 0,003). Effective radiation dose of axial scanning was significantly higher on 43% in group A (231,5 ± 110,9mGy*cm and 160,7 ± 58,7mGy*cm respectively, P < 0,007). Mean amount of CM of group B was lowered by 63,1% on average when compared to group A (75,5 ± 4,7 ml in group A and 27,8 ± 5,6 ml in group B, P < 0,0001). There were no significant differences in SNR (15,7 ± 3,4 vs. 14,9 ± 6,4, P = 0,704) as well as in image quality between groups (3,8 ± 0,4 vs. 3,8 ± 0,37, P = 0,85). New injection protocol of CCTA one-beat acquisition allows to significantly reduce the CM dose on 2,7 times and the radiation exposure on 43% with maintaining the high image quality. Thus, ultra low contrast and low radiation dose cardiac CT leads to patients safety and will increase accessibility for a broad category of patients.

Ultra low contrast dose coronary computed tomography angiography one-beat acquisition: Opening door to patients

The role of 256 slices coronary computed tomography angiography (CCTA) one-beat acquisition in the evaluation of coronary arteries is well established, but the volume of the contrast media (CM) is a serious limitation of using this method in patients with severe comorbidities, specially in renal insufficiency. Reducing the dose of contrast would allow to expand indications to CCTA by reducing side effects of CM administration. To minimize contrast media volume in cardiac CT one-beat acquisition by optimizing injection protocols with maintaining the high image quality. In total, 204 consecutive patients were enrolled and scanned on a 256-slices CT one-beat acquisition with standard tube voltage 120 kV. Patients were divided into two groups according to the injection protocols. Group A was scanned by using a standard three-phase injection protocol by using smart shot dual injector. Patients of group B underwent a new three-phase injection protocol with 63% CM dose reduction. Attenuation, image noise, signal-to-noise ratio (SNR) were calculated. Image quality was evaluated using 4-point Likert scale. The mean age was 61,5 ± 12,2, and 50,5% were males. The body mass index (BMI) was significantly lower in group B (28,1 ± 5,3 kg/m 2 vs. 24,4 ± 2,9 kg/m 2 respectively, P < 0,003). Mean amount of CM of group B was lowered by 63,1% on average when compared to group A (75,5 ± 4,7 ml in group A and 27,8 ± 5,6 ml in group B, P < 0,0001). There were no significant differences in SNR (15,7 ± 3,4 vs. 14,9 ± 6,4, P = 0,704) as well as in image quality between groups (3,8 ± 0,4 vs. 3,8 ± 0,37, P = 0,85). CCTA one-beat acquisition by using new injection protocol with 63% contrast media dose reduction maintain the high image quality of coronary arteries in patient with normal BMI. This 2,7 times contrast dose reduction opens the door and expands the boundaries for cardiac CT in patients with multiple comorbidities and renal insufficiency.

Spiral flow-generating tube for saline chaser improves aortic enhancement in Gd-EOB-DTPA-enhanced hepatic MRI.

To evaluate the effect of a spiral tube on contrast enhancement in the hepatic arterial phase (HAP) of gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI). In this retrospective study, we observed 104 patients who underwent dynamic MRI of the liver between October 2017 and December 2017. Three Gd-EOB-DTPA injection protocols were compared: (A) conventional method (undiluted Gd-EOB-DTPA, injection rate 1 ml/s, n = 36); (B) spiral dilution method (1:1 diluted Gd-EOB-DTPA with saline [off-label], injection rate 2 ml/s via spiral tube, n = 38); (C) spiral-flushed method (undiluted Gd-EOB-DTPA, injection rate 1 ml/s via spiral tube, n = 30). We regarded protocol-A as a control. The signal-to-noise ratio (SNR) of the abdominal aorta was calculated using arterial phase images. Image contrast and artefacts were evaluated by two board-certified radiologists, using a four-point scale. Statistical analyses included Dunnett's test, the Kruskal-Wallis test and the Steel test. The SNR of the aorta was significantly higher with protocol-C (25.4 ± 8.8) than protocol-A (20.8 ± 5.4, p = 0.01). There was no significant difference in SNR between protocols A and B (p = 0.47). The contrast score of protocol-C was significantly higher than that of protocol-A (p = 0.0019). There was no significant difference in contrast score between protocols A and B (p = 0.50). There was no significant difference in artefacts among the three protocols (p = 0.96). Use of a spiral tube with a slow injection protocol contributed to improved aortic contrast enhancement in the HAP of GD-EOB-DTPA-enhanced hepatic MRI. • Gadoxetic acid shows weaker arterial enhancement at recommended doses, compared with nonspecific gadolinium agents; selection of an appropriate injection protocol is important. • A spiral flow-generating tube improves the transport efficiency of the contrast media, and increases the signal-to-noise ratio of the aorta in hepatic arterial phase. • A spiral flow-generating tube does not contribute to artefact reduction in hepatic arterial phase.

Methods for solving the neck two-point T2-DIXON fat-water separation misalignment

Objective To explore the methods for solving the neck two-point T2-DIXON fat-water separation misalignment. Methods During August 2015 to July 2016, 140 patients with fat-water separation on the nasopharynx and cervical axial T2-DIXON images were prospectively recruited from Sichuan Cancer Hospital. There was no metal implant in the fat-water separation misalignment area. The patients were divided into 7 groups by random number table method with 20 patients in each group for the axial T2-DIXON scan: Group A adopted plan 1(increasing localized shim box on the fat-water separation misalignment area);Group B adopted plan 2(increasing the times of repeated acquisition to 2 of the T2-DIXON sequence);Group C adopted plan 3 (placing the shimming assist device on the inspection area);Group D adopted plan 1+ plan 2;Group E adopted plan 1+ plan 3;Group F adopted plan 2+ plan 3;Group G adopted plan 1+plan 2+ plan 3. The images quality of two scans were graded and compared. We compared the signal-to-noise ratio (SNR) of T2-DIXON image on the same muscle tissue between the two scans of each group. The difference of SNR on the two scan images was compared with the paired t test, the difference of SNR among seven groups was conducted with independent sample t test, and the comparison of image quality classification was conducted by rank sum test. Results The image quality of all the seven groups was improved to some different degrees. The cases with image quality reaching level 3 were 12, 15, 15, 16, 17, 18 and 18 in A to G groups, respectively. It was better to use the combination of two or more methods to improve the quality of the image than to use a single method. There were no statistically significant differences in SNR between two scans in A, C and E group (all P>0.05).There were statistically significant differences in SNR between two scans in groups of B, D, F and G(all P 0.05);there were significant differences in the second scans among the 7 groups (P<0.05). Conclusions This study suggests that placing localized shim box, increasing the times of repeated acquisition, and use of shimming assist device in MRI correct the fat-water separation misalignment, help to provide images with high quality. The combination of the above method was better than using the single method. The SNR can be improved when increasing the times of repeated acquisition. Key words: Magnetic resonance imaging; Two-point T2-DIXON; Fat-water separation misalignment

Evaluating Low-kV Dual-source CT Angiography by High-pitch Spiral Acquisition and Iterative Reconstruction in Pediatric Congenital Heart Disease Patients.

We retrospectively evaluated the qualities of pediatric cardiovascular dual-source computed tomography (DSCT) images reconstructed by sinogram-affirmed iterative reconstruction (SAFIRE) and filtered back projection (FBP). We analyzed the cases of 287 congenital heart disease (CHD) patients < 5 years old, referred to our department in August 2013-March 2015. We divided them into two groups according to tube voltage (70 kVp, n=147; 80 kVp, n=140). All images were acquired by a CARE kV system and reconstructed by FBP and SAFIRE. The attenuation, noise, and signal-to-noise ratio (SNR) at each region of the heart and great vessels were measured. The volume CT dose index and dose-length product values were recorded. Compared to FBP, reconstruction by SAFIRE showed that the attenuation volume was significantly lower by 0.4% except for the ascending aorta (p<0.05), the noise value was lower by about 20% (p<0.05), and the SNR was higher by approx. 25% (p<0.05). The radiation dose in the 70 kVp group was significantly lower than that in the 80 kVp group. No significant differences in SNR were observed between the patient groups. DSCT image acquisition with SAFIRE using the CARE kV system results in low image noise and radiation dose in pediatric patients with CHD.

Patient-specific three-dimensional printed pulmonary artery model: A preliminary study

ABSTRACT Background and Objectives: Three-dimensional (3D) printing has potential value in medical applications with increasing reports in the diagnostic assessment of cardiovascular diseases. The use of 3D printing in replicating pulmonary artery anatomy and diagnosing pulmonary embolism is very limited. The purpose of this study was to develop a 3D printed pulmonary artery model and test different computed tomography (CT) scanning protocols for determination of an optimal protocol with acceptable image quality but low radiation dose. Materials and Methods: A patient-specific 3D printed pulmonary artery model was created based on contrast-enhanced CT images in a patient with suspected pulmonary embolism. Different CT pulmonary angiography protocols consisting of 80, 100, and 120 kVp, pitch 0.7, 0.9, and 1.2 with 1 mm slice thickness, and 0.6 mm reconstruction interval were tested on the phantom. Quantitative assessment of image quality in terms of signal-to-noise ratio (SNR) was measured in the images acquired with different protocols. Measurements in pulmonary artery diameters were conducted and compared between pre- and post-3D printed images and 3D printed model. Results: The 3D printed model was found to replicate normal pulmonary artery with high accuracy. The mean difference in diameter measurements was &lt;0.8 mm (&lt;0.5% deviation in diameter). There was no significant difference in SNR measured between these CT protocols (P = 0.96-0.99). Radiation dose was reduced by 55% and 75% when lowering kVp from 120 to 100 and 80 kVp, without affecting image quality. Conclusions: It is feasible to produce a 3D printed pulmonary artery model with high accuracy in replicating normal anatomy. Different CT scanning protocols are successfully tested on the model with 80 kVp and pitch 0.9 being the optimal one with resultant diagnostic images but at much lower radiation dose.