Hybrid of Compressed Sensing and Parallel Imaging Applied to Three-dimensional Isotropic T2-weighted Turbo Spin-echo MR Imaging of the Lumbar Spine.

PURPOSE: The hybrid compressed sensing (hybrid-CS) technique can shorten the acquisition time compared with the sensitivity encoding (SENSE) technique in lumbar MRI. To evaluate the feasibility of a hybrid-CS technique in comparison with 3D isotropic T2-weighted turbo spin-echo (3D volume isotropic turbo spin-echo acquisition [VISTA]) MRI of the lumbar spine. MATERIALS AND METHODS: The Institutional Review Board approved this study and informed consent was obtained from participants prior to study entry. Sixteen healthy volunteers underwent lumbar spine 3D VISTA with conventional parallel imaging for SENSE and hybrid-CS at 3T. We recorded the image acquisition times of SENSE and hybrid-CS. We compared the signal-to-noise ratio (SNR) in spine, cerebrospinal fluid (CSF), lumbar disc, epidural fat, and erector spinae muscle, and the contrast of spine, CSF, and disc, and performed qualitative image analysis assessment, between the two image sequences. RESULTS: The image acquisition time for hybrid-CS was 39.2% shorter than that of SENSE (218.4/358.8 s). The contrast of CSF and SNR of the spine was significantly higher with hybrid-CS than with SENSE (P < 0.05). The SNR of the disc and muscle was significantly higher with SENSE than with hybrid-CS (P < 0.05). There were no significant differences in the contrast of spine, disc, and fat, and SNR of CSF and fat between hybrid-CS and SENSE. There were no significant differences in the qualitative evaluation between hybrid-CS and SENSE. CONCLUSION: Compared with SENSE, hybrid-CS for 3D VISTA can shorten image acquisition time without sacrificing image quality.

Machine Learning to Differentiate T2-Weighted Hyperintense Uterine Leiomyomas from Uterine Sarcomas by Utilizing Multiparametric Magnetic Resonance Quantitative Imaging Features.

RATIONALE AND OBJECTIVE: Uterine leiomyomas with high signal intensity on T2-weighted imaging (T2WI) can be difficult to distinguish from sarcomas. This study assessed the feasibility of using machine learning to differentiate uterine sarcomas from leiomyomas with high signal intensity on T2WI on multiparametric magnetic resonance imaging. MATERIALS AND METHODS: This retrospective study included 80 patients (50 with benign leiomyoma and 30 with uterine sarcoma) who underwent pelvic 3 T magnetic resonance imaging examination for the evaluation of uterine myometrial smooth muscle masses with high signal intensity on T2WI. We used six machine learning techniques to develop prediction models based on 12 texture parameters on T1WI and T2WI, apparent diffusion coefficient maps, and contrast-enhanced T1WI, as well as tumor size and age. We calculated the areas under the curve (AUCs) using receiver-operating characteristic analysis for each model by 10-fold cross-validation and compared these to those for two board-certified radiologists. RESULTS: The eXtreme Gradient Boosting model gave the highest AUC (0.93), followed by the random forest, support vector machine, multilayer perceptron, k-nearest neighbors, and logistic regression models. Age was the most important factor for differentiation (leiomyoma 44.9 ± 11.1 years; sarcoma 58.9 ± 14.7 years; p < 0.001). The AUC for the eXtreme Gradient Boosting was significantly higher than those for both radiologists (0.93 vs 0.80 and 0.68, p = 0.03 and p < 0.001, respectively). CONCLUSION: Machine learning outperformed experienced radiologists in the differentiation of uterine sarcomas from leiomyomas with high signal intensity on T2WI.

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

OBJECTIVES: 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). METHODS: 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. RESULTS: 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). CONCLUSIONS: 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. KEY POINTS: • 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.

Machine learning based on multi-parametric magnetic resonance imaging to differentiate glioblastoma multiforme from primary cerebral nervous system lymphoma.

PURPOSE: To evaluate the performance of a machine learning method based on texture features in multi-parametric magnetic resonance imaging (MRI) to differentiate a glioblastoma multiforme (GBM) from a primary cerebral nervous system lymphoma (PCNSL). MATERIALS AND METHODS: We included 70 patients who underwent contrast enhanced brain MRI at 3 T with brain tumors diagnosed as GBM (n = 45) and PCNSL (n = 25) in this retrospective study. Twelve histograms and texture parameters were assessed on T2-weighted images (T2WIs), apparent diffusion coefficient maps, relative cerebral blood volume (rCBV) map, and contrast-enhanced T1-weighted images (CE-T1WIs). A prediction model was developed using a machine learning method (univariate logistic regression and multivariate eXtreme gradient boosting-XGBoost) and the area under the receiver operating characteristic curve of this model was calculated via 10-fold cross validation. In addition, the performance of the machine learning method was compared with the judgments of two board certified radiologists. RESULTS: With the univariate logistic regression model, the standard deviation of rCBV offered the highest AUC (0.86), followed by mean value of rCBV (0.83), skewness of CE-T1WI (0.78), mean value of CET1 (0.78), and max value of rCBV (0.77). The AUC of the XGBoost was significantly higher than the two radiologists (0.98 vs. 0.84; p < 0.01 and 0.98 vs. 0.79; p < 0.01, respectively). CONCLUSION: The performance of machine learning based on histogram and texture features in multi-parametric MRI was superior to that of conventional cut-off method and the board certified radiologists to differentiate a GBM from a PCNSL.

The effect of heart rate on coronary plaque measurements in 320-row coronary CT angiography.

Repeatability of quantitative assessment of atherosclerotic plaques is important for the accurate detection of high-risk plaques in coronary CT angiography (CTA). We assessed the effect of heart rate (HR) on plaque CT number using a coronary artery model and a cardiac phantom capable of simulating cardiac motion. The coronary artery model with luminal stenosis on a cardiac phantom was imaged with a simulated HR of 0, 50, 60, and 70 beats per minute using a 320-row CT scanner. We reconstructed CT images for cardiac diastolic phases (for 75% R-R interval) using filtered back projection (FBP), hybrid iterative reconstruction (AIDR3D), and model-based iterative reconstruction (FIRST). Two observers measured plaque attenuation in the lesion with 75% stenosis. The coefficient of determination (R2) was obtained to evaluate interobserver agreement. At HR 70, FIRST improved the correlation between two observers compared with FBP and AIDR3D (FIRST: R2 = 0.68, p < 0.05; FBP: R2 = 0.29, p = 0.31; AIDR3D: R2 = 0.22, p = 0.18). These R2 at HR 70 were lower compared with at HR 50 (FIRST: R2 = 0.92, p < 0.05; FBP: R2 = 0.83, p < 0.05; AIDR3D: R2 = 0.87, p < 0.05) and HR 0 (FIRST: R2 = 0.97, p < 0.05; FBP: R2 = 0.89, p < 0.05; AIDR3D: R2 = 0.95, p < 0.05). Higher HR affected plaque measurement repeatability in coronary CTA. FIRST may improve plaque measurement repeatability at the higher HR compared with FBP and AIDR3D.

Comparison of the image quality of turbo spin echo- and echo-planar diffusion-weighted images of the oral cavity.

The purpose of this study was to compare the image quality of turbo spin echo (TSE) diffusion-weighted imaging (DWI) and echo-planar imaging (EPI) of the oral cavity region.This retrospective study included 26 patients who had undergone both TSE- and EPI-DWI. Misregistration of DWI with T2-TSE images was assessed in the oral cavity. We also compared geometric distortion, the signal-to-noise ratio (SNR), contrast, and the apparent diffusion coefficient (ADC) for the tongue parotid gland, and spinal cord. On a 5-point scale, 2 radiologists scored the TSE- and EPI-DWI of each patient for ghost artifacts, image contrast, and overall image quality.Distortion in the phase-encoded direction was significantly lower on TSE- than EPI-DWI. The SNR of the tongue and parotid gland was significantly higher on TSE than EPI-DWI except spinal cord. No significant difference was found in contrast and ADC values (except for the ADC of tongue). TSE-DWI yielded higher qualitative scores for all parameters except image contrast.For the oral cavity region, TSE-DWI was superior to EPI-DWI with respect to distortion-free images and superior image quality.

Reducing artifacts of gadoxetate disodium-enhanced MRI with oxygen inhalation in patients with prior episode of arterial phase motion: intra-individual comparison.

PURPOSE: To determine whether oxygen inhalation reducing artifacts in patients with previous transient severe motion (TSM) on gadoxetate-disodium-enhanced MRI. MATERIALS AND METHODS: Fifty-one patients with TSM on previous gadoxetate-disodium-enhanced MRI (Baseline examination) were evaluated. Image quality in the examination with oxygen inhalation (Oxygen examination) and that in Baseline examination and the examination before Baseline examination without oxygen inhalation (Past examination) were qualitatively compared in dynamic study. RESULTS: Image quality was significantly higher in Oxygen examination than Baseline examination in arterial phase, but there was no statistical difference between Baseline and Past examinations. CONCLUSION: Oxygen inhalation improved image quality in patients with a prior episode of arterial phase TSM.

Hepatic sclerosed hemangioma with special attention to diffusion-weighted magnetic resonance imaging.

BACKGROUND: A hepatic sclerosed hemangioma (HSH) is a very rare benign liver tumor. The correct preoperative diagnosis of HSH is very difficult because its features of imaging are similar to those of intrahepatic cholangiocarcinoma or colorectal liver metastasis. CASE PRESENTATION: We experienced five patients who were diagnosed histologically with HSH. The preoperative diagnoses were HSH in two patients, cavernous hemangioma in one, intrahepatic cholangiocarcinoma in one, and colorectal liver metastasis in one. All patients were treated with hepatectomy (one laparoscopic and four laparotomies), and the diagnosis was completed by histological investigation of the resected specimen. In particular, we investigated the apparent diffusion coefficient (ADC) mean value using diffusion-weighted sequences of magnetic resonance imaging (DW-MRI). The average of the ADC mean (ADCmean) value of HSH was 1.94 × 10-3 mm2/s (range 1.73-2.10 × 10-3 mm2/s), which was higher than the value of common malignant liver tumors. Interestingly, the ADCmean values were almost the same between the degenerate (1.90 ± 0.17 × 10-3 mm2/s) and the non-degenerate areas (1.95 ± 0.26 × 10-3 mm2/s) in HSH. CONCLUSIONS: The ADCmean value seemed to be quite useful to preoperatively distinguish HSH from other malignant liver tumors.

Simultaneous acquisition of MR angiography and diagnostic images of abdomen at view-sharing multiarterial phases and comparing the effect of two different contrast agents.

BACKGROUND: Simultaneous acquisition of magnetic resonance angiography (MRA) and diagnostic images is challenging in contrast-enhanced upper abdominal MRI. PURPOSE: To evaluate the image quality of MRA of the abdomen acquired simultaneously with diagnostic MR images, and to compare the contrast effect, conspicuity of aortic branches, and pancreatic lesions in MRA between gadobutrol and gadoterate meglumine. STUDY TYPE: Prospective. POPULATION: Eighty-eight patients with known and suspected upper abdominal disease. FIELD STRENGTH/SEQUENCES: 3T/4D-eTHRIVE (T1 -weighted fat-suppressed 3D fast gradient echo) for multiarterial phase imaging. ASSESSMENT: The artery-to-muscle signal intensity ratio (SIR), conspicuity of aortic branches on the axial, maximum intensity projection (MIP), and volume-rendered (VR) images, and conspicuity of focal pancreatic lesions were compared between gadobutrol and gadoterate meglumine. The diameters of aortic branches were measured on axial MRA and computed tomography angiography (CTA) images and then compared. STATISTICAL TESTS: Quantitative and qualitative data were assessed with the Mann-Whitney U-test. The diameters of aortic branches between MRA and CTA were compared with a Spearman rank correlation test. RESULTS: View-sharing multiarterial phase imaging was successfully performed in all patients. The SIRs of common hepatic artery (P = 0.0051) and left renal artery (RA) (P = 0.045), vascular conspicuities of right and left hepatic arteries (P = 0.010 and 0.030) and right and left RAs on axial (P = 0.0065 and 0.036), and that of gastroduodenal artery on MIP (P = 0.039) with gadobutrol were significantly higher than those with gadoterate meglumine. The conspicuity of focal pancreatic lesions were comparable between the gadobutrol and gadoterate meglumine (P = 0.73). The vascular diameters on MRA and CTA were strongly correlated in all aortic branches (r = 0.842-0.942, P < 0.0001). DATA CONCLUSION: High-quality MRA of the abdomen was obtained simultaneously with the diagnostic MR images using view-sharing multiarterial phase imaging that also demonstrated comparable image quality between gadobutrol and gadoterate meglumine. LEVEL OF EVIDENCE: 2 Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2017.

Contrast enhancement in abdominal computed tomography: influence of photon energy of different scanners.

OBJECTIVE: Different CT scanners have different X-ray spectra and photon energies indicating that contrast enhancement vary among scanners. However, this issue has not been fully validated; therefore, we performed phantom and clinical studies to assess this difference. METHODS: Two scanners were used: scanner-A and scanner-B. In the phantom study, we compared the contrast enhancement between the scanners at tube voltage peaks of 80, 100 and 120 kVp. Then, we calculated the effective energies of the two CT scanners. In the clinical study, 40 patients underwent abdominal scanning with scanner-A and another 40 patients with scanner-B, with each group using the same scanning protocol. The contrast enhancement of abdominal organs was assessed quantitatively (based on the absolute difference between the attenuation of unenhanced scans and contrast-enhanced scans) and qualitatively. A two-tailed independent Student's t-test and or the Mann-Whitney U test were used to compare the discrepancies. RESULTS: In the phantom study, contrast enhancement for scanner-B was 36.9, 32.6 and 30.8% higher than that for scanner-A at 80, 100 and 120 kVp, respectively. The effective energies were higher for scanner-A than for scanner-B. In the quantitative analysis for the clinical study, scanner-B yielded significantly better contrast enhancement of the hepatic parenchyma, pancreas, kidney, portal vein and inferior vena cava compared with that of scanner-A. The mean visual scores for contrast enhancement were also significantly higher on images obtained by scanner-B than those by scanner-A. CONCLUSION: There were significant differences in contrast enhancement of the abdominal organs between the compared CT scanners from two different vendors even at the same scanning and contrast parameters. Advances in knowledge: Awareness of the impact of different X-ray energies on the resultant attenuation of contrast material is important when interpreting clinical CT images.

Dual-layer DECT for multiphasic hepatic CT with 50 percent iodine load: a matched-pair comparison with a 120 kVp protocol.

OBJECTIVES: To evaluate the image quality and lesion conspicuity of virtual-monochromatic-imaging (VMI) with dual-layer DECT (DL-DECT) for reduced-iodine-load multiphasic-hepatic CT. METHODS: Forty-five adults with renal dysfunction who had undergone hepatic DL-DECT with 300-mgI/kg were included. VMI (40-70-keV, DL-DECT-VMI) was generated at each enhancement phase. As controls, 45 matched patients undergoing standard 120-kVp protocol (120-kVp, 600-mgI/kg, and iterative reconstruction) were included. We compared the size-specific dose estimate (SSDE), image noise, CT attenuation, and contrast-to-noise ratio (CNR) between protocols. Two radiologists scored the image quality and lesion conspicuity. RESULTS: SSDE was significantly lower in DL-DECT group (p < 0.01). Image noise of DL-DECT-VMI was almost constant at each keV (differences of ≤15%) and equivalent to or lower than of 120-kVp. As the energy decreased, CT attenuation and CNR gradually increased; the values of 55-60 keV images were almost equivalent to those of standard 120-kVp. The highest scores for overall quality and lesion conspicuity were assigned at 40-keV followed by 45 to 55-keV, all of which were similar to or better than of 120-kVp. CONCLUSIONS: For multiphasic-hepatic CT with 50% iodine-load, DL-DECT-VMI at 40- to 55-keV provides equivalent or better image quality and lesion conspicuity without increasing radiation dose compared with standard 120-kVp protocol. KEY POINTS: • 40-55-keV yields optimal image quality for half-iodine-load multiphasic-hepatic CT with DL-DECT. • DL-DECT protocol decreases radiation exposure compared with 120-kVp scans with iterative reconstruction. • 40-keV images maximise conspicuity of hepatocellular carcinoma especially at hepatic-arterial phase.

Single-Breath-Hold Whole-heart Unenhanced Coronary MRA Using Multi-shot Gradient Echo EPI at 3T: Comparison with Free-breathing Turbo-field-echo Coronary MRA on Healthy Volunteers.

PURPOSE: We investigated the feasibility of single breath hold unenhanced coronary MRA using multi-shot gradient echo planar imaging (MSG-EPI) on a 3T-scanner. METHODS: Fourteen volunteers underwent single breath hold coronary MRA with a MSG-EPI and free-breathing turbo field echo (TFE) coronary MRA at 3T. The acquisition time, signal to noise ratio (SNR), and the contrast of the sequences were compared with the paired t-test. Readers evaluated the image contrast, noise, sharpness, artifacts, and the overall image quality. RESULTS: The acquisition time was 88.1% shorter for MSG-EPI than TFE (24.7 ± 2.5 vs 206.4 ± 23.1 sec, P < 0.01). The SNR was significantly higher on MSG-EPI than TFE scans (P < 0.01). There was no significant difference in the contrast on MSG-EPI and TFE scans (1.8 ± 0.3 vs 1.9 ± 0.3, P = 0.24). There was no significant difference in image contrast, image sharpness, and overall image quality between two scan techniques. The score of image noise and artifact were significantly higher on MSG-EPI than TFE scans (P < 0.05). CONCLUSION: The single breath hold MSG-EPI sequence is a promising technique for shortening the scan time and for preserving the image quality of unenhanced whole heart coronary MRA on a 3T scanner.

Comparison between multi-shot gradient echo EPI and balanced SSFP in unenhanced 3T MRA of thoracic aorta in healthy volunteers.

PURPOSE: The purpose of this study was to compare scan time and image quality between magnetic resonance angiography (MRA) of the thoracic aorta using a multi-shot gradient echo planar imaging (MSG-EPI) and MRA using balanced steady-state free precession (b-SSFP). MATERIALS AND METHODS: Healthy volunteers (n=17) underwent unenhanced thoracic aorta MRA using balanced steady-state free precession (b-SSFP) and MSG-EPI sequences on a 3T MRI. The acquisition time, total scan time, signal-to-noise ratio (SNR) of the thoracic aorta, and the coefficient of variation (CV) of thoracic aorta were compared with paired t-tests. Two radiologists independently recorded the images' contrast, noise, sharpness, artifacts, and overall quality on a 4-point scale. RESULTS: The acquisition time was 36.2% shorter for MSG-EPI than b-SSFP (115.5±14.4 vs 181.0±14.9s, p<0.01). The total scan time was 40.4% shorter for MSG-EPI than b-SSFP (272±78 vs 456±144s, p<0.01). There was no significant difference in mean SNR between MSG-EPI and b-SSFP scans (17.3±3.6 vs 15.2±4.3, p=0.08). The CV was significantly lower for MSG-EPI than b-SSFP (0.2±0.1 vs. 0.5±0.2, p<0.01). All qualitative scores except for image noise were significantly higher in MSG-EPI than b-SSFP scans (p<0.05). CONCLUSION: The MSG-EPI sequence is a promising technique for shortening scan time and yielding more homogenous image quality in MRA of thoracic aorta on 3T scanners compared with the b-SSFP.

Measuring hepatic functional reserve using T1 mapping of Gd-EOB-DTPA enhanced 3T MR imaging: A preliminary study comparing with 99mTc GSA scintigraphy and signal intensity based parameters.

PURPOSE: To determine the utility of liver T1-mapping on gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) enhanced magnetic resonance (MR) imaging for the measurement of liver functional reserve compared with the signal intensity (SI) based parameters, technetium-99m-galactosyl serum albumin (99mTc-GSA) scintigraphy and indocyanine green (ICG) clearance. MATERIALS AND METHODS: This retrospective study included 111 patients (Child-Pugh-A 90; -B 21) performed with both Gd-EOB-DTPA enhanced liver MR imaging and 99mTc-GSA (76 patients with ICG). Receiver operating characteristic (ROC) curve analysis was performed to compare diagnostic performances of T1-relaxation-time parameters [pre-(T1pre) and post-contrast (T1hb) Gd-EOB-DTPA], SI based parameters [relative enhancement (RE), liver-to-muscle-ratio (LMR), liver-to-spleen-ratio (LSR)] and 99mTc-GSA scintigraphy blood clearance index (HH15)] for Child-Pugh classification. Pearson's correlation was used for comparisons among T1-relaxation-time parameters, SI-based parameters, HH15 and ICG. RESULTS: A significant difference was obtained for Child-Pugh classification with T1hb, ΔT1, all SI based parameters and HH15. T1hb had the highest AUC followed by RE, LMR, LSR, ΔT1, HH15 and T1pre. The correlation coefficients with HH15 were T1pre 0.22, T1hb 0.53, ΔT1 -0.38 of T1 relaxation parameters; RE -0.44, LMR -0.45, LSR -0.43 of SI-based parameters. T1hb was highest for correlation with HH15. The correlation coefficients with ICG were T1pre 0.29, T1hb 0.64, ΔT1 -0.42 of T1 relaxation parameters; RE -0.50, LMR -0.61, LSR -0.58 of SI-based parameters; 0.64 of HH15. Both T1hb and HH15 were highest for correlation with ICG. CONCLUSION: T1 relaxation time at post-contrast of Gd-EOB-DTPA (T1hb) was strongly correlated with ICG clearance and moderately correlated HH15 with 99mTc-GSA. T1hb has the potential to provide robust parameter of liver functional reserve.

Hepatic fat quantification using automated six-point Dixon: Comparison with conventional chemical shift based sequences and computed tomography.

PURPOSE: To compare automated six-point Dixon (6-p-Dixon) MRI comparing with dual-echo chemical-shift-imaging (CSI) and CT for hepatic fat fraction in phantoms and clinical study. MATERIALS AND METHODS: Phantoms and fifty-nine patients were examined both MRI and CT for quantitative fat measurements. RESULTS: In phantom study, linear regression between fat concentration and 6-p-Dixon showed good agreement. In clinical study, linear regression between 6-p-Dixon and dual-echo CSI showed good agreement. CT attenuation value was strongly correlated with 6-p-Dixon (R2=0.852; P<0.001) and dual-echo CSI (R2=0.812; P<0.001). CONCLUSION: Automated 6-p-Dixon and dual-echo CSI were accurate correlation with CT attenuation value of liver parenchyma. 6-p-Dixon has the potential for automated hepatic fat quantification.

Paradoxical Effect of Cardiac Output on Arterial Enhancement at Computed Tomography: Does Cardiac Output Reduction Simply Result in an Increase in Aortic Peak Enhancement?

OBJECTIVE: The aim of this study was to evaluate the effect of cardiac output (CO) on aortic peak enhancement using protocols with different contrast material (CM) injection durations. METHODS: We used a flow phantom that simulated the human circulatory system. Contrast material was injected at a rate of 4.0 mL/s for a period of 2.5, 5, 10, 15, or 20 seconds for a CO of 2.8, 4.2, and 5.6 L/min. Single-level serial computed tomography scans of the simulated aorta were acquired after the start of CM delivery, and aortic peak enhancement was recorded under the different injection protocols. RESULTS: Under a long injection duration protocol (20 seconds), a decrease in CO increased aortic peak enhancement proportionally (CO of 2.8 L/min, 420 Hounsfield units [HU]; CO of 4.2 L/min, 365 HU; CO of 5.6 L/min, 291 HU). However, this effect was decreased under shorter injection duration protocols (5, 10, and 15 seconds); under the shortest (2.5-second) injection duration protocol, a decrease in CO resulted in a decrease in aortic peak enhancement (CO of 2.8 L/min, 36 HU; CO of 4.2 L/min, 51 HU; CO of 5.6 L/min, 55 HU). CONCLUSIONS: The magnitude of the effect of CO on aortic peak enhancement depends on the CM injection duration.

Fat Suppressed Contrast-Enhanced T1-Weighted Dynamic Magnetic Resonance Imaging at 3T: Comparison of Image Quality Between Spectrally Adiabatic Iversion Recovery and the Multiecho Dixon Technique in Imaging of the Prostate.

OBJECTIVE: To compare the quality of fat suppression and image quality between multiecho Dixon technique (mDixon) and spectrally adiabatic iversion recovery (SPAIR) in dynamic contrast-enhanced magnetic resonance imaging of the prostate. METHODS: This prospective study assigned thirty consecutive patients to scanning with SPAIR technique (SPAIR protocol) and another consecutive 30 patients to scanning with mDixon technique (mDixon protocol). We calculated the contrast, signal to noise ratio (SNR), contrast to noise ratio (CNR) and the coefficient of variation between the 2 protocols. Two readers compared homogeneity of fat suppression, image noise, image contrast, and image sharpness between the two protocols. RESULTS: The SNR, CNR, and contrast of mDixon protocol were significantly higher than those of the SPAIR protocol (SNR: 14.7 ± 4.1 vs 11.0 ± 2.6; P < 0.05; CNR: 6.3 ± 1.6 vs 0.5 ± 1.5; P < 0.01; contrast: 4.4 ± 1.4 vs 1.3 ± 0.5; P < 0.01), whereas the coefficient of variation of mDixon protocol was significantly lower than that of SPAIR protocol (34.7 ± 15.5 vs 43.7 ± 23.1, P < 0.01). In qualitative image analysis, the image scores for the homogeneity of fat suppression, image noise, and image sharpness were significantly higher with mDixon protocol than those with SPAIR protocol (P < 0.01). There was no significant difference in image contrast between 2 fat suppression protocols (P > 0.05). CONCLUSIONS: In dynamic contrast-enhanced magnetic resonance imaging of the prostate, mDixon technique improved the homogeneity of fat suppression without degrade of image quality compared with SPAIR technique.

Cardiovascular magnetic resonance myocardial T1 mapping to detect and quantify cardiac involvement in familial amyloid polyneuropathy.

OBJECTIVES: This study sought to explore the potential role of non-contrast T1 mapping for the detection and quantification of cardiac involvement in familial amyloid polyneuropathy (FAP). METHODS: Japanese patients with FAP [n = 41, age 53.2 ± 13.9 years, genotype Val30Met (n = 25), non-Val30Met (n = 16)] underwent cardiac magnetic resonance imaging that included T1 mapping (saturation-recovery method) and late gadolinium-enhanced (LGE) imaging on a 3.0-T MR scanner. Their native T1 was measured on mid-ventricular short-axis images and compared with 30 controls. RESULTS: Of the 41 FAP patients 29 were LGE positive. The native T1 was significantly higher in FAP patients than in the controls (1,634.1 ± 126.3 ms vs. 1,432.4 ± 69.0 ms, p < 0.01), significantly higher in LGE-positive- than LGE-negative FAP patients (1,687.1 ± 104.4 ms vs. 1,505.4 ± 68.5 ms, p < 0.01), and significantly higher in LGE-negative FAP patients than the controls (p < 0.01). A native T1 cutoff value of 1,610 ms yielded 85.4% accuracy for identifying LGE-positive FAP. The native T1 significantly correlated with the interventricular septum wall thickness, the left ventricular mass, the LGE volume, the plasma B-type natriuretic peptide level, and the E/e' ratio (all p < 0.01). CONCLUSION: T1 mapping is of high diagnostic accuracy for the detection of LGE-positive FAP. The native myocardial T1 may be correlated with the severity of cardiac amyloid deposition. KEY POINTS: • The native T1 was higher in FAP patients than the controls. • The native T1 was higher in LGE-positive- than LGE-negative FAP patients. • The native T1 was higher in LGE-negative FAP patients than the controls. • The native T1 correlated with clinical markers of systolic and diastolic dysfunction. • Myocardial T1 mapping is of high diagnostic accuracy for detecting LGE-positive FAP.

CT venography after knee replacement surgery: comparison of dual-energy CT-based monochromatic imaging and single-energy metal artifact reduction techniques on a 320-row CT scanner.

BACKGROUND: An optimal metal artifact reduction (MAR) technique is needed for a reliable and accurate image-based diagnosis. PURPOSE: Using a 320-row scanner, we compared the dual-energy computed tomography (CT)-based monochromatic and the single-energy metal artifact reduction (SEMAR) techniques for CT venography (CTV) to identify the better imaging method for diagnosing deep vein thrombosis (DVT) in patients who had undergone knee replacement surgery. MATERIAL AND METHODS: Twenty-three consecutive patients with suspected DVT after unilateral knee replacement surgery underwent dual-energy CT (135/80 kVp). Monochromatic images of 35-135 keV were generated; the monochromatic image with the best signal-to-noise ratio (SNR) of the popliteal vein near the metal prosthesis were selected. The projection data of 80 kVp were reconstructed using MAR algorithm. The mean SNR ON MAR and the best SNR ON monochromatic images were compared. Two radiologists evaluated visualization of the metal artifacts on a four-point scale where 1 = extensive artifacts, 2 = strong artifacts, 3 = mild artifacts, and 4 = minimal artifacts. RESULTS: The mean SNR was significantly higher on the MAR than the monochromatic images (12.8 ± 4.7 versus 7.7 ± 5.1, P < 0.01) and the visual scores were significantly higher for MAR than monochromatic images (2.6 ± 0.8 versus 1.3 ± 0.4, P < 0.01). CONCLUSION: For CTV after knee replacement surgery, the MAR technique is superior to the monochromatic imaging technique.

Comparison of the Timing of Hepatic Arterial Phase and Image Quality Using Test-Bolus and Bolus-Tracking Techniques in Gadolinium-Ethoxybenzyl-Diethylenetriamine Pentaacetic Acid-Enhanced Hepatic Dynamic Magnetic Resonance Imaging.

OBJECTIVES: The aim of this study was to compare the image quality, the degree of artifacts and the percentage of timing of the optimal hepatic arterial phase (HAP) between test-bolus and bolus-tracking methods on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI). METHODS: In this prospective study, 60 patients who underwent 3-dimensional dynamic Gd-EOB-DTPA-enhanced hepatic 3-T MRI were enrolled in this study. We randomly assigned the 30 patients to the bolus-tracking method, and another 30 patients to the test-bolus method. Signal-to-noise ratios of the liver and spleen in HAP were compared in the 2 groups. Two radiologists independently assessed the ratio of optimal timing of HAP and the degree of ringing and motion artifacts of the 2 protocols. RESULTS: The signal-to-noise ratios of the liver (24.0 [SD, 6.4] vs 20.4 [SD, 4.0]) and spleen (30.0 [SD, 13.3] vs 23.6 [SD, 9.9]) were significantly higher in the test-bolus protocol than in the bolus-tracking protocol. The ratio of optimal timing was also significantly higher with the test-bolus protocol than with the bolus-tracking protocol (76.7% vs 40.0%). The degree of ringing and motion artifacts of test-bolus protocol was significantly lower than that of the bolus-tracking protocol (P < 0.01). CONCLUSIONS: The test-bolus protocol in dynamic 3-T MRI can yield better qualitative image quality and more optimal timing of HAP images, while reducing the degree of artifacts compared with the bolus-tracking protocol.